Humidity-Enhanced Effects of Sputtered Au Nanoparticleson the Ethanol Sensing Performance of Thermally Evaporated ZnO Nanowires
Year: 2026
Authors: Singkammo S., Wisitsoraat A., Sberveglieri G., Ponzoni A., Zappa D., Comini E., Liewhiran C., Punginsang M.
Autors Affiliation: Synchrotron Light Res Inst, Nakhon Ratchasima 30000, Thailand; Natl Sci & Technol Dev Agcy NSTDA, Natl Nanotechnol Ctr NANOTEC, Pathum Thani 12120, Thailand; Univ Brescia, Dept Informat Engn DII, SENSOR Lab, I-25123 Brescia, Italy; Univ Brescia, Natl Res Council CNR INO, Natl Inst Opt, I-25123 Brescia, Italy; Chiang Mai Univ, Fac Sci, Dept Phys & Mat Sci, Chiang Mai 50200, Thailand; Chiang Mai Univ, Off Res Adm, Chiang Mai 50200, Thailand.
Abstract: Mitigating the adverse effects of humidity on the sensing performance of one-dimensional (1D) metal oxide semiconductors has been a key challenge in gas sensor development. This study investigated the humidity-enhanced effect of gold (Au) nanoparticles on the ethanol response of 1D ZnO nanostructures. ZnO nanowires were grown using a thermal evaporation-condensation method with Au-catalyzed growth kinetics for the fabrication of conductometric chemical sensors. Au nanoparticles were then additionally decorated on ZnO nanostructures by sputtering with varying times from 2 to 10 s. Structural examinations demonstrated Au nanoparticles with diverse diameters (10-70 nm) widely distributed on ZnO nanowires exhibiting lengths of 0.1-1 mu m and diameters of 10-30 nm. All fabricated sensors were systematically evaluated toward NO2, NH3, C3H6O, CO, and C2H5OH at 250-400 degrees C under dry and humid conditions. ZnO nanowires functionalized with Au for 5 s were found to exhibit the highest response of 93.75 to 70 ppm of C2H5OH, which was significantly greater than that of the pristine ZnO nanowire sensor (1.86) at 50% relative humidity (RH) and the optimum sensing temperature of 350 degrees C. Interestingly, the optimally Au-decorated ZnO nanowire sensor showed humidity-enhanced behaviors with significantly boosted ethanol responses at 50% RH. In addition, the optimal sensor displayed a low theoretical limit of detections (3.7 ppb) and high C2H5OH selectivity against interfering gases, including NO2, NH3, C3H6O, and CO. The observed ethanol response improvement and humidity-enhanced effect might be ascribed to the attributes of ohmic metal-semiconductor junctions formed at Au-ZnO interfaces and the capabilities of very fine sputtered Au nanoparticles to enhance oxygen chemisorption and suppress the formation of surface hydroxyl and hydronium species on ZnO nanowires. According to the results, Au-decorated ZnO nanowires fabricated by evaporation-condensation and sputtering could be potential candidates for use as practical C2H5OH sensors.
Journal/Review: ACS OMEGA
More Information: The authors gratefully acknowledge the financial support provided by the Erasmus Mundus LEADER: Links in Europe and Asia for engineering education, Enterprise and Research scholarship 2016/2017, and partial support from Chiang Mai University through the Office of Research Administration under the CMU Proactive Researcher, Chiang Mai University program [grant number 847/2566 and 788/2567]. Additionally, this project is funded by the Mid-Career Research Grant 2026 (N42A690459) from the National Research Council of Thailand (NRCT) and Faculty of Science, Chiang Mai University. Special thanks are extended to the Department of Physics and Materials Science, Faculty of Science, Chiang Mai University; the National Electronics and Computer Technology Center (NECTEC), Pathumthani, Thailand; and the Sensor Lab, Department of Information Engineering, University of Brescia, Italy, for their assistance with material preparation and access to sensor fabrication facilities.KeyWords: Sensor; Surface; Heterostructures; Nanostructures; Mechanisms; Alcohol; Growth; Vapor; VocsDOI: 10.1021/acsomega.6c04802
