Discovery of deep and shallow trap states from step structures of rutile TiO2 vicinal surfaces by second harmonic and sum frequency generation spectroscopy

In this report, local electronic structures of steps and terraces on rutile TiO(2) single crystal faces were studied by second harmonic and sum frequency generation (SHG∕SFG) spectroscopy. We attained selective measurement of the local electronic states of the step bunches formed on the vicinal (17 18 1) and (15 13 0) surfaces using a recently developed step-selective probing technique. The electronic structures of the flat (110)-(1×1) (the terrace face of the vicinal surfaces) and (011)-(2×1) surfaces were also discussed. The SHG∕SFG spectra showed that step structures are mainly responsible for the formation of trap states, since significant resonances from the trap states were observed only from the vicinal surfaces. We detected deep hole trap (DHT) states and shallow electron trap (SET) states selectively from the step bunches on the vicinal surfaces. Detailed analysis of the SHG∕SFG spectra showed that the DHT and SET states are more likely to be induced at the top edges of the step bunches than on their hillsides. Unlike the SET states, the DHT states were observed only at the step bunches parallel to [1?1?1] [equivalent to the step bunches formed on the (17 18 1) surface]. Photocatalytic activity for each TiO(2) sample was also measured through methylene blue photodegradation reactions and was found to follow the sequence: (110) < (17 18 1) < (15 13 0) < (011), indicating that steps along [0?0?1] are more reactive than steps along [1?1?1]. This result implies that the presence of the DHT states observed from the step bunches parallel to [1?1?1] did not effectively contribute to the methylene blue photodegradation reactions.     

Infrared spectroscopy of endohedral HD and D2 in C60

We report on the dynamics of two hydrogen isotopomers, D(2) and HD, trapped in the molecular cages of a fullerene C(60) molecule. We measured the infrared spectra and analyzed them using a spherical potential for a vibrating rotor. The potential, vibration-rotation Hamiltonian, and dipole moment parameters are compared with previously studied H(2)@C(60) parameters [M. Ge, U. Nagel, D. Hüvonen, T. R??m, S. Mamone, M. H. Levitt, M. Carravetta, Y. Murata, K. Komatsu, J. Y.-C. Chen, and N. J. Turro, J. Chem. Phys. 134, 054507 (2011)]. The isotropic part of the potential is similar for all three isotopomers. In HD@C(60), we observe mixing of the rotational states and an interference effect of the dipole moment terms due to the displacement of the HD rotation center from the fullerene cage center.     

The inhibition abilities of multifunctional polyelectrolytes for silica scale formation in cooling water systems: role of the nonionic functional group

The abilities of multifunctional polyelectrolytes to enhance aluminum hydroxide dispersion and inhibit silica scale formation were examined in a pilot cooling water system. The following multifunctional polyelectrolytes were studied: a terpolymer of acrylic acid (AA), 2-acrylamide-2-methyl propane sulfonic acid (SA) and N-vinylpyrrolidone (NVP) (P(AA/SA/NVP)), acrylic acid homopolymer (P(AA)) and a copolymer of AA and SA (P(AA/SA)). The order of inhibition ability was P(AA/SA/NVP)>P(AA/SA)>P(AA), and was consistent with that of the dispersing ability for aluminum hydroxide. Other terpolymers incorporating different nonionic monomers were also examined and factors affecting their inhibition abilities were investigated, based on interaction energies calculated by density functional theory. Based on the correlation between scale inhibition abilities and interaction energies, we elucidated that the effective nonionic monomer of terpolymer for silica scale inhibition had low affinity for aluminum hydroxide and high affinity for H(2)O and Si(OH)(3)O(-). The affinities of nonionic monomer for aluminum hydroxide and H(2)O suggested that there was proper conformation of polyelectrolyte adsorbed for effectively dispersing aluminum hydroxide. Also, high affinity of nonionic monomer for Si(OH)(3)O(-) suggested that interacting Si(OH)(3)O(-) is an important role of inhibition of silica scale formation.     

