Overall, this work opens three prominent favorable prospects: exploring the usage of nano-materials prepared by liquid phase exfoliation approach, their effective usage in ion-transport membrane region of MEA and enhancing fuel cell power performance.Graphene, in spite of exceptional physio-chemical properties, still faces great limitations in its use and industrial scale-up as highly selective membranes (enhanced ratio of proton conductivity to fuel cross-over) in liquid alcohol fuel cells (LAFCs), due to complexity and high cost of prevailing production methods. To resolve these issues, a facile, low-cost and eco-friendly approach of liquid phase exfoliation (bath sonication) of graphite to obtain graphene and spray depositing the prepared graphene flakes, above anode catalyst layer (near the membrane in the membrane electrode assembly (MEA)) as barrier layer at different weight percentages relative to the base membrane Nafion 115 was utilized in this work. The 5 wt.% nano-graphene layer raises 1 M methanol/oxygen fuel cell power density by 38% to 91 mW·cm A massive increase in population, day-to-day technological improvements and their related projects, in this era have prompted exponential needs in our energy supply ,2,3. In In spite of LAFC’s advantages, its commercialization is greatly hindered by excess fuel crossover (or permeability) issues degrading power performance at both short and long time-scale operations ,6. Fuel To reduce the impact of this crossover issue so as to improve the power performance of the fuel cell, a barrier layer is applied between the anode electrode and membrane region in their membrane electrode assembly (MEA) ,9. Previ−1·K−1), mechanical stability (Young’s modulus of 1 TPa), electron mobility , surface area (2630 m2·g−1) and optical transparency (97.7%) [From a materials perspective, graphene, the first in the 2D materials family gets enhanced importance due to its exceptional physio-chemical properties: high thermal conductivity (5000 W·m (97.7%) ,14. Espe (97.7%) ,16. This (97.7%)  and Su e (97.7%)  where grFurthermore, Hu et al.  have shoThis concept was utilized in an actual fuel cell system by Holmes et al.  and Yan Xu et al.  used graConsidering the drawbacks of all the previous reports and in an effort to widen the horizons of this research, in this work we have used graphene from liquid phase exfoliation–bath sonication of graphite and utilized them as a barrier layer— showing an effective membrane with high selectivity (proton conductivity to fuel crossover ratio) for performance improvements in various LFACs—methanol, ethanol and propanol, respectively.N-methyl pyrrolidone (NMP), acetone, dimethyl sulphoxide (DMSO), 1,2-dichloro benzene (DCB), acetophenone, water, benzonitrile, 1,4-dioxane) and subjecting to exfoliation by bath sonication [Liquid phase exfoliation involves dispersion of the precursor in a solvent , using spray deposition, which is considered easier compared to the transfer process from furnace to electrode where CVD is used and the mechanical exfoliation method was used ,28,29,30These 2D materials from liquid phase exfoliation methodology were reported to have been utilized in several opto-electronic applications (solar cells and thin film transistors), nano-sensors and nano-composites ,24. To tIn the fuel cell membrane region, it is known that methanol permeability (MP) and proton conductivity are inter-related ,7,8. To The results are evaluated by materials characterization (atomic force microscopy (AFM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) with elemental mapping and Raman spectroscopy), electrode/membrane characterization—fuel permeability (MP—methanol permeability in case of methanol fuel usage) , water uptake, ion-exchange capacity, proton conductivity, fuel oxidation propensity (FOP)—oxidation current and peak oxidation potential, electrode reaction resistance (ERR), wettability and fuel cell polarization curves  at different fuel concentrations and temperatures.Overall, this work of utilizing a liquid phase exfoliation approach of graphene synthesis, usage as a barrier layer on the anode side of MEA using simple spray deposition and with significant power performance increments obtained, will lead to advantages in multiple fronts: improving the commercial standpoint of LAFCs (efficiency and durability improvements as reported), influx of various liquid exfoliated 2D materials as high selective membranes into the fuel cell field and their further mechanism exploration studies.3)2CO) medium exfoliation, as analyzed thoroughly by previous studies [The above results confirm the exfoliation of multiple carbon layers (40 µm thick) containing graphite onto a few layers of graphene with ~2–4 µm size, as illustrated schematically in the  studies ,15. Thes studies . Further−1, compared to graphite, indicates evaluation of defects and disorders in a sample arising from the exfoliation process [−1) confirms that the material is of few layers [ process ,32. The w layers . These oMore precise information obtained from atomic force microscopy (AFM) and their corresponding surface profiles (marked in grey line) taken for different samples, shows that flake thickness is of 2–5 nm a–d 33,3,35. ThesTo precisely estimate the effect of graphene, this spray was deposited at: 2.5 wt.%, 5 wt.%, 7.5 wt.%, 10 wt.%, 20 wt.% and 25 wt.% values (0 wt.% graphene is noted as standard) on the anode electrode  and evaluated. It can be seen that the average crack separation length changed for the 5 wt.% graphene electrode c, comparChanges in crack separation length are crucial, as previous studies by Hiramitsu et al. , MohseniSince water transport changes also affect the methanol, which has direct influence on power performance ,5,6, it Electrode porosity  by weight loss method offers enhanced simplicity compared to gas-liquid porosimetry methods, and pertains to methanol/water transport in their structure ,39. SimiHence, electrode porosity and contact angle values of different electrodes are determined as explained in the experimental procedure and given in The hydrophobic porosity of electrodes increased with the graphene content, (60% to 73%), higher than that of standard electrode (60%). This is due to high carbon to oxygen (C/O) of 4.5 of the prepared graphene from electron dispersive spectroscopy (EDS) results, compared to platinum (and Nafion ionomer)-containing standard, which are well known for their water-affinity nature. The similar trend is observed in the contact angle measurements due to the above reasons. Studies by Bera et al.  and otheThese changes in hydrophobicity and contact angle values of the electrodes, along with the crack separation (as observed earlier) are expected to play a role in the water/methanol repelling characteristics of the electrode (as previous studied well in literature) and it will be interesting to observe the power performance.Water uptake (WU) and ion-exchange capacities characteristics of a MEA gives an understanding of proton conductivity since protons undergoes Grotthus mechanism movement through functional groups of the membranes ,6,7. HenFrom Membrane characterizations results (methanol permeability (MP), electrochemical mode) and proton conductivity were carried out, as explained in the experimental section and tabulated in It can be seen that MP, electrochemical mode values decrease with the increase in graphene weight percentage, showing that this graphene acted as a barrier layer, preventing fuel permeability thereby preventing undesirable fuel oxidation on the cathode. Meanwhile the proton conductivity has shown a declining trend, indicating that this layer though reduced MP has caused hindrance to proton conductivity. Hence, it can be inferred that the water-repelling nature of the graphene  has resulted in reduced methanol permeation. −1, indicating this layer prevented fuel permeation at the same time minimally affecting proton transfer route.Calculating membrane selectivity for all samples, the 5 wt.% graphene exhibited a high value of 0.77 mS·cm·mA−1) and oxygen (250 mL·min−1) operating parameters, as best standard power performance is obtained in these conditions. To test their effect in fuel cells, standard and graphene-containing membrane electrode assemblies (MEAs) are compared at 60 °C cell temperature, 1 M methanol  has reduced to 110 mA·cm−2, compared to 150 mA·cm−2 for the standard  than 210 mA·cm−2 for the standard —methanol oxidation current of 270 mA·cmstandard b. Also, −1—calculated from x-axis intercept (2) are lower than the standard (1.35 Ω·cm2), (Impedance spectroscopy plot shows that this 5 wt.% graphene barricade layer has reduced proton conductivity from 100 to 85·mS·cmntercept c. Howeve Ω·cm2), c reflectMP results by gravimetric modes as shown in −2 (standard) to 45 mW·cm−2 for 10 wt.% graphene, then to 29 mW·cm−2 for 20 wt.% graphene. This is due to the dominant impact of proton resistance on cell performance  and 75% (22 mW·cm−2 peak power density compared to 12 mW·cm−2 for the standard) performance improvements at 5 and 10 M concentrations, which are far higher than at 1 M concentration power performance results (36% improvement) as shown in polarization curve (voltage and power density profile) in Testing at high methanol concentration is essential, as this can be of great use for comparison to commercial portable sources, henceforth carried out at 5 and 10 M concentrations ,8,9. The−2. Durability testing aids in evaluation of graphene stability for prolonged periods of time henceforth carried out for 20 h at constant current density of 50 mA·cmAfter durability testing, minor reductions in open circuit voltage, peak power density and selectivity values are observed. This is attributed to the dissolution of graphene from the fuel cell electrode due to the high flow rate of incoming fuels. This is evident from top view  and crosIt well-known that graphene prevents ethanol and propanol flow through its channels ,14,15, hOverall, 2D graphene prepared by facile liquid phase exfoliation approach has been utilized as a barrier layer onto the anode side  due to its imparting high selectivity to the membrane region (fuel passage prevention characteristics) and thereby enhanced improvements in performance in methanol/ethanol/propanol systems are obtained. Starting from material characterization results, the high C/O ratio of prepared graphene has aided in enhanced hydrophobicity to the fuel cell electrode, whereas few layer thicknesses resulted in insignificant proton resistance. Combined effect of water/fuel transport on the anode due to changes in electrode crack separation, reduced fuel crossover , enhanced fuel oxidation on anode side and barrier effect have led to high membrane selectivity. This is depicted in the Using this at low weight percentages—5 wt.%, has resulted in 40%, 56% and 75% improvement in 1, 5 and 10 M methanol concentrations in addition to enhancements in ethanol and propanol systems. These beneficial effects are also observed at ethanol and propanol fuel cell systems over a wide temperature range (20 °C to 60 °C). Further increasing the graphene weight percentage (stacking), gives poor performance due to the dominant effect of proton transfer resistance affecting selectivity. In comparison to the previous work reported  the results obtained in this work offer advantages in various prospects: ease in preparation of graphene, utilization methodology, controllability, short- and long-term performance and diverse usage in various LAFCs, which are given in −2, rather than acetone in this work, effect of sonication time, centrifuge speed and duration), studying the effect of flake size, and testing in formic acid, ethanol, hydrogen fuel cells will be of significant interest and be the follow-up of this work.Also efforts like improving the efficiency of exfoliation  are dispersed in pure acetone (Fischer Scientific) and bath sonicated  for 1 h. The exfoliated dispersion is centrifuged at 5000 rpm for 1 h . The supernatant is collected and stored for further testing, whereas thick flakes settled at the bottom are discarded.Graphene from liquid phase exfoliation methodology was prepared according to the procedure by Coleman et al.  as follo−1 Raman shift) studies.Graphene dispersions in acetone were drop-casted (10–20 µL volume) on silicon wafers  and dried 48 h in an oven  at 200 °C, prior to atomic force microscopy (AFM) , scanning electron microscopy (SEM) (with energy dispersive spectroscopy (EDS) surface morphology analysis/elemental mapping by Hitachi S-3400 equipment, Hitachi High-Tech Corporation, Chaoyang District, Beijing, China) and Raman characterizations  with polytetrafluroethylene  in 10 wt.