Mapping the effect of geometry on the radiative rate in core/shell QDs: core size dictates the conduction band offset.

Computational models have been developed that can accurately predict the electronic structure and thus optical properties of a variety of quantum dot (QD) materials. However, the application of these models to core/shell and other heterostructured QDs has received less experimental corroboration owing to the difficulty in systematically synthesizing and characterizing large ranges of geometries. In the current work, we synthesized a library of core/shell CdSe/CdS QDs with varying core sizes and shell thicknesses, and have characterized their radiative recombination rates.

Gold-Decorated Silicon Nanowire Photocatalysts for Intracellular Production of Hydrogen Peroxide.

Hydrogen peroxide (HO) plays diverse biological roles, and its effects in part depend on its spatiotemporal presence, in both intra- and extracellular contexts. A full understanding of the physiological effects of HO in both healthy and disease states is hampered by a lack of tools to controllably produce HO. Here, we address this issue by showing visible-light-induced production of exogenous HO by free-standing, gold-decorated silicon nanowires internalized in human umbilical vein endothelial cells.

Tracking Longitudinal Rotation of Silicon Nanowires for Biointerfaces.

The rolling motion (i.e., longitudinal rotation) of nanomaterials may serve as a proxy to probe microscopic environments.

Learning from Solar Energy Conversion: Biointerfaces for Artificial Photosynthesis and Biological Modulation.

Three seemingly distinct directions of nanomaterials research, photovoltaics, biofuel production, and biological modulation, have been sequentially developed over the past several decades. In this Mini Review, we discuss how the insights gleaned from nanomaterials-based solar energy conversion can be adapted to biointerface designs. Because of their size- and shape-dependent optical properties and excellent synthetic control, nanomaterials have shown unique technological advantages as the light absorbers or energy transducers.

Temperature-Dependent Hole Transfer from Photoexcited Quantum Dots to Molecular Species: Evidence for Trap-Mediated Transfer.

The effect of temperature on the rate of hole transfer from photoexcited quantum dots (QDs) is investigated by measuring the driving force dependence of the charge transfer rate for different sized QDs across a range of temperatures from 78 to 300 K. Spherical CdSe/CdS core/shell QDs were used with a series of ferrocene-derived molecular hole acceptors with an 800 meV range in electrochemical potential. Time-resolved photoluminescence measurements and photoluminescence quantum yield measurements in an integrating sphere were both performed from 78 to 300 K to obtain temperature-dependent rates for a series of driving forces as dictated by the nature of the molecular acceptor.

Effect of Thermal Fluctuations on the Radiative Rate in Core/Shell Quantum Dots.

The effect of lattice fluctuations and electronic excitations on the radiative rate is demonstrated in CdSe/CdS core/shell spherical quantum dots (QDs). Using a combination of time-resolved photoluminescence spectroscopy and atomistic simulations, we show that lattice fluctuations can change the radiative rate over the temperature range from 78 to 300 K. We posit that the presence of the core/shell interface plays a significant role in dictating this behavior.

Application of a Palladium-Catalyzed C-H Functionalization/Indolization Method to Syntheses of cis-Trikentrin A and Herbindole B.

We describe herein formal syntheses of the indole alkaloids cis-trikentrin A and herbindole B from a common meso-hydroquinone intermediate prepared by a ruthenium-catalyzed [2+2+1+1] cycloaddition that has not been used previously in natural product synthesis. Key steps include a sterically demanding Buchwald-Hartwig amination as well as a unique C(sp(3) )-H amination/indole formation. Studies toward a selective desymmetrization of the meso-hydroquinone are also reported.

Hole Transfer from Photoexcited Quantum Dots: The Relationship between Driving Force and Rate.

We have investigated the relationship between driving force and rate for interfacial hole transfer from quantum dots (QDs). This relationship is experimentally explored by using six distinct molecular hole acceptors with an 800 meV range in driving force. Specifically, we have investigated ferrocene derivatives with alkyl thiol moieties that strongly bind to the surface of cadmium chalcogenide QDs.