Green synthesis of coffee-derived carbon quantum dots integrated with an imprinted polymer probe for penicillin detection in river water

Abstract A green and facile strategy was developed for the synthesis of carbon quantum dots (CQDs) derived from coffee extract and their integration with a molecularly imprinted polymer (MIP) for selective fluorescence detection of penicillin in river water. The CQDs were synthesized through a one-step thermal annealing process at 200 °C for 20 min, yielding highly luminescent nitrogen-doped nanodots with strong violet–blue emission. The as-prepared CQDs were incorporated into a sol–gel polymer matrix composed of 3-aminopropyltriethoxysilane (APTES) and tetraethyl orthosilicate (TEOS), using penicillin as the template molecule. Structural and morphological analyses such as x-ray photoelectron spectroscopy and scanning electron microscopy, confirmed the successful formation of imprinted binding cavities after template removal. The MIP exhibited a distinct fluorescence ‘turn-off/turn-on’ behavior governed by the shielding effect of penicillin and the restoration of emission upon template elution. Within the low-concentration regime (10 nM–10 µ M), the fluorescence response followed the Stern–Volmer relation, expressed as F 0 / F = 0.056 log( C peni ) + 1.39 ( R 2 = 0.9603), with a quantification limit of 10 nM. In contrast, the non-MIP showed only weak and nonspecific responses. The CQDs@MIP probe also demonstrated excellent selectivity toward penicillin in the presence of common coexisting ions. This work highlights a sustainable and cost-effective fluorescence sensing platform based on biomass-derived CQDs and molecular imprinting, offering promising potential for antibiotic monitoring in environmental samples.