Jong S. Park

Controllability for the impulsive semilinear fuzzy integrodifferential equations with nonlocal conditions

In this paper. we study the controllability for the impulsive semilinear fuzzy integrodifferential control system with nonlocal conditions in EN by using the concept of fuzzy number whose values are normal, convex, upper semicontinuous and compactly supported interval in EN.

Electron-rich π-extended phthalocyanine–thiophene–phthalocyanine triad for the sensitive and selective detection of picric acid

An electron-rich phthalocyanine–thiophene–phthalocyanine triad 3 (Pc-triad 3), newly synthesized, can function as a highly selective chemosensor against picric acid (PA). Pc-triad 3 showed efficient and selective fluorescence quenching towards PA, during which a photo-induced electron transfer (PET) complex arose from the electron-rich pendant Pc rings of 3 to the PA reagents.

Control of inkjet printed profiles by solvent-vapor annealing

The profile of colorant film produced in inkjet printing can be severely affected by the drying environment. This study found that a simple solvent-vapor annealing process can induce a drastic profile rearrangement of the subpixels on the entire substrate. The high surface tension and boiling point of the solvent play a critical role for the rearrangement to occur. The film surface is dissolved during the annealing process, and the high boiling point delays evaporation at the contact edge, which leads to the profile rearrangement. Due to the high surface tension of the solvent, the inks are confined inside the pixels. As a consequence, the profile becomes uniform without any outward color defect, regardless of the printed regions. This will be useful for organic electronics made by inkjet printing.

Properties of UHMWPE fabric reinforced epoxy composite prepared by vacuum-assisted resin transfer molding

Ultrahigh molecular weight polyethylene (UHMWPE) plain-woven-fabric-reinforced epoxy composites were prepared using a newly designed vacuum-assisted resin-transfer molding (VaRTM) apparatus. This VaRTM process involved pre-curing for 24 h at room temperature, and then post-curing at different temperatures from 80 to 120 ℃. The properties of the composite were then analyzed using TGA, DMA, tensile and flexural tests. The weight ratio of the UHMWPE-fiberreinforcement to epoxy-resin-matrix in the composite, reached about 60 wt%, as estimated by TGA. Post-curing at 80 ℃ provided the highest E’ at temperatures higher than the glass transition range, and Tg decreased with increasing post-curing temperature. Simultaneously, the tensile modulus decreased while the strain and toughness increased in a large degree.

1-Dimensional fiber-based field-effect transistors made by low-temperature photochemically activated sol–gel metal-oxide materials for electronic textiles

We report the high performance metal-oxide fiber field-effect transistors (F-FETs) for electronic textiles (e-textiles). By using low-temperature and a solution process, dense, pinhole-free, and relatively uniform metal-oxide layers were successfully deposited on a 1-dimensional fiber substrate. Particularly, the atomic layer deposited aluminum oxide gate dielectric layer, deposited at 100 °C, exhibited an extremely low leakage current density of ∼10−7 A cm−2 and a high breakdown field of 4.1 MV cm−1. Furthermore, the indium oxide F-FETs, which are photochemically activated at a low temperature, showed a field-effect mobility and on/off ratio of 3.7 cm2 V−1 s−1 and >106, respectively, which we believe are the highest performance among fiber-type FETs reported to date. Based on these results, it is believed that the metal-oxide F-FETs may provide a basic building block to accomplish 2-D woven e-textiles in the future, provided further combining with the weaving and interconnection technologies.

Efficient Fluorescence Quenching of tert - butyl substituted Phthalocyanines with Picric Acid

Two tert-butyl substituted phthalocyanines(Pcs), in metal-free and metallated forms, were synthesized and the fluorescence responses toward various nitro derivatives, including picric acid(PA), 2,4-dinitrotoluene(DNT), 1,4-dinitrobenzene(DNB), 4-nitrotoluene(NT), nitrobenzene(NB), 1,4-benzoquinone(BQ), and nitromethane(NM) were investigated. Among the various nitro derivatives, current Pc derivatives exhibited efficient and exclusive fluorescence quenching in the presence of picric acid, which was readily observed by a naked eye. Quenching efficiency was estimated by the Stern-Volmer relationship, in which quenching constant, KSV, was calculated to be in the range of 10 4 M -1 . It was also found out that the aggregational behaviors of these Pcs are heavily dependent on the nature of solvent systems, subsequently affecting the quenching efficiency.

