Time-resolved photoluminescence of pH-sensitive carbon dots

摘要: Abstract Time-resolved photoluminescence emission were performed to study the ≥100 ps time-scale photophysics of water soluble carbon dots (CDs) dispersed in different pH solutions. Excitation core and high-energy edge states at excitation wavelengths λex ≤ 350 nm produce hole-electron excitonic charge-carriers but do not yield any emission, implying efficient non-radiative recombination mechanisms for charge-carriers. Using λex ∼375 nm, surface fluorophores as well low-lying edge-states are excited, producing over a broad range. However, characteristics vary strongly depending on condition choice wavelength. In particular, state is abruptly extinguished pH ≥ 5, which also marks onset deprotonation surface-bound -COOH groups CDs, indicating that -COO- anionic centers promote quenching edge-state emission. ∼450 nm, only excited. The phenolic -OH group pH > 9 causes sharp red-shift spectra all wavelengths. pH-sensitive behavior CDs enable them serve optical sensors.