Exploring the application of the microbial pigment violacein as a sustainable probe molecule for recycled paper-based SERS substrates.

Paper and board represent 10%-39% of the total municipal solid waste generated. In order to address the European Commission (EC) recycling targets, this study aimed to develop flexible Surface-enhanced Raman Scattering (SERS) recycled-paper-based substrates tested by using a new eco-friendly and nontoxic molecule probe. This study reports for the first time the implementation of the microbial dye violacein, obtained by batch cultivation, as SERS probe, as a suitable substitutive to the most employed toxic chemical dye Rhodamine 6G (R6G). The interaction of the proposed natural probe with the metal surface after the adsorption and the presence of local electromagnetic fields were evaluated by computational approach. The SERS devices developed were decorated by applying a single-step pulsed laser deposition (PLD) decoration method and characterized using UV-Vis absorption spectroscopy. The platform showed a remarkable sensitivity, achieving a detection limit of 10 M for violacein, allowing to point out the strong potential of this natural microbial dye as a sustainable probe molecule for low-concentration analytes detection on SERS-active substrates, making them suitable for several application fields, such as environmental monitoring, food safety, cultural heritage analysis and diagnostics. This study demonstrates the feasibility of implementing eco-friendly materials in the development of chemical sensors as a sustainable innovation in environmental science by minimizing the ecological impact.