A molecular thermometer based on luminescence of copper(II) tetraphenylporphyrin

The photoluminescence (PL) spectra from solid samples consisting of polystyrene and 5,10,15,20-tetraphenyl-21H,23H-porphine copper(II) (CuTPP) revealed two sharp peaks at 653 and 720 nm, and indicated another broad peak at around 780 nm, which could not be observed in CuTPP solutions. The intensity ratio of the two peaks appearing at 653 nm and at around 780 nm demonstrated clear dependence on temperature. This dependence of the PL intensity ratio was observed under the atmosphere and even in water. The findings mean that we were able to utilize PL from CuTPP as a thermometer under various conditions. We measured the temperatures of an organic light-emitting diode (OLED) during operation based on its electroluminescence, where the OLED contained CuTPP as a light-emitting dopant, to demonstrate the CuTPP thermometer.ArticleThin Solid Films. 518(2):563-566 (2009)journal articl

Bi- or ter-pyridine tris-substituted benzenes as electron-transporting materials for organic light-emitting devices

We demonstrated that 1,3,5-tris([2',2 '']bipyridin-6'-yl) benzene (BpyB) and 1,3,5-tris([ 2',2 '',6 '',2''']terpyridin-6'-yl)benzene (TpyB) are good electron-transport (ET) layer materials for organic light-emitting devices (OLEDs). The new materials exhibit high electron mobilities of around 10 (4) cm(2) V (1) s (1), and OLEDs comprising the materials operate at lower voltage than the OLEDs with tris(8-hydroxyquinolinato) aluminum (Alq) as an ET material. The new materials are also useful for phosphorescent OLEDs in blue-, green-, and red-light-emitting devices, where they function as both electron-transporting and hole-blocking materials. Phosphorescent OLEDs with the new materials operate at lower voltage (while maintaining comparable external quantum efficiencies of electroluminescence) than does the corresponding reference device with bathocuproine/Alq as electron-transporting and hole-blocking layers.ArticleORGANIC ELECTRONICS. 11(12):1966-1973 (2010)journal articl

Thin-film and single-crystal transistors based on a trifluoromethyl-substituted alternating (thiophene/phenylene)-co-oligomer

We demonstrated the performance of thin-film transistors (TFTs) and single-crystal field-effect transistors (FETs) based on a trifluoromethyl-substituted alternating (thiophene/phenylene)-co-oligomer (AC5-CF3), 1,4-bis(5'-(4 ''-trifluoromethylphenyl)thiophene-2'-yl) benzene. An FET with a fine AC5-CF3 single-crystal demonstrated field-effect mobility as high as 3.1 cm(2) V-1 s(-1). This value implies that AC5-CF3 must be a useful n-type organic semiconducting material. The performance of AC5-CF3 TFTs depended on the substrate temperatures at which AC5-CF3 thin films were deposited. From the viewpoint of mobility, threshold voltage and sub-threshold slope, we obtained the highest performance at the substrate temperature of 100 degrees C. This was because a higher substrate temperature for deposition enlarged the size of grains in AC-CF3 thin films and improved the characteristics of grain boundaries. However, 120 degrees C depositions of AC5-CF3 induced deep valley-like cracks in the thin films, probably because of the difference between the coefficients of thermal expansion for AC5-CF3 thin films and silicon wafer substrates, resulting in effects such as worsening mobility. AC5-CF3 TFTs prepared at 100 degrees C deposition showed no channel length dependence of the field-effect mobility, and their average field-effect mobility was 0.55 +/- 0.05 cm(2) V-1 s(-1).ArticleOrganic Electronics. 11(9):1549-1554 (2010)journal articl

Bi- or ter-pyridine tris-substituted benzenes as electron-transporting materials for organic light-emitting devices

We demonstrated that 1,3,5-tris([2',2 '']bipyridin-6'-yl) benzene (BpyB) and 1,3,5-tris([ 2',2 '',6 '',2''']terpyridin-6'-yl)benzene (TpyB) are good electron-transport (ET) layer materials for organic light-emitting devices (OLEDs). The new materials exhibit high electron mobilities of around 10 (4) cm(2) V (1) s (1), and OLEDs comprising the materials operate at lower voltage than the OLEDs with tris(8-hydroxyquinolinato) aluminum (Alq) as an ET material. The new materials are also useful for phosphorescent OLEDs in blue-, green-, and red-light-emitting devices, where they function as both electron-transporting and hole-blocking materials. Phosphorescent OLEDs with the new materials operate at lower voltage (while maintaining comparable external quantum efficiencies of electroluminescence) than does the corresponding reference device with bathocuproine/Alq as electron-transporting and hole-blocking layers.ArticleORGANIC ELECTRONICS. 11(12):1966-1973 (2010)journal articl

Involvement of caspase-4 in endoplasmic reticulum stress-induced apoptosis and Aβ-induced cell death

Recent studies have suggested that neuronal death in Alzheimer's disease or ischemia could arise from dysfunction of the endoplasmic reticulum (ER). Although caspase-12 has been implicated in ER stress-induced apoptosis and amyloid-β (Aβ)–induced apoptosis in rodents, it is controversial whether similar mechanisms operate in humans. We found that human caspase-4, a member of caspase-1 subfamily that includes caspase-12, is localized to the ER membrane, and is cleaved when cells are treated with ER stress-inducing reagents, but not with other apoptotic reagents. Cleavage of caspase-4 is not affected by overexpression of Bcl-2, which prevents signal transduction on the mitochondria, suggesting that caspase-4 is primarily activated in ER stress-induced apoptosis. Furthermore, a reduction of caspase-4 expression by small interfering RNA decreases ER stress-induced apoptosis in some cell lines, but not other ER stress-independent apoptosis. Caspase-4 is also cleaved by administration of Aβ, and Aβ-induced apoptosis is reduced by small interfering RNAs to caspase-4. Thus, caspase-4 can function as an ER stress-specific caspase in humans, and may be involved in pathogenesis of Alzheimer's disease

Photopumped laser oscillation and charge-injected luminescence from organic semiconductor single crystals of a thiophene/phenylene co-oligomer

This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in APPLIED PHYSICS LETTERS. 87:221113(2005) and may be found at https://doi.org/10.1063/1.2138361 .ArticleAPPLIED PHYSICS LETTERS. 87:221113(2005)journal articl

Organic solid-state distributed feedback dye laser with a nonmorphological modification grating

This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in APPLIED PHYSICS LETTERS. 77(17):2641-2643 (2000) and may be found at https://doi.org/10.1063/1.1320034 .ArticleAPPLIED PHYSICS LETTERS. 77(17):2641-2643 (2000)journal articl