Ozone treatment of the graphene support not only eliminates the undesirable ligands of the pre-deposited metal precursors, but also regenerates active sites for the precise tuning of the density of Co atoms. The Co1/G SACs also demonstrate exceptional activity and high selectivity for the hydrogenation of nitroarenes to produce azoxy aromatic compounds, attributable to the formation of a coordinatively unsaturated and positively charged catalytically active center (Co–O–C) arising from the proximal-atom induced partial depletion of the 3d Co orbitals. Our findings pave the way for the precise engineering of the metal loading in a variety of SACs for superior catalytic activities.Controllable synthesis of single atom catalysts (SACs) with high loading remains challenging due to the aggregation tendency of metal atoms as the surface coverage increases. Here we report the synthesis of graphene supported cobalt SACs (Co Controllable synthesis of single atom catalysts with sufficiently high metal loading remains challenging due to the tendency of agglomeration. Here the authors synthesize a series of stable atomically dispersed cobalt atoms on graphene with high Co loadings via the regeneration of active sites by atomic layer deposition. For SACs to be practicably applicable, a sufficiently high loading of atomically-dispersed atoms on an appropriate support is required. Unfortunately, isolated metal atoms are thermodynamically unstable due to their high surface energy and thus prone to agglomeration at an increased loading during the synthetic process or the subsequent treatment. Common strategies to tackle this issue include reducing the metal loading to an extremely low level22 and enhancing metal-support interactions for a strong anchoring of the isolated metal atoms25. In respect of the former strategy, the loading of the majority of SACs synthesized by wet-chemistry methods has been kept below 1% to prevent the formation of metal nanoparticles27. For instance, aggregation of Pt atoms dispersed on α-MoC surface and mesoporous zeolite substrates occurred once the loading of precious metal catalyst was increased to 0.2 and 0.5%, respectively26. In the latter strategy which involves a judicious choice of supports, the loading of Pd single atoms can be increased up to 1.5% on modified TiO2 nanosheets28. In addition, a high loading of SACs has been achieved using a wet-impregnation29 or high temperature pyrolysis method30. In both methods however, it was challenging to control the loading of metal atoms on the support surface for optimizing the catalytic performance. Despite considerable progress in recent years, controllable synthesis of stable SACs with sufficiently high loading for high performance catalysis remains a major roadblock towards its practical applications.Single-atom catalysts (SACs) have emerged as a new frontier in the field of heterogeneous catalysis due to their remarkable catalytic performances and maximized atom utilization28. On the other hand, the metal-support interaction results in modification of the electronic properties of anchored metal atoms, which in turn alters the activity and selectivity of SACs31. It is therefore of importance to probe the local coordination environment of single metal atoms and their electronic coupling with support atoms in close proximity. Such a study offers a unique opportunity to further optimize the catalytic performance of SACs, which however, remains largely unexplored.On the one hand, a strong interaction between anchored metal atoms and neighboring support atoms is essential for achieving stable high-metal-loading SACs1/G SACs, which also allows the precise tuning of the density of isolated Co atoms on the graphene support. In contrast to solution-phase deposition, self-limiting surface reactions  technique for the preparation of stable high loading Co1/G SACs due to the following figures of merit: (i) chemically derived graphene offers an ideal low-cost platform for the anchoring of individual Co ALD precursors to the oxygen-decorated carbon sites;32 (ii) the density of anchoring sites on graphene can be tuned by controlling the pretreatment conditions34. Under typical oxidation conditions, the basal plane of graphene can be decorated with diverse oxygen functional groups including hydroxyl, epoxy, phenolic, carbonyl, and carboxyl groups32. However, only specific oxygen-containing functional groups on the graphene surface are expected to act as nucleation sites to react with the metal precursors used in the ALD. Hence, it is desirable to achieve homogenous oxidation of graphene to create a high density of identical anchor sites in order to optimize the loading density of Co1 single atoms. The exposure of graphene to ozone (O3) at an elevated temperature is most likely to produce uniform epoxy functional groups35, which are anticipated to be active anchor sites for Co(C5H5)2 precursors (CoCp2). Furthermore, the remaining ligands of the deposited metal precursors are often removed through a combustion reaction using O3 in the second pulse of each ALD cycle36. Hence, we expect the ozonation of a graphene support at elevated temperature to achieve two outcomes, namely allowing us to burn off organic ligands and to recreate desirable anchor sites for the subsequent Co ALD cycles, which would offer an effective method for tuning the metal loading of SACs.In our study, reduced graphene oxide was selected as the support for the preparation of Co3 at 150 °C  by performing 1, 2, 3, 4, 5 cycles of Co ALD respectively.To test the above hypothesis, we performed X-ray photoemission spectroscopy (XPS) measurements to investigate the evolution of the amount of oxygen-containing groups on graphene exposed to Oses Fig. . After g1/G SACs. The employed acceleration voltage is 60 kV, where the lower voltage significantly reduces the cross section of Co atoms dissociation or clustering events. The large-field of view STEM-ADF images of the as-prepared Co1/G SACs revealed the absence of larger clusters for all the samples prepared within the five cycles of Co ALD as shown in Fig. 1/G-0.4  and on  Co atom sites as marked in the inset of Fig. 2,3 edge and O K edge related peaks, suggesting that the anchoring of isolated Co atoms in graphene involves oxygen atoms. Furthermore, examination of the Co L2,3 edge fine structure shows sharp white features with an L3/L2 ratio of ~5, suggesting an oxidation state which is lower than +2 valence state37. Such an atomic insight not only provides compelling evidence for the presence of Co–O bonds at the catalytically active sites but also rationalises the proposed atomic structures of Co1/G SACs as will be discussed in more details later.State-of-the-art aberration-corrected scanning transmission electron microscopy – annular dark field (STEM-ADF) measurements were initially conducted to gain a detailed understanding of the morphologies of the as-prepared Co0.4 Fig.  and Co1/0.8 Fig.  prepared0.8 Fig. . Interes0.8 Fig. –9. To ou0.8 Fig. , which f1/G SACs with different loadings. As shown in Fig. 1/G SACs samples with different loadings are centered at 7727.1 eV, between that of the Co foil (7725.7 eV) and Co3O4 (7728.0 eV), consistent with the Co1/G SACs as-prepared being in the oxidized state rather than the metallic state. Additional structural information can also be explicitly inferred from the extended X-ray adsorption fine structure (EXAFS) spectra at the Co K-edge  spectrum of the CoCp2 molecule exhibits a dominant peak centered at 1.60 Å assignable to the Co–C bonds of the CoCp2 precursors. In contrast, the EXAFS spectrum (labeled as CoCp/G) acquired on the graphene support after exposure to CoCp2 vapor at 150 °C shows one main peak at 1.58 Å. This suggests the existence of a shorter bond which may result from the chemisorption of CoCp2 precursors to graphene. As illustrated in Fig. 2 precursors react with the epoxy groups on graphene by removing one of Cp ligands. Hence, the resultant Co atoms will be bonded to one remaining Cp ligand and oxygen atoms on graphene, giving rise to a shorter Co–C/O bond length as compared with that of Co–C bonds in CoCp2 molecules. In addition, the FT spectra for a series of Co1/G SACs show that the first shell peaks undergo a further downshift to 1.56 Å as compared to that of CoCp/G, indicating that the bonding of Co on the basal plane of graphene is further strengthened due to the Co atoms forming new chemical bonds with graphene after the complete removal of organic ligands via the O3 treatment. These observations are consistent with the bonding information extracted from the EXAFS fitting results , isolated Co atoms in the Co1/G SACs can be anchored to the divacancy of graphene through bonding with two interfacial O atoms and four C atoms, forming a new structure represented by Co1–O2C4 , wherein individual Co atoms are bonded to two interfacial O atoms and four C atoms.In order to determine the atomic structures of the Coely Fig. . Hence, 40. The catalytic selective hydrogenation of nitrobenzene has been a major method for the synthesis of azoxybenzene. Unfortunately, the catalysts employed for industrial-scale production of azoxybenzene are usually toxic41. Noble metal heterogeneous catalysts have recently emerged as promising catalysts for the synthesis of azoxybenzene44. However, these catalysts are not practical for the scalable synthesis of azoxybenzene due to their high cost. Here we employ the Co1/G SACs in the selective hydrogenation of a wide range of substituted nitrobenzene to produce azoxy products as illustrated in Fig. 1/G SACs exhibit much higher selectivity to 3, 3’-dichlorideazoxybenzene (98%), compared to Pt/carbon (18%) and Co-NPs/G (4%)  compared to Pt/carbon (18~21%) and Co-NPs/G (2-3%). The major product over Pt/carbon and Co-NPs/G catalysts is aniline compound, giving rise to a low selectivity to azoxy compounds47. In addition, the Co nanoparticles 48. Importantly, the Co1/G SACs with different loadings show negligible variations in the selectivity towards all azoxy compounds  of 0.33 s−1, which is 6 times higher than that of Co nanoparticles (0.05 s−1) as shown in Fig. 1/G SACs synthesized exhibit higher catalytic activity and selectivity in the hydrogenation of nitrobenzene as compared to non-noble metal catalysts reported in the previous work (Supplementary Table 1/G SACs is even higher than that of Pt/carbon (0.23 s−1), which proves their superior catalytic performance comparable to that of precious catalysts. To our delight, Co1/G SACs with a high loading of 2.5 wt% also exhibit a high durability in the selective hydrogenation of nitroarenes as revealed in the recyclability test .The excellent atomic dispersion of all the Co50. The adsorption energy of the intermediate compounds on catalytic surface is one of the key factors that determine the selectivity to certain target products51. In our system, we observed that azoxy compound is the major product when Co1/G SACs is applied. This indicates that the reaction stops at step 4  is prohibited, preventing the further hydrogenation of azoxy compound to aniline. Such a reasoning is also reported in the previous work52. Therefore, we performed DFT calculations of the adsorption energies of azoxybenzene molecules on Co (111), Co1/G SACs and catalytic centers consisting of isolated Co atoms coordinated to four carbon atoms in a graphene divacancy (labeled as Co1-C4/G). It’s worth mentioning here that the catalytic activity of graphene-based metal SACs has been predicted in previous theoretical studies55, but catalytic role