Development of functional multilayer coatings for gas sensing and smart wındow applications

Official URL: https://risc01.sabanciuniv.edu/record=b2766860_(Table of contents)

Functional coatings are used in many areas, from aircraft to optoelectronic devices, energy-saving applications, and sensors. This thesis focuses on designing and developing two functional multilayer coatings. Firstly is the development of a bandpass filter which we combine with a custom-made lithium tantalate pyroelectric detector in an infrared gas detection setup to detect and determine the concentration of ethanol vapor. The constructed bandpass filter that consists of 7-layers of alternating germanium and aluminum oxide materials has a center wavelength of 3250 ± 232 nm and a peak transmittance of 84.5%. This wavelength range overlaps with the characteristic absorption mode of ethanol molecules. In the presence of ethanol vapor in the measuring setup, the pyroelectric detector induces a voltage signal change, thus demonstrating the pyroelectric effect. The measurement system can electronically detect and quantify various concentrations of alcohol (6% - 100% by volume), including alcoholic beverages like beer and wine. The second study focuses on developing a smart window that modulates visible light while reflecting broadband infrared light (2000 – 25000nm). The window is made by placing a thermoresponsive layer between a transparent heater and plexiglass. On a hot day, the thermoresponsive layer (Poly(N-isopropylacrylamide)) can change from the transparent state to the opaque state at its lower critical solution temperature (32.5 °C). Hence, blocking the heat from entering the indoor space. At night, as the temperature drops, the window’s opacity can be activated on-demand by activating the transparent heater made from thin layers of aluminum oxide and silver. Therefore, providing users with privacy protection. The window can also reflect a broad spectrum in the infrared, which is well suited for use during cold days. These multiple functionalities of the smart window provide possible solutions to the problems of space heating and cooling that contribute to the high electricity consumption globally.