Construction Of Electrochemical Sensors Based On Heteroatom-doped Three-dimensional Graphene Deposited With Precious Metal And Their Applications In Food Testing

As society continues to progress,people relish an abundant variety of food;however,they also grapple with increasingly serious food safety concerns.Food testing,a crucial measure to ensure food safety,has garnered significant attention in recent years.Within the realm of food testing,electrochemical sensors demonstrate immense application potential,owing to their ease of operation,rapid response,and high sensitivity.Electrode modification materials,a vital component of electrochemical sensors,profoundly influence the overall performance of these devices.Threedimensional(3D)doped graphene,characterized by high catalytic activity,numerous defect sites,and robust ion adsorption,has been extensively employed in electrochemical sensing and electrocatalysis.Nevertheless,designing graphene-based materials as electrode modifiers that meet electrochemical requirements for food testing still poses numerous challenges.This dissertation utilizes graphene oxide(GO)as a precursor,employing hydrothermal and freeze-drying techniques to successfully synthesize 3D porous heteroatom single-doped,double-doped,and triple-doped graphene aerogels.Subsequently,through electrodeposition,heteroatom-doped graphene-precious metal nanoparticle composites are synthesized,and a range of highly sensitive and interference-resistant electrochemical sensors are successfully constructed.These sensors efficiently detect small molecules in food.The main content of the dissertation is as follows:1.The improved Hummers method was utilized to successfully synthesize graphene oxide(GO).Using GO as a precursor and phytic acid as a P source,a 3D phosphorus-doped reduced graphene oxide aerogel(3 D-PRG)was prepared via hydrothermal and freeze-drying methods.Furthermore,a phosphorus-doped reduced graphene oxide-gold nanoparticle modified electrode(Au NRBs/3D-PRG)was prepared using the constant potential method.The materials were systematically characterized using scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS)and X-ray diffraction(XRD).Using a glassy carbon electrode(GCE)as the working electrode,an electrochemical sensing platform of Au NRBs/3D-PRG/GCE was successfully constructed,and the electrochemical behavior of sodium nitrite on the electrode was investigated.Under optimal detection conditions,differential pulse voltammetry(DPV)was employed to detect sodium nitrite,exhibiting a good linear relationship within the detection range of 0.2-4.0×103 μM.The limit of detection(LOD)was 5.8×10-2 μM(S/N=3).Additionally,the experimental results indicated that the system possessed good stability and reproducibility.Finally,the constructed sensor was applied to the analysis of nitrite concentrations in actual samples,achieving satisfactory results.2.Using GO as a precursor,3D nitrogen-phosphorus co-doped reduced graphene oxide aerogel(3D-NPRG)was synthesized via hydrothermal and freeze-drying methods using phytic acid and ethylenediamine as P and N sources,respectively.Subsequently,Pt nanoparticles(Pt NPs)were deposited on the surface of the modified electrode(3D-NPRG/GCE)using cyclic voltammetry(CV)to construct a Pt NPs/3DNPRG/GCE sensor.The materials were characterized using SEM,TEM,XPS,and other instruments.The electrochemical behavior of the Pt NPs/3D-NPRG/GCE electrode in a PBS solution containing bisphenol A(BPA)was studied,and a highly selective BPA sensor was successfully constructed by optimizing the detection conditions.The linear range was 2.0×10-2-1.0×102μM,and the limit of detection(LOD)(S/N=3)was 1.2×10-2 μM.The constructed sensor exhibited excellent performance and was successfully used to test actual samples.3.Using boric acid as the B source,and phytic acid and ethylenediamine as the P and N sources,a nitrogen-phosphorus-boron triple-doped 3D reduced graphene oxide aerogel(3D-NPBRG)was successfully synthesized via a hydrothermal and freezedrying technique.An Au-Pt bimetallic nanoparticle was synthesized on the modified electrode surface via a constant potential method to prepare the Au-Pt NPs/3DNPBRG/GCE sensing platform.The materials were characterized using SEM,TEM,XPS,and other techniques.The effect of different modified electrodes on the electrochemical properties of dopamine in PBS solution was examined,and the electrochemical detection platform for dopamine was successfully constructed using the Au-Pt NPs/3D-NPBRG/GCE platform.Under optimal detection conditions,the sensor demonstrated good performance,with a detection range of 4.0×10-3-50.0 μM and a LOD(S/N=3)of 2.5×10-3 μM,and was able to successfully test actual samples.