The distribution, Raman and photoluminescence (PL) spectra of the above prepared heterostructure samples can be respectively observed and tested by optical microscopy and Raman spectrometry, which can be used to study their growth mechanisms and optical properties. Meanwhile, the uniformity and composition distribution of heterostructure films can also be analyzed by the Raman and PL spectra. The internal mechanism of Raman and PL spectral changes can be explained by comparing and analyzing the PL and Raman spectra of the junction and non-junction regions between 2D-2D vdWs heterostructure materials, and the effect of laser power on the optical properties of heterostructure materials can also be analyzed. These heterostructure materials exhibit novel and unique optical characteristics at the stacking or junction, which can provide a reliable experimental basis for the preparation of suitable TMDs heterostructure materials with excellent performance.Due to the attractive optical and electrical properties, van der Waals (vdWs) heterostructures constructed from the different two-dimensional materials have received widespread attention. Here, MoS Nanoscale PN heterostructure research is particularly important as the device size decreases. However, due to the dangling bonds and lattice mismatch, it is difficult for the traditional materials to achieve atomically flat heterostructure interfaces, which limits the development of nanoscale PN heterostructures ,2,3. TwoGraphene has the novel physical properties, strong mechanical stability, high mobility and the unique electronic properties of zero-band gap Dirac semimetals, which can make it a basic component of vdWs heterostructures ,15. The To solve the difficulties and challenges in the application of 2D-2D vdWs heterostructure materials, vdWs heterostructure materials were prepared by the direct CVD and wet transfer methods in this paper. The resulting vdWs heterostructures have ultra-clean and atomically clear interfaces, and novel physical properties appear when 2D materials with different properties are stacked together, which can provide a multifunctional research platform for the study of interface-related characteristics . In addi2 thin film is formed on a h-BN/SiO2/Si substrate by the Frank Van der Merwe mechanism. This is because the surface of h-BN is clean and smooth, which is beneficial to the sulfidation and diffusion of MoS2 molecules. The large-sized triangular MoS2 materials are evenly distributed on graphene when the CVD growth of MoS2 material is completed, and the MoS2 and graphene materials on SiO2/Si substrate can be well distinguished with the help of contrast as shown in 2/h-BN heterostructure at different positions on the SiO2/Si substrate. The average size of the WS2 material on h-BN/SiO2/Si substrate is about 30 µm, the thickness is uniform and the surface is smooth. The edge of the h-BN sheet has many dangling bonds, which can provide nucleation sites for the growth of WS2 material. 2/graphene heterostructure, where the triangle-shaped WS2 sheet has an average size of 60 μm. In addition, there is also a stack of small triangles on the large triangle of WS2 material, which indicates the existence of multilayer triangular WS2 sheets.The morphology of 2D-2D vdWs heterostructure materials can be observed by optical microscopy. In −1 and 2631.3 cm−1, and the intensity of the 2D peak is stronger than that of the G peak, so the monolayer graphene material has good quality [2D/IG decreases, which is due to the interaction change between graphene material and the underlying SiO2/Si substrate.In  quality . Figure 2 at different positions, the lattice vibration of MoS2 has the E12g and A1g Raman active characteristic phonon peaks, where the E12g and A1g characteristic peaks were respectively derived from intra-layer lattice and inter-layer lattice vibrations. The two lattice vibration modes change accordingly with the layer number of MoS2 material decreases, and the E12g and A1g characteristic peaks are respectively red-shifted and blue-shifted, so the number of MoS2 material layers can be determined by the peak position difference. In the Raman spectrum of MoS2, the characteristic peaks of E12g mode and A1g mode are respectively located at 382.1 cm−1 and 401.4 cm−1, and the characteristic peak position difference is 19.3 cm−1, which indicates that the MoS2 sample is a single layer. 2, the peak intensities of E12g and A1g characteristic peaks accordingly increase with the laser power increases and the peak position of A1g characteristic peaks is blue-shifted to some extent.2, the E12g and A1g mode characteristic peaks are respectively located at 351.5 cm−1 and 416.4 cm−1, the peak position difference is 64.9 cm−1, and there is no peak near 310 cm−1, which indicates the existence of monolayer WS2. It can be found by observing 12g vibration characteristic peak and the peak position of A1g vibration mode characteristic peak remains unchanged. This is because the electron concentration changes as the laser power increases, and the increase of electron concentration could cause a reforming of the band gap.2 material, the resonance Raman scattering of MoS2/h-BN heterostructure material can be studied by analyzing the band structure and exciton transition. −1 and 1358 cm−1.In order to match the excitation energy to the PL spectrum exciton peak energy of MoS12g and A1g mode characteristic peaks of MoS2 on a h-BN substrate. The in-plane vibration E12g mode characteristic peak and out-plane vibration A1g mode characteristic peak are respectively located at 384.6 cm−1 and 404.2 cm−1, and the frequency difference is 19.6 cm−1. Compared with the Raman spectrum of MoS2 on SiO2/Si substrate, the characteristic peak frequencies of E12g mode and A1g mode are respectively blue-shifted by 2.5 cm−1 and 2.8 cm−1 on h-BN/SiO2/Si substrate, and the substrate effect can explain the blue shift of the Raman peak on h-BN. Therefore, Raman spectroscopy at room temperature showed that the h-BN substrate can reduce the local strain and injected impurities into MoS2. Besides, the PL spectrum can be fitted by the Lorentz function, as shown in 2 is at 681 nm, and the corresponding energy electron volt band gap is 1.82 eV, which is consistent with the band gap of monolayer MoS2. The PL exciton emission of MoS2/h-BN heterostructure material is two times larger than that of MoS2 material, and the FWHM is 26.39 nm, which is narrower than that of MoS2 material. Therefore, MoS2/h-BN heterostructure material has a tighter interlayer contact and lower charged impurities levels.At the same time, the full width at half maxima (FWHM) of the IPM mode characteristic peak is much larger than that of the ISM mode. 2 material is grown directly on graphene to form a MoS2/graphene heterostructure, their lattice vibrations would inevitably affect each other. In a MoS2/graphene heterostructure, the work function of graphene is smaller than that of MoS2 material, which is beneficial to the formation of contacts.When monolayer MoS12g and A1g modes characteristic peaks of MoS2 material and the G and 2D peaks of graphene appear in the Raman spectrum, which indicates the presence of MoS2/graphene heterostructures. Among them, the E12g and A1g mode characteristic peak positions of MoS2 material are respectively located at 382.6 cm−1 and 400.3 cm−1, and the G and 2D peak positions of graphene are located at 1602.5 cm−1 and 2689.7 cm−1, respectively. The G and 2D peak positions of the MoS2/graphene heterostructure shift to larges wavenumbers compared with the spectrum of intrinsic graphene, the the G and 2D peaks respectively change from 1585.9 cm−1 and 2631.3 cm−1 to 1602.5 cm−1 and 2689.7 cm−1. The reason is that the hole concentration becomes smaller and the electrons from MoS2 material can be transferred to the graphene. Besides, the E12g and A1g mode characteristic peaks of MoS2/graphene heter-structure are respectively red-shifted and blue-shifted by 0.5 cm−1 and 1.1 cm−1 compared with the spectrum of monolayer MoS2, which is due to the Van der Waals force interactions between MoS2 and graphene. 2/graphene heterostructure material at different positions. The strongest PL spectrum peak position of MoS2/graphene heterostructure is at 674 nm, and the corresponding electron volt energy is 1.84 eV. The peak position of strongest PL spectrum shows the blue shift, graphene has the influence on the Raman spectrum of MoS2 material. The energy band of MoS2 material bends downward, and the Schottky barrier is lower when the Fermi level of graphene and MoS2 materials are aligned. It can be found by observing 2/graphene heterostructure becomes higher, it will cause the spectrum to change. The rise of 2D and G peaks position is related to the effective interlayer coupling of MoS2 nanosheets, and the strain effect, which is caused by the high temperature heating. Besides, due to the PL phenomenon of MoS2, the background Raman signal increases with the wavenumber increase. As shown in 2/graphene heterostructure is superimposed on B exciton, and the peak position has the blue shift, which can be explained by the stacking effect [2 sample directly grown on a graphene and MoS2 sample transferred on a graphene substrate. The E12g peak position of monolayer MoS2 material is blue-shifted by 1.3 cm−1 after the transfer, and the A1g peak position only changes slightly. There is a certain tension effect when monolayer MoS2 material is grown on the SiO2/Si substrate by CVD. After the transfer, the A1 peak position of PL spectrum in MoS2 sample has a blue shift about 40 meV, as shown in 2 sample transferred on a graphene is higher than that of MoS2 sample directly grown on a graphene. The reason is that the tension of the sample is effectively released while using PMMA to transfer MoS2 material to the new SiO2/Si substrate.In g effect . Figure 2 on h-BN and graphene substrates. As we all know, the MoS2 material has a suitable and adjustable band gap, strong exciton interaction, unique nonlinear effects and a novel spin valley effect, which has the great application potential in the fields of integrated electronic chips, photoelectric conversion and the energy environment. In 12g and A1g mode characteristic peaks of MoS2/graphene heterostructure are blue-shifted relative to the MoS2/h-BN heterostructure material. The reason is that the graphene substrate has the effect on the Raman spectrum of MoS2. Vertical heterostructures can be formed by the van der Waals force between the upper and lower layers, which would lead to a strong quantum confinement effect. This can not only change the electronic band and optical properties of MoS2 material, but also give it more excellent chemical activity. It can be found from 2/graphene heterostructure material is red-shifted compared with MoS2/h-BN heterostructure, and the peak intensity is weaker than that of MoS2/h-BN heterostructure. This is because graphene has the weakening effect on the fluorescence of MoS2. Besides, the exciton absorption peak of PL spectrum in MoS2/graphene heterostructure is located at 621 nm. The change of thickness and the abundance of heterostructures can further produce and broaden the new characteristics and application research of MoS2 material.A 633 nm red laser was used to compare and analyze the spectral characteristics of MoS2/h-BN heterostructure materials where the corresponding peak positions are located at 52 cm−1 and 1346 cm−1, respectively.2/h-BN heterostructure, the peak position of ISM and IPM mode characteristic peaks are blue-shifted. The reason is that WS2 material has an influence on the spectrum of h-BN. It can be clearly observed from 12g and A1g Raman activation mode peak positions of WS2 are respectively located at 354.8 cm−1 and 419.4 cm−1, and the peak spacing is 64.6 cm−1, which corresponds to the peak spacing of monolayer WS2 on SiO2/Si substrate. The peak position of WS2/h-BN heterostructure is different from that of WS2 on SiO2/Si substrate. The reason is that the van der Waals interaction between layers, and the effective transfer between dielectric screen of long-distance Coulomb interactions. In 2 material. The FWHM of PL emission peak is related to the exciton lifetime and interface quality, which can be attributed to