This work reports the synthesis of chiral perovskite heterostructure films by combining a two-dimensional (2D) chiral (R-/S-MBA)2PbI4 perovskite with CsPbBr3 quantum dots (QDs). The as-synthesized chiral heterostructure films exhibit obvious circularly polarized luminescence (CPL) properties, even though pure 2D chiral perovskite cannot present photoluminescence. It indicates that the chirality of the excited state of the QDs originates from the 2D chiral perovskite. The circular polarization-resolved transient absorption (TA) spectra further demonstrate that the CPL response of heterostructure films originates from the energy transfer between the chiral perovskite layer and QDs layer and the suppression of spin relaxation, which induces the imbalance of the spin population of excited states in QDs layer. In addition, the photoluminescence (PL), circular dichroism (CD), and CPL spectra of these heterostructure films can be controlled by varying the thickness and component of the chiral perovskite layer, which demonstrates that the anion exchange between chiral perovskite and CsPbBr3 QDs can tune the chemical composition and optoelectronic properties due to the low bonding energy difference between them and decrease the strain within the QDs layer to reduce the radiative recombination lifetime. This work provides guidance for the synthesis of chiral perovskites with a strong CPL response and further provides insight into the origination of CPL.

Lanthanide photoluminescence (PL) emission has attracted much attention for technological and bioimaging applications because of its particularly interesting features, such as narrow emission bands and very long PL lifetimes. However, this emission process necessitates a preceding step of energy transfer from suitable antennas. While biocompatible applications require luminophores that are stable in aqueous media, most lanthanide-based emitters are quenched by water molecules. Previously, we described a small luminophore, 8-methoxy-2-oxo-1,2,4,5-tetrahydrocyclopenta[de]quinoline-3-phosphonic acid (PAnt), which is capable of dynamically coordinating with Tb(III) and Eu(III), and its exchangeable behavior improved their performance in PL lifetime imaging microscopy (PLIM) compared with conventional lanthanide cryptate imaging agents. Herein, we report an in-depth photophysical and time-dependent density functional theory (TD-DFT) computational study that reveals different sensitization mechanisms for Eu(III) and Tb(III) in stable complexes formed in water. Understanding this unique behavior in aqueous media enables the exploration of different applications in bioimaging or novel emitting materials.

Metal halide perovskite light-emitting diodes (PeLEDs) have exceptional color purity but designs that emit deep-blue color with high efficiency have not been fully achieved and become more difficult in the thin film of confined perovskite colloidal quantum dots (PeQDs) due to particle interaction. Here it is demonstrated that electronic coupling and energy transfer in PeQDs induce redshift in the emission by PeQD film, and consequently hinder deep-blue emission. To achieve deep-blue emission by avoiding electronic coupling and energy transfer, a QD-in-organic solid solution is introduced to physically separate the QDs in the film. This physical separation of QDs reduces the interaction between them yielding a blueshift of ≈7 nm in the emission spectrum. Moreover, using a hole-transporting organic molecule with a deep-lying highest occupied molecular orbital (≈6.0 eV) as the organic matrix, the formation of exciplex emission is suppressed. As a result, an unprecedently high maximum external quantum efficiency of 6.2% at 462 nm from QD-in-organic solid solution film in PeLEDs is achieved, which satisfies the deep-blue color coordinates of CIEy < 0.06. This work suggests an important material strategy to deepen blue emission without reducing the particle size to <≈4 nm.

The objective is to study the harmonic forced wave motion over a beach by a finite Fourier transform technique. The constructed approximate solution has a logarithmic singularity at the shoreline. It accounts for reflexion and local perturbations. Trapping of waves may take place for particular choices of the applied surface pressure excess. The case of a wave incident against a cliff with horizontal bottom is solved exactly. The method deals invariably with a variety of bottom shapes, including the case where there is an additional corrugation of the bottom on a finite interval. Other bottom boundary conditions than impermeability can be treated as well. The results may be of interest in several practical applications, in particular the evaluation of the reflected wave. Numerical applications for a plane sloping beach, a parabolic-type beach and a shelf-type beach are presented and the systems of streamlines have been drawn over and in the proximity of the beach.

Hybrid nanomaterials containing both noble metal and semiconductor building blocks provide an engineerable platform for realizing direct or indirect charge and energy transfer for enhanced plasmonic photoconversion and photocatalysis. In this work, silver nanoparticles (AgNPs) and chalcopyrite (CuFeS2) nanocrystals (NCs) are combined into a AgNP@CuFeS2 hybrid structure comprising NCs embedded in a self-assembled lipid coating around the AgNP core. In AgNP@CuFeS2 hybrid structures, both metallic and semiconductor NCs support quasistatic resonances. To characterize the interactions between these resonances and their effect on potential charge and energy transfer, direct interfacial excitation transfer between the AgNP core and surrounding CuFeS2 NCs is probed through single particle line shape analysis and supporting electromagnetic simulations. These studies reveal that CuFeS2 NCs localized in the evanescent field of the central AgNP induce a broadening of the metal NP line shape that peaks when an energetic match between the AgNP and CuFeS2 NC resonances maximizes direct energy transfer. Dimers of AgNPs whose resonances exhibit poor energetic overlap with the CuFeS2 NC quasistatic resonance yield much weaker line shape broadening in a control experiment, corroborating the existence of resonant energy transfer in the AgNP@CuFeS2 hybrid. Resonant coupling between the metallic and semiconductor building blocks in the investigated hybrid architecture provides a mechanism for utilizing the large optical cross-section of the central AgNP to enhance the generation of reactive charge carriers in the surrounding semiconductor NCs for potential applications in photocatalysis.

