A novel and facile pretreatment method is introduced based on ultrasonic treatment with nickel nano-particles as the catalytic core. This method abandons the sensitization and activation process in the traditional pretreatment that reduces the time and economic cost dramatically. The static contact angle was determined by an Olympus BX51M optical microscope. The surface morphology and plating composition were characterized via scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS), the infrared radiation (IR) transmittance spectra of the copper plated graphene were measured by Fourier transform infrared spectroscopy (FTIR), the layer structure was measured by Raman spectrum, the phase identification was identified by X-ray diffraction (XRD), the thermogravimetric analysis (TGA)  was carried out to detect the thermal characteristics. The electrical resistivity of copper-plated graphene was performed in an especially designed apparatus. The results show that the surface of graphene is coarsened, and the size is reduced after ultrasonic treatment, which can facilitate the nucleation and fine particle distribution of metal. The electroless plated efficiency of copper of the nickel pretreatment copper-plated graphene is 64.27 wt%, higher than that of generic copper-plated graphene at 58.62 wt%. The resistivity decreases rapidly from 1.69 × 10 The attractive properties of graphene have made them desirable templates for “core–shell” 2D metal/graphene nanocomposites , with graphene as the matrix and metal as the outer shell4. This metallization process belongs to a sort of surface modification of graphene, not only add the surface active sites to improve the bonding strength between graphene and other materials  but can maintain the superior intrinsic properties of graphene in the composites5. This metallization of graphene has been demonstrated to have significant potential for the fabrication of noble powdered metal/graphene composites, thus extending the application fields of graphene in corrosive resistance coating6, electrical contact materials7, electromagnetic interference8, active catalyst9.Since the discovery of graphene in 2004, a window to new technological fields has been unbarred. Due to its perfect two-dimensional (2D) lattice structure of sp28/m3). Due to its low cost, high solder ability, electro-migration resistance, and high electrical conductivity and thermal conductivity, copper has attracted the special attention of researchers for a wide range of applications. Due to its special structural properties and hydrophobic nature, the common methods such as low-temperature powder metallurgy, and chemical vapor deposition are insufficiently strong to guarantee significant adhesion between copper and graphene. Also, the tendency of agglomeration through strong Van der Waals interaction reduces the active site of graphene and curbs the formation of a copper layer with a homogenous distribution. Electroless plating is a kind of process which is widely used in modifying the surface of various materials like non-conductors, semiconductors, and metals, during which the metal ions in the solution are reduced into metal nanoparticles under a strong and appropriate reducing agent without external electrical assistance, and deposited on the surface with catalytic active sites of the matrix for forming a compact metal plating layer10. In particular, electroless plating is of great significance for improving the conductivity and service life span of some materials with high abrasive resistance requirements, such as electric contact materials. In addition, the core–shell structure composites prepared by electroless plating have good anti-fretting corrosion and anti-wear resistance properties11. Due to lack of catalytic sites, inert graphene does not possess autocatalytic activity, which generally needs to be pretreated by sensitization and an activation process during electroless plating, some complex technical problems still exist in these two-step processes12. For instance, if the activation solution contains noble metal salts , the cost of noble metal would limit the wide applications of noble metal activation13. Stannous chloride (SnCl2) is frequently used in the sensitization process, and it can be hydrolyzed to form hydrogel and adhere to the surface of material easily14. However, the residual tin ions on the surface have an adverse impact on the uniformity and adhesion of the copper plating, resulting in an undergrade quality of electroless plating15. Most studies used strong acids, strong bases, strong oxides, or high temperatures to obtain new and rough surfaces, which are not environmentally safe17.Metal Cu has the second lowest resistivity in the natural environment and has a large free electron density  solution and supersonic wave for the pretreatment of the surface of graphene to produce metal catalytic cores and surface defects as the active site for the direct electroless copper plating. Compared to the conventional process, this approach is simplified effectively. It does not refer to any noble or poisonous metals or an expensive instrument that will dramatically reduce the process cost and cause less environmental pollution. The surface morphologies, phase composition, and electrical properties of resulting Cu/Ni@Gr composites were characterized.In this paper, a simple and economical pretreatment without two-step sensitization and activation is carried out on graphene. It utilizes a nickel sulfate hexahydrate  chloride (PdCl2), copper (II) sulfate pentahydrate (CuSO4·5H2O), EDTA Disodium Salt 2-hydrate (EDTA 2Na), potassium Sodium Tartrate (NaKC4H4O6·4H2O), formaldehyde, Potassium hexacyanoferrate(II) trihydrate (K4[Fe(CN)6]·3H2O), NiSO4·6H2O, sodium borohydride (NaBH4) were all from ALCHIMICA s.r.o. and of analytical grade without further purification. Hydrochloric acid (37%), nitric acid (70%), sodium hydroxide, and ethanol were provided by Sigma-Aldrich.The average sizes of graphene used in this research are 18–25 μm, purchased from supplier Epinikon a.s. as the main ingredient in this research. SnCl4·6H2O (20 g/L) was dissolved in deionized water with mechanical agitation. After degreasing, the graphene was added at room temperature with probe-type ultrasonic processing for 12 min and then transferred to mechanically stirring for 30 min. During this procedure, the surface coarseness of graphene and the adsorption of nickel ions can be accomplished simultaneously and efficiently. After filtration, the graphene deposited with nickel ions was added into a NaBH4 solution (0.5 mol/L) with mechanically stirring to reduce the Ni2+ to Ni0  and HCl (60 mL/L) mixed solution by mechanically stirring for 15 min. After that, the sensitized graphene was blended with the solution of PdCl2 (0.25 g/L) and HCl (10 mL/L) by agitating for 15 min to actualize activation 6]·3H2O and NaOH, the NaBH4 as reducing agent. The detailed composition of the electroless copper plating bath is listed in Table The activated graphene was taken into an electroless copper plating bath in 100 mL quantity. The plating bath containing CuSO25:The synthesized graphene composites were characterized by UHR-SEM Zeiss Ultra Plus with an accelerating voltage of 2 kV equipped with an Energy Dispersive X-ray (EDX) spectrometer Oxford X-max 20. EDX analysis of the resulting composites was performed at 10 kV accelerating voltage to confirm the elemental configuration of the deposited materials on the surface of graphene, all the samples were gold-sputtered and carefully handled to avoid contaminations. Malvern zetasizer nanoparticle characterization system was used to study the particle size distribution. The static contact angle was determined to describe the hydrophilicity improvement of graphene after ultrasonication treatment by an Olympus BX51M optical microscope fitted with an Olympus E-510 digital single-lens reflex camera. The electroless plated efficiency of copper  with a 532 nm laser and full range grating with 900 lines/mm was used. Samples were placed under the lens of an Olympus optical microscope at 10 × magnification. The spectra were obtained in the range of 3500–50 cm−1. X-ray diffraction (XRD) was carried out using X׳Pert PRO MPD diffractometer  in Bragg–Brentano geometry equipped with a Co X-ray tube (iron filtered CoKα radiation: λ = 0.178901 nm), all materials were prepared on zero-background Si slide and measured in 2θ range 5°–105° (resolution 0.017° 2θ).The Fourier transform infrared spectroscopy (FTIR) spectra of the copper-plated graphene were measured by Nicolet iZ10 Thermo Scientific infrared spectrophotometer (KBr pellets) in the range of 4000–400 cmThermogravimetric analysis (TGA)  was carried out to detect the thermal characteristics of copper plated graphene in the temperature range of 25–800 °C at a heating rate of 10 °C/min. The measurements were performed under a nitrogen atmosphere at a flow rate of 25 mL/min. The ohmic heating behavior of samples was estimated using an electrical power supply (TIPA SP3010) with a clamping distance of 0.5 cm, and an infrared camera  was used to monitor the temperature change on the sample surface. Before testing, the particles were compressed into a circular sheet with a diameter of 1 cm by a mold.26:The electrical resistivity of copper-plated graphene was performed in an especially designed apparatus, which is schematically shown in Fig. Manuscripts reporting studies that do not involve human/animal participants, human/animal data, or human/animal tissue.The ultrasound cavitation in low frequency can etch the surface of the metal and make it rough. Figure a) and after (b) nickel pretreatment under ultrasonic sound. The