the extension of high crystallinity WS2 material, and the clean heterojunction interface.Compared to the spectrum of MoS2 and WS2/graphene heterostructures is shown in 1g mode characteristic peak of WS2/graphene heterostructure shifts to the short wavelength compared with the Raman spectrum of WS2, and the peak position of A1g characteristic peak has the blue shift. And the E12g and A1g mode characteristic peak intensity of WS2/graphene heterostructure is higher than that of WS2.Raman spectroscopy is used to evaluate the crystal quality and film thickness of 2D materials. The Raman spectrum contrast analysis of WS2/graphene heterostructure film has excellent crystallinity. In addition, monolayer WS2 and multilayer WS2 materials are respectively the direct bandgap semiconductor and indirect semiconductor, so the PL spectroscopy can also be used to identify the number of layers. In 2 and WS2/graphene heterostructure both show the strongest PL emission peak is located at 634 nm, and the band gap is about 1.94 eV, which indicates that it is consistent with a mechanically peeled monolayer WS2. The PL intensity of WS2/graphene heterostructure is weaker than that of monolayer WS2. This is because the work function between graphene and WS2 material does not match, thus forming the internal field, which would cause the photoelectrons from WS2 can transfer to graphene, and leave holes in WS2.There is the sharp Raman characteristic peak, which indicates that WS−1 and 2667.5 cm−1, and the intensity of 2D peak is almost twice that of D peak, which indicates the presence of monolayer graphene. The D peak appears in the Raman spectrum of graphene material when the growth of WS2 material is completed. Meanwhile, the peak position of 2D peak shifts downward, which is due to the effective interlayer coupling and strain effect. As shown in 2. At the same time, the internal field can be formed, which is due to the work function mismatch between graphene and WS2.In 2/h-BN and WS2/graphene heterostructure is shown in 2/h-BN heterostructure, the E12g and A1g mode characteristic peaks of WS2/graphene heterostructure are respectively red-shifted and blue-shifted. The reason is that graphene material has a influence on the spectrum of WS2 material. In 2/graphene heterostructure is blue shifted. The difference of peak position shift can be attributed to the influence of different substrates and the change of interaction.A Raman spectrum characteristics comparison of WSFirst, the copper foil substrate was used in the growth process of graphene and h-BN materials by the CVD growth process. Before the growth of graphene and h-BN films on copper foil substrate, it is necessary to immerse the copper substrate in hydrochloric acid for 15 min to remove the local surface oxides. Finally, the copper foil substrate can be rinsed with the acetone and isopropanol solution.2 was also punched. Next, the tube furnace was charged with 35 sccm CH4, while the flow rate of H2 was adjusted to 10 sccm, and the growth time of graphene was 30 min, as shown in 4 gas from flowing into the tube furnace.2 gas), aminoborane polymer (aminoborane) and borazine under the action of heating belt [2. Next, the borazine can dehydrogenated again due to the catalytic effect of the copper foil metal, and the B and N atoms combined to form h-BN on SiO2/Si substrate. Finally, the power supply of heating belt and furnace is quickly cut off when the h-BN growth reaction is completed, and the tube furnace enters the cooling stage. The specific temperature change curve is shown in ing belt . At the 2/Si substrate, which can be achieved by the PMMA transfer method. First, the 500 nm PMMA layer was spin-coated on the graphene or h-BN/copper foil substrate, and the PMMA film was cured at 120 °C for 3 min when the spin coating was completed. Then, the copper foil substrate was etched by 1M FeCl3 solution. Next, the PMMA/graphene or PMMA/h-BN layers were rinsed several times in deionized water, which can be transferred to the SiO2/Si substrate. Subsequently, the sample was dried in the N2 gas environment for 12 h to make the graphene or h-BN and SiO2/Si substrate adhere more closely. Immediately after, the PMMA film was washed away in the acetone solution.The graphene or h-BN material grown on Cu foil substrate by CVD method was transferred to SiO2/Si substrate hydrophilic, and the treatment is 2 min, which can help the transfer of graphene or h-BN film and the growth of MoS2 or WS2 materials [2/Si substrate was annealed at 400 °C for 8 h when graphene or h-BN thin film was transferred to SiO2/Si substrate. Meanwhile, the Ar gas with 5% H2 was continuously provided to remove residues during the transfer process.The purpose of oxygen plasma treatment is to make the SiOaterials . The SiO2 or MoS2 materials were grown on the graphene/SiO2/Si or h-BN/SiO2/Si substrate in the tube furnace, and the SiO2/Si samples coated with graphene or h-BN materials were used as the substrates. The quartz boat containing 200 mg sulfur powder was placed upstream of the tube furnace, which is the low-temperature heating zone. At the same time, the graphene/SiO2/Si or h-BN/SiO2/Si substrate were placed upside down on the quartz boat containing WO3 or MoO3 powder, which is located in the high temperature heating area of tube furnace, as shown in 3 powder (or WO3 powder) respectively rises to 50 °C, 100 °C, 100 °C within 5 min, and maintains at this temperature for 10 min. Next, the temperature of sulfur powder and MoO3 powder (or WO3 powder) can respectively reach the sublimation temperature of 150 °C, 800 °C and 950 °C within 50 min, and the growth temperature is maintained for 10 min. Finally, the tube furnace was naturally cooled to room temperature.The WSRaman spectrometry can confirm the molecular structure by the Raman shift. The incident light is scattered when a certain wavelength of laser is irradiated on the sample surface, and the frequency of most scattered light does not change, which is the Rayleigh scattering. The small part scattering of scattered light frequency is referred to as Raman scattering, and the frequency difference between scattered light and incident light is called Raman shift. Raman spectroscopy is used to monitor the crystal quality, polymorphism, doping, defects, strain, disorder, chemical modification and relative orientation of 2D materials. Besides, Raman analysis has the high spatial resolution, the fast and easy spectral imaging, which is suitable for identifying the characteristics and structure of various materials . The phoThe distribution of heterostructure samples on the substrate surface can be observed by optical microscopy, which can test and characterize the aboveprepared heterostructure materials. The spatial resolution depends on the choice of excitation laser to a certain extent, and the excitation wavelength can be optimized based on the characteristics of the sample. Meanwhile, a Raman spectrometer  with a 633 nm laser red light was used to measure and obtain the single-point Raman and PL spectrum of the heterostructure materials, and the surface uniformity and composition distribution of heterostructure film were analyzed by Raman and fluorescence surface scanning. The surface morphology of heterostructure materials can be observed by optical microscopy. For the Raman and PL spectrum tests, the corresponding laser power is respectively fixed at 10 mW and 20 mW, the laser spot diameter is 1 μm, and the objective magnification of microscope is 10. The Raman data of characteristic peaks were analyzed by the classical least squares (CLS) fitting.2/h-BN, MoS2/graphene, WS2/h-BN and WS2/graphene van der Waals heterostructures were successfully prepared in this paper. The growth mechanism and optical characteristics of heterostructure materials can be studied by optical contrast microscopy and Raman PL spectroscopy, which can obtain the spectral characteristics of heterostructure materials. These heterostructures exhibit the novel and unique optical properties at the stacking or junction of several materials. The Raman and PL spectroscopy models are complementary and can describe the temperature-dependent relationships between interlayer coupling and physical origin. Meanwhile, the electron-phonon coupling and vdW interaction can be enhanced by reducing the local strain and charged impurities. Compared with the Raman spectrum of MoS2 on SiO2/Si substrate, the characteristic peak frequencies of E12g mode and A1g mode are blue-shifted by 2.5 cm−1 and 2.8 cm−1 respectively on a h-BN/SiO2/Si substrate, and the E12g and A1g mode characteristic peaks of MoS2/graphene heterostructure are respectively red-shifted and blue-shifted by 0.5 cm−1 and 1.1 cm−1. The G and 2D peak positions of MoS2/graphene heterostructure shift to the large wavenumber compared with the spectrum of intrinsic graphene. Besides, E12g and A1g mode characteristic peaks of MoS2/graphene heterostructure are blue-shifted compared with MoS2/h-BN heterostructure, and the strongest peak position of PL spectrum is red-shifted. The crystal orientation between WS2 or MoS2 growth and hBN or a graphene substrate is significantly different, which is due to the interlayer Coulomb interactions. Our research can effectively improve the interlayer coupling basic understanding of heterostructures and temperature-dependent Raman and PL spectra were used to explore the optical properties of vdWs heterostructures. Therefore, nanoscale vdW heterostructures have the great application prospects in the fields of nanoelectronics and optoelectronics.MoS


KL determined for the Langmuir isotherm is high: KL = 1.27 × 108 M−1, enabling highly sensitive control of the gated-RET by PD-L1. Thus, with the gated-RET technique, one can determine PD-L1 within the dynamic range, extending from 1.2 to 50 nM. Moreover, we have found that the Gibbs free energy for PD-L1 binding to AuNP@Cit is −46.26 kJ/mol , indicating a strong adsorption with supramolecular interactions. The proposed gated-RET system, with the fluorescence intensity of the fluorophore probe molecule modulated by plasmonic quenching with AuNP and shielding of energy transfer by the adsorbed PD-L1 can be further developed for determination of PD-L1 in pharmaceutical formulations for immune checkpoint control in cancer therapy.The resonance energy transfer (RET) between an excited fluorescent probe molecule and a plasmonic nanoparticle (AuNP) has been investigated to evaluate the effect of protein molecules on the RET efficiency. We have found that the energy transfer to a functionalized AuNP can be modulated by a sub-monolayer film of programmed death-ligand 1 (PD-L1) protein. The interactions of PD-L1 with AuNP@Cit involve incorporation of the protein in AuNP shell and formation of a submonolayer adsorption film with voids enabling gated surface plasmon resonance energy transfer (SPRET). A model of the gated-RET system based on the protein size, estimated using Fisher–Polikarpov–Craievich density approximation, has been developed and can be utilized for other proteins, with minimum data requirement, as well. The value of the equilibrium constant  Significant progress, achieved in the last two decades, in understanding processes that enable cancer to grow and metastasize freely, while evading the immune response of the host, has largely been associated with exploring pathways controlling the apoptosis  and the immune checkpoints . Still, many other proteins may influence the expression of cancer controlling genes and they may also need to be regulated to win the battle with cancer. The use of nanomaterials in cancer research, diagnostics, and therapy is rapidly growing and spans from the targeted drug delivery using nanocarriers ,3,4, to The programmed death-ligand 1  is a transmembrane protein of 290 amino acids, consisting of immunoglobulin V- and C-like domains, a hydrophobic transmembrane domain, and a cytoplasmic tail of 30 amino acids. The elevated expression of PD-L1 is observed on the surface of tumor cells and associated with worse prognosis for many tumors ,22,23,24The structure of human PD-L1 (hPD-L1) was determined by Garboczi’s group  and ChenIn our previous paper, we have demonstrated that the resonance energy transfer (RET) from a fluorescein