of atoms proximal to single metal atom remains largely unexplored. Here, we found that holding Co and oxygen atoms in the close proximity is the key that allows the reaction to proceed with extremely high selectivity in the partial hydrogenation of nitrobenzene to azoxybenzene. Such an excellent catalytic performance can be attributed to the different binding nature of the reactants adsorbed at different catalytic sites. As shown in the Fig. 1–C4/G, the azoxybenzene exhibits a flat adsorption geometry over the Co1–C4 site with an even larger adsorption energy of −1.55 eV  . Furthermore, it is observed that the charge redistribution at the interface in the cases of Co (111) and Co1–C4/G is more significant than that of azoxybenzene adsorbed on the Co–O2C4 site of Co1/G SACs . The weak adsorption of azoxy compounds over Co1/G SACs might be insufficient to break the N–O bond of azoxybenzene for further hydrogenation, giving rise to a high selectivity to azoxybenzene 52.The hydrogenation of nitrobenzene is expected to occur through multiple steps, involving the generation of different reaction intermediates  eV Fig. . In contd and s orbitals for both Co1/G and Co1–C4/G . As shown in Fig. F) is dramatically different in the two examined structures while the difference for PDOS of Co 4 s orbitals is much less significant. The PDOS of Co 3d of Co1–C4/G exhibit a noticeable peak at EF contributed by the partially filled d orbitals. In contrast, the presence of oxygen atoms proximal to Co1 in Co1/G SACs pushes these partially filled d orbitals above EF, resulting in a lower PDOS at EF and thus a more positively charged Co atom. Consistently, Bader charge transfer analysis56 also reveals that each Co atom in Co1/G SACs loses more electrons (~0.8 electrons) to the surrounding O and C atoms compared to Co atoms in Co1–C4/G (lose 0.65 electrons to the surrounding atoms). A more positively charged Co1–O2C4 active center disfavors the adsorption of electron-deficient azoxybenzene on the Co1–O2C4 of Co1/G SACs for the further hydrogenation to azobenzene, which in turn leads to a higher selectivity towards azoxybenzene 57. The excellent catalytic performance of Co1/G SACs discovered in our study attests to their great potential in a wide range of selective hydrogenation reactions.To gain more insights into the catalytic role of proximal atoms in the SACs, we also calculated the projected density of states (PDOS) of the Co atom to 1/G SACs with high and precisely tunable loadings. Our results reveal that the ozone treatment of a graphene support at mild ALD conditions not only burns off metal ligands, but also recreates active sites for the subsequent anchoring of another batch of Co atoms. This unique approach allows us to precisely tune the density of the supported Co atoms from 0.4% up to 2.5% without formation of any Co nanoparticle or clusters. As compared to conventional Co nanoparticles and precious Pt /carbon catalysts, all the Co1/G SACs exhibit remarkably high selectivity towards azoxy compounds in the hydrogenation of nitrobenzene aromatics. This can be attributed to the electronic coupling between Co atoms and adjacent oxygen atoms that results in a positively charged catalytic center. Consequently, the adsorption of electron deficient azoxy compounds is weaker and thus the full hydrogenation of nitroarenes is prevented. Our findings have opened up an unprecedented avenue to precisely control the loading of single metal atoms in a wide range of SACs for industrially important chemical transformations.In conclusion, we have developed a stepwise approach to fabricate a series of Co2, 98%), Co(NO3)2·6H2O , the Pt/carbon catalyst, sodium borohydride  and all the subsitituted nitrobenzenes . Few-layer graphene oxide and pristine graphene nanosheet (99.5%) were purchased from Nanjing XFNANO Materials Tech Co. Ltd. and Chengdu Organic Chemicals Co. Ltd., Chinese Academy of Sciences respectively.All the chemicals were purchased from Sigma Aldrich and were used as received without further purification. These includes Bis (cyclopentadienyl) cobalt  by alternatively exposing thermally-reduced graphene oxide to CoCp2 precursor and O3 at 150 °C. Ultrahigh purity N2 (99.99%) was used as carrier gas with a flow rate of 50 mL/min. The Co precursor was heated at 100 °C to generate a high enough vapor pressure. The reactor and reactor inlets were held at 150 °C and 120 °C respectively to avoid any precursor condensation. An in-situ thermal reduction of as-received graphene oxide support was conducted at 300 °C for 5 min before performing Co ALD. The timing sequence was 100, 120, 150, and 120 seconds for the CoCp2 exposure, N2 purge, O3 exposure and N2 purge, respectively. Conducting Co ALD with 1, 2, 3, 4 and 5 cycles allows for the synthesis of Co1/G-0.4, Co1/G-0.8, Co1/G-1.3, Co1/G-2.0, and Co1/G-2.5, respectively.The synthesis of Co58. In brief, 100 mg of the graphene oxide was dispersed in 15 mL of ethanol with sonication. Meanwhile, 10 mg of Co(NO3)2·6H2O (1 mmol) was added into 15 mL of ultrapure water. After that, NaOH solution (6 M) was added into as-prepared Co(NO3)2 solution. Co(OH)2 precipitated was filtrated and washed multiple times using ultrapure water and ethanol. The Co(OH)2 solid was then dispersed into ethanol with sonication, and gradually added into graphene oxide dispersion followed by a continuous stirring for 1 h. In order to keep the pH at 11, 6 M NaOH solution was used during the synthesis. Then, 1 ml of N2H4·H2O was added and stirred for another 30 min. The obtained mixture was put into Teflon-lined stainless autoclave at 180 °C for 12 h. The sample was dried at 60 °C after filtration and washing. Before used in the catalytic reaction, as-prepared samples were calcined at 150 °C in air, and reduced under a flow of 10% H2/Ar gas at 150 °C.The Co-NPs/G was synthesized using the previous method–10 mbar. Al Ka (hν = 1486.7 eV) was used as the excitation sources for XPS. 1H and 13C NMR spectra were recorded on a Bruker AV 300 (300 MHz) and Bruker AV500 (500 MHz) spectrometer. Chemical shifts were reported in parts per million (ppm), and the residual solvent peak was used as an internal reference: 1H (chloroform δ 7.27), 13C (chloroform δ 77.0).The Co loadings in all the samples were measured by an inductively coupled plasma atomic emission spectrometer (ICP-AES); therein all samples were dissolved in hot fresh aqua regia. XPS measurements were carried out in a custom-designed ultrahigh vacuum (UHV) system with a base pressure better than 2 × 105 e/nm2·s with a total dose of 1.6 × 107 e/nm2. The dwell time for STEM-ADF image is set as 20 us/pixel. The EELS 2D maps were taken by Gatan Quantum ER Spectrometer with a spectrum pixel time of 2 s.STEM-ADF characterization and image simulation: STEM-ADF imaging was carried out in an aberration-corrected JEOL ARM-200F system equipped with a cold field emission gun and an ASCOR probe corrector at 60 kV. The images were collected with a half-angle range from ~85 to 280 mrad, and the convergence semiangle was set at ~30 mrad. The imaging dose rate for single frame imaging is estimated as 8 × 1059. The storage ring of SSLS operated at 700 MeV with beam current of 250 mA. A Si (111) double-crystal monochromator was applied to filter the X-ray beam. Co foils were used for the energy calibration, and all samples were measured under transmission mode at room temperature. The EXAFS oscillations χ(k) were extracted and analyzed using the Demeter software package60.The X-ray absorption near edge structure (XANES) and the extended X-ray absorption fine structure (EXAFS) measurements of Co K-edge were carried out at the XAFCA beamline of the Singapore Synchrotron Light Source (SSLS)61. The generalized gradient approximation (GGA) in the Perdew-Burke-Ernzerh (PBE) format63 and the projector-augmented wave (PAW) method64 are employed in all calculations. A plane wave basis with a cut-off energy of 450 eV along with spin polarization and 4 × 4 × 1 k-sampling in Brillouin zone are used for all calculations. The convergence criterion for structural relaxations is set to 0.01 eV/Å. Effects of Van der Waals force (through DFT + D2)65 are also considered. Defective graphene is defined with an 8 × 8 unit cell with a divacancy consisting of two missing adjacent C atoms  by utilizing the Vienna ab-initio Simulation Package (VASP)s Figure . The Co 66. For the FDMNES calculation, the Schrödinger equation is solved with a free shape of potential, which avoids using the muffin-tin approximation and thus better reproduce the theoretical XANES spectrum. For all the calculated XANESs, the final states are calculated inside a sphere with a size of 8 Å. The energy step at the Fermi level is 0.2 eV.The XANES spectra of Co K edges of all the structures predicted by DFT were modeled using a finite difference method implemented by FDMNES program−3 mmol of catalyst, 2 mmol sodium borohydride, 8 mL of Tetrahydrofuran (THF) and 2 ml of ultrapure water were mixed in a round-bottom flask to carry out the reaction. Then the reaction mixture was stirred at 25 °C for one hour. The as-obtained products were analyzed by GC-MS .0.1 mmol of substrates, 1.4 × 10The data that support the findings of this study are available from the corresponding author upon reasonable request.Supplementary InformationPeer Review File


Optical devices are highly attractive for biosensing as they can not only enable quantitative measurements of analytes but also provide information on molecular structures. Unfortunately, typical refractive index-based optical sensors do not have sufficient sensitivity to probe the binding of low-molecular-weight analytes. Non-optical devices such as field-effect transistors can be more sensitive but do not offer some of the significant features of optical devices, particularly molecular fingerprinting. We present optical conductivity-based mid-infrared (mid-IR) biosensors that allow for sensitive and quantitative measurements of low-molecular-weight analytes as well as the enhancement of spectral fingerprints. The sensors employ a hybrid metasurface consisting of monolayer graphene and metallic nano-antennas and combine individual advantages of plasmonic, electronic and spectroscopic approaches. First, the hybrid metasurface sensors can optically detect target molecule-induced carrier doping to graphene, allowing highly sensitive detection of low-molecular-weight analytes despite their small sizes. Second, the resonance shifts caused by changes in graphene optical conductivity is a well-defined function of graphene carrier density, thereby allowing for quantification of the binding of molecules. Third, the sensor performance is highly stable and consistent thanks to its insensitivity to graphene carrier mobility degradation. Finally, the sensors can also act as substrates for surface-enhanced infrared spectroscopy. We demonstrated the measurement of monolayers of sub-nanometer-sized molecules or particles and affinity binding-based quantitative detection of glucose down to 200 pM (36 pg/mL). We also demonstrated enhanced fingerprinting of minute quantities of glucose and polymer molecules. A highly sensitive glucose sensor has been constructed from a functionalized graphene-metallic hybrid metasurface. Pioneered by a US-Chinese collaboration from Columbia University, University of South Carolina, Brookhaven National Laboratory and Nanjing University the device by detecting the changes in graphene optical conductivity, enables ultrasensitive detection of glucose concentrations as small as 200 pM via a