Designing of glutathione-lactose derivative for the fabrication of gold nanoclusters with red fluorescence: Sensing of Al3+and Cu2+ ions with two different mechanisms

Abstract

In this work, a simple and novel glutathione-lactose (GSH-lactose) derivative was synthesized and used as a template for the fabrication of fluorescent gold nanoclusters (GSH-lactose-AuNCs). The synthesized fluorescent GSH-lactose-AuNCs were stable and showed red emission color by irradiating with 365 nm of UV light. At 410 nm of excitation wavelength, the fluorescent GSH-lactose-AuNCs exhibited a strong emission peak at 635 nm. The fluorescent GSH-lactose-AuNCs acted as a fluorescent sensor for the rapid and sensitive detection of two metal ions i.e., Al3+ and Cu2+ ions with different sensing mechanisms such as fluorescence enhancement for Al3+ ion and fluorescence quenching for Cu2+ ion). As a result, the emission peak of GSH-lactose-AuNCs at 635 nm exhibited independent behaviour i.e., a linear enhancement with the addition of Al3+ ion and a linear quenching efficiency with Cu2+ ion. Thus, good linear relationships were noticed between intensity (I and I0/I) over the concentration ranges of 0.075–100 μM for Al3+ ion and of 0.050–100 μM for Cu2+ ion with correlations coefficients of 0.9962 and 0.9964. The detection limits are 12 and 52 nM for Al3+ and Cu2+ ions. The GSH-lactose-AuNCs-based analytical approach was successfully applied to quantify Al3+ and Cu2+ ions in real samples.