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Sensors 2019, 19(1), 211; https://doi.org/10.3390/s19010211

Synthesis of Cu2O/CuO Nanocrystals and Their Application to H2S Sensing

1
Department of Applied Chemistry and Biochemistry, Graduate School of Science and Technology, Kumamoto University, Kumamoto 860-8555, Japan
2
College of Cross-Cultural and Multidisciplinary Studies, Kumamoto University, Kumamoto 860-8555, Japan
3
Faculty of Advanced Science and Technology, Kumamoto University, Kumamoto 860-8555, Japan
*
Author to whom correspondence should be addressed.
Received: 13 December 2018 / Revised: 28 December 2018 / Accepted: 7 January 2019 / Published: 8 January 2019
(This article belongs to the Special Issue Functional Materials for the Applications of Advanced Gas Sensors)
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Abstract

Semiconducting metal oxide nanocrystals are an important class of materials that have versatile applications because of their useful properties and high stability. Here, we developed a simple route to synthesize nanocrystals (NCs) of copper oxides such as Cu2O and CuO using a hot-soap method, and applied them to H2S sensing. Cu2O NCs were synthesized by simply heating a copper precursor in oleylamine in the presence of diol at 160 °C under an Ar flow. X-ray diffractometry (XRD), dynamic light scattering (DLS), and transmission electron microscopy (TEM) results indicated the formation of monodispersed Cu2O NCs having approximately 5 nm in crystallite size and 12 nm in colloidal size. The conversion of the Cu2O NCs to CuO NCs was undertaken by straightforward air oxidation at room temperature, as confirmed by XRD and UV-vis analyses. A thin film Cu2O NC sensor fabricated by spin coating showed responses to H2S in dilute concentrations (1–8 ppm) at 50–150 °C, but the stability was poor because of the formation of metallic Cu2S in a H2S atmosphere. We found that Pd loading improved the stability of the sensor response. The Pd-loaded Cu2O NC sensor exhibited reproducible responses to H2S at 200 °C. Based on the gas sensing mechanism, it is suggested that Pd loading facilitates the reaction of adsorbed oxygen with H2S and suppresses the irreversible formation of Cu2S. View Full-Text
Keywords: gas sensor; nanocrystal; Cu2O; CuO; H2S gas sensor; nanocrystal; Cu2O; CuO; H2S
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Mikami, K.; Kido, Y.; Akaishi, Y.; Quitain, A.; Kida, T. Synthesis of Cu2O/CuO Nanocrystals and Their Application to H2S Sensing. Sensors 2019, 19, 211.

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