Solid-State, Near-Infrared to Visible Photon Upconversion via Triplet-Triplet Annihilation of a Binary System Fabricated by Solution Casting.

Herein, triplet-triplet annihilation upconversion (TTA-UC) from near-infrared (NIR, 785 nm) to visible (yellow, centered at 570 nm) regions has been demonstrated in the binary solid of condensed chromophores. Microparticles of the binary solid comprising rubrene as a matrix (emitter) and π-extended Pd-porphyrin as a dopant (sensitizer) in a mole ratio of 1000:1 were obtained by solution casting. Excitation intensity dependence and quantum yield (QY) of the upconverted emission were characterized for individual particles under a microscope and revealed a low threshold intensity (∼100 mW/cm2) as compared to the solution and moderate UC-QY (∼0.5%) in the NIR range. The factors contributing to the UC-QY were investigated by time-resolved and steady-state spectroscopies. It was found that the intersystem crossing of the sensitizer, triplet energy transfer, and TTA occurred efficiently in the binary solid, and the fluorescence QY of the emitter governed the UC-QY.

Hydrogen evolution from glycerol aqueous solution under aerobic conditions over Pt/TiO2 and Au/TiO2 granular photocatalysts.

Hydrogen was efficiently evolved from glycerol aqueous solution upon vertical photoirradiation of a Pt/TiO2 or Au/TiO2 bed under aerobic conditions. Granular photocatalysts were easily deposited, leading to high H2 selectivity (80-95%), whereas glycerol oxidation with CO2 evolution became dominant when suspended powder photocatalysts were used.

Orientation of α-sexithiophene on friction-transferred polythiophene film.

Controlling the molecular orientation of the conjugated oligomer, α-sexithiophene (6T), is crucial to improve organic optoelectronic device performance. Most 6T molecules evaporated onto quartz and SiO(2)/Si substrates orient nearly perpendicular to the substrate. Here, we report the formation of oriented thin films of 6T on in-plane-oriented polythiophene (PT) films formed by the friction-transfer method. 6T was evaporated onto oriented PT films under vacuum. The films were investigated by polarized optical microscopy, polarized ultraviolet-visible light (UV-vis) absorption spectroscopy, and grazing incidence X-ray diffraction measurement (GIXD). In all spectra, larger absorbance derived from PT and 6T was observed, in parallel polarization to the friction direction, compared to that of orthogonal polarization. These results indicate that the 6T molecular axis is aligned in the friction direction (PT chain direction) of PT films. GIXD also confirmed that the 6T molecular axis was aligned parallel to the PT chain axis. In contrast, 6T molecules evaporated onto quartz and poly(ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)-coated silicon substrates aligned nearly perpendicular to the substrate. These results indicate that oriented PT films induce 6T orientation parallel to the PT chain direction.