The Preparation,Surface Modification And Antibacterial Application Of Two-dimensional Transition Metal Chalcogenide Nanosheets

Two-dimensional transition metal chalcogenides(2D TMDs)are MX2 compounds composed of transition metal atoms(M)and chalcogen atoms(X).2D TMDs have layered structures similar to graphene.The metal atoms in the layers of 2D TMDs are covalently bonded to the chalcogen atoms,and the weak van der Waals force exists between the layers.Therefore,it is easy to prepare 2D TMDs nanosheets by destroying the weak van der Waals force between the layers.2D TMDs have unique physical and chemical properties,and have been widely used in transistors,lithium-ion batteries,gas sensors,integrated circuits,and photodetectors.At the same time,2D TMDs show great potential in biomedical applications,such as biosensing,imaging and tumor therapy.This paper developed novel methods for the preparation and surface modification of 2D TMDs nanosheets.A simple and universal ultrasonic-assisted aqueous phase method has been used to controllably prepare WSe2 nanosheets with small size.Monolayer MoS2 nanosheets were prepared by lithium intercalation and further modified with polydopamine(PDA)to obtain MoS2@PDA nanosheets.PDA can improve the stability of the MoS2 nanosheets and facilitate their further surface functionalization.Then,glucose was used as reducing agent to achieve uniform growth of small-sized silver nanoparticles(Ag NPs)on the surface of MoS2@PDA(MP)nanosheets to obtain MoS2@PDA-Ag(MPA)nanocomposites,due to PDA with great ability to bind with metal ions.Combining the photothermal properties of MoS2 and the antimicrobial activity of Ag NPs,MPA nanocomposites could synergistically treat Staphylococcus aureus(S.aureus)biofilms and wound infection.The main content of the paper is as follows:First,small-sized WSe2 nanosheets were prepared by exfoliating the bulk materials using the ultrasonication-assisted aqueous phase method.With the triblock copolymer PEO-PPO-PEO(F127)as the surfactant,water bath ultrasonication and probe ultrasonication were combined to prepare small size WSe2 nanosheets.After exfoliation,WSe2 nanosheets about 10 nm-55 nm can be obtained by gradient centrifugation.The advantage of this method is that the operation is simple,the size of the exfoliated material is controllable and the biocompatibility of the exfoliated material is good.Secondly,PDA-modified monolayer MoS2 nanosheets were prepared by using different methods including magnetic stirring,bath ultrasonication and microwave irradiation.The experimental results showed that PDA-modified MoS2 nanosheets could be produced by the above methods,and there is no obvious difference in the size and morphology of MP nanosheets.However,the reaction time required for magnetic stirring and bath ultrasonication was 24 h and 1 h,respectively,while the microwave reaction requires only 10 minutes to prepare MP nanosheets,which is more simple and efficient.Subsequently,Ag NPs were grown on the surface of MP nanosheets to prepare MPA nanosheets.The morphology,structure,composition,optical property,photothermal property and toxicity of MP nanosheets and MPA nanosheets were studied through various characterization methods.Third,effective inhibition of the S.aureus biofilms growth,damage of the established S.aureus biofilms in vitro and treatment of S.aureus biofilms infection in vivo has been successfully achieved by MPA nanosheets.Because MPA nanosheets have excellent photothermal properties,and Ag NPs have strong antibacterial activity,MPA nanosheets could kill planktonic S.aureus,inhibit the formation of S.aureus biofilms,destroy the established S.aureus biofilms by the synergistic effect of photothermal therapy(PTT)and antibacterial activity of Ag NPs,and effectively kill bacteria inside the biofilms.For the treatment of S.aureus infected wound on mice,the MPA + NIR group shows significantly enhanced therapeutic effect to kill the bacteria in the wound and promote wound healing on mice compared with the MPA nanosheets or NIR laser irradiation treatment alone.The results of the toxicity experiments show that MPA nanosheets have little toxicity to cells and mice,and exhibit excellent biocompatibility,which suggests that MPA nanosheets have great potential for effective treatment of bacterial infection.