isothiocyanate (FITC) fluorescent dye to citrate-capped gold nanoparticles (AuNP@Cit) can be modulated by a gating sub-monolayer film of cytochrome c (Cyt c) , bovine KL for the Langmuir adsorption isotherm and the Gibbs free energy ΔG°ads for PD-L1 binding to a citrate-capped gold nanoparticle surface. Furthermore, we have been able to utilize the principle of gating of a plasmon-enhanced RET for the detection of PD-L1 at low concentrations. A generalized model of the gated-RET for any protein that binds to a functionalized AuNP has been developed based on the average protein density calculated using Fisher–Polikarpov–Craievich equation  and d is the average density [g/cm3]. Thus, for M = 52 kDa, one obtains d = 1.4136 g/cm3. Assuming a spherical shape of PD-L1, one obtains for 5 nm dia. AuNPs, the maximum monolayer surface coverage γmax of PD-L1 on AuNPs as 8.9 pmol/cm2. It corresponds to 9.3 molecules of the protein per single AuNP@Cit at close packing density. To estimate the protein surface coverage for this model, for any protein, we can assume a spherical shape for the protein molecules and calculate their maximum surface coverage based on the protein molar mass. The average protein density, needed for these calculations, can be determined using Fisher–Polikarpov–Craievich equation :d = 1.41The thickness of the PD-L1 layer was estimated from the volumetric density of the protein and its molecular mass, assuming the spherical shape and a compacted cube shape, as follows.M is the molar mass of a protein and d is the protein density.The molar volume of a protein is given by:N0 is the Avogadro number (N0 = 6.023 × 1023 mol−1). Assuming spherical shape of the protein molecule, we can estimate the diameter 2r of the protein and thus, the monolayer film thickness h:Thus, the volume of a single molecule of a protein can be estimated using the equation:a:Similarly, we can estimate the film thickness for protein molecules compacted to cubes with sides r and a, is:The ratio of the two values, 2h for any protein shape from an ideal sphere to a compacted cube by taking the mean value between 2r and a:Emax in the estimated height h of the film will be less than ±10.7%:Hence, if we characterize the film thickness M = 52 kDa and d = 1.4136 g/cm3, one obtains: 2r = 4.89 nm, a = 3.94 nm, and h = 4.41 ± 0.48 nm. A slight modification of this number could be due to the non-regular protein shape, orientation on the surface, and denaturation (if it would occur). For KL as follows:θ is the fraction of the AuNP@Cit surface covered by PD-L1 and CPD-L1 is the concentration of PD-L1 in solution. For such a gated-RET system, the fluorescence intensity of FITC modulated by plasmonic quenching by AuNP and shielding of energy transfer by the adsorbed PD-L1, according to our recent studies [Another model parameter for gated-RET system is the equilibrium constant for the adsorption of PD-L1 on AuNP@Cit. Assuming Langmuirian adsorption with no self-interactions between the adsorbed PD-L1 molecules, we can express the equilibrium constant  studies , is giveI0 in the absence of PD-L1 and the saturated intensity Isat observed for a full monolayer coverage of PD-L1. It is clearly seen from this equation that KL is the key parameter controlling the RET behaviour of the system. To determine the value of the Langmuir constant KL, we note that for:This equation describes the modulation of fluorescence intensity of a FITC probe between the intensity Equation (4) reduces to:KL can be determined graphically from the graph in C1/2 for the fluorescence intensity equal to I1/2. The value of KL is given by:Therefore, C1/2 = 7.9 × 10−9 M and the value of KL is 1.27 × 108 M−1. Based on the value of KL, the Gibbs free energy ΔG° for PD-L1 binding to AuNP@Cit can then be calculated using the formula: R is the gas constant (R = 8.3144 J/(mol K)) and T is the absolute temperature. For T = 298.1 K, the Gibbs free energy of PD-L1 binding to AuNP@Cit is −46.26 kJ/mol . This value of ΔG° indicates on a strong adsorption with supramolecular binding.Hence, from the graph in IPD-L1 = 6.76. The FITC molecules in this solution are deprotonated (pKFITC = 6.4) and most of the citrate ions are also deprotonated as well  [The surface of PD-L1 protein is predominantly negatively charged at pH = 7.4 of the measurement buffer since the solution pH > p = 6.39) . Therefo = 6.39) , which iDue to the small size of the citrate ligands and their surface mobility in AuNP’s shell, the adsorption of PD-L1 on the surface of AuNP@Cit nanoparticles is random. Since PD-L1 protein contains six cysteine residues in its structure, some of them exposed on its surface, a direct local covalent binding to a gold nanoparticle is also possible after replacement of citrate ions from AuNP surface. However, due to the large PD-L1 size and complex nature of the protein surface, only some of the citrates can be displaced by these cysteine residues. E of gRET is evaluated from the equation:IFL,0 and IFL are the fluorescence intensities for a FITC probe in the absence of AuNP quenchers and in the presence of AuNP@Cit/PD-L1sub-mono quenchers with different sub-monolayer films of PD-L1, respectively.The quenching efficiency of gated resonance energy transfer (gRET) for different concentrations of PD-L1 protein is shown in E = 0.55. The protein forming an external shell around AuNP partially blocks the energy transfer process and creates the gates (voids) for controllable FITC access to AuNP surface. At the maximum PD-L1 surface coverage by PD-L1, the gates are minimized, resulting in the residual RET with E = 0.31 (E greater than 0 is due to the remaining voids between PD-L1 molecules at saturated coverage on AuNP and direct quenching of the probe through the protein if any. This value would be lowered virtually to zero if a protein would undergo a denaturation while binding to a plasmonic host. The non-zero residual RET efficiency at surface saturation with PD-L1 indicates that no denaturation of the protein occurs. The linear part of the graph of E vs. CPD-L1 for low analyte concentration has been expanded in σ-method.The FITC quenching efficiency calculated for AuNP@Cit solution in the absence of PD-L1 is: E = 0.31 A. Note tKL = 1.27 × 108 M−1. A model mechanism of the gated-RET controlled by PD-L1 has been developed. This work demonstrates the interactions of immune checkpoint protein PD-L1 with AuNP@Cit and the high sensitivity of gRET transduction, thus developing the base model for future applications of gRET biosensors with biorecognition capabilities for the detection of proteins in complex real samples in studies of immune checkpoint cancer therapy.The experiments performed in this work indicate that the immune checkpoint protein ligand PD-L1, in the form of a sub-monolayer adsorption film on a functionalized AuNP, is able to control the gated-RET between a fluorophore probe molecule and a plasmonic core of AuNP@Cit. We have demonstrated a substantial de-quenching of the FITC probe fluorescence by partial coating of AuNP@Cit with PD-L1. The strong adsorption of PD-L1 on citrate-capped AuNPs occurs despite of electrostatic repulsions, as both the PD-L1 and AuNP@Cit are negatively charged at neutral pH. Therefore, the dominant binding forces must be due to thiolate binding and supramolecular interactions. In fact, several hydrogen bonds may be formed between high-oxygen content citrate shell on AuNPs and numerous functional groups on the protein surface. Also, the counterions in electrolyte ensure effective screening of excessive negative charges and cations provide bridging options to negatively charged surface functional groups. The strong supramolecular binding of PD-L1 to AuNP@Cit is corroborated by the high value of the equilibrium constant characterizing the Langmuir adsorption isotherm for PD-L1 on AuNP@Cit:


Blumeria graminis f. sp. hordei. However, the mechanism is not well understood. In this study, the morphological and cytochemical analyses revealed that substances containing proteins leaked from the tip of the appressorial germ tube of conidia without the formation of appressorium under a high humidity condition. In addition, exposure to high humidity prior to the formation of appressorium caused the aberrant formation of the appressorial germ tube without appressorium formation, resulting in failure to penetrate the host cell. These findings suggest that the formation and maturation of the appressorium requires a low humidity condition, and will be clues to improve the disease management by humidity control.High humidity decreases the penetration rate of barley powdery mildew  Blumeria graminis f. sp. hordei (Bgh). An obligate biotrophic pathogen Bgh can make a success of the asexual life cycle only on the living host cells, resulting in the spread of airborne conidia through the formation of conidiophores. After the arrival to the leaf epidermis, the primary germ tube (PGT) emerges within 2 h. Although PGT does not penetrate the host cell wall, it is hypothesized that PGT has roles not only in the transduction of host-derived signals to initiate the coming morphogenesis and the suppression of host resistance, but also in the absorption of water from host cells under dry condition [Bgh forms the second lobe from the lateral part of AGT as another attempt to penetrate a neighbor cell. Successfully penetrating Bgh forms a haustorium surrounded by a host-derived extrahaustorial membrane and establishes infection. Subsequently, the fungus develops secondary hyphae by absorbing nutrients with the haustorium and forms conidiophores to produce new conidia. Because the entire life cycle is accomplished on the surface of host leaves, it is assumed that the infection processes are largely affected by conditions surrounding the leaves  [Bgh. For example, as with other fungi, high humidity is required for the sporulation and the germination of conidia [Bgh more likely to fail the normal development of the germ tubes [Bgh.Powdery mildew is a major fungal disease of barley, caused by ondition ,2,3. A sondition . In casendition) ,6. Of pa conidia ,8. Howevrm tubes ,10,11. BBgh were exposed to the high humidity condition (more than 95% relative humidity (RH)), the infection was considerably suppressed  or more than 95% RH (high humidity) after inoculation with Bgh conidia. The penetration rates were measured 24 h after inoculation. As a result, the penetration rate was significantly reduced under the high humidity condition  staining was carried out after incubation under the high humidity condition. The barley coleoptiles were inoculated with Bgh conidia and kept at more than 95% RH for 4 h. The inoculated coleoptiles were transferred to the incubator kept at about 70% RH and then stained with CBB solution 20 h later. As a result, the leaked substances were observed at the tip of AGT and stained blue  were grown in vermiculite supplemented with 300-fold diluted HYPONeX  in growth chambers  at 20 °C under continuous light condition (ca. 23.6 Wm−2). Powdery mildew fungus Bgh RACE1 isolate was cultured on the barley leaves at 70% relative humidity (RH) in culture chambers  as described by Wahara et al. [Seedlings of barley .Conidia were collected from barley leaves around 7 days after inoculation and were inoculated onto coleoptiles or cellulose membranes. The coleoptiles were inoculated with fresh conidia with a brush and were floated on 1 mM CaCleviously . In vitrescribed  with sliBgh on the coleoptiles or the cellulose membranes were soaked in CBB solution  for 5 min, rinsed with 30% ethanol and gently washed with distilled water three times. Leaf segments inoculated with Bgh were stained with trypan blue solution 4 d after inoculation as described by Yaeno et al. [o et al. . To quanBgh were fixed and dehydrated with a series of ethanol 75%, 80%, 95%, twice 100%, isoamyl acetate–ethanol (1:1) for 30 min and twice isoamyl acetate for 1 h. Samples were dried with a critical point dryer , coated with platinum, and observed by a scanning electron microscope  with a secondary electron detector at an accelerating voltage of 5 kV. To observe the penetration pore, Bgh conidia with the appressorium or the second lobe were shifted with a micromanipulator  before fixation.Coleoptiles inoculated with The cellulose dialysis membranes on agar plates were inoculated with conidia and were transferred from 70% RH to more than 95% RH. The germinated conidia were photographed 18 h after inoculation and the conidia with the leakage at the tip of AGT were counted in randomly selected photographs. The length of AGT was measured using software .


