Temperature sensing at micro/nano scale with materials by direct fluorescence excitation is widely used in the recent years. Here, we report the green hydrothermal synthesis of sulfur-doped carbon nanoparticles (S-CNPs) from inexpensive precursors such as sucrose and sodium thiosulfate. The resultant S-CNPs exhibit luminescence both in aqueous and solid states. The variation of steady–state photoluminescence intensity of S-CNPs with temperature is investigated and the sensitivity of S-CNPs solid film with 355 nm excitation is found to be 2.63 × 10−2 K−1, which is slightly higher than that with 532 nm excitation (2.15 × 10−2 K−1). The activation energy is found to be 141.87 and 30.7 meV for 355 and 532 nm excitation, respectively. Similarly, the sensitivity of S-CNPs in solution is found to be 7.3 × 10−3 K−1 and the the range of temperature is wider than physiological range (288–333 K) which suggests that S-CNPs can be used in the biological cells temperature sensing as well. Overall, the results suggest that S-CNPs can be used as nano thermometers.
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The authors also acknowledge IISc for the financial assistance in acquiring a 200 kV FETEM.