Surface Oxidation Modulates the Interfacial and Lateral Thermal Migration of MXene (TiCT) Flakes.

The thermal management of MXene (TiCT) plays a crucial role in its performance during various emerging applications. However, it is unclear how the inevitable oxidation structure of TiCT influences the thermal dissipation, which might hinder its long-term performance and even create thermal damage. Here we show the thermal migration of a TiCT flake with surface oxidation in film and water by combining ultrafast pump-probe technique with molecular dynamics (MD) simulations.

Negligible Isotopic Effect on Dissociation of Hydrogen Bonds.

Isotopic effects on the formation and dissociation kinetics of hydrogen bonds are studied in real time with ultrafast chemical exchange spectroscopy. The dissociation time of hydrogen bond between phenol-OH and p-xylene (or mesitylene) is found to be identical to that between phenol-OD and p-xylene (or mesitylene) in the same solvents. The experimental results demonstrate that the isotope substitution (D for H) has negligible effects on the hydrogen bond kinetics.

Two distinctive energy migration pathways of monolayer molecules on metal nanoparticle surfaces.

Energy migrations at metal nanomaterial surfaces are fundamentally important to heterogeneous reactions. Here we report two distinctive energy migration pathways of monolayer adsorbate molecules on differently sized metal nanoparticle surfaces investigated with ultrafast vibrational spectroscopy. On a 5 nm platinum particle, within a few picoseconds the vibrational energy of a carbon monoxide adsorbate rapidly dissipates into the particle through electron/hole pair excitations, generating heat that quickly migrates on surface.

Comparison Studies on Sub-Nanometer-Sized Ion Clusters in Aqueous Solutions: Vibrational Energy Transfers, MD Simulations, and Neutron Scattering.

In this work, MD simulations with two different force fields, vibrational energy relaxation and resonant energy transfer experiments, and neutron scattering data are used to investigate ion pairing and clustering in a series of GdmSCN aqueous solutions. The MD simulations reproduce the major features of neutron scattering experimental data very well. Although no information about ion pairing or clustering can be obtained from the neutron scattering data, MD calculations clearly demonstrate that substantial amounts of ion pairs and small ion clusters (subnanometers to a few nanometers) do exist in the solutions of concentrations 0.