Identification of Trace Polystyrene Nanoplastics Down to 50 nm by the Hyphenated Method of Filtration and Surface-Enhanced Raman Spectroscopy Based on Silver Nanowire Membranes

Abstract

Nanoplastics are emerging pollutants that pose potential threats to the environment and organisms. However, in-depth research on nanoplastics has been hindered by the absence of feasible and reliable analytical methods, particularly for trace nanoplastics. Herein, we propose a hyphenated method involving membrane filtration and surface-enhanced Raman spectroscopy (SERS) to analyze trace nanoplastics in water. In this method, a bifunctional Ag nanowire membrane was employed to enrich nanoplastics and enhance their Raman spectra in situ, which omitted sample transfer and avoided losing smaller nanoplastics. Good retention rates (86.7% for 50 nm and approximately 95.0% for 100–1000 nm) and high sensitivity (down to 10–7 g/L for 50–1000 nm and up to 105 SERS enhancement factor) of standard polystyrene (PS) nanoplastics were achieved using the proposed method. PS nanoplastics with concentrations from 10–1 to 10–7 g/L and sizes ranging from 50 to 1000 nm were successfully detected by Raman mapping. Moreover, PS micro- and nanoplastics in environmental water samples collected from the seafood market were also detected at the μg/L level. Consequently, the proposed method provides more possibilities for analyzing low-concentration nanoplastics in aquatic environments with high enrichment efficiency, minimal sample loss, and high sensitivity.

Strategies and Challenges of Identifying Nanoplastics in Environment by Surface-Enhanced Raman Spectroscopy

“…The actual sample is filtered in AgNWs Membrane (AgNWs assembled to AAO filter membranes) for SERS determination, which both omits the nanoplastic transfer step and enhances the Raman signal of nanoplastics in situ. 106 Yin et al 107 designed sponge substrates loaded with Au NPs to achieve PS plastic detection in seawater, rainwater, river water, and snow water spiked samples without pretreatment (Figure 5i). Moreover, the selection of solid substrates with regular morphology for metal nanoparticle assembly is beneficial to maintain the stability and reproducibility of the substrates.…”

“…It is common practice to combine the separation capabilities of the membrane with the enhanced performance of the SERS substrate. The actual sample is filtered in AgNWs Membrane (AgNWs assembled to AAO filter membranes) for SERS determination, which both omits the nanoplastic transfer step and enhances the Raman signal of nanoplastics in situ . Yin et al designed sponge substrates loaded with Au NPs to achieve PS plastic detection in seawater, rainwater, river water, and snow water spiked samples without pretreatment (Figure i).…”

Multi-feature round silicon membrane filters enable fractionation and analysis of small micro- and nanoplastics with Raman spectroscopy and nano-FTIR

“…The same is true for lter substrates prepared by deposition of SERS-active silver nanowires on lter paper. 16 Substrates with ordered micro-and nanoscale cavities are intended to both x the particles in position and increase recorded Raman signals by formation of hot spots. 9,39 The impermeability of such structures as well as a tendency of aggregate formation between several particles smaller than the cavity were seen as problematic for our purpose.…”

“…The same is true for filter substrates prepared by deposition of SERS-active silver nanowires on filter paper. 16…”

Determination of Anthracene Derivatives in Baltic Amber Using SERS

“…Silver nanoparticles also help to perform SERS mapping on silicon wafers [ 50 ]. To detect nanoplastics, a method was proposed using a bifunctional Ag nanowire membrane [ 51 ].…”