Optical detection probes and sensors for micro-/nano-plastics

Plastics and other polymer-based compounds are inevitable in our day-to-day life starting from packaging to consumer goods. Awareness about recycling plastics is all known; however, it is not sufficient to contain their negative effects on the environment and health. Disintegration products of plastic called micro- and nano-plastics (M/NPs) are increasingly found in food and environmental samples, which are considered to be an invisible threat with greater impact. Yet, there are no comprehensive regulations to monitor the M/NPs in food and water samples. Considering their harmful effects, there is a need for appropriate detection techniques to effectively identify and quantify the M/NPs in food and environment. Conventional techniques such as the Fourier transform infrared spectroscopy, Raman spectroscopy and scanning electron microscopy are expensive, require lab and labor, and are not suitable for on-field real-time monitoring. Optical detection techniques using various probes and sensors have been extensively used in the fields of bioimaging, biosensing, molecular fingerprinting etc. Recent research suggests that these probes and sensors are effective in detecting and quantifying the M/NPs. In this regard, the distinctive features of visual, colorimetric and plasmonic detection techniques have proved their high-end applicability. Most of these detectors are based on the principles of fluorescence, localized surface plasmon resonance, colorimetry, surface-enhanced Raman spectroscopy and speckle pattern analysis. This review discusses the recent advancements in the field of optical detection for M/NPs, summarizing its advantages, salient features, drawbacks, and ideas for future research.