Controlling Thermally Activated Delayed Photoluminescence in CdSe Quantum Dots through Triplet Acceptor Surface Coverage.

Quantum-dot/molecule composites (QD/mol) have demonstrated useful photochemical properties for many photonic and optoelectronic applications; however, a comprehensive understanding of these materials remains elusive. This work introduces a series of cadmium(II) selenide/1-pyrenecarboxylic acid (CdSe/PCA) nanomaterials featuring bespoke PCA surface coverage on CdSe585 (coded by the peak of the first exciton absorption band) to glean insight into the QD/mol photophysical behavior. Tailoring the energy gap between the CdSe585 first exciton band (2.

TIPS-pentacene triplet exciton generation on PbS quantum dots results from indirect sensitization.

Many fundamental questions remain in the elucidation of energy migration mechanisms across the interface between semiconductor nanomaterials and molecular chromophores. The present transient absorption study focuses on PbS quantum dots (QDs) of variable size and band-edge exciton energy (ranging from 1.15 to 1.

Thermally Activated Delayed Photoluminescence: Deterministic Control of Excited-State Decay.

Thermally activated photophysical processes are ubiquitous in numerous organic and metal-organic molecules, leading to chromophores with excited-state properties that can be considered an equilibrium mixture of the available low-lying states. Relative populations of the equilibrated states are governed by temperature. Such molecules have been devised as high quantum yield emitters in modern organic light-emitting diode technology and for deterministic excited-state lifetime control to enhance chemical reactivity in solar energy conversion and photocatalytic schemes.

Energy Migration Processes in Re(I) MLCT Complexes Featuring a Chromophoric Ancillary Ligand.

We present the synthesis, structural characterization, electronic structure calculations, and ultrafast and supra-nanosecond photophysical properties of a series of five Re(I) bichromophores exhibiting metal to ligand charge transfer (MLCT) excited states based on the general formula -[Re(NN)(CO)(PNI-py)]PF where PNI-py is 4-piperidinyl-1,8-naphthalimidepyridine and NN is a diimine ligand (-), along with their corresponding model chromophores where 4-ethylpyridine was substituted for PNI-py (-). The diimine ligands used include 1,10-phenanthroline (phen, ), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (bcp, ), 4,4'-di--butyl-2,2'-bipyridine (dtbb, ), 4,4'-diethyl ester-2,2'-bipyridine (deeb, ), and 2,2'-biquinoline (biq, ). In these metal-organic bichromophores, structural modification of the diimine ligand resulted in substantial changes to the observed energy transfer efficiencies between the two chromophores as a result of the variation in MLCT excited-state energies.

Realization of high-efficiency fluorescent organic light-emitting diodes with low driving voltage.

It is commonly accepted that a full bandgap voltage is required to achieving efficient electroluminescence (EL) in organic light-emitting diodes. In this work, we demonstrated organic molecules with a large singlet-triplet splitting can achieve efficient EL at voltages below the bandgap voltage. The EL originates from delayed fluorescence due to triplet fusion.

Energy Transfer Dynamics in Triplet-Triplet Annihilation Upconversion Using a Bichromophoric Heavy-Atom-Free Sensitizer.

A heavy-atom-free triplet sensitizer suitable for triplet-triplet annihilation-based photon upconversion was developed from the thermally activated delayed fluorescence (TADF) molecule 4CzPN by covalently tethering a pyrene derivative (DBP) as a triplet acceptor. The triplet exciton produced by 4CzPN is captured by the intramolecular pyrenyl acceptor and subsequently transferred via intermolecular triplet-triplet energy transfer (TTET) to freely diffusing pyrenyl acceptors in toluene. Transient absorption and time-resolved photoluminescence spectroscopy were employed to examine the dynamics of both the intra- and intermolecular TTET processes, and the results indicate that the intramolecular energy transfer from 4CzPN to DBP is swift, quantitative, and nearly irreversible.

Electrochemical Synthesis of Binary and Ternary Niobium-Containing Oxide Electrodes Using the p-Benzoquinone/Hydroquinone Redox Couple.

New electrochemical synthesis methods have been developed to obtain layered potassium niobates, KNb3O8 and K4Nb6O17, and perovskite-type KNbO3 as film-type electrodes. The electrodes were synthesized from aqueous solutions using the redox chemistry of p-benzoquinone and hydroquinone to change the local pH at the working electrode to trigger deposition of desired phases. In particular, the utilization of electrochemically generated acid via the oxidation of hydroquinone for inorganic film deposition was first demonstrated in this study.

Brain size and visual environment predict species differences in paper wasp sensory processing brain regions (hymenoptera: vespidae, polistinae).

The mosaic brain evolution hypothesis predicts that the relative volumes of functionally distinct brain regions will vary independently and correlate with species' ecology. Paper wasp species (Hymenoptera: Vespidae, Polistinae) differ in light exposure: they construct open versus enclosed nests and one genus (Apoica) is nocturnal. We asked whether light environments were related to species differences in the size of antennal and optic processing brain tissues.