Glutathione-directed synthesis of Cr(VI)- and temperature-responsive fluorescent copper nanoclusters and their applications in cellular imaging

Water-soluble and highly fluorescent copper nanoclusters (Cu NCs) using glutathione as a stabilizing agent have been prepared. The as-prepared Cu NCs have an average diameter of about 2.2 nm and are shown to be viable fluorescent probes for the determination of Cr(VI) ions owing to the inner filter effect of Cr(VI) ions. The Cu NCs have been characterized in terms of photoluminescence excitation spectroscopy, photoluminescence spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy. Furthermore, the nanosensor exhibits high sensitivity to Cr(VI) ions with a detection limit of 1.5 mu M and has been demonstrated for the determination of Cr(VI) ions in real water samples including tap water, mineral water, and Taihu lake water. In addition, the as-prepared NCs could be used as versatile nanothermometry devices in cellular and in vivo temperature sensing based on obvious temperature dependence on the fluorescence emission intensity, which changes obviously over the physiological temperature range (279-323 K).