Colorimetric detection of in situ metal acetates and fluorides by a bipyridyl-linked Schiff base.

Here, we present a new bipyridyl moiety linked Schiff base (bipy‐1) that is well characterized using spectroscopic techniques. Colorimetric and UV‐vis titrations were used to study the photophysical properties of bipy‐1 in the presence of various tetrabutyl ammonium salt of anions and metal salts containing different counter cations. bipy‐1 showed selective recognition of dimethyl sulphoxide solution of tetrabutyl ammonium salt of F− ion accompanied with a UV‐vis band at 529 nm and interesting binding of aqueous Co, Ni, and Cu acetates/fluorides, as confirmed by distinct color changes from fluorescent green to pink or orange and a strong band around 480–510 nm in the UV‐vis spectrum. However, in the presence of Co, Ni, and Cu countercations, any form of metal acetate/fluorides was found to be able to respond to similar color changes from fluorescent green to pink or orange, showing a band around 480–510 nm. This type of output clearly indicates that the in situ formation of Co, Ni, and Cu acetates/fluorides also coordinates with bipyridyl nitrogen atoms. Copyright

Preparation of Polymeric Metal Complex Containing Azo Dye Rotaxane

In this article, we synthesized an azo dye rotaxane containing bis(8-hydroxyquinoline) group and its polymeric metal complex with zinc. The azo dye rotaxane exhibits high pH sensitivity, solvatochromism and zinc (II) ion sensings in aqueous solution. These behaviors came from the tautomeric equilibrium between azo-hydrazone tautomers and the formation of extended conjugation. The structure of polymeric zinc complexed dye rotaxane was confirmed with NMR and FT-IR measurements. The existence of CD rings, provided by dye rotaxane formation, was found to be very beneficial in improving aqueous solubility of polymeric metal complex.

Enhanced in vitro photocytotoxicity of water-soluble dendritic pheophorbide-a

Photosensitizers can produce highly reactive singlet oxygen with exposure to visible light and are used in photodynamic therapy to treat a variety of tumors. We report on the synthesis of triethylene glycol dendron-conjugated pheophorbide-a5, a novel photosensitizer. The characteristic absorption bands (Soret and Q-bands, λmax = 405 and 670 nm, respectively) of 5 were appeared clearly in aqueous solution, due to the improved water-solubility of the dendron moiety. The value of singlet oxygen quantum yield of 5 (ΦΔ = 0.22) was higher than free pheophorbide-a (ΦΔ = 0.17) as reference in aqueous solution. Compound 5 also exhibited an enhanced in vitro phototoxicity than pheophorbide-a (PhA) in the concentration range of 1.0–5.0 μg/mL: cell viability in cells treated with 5 was reduced by ~20%, indicating a cell death rate of ~80%, while PhA treatment resulted in a cell death rate of only about 10%. These results indicate that 5 will likely be more efficient in PDT applications. Compared with free PhA, compou...

Metallo-Supramolecular Polymers Made of Cobalt and 3,4-Propylenedioxythiophene-Bisterpyridine Complexes for Electrochromic Applications

In this study, a series of organometallic hybrid polymers were synthesized through the complexation of cobalt metal ions with bisterpyridine derivatives bearing substituted 3,4-propylenedioxythiophene. The prepared polymers exhibited specific color changes from orange to dark green based on the metal-to-ligand charge transfer transitions. Cyclic voltammograms of the polymers showed a reversible redox wave according to the redox reaction of the cobalt metal ions. In addition, the electrochromic devices containing the polymer film cast on an indium-tin-oxide electrode exhibited good electrochromic properties, with reversible and stable spectral transitions of the cobalt-bisterpyridine complexes.