Studies On The Preparation And Electrochemical Sensing Performance Of Reduced Graphene And ZnO,Ni Composites

At present,graphene has been widely employed in electrochemical sensing analysis.With the deepening of graphene research,it is found that certain properties of graphene composites are significantly better than graphene itself.Therefore,the development of graphene composites and electrochemical sensing research is conducive to the construction of high-performance electrochemical detection systems.This paper is based on in-situ synthesis strategies:A zinc oxide@reduced graphene oxide composite(ZnO@rGO)was prepared easily by in-situ reduction of graphene oxide(GO)using Zn powders and NH₄Cl inducing at room temperature;A carbon-coated Ni nanoparticles supported rGO composite(Ni@C@rGO)was prepared by one-step in-situ reduction at high temperature.The composition,morphology,structure of the two electrochemical sensing materials were characterized respectively,and their respective electrochemical sensing performance and analysis applications were studied.A highly sensitive electrochemical detection method for organic dye molecules,heavy metal ions,tumor markers and other substances was established and used in the analysis of actual samples.The specific research content is as follows:(1)Based on the in-situ reduction of GO with Zn powders,a composites of zinc oxide and graphene was very easily prepared(ZnO@rGO).The electrochemical sensing characteristics were studied,and a new highly sensitive electrochemical detection method was established.SEM,TEM,XRD,Raman,and FTIR characterization tests confirmed that the product consists of ZnO and rGO,and ZnO nanorods are evenly distributed in the curled and thin rGO layers.CV and EIS experiments show that the ZnO@rGO has a large electrochemical response area and a high interfacial electron exchange capacity.Taking Sudan ? and Pb²⁺as representatives,and it was found that ZnO@rGO showed high enrichment efficiency for trace amounts of Sudan ? and Pb²⁺,which significantly improved their response signal and detection sensitivity.The linear ranges of Sudan ? was 1-300?g L^-1,and the detection limits was 0.38?g L^-1;The linear ranges of Pb²⁺was 0.05-100?g L^-1,and the detection limits was 0.019?g L^-1.The method was applied to the analysis of environmental water samples,and the spiked recovery was between 96.53%and 103.2%.(2)Based on the signal enhancement ability of ZnO@rGO combined with uricase,a new method for electrochemical detection of 8-hydroxy-2'-deoxyguanosine(8-OHd G)with high sensitivity and resistance to interference for high concentration uric acid(UA)was established.Not only the sensitivity problem must be solved,but also the interference of high concentration UA in the actual sample must be overcome in electrochemical detection of 8-OHd G.The study found that ZnO@rGO showed a significant enhancement effect on the electrochemical oxidation of 8-OHd G,which greatly enhanced the response signal of 8-OHd G.In addition,uricase is used to specifically convert electrochemically active UA into non-electrochemically active allantoin,thereby eliminating the interference of high concentration UA.The linear range of 8-OHd G is 5-5000 n M,and the detection limit is 1.25 n M.This method is used for the analysis of urine samples of tumor patients,and the spiked recovery was between97.70%and 102.8%.(3)Based on the excellent sensing performance of ZnO@rGO modified carbon paste electrode and magnetic bead enzyme-linked immunoassay,a highly sensitive and selective electrochemical detection method for carcinoembryonic antigen(CEA)was established.The capture antibody was modified onto the magnetic beads(MB-Ab₁)by chemical cross-linking,and then CEA was captured from the sample(MB-Ab₁-CEA),which was combined with the detection antibody and the alkaline phosphatase coated gold nanoparticles(Ab₂-Au NPs-ALP).ALP converts 1-naphthyl phosphate(1-NPP)in solution into electrochemically active 1-naphthol(1-NP),thereby generating a sensitive oxidation signal,and the oxidation peak current of 1-NP increases linearly with the concentration of CEA.Therefore,the quantitative detection of CEA was realized.In addition,it was found that the oxidation signal of 1-NP was significantly increased in the presence of cetyltrimethylammonium bromide(CTAB).Based on the zero background conversion efficiency of ALP,the ultra-low background current of the carbon paste electrode,and the dual signal amplification effects of ZnO@rGO and CTAB,a highly sensitive and selective CEA measurement was successfully achieved with a linear range of 0.01-6.0 ng m L^-1 and the detection limit of 4.0 pg m L^-1.The system was used to detect CEA in serum samples from cancer patients,and the spiked recovery was between 96.4%and 109.7%.(4)Based on one-step high-temperature in-situ reduction strategy,a carbon-encapsulated nickel metal nanoparticle-supported rGO composites was prepared(Ni@C@rGO),the catalytic sensitization effect was studied,and a high-performance electrochemical sensing system was constructed.The experimental results of BET,EIS,and ECSA show that compared with the prepared Ni@rGO by the same conditions without Na Cl crystals,Ni@C@rGO has a larger specific surface area and pore volume,and higher electrical chemical sensing activity.In addition,it was found that Ni@C@rGO has high catalytic activity for glucose oxidation,which is attributed to the excellent interface electron rate,electrochemical active area and structural stability.Based on this,a glucose detection system with a wide linear range(2-951?M)and low detection limit(0.34?M)was constructed.The system was successfully employed to the detection of glucose levels in human serum,and the spiked recovery was between97.76%and 101.8%.This method can provide a reference for the preparation of electrochemical sensing composites of other carbon-coated metal nanoparticles and rGO.