small shift in its plasmonic resonant wavelength which is then measured. Importantly, the new sensing principle overcomes the detection limit defined by the molecular weight or the changes in local refractive index, which for a long time has impeded the development of more sensitive optical biosensors. The device consists of a monolayer of graphene covering an array of gold nanorods, atop a platinum-silicon dioxide-platinum sandwich that serves as an optical cavity. When the graphene is functionalized with boronic acid which serves as a glucose binding agent, the device’s wavelength response was seen to clearly red shift with increasingly glucose concentration. Experiments indicate a dynamic range of measurement of over 6 orders of magnitude from 2nM to 10mM. Most optical sensors, such as those based on surface plasmon resonance9 or optical fibers10, rely on the detection of changes in refractive indices to quantify analytes or monitor binding processes, but they unfortunately lack the sensitivity to probe the binding involving low-molecular-weight molecules12. Spectroscopic methods can reveal molecular fingerprints and quantify analytes according to signal intensities but are limited by noisy background and low sensitivity as well14. Non-optical devices such as field effect transistors may provide more sensitive alternatives17 at the expense of molecular spectroscopic information, convenient wireless communication between optical devices, and other features of optical methods. Also, use of these devices may face other complexities in biosensing, such as unstable contact, electrochemical corrosion, current leakage, and reduced sensitivity in high-ionic-strength media21.Optical transducers are one of the most promising candidates for label-free, sensitive, and specific on-chip biosensing.25. In particular, graphene is very well-suited to develop optical modulators or photodetectors operating in the mid-infrared (mid-IR)28 range, where spectral fingerprints of many molecular bonds can be found. However, the potential of these new device architectures in biosensing has not been widely explored, especially for the detection of low-molecular-weight analytes. While many studies have reported enhancement of the mid-IR fingerprints of protein or polymer layers using metal or graphene plasmons32, to date very limited advances have been made in the measurement of the binding of low-molecular-weight analytes in the mid-IR range; such measurements are challenging because of the significant mismatch in size between their sub-nanometer size and micrometer-scale IR wavelengths33.Very recently, with highly tunable electrical and optical properties, two-dimensional materials have been employed to construct novel optoelectronic devices35 Meanwhile, the optical measurements are readily amenable to wireless deployment and avoid the complexities involved in electrical measurements that are typically used to measure carrier doping. Second, the sensors can resolve molecules with similar molecular masses by differentiating the resonance shifts caused by the changes in graphene optical conductivity, which is not possible with refractive index-based sensors. Third, the hybrid metasurface features a quality factor that is insensitive to variation in graphene carrier mobility and thus can be more stable than the devices using graphene as their sole functional material, which in general are affected by the degradation of carrier mobility37. Finally, the sensors can act as substrates for surface-enhanced IR absorption (SEIRA) spectroscopy to enhance the fingerprints in the mid-IR range and facilitate the identification of analytes.In this paper, we demonstrate optical conductivity-based mid-IR biosensing that allows the sensitive measurement of low-molecular-weight analytes as well as the enhancement of their spectral fingerprints. The sensors used in this work employ a hybrid metasurface consisting of monolayer graphene and a metallic nano-antenna array. They offer a unique set of advantages that are not simultaneously available from existing electrically or optically based devices. First, the plasmonic resonance frequency of the sensors varies with the carrier doping introduced by target molecules adsorbed on graphene; therefore, the sensor is not limited by the molecular mass and can sensitively detect low-molecular-weight molecules thanks to the high sensitivity of graphene to molecular dopingWe demonstrated the use of these hybrid metasurface sensors for sensitive detection of low-molecular weight analytes. Sub-monolayers of sub-nanometer analytes were detected and differentiated from each other. Glucose from 2 nM to 20 mM was quantified via its reversible binding with boronic acid anchored on graphene. We experimentally and theoretically studied the relationship between the metasurface geometry, electric-field confinement, and sensor sensitivity. This led us to further optimize the sensor design and achieve a detection limit of 200 pM glucose by confining the electric-field on ultra-narrow (10 nm) suspended graphene. Additionally, we demonstrated enhanced fingerprinting of minute quantities of glucose and polymer molecules on the metasurface, which are otherwise unrecognizable without enhancement. This work opens a path to the development of high performance, multifunctional sensors using 2D–3D hybrid structures for biomedical applications.L = 1.64 μm) covered by monolayer graphene, atop a Pt mirror with a SiO2 spacer layer in between  in the antenna, the optical cavity can introduce imaging dipoles at the same distance underneath the Pt mirror, oscillating in opposite directions. A pair of such dipoles are coupled via near-field interactions and can form a quadrupole to suppress radiation loss in the far field and improve the quality factor of the plasmonic resonance band38. Benefiting from its excellent mechanical strength and flexibility, graphene conformed to the antennas and was suspended at the 30 nm gaps over a large device area  and 1000 cm−1 (ωrr) in the mid-IR spectral region where the optical conductivity of graphene is highly tunable40. In this work, the peak near 1500 cm−1 was used as the primary plasmonic resonance band for biosensing, as it showed stronger absorption  (PMMA) residue from device fabrication, would not significantly influence the profile of the plasmonic resonance band.The hybrid metasurface consisted of an Au nanorod antenna array  by 2.3 × 1012 cm−2  and two pyrene derivatives dissolved in ACN: amino-pyrene  and boronic acid-pyrene . Raman spectroscopy and atomic force microscopy (AFM) indicated that the AP or BAP molecules were immobilized on graphene via π–π interactions Figure S2a). Measurements of transport characteristics of graphene field effect transistors indicated that the pure ACN bath introduced p-doping to graphene, increasing the hole density  Al layer was vapor-phase deposited onto the bare Au metasurface (without graphene) and the hybrid metasurface, respectively. Different from the pyrene derivatives, the Al nanoparticles could be homogeneously coated on the bare sensor surface without graphene so that the effect of the refractive index changes on the shift of ωr could be examined independently. As the work function of Al (4.28 eV) is lower than that of pristine graphene (4.6 eV), the Al nanoparticles upshifted the graphene Fermi level and donated electrons to graphene. The increase in carrier density caused by the Al nanoparticles was 2 × 1012 cm−2 , leading to an apparent 24.1 cm−1 blue-shift of ωr in the hybrid metasurface .To further examine the contributions of the changes in optical conductivity and refractive index to the shift of ace Fig. . After en), the carrier mobility (μ) of graphene usually also influences the performance of graphene-based devices. For example, the intensity and quality factor of the plasmonic resonance excited on graphene nanoribbons vary significantly with graphene carrier mobility37. Interestingly, in our hybrid metasurface sensor, the profile of the plasmonic resonance peak did not show appreciable variations. In contrast, the carrier mobility of graphene decreased significantly after chemical treatment, as was evident from the considerably less sharp transfer characteristics . This is in agreement with the results of the finite-difference time-domain (FDTD) simulation . To better understand the effects of the carrier mobility, we also developed an equivalent circuit model of the hybrid metasurface . Such weak dependence of ωr on graphene carrier mobility can be explained by the insensitivity of graphene impedance to the carrier mobility. We note that the graphene impedance referred to here is not equivalent to the electrical resistance but is a function of graphene optical conductivity (see Section 3 in the Supplementary Information for details). The calculated impedance of the graphene load shows approximately 100 times stronger dependence on carrier density than on carrier mobility  Fig. . X-ray pm−1 Fig. , which cωr did not change after exposure of the device to glucose solutions . In contrast, when the graphene was treated by BAP, ωr significantly shifted to lower wavenumbers after exposure to glucose solutions . Fig. ωr|, observed after rinsing with glucose solutions and fresh buffer solutions, respectively, demonstrated that the sensor was able to detect both increases and decreases in glucose concentrations thanks to the reversibility of the glucose-boronic acid binding.We then performed measurements on the hybrid metasurface. Without any intended functionalization of graphene, ns Figs. . This waωr0, of the metasurfaces  were close to each other. The relative shifts of the plasmonic resonance, defined as ∆ωr normalized by ωr0, were used to measure sensitivity. After exposure to 2 mM glucose solution, ∆ωr/∆ωr0 were 0.54 and 0.38% for disk and diamond-shaped antennas, respectively , ∆ωr/∆ωr0 introduced by 20 mM glucose decreased by nearly 50% and 80%, respectively, qualitatively agreeing with the simulation results.We further investigated the influence of the antenna’s geometry on its biosensing sensitivity. First, with a fixed 30- nm gap size between the neighboring antennas, we conducted studies to compare the sensitivities of rod, disk, and diamond-shaped antennas Fig. . The dimely Fig. , which wTo explain the dependence of sensitivity on the antenna geometry, we also calculated the sensitivities for different antenna geometries based on perturbation theory. The equation below relates the sensitivity to the electrical field energy confined by the metasurface (see the Supplementary Information for a detailed derivation of this equation):E0 and E are, respectively, the electrical fields before and after perturbation . S in the numerator integration is the area of the graphene suspended over the nanogap, while V in the denominator covers all the space where E0 is non-zero (see Supplementary Information section 5.1 for details). The factor K is a variant representing the relative change in electric-field energy distribution, which depends on the antenna geometry and can be calculated from the near-field distributions  and the simulated ∆ωr/ωr0 agreed nicely with each other for the above five antenna geometries . Then, Pt antennas with initial gaps of 30 nm were fabricated and an additional 10-nm Pt layer was homogeneously grown using ALD. Finally, a 10-nm Pt layer was anisotopically etched away using inductively coupled plasma (ICP) to create 10- nm gaps between adjacent antennas  was detectable on our 10- nm gap metasurface , which is an important