Study On The Preparation And Performance Of Cu/C-dots Composite Nanoparticles

C-dots were novel carbon nanomaterials with excellent performance and have wide application value in bioassay,photocatalysis and other fields.Copper particles were active sites for hydrogenation and have been widely used in methanol reforming,lipid hydrogenation and so on.The composite nanoparticles produced by the combination of metal nanoparticles and C-dots have many applications as a new type of material.In this paper,Cu/C-dots nanoparticles were prepared by using C-dots as reducing agents and stabilizers.The properties of various aspects were studied and their applications in cellulose conversion were evaluated.C-dots were prepared by hydrothermal method and microwave method using different small molecular compounds as carbon sources.The particle size,surface groups and fluorescence properties of C-dots prepared by different methods were characterized.The results showed that the C-dots synthesized by hydrothermal method of trisodium citrate and urea have good particle size morphology,average particle size of 2.5 nm,and a large number of hydroxyl,amino,carbonyl and carboxyl groups on the surface,which have typical fluorescence.feature.The degree of crystallization of C-dots prepared by microwave method is not uniform,and the particle size distribution has no obvious distribution characteristics,and the average particle size is 3.62 nm.Its fluorescence mechanism is dominated by surface defect emission,and surface groups have a non-negligible effect on luminescence.The comparison of hydrothermal method and microwave method showed that the synthesis method hardly affects the surface groups and fluorescence properties,and the particle size morphology may be different.The prepared C-dots were combined with Cu²⁺by hydrothermal method,water bath method and room temperature stirring method,respectively.And the structure and surface characteristics of the composite particles were characterized.The results showed that the Cu/C-dots nanoparticles prepared by the normal temperature stirring method have a stable encapsulation structure,and the C-dots act as the core to complex the stable copper nanoparticles,which improves the dispersion of copper and reduced the geometrical size of the catalyst.The main function in the complex reaction was the C=O group,which played the dual role of reducing Cu²⁺and complexing stable copper nanoparticles.Different preparation methods directly affect the structure of the composite particles.The composite structure prepared by hydrothermal method was unstable,and the composite form of copper nanowires and carbon dots appears in the composite structure prepared by the water bath method.Different material ratios have less influence on the structure of the composite particles,which will have certain influence on the crystal state and dispersion.The Cu/C-dots nanoparticles prepared in this paper have stable properties.The composite precursor solution was dried and then redispersed in aqueous solution.The fluorescence characteristics of the two are approximately the same.In order to study the catalytic performance of Cu/C-dots nanoparticles in the conversion of lignocellulosic biomass in the supercritical methanol,Cu/C-dots nanoparticles prepared by room temperature stirring at a material ratio of 4:1.The medium-catalyzed liquefied cellulose has a cellulose conversion rate of 88.9%,and the composite nanoparticles have good catalytic activity.The research in this paper aimed to provide a new way for the selection of cellulose liquefaction catalysts.