Waste to wealth translation of e-waste to plasmonic nanostructures for surface-enhanced Raman scattering

Here we report, for the first time, a simple one-step recycling of discharged batteries, a major constituent of electronic waste (e-waste), into value-added fluorescent nanomaterials-carbon quantum dots (CQDs). The e-waste derived CQDs (eW-CQDs) were systematically characterized for their optical properties, including absorption, photoluminescence, quantum yield, and emission lifetime. The morphology of these nanomaterials was determined by high-resolution transmission electron microscopy, selected area electron diffraction, and X-ray diffraction, whereas Raman spectroscopy was used to confirm their carbonaceous architecture. To broaden the range of applications, the eW-CQDs were employed in the synthesis of plasmonic nanostructures (eW-Au@CQDs) via a one-step chemical reduction strategy. Both eW-CQDs and eW-Au@CQDs were further tested for their suitability to be used as surface-enhanced Raman (SERS) substrates for the detection of methylene blue (MB), a model dye and Raman reporter. Our results show that while eW-CQDs are not ideal for SERS applications, eW-Au@CQDs, when deposited on a gold-modified screen-printed carbon electrode (SPE), produce strong MB SERS signals. With further optimization, these eW-Au@CQDs-modified SPEs could find applications in SERS-based sensing. This study demonstrates a new, promising, and sustainable approach of converting e-waste such as discharged batteries into value-added products with potential for a wide range of applications.