figure of merit for surface-based sensors. In the specific case of glucose sensing, the detection limit was approximately 1.3 pg/mm2 when the gap was 30 nm, and further lowered to 0.043 pg/mm2 when the gap was 10 nm, which was three times better than that for the state-of-the-art Vernier effect plasmonic resonance biosensors 50. However, these values should not represent the theoretical limit of our method, considering that the optical conductivity change is mainly dependent on the number of charges transferred to graphene rather than the molecular weights of the adsorbed molecules. Therefore, this limit value can be even lower for the detection of stronger dopants with lower molecular weights. It can also be improved by engineering the antenna geometry. Figure 52.The monotonic increase of the sensitivity with decreasing antenna gap size predicts that the sensitivity would continue to improve by bringing the neighboring antennas closer to each other. However, reducing the gap size to below 30 nm would be very challenging for standard lithography and lift-off processes considering the high aspect ratio of the nanostructures (antenna width of ~200 nm and thickness of ~50 nm). Therefore, a new method was developed to fabricate antenna arrays with a  nm Fig. . First, nas Fig. . BAP funaps Fig. . Exposurace Fig. , which i−1, which typically show weaker absorption than glucose OH groups do near 3000 cm−1. We first drop-coated, in total, 1 nmol  of glucose on a metallic metasurface device. In measurements performed on the bare substrate (SiO2-Pt cavity on Si) out of the metasurface region, we found that when the absorption of the OH band was 4.2% (see the Supplementary Information for details), other bands of glucose were hardly recognizable , when the intensity of the OH band was close to that measured on bare substrate, the spectrum revealed prominent peaks at 1470 and 1320 cm−1, which were attributed to glucose OCH deformation. The enhancement effect was also observed at 1740 cm−1, which corresponded to the C=O bond of the polymethyl methacrylate (PMMA) residue from the fabrication. Further, when the glucose quantity was reduced to 100 pmol , the OCH band at 1470 cm−1 was still recognizable  spectroscopy. Here, we qualitatively examined the enhancement effect on the glucose fingerprints located within 1300–1500 cmble Fig. . In contble Fig.  with a sIn summary, the hybrid graphene-metallic metasurface enables ultrasensitive optical measurements of small molecules as well as an enhancement of their fingerprints. The optical conductivity-based sensing shows detection limits orders of magnitude lower than conventional optical sensing techniques based on local refractive index changes. It also allows for differentiation between low-molecular-weight analytes based on different types and/or concentrations of dopants introduced to graphene.2 with CaF2 and removing the Pt layer, which may allow for integration of the sensor with microfluidic channels for on-chip real-time sensing or monitoring of the binding process33. To enable the application of the sensor in complex physiological fluids, it is important to develop a functionalization process of graphene to reject non-specific absorption, which is a challenge in general for biosensors employing nanomaterials. In addition, the long-term stability and consistency of sensor output needs to be further studied and improved, possibly by protection of the graphene surface and enhancement of graphene-substrate adhesion54.While this paper is focused on demonstrating the principle of this new sensing approach by performing measurements in air, the use of such a sensor is not limited to dry environments and can be further complemented. For example, it would be possible to make the device mid-IR transparent by replacing SiO2 layer using plasma-enhanced chemical vapor deposition (PECVD). Gold nanorods 50 nm in thickness were then fabricated over a 400 µm by 400 µm area on the SiO2 layer using electron beam lithography, electron beam evaporation and lift-off processes. A monolayer graphene film grown on a copper foil via chemical vapor deposition (CVD) was then transferred onto the gold nanorod array using a PMMA-assisted wet transfer method. The PMMA layer was lastly removed by rinsing the device in acetone for over 3 h at room temperature. (b) Fabrication of graphene FETs. A CVD graphene film was transferred onto a thermally oxidized (285-nm SiO2) silicon substrate, and metallic contacts (2-nm Ti and 45-nm Au) were patterned using electron beam lithography, A monolayer graphene film grown on a copper foil via chemical vapor deposition (CVD) was then transferred onto the gold nanorod array using a PMMA-assisted wet transfer method. The PMMA layer was lastly removed by rinsing the device in acetone for over 3h at room temperature. (b) Fabrication of graphene FETs. A CVD graphene film was transferred onto a thermally oxidized (285-nm SiO) silicon substrate, and metallic contacts (2-nm Ti and 45-nm Au) were patterned using electron beam lithography, electron beam evaporation and lift-off processes.electron beam evaporation and lift-off processes.(a) Fabrication of the hybrid graphene-metallic metasurfaces. A 50-nm Pt layer was deposited on a heavily doped silicon substrate, followed by deposition of a 285-nm SiO(a) Immobilization of pyrene derivatives on graphene. 0.5 mM amino-pyrene (AP) or boronic acid-pyrene (BAP) solutions were prepared by dissolving the powders in anhydrous acetonitrile (Sigma-Aldrich). Metasurface devices with as-transferred graphene were immersed in a 2 mL AP or BAP solution for 12 h, and then rinsed with fresh acetonitrile, isopropanol and deionized water baths sequentially to remove molecules that were not immobilized on the graphene. The devices were then gently blow-dried using compressed nitrogen and left in vacuum desiccator for over 30 min at room temperature to completely remove solvents without impacting the properties of graphene. To immobilize boronic acid on gold antennas, devices with bare gold nanorods were immersed in 4-mercaptophenylboronic acid (Fisher Scientific) solution (1 mM in ethanol) for 12 h at room temperature, and then rinsed with fresh ethanol and deionized water baths sequentially. (b) Aluminum nanoparticles were deposited using thermal evaporation. The devices with graphene and the control devices without graphene were secured on a same glass slide for deposition under the same conditions (0.1 A/s). (c) Glucose solutions were prepared by dissolving D-glucose (Sigma-Aldrich) in 1 × phosphate buffered solutions (ThermoFisher Scientific) and diluted to desired concentrations. At each concentration, the device was exposed to glucose solution for 8 min to ensure that the glucose-boronic acid binding reached equilibrium. The devices were then dipped in fresh buffer and ultrapure water (ThermoFisher) and gently blow-dried using purified nitrogen.The hybrid graphene-metallic metasurfaces and deposited Al nanoparticles were characterized using a scanning electron microscope . Characterization of the functionalized graphene was conducted using Raman spectroscopy (Renishaw) with an exciting laser at λ = 532 nm. Functionalization of gold nanorods with 4-PBA was characterized using X-ray photoelectron spectroscopy . The thicknesses of the graphene before and after chemical treatment were measured using an atomic force microscope .(a) Electrical measurements: Transport characteristics of graphene were measured using Keithley 2400 source-meters. (b) Optical measurements: Infrared reflectance spectra of metasurfaces were measured using a Fourier transform infrared (FTIR) microscope (Bruker Vertex 70 v) with light polarized along the antenna rods. A spectrum measured on a gold mirror was used as the reference for reflectance spectral measurements. Measurements at different glucose concentrations were carried out on the same metasurface from the same location with a window size as large as the metasurface area (400 µm by 400 µm). All spectral measurements were carried out in ambient atmosphere at room temperature.Supplementary information for Optical Conductivity-Based Ultrasensitive Mid-Infrared Biosensing on a Hybrid Metasurface


PYCR1 mutations. Approximately 22 and 32 candidate genes were found to be up- and downregulated, respectively, in fibroblasts from patients. Among the downregulated candidates in fibroblasts with PYCR1 mutations, a strong reduction in the expression of 17 genes (53.1%) which protein products are localized in the extracellular space was detected. These proteins included several important ECM components, periostin (POSTN), elastin (ELN), and decorin (DCN); genetic mutations in these proteins are associated with different phenotypes of aging, such as cutis laxa and joint and dermal manifestations. The differential expression of ten selected extracellular space genes was further validated using quantitative RT-PCR. Ingenuity Pathway Analysis revealed that some of the affected genes may be associated with cardiovascular system development and function, dermatological diseases and conditions, and cardiovascular disease. POSTN, one of the most downregulated gene candidates in affected individuals, is a matricellular protein with pivotal functions in heart valvulogenesis, skin wound healing, and brain development. Perturbation of PYCR1 expression revealed that it is positively correlated with the POSTN levels. Taken together, POSTN might be one of the key molecules that deserves further investigation for its role in this progeroid neurocutaneous syndrome.Aging is a complex biological process. A study of pyrroline-5-carboxylate reductase 1 (PYCR1) deficiency, which causes a progeroid syndrome, may not only shed light on its genetic contribution to autosomal recessive cutis laxa (ARCL) but also help elucidate the functional mechanisms associated with aging. In this study, we used RNA-Seq technology to examine gene expression changes in primary skin fibroblasts from healthy controls and patients with  EFEMP2 or FBLN4), fibulin 5 (FBLN5), and latent transforming growth factor-beta-binding protein-4 (LTBP4). Unlike ARCL1, ARCL2  is caused by mutations in genes involved in different metabolic pathways, including glycosylation (ATPase H+ transporting V0 subunit A2 (ATP6V0A2); ARCL2A), proline biosynthesis (pyrroline-5-carboxylate reductase 1 (PYCR1); ARCL2B), and Golgi apparatus function (RAB6-interacting golgin (GORAB)). In addition to connective tissue abnormalities, a spectrum of syndromes with growth and developmental delay, joint laxity, and mental retardation are also found in most ARCL2B patients  IgG secondary antibody  at room temperature for 1 h, and the immune reactions were detected using an ECL detection system .PYCR1 gene  and TRC1 obtained from the National RNAi Core Facility at Academia Sinica, Taipei, Taiwan were subcloned into the pLKO plasmid to obtain shPYCR1 #1 to #5 and the scramble control. For silencing PYCR1 in primary skin fibroblasts, shPYCR1-#1-#5 lentiviruses were generated by transfecting 293T cells with the recombinant DNAs and the lentiviral helper plasmids by using the TransIT-LT1 in vitro transfection reagent . After removing the cell debris in the supernatant by centrifugation according to the recommended procedure, lentiviruses were harvested 48 h post-transfection by filtration through 0.22-µm cellulose acetate filters. Subsequently, skin fibroblasts (105 cells/well in a 6-well plate) were cultured in a medium containing 8 µg/mL polybrene, infected with the lentiviruses (MOI = 2 or 5), and incubated