Preparation And Photothermal Conversion Performance Of Cobalt Sulfide Nanomaterials

Due to the excessive exploitation and destruction of natural resources,water pollution,lack of energy,and various diseases and other problems come one after another.It is imperative to develop non-toxic,non-polluting,and sustainable solutions.In recent years,researchers have developed various new photothermal conversion materials,which can efficiently convert light energy into heat energy,thus solving energy and biomedical problems.The above-mentioned photothermal conversion materials usually have the advantages of high photothermal conversion efficiency,cheap and easy raw materials,and simple preparation methods,etc.,which are widely used in sewage treatment,seawater desalination,photothermal antitumor,and photothermal antimicrobial fields.However,the developed photothermal materials still have many disadvantages,such as poor photothermal stability,narrow optical absorption range,and high biological toxicity.Therefore,it is extremely urgent to develop photothermal conversion materials with excellent photothermal stability,wide spectral absorption,and good biosafety.Cobalt sulfide is a semiconductor,usually has excellent photothermal stability,is a potential solar energy capture material;In addition,due to its narrow bandgap and excellent near-infrared absorption characteristics,it can be used for tumor photoacoustic tomography（PAT）imaging,photothermal antitumor and antimicrobial.This paper constructed the cobalt sulfide based photothermal conversion material and studied its application in water evaporation,photothermal antitumor,and photothermal antimicrobial.Specific research contents are as follows:（1）Co_2.67S₄ nanoparticles,a photothermal material with low cost,high yield,and simple manufacturing process,were synthesized by solvothermal method.Polytetrafluoroethylene（PTFE）membranes have higher mechanical properties than cellulose acetate membranes（CA）,polyvinylidene fluoride membranes（PVDF）,polyethersulfone membranes（PES）,and polypropylene membranes（PP）.Co_2.67S₄nanoparticles were deposited on the surface of PTFE film,and a new type of cobalt sulfide based photothermal film(Co_2.67S₄@PTFE)was successfully prepared.Under sunlight irradiation,efficient solar energy-driven water evaporation and photothermal antimicrobial activity could be achieved.In addition,after hydrophobic treatment,the contact angle of Co_2.67S₄@PTFE film changed from 0°to 133°and showed excellent durability.Under two solar power densities,the photothermal conversion efficiency of Co_2.67S₄@PTFE film is up to 82%.The antibacterial mechanism of Co_2.67S₄@PTFE membrane was studied.It was found that the antibacterial mechanism was mainly caused by the damage of bacterial cell walls caused by heat effect.（2）Developed the stoichiometric Co_2.19S₄ nanodots（NDs）with superior photothermal conversion efficiency under near-infrared light irradiation（?=52%）,which can be used for tumor photothermal therapy（PTT）and photoacoustic imaging（PA）.In addition,Co_2.19S₄ NDs can be rapidly degraded into cobalt ions(Co²⁺),and sulfur ions(S^2-),and the Co²⁺generated by its degradation can catalyze the decomposition of endogenous hydrogen peroxide in tumor cells to produce highly toxic hydroxyl radical（·OH）,thus realizing tumor chemodynamic therapy（CDT）.At the same time,the S^2-produced by its degradation can capture copper ions(Cu²⁺)in the tumor microenvironment（TME）to realize starvation therapy of tumors.Cu²⁺-based starvation therapy is independent of tumor oxygen content and can enhance PTT and CDT.The mechanism of starvation therapy based on Cu²⁺was explored by western blotting,and the results showed that blocking Cu²⁺absorption by tumor cells could inhibit the BRAF/MEK/ERK signaling pathway,thus inhibiting the growth and proliferation of tumors.Co_2.19S₄ NDs serve as a multifunctional diagnosis and treatment platform to realize the photoacoustic/photothermal imaging of breast tumors and starvation therapy enhanced PTT and CDT.（3）Sodium alginate hydrogel（SAHG）was combined with photothermal conversion material Co_2.19S₄ ND to obtain Co_2.19S₄@SAHG composite.The results of the scanning electron microscope（SEM）show that the SAHG surface is a typical porous structure,not only has excellent biocompatibility but has a higher viscosity.SAHG can attach to the bacteria from the wound,and with the aid of Co_2.19S₄ NDs of hyperthermia can kill many pathogenic bacteria precisely and effectively under the NIR irradiation,thus avoiding the wound inflammation effectively.As a new wound dressing,SAHG can create a closed environment for the wound,thus preventing the threat of foreign bacteria and speeding up the wound healing.Co_2.19S₄@SAHG has been found to have an excellent antibacterial effect and promote wound healing through in vitro and in vivo antibacterial experiments.