Preparation And Electrochemical Sensing Application Of Ferrite Based Composite Materials

Spinel ferrite with the chemical formula MFe₂O₄ has a cubic crystal structure and belongs to the Fd3 m space group with 56 atoms per cell.The M in the spinel structural formula represents a divalent metal ion like Co²⁺,Mg²⁺,Mn²⁺,Cu²⁺,Ni²⁺,Zn²⁺,and so on.In the spinel structure,the O^2-anion is filled into the face center cubic（FCC）lattice,while the metal occupies tetrahedral and octahedral sites.Each molecular formula unit has eight tetrahedral and four octahedral sites,usually with larger gaps in the octahedral sites than in the tetrahedral sites.Spinel ferrite nanomaterials have inherent advantages as catalysts for metallic materials.These include high catalytic efficiency,ease of preparation,good stability,and easy recycling.Furthermore,the flexible position and valence variability of metal cations dominate the catalytic activity of spinel ferrites,offering the possibility of designing suitable catalysts.To date,spinel ferrites have attracted the attention of researchers due to their excellent magnetic,biocompatible,and catalytic properties.In this work,two nanoprobes were prepared that can be applied to analytical assays: 1)CoFe₂O₄ nanocubes were prepared using Cobalt-Ferrum Prussian Blue Analogue（Co-Fe PBA）,as a precursor,followed by sintering and finally successfully dispersed in Reduced Graphene Oxide（rGO）;2)surface modification of tin disulphide（SnS₂）using ZnFe₂O₄ nanocrystals by a two-step hydrothermal method.The details are as follows:Part Ⅰ: Electrochemical biosensor based on Prussian blue analogue derived CoFe₂O₄ nanocubes for dopamine detectionDopamine（DA）plays an important role in the functioning of the central nervous system.It is one of the neurotransmitters at muscle tone synapses.Abnormal dopamine levels have been implicated in the onset and progression of several diseases.These include parkinson’s disease,alzheimer’s disease,schizophrenia,hypertension,heart failure,and so on.In the present work,we have successfully designed a CoFe₂O₄/rGO based electrochemical sensor for the reliable and selective detection of DA in complex physiological environments.Among them,rGO with a large specific surface area solves the aggregation behavior of CoFe₂O₄ nanocubes,providing a large number of active sites and reducing the activation energy of electron transfer.The synergistic interaction between CoFe₂O₄ and rGO enhances the sensitivity and linear range of DA detection.The linear range of the sensor was 0.625-201.2 μM,with a limit of detection（LOD）of 0.03μM.In the actual sample serum DA assay,the recovery of the sensor was 94.9%-99.8%,with a relative standard deviation（RSD）of 2.60%-3.95%.Based on these advantages,the proposed DA sensor is expected to provide a versatile method for designing electrochemical sensors with high selectivity for detecting other electroactive molecules.Part Ⅱ: Synthesis of ultrafine ZnFe₂O₄ nanocrystals and construction of an electrochemical sensing platformLuteolin（Lu）is widely found in vegetables,herbs,and fruits.It possesses a variety of beneficial biological properties for health,such as anti-inflammatory,antibacterial,and antioxidant properties.In this work,firstly,ZnFe₂O₄ nanocrystals were prepared by hydrothermal method.Then,ZnFe₂O₄/SnS₂ composites were prepared using SnS₂ nanosheets as the carrier and ZnFe₂O₄ as a modifying layer.The composite showed high electrochemical activity and more active sites,which facilitated the improvement of its electrochemical sensing performance.The ZnFe₂O₄/SnS₂ sensing platform exhibits remarkable linear range,detection limit,and interference immunity for the detection of Lu.In addition,the sensing platform has been successfully applied to the detection of Lu in dried chrysanthemums,with a recovery rate of 97.2%-101% and an RSD of 1.29%-2.22%.This work could provide some theoretical support for the application of ZnFe₂O₄/SnS₂ composite materials for the qualitative and quantitative detection of Lu in other herbal medicines containing Luteolin.