Sustainable one-step synthesis of rare-earth-doped carbon quantum dots from agro-industrial and electronic waste precursors

Wojtaszek, Konrad and Michałek, Tomasz and Skibińska, Katarzyna and Pach, Adrianna and Pitala, Krzysztof and Mech, Krzysztof and Aghajani, Hossain and Csapó, Edit and Socha, Robert P. and Wojnicki, Marek (2026) Sustainable one-step synthesis of rare-earth-doped carbon quantum dots from agro-industrial and electronic waste precursors. CHEMICAL ENGINEERING JOURNAL, 542. No. 177824. ISSN 1385-8947

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Abstract

The key scientific question addressed in this study is whether an agro-industrial biomass precursor and a real electronic-waste-derived rare-earth source can be coupled in a single hydrothermal process to produce carbon quantum dots (CQDs) with preserved carbon-core structure and tunable optical/magnetic properties. A one-step, waste-based hydrothermal synthesis of CQDs directly from cherry-seed biomass and spent fluorescent-lamp phosphor powder is reported, achieving in situ modification with rare-earth elements (REEs). The method simultaneously enables carbonization, nanoparticle formation, and REE coordination without multi-stage post-functionalization Structural and morphological characterization by HR-TEM reveals small graphitic domains (∼2–4 nm) preserved upon REE modification. XPS and EDX provide evidence for surface-associated REE species, particularly Dy- and Ho-containing environments, coordinated to oxygen- and nitrogen-containing functional groups. Carbon K-edge XAS analysis indicates that the CQDs preserve a stable sp2-dominated carbon framework, with structural features governed primarily by surface-localized oxygen-containing functional groups. FT-IR and UV–Vis spectroscopy indicate changes in the surface ligand environment and the emergence of subtle metal-related electronic states. Photoluminescence studies demonstrate tunable emission: undoped CQDs blue-shift upon dialysis (λₑₘ ≈ 440 nm), whereas REE-doped show red-shifted emission (λₑₘ ≈ 500 nm) and enhanced radiative pathways via metal-ligand charge transfer. Magnetic measurements reveal a three-fold increase in paramagnetic responsiveness in REE-doped CQDs compared to undoped counterparts. These findings establish a sustainable, facile route to multifunctional CQDs with combined optical and magnetic properties, highlighting their potential relevance for future imaging-related applications, provided that cytotoxicity, colloidal stability in biological media, and REE ion-leakage are systematically evaluated.

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