Nanocomposites Of Exfoliated Layered Double Hydroxide Nanosheets And Loaded Nanoparticles

The exfoliated layered double hydroxide nanosheets(LDH nanosheets)is a positively charged two-dimensional material with a larger specific surface area,more active sites,ultra-thin polar layers than unexfoliated LDH particles,and thus can be considered as an ideal material for the construction of functional composite nanomaterials.The combination of LDH nanosheets with nanomaterials often exhibit a combination of physical or chemical properties from the individual components,further enhanced property tunability and even exhibit a new synergistic properties.Herein,several types of large-size LDH plates were prepared and exfoliated to positively-charged LDH nanosheets as carrier,then the nanocomposites of LDH nanosheets and negatively-charged small nanoparticles were fabricated based on the electrostatic interaction between LDH nanosheets and other nanoparticles,the properties and potential applications of the nanocomposites were also studied.1.ZnAl-LDH,ZnFeAl-LDH,Zn Fe-LDH intercalated with acetate,Zn Al-LDH,ZnFeAl-LDH intercalated with nitrate,and ZnFe-LDH intercalated with sulphate were prepared in this paper.It was shown that ZnAl-LDH and ZnFeAl-LDH were easily synthesized by microwave method and the morphology of LDH was better when the addition amount of alkali was less,while ZnFe-LDH was not easily synthesized by this method.ZnAl-LDH prepared by unsteady coprecipitation method showed an obvious hexagonal structure,as well as ZnFeAl-LDH prepraed by steady coprecipitation method.The ZnFe-LDH intercalated by SO42-anions by two-step prepraration method showed a thick lamellar structure and a relatively good crystallinity.2.LDH intercalated with nitrate was easier to be exfoliated than the LDH intercalated with sulfate or carbonate.The exfoliated hydrotalcite nanosheets and the negatively charged gold nanoparticles could form nanocomposites by electrostatic interaction.When the ratio of the mass of LDH to the mass of gold atoms was between 7.5 and 20,gold nanoparticles could closely bound with and be well dispersed on LDH nanosheets.The gold nanoparticles supported on the surface of LDH nanosheets still had catalytic activity.The results showed that the catalytic activity in reduction of 4-nitrophenol by sodium borohydride decreased with the increase of the carrier content,and the catalytic reaction of benzyl alcohol to benzaldehyde by supported gold nanoparticles on LDH nanosheets reached a conversion of 27%.3.The exfoliated nanosheets could adsorb carbon quantum dots prepared by pyrolysis method using citric acid as reagent based on electrostatic interaction.The composite could still maintain strong fluorescence performance of carbon quantum dots assembled by layer-by-layer self-assembly(LBL)method and self-assembly method in the solution.And the carbon quantum dots were well dispersed on the surface of nanosheets.