Lambertian Extraction of Light from Organic Light-Emitting Devices Using Randomly Dispersed Sub-Wavelength Pillar Arrays.

A simple light extraction method is reported to minimize the variation in emission spectrum with viewing angle by embedding a light extraction layer, consists of randomly dispersed nano-pillars on a substrate. Nano-imprint lithography technique was employed to fabricate the nano-pillars using ultra-violet curable acrylate. An organic light emitting diode device employing the imprint technology showed 46% enhancement in light extraction efficiency in the forward direction with Lambertian emission pattern and no color change with viewing angle. Moreover, the emitted light does not show any specific periodic patterns.

Fluorescent Nano-Assembly of Organic Conjugate Molecules with Benzoxazole Moiety and Its Application in Sensor.

Fluorescence labeling or sensing is a very useful analytical technique for investigating the structure of living cells or for detecting ionic metals. Numerous materials including inorganic quantum dots and organic fluorescent dyes have been used and investigated for further development so far. However, they are inherited natural discrepancies of cyto-toxicity or easy degradation. Thus, developing highly emissive, biocompatible, and chemically readily modifiable luminescent materials is strongly desired. Here, we report the enhanced photoluminescence of an oxazole derivative for possible use in the field of fluorescent sensor.

Slanted Titanium Dioxide Nano-Rod Based Hybrid Solar Cells.

A slanted columnar titanium dioxide nano-rod was fabricated with the aid of glancing angle deposition and further annealed to change its crystallinity into the anatase phase. The nano-rod hybrid solar cell with 1:0.7 w:w poly-3-hexylthiopene:methanofullerene showed power conversion efficiency of 1.67%.

Activating efficient phosphorescence from purely organic materials by crystal design.

Phosphorescence is among the many functional features that, in practice, divide pure organic compounds from organometallics and inorganics. Considered to be practically non-phosphorescent, purely organic compounds (metal-free) are very rarely explored as emitters in phosphor applications, despite the emerging demand in this field. To defy this paradigm, we describe novel design principles to create purely organic materials demonstrating phosphorescence that can be turned on by incorporating halogen bonding into their crystals. By designing chromophores to contain triplet-producing aromatic aldehydes and triplet-promoting bromine, crystal-state halogen bonding can be made to direct the heavy atom effect to produce surprisingly efficient solid-state phosphorescence. When this chromophore is diluted into the crystal of a bi-halogenated, non-carbonyl analogue, ambient phosphorescent quantum yields reach 55%. Here, using this design, a series of pure organic phosphors are colour-tuned to emit blue, green, yellow and orange. From this initial discovery, a directed heavy atom design principle is demonstrated that will allow for the development of bright and practical purely organic phosphors.

Solution-processed photonic crystals to enhance the light outcoupling efficiency of organic light-emitting diodes.

We report an effective solution process to fabricate planarized photonic crystal substrates to enhance the outcoupling efficiency of organic light-emitting diodes (OLEDs). The photonic crystal structure was fabricated using nanoimprint lithography using a UV-curable acrylate and was planarized by using a ZnO layer formed by the solgel process. The solgel process resulted in a smooth surface, and OLEDs have been successfully integrated on the planarized photonic crystal layer with a low leakage current. The resulting light outcoupling efficiency was enhanced by 38% compared with that of conventional OLEDs, which is well matched with a theoretical prediction.

A case of aortopulmonary fistula caused by a huge thoracic aortic aneurysm.

Aortopulmonary fistula is an uncommon but often fatal condition resulting as a late complication of an aortic aneurysm. The most common cause is erosion of a false aneurysm of the descending thoracic aorta into the pulmonary artery, resulting in the development of a left-to-right shunt and leading to acute pulmonary edema and right heart failure. We report an our experience with aortopulmonary fistula as a rare complication associated with thoracic aortic aneurysm and high output heart failure.

A case of right atrial aneurysm incidentally found in old age.

Right atrial aneurysm is a rare abnormality of unknown origin. Approximately half of patients with right atrial aneurysm show no symptoms. Right atrial aneurysm is usually detected by chance at any time between fetal and adult life and can be associated with atrial arrhythmia and systemic embolism. The diagnosis of right atrial aneurysm can be established with echocardiography, computed tomography (CT) or magnetic resonance imaging (MRI). Because of thromboembolic risk, aneurysmectomy is usually recommended. We review the case report of a 69-year-wold woman with right atrial appendiceal aneurysm, whose diagnosis was established by echocardiography and CT angiography.

Polydiacetylene liposome arrays for selective potassium detection.

Potassium is an important cation in biology, and quantitative detection of the extracellular potassium level is important. However, selective detection of extracellular physiological potassium is a challenging task due to the presence of sodium in a much higher concentration. In this contribution, we describe the development of practical polydiacetylene (PDA) liposome-based microarrays to selectively detect potassium even in the presence of sodium. We utilize the fact that the G-rich ssDNA can fold into a G-quadruplex via intramolecular hydrogen bonding by wrapping around a potassium ion exclusively. We rationally design the PDA liposome in such a way that the G-rich ssDNA probes are presented densely at the liposome surface and form bulky quadruplexes upon binding with K+. The resulting bulky quadruplexes are sterically hindered and repulse each other and impose mechanical stress on the PDA backbone, resulting in the conformational change of the ene-yne backbone of the PDA. As a result, polydiacetylene liposomes turn into the emissive red phase from the nonfluorescent blue phase.

