Deuterated water impact on the luminescence of quantum dots

Quantum dots (QDs) are widely recognized for their outstanding photoluminescent properties, tunable emission, and potential for bioimaging and sensing. This study systematically investigates the effect of solvent isotope exchange (H₂O → D₂O) on the luminescence behavior of three classes of commercially available QDs: graphene QDs (GQDs), CdTe core-type QDs (C-QDs), and CdSe/ZnS or CdS/ZnS core/shell QDs (CS-QDs). Luminescence intensity, quantum yield (QY), and fluorescence lifetime were measured under identical conditions in both H₂O and D₂O solvents. Significant fluorescence enhancement was observed for GQDs (up to 1.62 times higher for GQDs Aqua Green) and C-QDs (up to 1.79 times for CdTe 520 Sigma) in D₂O, while CS-QDs showed a negligible response (0.96 to 1.10 times more intense signal), indicating efficient surface passivation by the shell layer. The degree of fluorescence enhancement and lifetime prolongation for GQDs correlated with increasing emission wavelength, supporting a dynamic quenching model via solvent interaction. In contrast, C-QDs exhibited amplification related to the complex interplay between particle size and surface functionalization. The results highlight that solvent isotope effects on luminescence are strongly modulated by QD structure and surface functionalization. Although the use of D₂O may be limited in large-scale applications, it offers significant advantages in microscale fluorescence studies (e.g., fluorescence imaging, capillary electrophoresis) where enhanced sensitivity and signal stability are critical.