Tailoring the selectivity of ultralow-power heterojunction gas sensors by noble metal nanoparticle functionalization

• Published in: Nano energy 2021-10, Vol.88, p.106241, Article 106241
• Main Authors: Lupan, Oleg, Ababii, Nicolai, Santos-Carballal, David, Terasa, Maik-Ivo, Magariu, Nicolae, Zappa, Dario, Comini, Elisabetta, Pauporté, Thierry, Siebert, Leonard, Faupel, Franz, Vahl, Alexander, Hansen, Sandra, de Leeuw, Nora H., Adelung, Rainer
• Format: Article
• Language: English
• Subjects: Gas sensing; Heterojunctions; Low-energy; Nanolayered materials; Semiconductor oxides; Ultralow power
• ISSN: 2211-2855
• DOI: 10.1016/j.nanoen.2021.106241

Heterojunctions are used in solar cells and optoelectronics applications owing to their excellent electrical and structural properties. Recently, these energy-efficient systems have also been employed as sensors to distinguish between individual gases within mixtures. Through a simple and versatile functionalization approach using noble metal nanoparticles, the sensing properties of heterojunctions can be controlled at the nanoscopic scale. This work reports the nanoparticle surface functionalization of TiO2/CuO/Cu2O mixed oxide heterostructures, where the gas sensing selectivity of the material is tuned to achieve versatile sensors with ultra-low power consumption. Functionalization with Ag or AgPt-nanoclusters (5–15 nm diameter), changed the selectivity from ethanol to butanol vapour, whereas Pd-nanocluster functionalization shifts the selectivity from the alcohols to hydrogen. The fabricated sensors show excellent low power consumption below 1 nW. To gain insight into the selectivity mechanism, density functional theory (DFT) calculations have been carried out to simulate the adsorption of H2, C2H5OH and n-C4H9OH at the noble metal nanoparticle decorated ternary heterostructure interface. These calculations also show a decrease in the work function by ~2.6 eV with respect to the pristine ternary heterojunctions. This work lays the foundation for the production of a highly versatile array of sensors of ultra-low power consumption with applications for the detection of individual gases in a mixture. [Display omitted] •Noble NP functionalization and thickness control tune selectivity and sensitivity.•Ultra-low energy consumption of up to 1 nW with large gas responses of 390%.•Highly sensitive detection of H2 and VOCs vapours at low concentrations of a few ppm.•Deposition of metal nanodots reduces the work function of ternary heterojunctions.•DFT calculations elucidate the sensing mechanism of the functionalized junctions.