Manipulation of nanoscale objects using molecular self-assembly is a potent tool to achieve large scale nanopatterning with small effort. Coordination polymers of bis-salphen compounds based on zinc have demonstrated their ability to align carbon nanotubes into micro-scale networks with an unusual “rings-and-rods” pattern. This paper investigates how the compounds interact with pristine and functionalized graphene using density functional theory calculations and molecular dynamic simulations. Using the free energy perturbation method we will show how the addition of phenyl side groups to the core compound and functionalization of graphene affect the stability, mobility and conformation adopted by a dimer of bis-(Zn)salphen compound adsorbed on graphene surface and what it can reveal about the arrangement of chains of bis-(Zn)salphen polymer around carbon nanotubes during the self-assembly of microscale networks. The last decades brought significant breakthroughs in nanoscale synthesis and property engineering ,2,3. HowOne particularly interesting way of constructing interconnected networks of nanotubes was reported by Escarcega-Bobadilla et al. , who obsThe chemical structure of the compounds, for which self-assembly of networks was achieved, is shown in the A subsequent study  has explHowever, the interaction of bis-(Zn)salphen compounds and carbon nanotubes, more specifically their incorporation in the core of the self-assembled networks, remains unexplored. This aspect is especially crucial for applications as electrical conductivity of CNT-based films and composites depends drastically on the contact between nanotubes ,15. Furti and f, characterized by potential energies T is the ambient temperature, i. The main factor hindering the application of Equation (1) is high computational cost required for its calculation, as a good sampling over the configuration space is required. As the Zwanzig equation is valid only for states that are close enough in the configuration space, a typical transition needs to be split into many intermediate steps for which Equation (1) holds, and in doing so the free energy along the resulting path can be calculated, which is referred to as the potential of mean force (PMF). For instance, Umbrella Sampling method [The free energy is a key quantity to understand the physical processes in a solvent environment, such as conformational changes, protein-ligand binding and molecule-substrate adsorption . A numer formula , which ig method ,20 consig method  is used f/kBT)〉) . Then onf/kBT)〉) ,24. On tf/kBT)〉)  implies Alternatively, the free energy perturbation method (FEP) ,27,28 suo method ,30. FEP o method .An intriguing way to use FEP to reduce the computational cost of free energy calculations bases on the fact that the Gibbs free energy differences depend only on the initial and final states and not on the path connecting them. Such approach, known as alchemical transformations  substituenergies ,33, as wenergies .In this study we combine density functional theory and free energy perturbation calculations to compare possible mechanisms of adhesion of Zn-salphen compounds to carbon nanotube surface. Given a significant difference in scale between CNT diameter (tens of nm) and size of a bis-(Zn)salphen compound (>2 nm), we replace nanotube surface with a periodic sheet of plane graphene. Focusing on the atomistic details of coordination polymer adhesion to CNT we model the interacting tip of a polymer chain with its single building block—a dimer of bis-(Zn)salphen compounds. In the following sections we will describe the calculation setup used in our simulations and the effect of compound and graphene functionalization on the strength of adhesion and geometry of the adsorbed compounds in dichloromethane solvent.ab initio calculations for the systems consisting of single salphen base compound of Zn and a periodic sheet of pristine or functionalized graphene. Since the chemical structure of a salphen ligand is rich in aromatic rings, π-π interaction is a primary factor of adhesion. However, compound’s cation center surrounded by negative oxygen and nitrogen atoms would be attracted to charged impurities on graphene surface. For this reason, besides pristine graphene we include sheets modified with: boron and nitrogen substitutions, chemisorbed oxygen, hydroxyl and carboxyl groups, which have been reported to improve graphene adhesive properties [To estimate the energy of adhesion of the (Zn)salphen-based compounds to graphene surface we have performed operties ,36,37.System under study  was enclThe calculations were performed with the SIESTA DFT package (v. 4.1) . ExchangThe set of calculations included geometry optimizations to obtain relaxed structures followed by single point energy calculations to get ground state energies of the standalone compound (2+ ion and organic ligand were treated within a free cation model [To estimate the free energy of adhesion of bis-(Zn)salphen dimers to graphene surface we have performed all-atom free energy perturbation simulations with LAMMPS package . The solon model  in orderon model . During on model .Both covalent and van der Waals interactions were described by OPLS-AA force field ,51, withx & y). Due to the symmetry of the bis-salphen dimer the number of its orientations relative to graphene surface which needs to be studied can be reduced. To obtain initial positions the dimer was placed in one of the orientations shown in the z). The dimer was placed in each orientation and relaxed 5 times, resulting in 20 independent simulations.The system under study consisted of a dimer of bis-(Zn)salphen compound, put at random orientation on top of 4 layered graphene sheet of 12 by 20 rectangular unit cells of the hexagonal graphene structure (approx. 5 × 5 nm), periodic in 2 in-plane directions . On the second stage van der Waals interactions between the atoms of compound and environment were scaled down. To make the transition smoother on the second stage the compound was decoupled atom by atom starting from exterior hydrogen atoms and finishing with the core Zn, O, N atoms. For each atom 10 intermediate λ-values were used, each simulated during 0.025 ns. Total simulation time was 40–50 ns depending on the variation of the bis-salphen compound (with or without phenyl groups). Every 10 simulation steps (20 fs) backward and forward difference of interaction potential was recorded and subsequently processed using the Bennett acceptance ratio method to estimate accumulated change of Gibbs free energy n of VMD ,63.The thermodynamic cycle corresponding to this study is shown in the Using the decoupling transition to estimate the free energy of adhesion in this case is technically simpler than solvation (immersion) as in the latter process it is not guaranteed that during finite simulation time the compound will adopt the desired conformation on top of the graphene surface. On the contrary, in the case of decoupling process both starting and final states are well defined and if the set of initial positions of the adsorbed compound molecules contained the most favorable position, the largest estimated A slightly different approach was used in case of the functionalized graphene . Rather In this case, approximating the free energy of immersion of the compound dimer on top of functionalized graphene by The initial guesses for the positions of the bis-salphen dimer, interacting with the functional groups were obtained by placing of the separately optimized geometries of the dimers so that the coordinates of the Zn, O and N atoms of one of its non-bonded salphen groups closely approximate the position of the corresponding atoms of the single Zn-salphen base interacting with -OH or -COOH functional group of graphene patch from DFT study. To obtain the relaxed initial positions vacuum simulations were performed in which the hydrogen and oxygen atoms of the functional groups were initially attached to the oxygen and zinc atoms of the compound with gradually relaxing spring force.ab initio calculations for a single compound adsorbed on the surface of pristine and functionalized graphene as shown in the To compare the influence of functionalization on the adhesion of the (Zn)salphen-based compounds to graphene surface we have performed On the surface of a pristine graphene the adsorbed (Zn)salphen compound assumes completely flat shape lying parallel to the graphene surface at the distance of 3.04 Å. This together with the high negative value of the energy of adhesion of a (Zn)salphen compound to pristine graphene, indicates that the π-π interactions between graphene surface and aromatic rings of the salphen base play the major part in attraction of the compound.Doping graphene with B or N impurities provides a moderate improvement of adhesion due to electrostatic attraction between the impurity and the Zn or O atoms of salphen compound without affecting the π-π interactions: the flat shape of the compound and separating distance of 3.04 Å is maintained.2− center of the oxidized graphene requires the salphen compound to leave its favorable flat conformation and overcome the potential barrier created by N and O atoms, surrounding Zn in salphen complex. Ass the result, the average distance between salphen aromatic rings and graphene surface increases to 3.23 Å and adhesion energy decreases by 3.3 kcal/mol.At the same time, the presence of a carbonyl oxygen, i.e., connected to the two graphene atoms, has an opposite effect. Despite the ability of Zn to form additional coordination bonds, connecting to out-of-plane OOn the contrary, functionalizing graphene with hydroxyl (-OH) and carboxyl (-COOH) groups makes the compound to bind better to the graphene surface, as these groups form hydrogen bonds with the salphen compound. Hydrogen bond lengths are estimated as 1.75 Å in case of hydroxyl group and 1.50 Å in case of carboxyl group. However, while both groups provide a single hydrogen bond, the benefit is significantly higher in case of carboxyl group. The reason for this is that hydroxyl group is situated closer to the graphene surface and attraction of one of salphen’s oxygens to hydroxyl hydrogen simultaneously with repulsion of the other salphen’s oxygen from the oxygen of the functional group creates a distortion of the plane shape of salphen compound, counteracting with the π-π interactions. On the contrary, the higher position of the carboxyl group and flexibility of rotation of its bonds allows the hydrogen bond to be formed without distorting the π-π interactions: salphen compound maintains its flat shape and distance to graphene of 3.06 Å.Although the observed improvement of binding energy is comparatively small in comparison with the impact of aromatic interactions in vacuum, in a good solvent, such as dichloromethane (DCM), the molecules of the compound will experience a competing attraction by the solvent molecules. In such case these additional interactions with functionalized graphene may give a significant boost in favor of adsorption.A better criterion for the tendency of a molecule to be adsorbed on a surface is the Gibbs free energy of adsorption . For this purpose, for each of compounds we have conducted series of FEP calculations as described in section Materials and Methods. The accumulated change of Gibbs free energy during the transitions are shown in the First, we study the adhesion of a dimer of the reference bis-(Zn)salphen compound , the discrepancy of Binding of dimers of bis-(Zn)salphen compound to a graphene surface is favorable ), dispersive attraction (~ −λ/(1−λ)2), and core repulsion (~ + λ/(1−λ)4) of the soft Lennard-Jones potential between the surrounding molecules and the functional group [al group ,65,66. TThe The resulting estimate of rgy scan , which iThe effect of functionalization on the dimer orientation can be also seen in the distributions of the angle (ne plane . The ori solvent c.OH =r 1.9 ± 0.2 Å and 1.8 ± 0.1 Å in case of hydroxyl and carboxyl groups correspondingly. In the latter case (-COOH group), carbonyl oxygen (C=O) provides additional attraction for zinc cation of the compound: ZnO =r 2.0 ± 0.1 Å. As the FEP results in the In the earlier publication  the two The consequence of this is twofold. Firstly, CNTs or graphene sheets can serve as centers of condensation for bis-salphen chains, which first stick to their large surface, then slide along their surface due to low friction in π-π interacting systems until entangling with other adsorbed chains.Secondly, long chains, partially adsorbed to the surface of CNTs not only stabilize the nanotubes in solution , but alsOn the latter stage, a stronger binding of bis-salphen compounds together and mutual attraction of nanotubes’ extended conjugated surfaces, promotes phase separation of the condensed mixture of CNTs and coordinated polymer chains, producing self-assembled network with the core of well aligned nanotubes covered with a shell of aggregated metal-organic chains, as appears on the microphotographs of the original paper .These conclusions lay the ground for any subsequent study of self-assembly of nanotube—coordination polymer networks, as well as their mechanical and transport properties, which must consider orientation and alignment of metal-organic compounds around CNTs and the role of hydrogen bonds.


