Preparation Of Oxygen Reduction Electrocatalysts And Their Application In Biosensors

Oxygen reduction reaction?ORR?has become a research hotspot due to its crucial role in electrochemical energy storage and conversion.Nevertheless,its multi-electron transfer process often accompanies with the sluggish kinetics,which greatly restrains the practical application of ORR.In this paper,nanomaterial electrocatalysts were prepared for catalytic oxygen reduction signal amplification,and were used in the theoretical study of electrochemical biosensors.In this paper,by combining TiO₂ nanorods with Pt and Sn nanoparticles,and combining CeO₂ nanorospheres with NiCo₂S₄ nanoparticles,different electrocatalysts of oxygen reduction reaction were prepared and applied to the construction of electrochemical biosensors.The synergistic effects of the various components in the composite materials help to improve the performance of the sensor.The main contents are as follows:1.Amplified oxygen reduction signal at a Pt-Sn-modified TiO₂ nanocomposite on an electrochemical aptasensorFirstly,TiO₂ nanorods were prepared by a hydrothermal method,and then Pt-Sn nanoparticles were loaded on TiO₂ nanorods by an alcohol reduction method to construct a ternary electrocatalyst?Pt-Sn@TiO₂?.Then the Pt-Sn@TiO₂ nanomaterial was modified on the glassy carbon electrode with chitosan.The interaction between Pt and Sn as well as the high exposure of the Pt?111?plane catalyse the reduction of dissolved oxygen in an analyte solution and generate an amplified oxygen reduction current signal.In the next step,using BS³ as a cross-linking agent,a DNA with a complementary sequence?c DNA?to a streptomycin aptamer is immobilised on the electrode,followed by a streptomycin aptamer that hybridises with c DNA to obtain an electrochemical streptomycin aptasensor.In this way,the immobilized aptamer-c DNA structure on the electrode will hinder the oxygen reduction reaction.By introducing a streptomycin-Rec Jf exonuclease mixture,both the streptomycin-aptamer complex and c DNA are cleaved by Rec Jf from the electrode surface,which then facilitates an enhanced oxygen reduction reaction,thereby promoting the oxygen reduction reaction and amplifying electrochemical oxygen reduction signal.2.Preparation of NiCo₂S₄@N/S-CeO₂ composite with a simultaneous in-situ growing and doping technique as an electrocatalytic signal amplification label for aptasensingInitially,the CeO₂ nanospheres were prepared by a hydrothermal method,and then NiCo₂S₄ nanoparticles were in-situ grown on the CeO₂ nanospheres by an alcohol reduction method accompanied by trace amounts of nitrogen and sulfur doped into CeO₂ nanospheres to construct a novel ORR electrocatalyst?NiCo₂S₄@N/S-CeO₂ nanocomposites?.Sulfadimethoxine?SDM?as target analyte,a thiol-modified SDM aptamer was next anchored on Au nanoparticles?AuNPs?modified GCE through Au-S bond,and then the cDNA-NiCo₂S₄@N/S-CeO₂ bioconjugate was modified on the modified electrode by DNA hybridization to construct an electrochemical aptamer sensor.The NiCo₂S₄@N/S-CeO₂ electrocatalyst will catalyse the reduction of dissolved oxygen in an analyte solution and generate an amplified oxygen reduction current signal.After the introduction of the target SDM,aptamer specifically binds to target SDM,which causes the cDNA-NiCo₂S₄@N/S-CeO₂ bioconjugate to separate from the double-stranded DNA on the electrode surface,and oxygen reduction current decreases along with the increasing concentration of SDM.