% in iso-propanol . After spray-coating this was placed in an oven (Quincy lab 10 GC model) at 150 °C for 1 h and 70 °C overnight.The MEA was fabricated as described in the procedure ,41 as fo−2 for both anode and cathode was reached. Catalyst ink contains catalyst (60 wt.% platinum on Vulcan XC-72 for cathode and 60 wt.% platinum: ruthenium on anode—from Fuel Cell Store) with 15 wt.% Nafion  in acetone (bath sonicated and stirred to obtain a homogeneous ink).Then catalyst ink is sprayed above the MPL, till a platinum loading of 1.5 mg·cmPolymer electrolyte membrane—Nafion 115  was pre-treated by heating in de-ionized water , 10 wt % hydrogen peroxide  and 1 M sulphuric acid (98% purity from Fischer Scientific and diluted) solutions at 80 °C for an hour, approximately. Then, this is placed between the anode and cathode electrode and fixed in fuel cell test system at 1.5 N·m pressure using Checkline DTW 100f  wrench.−1 of 1 M methanol and 250 mL·min−1 (2 bar) of dry oxygen  by p2) on the anode electrode above the catalyst layer. All other materials and deposition methods used in the MEA preparation, remained the same.In this work, graphene is sprayed at different weight percentages, 2.5 wt.%, 5 wt.%, 7.5 wt.%, 10 wt.%, 20 wt.% and 25 wt.%  is obtained by using DC power supply  by sweeping current from zero to maximum and recording the voltage by multimeter , till the voltage value reaches zero ,41.n-decane (Fischer Scientific) solvent, followed by weighing, where porosity is calculated from the difference in weight of electrodes before and after immersion and then divided by the density of n-decane as described in the procedure [Electrode porosity is obtained by immersing the electrode in pure rocedure ,38.Hydrophilic porosity is obtained by placing the sample in a lab-made set-up, where the electrode is exposed to incoming water vapor as illustrated in the −1) and nitrogen (2 bar—200 mL·min−1) on the cathode, in the fuel cell (anode side as working electrode and cathode as reference/counter electrode) from 0 to 1 V as described in the procedure [This is obtained by running cyclic voltammetry  by passing fuel (methanol or ethanol or propanol depending on experiments) on the anode (10 mL·minrocedure .These are obtained by running impedance spectroscopy (potentiostatic mode) in electrochemical work station CHI 660 model, China, in a working fuel cell at 0.4 V, with the cathode side as working electrode and the anode as a reference/counter electrode, in the frequency range from 25 kHz to 0.02 Hz at an amplitude of 5 mV as described in the procedure ,37. X-ax−1 by passing 10 mL·min−1 of methanol on the anode side and passing 200 mL·min−1 of nitrogen (2 bar pressure) on the cathode side by connecting the working electrode to the cathode and reference/counter electrode to the anode. The value of current plateau at which methanol oxidation becomes constant is noted as ‘MP current density’ and is carried out as described in the procedure from other work [MP  is obtained by running linear sweep voltammetry and scanning from 0 to 1 V at rate of 5 mV·sher work .MP (by gravimetric mode) measurement is carried out in the lab-made set up as given in Electrode wettability (by contact angle) is attained by placing a 20 µL drop of water on a fuel cell electrode and the contact angle was measured between the droplet and the electrode surface after 60 s, using a KRUSS surface analyzer camera ,45,46.MEA) and immersing in water for 24 h (for obtaining wet MEA weight—WetMEA). The difference in weight of the dry and wet sample gives the percentage of water uptake (WU) as given in Equation (2) below. All these measurements are carried out as described in the procedure [MEA—Weight of the wet MEA (grams) and DryMEA—Weight of the dry MEA (grams). WU is attained by drying the MEA at 50 °C for 24 h in an oven  approach of graphite in acetone medium and utilizing them as barrier layer by mounting them next to the membrane on the anode side  in direct liquid alcohol fuel cells (LAFCs) involving methanol, ethanol and propanol systems is proposed. The material characterizations by atomic force microscopy (AFM), Raman spectroscopy and scanning electron microscopy (SEM), show that graphene is of 2–5 nm thickness and 4 µm uniform lateral size.−2. This barrier layer reduces the methanol permeation (MP) from 153 to 112 mA·cm−2, with slight decrease in proton conductivity from 101 to 84 mS·cm−1, which has led to better methanol utilization—overall improving membrane selectivity (proton conductivity to fuel crossover ratio).The cell performance tests exhibit that 5 wt.% graphene barrier layer, at direct methanol fuel cell (DMFC) testing conditions (60 °C and 1 M methanol), increases the maximum power density from for the standard 63 to 91 mW·cmThis methanol barrier effect is more visible at highly concentrated methanol operations, where 36% and 75% improvements in fuel cell performance are observed. Long-term testing for 20 h also confirms this effect by displaying minimal voltage losses.2) and molybdenum di sulphide (MoS2) to be used as barrier layers, overall pushing the commercial circle of direct LAFCs.This newly reported work tends to eliminate limitations by using liquid phase exfoliated graphene as a barrier layer due to its feasibility, environmental friendliness and mass production characteristics—yielding few layer nano-materials, posing competition to expensive and complex—chemical vapor deposition (CVD) and mechanical exfoliation methods, in addition to power performance improvements. This also opens new possibilities for other crystals: hexagonal boron nitride (hBN), tungsten di sulphide (WS


It is widely accepted that solid‐state membranes are indispensable media for the graphene process, particularly transfer procedures. But these membranes inevitably bring contaminations and residues to the transferred graphene and consequently compromise the material quality. This study reports a newly observed free‐standing graphene‐water membrane structure, which replaces the conventional solid‐state supporting media with liquid film to sustain the graphene integrity and continuity. Experimental observation, theoretical model, and molecular dynamics simulations consistently indicate that the high surface tension of pure water and its large contact angle with graphene are essential factors for forming such a membrane structure. More interestingly, water surface tension ensures the flatness of graphene layers and renders high transfer quality on many types of target substrates. This report enriches the understanding of the interactions on reduced dimensional material while rendering an alternative approach for scalable layered material processing with ensured quality for advanced manufacturing. A study of a newly discovered graphene‐water membrane is accomplished. It provides a promising technique for high‐quality graphene process with ultra‐high flatness, and free of defects, leveraging the high surface tension of pure water. These advantages enable high‐performance device fabrication for electronic and biological research. These membranes provide outstanding operational flexibility for the transfer process, but inevitably lead to concerns about mechanical deformation, contaminations, and trapped interfacial residues that impact the performances of graphene‐based devices. On the other hand, graphene process assisted with liquid membranes has rarely been explored or reported before, due to the assumption that liquid surface tension could potentially damage the graphene integrity, or it is impossible to establish free‐standing and stable graphene‐liquid membrane structures.Solid‐state membranes, including polymethyl methacrylate (PMMA),1 para quantum devices, micro‐electromechanical systems, and flexible biosensors.Here, we report a newly observed graphene‐water membrane (GWM) structure, which refreshes our understanding of graphene‐liquid interaction, meanwhile rendering a new material process procedure. We thoroughly investigate the formation mechanism of the as‐observed GWM, particularly the roles of surface tension and contact angle playing, and discover that the GWM enables a new graphene transfer method that directly renders free‐suspended layer or on‐substrate film with improved flatness, thanks to the high water surface tension, which has long been misinterpreted to jeopardize the graphene transfer process. Further, the GWM transfer eliminates residuals induced by conventional solid‐state membranes, inspiring high‐quality and contamination‐free graphene process pathways toward the subsequent development of novel graphene‐based electronics,5 quan2Figure with a leakage rate lower than 10–9 bar cm3 s−1 to minimize defects induced by oxygen during the growth.  Following the growth, we preserve the graphene on one side of the copper foil, while etching the layer deposited on the other side with argon plasma. In this process, instead of protecting the desired surface with polymer coating, we designed a plasma treatment fixture, as demonstrated in Figure −1 ammonium persulfate ((NH4)2S2O8) water solution for copper etching for 3 h, leaving monolayer graphene on the etchant surface. Due to the high surface tension of water (72 mN m−1), the thin copper film and the finally released graphene float freely on the surface and are confined by a polyethylene terephthalate (PET) frame with a 1 × 1 cm2 opening in the center. Subsequently, we exchanged the etchant with deionized (DI) water and rinsed the monolayer graphene several times to remove all ions, including Cu2+ generated during the etching step illustrated in Figure  In contrast, we did not observe any deformations generated through the entire process, suggesting CVD graphene can stand the high surface tension of DI water as long as the graphene quality is carefully preserved. Otherwise, defects developed during growth and physical damage due to improper handling indeed impair the graphene layer, bringing cracks, wrinkles, shrinking, etc., as shown in Figure With the preserved graphene layer facing up, the copper foil is relocated into a specially designed reactor  of monolayer graphene is in the range from 1.05 to 1.1 TPa. Considering a graphene thickness (t) of 0.33 nm, we can calculate the strain (ε) on monolayer graphene induced by the water surface tension (γwater) via the equation:A potential concern of the GWM is whether the large surface tension can tear the graphene layer after it is lifted from the water surface. To determine this, we performed the following analysis. The Young's modulus  1.1 TPa.10 Con10 ConE3D) is provided by the surface tension (γl) of water in the form of D = 2γl. The force per unit width (P) required to peel the graphene can be derived from the energy balance between the work done by the peeling force and the variation of graphene/liquid interfacial energy,θsl denotes the contact angle between graphene and water, and α labels the peeling angle as defined in Figure D ≥ P, i.e., Theoretical prediction resulting from Equation  simulations on the entire peeling process. A graphene film with 4 nm x 10 nm was placed on the surface of the liquid and peeled by applying a mechanical force with the peeling angle of 57.5° at a velocity of 1 nm nsEquation  with wattion , a stable GWM forms when free‐floating graphene is peeled out of the water surface with a frame structure. This observation refreshes our understanding of graphene‐water interaction and exhibits a new hybrid membrane structure that