A flexible method for modulating the Casimir force is proposed by combining graphene and hyperbolic materials (HMs). The proposed structure employs two candidates other than graphene. One is hexagonal boron nitride (hBN), a natural HM. The other is porous silicon carbide (SiC), which can be treated as an artificial HM by the effective medium theory. The Casimir force between graphene-covered hBN (porous SiC) bulks is presented at zero temperature. The results show that covering HM with graphene increases the Casimir force monotonically. Furthermore, the force can be modulated by varying the Fermi level, especially at large separation distances. The reflection coefficients are thoroughly investigated, and the enhancement is attributed to the interaction of surface plasmons (SPs) supported by graphene and hyperbolic phonon polaritons (HPhPs) supported by HMs. Moreover, the Casimir force can be controlled by the filling factor of porous SiC. The Casimir force can thus be modulated flexibly by designing desired artificial HMs and tuning the Fermi level. The proposed models have promising applications in practical detection and technological fields. The Casimir force is an intriguing macroscopic effect caused by the quantum fluctuations of electromagnetic fields. Casimir predicted the existence of attractive forces between two parallel perfectly conducting plates in 1948 . The CasGraphene, a two-dimensional sheet of carbon atoms arranged in a hexagonal lattice, has piqued the curiosity of many scientists . The linHyperbolic materials have gotten a lot of attention in the last decade because of their unique electromagnetic properties . DiagonaIt is well known that the electromagnetic properties of the boundary material can modify the Casimir force . In thisd is investigated in each model. One model’s samples are graphene-covered hBN bulks, as shown in e is the electron charge, essed as (1)σ(ω)=The hBN is a naturally anisotropic material that exhibits hyperbolic dispersion. The permittivity of hBN is a tensor, and the elements of the anisotropic permittivity tensor are as follows (2)εl,hBobtained .f is the area percentage occupied by air holes in the Bulk SiC is an isotropic material, and its permittivity can be described by the Lorentz model (3)εs(ω)t method , the effp polarized wave is denoted by By utilizing the Maxwell electromagnetic stress tensor method with the properties of macroscopic field operators, the Casimir force at zero temperature is eventually expressed as (6)F=−ℏπTo compute the Casimir force, the reflection coefficients are obtained using the approach described in . Graphend for various Fermi levels are presented in d. Because two samples have the same electric and magnetic properties, the force is obviously attractive at any distance. The relative force between two identical hBN bulks is also plotted for comparison purposes, as shown by the blue line in d, and curve slopes are large. However, for large d, the relative force is sensitive to The relative Casimir forces between two identical graphene-covered hBN bulks as a function of separating distance The Casimir force is related to all electromagnetic modes supported by two samples. From Equation , we knowEquation , when thd. In d, i.e., decreasing radius, the proportion of high reflection coefficients is increasing. As a result, the Casimir force tends to d, as illustrated in To extract the contribution of SPs and HPhPs to the enhancement of the Casimir force, the TM reflection coefficients as a function of imaginary frequency d. The filling factor is The Casimir force between two identical graphene-covered porous SiC bulks is also investigated in relation to the separating distance f. Therefore, f influences the coupling of SPs supported by graphene and HPhPs supported by porous SiC, which can be used to control the Casimir force. d for different filling factors. When f increases, the relative force for arbitrary separations decreases dramatically. This outcome is simple to comprehend. As f increases, so does the proportion of air holes. According to Equations ,,f. Theredistance . As showd, when F is around F is about The Casimir force per unit area between two parallel graphene sheets is inversely proportional to g plates . Accordig plates , the Cas d ≈ 2μm . To compSince the samples in this study are in free space, the detection system should be set in a high-vacuum chamber to measure the Casimir force between graphene-covered HMs. Furthermore, the quality of the graphene layer should be checked to guarantee that it is a monolayer. The gradient of the Casimir force may be measured using the experimental setup described in . HoweverEquation  with thef increases, the force decreases for arbitrary separation distances. The electromagnetic responses of porous SiC are used to understand this phenomenon. As a result, by designing suitable artificial HMs and tuning the Fermi level In conclusion, we investigate the Casimir force between two identical graphene-covered HMs. The first model’s samples are graphene-covered hBN bulks. When graphene covers hBN, the Casimir force increases for arbitrary separation distances, and as the Fermi level


A novel photochemical technological route for one-step functionalization of a graphene surface with an azide-modified DNA aptamer for biomarkers is developed. The methodology is demonstrated for the functionalization of a DNA aptamer for an N-terminal B-type natriuretic peptide (NT-proBNP) heart failure biomarker on the surface of a graphene channel within a system based on a liquid-gated graphene field effect transistor (GFET). The limit of detection (LOD) of the aptamer-functionalized sensor is 0.01 pg/mL with short response time (75 s) for clinically relevant concentrations of the cardiac biomarker, which could be of relevance for point-of-care (POC) applications. The novel methodology could be applicable for the development of different graphene-based biosensors for fast, stable, real-time, and highly sensitive detection of disease markers. B-type natriuretic peptide (BNP) has an important role in regulating circulation by acting on blood vessels in response to wall stress. The biologically active BNP is being cleaved from proBNP upon its secretion, in a process that also produces a biologically inactive N-terminal proBNP . CompareConventional methods for aptamer immobilization are based on π-π stacking of pyrene-based linkers, which require multiple steps for receptor layer binding. In addition, due to the noncovalent nature of functionalization, these biosensors may suffer from instability and fast degradation of characteristics during multiple washings and measurements ,12. The In this work, we demonstrate the principle for the construction of biosensors, through the photochemical covalent binding of aptamers to graphene channels of a field effect transistor (GFET). The novel biosensor is developed to analyze NT-proBNP as a biomarker for the early detection of heart failure. Previously, GO-FET modified with an NT-proBNP antibody was successfully used to detect a biomarker with a quantified limit of detection (LOD) of 10 pg/mL . Herein,Phosphate buffer tablets  and Tween were purchased from Sigma-Aldrich . The 3′-azide-modified NT-proBNP aptamer (5′-NH2-GGCAGGAAGACAAACAGGTCGTAGTGGAAACTGTCCACCGTAGACCGGTTATCTAGTGGTCTGTGGTGCTGT-N3-3′) was purchased from DNA Synthesis, LLC  and purified using denaturing polyacrylamide gel electrophoresis (PAGE) to reach a mass of 3.1 nM (69.5 µg). The azide group was introduced in the oligonucleotide during the synthesis using azide-modified controlled pore glass (CPG). Frozen solutions of 1.18 mg/mL of NT-proBNP in 10 mM potassium phosphate, pH 7.4, 150 mM NaCl, and 0.7 mg/mL of cTnI in 10 mM HCl were purchased from HyTest Ltd. .GFET chips were provided by Dr. Dmitry Kireev  and metal feedlines were covered by a passivation layer to prevent current leakage during measurements in a liquid a. More dAzide-modified aptamer was dissolved in 1 mL of 1 × PBS to achieve 3 μM at a room temperature . A 100 µ2 and laser power of 0.5 mW.Atomic force microscopy  was used to estimate the change of thickness and surface roughness of graphene channel after aptamer binding. The graphene surface before and after aptasensor assembling was investigated by microRaman spectroscopy  with a 100× objective (NA = 0.9) at a 532 nm wavelength  with a beam spot of 1 µmElectrical measurements were conducted using a homemade probe station with semiconductor parameter analyzer IPPP1/5 . For liquid gate measurements, Ag/AgCl pellet electrode  with a diameter of 1 mm was introduced in the PDMS well containing the cardio marker (CM) solution. The NT-proBNP was dissolved in 0.1 × PBS with addition of tween (0.01%) to avoid sticking of proteins to the tube wall. Solutions of CM were prepared at different concentrations  to cover the range of its clinical significance . The mea2 at 254 nm irradiation, while staying stable at a dose of 120 kJ/m2 in the case of irradiation at 365 nm UV [−1, for an exposure rate at 2 mJ cm−2 s−1 [The azide-based covalent modification of carbon nanomaterials was demonstrated previously for both carbon nanotubes  and grap65 nm UV . Recent cm−2 s−1 . Further2 during 10 min irradiation might still yield an FET-surface functionalization, with a sufficient portion of functionally intact aptamers to enable the desired biosensing of NT-proBNP. Hence, it can be considered that irradiation at 310 nm for up to 10 mW/cmG curves were observed in the presence of aptamers without exposure to UV, which supports the main role of the photochemical process in aptamer immobilization. The GFET channel consists of a single layer of graphene with randomly distributed bilayer islands a. Upon U2 C network to form the aziridine adduct [In conditions of light or thermal activation, the azide functionality dissociates into molecular nitrogen and a highly reactive singlet nitrene species, which can chemically bind to graphene . Upon lie adduct . The nite adduct . Comparee adduct , the use2 hybridization of C-C bonds and electron mobility is preserved  (G = 350 mV) curve branches  c and elebranches d. The toD(C0) is a drain current at concentration C0, ID(C∞) is a drain current at an infinite concentration of analyte. The dissociation constant was estimated for both electron and hole regimes and was found to be equal to KD = 30 pg/mL  did not produce a significant sensing response  of 0.01 pg/mL  and fast−1 to 104 pg/mL, which is the range that overlaps with the risk stratification range for heart failure. The developed aptabiosensor provides the lowest limit of detection and response time compared to the other field-effect transistor-based sensors to NT-proBNP from the literature.The results indicate that after exposure to UV light, the azide-modified aptamers were successfully bound to the GFET surface. The produced functionalized GFET-based sensor was demonstrated for the detection of NT-proBNP in a wide range of concentrations from 10The functionalization methodology is based on a simple photochemical process, which, despite possible partial UV-induced damage to the aptamers, still enables graphene functionalization and the construction of GFET sensors with clinically relevant sensitivity. The one-step photochemical methodology of graphene surface functionalization may show promising attributes in terms of scalability and compatibility with CMOS processes for graphene device production. The methodology could be applicable for the construction of different graphene-based sensors in the future, as well as for the possible maskless light-assisted patterning of multiple receptors on a single chip, paving the way for the development of multiplex sensors.


