Fabrication And Sterilization Properties Of Prussian Blue-based Photothermal Nanomaterials

Being one of the global grand challenges,environment safety of water resources is utmost important for human health and life.Drinking water pollution is one of the main causes of death in less-developed countries.Water pollution mainly comes from organic/inorganic pollutants of pesticides,industrial wastewater and domestic sewage,as well as microbial contamination,e.g.pathogenic bacteria.Traditional water sterilization technologies include boiling,multi-layer filtration,ultraviolet irradiation and application of sterilizing agents.These methods often have inherent disadvantages,such as high energy consumption,high cost,incomplete sterilization and carcinogenic risk from the by-products.Therefore,the development of green,efficient and energy-saving new sterilization technologies for water treatment has particular significance and application prospects.Prussian blue?PB?nanomaterials have been found showing excellent biocompatibility,strong optical absorption and photothermal conversion properties,besides low cost,high chemical stability and good water solubility,showing promising antitumor and bactericidal potential upon near infrared?NIR?laser irradiation.Superior to NIR laser,solar radiation has clearly more advantages in terms of energy saving and practical application feasibility.However,the target of photothermal materials requires wide and strong absorption in the full solar spectrum.Since the first report in 2018,the reprots of photothermal sterilization by solar irradiation are still very scarce,while photothermal sterilization based on PB nanoparticles under solar irradiation remains blank.This work focuses on the construction of Prussian blue-based nanoparticles with high photothermal properties,and photothermal sterilization in water with PB-based nanoparticles irradiated by both solar and NIR light.The main contents are as follows:Firstly,PB nanocages?PBNs?with typical hollow structure were prepared by hydrothermal method,and their optical absorption property,photothermal conversion performance and photothermal stability under both solar and NIR light were studied.Moreover,the photothermal sterilization performances of the PBNs were investigated by choosing Escherichia coli?E.coli?and mixed total bacteria in water as the objects.The experimental results showed that PBNs had good monodispersity and stability,and enhanced wide-band optical absorption,photothermal conversion and photothermal stability than conventional PB nanoparticles.Under NIR irradiation,PBNs at a low concentration can effectively kill E.coli and mixed total bacteria in water within a short time.Even under mild sunlight?0.1 W/cm²?,the PBNs also achieved highly efficient sterilization under a short irradiation.By comparing the morphology of E.coli before and after the treatment,the photothermal sterilization mechanism of PBNs was discussed.In order to further improve the photothermal properties,Mn²⁺ doped Prussian blue nanocage?HMn PB?with higher photothermal conversion ability was fabricated.The effects of various Mn²⁺ doping level on the optical absorption and photothermal conversion properties were studied.The experimental results showed that HMn PB had high biocompatibility and dispersibility in water,with evidently higher absorption in NIR region than PBNs.Meanwhile,the photothermal conversion efficiency of HMn PB was also significantly higher than that of undoped PBNs.As a result,similar bactericidal effect to that of undoped PBNs can be obtained with much lower concentration for HMn PB.The effective killing of E.coli and Staphylococcus aureus?S.aureus?was achieved by using the photothermal effect of HMn PB under either NIR or sunlight.In addition,the hollow structured HMn PB was used for drug loading,and a synergistic photothermal therapy and chemotherapy was accomplished,resulting in powerful anticancer efficacy.Aiming on the recyclability and reusability of these PB-based photothermal materials,magnetic Fe₃O₄ nanospheres were caged in PBNs as core,and core-shell structured Fe₃O₄@PB was obtained.The experimental results showed that Fe₃O₄@PB had good dispersion,strong magnetism and optical absorption from 200 to 1200 nm.Under NIR irradiation,Fe₃O₄@PB can kill E.coli and mixed total bacteria in water effectively.The killing efficacy was a concentration and irradiation time-dependent manner.Fe₃O₄@PB also showed excellent bactericidal efficacy under sunlight.Importantly,after 4 cycles of photothermal sterilization,Fe₃O₄@PB still maintained a sterilization rate of over 98% against E coli and S.aureus.This work provides crucial support for promoting the practical application of reusable photothermal sterilization materials.