Structural Design And Properties Of Silk Fibroin-based Photothermal Aerogels

Silk fibroin（SF）contains lots of polar groups,and the aerogel processed from SF has the characteristics of low density,high porosity,and high specific surface area,which can be used as a good thermal insulation material.As an important transition metal sulfide,copper sulfide nanocrystals（Cu S NPs）have excellent photothermal properties.According to this feature,Cu S NPs with a photothermal conversion effect can be combined with SF-based aerogels to prepare composites with excellent photothermal properties.In the present work,the factors affecting the thermal insulating performance of SF aerogels were explored;SF/Cu S NPs composite aerogels with photothermal effect were prepared using SF macromolecules as the growth template and stabilizer of Cu S NPs.Meanwhile,the application effect in rapid sterilization and atmospheric water harvesting was explored.More details on specific research work and the obtained results are listed as follows:Firstly,the effects of concentration of SF solution and polyethylene glycol（PEG）on the thermal insulation and mechanical properties of SF-based aerogels were investigated,laying the foundation for the construction of SF-based aerogels with excellent performance.Secondly,the Cu S NPs solution was prepared using SF macromolecules as growth template and stabilizer,and the photothermal SF-based aerogel（Cu S@SF-PEG）was prepared by freeze-drying method;subsequently,the photothermal conversion ability of the composite aerogel was evaluated using infrared thermal imager and online temperature detector,and its sterilization ability was also evaluated.Finally,a hydrophobic polydimethylsiloxane（PDMS）film was coated on the surface of Cu S@SF-PEG aerogel,and after that the bactericidal ability and the absorbing ability of viscous oily liquids of the hydrophobic aerogel（Cu S@SF-PEG/PDMS）under light irradiation was explored.The research results show that the thickness of the aerogel affects its thermal insulating performance,and the aerogel prepared at the concentration of 40 g/L SF has a better thermal insulating effect and mechanical properties;PEG can improve not only the resilience and flexibility of SF-based aerogels but also has less effect on the thermal insulation properties of silk fibroin-based aerogels;SF aerogels containing Cu SNPs have excellent photothermal conversion ability,which can induce a rapid heating effect in a closed environment and at the same time have rapid sterilization function（e.g.,the antibacterial rate of E-coli under light irradiation is more than 90%）.Besides,the Cu S@SF-PEG/PDMS aerogel also showed good photothermal oily liquid adsorption and separation.In the study,the effect of reaction temperature on the photothermal performance of Cu S NPs was also investigated,and after that the hygroscopic material CMCS-Ca²⁺layer was coated on the surface of the SF-based aerogel with an enhanced photothermal effect.At the same time,the hygroscopicity and the dehumidification induced by light irradiation of the composite aerogel were investigated.The results show that the photothermal aerogel prepared at 60℃has a better photothermal conversion effect,and the optimal concentration for the reaction between CMCS and Ca²⁺was 12 g/g and 1.13 mol/L,respectively.It was found that the composite hygroscopic aerogel exhibited a good bactericidal effect and satisfactory water absorption（water absorption of 1.35 g/g under 90%RH）,which has potential application in the field of atmospheric water harvesting.The SF-based photothermal aerogel described in this study provides a new way for the functionalized preparation and practical application of SF-based composites.