at 37°C with 5% CO2 according to the recommended procedure. Selection of the infected cells began on day 3 with medium containing 1 µg/mL puromycin, which was replaced every 3 days.Five recombinant shRNAs for the PYCR1 (Acc. no. NM_001282280), and BamHI and EcoRI adaptors, into a lentiviral vector pCDH-CMV-MCS-EF1-Puro . The cDNA fragment was prepared by PCR amplification of a cDNA library originating from healthy human skin fibroblasts with forward and reverse primers  unless indicated otherwise. The significance of pairwise comparisons was determined by Student’s t-test.PYCR1 gene. Two of the patients (P2 and P3) had a common homozygous single-base deletion (c.345delC) in exon 4, leading to a frame shift and premature termination of translation (p.P115fsX7) of PYCR1. The other two patients had compound heterozygous mutations, including the same single-base deletion (c.345delC) and the missense 743G-to-A (P1) and 559G-to-A (P4) transitions in PYCR1. The clinical features of patients P1, P2 and P3 have been reported in our previous papers [The clinical features of four affected individuals (P1 to P4) from three families are listed in ation p.P5fsX7 of s papers . PatientAt the time of our assessment at 4 years old, patient P4 has achieved weight (19.6 kg) and height (110.5 cm) catch-up. Clinical assessment demonstrated features of prominent forehead, large helices, protruding ears, hypermobility of small joints of the hands and feet, and wrinkled and inelastic skin with prominent veins over the dorsum of the hands and feet. The ophthalmic examination revealed preglaucoma, estropia, amblyopia, astigmatism and mild vitreous opacities. Brain MRI revealed no abnormality, while echocardiographic evaluation revealed dilated aortic root with Z-score of 2.46  and skelPYCR1 deficiency leads to a premature aging phenotype in multiple systems, including vision (preglaucoma and cataract), cardiovascular system , bone , central nervous system , typical triangular facial gestalt, and progeroid cutaneous manifestations , 10-12. PYCR1 mutations had lower intracellular proline levels  and the most upregulated gene homeobox B7 (HOXB7)  and two controls detected approximately 60.8 to 75.9 million read pairs per sample, which were unambiguously mapped to 21,141 reference gene sequences . Among the putative differentially expressed genes with at least 2-fold change and a minimum of 10 TPM in patients or controls, sequence annotations indicated the proteins of 17 (53.1%) of the genes downregulated and 2 (9.0%) of the the genes upregulated in patients are localized in the extracellular space. Expression changes of the most downregulated gene periostin  (HOXB7)  in fibro (HOXB7) .PANTHER Classification System indicated ECM and extracellular region proteins were enriched in patients with PYCR1 mutations (www.pantherdb.org/). A biased distribution of essentially downregulated candidates of ECM and extracellular protein genes was found  and decorin (DCN), are associated with different phenotypes of aging, such as cutis laxa and joint and dermal manifestations , 19. In PYCR1 mutations, 54 differentially expressed gene candidates with TPM > 10 and with fold changes ≥ 2 were analyzed using the Ingenuity Pathway Analysis (IPA) software. With the pertinent parameter settings, IPA of “Diseases and disorders” and “Physiological system development and function” revealed these genes in 16 modules (p < 0.05)  . The top < 0.05) . Among t qRT-PCR .POSTN. The expression of the POSTN protein was also decreased in fibroblasts from the four patients , and that shPYCR1 #1 had the highest knockdown efficiency in PYCR1 and POSTN . However, knockdown with shPYCR1 #1 also partly affected the expression of PYCR2  and compound heterozygous frameshift and missense mutations (P1 and P4). These patients only showed the truncated protein p.P115fsX7 and the truncated plus mutant protein with the G248E or A187T substitution. The results differed from those of Reversade et al. [Diverse al level . BecausePYCR1 mutations and controls revealed that many of the differentially expressed genes coded for proteins localized in the extracellular space. Genetic mutations in these proteins are associated with different phenotypes of aging. Many ECM components are found to be decreased in patients with cutaneous syndromes because alterations of ECM composition may lead to abnormal elastic fibers, thus causing cutis laxa [DCN, ELN, IGFBP3, POSTN, PTX3, THBS1, and THBS2), which were downregulated in fibroblasts from ARCL2B patients. POSTN, the most downregulated gene in affected individuals, is a heterofunctional regulator of cardiac development and disease [POSTN, IGFBP3, ELN, DCN, PTX3, and THBS2) are affected by PYCR1. This study also provided a comprehensive linkage of extracellular space genes for the neurocutaneous syndrome caused by PYCR1 mutations.Transcriptome analysis of the fibroblasts from patients’ with tis laxa . In additis laxa . Therefotis laxa . Further disease , 24. OurPOSTN expression in skin fibroblasts is correlated with the PYCR1 expression level and is significantly decreased in adult skin fibroblasts    were alsPYCR1 knockdown or overexpression was found ; it has multiple effects on cell proliferation, differentiation, and angiogenesis. It becomes re-activated in response to injury. PTN had been reported to have roles in bone [Postn-/- mice, and that POSTN suppressed PTN expression [CRIP2, which plays a crucial role in atrioventricular valve development  and coroas found . The res in bone  and hear in bone  and as a in bone . A previpression . This suPYCR2 expression in fibroblasts from individuals with PYCR1 mutations [PYCR2 and PYCRL in affected individuals  and the more distantly related PYCRL (45% homology to the other two forms). Both PYCR1 and PYCR2 are thought to localize to the mitochondria and primarily catalyze the conversion of glutamate to proline, and PYCRL is a cytoplasmic enzyme . A studyividuals . RecentlPYCR1 mutations significantly reduced the expression of many extracellular space genes , and that PYCR1 may modulate the expression of these extracellular space genes in skin fibroblasts. ELN mutations resulting in autosomal-dominant cutis laxa are known to be associated with different phenotypes of aging , and the DCN mutation leads to abnormal collagen fibril morphology and skin fragility [In conclusion, we found that ragility , 47. Moswww.aginganddisease.org/EN/10.14336/AD.2018.0222Supplementary data is available online at


Hence, we can combine free volume theory with the designed PIL structures and their affinity with moisture to obtain a high concentration of free ions in PIL sensing films. Furthermore, the PIL humidity sensors also show fast, substantial impedance changes with changing humidity for real-time monitoring of the human respiratory rate due to a fast response and recovery performance. Therefore, our findings develop a new perspective to understand the humidity performance of PILs based on free volume theory, resulting in fast response and recovery properties realized by the rational design of PIL sensing films.The swelling mechanism is widely used to explain the response of ionic liquids (ILs) or poly(ionic liquid)s (PILs) to moisture. While a fairly broad consensus has been attained, there are still some phenomena that are not well explained. As a complement to the swelling mechanism, we systematically studied the free volume theory in the rapid response and recovery of PIL humidity performance. We chose poly(1-ethyl-3-vinylimidazolium bromide) (PIL-Br), poly(1-ethyl-3-vinylimidazolium tetrafluoroborate) (PIL-BF The advent of air-stable ionic liquids (ILs) is a milestone in modern analytical science and ILs have been widely used as signal-enhancing elements in electroanalytical applications . As is w2 [2O2CO3 nanoparticles [PIL responses to chemical species include changes in optical, electric and charge transport properties, each of which have been explored for PIL chemical sensors ,12,13. I2 , volatil2 , etc.) v2  fabricat2 . To impr2  and La2Oarticles  were intarticles  has beenarticles , there aOwing to flexibility and easy processing, polymers are considered as attractive sensing materials for humidity sensors, and some polymeric humidity sensors are commercially available . However4) and lithium bis(trifluoromethane sulfonimide) (LiTFSI) were purchased from the Sigma-Aldrich Company  and were used as received without further purification. The water that was used was deionized.1-vinyl-3-ethylimidazolium bromide (VEIm-Br) was obtained from Lanzhou Greenchem ILS, LICP, CAS, China. Then, 2,2′-azobis(2-methylpropionitrile) (AIBN), sodium tetrafluoroborate  and then dried at 70 °C overnight. The schematic diagram is as follows:4 was dissolved in another mixed solution composed of 9 mL of deionized water and 9 mL of absolute ethanol (solution B) under magnetic stirring in an ice-water bath for 30 min. Subsequently, solution B was slowly added into solution A and then the mixture was stirred in an ice-water bath for 30 min and was left to stand for 1 h. Finally, the resulting yellowish white solid was cleaned with deionized water and absolute ethanol several times before drying at 70 °C for 24 h. The schematic diagram is as follows:In this synthesis process, 2.04 g of PEVIm-Br was dissolved in a mixed solution composed of 9 mL of deionized water and 9 mL of absolute ethanol (solution A) under magnetic stirring in an ice-water bath for 30 min. Then, 1.10 g of NaBF4: 2.04 g of PIL-Br reacts with 2.81 g of bis(trifluoromethane sulfonimide) through an ion exchange reaction and the resulting yellowish solid was finally gained. The schematic diagram is as follows:The protocol for the synthesis of PIL-TFSI is similar to that of PIL-BF1H NMR spectra, etc. TMDSC (NETZSCH DSC 204 F1) was used to determine the gT of PIL-Br equilibrated at varying RH levels under nitrogen. First, a 250 mL bottle containing saturated aqueous solutions of K2SO4 salts was used to equilibrate PIL-Br for 2 h. Then, the sample was placed into a non-hermetically sealed aluminium differential scanning calorimeter (DSC) pan for measurement. The TMDSC runs consisted of cooling at a rate of 5 °C/min to −60 °C, followed by heating to 100 °C (with the same heating rate of 5 °C/min) and a temperature modulation of ±0.80 °C every 60 s. The DSC heats from 30 to 250 °C at a heating rate of 10 °C/min.The as-prepared PILs were characterized by Fourier-transform infrared spectroscopy (FTIR), The humidity sensors were fabricated by spin-coating the PIL dispersion onto pre-cleaned interdigitated electrodes. Alumina ceramic was used as the substrate due to its high dielectric strength and excellent stability. Interdigitated electrodes composed of 10 nm of titanium and 80 nm of gold with a linewidth of 80 μm were fabricated by sputtering, as shown in 4, the solution was replaced by N,N-dimethylformamide (DMF) with the other conditions preserved to be the same. The PIL-Br thickness can be easily tuned by adjusting the solution concentration and revolving speed.Spin-coating PIL onto the interdigitated electrodes: 0.06 g of PIL-Br was added into 600 mL of absolute ethanol and the mixture solution was then stirred for 2 h until completely dissolved. The sensors were fabricated by spin coating 4.0 μL of the mixture solution onto the pre-cleaned interdigitated electrodes at a speed of 4000 rad/s for 60 s. After that, the sensor was dried at room temperature for 48 h. For the case of PIL-BF2, K2CO3, NaBr, NaCl, KCl and K2SO4 were used as the sources of humidity for 11%, 33%, 