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The atomic precision of magic-sized clusters offers a route toward narrow emission by eliminating heterogeneous broadening. Herein, we report ultranarrow 467 nm blue emission from cadmium phosphide clusters with a 96 meV line width and as high as 26% photoluminescence quantum yield (PLQY) enabled by tightly bound, bidentate phosphinate ligands. They are obtained through postsynthetic ligand exchange from oleate-capped clusters. The phosphinate maintains the bidentate coordination motif, which does not disturb the metastability of the material but does induce a change in the surface dipole, causing a bathochromic shift in the emission from 457 to 467 nm, which is an optimal wavelength for blue emission. We find that the structure of the ligand tail can heavily influence PLQY and other aspects of the charge carrier dynamics. The ligand exchange protocol can be applied to the related cadmium arsenide clusters, resulting in a narrow 550 nm green emission with a 9% PLQY. 

In nanoscale chemistry, magic-sized clusters (MSCs) stand out for their precise atomic configurations and privileged stability, offering unprecedented insights into the atomic-level structure of ligand-capped nanocrystals and a gateway to new synthesis and functionality. This article explores our efforts to shed light on the structure and reactivity of II-VI and III-V semiconductor MSCs. We have specifically been interested in the synthesis, isolation, and characterization of MSCs implicated as key intermediates in the synthesis of semiconductor quantum dots. Our exploration into their synthesis, structure, transformation, and reactivity provides a roadmap to expand the scope of accessible semiconductor clusters with diverse structures and properties. It paves the way for tailor-made nanomaterials with unprecedented atom-level control. In these studies, atomic level structure has been deduced through advanced characterization methods, including single-crystal and powder X-ray diffraction, complemented by pair distribution function analysis, nuclear magnetic resonance spectroscopy, and vibrational spectroscopy. We have identified two distinct families of CdSe MSCs with zincblende and wurtzite-like structures. We have also characterized two members of the wurtzite-like family of InP clusters and a related InAs cluster. Our research has revealed intriguing structural homologies between II-VI and III-V MSCs. These findings contribute to our fundamental understanding of semiconductor MSCs and hint at broader implications for phase control at the nanoscale and the synthesis of novel nanomaterials. We have also explored three distinct pathways of cluster reactivity, including cluster interconversion mediated by controlling the chemical potential of the reaction environment, both seeded and single source precursor growth mechanisms to convert MSCs into larger nanostructures, and cation exchange to access new cluster compositions that are precursors to nanocrystals that may be challenging or impossible to access from traditional bottom-up nucleation and growth. Together with the collective efforts of other researchers in the field of semiconductor cluster chemistry, our work establishes a strong foundation for predicting and controlling the form and function of semiconductor MSCs. By highlighting the role of surface chemistry, stoichiometry, and dopant incorporation in determining cluster properties, our work opens exciting possibilities for the design and synthesis of new materials. The insights gained through these efforts could significantly impact the future of nanotechnology, particularly in areas like photonics, electronics, and catalysis.