Over the past ~20 years there has been considerable effort towards the optimization of the photophysical properties of semiconductor nanomaterials to engender efficacy for biological imaging and sensing as well as for electronics and catalysis. The development of core/shell quantum dots (QDs) was instrumental due to their robust properties and high quantum yields. Some of the first demonstrations for practical applications using QDs included biological imaging; however, these particles experience fluorescence intermittency (“blinking”), which is detrimental for single particle tracking studies. Furthermore, ~10 nanosecond lifetimes are not compatible with time-gating visualization, a technique that reduces background noise. To address these issues, long lifetime, &gt;100 ns non-blinking behavior have been realized in “giant” quantum dots with a highly alloyed core. Growth of a shell results in type-II behavior that separates the electron and hole, which slows emissive recombination. Also presented is a novel cell-penetrating peptide that can be conjugated to surfactants that are commonly employed for QD water solubilization. These materials can be passively delivered to the cytosol of live T-cell lymphocytes. Single particle tracking studies reveal fast diffusion of single dots that are not consistent with endosomal capture.<br/>Also presented is a paradigm shift in exciton dynamics of core/shell quantum dots by the demonstration of highly efficient CdS/ZnS reducing agents. The role of a shell in a heterostructure is generally viewed as confining the charge carriers within the core of a nanomaterial. However, it was discovered that the electron may be free to reduce a surface-bound substrate so long as the hole can delocalize into the shell, which stabilizes the intermediate state. In fact, by tuning the size of the shell a heterostructure can be a better reducing agent compared to the core alone. The fact that core/shell QDs are resistant to degradation engenders greater utility for these species in catalytic applications.

Tuning excition dynamics in core/shell heterostructures:Type-II giant quantum dots and efficient reducing agents

ACS Fall 2021

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