Detection of Sub-Micro- and Nanoplastic Particles on Gold Nanoparticle-Based Substrates through Surface-Enhanced Raman Scattering (SERS) Spectroscopy

Abstract

Small plastic particles such as micro- (<5 mm), sub-micro- (1 µm–100 nm) and nanoplastics (<100 nm) are known to be ubiquitous within our surrounding environment. However, to date relatively few methods exist for the reliable detection of nanoplastic particles in relevant sample matrices such as foods or environmental samples. This lack of relevant data is likely a result of key limitations (e.g., resolution and/or scattering efficiency) for common analytical techniques such as Fourier transform infrared or Raman spectroscopy. This study aims to address this knowledge gap in the field through the creation of surface-enhanced Raman scattering spectroscopy substrates utilizing spherical gold nanoparticles with 14 nm and 46 nm diameters to improve the scattering signal obtained during Raman spectroscopy measurements. The substrates are then used to analyze polystyrene particles with sizes of 161 nm or 33 nm and poly(ethylene terephthalate) particles with an average size of 62 nm. Through this technique, plastic particles could be detected at concentrations as low as 10 µg/mL, and analytical enhancement factors of up to 446 were achieved.

Applications of surface‐enhanced Raman spectroscopy in environmental detection

“…SERS is advantageous for plastic detection as it is highly sensitive and non‐destructive, allows for the detection of particles down to the nanometer size, and has been shown to be capable of detecting particles in complex samples 113 . AgNPs and AuNPs are the most common SERS substrates for MPL and NPL detection 62,109,114,115 . Research on MPLs and NPLs often focuses on detection of PS particles, as these are one of the most commonly found plastics in the natural environment.…”

Latest Advances and Developments to Detection of Micro‐ and Nanoplastics Using Surface‐Enhanced Raman Spectroscopy

“…On the other hand, Caldwell et al. [ 130 ] developed a SERS method to identify PS particles with diameters of 161 and 33 nm and PET particles of 62 nm in diameter. Their method used Au NPs of two different sizes (14 and 46 nm) as plasmonic substrates.…”

“…As demonstrated in Tables 1 and 2, SERS represents a suitable alternative for the analysis and detection of both micro‐ and nanoplastics. The smallest particle size detected in the mentioned studies was of 33 nm, [ 130 ] and the largest was of 450 nm. [ 129 ] Regarding the application of this technique for the analysis of such samples, the laser wavelength that is most used is 785 nm, [ 133 ] and this could be due to the fact that this wavelength is in the near infrared region, which helps to effectively suppress fluorescence in the obtained Raman spectra.…”

Nanoplastic Labelling with Metal Probes: Analytical Strategies for Their Sensitive Detection and Quantification by ICP Mass Spectrometry

“…Besides the studies that deal with the detection of NPTs [ 10 , 11 ], methods devoted for their quantification are still lacking. The determination of mass concentration is mostly performed using mass spectrometry techniques [ 12 , 13 , 14 ], making possible the simultaneous identification and quantification of NPTs present in the samples.…”