No abstract

No abstract

Enhancing the kinetics of liquid–vapor transition from nanoscale confinements is an attractive strategy for developing evaporation and separation applications. The ultimate limit of confinement for evaporation is an atom thick interface hosting angstrom-scale nanopores. Herein, using a combined experimental/computational approach, we report highly enhanced water evaporation rates when angstrom sized oxygen-functionalized graphene nanopores are placed at the liquid–vapor interface. The evaporation flux increases for the smaller nanopores with an enhancement up to 35-fold with respect to the bare liquid–vapor interface. Molecular dynamics simulations reveal that oxygen-functionalized nanopores render rapid rotational and translational dynamics to the water molecules due to a reduced and short-lived water–water hydrogen bonding. The potential of mean force (PMF) reveals that the free energy barrier for water evaporation decreases in the presence of nanopores at the atomically thin interface, which further explains the enhancement in evaporation flux. These findings can enable the development of energy-efficient technologies relying on water evaporation.

No abstract

No abstract

Colloidal perovskite nanocrystals are emerging as one of the most promising candidates for next-generation monochromatic light sources that require precise bandgap tunability. However, the current efficiency (ηCE) and operational lifetime in their light-emitting diodes (LEDs) remain low due to impeded carrier transport and exciton quenching through the NC ligand layer. Here, we show that the fundamental limitation can be overcome in the superstructures containing polydisperse colloidal quantum wells of organic–inorganic hybrid perovskites. The mixing entropy-induced layering polydispersity promotes the delayed radiative energy transfer (DRET) that guides exciton transport with negligible nonradiative losses, boosting the thin-film photoluminescence quantum yield >96%. By using the superstructures in LEDs, we report a ηCE of 30.4 cd A–1, with an operational lifetime (LT50) of 184 min at a high constant driving current of 10 mA cm–2. These are among the most high-performance colloidal perovskite nanocrystals LEDs ever demonstrated.

No abstract

Predictable and tunable etching of angstrom-scale nanopores in single-layer graphene (SLG) can allow one to realize high-performance gas separation even from similar-sized molecules. We advance toward this goal by developing two etching regimes for SLG where the incorporation of angstrom-scale vacancy defects can be controlled. We screen several exposure profiles for the etchant, controlled by a multipulse millisecond treatment, using a mathematical model predicting the nucleation and pore expansion rates. The screened profiles yield a narrow pore-size-distribution (PSD) with a majority of defects smaller than missing 16 carbon atoms, suitable for CO 2 /N 2 separation, attributing to the reduced pore expansion rate at a high pore density. Resulting nanoporous SLG (N-SLG) membranes yield attractive CO 2 permeance of 4400 ± 2070 GPU and CO 2 /N 2 selectivity of 33.4 ± 7.9. In the second etching regime, by limiting the supply of the etchant, the nanopores are allowed to expand while suppressing the nucleation events. Extremely attractive carbon capture performance marked with CO 2 permeance of 8730 GPU, and CO 2 /N 2 selectivity of 33.4 is obtained when CO 2 -selective polymeric chains are functionalized on the expanded nanopores. We show that the etching strategy is uniform and scalable by successfully fabricating high-performance centimeter-scale membrane.