raw graphene particles have a stacked layered structure that the surface is comparatively smooth. While the nickel pretreated graphene shows a crimping and rough surface, the particles changed into angular ones. Therefore, the specific surface of graphene increased. And the average particle size also reduced from 19.620 ± 0.395 μm of the raw graphene to 14.287 ± 0.326 μm after pretreatment, indicating that the nickel pretreatment not only gave it more metal catalytic cores but also reduced the size of graphene. As shown in Fig. 27. But for graphene, very few functional groups take part in chemical reactions during the electroless plating process. Metal ions are inclined to aggregate and nucleate at the defects and activated sites where nucleation energy is low on the surface of graphene28. The typical cauliflower structure of copper deposition is observed at the edge of graphene with higher magnification  characteristic reflection peak of nickel, located at 2θ = 44.5° is observed in the Ni@Gr, whereas it disappeared in the Cu/Ni@Gr. This might be due to the copper layer deposited on the surface of Ni@Gr, where the nickel had functioned as nucleate points. And the peak observed at 2θ = 63.4°(440) could be attributed to face-centered cubic Fe3O4, which came from residual K4[Fe(CN)6]·3H2O during copper plating process.Figure 30. Figure −1, 1581.66 cm−1, and 2680.28 cm−1 are displayed in original graphene and nickel functionalized graphene, which corresponds to D, G, and 2D peaks, respectively. The G peak (1580–1590 cm−1) is the main characteristic peak of graphene, mainly formed by the in-plane vibration of carbon atoms, which is very sensitive to the number of graphene layers. As the number of layers increases, the G peak moves toward the direction of the lower position, indicating the weakening of bond energy between graphene layers. An empirical formula for calculating the number of graphene layers31:−1) is generally considered to be the disordered vibration peak of graphene, which is caused by the lattice movement away from the center of the Brillouin region and is used to characterize defects in the graphene specimen. The 2D peak (2680–2700 cm−1) is a biphonon resonant Raman peak, which can also be used to evaluate the number of graphene sheets. It is known that the electronic dispersion of multilayer and monolayer graphene is different, leading to the obvious difference in Raman spectra32. From Fig. 2D/IG of Gr and Gr/Ni are about 0.24 and 0.29, respectively, compared with that of the single-layer graphene is around 2 and bi-layer graphene is around 1. However, after electroless copper plating onto the surface of the particles, the characteristic peak of grapheme disappeared, indicating that the graphene had been deposited with copper nanoparticles.Raman spectroscopy is an ideal tool to analyze the quality, thickness, and uniformity of graphene and its derivatives in detail34. It coincides with two wide peaks of the DTA curve in Fig. 4 to NiO and SO3. As for Fig. 35. Figure Thermal stability measurement is a versatile approach to characterize the property of the plating layer, it describes the thermal resistance of the compounds by heating them. Thermal stability can be analyzed by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). Figure 36:28/m3), after electroless copper plating on graphene by ultrasonic-assistant, the resistivity of the samples has been greatly improved.Figure –2 Ω cm of the original Gr to 0.79 × 10–2 Ω cm of Cu/Ni@Gr and 1.07 × Ω cm of Cu@Gr due to the large number of fine copper particles scattered around the graphene, which can be beneficial to build a high qualified conductive path. Besides, the smaller the size of graphene, the larger the specific surface area and the better the surface adhesion of particles, which is beneficial to the formation of copper crystal nuclei and the growth of crystalline grains. Compared to Cu@Gr, Cu/Ni@Gr has a smaller particle size, leading to a better-plated efficiency of copper on its surface. The above phenomenon is in good agreement with the SEM observations. Novoselov et al.37 found that the electrical resistivity of monolayer graphene is approximately 1 μΩ cm, which is fairly lower than that of the above results. This could be explained as follows, the electrical resistivity of graphene increases with the increasing thickness (a similar behavior can be observed for graphite) due to the inhibited carrier mobility. This is consistent with the results obtained by SEM and Raman analysis that the graphene used in this research has multilayers and contains more defects. And contact resistance between particles must be taken into account in the case of granular materials38.Figure –2 Ω cm of the Gr to 0.79 × 10–2 Ω cm of Cu/Ni@Gr and 1.07 × Ω cm of Cu@Gr, since the large number of fine copper particles scattered around the graphene which can be beneficial to build a high qualified conductive path.The contact angle of ultrasonic treated graphene is 95.5°, much lower than that of pristine graphene 144.7°, demonstrating that graphene made a transition from hydrophobic to hydrophilic properties after the treatment through ultrasonication. The EDS, FTIR, Raman, and XRD spectra show that copper particles were successfully deposited and densely distributed on the surface of graphene. Compared with Cu@Gr, the copper content on the Cu/Ni@G increases from 58.62 to 64.27 wt%. Due to the deposition of the metal layer, the thermal stability of copper-plated graphene has been greatly improved. Thermal IR thermal images of Cu/Ni@G and Cu@Gr display the highest temperature of ∼ 135 °C and ∼ 134 °C, whereas Gr shows the highest temperature of ∼ 112 °C only. The resistivity decreases rapidly from 1.69 × 10


Graphene grown on quartz glass by the CVD method can effectively reduce the wrinkles and pollution caused by traditional transfer methods. The addition of the CF4 plasma-etched process accelerates the growth rate of graphene on quartz glass. The platinum nanoparticles (PtNPs) prepared by in situ sputtering have favorable dispersibility and maximize exposed active catalytic sites on graphene, providing performance advantages in the application of H2O2 detection. The resulting sensor's detection limit , detection linear range (10 nM to 80 μM) and response time (less than 2 s) were significantly superior to other graphene supported PtNPs materials in sensing of H2O2. In addition, the material preparation method was related to the non-transfer CVD method and in situ sputtering technology, allowing for the creation of independent electrodes without additional electrode modification processes. This primitive material preparation and electrode assembly process were promoted for the application and development of practical H2O2 sensors.In this work, chemical vapor deposition (CVD) method-grown graphene on plasma-etched quartz glass supported platinum nanoparticles (PtNPs/eQG) was constructed as an independent transparent electrode for non-enzymatic hydrogen peroxide (H 2O2) detection.In this work, chemical vapor deposition (CVD) method-grown graphene on plasma-etched quartz glass supported platinum nanoparticles (PtNPs/eQG) was constructed as an independent transparent electrode for non-enzymatic hydrogen peroxide (H In recent years, many methods have been developed for the effective detection of H2O2, including the chemiluminescence method,3 spectral method,4 chromatographic method,5 electrochemical method6 and so on. Of these, non-enzymatic electrochemical H2O2 sensors were especially widely used because of their simple equipment, easy miniaturization, high sensitivity, good selectivity and fast response.7–9Hydrogen peroxide  have higher catalytic ability and stability for the detection of H2O2 due to their lower oxidation/reduction overvoltage.20 Therefore, graphene supported PtNPs has attracted great attention for non-enzymatic detection of H2O2 due to favorable properties of graphene as transparent electrodes and ultra-high detection performance of PtNPs.21 For example, Selvakumar Palanisamy22et al. reported a single step electrochemical fabrication of a platinum nanoparticle decorated reduced graphene oxide (RGO–PtNPs) composite for enhanced electrochemical sensing of H2O2. It was linear over the concentration ranging from 0.05 to 750.6 mM with the limit of detection of 16 nM. Their study conclusively reveals the feasibility of the application of graphene nano-platinum composites in electrochemical H2O2 sensing.The sensitivity, selectivity and stability of electrochemical sensors are strongly dependent on the structure and performance of the electrode materials.23 For example, graphene prepared by mechanical exfoliation24 and redox methods25 are agglomerated and have functional group residue, which leads to a decrease in the conductivity and sensing properties of sensors.26,27 At present, graphene grown by chemical vapor deposition (CVD) method has become the most promising material due to their large specific surface area and high crystalline quality.28,29 However, this additional transfer process is extremely prone to resulting in wrinkles, cracks, contamination and defects in graphene. This greatly limits CVD graphene from developing the proper electrochemical properties.30,31Nevertheless, it is still a tremendous challenge to prepare high-quality, large-scale and non-polluting graphene for electrochemical sensing.32 The direct growth of graphene on the target substrate can reduce defects and contamination caused by complex transfer processes and better preserve the physical and chemical properties of graphene. The excellent electrochemical properties of graphene grown on target substrate can improve its potential