Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Chemistry

Abstract

Micrometer-sized superparticles, self-assembled from metallic or semiconducting nanoclusters, can be used as convenient building blocks for preparing functional materials, utilizing the electronic and photophysical properties resulting from the quantum confinement as well as from the coupling between individual nanoscopic constituents.

This research aimed at developing a novel approach utilizing the conversion of a cadmium phenylchalcogenolate precursor (Me4N)2[Cd(EPh)4] (where E = S or Se) under solvothermal conditions for the preparation of nanoscopic CdE, including both crystalline superlattices of large discrete nanoclusters and superstructures with more complex morphology. In particular, 3D cubic superlattices of molecular CdS nanoclusters of 1.9 and 2.3 nm in diameter were prepared and characterized by a set of techniques, including UV−vis absorption and photoluminescence studies under various conditions, Raman spectroscopy, and thermogravimetric analysis. Structural information was obtained by methods complementary to single crystal X-ray diffraction such as 111Cd SSNMR spectroscopy, electron microscopy, and electron tomographic reconstruction. Observed structural features demonstrate the significance of the prepared materials as a transition point from known families of smaller CdS nanoclusters to unexplored larger ones. Even more unusual 3D superstructures comprised of nanoscopic constituents, i.e., spherical CdS superparticles and porous CdSe single crystal, were reported and possible mechanisms of formation were discussed. The importance of this research lies in improving the ability to manipulate the size and organization of primary nanocluster building blocks into particular superstructures and to tailor the photophysical properties of the resulting material, which enables the creation of new multifunctional systems and broadens potential areas of application.

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