Hexaphenylbenzene (HPB) derivatives 5 and 7 having rhodamine B moieties have been designed and synthesized, and have been shown to display solvent dependent. Fluorescence resonance energy transfer (FRET) and through bond energy transfer (TBET) in the presence of Hg(2+) ions among the various cations (Cu(2+), Pb(2+), Zn(2+), Ni(2+), Cd(2+), Ag(+), Ba(2+), Mg(2+), K(+), Na(+), and Li(+)) have been tested. Derivative 5 displays quite high through bond energy transfer efficiency in the presence of Hg(2+) ions in methanol whereas derivative 7 exhibits better FRET efficiency in the presence of Hg(2+) ions in THF and CH(3)CN than derivative 5.

A new series of D-A-D molecules (1-3) with carbazole as a donor and 2,5-diaryl-1,3,4-oxadiazole, dibenzothiophene-S,S-dioxide and benzo[1,2,5]thiadiazole as acceptors have been synthesized. Polyphenylene dendrons have also been incorporated to prevent the face to face π-π stacking in aggregates. Unlike traditional D-A systems, which show ACQ problems and large red shifts in the solid state, these derivatives (1-3) exhibit good solid state luminescence behavior without undergoing a red shift or fluorescence quenching. The present results indicate that just the combination of a donor-acceptor system with bulkier dendrons is not enough to generate efficient solid state emissions but the prevention of co-facial interaction between donors and acceptors in aggregates is more important. In the case of derivative 3, restriction of complete molecular planarization and steric hindrance near the acceptor can effectively prevent intermolecular donor-acceptor interactions, thus leading to enhanced emission in aggregates. While in the case of derivative 1, a sterically unhindered acceptor is easily approached by a donor due to close molecular packing in aggregates forming weakly luminescent species.

We report on a method of fabricating lanthanum hexaboride (LaB 6) cold field emission tips with sub-100-nm apices by using a combination of electrochemical etching and focused ion beam milling. The primary advantage of combining the two methods is rapid fabrication while maintaining reproducibility. The LaB 6 tips have low work functions and high mechanical stabilities and are chemically inert to residual gases. Field emission characterization was performed on three tips, with apex sizes of 15, 85, and 80 nm yielding 10 nA cold field emission currents at 0.76, 3.9, and 3.6 kV extraction potentials, respectively. All three tips showed excellent emission current stability for periods exceeding 30 min in a 5 Â 10 À9 mbar vacuum.

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A series of blue fluorescent, 3,39-linked carbazole-based linear conjugated molecules (1-5) have been synthesized with phenyl, ethynylene, and ethynylphenyl spacers. Their photophysical, electrochemical and thermal properties have been studied to elucidate structure-property relationships. These chromophores have a high thermal stability and exhibit high fluorescence quantum yields of the order of 0.98. In addition, an OLED device was fabricated using compound 4 which shows bluish electroluminescence (CIE, x = 0.25, y = 0.23).

Oscillations in subnormal glow discharges under DC excitation at different pressures have been studied. A residual current has been observed in these oscillations. A study of this current is presented. A possible method for measuring the characteristic loss time for ions and electrons, under given experimental conditions, is also indicated.

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