application in the field of electrochemistry. High-quality graphene produced by non-transfer CVD method can be directly used in self-assembly electrode devices, which is convenient in electrochemistry and promoting the industrialization of CVD graphene.33Direct CVD growth of graphene on the target substrate has immensely aroused research enthusiasm.34 Graphene grown on plasma-etched quartz glass (eQG) combined with sputtered Pt nanoparticles (PtNPs) were used as independent electrodes to assemble electrochemical sensors for non-enzymatic detection of low concentration of H2O2.In this paper, graphene was directly grown on the surface of quartz glass by atmospheric pressure chemical vapor deposition (APCVD). The effect of plasma etching of quartz glass on the growth behavior of graphene was studied.2.2.12) of size of 10 × 5 × 0.5 mm was purchased from Hefei Kejing Crystal Technology CO., LTD . Hydrogen (H2), methane (CH4), carbon tetrafluoride (CF4), nitrogen (N2) and argon (Ar) gases with 99.99% purity were all purchased from Jinan Deyang Special Gas Company . Hydrogen peroxide (H2O2) with a 30% mass fraction, acetone (CH3COCH3), sulfuric acid , sodium dihydrogen phosphate dihydrate (NaH2PO4·2H2O), disodium hydrogen phosphate (Na2HPO4), ascorbic acid (AA), dopamine (DA) and uric acid (UA) were purchased from Sinopharm Chemical Regent Company . Phosphate buffer solution  was a mixture of NaH2PO4 solution (0.1 mol L−1) and Na2HPO4 solution (0.1 mol L−1). All reagents used in the experiments were of analytical grade and used without further purification process. Deionized water with a resistivity of 18.25 MΩ cm was used in all aqueous solutions.Quartz glass (SiO2.2The compact etcher (RIE-1C) was obtained from SAMCO Inc. . The atmospheric pressure chemical vapor deposition (APCVD) equipment was purchased from Xicheng company . Vacuum sputter equipment (DESK V Cold Sputter) was purchased from Denton Vacuum Company . The platinum target with 99.999% purity was obtained from GRIKIN Advanced Material Company . The electrochemical workstation (CHI-660C), containing a standard three-electrodes system, was purchased from Shanghai ChenHua Instrument Company .The morphologies and structures of the samples were characterized by scanning electron microscopy , Raman spectrometer , UV-Visible Spectrophotometer . X-ray photoelectron spectrometer  and high resolution transmission electron microscope .2.3V2SO4H/V2O2H = 7 : 3) and heated to 120 °C for 30 min. It was then rinsed with ultrapure water and dried with nitrogen. The cleaned quartz glass was then placed in the compact etcher to etch with 30 sccm CF4 for a designated period of time. Then the plasma-etched quartz glass was placed in silica tube under a mixed atmosphere of argon  and hydrogen (40 sccm) and heated to 1030 °C. A certain amount of CH4 gas (11 sccm) was subsequently introduced into the reactor at 1030 °C for a certain period of time. Then, the silica tube was cooled to room temperature within 30 minutes. The sample was recorded as graphene grown on plasma-etched quartz glass (eQG). Graphene was grown on the surface of quartz glass for 180 min after etching for 5 min, 10 min and 15 min to confirm the effect of etching time on the growth of graphene. The effect of growth time of graphene was also studied: the growth time of graphene on quartz glass plasma-etched for 10 min was 150, 1180 and 210 min, as denoted by eQG150, eQG180 and eQG210, respectively.Graphene was grown on quartz glass substrate using the atmospheric pressure chemical vapor deposition (APCVD) method. Firstly, the quartz glass was ultrasonically washed with ethanol, acetone, and ultrapure water for 30 minutes in that order. After drying, the quartz glass was immersed in a piranha solution  finally, eQG was moved into the vacuum sputter equipment with the plasma-etched side of the quartz glass facing up. The power of the sputter equipment was 50 W and the sputtering time was 5 min. The prepared Pt nanoparticles/graphene grown on plasma-etched quartz glass is denoted as PtNPs/eQG. The samples of sputtering Pt nanoparticles on graphene grown on quartz glass at growth times of 150, 180 and 210 min were denoted PtNPs/eQG2.4For comparison, graphene grown on quartz glass (QG) was prepared by immediately placing cleaned quartz glass in silica tubes without etching under the same conditions for graphene growth.4 for 10 min labeled as platinum nanoparticles/plasma-etched quartz glass (PtNPs/eQ) were created by directly sputtering PtNPs on plasma-etched quartz glass for 5 min.As mentioned above, the cleaned quartz glass was placed in the compact etcher to etch with 30 sccm CF2.5−1, pH = 7.2) was added to a self-made electrochemical test system that includes a 25 mL beaker and a cover plate. The three-electrode electrochemical system contained a saturated calomel electrode as the reference electrode, PtNPs/eQG as the working electrode and platinum plate as the counter electrode. Then nitrogen was injected for 30 min to discharge oxygen. Cyclic voltammogram (CV) measurements were implemented from −0.3 V to 0.8 V both in the presence and the absence of 10 μM H2O2 with a scan rate of 50 mV s−1. The amperometric i–t curve was measured with 25 μL different concentrations of H2O2 at regular intervals of 50 s. Ascorbic acid (AA), dopamine (DA) and uric acid (UA) were intermittently added to detect the anti-interference performance , G (1600 cm−1) and 2D (2650 cm−1) peaks of graphene.36–38 The ratio of G peak to 2D peak was about 1 and the peak width of the 2D peak was greater than 50 cm−1, which shows that there were a few layers of graphene. The D peak at 1323 cm−1 shows the defect of graphene, which indicates that the defect structure of graphene was easier to form when quartz glass was treated by etching. In contrast, there was no obvious characteristic peak of graphene on the non-plasma-etched quartz glass substrate for the same growth time.The growth mechanism of graphene film on plasma-etched quartz glass is similar to that on heat-treated quartz glass.IG/I2D became larger  prepared by vacuum sputter equipment were characterized by HRTEM and corresponding selected area electron diffraction (SAED) pattern, as depicted in 2 phase in PtNPs/eQG. In addition, the presence of SiO2 could be further confirmed by the O 1s XPS peak at 532.8 eV, which was regarded as the oxygen species in the SiO2. As shown in Fig. S2b, PBM data was replaced with SVG by xgml2pxml:<glyph-data id="z.dbd" format="PBM" resolution="300" x-size="8" y-size="10" xml:space="preserve">00000000000000000000000000000000111111110000000011111111000000000000000000000000</glyph-data><svg xmlns="http://www.w3.org/2000/svg" version="1.0" width="13.200000pt" height="16.000000pt" viewBox="0 0 13.200000 16.000000" preserveAspectRatio="xMidYMid meet"><metadata>Created by potrace 1.16, written by Peter Selinger 2001-2019</metadata><g transform="translate scale" fill="currentColor" stroke="none"><path d="M0 440 l0 -40 320 0 320 0 0 40 0 40 -320 0 -320 0 0 -40z M0 280 l0 -40 320 0 320 0 0 40 0 40 -320 0 -320 0 0 -40z"/></g></svg>C bond. The remarkable carbon peak of sp2 hybrids indicates that the sample had obvious graphite structure. The C 1s peak in the sample could be divided into four peaks, with the other three peaks at 285.8 eV, 287.6 eV and 289.1 eV representing C–C, C–O and OC–O bonds, respectively. Fig. S2c7/2 and Pt (0) 4f5/2, respectively,39 indicating the feasibility of nanoparticle sputtering technology in applications.The surface composition and element characterization of PtNPs/eQG were analyzed by X-ray photoelectron spectroscopy (XPS), as depicted in Fig. S2.180 in Fig. S3bThe effects of different growth time were investigated by comparing the Raman and UV-Vis transmission spectra of graphene grown on quartz glass with etching time of 10 min and growth time of 150 min, 180 min and 210 min. As shown in Fig. S3a,3.22O2, PtNPs/eQG150 and PtNPs/eQG210 increased current value without any peaks in this voltage window. The CV curve of PtNPs/eQG180 shows significant peaks at −0.05 V and 0.60 V in the presence of H2O2 (red solid line). This indicates the best electrochemical response electrode for H2O2 detection is PtNPs/eQG180, meaning that the optimal preparation time for graphene growth is 180 min. Therefore, the transparent electrode prepared under this condition was used as the working electrode for subsequent electrochemical performance measurements. We'll use PtNPs/eQG to denote PtNPs/eQG180.Fig. S42O2 was explored using CV tests. 