Based upon the approximate Crank–Nicolson (CN) finite-difference time-domain method implementation, the unconditionally stable algorithm is proposed to investigate the wave propagation and transmission through extremely thin graphene layers. More precisely, by incorporating the CN Douglas–Gunn algorithm, the piecewise linear recursive convolution method and the auxiliary differential equation method, the analytical model is proposed for Drude-like graphene model. To obtain the solution of the governing equations, the perfectly matched layer and the periodic boundary condition are applied to the graphene structure with two dimensional nano-materials. Numerical examples are carried out for further investigation. During the simulation, the influences of the parameters such as the grating slit and its thickness on the wave transmission are investigated and discussed. The result shows that not only the graphene grating has high transmission performance but also the proposed methods have considerable performance and accuracy. Graphene has attracted much attention during the last decades due to its very interesting properties, such as mechanical, physical, electrical and optical properties4. For the remarkable physical property, GSs are being studied in the field of communication and optoelectronic nanodevices6. Graphene is an ideal plasmonic material to explore tunable devices, including the tunable nanoantennas and the tunable reflectors in the range of terahertz and mid-infrared frequencies7. In the recent year, the absorption enhancement of graphene in near-infrared light has attracted considerable interest due to its unique electronic and optical properties9. Graphene is a kind of lossy and multi-scale material, and thus it is difficult to accurately simulate the wave propagation characteristics of GSs10.Graphene sheet (GS), a two dimensional one-atomic-thick monolayer of graphite, is the strongest ever measured and the thinnest known material11. Shen et. al. studied the wave propagation in thin GSs by using the FDTD method12. Compared with a theoretical solution, they verified the proposed FDTD method through two numerical examples, and proved its accuracy and efficiency. Liang et. al. investigated the extraordinary optical transmission of periodic metallic gratings based on the locally one-dimensional FDTD13. In14, the analysis of electromagnetic phenomena in graphene structures was carried out by an efficient FDTD formulation. Numerical verification, involving comparison with closed-form solutions and the results of other schemes, exhibited the high accuracy of the algorithm.The finite-difference time-domain (FDTD) method can be used as an effective numerical analysis technique to model the wave propagation in GSs because of its direct iterative solution in the time domain15. However, when calculating the large amount of time steps problems, the simulation duration will be unacceptable resulting in the limitation application of the FDTD algorithm. In order to improve the computational efficiency and maintain the accuracy, the unconditionally stable algorithms are proposed. Among existed algorithms, the Crank–Nicolson (CN) algorithm with higher computational accuracy is firstly proposed in one dimensional cases16. By applying the original CN algorithm directly to 2D problems, large sparse matrices must be calculated at each step resulting in the computational more expensive. To avoid the calculation of the sparse matrices, approximate CN algorithms are introduced including the CN approximate-decoupling (CNAD) and CN Douglas–Gunn (CNDG) algorithms18. It has been testified that the CNDG algorithm shows higher accuracy compared with CNAD algorithm19. In addition, from the previously works, CNDG algorithm has been extensively employed merely in TM cases21. This limits the development of the CNDG algorithm.However, analytical models and mesh sizes are key for obtaining correct results in numerical analysis technique. In order to ensure the stability of the numerical scheme, an adequate time step must be taken to assure the Courant-Friedrichs-Lewy (CFL) condition. The CFL limit is determined by the smallest cell size in the space domain22. Among modified PML schemes, unsplit-field SC-PML is developed to simplify the corners and edges of the PML regions23. The CFS-PML with advantages in attenuating low-frequency propagation waves and reducing late-time reflections is carried out24. It has been testified that the low-frequency propagation waves can not be absorbed efficiently by employing both SC-PML and CFS-PML. Thus, the higher order PML is proposed not only to alleviate such problem but also further enhanced the absorbing performance27.In order to simulate the infinite computational domain in the limited space, an efficient absorbing boundary condition is necessary to truncate the computational domain, such as the perfectly matched layer (PML)15. Among existed CN-PML algorithms, the employment of PBC have not been investigated21. Due to the existence of PBC, the Thomas algorithms can not be employed directly to the unconditionally stable algorithm. Thus, an alternative method should be investigated.Moreover, the periodic boundary condition (PBC) is also applied due to the existence of the periodic structureHere, based on the CNDG algorithm, higher order PML and Drude model, unconditionally stable implementation is proposed for evaluating the wave propagation characteristics through GSs in TE case. Combining with the piecewise linear recursive convolution (PLRC) and the auxiliary differential equation (ADE) methods, the extraordinary optical transmission through extremely thin periodic graphene can be simulated and calculated. Two numerical examples with different situations in one period are discussed. The results reveal the characteristics of extremely thin graphene and efficiency of the proposed algorithm.22. According to the Drude model, the relative dielectric function n is the density of electrons, e is the electron charge, and 24. The source-free and normalized frequency-domain modified Maxwell’s curl equations in two dimensional Drude media can be written asThe Drude dispersion model can be applied to GSsIntroducing the auxiliary variables, they can be given as the following formsBy substituting (11)-(14) into (15)-(17), the equations can be rewritten as26Based on the CN scheme and PLRC methods, we obtain the FDTD difference equations as followsAnd the operator The updated equation of auxiliary field obtained by PLRC method can be calculated asBy substituting (21) and (22) into (23), the updated equation of magnetic component in the y-direction can be given asTo obtain the solution of Maxwell’s equations for the periodic structure, the PBC is introduced. Figure For the top boundary condition, we obtainThus, by employing the PBC, the matrices in (29)-(30) can be given as27.It can be observed that the matrices are no longer tri-diagonal matrices which can not be solve by employing the Thomas algorithm. Thus, an alternative method, the RCM method is employed to decrease the dimension of the matrices and improve the computational efficiency,28. The observation point is located at the left bottom corner of the domain to observe the waveform.Before the investigation of GSs, the effectiveness and efficiency of the proposed CNDG-HO-PML algorithm is validated through a full-filled domain with graphene with the parameters of entclass1pt{minimaTo ensure the accuracy of the calculation and validate the effectiveness of the algorithm, cell per wavelength (CPW) is chosen as 200. The CFL number (CFLN) is defined as The waveform observed at the observation point obtained by different CFLNs are shown in Fig. The accuracy of the calculation also affects by the absorbing performance of the PML regions. The absorbing performance of the PML regions can be reflected by the relative reflection error in the time domain which can be defined as29. The computational efficiency, memory consumption and time reduction are shown in Table Figure The wave transmission through a graphene sheet is studied with regard to transverse electric The sketch picture of the computational domain for investigation is shown in Fig. It should be noticed that the mesh size and the time step is no longer limited by the CFL condition. Thus, the physical size can be employed during the simulation. To ensure the accuracy of calculation, the thickness of single-layer GS is divided into 10 cells as Firstly, the wave transmission through GSs can be investigated through the maximum value of the waveform obtained from the observation point. Figure In addition, it can be observed that the normalized transmitted energy decreases with the increment of the thickness. This indicates that the thicker sheet transmits less energy. This phenomenon can be reflected by the normalized reflection energy, shown in Fig. 30. As defined in the microwave theory, the transmission can be reflected by S21. Thus, the port 1 is defined at the left side of sheet with the incidence plane wave. Port 2 is defined at the right side of the sheet. In this simulation, the S21 is obtained by CNDG-HO-PML when CFLN = 20, as shown in Fig. 21 decreases with the increment of the thickness. At the frequency of 6.2 PHz, the graphene sheets show the least S parameters. At the low-frequency, the graphene sheets have higher S parameters indicating the less loss during the wave transmission. Figure 21 parameters obtained by different thickness. It can be observed that the S21 becomes lower in small wavelength.To demonstrate the wave transmission in the frequency domain, the S parameters in the microwave theory is introduced during the simulationTo investigate the extraordinary optical transmission phenomenon through the graphene sheet, a periodic graphene structure with slit is proposed. Figure Compared with the graphene sheet without slit in the previously numerical example, due to the existence of slit, the interference of wave transmission results in the generation of the crest and trough in the observation plane. Thus, it should be noticed that the energy from each mesh grid in the observation plane should be employed during the calculation. Figures 21 parameters can be employed in evaluating the performance and investigating the properties of graphene. Figures 21 parameters versus frequency and wavelength with different slit width under 8-layer-sheet, respectively. It can be observed that the S parameters increases obviously with the increment of slit width. This indicates that the wave is much easier to transmit with the increment of slit width before the 6 PHz frequency.Following the same step as the numerical example above, the SAs is demonstrate in the previously that the wave is no longer uniform at the observation plane. The reason is that the interference of electric current occurs when wave transmitting through the slit. The crest and the trough are formed at the observation point. Thus, it is important to investigate the crest and the trough of the waveform.34.In this simulation, the parameter 21 parameters.Figures Based on the CNDG algorithm, the Drude-like model and higher order concept, an unconditionally stable CNDG-HO-PML algorithm is presented to investigate the wave propagation through graphene gratings. The Maxwell’s equations are applied to the model to study the transmission characteristics. The ADE- and PLRC-FDTD methods with faster calculation and less memory is used to solve the partial differential equations for time stepping of the electromagnetic fields. The effectiveness and efficiency are testified through a full-filled structure, a single sheet and the sheet with slit. Based on numerical analysis, the obtained result shows that the characteristics of graphene with high transmission performance. The grating graphene layer structures can be used in the field of optoelectronic detection technology and systems.


