TiO₂ Films for Self‐Detection and Decontamination

Abstract

Methods that rapidly detect, characterize, quantify, and decontaminate surfaces are essential following chemical or biological incidents. Our work focused on developing a "smart" surface, one that monitors itself and the overlying atmosphere and triggers a decontamination step when surface contamination is detected. Titanium dioxide was used to coat a ceramic surface containing skeletal impregnated platinum electrodes. The electrical resistance of the surface became altered by the introduction of a contaminant into the overlying atmosphere and its chemisorption to the surface. This change in resistance in turn initiated illumination by an external ultraviolet lamp to induce photocatalytic oxidation of the sorbed contaminant. Film resistance was concentration-dependent, allowing self-decontamination to be triggered at set pollutant levels. Preliminary results suggest that advanced surfaces and films can be developed to identify contaminant type and concentration and to initiate photocatalytic decontamination to meet regulatory or safety standards.

Microfabricated Formaldehyde Gas Sensors

“…TiO 2 is one of the most commonly used photocatalysts, with anatase (E g = 3.23 eV) and rutile (E g = 3.02 eV) crystal forms commonly used for this application. It can be activated by near UV illumination (300–370 nm) as well as UV light (254 nm), and it can degrade a broad range of molecules for use in indoor air purification [48], including alkanes, ketones, alcohols, phenols, and aromatic compounds [49]. The photodegradation of formaldehyde results in carbon dioxide [50]: $\begin{array}{c}{\text{TiO}}_2\stackrel{h\nu }{true⟶}{e}^{-}+h^{+}\\ {\text{H}}_2\text{O}\to {\text{H}}^{+}+{\text{OH}}^{-}\\ h^{+}+{\text{OH}}^{-}\to {\text{OH}}^{•}\\ e^{-}+{\text{O}}_2\to {\text{O}}_2^{-}\\ \text{HCHO}+{\text{OH}}^{•}\to {\text{HCO}}^{•}+{\text{H}}_2\text{O}\\ {\text{HCO}}^{•}+{\text{OH}}^{•}\to \text{HCOOH}\\ \text{HCOOH}+2h^{+}\to {\text{CO}}_2+2{\text{H}}^{+}\end{array}$…”

Ethanol and methanol sensing characteristics of Nb‐doped TiO2 porous thin films

“…Within the past decades TiO 2 thin films have found a large number of interesting applications in catalysis 1–4, anti‐reflection interference filters 5, solar cells 6–9, rechargeable batteries 10, photo‐decomposition of environmental pollutants 11–14, biomedical application 15, capacitors 16, 17, optical waveguides 18, electrochromic applications 19, and smart windows 20. More recently, titania was found to exhibit chemoresistive properties, i.e., it was found that it can sense gases at moderate temperatures (200–400 °C) and the sensing properties have been presented in a large number of publications over the years 21–25.…”