Pristine, Au and Cu Decorated Nanoporous NiO Films for Selective CO and NO2 Gas Sensing

We report on a one-step, on-chip fabrication process of high-quality nanoporous p-type NiO thin films for gas sensing application. Highly nanoporous and polycrystalline NiO thin films were fabricated and deposited onto alumina substrates employing advanced gas deposition (AGD) technique. AGD-fabricated NiO films were further decorated with gold (AuNP) and copper (CuNP) nanoparticles, respectively. The nano-sensors array thus fabricated were integrated into a purpose-built hybrid senor unit that allows for in-situ conditioning and gas sensing measurement of volatile gases. The results revealed that the relative sensor responses of pure NiO towards CO gas exposures (reducing gas), were higher than the corresponding NP decorated NiO films. In contrast, AuNP decorated NiO sensors exhibited relatively higher sensor response towards oxidizing gases, NO 2 , than CuNP decorated and pure NiO based nano-sensors. It is noted that the relative sensor response changes are mainly governed by the high porosity of the as-fabricated NiO films and the corresponding grain-grain Schottky barriers. Limits of detection (LOD) was estimated to be 1.5 ppm for CO and 400 ppb for NO 2 for pure and AuNP decorated NiO based sensors, respectively. The results are promising for further development of nanoporous p-type metal oxide sensors for specific volatile biomarkers detection, for example, in exhaled breath analysis for disease diagnosis.