Formaldehyde, as
a carcinogenic substance, is often intentionally
used to adulterate vegetables to increase their shelf life, and the
adhesive tape used to attach labels can also leave formaldehyde on
the surface of vegetables. However, as the “gold” standard,
gas chromatography (GC) and high-performance liquid chromatography
(HPLC) are expensive for individual tests and confined to the laboratory
owing to their size and a suitable detector (low-cost, portable, fast
detection speed) to check formaldehyde contamination in vegetables
not being available. Here, we tested formaldehyde contamination in
vegetables using a low-cost and hand-held detector combined with a
screen-printed electrode (SPE) amperometric sensor and an open-sourced
potentiostat. The analyzer can detect a concentration of 100 μmol/L
formaldehyde and achieve a good linear range between 100 and 1000
μmol/L. Furthermore, the detector successfully identified formaldehyde
contamination in 53 samples of six different kinds of vegetables even
after residual formaldehyde on the surface was evaporated. Most importantly,
under the practicability-oriented idea, a cost-effective strategy
was implemented for this detector design rather than using other pricey
methods (e.g., photolithography, electron-beam evaporation, chemical
deposition), which enormously reduces the cost (under ∼USD
0.5 per test) and meets all of the requirements of ASSURED device.
We believe this cheap, portable detector could help law-enforcing
authorities, healthcare workers, and customers to screen formaldehyde
contamination easily. Also, the cost-saving strategy is appropriate
for low-income areas, where there is a lack of laboratories, funds,
and trained experts.
As one of the most promising platforms for wireless communication, radiofrequency (RF) electronics have been widely advocated for the development of sensing systems. In particular, monolayer and few-layer two-dimensional (2D) materials exhibiting extraordinary electrical properties not only can be integrated to improve the performances of RF circuits, but also to display exceptional sensing capabilities. This review provides an in-depth perspective of current trends and challenges in the application of 2D materials for RF biochemical sensing, including: i) theoretical bases to achieve different sensing schemes; ii) unique properties of 2D materials for reasoning their applications in RF sensing; iii) developments in 2D RF sensors to facilitate the practice of biochemical sensors with ever-demanding sensitivities, as well as their potential uses in meeting the requirements and challenges of biochemical sensors in the Internet-of-Things (IoT) era.
Trace hydrogen detection
plays an important role in the safety
detection of lithium-ion batteries (LIBs) due to the generation and
leakage of trace hydrogen in the early stage of LIBs damage. In this
work, an amperometric hydrogen sensor based on solid polymer electrolyte
was reported. The sandwich device structure was realized, which could
directly diffuse the gas from both sides to the three-phase interface
(gas/electrode/electrolyte) to participate in the reaction through
the optimal design of the gas diffusion path. Then, platinum nanoparticles
(Pt-NPs) were loaded on the metal foam by electroplating, and the
porous electrode was filled with solid polymer electrolyte. A sensor
with high specific surface area, high catalytic activity, and high
sensitivity was obtained. Finally, the hydrogen oxidation reaction
(HOR) mechanism of the platinum-loaded (Pt-loaded) titanium foam (Ti
foam) electrode under both anaerobic and aerobic conditions was verified,
and the properties of the sensor was evaluated. The hydrogen sensor
with a “sandwich” structure has the advantages of high
sensitivity, good stability, low detection limit and low cost, which
provides a technical solution for the safety and real-time monitoring
of LIBs.
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