Double-Layered TiO₂−SiO₂ Nanostructured Films with Self-Cleaning and Antireflective Properties

Abstract

Dual function of self-cleaning and antireflection can be created in double-layered TiO2-SiO2 nanostructured films. The film were prepared by (1) layer-by-layer deposition of multilayered SiO2 nanoparticles with polydiallyldimethylammonium (PDDA) cations, (2) layer-by-layer deposition of multilayered titanate nanosheets with polications on PDDA/SiO2 multilayer films, and (3) burning out the polymer and converting titanate nanosheets into TiO2 by hearing at 500 degrees C. The as-prepared films, consisting of a porous SiO2 bottom layer and a dense TiO2 top layer, improved the transmittance of glass or quartz substrates, as demonstrated by transmission spectra collected at normal incidence. The photocatalytic properties of the films were studied by the change of the water contact angle together with the decay of the IR absorption of the hydrocarbon chain of octadecylphosphonic-acid-modified films under 2.6 mW cm-2 UV illumination. Both the antireflective and the photocatalytic properties of the films were dependent on the number of PDDA/nanosheet bilayers deposited. however, excellent surface wettability of the films for water was obtained, independent of the preparation conditions. The experimental findings are discussed in terms of the special structure of the double-layered nanostructured film.

Interfacial band alignment and structural properties of nanoscale TiO2 thin films for integration with epitaxial crystallographic oriented germanium

“…21 anti-reflection coating, 21 white pigment in paints, 22 gas sensors, 23 etc. Recently, the application base for TiO 2 has been growing rapidly, in particular due to its promising properties at nanoscale.…”

Self-Cleaning Antireflective Optical Coatings

“…In several previous studies, the amount of TiO 2 that could be added to the ARC was small because of the resulting increase in refractive index. 7,29,31,33 To improve the photocatalytic efficiency, we make use of the exceptionally low refractive index of our ARCs to maximize titania loading. Crystalline 4 nm sized TiO 2 nanocrystals were synthesized using a nonhydrolytic sol−gel chemistry route 36,37 and added to the sol solution.…”

A Mini Review: Antireflective Coatings Processing Techniques, Applications and Future Perspective

“…To fulfil the destructive interference, the thickness of each layer in a bilayer coating is equivalent to half (λ/2)or quarter (λ/4) of the wavelength. Different research groups fabricate bilayer AR coatings following this principle, SiN and SiO 2 [34] deposited by Plasma Enhanced Chemical Vapour Deposition (PECVD) for solar cell applications, MgF/SiNx for crystalline solar cells [35] , SiO 2 /TiO 2 self-cleaning AR coatings are few examples of bilayer coatings [36][37][38] .…”