Synthesis Of Cobalt-based Oxides Double-Shelled Hollow Nanocomposites For Electrochemical Sensing Applications

Many countries,especially developed countries,pay great attention to the synthesis of new catalytic materials.With the further research,catalytic technology will be developed as an important field in the new century.Transition metal oxides?TMOs?have a series of excellent physical and chemical properties.It has broad application prospects in the fields of electrochemical sensing and photoelectrocatalysis.Among them,p-type semiconductor Co₃O₄ plays an important role in the field of electrochemical sensing.However,Co₃O₄ has poor conductivity and kinetic hysteresis.The catalytic activity cannot meet the application requirements.In order to effectively improve the response sensitivity and electrocatalytic activity of cobalt-based oxide electrochemical sensors,three kinds of electrochemical methods for detecting glucose were synthesized by regulating the morphology of Co₃O₄ and constructing a hollow double-shell structure of doped metal oxide or composite carbon material.The sensitivity,detection limit and detection range of the sensor can meet the requirements of practical applications.It also has good repeatability,stability and anti-interference.The specific research contents are as follows:?1?Regulatory synthesis of Co₃O₄ nanomaterials and non-enzyme glucose sensing performanceCo₃O₄ was prepared using microwave.The effects of reaction time,temperature and the amount of substrate on the morphology of the product were investigated.The growth mechanism of the product was discussed.The performance of non-enzyme glucose sensing was detected by constructing Co₃O₄ modified electrode.The effects of the morphology change of Co₃O₄ on the sensitivity,linear range,detection limit,repeatability and anti-interference of the modified electrode were evaluated.The experimental results show that the urchin-like Co₃O₄ modified electrode exhibits higher sensitivity,wider linear range and low detection compared to nano-microspheres and nanorod structure Co₃O₄.The detection range were 0-0.44 mM,1.05-2.70mM,The corresponding sensitivities were 563.3,310?A·mM^-11 cm^-2,and the LOD was 3.6?M.The experimental results also show that after one month,the electrode retained 86.4%of the initial response current;The common distractors should be AA and UA,and the interference current was only reached?7.4±0.5?%and?5.2±0.2?%.A better result of this is that the urchin-like structure can effectively prevent the material agglomeration from closing the diffusion channel of the target molecule.?2?Preparation of Co₃O₄@NiCo₂O₄ hollow double-shell composite nanomaterials and non-enzyme glucose sensing performanceFirstly,Cu₂O was used as a template to prepare cubic hollow structure Co₃O₄ by coordination etching deposition?CEP?.Subsequently,a layer of NiCo₂O₄ was coated on the surface of Co₃O₄ by chemical bath deposition?CBD?to prepare a hollow double-shell structure Co₃O₄@NiCo₂O₄.Composite nanomaterials and their synthesis mechanism were explored.The experimental results show that the cubic hollow structure is stable,it is not easy to collapse and deform during the calcination process,and the cavity is large.The Co₃O₄@NiCo₂O₄ modified electrode showed good electrocatalytic activity,stability,repeatability and anti-interference to the non-enzyme glucose.The detection range were 0.015-0.68 mM,0.74-0.36 mM;the corresponding sensitivities were789.3 uA mM^-11 cm^-2,2254.1 uA mM^-11 cm^-2,respectively;the LOD was 4.1?M.It still maintained89.6%of the initial response current after one month;The main distractors DA showed only about13.7%of the interference current to glucose.In addition,the second time?92±0.1?%of its original response current was retained after the addition of 0.05 mM glucose.The experimental results show that the design of the hollow structure improves the kinetic hysteresis of the catalyst.At the same time,the coating of NiCo₂O₄ makes the synergy between cobalt and nickel in the process of oxidizing glucose,the active site increases,and the catalytic performance is greatly improved.?3?Preparation of C@NiCo₂O₄ hollow double-shell composite nanomaterial and non-enzyme glucose sensing performanceThe hollow carbon spheres were prepared by SiO₂ template.The surface of the carbon spheres was coated with NiCo₂O₄ shell by CBD method.The optimal NiCo₂O₄ coating thickness was determined by the difference of electrocatalytic properties.The modified electrode was subjected to non-enzyme glucose sensing performance.Study to assess its stability,repeatability and immunity to interference.The experimental results show that the electrocatalytic performance of C@NiCo₂O₄modified electrode increases first and then decreases with the increase of NiCo₂O₄ coating thickness.This is mainly because as the coating thickness increases,the specific surface area increases,the active site increases,and the electrocatalytic performance increases.When the NiCo₂O₄ coating thickness exceeds 25 nm,the target molecular diffusion channel is partially blocked and the active site is covered.The electrocatalytic performance is instead reduced.The electrocatalytic performance is best when NiCo₂O₄ is about 25 nm,which is in the detection range of 0.030-0.82mM,1.05-2.74 mM;the corresponding sensitivity were 845,2817?A·mM^-1cm^-2;LOD was 8.3uM.AA has the largest interference effect,in fact,the interference current only reaches?5.4±0.8?%.The interference current of other substances were less than 4%.