Metalloporphyrin-modified carbon nanotube layers for gas microsensors

Networked films of carbon nanotubes (CNTs) have been grown by CVD technology onto low-cost miniaturized alumina substrates. The sidewalls of the CNTs films have been modified by spray-coating with two different metalloporphyrins (MPPs) consisting of a TetraPhenylPorphyrin coordi-nated by a central metal of zinc (Zn-TPP) and manganese (Mn-TPP) for enhanced sensitivity and tailored specificity. Hazardous gases such as NO2, NH 3, H2S, SO2, and CO have been detected with various responsiveness in the range of concentration from 0.1 to 1000 ppm. The response of the chemiresistors in terms of p-type electrical conductance has been investigated as a function of the thickness of the functionalizing MPPs; and the effect of the temperature ranging from 20 to 150 °C on the sensor response has been addressed as well. A response of the CNT-sensor functionalized by 2 layers of Mn-TPP has been measured as 0.025% towards 0.5 ppm NO 2, at 150 °C