Controlled Preparation Of Hierarchical Structured Metal/Metal Oxide-Carbon Composites And The Study Of Their Electrochemical Sensing Performances

Carbon can form substances with completely different structure and morphology as a single element,which is not easy to be corroded and has the characteristics of high thermodynamic stability and excellent electrical conductivity.Furthermore,carbon can combine with metal elements closely through hybridization to produce synergistic effect,so that it has shown improved performance in the areas of energy,catalysis and sensing,and has been widely favored by scientists.How to use easy and efficient approaches to construct novel and excellent structured hierarchical carbon-based metal/metal oxide materials with different size and morphology,and investigate the relationship between the structure and the properties of the materials have become the hotspots.For that reason,this paper intends to combine the carbon materials and metal/metal oxide effectively to study the controlled preparation of hierarchical structured carbon-based metal/metal oxide composite materials.Through the structural regulation of these composites at the nanoscale,it is expected to take full advantage of the synergistic effect among the components,and greatly improve the electrochemical sensing performance of the composites.Based on this,four kinds of electrochemical sensors with high sensitivity,fast response and good selectivity were constructed and their application was studied.The main contents and results are as follows:1.A template-activated strategy was developed to construct core/shell structured carbon sphere@silver composite based on one-pot hydrothermal treatment.The C@Ag possessed a uniform three-dimensional interconnected microstructure with an enlarged surface area and catalytic activity,which was further mechanically protected by graphene oxide?GO?nanolayers to fabricate intriguing configuration,which was beneficial for efficiently preventing the aggregation and oxidation of Ag NPs and improving the electrical conductivity through intimate contact.By immobilizing this special material on electrode surface,the C@Ag@GO was further used for sensitive determination of chlorinated phenols including 2-chlorophenol,4-chlorophenol,2,4-dichlorophenol and 2,4,6-trichlorophenol.The tailored structure,fast electron transfer ability and facile preparation of C@Ag@GO made it a promising electrode material for practical applications in phenols sensing.2.A simple coupled synthesis and encapsulation route was developed to fabricate monodisperse,uniform Ag@C@Ag core-shell structured nanocompositeswith excellent electrochemical and catalytic properties,in which Ag nanoparticles were first encapsulated in a carbonaceous shell through the catalyzed dehydration of glucose under hydrothermal conditions,and then the surface-activated Ag@C spheres were subsequently used to accumulate [Ag?NH3?2]+ or Ag+ ions through electrostatic attraction to anchor the Ag coating.The as-prepared nanocomposites were demonstrated to have a great potential for the simultaneous multiplexed detection of thymol and phenol,and exhibited high sensitivity and good reproducibility.In addition,the practical analytical application of the sensing platform was assessed by the determination of thymol and phenol in real honey samples,and satisfactory results were achieved.3.The study presents a new approach for rapid and ultrasensitive detection of maltol using a glassy carbon electrode?GCE?modified with graphene oxide-wrapped tin oxide@carbon nanospheres?SnO₂@C@GO?.The morphological and components properties of SnO₂@C@GO nanocomposites were investigated by means of X-ray diffraction spectroscopy,Raman spectroscopy,field emission scanning electron microscopy,high resolution transmission electron microscopy,and electrochemical impedance spectroscopy.SnO₂@C@GO nanocomposite on a GCE had a synergetic effect on the electrochemical oxidation of maltol by means of square wave voltammetry.Under the optimum conditions,anodic peak current response of maltol was linear with its concentration in the range of 80 nmol/L-10 ?mol/L,and a detection limit of 12 nmol/L was achieved for maltol.The experiment results presented that the method showed good selectivity,sensitivity,reproducibility,and long-term stability,as well as excellent potential for use as an ideal inexpensive voltammetric method applicable for complex food matrices.4.This work describes a novel,simple and reliable semi-derivative differential pulse voltammetric method for determining chlorotetracycline?CTC?residue in foods based on the signal enhancement of yolk-shell structured carbon sphere@MnO₂?C@MnO₂?.The C@MnO₂ was characterized by scanning electron microscopy,transmission electron microscopy and X-ray diffraction,which showed an excellent accumulation ability and high electrochemical activity to CTC due to the porous structure and low density.Under optimized conditions,the method showed a wide linear response in the range of 0.5-300 ?mol/L with a detection limit of 0.26 ?mol/L.Additionally,the method exhibited good stability and acceptable repeatability.The proposed method could be used for the determination of CTC in food samples withthe recoveries of 98.80-101.5%,showing a promising potential in practical application.