Colorimetric detection of Pb2+ ions using curcumin silver nanoparticles

• Silver nanoparticles extracted from turmeric were synthesized for sensor solution. • Colorimetric detection of Pb 2+ based on curcumin complexed with silver nanoparticles. • Optical sensor of Pb 2+ using AgNPs-CUR with low detection limits of 13.6 µM. • Detection of lead in water samples applying low-cost and rapid AgNPs-CUR sensor. The silver nanoparticles (AgNPs) complexed with curcumin (CUR) extracted from turmeric (TMR) were synthesized and applied for a simple and rapid colorimetric technique for Pb 2+ detection. The results reveal that our low-cost and rapid AgNPs-CUR sensor is highly selective for Pb 2+ ions with the detection limit of 13.6 µM (2.8 mg.L −1 ) and can be applied for real water samples. Not only the observed absorption spectrum and the solution color can reveal the contamination of Pb 2+ in the sample, but also an orange floccules precipitate can be clearly observed by naked-eye within 20 min. In addition, the results obtained from DFT calculation agree well with the experiments. Density functional theory (DFT), at the M06 level with mixed basis set of 6-31G(d) and def2-tzvp, was applied to propose the binding mechanism of AgNPs with CUR and AgNPs-CUR with Pb 2+ . Calculated binding energies of the compound of AgNPs with CUR and the AgNPs-CUR with Pb 2+ are −145.8 and −361.4 kcal mol −1 , respectively, indicating that the AgNPs-CUR is strongly interact with Pb 2+ ions through formation of highly stable Pb 2+ AgNPs-CUR complexes indicating the stable aggregative phenomena which agrees well with FTIR spectrum.