2O2. The voltammogram ranged from −0.3 V to 0.8 V at a scan rate of 50 mV s−1. As shown, PtNPs/eQ and eQG had increased current value with the addition of H2O2. The CV curve of PtNPs/eQG shows higher capacitance and significant peaks of −0.05 V and 0.60 V in the presence of H2O2 (red solid line), which indicates PtNPs/eQG had an exceptional electrochemical response to low concentration of H2O2. In summary, comparing the response CV curves of different materials to H2O2, PtNPs/eQG had an impeccable electrochemical response to low concentration of H2O2.The electrochemical behavior of Pt nanoparticles/graphene grown on plasma-etched quartz glass (PtNPs/eQG) towards the sensing of H2O2, cyclic voltammetric curves with various scanning rates (40 mV s−1–180 mV s−1) were recorded in I = 0.0168 × ν + 1.1829 , indicating the dynamics control was an adsorption process.In order to demonstrate the charge transport characteristics of PtNPs/eQG in the process of electrochemical sensing H3.3i–t curve was used to test the electrochemical performance of the PtNPs/eQG toward H2O2 by adding different concentrations of H2O2 solution into the stirring system at 0.60 V. The interval was 50 seconds and H2O2 was injected twice. As shown in 2O2 increased from 10 nM to 50 μM. The results show PtNPs/eQG had excellent electrochemical performances for H2O2 detection.Amperometric 2O2 as shown in 2O2 concentration, which is in accordance of the formula I = 0.10392 + 0.00012 × c . In the range of 2–80 μM, the response current value had a strong linear relationship with the H2O2 concentration, in accordance of the formula I = 0.46593 + 0.09077 × c . In the case of a signal-to-noise ratio of 3, the detection limit was 3.3 nM, which shows the good sensitivity of PtNPs/eQG for the detection of ultralow concentration of H2O2.The response current varied with the concentration of H2O2 detection were shown in 2O2 sensors with low detection limit, short response time and wide linear range.The comparison of detection limits and linear ranges between graphene-supported PtNPs towards H2O2 detection was investigated in Fig. S5.2O2 (0.05 mmol L−1) and dopamine , ascorbic acid  and uric acid  at 0.60 V was measured. It can be seen from Fig. S52O2. The results show that PtNPs/eQG had strong anti-interference performances. This makes it an ideal candidate to be applied to the low-concentration qualitative and quantitative detection of H2O2 in the determination of actual biological samples.The selectivity of PtNPs/eQG for H4.2O2. The growth rate of graphene on quartz glass was accelerated by adding a CF4 plasma etched process. The electrochemical properties of CVD graphene without transfer and the active sites exposed of PtNPs contributed to the catalytic performance of PtNPs/eQG for H2O2 detection. The sensor has an ultra-low detection limit of 3.3 nM (S/N = 3), lower than previous similar sensors. The combination of CVD-grown graphene without transfer and in situ sputtering technology is beneficial in the practical application of non-enzymatic detection of H2O2.In conclusion, we have successfully prepared CVD-grown graphene on plasma etched quartz glass (eQG) and loaded Pt nanoparticles (PtNPs) to prepare composite materials, and used it as an independent transparent electrode for non-enzymatic detection to HThere are no conflicts to declare.RA-010-D0RA01963A-s001


Data are currently limited on the performance of SARS-CoV-2 RNA levels as predictors or surrogate markers for clinical outcomes in outpatients with mild-to-moderate COVID-19.This exploratory analysis used data from 2205 non-hospitalized adults who enrolled between August 2020 and July 2021 and participated in placebo-controlled evaluations of two monoclonal antibody (mAb) agents (bamlanivimab [n=317] or amubarvimab/romlusevimab [n=837]), and an open-label cohort of bamlanivimab recipients [n=1051] as part of the ACTIV-2/A5401 platform trial. SARS-CoV-2 RNA levels were measured in anterior nasal (AN) swabs and plasma at day 0 (pre-treatment) and AN at day 3. We fit regression models to estimate the association between RNA level or detection and subsequent hospitalization/death within 28 days of enrollment.10 copies/mL [cp/mL]) and mAb (2.3 vs 4.9) groups. For placebo recipients, higher Day 0 AN RNA was associated with an increasing risk of hospitalization/death, ranging from 3% to 16% for < 2 and ≥ 6 log10 cp/mL, respectively. Although only 1% had quantifiable plasma SARS-CoV-2 RNA, there was a similar trend for day 0 plasma RNA: 5% hospitalizations/death for undetectable RNA, 16% for detectable but not quantifiable RNA, and 80% for ≥ 2 log10 cp/mL. Among 485 placebo recipients with days 0 and 3 AN RNA results, the risk of subsequent hospitalization/death was highest among those with ≥ 5.0 log10 cp/mL at both days  and lowest for those with unquantifiable levels at both days . Higher AN RNA at day 3 (adjusted for day 0 RNA) was associated with subsequent hospitalization/death among placebo recipients (relative risk (RR): 1.4 per log10 cp/mL; 95%CI: 1.0, 2.1), but not mAb recipients .One-hundred four participants (53/571 [9%] on placebo and 51/1634 [3%] on mAb) died or were hospitalized through day 28. Median AN RNA levels were lower at day 3 compared to day 0 in both placebo |Merck: Advisor/Consultant|Ridgeback Biopharmaceuticals: Research funding provided to the University of North Carolina|Roche: Advisor/Consultant|Syneos: Adjudication committee (Influenza) Paul Klekotka, MD, PhD, Eli Lilly: Employee|Eli Lilly: Stocks/Bonds David A. Margolis, MD MPH, Brii Biosciences: Stocks/Bonds David A. Wohl, M.D., Gilead: Advisor/Consultant|Gilead: Grant/Research Support|Lilly: Grant/Research Support|ViiV: Advisor/Consultant|ViiV: Grant/Research Support Eric S. Daar, M.D., Gilead: Advisor/Consultant|Gilead: Grant/Research Support|Merck: Advisor/Consultant|ViiV: Advisor/Consultant|ViiV: Grant/Research Support Davey M. Smith, M.D., M.A.S., Arena Pharmaceuticals: Advisor/Consultant|Bayer Pharmaceuticals: Advisor/Consultant|Brio Clinical.: Advisor/Consultant|Fluxergy: Advisor/Consultant|Kiadis: Advisor/Consultant|Linear Therapies: Advisor/Consultant|Matrix BioMed: Advisor/Consultant|Model Medicines: Advisor/Consultant|Signant Health: Advisor/Consultant|VxBiosciences: Advisor/Consultant Judith S. Currier, M.D., MSc, Merck: Advisor/Consultant.


Indeed,nanomaterials hidden under the common “graphene” signboardare very rich in morphological and physicochemical variants. In thiswork, inspired by the adhesion chemistry of mussel biomaterials, wehave synthesized novel, water-processable graphene–polylevodopa(PDOPA) hybrids. Graphene and PDOPA were covalently amalgamated viathe “growth-from” polymerization of l-DOPA monomer in air, yielding homogeneouslyPDOPA-coated (23 wt %) (of thickness 10–20 nm) hydrophilicflakes. The hybrids formed >1 year stable and water-processableaqueousdispersions and further conveniently processable paints of viscosity0.4 Pa·s at 20 s–1 and a low yield stress τ0 up to 0.12 Pa, hence exhibiting long shelf-life stabilityand lacking sagging after application. Demonstrating their applicability,we have found them as surfactant-like nanoparticles stabilizing thelarger, pristine graphene agglomerates in water in the optimized graphene/graphene–PDOPAweight ratio of 9:1. These characteristics enabled the manufactureof conveniently paintable coatings of low surface resistivity of 1.9kΩ sq–1 (0.21 Ω·m) which, in turn,emerge as potentially applicable in textronics, radar-absorbing materials,or electromagnetic interference shielding.Water-based processingof graphene—typically consideredas physicochemically incompatible with water in the macroscale—emergesas the key challenge among the central postulates of green nanotechnology.These problematic concerns are derived from the complex nature ofgraphene in the family of sp Water-based processing of graphene bymeans of a naturalpolymer polylevodopa toward stable and functional electroconductivecoatings for textronics was elaborated and cross-verified. Unfortunately, dispersion of graphene is challengingdue to the strong intersheet van der Waals attractions (via π–πstacking) causing aggregation and/or precipitation.15Water-basedprocessing of graphene—the most studied 2D spN-methyl-2-pyrrolidone, and dimethyl sulfoxide could beapplied as graphite exfoliating agents and graphene dispersants, respectively.16 However, the most pressing technological requirementsfor the dispersing media are volatility and zero/minimal toxicity,as for water or ethanol.17 The latter greendispersants, as the key components in the more complex systems suchas elastomers, could lead to more convenient and safer processabilitytoward flexible electroconductive coatings18 for textronics,20 radar-absorbing materials (RAMs),22 or electromagnetic interference (EMI) shielding.23A variety of organic solvents inducing repulsiveforces after interflakepenetration and on-flake adsorption such as benzyl benzoate, 26 or physicaladsorption of stabilizers such as surfactants,29 polymers,32 or small molecules.35 Consequently, rather than using high crystallographicquality and pristine graphene—the availability of which islimited to small quantities due to the troublesome large-scale production—GOor rGO emerged thus far as the materials of choice.39 However, GO flakes which have no clearly defined chemical structureare not only difficult to process40 butalso exhibit the yet unraveled and complex cyto- and ecotoxicity profiles42 and undergo fragmentation in the aqueous environments.43 However, predominantly, GO does not retain thefundamental properties of graphene, with mechanical and electricalas the key ones.45 In turn, scalable water-baseddispersions, inks, or paints/pastes can be prepared under a ratherintense mechanical assistance from (bath to probe) ultrasonicationto microfluidization and have led so far to the functional solutionsmainly in the area of textronics. Nevertheless, they still requirea pretreatment with ethylcellulose,46 amixture of sodium deoxycholate and carboxymethylcellulose sodium salt,47 sodium silicate,48 sodium salt of flavin mononucleotide,49 or poly(N-vinyl pyrrolidone)50 (ultrasonication). Proteins can also serve as biofriendlysurfactants, while adhesion is the key prerequisite for the stabilizationof nanoparticles in water. It is well known that mussels stronglyadhere to wood/stones under high shear stress conditions from thewater flows. This behavior stems from the mussel foot functional proteinscontaining high contents of two amino acids: l-3,4-dihydroxyphenylalanine  and lysine.51 Such characteristics have instantly paved the way for themimicking of sustainable adhesives and stabilizers toward the newapplications in materials science , biology, and biomedicine.53To enhance the water dispersibility of graphene (understoodinthe broadest sense according to the ISO standardization ISO/TS 