Construction Of Highly Sensitive Electrochemical Sensors Based On Perovskite Oxide Nanofibers

Electrochemical sensing technology has high application prospects in the qualitative or quantitative monitoring of dangerous small molecules in food,environment,and other industries because of its sensitive response,convenient operation,wide detection range,and real-time detection.Electrochemical sensor performance is influenced by the materials used for electrode modification.The easily regulated redox ability,conductivity,stoichiometric oxygen,and related physicochemical properties of ABO₃perovskite transition metal oxides are key to the designing and developing of highly sensitive electrochemical sensing materials.In this paper,a variety of ABO₃perovskite oxide nanofibers（ABO NFs）were prepared by A-site doping,B-site doping,and AB-site co-doping using a strategy combining electrospinning with high-temperature calcination oxidation technology.The relationship between the microstructure,oxygen vacancy concentration,phase and crystal structure of ABO NFs prepared by different doping strategies and the sensing performance was deeply discussed.The following are the primary contents:（1）The technique of doping LaNiO₃type perovskite oxide with A-site Sr²⁺was proposed and is based on electrospinning and high-temperature calcination oxidation technology.Carbon nanofibers（CNFs）effectively connected the elements La,Sr,Ni,and O in series,and through the oxidation limit effect at high temperature,uniform-sized hollow porous tubular La_0.9Sr_0.1Ni O₃NFs（La Sr Ni O NFs）were synthesized.Large surface area and high porosity give abundant active sites for H₂O₂electrochemical detection.In addition,the co-occupation of La³⁺and Sr²⁺at the A-site alters the structure of the pure perovskite phase to allow for the coexistence of the perovskite phase and spinel phase creates oxygen vacancies,which improves the redox ability,and conductivity of materials.Under the synergistic action of the two,the sensitivity and the lowest detection limit（LOD）of La Sr Ni O electrochemical sensor H₂O₂are 1667.9μA m M^-1cm^-2and 0.018μM,respectively.（2）Considering NO₂^-highly sensitive electrochemical sensing often needs to be realized through a multi-step electrochemical oxidation process.The B-site co-doping strategy,which is rich in redox sites and can effectively promote charge separation and transfer,is proposed in this chapter based on the previous chapter.A series of homogeneous metal particles loaded with La_0.9Sr_0.1B1_0.5B2_0.5O₃NFs type perovskite oxide.The crystal structure distortion（hexagonal-orthogonal-hexagonal）and the relative content difference of oxygen vacancy caused by different B-site co-doping and thermodynamic induction effect were revealed.The hollow porous tubular structure formed by NFs uniformly loaded metal nanoparticles showed a strong current response and electrochemical stability.Among them,La_0.9Sr_0.1Fe_0.5Ni_0.5O₃NFs with hexagonal-crystal structure prepared by Fe Ni co-doping has more dense and homogeneous pore structure and the highest relative oxygen vacancy content;and realizes the highly sensitive electrochemical sensing of NO₂^-at a lower working voltage（0.75 V）.Its sensitivity is 218.5μA mM^-1cm^-2,LOD is 0.13μM.（3）The highly sensitive electrochemical sensing of Pb²⁺and Cu²⁺depends on the rapid deposition and stripping of ions.This chapter suggests a regulation technique that uses triple-B-site and double-A-site co-doping for rapid ion diffusion and transfer.By electrospinning CNFs via a high-temperature oxidation limiting domain,a series of five-member La_xSr_1-xB_0.8B1_0.1B2_0.1O₃NFs perovskite oxides with the hollow porous tubular structure were created.The relationship between phase structure,crystal structure and oxygen vacancy concentration caused by different doping types was revealed.Among them,the structure of the cubic crystal system La_0.5Sr_0.5Co_0.8Fe_0.1Ni_0.1O by a small amount of strontium carbonate and perovskite phase composition,which has the highest oxygen vacancy concentration as well as the best performance for Pb²⁺and Cu²⁺electrochemical sensing.The sensitivity of Pb²⁺and Cu²⁺was 1623.6971μAμM^-1cm^-2and 1053.4819μAμM^-1cm^-2,respectively.The LODs were 0.018 n M and 0.028 n M,respectively.The linear detection range of both was 0.1～1.1μM.