Photoelectrochemical detection of copper ions by modulating the growth of CdS quantum dots

We discovered that copper ions (Cu2+) catalyze the oxidation of cysteine (CSH) by oxygen (O2) to modulate the growth of CSH-capped cadmium sulfide (CdS) nanoparticles (NPs). This new chemical process was applied to sensitive fluorogenic and photoelectrochemical (PEC) detection of Cu2+ ions in real samples of mineral and tap water using the photocatalytic activity of the resulting NPs. Disposable screen-printed electrodes (SPCEs) modified with electroactive polyvinylpyridine bearing osmium complex (Os-PVP) by cyclic voltammetry (CV) were employed for PEC analytical system. CdS NPs formed during the assay photocatalyze oxidation of 1-thioglycerol (TG) upon application of 0.3 V vs. Ag/AgCl to SPCEs. Os-PVP complex mediated the electron transfer between the electrode surface and CdS NPs. We proved that our assays did not suffer from interference from other ions accompanying Cu2+ and the sensitivity of our assays covers the European Union standard limit of Cu2+ ions in drinking water. Modulating growth of CdS nanoparticles by copper as redox catalyst allows designing very simple and sensitive assays using disposable photoelectrochemical screen-printed electrodes (SPCEs) sensitized by conductive osmium complex. [Display omitted] •CdS QDs growing in aqueous buffered solutions are stabilized by cysteine (CSH).•Copper ions (Cu2+) modulate the growth of CSH-capped CdS QDs.•This system allows quantification of Cu2+ in real samples: bottled mineral and tap water.•Photoelectrochemical (PEC) analysis was performed using SPCEs modified with Os-PVP polymer.•PEC method for detection of Cu2+ ions outperforms the optical assays.