80004-13:2017)and to improve the performance of the graphene-based nanocomposites,several physicochemical modifications have been applied. These structuraladaptations involve, inter alia, treatment of carboxylic acid groupsretained on the chemically reduced graphene oxide (rGO), graftingof hydrophilic groups  ongraphene oxide (GO) through chemical reactions,l-DOPA (precursor ofdopamine) as the particularly promising one. l-DOPA, beingan in vivo instantly available catecholamine, oxidizes to polylevodopa(PDOPA). This reaction, proceeding under only the mechanical stirringregime, at the solid–liquid interface might form a controllablelayer of excellent adhesiveness/affinity to numerous materials.57 Such a biologically inspired functionalization, essential in theformation of mussels, could be “translated” into thesurface modification of graphene with l-DOPA and the subsequentinterface polymerization via the “grafting-from” mechanism.This route could be effective in preventing graphene from the excessiveagglomeration in the polar solvents.In the pursuit of developing novel physicochemicallymodified grapheneof enhanced hydrophilicity and simple but green processing, we hypothesizedits covalent functionalization with Taking all the above intoaccount, we have successfully performedthe functionalization of graphene toward its individualized, hydrophilic,and thus water-processable nanoparticles. The resulting material displaysthe enhanced stability of dispersions among variously functionalizedgraphene flakes. The optimized hybridization with the pristine grapheneflakes, serving as the active components of acrylic paints, led tothe flexible, on-textile electroconductive coatings of excellent electricalcharacteristics yet not achieved by the other available green approaches.l-DOPA (≥98%) and Tris-base(tris(hydroxymethyl)aminomethane, 2-amino-2-(hydroxymethyl)-propane-1,3-diol)(≥99.8%) were purchased from Sigma-Aldrich. All of the solutionsand dispersions were prepared using distilled water (0.5 μScm–1). Transparent aqueous base SX 150 acrylic (dedicatedto screen printing), used for the preparation of electroconductivepaints, was purchased from Sico Screen Inks NV .GrapheneCamGraph G3 was supplied by CambridgeNanosystems Ltd., UK. l-DOPA (2.00 g) were dispersed/dissolvedin the solution of Tris-base in water (10 mM) . Thereaction mixture was placed in a round-bottom flask (2 L) equippedwith a reflux condenser and a mechanical stirrer and sealed.53 After that, the polymerization reaction wasinitiated thermally and continued for 48 h at 60 °C using a heatingmantle. Upon processing, the dispersion changed color from yellowto brown. The postreaction mixture was centrifuged , and the resulting black powder (1.20 g),58 that is, poly(l-DOPA)-functionalized graphene(G3@PDOPA), was washed with water (1.0 L) and dried at 80 °Cfor 48 h. Exactly the same procedure was applied for the blank experiments,that is, the samples composed only from l-DOPA or only fromgraphene G3 flakes.Graphene  and –1) were prepared. After weighing out theappropriate amounts of graphene and water, the mixtures were ultrasonicated for 10 min.Additionally, in order to evaluate the dispersion effect of l-DOPA operating via the optional noncovalent modifications, we alsohave prepared the graphene dispersion but disabling polymerizationof l-DOPA.To evaluate the hydrophilic/hydrophobicbehavior of graphene and G3@PDOPA, the corresponding aqueous dispersions. The coating thickness wasmonitored during the painting and determined using an ElectronicaUniversal Micrometer LINEAR 0–25 mm/0.001 mm thickness gauge. Similarly, paints containing G3@PDOPA and the mixtureof pristine graphene G3 and G3@PDOPA in various ratios  were prepared.Pristine graphene G3 and G3@PDOPA were used forthe preparation ofelectroconductive paints. Deionized water (70 mL) and graphene (1.00g) were ultrasonicated for 15 min. Next, the dispersions were homogenized for 15 min in SX-150  to obtain the final graphene nanoparticle concentrationof 10 wt % per base.1H nuclearmagnetic resonance (1H NMR), electrospray ionization massspectrometry (ESI-MS), and thermogravimetric analysis (TGA) were performedto characterize the changes in morphology and (surface) physicochemistryof G3 flakes, PDOPA, and G3@PDOPA. The SEM images were taken on aSIX HITACHI S-3400 N SEM system . Nanomorphology ofthe graphene nanofillers was observed using HR-TEM with a TEM F20X-TWINsystem (FEI-Tecnai)  operated at 200 kV. One dropof a sample dispersion in ethanol  was placed on a coppergrid coated with an ultrathin amorphous carbon film and then driedunder ambient conditions. Raman spectra were obtained using  a green laser (532 nm) focused on a sample using 20×optical zoom, with the laser power of 5% and the exposure time of10 s. For each material, three accumulations were collected in threelocations of the sample. A Thermo Scientific FTIR Nicolet 6700 spectrometerwas used for the IR spectroscopic studies of the samples. ESI-MS spectrawere acquired on an ESI/MS spectrometer 4000 QTRAP LC/MS/MS system(AB SCIEX) in the positive and negative modes of ionization from thesamples dissolved/dispersed in methanol. Combustion elemental analyseswere obtained using a PerkinElmer 240C apparatus. TGA curves wererecorded using a PerkinElmer TGA 8000 thermobalance in a heating rateof 10 °C min–1 under an argon atmosphere. Additionally,particle size distribution  and zeta potential analyses were performed. The microstructureof dispersions was characterized using an optical microscope Levenhuk870t. The electric resistance (Ω) of the paths was measuredusing the voltage method in a custom-designed voltage measurementsystem.59 Due to the possibly heterogeneousnature of the electroconductive coatings, the system was customizedto textiles with the extended contact surface of the path/electrode.This approach enabled us to reduce the heterogeneity of the electricfield and the distribution of the current density.59 The measurements were done by placing multimeter aluminumelectrode block probes, with the distance between them of 10 cm, ontothe surface of coating. We have measured the resistance for each ofthe coatings in triplicate.Scanning electronmicroscopy (SEM),high-resolution transmission electron microscopy (HR-TEM), Raman spectroscopy,Fourier transform infrared spectroscopy (FTIR), 60 and the procedure was as follows: functionalized  graphene (60 mg) was dispersed for 48 h undercontinuous magnetic stirring in the specified aqueous reaction basesolutions: (1) 0.01 M NaOH, 60 mL; (2) 0.01 M Na2CO3, 30 mL; and (3) 0.01 M NaHCO3, 60 mL. The mixturewas filtered using a 0.2 mm PTFE filter and then 10 mL (or 5 mL inthe case of Na2CO3) of the appropriate filtrateswas titrated with 0.01 M HClaq (20 mL). The pH of the finalsolutions was measured using an EcoTestr2 pH meter. Each titrationwas performed in triplicate. As blank samples, 10 mL of each reactionbase (5 mL in the case of Na2CO3) was used.In turn, to determine the content of amine group,61 20 mg of each sample was added to 10 mL of HClaq (0.05 M). The mixture was shaken for 30 min in a sealed containerunder a N2 atmosphere and then filtered to remove graphenefrom the solution. Immediately after the filtration, the solutionwas titrated with NaOH (0.05 M). The pH of the final solutions wasmeasured using the abovementioned pH meter.The content of surface oxygen groupsin all samples was determined by Boehm titration,62 The samples of G3, G3@PDOPA, and PDOPA were sprayed on the surfaceof polished silicone  using airunder a pressure of 2.5 bar airbrush . The dispersions/solutions were sprayed up to a coverageof 0.1 mg cm–2. For G3 and G3@PDOPA, the suspensions(1.0 mg mL–1) in isopropanol  were used after sonication . For the PDOPA sample, 20% MeOHaq  addition wasrequired to stabilize the suspension (but still 10 mL of 1 mg mL–1 suspension was prepared). Spray-coated silicone sampleswere air-dried at room temperature for 24 h to evaporate the remainingsolvents.The water contactangle (WCA)  was measured at 25 °C  usingthe goniometric system used by us previously.–1) and ramp-down  tests with 30 s intervals.Also, we experimentally determined the yield stress of the samplesby subjecting them to very low shear  and then stopping the rheometer drive. The deformed spring causedthe rotating cylinder to move back, reducing the torque and shearstress on the surface until the cylinder stopped. When it happened,the value of the shear stress indicated by the viscometer was preciselythe yield stress of paints.63 The uncertaintyof rheological measurements was ±5.4%.The rheological properties of paints were characterizedat 40 °Cusing a Brookfield LVDVII+Pro spring-type rotational viscosimeterwith DIN-87 spindles. We conducted shear rate ramp-up .11 Thesynthesis of G3@PDOPA was performed via the complex “growth-from”polymerization mode . Thein-plane dimension of the G3 graphene flakes (the flake diameter)was in the range of 400 ± 150 nm, as determined by SEM, and theBrunauer–Emmett–Teller (BET) surface area equaled to130 ± 5 mion mode 1.642-and sp3-carbon as wellas oxygen atoms from hydroxyl groups —shownin x in the G3@PDOPA structure, where x = 0 and 1—could serve as the reactive hot spots.65 These centers could capture the l-DOPAradicals generated from the oxidation of monomer molecules by dissolvedair. This behavior was confirmed in the polymerization of catechol moieties in the presence of metallic surfaces suchas silver66 or surface hydroxyl groupsfrom iron oxides.67 This reaction wouldyield covalently modified graphene, excessively coated with PDOPAnegatively charged in water by carboxylates and phenolates. Overall,these prerequisites would correspond to the covalent