Design And Synthesis Of Transition Metal Core-shell Nanocages And Their Applications In Electrochemical Sensors

Electrochemical sensors have the advantages of high sensitivity,low detection limit,low cost,etc.,and have potential application value in the fields of biomedicine,national defense and military industry,and food supervision.Studies have shown that the electrochemical detection process is essentially an electrocatalytic process.In order to maximize the performance of electrochemical sensors,there is an urgent need to develop high-efficiency electrocatalysts to overcome the kinetic problems of electrocatalysis:substance transport and electron transfer.The microstructure of the electrocatalyst can have a huge impact on these two kinetic problems,so changing the microstructure is one of the effective ways to improve the electrocatalytic activity of materials.The 3D hollow structure has abundant diffusion channels and a large specific surface area,which is conducive to material transmission.The thin permeable shell greatly shortens the path of rapid diffusion of ions and electrons,which can effectively overcome kinetic problems and improve electrocatalytic activity.In addition,the 2D structure has aroused widespread interest in the field of catalysis due to its high surface-to-volume ratio.It has a clear surface structure,abundant reactive sites,and excellent ability to attract electrons,thus having higher catalytic activity.The 2D material is modified on the 3D hollow material,and the two have a synergistic effect,which can further improve the electrocatalytic activity.In this paper,based on transition metal elements（Ni,Cu,Co）,two types of core-shell cage-like nano-active materials are designed and synthesized as electrocatalysts for the construction of high-sensitivity electrochemical sensors.The details are as follows:1.Design the core-shell structure of Ni（OH）₂ nanocages@CuS nanosheetsDesigning ideal sensing materials usually requires reasonable synergies nano structure and large specific surface area ensure high sensitivity and extremely low detection limit.Ni（OH）₂ nanocages@CuS nanosheets core-shells architecture（Ni（OH）₂ NCs@CuS NSs CSA）was synthesized through a coordinated etching and precipitation（CEP）involved sulfidation process（CES）.Interestingly,CuS nanosheets were vertically distributed on Ni（OH）₂ NCs,constructing a hollow porous structure.As a sensitive electrode for dopamine（DA）,the sensitivity of Ni（OH）₂ NCs@CuS NSs CSA modified glassy carbon electrode（GCE）was 1011.7μA m M^-1 cm^-2,which was greater than those of fragmentized Ni（OH）₂ NCs@CuS NSs CSA/GCE（Ni（OH）₂NCs@CuS NSs FCSA/GCE）(717.2μA m M^-1 cm^-2),CuS NSs/GCE(646.2μA m M^-1cm^-2)and Ni（OH）₂ NCs/GCE(848.2μA m M^-1 cm^-2).The detection limit of Ni（OH）₂NCs@CuS NSs CSA/GCE was 3.2 n M,which was much lower than those of three other modified electrodes（27.6,47.2 and 12.6 n M）.According to the theoretical calculation,the electrocatalytic kinitics of Ni（OH）₂ NCs@CuS NSs CSA/GCE was enhanced through the coupling of Ni（OH）₂ NCs and CuS NSs.Ni（OH）₂ NCs effectively inhibited the aggregation of CuS NSs,and increase the transfer rate of catalytic electrons.Briefly,the highly conductive CuS NSs provided more active sites and promoted the collection efficiency of electrons,resulting in enhanced electrocatalytic performance.Briefly,Ni（OH）₂ NCs@CuS NSs CSA/GCE had significantdynamiccharacteristics,sothethree-dimensional hollow@two-dimensional nanosheet core-shell structure has broad prospects in the DA sensing neighborhood.2.Design the core-shell structure of Ni（OH）₂ nanocages@Co（OH）₂ nanosheetsTwo-dimensional（2D）transition metal materials have broad application prospects in electrocatalysis due to their special physical structure.However,the 2D materials are prone to agglomeration owing to the huge longitudinal specific surface,which limits the electroactivity.In this work,Co（OH）₂ nanosheets（Co（OH）₂ NSs）were grown on Ni（OH）₂ nanocages（Ni（OH）₂ NCs）using a coordinated etching and precipitation（CEP）to prevent agglomeration.As an AA detection electrode,Ni（OH）₂NCs@Co（OH）₂ NSs/glassy carbon electrode（Ni（OH）₂ NCs@Co（OH）₂ NSs/GCE）presented a sensitivity as high as 113μA m M^-1 cm^-2 between 2.5μmol/L～1.55mmol/L,which is higher than Co（OH）₂ NSs/GCE[98μA m M^-1 cm^-2]and Ni（OH）₂NCs/GCE[84μA m M^-1 cm^-2].The deposition of 2D transition metal materials onto the hollow scaffolds can effectively improve the electrocatalytic activity.