Chung-Chiun Liu

Solar-Light Photoamperometric and Photocatalytic Properties of Quasi-transparent TiO2 Nanoporous Thin Films

Transparent photocatalytic surfaces are of ever increasing importance for many applications on self-cleaning windows and tiles in everyday applications. Here, we report the formation and photocatalytic testing of a quasi-transparent thin and nanoporous titania films deposited on glass plates. Sputtered Ti thin films were anodized in fluoride-ion-containing neutral electrolytes to form optically semitransparent nanoporous films, which transformed to be completely transparent after thermal annealing. The nanoporous films were studied at different stages, such as before and after anodization, as well as after thermal annealing using scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV-vis and Raman spectroscopy. It was observed that anodization at 20 V of high-temperature deposited titanium films resulted in regular nanopore films with pore diameters of 30 nm. Structural investigations on the transparent nanopore arrays reveal the presence of anatase phase TiO(2) even after annealing at 500 °C, which was confirmed by XRD and Raman spectroscopy measurements. The solar-light induced photocatalytic decomposition of stearic acid and photoconductivity characteristics of these nanoporous thin films are also presented.

Smart Chemical Sensor Systems for Fire Detection and Environmental Monitoring in Spacecraft

A fire in a spacecraft or habitat supporting NASA’s exploration mission could jeopardize the system, mission, and/or crew. Further, an understanding of the environment during standard operations as well as after a fire is important for both astronaut health and for monitoring of hazardous conditions. This paper describes the status of gaseous sensors to provide early warning of fires, eliminate false alarms, and provide environmental information. These gaseous sensors are miniaturized arrays of smart chemical sensors that accurately detect fire signature gases such as carbon monoxide and carbon dioxide, as well as other species such as oxygen. The approach we take can significantly reduce the size, mass, and power consumption of sensing technology allowing more strategic placement, extended operation, and improving overall awareness of the environment. In particular, this paper describes: 1) Maturation of the core chemical sensor technology and associated smart hardware; 2) Expansion of the sensor array for species of interest such as hydrogen cyanide and hydrogen chloride; and 3) Sensor system test results for two application environments. It is concluded that smart, multiparameter, microsensor based systems can serve as multiuse technology for a range of applications including fire detection and environmental monitoring, and can complement other sensor technologies.