nature of theherein graphene functionalization. Particularly, C-sp3 defects,also confirmed by complementary analyses, would be the reactive centersin the free-radical initiation of air-induced polymerization of l-DOPA as, in fact, they would exhibit benzylic-type (Ph3CH → Ph3C•) reactivity.69Both aromatic spThe morphology of the functionalized graphene flakes has beenevaluatedusing SEM and TEM 2. The imH-indole rings as well as the π–cation interactionsbetween the protonated amine group (−NH3+) from the PDOPA zwitterionic blocks and π–graphenelayer—could benefit from the steric stability in the aqueousenvironments. On the other hand, van der Waals and π–πstacking interactions between the graphene flakes—particularlyat the highly developed surface area of intrinsically hydrophobicflakes—might yield a substantial agglomeration over time. Thisphenomenon makes graphene a hard-to-process material to such an extentthat it is practically impossible to disperse graphene sheets in waterwithout the assistance of dispersing agents. However, when placedin an oil/water mixture, graphene becomes wettable and actually exhibitsamphiphilic properties driven by the hydrophilic edge domains.11Such a molecular hybridization—associatedwith the π–πstacking between the few-layer graphene flakes and PDOPA benzene/1l-DOPA monomer  behavior in water, with the support of opticalmicroscopy and (b) wettability 3. Pristi monomer 3B. The n monomer 3C. After monomer 3D.70 Indeed, G3 does notcontain a significant amount of oxygen functionalities, but one couldalso expect a perpendicular orientation of some flakes, causing astrong Cassie–Baxter effect, further increasing the WCA value.On the other hand, the abundance of oxygen-containing groups makesthe PDOPA surface hydrophilic—the WCA was found equal to 83°.The surface of the target G3@PDOPA hybrid showed almost the averageWCA value between G3 and PDOPA, that is, 123°. Overall, the hydrophilicityof graphene was increased due to, from one side, strong π–πinteractions of the aromatic PDOPA rings (tail-like) and the grapheneflakes,73 while from the otherside, the high content of the −COOH, −OH, and −NH2 serving as polar heads oriented outward water. Such a superstructurewould hence promote dispersibility and wettability of graphene in/bywater.Supporting Information, Figure S1). The z-average particle diameter corresponds to the intensity-weightedmean hydrodynamic size of the investigated particles. The z-average values in As a technique complementary to optical microscopy, dynamiclightscattering (DLS) was performed to obtain the lateral size distributionof the water-dispersed flakes, which actually confirmed the above-observedtendencies. 74 However, measuring the hydrodynamic diameterof graphene flake agglomerates can be done by DLS,75 though one must consider that DLS rather shows only thesize distribution of different particles. Accordingly, the hydrodynamicdiameter of G3@PDOPA particles was reduced up to 342 nm as comparedto the immeasurably large pristine graphene flakes in the suspension.In turn, zeta-potential measurement is one of the useful techniquesto determine the stability of the carbon nanomaterials in the solvents,as the optical observation could not determine the absolute stabilityof dispersions. Again, the zeta-potential of pristine graphene G3could not be recorded due to the strong hydrophobic character andits immiscibility/nonwettability with/by water. The stability of G3@PDOPAdispersion could be directly correlated to high negative ζ-values(−25.4 ± 1.52 mV). For PDOPA solution, the ζ-valuesare even more negative (−31.9 ± 0.79 mV) that correspondsto even better stability of the PDOPA dispersion  analysis(EA) 4, left4, right 46H2O) was composedof 97 wt % of carbon and only a small number of oxygen groups accompaniedby adsorbed water. In the case of G3@PDOPA, the oxygen and nitrogencontent increased to ca. 9 and 1%, respectively, clearly revealingthe presence of PDOPA. The more qualitative approach, that is, Boehmtitration, has further verified these results (Pristine graphene (ca. C results 2.–1) and phenol-like groups (1.14 mmolg–1)––which correspond to the minimumof 3.6 wt % of oxygen. After functionalization with PDOPA, the contentof carboxylic groups in G3@PDOPA increased to 1.10 mmol g–1, phenol-like groups to 1.75 mmol g–1, and lactoneto 0.49 mmol g–1. These characteristics emerge withthe grafting of graphene with the complex and cross-linked poly(l-DOPA). Additionally, during the l-DOPA polymerization,a fraction of carboxylic groups could undergo decarboxylation, whilesome hydroxyl groups oxidize to quinone-like moieties  and 1100 cm–1 (νC–O),absent in pristine graphene, resulted from the −OH stretchingvibration from PDOPA. In addition, the intense peak at 1630 cm–1 could be ascribed to the stretching vibration ofthe carbonyl group (νC=O). Further, weakersignals at ca. 3000 cm–1 correspond to the stretchingvibrations of CAr–H (νC–H). The N–H bending as well as the C–N stretching vibrationsresulting from the presence of amine groups can be observed at 1520(δN–H) and 1270 cm–1 (νC–N), respectively. Additionally, the 1HNMR spectra of PDOPA and G3@PDOPA confirmed: (1) a more pronouncedoxidation level of phenolic hydroxyl to 1,2-keto groups as signalsat 8.10 and 8.25 ppm were significantly reduced in G3@PDOPA and (2)a higher level of cross-linking as all of the 1H NMR signalswere significantly broadened . The presence of l-DOPA units in the oligo-and polymers (linear and cross-linked) in PDOPA and G3@PDOPA was furtherconfirmed via ESI-MS with an exemplary identification of the partiallyoxidized l-DOPA pentamer and dimer .Pristine graphene had a small amountof oxygen groups on the surface—carboxylic in TGA could be connected with the desorption of water. Above220 °C, PDOPA started to decompose, which was connected withthe degradation of the catechol moiety and decompositional volatilizationof the amine groups and decarboxylation.80 Thermal degradation of G3@PDOPA has been found to be qualitativelysimilar to that of pure PDOPA, although the degradation of the adsorbedpolydopamine occurred at a higher temperature around 300–400°C , G-band (∼1570–1590 cm–1), and the second-order band 2D at ∼2670 cm–1. According to Sadezky et al.’s deconvolution method, thespectra in the range of 1000–2000 cm–1 canbe separated into the following bands: G, D, A, and D4.81 The G-band (∼1591 cm–1) corresponds to the ideal graphitic lattice, the D-band (∼1332cm–1) to the disordered graphitic lattice , A-band (∼1497 cm–1)—amorphous carbon, and D4-band (∼1308 cm–1)—disordered graphitic lattice (A1g symmetry).The 2D-band (∼2656 cm–1) displays the highestintensity which is connected with the crystal size in the interlayerdimension.82 The other band is overtoneD + D′ at 2913 cm–1. It should be noted thatthe D-band is typically qualitatively and quantitatively related tothe non-sp2-C defects, that is, a number of sp3-C atoms. The G-band in the spectra of graphene samples revealedsignals at 1586 cm–1 (pristine graphene) and at1591 cm–1 (G3@PDOPA). The ID/IG ratio could be taken as ameasure of the sp3-carbon defect concentration. The crystallographicdefects here can be assigned to the C atoms which underwent additionand subsequent polymerization. The ID/IG ratio increased from ca. 0.54 (pristine graphene)to 0.88 (G3@PDOPA), indicating the conversion of sp2- to sp3-C atoms in the basal plane of thefunctionalized graphene, confirming the earlier observations. Theother Raman parameter of diagnostic relevance used for the characterizationof graphene is the ID/I2G ratio. The small ID/I2G ratio is the evidence of high crystallographicorder in the initial graphene structure. Therefore, after functionalizationwith PDOPA, the ID/I2G ratio increased from ca. 0.80 (pristine graphene) to ca.0.87 (G3@PDOPA). Nevertheless, not only intensity but also shiftsof the D- and G-bands provide information on the functionalizationof graphene. Therefore, while the positions of the D-band remainedpractically unchanged for all of graphene samples, the G-bands forG3@PDOPA were shifted to higher frequencies. To track the changesin the G-band positions, we have carried out a line-shape analysisto minimize the number of independent fitting parameters. After functionalization,the signals were shifted ca. 5 cm–1 to higher wavenumbers,indicating the consequence of electron transfer from the π-statesof graphene upon trapping radicals generated at the stage of initiationof polymerization. Subsequently, the growth of the polymer chain proceededfrom the graphene flake being an active sp2-carbon radicalscavenger.83 Importantly, chemisorptionof this first radical opens up the cascade of covalent bond formation,84 which eventually drives the process to the effectivecoating of graphene with PDOPA. This behavior has found clearly areflection in the results we obtained from the physiochemical studieson G3@PDOPA.The Stokes phonon energy shiftsin graphene correspond to the threemain peaks in the Raman spectrum: D-band  helps maintain product consistency and prevents phaseseparation and running or streaking after application to a verticalsurface, while low viscosity at medium/high shear rates during theprocessing and application of paints makes them easy to mix, pump,transport, and spread with brushes, rollers, and so forth.86 Furthermore, we observed very little differencebetween the shear rate ramp-up and ramp-down curves (no hysteresisloops); thus, the paints practically do not have time-dependent thixotropicproperties. Such an almost immediate rebuilding of the fluid structureupon the application of stress/strain indicates that the paints willbe devoid of sagging and droplet formation after application.87 In addition, the samples of G3 10 wt % and G39 wt % + G3@PDOPA 1 wt %, unlike the neat base SX-150, show the existenceof a low yield stress τ0 of 0.10 and 0.12 Pa, respectively.The yielding behavior of paints is important in many areas, includingthe evaluation of shelf-life stability and sagging after applicationto the surface. 