STABILIZER-MEDIATED PHOTOLUMINESCENCE QUENCHING IN QUANTUM-CONFINED CADMIUM-SULFIDE CLUSTERS

In this account the influence of charge possessed by the stabilizing medium on the steady-state quenching behavior of quantum confined cadmium sulfide (Q-CdS) semiconductor clusters is reported. Q-cluster stabilizers such as the inverse micelle/hexametaphosphate (HMP) system and thiophenol caps, which afford an anionic solution/stabilizer interface, permit quenching of the integrated trap photoluminescence (PL) intensity (lambda(max) between 550 and 650 nm) up to approximately 45% (HMP) or 54% (thiophenol) by the cation methyl viologen (MV2+). However, minimal quenching is observed upon addition of the anion iodide (I-), and virtually no quenching is observed following the addition of neutral molecules (amines and ketones). This is in stark contrast to Q-CdS clusters stabilized by macrocyclic aminocalixarene stabilizer molecules, which give rise to a cationic layer (-NR2H+) at the solution/stabilizer interface. Integrated PL from aminocalixarene stabilized Q-CdS clusters can be quenched up to approximately 70% by the addition of I-; however, negligible quenching is observed upon the addition amines, MV2+, or ketones. These differences in Q-cluster photoluminescence behavior are discussed in terms of possible electrostatic interactions of the various quenchers with the cationic/anionic Q-CdS charge layers.