NIR upconversion characteristics of carbon dots for selective detection of glutathione

In the current study, we report the near infrared (NIR) upconversion (in the range of 850-950 nm) properties of carbon nanoparticles and their utility as a fluorescence probe for selective and sensitive detection of glutathione (GSH). The fluorescence probe comprises of carbon dots (CDs), which possess the capacity to absorb NIR photons (@930 nm) with consequent emission in the visible region (@520-540 nm). CDs, in the presence of Cu2+, suffer severe quenching of its photoluminescence behavior. As a result, the upconversion green emission at 530 nm gets hindered. However, in the presence of GSH, anti-Stoke emission is reinstated courtesy of prominent complexation between GSH and Cu2+. Correlation between the restored upconversion intensity and GSH concentration shows a linear agreement effective for a wide range (0.5-100 mu M) with the limit of detection of 0.35 mu M. The developed sensing platform also possesses high selectivity in the presence of other amino acids and thiols. Detection of GSH was further carried out in diluted human serum, which revealed a high percentage of recovery. Thus, this study demonstrates the potential of CDs as a cheap, effective and highly selective NIR upconversion based fluorescence probe for the detection of GSH. Such nanoparticles with stable emission could be utilized as the alternative to conventional upconversion organic dyes and semiconductor quantum dots.