IV and non-linearity of FN curves at room-temperature can be interpreted by the adsorption effects. Water is speculated as the most responsible gas specie. We have calculated the work function of graphene by VASP. The results show that water adsorption will lower the work function of the graphene edge, while increasing the work function of the graphene surface.Water adsorption on graphene edges was studied by field emission (FE) experiments and first principles simulation. By analyzing the FE current change with temperature, it was concluded that the intrinsic FE of a graphene edge is consistent with Fowler–Nordheim (FN) theory. The noise of  Water adsorption on graphene edges was studied by field emission (FE) experiments and first principles simulation. Small gas molecules such as H2O, H2, O2, CO, NO2, and NO, will influence the electronic structure and other properties of graphene,16–26 the adsorption of some metal atoms such as lithium27 potassium28 have been calculated. However, there is no convenient and efficient experimental method to study the adsorption on graphene edge. Graphene edge show significant field emission (FE) ability,29–32 which can be a very suitable and simple method to study the adsorption on nanomaterial. We have studied the water adsorption on multiwalled carbon nanotube by analyzing the FE behavior at different temperature.33 In this paper, we have studied water adsorption on graphene edge by FE method. It has been found that the water adsorption will lower the work function of graphene edge. The first principle calculation based on VASP further verified the experimental results.Graphene, a two-dimensional (2D) single layer of carbon atoms bonded in a hexagonal lattice,2.34 Scanning electron microscopy (SEM) and Raman spectroscopy indicate that the sample is few-layer graphene. 35 The graphene field emitter is fabricated by sticking them on a molybdenum wire of 0.1 mm diameter with organic binder, which can be thoroughly evaporated after being heated at 350 °C in air a few minutes. The FE experiment was conducted in a high-vacuum chamber with a base pressure of 10−5 Pa. Graphene were prepared by the chemical method.IV curve of the graphene at room temperature (RT). Here a DC voltage sweeping from 300 V to 1100 V was applied to the sample. It can be seen that the curves show obvious noise. The emission current is 0.2 μA at 3.75 V μm−1 and 4 μA at 5.5 V μm−1. IV curve of the graphene at 1198 K. It can be seen that the IV curve is very smooth. 36 heating can be used as a useful method to remove adsorbents. The dwelling time of the adsorbents will be shortened at high temperature. Therefore, the FE at 1198 K in this experiment is determined as the intrinsic FE of graphene after the removal of adsorbents .37J is the current density, λM a macroscopic pre-exponential correction factor, a and b are constants , ϕ is the work function of the emitter (4.74 eV for graphene33), E is the applied electric field38 . β is the local electrical field enhancement factor, vF (correction factor) is a value of the Schottky–Nordheim barrier function v. The field enhancement factor β can be calculated from the slope ‘m’ of the FN curves (the curves of ln(1/V2) versus 1/V), using the following equation.According to the FN equation,β) of graphene was calculated and listed in β of graphene was 13 063.81424, 11 725.88950, 10 676.06139 at 830V–947 V, 948–973 V, 994–1052 V. There is no big difference for the β of three segments, which is also close to the aspect ratio estimation based on the SEM image shown in β verified that the FE comes from graphene edge. Because adsorption can not change geometric structure of graphene, the β at RT can be viewed as almost same as that at high temperature. The work function at RT calculated was 3.29 through solving β and the slope of FN plot at RT. The substituted β was the average value of three segments at high temperature. The work function at RT was small than this calculated by the Zhu F.33 This implies that adsorption can lower the work function of graphene edge.The field-enhancement factor 40 formalism of DFT, as implemented in the VASP.41 The adopted exchange–correlation functional is the generalized gradient approximation with the Perdew–Burke–Ernzerhof (PBE).42 The cutoff energy for the plane wave basis set was taken as 400 eV. The geometry optimization of each isomer was carried out till the energy was converged to an accuracy of 10−4 eV. Brillouin zone integration is performed using Monkhorst–Pack grids43 for all calculations. We build three kinds of models as shown in 3 in K-point sampling is chosen as 5 × 5 × 1 and 1 × 1 × 1 for the slab and the cubic, respectively.Work function is the most direct parameter which can reflect the influence of the adsorption. We have calculated the work function of H2O in three kinds of models as shown in 2O and the graphene as shown in 2O and the graphene surface up to 3.70 Å after relaxation. The interaction between them is only about 0.18 eV. In order to affirm our results, we simulate the graphite surface with five-layer graphene as shown in 2O and the surface of graphite is up to 3.81 Å after relaxation. The interaction between them is 0.23 eV. Since the FE and adsorption/desorption happened on graphene edge in our experiment, we simulate the adsorption of H2O on the edge of graphene as shown in 2O and adsorb at two zig–zag carbon atoms after relaxation. The adsorption energy of H and hydrogen bond is up to 5.93 eV, which is a strong interaction. Obviously, it is physical adsorptions for H2O on the surface of graphene and graphite, and it is chemical adsorption for H2O dissociation on the edge of graphene.We calculated the adsorption of H2O are very close to the calculated work function using the average electrostatic potential of 7 × 7 pure grapheme44 and the experimentally measured work function 4.45–4.74 eV.33,45–47 It can be found that work function for graphene slabe surface increase from 4.24 eV to 5.15 eV due to H2O adsorption, work function for 5-layer graphene increase from 5.00 eV to 5.09 eV due to H2O adsorption, while work function for graphene edge decrease from 5.73 eV to 5.63 eV due to H2O adsorption. This is in good accordance with our experimental results that the FE comes from graphene edge and the FE current change with the adsorption/desorption.The work functions results are tabulated in 4.2O has calculated by VASP. The calculated results show that the water adsorption will lower the work function of graphene edge, while increase the work function of graphene surface. This is in good accordance with the experimental results.In summary, the water adsorption on graphene edge has been studied. It was found that the adsorption induced the deviation from the FN model at RT. After removing the adsorbates by heating, the intrinsic FE of graphene edge follows the FN model very well. Water is speculated as the most responsible gas specie. The work function of graphene with HThere are no conflicts to declare.


