Microplastics are persistent pollutants that accumulate in the environment and can cause serious toxicity to mammals. At present, few technologies are able to quantitatively detect chemicals and provide morphological information simultaneously. Herein, we developed a dragonfly-wing-mimicking ZnO nanorod array decorated with AgNPs on polydimethylsiloxane (PDMS) as a surface-enhanced Raman spectroscopy (SERS) and photo-induced enhanced Raman spectroscopy (PIERS) substrate for trace analysis of microplastics. The Ag/ZnO@PDMS hybrid nanorod array endows the sensor with high sensitivity and signal repeatability (RSD ∼ 5.89%), ensuring the reliable quantitative analysis of microplastics. Importantly, when the noble metal−semiconductor substrate was preradiated with ultraviolet light, a surprising PIERS was attained, achieving an additional enhancement of 11.3-fold higher than the normal SERS signal. By combining the PIERS technology with the "coffee ring effect", the sensor successfully discerned microplastics of polyethylene (PE) and polystyrene (PS) at a trace level of 25 μg/mL even with a portable Raman device. It was capable of identifying PS microspheres in contaminated tap water, lake water, river water, and seawater with detection limits of 25, 28, 35, and 60 μg/mL, respectively. The recovery rates of PS microspheres in four water environments ranged from 94.8 to 102.4%, with the RSD ranging from 2.40 to 6.81%. Moreover, quantitative and visualized detection of microplastics was readily realized by our sensor. This portable PIERS sensor represents a significant step toward the generalizability and practicality of quantitative and visual sensing technology.

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Rapid and on-site Raman spectroscopic identification and quantification of pesticide residues have been restricted to the low instrumental sensitivity of the portable Raman instrument, no ideal platforms have been reported...

Perfluoro- and polyfluoroalkyl substances (PFAS) are widely used throughout the world and are extensively found in the environment. The detection of PFAS has become essential to ensuring environmental sustainability and human health. Herein, AuNRs were synthesized by the seed growth method and then the samples were coated with silver shells to form Au@Ag core–shell nanorods (Au@AgNRs). Au@AgNRs monolayer was prepared by oil–water self-assembly on a silicon wafer and then was constructed as a plasmonic AgNPs/Au@AgNRs sandwich structure for surface-enhanced Raman scattering (SERS) detection of PFAS. The shell thickness of Au@AgNRs was optimized and displayed a 11.9-fold SERS intensity higher than the pristine AuNRs. Moreover, the hotspots generated by the electromagnetic field coupling between the interlayer gap achieved 3.6-fold SERS signal enhancement compared to that of the Au@AgNRs monolayer. Besides, the excellent structural uniformity (RSD ∼ 8.0%) makes it ideal for quantitative SERS detection applications. More importantly, the use of the AgNPs/Au@AgNRs sandwich structure sensor enables the highly sensitive detection of model molecules (10–11 M) and quantitative detection of a wide range of fluorinated alkyl substances of perfluorooctanoic acid (PFOA), perfluorohexanoic acid (PFHxA), and potassium perfluoro­butanesulfonate (PPFBS), even with a portable Raman device. And the detection concentration can be down to 0.1 ppm for PFAS. This sensitive and quantitative SERS technique has promising prospects in the monitoring of fluorinated alkyl substance contaminations.