Molecules that undergo reverse intersystem-crossing (RISC), which enables thermally activated delayed fluorescence, represent an important advance in the development of organic-based light-emitting diodes (OLEDs). The current study focuses on two blue-emitting RISC molecules employing carbazole as the donor and benzothiazole or benzoxazole derivative as the acceptor (BTZ/BOX-carbazole (CBZ)). Although the emission maxima of these compounds are deep blue (∼410 nm) in hydrocarbon solvents, their spectra broaden, red shift, and decrease in intensity with even a modest increase in solvent polarity because of their strong charge-transfer (CT) character. These effects are qualitatively predicted from time-dependent density functional theory calculations using the state-specific polarizable continuum model, though the emission spectral shifts are significantly overestimated. The desired blue emission peak of both compounds (∼425 nm) is recovered by rigidifying the environment, either in low-temperature glasses or in room-temperature polymer films, independent of local polarity. The polarity-induced emission red shift is therefore due to the solvent orientational polarizability. The effects of an applied electric field on the spectra (Stark effect) are used to quantify the CT character of the absorbing and emitting states. Significantly less field-induced emission quenching is observed in BOX-CBZ versus that in BTZ-CBZ. Minimizing this effect is important for the performance in the large (1–10 MV) fields present within OLED devices.

propnet is a computational framework to explore the network of relationships between fundamental materials properties. There exist many equations and models known from the materials science literature that provide the links between these properties, and this allows the representation of property connections as a larger, interconnected graph. Exploring this graph in a systematic away allows the automatic augmentation of existing materials databases and also provides new ways to gain insight into the relationships between the material properties themselves.

Although bulk silicon (Si) is known to be a poor emitter, Si nanoparticles (NPs) exhibit size-dependent photoluminescence in the red or near-infrared due to quantum confinement. Recently, it has been shown that surface modification of Si NPs with nitrogen-capped ligands results in bluer emission wavelengths and quantum yields of up to 90%. However, the emission mechanism operating in these surface-modified Si NPs and the factors that determine their emission maxima are still unclear. Here, the emission in these species is shown to arise from a charge-transfer state between the Si surface and the ligand. The energy of this state is linearly correlated to the calculated ground-state dipole moment of the free ligand. This trend can be used in a predictive fashion for the design and synthesis of Si NPs with a broader range of emission wavelengths.

Field-induced fluorescence quenching of poly(p-phenylene vinylene) (PPV) oligomers due to nonradiative relaxation through free electron-hole pair (FEHP) states is modeled using singles configuration interaction computations with the intermediate neglect of differential overlap Hamiltonian. The computations find FEHP states with energies that drop linearly with applied field and undergo avoided crossings with the fluorescent state. The coupling between the FEHP and fluorescent state, computed for multiple FEHP states on a variety of oligomer lengths, is found to depend primarily on the field strength required for the state to cross the fluorescent state. The rate of decay to these dark FEHP states is then calculated from Marcus theory, which is modified to take into account dielectric in addition to other bulk measurement considerations. The results predict that individual molecules go from being emissive to fully quenched over a small range of applied field strengths. Phenomenological introduction of inhomogeneous broadening for the energies of the FEHP states leads to a more gradual dependence on applied field. The fluorescence quenching mechanism considered here is found to be important for applied fields above about 1 MV cm(-1), which is similar in magnitude to those present in light-emitting diodes.

EL4 is a murine lymphoma cell line developed in 1945 by treating C57 black mice with 9:10-dimethyl-1:2-benzanthracene (1). The cells were originally propagated in animal hosts, prior to adaptation to cell culture. EL4 cells were used for many years as a source of interleukin-2 (IL2), which they secrete when treated with phorbol 12-myristate 13-acetate (PMA).The EL4 cell line originally provided to us, by a colleague at the University of Washington, was heterogeneous with respect to PMA response. We, therefore, developed and characterized EL4 sub-lines. Wild-type (WT)-derived cell lines, which are PMA responsive, grow readily in suspension culture as did the original strain. Variant (V)-derived (PMA-resistant) sub-lines were selected for enhanced adhesion to tissue culture plastic (2). Clonal lines were developed from both cell types by limiting dilution (3). The PMA sensitivity of WT-derived cells, as reflected by PMA-induced IL2 production and mitogen-activated protein kinase (ERK1/2) activation, has been attributed to expression of Ras guanyl nucleotide releasing protein 1 (RasGRP1), which binds PMA and directly activates Ras (4); V-derived cells do not express RasGRP1.Clonal EL4 cell lines were used for experimental metastasis studies in syngeneic mice, with WT2 and V7 as prototypes (5, 6). WT2 cells do not form tumors (nonmetastatic), while V7 cells form liver tumors (metastatic) after tail vein injection. 'Metastasis' more strictly refers to tumorigenesis in this model, since circulating EL4 cells home to the liver to form tumors (5). The clonal C5 cell line was developed after stably overexpressing human hemagllutinin (HA)-tagged phospholipase D2 (PLD2) in V7 cells in order to characterize the signaling role of PLD2 using a cell line expressing little or no endogenous PLD2 (5). As compared to V7, C5 cells exhibit increased cell migration (7) and tumor growth (5), providing an early example of the positive role of PLD2 in tumorigenesis.This report presents data from microarray analyses comparing transcripts expressed by these three EL4 cell types, with the goal of further defining their phenotypes.