Synthesis and Electroluminescent Properties of Disubstituted Polyacetylene Derivatives Containing Multi‐Fluorophenyl and Cyclohexylphenyl Side Groups

A new series of disubstituted polyacetylene derivatives that contain multi‐fluorine atoms on the pendent phenyl ring have been synthesized and characterized. The results reveal a greater red‐shift in UV‐vis absorption and PL emission upon incorporating more fluorine atoms on the pendent phenyl ring. Among them, disubstituted polyacetylene with a difluorophenyl group ( PDPA‐2F ) showed the highest luminescent efficiency. The device performance can be promoted by blending a hole‐transporting material TM‐TPD into PDPA‐2F as the active layer or by using a light‐emitting copolymer in which PDPA‐2F was copolymerized with a carbazole group ( PDPA‐2Fcab ). A light‐emitting diode of ITO/PEDOT/ PDPA‐2Fcab /Ca/Al revealed a maximum luminescence of 4230 cd · m^?2 at 14 V and a maximum current efficiency of 3.37 cd · A^?1 at 7 V.

     

Burn depth assessment by dual-wavelength light emitting diodes-excited photoacoustic imaging in rats

Accurate burn depth assessment is crucial to determine treatment plans for burn patients. We have previously proposed a method for performing burn depth assessments based on photoacoustic (PA) imaging, and we have demonstrated the validity of this method, which allows the successful detection of PA signals originating from the blood under the bloodless burned tissue, using rat burn models. Based on these findings, we started a clinical study in which we faced two technical issues: (1) When the burn depth was shallow, PA signals due to skin contamination and/or melanin in the epidermis (surface signals) could not be distinguished from PA signals originating from the blood in the dermis; (2) the size of the system was too large. To solve these issues, we propose a burn depth diagnosis based on dual-wavelength light emitting diodes (LEDs)-excited PA imaging. The use of LEDs rendered the system compact compared to the previous one that used a conventional solid-state laser. We replicated human burned skin by applying a titrated synthetic melanin solution onto the wound surface in albino rat burn models and measured their burn depths by PA excitation at 690 and 850 nm, where melanin and haemoglobin show greatly different absorption coefficients. As a result, the surface signals were eliminated by subtracting the PA signals at 690 nm from those at 850 nm. The resultant estimated burn depths were strongly correlated with the histological assessment results. The validity of the proposed method was also examined using a burn model of rats with real melanin.     

Electroluminescent Behaviors of Electrochemically Cross‐Linkable Poly(benzyl ether) Terthiophene Dendrimers

In this study, the electroluminescent (EL) properties of electrochemically cross‐linkable, terthiophene terminated poly(benzyl ether) dendrimers (G₀‐3T and G₁‐3T DNs) are investigated. In noncross‐linked 3T DNs, there is either no emission or a low‐intensity emission due to poor charge transfer of the isolated terthiophene (3T) oligomers at the periphery of the DNs. However, increase in the length of conjugation via electrochemical cross‐linking leads to the emission of a yellowish color. It is seen that the emission of this color is dependent on the dendritic structures and effectively controlled charge trapping. Thus, these results suggest that the dendritic molecular structure, which is associated with the conjugated length of the emissive peripheral units and the generation of the dendrimers, is an important factor in controlling EL properties.

     

A New Class of Organosoluble Rigid‐Rod,Fully Aromatic Poly(1,3,4‐oxadiazole)s and Their Solid‐State Properties, 2. Solid‐State Properties

New symmetrical and unsymmetrical dialkoxy‐substituted aromatic poly(1,3,4‐oxadiazole)s are investigated by cyclovoltammetric measurements. The electrochemical redox behaviour of these materials is compared with the chemical structure. The reduction behaviour allows the estimation of the electron affinity, and shows that these polymers are suitable candidates for electron‐transport materials in electronic devices. Surprisingly it is found from UV‐vis and fluorescence spectroscopic measurements that the polyoxadiazole with linear alkoxy side chains (C16) shows a reversible thermochromism in solution as well as in the solid state. The changes in this temperature range are ascribed to a phase transition between aggregated chains, in solution as well as in the film, at room temperature and molecularly dissolved polymer chains at higher temperature. The other poly(1,3,4‐oxadiazole)s with branched alkoxy side chains exhibit an improved solubility and they are completely soluble in o‐dichlorobenzene at room temperature. The absorption and emission behaviour does not change in the temperature range from 25°C to 100°C. The fluorescence excitation studies of these poly(1,3,4‐oxadiazole)s show a blue emission in solution and in the film. Due to these results the poly(1,3,4‐oxadiazole)s are used as electron transport and blue emitting layers in electronic devices like diodes or polymer light emitting diodes (PLED).     

Strain Compensation and Trade-Off Design Result in Exciton Emission at 306 nm from AlGaN LEDs at Temperatures up to 368 K

In this study, we suppressed the parasitic emission caused by electron overflow found in typical ultraviolet B (UVB) and ultraviolet C (UVC) light-emitting diodes (LEDs). The modulation of the p-layer structure and aluminum composition as well as a trade-off in the structure to ensure strain compensation allowed us to increase the p-AlGaN doping efficiency and hole numbers in the p-neutral region. This approach led to greater matching of the electron and hole numbers in the UVB and UVC emission quantum wells. Our UVB LED (sample A) exhibited clear exciton emission, with its peak near 306 nm, and a band-to-band emission at 303 nm. The relative intensity of the exciton emission of sample A decreased as a result of the thermal energy effect of the temperature increase. Nevertheless, sample A displayed its exciton emission at temperatures of up to 368 K. In contrast, our corresponding UVC LED (sample B) only exhibited a Gaussian peak emission at a wavelength of approximately 272 nm.     

Random Copolymers with Pendant Cationic Mixed‐Ligand Terpyridine‐Based Iridium (III) Complexes: Synthesis and Application in Light‐Emitting Devices

The synthesis of two random copolymers bearing pendant mixed‐ligand orthometallated terpyridine‐based cationic iridium (III) complexes, as well as their uses as single‐layered electrophosphorescent emitters in polymer light‐emitting diodes is described. Both solution‐processable iridium metallopolymers are prepared by copolymerization of styrene with a complex‐substituted styrene by nitroxide mediated polymerization. Results on devices based on metallopolymers used as dopant of poly(N‐vinylcarbazole) or alone as single layers are presented.

     

不同光谱的发光二极管阵列光源照射对体外游离胆红素光化学降解效应的影响

目的:探讨三种不同光谱范围的发光二极管(LED)阵列光源对体外游离胆红素降解效应的影响。方法:将500μL浓度为205.2μmol/L的胆红素标准液封入5mL的耐热玻璃管制成一个样本管。将所有共54个样本管分为三组,分别经相同光照强度的蓝光、蓝绿混合光和绿光LED阵列照射0h、0.5h、1h、2h、4h和8h,然后通过咖啡因法检测胆红素溶液的吸光度值。结果:与空白对照组比较,蓝光、蓝绿混合光和绿光LED光照均对胆红素有明显的降解作用(P<0.05);其中又以蓝光LED的光化学降解效应最强。结论:光谱是影响新生儿黄疸LED光疗疗效的重要参数,并且蓝光(465±20)nm为LED光疗较适宜光谱范围。