Visible/Near Infrared Light Regulation Inspired By Biomimetic Micro-Nanostructure

With the increasing of greenhouse effect,global warming is one of inevitable environmental problems.But still cooling in the life or industrial basic rely on active cooling way such as air conditioning which consuming large amounts of energy.And fossil fuels still are the main way to produce power at the same time,growing the energy shortage and environmental issues.Radiative cooling and photocatalysis are the best choices to solve the cooling and energy problems respectively.However,at present,the cooling effect of daytime radiative cooling is not enough,and there are many restrictions and complex synthesis problems.Photocatalysis also faces the problem of low efficiency,which needs to be solved urgently.Both of them involve the interaction between materials and light.In the nature,all kinds of organisms have evolved for hundreds of millions of years on the earth,and most of them have formed structure that can adapt to the environment.Therefore,by following the nature and selecting appropriate biological structures,the regulation of light by materials can be improved.This study used cicada?Platypleura kaempferi?surface hairs and diatom?Coscinodiscus sp?as bionic object.Through the finite difference time domain FDTD optical simulation software to study the microstructure and the influence of the interaction mechanism between light and structure.The results reveal the cicadas hairs structure enhancing the visible light reflection and the hierarchical porous shell of diatom enhancing visible light absorption,and further optimize the structure.With micro-nano fabrication means such as electric beam lithography,ultraviolet lithography,nano-imprinting,we synthesized the optimized structure.Various characterization methods including absorption spectra,visible near-infrared reflectance spectra,photocatalytic carbon dioxide reduction test,and actual cooling test were used to verify the effect of cicada hairs on the body surface and the microstructure of the hierarchical porous diatom shell.The optimization of the preparation of biomimetic cicada surface hairs structure materials in the daytime has a 7?cooling below the environment temperature.On the one hand,due to enhanced visible near infrared reflection structure,at the same time,using aluminium oxide composite silica makes materials infrared absorption rate reaches over90%in the atmospheric window band?8-13?m?,which effectively enhance the radiation cooling performance of materials.With the structure and material,under the function of the system can effectively achieve the daytime cooling.The optimized diatom structure was prepared,and the yield of CO and CH₄increased 2.8 times and 2.3 times respectively in the photocatalytic CO₂reduction performance of the artificial diatom structure compared with the powdery sample under UV irradiation.The synthetic processing method can also be applied to other common photocatalytic materials.This study provides an idea and method for the construction of fine bionic structure.