880 is the yield stress , K is the consistency index, and n is the flow behavior index.The investigatedpaints at 40 °C are highly viscous, non-newtonian shear-thinningfluids, the viscosity of which declines with an increasing shear rateup to 83.7% for G3 9 wt % + G3@PDOPA 1 wt % 7. It is Having obtained the prospective characteristics,that is, the PDOPAcapability of individualizing graphene flakes, we attempted to preparea paint and consequently the functional, electroconductive textilecoating. Sheet resistance measurement is the first-of-choice parameter describingthe electrical properties of the coatings. It is also a method whichimmediately informs whether further deposition of new layers of paintwould bring any significant changes in the electrical conductivity.As presented in –1, which is slightly lower89 or an orderof magnitude lower90 than that reportedpreviously for the green solvent-based inks. Importantly, from themechanical properties point of view , the resistance for the most conductiveand graphene-only coating upon 100 bending cycles from 180 to 0°(a sharp edge) increased to 8 and 10 Ω sq–1, respectively. At the same time, the most perspective cotton coatingG3 9 wt % + G3@PDOPA 1 wt % emerged as more resistant to washing andstrain than G3 10 wt %, with an increase in ΔR/R0 as low as 7% after five cycles ofwashing/drying and a 90% increase upon 10% elongation, respectively.Deterioration of the electrical properties of G3@PDOPA wascausedby a high content of PDOPA ∼23 wt %. However, after the depositionof the paints containing a mixture of pristine graphene and G3@PDOPA,the electrical properties were synergistically augmented. We studiedlower (1–5 wt %) weight fractions of G3@PDOPA and found thatthe lowest resistance could be achieved for the composite containing1 wt % of G3@PDOPA . The electricalresistance after the deposition of 15 layers l-DOPA. Our method allows for a promptand simple production of excellent and time-stable aqueous graphenedispersions—at the same time opening up opportunities for thesustainable use of the green surface compatibilizers like PDOPA. Thecross-verified method emerges as an attractive alternative to themost frequently used ones, that is, those exploring structurally deeplyaltered graphene relatives—GO and rGO. It should be emphasizedthat it is also an effective way to modify the hydrophilicity andbiocompatibility of graphene toward the awaiting biomedical applications.Importantly, the uniform coating of graphene with PDOPA was achievedvia thermally driven polymerization of LDOPA. The PDOPA content inthe hybrid graphene/PDOPA solid reached 23 wt %, while the coatingrich in hydroxyl, carboxyl, and amine moieties guaranteed excellentwettability with water. Taking the results toward upscaling, we havedemonstrated that the graphene@PDOPA nanohybrid acts as a dispersingagent for the pristine graphene flakes, allowing to form long-lastingacrylic dispersions. As a consequence, flexible and printable/paintablecoatings of significantly lowered electrical resistance up to 1.9kΩ sq–1 could be straightforwardly manufactured,minimizing the need for graphene functionalization which, in turn,lowers the cost and the environmental impact. These value-added characteristicsmake graphene@PDOPA hybrids suitable for textronic sensors, chargedissipation, or EMI shielding. Importantly, the modification appearsas directly extendable to other sp2-carbon allotropes suchas CNTs, fullerenes, nano-onions, nanohorns, or quantum dots.Wedemonstrated the water-based hence green approach to the covalentlyfunctionalized graphene via the bioinspired “growth-from”polymerization of


Respiration monitoring is a promising alternative to medical diagnosis of several diseases. However, current techniques of respiration monitoring often require expensive and cumbersome devices which greatly limit their medical applications. Here, we present a fully integrated wearable device consisting of a flexible LCP-copper interdigital electrode, a sensing layer and a wireless electrochemical analysis system. The developed humidity sensor exhibits a high sensitivity, a good repeatability and a rapid response/recover time. The long-term stability is over 30 days at different relative humidity. By integrating the flexible humidity sensor with miniaturized electrochemical analysis system (0.8 cm × 1.8 cm), response current concerning respiration can be wirelessly transmitted to App-assisted smartphone in real time. Furthermore, the fabricated humidity sensor can realize skin moisture monitoring in a touch-less way. The large-scale production of miniaturized flexible sensor (4 mm × 6 mm) has significantly contributed to commercial deployment. Advancements in wearable flexible sensors and smartphone healthcare systems have contributed to the commercial market for wearable technology . At pres2) (2) (2)  board into a wearable sensor for respiration monitoring.Recently, transition metal dichalcogenides (TMDs) such as molybdenum disulfide (MoS2) , rhenium2) (2) , and tun (2) (2)  have gai sensing . Otherwi sensing . Here we sensing . Using i2, absolute ethanol (99.7 wt%) were purchased from Aladdin Ltd. . Poly (N-vinylpyrrolidone)  was purchased from Sigma-Aldrich Co., Ltd. . LCP substrate of 50 μm was provided from Taiflex Scientific Co., Ltd. All chemicals were of reagent grade.MoSAll electrochemical experiments were conducted on a CHI660E electrochemical workstation. Electrode appearance scanning microscopy was handled using VHX-5000 Ultra-depth three-dimensional microscope . Scanning electron microscopy (SEM) images were collected on a Sigma HV . Fourier transform infrared spectroscopy (FT-IR) spectra were collected on a Nicolet iN10 FT-IR spectrometer .2 was suspended in a mixed solution of absolute ethanol and deionized water  and subjected to ultrasonication with 380 W power. After exfoliating at room temperature for 1 h, 0.2 g PVP was added as surfactants and stabilizer for another 48 h under the same conditions. Then the suspension was centrifuged for 15 min at 7,500 rpm, and the resulting supernatant was preserved as the MoS2/PVP ink for inkjet printing .The humidity sensor was fabricated on a 50 μm thick LCP substrate with copper cladding on one side. The copper interdigital electrodes were fabricated on the initial flexible substrate by FPC technology, which involves two main steps as followed: First, optical dry film photoresist lithography (DFPL) was performed by roller lamination of the dry film photoresist  on LCP copper clad plate at 100°C and a speed of 1.4 m/min, followed by UV-exposure with the energy density of 130 mJ/cm2/PVP ink was inkjet-printed on LCP-copper interdigital electrodes which were pre-treated by oxygen plasma treatment  to fabricate humidity sensors. Inkjet printing was conducted using a commercial drop-on-demand Epson L310 printer. The printer cartridge was designed to dispense droplets with a volume of 3 pL based on the orifice of 63.5 μm in diameter 2 for 54% RH, NaCl for 75% RH, KCl for 84% RH and KNO3 for 94% RH, respectively 3O+) transfer is difficult to occur under the electrostatic field. With relative humidity increasing to high level, more water molecules are physiosorbed above the chemisorbed layer by hydrogen bonding to form continuous water multilayer. According to the Grotthuss chain reaction, the protons hopping-transfer is generated and used to ionic conductivity, leading to a rapid decrease in electrical resistance and increase in response current.At low relative humidity, chemisorption of water molecules occurs on the surface of the sensing layer. These chemisorbed water molecules act as electron donors for the sensing materials, allowing for decreased electrical resistance. However, due to the discontinuous of the water layer at this process, the hydronium ion . The consistent baseline (current response of device under 45% RH) and the current changes of the device under 30 cycles of exposure to the high relative humidity (above 90% RH) indicate good repeatability of the proposed humidity sensor . Long-teThe normal respiration of an adult lasts 3–5 s and exhaled air humidity is above 90% RH. In consideration of the high performance of the humidity sensors fabricated in this study, we further integrated the flexible copper interdigital electrode components, sensing layer, and miniaturized PCB board into a wearable patch sensor for respiration monitoring.The PCB board of electrochemical workstation with miniaturized format (0.8 cm × 1.8 cm) consists of a signal conditioning part, a Bluetooth transceiver and a programmable electrochemical chip. The signal is wireless communication between wearable humidity sensor and smartphone-based platforms. The system is powered by a 150 mAh rechargeable lithium battery. The applied potential was set as 200 mV during operation. Due to a low soldering temperature of LCP , conductive silver paste was used for the connection between wire and LCP-copper interdigital electrode.In order to evaluate the real-time breath monitoring application of the fabricated humidity sensor, the device was attached under a volunteer’s nose about 5 mm. As shown in 2 to nanoscale, increased the surface volume ratio and the edge active sites. Meanwhile, the lactam units of PVP are active binding sites for water molecules which enhance the mobility of charge carriers during polarization. Compared with other humidity sensors for respiration monitoring in literatures (In this study, we have developed a fully integrated flexible humidity sensor that enables wearable respiration monitoring. LCP proved to be one of the most desirable flexible materials for humidity sensing applications as its excellent chemical properties, electrical insulator and ultra-low water absorption. The humidity sensing material was prepared by simple liquid-phase ultrasonic exfoliation method. PVP-assisted exfoliation has considerably reduced the dimension of MoSeratures , the dev