inspires us with a new large‐scale polymer‐free graphene process technique with excellent outcomes.4FigureOne obvious benefit of this GWM is the ensured cleanness of the graphene layer by eliminating the usage of PMMA or other supporting media for processing. Thus, small organic molecules dispersed in the air turn out to be the only contamination source, which can be readily removed by afterward annealing. Indeed, the transition electron microscopy (TEM) image shown in  Figure 2 openings. The inset magnification exhibits the uniform and flawless graphene layer. This one‐step graphene suspension can be attributed to the high graphene quality, and more importantly, the reduced amount of water adhered to the graphene surface when the GMW forms, as indicated by our molecular dynamics simulation that no water adheres to the graphene layer  = 4:1) to remove organic residues thoroughly. Figure  To further confirm the microscopic structure and flatness, we conducted an atomic force microscopy (AFM) study on the graphene transferred with our new method and confirmed a low morphology roughness  of the surface height) of 1.5 nm, as demonstrated in Figure The GWM can also be leveraged for graphene transfer onto many types of substrates. Briefly, we can readily pick up the free‐floating graphene layer from the water surface with the PET retainer, then align and laminate it onto the target substrate, as shown in  target substrates are typically fully merged into the transfer liquid  used in our study. The improvement in graphene flatness drastically enhances its electronic performance. For example, compared with the conventional polymer‐free transfer method shown in Figure One primary reason for this drastic improvement can be attributed to the water film, which bridges the PET frame and graphene layer while stretching and flattening the atomic layer with its surface tension, as explained by Equation . Another22 tarFigure2 frame was patterned on Si substrate  to achieve the graphene growth later at 1000° C by controlling methane (CH4) flowrate at 35 sccm and a mixture of argon and hydrogen (Ar 90%: H2 10%) at 6 sccm.A homebuilt CVD system had been used to grow the monolayer graphene. It is electropolished 0.025 mm copper foil (CU000358 from Goodfellow) is mainly 80% phosphoric acid (H4)2S2O8) (from Sigma‐Aldrich) in 200 ml of DI water to prepare 0.1 M concentration.To etch copper, it is dissolved 4.56 g of ammonium persulfate  is used. All the FET devices were annealed after fabrication at 300° C for one hour under vacuum. Finally, it is shaped to transfer graphene to narrow channels (width = 1 mm) using radiofrequency argon plasma and the strips’ shadow masks.We fabricated shadow masks by following photolithography methods. Later, the electrode shaped mask to deposit Cr 5 nm AuRaman study on suspended and on‐substrated graphene was performed with 785 and 514.4 nm excitations, respectively. AFM scanning of graphene on the Veeco MultiMode AFM system under tapping mode is performed. The measurements of electron mobility on graphene FET devices were done on a homebuilt probe station combined with a source meter unit . SEM was performed on a Zeiss Merlin FE‐SEM system, and the STEM imaging was captured at room temperature using a Nion UltraSTEM U200 microscope operated at 60 kV. Graphene with a width of 4 nm and a length of 10 nm was placed on the surface of the liquid mixture of water and IPA with 42 000 water molecules. The simulation box size for peeling was 9.947 nm × 20.4192 nm × 20.0 nm, and the adaptive intermolecular reactive bond order modeled flexible graphene. The SPC/E and TraPPE‐UA potential models were adopted for water and IPA molecules, respectively. For the nonbonded interactions, the 12–6 pairwise Lennard–Jones potential V (r) = 4ε(σ12/r12 − σ12/r12) and Coulomb interaction qV (r) = iqjq/4πε0r were applied where r is the interatomic distance. At the same time, σ and ε are the equilibrium distance and the interactive well depth of the potential, respectively, iq and jq are the electronic charge counterpart, and ε0 is the permittivity of the vacuum. Specifically, the Lennard–Jones parameters for graphite‐water interaction were σCO = 3.19 Å and εCO = 0.00407 eV. The cut‐off distance was 1 nm in this study. The Lorentz–Berthelot mixing rule was used to determine the inter‐L–J parameters for different components. The particle–particle‐particle–mesh algorithm with a root mean of 0.0001 was used to minimize the error of long‐range Coulombic interactions. All simulations were run in an NVT ensemble with a Nose/Hoover thermostat set at 300 K unless otherwise stated.All graphene layers employed in this study had a size of about 7 mm × 7 mm, and the GWM has a size of 1 cm × 1 cm. The graphene roughness RMS of the three types of transfer was measured from Veeco AFM Nanoscope software. All MD simulations were carried out by the Large‐scale Atomic/Molecular Massively Parallel Simulator package.23 GraThe authors declare no conflict of interest.Supporting InformationClick here for additional data file.


The monolayer graphene feedthrough exhibits a minor resistance increase from 22.5 Ω to 31 Ω after anodic bonding, showing good electrical conductance. The pressure of the vacuum chamber is estimated to be 185 Pa by measuring the breakdown voltage. Such a vacuum is found to maintain for more than 50 days without obvious degradation, implying a high sealing performance with a leak rate of less than 1.02 × 10−16 Pa·m3/s.On-chip microscale vacuum chambers with high sealing performance and electrical feedthroughs are highly desired for microscale vacuum electronic devices and other MEMS devices. In this paper, we report an on-chip microscale vacuum chamber which achieves a high sealing performance by using monolayer graphene as lateral electrical feedthrough. A vacuum chamber with the dimensions of π × 2 mm × 2 mm × 0.5 mm is fabricated by anodically bonding a glass chip with a through-hole between two Si chips in a vacuum, after monolayer graphene electrodes have been transferred to the surface of one of the Si chips. Benefiting from the atomic thickness of monolayer graphene, the leak rate of Si–glass bonding interface with a monolayer graphene feedthrough is measured at less than 2 × 10 Micro-Electro-Mechanical System (MEMS) devices have attracted much attention due to their compact size and low cost. Many MEMS devices, such as gyroscopes , RF devi−8 Pa·m3/s [Electrical feedthroughs in MEMS devices can be summarized as being in two classes: vertical feedthrough and lateral feedthrough. Vertical feedthrough usually achieves a conducting channel by drilling a via-hole through a glass  or silic Pa·m3/s . To ensu Pa·m3/s . An easyGraphene, a one-atom-thick nanomaterial, has been of wide interest in recent years . Its monA sandwich-like on-chip microscale vacuum chamber was constructed by anodic bonding. The schematic structure of the device and its fabrication processes are shown in 2 (500 µm/300 nm) chip was first treated by reactive ion etching (RIE) with O2 plasma for hydrophilicity [2 chip, as shown in 2 chip ) with a semiconductor characterization system (Keithley 4200). It can be seen from the image that both of the I–V curves have a good linear relationship. The resistance of the graphene electrode is 22.5 Ω before bonding and 31 Ω after. Such a resistance is better than many other devices using lateral [As shown in  lateral  or verti lateral ,19,20, wOn-chip microscale vacuum chambers often require high sealing performance, so airtightness of bonding interface is a very important issue. The bonding interface’s airtightness with respect to the two-layer device shown in 2–glass bonding interface  and the pressure P (Pa) of the intervening gas. For large gaps (d > 100 μm [BV(V) asA and B are two fitting parameters, γ is the second Townsend coefficient which describes the mean number of generated secondary electrons per ion. Parameters A = 10.95 Pa−1m−1, B = 273.78 VPa−1m−1 in air are well determined by ref [Pd. As Pd increases, BV first decreases to a minimum at several hundred Volts and then increases again. At low pressures, few collisions require high probability of ionization, so a higher electric field is needed. At high pressures, short mean free path makes it difficult for electrons to accumulate enough energy to reach ionization energy, which also requires a higher electric field, resulting in a minimum in Paschen’s law.Paschen’s law  describe> 100 μm ), the “Pd by ref . EquatioBV was 2192.5 V. Taking P = 1.01 × 105 Pa, d = 0.5 mm, A = 10.95 Pa−1m−1, B = 273.78 VPa−1m−1, VB = 2192.5 V, the second Townsend coefficient is calculated as 0.57 according to Equation (1). Therefore, the parameter values of Paschen’s law are A = 10.95 Pa−1m−1, B = 273.78 VPa−1m−1, γ = 0.57, which will next be used to estimate the vacuum level of a three-layer device with a microscale vacuum chamber.We first prepared a three-layer device by stacking Si–glass–Si chips in the air without bonding, with the sizes of the glass spacer and the Si chips the same as those described above. The gap between electrodes in our configuration is 0.5 mm, which is well above the microscale boundary where Paschen’s law may deviate due to field emission . The meaA simple apparatus was developed to test the breakdown voltage of our device, as shown in 6 s (50 days) within the allowable range of errors. The breakdown voltage corresponds to a pressure of the chamber of 185 Pa according to Paschen’s law with the above determined parameters. Considering the flow resistance caused by our bonding apparatus and the residual gas generated in the bonding process and released from inner surfaces, such a vacuum level is reasonable [PV in the chamber with time is obtained, as shown in PV (difference between maximum and minimum) is no more than 4.6 × 10−10 Pa·m3, the leak rate is estimated to be under 1.02 × 10−16 Pa·m3/s. Although the vacuum degree of the microscale vacuum chamber is not good enough for some high-vacuum applications, the result shows that using monolayer graphene as lateral feedthrough could maintain a vacuum of 185 Pa and a leak rate of less than 1.02 × 10−16 Pa·m3/s for about two months, realizing a high sealing performance. In the future, a high-vacuum microscale chamber using a graphene electrode as lateral feedthrough could be realized by improving the bonding process to further improve the initial vacuum degree of the chamber.Finally, a microscale vacuum chamber device using a graphene electrode as lateral feedthrough with a high sealing performance was fabricated shown in g. The brasonable  and can asonable  to the c2–glass bonding interface with a monolayer graphene feedthrough was measured to reach the measurement limit of the detector, namely less than 2 × 10−11 Pa·m3/s. For a bonded three-layer device with a microscale chamber, the pressure of the chamber was estimated as 185 Pa and had been maintained for more than 50 days. During this period, the leak rate was less than 1.02 × 10−16 Pa·m3/s, achieving a high sealing performance. In summary, the on-chip microscale vacuum chamber using graphene as lateral feedthrough is a reliable, simple and promising electrical feedthrough solution for vacuum electronic devices and other MEMS devices.In this paper, an on-chip microscale vacuum chamber with dimensions of π × 2 mm × 2 mm × 0.5 mm was fabricated, where a graphene electrode was innovatively used as a lateral electrical feedthrough. The monolayer graphene feedthrough shows a slight increase in resistance from 22.5 Ω to 31 Ω after anodic bonding, showing good electrical conductance. Benefiting from the atomic thickness of monolayer graphene, the leak resulting from the height difference between the electrode and the substrate surface was reduced, which effectively improved the sealing performance. The leak rate of Si/SiO