Graphene, a two-dimensional structure of carbon, due to its structure has unique physico-chemical properties that can be used in numerous research and industry areas. Although this structure is already well known, there are still technological (and cost) barriers which do not allow to produce this material in large quantities and hence prevent its use in various applications. For this reason, many technologies are currently being developed to obtain graphene in forms that would enable its widespread use. The graphene-like ceramics were fabricated by the high isostatic pressure method at different temperatures. This technique allows to obtain dense ceramics with various shapes. The structure and morphology of sintered graphene were investigated by XRD, SEM and the Raman spectroscopy. The hardness, thermal conductivity and electric transport measurements recorded in a wide range of temperatures were used to analyze the physical properties of the obtained ceramics. However, the first graphene flakes were obtained by Novoselov2 by exfoliation of highly oriented pyrolytic graphite (HOPG). This was done by pressing an adhesive tape onto the HOPG and then pulling it off; this leaves graphene in the adhesive tape. Subsequently, the adhesive strip is pressed onto a silicon wafer with a thin silicon dioxide layer and pulled off again. Thereafter, graphene becomes visible by suitable optical methods. This method is very time-consuming, and only very few, albeit high-value, samples are obtained. After this discovery, many new graphene preparation techniques such as epitaxy4, reduction from SiC5, reduction of graphite oxide7 carbon nanotube slicing8 or solvent exfoliation9 were developed.The term graphene appeared for the first time in 19872 g−1), high intrinsic mobility (200 000 cm2 v−1 s−1)10, high Young’s modulus (∼ 1.1 to 2.0 TPa)11, thermal conductivity 12, optical transmittance (up to 98%)13, and good electrical conductivity15. The combination of these unique properties makes graphene an excellent candidate for many potential applications as supercapacitors17, ultrafast transistors18, biosensors20, chemical sensor21, light source22, photocatalysts25 or medium improving mechanical properties26. In all these applications graphene is used in different forms, such as polymer-based composites28, coloids29, foam30, thin films32 or ceramics34.Graphene demonstrates a series of exceptional physical, chemical and mechanical properties. It has a large theoretical specific surface area  and Hot Isostatic Pressing (HIP) allows sintering of ceramics with relatively long processing times and high temperature. Both factors result in grain growth and simultaneous degradation of graphene in ceramic composites. In order to avoid these problems, novel sintering techniques for ceramics, such as spark plasma sintering (SPS) or microwave sintering are being exploited. These methods allow to lower the sintering temperature and shorten the dwell times. Well consolidated ceramic composites in the form of plates prepared by SPS were reported by Walker et al.36. The prepared ceramics were characterized by XRD, SEM, Raman, thermal and electric measurements. It was found that sintering temperature and pressure have great impact on the thermal and electrical properties of the graphene ceramic.The paper describes a new method of obtaining tough graphene ceramics without any additives. Sintering is based on high pressure (up to 5 GPa) and relatively low temperature (from 500 °C). The high pressure applied during sintering arranges graphene flakes parallel to each other and does not allow for grain growth, which results in keeping the structure and properties of the graphene in the ceramics. Since the pellet is closed in a hermetic container only a small part of graphene is oxidized. The advantage of obtaining graphene ceramics by high pressure sintering is the possibility of using any type of graphene (or graphene oxide). Additional sintering of graphene flakes does not require its further chemical or physical treatment. The high pressure sintering method allows for a simple formation of the composites by introducing additional compounds into the graphene powder. In addition, it should be emphasized that the method of obtaining ceramics in this way is relatively inexpensive and very fast. The development of this technology will allow to produce graphene ceramics as well as composites with designed unique physical properties, such as efficient persistent conductivity with a possibility of application in photovoltaic cells37. For sintering commercial available graphene flakes were used . Before sintering, the pellets (10 mm in diameter and 2 mm in thickness) were formed by cold pressing under 0.2 GPa . The sintering process was carried out in a high-pressure container. The samples of graphene ceramics were prepared by hot-pressing up to 5 GPa and temperatures in the range from 500 to 1,500 °C during 1 min.The preparation of graphene ceramics was performed using the high isostatic pressure (HIP) technique as described elsewhere1 radiation . TEM images were made using Tesla BC 500 . SEM images were made with a FE-SEM microscope (FEI NovaNanoSEM 230). The Raman spectra were collected using Renishaw inVia Raman Microscope equipped with an IR laser (830 nm) and CCD camera under ambient conditions. The Raman wavelength shift ranged from 1,000 to 2,500 cm−1 and the spectral resolution was 0.7 cm−1. The laser spot size was 1.5 μm in diameter with × 50 magnification of the objective.The crystal structures, phase purities and morphology of the ceramics were analyzed with the X-ray diffraction (XRD) and electron microscopy (TEM/SEM) measurements. The XRD patterns were collected at room temperature between 10 and 60 degrees (in 2θ) by an X’PERT PRO PANalytical diffractometer using CuKαThe hardness of the ceramic was characterized using a micro- and nano-hardness tester. Microhardness was checked using a Vickers indenter (Zwick Roel) with 25 g loading. Nanohardness was checked using a Berkovich indenter (Nanoindentation Tester Anton Paar NHT3).38. The experiment was conducted in the temperature range 4–300 K. Samples were prepared in a cuboid-like shape in order to provide heat flow through the same area along the sample and simultaneously minimize the geometrical error. The temperature gradient along the sample was induced by a small resistive heater glued to the top of a specimen and it was determined by means of a differential thermocouple, typically it was kept between 0.1 and 0.2 K. The measurement chamber temperature estimated by germanium and platinum thermometers was stabilized at the level higher than ± 3 mK. The temperature of the sample was measured by a constantan–manganin thermocouple. To avoid heat transfer between the sample and the environment, the measurements were performed under high vacuum conditions and four shields were mounted around the sample to reduce the heat losses due to radiation at the finite temperature39. The maximum experimental systematic error was below 15% (caused mainly by the uncertainty of sample geometry) and the spurious errors estimated from the point scattering did not exceed ± 2%.The thermal measurements were carried out by the axial stationary heat flow method−2–106 Hz at room temperature with an ac voltage amplitude of 0.1 V40. The studied sample was placed between golden electrodes. The dc resistivity was examined by the four-contact method41. The thermoelectric power was determined in the temperature range 7–300 K by a steady-state mode using a semiautomatic instrument fitted into the transport liquid-helium Dewar42.The electrical impedance was measured employing an Alpha analyzer (Novocontrol GmbH) with an active sample cell operating in the frequency range 1043 observed that with an increasing temperature reduction of graphene oxide to graphene, the peak 2Θ ≈ 26° was shifted to a higher degree, which was related to reducing distance d002 caused by removing intercalated water molecules and the oxide groups of hydroxyl and carboxyl groups. In the cold pressed pellets, the position of the peak is around 26.4°, and after sintering at 500 °C it was shifted to 26.6°, which indicates that the application of pressure results in decreasing interatomic distance. This behavior, combined with the fact that with increasing the sintering temperature the band observed at 26° becomes narrower, suggests a decrease in the strains in the ceramic. The average sizes of flakes (thickness) were determined by means of the Scherrer equation44 and was found to be about 14 nm for ceramics and 35 nm for graphene flakes. The