Pyrolysis of lignocellulosic biomass (hard carbon) produces poorly graphitic biochar. In this study, nano-structured biochars were produced from microcrystalline cellulose using calcium as a non-conventional catalyst. Calcium is abundant, environmental-friendly and widely accessible. Graphitization of calcium-impregnated cellulose was carried out at 1800 °C, a temperature below 2000 °C where the graphitization usually occurs. XRD, Raman spectroscopy, high-resolution TEM together with the in-house numerical tool developed enable the quantification of the graphene fringes in the biochars. The non-impregnated cellulose biochar was composed of short and poorly stacked graphene fringes. The impregnation with 2 wt.% of calcium led to the conversion of the initial structure into a well-organized and less defective graphene-like one. The graphene-like structures obtained were composed of tens of stacked graphene fringes with a crystallite size up to 20 nm and an average interlayer spacing equal to 0.345 nm, close to the reference value of standard hexagonal graphite (0.3354 nm). The increase of the calcium concentration did not significantly improve the crystallite sizes of the graphene-like materials but rather drastically improved their rate. Our results propose a mechanism and provide new insights on the synthesis of graphene-like materials from bio-feedstocks using calcium where the literature is focused on transition metals such as iron and nickel among others. The decrease of the graphitization temperature below 2000 °C should lower the production cost as well as the environmental impact of the thermal graphene-like materials synthesis using biomass. This finding should stimulate further research in the field and broaden the application perspectives. Graphene sheets are precursors to carbon nanotubes, fullerene, carbon fibers, carbon black or graphite4. Depending on the characteristics such as the length and the orientation of the graphene sheets, various properties could be developed among which, the electrical conductivity, the mechanical or thermal resistance6. Therefore, graphene is considered as a high-performance material, promising for a wide range of applications such as batteries, energy storage, electronics, and biology11.Graphene is a bidimensional carbon material with one atomic layer as thickness16. Top-down processes include mechanical or chemical exfoliation of extracted graphite to isolate the graphene sheets. Bottom-up processes involve the synthesis of graphene from gaseous hydrocarbon precursors. The advantages and drawbacks of each process have been previously discussed in the literature18. Almost all processes use fossil carbon sources and are high energy demanding. Managing industry-scale and more eco-friendly production of homogenous and defect-free graphene is one of the main challenges to envisage further commercial use of graphene. The production of graphene-like materials from bioresources  would open ways for new materials with outstanding properties. This approach, as opposed to the standard graphene manufacturing techniques using chemicals and various solvents, would lower the environmental impact of graphene-like materials synthesis.Nowadays, graphene can be produced from fossil feedstocks by either top-down or bottom-up processes3 carbons. During cellulose pyrolysis, sp3 carbons follow multiple and complex chemical rearrangement to be converted into sp2 carbons and form aromatics rings19. Because of this, cellulose is not a favorable material for graphitization.Cellulose is a renewable resource and the most abundant organic polymer on Earth. Cellulose is used all over the world for paper production and is widely accessible at cheap cost. Its structure is also relatively homogenous among lignocellulosic biomass, compared to lignin or hemicellulose. The main approach for graphene-like materials synthesis from biomass is pyrolysis to generate graphenic-like biochars. Cellulose is composed of a long chain of D-glucose molecules, with exclusively sp23, agricultural35 or food wastes37, insects39 or sewage sludges40. These studies showed a poor organization of the graphenic materials even with high temperatures treatments (> 2000 °C).The graphitization of biomass has been previously investigated in the literature. Graphenic materials were previously obtained from a wide range of biomass, such as woody biomassThe use of high temperatures implies a significant energetic cost which limits the industrial development of graphene derived from biomass.41. A wide range of mineral species was investigated. Transition metals, especially iron and nickel, were considered as the most promising catalysts for their lower cost and great catalytic power47.Catalytic graphitization was extensively investigated in the past for the production of graphene-like materials from carbon black50. Calcium is cheap, non-toxic and more environmental-friendly than standard catalysts for graphitization. Alkali  and alkaline earth metal  are known to be promoters for the pyrogasification of biomass while producing the biochar53. These metals and transition metals like iron and nickel have demonstrated their impact of the structuration of the carbon structure in biochar. Calcium was previously reported to catalyze the graphitization of charcoal55. The metal catalyzed graphitization mechanism has been explained in the literature58. The work mostly referred to iron and to nickel to a lesser extent. It is suggested that both particle size and degree of reduction of the iron catalyst positively impact biochar graphitization. In particular, facets of metal catalyst in reduced form provide regions for and promote the precipitation of graphitic carbon. The metal reduces the barrier for carbon nucleation and makes it easier for graphene sheets to form. High dispersion of calcium in cellulose could be expected thanks to linkage of calcium ions with the carboxyl groups59. As such, calcium could possibly be a promising catalyst for the graphitization of cellulose biochar and, by extension, of lignocellulosic biomass.However, only few research addressed the catalytic graphitization of biomass. Calcium is the fifth most widespread minerals in the world and is inherently abundant in lignocellulosic biomassstructure, texture and nanotexture will be used as defined by Monthioux et al.60. The carbon structure is amorphous, turbostratic or crystalline; the texture defines the organization of the graphene sheets  while the nanotexture describes the length and the stacking of the graphene sheets in the crystal coherence domains.This study focuses on the effect of Ca-loaded for the efficient graphitization of the resulting biochar. For this purpose, commercial cellulose was impregnated with calcium nitrate prior to pyrolysis at 1800 °C. For clarity reasons, the terms The carbon organization in the resulting biochar was characterized at a macroscopic , local (with Raman spectroscopy) and nanoscopic scales . XRD provides a general description of the various carbon structures  in the samples and estimations of the crystallite sizes. Raman spectroscopy informs about the level of amorphousness and defectiveness of the graphenic structures at the surface of a char particle. HRTEM complements XRD and Raman spectroscopy by investigating at nanoscale the graphenic structures. The results from each characterization technique were further exploited to extract quantitative information about the graphenic structures. Especially, the HRTEM images were processed through a home-made image analysis numerical tool to estimate the crystallite sizes. The combination of experimental methods such as XRD, Raman spectroscopy and HRTEM together with the numerical processing of the data have enable to provide new insights on the mechanism driving the calcium-catalyzed cellulose graphitization.2 at 1800 °C. The impregnation was conducted by immersion, for 6 h, of 40 g of cellulose in 200 mL of deionized water with dissolved calcium nitrate under agitation. The impregnated cellulose is then filtered and dried. A respective mass of 3, 6, 12, 15, 18, 25 and 40 g of calcium nitrate were dissolved for the preparation of the Ca-1 to Ca-7 samples, the sample Ca-8 was obtained with 40 g of calcium nitrate but with a shorter filtration time than Ca-7. The impregnated cellulose was pyrolyzed at 800 °C during 1 h under N2 with a heating ramp of 2 °C min−1 and a gas flow of 1 L min−1 in a vertical tubular oven (Carbolite tubular furnace). The resulting biochar was then collected and heated up to 1800 °C (1 h plateau) under N2 with a heating ramp of 2 °C min−1 and a gas flow rate of 300 L min−1 in a tubular furnace (Nabertherm RHTH 80/300/18). A commercial graphite (ChemPur CAS: 7782-42-5) was also studied as a reference of highly organized carbon.Biochars, named Ca-1 to Ca-8, were produced by pyrolysis of calcium-impregnated microcrystalline cellulose (Sigma Aldrich CAS: 9004-34-6) under NThe calcium concentration in the impregnated sample (before pyrolysis) was determined by Inductively Coupled Plasma Optical Emission Spectrometry  and defined as follows:The calcium concentrations of the samples are summarized in Table -1 in the range 10°–100° in 2θ. The asymmetric 002 diffraction peak (2θ ≈ 24 °) of the biochars was fitted with two pseudo-Voigt functions. The symmetric 002 diffraction peak of graphite was fitted with a single pseudo-Voigt. The asymmetric 10 (2θ ≈ 43 °) and 11 (2θ ≈ 80 °) diffraction peaks were both fitted with a Breit–Wigner–Fano function. For the commercial graphite, the 100, 101 and 110 diffraction peaks at 2θ ≈ 42.5 °, 2θ ≈ 44 ° and 2θ ≈ 78 ° respectively were fitted with a pseudo-Voigt function. The crystallite sizes of the graphenic structures La (in-plane length) and Lc (stacking height) were determined from the XRD spectra using the Scherrer equation61:λ is the radiation wavelength (0.1543 nm), K is a constant equal to 1.84 and 0.89 for La of the biochars and commercial graphite63 respectively. K is equal to 0.89 for the determination of Lc for all samples. β is the Full Width at Half Maximum  of the 10 or 11 diffraction peaks for La and of the 002 peak for Lc. s is the FWHM of a standard specimen (silica) to adjust for instrumental broadening. θ is the Bragg position of the 10 (100 for graphite) and 002 diffraction peaks for La and Lc respectively. The mean value between La determined from the 10 and 11 peaks was taken. The interlayer spacing d002 was determined using Bragg’s law:The macro and nanotexture of the graphenic structures in the samples was studied by X-Ray Diffraction  with a Cu-Kα radiation source (λ = 1.542 Å), operating at 45 kV and 40 mA. Diffraction peaks were recorded at 0.5°snfringes in graphenic structures was obtained from Lc and d002 with:The average number of stacked graphene fringes WITec Alpha 300R, laser excitation = 532 nm). The analyses were performed with KBr/biochar pellets (weight ratio biochar/KBr = 0.025). Raman spectra were acquired by studying a 7 µm square  on the surface of a sample particle. When relevant, the spectra acquisition was refined with the cluster option to obtain a spatial distribution of the various chemical signatures. The D and G bands (at 1350 cm−1 and 1680 cm−1 respectively) were both fitted with a Lorentzian function. The crystallites size La was estimated from the Raman results with the Tuinstra and Koenig formula64.EL is the laser energy (2.3308 eV) and I the intensity of the D and G bands. α is a unique coefficient for each sample to account for the laser dependency. The precise determination of α was not possible. As such, α was taken as 4 in this study, which correspond to the α value obtained for ordered graphite. Since the laser energy used in this study (2.3308 eV) is close to the energy used by Tuinstra and Koenig for their formula (2.41 eV), this will limit the influence of α on La estimation and will not impact the approximate size and variation tendency of La.The structure and nanotexture of the samples were studied using Raman spectroscopy (JEOL cold-FEG JEM-ARM200F) operated at 200 kV equipped with a probe Cs corrector reaching a spatial