Fluorescent Carbon Dots an Effective Nano-Thermometer in Vitro Applications.

Fluorescent sensing of temperature in nanoscale regions has many advantages and applications in the biological field. Herein, blue emitting carbon dots (CDs) are designed and successfully developed using a one step hydrothermal method. As synthesized CDs exhibit temperature dependent photoluminescent (PL) intensity and PL decay lifetime over the physiological temperature ranging from room temperature (RT) to 70 °C. The PL intensity and PL decay lifetime of the obtained CDs correlate linearly to temperature (RT-70 °C) with correlation coefficient of 0.997 and 0.996, respectively. Additionally, dual mode thermal sensing (PL intensity/lifetime) make these CDs a promising optical nanothermometer over alternative semiconductors quantum dots and CD-based quantum dots. Moreover, the resultant aqueous CDs demonstrate excitation-independent blue emission, and the PL quantum yield (QY) is reached at 44.5%. The obtained CDs illustrate stable performance to high ionic environments and photobleaching even after keeping them for 2 h under continues UV irradiation. Furthermore, blue emitting CDs have low cytotoxicity for T-ca. cells and illuminate deep blue fluorescence under the excitation of 406 nm. As a result, high thermal sensitivity of these fluorescent CDs has potential to detect temperature in living cells in the range of 25-40 °C.