We pattern the platinum film, after which a CVD graphene layer is grown at the interface between the SiO2 and the Pt. After removing the Pt, Raman spectroscopy demonstrates the local growth of monolayer graphene on SiO2. By tuning the CVD process, we were able to fully cover 4-inch oxidized silicon wafers with transfer-free monolayer graphene, a result that is not easily obtained using other methods. By adding Ta structures, local graphene growth on SiO2 is selectively blocked, allowing the controlled graphene growth on areas selected by mask design.Since the transfer process of graphene from a dedicated growth substrate to another substrate is prone to induce defects and contamination and can increase costs, there is a large interest in methods for growing graphene directly on silicon wafers. Here, we demonstrate the direct CVD growth of graphene on a SiO Since the discovery of graphene in 2004, it has become increasingly clear that the exceptional electronic, optical and mechanical properties of this material can lead to revolutionary new devices. Next generation transistors, RF circuits, optoelectronic devices and sensors with huge performance merits might become feasible. For producing such devices in high-volume and creating hybrid circuits comprising both graphene and silicon devices, it is highly desirable to integrate them with advanced complementary metal-oxide-semiconductor (CMOS) technology.To realize this integration , productIn modern CVD processes, graphene is grown on foils, or thin films of transition metals, the most common of which are: Cu, Ni, Mo and Pt. For CMOS integration, the graphene needs to be transferred from these foils onto a silicon wafer. There are several ways to achieve this , but theThis transfer-based CVD graphene integration route has the advantage that the growth of graphene can be optimized completely independently from the substrate, enabling high-quality graphene to be integrated, without exposing the substrate to high temperatures. However, it also poses challenges, since the transfer procedure can result in imperfections in the CVD graphene due to (polymer) contamination, membrane fracture, wrinkling, and strain non-uniformities . The graConsidering the aforementioned drawbacks of transfer-based graphene flows, it is of interest to investigate alternative ’transfer-free’ methodologies, where the graphene is grown directly on the substrate, such that the transfer process can be eliminated. However, the number of substrates on which graphene can be grown has appeared to be limited. Moreover, the high electrical conductivity and reflectivity of the transition metal substrates that are commonly used for graphene growth prohibit many device applications. A notable exception appeared to be silicon carbide, which allows direct growth of single-layer graphene on its surface and is still a strong contender for enabling graphene integration, despite the high price of crystalline silicon carbide wafers limiting production volumes.An alternative route towards transfer-free graphene growth on silicon wafers is the use of a seed layer that is deposited on top of the substrate wafer for growing graphene. For such growth using a seed layer, the transition metals Cu, Ni, Mo and Pt, on which CVD graphene growth has been established, are logical choices. With Mo and Pt being the preferred seed materials, since Ni and Cu tend to form silicides or diffuse into the silicon faster.During the last years, it was shown that few-layer CVD graphene can be grown on Mo seed layers  that are2/Pt interface, as shown in 2 interface, after which the Pt seed layer is removed. This process reduces organic contamination, mechanical stress and other potential challenges of transfer-based process flows. Moreover, we show that an additional intermediate, adhesion layer of thin film of Ta metal between Pt and SiO2 can locally inhibit the graphene growth with designed patterns. A similar study has been done by implementing a Ni thin film as a seed layer [In this work we explore another route toward transfer-free graphene integration by using Pt seed layers in a process flow where graphene grows beneath the seed layer, at the SiOed layer ; howeverPlatinum was one of the first transition metals that was used as a substrate for graphene CVD growth ,17,18,19When graphene is grown on Cu or Ni foils, the foil is often etched away after the growth process. However, Pt foils are costly, and reuse of the foils is therefore often preferred, which has led to the development of processes to delaminate the graphene from the Pt surface , or grow2, thin platinum PVD films with a thickness of 50 nm are evaporated from a Pt target (99.95% purity). The platinum films are annealed at 1000 °C under atmospheric conditions or in nitrogen gas at 1 bar for 60 min, resulting in a typical Pt grain size of ∼0.5–1.0 µm as observed from the SEM and AFM, see 2 and ∼12.6 nm for N. Since differences were small we will further on only present results using the nitrogen anneal. This pre-anneal was found to be essential to prevent dewetting of the Pt film during subsequent growth of graphene and overall improves the continuity of graphene deposition.A 100 mm silicon wafer with a 90 nm thick film of thermally grown silicon dioxide is used as base substrate. On top of the SiO2 gas at a pressure of 25 mbar, at 950 °C, while using methane gas as carbon atom precursor. Subsequently, the whole system is gradually heated up to 920 °C and kept stable for about 5 min before adding methane to the CVD chamber. For graphene growth, a CH4 gas flow of 30 sccm is applied for a duration of 150 s, after which the sample is cooled down. For ensuring high quality graphene growth, a fast cool-down of the sample at a rate of 50 °C/min was applied.Graphene is deposited on these substrates using an Aixtron BlackMagic Pro cold-wall CVD system in a mixture of Ar and H2 surface and subsequent patterning by lift-off. Subsequently, a Pt thin film was evaporated, and graphene was grown using the same method described above. Ta was chosen for its high-temperature compatibility and because it withstands the aqua regia Pt etchant.Besides the growth on blanket wafers, graphene was also grown on substrates with patterned Ta structures, as shown schematically in 3 (99%)) in 4 min and subsequently the wafer was rinsed in DI water and air-dried.To assess whether graphene grows under the Pt seed layer like in c, the PtThe presence and the quality of graphene was investigated by a Renishaw inVia Reflex Raman spectrometer. The Raman microscope is equipped with a He-Ne laser (−1 was found, close to that of monolayer CVD graphene [−1 was found. Similar spectra were taken at different positions on the wafer, from which a mean integrated peak ratio 2 before Pt deposition and CVD graphene growth. Using Raman spectroscopy after Pt removal, it was established that graphene was only present on the SiO2 in between the Ta structures, and not on the Ta structures. A Raman spectrum of graphene on SiO2, with peak ratio and FWHM corresponding to monolayer graphene, is shown in terature ,27,28 ha2/Pt interface, since the adhesion forces between these surfaces are weak because Pt does not form chemical bonds with the SiO2 surface. Possibly, the low surface roughness of the SiO2 will promote the flatness and quality of the graphene growth and the purity of the layer might be increased by the requirement for the carbon atoms to diffuse through the Pt. Although no Raman signs of graphene growth were found on top of the Pt layer, we cannot fully exclude its presence since the Raman signal of graphene on Pt is very weak [2/Ta interface because of the chemical bonds between Ta and SiO2, and the low diffusivity of carbon in Ta at the graphene growth temperature [2 interface, we present an optical micrograph of the wafers with patterned Ta after CVD graphene growth in 2, which might both be a cause and an effect of the CVD graphene layer growth between SiO2 and Pt. Besides acting as a blocking layer, the Ta metal might be used as electrode material. However, in the characterized samples it was observed that no electrical contact was formed between the graphene on SiO2 and the Ta metal. Additional process steps, or local etching of Pt might be used to establish electrical contacts.The basic mechanism ,30 of inery weak . We alsoperature . As addi2. The high diffusivity of carbon in Pt, the high melting temperature and the high chemical inertness and catalytic activity of platinum metal make it ideally suited to promote the discussed growth mechanism. The ability to grow graphene directly on silicon substrates is clearly advantageous, since it circumvents the need for potentially detrimental graphene transfer steps. Moreover, we demonstrated selective graphene growth by using Ta thin films, which omits the need for graphene patterning steps. By process tuning, the quality of the graphene can probably be much further improved and integrated to provide a path towards high-quality graphene devices in application areas for sensing, data processing and high-speed communication.We present a route for the direct growth of graphene on a silicon dioxide surface at the interface between Pt and SiO


Exposure to green spaces contributes to residents’ physical and mental health and well-being. The equitable allocation of green space has also become an increasingly important issue for society and the government. This study takes 3281 communities in Shenzhen as the analysis units. Using web crawlers, semantic segmentation based on deep learning, web map path planning and entropy weighting methods, four types of residents’ daily green exposure indicators are calculated, including community green space ratio, green view index (GVI), park accessibility, and the weighted composite green exposure index. The results reveal inequalities in the level of green exposure in Shenzhen’s communities across economic classes, mainly in GVI and comprehensive green exposure. We also found that the level of composite green exposure is relatively stable; however, green space ratio attainment levels for newer communities are increasing and GVI and park accessibility attainment levels are decreasing. Finally, among the newly built communities: compared to the low-income level communities, the high-income level communities have a significant advantage in green space, but the mid-income level communities do not have such an advantage. The main findings of this study can provide policy implications for urban green space planning, including the need to prioritize the addition of public green space near older communities with poor levels of green exposure, the addition of street greenery near communities with poor levels of composite green exposure, and ensuring that parks have entrances in all four directions as far as possible. In the context of Chinese cities, one of the most common concerns is socio-economic inequality. Indeed, studies reveal that China has shifted from a relative doctrine of equality to a society marked by increasing economic disparity since the policy of the socialist-oriented market economy .The public resources represented by green spaces can increase housing prices in the surrounding communities ,3,4. EspThis article attempts to quantify the equity of community green exposure. The potential mechanism of human exposure to green space has been referred to as green exposure ,9,10. WeLabib et al., based on the definition of green exposure provided in the existing studies, classified the concept of green exposure into availability, visibility, and accessibility . FirstlyGreen space is a common generalized term used to describe natural areas in urban environments, such as parks, community gardens, and public green spaces ,19,20. TIn previous green exposure assessment studies, the green space objects are mainly parks, and few studies capture the problems of finer-scale green space . In factEarly on, urban green land ratios and per capita green areas were used to reflect the spatial construction level of urban green space in different regions; later, urban green space was studied for spatial equity and social equity . Urban pAccess to green space is a significant environmental justice issue. It means that everyone has the right to be protected from specific environmental issues (such as pollution and climate change) and to