Broadband coherent anti-Stokes Raman spectroscopy for small scale microplastic detection

Abstract

Microplastics contamination in water sources presents a pressing concern for environmental and public health, necessitating accurate detection and quantification methods. We investigate the application of broadband Coherent anti-Stokes Raman Spectroscopy (BCARS) as an innovative, rapid, and label-free spectroscopy method for the detection of microplastics in drinking water. Current methods for detecting microplastics, such as visual inspection, FTIR and spontaneous Raman spectroscopy, and gas chromatography, have limitations in terms of sensitivity, speed, specificity, or destructive analysis. BCARS, however, offers a non-destructive approach with the capability to identify particles smaller than a micron and to discern different types of plastics through chemical analysis. BCARS operates at a significantly faster rate than spontaneous Raman spectroscopy, reducing acquisition time from seconds to milliseconds. BCARS utilizes a dual excitation technique to simultaneously probe both the fingerprint and C-H band regions of the Raman spectrum and allows for the identification of different polymers in a sample, as demonstrated in this study with a mixture of Polystyrene and Poly(methyl methacrylate) (PMMA) micro-beads. Our results highlight the ability of B-CARS to distinguish between different types of polymers in a sample, using resonant peaks at specific wave-numbers to generate a false-color image for easy identification.