Citation: Zhang, B.; Zhang, S.; Xia, Y.;
Yu, P.; Xu, Y.; Dong, Y.; Wei, Q.; Wang,
J. High-Performance Room-
Temperature NO
2
Gas Sensor Based
on Au-Loaded SnO
2
Nanowires
under UV Light Activation.
Nanomaterials 2022, 12, 4062. https://
doi.org/10.3390/nano12224062
Academic Editor: Deepak Kukkar
Received: 24 October 2022
Accepted: 14 November 2022
Published: 18 November 2022
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Article
High-Performance Room-Temperature NO
2
Gas Sensor Based
on Au-Loaded SnO
2
Nanowires under UV Light Activation
Bo Zhang
1
, Shuai Zhang
1
, Yi Xia
2,
*, Pingping Yu
1
, Yin Xu
1
, Yue Dong
1
, Qufu Wei
3
and Jing Wang
4,
*
1
Engineering Research Center of IoT Technology Applications (Ministry of Education), Department of
Electronic Engineering, Institute of Advanced Technology, Jiangnan University, 1800 Lihu Avenue,
Wuxi 214122, China
2
Research Center for Analysis and Measurement, Analytic & Testing Research Center of Yunnan, Kunming
University of Science and Technology, Kunming 650093, China
3
Key Laboratory of Eco-Textiles (Ministry of Education), Jiangnan University, 1800 Lihu Avenue,
Wuxi 214122, China
4
Key Laboratory of Synthetic and Biological Colloids (Ministry of Education), School of Chemical and Material
Engineering, Jiangnan University, 1800 Lihu Avenue, Wuxi 214122, China
* Correspondence: xiayi0125@163.com (Y.X.); jingwang@jiangnan.edu.cn (J.W.)
Abstract:
Optical excitation is widely acknowledged as one of the most effective means of balancing
sensor responses and response/recovery properties at room temperature (RT, 25
◦
C). Moreover,
noble metals have been proven to be suitable as photosensitizers for optical excitation. Localized
surface plasmon resonance (LSPR) determines the liberalization of quasi-free electrons in noble metals
under light irradiation, and numerous injected electrons in semiconductors will greatly promote
the generation of chemisorbed oxygen, thus elevating the sensor response. In this study, pure
SnO
2
and Au/SnO
2
nanowires (NWs) were successfully synthesized through the electrospinning
method and validated using XRD, EDS, HRTEM, and XPS. Although a Schottky barrier led to a much
higher initial resistance of the Au/SnO
2
composite compared with pure SnO
2
at RT in the dark, the
photoinduced resistance of the Au/SnO
2
composite became lower than that of pure SnO
2
under UV
irradiation with the same intensity, which confirmed the effect of LSPR. Furthermore, when used as
sensing materials, a detailed comparison between the sensing properties of pure SnO
2
and Au/SnO
2
composite toward NO
2
in the dark and under UV irradiation highlighted the crucial role of the LSPR
effects. In particular, the response of Au/SnO
2
NWs toward 5 ppm NO
2
could reach 65 at RT under
UV irradiation, and the response/recovery time was only 82/42 s, which far exceeded those under
Au modification-only or optical excitation-only. Finally, the gas-sensing mechanism corresponding to
the change in sensor performance in each case was systematically proposed.
Keywords: Au-loaded; UV irradiation; synergistic effect; NO
2
; gas sensor
1. Introduction
NO
2
, one of the most typical and active oxidizing gases, has been thoroughly studied
as a target gas in terms of gas sensing. On the one hand, due to the wide presence, large
reserves, and great environmental harm caused by NO
2
[
1
], relevant research on sensing is
of great significance. On the other hand, the high activity and strong oxidizability make NO
2
more prone to gas-sensitive reactions, further stimulating the interests of researchers [2].
As is the case of other target gases, with the broadening of NO
2
sensing research,
the attention on gas sensitivity indicators has changed from a high response [
3
] to a low
operating temperature [
4
–
7
], to equal emphasis on these two indicators [
8
–
10
]. Nowadays,
with the increasing pursuit of low-temperature detection, the resulting low response and
lengthy response/recovery times are worrying and need prompt solutions. For NO
2
, its
superior electron-withdrawing ability makes it adsorb on the surface of sensitive materials
Nanomaterials 2022, 12, 4062. https://doi.org/10.3390/nano12224062 https://www.mdpi.com/journal/nanomaterials