obtain standard services (green spaces) . Green sMladenka et al. use empirical evidence from Chicago to show that socio-economic class may be a determining factor in the distribution of green space . NumerouAs technology continues to evolve, there are breakthroughs in acquiring community built-up time data and quantifying new types of green data. Firstly, obtaining community built-up time data published by developers on real estate transaction websites allows for a comparative assessment of green exposure in communities with different built-up periods. Community green space ratio from real estate websites can also support fine-scale assessment of green space within communities ,51. SecoIn summary, most existing green justice studies focus on park-oriented green objects, ignoring the fine-scale greenery that community residents are more frequently exposed to ,27,43. MIn other words, the latest data and methods are bringing fresh research possibilities to the fore. Our study incorporates green equity measures into more green data and introduces a time-based perspective to evaluate many types of green exposure levels in communities of different economic levels. This could help to accurately assess community green space equity and propose more precise green strategies.2, 980 km2 of which were built-up areas, and the city’s resident population had reached 17.6 million; with the city’s built-up area greening coverage rate of 43.38%, and a built-up area green space rate of 37.36%, the greening indicators ranked among the top in the country [Shenzhen is near Hong Kong and is part of the Pearl River Delta. Shenzhen has become one of China’s most populous and inventive cities since the Special Economic Zone was established in 1979. Although Shenzhen’s urban spatial structure is polycentric, there is a clear difference in urban development between the north and the south, based on the central boundaries of the city. At the end of 2020, the city covered an area of 1995 km country . HundredThe city is divided into ten administrative districts, as shown in Data access.https://sz.fang.com/ (accessed on 30 March 2021)) by the web crawler, which is one of the top three trading platforms for online housing in China. It was the first to be established and covers the largest data and number of website hits. The community data was gathered using the crawler technique, which included particular location, price, community kind, community age, and green space rate. Ultimately, after data clearance, we obtained information on 3281 observations in Shenzhen.Communities’ data were captured on the FANGTIANXIA website  to obtain each community’s latitude and longitude coordinate information. The residential points were projected onto a base map in ArcGIS. Using the Baidu Maps API (Application Programming Interface), a search was made by latitude and longitude of each community to obtain the actual boundaries of each community .2.Community economic classification.3281 communities were divided into five equal numbers of partitions ,17. Then3.Community built-up period classification.The particular year of housing reform, 1998, characterized by privatization and marketization, was used as the dividing point ,16, follThe community green space ratio is almost unchanged since the community was built, while the street greenery and parks (amount) are generally getting better all the time. Note that, due to the time limitation of street view images (SVIs) and park data acquisition, we only assessed the community green space by the current state of urban green space. Communities of different built-up periods were then grouped to compare their green exposure level.Green space data was collected in and around communities, including green spaces within the community, green spaces in streets around the community, and urban parks.Community green space.2.Street greenery.The vegetation in the street view images collected using the Baidu Map API is depicted in 3.Park.As shown in Community green space data is obtained directly from real estate websites and reflects the ratio of community green space to the total community area.Shenzhen Urban Planning Standards and Guidelines (2013), the width of urban roads in Shenzhen is 12 to 80 m. Therefore, a 100 m buffer can cover the sampling points around the community.The visibility metric represents the green space that community residents can see and perceive on the street. This study defines the resident activity area as the Euclidean buffer zone of 100 m around the community boundary outwards (excluding the community itself). The reason for choosing this distance is that, according to the The pyramid scene parsing network (PSPNet) is a pixel-level object detection and classification method that generates solid semantic segmentation results, with pixel-level accuracy of more than 80.2% . It has Finally, each community’s GVI is the average of the GVI values of all street points within the community’s 100 m boundary buffer. Each community has an average of 45 street points within its buffer zone, with a minimum of 10 points.Accessibility indicators describe the distance from the community to the nearest park. As the location of households in each community varies, when regarding departure points, using the community center point as the departure point can be considered the average location for all community residents to depart from. Regarding destinations, we defined the centroid and entrances of green spaces as destinations according to the level of the green space ,60,61. TAmap is a web map similar to Google Navigation ,62. A maStandard for urban residential area planning and design (GB50180-2018), a 30% green space rate was selected as the benchmark for community green space attainment. Next, the 10 min (800 m) walking distance was selected as the benchmark for park accessibility, based on the Spatial planning guidance to the community life unit (TD/T1062-2021). Finally, there is no national-level evaluation standard for street greening in China. Referring to the official document issued by the Ministry of Land, Infrastructure, Transport and Tourism, which is responsible for urban construction in Japan [Considering that different green spaces have different contact standards, we produced an evaluation standard through the normative standards of different green spaces. First, drawing on China’s residential area design code, in Japan , a 25% gStandardization of green indicators.Using standardized and entropy methods to calculate the comprehensive green evaluation index of each community, which is comprehensive in order to consider the green exposure level of the community, the calculation steps are as in Formulas (2) to (5):The level of community green exposure varies considerably under the same green indicator. To measure more the difference between the level of green exposure and the ideal standard , this stPositive indicator:Inverse indicator:2.Determination of green indicator weights.n is the total number of elements.The chi-square test is a very versatile hypothesis test for counting data, the purpose of which is to compare the degree of agreement or goodness of fit between the theoretical and actual frequencies. This method was used in this study to verify whether there was a significant difference in the level of green space compliance between high- or mid-income level communities and low-income level communities.If the results of the chi-square test are not significant, the original hypothesis cannot be rejected. It indicates that high- or mid-income level communities tend to have no significant difference in the attainment level of green exposure from low-income level communities; conversely, if the results of the chi-square test are significant, the original hypothesis is rejected. It indicates that high- or mid-income level communities tend to differ significantly from low-income level communities in terms of their attainment level for green exposure.Finding areas with weak levels of community green exposure.n is the total number of elements; The local Getis-Ord Gi* index is a local spatial autocorrelation index based on a distance weight matrix that detects high-value and low-value aggregation. This study analyses the degree of community green exposure aggregation at the local spatial level. The calculation formula is as follows.2.The spatial relationship between communities’ age and price and green exposure levels.N-by-N Euclidean distance weighting matrix for the spatial correlation between Using global bivariate Moran’s I, the spatial connection between community price and three forms of green exposure was studied. With the following computation steps (8) and (9), these analyses were used to examine spatial correlations across the research area :(8)IP,A=The values of bivariate Moran’s I range from −1 to 1. For the bivariate Moran’s I with statistical significance, the positive and negative values indicate spatial aggregation  and spatial fragmentation , respectively . The cluSpecifically, the structure of the data is shown in The spatial distribution of green spaces ratio, GVI, and accessibility was analysed in hotspots (Getis-Ord Gi*), and the results were visualized . The LuoUsing the baseline values of green space ratio, GVI, and accessibility, entropy values and weights were further calculated . FinallyFurther analysis through the hotspot analysis  reveals Standard deviation ellipses are commonly used to describe the spatial characteristics of geographical distributions, such as trends in concentration, dispersion, and trends in the direction of distribution . This stThe spatial distribution of communities of different economic classes is shown in The results of green space levels in communities of different economic classes are shown in After the level of green exposure has met the specification, absolute equality is no longer sought. Therefore, we further counted the level of attainment rates for green exposure in communities of different economic levels, and the results are shown in The results of our study in Shenzhen show that communities in central urban areas benefit more from public green facilities (GVI and park accessibility) than those in non-central urban areas. However, the central urban areas of Luohu and Futian district have a poorer community green space ratio. In comparison, the non-central areas have a better community green space ratio. Differences in community public green space are attributed to Shenzhen’s spatial distribution of green space resources. In contrast, private green space differences are attributed to communities’ built-up period.Firstly, we present an overview of the public green facilities. The Code of urban Residential Areas Planning & Design (GB50180-93), introduced in 1993 and implemented in 1994, began to emphasize the requirement for a green space ratio in communities, which means that the green space ratio in newly built communities should not be less than 30%. On the one hand, the earlier (pre-1994) built communities were not subject to this design standard; on the other hand, the later communities were mostly gated, and the concept of community green space began to take form and was gradually taken into account [Next comes private greenery, where the age of the community heavily influences the level of community green space.  