AN EXAMINATION OF THE INTERFACIAL INTERACTIONS BETWEEN QUANTUM-CONFINED CADMIUM-SULFIDE CLUSTERS AND AMINOCALIXARENE STABILIZER MOLECULES

Clusters of quantum-confined cadmium sulfide were prepared in acetonitrile employing p-[(dialkylamino)-methyl]calix[n]arene (n = 4, 5, 6, 7; alkyl = CH3, C4H9, C6H13) macrocycles as molecular stabilizers. A systematic variation of the CdS to aminocalixarene ratio leads to three distinct regimes of average particle size and photophysical properties. The monitoring of the cluster properties with time reveals a dynamic Q-CdS surface approaching a common structure (as reflected in its emission spectrum) regardless of cluster size or initial photophysical characteristics. Average Q-CdS particle sizes were determined utilizing high-resolution transmission electron microscopy (HREM) and UV-vis absorption spectroscopy. Photophysical characterization was accomplished through steady-state and time-resolved photoluminescence (PL) spectroscopy. The results of UV-vis spectroscopic titrations indicate that the aminocalixarene macrocycles bind Cd2+ ions up to a specific cadmium to aminocalixarene ratio, depending on the number of phenolic residues in the aminocalixarene. Based on the Cd2+ binding results and the cluster characterization data, a mechanism for the formation and subsequent stabilization of Q-CdS in each of the three CdS concentration regimes is proposed.