High-resolution soft X-ray photoelectron spectroscopy of liquid water

High-resolution soft X-ray photoelectron spectra of liquid water (H(2)O and D(2)O) were measured using a liquid beam photoelectron spectrometer. The 1a(1) (O1s) band and the lowest valence 1b(1) band had single peaks, which is not consistent with the split 1b(1)→ 1a(1) of the X-ray emission band of liquid water if the splitting is assumed to originate from level shifts in two different hydrogen bonding structures. The second valence 3a(1) band of liquid water exhibited a flat top implying that two bands exist underneath a broad feature, which is similar to the case of the 3a(1) band of amorphous ice. The energy splitting between the two 3a(1) bands is estimated to be 1.38 eV (H(2)O) and 1.39 eV (D(2)O). Ab initio calculations suggest that the large splitting of the 3a(1) band is characteristic of water molecules that function as both proton donor and acceptor. The overall result is consistent with the conventional model of a tetrahedral hydrogen-bonding network in liquid water.     

Combined experimental and computational study of intramolecular charge transfer in p-N,N-dimethylamino-p'-cyano-diphenylacetylene

A concerted experi-mental (time-resolved spectroscopies) and computational (TDDFT) study of p-N,N-dimethylamino-p'-cyano-diphenylacetylene (DACN-DPA) has been carried out to probe the intramolecular charge transfer (ICT) reaction that occurs in polar solvents. The picosecond transient absorption, as well as fluorescence, in acetonitrile reveals the formation of a twisted ICT(σ*) state, which involves transfer of an electron from the 4-(dimethylamino)benzethyne moiety (DMAB) to the benzonitrile (BN) group. This ICT(σ*) state, with a large dipole moment (24.7 D) and a geometry in which the plane of electron-accepting BN group is perpendicular to the plane electron-donating DMAB moiety and the angles of C(DMAB)C≡C is 135.0°, is responsible for the greatly Stokes-shifted (～8000 cm(-1)) fluorescence and the transient absorption bands (with peaks at about 630 and 425 nm), which decays with the same lifetime (～780 ps). It is proposed that the 630 nm picosecond transient absorption of the ICT state represents the absorption spectrum of dimethylaminobenzethyne radical cation and the 425 nm transient represents the absorption spectrum of benzonitrile radical anion. In nonpolar n-hexane, most of the fluorescence as well as the major component of the transient absorption originate from the S(1) (ππ*) state.     

Fluorescence PET (photo-induced electron transfer) sensors for water based on anthracene-boronic acid ester

Anthracene-boronic acid ester as a new class of fluorescence PET sensors for detection of a trace amount of water in organic solvents has been designed and developed.     

Modulation of intramolecular heterodimer-induced fluorescence quenching of tricarbocyanine dye for the development of fluorescent sensor

Various approaches have been used to modulate the fluorescence changes of sensors in the presence of target analytes, including intramolecular interaction between fluorophores or between fluorophore and other molecular species, like resonance energy transfer (RET). Here, we focus on fluorescence quenching by intramolecular heterodimer complex formation, which can be modulated over a shorter distance range than RET. We synthesized several conjugates of tricarbocyanine, which is a near-infrared fluorophore, with several quencher candidates via flexible short linker structure, and examined their fluorescence properties. Of our synthesized compounds, the dabcyl group proved to be the best quencher via heterodimer complex formation. The fluorescence of tricarbocyanine-dabcyl conjugates in aqueous media was almost completely quenched, and there was a dramatic fluorescence enhancement when heterodimer formation was blocked. These results suggested a design approach to develop fluorescence sensors for probing proximity relationships and structural transitions.     

Nuclear Magnetic Resonance Spectra of 1,2,3- and 1,2,4- Tribromobenzenes

Abstract

The nmr spectra of trisubstituted benzenes such as 1,2,4-chloro⁽¹⁾ and 1,2,5-bromo⁽²⁾ compounds have been reported already. We will report here the results on 1,2,3- and 1,2,4-tribromobenzenes. The samples were synthesized and purified by zone melting- method at the Chiba Institute of Technology. They were dissolved in CCl⁴ with the concentrations of ca. 20 and 75 wt % for 1,2,3- and 1,2,4-compounds, respectively. The spectrometers used are the ones of the types of JNMC-6OH and 100H of Japan Electron Optics Company. The nmr paparameters of 1,2,3- halogenocompounds were obtained by the direct analysis of the spectra taking the system as the one of the AB² type. Those for 1,2,4-compounds were obtained with the use of the electronic computer HITAC-5020 at the University of Tokyo and with the program supplied by Bothner-By. Tetramethyl silane, TMS, was used as the internal standard and the results of the analysis of the spectra at 60 MHz are shown in Table 1. Those values for 1,2,3-trichloro benzene were compared with those obtained from the spectrum at 100 MHz and those in the literature.⁽¹⁾     

A novel photo‐acid generator bound molecular glass resist with a single protecting group

A novel photo‐acid generator (PAG) bound molecular glass photoresist with a single protecting group has been developed as a promising resist material for use in microelectronics. This single component molecular resist was prepared in four steps starting from 9,9‐bis(4‐hydroxyphenyl)fluorene. The single component molecular resist exhibited good thermal properties, such as a 10% weight loss temperature of 200 °C and a glass transition temperature of 91 °C. This resist showed a good sensitivity of 60 μC/cm² with e‐beam exposure (50 keV). On the other hand, the fine pattern with a half‐pitch of 50 nm in the presence of 4 wt % quencher, trioctylamine, was obtained using electron‐beam (100 keV) lithography. The LER value was 8.2 nm (3σ, 60 nm half‐pitch patterns). © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013