Catalytically Doped Semiconductors for Chemical Gas Sensing: Aerogel‐Like Aluminum‐Containing Zinc Oxide Materials Prepared in the Gas Phase

Abstract

Atmospheric contamination with organic compounds is undesired in industry and in society because of odor nuisance or potential toxicity. Resistive gas sensors made of semiconducting metal oxides are effective in the detection of gases even at low concentration. Major drawbacks are low selectivity and missing sensitivity toward a targeted compound. Acetaldehyde is selected due to its high relevance in chemical industry and its toxic character. Considering the similarity between gas-sensing and heterogeneous catalysis (surface reactions, activity, selectivity), it is tempting to transfer concepts. A question of importance is how doping and the resulting change in electronic properties of a metal-oxide support with semiconducting properties alters reactivity of the surfaces and the functionality in gas-sensing and in heterogeneous catalysis. A gas-phase synthesis method is employed for aerogel-like zinc oxide materials with a defi ned content of aluminum (n-doping), which were then used for the assembly of gas sensors. It is shown that only Al-doped ZnO represents an effective sensor material that is sensitive down to very low concentrations (<350 ppb). The advance in properties relates to a catalytic effect for the doped semiconductor nanomaterial.

Enhanced ethanol sensing properties of ultrathin ZnO nanosheets decorated with CuO nanoparticles

“…The enormous market demands for gas sensors in labour safety, environmental protection, medical treatment and related areas have stimulated huge interest in the development of high performance sensing materials. ZnO nanomaterials are among the most popular electrical and optical gas sensing materials, and continue to attract much attention as a result of their well-demonstrated high sensitivity (reflecting their large surface area, surface activity, and excellent electrical and luminescence properties), coupled with their low cost and simple and controllable fabrication [1][2][3][4][5][6]. A range of strategies have been applied to ZnO and ZnO-based nanomaterials in an effort to enhance the gas sensing response (sensitivity), selectivity and repeatability, and to reduce the response and recovery times, including morphology control, doping, surface modification and decoration [7][8][9][10][11][12].…”

Versatile Aerogels for Sensors

“…Therefore, these aerogel‐based gas sensors often have high sensitivity, low detection limit, and fast response and recovery rate . Moreover, the excellent selectivity and stability can be easily realized by the introducing different compounds together to get a composite aerogel due to the synergistic effect . These aerogel‐based gas sensors are shown in Table 1 .…”

“…Besides, TiO 2 can also be deposited onto the silica aerogel by the ALD, and the composite aerogel with lattice mismatch between them and smaller TiO 2 grain size was obtained, which can supply more active sites for H 2 S sensing . Polarz and co‐workers again utilized the gas‐phase synthesis method to prepare Al‐doping ZnO aerogels with a defined content of Al for the gas sensing (Figure h) . The doped Al on the surface of ZnO aerogels can act as a catalytic center undergoing surface reaction with the vapors and the performance of the resultant aerogels is related to the amount of Al (Figure i,j).…”

“…The sensing performance of ZnO, Al21ZnO, Al39ZnO, and Al64ZnO for i) ethanol and j) acetaldehyde at different analyte concentrations. Reproduced with permission . Copyright 2016, Wiley‐VCH.…”

Carbon‐Doped Metal Oxide Nanoparticles Prepared from Metal Nitrates in Supercritical CO2‐Enabled Polymer Nanoreactors

“…Nanostructured metal oxide semiconductors are utilized in a wide range of fields, including photovoltaics, photocatalysis, chemical sensing, electrodes, field effect transistors, and smart windows . In many of these applications, it is desirable that metal oxide nanoparticles (NPs) possess good conductivities and strong light absorption capabilities.…”