Metamaterial absorbers (MMAs) that absorb electromagnetic waves among an ultra-broad frequency band have attracted great attention in military and civilian applications. In this paper, an ultra-broadband and highly-efficient MMA is presented. The unit cell of the proposed MMA was constructed with two cross-placed stand-up gradient impedance graphene films, which play a key role in improving impedance matching. Considering the trade-off between absorbing performance and processing complexity, in our design, we adopted the stand-up graphene films that have a gradient with three orders of magnitude in total. The simulated results of the proposed absorber show an ultra-broadband absorption (absorptivity > 90%) from 1.8 GHz to 66.7 GHz and a highly-efficient absorption (absorptivity > 97%) in the range of 2–21.7 GHz and 39.6–57 GHz. The field analysis was adopted to explain the mechanism of the proposed absorber. To validate this design, a prototype of 20 × 20 units was processed and assembled. The graphene films were processed with graphene conductive ink using screen print technology. The measured results are in good agreement with the simulated ones. The proposed absorber may find potential applications in the field of stealth technologies and electromagnetic interference. Metamaterials are arrays of the periodic arrangement of subwavelength artificial units, with the electromagnetic properties undiscovered in natural mediums. It has attracted more and more attention because of its ability to control electromagnetic energy arbitrarily, and a large number of radio frequency devices based on metamaterials have emerged. By designing the structure of unit cells, the electric or magnetic resonance will occur in the metamaterials at the desired frequency band. The incident electromagnetic wave will enter the metamaterials without reflections and be stored in it. Since all parts of the structure are lossy, such as metal, substrate, and lumped elements, the incident energy will be absorbed and lost by absorbers. MMAs are widely used in the field of stealth technologies and electromagnetic interference/compatibility for their flexible design. Compared with traditional absorbing materials, the reported MMAs usually have a broader operating band and a lighter weight. Moreover, the center frequency could also be designed to the desired one easily. However, the absorptivity of traditional absorbing materials is higher than that of MMAs. So, it is important for MMA to achieve an ultra-broadband and highly-efficient absorption, which is an essential indicator of absorbers for practical applications.One of the most classic microwave absorbers, the Salisbury absorption screen , is compGraphene, as one of the most promising materials in the design of MMAs, has attracted wide attention in recent years ,6. SinceIn this paper, an ultra-broadband and highly-efficient metamaterial absorber with stand-up gradient impedance graphene films is proposed. This paper is arranged as follows. In In this part, we will present the proposed design and its performance in detail. We will indicate how this idea emerges as well. Firstly, the structures of the proposed MMA are presented in t as support. The p and g, respectively. The view in The unit cell, as shown in In the case of an extreme broadband frequency response, the results calculated by the Time Domain Solver are more accurate. So, the full-wave simulation was performed on CST Studio Suite 2021 with the Time Domain Solver in this paper. The simulation results under the TE and TM polarized incident wave are shown in As shown in To demonstrate the superiority of the proposed MMA over the reported 3D absorbers with stand-up uniform resistive films , we haveThe theory of small reflections  proves tN). If we increase N, the step changes in the characteristic impedance between the sections would become smaller, and the transformer geometry approaches a continuously tapered line. Please note that, since the electrical length . So, we can change the sheet resistances of graphene films by adjusting the film thickness.To verify the proposed absorber with gradient impedance graphene films, a prototype constructed with 20 × 20 units was fabricated and measured. In this paper, the graphene films were processed with graphene ink using screen-printing technology. The preparation and characterizations of graphene conductive ink have been reported in our previous works ,17,18. TIn terms of screen-printing technology, the thickness of printed film is affected by the mesh density of the screen, the printing force/angle, and the viscosity of ink. However, it was difficult for us to control these parameters precisely since we printed films manually with a manual screen printer. Finally, to facilitate processing and increase precision, we controlled the sheet resistances of graphene films by the number of print passes, because increasing the times of printing results in an increase in thickness. For example, in this paper, the graphene films with sheet resistances of 400, 200, and 100 correspond to 1, 2, and 4 print passes, respectively. That is why we keep the sheet resistances of graphene as a multiplicative relationship in simulations.The grooves on PMMA were reserved for assembly as in the schematic in The reflection coefficient was measured using the free space method. The measurement set-up is shown in The comparison of measurement and simulation results is shown in The performance comparison between the proposed MMA and other reported ultra-broadband absorbers is shown in It is well known that a 3D absorber can easily realize ultra-broadband absorption. However, in terms of the highly-efficient absorption with an absorptivity larger than 97%, it is also difficult for 3D absorbers to realize during a broad band. For example, the highly-efficient absorption bands in ,4,19 areCompared with those works, the proposed absorber exhibits an ultra-broadband and highly-efficient absorption at the same time due to the stand-up gradient impedance graphene films. The adopted gradient impedance structure maintains the performance at a low frequency efficiently. The stand-up resistive films structure creates the ultra-broad operating band.In this paper, we presented an ultra-broadband and highly-efficient metamaterial absorber with stand-up gradient impedance graphene films. The proposed absorber shows the ability of ultra-broadband and highly-efficient absorption. The theory of small reflections was used to help with understanding the better matching brought by gradient impedance. A field analysis was performed to illustrate the mechanism of ultra-broadband absorption. To verify our design, we fabricated a prototype with 20 × 20 units. In fabrication, conductive graphene ink and screen printing technology were adopted. To save processing cost and time, the sheet resistance of graphene in the gradient impedance structure was set as a multiplicative relationship. Then, we could print films with different sheet resistances by changing the print times. The measured results are in good agreement with simulated ones, which indicates that the design method of gradient impedance is effective. The proposed absorber realizes a highly-efficient absorption with an absorptivity larger than 97% during the most commonly used radar band (2–22 GHz), which makes it of great practical value and has application prospects in the field of stealth technologies.


The optical forces on the nanoparticles can be controlled by modulating the position of LSPR excitation. Controlling the position of LSPR excitation by bias voltage gates to configure the Fermi energy of graphene disks, the nanoparticles can be dynamically transported to arbitrary positions in the 2D plane. Our work is integrated and has multiple functions, which can be applied to trap, transport, sort, and fuse nanoparticles independently. It has potential applications in many fields, such as lab-on-a-chip, nano assembly, enhanced Raman sensing, etc.Optical tweezers are key tools to trap and manipulate nanoparticles in a non-invasive way, and have been widely used in the biological and medical fields. We present an integrated multifunctional 2D plasmonic optical tweezer consisting of an array of graphene discs and the substrate circuit. The substrate circuit allows us to apply a bias voltage to configure the Fermi energy of graphene discs independently. Our work is based on numerical simulation of the finite element method. Numerical results show that the optical force is generated due to the localized surface plasmonic resonance (LSPR) mode of the graphene discs with Fermi Energy E Since Ashkin first introduced the concept of optical tweezers through experiments and theoretical works in the 1970s , this teGraphene is a new two-dimensional material with a single-layer carbon atom structure. Due to its zero bandgaps and unique photoelectric properties, graphene has gained much attention in recent years due to its unique optical properties ,34,35,36Here we theoretically propose integrated multifunctional graphene discs 2D plasmonic optical tweezers for manipulating nanoparticles, which can trap and transport nanoparticles anywhere in the 2D plane by applying bias voltage without a preset path. Our work is based on numerical simulation of the finite element method. The distribution of optical forces on the nanoparticles and the trapping potential are simulated theoretically using the finite element method. Further, we perform simulations of the photothermal fluid and estimate the magnitude of other major forces on the nanoparticle, including the Brownian motion force, the Stokes’s drag force, and thermophoretic force. We numerically demonstrate the ability of this system to trap, transport, and fuse nanoparticles through the Langevin equation, and plot the motion trajectory of the nanoparticles. This work can be applied to trapping, transporting, sorting, and fusion of nanoparticles flexibly and has potential applications in many fields, such as optical sensing, enhanced Raman sensing, biophysics, Opto-mechanic, etc.n = 1.33) under a normal incident plane wave with an intensity of 1 mW/µm2. The material of the insulator substrate layer is designated as BaF2 (n = 1.45), which has high transmittance in the mid-IR and has been proven to be applicable in graphene optical tweezer systems [ systems . We choo systems . When th systems . Monolay systems . The chaWe perform a full 3D simulation using a finite element method (COMSOL Multiphysics). In our numerical study, Graphene is modeled as a two-dimensional transaction boundary condition with a thickness of 0.34 nm . The KubHere lated by :(2)Vg=td0 and εd are the dielectric constant and the thickness of the gate oxide. 