Dynamic sequential layer-by-layer deposition method for fast and region-selective multilayer thin film fabrication.

We present a newly devised technique, the dynamic layer-by-layer (LbL) deposition method, that is designed to take advantage of the LbL deposition method and fluidic devices. Polyelectrolyte solutions are sequentially injected through the fluidic LbL deposition device to quickly build well-defined multilayer films on a selected region with a linear increase in the material deposited. Multilayer film fabrication by this new method on a specific region was proven to be fast and effective. The effects on film quality of the processing parameters such as concentration of polyelectrolytes, flow rate, and contact time were investigated. A half-tethered self-standing film on a substrate was fabricated to demonstrate the effectiveness and the region-selective deposition capability of the devised dynamic LbL deposition method.

Blends of amphiphilic poly(dimethylsiloxane) and nonamphiphilic octaisobutyl-POSS at the air/water interface.

Brewster angle microscopy (BAM) shows that a nonamphiphilic polyhedral oligomeric silsesquioxane (POSS) nanofiller, octaisobutyl-POSS, forms aggregates at all surface concentrations at the air/water interface. When amphiphilic poly(dimethylsiloxane) (PDMS) is blended with the octaisobutyl-POSS (>10 wt % PDMS), the degree of POSS aggregation dramatically decreases. Thermodynamic analyses and morphology studies through surface pressure-area per monomer isotherm data and BAM, respectively, exhibit three distinct composition regimes: (1) Blends with >70 wt % POSS have unstable isotherms whose shapes deviate from those of PDMS and form large rigid domains comparable to but smaller than pure, octaisobutyl-POSS films. (2) At compositions between approximately 40 and 70 wt % POSS, the isotherms' features are qualitatively similar to those of pure PDMS, and extensive nanofiller "networks" are observed by BAM. (3) For compositions < or = approximately 30 wt % POSS, the isotherms are essentially those of pure PDMS with small POSS domains dispersed in the PDMS matrix. These results provide further insight into nanofiller aggregation mechanisms and dispersion that may be present in thicker films and bulk systems.

Blends of amphiphilic trisilanolisobutyl-POSS and phosphine oxide substituted poly(dimethylsiloxane) at the air/water interface.

Mixtures of a polyhedral oligomeric silsesquioxane, trisilanolisobutyl-POSS, and a polar silicone, poly(dimethyl-co-methylvinyl-co-methyl, 2-diphenyl phosphine oxide ethyl) siloxane (PDMS-PO), spread as Langmuir monolayers at the air/water interface are used to examine the surface phase behavior and aggregation of trisilanolisobutyl-POSS as a function of silicone composition. Analyses of the surface pressure-area per monomer (Pi-A) isotherms in terms of the collapse pressures and excess Gibbs free energies of mixing indicate the monolayers form slightly negative deviation mixtures. Direct observations of surface morphology with Brewster angle microscopy in the collapsed regime reveal that the governing factor for aggregation is the collapse Pi of the component with a stronger affinity for water. In trisilanolisobutyl-POSS/PDMS-PO blends, POSS aggregates as discrete domains and does not coalesce into larger aggregates or networklike structures for <80 wt % POSS, a feature that is vastly different from a previous study of POSS blended with regular poly(dimethylsiloxane).

Polyhedral oligomeric silsesquioxane amphiphiles: isotherm and brewster angle microscopy studies of trisilanolisobutyl-POSS at the air/water interface.

A trisilanol derivative of polyhedral oligomeric silsesquioxanes (POSS), trisilanolisobutyl-POSS, has recently been reported to form stable monolayers at the air/water interface. Moreover, the trisilanolisobutyl-POSS monolayer undergoes a nonequilibrium structural transition (collapse) around a surface pressure of Rho approximately 18 mN.m(-1). This paper explores the mono- and multilayer properties of POSS molecules at the air/water interface by the Wilhelmy plate technique and Brewster angle microscopy. Surface concentrations are controlled by four mechanisms: (1) compression at a constant rate, (2) stepwise compression followed by surface pressure relaxation to an "equilibrium" value, (3) successive additions of spreading solution followed by relaxation to a stable surface pressure value, and (4) hysteresis loops to test the reversibility of the structural transitions. Results show that both an increasing compression rate and a decreasing temperature lead to an increase in the surface pressure of the structural transition, which is consistent with the formation of solidlike multilayer domains during the collapse process. For the case of compression at a constant rate, small domains initially form and later aggregate to form large solid masses. Cessation of compression allows these large solid masses to relax into equilibrium ringlike structures with a lower surface pressure, Rho approximately 13 mN.m(-1). In contrast, if the film is expanded rapidly, these large solidlike domains relax into "spaghetti" like networks with a residual surface pressure that depends on the initial amount of the solidlike collapsed phase. Finally, successive addition and stepwise compression isotherm experiments lead to different and time-dependent morphologies. Understanding these surface properties of POSS molecules affords an excellent opportunity to design and study POSS/polymer blends for coating applications where POSS molecules with rigid inorganic cores, soft organic coronae, and dimensions comparable to polymeric monolayers can serve as perfectly monodisperse nanofillers.