Preparation Of Nickel Sulfide Based Materials And Their Photothermal Ninversion Performance

Along with social development and technological progress,some social problems have emerged,such as water shortages,cancer,bacterial infections,and other problems.In recent years,researchers have found that photothermal conversion materials can better solve the above problems by efficiently converting solar energy into thermal energy and forming a local high temperature at the interface of air and water,thus accelerating the production of water vapor.It can also be used for desalination and wastewater purification.In addition,the local high temperature formed by photothermal conversion materials combined with near-infrared light irradiation can also be used to kill cancer cells and bacteria,and some photothermal conversion materials can also catalyze the decomposition of hydrogen peroxide to produce strong toxic hydroxyl radicals（·OH）to achieve chemical kinetic therapy,thus improving the problem of drug resistance in chemotherapy and antibiotic therapy.The currently reported photothermal conversion materials have disadvantages such as poor stability and high biotoxicity,which limit their application in real-life production.Based on this,this thesis firstly synthesized nickel sulfide based materials by solvent thermal method with strong photothermal conversion performance,ideal thermal stability and good biocompatibility,etc.Further,NiS_2-x@PVP nanospheres were obtained by modulating the morphology and particle size of nickel sulfide(NiS_2-x)with polyvinylpyrrolidone（PVP）;subsequently,NiS_2-x was modified by Ag（8.5%）@NiS_2-x microspheres were prepared by Ag modification of NiS_2-x,which were used for solar-driven water evaporation,tumor therapy,and antibacterial therapy,respectively,as follows:（1）An efficient Janus hydrogel membrane was prepared using core-shell structured non-chemo-metric NiS_2-x microspheres and agar hydrogel.The NiS_2-x immobilized in the agar hydrogel has full-spectrum absorption properties at 200-2500 nm,allowing efficient photothermal conversion and modulating the water transport channel.In addition,the pure agar at the bottom can efficiently transport water and avoid heat loss.By the casting method,Janus hydrogel membranes are easy to prepare into various shapes,and therefore,they can be adapted to the environment in which they are used.The optimized Janus hydrogel membrane-1 has good hydrophilicity and its good solar water evaporation rate(1.45 kg m^-2 h^-1)with photothermal conversion efficiency（97.0%）under one sunlight irradiation.Theoretical simulation results show that the excellent water evaporation performance of Janus hydrogel membrane-1 is mainly due to its relatively free water transport channel.In addition,Janus hydrogel membrane-1 can be used for water evaporation applications in various media,including desalination,heavy metal ions,organic wastewater,and domestic wastewater purification.（2）By optimizing the amount of polyvinylpyrrolidone,NiS_2-x@PVP nanospheres were successfully prepared and mixed with metformin hydrochloride and dispersed in sodium hyaluronate（HA）hydrogel to construct the NiS_2-x@PVP@HA tumor therapy platform,which has excellent photothermal conversion performance under near-infrared light irradiation and can be used for tumor photothermal therapy（PTT）.NiS_2-x@PVP The nanospheres can be rapidly degraded into nickel ions and sulfur ions,and the nickel ions generated from their degradation can catalyze the decomposition of endogenous hydrogen peroxide（H₂O₂）in tumor cells,thus generating highly toxic·OH for chemodynamic therapy（CDT）of tumors.The loaded antitumor drug metformin hydrochloride can enhance the tumor-killing effect,and the therapeutic platform has drug-controlled release properties under the action of NIR and ultrasound.In vivo tumor experiments in mice showed that the NiS_2-x@PVP@HA multifunctional therapeutic platform achieved synergistic PTT/CDT/chemotherapy treatment of mammary tumors and effectively inhibited tumor growth.（3）Ag（8.5%）@NiS_2-x microspheres were successfully prepared by Ag doping and dispersed in polyacrylamide and chitosan to form a dressing with antibacterial and tissue healing promoting functions（dressing-2:1）.The internal Ag（8.5%）@NiS_2-xgives the hydrogel excellent photothermal conversion properties,and its temperature can be rapidly increased within 10 min by irradiation with an 808 nm(0.5 W cm^-2)laser.In addition,Ag（8.5%）@NiS_2-x has peroxidase activity,which can catalyze the production of reactive oxygen species at low concentrations of H₂O₂.Dressing-2:1combined with the local high temperature generated by NIR light at the wound site and the Ag enriched in it can destroy the outer membrane structure of bacteria,thus killing the bacteria at the wound site.The constructed hydrogel dressing is biocompatible,non-toxic,moisturizing and hemostatic,which provides the required environment and conditions for the growth of regenerative cells and can promote wound healing.Wound healing experiments in mice further demonstrated the excellent antibacterial effect of dressing-2:1 hydrogel.