Using femtosecond differential spectroscopy, excitation energy transfer in reaction centers (RCs) of the carotenoidless strain of purple bacteria Rhodospirillum rubrum G9 was studied at room temperature. Excitation and probing of the Qy, Qx and Soret absorption bands of the RCs were carried out by pulses with duration of 25-30 fs. Modeling of ΔA (light - dark) kinetics made it possible to estimate the characteristic time of various stages of excitation energy transformation. It is shown that the dynamics of the downhill energy flow in the RCs is determined both by the internal energy conversion Soret→ Qx → Qy in each cofactor and by the energy transfer H* → B* → P* (H - bacteriopheophytin, B - bacteriochlorophyll a, P - bacteriochlorophyll a dimer) between cofactors. The transfer of energy between the upper excited levels (Soret and Qx) of the cofactors accelerates its arrival to the lower exciton level of the P, from where charge separation begins. It turned out that all conversion and energy transfer processes occur within 40-160 fs: the conversion Soret → Qx occurs in 40-50 fs, the conversion Qx → Qy occurs in 100-140 fs, the transfer H* → B* has a time constant of 80-120 fs, and the transfer B* → P* has a time constant of 130-160 fs. The rate of energy transfer between the upper excited levels is close to the rate of transfer between Qy levels.

The vertical phase distribution of active layers plays a vital role in balancing exciton dissociation and charge transport for achieving efficient polymer solar cells (PSCs). The layer-by-layer (LbL) PSCs are commonly prepared by using sequential spin-coating method from donor and acceptor solutions with distinct solvents and solvent additives. The enhanced exciton dissociation is expected in the LbL PSCs with efficient charge transport in the relatively neat donor or acceptor layers. In this work, a series of LbL all-polymer solar cells (APSCs) were fabricated with PM6 as donor and PY-DT as acceptor, and triplet material m-Ir(CPmPB)3 is deliberately incorporated into PY-DT layer to prolong exciton lifetimes of active layers. The power conversion efficiency (PCE) of LbL APSCs is improved to 18.24% from 17.32% by incorporating 0.3 wt% m-Ir(CPmPB)3 in PY-DT layer, benefiting from the simultaneously enhanced short-circuit current density (JSC) of 25.17 mA cm-2 and fill factor (FF) of 74.70%. The enhancement of PCE is attributed to the efficient energy transfer of m-Ir(CPmPB)3 to PM6 and PY-DT, resulting in the prolonged exciton lifetime in the active layer and the increased exciton diffusion distance. The efficient energy transfer from m-Ir(CPmPB)3 to PM6 and PY-DT layer can be confirmed by the increased photoluminescence (PL) intensity and the prolonged PL lifetime of PM6 and PY-DT in PM6 + m-Ir(CPmPB)3 and PY-DT + m-Ir(CPmPB)3 films. This study indicates that the triplet material as solid additive has great potential in fabricating efficient LbL APSCs by prolonging exciton lifetimes in active layers.

Ultrafast spectroscopic techniques have been vital in studying excitation energy transfer (EET) in photosynthetic light harvesting complexes. In this paper, we simulate the pump-probe spectra of the B850 band of the light harvesting complex 2 (LH2) of purple bacteria, by using the hierarchical equation of motion method and the optical response function approach. The ground state bleach, stimulated emission, and excited state absorption components of the pump-probe spectra are analyzed in detail. The laser pulse-induced population dynamics are also simulated to help understand the main features of the pump-probe spectra and the EET process. It is shown that the excitation energy relaxation is an ultrafast process with multiple time scales. The first 40 fs of the pump-probe spectra is dominated by the relaxation of the k = ±1 states to both the k = 0 and higher energy states. Dynamics on a longer time scale around 200 fs reflects the relaxation of higher energy states to the k = 0 state.

We construct and analyze disconnectivity graphs to provide the first graphical representation of the vibrational energy landscape of a protein, in this study β2AR, a G-protein coupled receptor (GPCR), in active and inactive states. The graphs, which indicate the relative free energy of each residue and the minimum free energy barriers for energy transfer between them, reveal important composition, structural and dynamic properties that mediate the flow of energy. Prolines and glycines, which contribute to GPCR plasticity and function, are identified as bottlenecks to energy transport along the backbone from which alternative pathways for energy transport via nearby noncovalent contacts emerge, seen also in the analysis of first passage time (FPT) distributions presented here. Striking differences between the disconnectivity graphs and FPT distributions for the inactive and active states of β2AR are found where structural and dynamic changes occur upon activation, contributing to allosteric regulation.

Chemiluminescence resonance energy transfer (CRET) efficiency can be enhanced by confining CRET donors and acceptors within nanoscale spaces. However, this enhanced efficiency is often affected by uncertainties stemming from the random distribution of CRET donors and acceptors in such confined environments. In this study, a novel confined nanospace was created through the surfactant modification of carbon dots (CDs) exhibiting aggregation-induced emission (AIE) characteristics. Hydrophobic CRET donors could be effectively confined within this nanospace. The distance between the CRET donors and acceptors could be controlled by anchoring the AIE-CDs as the CRET acceptors, resulting in significantly improved CRET efficiency. Furthermore, this AIE-CDs-based CRET system was successfully applied to the detection of hydrogen peroxide (H2O2) in rainwater, showcasing its potential for practical applications.