account . So the p < 0.01), revealing a positive spatial correlation between year of community completion and green space rate. The relationship between community age and green space ratio is further shown in the clustering diagram of the local bivariate Moran’ I index , respectively  built-up communities, the attainment rates for the three green space levels and the comprehensive green exposure level have been almost equal between low-income and mid-income levels. Even in the communities built from 2004 to 2013, the attainment rates for park accessibility levels in low-income level communities have been significantly stronger than those in mid-income level communities.Low-income level communities were used as the control group, and mid-income and high-income level communities were treated as the experimental group, respectively. The chi-square test in SPSS was used to explore whether there were significant differences in the attainment rates of green space ratio, GVI, accessibility, and comprehensive green exposure indicators between the groups of communities of different economic levels at different built-up periods.The chi-square test results further confirm our view . OverallFinally, among the most recently built-up communities (2014–), only high-income level communities have a significant advantage over lower-income level communities in terms of park accessibility and comprehensive green exposure levels, with mid-income level communities no longer having a significant advantage. This is a phenomenon showing less social inequality, as access to qualifying levels of green space is not very different for all but the wealthiest.New communities are increasing their green space attainment rates based on the development trend of the built-up period. Still, GVI and park accessibility are generally lower than in previously built communities. These figures suggest the rising level of private greenery and the declining level of public greenery.Private green spaces.The relationship between the timing of community completion and green space rates is explained in the previous Public green spaces.On the one hand, current green space planning in China is based on a ‘top-down’ model, which, due to land constraints, does not complement public green space as easily as private community green space. Previously built-up communities already occupy good locations, and even in the same area new communities can only gradually move away from public green space. On the other hand, with the rapid growth of cities and the increasing size of built-up areas, the suburbanization of the residential population is a common phenomenon in large cities. However, urban green space is expanding slowly and has become a scarce resource, creating a spatial mismatch between its supply and demand .Urban renewal in downtown communities.With the level of private green space tending to be consistent across different economic classes and communities, the planning of public green space is a major concern for future green justice. Urban renewal and the suburbanization of green spaces have raised the level of green exposure in high-income and low-income level communities. This is why high-income level communities maintain the highest level of public green space most of the time, while low-income level communities can surpass the level of public green space of mid-income level communities during a certain period (2004 to 2013). Typical cases are as follows:A 74F super high-rise residential development located in the heart of Shenzhen’s downtown area, at Baishi Zhou, is surrounded by excellent greenery, with the OCT National Wetland Park to the east and the Dasha River Ecological Promenade to the west, both within a 10-min walk. This part of the residential block is planned to be built on the site of the old Baishi Zhou urban village redevelopment project. In urban regeneration, high-income inhabitants will be drawn to newly developed communities, while former low-income people will be screened out as part of the environmental gentrification process; approximately 150,000 low-income Baishi Zhou inhabitants have been displaced to low-quality communities on the edge of the city.The suburbanization of green space.Communities within the center of Longgang district in the northeast of Shenzhen, which are mostly of low-income level, have benefited from the Greenland suburbanization strategy. Because the 2011 Shenzhen Universiade was held right in the center of the Longgang district, the big event led to massive investment in green infrastructure, including new parks and improved street greening. Public green spaces in the region have been significantly enhanced . RegardiThe 2008 Olympic Games in Beijing and the 2010 Youth Olympic Games in Nanjing were also major sporting events. However, the venues tend to be on the edge of the downtown area and not really in the city’s suburbs. The results did not enhance the green infrastructure for low-income groups ,72.The impact of this trend on residents is not as bad as one might think. Firstly, the community green exposure attainment level trended consistently across economic classes (excluding low-income level communities in the period 1980–1993 to 1994–1998), reflecting social equity ; privateThe communities’ comprehensive green exposure level remains stable, suggesting some substitution between the various types of green space. Similarly, Zhang et al.  and XiaoFirstly, green space planning can be improved by considering communities’ green needs at different economic levels. Woo and Webster point out that traditional public goods provided by the government, such as urban green spaces, may be partially or completely replaced by club goods . TherefoSecondly, we have studied spatial inequalities between the three types of green space in Shenzhen, which can help municipalities and planners to identify where and what they should invest more resources in to improve communities’ green exposure. In Shenzhen, this work has identified a gap: only 31.3% of communities meet all three basic objectives for green space simultaneously, with the vast majority (68.7%) of the remaining communities still not meeting it. Previously, we have added up the scores of the three green indicators for the community with the help of Standardization and Entropy Weighting and then analysed them based on the hotspot analysis . FurtherIn practical terms, community green spaces and parks are difficult to change; meanwhile, Xu et al. confirmed through VR experiments that streets with high GVI could replace places such as parks and green spaces as places for residents to release their stress . TherefoFinally, creating new parks is essential, but parks are the most difficult green spaces to add because of land and economic constraints. The ParkScore index by The Trust for Public Land (TPL) suggests that, in some cases, cities can improve park accessibility by adding new park entrances . That isNearly 70% of Shenzhen’s municipal parks currently do not guarantee access in all four directions, and about 30% of municipal parks have access in only one to two directions, indicating that there is still much potential to improve accessibility. Specifically, as in It should be added that our emphasis is on the concept’s feasibility rather than the precise layout of each park entrance.The equitable distribution of green space is becoming more recognized as an issue of environmental inequality in China. This study uses multi-source big data to explore the green exposure inequality in built-up communities over time. The results show that: (1) green space ratio, GVI, accessibility, and comprehensive green exposure levels of Shenzhen’s communities are unevenly distributed among different economic classes, with lower-income level communities having poorer green exposure. (2) Compared to the old communities, the newly built communities have a higher green space ratio, lower GVI, and the comprehensive green exposure level scores remain stable. (3) Among the newly built-up communities, high-income level communities have a significant green space advantage over low-income level communities, but the difference between the mid-income and low-income level communities is not significant.This study implies that, firstly, the differences in the level of community green space may be related to the uneven spatial distribution of green space resources in Shenzhen. Then, the differentiation of urban residents’ needs and abilities allows people with high economic attributes to live in communities with better levels of green space, building gaps in the level of community green space among different economic classes. Secondly, the level of private green space in newly built-up communities is increasing, while the level of public green space is decreasing. This trend is influenced mainly by residential design regulations and land constraints, but is not very bad, as green spaces are interchangeable. Finally, government planning for green facilities includes ‘green gentrification’ and green space planning derived from major (sporting) events. It has continued to give upscale communities a significant green space advantage and has helped close the green space gap between low and midscale communities.For future green space planning, three policy implications are highlighted: (1) street greening should be enhanced in areas with weak performance in terms of comprehensive green exposure levels, (2) communities with poor private green spaces should be prioritized to enhance public green spaces around them, and (3) accessibility should be enhanced by ensuring that parks have entrances in every direction as far as possible.Our study has some limitations. Firstly, the GVI indicator is calculated from the greenery within 100 m of the community boundary, which is only relevant to those residents living directly within the community boundary. People whose daily activities pass through these areas also benefit from GVI. Secondly, park accessibility only takes into account the distance from the community to the nearest park and does not take into account the quality and quantity of parks within a certain range. Finally, some fee-paying parks were excluded from the study, but they may meet the daily use needs of some wealthy people. For example, residents of the community surrounding Happy Valley Park who have an annual pass can obtain free daily access to the fee-paying parks. The benefits of access to parks for the wealthy may have been underestimated.


Ultra-sensitive and responsive humidity sensors were fabricated by deposition of graphene oxide (GO) on laser-induced graphene (LIG) electrodes fabricated by a low-cost visible laser scribing tool. The effects of GO layer thickness and electrode geometry were investigated. Sensors comprising 0.33 mg/mL GO drop-deposited on spiral LIG electrodes exhibited high sensitivity up to 1800 pF/% RH at 22 °C, which is higher than previously reported LIG/GO sensors. The high performance was ascribed to the high density of the hydroxyl groups of GO, promoted by post-synthesis sonication treatment, resulting in high water physisorption rates. As a result, the sensors also displayed good stability and short response/recovery times across a wide tested range of 0–97% RH. The fabricated sensors were benchmarked against commercial humidity sensors and displayed comparable performance and stability. Finally, the sensors were integrated with a near-field communication tag to function as a wireless, battery-less humidity sensor platform for easy read-out of environmental humidity values using smartphones. Humidity sensors play an important role in many industrial and day-to-day life applications including environmental monitoring, smart agriculture/home, health, consumer electronics, and the IoT ,2,3,4. U2 lasers) of polyimide films leads to the formation of an electrically conductive laser-induced graphene (LIG) material [3 carbon atoms into sp2 carbon atoms and the formation of conductive and porous structures [−3% RH [In recent years, direct laser writing methods have been extensively used for the fabrication of graphene-like materials on flexible polymer substrates ,25. In tmaterial ,27,28. Pructures ,25. The ructures ,30 and fructures  and biosructures  for enviructures ,34 and hructures . Recentlructures . In anot [−3% RH .In this work, we fabricated ultrasensitive humidity sensors by the combination of spiral LIG electrodes and GO layers. A 450 nm laser was used. The sensors displayed a wide operating range (0–97% RH), excellent stability, and short response/recovery times. Sensor functionality was studied in the temperature range of 19 °C–27 °C. The effect of GO thickness was investigated, as well and the difference between spiral and interdigitated electrode geometries. In its optimized conditions, the sensor exhibited sensitivity of 1800 pF/% RH