6 m/s is Fermi velocity. dt is the distance from the graphene disc to the bias voltage gate. We use the Maxwell stress tensor to calculate the time-averaged optical force on the nanoparticle [Here εparticle ,55.(3)〈S is the outer surface of the nanoparticle and n is its discrete normal vector, T〉 is the Maxwell stress tensor which can be governed as:Here E and H are the intensity vectors of the electric and magnetic fields on the surface of the particle, respectively. Through Helmholtz Hodge decomposition, the optical force can be decomposed into conservative force and non-conservative force. We only take the conservative force into consideration [Here deration ,57. The deration :(5)Ur=−∫It is well known that plasmonic systems with different structures have specific resonance wavelengths. To better understand the resonance distribution of a graphene disc under incident light, We set up a probe at 50 nm above the center of the graphene disc (the center of the nanoparticle) to determine the efficiency of near-field enhancement. A normalized intensity map is represented in 0 = 1 mW/µm2, which has much lower than other plasmonic optical tweezer systems [x-axis, with y-center = 0 and z-center = 50 nm. When x-center = −160 nm~160 nm, Fz is always negative (Fz < 0 pN), which proves that the nanoparticle will be pulled to the interface between the dielectric material and the trapping environment. When x-center > 0, Fx is a positive force (Fx > 0 pN), x-center < 0, Fx is a negative force (Fx < 0 pN), x-center = 0, Fx = 0 pN. This means that the nanoparticle will be trapped by the optical force in the center of the graphene disk along the x-axis. As the result shown in x-axis, we calculate the trapping potential of the nanoparticle along the x-axis, which is greater than 10 KBT to ensure stable trapping. Corresponding to the graphene disks diagram at the top of the figure, the trapping region in the x-axis direction contains the entire area of the adjacent graphene discs. This demonstrates that, by dynamically configuring the Fermi level of graphene, the motion of nanoparticles can be controlled along the x-axis. y-axis, with x-center = 0 nm and z-center = 50 nm. Fy is a positive force (Fy > 0 pN), y-center < 0, Fy is a negative force (Fy < 0 pN), y-center = 0, Fy = 0 pN. This means that the nanoparticle will be trapped by the optical force in the center of the graphene disk along the y-axis. As the result shown in y-axis, we calculate the trapping potential of the particle along the y-axis, which is greater than 10 KBT to ensure stable trapping. Corresponding to the graphene disks diagram at the top of the figure, the trapping region in the y-axis direction contains the entire area of the adjacent graphene discs. This demonstrates that, by dynamically configuring the Fermi level of graphene, the motion of nanoparticles can be controlled along the y-axis. z-axis, with x-center = 0 nm and y-center = 0 nm. d is the distance from the bottom of the nanoparticle to the graphene disc. It can be found that the larger the radius of the nanoparticle the greater the optical force on it. By the line integral of the force along the z-axis, we calculate the trapping potential of the nanoparticle on the x-axis. The result is shown In BT. This can be improved by appropriately increasing the incident light intensity.We continue to investigate the optical forces on the nanoparticle  at different locations, Fermi energy of the graphene disc is configured as 0.6 eV. We assume that the intensity of the incident light is I systems ,43. The f = 0.6 eV) under an incident light intensity I0 = 1 mW/µm2. s − Te. Ts is the temperature at each point when the simulation reaches a steady state. Te is the operating room temperature. ΔT increases only 2 °C compared to room temperature. To estimate the thermal behavior in the proposed system, The thermally induced convective distribution is represented in We next numerically investigate the temperature distribution and convection field near the graphene disc r(t)=c dipole ,63.z-axis for the calculation of the force of the optical gradient. We propose here a 3 × 3 array of graphene discs. As mentioned before, the optical forces on the nanoparticles can be switched quickly by controlling the switching states of the adjacent trapping positions. 5 times. The nanoparticles are released at moment 0, and the initial positions are set at ,  in the x-y plane (z = 50 nm plane), respectively. As is shown in The optical force on the z-axis will make the nanoparticles cling to the partition interface of water and insulator and move in the x-y plane. So we only consider the motion of the nanoparticle in the x-y plane. We choose the electric field intensity at 50 nm above the 0 = 1 mW/µm2. Finally, we demonstrate its ability to trap, transport, and fuse nanoparticles with a 3 × 3 array of graphene discs by means of the Langevin equation. We anticipate that it will become a new tool for nanoparticle manipulation and open new directions for its wide range of potential applications in lab-on-chip, nano-assemble, enhanced Raman sensing, etc.In summary, integrated multifunctional graphene discs 2D plasmonic optical tweezers for manipulating nanoparticles is shown to be achievable. We demonstrate that, when the Fermi energy of the graphene disk is 0.6 eV and the incident light wavelength is 8.26 µm, LSPR with compact electric field enhancement is formed. We theoretically calculate the optical forces on the nanoparticles and the trapping potential in the near-field enhancement. The trapping potential generated by the graphene discs in the ON state can cover the adjacent graphene discs. We demonstrate that nanoparticles can be manipulated independently in the x-y plane by modulating the position of the LSPR. Our study shows that the optical force on the nanoparticle is positively correlated with the radius and the relative refractive index of nanoparticles. We investigate the photothermal and thermographic fluidization of our proposed systems, and estimate the forces on the nanoparticles other than the optical force. We consider that the other forces can be neglected under incident intensity I


The as-obtained nanocomposite possesses good hydrophilicity, excellent biocompatibility and high biomolecules loading capacity, which acts as an ideal platform for enzyme modification. Considering this fact, Horseradish peroxidase is expressively immobilized upon Au NPs-PDA-PAA-graphene surface, in order to lay the foundations of a biosensor that is majorly based on enzymatic activity. The biosensor exhibits higher sensitivity towards the determination of H2O2 with linearity ranging from 0.1 μm upto 20 mm, and the limit of detection going down to 0.02 μm. Encouraged by its acceptable electrocatalytic performance, this multicomponent system can also be easily employed for carrying out the real-time tracking of H2O2 coming out of Macrophage cells. Therefore, this work designs an extraordinarily updated platform for biosensing related applications, and also presents a reliable platform for the direct detection of H2O2in vivo and in vitro, which show great potential in bioelectroanalytical chemistry, cellular biology, and pathophysiology.Herein, an Au nanoparticles-polydopamine-poly acrylic acid-graphene (Au NPs-PDA-PAA-graphene) multicomponent nanohybrid is fabricated by surface functionalization of graphene alongside extensive  The structural shape of graphene based nanocomposites incorporated with polymers as well as metallic nanoparticles, and other species to harvest synergetic effects and integrated properties of the individuals, has claimed great interest due to their wide range of scientific as well as industrial implications . Graphenin situ reducing method, Au NPs could easily be distributed upon the surface of the graphene nanosheets in a homogeneous way. The resulting Au NPs-PDA-PAA-graphene nanocomposites work an ideal platform for the modification of biomolecules. Horseradish peroxidase (HRP), with this unique ability of catalyzing the oxidation for an ample amount of substrates via hydrogen peroxide or any other closely related components, is hailed as a