Density functional theory and its time-dependent extension are employed to investigate the intermolecular hydrogen-bonding- (Inter-HB-) induced fluorescence enhancement of benzaldehydes. The fluorescence quenching mechanism of benzaldehydes in chloroform is attributed to the low energy gap between the lowest ππ* and nπ* states at Franck–Condon (FC) point and conical interaction between ππ* and nπ* states. The Inter-HB between the aldehyde group of benzaldehydes and methanol can considerably increase the energy gap between ππ* and nπ* states at the FC point, and this type of hydrogen bond is strengthened in the excited ππ* state, thereby precluding the nonradiative transition from nπ* state and enhancing fluorescence. The Inter-HB between the hydroxy group of benzaldehydes and methanol is considerably stronger than that between the aldehyde group of benzaldehydes and methanol; which has a little effect on the energy gap of ππ* and nπ* states. Therefore, if Inter-HB exists between the hydroxy group of benzaldehydes and methanol, then it will play an important role in ground and excited ππ* states, and fluorescence enhancement by Inter-HB between the aldehyde group of benzaldehydes and methanol will be absent. Our proposed mechanism can explain the experimental observations and differs from that of “proximity effects”.

Heteroatom substitution of gold nanoclusters enables precise tuning of their physicochemical properties at single-atom level, which has importance impact on the applications related to excited states including photovoltaic, photocatalysis and...

To achieve efficient conversion and avoid loss of solar energy, ultrafast charge separation and slow electron−hole recombination are desired. Combining timedependent density functional theory (TD-DFT) with nonadiabatic molecular dynamics, Au 9 (PH 3 ) 8 /MoS 2 , as a prototype for zero-dimensional/two-dimensional (0D/2D) heterojunction, has been demonstrated to present excellent light absorption capacity and effective charge separation characteristics. In the heterojunction, photoexcitation of the Au 9 (PH 3 ) 8 nanocluster drives an ultrafast electron transfer from Au 9 (PH 3 ) 8 to MoS 2 within 20 fs, whereas photoexcitation of the MoS 2 nanosheet leads to hole transfer from MoS 2 to Au 9 (PH 3 ) 8 within 680 fs. The strong nonadiabatic coupling and prominent density overlap are responsible for the faster electron separation relative to hole separation. In competition with the charge separation, electron−hole recombination requires 205 ns, ensuring an effective carrier separation. Our atomistic TD-DFT simulation provides valuable insights into the photocarrier dynamics at the Au 9 (PH 3 ) 8 /MoS 2 interface, which would stimulate the exploration of 0D/2D hybrid materials for photovoltaic and optoelectronic devices.

We performed systematic ab initio calculations to explore the structures and electronic properties of ammonia ice by hydrostatic compression.