Research On Morphology Genetic Antireflective Structure Materials Inspired From Cicada Wings

Antireflective structures（ARSs）can dramatically suppress light reflection and thus enhances light absorption and transmission.The ever-growing demand for optical devices such as solar cells,optical displays,and optical detections has led research for broadband and omnidirectional antireflection structures.However,commercial antireflection structures fail to meet this expectation,because they are either limited to a narrow wavelength band or to a certain incident angles.Bio-inspired optical nanostructures,which survive million years of revolution can bring enlightenment for the design of state-of-art antireflective structures.Inspired from nature,biomimetic template synthesis is one of the most efficient way to replicate the natural function of the biotemplate.Since,nature has created a considerable amount of extraordinary structures with given functions.Cicada wing with two-dimensional nanostructured surface is one of the most useful existing biotemplate in nature.The cicada wings with ordered nano-nipple arrays structure were found to be suitable to fabricate the functional materials with nanostructure for antireflection properties over a wide range of wavelength.In this study,the optical functional materials were fabricated with ARSs by using cicada wings as a biotemplate.The antireflection properties at different angles of incidence for the titanium dioxide（TiO₂）and silicon dioxide（SiO₂）with ARSs were researched,respectively.In addition,the multifunctional properties of the optical functional materials were also investigated in this study.Moreover,the metal-semiconductor（Ag-TiO₂）with negative nano-holes structure was fabricated and the enhanced absorption of visible light and photocatalytic degradation property were discussed.The main results are as follows:1.The morphology genetic TiO₂ with ARSs was precisely fabricated using a simple,inexpensive,and highly effective sol-gel process followed by subsequent calcination.It was confirmed that the fabricated morphology genetic TiO₂ not only effectively inherited the ARS but also exhibited high-performance angle dependent antireflective properties ranging from normal to 45^o.Reflectance spectra demonstrated that the reflectivity of the morphology genetic TiO₂ with ARSs gradually changed from 1.4%to 7.8%with the increasing incidence angle over a large visible wavelength range.This angle dependent antireflective property is attributed to an optimized gradient refractive index between air and TiO₂ via ARSs on the surface.2.The multifunctional properties of morphology genetic SiO₂ with ARSs was investigated.The replica of SiO₂ was directly achieved from a cicada template at high calcination.The morphology genetic SiO₂ not only inherited the ARS effectively but also exhibited the excellent angle dependent antireflective properties over a wide range of incident angles（10^o-60^o）.The change in reflectance spectra（visible wavelength）of morphology genetic SiO₂ was observed from 0.3%to 3.3%with the increasing incident angles.The smooth surface of the SiO₂ crystal without nanostructures showed a high reflection of 9.2%compared to the SiO₂ with ARS.These excellent antireflective properties of SiO₂ can be attributed to the nanoscale structures which introduce a gradient in the refractive index between air and the material surface via ARS.In the meantime,morphology genetic SiO₂demonstrates high hydrophilic properties due to the existence of nanostructures on its surface.3.The negative replica of morphology genetic TiO₂ with nano-holes structure has been effectively fabricated directly from nano-nipple arrays structure of cicada wings.The nano-holes array structure was well maintained after calcination in air at 500°C.The Ag nanoparticles（10 nm-25 nm）were homogeneously decorated on the surface and to the side wall of nano-holes structure.It was observed that the morphology genetic Ag-TiO₂ showed remarkable photocatalytic activity by degradation of methyl blue（MB）under UV-vis light irradiation.The morphology genetic Ag-TiO₂ with nano-holes structure showed superior photocatalytic activity compared to the pure TiO₂ replica and commercial Degussa P25.This high-performance photocatalytic activity of the morphology genetic Ag-TiO₂ may be attributed to the nano-holes structure,localized surface plasmon resonance（LSPR）property of the Ag nanoparticles,and enhanced electron-hole separation.Moreover,the morphology genetic Ag-TiO₂ showed more absorption capability in the visible wavelength range.In general,the angle dependent antireflection properties of different optical materials were studied inspired from cicada wings.It was found that these optical properties were due to the ARSs on the surface of cicada wing.Moreover,this work provides a new insight of novel materials with nano-holes structure which can be used for the photo-degradation purpose.These conclusions provide new ideas that can be used to design such a structure which may lead to a range of novel applications.