Synthesis of red carbon quantum dots with solvatochromic properties as a selective luminescence probe of MnO4−

Red efficient luminescent carbon quantum dots are still difficult to be synthesized. In this work, red carbon quantum dots (RCQDs) isopropanol solution with quantum yield of 43.9 % have been synthesized using isopropanol as carbon source and solvent, N1-phenylbenzene-1,2,4-triamine as carbon and nitrogen source. The solvothermal synthesis was catalyzed surprisingly by SnO₂ nanoparticles, the optimal synthesis temperature was lowered to 130 °C, and the optimal synthesis time was reduced to 1 h. Moreover, the RCQDs nanoparticles showed excellent solvatochromic properties. The maximum emission wavelength for RCQDs in N, N-dimethylformamide dilute solution blue shifted to 504 nm, and the maximum emission wavelengths for RCQDs in acetone, isopropanol, dimethyl sulfoxide and water solutions were in the range of 592 nm ∼ 624 nm. The reason was investigated by the in-situ infrared absorption spectra. MnO₄⁻ ions could be selectively detected using RCQDs in PBS buffer solution (pH = 5.0), the linear range of MnO₄⁻ concentration was 0.1 μM ∼ 2.0 μM. This work provides a new synthesis method of efficient red carbon quantum dots, and it supplies a friendly candidate for detection of MnO₄⁻ ions in water.