mainstream tool metalloenzyme for establishing the electrochemical biosensors  was added. Later, the prepared mixture was stirred at 40°C for 36 h. Then, CH2Cl2 was removed by centrifugation, and sediment was washed thoroughly by acetone and water to get pure PAA-graphene.The preparation of PAA-graphene: The synthesis of PAA-graphene was performed by hydrolyzing poly tert-butylacrylate (PtBA). The synthetic procedure of PtBA-graphene was described in our previously published paper . Brifly,2CO3 solution was poured to adjust the pH to 8.5. After sonication for 0.5 h, the solution became homogeneous. This solution was then transferred to an ice-bath, and followed by the addition of N-Hydroxysuccinimide  and 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride , the mixture solution (denoted as solution A) was made to stir under N2 for about 15 min. Meanwhile, Na2CO3 (55 mg) was dissolved in 10 ml of deionized water in order to prepare solution B. This solution was also made to stir under N2 for about 15 min, and then dopamine HCl (240 mg) was poured in with yet another degassing for about 15 min. Later, solution B was mixed with solution A and was again stirred for about 30 min inside an iced-water bath for about 12 h at around 35°C. During this process, dopamine is easy to polymerize to form polydopamine in alkaline conditions. Eventually, the reaction mixture was made to centrifuge and was also washed thoroughly using deionized water to achieve PDA-PAA-graphene.The synthesis of PDA-PAA-graphene: PAA-graphene (200 mg) was dissolved in 10 ml of deionized water, Na4 solution (50 mm). The reaction was allowed to continue overnight at the expected room temperature. At the end of the reaction, the Au NPs deposited PDA-PAA-graphene was removed from the suspension via centrifugation process and were frequently washed with water.The preparation of Au NPs-PDA-PAA-graphene: PDA-PAA-graphene (10.0 mg) was put inside a reaction vessel, and was poured with 10 ml of HAuCl−1 HRP for overnight reaction, followed by washing with Milli-Q water and then drying at 4°C.The enzyme based electrode was designed by immersing Au NPs-PDA-PAA-graphene electrodes into phosphate buffer solution (PBS) with 0.2 mg ml2O as solvent. UV-vis spectra were observed on a Schimadu UV-2550 spectrometer. Scanning electron microscopy images were acquired by using FESEM instrument . CV and chronoamperometric analysis were undertaken by a CHI 660 D electrochemical workstation (CH Instrument Company). For this purpose, a traditional three-electrode system was selected. HRP/Au NPs-PDA-PAA-graphene electrode was used as a working electrode. The auxiliary and reference electrodes were Pt wire and Ag/AgCl, respectively. All the measurements were conducted at room temperature.A Kratos-Axis spectrometer having monochromatic Al KR of , an X-ray radiation of (15 kV and 10 mA) and a strong hemispherical electron energy analyzer, was used to carry out X-ray photoelectron spectroscopy (XPS) determinations. Casa XPS software was employed to accomplish curve fitting and background suppression. Fourier-transformed infrared spectrum (FT-IR) was observed on Perkin Elmer FTIR. Thermogravimetric Analysis (TGA) was achieved with the help of TA Instruments TGA/DSC. 1H NMR measurement was performed on a Bruker AVANCE NEO 400 M equipment with D® is a modified MCDB 131 formulation and is supplemented with 10 μg/ml hEGF , 1.0 mg/ml Hydrocortisone, 50 mg/ml Gentamicin, 50 μg/ml Amphotericin B, 3 mg/ml Bovine Brain Extract (2 ml), 2% v/v Fetal Bovine Serum (FBS) and stored at 37°C in humid conditions with 5% CO2. 24-well plate was used to seed macrophages where they gained 80% confluency before experiments. Calcein-AM was used for living cell staining. Macrophages cells were incubated at 37°C for 15 min before imaging.ATCC (United States) supplied the macrophages and the cells containing Bovine Brain Extract (BBE) supplement were stored in Endothelial Cell Growth Medium (EGM). EGMvia the condensation reaction between the NH2 group in DA and the carboxyl group in PAA, meanwhile, DA will polymerize to form polydopamine (PDA) in alkaline conditions. Next, Au NPs are immobilized onto PDA-PAA-graphene by in situ reducing of HAuCl4 by dopamine. Au NPs-PDA-PAA-graphene was coated on the glassy carbon electrode to build a platform for enzyme loading. Finally, HRP was absorbed on the electrode to construct an enzyme electrode.The detailed process employed for carrying out the preparation of the Au NPs-PDA-PAA-graphene composite is illustrated in 7/2 and Au 4f5/2 show up at the binding energies of 83.9 and 87.7 eV respectively  is first applied to trace the synthesis process. The condensation reaction between dopamine and PAA-graphene can be verified by noticing a new absorbance peak at 400.8 eV linked to the binding energy of N1s in an XPS spectrum of PDA-PAA-graphene . After iectively , suggestvidually   in PDA-PAA-graphene. Where, A stands for the integral part of the peaks at d 6.83–6.40 representing the quantity of H in the aromatic rings of the given catechol moieties, while A0 corresponds to the integral part of the peaks at d 2.2–1.2 showcasing the quantity of H in the PAA backbone. The dopamine ratio found in the resultant polymer is nearly 25% as per the given method. This result is a little lower than that calculated by thermogravimetric analysis (31%)  .4, a relatively new peak at 556 nm appears and the solution becomes violet black in color. This newly appearing peak can well be stemming from the surface plasmon resonance (SPR) absorptive band for Au NPs, highlighting the reducibility of AuCl4−1 to Au NPs in a successful way . A clearly distinguishable couple of redox peaks in the CVs of HRP/PDA-PAA-graphene are attributed to the FeIII/FeII redox coupling related to the heme protein for HRP  and anodic peak potentials (−0.267 V). Considering the conventional potential [Eo’ = (Epa + Epc)/2] of −0.294 V, and peak point separation (ΔEp) ∼53 mV at the scan rate of (50 mV/s), indicating a reversible electrochemical behavior of HRP, which is much better than other HRP-based biosensors known so far  and Faraday’s law, the electrochemically active HRP can be calculated from HRP/Au NPs-PDA-PAA-graphene surface from the equation.    ], 3-mercol cm−2) .2O2 has been used as an analyte to study the catalytic applications of the fabricated HRP/Au NPs-PDA-PAA-graphene films. 2O2. When the different concentrations of H2O2 were injected into PBS, there was a clear rise in the reduction peak current with a gradual decrease in the oxidation peak current. This phenomenon well explains the remarkable electrocatalytic process for the HRP oxidation via H2O2 which in turn was reduced. H2O2 oxidized the HRPre to HRPox which was further reduced through electron transfer upon the electrode surface. As H2O2 concentration increased it encouraged a large cathodic peak current value, in turn there was a fast rate of electron transfer between the quantities of electrode surface and immobilized HRP.H2O2 in PBS at −0.32 V is shown in 2O2 concentration and attains a steady state within 5 s, which is credited to the rise in electron transfer from the embedded Au NPs. The lowest limit of detection (0.02 μM S/N = 3) and an excellent linearity range from 0.1 μm to 20 mm (R = 0.999) is better than that in similar systems previously reported  of ∼3%. Furthermore, the RSD for the current responses for more than 10 sensors obtained by following the similar protocol is ∼5%. For the stability evaluation of the HRP/Au NPs-DA-PAA-graphene film electrode preserved at 4°C, it gives 90% response even after 2 months of refrigeration  has been observed on the HRP/Au NPs-PDA-PAA-graphene film electrode at the applied potential (−0.32 V), which then further decreases as the H2O2 scavenger catalase was spiked. The same procedure was carried out with control well plates (without macrophages) which showed no response as depicted by 2O2oxidation. All the above discussed results markedly validate that the as-fabricated biosensor can initiate a new opening in biosensing platforms for the unswerving determination of extracellular as well as intracellular H2O2 and could well be effectively helpful for advanced physiological and pathological related studies.By keeping in mind all the advantages of the excellent catalytic performances of the fabricated electrode such as lowest limit of detection, enhanced sensitivity, and quick response, it is noteworthy to say that the as-fabricated biosensor can be used for the determination of the extracellular Hst cells . Howeverst cells . The che healthy . Accordi2O2 detection. The biosensor exhibits remarkable results in terms of extraordinary sensitivity, wider linear range (0.1 μm–20 mm), noble stability, lowest limit of detection (0.02 mm), and reproducibility for H2O2 detection, which is superior to previously constructed biosensing podiums. Hence, this work brings up an advanced biosensing platform for the determination of H2O2in vivo and in vitro, which can be of utmost advantage for bioelectroanalytical chemistry, cellular biology, and pathophysiological studies.In summary, new Au NPs-PDA-PAA-graphene composite films have been synthesized by loading highly active enzyme immobilization. The material is introduced onto the electrode surface, and serves as biosensor for extracellular and intracellular H


