Carbon monoxide detection at low temperatures by semiconductor sensor with nanostructured Au-doped CoOOH films

A series of cobalt oxyhydroxide (CoOOH) nano-films (250-450 nm thick) containing a small percentage of Au by mass were prepared from the component oxides through special precipitation and were sintered on the sensor substrate between Pt electrodes at 300 degrees C for 2 h. The sensor response to CO and other combustion by-product pollutants typical for early stages of fire, defined as R-g/R-a, where R-g and R-a denote the sensor electrical resistance in the sample gas and in air, respectively, was strongly promoted by addition of a small amount of Au to the CoOOH nanostructures. The results revealed that the sensors attached with Au-doped CoOOH sensing electrode (SE) have good sensitivity to CO in the temperature range of 60-110 degrees C with the maximum CO response near 80 degrees C. Cross-sensitivity investigation of these sensors to various gases has shown that the sensitivity of the nanostructured Au-loaded CoOOH-SE to CO is the highest among other gases. As the amount of Au loaded increased up to 0.5%, the device was found to be more sensitive to CO, whilst the addition of 1 mass% Au substantially degraded the sensing properties of the device. The promoting effects of Au were discussed based on the behaviour of electrical resistance of the Au-loaded sensors. The results of this work may be applicable to further development of carbon monoxide sensors for fire detection at its earlier stages. (C) 2007 Elsevier B.V. All rights reserved.