resolution of 0.078 nm. HRTEM images were processed using a home-made image analysis numerical tool to obtain quantitative information about the graphene fringes. The algorithm of the tool was adapted from the method described by Yehliu et al.65. The mains steps of the algorithm are: Selection of regions of interest—Contrast improvement—Image filtering using the Fourier transform—Binarization—Skeletonization—Correction of errors—Calculation of chosen parameters. The tool was implemented in MATLAB software. The contrast of the entry image is first improved by black and white inversion and histogram equalization to better separate the fringes from the background. The image is then converted into the frequency domain with a fast Fourier transform and filtered with a gaussian lowpass filter. The cutoff frequency was selected as 3.333 nm−1 (0.300 nm)−1, meaning that objects separated by less than 0.300 nm are attenuated. As the interlayer spacing in a graphenic structure is usually greater than 0.3354 nm , no fringes information is lost. A top-hat transformation is then applied to highlight high contrasted areas by correcting nonuniform illumination. The structural element for the top-hat transformation was a disk with an adjustable diameter larger than the apparent thickness of a single fringe to ensure the conservation of the fringes. The image is then binarized with a threshold determined using Otsu’s method and skeletonized with MATLAB built-in skeletonization algorithm. Finally, a home-made algorithm is applied to correct Y or X fringe ends and aligned fringes separated by less than 0.492 nm (two aromatic rings) are reconnected. The fringes shorter than 0.492 nm are too short to have a physical meaning and are removed.The structure, texture and nanotexture of the samples were examined at a nanoscopic scale using High-Resolution Transmission Electron Microscopy , the average interlayer spacing d002 and the number of graphene fringes stacked in a graphenic structure. With this numerical tool, a quantitative comparison of the HRTEM images analysis with the XRD and Raman spectroscopy results can be made.The numerical tool measures the average crystallite size L66 (structures with irregular stacking of the graphene fringes) and the presence of Ca mineral species (peaks label *) for the impregnated samples. Indeed, non-impregnated and impregnated samples exhibited a broad and asymmetric peak at the 002 and 10 positions while graphite exhibited a sharp and intense 002 peak and a clear distinction between the 101 and 110 peaks. The large broadness of the peaks indicated materials with small crystallite sizes (short-order organization of the graphenic structures) or high curvature of the graphene fringes, as XRD requires flatness of the crystalline structures. This results is known for hard carbon66. The 10 and 11 peaks of the non-impregnated and impregnated samples did not differ greatly. The 002 peak position and profile changed significantly with impregnation. The 002 peak shifted from 2θ = 24.65 ° for the non-impregnated biochar to 2θ = 25.99 ° for Ca-8. This shows a decrease in the interlayer spacing d002 to a value closer to the one for graphite (2θ = 26.37 °), which is taken as reference material. The tip of the 002 peak became sharper and a shoulder appeared on its left-side after impregnation. This asymmetry was previously reported for materials with heterogenous carbon structures72. The left-side of the 002 peak was attributed to poorly organized graphenic structures (randomly oriented texture and weak nanotexture) as found in hard carbons. The sharp tip of the 002 peak of the impregnated samples was attributed to highly organized graphenic structures  as observed in graphitizable carbon or graphite.XRD provides insights on the average organization of the carbon matter in the samples. XRD patterns of the non-impregnated biochar and Ca-loaded biochars were acquired after graphitization and compared to a commercial graphite. Only the XRD patterns of the non-impregnated, Ca-4 %Ca = 2.12 wt.%), Ca-7 (%Ca = 3.83 wt.%), Ca-8 (%Ca = 4.39 wt.%) and commercial graphite samples are presented in Fig. 2 wt.%, C002 peak was fitted with two pseudo-Voigt functions. The left-side referred to Lower-Organized Region (LOR) while the right-side indicated Higher-Organized Region (HOR) as shown in Fig. c . HOR d002 showed the same profile, with an initial decrease to a stable value of 0.345 nm, close to that of the commercial graphite (d002 = 0.338 nm). Figure c versus Ca concentration. LOR Lc remained stable over the calcium concentration at the non-impregnated sample value (Lc = 1.24 nm). At the opposite, HOR Lc value increased for an initial calcium concentration below 2 wt.% and reached a plateau around 6 nm at an initial calcium concentration between 2 and 3 wt.%, then increased up to 8 nm at higher initial calcium concentrations. The average number of stacked graphene fringes (nfringes) increased from ≈ 4 fringes for the non-impregnated sample to ≈ 24 fringes for Ca-8 sample, meaning that calcium acted as a catalyst for cellulose graphitization in enhancing the graphenic structure rate.LOR dLOR/IHOR). It increased up to ≈ 2 wt.% of calcium and then decreased. This profile was unexpected since the HOR domain (and its peak intensity) would likely increase with Ca concentration, leading to a decrease of ILOR/IHOR. Indeed, highly organized graphenic structures developed with increasing calcium concentration, as it is confirmed by the high HOR Lc and low HOR d002 values for an initial calcium concentration superior to 2 wt.%. A possible explanation is a variation in the significance of the LOR and HOR peaks among the sample. For the non-impregnated sample, the 002 peak was mainly defined by the HOR peak (low ILOR/IHOR). The HOR peak corresponds to poorly organized graphenic structures  as it was observed for hard carbon73, whereas the LOR peak was attributed to a small fraction of highly disorganized (amorphous) carbon structures72. With calcium impregnation, the disorganized carbon structures rate decreased in favor of much more organized graphene-like structures. For an initial calcium concentration below 2 wt.%, HOR peak mainly composed the 002 peak but the material exhibited a low Lc value  that mainly referred to regions of the biochar in contact with the calcium particles, while the LOR peak represents hard carbon structures, resulting from free or less contact regions with the catalyst during the heat treatment. In this stage, HOR d002 and Lc did not vary significantly but ILOR/IHOR decreased. This could be attributed to a promoting effect of calcium in the conversion of LOR to HOR.Figure Therefore, additional calcium did not modify further the nanotexture of the graphenic structures but improved the rate of highly organized graphenic structures in the biochar.c (stacking), and d002. To better understand how the transformation occurred, we have also investigated the carbon organization at local scale.Finally, the bulk structure was almost turbostratic and became more graphenic with calcium impregnation, which is confirmed by the quantified nanotextural parameters LD/IG = 1.34) whereas the commercial graphite had a small D band and a narrow G band (ID/IG = 0.23). G band refers to graphenic signature and the D band is likely attributed to defects in the graphene-like materials75. The defects include, with various intensities, edges, curvature or vacancies among others74. Graphite, which is composed of long-ordered graphenic arrangement has a weak D band compared to the G band. For all samples, the D and G bands were clearly separated, which indicated the absence of amorphous carbon through the valley between both bands77. For each impregnated samples, different chemical signatures, called clusters, could be identified. Two clusters of the Ca-7 sample are displayed in Fig. D/IG = 1.40), this could correspond to spatial domains with limited effect of the catalyst. As these domains were highly defective, they could be attributed to the turbostratic structures previously evidenced by XRD. Some clusters showed a decrease and a thinning of the D band , meaning a reduction of the defects in the graphene fringes and more organized graphenic structures. The second order bands were observed for all samples, due to the increased organization. The 2D band (double resonance of the D band) gives information on the texture and nanotexture of the graphenic structures using its shape, intensity and position74. The D band of the non-impregnated cellulose sample (1341 cm−1) was slightly red-shifted from the D band position of the commercial graphite (1351 cm−1). This shift may be due to defects or curvature of the graphene fringes76. The D band position of the impregnated samples ranged between the D band positions of the non-impregnated cellulose and commercial graphite samples, which implied a slightly less defective nanotexture. HRTEM images could give insights on the kind of defects (edges/curvature) involved.At local scale, Raman spectroscopy gives chemical signature of the samples and can also highlight heterogeneity in chemical compositions. Only the non-impregnated cellulose biochar, Ca-7 and commercial graphite spectra are presented in Fig. a . It could correspond to spatial domains with little or no catalyst, leading to graphenic structures with weak nanotexture, as observed in the non-impregnated sample. The second specific feature corresponds to larger graphenic structures, with La values around 9 nm . La values from XRD were in accordance with the smallest La values obtained from Raman analysis, which referred to poorly organized graphenic structures. Since two different graphenic structures (turbostratic and graphene-like) were present in the materials, the contribution to the observed 10 and 11 peaks of the turbostratic structures may have overshadowed those of the graphene-like structures, thus preventing a good estimation of La from XRD.Lctra Eq.  are presc < 2 nm) stacked with a turbostratic structures (d002 > 0.361 nm), similar to the non-impregnated sample. Raman spectroscopy completed this description by indicated a high density of defects (ID/IG > 1) and poor fringes lengths (La < 6 nm) for this kind of graphenic domain. However, XRD informed about the existence of well-developed graphene-like structures . Raman spectroscopy described them as large (La > 6 nm) and low-defective (ID/IG < 1).Raman spectroscopy and XRD both showed a heterogeneity of the carbon structures in the Ca-impregnated samples. XRD indicated the existence of graphenic structures composed of few units of graphene fringes . Two of the most representative images, obtained from the non-impregnated cellulose biochar and Ca-6 sample, are presented in Fig. 78. The strong curvature and short length (implying lot of edges) of the graphene fringes may explain the significant shift of the Raman D band of the non-impregnated cellulose biochar sample from the D band position of graphite, as well as the broad and asymmetric 10 and 11 bands in the XRD spectra. This specific graphene fringes organization was also observed for the impregnated samples.The image of the non-impregnated cellulose biochar Fig. a showed For the impregnated samples, in addition to poorly organized structures, highly organized graphenic structures were observed Fig. b, characThe disorganization of the graphenic structures in the non-impregnated cellulose biochar prevents a quantitative evaluation of the crystallite sizes of the graphenic structures from the analysis of the HRTEM images alone. That is why a home-made image analysis numerical tool was applied to the HRTEM images to extract some quantitative information about the graphenic structures. For Ca-impregnated samples images, the image analysis tool enables a precise description of each apparent graphene-like structures.For the Ca-6 sample image, three distinguishable groups of graphene fringes were isolated prior running the tool, named A, B and C. The images obtained after application of the tool are presented in Fig. a and d002 values, nfringes and tortuosity value of the graphenic structures were