calculations were made for the peak observed at 26° for ceramics and for the band about 18° for the flakes. The derivation of the Scherrer equation was given for particles with a spherical shape and it is only an approximation, however, the analysis of the XRD patterns showed that applying the pressure and increasing the sintering temperature results in the formation of a multilayered structure with higher density.The sintered ceramics show no decomposition since only reflections resulting from graphene and graphite structure Fig.  are obseTo evaluate the surface morphology of the starting graphene flakes, TEM images were taken Fig. . It is sThe SEM images of graphene GB and ceramics show their surface after polishing Fig. . What sh−145, and the G-mode together with the D’-mode appears at approximately 1,590 cm−146. At 2,600 cm−1 a very weak signal from the 2D-mode can be observed. The low intensity of this peak is caused by the low sensitivity of the CCD camera in this region. In the Raman spectra obtained from the samples with a small crystallite size , the presence of an additional dispersive peak centered at approximately 1,350 cm−1 is observed. This feature is assigned to the breathing of the carbon hexagons that become Raman active at the borders of the crystallite areas owing to the loss of translational symmetry47. The high intensity of the peak at 1,790 cm−1 indicates high fraction of tetrahedrally coordinated carbon (sp3 hybridization)48. Peaks in the range 1,700–2000 cm-1 could also be the result of the appearance of linear carbon chains49.The Raman spectrum of cold pressed pellet and graphene ceramics is composed of three broad bands Fig. . The D-m−1 is known as the disorder band or the defect band (D band). This band appears when sp2 carbon rings interact with the graphene edge or network defects. If the structure has a lot of defects (or graphene), the intensity of this band increases. The G band observed around 1,590 cm−1 comes from the C–C bond in graphitic materials, and is common to all sp2 carbon systems. It was shown that the shift of this band toward higher frequencies indicates the number of graphene layers. The intensity ratio of these two bands (ID/IG) may be used to quantify the disorder of the examined structures, because for bigger grains, or a multilayer graphene structure, the sp2 carbon hexagonal structure starts to disappear. The ID/IG ratio is correlated with crystallite size (d) and is equal to the A/d ratio, where A is a constant for a fixed laser power50.The peak at approximately 1,350 cm51 and Chen et al.52, made for a compressed graphene foil. They showed that by increasing the sintering temperature, the disorder factor decreases. This behaviour is probably related to two facts. First, both groups used the hot pressing techniques, but at a relatively low pressure . In our case, the applied pressure reached 5 GPa (one order higher), which could introduce additional defects in the structure, and prevent the release of oxygen between the layers. The second difference compared to the presented publications is the fact that in our case the synthesis was not carried out under vacuum. Therefore, oxygen was not removed from the reaction atmosphere and the surface of graphene flakes. The oxygen trapped between the graphene flakes could additionally react with them, especially due to the fact that the synthesis conditions were extreme (very high pressure and temperature). The above facts are the reason for the increase in the disorder factor in ceramics with the growth of the sintering temperature. The high value of the intensities ratio calculated for pellets, obtained at room temperature, is related with a very small particle size in starting materials and high disorder in separated graphene sheets. After sintering at 500 °C, some graphene sheets are combined to form bigger particles, which could be observed in the SEM images.In our case the disorder in the ceramics increases with sintering temperatures Fig. . This beFor the ceramics prepared at different temperatures, hardness was measured using two methods. For every sample, several measurements were made at different points on the surface to obtain the real hardness of each ceramic. For all samples hardness was checked using a nano- and micro- indenter Fig. . Before 2 dependency, which is characteristic for an amorphous material53. This tendency is caused by some additional scattering mechanisms and may be explained by a closer observation of the structure of the investigated samples. The samples are significantly porous, and the investigations on such materials at low temperatures indicated that phonons are predominantly scattered by pores54. With increasing temperature, the conductivity of graphene samples grows at different rates—gently for the samples pressed with 5 GPa, and more firmly for the 4 GPa ones. For a high temperature range with increasing pressure, there is an unusual decrease in the value of thermal conductivity. It may be connected with the porosity of the samples or their quality. Consequently, in further research it would be recommended to carry out experiments with higher diversity in used pressure to see if maybe the influence of the sample origin on this particular case was not observed.The thermal conductivity of the graphene ceramic changed for samples obtained at different sintering pressures Fig. . The res55.Within electric transport investigations, high purity graphite and graphene ceramics obtained at 5 GPa were studied by a four-contact method in the temperature range 2–300 K Fig. . As can The extrapolation of resistivity in the high temperature region allows to determine the band gap of graphene ceramics. The band gap was obtained from the fitting of the temperature dependence of resistivity see Fig.  by the aEg is a band gap energy and kB—Boltzmann constant, T—temperature and ρ0 = 8 mΩ·cm. The fitting showed that the energy gap of graphene ceramic is smaller than thermal energy kBT in the whole temperature range and only near 40 K both of the values become similar. The calculated Eg reaches up to 7.6 meV at 237 K, whereas kBT = 20 meV at this temperature. Thus, it could be concluded that despite the semiconductor-like character of resistivity, the activation energy of graphene ceramic is rather smaller than kBT, which indicates the semimetallic-like dependency of this sample in the whole temperature range.where ƟD/5, where ƟD is the Debye temperature. It follows from this relation that ƟD can be estimated for both of the samples. Thus, ƟD = 150 K for the graphite sample and ƟD = 100 K for the graphene ceramic. These values are rather smaller than those obtained for graphite and graphene in different studies with ƟD = 402 K and ƟD = 2,100 K for graphite and graphene, respectively57. The thermopower value of graphene ceramic at 300 K is S = 20 μV K−1. However, the thermopower of single, double and even more layered graphene at 300 K varies in the range from 6 μV K−158 to 180 μV K−159, depending on the measurement method. Hence, it is difficult to compare them but one can conclude that this value is higher than that of pure graphite.For both graphite and graphene ceramics obtained at 5 GPa and 1,000 °C, the temperature dependence of thermopower was measured Fig. . It can −1 at 300 K. This suggests a weak influence of the sintering conditions on the thermoelectric properties of graphene.It should be noted that the graphene ceramic obtained at 5 GPa and 1,000 °C revealed S = 22 μV KThe frequency dependence of the ac conductivity of graphene ceramics obtained at 5 GPa and room temperature, 500 °C and 1,500 °C are shown in Fig. In the paper the preparation method of pure graphene ceramic was presented for the first time. It was shown that in some cases even ceramics may be treated as HOPG (Highly Oriented Pyrolytic Graphite) and that their physical properties are more likely to be similar to graphene materials. It was also demonstrated that at high pressure and suitably selected sintering temperature, it is possible to obtain graphene-like ceramics with semiconductor properties. An increase in the sintering temperature leads to the densification of the ceramics and the growth of thermopower or AC conductivity. The presented method of graphene ceramic preparation may be utilized in the production of various types of sensors or transistors. Thanks to the simple production method, it is possible to manufacture this type of ceramics with admixtures of other ions or compounds, which can greatly extend the application areas of this material and can significantly improve its physical properties.


