Synthesis, Electroanalysis, And Catalysis Application Of Graphene Based Nano-biomaterials Modified Electrode And Monolayer MoS_2（1-x）Se_2x Alloy

In this work, we prepared several composite materials by recombination reduced graphene with AuNPs, PDDA, Hemoglobin, MWCNTs-COOH, and monolayer MX2（X=S, Se, Te） via the solution synthesize and self assembly. Several analysis method have been developed including the electrochemical sensor. Large area monolayer MoS_2（1-x）Se_2x alloy were synthesized by physical vapor deposition, which could be the candidate materials for the electrochemical sensor and photoelctrocatalysis. The X-ray polycrystalline diffractometer, X-ray photoelectron spectroscopy, transition electronic microscope, field emission scanning electron microscope, fourier transform infrared spectrometer, ultraviolet and visible spectrophotometry, cyclic voltammetry, chronoamperometry,and electrochemical impedance spectroscopy were conducted to identify the materials morphology, structure and component. The main research work were shown below:1. Fabrication and electrobehavior study of layered Hb / AuNPs / PDDA-RGO modified electrode and it’s application in detection of biomolecular H₂O₂Fabricating layer eletrode interface structure Hb / AuNPs / PDDA-RGO by self-assembly, realizing direct electrochemistry of Hemoglobin. And the modified electrode was used to detect the biomolecular H₂O₂. The XRD, FE-SEM, FT-IR, UV-vis, CV, and i^t were conducted to confirm the as-synthsized materials and the constructed layer electrode structure. The surface concentration（Γ﹡） of electroactive Hb on the surface of GCE was calculated to be 3.85×10-9 mol cm-2. Moreover, the AuNPs / PDDA-RGO based sensor showed prominent electrocatalitic activity for the detection of H₂O₂ with a wide linear range from 6.00 μM to 1010 μM and a low detection limit of 0.39 μM at 3σ. Meanwhile, the apparent Michaelis-Menten constant（Km） was 0.51 mM. This biosensor exhibited high sensitivity and fast responses, which may provide a novel way for fabrication of other graphene-based sensors and broaden the application of graphene in biosensing.2. Fabrication of layer structure AuN PS / TTF-COOH / RGO heterojunction interface and electrochemical detection of biomolecular bilirubin.The redued graphene oxide was dispersed by tetrathiafulvalene-carboxylate（TTF-COOH） to form TTF-COOH / RGO layer structure though conjugate π-π bond. And then the gold nano-particles（AuNPs） were assembled on the surface of TTF-G composite to form the gold nano-particles / tetrathifulvalene-carboxylate functionalized graphene（AuNPs / TTF-G） layered composite throughthe Au-S bond between the sulfur atom（S） in the TTF and the AuNPs. And then, the bilirubin oxidase（BUD） was chemical adsorbed on the surface to construct a biosensor of bilirubin, and to investgate the degradation mechanism of bilirubin. The XRD, FE-SEM, FT-IR, UV-vis, CV, and i^t were conducted to confirm the synthesized materials. The result demonstrated that this layered heterostructure shows enhanced interface electron transfer rate and excellent biocompatibility. The biosensor showed prominent electrocatalytic activity for the detection of bilirubin with a linear range from 2.66 μM to 83 μM and a low detection limit of 0.74 μM at 3σ. Meanwhile, the apparent Michaelis–Menten constant（Km） was 10.45 μM. In addition, this sensor exhibited satisfying reproducibility, stability, and fast responses. This electronic heterojunction sensor could be used to detect bilirubin in real human lood.3. Fabricate the AuNPs / MWCNTs-COOH / RGO / GCE modified electrode and it’s application in detection of biomolecular bilirubin in human blood.In this work, the Multi-walled carbon nanotubes-COOH（MWCNTs-COOH） / reduced graphene oxide（RGO） / gold nanoparticles（AuNPs） composite materials were synthesized. And then, the Bilirubin oxidase（BUD） was immobilized on the surface of the film to construct a biosensor for determination of Bilirubin. Morphology, crystal structure, and electrochemical performance of the nanomaterials was analyzed by FE-SEM, HR-TEM, BET, XPS, FT-IR, UV-vis, CV, EIS, and i t. In this assay, the MWCNTs-COOH / RGO / AuNPs composite film based biosensor shown prominently electrocatalytic activity for the detection of Bilirubin with a linear range from 1.33 μM to 71.56 μM and a low limit of detection（LOD） is 0.34 μM based on a signal to noise ratio（S / N=3）. Meanwhile, the apparent Michaelis–Menten constant（Km） was 64.86 μM. In addition, this biosensor exhibited satisfying reproducibility, stability, feasibility and fast responses. These results provide a novel way for exact detection of Bilirubin in biotechnology and clinical diagnosis.4. Physical vapor deposition and performance investigation of large area monolayer MoS_2（1-x）Se_2x alloyHere we have reported synthesis of large-area 2D semiconductor alloys, MoS_2（1-x）Se_2x monolayers with x = 0.00-1.00 using physical vapor deposition（PVD）. Atomic-resolution scanning transmission electron microscopic（STEM） imaging revealed random arrangement of S and Se atoms in the 2D alloys. Large domain size of MoS_2（1-x）Se_2x monolayer alloys（x = 0.41- 1.00） up to 20 μm have been obtained by tuning the temperature gradient of the deposition zone. The band gap photoluminescence is continuously tuned from 1.86 eV（i.e., 665 nm, reached at x = 0） to 1.55 eV（i.e., 800 nm, reached at x = 1.00）. Field-effect transistors（FETs） fabricated on the MoS_2（1-x）Se_2x monolayer alloys have showed high on / off ratios（> 105）. Additionally, two- mode Raman behavior and Raman peak splitting was observed in MoS_2（1-x）Se_2x monolayer alloys. Therefore, this work provide a way to obtain MoS_2（1-x）Se_2x monolayer alloys with different edge orientations, which could be benefit to controlled growth of other 2D materials. The 2D semiconductor alloy films can have potential applications in flexible light-detection and light-harvesting devices.