Glutathione modified carbon-dots: from aggregation-induced emission enhancement properties to a turn-on sensing of temperature/Fe3+ ions in cells

In this paper, a novel turn-on chemosensor for detecting temperature and Fe3+ has been designed. This nanosensor is based on the aggregation-induced emission enhancement (AIEE) properties of fluorescent carbon dots (CDs). The CDs prepared by a facile hydrothermal route show blue emission (lambda(em) = 505 nm) with a quantum yield of 4.7%. The resultant CDs are modified by glutathione (GSH) on the surface through the carbodiimide-activated coupling reaction. The as-prepared GSH-CDs show good dispersion, high fluorescence and AIEE phenomenon. Resultant GSH-CDs would be aggregated by Fe3+ ions in aqueous solution which results in enhanced fluorescence. Therefore, such GSH-CDs would be excellent candidates as fluorescent probes for the label-free detection of Fe3+ ions with a limit of detection of 0.1 mu M. Moreover, the PL intensity of GSH-CDs increases progressively with increasing temperature and they could be used in optical thermometry over a wide temperature range (25-80 degrees C) with small temperature resolution (similar to 0.5 degrees C). Using MC3T3-E1 cells as the model, the resultant nanosensor is demonstrated to monitor temperature and Fe3+ ions in cells. Thus, resultant GSH-CDs could be used as a turn-on sensor for highly sensitive and selective detection of temperature and Fe3+ ions in aqueous solution and biosystems.