185: In-Situ Synthesis of Au@Ag Nanoparticles on Bacterial Cellulose: A SERS-Based Sensor for Micro- and Nanoplastic Detection

Introduction

The contamination of food and water systems by micro- and nanoplastics (MNPs) has become a critical environmental and public health concern. Research indicates MNPs in 94% of bottled water and tap water, with concentrations with ranging 1 to 5 particles per liter, raising serious questions about their infiltration into human and aquatic ecosystems. To meet the need for precise detection tools, this study introduces a bacterial cellulose (BC)-based sensor coupled with gold-silver core–shell nanoparticles. These nanoparticles significantly amplify detection signals, offering a robust platform for identifying MNPs using surface-enhanced Raman spectroscopy (SERS).

Methods

The BC-based sensor was fabricated via a two-step in-situ synthesis process. First, BC sheets were immersed in an aqueous gold solution to embed gold nanoparticles (AuNPs) within the BC matrix. Subsequently, the AuNP-loaded BC was immersed in a silver solution, forming Au@Ag core–shell structures. This configuration significantly enhances the Raman scattering effect through localized surface plasmon resonance (LSPR), resulting in amplified spectral signals for MNPs detection. The functionalized sensor was tested with polyethylene (PE) and polystyrene (PS) particles, both in micro and nano-size in water by identifying their characteristic spectral peaks using SERS.

Results

The BC-based SERS sensor achieved high sensitivity in detecting PE particles (1 µm and 65 nm) across concentrations ranging from 40 to 1000 ppm, with a minimum detection limit of 50 ppm. Similarly, it effectively detected PS particles (1 µm and 50 nm), with a concentration range of 1 to 100 ppm and a lower detection limit of 4 ppm. The SERS enhancement produced distinct spectral peaks for both plastic types, enabling clear differentiation from the BC substrate. Compared to conventional methods, the SERS sensor demonstrated superior sensitivity, which can be attributed to Au@Ag nanoparticles' ability to amplify Raman signals, particularly at low MNP concentrations.

Significance

This study developed a sustainable and highly sensitive BC-based SERS sensor, enhanced with core-shell nanoparticles, for detecting MNPs in water. The sensor achieved lower detection limits for MNP particles compared to previous methods, leveraging the enhanced sensitivity of SERS. The incorporation of biodegradable and renewable BC makes the sensor an eco-friendly solution for addressing plastic pollution.

Authors: Seyedehalaleh Kousheh, Mengshi Lin