Carbon dots synthesized by hydrothermal process via sodium citrate and NH4HCO3 for sensitive detection of temperature and sunset yellow

In this work, the carbon dots (CDs) were synthesized by an one-pot portable hydrothermal method from sodium citrate and NH4HCO3. The obtained CDs were found to show high fluorescence quantum yield (31%), excitation-wavelength independence, outstanding water-soluble, excellent chemical and optical stability. Interestingly, it was discovered that sunset yellow (SY) was sensitive and effective in quenching the fluorescence of CDs. Based on this observation, CDs could be applied as a novel fluoescent probe for detection of SY. The analytical potential of this probe was evaluated and illustrated a good linear relationship at the concentration range from 0.25 to 56.0 μmol L−1 with a detection limit (3σ/k) of 74.49 nmol L−1. Meanwhile, the practicality of this nanosensor for SY determination in real samples was validated with good accuracy and precision. In addtion, long time UV radiation and high ionic strength hardly influenced on the fluorescence intensity of CDs. However, the fluorescence intensity of CDs decreased at higher temperature and the fluorescence was recovered when temperature back to 5 °C. Therefore, CDs could be also employed as an fluorescent temperature sensor with significant sensitivity, linearity and remarkable reversibility.