Study On Oxidase-like Activity Of Vanadate Nanomaterials

The synthesis of stable and efficient nano-enzyme to replace natural enzyme is a research hotspot in the field of enzyme catalysis.A variety of nanomaterials have been reported to have enzyme-like activities,among which,most of the reported nanomaterials are peroxidase-like nanomaterials,but there are few studies on the oxidase-like nanomaterials.However,the instability of hydrogen peroxide limits the effiency of peroxide-like nano-enzyme and its application in complex systems.Therefore,it is more attractive and meaningful in practical sense to develop nano-enzyme with hydrogen peroxide-independent oxidase-like activity.Vanadium(V)oxides have unique photoelectrical,magnetic and thermal properties,especially the ternary metal vanadate,which is considered as a new type of multifunctional materials.In addition,it is very important for high-performance biosensing and biocatalysis to study the mechanism of oxidase-like activity.Therefore,this thesis mainly studies vanadate nanomaterials with oxidase-like activity and applied them in the field of analysis and detection.At the same time,the mechanism of the oxidase-like activity is studied in details.The main contents are as follows:(1)Crystalline of bismuth vanadate nanoparticles(c-BiVO₄NPs)and crystalline of bismuth vanadate nanowires(c-BiVO₄NWs)were synthesized by high temperature annealing and hydrothermal method,respectively.It was shown for the first time the oxidation-like activity of bismuth vanadate nanomaterial.Moreover,by studying the oxidase-like activity of crystalline bismuth vanadate(c-BiVO₄),we found that the oxidase-like activity of bismuth vanadate nanomaterials is closely related to its morphology and crystal structure.Finally,based on the oxidase activity of c-BiVO₄,a visual colorimetric sensor for SO₃^2-was constructed with the detection limit of 1.325?M.The results show that c-BiVO₄is a potential nano-enzyme material,which has potential applications in food safety,environmental detection,as well as analytical sensing.(2)A kind of amorphous bismuth vanadate(a-BiVO₄)with high oxidase-like activity was designed and synthesized.The surface of the a-BiVO₄has a high concentration of oxygen vacancy,which can effectively catalyze the conversion of oxygen to reactive oxygen species,thus leading to a specific mimetic reaction.The material structure and surface states,as well as the parameters influceing the mimetic activity of nanozyme were intensively studied,which reveal relationship between the structure and performance.synthesis of nano-enzyme was revealed by the comprehensive characterization of the material.The results obtained by comparison of the oxidase-like activities of a-BiVO₄and c-BiVO₄suggest the higher mimetic activity of amorphous BiVO₄.Such superior activity was found the consequence of higher concentration of oxygen vacancy of amorphous bismuth vanadate and its good ability to capture and activate O₂,as well as the strong electrostatic interaction between the negatively charged surface of A-Bivo4 and the protic substrate.These two characteristics shorten the distance between the substrate and the active site and promote the charge transfer between the substrate and the nano-enzyme,thus leading to the efficient simulated oxidase reaction.Finally,based on the oxidase-like catalytic mechanism of a-BiVO₄,a colorimetric sensing platform for L-cysteine detection was established,with a detection limit of 0.569?M.(3)Silver vanadate nanowires(?-Ag₃VO₄NWs)with high oxidase-like activity were synthesized by a simple solution co-precipitation method.The high length-to-length ratio and a large number of active sites of nanowires can effectively adsorb and activate molecular oxygen in solution to generate superoxide radicals and singlet oxygen,thus oxidizing substrates to generate colored oxidizing species.Kinetics studies showed that the enzymatic reaction of?-Ag₃VO₄NWs was close to the first order reaction in the range of tested concentrations,and the substrate could be completely oxidized within 5 minutes.After screening,the enzymatic reaction system showed good analytical and detection ability of ascorbic acid,with the detection limit of 6.9?M.The results show that silver vanadate nanowires are a potential nanometer enzyme material and have potential application value in disease diagnosis and treatment,biosensing,environmental detection and other fields.