Synthesis Of Transition Metal Oxides-based Nanofibers And The Study Of Their Enzyme-like Properties

Transition metal oxides are attracting much attention in the fields of energy storage and conversion systems,such as lithium-ion batteries,electrocatalysts and fuel cells,due to their complex chemical compositions,unique crystal structures,the presence of multiple valence cations and the abundant reserves in nature.As for the application in enzyme mimetics,with the advantages of rich oxidation states and good conductivity,transition metal oxides are supposed to emerge as outstanding candidates for artificial enzymes.In addition,it is well known that the surface area of the catalyst plays an important role in the catalytic performance of enzyme mimics,larger specific surface area is beneficial for the better catalytic property.According to that,we choose the electrospun nanofibers as enzyme-like materials due to their large aspect ratio,good flexibility,large specific surface area,high catalytic activity and simple synthetic process.In this paper,we prepared three kinds of transition metal oxides-based nanofibers via electrospun technique combining with calcination,lattice doping,and electrochemical deposition processes.Then we studied the catalytic properties,including the peroxidase-like and the oxidase-like activity of these enzyme mimics,and applied the catalytic systems for the detection of detecting hydroperoxide?H₂O₂?,sulfite,ascorbic acid?AA?and L-cysteine in the field of biosensing.These transition metal oxides-based nanofibers shows considerable catalytic properties with low limit of detection for the detection of the above substances.The details are shown as follow.1.Hollow Mo-doped Co₃O₄?Mo-Co₃O₄?nanofibers were synthesized via a simple electrospinning technique followed by a calcination and a lattice doping process.As for the samples whose molar fraction of Mo was less than 5%,Mo species were dispersed in cubic Co₃O₄ successfully and didn't change the crystal structure of Co₃O₄.The catalytic properties of hollow Mo-Co₃O₄ nanofibers with different molar fractions of Mo were explored,and the one whose molar fraction was 2%showed the best peroxidase-like activity.The hollow Mo-Co₃O₄ nanofibers in the optimum condition were applied to detect H₂O₂ and L-cysteine with excellent selectivity and low limit of detections?LODs?of 0.57?M and 24.2 nM.This LODs are better than those of the reported colorimetric chemosensors based on the similar systems.2.Hollow MnCo₂O₄ nanofibers were synthesized via a simple electrospinning technique followed by a calcination process.The prepared mixed transition-metal oxides hollow MnCo₂O₄ nanofibers exhibited a preferable oxidase-like activity superior to those of the corresponding single-metal oxides.Then,the influence of morphology and calcination temperature on the catalytic properties was explored and the optimum condition was fixed.The system of hollow MnCo₂O₄ nanofibers-TMB in the optimum condition were applied to detect sulfite and L-cysteine with excellent selectivity and low LODs of 27.9 nM and 34.3 nM.This LODs are better than those of the reported colorimetric chemosensors based on the similar systems.3.CNFs/MnCo₂O_4.5 composite nanofibers were synthesized via an electrospinning technique,an electrochemcial deposition process and a calcination method.The flexible CNFs membrane was directly used as the working electrode to deposit MnCo₂O_4.5 nanosheets on its surface during the electrochemical deposition process.The CNFs/MnCo₂O_4.5 composite nanofibers possessed an intrinsic oxidase-like activity superior to that of individual components.The catalytic activities of the samples with different electrochemical deposition time were studied.The system of CNFs/MnCo₂O_4.5 composite nanofibers-TMB were used to detect sulfite and AA with low LODs of 15.9 nM and 50 nM.This LODs are better than those of the reported colorimetric chemosensors based on the similar systems.