High Performance Acoustic Wave Nitrogen Dioxide Sensor with Ultraviolet Activated 3D Porous Architecture of Ag-Decorated Reduced Graphene Oxide and Polypyrrole Aerogel

Abstract

Surface acoustic wave (SAW) devices have been widely explored for real-time monitoring of toxic and irritant chemical gases such as nitrogen oxide (NO 2 ), but they often have issues such as a complicated process of the sensing layer, low sensitivity, long response time, irreversibility, and/or requirement of high temperatures to enhance sensitivity. Herein, we report a sensing material design for room-temperature NO 2 detection based on a 3D porous architecture of Ag-decorated reduced graphene oxide-polypyrrole hybrid aerogels (rGO-PPy/Ag) and apply UV activation as an effective strategy to further enhance the NO 2 sensing performance. The rGO-PPy/Ag-based SAW sensor with the UV activation exhibits high sensitivity (127.68 Hz/ppm), fast response/recovery time (36.7 s/58.5 s), excellent reproducibility and selectivity, and fast recoverability. Its enhancement mechanisms for highly sensitive and selective detection of NO 2 are based on a 3D porous architecture, Ag-decorated rGO-PPy, p-p heterojunction in rGO-PPy/Ag, and UV photogenerated carriers generated in the sensing layer. The scientific findings of this work will provide the guidance for future exploration of next-generation acoustic-wave-based gas sensors.

Recent Progress on Nanomaterials for NO2 Surface Acoustic Wave Sensors

“…The choice of techniques and equipment used for the characterization of the SAW-based sensors largely depends on the type of features to be analyzed. The Vector Network Analyser (VNA) is one of the most commonly used measuring equipment [13,31,37,62,86,87,90,[92][93][94] due to its advantages: extremely wide bandwidth, excellent frequency stability, outstanding accuracy of amplitude and phase measurements. The VNA measures complex parameters of single port devices, i.e., the reflection coefficients, or full scattering matrix [S] of two-port transmission type circuits.…”

“…As a gas detection mechanism, CP encounters an alteration in their electrical conductivity when they are exposed to NO 2 . The most widely used CP in the development of NO 2 sensors are polyaniline (PANI) [11], poly(3,4-ethylenedioxythiophene) (PEDOT) [31], and polypyrrole (PPy) [37].…”

“…Moreover, the combination of rGO-PPy was reported to be able to form aerogels [43], at room temperature. For this reason, GO was mixed with pyrrole to form a porous aerogel PPy-rGO, that was further functionalized with Ag nanoparticles (NPs) (Figure 2b) to increase the reversibility and room-temperature performances of the SAW device [37]. The water-based GO dispersion was mixed, under stirring, in heated media, with the monomer pyrrole (Py) to form a porous hydrogel.…”

“…Usually, the inner diameter of SWCNTs is between a few nm and a few tens of nm. Reprinted with permission from [37]. Copyright 2021 American Chemical Society.…”

“…In 2021, a new rGO-PPy/Ag-based SAW sensor with UV activation exhibiting high sensitivity, reproducibility, selectivity and fast response/recovery time was reported [37]. The NO 2 sensor was fabricated on Y-cut 128 • lithium niobate (LiNbO 3 ) piezoelectric substrate.…”