Piezoresistive Microcantilever with SAM-Modified ZnO-Nanorods@Silicon-Nanopillarsfor Room-Temperature Parts-per-Billion NO 2 Detection
2020
Organic–inorganic
hybrids are ideal for gas detection, considering
their selectivity and sensitivity to single gas species under moderate
working conditions. However, the poor surface-to-volume ratio and
low electron density of organic materials hinder their application
in high-performance resistive gas sensors. Instead herein, a gravimetric
sensor is realized on the basis of an in-plane self-actuating and
self-reading piezoresistive microcantilever-chip (PMC), which is patterned
with an (inorganic) 3D framework of ZnO nanorods on a Si-nanopillar
array (3D ZnO-NRs@Si-NPLs) and functionalized by a thin (organic)
self-assembled monolayer (SAM, (3-aminopropyl)trimethoxysilane (APTES))
for interacting with NO2. For stable adsorption/desorption
rates of NO2, this SAM-on-3D
ZnO-NRs@Si-NPL PMC (S3-PMC) was exposed to constant light
illumination by an LED (wavelength: 530 nm, intensity: 10 mW/cm2), realizing a limit of detection (LOD) of about 2 parts per
billion by volume (ppbv) for NO2 at room temperature, together
with fast response and complete recovery within times of 42.1 ±
6.6 s and 112 ± 17.4 s, respectively, to NO2 concentrations
ranging up to 1000 ppbv. Moreover, the sensor shows reliable stability
under both short- and long-time (31 days) exposure to NO2, where resonance frequency-shift deviations of merely at most ±5%
and ±9%, respectively, are observed. These unprecedented results
indicate an enormous potential of the S3-PMC for portable
gas sensor arrays in high-resolution real-time-monitoring applications.
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