Turn-on fluorescence sensor for glutathione in aqueous solutions using carbon dots-MnO2 nanocomposites

A novel fluorescence sensor based on carbon dots-MnO2 nanocomposites was fabricated successfully, which can detect glutathione (GSH) in aqueous solutions succinctly, rapidly and selectively. The carbon dots (CDs), which were synthesized by using organosilane as a coordinating solvent, had a highly luminescent quantum yield. The nanoflower-like MnO2 had an enormous specific surface area, which could react with more CDs. Subsequently, CDs-MnO2 nanocomposites were synthesized through a facile one-step method. As a result of fluorescence resonance energy transfer (FRET) from CDs to the MnO2, the fluorescence of CDs can be quenched by MnO2. However, when GSH was introduced into the system, the quenched fluorescence could be restored because MnO2 was reduced to Mn2+ by GSH, which led to the elimination of FRET. Compared with other electrolytes and biomolecules, we find that the chemical response of the CDs-MnO2 nanocomposites exhibited good selectivity toward GSH. Under the optimal conditions, the proposed immunosensor was successfully performed with a linear range of 0.03-974.1 mu mol L-1, with a detection limit of 0.015 mu mol L-1. In addition, the proposed fluorescence sensor has several merits, such as low cost, good selectivity, great biocompatibility and chemical turn-on fluorescence response. (C) 2015 Elsevier B.V. All rights reserved.