43%, 59%, 75%, 85% and 98% RH, respectively.Humidity sensing properties were tested by an impedance analyser . The applied voltage amplitude was 500 mV and the measuring temperature was approximately 25 °C. Several 250 mL bottles containing different saturated salt solutions including LiCl, MgCl1H NMR. The FT-IR spectra for the IL and PILs are shown in −1 and external bending vibration peaks at ~750 cm−1, ~650 cm−1. The absorption peak at ~3140 cm−1 arises from the stretching vibration of the C−H bonds, and that at ~1570 cm−1 is due to the C=N bonds in the imidazolium rings. Thus, the results from the FT-IR spectra can clearly confirm the integrity of the imidazolium ring in the PILs. However, a complete disappearance of the band corresponding to Br− (960 cm−1) is observed with the appearance of new bands attributed to BF4− (1053 cm−1) or TFSI− (~1187 cm−1), which also proves the success of the anion exchange. In addition, the absorption peak at 3450 cm−1 is attributed to the hydroxyl groups (H−O) of water molecules mechanically adsorbed by the IL or PILs.The obtained PILs were first characterized by FTIR and 1H NMR spectra for PIL-Br and IL-Br is shown in 1H NMR test.The 4 (52.9°) and PIL-TFSI (97.8°) are shown in 4>PIL-TFSI. The result corresponds to the effect of the anionic polarity to water molecules in theory.Wetting, usually associated with hydrophilicity, is a phenomenon based on two-phase interface changes from a solid-gas interface to a solid-liquid interface. The wettability of a film material can be expressed by the contact angle (1–180°) and a large contact angle indicates a worse wettability. The static water contact angles for PIL-Br (34.6°), PIL-BFWhen polymers are used in humidity sensing, the swelling process is usually exploited: (i) diffusion of water molecules through the polymer matrix, (ii) relaxation of polymer chains and (iii) expansion of the polymer network upon relaxation. To confirm that the humidity performance of the PILs can be affected by their swelling behaviour, a series of controllable experiments were exemplified using hydrophilic PIL-Br. Since the swelling behaviour of a PIL sensing film is directly related to its thickness, we thus investigate the effect of PIL-Br thickness on the humidity performance. The thickness of PIL-Br sensing films can be easily controlled by adjusting the concentration of the spin-coating solution, denoted as PIL-Br-10, PIL-Br-20 and PIL-Br-30, respectively. It is well known that the working frequency has an important impact on the humidity performance of a PIL sensor. To explore the optimum frequency for the PIL humidity sensors, we first investigated the impedance as a function of RH at different frequencies. The relationships between the impedance modulus of PIL-Br-10 and RH with measuring frequency from 100 Hz to 25 kHz are shown in The repeatability of PIL-Br sensors was further characterized by switching the measurement environments between 11% RH and various RH for five cycles, as shown in SR is related to the resistance of the electrode/film, R1 is the bulk resistance of film, CPEZ is a constant phase element (CPE) and WZ is a Warburg impedance [SR and CPEZ were hardly affected by ambient humidity, as shown in SR relates only to the inter-contact between the electrode and film and ZCPE is characterized as the influence of polarization in the sensing film. In addition, WR decreases drastically as RH increases from 43% to 98%, leading to high-concentration and fast-action of mobile ions in the diffusing process due to the formation of continuous multi-water layers at 33%RH(PIL-Br-30) or 44%RH. It is worth noting that continuous multi-water layers can promote jumping of hydronium ions (H3O+) and free hydrogen ions (H+) for conduction based on the Grotthuss mechanism [+ (H3O+) passes from one end to the other through an adjacent water molecule, rather than a H+ (H3O+) going from one end to the other, with the former being faster. The value of R1 decreases linearly by approximately three orders of magnitude within the full measured RH range  of the polymer. Following derivation from the Williams-Landel-Ferry (WLF) expression [f is the free volume of a polymer, f0 is the free volume fraction of a sample at the reference temperature T0; M0 is the water content of a sample at the reference temperature T0. Assuming that a sample remains in the same ambient temperature, the free volume will increase as the ambient humidity increases. According to the free volume theory, the relationship between the viscosity (η) and the free volume (f) of the polymer follows the Doolittle equation [A and B are constants for a given material. Thus, the viscosity of PILs will decrease as the free volume increases. Furthermore, the relationship between conductivity (η) and viscosity (σ) of the PILs can be built by the following Walden equation:k is a temperature dependent constant and α is a fitting parameter [As mentioned above, PILs are usually considered to be single-ion conductors that are comprised of polymeric imidazolium-based cations and anions. In these cases, cations are structurally constrained as part of the polymer skeleton, which largely restricts their movement. Owing to the asymmetric volume of the cation and anion, there are large spaces  in the PILs. These spaces are also denoted as free volume, which can provide sorption sites to accommodate penetrate of water molecules and to allow ion-movement through the PIL matrix . The perpression , the timequation :(2)lnη=larameter . TherebygT) is defined as the temperature at which the mechanical properties of a polymer material radically change due to internal movement of the polymer chains [gT promotes a higher ionic conductivity. To verify that the PIL conductivity changes with a change in humidity based on free volume theory, we take PIL-Br as an example and investigate its gT change under varying RH levels using temperature-modulated differential scanning calorimetry (TMDSC). From gT of PIL-Br under dry conditions was measured to be 185.2 °C according to a DSC scan. For comparison, a typical TMDSC scan obtained from PIL-Br equilibrated to 98%, as shown in gT of PIL-Br under a 98% RH condition. Thus, the gT of PIL-Br decreases with increasing RH, which benefits improved ion movement. According to the Vogel-Tamman-Fulcher (VTF) equation: Generally, the glass transition temperature (r chains . For theTg−50 K) . Therefo4 and PIL-TFSI were applied as humidity materials in our work because of their different hydrophilic performances. The method used to spin-coat PIL onto the interdigitated electrodes is similar to that used for the humidity sensor based on PIL-Br, as shown in S/T-res is defined as the ratio of the sensitivity to response time and, similarly, S/T-rec is defined as the ratio of the sensitivity to recovery time. These ratios are perfect for reflecting the velocity for response or recovery, especially for a response with different orders of magnitude. Molecules with polar groups, which have a great affinity with water, can attract water molecules or be dissolved in water easily. Furthermore, the excellent hydrophilic PILs can absorb a large volume of water to increase their free volume according to the WLH equation. Thus, it is interesting to study the sensing performance of different hydrophilic PILs films. Adjusting the anion type in PILs film is an effective route to change free volume. A series of controllable experiments were designed using PILs with different anions to investigate the effect of anion type on humidity performance. PIL-BF4 > PIL-TFSI. Among the PILs in our work, the PIL-Br sensor which has the optimum hydrophilicity possesses a biggest free volume based on the swelling theory. Fortunately, the larger free volume can provide more absorption sites to make water molecules permeate into the PIL film for more carrier transport channels at the same ambient humidity and temperature. Due to the electrostatic fields of the PIL-Br film, the absorbed water molecules will dissociate as 2H2O → H3O+ + OH−. In addition, the conduction in polymer films mainly occurs along the hydrogen bond via hydrogen-ion jumps based on the Grotthuss mechanism, i.e., H2O + H3O+ → H3O+ + H2O. Thus, the PIL-Br film has more free ions and carrier transport channels to achieve outstanding conductivity, high sensitivity and a large response and recovery velocity, which is verified by our experimental data.The PIL structure is special because of the many three-dimensional spaces which are due to the staggered connections between the polymer chains, similar to an overpass-type structure. Meanwhile, these three-dimensional spaces are conducive to increase the free volume by absorbing water molecules for current carrier transport. At this basis, the synergistic effect of three-dimensional space and hydrophilic PIL can significantly improve the humidity performance of sensors. For example, the PIL-based humidity sensors exhibit varying sensitivity from 11% to 98% RH at room temperature (25 °C), as shown in +, H3O+, Br− and BF4− can increase as the ambient humidity increases. Therefore, our findings develop a new perspective to understand the humidity performance of PILs based on free volume theory and we can rationally design PIL structures including anion types and film thickness to obtain super properties including fast response and recovery in PIL sensing films.As mentioned above, the conductivity of the PIL is inversely proportional to the viscosity and proportional to the free volume through the free volume theory. At the same time, the free volume of PIL has affinity with moisture. Therefore, the mechanism of the fast response and recovery of the PILs can be explained by the free volume theory, as shown in Human breath is a highly complex mixture of more than 100 types of gases, many of which can provide useful information in the monitoring of the human health condition . Water v; the frequency of the curve varies with the rate of respiration, revealing that our PIL-Br-10 sensor can capture the signals of humidity change under different rates. This proves that the sensor has practicable application for real-time monitoring of human respiratory rates.In recent years, great breakthroughs have been made in research on human respiration monitoring. For example, Yun-Ze Long et al.  preparedFigure 11In summary, PILs were successfully synthesized by typical polymerization and an anion exchange method and were used as humidity materials. We studied the effects of the PIL structure including film thickness and anion type on PIL-based humidity sensor performance. The results showed that a hydrophilic anion and slightly thick film can benefit an increase in the free volume of PIL films to obtain a high concentration of free ions and effective carrier transport channels. Furthermore, the humidity sensing mechanism of PILs was superbly explained by the free volume theory. It is worth noting that our work develops a new perspective to understand the humidity performance of PILs based on free volume theory, resulting in fast response and recovery properties realized by the rational design of PIL sensing films. In our work, the PIL-Br-10 humidity sensor shows high sensitivity (1190), small hysteresis (3.2%), enhanced durability and rapid response (6s)/recovery (10s). We also apply the PIL-Br-10 sensor to monitor human breath under varying conditions, revealing excellent performance and practicability values. Therefore, the PIL-based sensor with novel and reasonable design is highly promising for a broad range of applications.


