Synthesis of ultra - stable copper nanoclusters and their potential application as a reversible thermometer.

A new strategy for the synthesis of luminescent copper nanoclusters (Cu NCs), by virtue of the reduction of Cu2+ using ascorbic acid and the protection of polyvinylpyrrolidone at 75 °C, was reported. Blue emitting Cu NCs with photoluminescence (PL) quantum yield of 12% and high stability up to at least 1 month were obtained. Moreover, the PL of Cu NCs showed a reversible response to temperature, and a linear relationship between PL intensity and temperature even after 10 cycles of repeated heating and cooling process was obtained, indicating great potential application in thermal sensors.