Biodegradable leaf substrate with plasmonic silver nanoflowers for disposable sensitive SERS detection of cationic dyes

Abstract The extensive use of various disposable detection substrates has led to significant environmental pollution due to their non-biodegradable nature. There is an urgent need to develop eco-friendly, biodegradable alternatives to significantly reduce waste accumulation while maintaining analytical detection performance. In this study, we present a biodegradable and sensitive surface enhanced Raman spectroscopy (SERS) substrate by depositing plasmonic silver nanoflowers (Ag NFs) on the naturally dried leaf substrate. The leaves from Psychotria rubra posses the natural topography with the epicuticular wax texture patterns, which favor the aggregation of Ag NFs for effective electromagnetic hotspot formation at the expense of uniformity. The densely distributed petals in the Ag NFs provide increased light collection and form numerous electromagnetic hotspots in the nanoscale gaps between petals for effective Raman signal enhancement. The SERS substrate consisting of Ag NFs on the Psychotria rubra leaf (AgNFs@PRL) demonstrates the sensitive detection of cationic dye methylene blue (MB), which achieves an enhancement factor of 3.45 × 10 6 and a limit of detection of 1.14 × 10 −9 M, which is superior compared to most of the reported SERS substrates for MB detection. The practical applicability of the AgNFs@PRL SERS substrate is examined by detecting MB in the fish feed solution and the pond water with the recovery rates from 79.6 % to 113.3 %. These results underscore its practical potential in environmental monitoring and pave the way for the development of cost-effective, disposable, eco-friendly SERS sensors.