estimated from the HRTEM images and are presented in Table Average L002 computed from the HRTEM image of the non-impregnated cellulose biochar was equal to 0.370 nm, far above the d002 of graphite obtained from XRD (d002 = 0.338 nm) but close to the d002 of the hard carbon structures (d002 = 0.361 nm) determined from XRD. The average number of graphene fringes stacked nfringes in the HRTEM image of the non-impregnated cellulose biochar was equal to 3.3 and the graphene fringes in this sample were also moderately curved (average tortuosity of 1.18). The carbon structures represented in the HRTEM image of the non-impregnated cellulose biochar show a good agreement with the results obtained by XRD and Raman spectroscopy for hard carbon, and highlights their poor organization, with random orientation and defective texture (short and curved fringes).The interlayer spacing d002 below 0.353 nm and a stacking up to 26 fringes. These values were in accordance with the crystallite sizes  computed from XRD for the graphene-like structures. The HRTEM image of Ca-6 sample confirmed the formation of well-organized graphenic structures with calcium impregnation.The three graphenic structures represented in the HRTEM image of the Ca-6 sample had a tortuosity below 1.04, an interlayer spacing da obtained from HRTEM images increased from 1.39 nm for the non-impregnated cellulose biochar to 3.21 nm (domain C) and 7.87 nm (domain A) for the Ca-6 sample image. Defects in domains B and C, such as superimpositions and crossings of the graphenic structures, led to fragmentation of the graphene fringes after image processing, explaining the shorter La values obtained for domains B and C compared to domain A. However, all the graphenic structures formed by calcium impregnation were composed of longer graphene fringes that for the non-impregnated cellulose biochar. The La calculated by the numerical tool was lower than the values of La previously reported from XRD and Raman spectroscopy. Only the length of the exposed side of the graphene fringes that are parallel to the direction of observation could be measured from the HRTEM images, whereas XRD and Raman spectroscopy measure the average length of the graphenic structures in the basal plane. As such, La calculated from the HRTEM images cannot be rigorously compared to La calculated from XRD and Raman spectroscopy.LThe study of HRTEM images showed that calcium impregnation led to formation of long and straight graphene fringes, gathered in isotropic structures with multiple fringes stacked. All these observations confirmed the XRD and Raman spectroscopy analyses, that suggested the beneficial effect of calcium to form highly organized graphene-like structures at a relatively low temperature.Graphitization of cellulose, a poorly organized carbon structure, was achieved after impregnation with calcium, a non-conventional environmental and abundant catalyst. The graphitization was carried out at 1800 °C, below the standard temperature above 2000 °C for thermal synthesis of graphene-like materials. Outstanding investigation of the carbon structures of the samples considered was achieved by studying the biochar organization at macro, micro and nanoscale using X-ray diffraction, Raman spectroscopy and high-resolution transmission electron microscopy paired with an image analysis numerical tool. The results highlighted that calcium promotes the conversion of the hard carbon turbostratic structure into a well-organized and less-defective graphene-like structure.The graphene-like structures had an in-plane length up to 20 nm and an interlayer spacing of 0.345 nm, near to the crystallite sizes of a standard graphite. An increase of the calcium concentration resulted in a slight improvement of the crystallite sizes of the graphene-like structures but drastically enhanced their rate in the biochar. Further research will focus on the description of the calcium–carbon interactions to better understand the catalytic graphitization mechanism for poorly organized carbon materials such as biomass for further applications.Supplementary Figures.


ZnO/graphene nanocomposites were prepared using a facile approach. Graphene nanosheets were prepared by ultrasonication-based liquid phase exfoliation of graphite powder in a low boiling point organic solvent, 1,2-Dichloroethane, for the preparation of ZnO/graphene nanocomposites. Structural properties of the synthesized ZnO/graphene nanocomposites were studied through powder XRD and micro-Raman analysis. The characteristic Raman active modes of ZnO and graphene present in the micro-Raman spectra ensured the formation of ZnO/graphene nanocomposite and it is inferred that the graphene sheets in the composites were few layers in nature. Increasing the concentration of graphene influenced the surface morphology of the ZnO nanoparticles and a flower shape ZnO was formed on the graphene nanosheets of the composite with high graphene concentration. The efficiencies of the samples for the photocatalytic degradation of Methylene Blue dye under sunlight irradiation were investigated and 97% degradation efficiency was observed. The stability of the nanocomposites was evaluated by performing five cycles, and 92% degradation efficiency was maintained. The observed results were compared with that of ZnO/graphene composite derived from other methods. The mications ,12,13,14ications ,16. ZnO ications . An enhaications ,19. Due ications ,21. Mostications , and manications ,24,25, wications , and theications .3 defects [Nanocomposites of GO/ZnO and rGO/ZnO are highly efficient and widely studied candidates in the photocatalytic degradation of industrial Methylene Blue (MB) dye, and various methods have been adopted to synthesize ZnO/graphene nanocomposite materials ,29,30. H defects ,32. HencHere, we have reported a facile technique for the development of ZnO/graphene nanocomposite using few-layer graphene sheets produced by ultrasonic exfoliation of graphite in 1,2-Dichloroethane. To our knowledge, there are no available reports of graphene/ZnO nanocomposite prepared using ultrasonic-based liquid phase exfoliated graphene nanosheets. Further, the structural, morphological, and optical properties of the synthesized graphene/ZnO nanocomposites were studied. Additionally, the produced composites’ photocatalytic activity was examined in relation to MB dye degradation when exposed to sunlight.(i) Preparation of GrapheneGraphite powder of nearly 0.15 g purchased from Sigma Aldrich was added into the 50 mL of 1,2-Dichloroethane taken in measuring flasks. Then, the graphene and solvent mix was sonicated for 5 h by means of an ultrasonic bath. The sonicated dispersions were centrifuged at 3000 rpm for up to 30 min. After that, the supernatant dispersions were collected, and the solvent was evaporated at room temperature for nearly 48 h to obtain the exfoliated graphene nanosheets.(ii) Preparation of ZnO/Graphene compositeZinc nitrate hexahydrate dissolved in double distilled water was added to the exfoliated graphene dried from 85 mL of graphene dispersion. The solution of NaOH was added to increase the pH of the graphene/zinc nitrate hexahydrate dispersion to 12. Then the solution mixer was heated at 70 °C for 2 h by maintaining the pH of the solution. The obtained precipitate was washed with distilled water and dried at 100 °C. Then, the final particles were heated at 400 °C for 2 h. The same procedure was carried out with graphene sheets dried from 175 mL of graphene dispersion. The ZnO/graphene nanocomposite prepared from 85 and 175 mL of graphene dispersion are named S1 and S2, respectively.(iii) Characterizationsα radiation and room temperature micro-Raman spectra were measured using HORIBA Jobin Yvon LabRAM HR 800 with He-Ne laser of wavelength 632.81 nm as an excitation source. FEI NOVA NANOSEM 450 was used to study the surface morphology of the samples. The diffused reflectance spectrum of the powder samples and UV-Vis absorption spectra of the collected samples after irradiation with nano photocatalyst were recorded using a SHIMADZU UV-2450 spectrophotometer.Structural properties of the ZnO/graphene nanocomposites were studied using powder XRD pattern recorded for the 2θ range of 20° to 80° with a step size of 0.01° using PANanalytical Empyrean with Cu-K(iv) Photocatalytic experiments−5 M concentration. Then, the dispersion with the nano photocatalyst was stirred in a dark room for 30 min. Further, the solution was exposed to sunlight irradiation and 2 mL of sample solution was collected after a regular interval of 20 min. The collected samples were centrifuged at 3000 rpm speed. The concentration of MB in the supernatant of centrifuged samples was estimated from the absorption spectra of MB. The photocatalysis experiment was performed on a sunny day during summer (April) between 12:00 PM to 3.30 PM (average solar radiation is ~20 MJ/m2) at National Institute of Technology Tiruchirappalli, Tamilnadu, India in an atmospheric environment.The photocatalytic property of the synthesized ZnO/graphene nanocomposites was studied by examining the photodegradation of MB dye under sunlight irradiation. Nearly 50 mg of ZnO/graphene nanocomposites were added into 150 mL aqueous solution of MB with 1 × 10The XRD patterns of the ZnO/graphene nanocomposite with different concentrations of graphene are given in −1 are corresponding to E2L, 2E2L, E2H-E1L, E2H, A1L/E1L, 2E2H-E2L, and A1 + E2L modes, respectively, of hexagonal wurtzite ZnO structure [−1 belongs to A1L/E1L mode which is related to zinc interstitial and oxygen vacancy defects in the ZnO lattice [tructure . The Ram lattice ,40.−1 (D band), ~1567 cm−1 (G band), 1608 cm−1 (D’ band), and ~2639 cm−1 (2D band) for S1, and at ~1322 cm−1 (D band), ~1563 cm−1 (G band), 1595.7 cm−1 (D’ band), and ~2641 cm−1 (2D band) for S2. The D and G band positions and the intensities were slightly changed for S2 when it is compared to S1 nanocomposites, which might be due to the higher fraction of graphene in the ZnO/graphene nanocomposites (S2). The intensity ratio of 2D and G band (I2D/IG) of graphene bands of S1 and S2 is 0.53 and 0.30, respectively, indicates the few-layer nature of the graphene nanosheets in both composites. The number of graphene nanolayers per flake of graphene is calculated from the Raman shift of the G band using the following relation [Along with the Raman active modes of ZnO, the Raman bands of graphene are also observed at ~1318 cmThe calculated values of the number of graphene layers using the relations (1) and (2) are given in The D band gives information on the edge and topological defects and the ratio of the intensity of the D to G band (ID/IG) provides the details of the defect population. The value of ID/IG for samples S1 and S2 are 0.54 and 0.40, respectively, greater than that of exfoliated graphene sheets (ID/IG = 0.3)  and bulkAs it is evident that the samples consist of only edge defects, we can calculate the approximate mean lateral size (L) of the flakes and crystallite size (La) from the following relations (3)Mean Crystallite SizeWell-dispersed graphene sheets with agglomerated particles of ZnO are clearly seen in the SEM micrograph of sample S1 shown in 3/2 and Zn 2p1/2. The binding energy peaks at 531.1 and 533.5 eV in 2− in the oxygen-deficient regions in the ZnO matrix [2 hybridization and C-O bonding, respectively, whereas the weak binding energy peak at 289.6 eV is belonging to the O-C=O bonding [The elemental compositions of the samples and functional groups/elements attached to the carbon atoms of graphene are studied using X-ray photoelectron spectroscopy. O matrix , and surO matrix ,46. The  bonding . The pea bonding ,49,50. T2 versus hν)[ersus hν) as shownersus hν),54,55. Tzn), and the transition between the zinc interstitials and valence band maximum [o) and free excitons (FX) that existed in the ZnO crystal lattice of the composite [The PL spectra of the samples excited at 330 nm are shown in  maximum ,57. The omposite . The obsomposite .2O molecules and produce hydroxyl radicals. These reactive hydroxyl radicals degraded the dye molecules into non-toxic