10.1021/ja048222a.s001 Sander F. Wuister Sander F. Wuister Celso de Mello Donegá Celso de Mello Donegá Andries Meijerink Andries Meijerink Luminescence Temperature Antiquenching of Water-Soluble CdTe Quantum Dots:  Role of the Solvent American Chemical Society 2004 Luminescence Temperature Antiquenching Solvent Luminescence temperature antiquenching Short carbon chains LTAQ AET NH surface quenching states AUT solvation water molecules transition temperature strain CdTe quantum dots QD 2004-08-25 00:00:00 Media https://acs.figshare.com/articles/media/Luminescence_Temperature_Antiquenching_of_Water_Soluble_CdTe_Quantum_Dots_Role_of_the_Solvent/3327334 Luminescence temperature antiquenching (LTAQ) is observed for water-soluble CdTe quantum dots (QDs) capped with aminoethanethiol (AET). The efficient exciton emission (quantum efficiency of ∼40% at 300 K) is quenched almost completely as the QD solutions are cooled to below 230 K and is fully recovered around 270 K upon warming up to room temperature (LTAQ). Temperature-dependent lifetime measurements show that the quenching rate is high, resulting in an on/off behavior. No LTAQ is observed for CdTe QDs capped with aminoundecanethiol (AUT). The LTAQ is explained by the influence of solvent freezing on the surface of the QD core. Freezing of the solvation water molecules surrounding the QD will induce strain in the capping shell, due to the interaction between water and the charged heads of the capping molecules. Short carbon chains (AET) will propagate the strain to the QD surface, creating surface quenching states, whereas long and flexible chains (AUT) will dissipate the strain, thus avoiding surface distortion. Freezing-point depression by the addition of methanol results in a lowering of the transition temperature. Additional support is provided by the size dependence of the LTAQ:  smaller particles, with higher local ionic strength due to a higher density of charged NH<sub>3</sub><sup>+</sup> surface groups, experience a lower transition temperature due to stronger local freezing-point depression.