at 22 °C and response/recovery times shorter than 16 s. The sensor was also integrated into a near-field communication tag to function as a wireless, battery-less humidity sensor that could read environmental humidity values using a smartphone.3COOK), magnesium chloride (MgCl2), potassium carbonate (K2CO3), magnesium nitrate (Mg(NO3)2), copper chloride (CuCl2), sodium chloride (NaCl), potassium chloride (KCl), and potassium sulphate (K2SO4) were purchased from SIGMA ALDRICH and used directly without any further modification. Polyimide films with a thickness of 80 μm were purchased from Radionics and used without further treatment. All solutions were prepared using deionized Milli-Q water .Sodium hydroxide (NaOH), lithium chloride (LiCl), potassium acetate  on the LIG electrodes. GO was synthesized based on a two-step oxidation process, as previously reported , where s−1 nominal spring constant of the cantilever. Raman Spectra were taken with at 514.5 nm (2.41 eV) laser using a MicroRaman  setup. The laser power was kept below 1.5 mW on the sample to avoid laser-induced local heating, while an Olympus MPLN100x objective (NA = 0.90) was used to focus the beam on the samples. The XPS measurements were carried out in an ultra-high vacuum system (UHV), which consists of a fast entry specimen assembly, a sample preparation, and an analysis chamber equipped with a dual anode (Al/Mg) X-ray gun and an LH10 electron analyzer. The base pressure in both chambers was 1 × 10−9 mbar. The unmonochromatized MgKα line at 1253.6 eV and an analyzer pass energy of 36 eV, giving a full width at half maximum (FWHM) of 0.9 eV for the Au 4f7/2 peak, were used in all XPS measurements. The XPS core level spectra were analyzed using a fitting routine, which can decompose each spectrum into individual mixed Gaussian-Lorentzian peaks after a Shirley background subtraction. The sample was mounted onto a Si substrate with dimensions 1.5 × 1.5 cm2. Finally, the capacitance and impedance of the sensors were recorded by a computer-controlled LCR .The morphological characterization of the obtained sensors was performed by a cold-cathode field-emission scanning electron microscope  operating at a 5 kV acceleration voltage. AFM images of the sensor surface were collected by contact mode . Images were obtained using ScanAsyst-Air probes  with a 0.4 N m2 flow, which provided a stable and controlled RH level at their equilibrium states in a closed container 2, CuCl2, NaCl, KCl, and K2SO4 in a closed vessel were used to obtain approximately 7.5%, 11%, 23%, 33%, 43%, 53%, 67%, 75%, 85%, and 97% RH levels, respectively  and sensitivity (S), determined by R = C/C0 = (Cx − C0)/C0 × 100% and S = (Cx − C0)/(RHx − RH0), where Cx and C0 are the capacitance of the sensor at the x% and 0% RH levels, respectively. For stability and repetitive measurements, a custom-made relative humidity chamber was designed for rapid switching between high and low relative humidity, at a constant temperature of 22 °C. This gas flow system is displayed in 2 flows were used for the system. The humidified air was created using two bubble systems at 50 °C and 22 °C, respectively, while for the dry air, the N2 flow was used. Finally, the different RH levels were achieved by different mixing ratios of the two flows. In addition, a commercial humidity and temperature sensor, AM2302, was used to monitor and record the humidity and temperature in the chamber, which was controlled by an Arduino UNO.vely see b. A 0% RHumidity sensors were fabricated by drop-casting GO aqueous solutions of different concentrations on LIG spiral electrodes fabricated by direct laser writing of polyimide, as illustrated in γ . In addiγ : C=. The recovery time was the time interval from the last value at 80% RH until the capacitance reached 90% of the minimum value at 0% RH (Cmin × 1.1). The recorded response time was 16 s. The recovery time was also fast, with the sensor reaching its initial capacitance value in 9 s. Furthermore, the sensor exhibited a maximum hysteresis of 3.03% at 75% RH, which was calculated based on the absorption and desorption characteristics of An in-depth characterization of the effect of GO concentration was performed. x − C0)/(RHx − RH0). Based on the capacitance values (at 500 Hz) observed in x − C0)/C0 × 100%. As shown in 3, 3430 × 103, 3604 × 103, and 11,710 × 103% were calculated for the same RH range, for the sensors developed using 0.33, 0.67, 1.33, and 2 mg/mL GO dispersions, respectively. Both R and S can be considered as figures of merit for the sensors—they express the variation of capacitance in the measured range and its fluctuations in each RH level, respectively.The sensitivity of all sensors see  was calc2) than the active area of the spiral electrodes (265 mm2). The sensing film consisted of a 50 nm GO film in both cases. 3%. However, the response and recovery time 2 solution. After an equilibrium period, the vessel was placed in the cooling chamber for 2 h, and then, it was placed under the room conditions. It was observed that both sensors instantaneously detected a drop in absolute humidity at the beginning of the cooling process, due to the lower solubility of water in the atmosphere at decreasing temperatures. The absolute humidity response of both sensors began to increase after two hours, signaling the beginning of the heating cycle, where the solubility of water molecules in the atmosphere increases as a function of temperature.Finally, the integration of the GO/LIG relative humidity sensor with a battery-less near-field communication (NFC) device was performed to demonstrate fast interrogation of the sensor using a smartphone. The developed sensor was connected to a capacitance-to-digital converter (CDC), which was interfaced with a microcontroller unit (MCU) using the Inter-Integrated Circuit (I2C) protocol, as shown in fCLK) = 0.524 MHz; I2C core input clock (fI2C_IN) = 1.028 MHz; MCU core voltage (VCORE) = 1.2 V; supply voltage (VDD) of 2.1 V. As a result, the NFC-enabled humidity sensor required a peak DC power of just 900 µW, which is one of the lowest reported in the literature [In the presented design, both voltage and frequency scaling (VFS) techniques were used to minimize the DC power consumption of the developed sensor with the aim to maximize the wireless communication range. To achieve sub-mW DC power consumption, the NFC-enabled humidity sensor was designed with optimal settings: MCU peripheral clock  was taken into consideration, and it was found that the higher surface area of the spiral design had a positive effect on the sensitivity. Compared to similar GO-based humidity sensors, the GO/LIG platform displayed comparable or superior sensitivities, a wide RH range, stability, and short response and recovery times. Finally, towards practical applications, the sensor was integrated with an NFC tag that enabled humidity readings through a commercial smartphone.


Physiological saline is an indispensable element for maintaining the functions of life. The spreading performance of physiological saline droplets on the surface of graphene under different NaCl concentrations and electric field intensities was studied in the present work. The results show that the increase in NaCl concentration reduces the displacement vector value of molecules in droplets. In addition, NaCl is easy to aggregate on the surface of graphene. The increase in NaCl concentration makes it more difficult for droplets to penetrate the surface of graphene, and the penetration angle of droplets increases with the rise in NaCl concentration. With the increase in electric field intensity, the wetting effect of droplets is more obvious. The greater the electric field intensity is, the smaller the penetration angle is, which is mainly due to the polarity of water molecules. This study has reference significance for the study of body fluid volatilization on the human surface. Sweat is an indispensable substance in human body and has the functions of maintaining body temperature, accumulating energy, and maintaining cell activity and human function . HoweverThe evaporation and diffusion of nano-droplets is a relatively novel research method that has many potential applications in the fields of DNA chip manufacturing, medicine, inkjet printing, surface coating, and self-assembly based nanostructure formation ,12. SimiThe simulation of molecular dynamics (MD) is widely used in materials, machinery, medicine, aerospace, and other fields to study the physical and chemical properties of microscopic substances ,17,18. MAs a large number of fluid substances are distributed on the skin’s surface, human sweat has an important heat-transfer function on this surface. This is also an important factor affecting athletes’ long-term, high-load exercise under high-temperature conditions ,26,27. H2O and NaCl molecules outside the black circle were deleted to obtain the initial model shown in The molecular simulation software Materials Studio (MS) was employed to create the simulation model. Firstly, the disordered simulation structure in The well-known software of Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) is utilized to undertake all the calculation work . The intThe local displacement distributions of physiological saline droplets with 0% and 6% NaCl concentration were extracted, as shown in 2O in the droplets and the surface of graphene have polarity and presence of electric field exerts a directional force on it, making H2O break the binding of surface tension and have a strong interaction with the surface of graphene [Compared with the effect of NaCl concentration on the infiltration of physiological saline, the effect of the electric field on physiological saline droplets is more obvious. The infiltration of droplets with 26.35% NaCl concentration was extracted, as shown in graphene ,34,35.The density distribution of droplets is of great significance to understand the infiltration mechanism of droplets on the surface of graphene. 3, 0.21 g/cm3, and 0.24 g/cm3, respectively) under higher electric field intensity. Under a high-intensity electric field, due to the decrease in droplet height, the diffusion space of NaCl molecules was sharply compressed, and the NaCl concentration in droplets was higher and more uniform.In order to explore the effect of electric field intensity on droplet density distribution, the concentration distribution of the simulation system with 26% of NaCl concentration was extracted, and electric field intensities of 0.02 V/Å, 0.04 V/Å, 0.06 V/Å, and 0.08 V/Å were applied. As shown in In this section, we explore the effects of droplet concentration and electric field intensity on the contact angle of droplets on the surface of graphene. In this paper, the infiltration of physiological saline droplets on the surface of graphene under different NaCl concentrations and different electric field intensities was studied. The results show that an increase in NaCl concentration reduces the displacement value of molecules in droplets. At the same time, the displacement of the molecules in the contact area on both sides of the droplet is much higher than that in the middle of the droplet. In addition, the increase in NaCl concentration increases the overall concentration of droplets, and the NaCl is easy to aggregate on the surface of graphene. The increase in NaCl concentration makes it more difficult for droplets to infiltrate on the surface of graphene, and the contact angle of droplets increases with the increase in NaCl concentration. The effect of voltage intensity on droplet infiltration is much greater than that of NaCl concentration. With the increase in electric field intensity, the infiltration effect of droplets is more obvious. The droplets were completely tiled on the surface of graphene under an electric field intensity of 0.08 V/Å. The larger the electric field intensity, the smaller the infiltration angle, which is mainly due to the polarity of water molecules and graphene. This study has reference significance for the study of body fluid volatilization on the surface of human skin.