Complexation of Silicic Acid with Tiron in Aqueous Solution Under near Natural Condition

The formation of a silicic acid–tiron (a derivative of catechol) complex was investigated in aqueous solution with various molar ratios of tiron to silicic acid (tiron/Si) or with various pH using ²⁹Si NMR. Only the 1:3 silicic acid–tiron complex was detected in despite of the range of tiron/Si molar ratios. This complex is stable in the pH range from 6 to 10. This indicates that the formation of a hydrogen bond (SiOH⋅⋅⋅O− in tiron), due to dissociation of H⁺ from hydroxy groups of tiron, may be a trigger for the formation of the complex. Around pH=6, the formation of the complex occurs when the tiron/Si molar ratio is larger than 3 and most of silicic acid is converted to the complex when the ratio is larger than 25. Based on the temperature dependence of the ²⁹Si NMR spectra for the complex, the existence of two possible meridional and facial isomers was confirmed. The conditional formation constant for the 1:3 silicic acid–tiron complex was defined as Eq. 8 and estimated to be 2.0 mol⁻¹⋅dm³ for the facial complex and 4.1 mol⁻¹⋅dm³ for the meridional complex, respectively.     

Selective decomposition of nucleic acids by laser irradiation on probe-tethered gold nanoparticles in solution

We have developed a new method for selective decomposition of nucleic acids. The method utilizes a high temperature and pressure region (HTP region, hereafter) around a gold nanoparticle, which was generated when the gold nanoparticle was irradiated with a pulsed laser in aqueous solution. A probe DNA molecule whose sequence was complementary to a part of a target DNA molecule was bound to the gold nanoparticle surface. In a solution containing both the target and non-target DNA molecules, the gold nanoparticle selectively attached to the target DNA through hybridization of the probe DNA. When the gold nanoparticle was excited by a pulsed laser, the HTP region was generated in the close vicinity of the gold nanoparticle and then the target DNA molecules inside of this region were decomposed. The non-target DNA molecules having no part complementary to the probe DNA were scarcely decomposed by laser irradiation. When the gold nanoparticle was excited by an intense laser, the non-target DNA molecules were also decomposed, because some of them were located inside the inflated HTP region. We discussed the mechanism of the decomposition of the DNA molecules by the HTP region.     

Photoelectron imaging spectroscopy of S1(1B2u π,π*) benzene via 6(1)1n (n = 0-3) levels

We report resonance-enhanced two-photon ionization photo-electron spectroscopy of jet-cooled benzene via the 6(1)1(n) (n = 0-3) vibronic levels in S(1)((1)B(2u) π,π*) using a nanosecond UV laser and photoelectron imaging. The best energy resolution (ΔE/E) was 0.7%. The photoelectron spectrum from the S(1) 6(1)1(3) level (E(vib) = 3284 cm(-1)) in the channel three region exhibited a clear signature of intramolecular vibrational redistribution (IVR). The spectral features were consistent with picosecond zero kinetic energy photoelectron (ZEKE) spectra reported by Smith et al. [ J. Phys. Chem. 1995, 99, 1768]. The photoelectron angular anisotropy parameter β(2) was found to be negative in ionization from the 6(1)1(n) (n = 0-3) levels with photoelectron kinetic energies up to 5000 cm(-1). No influence of a shape resonance was identified.     

Direct synthesis of nanoporous carbon nitride fibers using Al-based porous coordination polymers (Al-PCPs)

We report a new synthetic route for preparation of nanoporous carbon nitride fibers with graphitic carbon nitride polymers, by calcination of Al-based porous coordination polymers (Al-PCPs) with dicyandiamide (DCDA) under a nitrogen atmosphere.     

Branched RNA nanostructures for RNA interference

Branched RNAs with three- or four-way junctions were designed by assembling single-stranded RNA for RNA interference. Human Dicer transformed branched RNAs into about 20 base pairs of double-stranded RNA, which is a standard siRNA species. Our tetramer design provides a potent silencing effect over a period of 5 days.     

Manganese(III) acetate-mediated radical reaction of [60]fullerene with phosphonate esters affording unprecedented separable singly-bonded [60]fullerene dimers

Radical reaction of [60]fullerene with phosphonate esters mediated by manganese(III) acetate in chlorobenzene afforded singly-bonded fullerene dimers, of which the individual meso and racemic isomers could be unexpectedly separated out for the first time.     

New layered cobalt oxyfluoride, Sr2CoO3F

The first Ruddlesden-Popper type layered cobalt oxyfluoride, Sr(2)CoO(3)F, has been synthesized under a pressure of 6 GPa at 1700 °C and shown to adopt a K(2)NiF(4)-type structure with distorted square pyramidal coordination around Co and with O/F disorder at the apical sites.