Raman spectroscopy of solutions and interfaces containing nitrogen dioxide, water, and 1,4 dioxane: evidence for repulsion of surface water by NO2 gas.

The interaction of water, 1,4 dioxane, and gaseous nitrogen dioxide, has been studied as a function of distance measured through the liquid-vapour interface by Raman spectroscopy with a narrow (<0.1 mm) laser beam directed parallel to the interface. The Raman spectra show that water is present at the surface of a dioxane-water mixture when gaseous NO2 is absent, but is virtually absent from the surface of a dioxane-water mixture when gaseous NO2 is present.

Electroluminescent, polycrystalline cadmium selenide nanowire arrays.

Electroluminescence (EL) from nanocrystalline CdSe (nc-CdSe) nanowire arrays is reported. The n-type, nc-CdSe nanowires, 400-450 nm in width and 60 nm in thickness, were synthesized using lithographically patterned nanowire electrodeposition, and metal-semiconductor-metal (M-S-M) devices were prepared by the evaporation of two gold contacts spaced by either 0.6 or 5 μm.

Oxidative quenching within photosensitizer-acceptor dyads based on bis(bidentate) phosphine-connected osmium(II) bipyridyl light absorbers and reactive metal sites.

For the first time oxidative quenching of OsPN chromophores by reactive Pt or Pd sites containing , , -1,2,3,4-tetrakis(diphenylphosphino)cyclobutane (dppcb) is directly observed despite the presence of a saturated cyclobutane backbone "bridge". This dramatic effect is measured as a sudden temperature-dependent onset of a reduction in phosphorescence lifetime in [Os(bpy)(dppcb)MCl](SbF) (M = Pt, ; Pd, ). The appearance of this additional energy release is not detectable in [Os(bpy)(dppcbO)](PF) (), where dppcbO is , , -1,2-bis(diphenylphosphinoyl)-3,4-bis(diphenylphosphino)cyclobutane.

Light-triggered charge reversal of organic-silica hybrid nanoparticles.

A functional nanoparticle with light-triggered charge reversal based on a protected amine-bridged polysilsesquioxane was designed. An emulsion- and amine-free sol-gel synthesis was developed to prepare uniform nanospheres. Photolysis of suspensions of these nanoparticles results in a reversal of the ζ potential.

High-throughput fabrication of photoconductors with high detectivity, photosensitivity, and bandwidth.

Nanocrystalline cadmium selenide (nc-CdSe) was electrodeposited within a sub-50 nm gold nanogap, prepared by feedback-controlled electromigration, to form a photoconductive metal-semiconductor-metal nanojunction. Both gap formation and electrodeposition were rapid and automated. The electrodeposited nc-CdSe was stoichiometric, single cubic phase with a mean grain diameter of ∼7 nm.

Tunable photoconduction sensitivity and bandwidth for lithographically patterned nanocrystalline cadmium selenide nanowires.

Nanocrystalline cadmium selenide (nc-CdSe) nanowires were prepared using the lithographically patterned nanowire electrodeposition method. Arrays of 350 linear nc-CdSe nanowires with lateral dimensions of 60 nm (h) × 200 nm (w) were patterned at 5 μm pitch on glass. nc-CdSe nanowires electrodeposited from aqueous solutions at 25 °C had a mean grain diameter, d(ave), of 5 nm.

Surprising photochemical reactivity and visible light-driven energy transfer in heterodimetallic complexes.

The bis(bidentate) phosphine cis,trans,cis-1,2,3,4-tetrakis(diphenylphosphino)cyclobutane (dppcb) has been used for the synthesis of a series of novel heterodimetallic complexes starting from [Ru(bpy)(2)(dppcb)]X(2) (1; X = PF(6), SbF(6)), so-called dyads, showing surprising photochemical reactivity. They consist of [Ru(bpy)(2)](2+)"antenna" sites absorbing light combined with reactive square-planar metal centres. Thus, irradiating [Ru(bpy)(2)(dppcb)MCl(2)]X(2) (M = Pt, 2; Pd, 3; X = PF(6), SbF(6)) dissolved in CH(3)CN with visible light, produces the unique heterodimetallic compounds [Ru(bpy)(CH(3)CN)(2)(dppcb)MCl(2)]X(2) (M = Pt, 7; Pd, 8; X = PF(6), SbF(6)).

