Recent developments in rechargeable battery technology have seen a shift from the well-established Li-ion technology to new chemistries to achieve the high energy density required for extended range electric vehicles and other portable applications, as well as low-cost alternatives for stationary storage. These chemistries include Li-air, Li-S, and multivalent ion technologies including Mg , Zn , Ca , and Al . While Mg battery systems have been increasingly investigated in the last few years, Ca technology has only recently been recognized as a viable option. In this first comprehensive review of Ca ion technology, the use of Ca metal anodes, alternative alloy anodes, electrolytes suitable for this system, and cathode material development are discussed. The advantages and disadvantages of Ca ion batteries including prospective achievable energy density, cost reduction due to high natural abundance, low ion mobility, the effect of ion size, and the need for elevated temperature operation are reviewed. The use of density functional theory modeling to predict the properties of Ca-ion battery materials is discussed and the extent to which this approach is successful in directing research into areas of promise is evaluated. To conclude, a summary of recent achievements is presented and areas for future research efforts evaluated.

Postfunctionalization of poly(3-hexylthiophene) (P3HT) enables the systematic study of electronic and steric effects of various functional groups on the optical and photophysical properties of 3,4-disubstituted poly(thiophene)s. In solution, these 3,4-disubstituted poly(thiophene)s exhibit a lower fluorescence yield (Φ fl) than P3HT. In the solid state, bromo, chloro, and formyl groups increase Φfl, whereas nitro groups completely quench fluorescence. Phenyl, p-tolyl, 2-and 4-methoxyphenyl, 2-thienyl, biphenyl, and 1-naphthyl substituents increase the solid-state fluorescence of P3HT by a factor of 2-3 as a result of steric interactions that force the aromatic substituents perpendicular to the main chain. An extensive enhancement in the solid-state Φ fl, 12 times greater than that of P3HT, is observed for polymers containing ortho-alkylphenyl or 2-(3-alkyl)thienyl groups, because of additional steric interactions between methyl or R-methylene hydrogens on the phenyl or thienyl substituents and main-chain thienyl groups. These interactions further increase the planarity of the polymer backbone and lead to an enlargement of the interplanar distance. Partial substitution of P3HT with o-tolyl groups affords polymer films with a solid-state Φ fl of up to 22%.

We have investigated a series of branched fluorescent sensing compounds with thiophene units in the arms and triphenylamine centers for the detection of nitrated model compounds for 2,4,6-trinitrotoluene (TNT) and the plastic explosives taggant 2,3-dimethyl-2,3-dinitrobutane (DMNB). Stern−Volmer measurements in solution show that the fluorescence is more efficiently quenched by nitroaromatic compounds when compared to a non-nitrated quencher, benzophenone. Simple modification of the structure of the sensing compound was found to result in significant changes to the sensitivity and selectivity toward the nitrated analytes. A key result from time-resolved fluorescent measurements showed that the chromophore−analyte interaction was primarily a collisional process. This process is in contrast to conjugated polymers where static quenching dominates, a difference that could offer a potentially more powerful detection mechanism.

Mes 2 B(p-4,4′-biphenyl-NPh(1-naphthyl)), (BNPB) a novel luminescent molecule that contains part of the well-known NPB functionality (NPB ) N, N′-di-1-naphthyl-N,N′-diphenylbenzidine) and a threecoordinate boron center has been synthesized. BNPB is a bright blue emitter with λ max (emission) ) 452 nm and a photoluminescent quantum yield of 95% in solution and 31% in the solid state. BNPB is an amorphous material and forms films readily via either solution casting or vacuum vapor deposition. A single layer EL device A with the device structure of ITO/BNPB/LiF/Al, two double-layer EL devices B and C with the device structure of ITO/NPB/BNPB/Ag for B and ITO/BNPB/Alq 3 /LiF/Al for C, and a triple-layer device D with the structure of ITO/NPB/BNPB/Alq 3 /LiF/Al have been fabricated and their performance has been evaluated. Device A produces a weak blue electroluminescence (EL). Device B produces a bright blue EL, identical to that of device A. Device C produces a green EL, typical of Alq 3 . Device D produces a broadband whitish-blue EL attributable to dual emission from the BNPB zone and the Alq 3 zone. Devices A-D demonstrate that BNPB is capable of transporting both holes and electrons in addition to being a blue emitter for EL devices.