Preparation Of Transition Metal Phosphate-Based Nanocomposites And Their Photothermal And Antibacterial Properties

Globally,millions of people die from microbial infection-related diseases every year.The more terrible situation is that due to the overuse of antibiotics,especially in developing countries,people are struggling to fight with the bacteria variation.The emergence of superbacteria will be an intractable environmental and health hazard in the future.Consequently,it is critical to develop viable antibacterial approaches to sustain the prosperous development of human society.Recent researches indicate that transition metal phosphides(TMPs)have suitable band gap structures,rich and tunable morphologies,excellent solar energy utilization efficiency,extremely high photothermal conversion properties,easy surface functionalization,and superb biocompatibility.Additionally,TMPs are easy to be metabolized and degraded and then excreted from the body.Therefore,it has outstanding application potential in the field of biological detection and treatment.However,there are few studies on the photothermal and antibacterial properties of TMPs and the construction of multimodal synergistic antibacterial systems based on TMPs as matrix materials.Therefore,the development of TMPs-based antibacterial materials and multimodal synergistic antibacterial materials with TMPs as the matrix has certain reference significance in the field of bacterial infection treatment.In this paper,TMPs with different morphologies were prepared by solvothermal and high temperature phosphating methods,and the effects of different morphologies and material systems on photothermal and antibacterial properties were studied.On this basis,rational material optimization design was carried out,and the application potential of TMPs in photothermal/photodynamic synergistic antibacterial and photothermal/drug synergistic antibacterial was studied.The main research contents of this work are as follows:(1)Since the morphology has a great influence on the material properties,we prepared transition metal phosphide precursors with different morphologies by means of solvothermal method and ion etching method.Subsequently,stematically study the photothermal antibacterial properties of the obtained Co-P and Ni-P with different morphologies by phosphating.its.The research results show that the microstructure has a great influence on the photothermal properties of transition metal phosphide materials.The nanoneedles and nanocages have good photothermal properties,while sea urchin-like and nanoparticle-like transition metal phosphides have poor photothermal properties.In addition,both Co-P and NiP systems exhibited good photothermal antibacterial effects.(2)Due to the high temperature required for sterilization of simple CoP materials,rapid sterilization at low doses is not possible.Therefore,it is necessary to modify it to enhance its antibacterial properties.CoP nanoneedles were modified by noble metal Ag loading and quaternized chitosan(QCS)coating to prepare QCS-coated Ag/CoP(QCS/Ag/CoP)nanocomposites.The loading of Ag nanoparticles can simultaneously improve the photothermal and photocatalytic properties of CoP nanoneedles.Specifically,the Ag-CoP heterojunction structure constitutes a Schottky junction,thereby promoting ROS generation.The plasmon resonance effect of Ag nanoparticles leads to a strong electric field at the interface between Ag and CoP,which can enhance the photothermal performance of CoP nanoneedles.At the same time,the photothermal heating also promoted the release of Ag+ions.The coating of QCS can increase the stability of the material and make the surface of the material positively electrified,which is beneficial to the contact between the antibacterial material and the bacteria.The photothermal,photodynamic and Ag ion release synergistic antibacterial means and electrostatic attraction of QCS/Ag/CoP are used to achieve high-efficiency antibacterial effect.The nanocomposite antibacterial material can kill more than 99.5%of E.coli and S.aureus when irradiated with 808 nm near-infrared light for 15 min at a low concentration(50 μg/mL).(3)First of all,Ni2P nanocages with adjustable shell thickness were prepared,and then the antibacterial agent chlorhexidine(CHX)was further loaded and then coated with bovine serum albumin(BSA)to form BSA-CHX-Ni2P nanocapsules.The research results show that there is a relationship between the photothermal properties of Ni2P nanocages and the thickness of their shell layers,and the thin-layer Ni2P nanocages have the best photothermal properties,and the photothermal conversion efficiency can reach 61.8%.The Ni2P nanocages can effectively load the antibacterial agent CHX,and the nanocapsules can be released in response to photothermal and pH dual-switching effects.Finally,an antibacterial model of the synergistic effect of photothermal and antibacterial agents was established.Near-infrared light irradiation for 15 min and maintained under mild conditions(photothermal temperature near 50℃)can achieve efficient bacterial inactivation effect.The bactericidal rate against Methicillin-resistant S.aureus and P.aeruginosa both exceeded 99.4%.