Semiconductor photoconductive switches are useful and versatile emitters of terahertz (THz) radiation with a broad range of applications in THz imaging and time-domain spectroscopy. One fundamental challenge for achieving efficient ultrafast switching, however, is the relatively long carrier lifetime in most common semiconductors. To obtain picosecond ultrafast pulses, especially when coupled with waveguides/transmission lines, semiconductors are typically engineered with high defect density to reduce the carrier lifetimes, which in turn lowers the overall power output of the photoconductive switches. To overcome this fundamental trade-off, here we present a new hybrid photoconductive switch design by engineering a hot-carrier fast lane using graphene on silicon. While photoexcited carriers are generated in the silicon layer, similar to a conventional switch, the hot carriers are transferred to the graphene layer for efficient collection at the contacts. As a result, the graphene-silicon hybrid photoconductive switch emits THz fields with up to 80 times amplitude enhancement compared to its graphene-free counterpart. These results both further the understanding of ultrafast hot carrier transport in such hybrid systems and lay the groundwork toward intrinsically more powerful THz devices based on 2D-3D hybrid heterostructures. THz imaging and spectroscopy always request even more efficient components. Here the authors, thanks to a modified photoconductive switch that includes a graphene layer, demonstrate a high-speed photoconductive switch without sacrificing the generated power. A THz PCS is composed of two metal pads contacting a semiconductor channel , typically composed of GaAs, InP, or silicon with high defect density. When operated as an emitter, a PCS is voltage-biased and illuminated with ultrafast femtosecond laser pulses. Electron–hole pairs are excited in the channel and separated by the bias field, creating a transient current. The transient current decays rapidly due to the sub-picosecond relaxation of excited carriers in the heavily defective semiconductor channel. The transient current in PCS couples with a THz antenna to emit the THz signal to the far field. While substrates with longer carrier lifetime (such as semi-insulating GaAs) can be used for efficient broadband THz emitter through clever engineering (such as the use of interdigitated antenna)7, short carrier lifetimes (picosecond) are in general preferred for efficient THz generation when the PCS is coupled with transmission lines/waveguides for THz modulation, studies of device transient phenomena, or almost any other application employing confined fields. The early work on PCS showed very low conversion efficiency for converting pump intensity to THz field9. The reason is a tradeoff between speed and amplitude: to enable sub-picosecond carrier lifetime, the channel materials are made defect-rich with either low-temperature growth or ion implantation. As a result of increased scattering, the carrier mobility drops substantially12, typically to around 1–200 cm2 V−1 s−1. The low mobility prevents the excited carriers from traveling a long distance before recombination, leading to a small transient current and weak THz emission. To mitigate this problem, researchers employ interdigitated15 and nanostructured plasmonic19 metal contacts. These designs reduce the carrier transport path length and increase absorption near the contact, making the carrier separation more efficient. However, they all require substantial surface patterning with sub-micrometer feature sizes, increasing the fabrication complexity.The photoconductive switch (PCS) is an important and widely used technology in pulsed THz field generation and detection, making it a critical building block in THz imaging and time-domain spectroscopy applications2 V−1 s−1 when suspended and 60,000 cm2 V−1 s−1 when encapsulated by hBN at ambient temperature21. It has been shown that hot carriers in graphene relax within a few picoseconds24, orders of magnitude faster than in conventional defect-free semiconductors. These features make graphene an exciting platform to study ultrafast hot carrier dynamics and THz generation. THz emission has been reported on graphene devices with a suspended graphene–metal interface due to built-in electric fields and photo-thermoelectric effects25. Other work has shown THz emission due to photoconductive effects26 and thermally excited plasmons27. However, all these approaches showed a rather low efficiency due to the low optical absorption  illuminates the metal–graphene–silicon heterostructure. The ultrafast hot carrier transport generates a THz field which is then coupled to the coplanar waveguide. After 100 μm propagation, the signal reaches the second Auston switch functioning as the detector. The detector switch is opened by a time-delayed probe pulse to enable sampling of the transient THz field. We tune the time delay of the pump and probe (or “gate”) beams via a motorized delay line  is applied across the graphene channel. A higher voltage up to 45–105 V is possible given the high breaking field of graphene with optimized sample preparation and 9 V We first directly compare the performance between our graphene–silicon hybrid PCS and silicon PCS with identical design except for the top graphene layer. Figure 38. We derived the values by fitting the rise slopes and fall slopes in Fig. We then measured the bandwidth from hybrid PCS with both the width of fitted Gaussian peaks Fig.  and Fourvel Fig.  due to g41 and local built-in field effects.Next, we investigated the possible mechanisms contributing to the large enhancement of THz generation in the graphene–silicon hybrid PCS. The generated THz field’s amplitude linearly increases for larger channel bias  model, as depicted in Fig. 2O3 as gate dielectrics) on top of the hybrid PCS structure  current at the more positive gate bias (Vg) is suppressed heavily. Similar behavior was observed on all 8 devices characterized  and sweeping the gate bias and the beam spot position along the channel  geometries. Ultrafast measurements on nanoelectronic devices, ballistic conductors, high-speed on-chip switching devices, etc. are often best-performed on-chip.By engineering a hot carrier fast lane in graphene–silicon hybrid PCS, we demonstrated significant enhancement of THz field amplitude without sacrificing bandwidth or SNR. Our investigation supports that photocarrier generation mainly happens in the silicon layer; hot carriers are then transferred from silicon to the graphene layer via CT mechanism and use graphene as the hot carrier fast lane to the metal contacts. Despite the earlier envisions of weak THz emission in graphene-based devices+ ions at 100 keV with a flux of 1015 cm−2. The ion-induced defects work as recombination centers. Previous studies reported that the excited carrier lifetime reduces to around 0.7 ps50 at our implantation flux, as verified by time-resolved reflectivity measurements. A CVD-grown graphene layer is then wet-transferred to the substrate and patterned into aμ graphene channel  using photolithography and oxygen plasma etching. Finally, a 300-nm-thick layer of gold is deposited onto the sample to form both metal contacts and double-stripe THz waveguides45 using standard lithography and lift-off processes.The device was fabricated on a silicon-on-sapphire substrate, with a silicon thickness of 300 nm. The silicon was first damaged by ion implantation with O50.The lifetime of transient carriers in silicon Auston switch is characterized by the same on-chip pump–probe measurement with an identical layout to our main measurements, with the only difference being that the emitter does not have a graphene layer on top. Supplementary Fig. Supplementary InformationPeer Review File


The as-prepared rGO-TPEP not only has good dispersion in solution but also processes the AIE feature. Its fluorescence intensity is 2.23 times higher than that of TPEP at the same condition. The unique optical properties and AIE effect enable the rGO-TPEP as a chemical sensor for highly sensitive explosive detection in aggregated state and solid state. In the aggregated state, trace 2,4-dinitrotoluene (DNT) can be detected by the rGO-TPEP even when the concentration is as low as 0.91 ppm, and the quenching constant is as high as 2.47 × 104 M-1.In this work, a dispersible graphene-based material with a characteristic of aggregation-induced emission (AIE) was prepared by wet chemical reduction of graphene oxide (GO). During the GO reduction process, a conjugated molecule TPEP containing tetraphenylethylene (TPE) and pyrene was employed as a stabilizer because of the  However, the performance of graphene is dependent on its dispersion in practical application. The graphene is easy to aggregate due to the strong van der Waals force between the graphene layers  was designed and synthesized, which was used as a stabilizer to prepare the non-covalent functionalized rGO via wet chemical reduction of graphene oxide (GO). The as-prepared rGO-TPEP not only had good dispersion in solution but also processed the AIE feature. Compared with TPEP, the AIE effect of rGO-TPEP was greatly enhanced. Furthermore, rGO-TPEP can be used for the detection of explosive as low as 0.91 ppm, and could be employed as a solid probe for the detection of DNT.2-conjugated structures. The as-prepared rGO-TPEP was stable in THF after removing the insoluble rGO via centrifugation. Compared with TPEP, rGO-TPE displayed a more transparent color, revealing