André Decroly

Electrical resistance of copper phthalocyanine thin films as influenced by substrates, electrodes and physical features of the films

The influence of several features upon the electrical resistance of gas-sensitive copper phthalocyanine (CuPc) thin films has been investigated. The main factors studied concern the substrate nature (Al2O3 or Si/SiO2), electrode layout, film thickness and deposition rate. Subsequent annealing round 200°C may induce more or less deep structural changes subject to the type of substrate. Molecular deterioration may also occur by way of electrochemical processes under some conditions. The effect of humidity on the electricla resistance also appears to be substrate dependent.

A Formaldehyde Sensor Based on Molecularly-Imprinted Polymer on a TiO2 Nanotube Array

Today, significant attention has been brought to the development of sensitive, specific, cheap, and reliable sensors for real-time monitoring. Molecular imprinting technology is a versatile and promising technology for practical applications in many areas, particularly chemical sensors. Here, we present a chemical sensor for detecting formaldehyde, a toxic common indoor pollutant gas. Polypyrrole-based molecularly-imprinted polymer (PPy-based MIP) is employed as the sensing recognition layer and synthesized on a titanium dioxide nanotube array (TiO2-NTA) for increasing its surface-to-volume ratio, thereby improving the sensor performance. Our sensor selectively detects formaldehyde in the parts per million (ppm) range at room temperature. It also shows a long-term stability and small fluctuation to humidity variations. These are attributed to the thin fishnet-like structure of the PPy-based MIP on the highly-ordered and vertically-aligned TiO2-NTA.

Influence of Shaping on Pd and Pt/TiO2 Catalysts in Total Oxidation of VOCs

The catalytic performance of a commercial TiO2 was investigated towards the total oxidation of toluene. A variety of two titania supports was used in this work, shaped (pellets) and non-shaped (powder) materials. 0.5wt% Pd or Pt were impregnated onto both types of titania supports using the wet impregnation method. A decrease in the surface area of the obtained catalysts was noticed after the catalytic test, although it was still much higher than that of classical titania supports. The catalysts were tested in the total oxidation of toluene, and a major decrease in activity was noticed for Pt impregnated “shaped” supports.

Nanostructured TiO2 Layers for Photovoltaic and Gas Sensing Applications

Titanium dioxide (TiO2) has been an important material for decades, combining numerous attractive properties in terms of economy (low price, large availability) or ecology (nontoxic), as well as broad physical and chemical possibilities. In the last few years, the development of nanotechnologies offered new opportunities, not only in an academic perspective but also with a view to many applications with particular reference to the environment. This chapter focuses on the many ways that allow to tailor and organize TiO2 crystallites at the nanometre scale to make the most of this amazing material in the field of photovoltaics and gas sensing.