Facile, rapid synthesis of N,P-dual-doped carbon dots as a label-free multifunctional nanosensor for Mn(VII) detection, temperature sensing and cellular imaging

We rapidly synthesized N,P-dual-doped carbon dots (N,P-CDs) via the acid-base neutralization spontaneous heat using a simple blend of phthalic acid, 1,2-ethylenediamine, and concentrated phosphoric acid. The approach is automatic without external heat treatment to speedily produce dozens of N,P-CDs, which refrain high temperature, sophisticated manipulations, and long reaction times. As-fabricated N,P-CDs with excellent luminescent properties, superior biocompatibility and respectable fluorescence quantum yield (QY) of 15% have been employed for the development of a label-free multifunctional fluorescence sensing platform for the detection of Mn(VII), temperature sensing and cellular imaging. Mn(VII) is able to effectively quench the fluorescence of N,P-CDs based on inner filter effect (IFE) because the absorption bands of Mn(VII) can perfectly overlap the emission and excitation wavelengths of N,P-CDs. The system had high selectivity toward Mn(VII) and the detection limit was 48.3 nM in the broad linear span from 10 μM to 200μM. Moreover, the N,P-CDs were extended for sensing Mn(VII) in living cell due to favorable biocompatibility and negligible cytotoxicity. Furthermore, the sensors showed a linear and reversible variation of emission intensity for a temperature range from 25℃ to 80℃, with a sensitivity of −1.79% per ℃. The practical implications of N,P-CDs for Mn(VII) detection have been demonstrated in Teas leaves and Medicinal herbs samples with satisfactory results.