Research On Photothermal Antibacterial And Interfacial Water Evaporation Performances Of MXene-based Nanocomposites

The uncontrolled reproduction of pathogenic bacteria has become a global problem that seriously endangers public health,and humid water bodies are the hardest hit areas for its flooding.Photothermal antibacterial application and evaporation purification driven by solar energy have become the research focus of many scholars because of their clean energy source and weak environmental impact.For this reason,researchers have developed a series of photothermal materials.MXene has become an excellent candidate for related applications because of its superior photothermal performance and ultra-high dispersibility in aqueous systems.In this work,firstly,the flaky MXene material was prepared by etching,and then the material design was optimized,and the synergistic antibacterial properties of photothermal/photodynamic and photothermal/metal ion dissolution of MXene-based nanocomposites were researched,to realize the direct disinfection and purification of water.In order to further develop a more comprehensive and efficient water purification strategy,MXene-based nanocomposites were combined with chitosan(Ch)hydrogel.The photothermal antibacterial performance of Ag/MXene@Chitosan hydrogel(AM/Ch gel)and the interfacial water evaporation performance based on hydrogel carrier were researched,which provided a new design idea for developing antibacterial soft materials with adjustable performances.The main research contents and findings are as follows:(1)In order to explore the synergistic antibacterial effect of photothermal/photodynamic and improve the single photothermal antibacterial therapy of MXene,a series of 2D/2D g-C3N4/MXene nanocomposites were prepared by combining protonated g-C3N4 with negatively charged MXene.Under 0.35 W cm-2 simulated sunlight,the antibacterial performance was the best when the mass ratio of g-C3N4 to MXene was 1:1.C1M1 group can kill 100%of E.coli and 99.76%of S.aureus within 15 min.The research and analysis showed that the introduction of g-C3N4 component effectively improved the separation efficiency of electron-hole pairs,promoted the production of reactive oxygen species with strong lethality,such as superoxide radical,hydroxyl radical and singlet oxygen,further oxidized surrounding biomolecules with the help of photothermal effect,and accelerated the death of pathogenic bacteria.The results showed that g-C3N4/MXene nanocomposites exhibited excellent potential in photothermal/photodynamic synergistic antibacterial applications.(2)In order to explore the synergistic antibacterial effect of photothermal/metal ions dissolution and endow MXene with high-efficiency and long-term antibacterial effect,a series of Ag/MXene nanocomposites were prepared by in-situ reduction of Ag+ on MXene nanosheets with sodium borohydride solution.Under the irradiation of 0.3 W cm-2 simulated sunlight,the antibacterial performance was the best when the mass ratio of Ag to MXene was 1:4.99.76%of E.coli and 99.41%of S.aureus can be destroyed in 15 minutes by Ag0.2MXene0.8 group,and its antibacterial activity was superior to that of MXene group at higher temperature.The research and analysis showed that the Ag/MXene nanocomposites dispersed in the bacterial liquid can drive the whole system to heat up,increase the permeability of bacterial cell membrane,and promote the release of bactericidal Ag+from Ag components,thus achieving the effect of rapid light response sterilization.The photothermal synergistic strategy of the material can effectively reduce the dosage of silver nanoparticles,reveal the antibacterial potential of photothermal/metal ion dissolution synergistic effect,and improve the safety of antibacterial system.(3)In order to expand the application of the above Ag/MXene nanocomposites,Ag/MXene@Chitosan hydrogel materials with photothermal antibacterial properties were prepared by combining Ag/MXene nanocomposites with chitosan hydrogel.Next,the hydrogel was further built as a water evaporator to explore the interfacial water evaporation performance.Ag/MXene@Chitosan hydrogel can achieve 100%antibacterial activity within 30 min under 0.2 W cm-2 simulated sunlight irradiation.Under the same irradiation conditions,the evaporation rate of Ag/MXene@Chitosan hydrogel evaporator(AM/Ch gel evaporator)reached 3.22 kg m-2 h-1,and the evaporation efficiency reached 94.9%.After seawater and dye wastewater were purified by the water evaporator,the ion concentration decreased by 3-4 orders of magnitude,and the dye absorbance was close to 0.The research showed that the excellent evaporation and purification performance of the water evaporator was mainly due to the porous network structure providing a suitable carrier for water evaporation,and the Ag/MXene nanosheets endowed the carrier with outstanding photothermal ability,which exhibited the application potential of MXene-based hydrogel materials in the field of clean water production.