Efficient photon upconversion enabled by strong coupling between silicon quantum dots and anthracene.

Hybrid structures formed between organic molecules and inorganic quantum dots can accomplish unique photophysical transformations by taking advantage of their disparate properties. The electronic coupling between these materials is typically weak, leading photoexcited charge carriers to spatially localize to the dot or to a molecule at its surface. However, we show that by converting a chemical linker that covalently binds anthracene molecules to silicon quantum dots from a carbon-carbon single bond to a double bond, we access a strong coupling regime where excited carriers spatially delocalize across both anthracene and silicon.

Multidimensional Nano-Imaging of Structure, Coupling, and Disorder in Molecular Materials.

A hierarchy of intramolecular and intermolecular interactions controls the properties of biomedical, photophysical, and novel energy materials. However, multiscale heterogeneities often obfuscate the relationship between microscopic structure and emergent function, and they are generally difficult to access with conventional optical and electron microscopy techniques. Here, we combine vibrational exciton nanoimaging in variable-temperature near-field optical microscopy (IR -SNOM) with four-dimensional scanning transmission electron microscopy (4D-STEM), and vibrational exciton modeling based on density functional theory (DFT), to link local microscopic molecular interactions to macroscopic three-dimensional order.

The Motion of Trapped Holes on Nanocrystal Surfaces.

This Perspective discusses the phenomenon of trapped-hole diffusion in colloidal semiconductor nanocrystals. Surface charge-carrier traps are ubiquitous in nanocrystals and often dictate the fate of photoexcited carriers. New measurements and calculations are unveiling the nature of the nanocrystal surface, but many challenges to understanding the dynamics of trapped carriers remain.

On the Nature of Trapped-Hole States in CdS Nanocrystals and the Mechanism of Their Diffusion.

Recent transient absorption experiments on CdS nanorods suggest that photoexcited holes rapidly trap to the surface of these particles and then undergo diffusion along the rod surface. In this Letter, we present a semiperiodic density functional theory model for the CdS nanocrystal surface, analyze it, and comment on the nature of both the hole-trap states and the mechanism by which the holes diffuse. Hole states near the top of the valence band form an energetic near continuum with the bulk and localize to the nonbonding sp orbitals on surface sulfur atoms.

HEART Failure? Episodes of Missed Major Cardiac Events When Applying the HEART Pathway to an Observation Unit Population.

Objective: The HEART Pathway risk prediction tool (HEART score plus serial troponin measures at 0 and 3 hours post-presentation) is used to identify low-risk patients with chest pain who may qualify for safe, early discharge. We calculated the percentage of patients in our observation unit that qualified as low risk using HEART Pathway, as well as their associated outcomes.

Methods: We retrospectively reviewed charts on 966 consecutive patients admitted to our observation unit for chest pain (January 2015 to February 2016); HEART Pathway scores were retrospectively calculated and serial cardiac troponin values logged.