Applications Of Functionalized TiO₂/GNFs Composites In Electrochemical Sensors

Transition metal nanomaterials have attracted much attention due to their high electrocatalytic activity,large specific surface area,controllable morphology and low cost.Among them,titanium dioxide(TiO₂)has the advantages of non-toxicity,good biocompatibility and strong hydrophilicity,and has been widely used in the fields of photocatalysis and biosensing.In addition,the coordination bond formed by Ti atom in TiO₂ and the amino and carboxyl groups of the enzyme could maintain the electrocatalytic activity of the enzyme and promote the electron transfer between the enzyme and the electrode surface,which was a novel effective material for the immobilization of protein molecules.However,TiO₂ is usually in the form of powder,and the nano-particles are easily stacked and agglomerated,which affects the electrochemical activity.In addition,TiO₂ is a semiconductor,which has poor conductivity.The electrospun carbon nanofibers(CNFs)with three-dimensional self-supporting structure are taken as the substrate,and the TiO₂ is loaded on the surface of the fibers,so that the agglomeration of nano particles(NPs)can be effectively reduced,and the specific surface area of the material is increased;and the CNFs also have excellent conductivity,so that the conductivity of the TiO₂nanomaterial can be effectively improved.The CNFs can be continuously prepared by combining the electrostatic spinning and the carbonization technology,and no catalyst is needed in the preparation process,so that the possibility of introducing impurities is avoided.In this paper,the TiO₂ NPs-loaded CNFs-based composites(TiO₂/CNFs)were prepared on the basis of CNFs;In order to further improve the electrocatalytic performance of the materials,the bimetallic PdNi was introduced and the PdNi@TiO₂/GNFs composite was prepared.Finally,the composite was used to construct glucose,ethyl p-oxyphosphate and insulin biosensors and the performance of the sensors was studied.The specific work is as follows:1.TiO₂/CNFs composites were synthesized in one step by combining electrospinning and carbonization technology.Among them,the carbonization of carbon supports(CNFs)and the formation of TiO₂ NPs occur simultaneously,which simplifies the preparation process.The materials were characterized by SEM,TEM,Mapping,XPS,XRD and EIS.it was found that TiO₂ NPs(with a particle size of35-45 nm)was wrapped in the fiber,and part of TiO₂ NPs was dispersed on the fiber surface,and TiO₂ NPs changed from anatase phase to rutile phase.Used to immobilize glucose oxidase(GOD)and construct glucose sensor.The prepared sensor has high sensitivity,wide linear range,low detection limit,excellent anti-interference and long-term stability.The excellent sensing performance is mainly due to the synergistic effect of rutile TiO₂ and CNFs,which improves the electrocatalytic activity and electron transmission rate.2.TiO₂ NPs is not uniformly dispersed in TiO₂/CNFs and has little loading on the surface of fiber.Therefore,using graphitized CNFs(GNFs)as the template,and in combination with the sol-gel and carbonization techniques,the TiO₂/GNFs composites were prepared.The composite was characterized by SEM,TEM,EDS,X-ray photoelectron spectroscopy(XPS),X-ray diffraction(XRD),and EIS.The results showed that the TiO₂/GNFs structure was three-dimensional network structure,and the TiO₂ NPs was uniformly loaded.The sensor constructed by immobilizing acetylcholinesterase(ACh E)on the fiber surface exhibited a small Michaelis constant(0.252 m M),a linear range of nine orders of magnitude,and a detection limit as low as 3.3 f M.In addition,the sensor has good anti-interference,stability,repeatability and applicability to actual samples.The unique structure,good biocompatibility and electrical conductivity of TiO₂/GNFs composite can effectively prevent material accumulation and promote electron transfer,and efficiently immobilize and maintain that activity of enzyme,thereby achieve a rapid,sensitive and stable response.3.PdNi particles supported TiO₂/GNFs(PdNi@TiO₂/GNFs)composites were prepared by introducing bimetallic pdni on the surface of TiO₂/GNFs.SEM,TEM,Mapping,XPS,XRD and other characterization show that the fiber is a three-dimensional self-supporting structure,TiO₂ and PdNi NPs are uniformly distributed on the fiber surface,and the synergistic effect between bimetallic nanoparticles accelerates the electron transmission.The constructed insulin sensor has the characteristics of fast response,wide linear range,low detection limit(31.5pM,S/M=3),good selectivity and high stability,and also shows good analytical performance in practical application.