Three coumarin-based boron complexes  were designed and successfully incorporated into polymeric matrixes for evaluation as temperature probes. The photophysical properties of the complexes were carried out in different solvents and in the solid state. In solution, compound L1 exhibited the highest fluorescence quantum yield, 33%, with a positive solvatochromism also being observed on the absorption and emission when the polarity of the solvent increased. Additionally in the presence of anions, L1 showed a colour change from yellow to pink, followed by a quenching in the emission intensity, which is due to deprotonation with the formation of a quinone base. Absorption and fluorescence spectra of L1 were calculated at different temperatures by the DFT/B3LYP method. The decrease in fluorescence of compound L1 with an increase in temperature seems to be due to the presence of pronounced torsional vibrations of the donor and acceptor fragments relative to the single bond with C(carbonyl)-C (styrene fragment). L1, L2 and L3, through their incorporation into the polymeric matrixes, became highly emissive by aggregation. These dye@doped polymers were evaluated as temperature sensors, showing an excellent fluorescent response and reversibility after 15 cycles of heating and cooling. The combination of conventional fluorophores into a single hybrid structure containing a difluoronated boron centre is a powerful approach to modulating the photophysical properties of such fluorophores . In factBoron complexes have been widely explored for chemical sensing, drug discovery and optical materials and devices. Boron can coordinate with oxygen and nitrogen atoms through B-O and B-N bonds, respectively . BortezoCoumarin derivatives are biocompatible, with large Stokes shifts and high fluorescence quantum yields, but most of them are excitable in the UV-vis, region limiting their environmental and biological applications . Thus, c2 complexes in different solvents. Their results showed that the emission spectra were red-shifted as the polarity increased. When the donor group H was replaced by NEt2, there was an evident red shift in both the absorption and emission spectra, which was attributed to efficient charge transfer (CT) as the electron-withdrawing power of the coumarin carbonyl group increased with the complexation of the BF2 group. Moreover, they proved that the emission intensity increases with higher viscosity [Coumarin-based boron complexes with outstanding properties and applications have been reported in the literature. For example, a near-infrared fluorescent probe coumarin-based boron complex with positive solvatochromism and AIE effects, was reported by Lai et al. as a powerful tool for fluorescence monitorization of liquid droplets, imaging gastric fat in living obese mouse . Tathe eiscosity . These cDespite the outstanding biological properties of metal complexes containing coumarin derivatives as core in the literature , the app2) adducts exhibit unique optical and electrochemical properties showing a wide range of applications, being applied in fluorescence imaging, spectroscopic sensing [Polymeric matrixes containing boron difluoride , Acetonitrile , Fluorescein , Rhodamine B , Cresyl Violet , Tetrabutylammonium cyanide , Tetrabutylammonium fluoride, Tetrabutylammonium bromine , Tetrabutylammonium chlorine . 4-Hydroxybenzaldehyde , Acetic acid , Sulphuric acid .Chloroform , DMSO , Acetone , Poly(methyl methacrylate) (PMMA) , Ethylenediamine tetraacetic acid (EDTA) , Ethanol , tetrahydrofuran (THF) , 1,4-Dioxane , Dimethylformamide (DMF) , LUDOX® spectrofluorometer using an optic fibre connected to the equipment, by exciting the solid compounds at appropriated λ (nm). A correction for the absorbed light was performed when necessary. Lifetime studies were carried out on TemPro, Deltahub Nanoled of Horiba Jobin-Yvon, with a 455 nm Nanoled. All instruments were provided by Proteomass-BIOSCOPE facility.The absorption spectra were recorded on a JASCO V-650 UV-Vis Spectrophotometer and the fluorescence emission spectra on a Horiba Jobin-Yvon Scientific Fluoromax-4. Spectra of solid samples were collected with a Horiba-Jobin-Yvon Fluoromax-4The mass spectra were obtained using the Thermo Scientific mass spectrometer (ISQ LT Single Quadrupole Mass Spectrometer) by electron impact with ionizing electron energy of 70 eV.6 at 25 °C using glass ampoules: 1H NMR spectrum at 500 MHz and 13C NMR spectrum at 126 MHz. An internal standard was used for tetramethylsilane (SiMe4) or a signal of residual protons and carbon of 13C solvent with respect to SiMe4 . The following abbreviations were used to describe the spectrum 1H NMR: s—singlet, d—doublet, m—multiplet.The NMR spectra were recorded on a Bruker Avance spectrometer in DMSO-dMelting points were measured on a Stuart melting point apparatus SMP30 and were uncorrected.2SO4 (0.55 mL) was added dropwise. Next, the reaction mixture was heated at a boil for 5 h. The precipitate obtained was filtered off, washed with concentrated acetic acid (2 × 10 mL) and recrystallized in concentrated acetic acid. The substance was obtained in the form of a red powder, yield 1068 mg (60%), mp. 291–293 °C. HRMS (ESI), m/z: 357.0693 (M + H)+ . MS (ES+) calcd for C18H11BF2O5 m/z: 356.07, found m/z: 356.24. 1H NMR (DMSO-d6), δ (ppm): 6.90 , 3J = 8.8 Hz); 7.41–7.47 ); 7.68 , 3J = 8.8 Hz); 7.79–7.85 ); 8.01–8.20 ); 10.44 . 13C NMR (DMSO-d6), δ (ppm): 100.3; 116.3 (2C); 116.8; 117.9; 124.7; 125.4 (4C); 131.8 (2C); 134.2; 136.5; 138.3; 141.7; 148.0; 154.1.Synthesis of L1 : To a suCompounds L2 and L3, boron difluoride complex 3-acetyl-4-hydroxycoumarin have been completely characterized by NMR, IR, elemental analysis and mass spectrometry in ,15,16. T−3 M), prepared by dissolving the appropriate amounts of complexes L1, L2 and L3 in chloroform. The studied solutions were prepared by appropriate dilution of the stock solutions up to 10−5–10−6 M. L1 was also prepared in ethanol, dioxane, THF, DMF.The spectroscopic characterizations and titrations were performed using stock solutions of the compounds  used in the correlations are gathered in DFT and TD-DFT calculations were run with Gaussian 03 software package  and Orca version 5.0.3 . The molTM LA4285 Kurashiki, Okayama, Japan, polymer for L1.The coumarin-doped polymethylacrylate (PMMA) polymers were obtained at room temperature by dissolving 100 mg of PMMA in 5 mL of chloroform, followed by the addition of 1 mg of compounds L1, L2 or L3, previously dissolved in 1 mL of chloroform. The polymer films were obtained after slow evaporation at room temperature (~24 h). The procedure was repeated for KURARITYThe emission spectra of the doped polymer films with temperature variation were registered using a fibre optics probe connected to the spectrofluorometer and a heating plate with controlled temperature. A 1 × 1 cm square of each doped polymer film was cut and immobilized between two quartz glass slides and placed onto the heating plate for the measurements. The measures were performed from 25 °C to 180 °C and from 180 to 25 °C. Emission spectra were acquired at 10 °C intervals.−1.cm−1), 495 nm  and 574 nm , respectively, which is characteristic of the π conjugation skeleton produced by the coumarin-based boron complexes [3 < N(CH3)2) lead to an increase in the electron density in the ground state, resulting in large dipole moment changes upon excitation and stronger solvatochromic effects [The optical properties of coumarin-based boron complexes, L1, L2 and L3 were investigated in chloroform, and in THF, dioxane, ethanol, DMSO and DMF in the case of L1. As shown in omplexes ,25. As cThrough the analysis of the absorption and excitation spectra for the three compounds, it is also possible to observe an overlap between the absorption spectra and the excitation spectra in the three cases, proving the absence of emissive impurities. Complex L1 was the only one to display emission in solid state with a single band at 624 nm, red-shifted in comparison to the emission spectra in solution. This red shift can be attributed to the close packing of the molecules in the solid-state analysis, as was observed previously in our group with other aromatic compounds ,27.The fluorescence quantum yields of the three compounds were also measured, using fluorescein, rhodamine B and cresyl violet as standards for complexes L1 to L3. The boron complexes L1, L2 and L3 exhibit a fluorescence quantum yield of 33%, 4% and 1%, respectively.The fluorescence lifetime of L1, L2 and L3 were calculated see , and theThe boron complex L1 was also characterized in other solvents see . In all 0 is the value of absorption and/or emission in a reference solvent, α is the hydrogen-bonding acceptor ability polarity scale; β is the hydrogen-bonding donor ability polarity scale; π* is the dipolarity/polarizability polarity scale; and the parameters a, b and p (corresponding to the responses of the solute property to the solvent property) are determined through a multiparametric fitting.Considering these results, the multiparametric fitting of the Kamlet–Taft equation (Equation (1)) was performed using the solvent parameters listed in exp versus υcalc were obtained for L1  and the slope and correlation coefficients are presented in Based on this fitting, linear plots of υd for L1 , and the2 values of 0.99 and 1 for absorption and emission data.As can be seen in −, Cl−, Br−), and linear (CN−) anions were carried out in THF, followed by the addition of small amounts of anion in acetonitrile. −. In the absorption spectra, as the anions are added, a decrease is observed in the absorbance at 469 nm, followed by the appearance of a new band at ca. 550 nm. Concerning the excited state, a quenching in the emission intensity at ca. 525 nm is detected. These results are in accordance with colour changes, where a change of the original yellow to pink with a consequent disappearance of the green emission is visualized. This behaviour is due to the loss of protons that leads to the formation of a quinone base with increased conjugation that red shifts the absorption. This was confirmed by NMR titration by the disappearance of a peak at 9.64 ppm  and a singlet oscillator strength value of 0.9204. The remaining nonzero oscillator strength excitation corresponds to S0 → S2 and S0 → S3 transitions at 3.34 eV (λ = 370.70 nm) and 3.44 eV (λ = 360.45 nm), respectively  ,24, cons−1 in the IR spectrum. The range of fluctuations at normal temperature reaches 25 °C. One can assume that with heating, this range can increase up to complete loss of conjugation of these fragments. It leads to the loss of emission when the temperature increases. The mentioned fluctuations are also well seen in the dimer -C (styrene fragment), which are characterized by a band of 29 cmimer see , and canTM LA4285 polymer was also doped with compound L1 and characterized , even in the case of L2 and L3, where in solution, no emission was observed. This is a very promising result, since most dyes have π-conjugated systems leading to non-emission compounds when they are in thin films. The behaviour of L1 was also evaluated by DFT, and the absorption and fluorescence spectra were calculated at different temperatures.In general, when heating, the whole molecular energy increased, and the molecules had a high degree of freedom to tune the excited-state conformation. In this process, the excited-state energy was consumed, leading to weaker emission. Particularly, the decrease in fluorescence of compound L1 with the increase in temperature seems to be due to the presence of pronounced torsional vibrations of the donor and acceptor fragments relative to the single bond with C(carbonyl)-C (styrene fragment). With heating, these vibrations are increased up to an expressed loss of conjugation of donor and acceptor fragments.Based on the aforementioned results, all complexes@polymers were submitted to several cycles of heating and cooling stages, showing in all cases a total recovery of the emission and reversibility, opening a range of applications as low-cost temperature probes.