Nicotine
is highly addictive and harmful. It is one of the main
active ingredients in tobacco and a major pollutant in environmental
tobacco smoke. Thus, it is important to detect the nicotine content
in tobacco and to monitor the nicotine content in environmental tobacco
smoke. However, until present, there still has been no effective device
for on-site determination of nicotine content in tobacco and environmental
tobacco smoke. In this work, a portable device is fabricated for sensitive
on-site evaluation of nicotine in tobacco and environmental tobacco
smoke based on surface-enhanced Raman scattering (SERS). The weight
of the entire device is less than 1 kg, and it uses a chargeable battery
to drive both the pump and the Raman spectrometer. The total analysis
time can be completed within 3–5 min. Thus, it has great potential
for on-site analysis of nicotine in tobacco and environmental tobacco
smoke.
Volatile organic compounds (VOCs) are detrimental to the environment and human health and must be eliminated before discharging. Oxidation by heterogeneous catalysts is one of the most promising approaches for the VOCs abatement. Precious metal catalysts are highly active for the catalytic oxidation of VOCs, but they are rare and their high price limits large‐scale application. Supported metal single‐atom catalysts (SACs) have a high atom efficiency and provide the possibility to circumvent such limitations. This Review summarizes recent advances in the use of metal SACs for the complete oxidation of VOCs, such as benzene, toluene, formaldehyde, and methanol, as well as aliphatic and Cl‐ and S‐containing hydrocarbons. The structures of the metal SACs used and the reaction mechanisms of the VOC oxidation are discussed. The most widely used SACs are noble metals supported on oxides, especially on reducible oxides, such as Mn2O3 and TiO2. The reactivity of most SACs is related to the activity of surface lattice oxygen of the oxides. Furthermore, several metal SACs show better reactivity and improved S and Cl resistance than the corresponding nanocatalysts, indicating that SACs have potential for application in the oxidation of VOCs. The deactivation and regeneration mechanisms of the metal SACs are also summarized. It is concluded that the application of metal SACs in catalytic oxidation of VOCs is still in its infancy. This Review aims to elucidate structure–performance relationships and to guide the design of highly efficient metal SACs for the catalytic oxidation of VOCs.
The application of surface-enhanced Raman scattering (SERS) in aqueous sample detection is normally limited by the low affinity between analytes and SERS-active nanoparticles. Furthermore, a tendency of uncontrollable aggregation of solute (nanoparticles or analytes) can cause poor reproducibility of the detected SERS signal. Herein, a ready-to-use plasmonic gel bead was developed for rapid and effective detection of aqueous samples with high sensitivity and reproducibility. The SERS gel bead is made of calcium alginate gel beads (CAGBs) that contain gold nanobipyramids (Au NBPs) and an aqueous sample, which can be prepared and detected within only 1 min. Au NBPs/CAGBs can generate an in-depth three-dimensional SERS-active gel network for trapping analytes and offering a uniform hotspot region, which produces a reproducible and uniform signal. Using rhodamine 6G as a model target, the proposed method exhibits excellent reproducibility with a relative standard deviation of 6.57% and a detection limit of 0.4 nM. Then, Au NBPs/CAGBs were applied to quantitatively detect serum uric acid in the range of 10−1000 μM and a limit of detection of 0.18 μM, and the results were strongly consistent with those of the commercial ELISA method. This work offers a low-cost and easy route for the fabrication of a versatile SERS substrate for monitoring disease-related biomarkers and point-of-care testing.
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