less rGO in rGO-TPE than that in rGO-TPEP. Without conjugated molecules, rGO was only stable for several minutes, presenting its poor dispersion in THF solution. Therefore, TPEP is a better stabilizer for functionalized rGO due to the π–π interaction between rGO and TPEP.As illustrated in -1 were ascribed to the hydroxyl, carbonyl groups, and C=C skeletal vibration, respectively , 2,4-dinitrotoluene (DNT), and picric acid (PA). They not only pose a threat to the security of the country and society but also pose serious health hazards to human body. The explosive sensor based on photoluminescence (PL) has attracted extensive attention because of its high sensitivity. Explosives can cause fluorescence quenching of electron-rich probes through the photoinduced electron transfer (PET) mechanism . However0/I) and DNT concentration (2) was 0.95315, and the quenching constant was 2.47 × 104 M-1. In the concentration range of 50–250 µM (9.1–45.53 ppm), the quenching constant was 5.71 × 103 M-1. The higher value of quenching constant in the lower concentration means higher sensitivity and accuracy of detection for a small amount of explosives, so rGO-TPEP is more suitable for the detection of trace DNT.Fluorescence quenching could be detected even when the DNT concentration was as low as 5 µM (0.91 ppm), and the degree of quenching increased with the increase of DNT concentration . In the ntration , when DNIn addition to the aggregated solution state, it can also be detected in the solid state, which is even more convenient. The filter paper was dipped in the rGO-TPEP solution and dried to get the test paper. When the paper was dipped in explosive solution, it could be seen that the luminescence of the filter paper (right picture) was significantly weakened, while the fluorescence effect of the filter paper not soaked by DNT was very strong. This confirms the prepared rGO-TPEP could also be used as a solid probe in real application. It can be seen that the luminescent graphene has a good application prospect in explosion detection.In conclusion, non-covalent functionalized graphene was designed and prepared based on the π−π interaction between graphene and TPEP via the wet chemical reduction of GO. The as-prepared rGO-TPEP not only had good dispersion in solution but also processed the AIE feature. Compared with TPEP, the AIE effect of rGO-TPEP was greatly enhanced. Furthermore, rGO-TPEP could be used for the detection of explosive as low as 0.91 ppm and could be employed as a solid probe for the detection of DNT. These results offer new opportunities for developing new graphene-based materials with promising applications in chemical sensors, optoelectronic devices, and biomedicine.


Artificially-induced defects in the lattice of graphene are a powerful tool for engineering the properties of the crystal, especially if organized in highly-ordered structures such as periodic arrays. A method to deterministically induce defects in graphene is to irradiate the crystal with low-energy (<20 keV) electrons delivered by a scanning electron microscope. However, the nanometric precision granted by the focused beam can be hindered by the pattern irradiation itself due to the small lateral separation among the elements, which can prevent the generation of sharp features. An accurate analysis of the achievable resolution is thus essential for practical applications. To this end, we investigated patterns generated by low-energy electron irradiation combining atomic force microscopy and micro-Raman spectroscopy measurements. We proved that it is possible to create well-defined periodic patterns with precision of a few tens of nanometers. We found that the defected lines are influenced by electrons back-scattered by the substrate, which limit the achievable resolution. We provided a model that takes into account such substrate effects. The findings of our study allow the design and easily accessible fabrication of graphene devices featuring complex defect engineering, with a remarkable impact on technologies exploiting the increased surface reactivity. Defects in the crystal lattice of graphene are usually undesired as they hinder many of the remarkable properties of graphene devices. For instance, the presence of defects causes the broadening of the phonon dispersion and the lowering of the electronic mobility ,2. HowevWhen periodically repeating defected features, additional novel graphene functionalities can be unlocked. For example, a periodic array of defect lines in a graphene sheet can further tailor graphene’s thermal properties by introducing an anisotropy in the thermal conductivity ,14. MultLow-energy <20 keV, ) electro keV,  elp, showing that the resolution of a multiple-line pattern is not only determined by the EBI system characteristics  but is also limited by the pattern parameters themselves.Defect-engineered graphene for plasmonic and electronic applications requires well-defined patterns, where defect-rich and defect-free areas are well distinguished. For this reason, when introducing defective patterns such as line gratings via EBI, the investigation of both the defect density and surface topography is fundamental in order to establish the efficacy of the pattern creation. In this context, we present the study of the periodic arrays of defective lines induced in exfoliated graphene on a silicon oxide/silicon  with a scanning velocity of 500 nm/min. Such settings allowed a resolution of ∼2 The impact of the defects on the crystal lattice was studied by micro-Raman spectroscopy just after the electron irradiation in ambient air. The flakes were analysed by a 532 nm laser with 100× objective (NA = 0.85), giving a lateral resolution AFM and micro-Raman were performed to study the role of the pattern pitch on the surface topography and the defect density of electron-irradiated graphene sheets.In the AFM scans, the patterned arrays always resulted in a regular local increase of the topographic height. An example of an AFM map is shown in p of as low as 50 nm. Contrarily, the extracted line for 35 nm shows an overall height increase of ∼1 p varying from 50 nm to 100 nm exhibit a clear first harmonic peak at p = 35 nm shows a distinct first harmonic peak at 35 nm  of the height oscillations, we observed a pitch dependency of the defective graphene topography also for the patterns having a pitch longer than the beam radius. In particular, as shown in p increased, suggesting an unexpected dependency of the surface chemical reactivity on the pattern pitch and thus a variation of the defect density when changing p. Instead, the width of the patterned lines was constant within the error at a value that is compatible with the e-beam spot dimensions (p dependency of the height may arise from the interaction of electrons back-scattered by the substrate (BSEs) with the adjacent lines previously irradiated. Indeed, BSEs retain most of the energy of the primary electrons and can be spread in an area of radius To analyse the height variations, a single profile line was extracted from the AFM scans by averaging multiple lines for all the patterns. As shown in hene see , albeit mensions b, demonsted spot . Therefoted spot . Indeed,ted spot .D and 3-like and vacancy/boundary-like defects reported for short pitches  ,30 when graphene  and theiches see . The peaorted in :(1)nD[cmn eV see . The ext defects ,34. As sp dependency of the induced defects, we have to consider that the EBI induces a certain density of defects A has the same unit of p. The fitting parameter values are listed in A transposed by the equation, the term To interpret the observed adiation  and A haG (G and G peaks, which means that there was a change in the doping of the crystal, i.e., from ∼3–4 p, which went from ∼4.5 p = 100 nm to ∼6.5 p = 20 nm [G peak before and after the irradiation [G peak is determined by the competitive action of the carrier concentration, which narrows the G peak and defects density, which broadens the peak. However, electron-defect scattering mainly dominated when To investigate how the pattern pitch influenced the doping and strain of the defective graphene flakes, we studied the behaviour of the positions of the  = 20 nm  This behadiation , as repoD/IG ≥ 3  and in bubstrate . Indeed,ubstrate ,37, thusp = 100 nm to p = 20 nm. In Set 2, it varied from p = 100 nm to p = 35 nm [On the other hand, ased see b,d. The rn pitch . Indeed,D/IG ≤ 3 ,39, wherD/IG ≤ 3 ,40. As ap as small as The features of periodic arrays of structural defects in graphene were studied by combining AFM and micro-Raman spectroscopy. Defected lines were generated by low-energy EBI in monolayer graphene. The AFM measurements demonstrated that it was possible to create well-defined periodic patterns with a pitch The analysis of the Raman signal showed that the 2D density of defects induced in the crystal increased when the distance between each line decreased. Both Raman and AFM analyses confirmed that such a change was not a simple In conclusion, we demonstrated that it was possible to generate periodic arrays of defects in a graphene sheet, which could be exploited for designing engineered electronic devices or for inducing optically active features of unprecedented resolutions. Such features, combined with the increased surface reactivity of defected graphene, could have a great impact on both novel solid-state studies and the design of closely-packed chemical and radiation sensors.


