The Effect Of The Structure Of Titania On The Performance Of Photoelectrochemical Enzymatic Glucose Biosensor

Enzyme-based biosensors are widely used in healthcare,especially in disease diagnosis and bioanalysis,mainly due to their high selectivity.Photoelectrochemical(PEC)technologies are relative recently developed analytical methods,using a quite simple experimental setup,low background currents,and high sensitivity.Photoelectrochemistry is electrochemically derived,thereby showing advantages such as even limit of determination than those obtained for“traditional”electrochemical approaches.PEC uses electrochemical processes to yield signals with high sensitivity and elevated accuracy with low background signal noise due to combination of light and electricity.The combination of the photoelectrochemistry and enzymatic reaction processes allows the photoelectrochemical enzyme-based biosensors can combine the advantages from both approaches,mixing high selectivity and sensitivity.After the formation of the photoelectrochemical biosensor system,the change in the electrical signal can be mainly attributed to the mutual reaction of the photoelectrochemically active unit and the enzymatic product.Thus,the catalytic efficiency of the enzyme is equally essential.However,in previously reported PEC enzyme-based biosensors,the utilization of enzymes is still low due to the lack of optimum spatial control of substrate and product diffusion.Therefore,it is crucial to select an electrode material with excellent diffusion efficiency and a high turnover frequency.Titanium dioxide(TiO₂)is one of the most popular candidate materials for biosensors due to its strong light absorption,good band arrangement and environmental friendliness.Therefore,the selection of TiO₂ electrode materials with excellent diffusion efficiency and high turnover frequency is the main direction of our research.(1)Ultra-high sensitivity is difficult to achieve using conventional enzymatic glucose biosensors due to the lack of exposed active sites and steric-hinderance effect.Thus,in the present work,we report a photoelectrochemical(PEC)enzymatic glucose biosensor based on 3-dimensional(3D)hollow-out titanium dioxide(TiO₂)nanowire clusters(NWc)/glucose oxidase(GOx),with providing more exposed active sites,constructing a sensor with a higher affinity toward glucose reaction.Excellent performance with an ultra-high sensitivity of 58.9?A m M^-1 cm^-2,0-2 m M linear range with a limit of determination of 8.7?M was obtained for the detection of glucose.The unique structure we designed achieved a breakthrough in performance in the field of enzymatic photoelectric glucose sensors.(2)The method of synthesizing TiO₂ nanorod arrays(NRs)on the FTO/ITO with titanium salt solution as the titanium source has been widely used in the preparation of TiO₂ electrodes because of its simple equipment,low price and high yield.In this work,we used titanium isopropoxide hydrochloride as a precursor to synthesize rutile TiO₂NRs on FTO.For the detection of glucose,the TiO₂ NRs/GOx electrode achieved a sensitivity of 4.33?A m M^-1 cm^-2 with a linear range of 0-3 m M.In addition,in order to compare the effects of transducer and enzymatic efficiency,we successfully synthesized TiO₂ quantum dots(QDs)and polydopamine(PDA)membranes on the surface of TiO₂ NRs by means of hydrothermal reaction and photopolymerization.Electrochemical tests show that with the help of high-quality electron-transport interfaces constructed by TiO₂ QDs/PDA,TiO₂ NRs/TiO₂ QDs/PDA/GOx biosensors have achieved better sensing performance under simulated sunlight,the detection limit is 0.058 m M,the linear range is 0-7 m M,and the sensitivity is 9.93?A m M^-1 cm^-2.(3)TiO₂ nanotube array(NTs)is the most widely used structure.In this study,TiO₂NTs were obtained by anodization,and TiO₂ NTs/GOx biosensors obtained a linear range of 0-3 m M and a sensitivity of 6.13?A m M^-1 cm^-2.In addition,in order to compare the effects of transducer and enzymatic efficiency,we constructed ultrasensitive photoelectrochemical dual-electron-acceptor biosensor was constructed by modifying the TiO₂ nanotubes(NTs)with polydopamine(PDA)and amino-functionalized graphene quantum dots(N-GQDs)/GOx.PDA is grown on the top of the TiO₂ NTs by the electropolymerization and N-GQDs are loaded into the inner of the TiO₂ NTs by a microwave-assisted method.The TiO₂ NTs/PDA/N-GQD dual-electron-acceptor biosensor exhibited a highly enhanced photoelectric response,excellent electron–hole separation efficiency,low detection limit(0.015 m M),wide linear range(0–11 m M),and ultrahigh sensitivity(13.6?A m M^-1 cm^-2).Compared to the 4.33?A m M^-1 cm^-2 of TiO₂ NRs/GOx and 6.13?A m M^-1 cm^-2of TiO₂ NTs/GOx,the new 3D hollowed TiO₂ NWc/GOx biosensor achieved an amazing 58.9?A m M^-1 cm^-2 performance.In addition,after heterojunction and multiple electron channel construction of TiO₂ NRs and TiO₂ NTs,the 3D hollow-out TiO₂ NWc biosensor still maintains absolute performance advantages,this is enough to show that the catalytic efficiency of the enzyme in the enzymatic sensor has a much greater impact on performance than the conversion efficiency of the transducer.Therefore,the titanium dioxide with a three-dimensional network hollow-out structure is more conducive to maintaining the enzymatic efficiency and the performance of the enzyme-based glucose biosensor.