Fluorescence resonance energy transfer by quencher adsorption into hydrogels containing fluorophores

We synthesized anionic hydrogels containing fluorophores and investigated the adsorption of a cationic quencher having an amino group into hydrogels by fluorescence resonance energy transfer (FRET). FRET from the fluorophore to the quencher in hydrogels was examined by fluorescence intensity and fluorescence decay using a fluorescence spectrophotometer and femtosecond laser spectroscopy. The fluorescence intensity of the fluorophore‐containing hydrogels decreased rapidly with increasing amounts of adsorbed cationic quencher. The fluorescence emission of the fluorophore in the quencher‐adsorbed hydrogels containing fluorophores decayed more rapidly than that of the original hydrogels. The aforementioned result indicates that the fluorescence of the fluorophore‐containing hydrogels is quenched due to FRET from the fluorophore to the quencher as the cationic quenchers can approach the fluorophores in hydrogels by electrostatic interactions. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3245–3252, 2006     

Synthesis and electrochemical and electroluminescent properties of N‐phenylcarbazole‐substituted poly(p‐phenylenevinylene)

An N‐phenylcarbazole‐containing poly(p‐phenylenevinylene) (PPV), poly[(2‐(4′‐carbazol‐9‐yl‐phenyl)‐5‐octyloxy‐1,4‐phenylenevinylene)‐alt‐(2‐(2′‐ethylhexyloxy)‐5‐methoxy‐1,4‐phenylenevinylene)] (Cz‐PPV), was synthesized, and its optical, electrochemical, and electroluminescent properties were studied. The molecular structures of the key intermediates, the carbazole‐containing boronic ester and the dialdehyde monomer, were crystallographically characterized. The polymer was soluble in common organic solvents and exhibited good thermal stability with a 5% weight loss at temperatures above 420 °C in nitrogen. A cyclic voltammogram showed the oxidation peak potentials of both the pendant carbazole group and the PPV main chain, indicating that the hole‐injection ability of the polymer would be improved by the introduction of the carbazole‐functional group. A single‐layer light‐emitting diode (LED) with a simple configuration of indium tin oxide (ITO)/Cz‐PPV (80 nm)/Ca/Al exhibited a bright yellow emission with a brightness of 1560 cd/m² at a bias of 11 V and a current density of 565 mA/cm². A double‐layer LED device with the configuration of ITO/poly(3,4‐ethylenedioxy‐2,5‐thiophene):poly (styrenesulfonic acid) (60 nm)/Cz‐PPV (80 nm)/Ca/Al gave a low turn‐on voltage at 3 V and a maximum brightness of 6600 cd/m² at a bias of 8 V. The maximum electroluminescent efficiency corresponding to the double‐layer device was 1.15 cd/A, 0.42 lm/W, and 0.5%. The desired electroluminescence results demonstrated that the incorporation of hole‐transporting functional groups into the PPVs was effective for enhancing the electroluminescent performance. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5765–5773, 2005     

Synthesis and properties of π‐conjugated dithiafulvene oligomers by addition of a monofunctionalized compound

Dithiafulvene oligomers ( 3 ) were prepared by cycloaddition polymerization of aldothioketenes with their alkynethiol tautomers derived from 1,4‐diethynylbenzene ( 2 ) with the addition of 1‐ethynyl‐4‐methylbenzene ( 1 ) as a monofunctionalized compound. Different feed ratios of 2 / 1 were used to control the molecular weights of 3 . The structures of 3 were confirmed by IR and ¹H NMR spectroscopies in comparison with those of 2‐(4‐tolylidene)‐4‐tolyl‐1,3‐dithiol ( 4 ) as a model compound, which was obtained by the treatment of lithium 2‐tolylethynethiolate with water in Et₂O. The number‐average degree of polymerization (DP) and the number‐average molecular weight were measured by gel permeation chromatographic and ¹H NMR analysis. DP increased with an increasing feed ratio of 2 / 1 . The ultraviolet–visible spectra of 3 in diluted acetonitrile showed that the absorption maxima of 3 increased with an increasing DP of 3 . These redshifts are ascribed to an effective expansion of the π‐conjugation system in 3 . The oligomers exhibited a maximum conjugation length of seven repeating units. The redox properties of 3 were examined by cyclic voltammetry. The oxidation half‐peak potentials (E_p/2) of 3 were slightly cathodically shifted with increasing DP. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 708–715, 2003     

Classification of non‐well‐founded sets and an application

A complete list of Finsler, Scott and Boffa sets whose transitive closures contain 1, 2 and 3 elements is given. An algorithm for deciding the identity of hereditarily finite Scott sets is presented. Anti‐well‐founded (awf) sets, i. e., non‐well‐founded sets whose all maximal ∈‐paths are circular, are studied. For example they form transitive inner models of ZFC minus foundation and empty set, and they include uncountably many hereditarily finite awf sets. A complete list of Finsler and Boffa awf sets with 2 and 3 elements in their transitive closure is given. Next the existence of infinite descending ∈‐sequences in Aczel universes is shown. Finally a theorem of Ballard and Hrbá?ek concerning nonstandard Boffa universes of sets is considerably extended.     

Fabrication of a Near-Field Optical Fiber Probe with a Nanometric Metallized Protrusion

We have developed a novel probe with a nanometric metallized protrusion extending through a subwavelength aperture to increase optical near-field excitation and collection efficiencies. The apex diameter of the fabricated metallized protrusion was 35 nm. The Intensity distribution of the optical near-field at the apex of the probe was measured by scanning another probe across the apex, and it was observed that strong optical near-field was generated at the apex of the metallized protrusion. The width of the intensity distribution was 150 nm including instrumental resolution. Probes with spherical and ellipsoidal metallized protrusion were also fabricated, by which enhancement of the optical near-field is expected due to localized plasmon excitation.     

K1 of Some Non-Commutative Completed Group Rings

We compute K₁ of completed group rings of some two dimensional p-adic Lie groups. Dedicated to Professor Spencer Bloch on his sixtieth birthday     

Total synthesis of (+)-obtusenyne

The stereoselective total synthesis of (+)-obtusenyne is described. The oxonene skeleton possessing trans-orientated alkyl substituents at the α,α′-positions was stereoselectively constructed via cyclization of the corresponding hydroxy epoxide promoted by Eu(fod)₃.     

Synthetic studies on oligomycins. Enantiospecific synthesis of the oligomycin B spiroketal portion and establishment of the absolute stereochemistry of oligomycin B

The enantiospecific synthesis of the oligomycin B degradation product 2, corresponding to the C19–C34 spiroketal portion, has been achieved by sequential coupling of the C19–C21, C22–C27, and C28–C34 subunits, establishing the absolute stereochemistry of oligomycin B.