molecules [The mechanism of ZnO/graphene’s photocatalytic activity on MB dye in sunlight is schematically depicted in olecules ,61. Accoolecules . The preolecules .0 represents the starting concentration of MB and C represents the concentration of MB at time t under the influence of sunlight. The degradation of MB with S2 is gradual and nearly 83.5% of MB was degraded after 180 min of sunlight irradiation. The sample S1 with low graphene concentration shows better degradation performance than S2. The poor performance of S2 compared to S1 is due to the formation of thicker graphene layers in S2. According to SEM pictures, the thicker graphene layers created on ZnO absorb a significant amount of incidental light and lowered ZnO photo-absorption, which lowers the effectiveness of S2 photocatalytic degradation [The UV-Vis absorption spectra of the MB solution after various periods of sunlight irradiation with S1 and S2 samples are shown in radation .However, the greater surface area and higher defect concentration of S1’s sample, which is smaller than S2’s, can be attributed to its improved degrading efficiency. The improved degrading performance of the S1 sample is also significantly influenced by the point defects in the ZnO. The ZnO lattice’s zinc and oxygen vacancies served as a focus for charge carriers to be trapped, delaying the recombination of electrons and holes. The better electron transfers of sample S1, as proved by less PL intensity compared to S2, may lead to its enhanced photocatalytic activity. The degradation efficiency of sample S1 on MB dye is comparable with that of ZnO/graphene, ZnO/GO and ZnO/rGO reported recently. Moreover, in the previously reported works, in 0/C) vs ‘t’ plots shown in −1 and 0.0034 min−1, respectively. This value is comparable with the degradation rate constant of rGO/ZnO nanocomposites for the photocatalysis of MB under UV light radiation [The following pseudo-first-order equation is used to study the photocatalytic degradation of MB for ZnO/graphene nanocomposites,adiation ,77.The stability of the sample S1 with high degradation efficiency is studied by performing the photocatalytic test for five repeated cycles and it is shown in The present work has the following advantages, such as (i) the synthesis process is simple, cost and time-effective, and is also free from hazardous chemicals, (ii) the synthesized ZnO/Graphene composite contains few-layer graphene sheets without any basal plane defects, (iii) the solvent used for the graphene exfoliation gives a considerable yield of exfoliated graphene and it can be evaporated (low boiling point 84 °C) at room temperature, hence, the removal of solvent from the graphene is quite easy, which is not possible for other well-known solvents used for graphene exfoliation like, DMF, NMP, etc., and (iv) the graphene sheets prepared by the present method show a better quality than that of graphene sheets prepared from shear exfoliation.In this work, a simple, inexpensive two-step solution processing technique was reported for the synthesis of ZnO/graphene nanocomposite. The results obtained from the XRD pattern, micro-Raman spectrum, SEM images, XPS spectrum, and UV-Visible spectrum have confirmed the successful preparation of ZnO/graphene composite from graphene nanosheets exfoliated in 1,2-Dichloroethane. The graphene sheets lack basal plane flaws, and the present edge defects make it easier for oxygen to connect to a carbon atom, forming the C-O-Zn binding complex. The results have also implied the influence of graphene concentration on the growth of ZnO on the surface of graphene nanosheets. The ZnO/graphene nanocomposite prepared with less graphene concentration showed a remarkable photocatalytic degradation efficiency of 75% within 10 min and 97% after 180 min of sunlight irradiation. These results indicated the successful preparation of ZnO/graphene nanocomposite from few-layer graphene sheets exfoliated in 1,2-Dichloroethane by ultrasonication and revealed an excellent performance in the photocatalytic degradation of MB dye under sunlight irradiation. The new synthesis method could be adopted for further synthesis of graphene materials.


Due to the limitation of graphene processing technology, the prepared graphene inevitably contains various defects. The defects will have a particular influence on the macroscopic characteristics of the graphene. In this paper, the defect-based graphene nanoresonators are studied. In this study, the resonant properties of graphene were investigated via molecular dynamic simulations. The effect of vacancy defects and hole defects at different positions, numbers, and concentrations on the resonance frequency of graphene nanoribbons was studied. The results indicated that single monatomic vacancy has no effect on graphene resonant frequency, and the concentration of the resonant frequency of graphene decreases almost linearly with the increase of single-atom vacancy concentration. When the vacancy concentration is 5%, the resonance frequency is reduced by 12.77% compared to the perfect graphene. Holes on the graphene cause the resonance frequency to decrease. As the circular hole defect is closer to the center of the graphene nanoribbon, not only does its resonant frequency increase, but the tuning range is also expanded accordingly. Under the external force of 10.715 nN, the resonant frequency of graphene reaches 429.57 GHz when the circular hole is located at the center of the graphene nanoribbon, which is 40 GHz lower than that of single vacancy defect graphene. When the circular hole is close to the fixed end of graphene, the resonant frequency is 379.62 GHz, which is 90 GHz lower than that of single vacancy graphene. When the hole defect is at the center of nanoribbon, the frequency tunable range of graphene reaches 120 GHz. The tunable frequency range of graphene is 100.12 GHz when the hole defect is near the fixed ends of the graphene nanoribbon. This work is of great significance for design and performance optimization of graphene-based nanoelectro-mechanical system (NEMS) resonators. Theon atoms . Graphenon atoms . It has on atoms . Graphenon atoms , microwaon atoms , high seon atoms , single on atoms , and macon atoms . Bunch eon atoms . Jiang eon atoms . NumerouHowever, graphene is not perfect during the production process and structural defects are inevitable . GraphenThe presence of defects breaks the symmetric lattice structure of graphene, which has a significant impact on the mechanical, thermal, and electrical properties. Due to this reason, a lot of experimental and theoretical research has concentrated on investigating the effects of these defects. For instance, Li et al. found that the mechanical properties were significantly reduced with the existence of defect by the molecular dynamic (MD) simulations, and the thermal conductivity of graphene containing SV, DV, and SW decreased ~57.6%, ~43.4%, and ~31% . AhangarIn the literature, abundant experimental and theoretical simulation reports are available on the effects of various defects on the thermal conductivity , electro2 substrate, therefore the two ends of the graphene nanoribbon structure are fixed in the simulation model. The red area at both ends is the fixed part, and the fixed atomic number is 104 × 2. The middle blue region is the vibrating part, which contains 1020 carbon atoms. The distance from the graphene resonant beam to the substrate is 5 nm.Molecular dynamics simulation is one of the effective methods to study the characteristics of micro-nano structures . It deep−3 ps (1 fs). The Boltzmann constant in the system is 1.38 × 10−23 J/K. An Adaptive Intermolecular Reactive Empirical Bond Order (AIREBO) potential function is used to simulate the C–C interaction. The AIREBO potential function includes not only the interaction force generated by the potential but also the long-range interaction force. The C-C bond length is 3.4 Å. The cut-off radius is set to 10.2 Å. In the system numerical solution uses the Velocity-Verlet algorithm with high computational efficiency. The boundary condition of setting the nanoribbon X direction in the horizontal plane is periodic boundary condition. The boundary condition of the nanoribbon in the Y direction is periodic boundary condition. An infinite parallel plate capacitor is simulated. A boundary condition is set as a fixed boundary condition in the normal direction of the capacitor, that is, in the Z direction. Nosé-Hoover thermostat was used to control the temperature in the simulation.In this paper, Large-scale Atomic/Molecular Parallel Simulation (LAMMPS) software  is used for simulation. The time step is 1 × 10The external force applied in this paper is calculated based on the electrostatic force of an infinite parallel plate capacitor. The electrostatic force between the substrate and the resonant beam can be calculated by the following formula without considering the edge effect :(1)F = −W is the potential energy of the resonator, ε is the dielectric constant, L is the length of the resonant beam, w is the deflection of the resonant beam, V is the voltage between the upper and lower plates, including direct current (DC) bias voltage and small alternating voltage. Derivation of potential energy in displacement direction is the magnitude of electrostatic force between two plates:Among them, The minus sign represents the direction of electrostatic attraction between the parallel plates of the capacitor. The external force in molecular dynamics simulation is the electrostatic force calculated by Formula (2), which is uniformly distributed on each atom in the effective region of graphene nanoribbons.Considering the effects of the location, size, and concentration of vacancy defects on the resonant properties of graphene, single-atom vacancies were set on the graphene nanoribbon. Atoms D1  at the center position, D2  at the edge position, and D3  at the other positions were removed from the model, respectively. The corresponding structures of graphene nanoribbon models SV-1, SV-2, and SV3 containing single vacancies were obtained, as shown in In the molecular dynamics simulation, the potential function selects the AIREBO potential. The time step is set to 1 fs, and relaxation of 50,000 time steps is performed first. After the relaxation was completed, external forces of 0.297 nN, 1.191 nN, 4.762 nN, and 10.715 nN were loaded, respectively. After that, the energy was minimized again. Then the external force was removed, and the NVT ensemble was changed to the NVE ensemble. At this moment, the kinetic energy of the system and the potential energy between the bonding atoms transform to each other, and graphene nanoribbons vibrate freely. Selecting the kinetic energy or potential energy change of the system as the time-domain signal, the corresponding frequency response curve can be obtained by Fourier transform. The graphene resonant frequency of the different vacancy positions under the action of 10.715 nN external force is shown in As can be seen in Since the effect of a single atomic vacancy on the resonant frequency of graphene nanoribbons is small, the number of defects is increased to consider the impact of different defect concentrations on the resonant frequency of graphene. In fact, vacancy defects are the most typical defects that can exist stably in graphene and will inevitably be generated in the processing of graphene. For example, when graphene is treated by ion irradiation technology, the number of defects increase with the increase of irradiation dose, and the defects are mainly vacancies. In this paper, the concentration of vacancy defects is expressed as the ratio of missing carbon atoms to the total number of intact graphene atoms. The graphene nanoribbons with vacancy defect rates of 0.294%, 1.4705%, 2.647%, 3.8235%, and 5% were modelled, and the distribution of vacancies on the graphene nanoribbons remained symmetrical and uniform. E, D, ρ, l, w, and t are Young’s modulus, third-order modulus of elasticity, density, length, width, and beam thickness, respectively. Obviously, from Equation (3), the fundamental frequency