The Study On Construction And Photoelectrochemical Sensing Performance Of Si-CuO Core-shell Nanowire Heterojunction

Photoelectrochemical(PEC)sensors have the advantages of high sensitivity and low background noise and have been a popular research topic in recent years.The construction of novel heterojunctions has become an effective strategy to improve the performance of photoelectrochemical biosensors,but the widely used sensing electrodes are usually modified by enzymes,and their morphology is usually flat or semi-confined pore-like structure.The environmental sensitivity of enzymes limits the conditions of use and lifetime of the sensors,and the flat or semi-confined morphology limits the contact area between the sensors and the substances to be measured,which reduces the sensor performance.To address the above issues,a Si-CuO core-shell nanowire heterojunction is proposed in this thesis and demonstrated to be used for PEC sensing of glucose.The main elements are as follows:(1)The controllable preparation of Si-CuO core-shell nanowire heterojunction was investigated.Firstly,Si nanowire arrays(SiNWs)with controllable diameter,spacing and period were prepared based on microsphere lithography,which showed highly ordered and open structures;then a CuO film was deposited on the surface of the SiNWs by magnetron sputtering;the CuO(shell layer)was finally grown by hydrothermal synthesis on the substrate of the SiNWs(core layer)covered with a thin film of CuO.The CuO obtained by the hydrothermal method exhibits the morphology of nanospikes(CuONSs)and grows densely on all surfaces and interstices of the SiNWs.The length of SiNWs increases with metal-assisted chemical etching time,but an overlong etching time will destroy the perpendicularity and regularity of Si nanowire arrays,thus decreasing the specific surface area;the number of CuO modifications increases with hydrothermal growth time,but an overlong growth time will cause excessive modification of CuO,and the gaps of opened silicon nanowire arrays will be filled,thus losing the original good circulation and reducing the sensing performance.(2)The photoelectrochemical response and sensing performance of Si-CuO coreshell nanowire heterojunction photoelectrodes were tested and evaluated,while planarSi-CuONSs and FTO-CuONSs were taken as comparison samples.The sensing mechanism of the core-shell heterojunction photoelectrodes has been analyzed in conjunction with carrier transport analysis,and comparative studies can be obtained:(i)the size-controllable SiNWs provide a large specific surface area and open morphology substrate for the growth of CuONSs;(ii)the CuONSs act as the shell layer of the heterojunction photoelectrodes with specific electrocatalytic activity for glucose;(iii)the Si-CuO core-shell nanowire heterojunction has excellent light absorption and the separation and transfer efficiency of photogenerated carriers are significantly improved compared to the comparison samples.The sensing sensitivity of the optimized Si-CuO core-shell nanowire heterojunction photoelectrode for glucose in the concentration range of 0-1 mM was 2324.09 μAmM-1cm-2,with a detection limit as low as 0.74μM(Signal/Noise=3),while exhibiting satisfactory reproducibility,stability,and interference resistance.This work demonstrates that the enzyme-free and highly-sensitive glucose detection can be realized by morphology-controllable heterojunction,and provides an alternative route to portable and noninvasive sensing chips.