Fabrication of Ag/ZnO nanowire thin films and their photocatalytic reactivities
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Fabrication of Ag/ZnO nanowire thin films and their photocatalytic reactivities Masato Takeuchi1 · Takuya Koba1 · Masaya Matsuoka1 Received: 27 July 2020 / Accepted: 7 August 2020 © Springer Nature B.V. 2020
Abstract We have successfully prepared the ZnO nanowire (nw) thin films which show different surface wettabilities to discuss the correlation between the photocatalytic reactivities and the surface morphologies. When the ZnO(seed)/glass was horizontally placed in the ZnO precursor solution, relatively short and thick ZnO hexagonal cylinders were randomly accumulated on the substrate (denoted as “h-ZnO(nw)/ glass”). The h-ZnO(nw)/glass showed high surface wettability (water contact angle: 0°) because liquid water easily went into the micrometer-sized inter-particle voids via capillary effect. In contrast, when the ZnO(seed)/glass was vertically placed in the ZnO precursor solution, relatively long and thin ZnO nanowires perpendicularly grew and aligned on the substrate (denoted as “v-ZnO(nw)/glass”). The v-ZnO(nw)/ glass showed high water-repellent property (water contact angle: 100°–143°) because of a lotus effect exhibited by the thin ZnO nanowires. The v-ZnO(nw)/glass had about twice the surface area of the h-ZnO(nw)/glass but did not show sufficiently high photocatalytic reactivity for the decomposition of methylene blue (MB) in aqueous solution because of its water-repellent property. However, the high surface area of the v-ZnO(nw)/glass was useful for the photocatalytic decomposition of acetaldehyde in gaseous phase. The deposition of Ag particles especially improved the photocatalytic reactivity of the h-ZnO(nw)/glass up to 2.8–6 times, because lots of Ag particles were deposited on the sidewalls of the ZnO hexagonal cylinders due to their high surface wettability. However, since the Ag particles were deposited only on the tips of the ZnO nanowires due to the water-repellent property of the v-ZnO(nw)/glass, the photocatalytic reactivity was only improved up to 1.6–2.4 times.
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s1116 4-020-04249-x) contains supplementary material, which is available to authorized users. * Masato Takeuchi masato‑[email protected]‑u.ac.jp 1
Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, 1‑1, Gakuen‑cho, Naka‑ku, Sakai, Osaka 599‑8531, Japan
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Graphic abstract without Ag deposition
water droplet
with Ag deposition
Reaction rate constants/min-1
0.015
0.010
0.005
0
h-ZnO(nw)/glass (WCA : 0r)
Ag particles (ave. 18.5 nm)
ZnO hexagonal cylinder
v-ZnO(nw)/glass (25 mmol/L) (WCA : 103.4r)
v-ZnO(nw)/glass (50 mmol/L) (WCA : 143.2r)
Ag particles (ave. 35.4 nm)
ZnO nanowire
ZnO nanowire
Keywords ZnO nanowire thin film · Surface wettability · Water-repellent property · Lotus effect · Ag nanoparticle · Photocatalytic reactivity
Introduction ZnO nanowire (nw) thin films have widely been reported for their use as luminescent materials
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