Owing to its novel properties, such as high electrical conductivity and large specific surface area, graphene has been found as suitable support material for the electrocatalyst design. This work reports the preparation of platinum-nickel alloy nanoparticles (PtNi NPs) electrocatalyst by electrodeposition of PtNi NPs onto graphene support. The obtained PtNi/graphene electrocatalysts were characterized by high resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray microscopy (EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA) indicating the controllable morphological and compositional profiles of PtNi NPs on graphene. The electrocatalytic characteristics of PtNi/graphene toward oxygen reduction reaction (ORR) were systematically investigated showing comparable kinetic performance. Moreover, the graphene during electrodeposition process induces carbon vacancies and defects, increasing interaction between nanoparticles and graphene and enhancing electrocatalytic stability by limiting aggregation of the nanoparticles during accelerated stability test. This work opens a promising path for the preparation of graphene-supported alloy electrocatalyst. Electrochemical energy conversion and storage devices are critical enabling technologies for carbon-neutral renewable energy . These sAs an atomically thin sheet of hexagonally arranged carbon atoms which offer fast electron transferring, graphene has attracted a lot of interest for various applications . The univia electrodeposition method as developed by In this study, we used one-pot flash Joule heating (FJH) method to obtain high-quality graphene , and syn2PtCl4, 98%, RHAWN), nickel dichloride , sulfuric acid , perchloric acid . Argon and oxygen gases having high purity (>99.99%) were purchased from Yihong Gas Company, China. Deionized water  was purified by passing through pure compact ultrapure water system .All of the chemicals are of analytical grade and used without further purification. Commercial references of Vulcan carbon-supported Pt electrocatalyst  was purchased from TKK, Japan. Other reagents are as follows: isopropanol , Nafion D521 dispersion , potassium tetrachloroplatinate  glassy carbon (GC) disk  was immersed into 0.1 M HClO4 as the working electrode. The thin film catalyst layer on GC was formed by drop casting from a catalyst ink and drying under a flow of Ar. The catalyst ink was prepared by sonicating solid catalyst powder in a 4:1 H2O:IPA volume ratio solvent solution with concentration of 1 mgcatalyst ml−1. In order to well disperse and stabilized the catalyst particles on the GC surface, 0.5 µL of Nafion 5 wt% solution per mg of catalyst was added to the ink. Cyclic voltammograms (CVs) were performed with Ar purging at 294 K, with the potential scanned from 0.0 to 1.1 V vs. RHE at 20 mV s−1, and were used to determine the electrochemically active surface area of the Pt catalyst by integrating hydrogen desorption (∼0–∼0.35 V vs. RHE). ORR activities were measured in O2-saturated 0.1 M HClO4 at 294 K, with the potential scanned between 0.1 and 1.1 V vs. RHE at 20 mV s−1 at a rotation rate of 1600 rpm. All potentials are corrected for iR drop within the electrochemical cell.The electrocatalysts were electrochemically characterized in a three-electrode cell with a rotating disk electrode (RDE) setup (Pine Instruments) controlled by a Donghua potentiostat DH7003). The Pt wire  was used as the counter electrode, and the Ag/AgCl (BASi) was used as the reference electrode. The Pt loaded  at a constant rate of 10°C min−1, using a Netzsch STA 449 F3 system. The catalyst (≈10 mg) was loaded into an alumina crucible and heated from room temperature to 1000°C. X-ray diffraction (XRD) profiles were collected on Bruker D8 spectrometer with Cu Kα radiation (λ = 0.15406 nm). X-ray photoelectron spectra (XPS) were carried out using a Thermo Scientific K-Alpha X-ray photoelectron spectrometer. The binding energy was corrected using the C 1 s peaks (284.5 eV) as reference. Raman measurement was performed on a Renishaw in via Raman spectrometer with an excitation wavelength of 785 nm.High angle annular dark field scanning transmission electron microscopy (HAADF-STEM) images were taken of samples supported on lacey carbon grids in a FEI talos F200x G2 TEM/STEM operated at 200 keV. Energy dispersive spectroscopy (EDS) in the STEM mode was employed for elemental composition and distribution of the catalyst particles. Thermogravimetric analysis (TGA) of the catalysts was carried out under a mixed gas atmosphere  conversion of the surface complexes to PtNi alloy nanoparticles through potential cycling. The electrochemical deposition route of PtNi NPs on graphene is illustrated in via translation or rotation while the interlayer spacing approaches that of crystalline graphite (0.335 nm) (The XRD pattern of bare flash graphite obtained by FJH and as-made PtNi/graphene is shown in .335 nm) . After d.335 nm) . No char.335 nm) . The sli.335 nm) .0, PtⅡ, and PtⅣ. The observed binding energy of Pt0 is 71.49 and 74.93 eV agreeing well with the reported value of Pt0  in an electrochemical system can be used to determine electrochemical active surface area (ECSA), which is essential for understanding the utility of Pt by evaluating the number of available electrochemically active sites , and the value of 0.21 is known as the charge for the monolayer if hydrogen adsorption on the Pt surface. The corresponding ECSA of Pt is determined to be 73.9 m2/g for the PtNi/graphene which is comparable to commercial reference of Pt-based electrocatalyst supported by Vulcan carbon , jd is the diffusion limiting current density under the potential region of 0.2–0.65 V vs. RHE, and jk is the kinetic current density which can be obtained based on K-L equation to adjust for mass transport limitations.  due to excellent electrical conductivity of the graphene. RCT of graphene obtained using FJH method in our previous work,  is commonly used to illustrate the defect nature in the atomic structure of the graphene , suggesting the formation of many structural defects or disorders on the graphene support where PtNi NPs are deposited(ID/IG)  . This deID/IG) . Using dID/IG)  has revetivities . (Lim antivities vs. RHE in 0.1 M HClO4 at 50 mV s−1 under Ar atmosphere as suggested in our previous work (An accelerated stability test (AST) of PtNi/graphene was also performed by cycling potentials between 0.6 and 1.1 V ous work , and theous work  reservesous work , preventIn summary, novel Pt-Ni binary alloy nanoparticles electrocatalysts supported on graphene nanomaterials were successfully prepared by electrodeposition method. The PtNi NPs with sizes of ∼3 nm uniformly dispersed on graphene surface and loading of metals was determined to be 20 wt%. The resultant PtNi/graphene exhibits excellent electrocatalytic activity and stability toward the reduction of oxygen. In addition to the improved surface electronic properties due to characteristic of graphene, the formation of structural defects and disorders on graphene support during electrodeposition process can also attribute to the electrocatalytic performance of PtNi NPs. These results indicate that graphene nanomaterials could be a good candidate as a supporting material of electrocatalysts, and electrodeposition method is promising for the preparation of high-performance graphene-supported alloy electrocatalysts.