Activation of peroxidase-like catalytic function of GO required hydrogen peroxide (H2O2) and ammonia (NH3) in pH 4.0 disodium hydrogen phosphate (Na2HPO4). Carbocatalytic abilities of GO were triggered in pH 4.0 deionised distilled water (ddH2O). Transmission electron microscope (TEM), scanning electron microscope (SEM), cyclic voltammetry (CV) and UV-Vis spectroscopy aided in qualitatively and quantitatively assessing GO/Ag nanocomposites. TEM and SEM analysis demonstrated the successful use of GO’s peroxidase-like and carbocatalytic properties to produce GO/Ag nanocomposite. UV-Vis analysis indicated a higher yield in optical density values for GO/Ag nanocomposites created using GO’s carbocatalytic ability rather than its peroxidase-like counterpart. Additionally, CV demonstrated that GO/Ag nanocomposite fabricated here is a product of an irreversible electrochemical reaction. Our study outcomes show new opportunities for GO as a standalone catalyst in biosensing. We demonstrate a sustainable approach to obtain graphene nanocomposites exclusive of harmful chemicals or physical methods.The present study evaluates the role of graphene oxide’s (GO’s) peroxidase-like and inherent/carbocatalytic properties in oxidising silver nitrate (AgNO Graphene is an ideal composite counterpart to create flexible electronics6, design batteries with enhanced storage capability7, prevent steel corrosion8, and shield aircraft from heat9. Real-world graphene applications have originated across several industries like the Inov-8 running trainers that employ thermal and mechanical qualities of graphene to improve their durability10. The famous sports equipment manufacturer, HEAD applied graphene to create stronger tennis rackets with lighter weight distribution10. The BAC-Mono formula racing car also uses graphene to boost strength and reduce the mass of its body parts by 20%11. Miniaturization of biochemical assays using graphene-based sensors for research and clinical purposes is now a reality with AGILER10012.Remarkable optical, thermal, mechanical, and electrical properties of graphene have captivated the imaginations of scientists worldwide10, HEAD10, BAC-Mono12, and AGILER10012 is the tip of an iceberg considering graphene’s estimated market size of $680 million by 202013. However, the reported market size for graphene was a mere $12 million in 2013, indicating that sales in the graphene industry are predominantly raw material driven14. Graphene’s annual production has peaked at 1200 tonnes per annum compared to 4600 tonnes per year of carbon fibre or carbon nanotubes14. Reported growth in the graphene industry may seem uninspiring but demonstrates the need for technological innovations that will increase graphene consumption. A surge in patent and scientific citation trends hint graphene nanocomposites as a promising area for research and application13. Unlike graphene, the role of graphene nanocomposites extends beyond improving the existing physiological properties of a host matrix13.Utilization of graphene by Inov-815. Currently, research on graphene nanocomposites heavily relies on physically or chemically coupling graphene with metal nanoparticles for utilization in a spectrum of catalytic processes24. Thus, understanding graphene’s role as a standalone heterogeneous carbon catalyst  to create nanocomposites by modifying inorganic or organic compounds is required. A simple PubMed search using the term “Graphene AND catalysis” will render over 2000 scientific articles, and the term “Graphene AND carbocatalysis” gives about ten results. Hence, less than 1% of research articles have explored graphene’s inherent or carbocatalytic properties.Catalytic properties of graphene nanocomposite help generate or store energy, reduce emission from modern automobiles, and remove pollutants from water, soil, and air26. However, pure graphene does not dissolve in organic or inorganic solvents27. Thus, researchers have functionalized the graphene surface with epoxy, hydroxyl, or carboxyl groups to obtain readily soluble graphene oxide (GO)28. Apart from GO’s carbocatalytic applications, the use of the peroxidase-like catalytic feature of GO29 is popular among researchers developing biochemical assays or biosensors to transform organic compounds30. Briefly, in the presence of hydrogen peroxide, GO can replace the horseradish peroxidase enzyme to reduce 3,3′,5,5′-Tetramethylbenzidine (TMB) from colourless to blue29. Surprisingly, GO’s peroxidase-like and carbocatalytic abilities are unexplored with the inorganic elements26.Density functional theory (DFT) calculations reveal the potential use of metal-free graphene to stabilize ground state molecules through non-covalent π-π interactionsAs a consequence, this study has investigated GO’s peroxidase-like and natural or carbocatalytic oxidation capabilities with inorganic compounds to show new opportunities for graphene as a standalone catalyst in biosensing. Specifically, the role of GO in changing silver nitrate to silver nanoparticles (Ag) to create GO/Ag nanocomposite without the use of extreme physical and chemical redox methods is explained here.29. Disodium phosphate (Na2HPO4), silver nitrate (AgNO3), hydrogen peroxide (H2O2), and ammonia (NH3) were purchased from Sigma-Aldrich, Finland29.Highly concentrated GO dissolved in water with over 95% monolayer content was purchased from Graphenea, Spain29 and facilitate the oxidation of aqueous AgNO3 to Ag nanoparticles. Therefore, GO/Ag nanocomposite synthesis was achieved by changing the concentration of GO in the presence of AgNO3 at a constant concentration and vice versa. Firstly, different GO concentrations  were independently introduced along with 100 mM H2O2, 0.1 mM AgNO3, and 40 mM NH3 to a final volume of 1 ml in 25 mM Na2HPO4 buffer at pH 4.0 and 37 °C. Secondly, several AgNO3 concentrations  were separately added with 100 mM H2O2, 40 µg GO, and 40 mM NH3 to a final volume of 1 ml in 25 mM Na2HPO4 buffer at pH 4.0 and 37 °C.GO surroundings were tailored to stimulate its peroxidase-like catalytic properties2HPO4, H2O2, and NH3 to create GO/Ag nanocomposite was assessed by lowering Na2HPO4 concentration  in the presence of 40 µg GO, 3.2 mM AgNO3, 100 mM H2O2, and 40 mM NH3 in total 1 ml solution. Particularly, the 0 mM Na2HPO4  experiment was performed with 40 µg GO and 3.2 mM AgNO3 in the presence and absence of 100 mM H2O2 and 40 mM NH3 at pH 4.0 and 37 °C. Without Na2HPO4, H2O2, and NH3, GO will depend on its natural abilities25 to convert aqueous AgNO3 to Ag nanoparticles.The need for Na3 to control for GO and vice versa. Thus, experimental controls have been referred to as GO alone or AgNO3 alone hereon. The reaction temperature for all experiments was maintained at 37 °C using a heat block, and each component was added at 15 min intervals29. The order in which each chemical was added to Na2HPO4 buffer was GO, H2O2, AgNO3, and NH3. Further, UV-VIS spectral analysis (Perkin Elmer Lambda 650) was performed between 300 nm to 700 nm 15 min after adding the last element. Specimens for changing GO and AgNO3 were performed in triplicates to measure average standard deviation across all wavelengths from 300 nm to 700 nm.In the case of experimental controls, all reaction components were included except AgNO3 alone,“Nanocomposite” refers to the GO/Ag nanocomposite absorbance at 450 nm and “Control” denotes matching GO or AgNO3 alone absorbance at 450 nm. The horseradish peroxidase (HRP) enzyme reacts with 3,3’,5,5’- tetramethylbenzidine (TMB) and is detectable at 450 nm that is extensively used for various biochemical applications32. As GO can mimic peroxidase-like activity29, the nanocomposite-to-control percentage measurements were performed at 450 nm. Equation 3. Following previously described set-up for CV33, an in-house CV was created using glassy carbon electrodes as the working and counter electrodes with an Ag/AgCl reference electrode (66-EE009) from Cypress systems. A Keithley electrometer series 2400 was utilized together with a homebuilt LabView measurement program to measure current (mA) between the working and counter electrodes, as well as difference in potential (V) between the working and reference electrodes. To avoid interference from dissolved O2, the electrolyte solution was purged with N2 gas. In all CV measurements, ±3 V was applied with a step size of 10 mV and scan rate of 38 mVs−1.Following equation was applied to measure the difference in absorbance between GO/Ag nanocomposite to GO or AgNOhttps://imagej.nih.gov/ij/ version 1.51) was utilized for measuring the average size of Ag nanoparticles on GO and adding a scale bar.Visualization studies were conducted to view the nanocomposite structures and aid in elemental analysis. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) required 5 μl of sample on Formvar/carbon coated 200 mesh copper grids. In the case of TEM, digital micrographs were acquired with Jeol JEM-1400HC  that is equipped with Quemesa  bottom mounted CCD-camera. Chemical characterization for GO/Ag nanocomposite was achieved with Zeiss EVO-50XVP SEM that is integrated with Bruker Quantax 400 energy dispersive spectrometer (EDS). Elemental maps from EDS were obtained using Bruker AXS detector 3001 with energy resolution <133 eV . The counts per second values in elemental maps were normalized. Image J (https://products.office.com/en-in/ excel version 16.32 (19120802)), Microsoft PowerPoint (https://products.office.com/en-in/powerpoint version 16.16.3 (181015)), QtiPlot (https://www.qtiplot.com/ version 10.9), Adobe Photoshop 2020 (https://www.adobe.com/in/products/photoshop.html version 21.0.2), and Adobe Illustrator 2020 (https://www.adobe.com/in/products/illustrator.html version 24.0.1).All figures were created using Microsoft Excel  to 2.93% (160 µg GO/0.1 mM AgNO3). The decline in nanocomposite-to-control percentage is observed because varying GO concentrations in the presence of 0.1 mM AgNO3 produce spectra that are only GO dominant. However, as rising concentrations of AgNO3  are subjected to 40 µg/ml GO, 100 mM H2O2, and 40 mM NH3 in 25 mM Na2HPO4, a four-fold increase in absorbance is noted between AgNO3 alone and their respective GO/Ag nanocomposites  with 0.1 mM AgNO nm Fig. . Neverth nm Fig.  at 450 ntes Fig. .Figure 13 alone rises from 47% (40 µg GO/0.4 mM AgNO3) to 77% (40 µg GO/12.8 mM AgNO3). Therefore, varying AgNO3 amounts in the presence of 40 µg/ml GO yields spectra that are GO/Ag nanocomposite dominant  or at high AgNO3 concentration (40 µg GO/12.8 mM AgNO3) as depicted in Fig. 3 concentrations  alone  or AgNOone Fig.  were vis3 1.8 mM alo3 1.8 mM alo3 1.8 mM aloant Fig. , silver ant Fig. . Nucleatant Fig. . On incrted Fig. .Figure 23 to Ag nanoparticles  in the presence of 3.2 mM AgNO3, 100 mM H2O2, and 40 mM NH3 gradually decreases the background produced by AgNO3 controls 21, and cobalt (II) acetate (Co(CH3COO)2)22 include deionized distilled water19, ethanol22, 1% BSA17, citrate buffer16, or sulphuric acid23. Ultimately, blending of GO with metal nanoparticles demands the presence of chemical agents like hydroquinone17, hydrazine hydrate20, sodium borohydride (NaBH4)24, or ammonium hydroxide (NH4OH)22 to reduce and stabilize the metal clusters on GO surface. Alternatively, extreme physical methods such as autoclave22, annealing or heating at 60 °C to 600 °C23 have been reported to create metal nanoparticles over GO.The GO/Ag nanocomposite created in this study using only natural catalytic properties of GO is simple, resource-efficient, and swift compared to old techniques Fig. . Traditi15 and our research findings . Also, the size and density of Ag nanoparticles on GO is determined by the starting quantity of AgNO3  over a finite size of GO sheet  on the fabrication of carbon nanocomposites.Among various inorganic compounds, applications of silver nanoparticles in the biomedical field is widespread and ever-increasing due to its low-cost, abundance, and fascinating properties54. Currently, the lack of standardized health and safety guidelines to assess the toxic influence of unique graphene-based technologies on human health and the environment is staggering14. In Europe, the registration, evaluation, authorization, and restriction of chemicals (REACH) regulation (EC 1907/2006) by the European Agency for Safety and Health at Work instructs wellbeing at organizations that manufacture or import harmful chemicals55. Nonetheless, the REACH regulation only applies to establishments dealing with one tonne or more graphene per year14. In 2017, the International Organization for Standards (ISO) published ISO/TS 80004:13:201756 that only clarifies technical pre-requisites for a material to be deemed as graphene or otherwise.What plastic was for the 20th century, graphene is to the 21st century. The World Bank and the United Nations have adopted several sustainable development goals to reduce the risk that plastic poses to our environment and public healthGiven the inevitable mass application of graphene and missing guidelines to prevent public health hazards and environmental risks, the research community may become the frontline in consciously assessing the carbon footprint of their innovations. In the spirit of new opportunities for graphene in catalysis like biosensing, we show that using GO’s standalone catalytic abilities will reduce the widespread dependence on harmful chemicals and extreme physical methods to obtain graphene nanocomposites.


