| Two-dimensional(2D)nanomaterials have received wide attention in many fields due to their unique physical,optical,chemical and electronic properties.Graphene-like 2D nanomaterials such as transition metal chalcogenides(TMCs)with strong absorption in the near-infrared window exhibit great advantages and potential application prospects in the field of photothermal therapy.From the viewpoint of band theory,reducing the thickness is of great significance for the enhancement of photothermal properties of TMCs nanosheet materials.Normally,ultrathin 2D TMCs nanosheets were synthesized based on "top-down"exfoliation methods,chemical vapor deposition(CVD)and wet-chemical synthesis methods,which suffers from laborious operation,low yield production and controllable morphology.This would lead to unsatisfactory photothermal conversion efficiency.Therefore,how to achieve elaborate synthetic routes of ultrathin TMCs with tunable composition,uniform morphology,as well as superior therapeutic and diagnostic performance,still remains a big challenge.In this thesis,based on the topological transformation properties of layered double hydroxides(LDHs)nanosheets,a new synthetic route was explored to prepare ultrathin TMCs nanosheets by using the monolayer LDHs as a precursor.By regulating the composition and proportion of metal elements in LDHs precursor,improved photothermal therapy and diagnostic performance(photoacoustic and MRI imaging)are realized.The specific research contents of this thesis are as follows:1.Preparation of ultrathin CFS-PEG nanosheets toward photothermal therapyThe monolayer CoFe-LDH nanosheets were synthesized by a"bottom-up" wet-chemical method,and the ultrathin CoFe-selenide(CFS)was further prepared via an in situ transformation from monolayer LDHs nanosheets.In order to obtain better biocompatibility,the surface of CFS nanosheets was functionalized with polyethylene glycol(PEG)to obtain stable and dispersed CFS-PEG nanosheet materials.TEM,AFM,zeta potential and size analysis showed that the as-synthesized CFS-PEG nanosheets possess uniform morphology and size distribution,and were rather stable in water and physiological solution.By optimizing the elements proportion of precursor,a temperature change of 41.6? can be obtained within 10 min with 808 nm irradiation,and the photothermal conversion efficiency is as high as 74.5%.Meanwhile,excellent photoacoustic(PA)imaging(minimum detection limit of 5 ppm)and magnatic resonance(MR)imaging(transverse relaxation rate of 347.7 mM-1 s-1)make CFS-PEG nanosheets an effective cancer diagnostic reagent.In vitro and in vivo evaluations show that CFS-PEG nanomaterial is potential in PTT and PA/MRI dual-mode imaging.2.Cu-doped ultrathin TMCs nanosheets toward photothermal/gas therapy and PA imagingCu-doped ultrathin CoFe-selenide(CCFS)nanosheets were prepared by doping copper element into the host layer of LDHs precursor,with a further surface modification by polyvinyl pyrrolidone(PVP).After loading the NO donor L-arginine molecule(L-Arg),CCFS-PVP-Arg(CPA)generates and releases nitric oxide(NO)gas molecules which can cause apoptosis of tumor cells in the presence of H2O2.The photothermal effect of as-prepared ultrathin CPA material was further improved by the local surface plasmon resonance of Cu element,and the absorption at 808 nm of CCFS nanosheets(30%Cu)increases significantly.The temperature change reaches to 45.9? whitin 10 min upon NIR irradiation,with a photothermal conversion efficiency of 72.0%.Moreover,CPA with excellent PA imaging can be used as a proming material toward cancer theranostics with the performance of PTT/gas therapy and PA imaging.In summary,based on the topological transformation property of LDHs,a new synthetic strategy of ultrathin TMCs nanosheets was developed via an in situ transformation from monolayer LDHs nanosheets.Through tuning the metal composition and proportion of LDHs precursor,an excellent cancer theranostics agent was obtained. |
PDF Full Text Request