The operating principle of the humidity sensor is based on the resonant method, in other words, it utilizes the resonant properties of the sensor as signatures to detect the humidity condition of the ambient environment. To this end, a mathematical model quantitatively relating the resonant frequency of the sensor and the relative humidity (RH) level was established according to the cavity perturbation theory. The sensing performance of the sensor was experimentally validated in a RH range of 30%–80% by using a humidity chamber. The measured absolute sensitivity of the sensor was calculated to be 135.6 kHz/%RH, and the corresponding normalized sensitivity was 0.00627%/%RH. It was demonstrated that our proposed sensor not only has the merits of compact size and high sensitivity, but also benefits from a high Q-factor and ease of fabrication and integration. These advantages make it an excellent candidate for humidity sensing applications in various fields such as the agricultural, pharmaceutical, and food industries.In this study, an ultra-compact humidity sensor based on a double-folded substrate integrated waveguide (SIW) re-entrant cavity was proposed and analyzed. By folding a circular re-entrant cavity twice along its two orthogonally symmetric planes, the designed structure achieved a remarkable size reduction (up to 85.9%) in comparison with a conventional TM Humidity is one of the most important indexes for evaluating environmental quality, and it is crucial to monitor and control humidity accurately in many scenarios. For instance, the relative humidity (RH) level in greenhouses is a key factor that affects the growth and disease incidence of crops . For fooTraditional humidity sensors involve various types including resistive ,6,7, capAmong various topologies, substrate integrated waveguide (SIW) has gained increasing attention due to its low cost, low profile, high power capacity, and easy integration with other planar circuits. An SIW cavity available for RH sensing was first presented by Matbouly et al. . Thereaf010-mode SIW circular cavities. The high sensitivity property of the sensor is achieved by introducing sensitive regions inside the cavity where the electric field is highly concentrated. When moist air enters the sensitive regions, it causes a strong perturbation to the electric field and results in a large resonant frequency shift of the cavity. This structural design offers an effective solution for balancing the sensing performance and physical dimensions of a passive microwave humidity sensor, which is of great significance for promoting the development and application of microwave humidity sensing devices.Herein, we propose a novel double-folded SIW (DFSIW) re-entrant cavity and demonstrate its ability for highly sensitive humidity sensing both numerically and experimentally. The overall size of the cavity is dramatically miniaturized by combining the folding technology with re-entrant configuration. Numerical analyses show that it only occupies 14.1% of the overall size of conventional TMRH (unit: %) as follows [The working principle of the designed DFSIW re-entrant cavity humidity sensor is based on the cavity perturbation method. The moist air can be regarded as a dielectric medium, whose dielectric constant is related to  follows ,22:(1)εrμ = 0). Then, by using a quasi-static approximation of the field internal to the air sample [When the cavity is exposed to a humid environment, the moist air spreads into the sensitive region of the cavity, and then causes perturbation to the induced electric field of the cavity, finally leading to a remarkable change in the resonant frequency. According to the cavity-material perturbation theory ,28, the r sample , Equatiogiven as (4)Eint=A = A should be in the range of 0 AA would be kept as a constant. Its value can be determined accurately using a calibration method. The above theoretical model shows that the fractional frequency shift of the sensor is a function of the RH level. That is, the RH condition of the ambient air can be easily retrieved by measuring the corresponding resonant frequency variation of the sensor.Substituting Equation (4) into Equation (3), we finally obtaindvc) and the spacing between two adjacent vias (svc) should obey the constraint of dvc = 1 mm and svc = 1.4 mm were used in this design. The excitation of the cavity was accomplished using a tapered coplanar waveguide (CPW) feedline with a characteristic impedance of 50 Ω. The geometrical parameters of the final optimized cavity are listed in 11 of these three cavities, as well as their electric field distributions at resonances. For better comparisons, the resonant cavity areas and heights of these three cavities were set to be identical . If its cavity area was not scaled, the DFSIW re-entrant cavity would have the same resonant frequency with the unfolded re-entrant cavity. This can also be demonstrated by the electric field distributions of the cavities  were investigated using the Finite Difference Time Domain (FDTD) method. t cavity . Taking hs were simulated, and the corresponding results are shown in hs. This suggests that the size miniaturization of the sensor can be further enhanced by setting a smaller hs. However, the decreasing hs also contributed to the deterioration of the normalized sensitivity of the sensor  technology. The four layers shown in c were se11 of the sensor was measured using a vector network analyzer (VNA) . Before the measurement, the VNA was calibrated using a standard calibration kit 85052D. In order to verify the repeatability of the sensor, the measurement for each RH condition was repeated at least four times, and the final results are the averaged values of multiple measurements.11 of the designed humidity sensor at 30% RH. It can be seen that the measured results are in good agreement with the simulated ones except for a tiny frequency deviation and a minor decrease in return loss. The frequency deviation could be mainly attributed to the imprecise dielectric constant of the actual substrate or the fabrication tolerance . The amplitude decrease may be caused by the losses incurred from the substrate or the mismatch between the SMA connector and the cavity. The measured loaded Q-factor of the sensor was calculated to be 266. Such a high Q-factor, corresponding to a sharp resonant peak, makes it easier to trace the resonant frequency shift for small variations of RH and, therefore, improves the resolution of the sensor.11 of the designed humidity sensor at different RH conditions. It is clear that the measured resonant frequency of the sensor exhibits a continuous redshift with the increase of RH. This phenomenon is in accordance with the sensing mechanism analyzed in a=ΔfΔ%RH ,24, the A novel DFSIW re-entrant cavity dedicated to humidity detection is presented in this paper. The concept of incorporating folding technology with re-entrant configuration is proposed and is proven to be an effective solution for realizing ultra-compact resonator design. Compared to the conventional circular SIW cavity, the proposed structure has achieved a size miniaturization up to 85.9%. It also can be readily integrated with other planar circuits thanks to the SIW technology. The sensing mechanism of the humidity sensor was analyzed using cavity perturbation theory. It was found that the resonant frequency of the senor behaves as a function of the RH level. Consequently, the resonant frequency was employed as the signature of the sensor to monitor the RH condition of ambient air. A sensor prototype operating at 2.16 GHz was fabricated and its sensing performance was experimentally tested. The measured results demonstrate that in the RH range of 30%–80%, the designed sensor exhibits an absolute sensitivity of 135.6 kHz/%RH and a relative sensitivity of 0.00627%/%RH . The proposed humidity sensor, characterized by a compact size, low cost, high Q-factor, high sensitivity, and ease of fabrication and integration, is expected to find potential applications in environment monitoring or gas sensing.


Background: Antifibrotic agents have been approved for the treatment of idiopathic pulmonary fibrosis (IPF). However, the efficacy of these drugs in the treatment of familial IPF (FIPF) has not been previously reported. Case presentation: We report the case of a 77-year-old man with FIPF, successfully treated with pirfenidone. His uncle died due to IPF, and his niece was diagnosed with the disease. He had worsening dyspnea two months prior to admission to our hospital. Upon admission, he had desaturation when exercising and broad interstitial pneumonia. Administration of pirfenidone improved his dyspnea, desaturation, and the reticular shadow on his chest radiograph. Increased fibrotic marker levels KL-6 and SP-D were also normalized in six months; treatment had no effect on his serum periostin level. Pirfenidone has been effective for over two years. Conclusion: Antifibrotic agents such as pirfenidone may be useful for the management of FIPF, as well as cases of sporadic IPF. MUC5B or telomerase genes has been reported [It is known that familial idiopathic pulmonary fibrosis (FIPF) makes up 0.5% to 2.2% of idiopathic pulmonary fibrosis (IPF) cases , and doereported ,4. HowevA 77-year-old man with no history of smoking was admitted to our hospital due to worsening dry cough and dyspnea on exertion over the previous two months. The previous year, he was tentatively diagnosed with asymptomatic idiopathic interstitial pneumonia (IIP) at another hospital. Reticular infiltrates on computed tomography (CT) examination, performed at the time of his initial admission to our hospital, revealed the progression of IPF when compared with CT images obtained one year previously .Laboratory findings did not reveal any collagen disorders associated with interstitial pneumonia (IP). These investigations, however, did reveal elevated levels of fibrotic markers KL-6 (1448 U/mL), SP-A (66.4 ng/mL), and SP-D 353 ng/mL). The patient also had a familial history of IPF: his uncle had died from it and his niece had the disease. We diagnosed this case as probable usual interstitial pneumonia pattern with bronchiectasis in the lower lung field via the multidisciplinary-discussion approach, and prescribed a low dose of pirfenidone (600 mg/day) for a month and 1200 mg/day for the following month, after which his symptoms of dry cough and dyspnea during exercising improved. Although the history of cough occurrence/persistence was not investigated by the questionnaire, symptoms of dyspnea improved from 2 to 0, as measured by the modified British Medical Research Council (mMRC) questionnaire [3 ng/mL. Written informed consent was obtained from the patient for publication of this article and accompanying images. This work was supervised by the Ethics Committee of Gunma University Hospital (No. 13-66) approved on 15 April 2014.While FIPF is defined as a form of IPF that affects two or more members of the same primary biological family, it is often assumed to have a wider familial definition, with two or more affected relatives . There aCurrently, fibrotic markers such as KL-6, SP-A, and SP-D have not been utilized as markers for IPF diagnosis and/or follow-up of IPF disease activity. It remains unknown if the decreased levels of fibrotic markers reflect the reduced activity of IPF in response to antifibrotic agents because the relationship between serial analysis of fibrotic markers and the physiological variables of IPF has not yet been established. Previously, Collard et al. reported that changes in clinical and physiological variables, such as symptom-based dyspnea score, predicted FVC percentage, and AaPo2 , are predictors of overall survival in IPF patients. Furthermore, serial changes in serum KL-6 levels are associated with changes in physiological variables and can predict survival in IPF cases . RecentlPeriostin is known to be involved in the progression and development of IPF , and theIt is known that periostin is primarily produced by myofibroblasts, but not by bronchial epithelial cells, in pulmonary fibrosis , whereasWe reported a case of FIPF treated with pirfenidone, which may contribute to a therapeutic strategy for its management. Antifibrotic agents such as pirfenidone may be useful for the management of FIPF, as well as sporadic IPF. Furthermore, differential changes in the parameters of fibrotic markers KL-6, SP-D, and periostin may suggest a possible mechanism of the antifibrotic effects of pirfenidone for IPF.


