We propose an organic heterojunction phototransistor stacked with organic layers of electron and hole transport materials. The materials used in this study are perylene derivative (td-PTC) as the ultrathin base layer and triphenylamine derivative (TPD) as the emitter and collector layers. The current versus voltage characteristics as a function of incident optical intensity are typical of a phototransistor with current saturation. The bipolar transistor operation is confirmed by a comparison with the diode structure of the TPD/td-PTC device and because of the base thickness dependence of the current. External quantum efficiency is 2.9% under blue light-emitting diode illumination. In the current response, the initial displacement current is superimposed. Obtained response times are 600 μs for both transient turn-on and turn-off currents.

We oxidized histidine residues in monoclonal antibody drugs of immunoglobulin gamma 1 (IgG1) using ultraviolet C irradiation (UVC: 200-280 nm), which is known to be potent for sterilization or disinfection. Among the reaction products, we identified asparagine and aspartic acid by mass spectrometry. In the photo-induced oxidation of histidine in angiotensin II, 18 O atoms from H 2 18 O in the solvent were incorporated only into aspartic acid but not into asparagine. This suggests that UVC irradiation generates singlet oxygen and induces [2 + 2] cycloaddition to form a dioxetane involving the imidazole c γ − C δ2 bond of histidine, followed by ring-opening in the manner of further photo-induced retro [2 + 2] cycloaddition. This yields an equilibrium mixture of two keto-imines, which can be the precursors to aspartic acid and asparagine. The photo-oxidation appears to occur preferentially for histidine residues with lower pK a values in IgG1. We thus conclude that the damage due to UVC photo-oxidation of histidine residues can be avoided in acidic conditions where the imidazole ring is protonated.

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Plasma display panels (PDPs) with an MgCaO protective layer and a new manufacturing process were achieved, with discharge voltage decreased while productivity was maintained. The evaporation rate of MgCaO became lower with the increasing Ca content, decreased by 20% at Ca 8 wt%. However, by changing several settings of evaporation, the evaporation rate of the Ca 8 wt% was improved to be comparable to that of MgO. The PDP with the Ca 8 wt% MgCaO protective layer decreased the discharge voltage by 12 V compared to that with the MgO protective layer. The life characteristics of the PDP with the MgCaO protective layer were the same as those with the MgO protective layer.