The capability of graphene-based biosensors used to detect biomolecules, such as DNA and cancer marker, is enormously affected by the quality of graphene. In this work, high quality and cleanness graphene were obtained by CVD based on acetic acid (AA) and ammonium persulfate (AP) pretreated copper foil substrate. Hall effect devices were made by three kinds of graphene which were fabricated by CVD using no-treated copper foil, AA pre-treated copper foil and AP pre-treated copper foil. Hall effect devices made of AA pre-treated copper foil CVD graphene and AP pre-treated copper foil CVD graphene can both enhance the sensitivity of graphene-based biosensors for DNA recognition, but the AA pre-treated copper foil CVD graphene improves more (≈4 times). This may be related to the secondary oxidation of AP pre-treated copper foil in the air due to the strong corrosion of ammonium persulfate, which leads to the quality decrease of graphene comparing to acetic acid. Our research provides an efficient method to improve the sensitivity of graphene-based biosensors for DNA recognition and investigates an effect of copper foil oxidation on the growth graphene. Graphen2 annealing and nitric acid treatment. They synthesized high quality and uniform graphene on Cu by this method which can effectively reduce the impurities on Cu. Raman mapping results showed that 98.3% of the mapped area exhibited monolayer characteristics with I2D/IG > 2 compared to 75% monolayer characteristics for that grown on untreated Cu foil [Owing to all these great properties, graphene has important research value as a biosensing application ,9,10,11. Cu foil . Jeong H Cu foil . Senyild Cu foil .2/Si substrate for fabrication of Hall effect biosensor by commonly-used PMMA. As shown by microscopy, the surface of AA pre-treated copper foil and the grown graphene were the cleanest and flattest among others. At the same time, AA grown graphene and AP grown graphene could both improve the sensitivity of the biosensors to detect DNA. At the same time, the sensitivity of the Hall effect biosensor fabricated by graphene grown on AA pre-treated copper foil for the detection of DNA was significantly (≈4 times) enhanced compared with that of non-treated graphene grown on pristine copper foil and the specificity of Hall effect biosensor made of graphene grown on AA pre-treated copper foil for the detection of DNA was also greatly enhanced (≈14 times) in comparison to graphene grown on pristine copper foil. This research offers a commercial and easy way to pre-treat the copper foil for the quality improvement of graphene which has a great influence on the sensing performance of the biosensors. The Hall effect biosensor also possesses an excellent sensitivity and specificity, which can effectively distinguish complementary target DNA from one-base mismatched DNA.In this work, we adopted a convenient and economical way to pre-treat the copper foil surface by chemical etching method attempting to optimize the roughness and cleanliness of copper foil as well as the growth quality of graphene and device sensitivity based on graphene grown on pre-treated copper foil. Before CVD growth, copper foils were immersed in acetic acid and ammonium persulfate separately for 10 s. Three kinds of graphene were used to produce graphene including, non-treated copper foil, AA pre-treated copper foil and AP pre-treated copper foil. After graphene growth ended, these three kinds of graphene were transferred onto SiO4S2O8) were purchased from Sinopharm Chemical Reagent Co. Ltd. . Si substrate with 300 nm-thick SiO2 coating was bought from Bokete Technology Co. Ltd. . PMMA as well as Silicone rubber was obtained from Micro Chem Co. Ltd.  and Dow Corning Co. Ltd.  separately. All the other chemical reagents used in this experiment, including PBS buffer solution, probe DNA (5′–AGG–TCG–CCG–CCC–3′), complementary target DNA (3′–TCC–AGC–GGC–GGG–5′) and one base-mismatched DNA (3′–TCC–AGC–GGC–AGG– 5′) were all purchased from Sangon Biotech Co. Ltd. .Copper foils with 25 µm thickness (purity: 99.8%) for the growth of graphene were obtained from Alfa Aesar Chemical  Co. Ltd. Acetic acid, ammonium persulfate  was introduced for the growth of graphene on Cu foil for 20 min at 1050 °C. The CVD tube was naturally cooled down and the graphene sheet was then transferred onto a target substrate for further investigation.Three kinds of graphene were synthesized on three kinds of Cu foil by the CVD method under the same reaction conditions. The Cu foils were firstly heated from 27 °C to 1050 °C in 60 min with a fixed rate. A continuous 20 sccm HThe surface topography was characterized using scanning electron microscope  and atomic force microscope . The quality of the graphene was studied by Raman spectroscopy . The chemical compositions of graphene were analyzed by X-ray photoelectron spectroscopy . The surface free energy was analyzed by a surface tension/dynamic contact angle measurement system . The room temperature Hall effect measurements were performed with the four-point probe method, which was based on the Van der Pauw theory in our self-built system.For each detection experiment with the Hall effect biosensor, a 100-μL drop of PBS buffer was added into the testing window and maintained for 2 h to remove the influence of PBS doping on graphene, as well as infiltrate the graphene surface. Then pre-immobilization of probe DNA was maintained on the graphene surface for 12 h as to substrate the influence of probe DNA and enable it to achieve the saturation adsorption on graphene. Rinsing was then done in 1 mL PBS buffer to remove any loosely bound DNA three times. Afterwards, the target or one-base mismatched DNA varying from 1 pM to 100 nM were dropped onto the device in turn for hybridization with probes. For each concentration of target DNA, it took 3 h for hybridization, which was always followed by a rinsing step.2/Si substrate separately. In this process, PMMA played a role of the supporting layer. Firstly, a 100 nm-thick PMMA layer was spin-coated on graphene. Then, the subjacent Cu foil was removed through etching in a 0.1 M aqueous (NH4)2S2O8 solution for 5 h. After the removal, the graphene/PMMA layer was moved into deionized water three times for cleaning. The layer was then transferred onto the target substrate. Baked on a hot plate at 60 °C for 2 h, the sample would obtain a stronger bonding of graphene and the target substrate. Ultimately, the PMMA layer was removed through etching in acetone on a hot plate at 60 °C for 8 min. As shown in Scanning electron microscope (SEM) can directly reflect the micro-topography information of the sample surface. + in AA reacted with the oxide impurities on the surface of the copper foil so as to remove them from the surface of the copper foil. On the country, AP can not only remove the impurities on the surface of the copper foil but can also etch the copper foil to some extent, while AA Cu cannot directly react with Cu. Therefore, there appeared etching pits in some areas of the copper foil surface pre-treated by AP.The surface etching process of copper foils by AP and AA was illustrated in Then the graphene grown on three kinds of copper foils was observed by SEM. Through AFM, it can be observed from At the same time, the morphology of the graphene surface grown on the three types of copper foil were observed by AFM. As shown in 2 carbon atoms which can reflect the symmetry and crystallinity of graphene. The intensity ratio of G-band to D-band (IG/ID) represents the amounts of defects on graphene and structural regularity of the graphene. Larger IG/ID ratio means fewer defects, better structural regularity, and better quality of graphene. The 2D-band appears by the two-phonon participation in the resonance process. The intensity of the 2D-band is about twice that of the D-band. The appearance of 2D-band marks the electronic structure is dominated by Dirac-Weyl dispersion. The intensity ratio of 2D-band to G-band (I2D/IG) can help to verify the amount of graphene layers [2D/IG is greater than 2, graphene can be regarded as monolayer [−1, and the I2D/IG value was 2.12 indicating that this kind of graphene displayed obvious structural defects. The intensity of D peak was reduced for graphene grown on copper foil pre-treated by AP with 2D peak FWHM of 30.5 cm−1, and the I2D/IG value increased to 3.31. Almost no D peak can be seen in graphene grown on pristine copper foil pre-treated by AA which had the highest quality with the I2D/IG value of 3.74 and the FWHM of 27.9 cm−1 respectively. In general, the spectra of three kinds of graphene in this experiment all exhibited the characteristic peaks of high-quality single-layer graphene including a negligible D-band (≈1350 cm−1), an obvious G-band (≈1580 cm−1), and I2D/IG ration over 2. The value of IG/ID for pristine graphene, AP graphene and AA graphene are 6.08, 5.88 and 10.53 separately. Compared with the original graphene, AA can reduce the defects of graphene, and also improve the monolayer and surface cleanliness of graphene. According to the value of IG/ID, AP may increase some defects of graphene, which is caused by the etching of copper foil by AP directly, but the monolayer of graphene has been improved and the surface of AP graphene is cleaner. The monolayer and surface cleanliness of the graphene are the main influencing factors for the biosensor, so even if the defects are slightly improved, the performance of the biosensor can still be enhanced. In general, pre-treatment copper foil by AP and AA can both boost the monolayer and surface cleanliness of graphene while AA had the most positive effect on the improvement of graphene quality.The Raman spectrum of graphene is closely related to its molecular structure. The D-band is an important criterion for the degree of chemical modification of graphene. It can be used to determine the magnitude of defects in graphene. The increasement of D-band intensity means there are more defects on graphene . The G-be layers . If the onolayer . It can 2/V·s from 2/V·s and 942 cm2/V·s relatively which were 1.30 times and 1.80 times of the graphene grown on pristine copper foil. The sheet resistance of three kinds of graphene were 886 ohm/sq, 612 ohm/sq and 408 ohm/sq separately  between complementary target DNA and single-base mismatched DNA and a wide linear range from 1 pM to 100 nM. The device made of AA graphene processed an approximately 4 times higher sensitivity than pristine graphene device and an approximately 1.9 times higher sensitivity than AP graphene devices, respectively. Meanwhile, AP graphene can also improve the sensitivity of the device by 1.8 times compared to pristine graphene. In general, this work provides a deeper understanding of the relationship between surface quality of graphene, as well as copper foil and sensing performance of devices, enabling the advancement and optimization of graphene-based biosensors in the future.