Subsequently, the Pt/Al2O3 lift-off step has been attained using a dimethyl sulfoxide (DMSO) bath. The FLG was grown directly on the patterned Pt seed layer by Chemical Vapor Deposition (CVD). Raman spectroscopy was applied on the patterned area in order to investigate the quality of the obtained graphene. Following the novel lift-off assisted patterning technique a minimization of the de-wetting phenomenon for temperatures up to 1000 °C was achieved and micropatterns, down to 10 µm, were easily covered with a high quality FLG.Graphene and 2D materials have been exploited in a growing number of applications and the quality of the deposited layer has been found to be a critical issue for the functionality of the developed devices. Particularly, Chemical Vapor Deposition (CVD) of high quality graphene should be preserved without defects also in the subsequent processes of transferring and patterning. In this work, a lift-off assisted patterning process of Few Layer Graphene (FLG) has been developed to obtain a significant simplification of the whole transferring method and a conformal growth on micrometre size features. The process is based on the lift-off of the catalyst seed layer prior to the FLG deposition. Starting from a SiO The trachniques ,8. Removchniques  or by elchniques . Finallychniques . As an achniques  or ultrachniques ,14 and Nchniques  films aschniques  ensuringSeveral applications require the use of Pt electrodes coated with graphene. These include atomic force microscope (AFM) tips for nanoscale electrical characterization , frictiom = 1768 °C) and low vapor pressure (1.3 × 10−14 mmHg), Pt is a well-known catalyst for growing graphene by CVD [2 wafers can be also tuned and improved by increasing the thickness of the film [2O3) is preferred as Pt adhesion layer in high temperature applications [Due to the high melting point  followed by 60 nm of Pt (purity 99.99%) by electron beam evaporation  with a deposition rate of 2–3 Å/s, both for Al2O3 and Pt, in high vacuum (<10−5 mTorr) and heating the samples at 150 °C during the deposition process.The proposed novel method is based on the lift-off of the catalyst seed layer prior to the FLG deposition . Single After the deposition, the photoresist was stripped with dimethyl sulfoxide (DMSO) at 50 °C and the samples were rinsed with deionized water (DI) and dried with nitrogen.2/Al2O3/Pt substrates by a cold-wall chemical vapor deposition (CVD) reactor operating at low pressure. To remove contaminants from the surface, a two-step annealing of the substrates was performed: 2 min at 900 °C under reducing flow of Ar at 190 sccm and H2 at 10 sccm (flow control regime) and then 30 s at 1000 °C in an atmosphere composed of Ar 90% and H2 10% at 10 torr (pressure control regime). The growth of graphene was then carried out at 1000 °C for 300 s, in a mixed atmosphere of Ar (80%), H2 (10%) and CH4 (10%) at 10 torr. The samples were finally cooled down to 200 °C under a reducing flow of Ar + H2 (190 sccm and 10 sccm) and then to room temperature in Ar atmosphere.Graphene was grown on Si/SiO2O3/Pt thin films were characterized with field emission scanning electron microscopy (FESEM) after an annealing treatment at 900 °C, 1000 °C and 1050 °C to investigate the high temperature effect related to the CVD graphene growth process. Images were obtained with FESEM ZEISS Supra 40 . For this purpose, the annealing was performed in the same atmosphere and time duration previously described for the growth of graphene but excluding CH4 in the gas mixture.Un-patterned Al2/Al2O3/Pt substrates with the twofold aim of analysing the corresponding crystal structure and orientation and evaluating the effect of the thermal annealing at 1000 °C. XRD patterns were collected using a Panalytical X’Pert Diffractometer  in Bragg-Brentano configuration, equipped with a Cu Kα radiation as X-ray source (λ = 1.54059 Å).X-Ray Diffraction (XRD) was performed on un-patterned Si/SiOPt/FLG substrates were characterized by means of a Renishaw InVia Reflex micro-Raman spectrometer , equipped with a cooled CCD camera. The Raman source was a laser diode (λ = 514.5 nm) and samples inspection occurred in backscattering light collection through a 50× microscope objective for all the single spectra acquisition. The spectra of the patterned structures were obtained by focusing the laser spot on their centre, while a Raman map of the 10 µm-wide circle was collected by scanning, by means of a long working distance 100× objective, a 16 µm × 16 µm area, with a 0.5 µm step. The spectral map analysis was performed by means of the Renishaw WiRE 3.2 software. To collect both the single spectra and the map, 50 mW laser power, 60 s of exposure time and 4 accumulations were employed.Optical images were acquired with a Nikon Eclipse ME600 microscope .2O3/Pt catalyst film.Lift-off assisted patterning of FLG has been successfully obtained  on Al2O32O3/Pt layer at 900 °C, 1000 °C and 1050 °C , a single diffraction peak is detected at 40.1° in both cases and ascribed to the family of Pt(111) crystal planes (JCPDS Card 04-0802). After annealing, the crystal quality of the Pt layers turns out to be improved, as demonstrated by the higher Pt(111) peak intensity. Moreover, the (111) crystal orientation is also highly desirable for promoting graphene growth [2O3 as adhesion layer for this kind of application; indeed, with respect to previous work on a similar process [2O3 prevents a premature de-wetting for e-beam evaporated Pt film.The diffraction spectrum obtained by XRD investigation  shows a e growth . This ch process , Al2O3 p2O3/Pt was characterized by Raman spectroscopy to evaluate the quality of the grown graphene, which according to Wang et al. was about 2–3 layers [The patterned Al3 layers .2 and the correlation between the FLG defectivity and the patterns sizes. Furthermore, growing temperature effect was investigated. Raman spectra of FLG on both un-patterned (red curve) and patterned Pt samples ranging from 5 to 100 µm wide strips were reported (−1 respectively) are similar for the 100 µm patterned and un-patterned areas but the intensity of the D peak differs on the 5 µm pattern. The presence of an ubiquitous peak at ~2324 cm−1 can be related to atmospheric N2 gas fundamental vibration-rotation as previously reported [The analysis was performed with the aim to evaluate the selective growth of FLG on Pt patterns with respect to SiOreported . For thereported .D/IG ratio of ~0.20 are observable. Moreover, the calculated ID/IG is ~0.31 on the 100 µm pattern and ~0.73 on the 5 µm pattern suggesting that the presence of the microstructures could induce a more disordered superposition of the graphene few layers. As pointed out in the review by Ferrari and Basko [−1, 64 cm−1 and 84 cm−1 respectively for un-patterned, 100 µm and 5 µm patterns, which are compatible with the characteristics of FLG grown on a nickel-coated SiO2/Si substrate, previously reported by Park et al. [For the FLG growth on the un-patterned Pt sample, the G peak only differs from the patterned ones in shape and intensity with respect to the D band: a narrower and more symmetric band and an Ind Basko , other fk et al. .Patterned Pt/FLG grown at 900 °C, 1000 °C and 1050 °C was further characterized by Raman spectroscopy . It can 2 carbon with a consistent number of defects as previously reported [reported .2 area, including circle-shaped patterns (10 µm in diameter), was performed. The collected spectral Raman map . The use of a proper adhesion layer, Al


To overcome this drawback, we synthesized ZnO/graphene composites using the combination of a simple hydrothermal reaction and spray drying. These composites consisted of well-dispersed ZnO nanorods anchored to graphene. The folded three-dimensional graphene spheres provided a high conductivity, high surface area, and abundant defects. LIB with an anode composed of our novel ZnO/graphene material demonstrated a high initial discharge capacity of 1583 mAh g The2 , Fe3O4 [2 [3O4 , MnO2 [7 [3O4 [2 , etc., h [3O4 [2 ,10,11, l [3O4 [2 . To over [3O4 [2 , metal-m [3O4 [2  and ZnO/ [3O4 [2 ,16 were  [3O4 [2 ,18,19,20−1 after 100 cycles at 200 mA g−1 current density was obtained for anodes consisting of ZnO/graphene composites [Carbon materials have high electronic conductivity and negligible volume change. In particular, graphene is a very appealing three-dimensional (3D) substrate for various metal oxides ,22 becau−1 at 200 mA g−1 current density. After 100 cycles, the discharge capacity was as high as 886 mAh g−1.Inspired by these results, we also synthesized a high performance ZnO/graphene composite using the combination of a simple hydrothermal reaction and spray drying. Different from that previously reported (10.1039/c7se00102a), we use the spray-drying method to prepare a ZnO/graphene composite which not only can uniformly mix the raw materials but also causes the mixture to form granules. Graphene in the electrode materials forms a three-dimensional conductive network, which will facilitate electron migration. The initial discharge capacity of the anode composed of ZnO/graphene composite as an active material was 1583 mAh g3COO)2Zn·2H2O) were dissolved in 40 mL of deionized water, stirred for 2 h, then transferred into a 50 mL stainless steel vessel and heated at 140 °C for 2 h. Finally, the resultant ZnO were collected and washed by deionized water five times and then dried under vacuum overnight.First, 0.8 g of sodium hydroxide (NaOH) and 0.2 g of zinc acetate . First of all, graphene oxide (GO) was prepared according to Hummers’ method and diluted by distilled water to obtain a GO suspension with a concentration of 2 mg mLComposites were tested by X-ray diffraction  from 10° to 80° of 2θ at 12 °/min. Scanning electron microscopy  was implemented using Hitachi S-4800. Transmission electron microscopy  images were obtained using a JEOL-2100F operated at 200 kV. Raman spectra and X-ray photoelectron spectroscopy were recorded by Lab RAM HR800  and Thermo Scientific K-Alpha XPS spectrometer , respectively. The thermogravimetric analysis  was carried out under oxygen using a TGA Q600 system. Cyclic voltammogram (CV) curves were performed by an electrochemical workstation  in a voltage range of 0.01–3.00 V.−2. Coin-type (CR2032) half-cells were assembled in an argon-filled glove box using these anodes as well as lithium foil as a counter electrode and Celgard 2300 as a separator. The electrolyte was 1.0 M LiPF6/ (EC + DMC + DEC + EMC) (with the 1:1:1:3 ratio by volume). The galvanostatic charge–discharge tests were conducted using Neware battery tester  in the 0.01–3.0 V voltage window (vs. Li+/Li).Then, 80 wt% ZnO/graphene composite, 10 wt% Ketchen black and 10 wt% polyvinylidene fluoride (PVDF) were mixed in 1-methyl-2-pyrrolidinone (NMP) to form a slurry and applied onto the Cu foil by a draw-down blade. After drying at 60 °C for 12 h, 9 mm disks were punched that served as anodes. The ZnO/graphene loading amount of each electrode sheet was around 2 mg cmThe preparation process and structure diagram of of ZnO/graphene composite is depicted in All XRD peaks matched to the pattern of hexagonal ZnO (PDF#36-1451)  is 1.03, indicating a high degree of defects of graphene in the composite, which can facilitate Li+ transportation during charge and discharge cycling. Weak peaks between 250 and 500 cm−1 can be attributed to ZnO.Raman spectroscopy of the ZnO/graphene composite showed two peaks at ~1346 and 1581 cm−1 see , which bIn order to investigate the quality of the graphene in the ZnO/graphene composite, the thermogravimetric analysis (TGA) of the ZnO/graphene was performed under oxygen see . The weiXPS showed only Zn, O and C, confirming the high purity of the synthesized ZnO/graphene composites. Peaks at 1021.2 and 1044.1 eV can be attributed to Zn 2p 3/2 and Zn 2p 1/2, respectively. Peaks corresponding to the graphene functional groups were observed at 283.4 eV for the C-C bond, 284.3 eV for C-O bond and 287.4 eV for C=O bond see c. Intens−1. The discharge curve for the first cycle of the ZnO/graphene electrodes at 200 mA g−1 showed a plateau at 0.5–0.7 V, which can be linked to the reduction of ZnO into Zn. A platform at ~1.2 V on the corresponding charge curve was because of the reappearance of ZnO from Li–Zn alloy and Zn [−1, respectively. Such a big difference is very likely due to the solid electrolyte interphase (SEI) formation as well as to the incomplete Zn oxidation relative to the initial ZnO amount. Charge and discharge capacities for the second cycle of the ZnO/graphene anode were the same, demonstrating good electrode stability. Compared with the ZnO/graphene composite, both the pure ZnO and graphene revealed low initial capacity , the discharge capacity increased to 859 mAh g−1 when cycling was performed again at 200 mA g−1. It can be observed that the ZnO/graphene anodes have a better rate of performance than pure ZnO and pure graphene anodes, indicating the good rate capability of the ZnO/graphene anode.Our rate capability tests showed discharge capacities equal to 938, 835, 718, 582 and 508 mAh gvely see e. After −1. Decomposition of the electrolyte and formation of the solid electrolyte interface on the surface of electrode particles also occurs during the first cathodic cycle, which causes part of the irreversible capacity [2Zn3, LiZn2, and Li2Zn5). Another bigger anodic peak at 1.26 V is attributed to the back-conversion of Zn and Li into ZnO [capacity . During into ZnO .ZnO/graphene composites were prepared by the combination of a simple hydrothermal reaction and spray drying. ZnO was prepared by a hydrothermal reaction and ZnO/graphene composites 2–5 μm in diameter were achieved during the second step of spray drying. ZnO nanorods in the composite overlapped with each other and were tightly wrapped in graphene. Graphene enhanced the conductivity of the composite electrode and served as a buffer for the volume change. The synergistic effect of graphene and ZnO gave the cell excellent cycle stability. The results illustrated that micro-spherical ZnO/graphene composite material is an excellent candidate as an anode material for LIBs.