Tunable Synthesis And Photothermal Conversion Properties Of CuS Nanocrystals And CuS-based Core-shell Nanostructure

CuS nanocrystals have the unique near-infrared localized surface plasmon resonances?LSPRs?properties due to their Cu vacancies.This family of nanomaterial has been a new type of photothermal agent showing promising potential applications in photothermal therapy,due to the good biocompatibility and the matching of their NIR plasmon absorption with biological windows.The present thesis reports on a simple synthtic method for the CuS@CuPd_xS core-shell nanostructures by post-chemical conversion reaction at room temperature with as-synthesized CuS as the base material.The LSPRs performances and the stability of CuS@CuPd_xS core-shell nanostructures are also studied.Secondly,a low-cost facile synthetic protocol for aqueous soluble CuS nanocrystals at room temperature are reported and photothermal conversion properties of CuS and CuS@CuPd_xS core-shell nanostructures are studied as well.The main achievements and innovations achieved are as follows:?1?We have demonstrated a chemical conversion method for preparing CuS@CuPdxS core-shell nanostructures at room temperature.CuS@CuPdxS core-shell nanostructures are synthesized by diffusion of guest ions(i.e.Pd²⁺)to the lattice of CuS NCs with as-synthesized CuS NCs as the base material at room temperature,in the presence of reductant?i.e.ascorbic acid?.By changing the reaction time and precursor Pd:Cu molar ratios,the thickness of the amorphous CuPd_xS shell and the performance of LSPRs could be tuned.The results show that,compared with CuS nanocrystals,the prepared CuS@CuPd_x S core-shell nanostructures make their plasmonic response less sensitive to harsh oxidation?i.e.,I₂?or reduction?i.e.,DIBAH?environment,which indicates that CuS@CuPd_xS core-shell nanostructures exhibit excellent optical stability properties.?2?We have also demonstrated a simple phase transfer method for transferring oil-phase nanocrystals into aqueous nanocrystals.Wth low-cost TGA as ligand,the organic phase NCs are transferred to the aqueous phase under a neutral environment.The results show that,compared to the organic nanocrystals,NIR plasma absorption of CuS and CuS@CuPd_xS transferred to the aqueous phase has a significant blue shift of about151 nm and 67 nm,respectively.In addition,the phase transfer method can realize the practical application of oil-nanocrystalline photothermal conversion.The results show that the photothermal conversion efficiencies of CuS NCs and CuS@CuPd_xS core-shell nanostructures are 15.67%and 15.36%,respectively.?3?We reported on a facile synthetic protocol for directly preparing covellite CuS nanocrystals with good NIR plasma absorption and photothermal conversion in air at room temperature.The results show that,by changing Cu precursor?i.e.CuCl2?2H2O,Cu?NO₃?₂?xH₂O,Cu?Ac?₂?H₂O?,S precursor?i.e.Na₂S?9H₂O,?NH₄?₂S?and their molar ratio,or various ligands?i.e.MPA,TGA,GSSG and GSH?,the morphologies of CuS NCs are tuned,including nanosheets and fingerprints-like.Furthermore,the composition can also be tuned from CuS to Cu₂S by controlling the S:Cu molar ratio.In addition,a gram-scale production?1.2275 g?of covellite CuS nanoplates was performed by scaling 100-fold amounts of precursors,solvent,ligand,and the yield was 83%.It was found that,among the as-prepared CuS,Cu₃₉S₂₈ and Cu₂S nanocrystals,CuS NCs exhibit excellent photothermal conversion efficiency?20.3%?and photothermal stability.And the CuS NCs collected by reacting CuCl₂,Cu?NO₃?₂ and Cu?Ac?₂,respectively,with Na₂S in the presence of different ligands display almost the same temperature increment underlaser irradiation?806 nm,1.2 W/cm²?.Compared with aqueous CuS NCs obtained by phase transfer,aqueous CuS NCs synthesized directly possess better photothermal conversion efficiency and photothermal stability.