Real-time dissociation dynamics of the Ne(2)Br(2) van der Waals complex.

We have characterized the vibrational predissociation (VP) of the Ne(2)Br(2) van der Waals complex using time- and frequency-resolved pump-probe spectroscopy. After exciting Br(2) within the complex to a vibrational level 16 View Article and Find Full Text PDF

20 micros photocurrent response from lithographically patterned nanocrystalline cadmium selenide nanowires.

Lithographically patterned nanowire electrodeposition (LPNE) provides a method for patterning nanowires composed of nanocrystalline cadmium selenide (nc-CdSe) over wafer-scale areas. We assess the properties of (nc-CdSe) nanowires for detecting light as photoconductors. Structural characterization of these nanowires by X-ray diffraction and transmission electron microscopy reveals they are composed of stoichiometric, single phase, cubic CdSe with a mean grain diameter of 10 nm.

Competition between electronic and vibrational predissociation dynamics of the HeBr2 and NeBr2 van der Waals molecules.

Direct measurements of the lifetimes of He(79)Br(2) and Ne(79)Br(2) B-state vibrational levels 10 < or = nu' < or = 20 have been performed using time-resolved optical pump-probe spectroscopy. The values do not obey the energy gap law for direct vibrational predissociation. For both molecules, the dissociation rate for nu'=11 is much faster than for nu'=12, and the nu'=13 rate is also faster than is consistent with the energy gap law.

Product state resolved excitation spectroscopy of He-, Ne-, and Ar-Br2 linear isomers: experiment and theory.

Valence excitation spectra for the linear isomers of He-, Ne-, and Ar-Br2 are reported and compared to a two-dimensional simulation using the currently available potential energy surfaces. Excitation spectra from the ground electronic state to the region of the inner turning point of the Rg-Br2 (B,nu') stretching coordinate are recorded while probing the asymptotic Br2 (B,nu') state. Each spectrum is a broad continuum extending over hundreds of wavenumbers, becoming broader and more blueshifted as the rare gas atom is changed from He to Ne to Ar.

Time and frequency resolved dynamics of ArBr2.

We report the first spectroscopic observation of and vibrational predissociation dynamics for ArBr(2). Measurements are reported for the linear and T-shaped isomers with time and frequency resolution near the Fourier limit of a 15 ps pulse. For the T-shaped isomer, the Ar-Br(2) bond energy D(0) for the B state, nu(')=19, is found to be 200 cm(-1), yielding a D(0)(X) value of 213 cm(-1).

Methylene blue inhibits amyloid Abeta oligomerization by promoting fibrillization.

Amyloid plaques are hallmark neuropathological lesions in Alzheimer's disease, which consist of abnormally aggregated Abeta protein. Multiple Abeta aggregated species have been identified, and neurotoxicity appears to be correlated with the amount of nonfibrillar oligomers. Therefore, selective inhibition of Abeta oligomer formation has emerged as an attractive means of therapeutic intervention.

Time-dependent pump-probe spectra of NeBr2.

Time- and frequency-resolved pump-probe measurements on NeBr2 have been performed to better characterize its fragmentation dynamics on the B electronic state for vibrational levels in the energy region of the transition from direct vibrational predissociation to intramolecular vibrational relaxation dynamics. Above nu'=20 of the Br2 stretching mode, it was observed that the dependence of lifetime on the vibrational quantum number deviates from the energy-gap law by leveling off in the range of 10 psE transitions of the complex.

Conductive carbon filled polymeric electrodes: novel ion optical elements for time-of-flight mass spectrometers.

A new technique employing conductive polymeric electrodes for the generation of linear electric fields is proposed and validated. A hollow cylinder comprised of DuPont's Vespel SP-22, a polymer loaded with conductive carbon particles, is used to enhance the performance of a hybrid reflectron compared to a conventional dual stage gridless reflectron composed of discrete metal ring electrodes. Both devices have comparable physical dimensions and nearly identical ion optical properties.