Hierarchical thermoelectrics: crystal grain boundaries as scalable phonon scatterers.

Thermoelectric materials are strategically valuable for sustainable development, as they allow for the generation of electrical energy from wasted heat. In recent years several strategies have demonstrated some efficiency in improving thermoelectric properties. Dopants affect carrier concentration, while thermal conductivity can be influenced by alloying and nanostructuring.

Probing lipid coating dynamics of quantum dot core micelles via Förster resonance energy transfer.

Lipid coated nanocrystal assemblies are among the most extensively investigated nanoparticle platforms for biomedical imaging and therapeutic purposes. However, very few efforts have been addressed to the lipid coating exchange dynamics in such systems, which is key to our understanding of the nanoparticles' coating stability and their interactions with the environment. Here, we apply the Förster resonance energy transfer (FRET) from quantum dot (QD) core to Cy5.

Morphological transformations and fusion of PbSe nanocrystals studied using atomistic simulations.

Molecular dynamics simulations are performed on capped and uncapped PbSe nanocrystals, employing newly developed classical interaction potentials. Here, we show that two uncapped nanocrystals fuse efficiently via direct surface attachment, even if they are initially misaligned. In sharp contrast to the general belief, interparticle dipole interactions do not play a significant role in this "oriented attachment" process.

Understanding interactions between capped nanocrystals: three-body and chain packing effects.

Self-assembly of capped nanocrystals (NC) attracted a lot of attention over the past decade. Despite progress in manufacturing of NC superstructures, the current understanding of their mechanical and thermodynamic stability is still limited. For further applications, it is crucial to find the origin and the magnitude of the interactions that keep self-assembled NCs together, and it is desirable to find a way to rationally manipulate these interactions.

Time-dependent photoluminescence spectroscopy as a tool to measure the ligand exchange kinetics on a quantum dot surface.

The exchange kinetics of native ligands that passivate CdSe quantum dots (hexadecylamine (HDA), trioctylphosphine oxide (TOPO), and trioctylphosphine (TOP)) by thiols is followed in situ. This is realized by measuring, in real-time, the decrease in emission intensity of the QDs upon addition of hexanethiol (HT) which quenches the emission. The effect of adding an excess of native ligands prior to thiol addition on the capping exchange is studied to provide insight in the bond strength and exchange kinetics of the individual surfactants.

Molecular simulations of interacting nanocrystals.

We compute the potential of mean force for two gold nanocrystals capped by alkylthiols from atomistic simulations and show how variables such as temperature, capping molecule length, and the presence of solvent affect these interactions. Our main findings are (1) the equilibrium distance in vacuum always equals approximately 1.25 times the core diameter, (2) incomplete capping layers promote sintering, and (3) the presence of a good solvent results in purely repulsive interactions.