of graphene nanoribbons decreases with decreasing elastic modulus without changing the size of the model and without strain. The simulation results of Han et al. showed that single atomic and diatomic vacancy defects have essentially no effect on the elastic modulus of graphene films [In the Euler–Bernoulli beam theory , the resne films . Therefone films . AccordiCircular hole defects are also one of the common defects in graphene. For example, in the preparation process of reduced graphene oxide there is a strong oxidation reaction, which leads to the loss of atoms and causes defects such as holes. Continuous electron beam irradiation will also cause small holes in the graphene film. 1 , H2 , H3 , H4 , H5 , H6  on the graphene nanoribbons are shown in Fabricate hole defects on perfect graphene nanoribbons: removal of all atoms in the circle with atomic H as the center and r = 0.1 nm as the radius of the hole. The positions of the centers of the circles are HThe parameters used are the same as those used for the simulation of single-atom defects. First, the relaxation process is analyzed, and the two ends of the graphene structure are fixed. Then, the full relaxation is carried out to minimize the energy of the system. The stress cloud chart in the relaxation process is shown in When sufficient relaxation is carried out, external forces of 0.297 nN, 1.191 nN, 4.762 nN, and 10.715 nN are loaded. After the stress is loaded, the original NVT ensemble is transformed into an NVE ensemble. Then the applied load is removed, and graphene enters the free vibration phase. The kinetic energy of the system is used as the time domain signal for the analysis of resonant frequency calculation. The resonant frequencies of the circular hole nanoribbons at different locations under each external force are statistically analyzed. The relationship between the resonant frequencies of graphene and different external loads, as well as different circular hole defect locations, is shown in Studying the effect of defects on nanomechanical resonators based on graphene is essential for obtaining a high-quality graphene resonator. In this paper, we employed molecular dynamic method to investigate the effects of vacancy defects and hole defects on vibration characteristics of graphene-based nanomechanical resonator. First, the vacancy defects of different positions and concentrations are modeled in detail. The LAMMPS software was used to simulate the resonance characteristics of the models. The relaxation performance and the frequency response characteristics of graphene with vacancies under different external loads were emphatically analyzed. The results show that the resonant frequency of graphene nanoribbon increases in a step-like manner as the external force increases. The non-linear deformation dominates the dynamic behavior of graphene. By Fourier transform calculation, we found that single monatomic vacancy has no effect on graphene resonant frequency, and the concentration of the resonant frequency of graphene decreases almost linearly with the increase of single-atom vacancy concentration. In the next stage, nanohole defects were imposed to the graphene nanoribbon. The effect of hole location on the resonant frequency of graphene was analyzed and the simulation results show that holes obviously reduce the resonant frequency of graphene. As the circular hole defect is closer to the center of the graphene nanoribbon, not only does its resonant frequency increase, but the tuning range is also expanded accordingly. The above findings can provide a comprehensive understanding in the resonant properties of defective graphene. Our work provides a necessary theoretical foundation for the following research on the design and performance optimization of graphene nanoresonators.


The fast and pronounced changes in dwelling space in urban fringe areas, caused by rapid urbanization, has led to the appearance of new centralized communities. These communities possess characteristics of both urban and rural communities and have been facing great pressure related to the reconstruction of social network relations and the cultivation of a community identity. The outcomes of public space satisfaction evaluations are related to the social functions they fulfill, such as motivating social interaction, cultivating community identity, and integrating social relationships. This study evaluates public space satisfaction based on the study of six new centralized communities in an urban fringe area of Suzhou, using grey relational analysis. The results show that the overall satisfaction value is a standard level. Moreover, public space satisfaction is related to patterns of centralization and factors of social culture; especially the latter has great influence on public space satisfaction. Factors related to public space satisfaction can generally be divided into quadrants of “Low Satisfaction–High Significance” and “High Satisfaction–Low Significance.” According to the inverse correlation between satisfaction level with public space and significance of indexes, we propose that indexes of public space satisfaction in the “Low Satisfaction–High Significance” quadrant should be improved greatly during the process of the optimization and construction of public spaces in new centralized communities. With rapid urbanization in many countries, rural areas have been integrating into urban areas at an accelerating pace. Traditional settlement patterns of urban fringe areas are being gradually assimilated by urban landscape, and they are beginning to collapse and divide. New centralized communities, as a kind of special and new form of dwelling or residence, are starting to appear. Recently, researchers have not been able to reach an agreement on the definition of “new centralized community”. Wang Yong pointed out that under the influence of the disordered construction of villages and the shortage of construction land use, the new centralized community is formed by the centralization of scattering villagers . Xiang CThe factor of level of satisfaction originated in the field of marketing management as a measure of coherence between expectations and reality . Since tIn this paper, grey correlation analysis is selected as the satisfaction evaluation method for a new concentrated community public space. Six communities with obvious concentrated characteristics are selected as the research objects in the marginal areas of Suzhou. Interviews, questionnaires, field surveys, and other means of community departments are adopted to evaluate the satisfaction of new concentrated community public space in the marginal areas of Suzhou.Currently, regression analyses, standard deviations, and factor analyses are the methods that are mainly applied to research public space satisfaction. A regression analysis is suitable for use in a space satisfaction analysis in which the sample distribution obeys the probability characteristic distribution ,27. The Suzhou is a regional megacity in China. Since its implementation of the policy of Three Concentrations in the late 1990s, many new centralized communities have appeared on the urban fringe of Suzhou. According to the Suzhou Bureau of Land and Resources, 680 new centralized communities had been built by the end of 2016. These communities include 727,000 central resettlement families; moreover, the centralization rate of residents is up to 53.2%. The new centralized community has become the most sensitive and active unit during the process of urban–rural integration. Considering the differences among different cities’ topographic features, production areas, and lifestyles, each area adopts a construction pattern according to its own characteristics during the development of new centralized communities. For example, Gan Xinkui divides communities into three construction patterns according to levels of economic development. These levels form patterns against the background of the urban sprawl, the in situ urbanization , and the self-governance of villagers . Based oBased on a study of communities in the urban fringe areas of Suzhou, this study divides new centralized communities into two types: heterogeneous centralization and local centralization, according to their space scale and causes of formation. The former community type was mainly constructed under the guidance of the government during the period when development zones and industry parks were built. They usually feature massive concentration, early ages, and multi-story buildings. The latter community type was mainly formed during a period of village collectives reviving construction land. They usually feature small-scale concentration, new ages, and multi-story and small high-rise buildings. Considering the integrity of the region, as well as the accuracy and scientificity of the research results, we selected the objects to survey according to some contrastive elements, such as community size, centralization pattern , and conSatisfaction with public space is affected not only by subjective factors such as residents’ age and education level, but also by visitor factors such as space environment, hardware facilities, and management level, which is a two-way interaction process between residents and places. This paper constructs a conceptual model of public space satisfaction in new-type concentrated communities, selects six typical new-type concentrated communities on the edge of Suzhou as empirical research objects, and uses grey correlation analysis to evaluate their public space satisfaction.Public space satisfaction levels are influenced not only by the activity perception of residents, but also by the environment, facilities, and management, for example. Several scholars have been studying this; for example, Winter constructed the index for community public space satisfaction in terms of landscape environment, facilities, maintenance, and management . RapoporFirst, a survey questionnaire on public space satisfaction was designed based on the objects being surveyed and the index system. The first part of the questionnaire recorded the participants’ characteristics, while the second part quantified the evaluation indexes. The Li Kete scale method was applied in the questionnaire , with 1 Second, the reliability of the 443 valid questionnaires was tested using SPSS v 22.0 software. The results show a Cronbach’s α coefficient of 0.786, higher than the least acceptable number, 0.6 ; this coThe core soul of public space in suburban concentrated communities is to serve residents, and the objective differences in environment, facilities, management, and other aspects will affect residents’ satisfaction with public space. Using grey correlation analysis, it was found that all objective factors are related to public space satisfaction, but there are significant differences in the influencing factors and degrees of public space satisfaction in different communities. GRA was used to determine the reference sequence and comparison sequence of public space satisfaction levels of new centralized communities based on qualitative analysis . To ensuWk is the weight of the evaluation index No. k in Formula (1).An analytic hierarchy process was applied to determine the index weight due to the difference in indexes’ influence on public space satisfaction. We invited 30 experts  and 80 residents to participate in the comparison and judgment of indexes. The weight result is shown in Grey weighted relational grade is the measurement that indicates the correlation strength between public space satisfaction and evaluation indexes. The higher the grade, the more satisfied residents feel with community public spaces, and the more influence there was on satisfaction by evaluation indexes. Furthermore, it is a distinguishing coefficient that always takes the value of 0.5 , and it Next, we determined the average numbers of the evaluation indexes of public space satisfaction as a comparison sequence, and the maximum value of each index as a reference sequence. We then applied Formula (2) to evaluate the public space satisfaction of new centralized communities and