Optical sensing of microplastics using advanced nanomaterials: a comprehensive review

Microplastic pollution has been recognized as a global environmental threat that significantly affects ecosystems, and its contamination may pose a risk to human health. Therefore, it is essential to detect microplastics both quantitatively and qualitatively. However, the accurate detection of microplastics remains challenging. This is due to their broad size distributions, irregular structures and morphologies, and diversity in chemical compositions. Consequently, there is a growing demand for rapid, sensitive, and reproducible analytical platforms capable of detecting microplastics in complex environmental and biological matrices. Recent developments in nanomaterial-enabled sensing technologies have shown significant promise for the analytical detection of microplastics. Nanomaterials, including plasmonic metal nanoparticles, carbon-based nanomaterials, and polymeric nanomaterials, with highly tunable optical, electronic, and surface-functional properties, have been widely employed for microplastic detection. In particular, fluorescence, colorimetry, surface-enhanced Raman scattering, and surface plasmon resonance have been demonstrated as promising methods for rapid screening of microplastics. The synergetic integration of nanomaterials with optical methods enables signal amplification, improves sensitivity, and may improve analysis in complex environmental matrices, although this has not yet been widely validated. This review comprehensively summarizes recent developments in nanomaterial-assisted optical sensing platforms for micro- and nanoplastic detection, focusing on sensing principles, analytical capabilities, practical applications, and future directions.