Hierarchical Ag NPs@BNC Aerogels with Multiscale Porosity and Plasmonic Hotspots for Applications to Synergistic Microplastic Capture and SERS Sensing

The escalating prevalence of microplastics in environmental matrices necessitates the development of sensitive, sustainable detection platforms. This study presents a green-synthesized aerogel composite (Ag NPs@BNC) engineered as a multifunctional surface-enhanced Raman spectroscopy (SERS) substrate, synergizing adsorption and sensing functionalities for micro-nano plastic (MNP) detection. Bacterial nanocellulose (BNC), a renewable biopolymer, serves as a three-dimensional scaffold enabling in-situ growth of uniformly distributed silver nanoparticles (Ag NPs), while freeze-drying generates hierarchical porous structures to optimize analyte entrapment. Three distinct adsorption mechanisms were elucidated: size exclusion and surface attachment, capillary force-mediated entrapment within interconnected pores, and hydrogen bonding-assisted physical adsorption at cellulose nanofiber junctions. Adsorption kinetics followed a pseudo-second-order model (R²=0.99). The substrate demonstrated exceptional sensitivity (limit of detection: 87 mg/L) and reproducibility (RSD < 3%), validated through practical analysis of MNPs in commercial tea bags. Finite-difference time-domain (FDTD) simulations confirmed electromagnetic hotspot formation at Ag NPs-MNPs interfaces, while BNC’s three-dimensional confinement enhanced signal uniformity by localizing analytes near plasmonic sites. The synergistic integration of physical entrapment, electrostatic adhesion, and localized surface plasmon resonance (LSPR) effect enables precise identification of microplastics in complex environmental samples. This work advances eco-friendly SERS platforms for sustainable pollution monitoring, bridging material innovation with environmental stewardship.