obtain the results, shown in We made a list of average numbers of evaluation indexes of public space satisfaction as a comparison sequence, and took the maximum numbers of indexes as the reference sequence. We then applied Formula (2) to evaluate the grey weighted relational grade of public space satisfaction evaluation indexes, as shown in The results show that the value of public space satisfaction of new centralized communities is 0.584, which is an average level . From this result, we can conclude that the overall level of public space satisfaction in new centralized communities is not high, indicating that although many opportunities are provided to improve the quality of public spaces due to the construction of new centralized communities, many problems still remain. This lowers the overall level of public space satisfaction. Somehow, during the construction of public spaces and distribution of facilities, residents’ demands for social culture, social relationships, public activities, and cultivating a sense of identity are overlooked. This makes residents feel downhearted and indifferent to the new community.By comparing the results of public space satisfaction of the two types of new centralized communities, it can be concluded that the level of public space satisfaction is related to the centralization patterns of communities. The satisfaction level of local centralization-type communities is higher than those of heterogeneous centralization-type communities, with values of 0.591 and 0.577, respectively.Compared with local centralization-type communities, heterogeneous centralization-type communities were always constructed earlier, with lower environment quality and older facilities. Most local centralization-type communities were constructed within the last seven years, with relatively better facilities. Furthermore, heterogeneous centralization-type communities were used to develop due to the cross-administration of villages, and properties were allotted by lot. Traditional acquaintance society has transformed into a semi-acquaintance society, or even stranger society, which is damaging to social communication between residents of the community. Furthermore, public activities became more individual, with the community identity remaining to be built up in heterogeneous centralization-type communities. A modern governance mode is applied to the governance of local centralization-type communities, while community organizations are relatively mature with a higher frequency of public activities and traditional celebrations that residents are willing to participate in. In addition, local centralization-type communities, where villagers have similar backgrounds, used to concentrate within villages with good conservation of the former social networks and emotional foundation. Therefore, the level of public space satisfaction of local centralization communities is a little higher than that of heterogeneous centralization-type communities.Based on the analysis of the key factors that influence the public space satisfaction of new centralized communities, we conclude that the evaluation indexes above are related to the level of public space satisfaction, while there are differences in the degree of influence on it . The indThere are two reasons for this. First, social relationships, social capital, and community identity have changed a lot since the centralization of communities. Offering various activities for residents to participate in regularly in community public spaces can not only help build close relationships between residents, but also help residents to share their sense of value and local customs with each other. This, in turn, may promote the development of community identity. In this sense, social environment factors have a great influence on the level of public space satisfaction. Second, although the new centralized community is constructed according to high standards, its management institutions must still be transformed. Sustainable development of residents’ social communication, relaxation, and community activities must all be guaranteed through effective management and maintenance in public spaces. In this sense, social management has a great influence on the level of public space satisfaction. Therefore, during the construction of new centralized communities, not only the perfection of physical space should be addressed, but also the social environment, with an emphasis on factors such as public activities, participation of residents, and the management institution of communities.Next, we address the degree of influence of indexes on public space satisfaction as the significance of indexes (Y axis) and levels of public space satisfaction on the X axis. We analyzed the correlation between levels of satisfaction (X axis) and significance (Y axis) to deduce four quadrants according to the value average of significance and satisfaction levels .The results show that the three indexes of accessibility, daylighting, and perfection of fitness facilities were located in the “High Satisfaction–High Significance” quadrant. Activity participatory, activity diversity, activity frequency, cultural landmark richness, management, and maintenance of facilities and environment were concentrated in the “Low Satisfaction–High Significance” quadrant. The perfection of resting facilities, vegetation richness, safety, perfection of lighting facilities, perfection of lighting installation, and brick rate are in the “High Satisfaction–Low Significance” quadrant. From the perspective of the factor distribution of satisfaction in public space, most factors are concentrated in the “Low Satisfaction–High Significance” and “High Satisfaction–Low Significance” quadrants, while few factors are distributed in the “High Satisfaction–High Significance” quadrant, showing a significant reverse relationship. This also shows that social and cultural factors that are more important to residents’ daily life, such as participation, diversity, and frequency of activities. The lack of corresponding attention in the construction and management of new centralized communities results in low satisfaction with public space. However, the relatively low level of importance of the brick rate, the perfection of sanitation facilities, lighting installation, etc., has a high degree of satisfaction, indicating that the construction of a new centralized community public space at the material level can basically meet the needs of residents at the current stage of life.(1)The overall satisfaction level of new centralized communities’ public spaces is 0.584, which is at an average level; there is still some way to go to reach the level of “very satisfied.” The construction of new centralized communities should emphasize not only the creation of high-quality physical public spaces but also the cultivation of social relationships and community identity to improve public space satisfaction levels.(2)When comparing public space satisfaction levels of heterogeneous centralization-type communities and local centralization communities, the results showed that different patterns of centralization are prerequisites that influence public space satisfaction. Different patterns of centralization are related to aspects of environment quality, perfection of facilities, degree of social relationship breakage, and community management institutions. By affecting the aspects above, centralization patterns influence the results of public space satisfaction.(3)Analyzing the leading factors that influence public space satisfaction levels, we discovered that factors of social environment have a much greater impact on the overall public space satisfaction of new centralized communities than those related to the physical environment. This indicates that social attributes are much more important than physical attributes when it comes to public space satisfaction.(4)By analyzing the correlation between levels of public space satisfaction and significance of indexes, we showed that there is an inverse correlation between satisfaction level and significance, with most of the indexes in the quadrants of “Low Satisfaction–High Significance” and “High Satisfaction–Low Significance.”The public spaces of new centralized communities in urban fringe areas are the vessel of residents’ daily life, where residents can have social communication and public participation. It is also the junction between inheriting community spirit and bearing social relationships. Research on the public space satisfaction of new centralized communities is of great significance, especially in terms of its influence on the sustainable development of residents’ activities, the reconstruction of social networks, and the cultivation of community identity ,38. ThisExisting research on public space satisfaction has rarely considered communities at the micro level before. This study eliminates the traditional method of evaluating public space satisfaction in terms of material based on existing studies. We chose six typical new centralized communities in the Suzhou fringe area as objects to perform empirical research from the perspective of social space. Although the reliability of the results may be influenced by the small sample, this study provides a new perspective for future research on the construction of similar new centralized communities and the improvement of public space satisfaction levels. According to the correlations between the levels of public space satisfaction and the significance of indexes, suggestions for the optimization and construction of differential public spaces are proposed as follows.(1) Keep indexes in the quadrant of “High Satisfaction–High Significance” as they are, including accessibility, daylighting, and perfection of fitness facilities. The advantages offered by these indexes should be maintained and improved. For example, the perfection of fitness facilities can help cultivate the vitality of public spaces, which is beneficial for social relationships. This can also inspire individual or social activities to promote residents’ communication. It is necessary to equip various fitness facilities and places to adapt to the demands of residents of different ages.(2) The promotion of indexes in the quadrant “Low Satisfaction–High Significance”, such as activity participation and activity diversity. These indexes are key factors that influence residents’ public communication, the cultivation of community identity, and the transformation of communities. Promoting these indexes will be highly beneficial for the promotion of public space satisfaction levels. The following aspects must be promoted urgently: First, propaganda and education should be conducted to raise residents’ awareness of and ability to participate in public activities and community affairs. Second, community collective activities, such as traditional celebrations and performances, should be held regularly to create more opportunities for local residents and immigrants to communicate with each other and develop collective memories, pushing forward the development of a community identity. It is also beneficial to maintain the countryside spirit by setting landmarks featuring local characteristics in community public spaces. Finally, property management companies or pluralistic organizations could be introduced by the force of market mechanisms to establish scientific space governance policies to guarantee the functions of public spaces.(3) Optimize the indexes in the quadrant of “High Satisfaction–Low Significance” gradually, including perfection of resting facilities, vegetation richness, and safety. These indexes play an important role in maintaining satisfaction and attraction in public spaces. However, the marginal profit of these indexes is a little small; while investing the same input compared with other indexes, it is not necessary to invest too much in funds and resources in the promotion of these indexes when there is a lack of funds. It is therefore advised to keep these indexes as they are, just in the case of reducing the overall satisfaction level of public space.