Construction And Applications Of Novel Three-dimensional Metal Oxides(Sulfides)-based Catalytic Materials In Electrochemical/Photoelectrochemical Sensing

With the improvement of modern living standards,people’s physical health has become the focus of attention.Seeking simple,rapid,and sensitive methods for the accurate determination of drug molecules and small biomolecules is of great significance for clinical medicine,environmental monitoring,and food safety,and has become a hot topic of research.In recent years,electrochemical/photoelectrochemical sensing technology show great advantages in the trace determination of analytes owing to its simple operation,fast response speed,high sensitivity and low cost.The development of catalytic materials with excellent electrochemical/photoelectrochemical properties is the focus.In this paper,four kinds of metal oxides（sulfides）-based functional composite materials were designed and prepared by adjusting the material morphology,controlling element ratio and reaction conditions,including 3D porous Co,N-MoO₂/MoC nanorods,3D hierarchical NiS/Ni/C hollow microspheres,3D hierarchical SnS@Co,N-C hollow microrods and 3D Bi/ZnSnO₃ hollow microspheres heterojunction.Corresponding electrochemical/photoelectrochemical analysis methods were established to achieve the simultaneous electrochemical determination of acetaminophen,epinephrine and serotonin and their important synthetic precursors and hydrolysis products,and label-free highly sensitive and selective photoelectrochemical detection of epinephrine based on the specific interaction between analytes and the electrode surface.The main contents are as follows:1.Using MoO₃ nanorods as templates,the 3D porous Co,N-MoO₂/MoC nanorod hybrids were synthesized by carbonizing the core-shell ZIF-67-cladded MoO₃ precursor at high temperature.The prepared Co,N-MoO₂/MoC/GCE exhibited excellent electrocatalytic activity towards the common antipyretic and analgesic,acetaminophen（AC）and its hydrolysate,4-aminophenol（4-AP）.Such excellent electrochemical performance was mainly attributed to the synergistic interaction between MoO₂ and MoC,which significantly improved the conductivity and catalytic activity.The 3D porous structure also provided abundant porosity and sufficient electrochemically active sites,which was conducive to the rapid transport of ions and electrons and accelerated the electrode reaction kinetics.The effects of the p H and scan rate on the test results were investigated,and the related electrochemical reaction mechanism was studied.An electrochemical analysis method for simultaneous determination of AC and 4-AP was established.Differential pulse voltammetry（DPV）was used to detect two target molecules.The linear detection ranges were 0.05-200.0μmol/L for AC and 0.05-140.0 μmol/L for 4-AP,respectively,with the low detection limits（S/N=3）of 0.013μmol/L and 0.012μmol/L.The 3D Co,N-MoO₂/MoC/GCE revealed excellent sensitivity,good reproducibility,stability and anti-interference ability.The developed electrode was evaluated towards the detecting AC and 4-AP in biological fluids,environment water and pharmaceutical formulations with satisfactory recovery.2.3D pomegranate-like NiS/Ni/C hollow microspheres were prepared by in situ carbonization followed by sulfurization strategy using Ni-MOF hollow microspheres as templates,which was used as electrocatalysts for the simultaneous determination of neurotransmitter serotonin（ST）and its important synthetic precursor L-tryptophan（L-Try）.The NiS/Ni/C/GCE showed enhanced electrochemical responses towards two targets.The reasonably designed 3D NiS/Ni/C composites not only had excellent catalytic activity and high electrical conductivity,but also effectively shortened the charge transport distance due to the hollow structure inside,and provided sufficient electrode/electrolyte contact area,which was beneficial to the target adsorption.In addition,abundant defects were generated during the in-situ vulcanization process,which provided more electrochemically active sites for the reaction.The corresponding electrochemical reaction mechanism was discussed in detail,and a highly sensitive electrochemical analysis method was established.The oxidation peak currents of ST and L-Try were linearly related to their concentration from 0.01 to 200.0μmol/L,and the detection limits（S/N=3）were 3.35 and 2.94 nmol/L,respectively.The practicability of the sensor in detecting the ST and L-Try in compound amino acid injection,human serum and urine had also obtained satisfactory results.3.3D hierarchical SnS@Co,N-C hollow microrods were successfully prepared by one-step hydrothermal method,followed by thermal annealing in N₂ using Co-MOF microrods as templates,which were used as electrocatalysts for the simultaneous determination of catecholamine neurotransmitter epinephrine（EP）and its important synthetic precursor L-tyrosine（L-TY）.The electrochemical behaviors of two small molecules on the modified electrode were studied,and the related electrochemical reaction mechanism was discussed in detail.The 3D hollow carbon frames as carriers not only improved the conductivity,but also effectively prevented the aggregation of SnS nanoplates.The synergistic effect increased electrocatalytic active sites,enlarged the effective working area of the electrode,showed highly sensitive catalytic response currents to the electro-oxidation of EP and L-TY,and reduced the oxidation overpotential.An electrochemical analysis method for simultaneous determination of EP and L-TY was established.This method offered wide linear ranges of 0.01-300.0 and 0.01-250.0μmol/L,and low detection limits（S/N=3）of 3.3 and 3.1 nmol/L for EP and L-TY respectively.The constructed sensor also showed excellent reproducibility,stability and anti-interference ability,and had been successfully applied to the detection of EP and L-TY in the milk,human serum and urine samples with satisfactory test results.4.3D Bi/ZnSnO₃ hollow microsphere heterojunctions were designed and synthesized via a simple solvothermal strategy,which were used as photoanodes for label-free highly sensitive and selective detection of catecholamine neurotransmitter adrenaline（EP）.Studies had shown that the formation of Bi/ZnSnO₃ heterojunction broadened the visible light absorption range,effectively suppressed the recombination of photo-generated carriers,and improved the photoelectric response performance of the sensor.The prepared 3D Bi/ZnSnO₃/FTO showd high photocurrent responses toward the EP,because the metallic Bi not only promoted the rapid separation and transfer of photogenerated carriers as an effective electronic medium,but also effectively retained the strong oxidation ability of photo-generated holes,greatly improving the detection sensitivity.A recognition unit-free photoelectrochemical analysis method was established for EP based on the unique chelation interaction between EP and Zn²⁺on the surface of the photoelectrode,which could achieve the selective recognition of EP among various catechol derivatives and well shield the interference of other coexisting amino acids,showing satisfactory anti-interference ability.In addition,the 3D hollow porous structure also provided abundant surface reaction sites and promoted the selective adsorption of target analytes.This simple but efficient PEC analysis platform provided a low detection limit（S/N=3）of 0.6 nmol/L and a wide response range from 2.0 to 300.0μmol/L for the detection of EP,and the applicability of this PEC ensor was realized for the selective analysis of EP in human serum and urine samples with satisfactory results,and also showed good reproducibility and test stability.