Those novel organic–inorganic hybrid composites can be efficiently prepared via both covalent and noncovalent bonds by classic organic reactions and supramolecular interactions, respectively. Pillararene-functionalised graphene materials have been used in various applications, such as electrochemical sensing guest molecules, performing as the platform for fluorescent probes, carrying out fluorescence quenching as the sensor, biosensing toxic molecules in cells, Raman and fluorescence bioimaging of cancer cells, photoacoustic and ultrasound imaging, as well as storage materials and reactors in energy fields.Pillararene-modified graphene materials integrate the advantages of both graphene and pillararenes;  The current research progress on diverse pillararene derivative functionalised graphene materials, including different synthesis strategies and various applications, is reviewed. Similarly, the rim-differentiated functionalised pillar[5]arene X6  and fluorescence spectroscopy.The classic organic synthesis methods were popular in the preparation of hybrid materials. For example, by using the EDC–NHS coupling reaction between carboxylate groups on X5  and hydrarene X6 24 was gr25Alternatively, per-hydroxylated pillar[5]arene X7,  could co2 and RGO were prepared by a hydrothermal reduction between Na2MoO4 and l-cysteine (l-Cys) in the presence of graphene oxide sheets.22 The positively charged trimethylammonium perfunctionalised pillar[5]arene , MoS2/RGO has the morphology of wrinkled thin flakes. In another example, by using a similar hydrothermal synthetic route and driving forces for the fabrication of hybrid materials, water-soluble N-methylimidazole perfunctionalised pillar[5]arene X8  electrochemical and fluorescence sensing, (2) biomedicines and biosensing, Raman and fluorescent bioimaging, as well as photoacoustic and ultrasound imaging, (3) lithium storage and catalysis.In their application to electrochemical sensing, the electrical properties of graphene materials allow them to generate significant electrical signals towards guest molecules introduced by the supramolecular recognitions of pillararene cavities. In their application in fluorescence sensing, the two-dimensional morphologies of graphene materials perform as the platform to load pillararenes on the surface, which further serve as the active recognition sites for fluorescent guests or probes.19 Particularly, ternary hybrid materials RGO–AP5–AuNPs exhibited the best sensing abilities towards dopamine with a broad linear range from 1.5 × 10−8 to 1.9 × 10−5 mol L−1, as well as a low detection limit of 1.2 × 10−8 mol L−1 at a signal-to-noise ratio of 3, due to the synergetic action of multifunctional properties such as the capacity for supramolecular recognition by pillararenes, catalytic properties of gold nanoparticles as well as the electrochemical properties of graphene  by cyclic voltammetry. For example, the hybrid nanocomposites RGO–AP5 and RGO–AP5–AuNPs have selective supramolecular recognition and the capacity for enrichment towards guest molecules, as analysed among electroactive candidates such as dopamine, 4-acetamidophenol, uric acid, methylene blue, tryptophan and imidacloprid.graphene .25 have a good capacity for recognising guest molecules such as dopamine, ascorbic acid and uric acid, and exhibit selective electrochemical response towards dopamine, due to the molecular recognition by the cavities of pillararenes. Pillararenes also perform as promotors for enhancing the electrochemical response. In comparison with cyclodextrin-modified RGO, CP5-RGO32 exhibit better electrochemical catalytic activity as a sensor, e.g., the trace detection of methyl parathion with the low detection limit of 3.0 × 10−10 mol L−1 (S/N = 3) and the linear response range of 1.0 × 10−9 to 1.5 × 10−4 mol L−1.In another example, the hybrid composites RGO-P5A23 due to the π–π stacking interactions between aromatic dyes and RGO, as well as possible host–guest interactions between dyes and the cavity of pillar[5]arenes.Pillararene-functionalised graphene materials could also be applied in fluorescent dye sensing. For example, due to the carboxylate perfunctionalised pillar[5]arenes (X5), the composite RGO-CP5 nanosheets exhibit enhanced fluorescence-quenching properties towards rhodamine 6G and neutral red in comparison to unmodified RGO,via hydrophobic interactions by the cavity of pillar[5]arene, the AmPA5-RGO composite can act as a fluorescent sensing platform for the detection of acetaminophen, in which the acridine orange performed as the signal probe.27 It has been proved that this fluorescence sensing system has a low detection limit of 5.0 × 10−8 mol L−1 with a S/N ratio of 3, as well as a linear response range of 1.0 × 10−7 to 4.0 × 10−6 and 4.0 × 10−6 to 3.2 × 10−5 mol L−1.Due to the difference in supramolecular recognition towards guest molecules such as acridine orange and acetaminophen 30 PCP6-RGO also performs as a selective and sensitive fluorescence platform for detecting trinitrophenol with acridine orange as the probe, exhibiting a low detection limit of 3.5 × 10−9 mol L−1 (S/N = 3) and a wider linear response of 1.0 × 10−8 to 5.0 × 10−6 and 5.0 × 10−6 to 1.25 × 10−3 mol L−1.By using a similar fabrication strategy,e.g., Raman imaging or irradiating under near-infrared (NIR) light.The introduction of modified pillararene derivatives can not only improve the aqueous solubility of graphene materials, but can also enhance the biocompatibility of hybrid materials. Furthermore, pillararenes donate their electron-rich cavities for the supramolecular recognition of electron-deficient guests, which provides the possibility of including and delivering particular guest molecules for biomedicines. The unique physiochemical properties of graphene materials have been primarily explored, such as thermal structural properties, via supramolecular recognition. For example, after integrating with water-soluble pillararenes, hybrid materials X2-GO and X3-GO @RGO33 @RGO33  performs+˙X9)Y7  nanobubbles under the irradiation of a NIR laser Y7 performed significant roles in increasing the NIR absorption as monitored by the changes in temperature shown by an IR camera.The water-soluble tertiary amine perfunctionalised pillar[6]arene X9, -modified+˙X9)Y7 29via hosIR laser . Due to 2 and RGO together. During the preparation, the positively charged pillar[5]arene X8 could mitigate the charge incompatibility between MoO42− and the graphene oxide sheets in the fabrication of the hybrid composites MoS2/RGO-NP, in which the MoS2 sheets were well dispersed on the surface of RGO containing exposed active edge sites 28 could deliver a reversible specific capacity as high as 1289 mA h g−1 at the same current density of 1000 mA g−1. Particularly, the reversible capacity of 996 mA h g−1 can be retained after 1100 cycles at unchanged current density. Furthermore, the hydrogen evolution reaction is the key step in producing hydrogen via electrochemical water splitting using solar energy or electricity. The MoS2/RGO-NP composites  Regarding organic components, 36 should be borrowed to expand the current categorization and morphology of 2D layered inorganic structures, which could provide the possibility for applying the obtained hybrid materials to, e.g., the hydrogen evolution reaction.37,38 Furthermore, the special physiochemical functions of graphene, including but not limited to nanoscale morphologies, as well as inert, thermal structural, optical and electrical properties should be deeply explored in these hybrid materials.39(2) Regarding the inorganic components, new synthesis strategies such as the strategy of covalent cross-linking(3) Regarding the study of the binding mechanism, the driving forces during the fabrication of pillararene-functionalised graphene materials need further investigations such as computational calculations, high-resolution electron microscopic observations as well as crystallographic studies. The different synthesis strategies regarding covalent and noncovalent interactions should be re-evaluated to ascertain their advantages and disadvantages.via either the modification of pillararene derivatives or the decoration of the outer surface of graphene materials. The introduction of various functional moieties40,41 could allow pillararene-functionalised graphene materials to, for example, have better water dispersity and solubility, which promote the materials to have better biocompatibility and lower cytotoxicity, leading to the expansion of application to more aspects of biomedicines such as diagnosis and combined therapy.42(4) Concerning the expansion of the application fields, more functional groups could be introduced into the hybrid composites 2DTwo-dimensionalAFMAtomic force microscopyCLSMConfocal laser scanning microscopyGCEGlassy carbon electrodeGOGraphene oxidel-Cysl-CysteineMTT3--2,5-diphenyltetrazolium bromideNIRNear-infraredRGOReduced graphene oxideSEMScanning electronic microscopyTEMTransmission electron microscopyTGAThermal gravimetric analysisXPSX-ray photo-electron spectroscopyThe authors declare no conflict of interest.