Forkhead Box Protein C2 (FOXC2) belongs to the Forkhead/Wing-helix family. The regulatory role of this transcription factor in physiological function and carcinogenic activity has been proven in subsequent investigations. However, there is still scarcity of evidence on the relationship between FOXC2 expression and prognosis in human solid tumors. We conducted this meta-analysis to evaluate the role of FOXC2 as a prognosis factor and a possible target marker in human solid tumors.PubMed, Web of Science, Embase, and the Cochrane library database were all searched methodically. Eligible publications on FOXC2 in human solid tumors were gathered and reviewed. The effect sizes were calculated using pooled hazard ratios (HRs) or odds ratios (ORs) with the corresponding 95% confidence interval (CI). Statistical analysis was conducted with Stata SE12.0.This meta-analysis comprised 3,267 patients from 20 studies covering a variety of solid tumors. Increased FOXC2 expression was related to shorter overall survival (OS) . High expression of FOXC2 is associated with lymph node metastases , TNM stage , and age , according to the pooled ORs. However, no significant association was observed between the high expression of FOXC2 and sex, tumor size or tumor differentiation.Increased expression of FOXC2 is associated with unfavored OS, lymph node metastases, TNM stage, and age. FOXC2 is a promising prognostic marker and a novel target marker in human solid tumors. The transcription factor forkhead box (FOX) is a family with a highly conserved winged-helix DNA-binding domain , 2. FOX in vivo and in vitro. FOXC2 has also merged as a potential molecular target in preclinical/clinical studies due to the dysregulated expression level and nuclear localization. Previous studies have associated expression levels of FOXC2 with clinical and pathological characteristics including tumor size, differentiation, metastasis, and stage  AND  AND . Additional research was found by looking through the references of the selected articles. The Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) statement was used in this analysis  patients with solid tumors diagnosed pathologically; (2) the expression FOXC2 in tissue were determined by immunohistochemistry (IHC) or quantitative real-time polymerase chain reaction (q-PCR); (3) available data for calculating odds ratio (OR) with 95% CIs were depicted; (4) only the study with the most extensive or recent data was considered, if multiple publications used employed overlapping samples from the same institution; (5) patients were categorized into groups based on high and low FOXC2 expression levels. Exclusion criteria in this meta-analysis were as follows: (1) duplicate publications; (2) research with no data or data from animal or cellular experiments; (3) only serum levels of FOXC2 expression were detected; (4) studies only provided Kaplan-Meier curves but no multivariate data; (5) reviews, letters, case reports, or expert opinions.The two independent investigators screened the all publications, classified and sorted out the titles and abstracts of the literature retrieved from reading, excluded duplicate literatures and literature failed inclusion criteria, contacted the original author for relevant information for the literature with incomplete information report, and determined whether it could be included in the final study after obtaining the full text. The research team shall assist in solving any dispute. The following information was retrieved from eligible articles: name of first author; publication year; sample size; cancer kind; criteria for increased expression of FOXC2; detecting methodology; outcome measuring; patient follow-up; HRs with corresponding 95% CI; and clinical characteristics . We preferred multivariate analysis in research with both univariate and multivariate analyses because it is better at explaining confounding factors. If there was a disagreement, a compromise was sought through debate until everyone agreed. The quality evaluation for eligible studies was undertaken by 2 independent investigators (CW and LZ), and any discrepancies were handled by consensus among all authors. The Newcastle-Ottawa Scale (NOS) tool was used to evaluate the quality of all eligible studies . The NOSI2 statistic , the fixed-effects model was adopted, and the random-effects model was used for others . The sensitivity analysis was conducted to check the stability of results. Begg's and Egger's tests were conducted to investigate potential publication bias . The heterogeneity of the included studies used Chi-square-based Q test and tatistic . P < 0.0ion bias . Differen = 12), Japan (n = 5), Singapore (n = 1), Spain (n = 1), and Norway (n = 1). Mean of patient sample size was 163 (from 61 to 338). In this meta-analysis, 15 varying solid tumor kinds were summarized, including 2 non–small-cell lung cancer, 2 breast cancers, 2 esophageal squamous cell carcinoma, 2 colorectal cancer, 2 cervical cancer, and 1 each of glioma, oral squamous cell carcinoma, pulmonary neuroendocrine tumors, extrahepatic cholangiocarcinoma, hepatocellular carcinoma, gastric cancer, oral tongue squamous cell carcinoma, ovarian cancer, prostate cancer, and phyllodes tumor of the breast. All of the specimens were well preserved, and diagnosis was made based on pathological findings. The main characteristics of enrolled studies are summarized in The procedure of literature retrieval was depicted in I2 = 13.1%, Ph = 0.313). HRs for the increased FOXC2 expression against the low FOXC2 expression were 2.31 (95% CI: 1.73–2.42)  was reported. The pooled hazard ratios (HRs) and corresponding 95% CI were estimated by the fixed-effects model. The results indicated a mild heterogeneity in studies (73–2.42) . PatientP < 0.05) (P < 0.05) (P < 0.05) (The pooled results  showed t < 0.05) , TNM sta < 0.05) , and age < 0.05) . However < 0.05) , sex, orSensitivity analysis was conducted to assess the FOXC2 expression and OS by gradually deleting each individual research from the pooled analysis. The purpose of this approach is to evaluate the impact of the deleted data set on the overall HRs. The fingdings were reliable, and the exclusion of any study had no effect on the results .Begg's Test and Egger's tests were conducted to evaluate the publication bias. Findings revealed that there was no publication bias between FOXC2 expression and OS in the included studies .As a kind of genomic disease, lots of somatic mutations, structural mutations and gene recombination occur during the carcinogenesis process . There wFOXC2 acts as a key mediator of tumor initiation and progression, involving tumor proliferation, migration, invasion, metastasis, and EMT . FOXC2 oThe limitations of this analysis were as follows: first, in this meta-analysis, the majority of the studies were conducted among Asian population. Other ethnic groups, such as Europeans, Africans and Americans, are relatively under-studied, which may limit the global applicability of the results discussed. Further high-quality studies from diverse ethnical origins are necessary to investigate the therapeutic importance of FOXC2. Second, despite the fact that FOXC2 overexpression was associated with patient age, tumor differentiation, lymph node metastasis and TNM stage, we were unable to evaluate the association between FOXC2 overexpression and other clinical and pathological characteristics due to insufficient data. Third, the number of studies included in this analysis could restrict its statistical power. Although no publication bias was found, potential publication bias may still exist due to the insufficient studies available for assessments. Then, inconsistencies in detecting platforms, methodologies, and criteria for IHC or RT-PCR, and distinct tumor kinds with varying prognostic differences may lead to skewed results. Furthermore, the mean of NOS scores is 6.5, implying that the quality of studies in this analysis is acceptable but not supreme, which might be inevitable in meta-analysis. Finally, the combined predictive significance of FOXC2 and other tumor markers was not assessed. As a result, higher quality multicenter studies with larger population, as well as consistent criteria for assessing the expression of FOXC2, are necessary for validation of the findings.In this analysis, increased expression level of FOXC2 is associated with poor prognosis, as well as TNM stage, lymph node metastases, and age. FOXC2 could serve as a novel prognostic marker in solid tumors. For these patients, targeting FOXC2 could be a feasible treatment option. To corroborate the findings, further well-designed pre-clinical/clinical studies with high-quality data are needed.


Dear Editor,Advanced basal cell carcinomas (BCCs), including metastatic BCC (mBCC) and locally advanced BCC (laBCC) have always represented a difficult‐to‐treat form of skin cancer; laBCC are primary, recurrent tumors that often progress to an advanced stage requiring treatments different from surgery or radiation therapy.None.Idea and design: Alessia Villani, Gabriella Fabbrocini and Massimiliano Scalvenzi. Data collection: Alessia Villani. Revision of the article: Alessia Villani, Massimiliano Scalvenzi.Approval of ethical committee was obtained from the University Federico II of Naples, Italy.