Preparation Of Gold Nanocomposites And Catalytic Degradation Of Methyl Orange

With the development of nanomaterials,gold nanoparticles(AuNPs)with various physicochemical properties such as optics,electricity and catalysis have received extensive attention and research.However,the characteristics of easy aggregation,instability and difficult recovery increase the difficulty of the application of AuNPs.In this paper,based on AuNPs,the preparation of AuNPs with carbon nanotubes(CNTs)and zeolitic imidazolate framework-8(ZIF-8)composite and the catalytic degradation of methyl orange were studied.The results show that the composite with special morphology can increase the stability of AuNPs and improve the catalytic degradation performance of methyl orange.The main research contents of this paper are as following:(1)Using chlorauric acid(HAuCl4)as the precursor,polyvinylpyrrolidone(PVP)as the protective agent,and sodium borohydride(NaBH4)as the reducing agent,the threedimensional network structure Au@CNTs composite was synthesized in situ in the suspension of carbon nanotubes.Among them,the gold nanoparticles show "coral" shape,about 10nm in diameter,"branches" long 20 to 50nm,about 20nm carbon nanotube diameter,length 10 to 30μm.Raman analysis results show that the graphene defect degree of carbon nanotubes increases,and electron doping occurs between gold nanotubes and carbon nanotubes.FT-IR and XPS spectra showed that the carboxyl functional groups on the carbon nanotubes participated in the composite reaction to form Au-O interface bonds,and chemical bonds were formed between gold and carbon nanotubes.The experimental results demonstrate that Au@CNTs has high catalytic activity,the degradation rate of methyl orange can reach 94.5%after 10min reaction and 82.5%after six cycles.(2)HAuCl4 was used as the precursor to synthesize AuNPs,and then the continuous adsorption mechanism of PVP-AuNPs was used to coordinate zinc ions with nitrogen atoms of deprotonated imidazole to form clusters.ZIF-8 was attached to the outside of the core of AuNPs through the clusters and grew rapidly to prepare the core-shell structure Au@ZIF-8 composite.The spherical AuNPs are about 10nm in diameter and the rhombic dodecahedron ZIF-8 is about 100nm in length.FT-IR and XRD test results showed that 2-methylimidazole was deprotonated and ZIF-8 was generated.Thermogravimetric(TG)results show that Au@ZIF-8 has lower mass loss and better thermal stability in the range of room temperature to 800℃.The consequences of catalytic degradation of methyl orange showed that the degradation rate could reach 68.31%in 30min Au@ZIF-8 and 54.8%after six cycles.Figure[33]Table[7]Reference[93]...