Chemical Physics Letters (v.379, #5-6)

Is molybdenum necessary for the growth of single-wall carbon nanotubes from CO? by Aidong Lan; Yan Zhang; Xueyan Zhang; Zafar Iqbal; Haim Grebel (395-400).
Catalytic mixtures of molybdenum and cobalt have been considered essential for the growth of single-wall carbon nanotubes (SWCNT) from carbon monoxide by the chemical vapor deposition method. Here we demonstrated extensive growth of SWCNT with only cobalt as catalyst. The typically subsequent stage of annealing the catalyst in the presence of hydrogen was also eliminated. This process resulted in a near-100% yield of essentially defect-free chiral tubes. Use of electrochemical deposition of the catalyst seed particles may open the door for the production of massive electronic interconnect assemblies of these nanotubes.

Methylene blue (MB) at small concentration is used as a photosensitizer in the solid state photoelectrochemical cells fabricated using doped and undoped polypyrrole (Ppy) coated electrodes sandwiched with solid polymer electrolyte (SPE) viz. polyvinylalcohol (PVA) doped with phosphoric acid. Different sensitization effects are observed for the same polymer–dye combination. MB sensitizes Ppy in doped state more efficiently as compared to undoped state of the polymer. The actual placement of the energy levels of dye with respect to polymer and ease with which polymer transports photogenerated charge carriers without recombination are observed to be important in such sensitization processes and governs the overall process.

Molecular structure and vibrational analysis of 2-vinyl furan by A. Giuliani; B. Gilbert; C. Kech; M.-J. Hubin-Franskin (406-411).
Infrared and vibrational Raman spectra have been recorded in the liquid phase and interpreted using semiempirical calculations (PM3, AM1 and MNDO). Molecular properties and relative conformational energies have been calculated and compared with literature data, when available. The trans conformer of the molecule seems to be the conformation of lowest energy and its computed structural parameters are reported.

We consider a 3D graphical representation of DNA sequences and their numerical characterization. The representation also avoids loss of information accompanying alternative 2D and 3D representation in which the curve standing for DNA overlaps and intersects itself. The method is illustrated on the coding sequence of the first exon of human β-globin gene.

Dynamics of amorphous water, via migration of 3- and 5-coordinated H2O by Natalia Grishina; Victoria Buch (418-426).
The dynamics of TIP4P amorphous water is explored at 155 K. Both translational and orientational mobilities are dominated by the activity of 3- and 5-coordinated defects. Significant molecular displacements occur concurrently with changes of coordination during defect jumps, defect pair formation, and defect pair annihilation.

Raman spectroscopic studies of the stretching band from water up to 6 kbar at 290 K by Qiang Sun; Haifei Zheng; Ji-an Xu; E Hines (427-431).
Raman scattering studies of the stretching band from liquid water have been conducted up to 6 kbar at 290 K. It shows that the (v 1)max decreases with increasing pressure initially and reaches the minimum at about 2 kbar, and increases with higher pressure up to about 4 kbar, then decreases with increasing pressure up to 6 kbar. This is accordance with the behavior of r OO at high pressure. Additionally, the influence of pressure on water structure is also discussed.

Fabrication and characterization of CdS nanotube arrays in porous anodic aluminum oxide templates by Tianyou Peng; Huanpin Yang; Ke Dai; Xuli Pu; Kazuyuki Hirao (432-436).
Semiconductor CdS nanotube arrays were synthesized within the pores of the PAO membranes by using molecular anchor templating synthesis method. The CdS nanotube arrays obtained were characterized using scanning electron microscopy (SEM), X-ray diffractomemter (XRD) and transmission electron microscopy (TEM) with energy-dispersive X-ray spectroscopic analyzer (EDS), respectively. The formation mechanism of CdS nanotube was also discussed. This is the first report on the highly ordered CdS nanotube arrays with 60 μm in length and 100 nm in outer diameter. The present method shows the advantages of simplicity, high efficiency and low cost.

Interaction of 1,8-acridinedione dye with urea dimer in methanol by Chellappan Selvaraju; Viruthachalam Thiagarajan; Perumal Ramamurthy (437-442).
The hydrogen-bonding interaction between acridinedione dye (ADD) and urea dimer in methanol is reported by using steady state and time resolved fluorescence techniques.

Synthesis, structure and spectroscopic characterization of water-soluble CdS nanoparticles by Ch Barglik-Chory; D Buchold; M Schmitt; W Kiefer; C Heske; C Kumpf; O Fuchs; L Weinhardt; A Stahl; E Umbach; M Lentze; J Geurts; G Müller (443-451).
We present a facile approach for synthesizing bio-stabilized CdS nanoparticles in gram quantities. The particles were characterized by optical spectroscopy, Raman spectroscopy, soft X-ray emission spectroscopy, XRD, thermal and chemical analysis. The size of the particles is about 2.3 nm, with a CdS core of 1.3 nm diameter and an organic shell of 0.5 nm thickness which is thermally stable up to 200 °C. The chemical composition, surface termination, and optical properties are analysed.

Lithium(I) ion hydration: a QM/MM-MD study by Hannes H Loeffler; Ahmed M Mohammed; Yasuhiro Inada; Shigenobu Funahashi (452-457).
The hydration structure of the lithium(I) ion has been studied by a combined quantum mechanical/molecular mechanical molecular dynamics (QM/MM-MD) method at the HF and B3LYP level of theory. Water molecules of both the first and the second hydration shell have been included in the QM treatment. The effect of differently sized QM regions is discussed. The structure obtained by B3LYP is quite insensitive to changes in QM size whereas the HF simulation predicts a weak second hydration shell structure with a large QM region.

We report on an investigation into the interaction between different neutral non-volatile solute molecules in a molecular beam produced by the spray-jet technique that enables us to produce a molecular beam from a sprayed mist of a sample solution. This technique is applied to poly(propylene imine) dendrimer and 4-dicyanomethylene-2-methyl-6-p-dimethylaminostyryl-4H-pyran (DCM) systems. Resonantly enhanced multiphoton ionization of DCM in the DCM/dendrimer molecular beam leads to an efficient reaction between the dendrimer and DCM. The REMPI excitation spectra provide insights into the interaction between DCM and dendrimer molecules in the gas phase for the first time in these experiments.

On the ionic diffusive motion in some fluoride doped polymer electrolytes by S.S. Sekhon; Manoj Kumar; K. Yamada; T. Okuda (466-470).
The ionic diffusive motion (translational and rotational) of cations (NH4 + / H+) and anions (F/BF4 ) in polyethylene oxide (PEO) based polymer electrolytes containing ammonium fluoride (NH4F) and ammonium tetrafluoroborate (NH4BF4) has been studied by 1H and 19F NMR. Long range protonic translational motion has been observed at temperatures above the glass transition temperature (T g) whereas rotational diffusion of fluoride has been observed in PEO–NH4BF4 at temperatures below T g. In PEO–NH4BF4, both cations and anions have been found to show translational motion above T g.

Solvation dynamics in a protein–surfactant aggregate. TNS in HSA–SDS by Saptarshi Mukherjee; Pratik Sen; Arnab Halder; Sobhan Sen; Partha Dutta; Kankan Bhattacharyya (471-478).
Solvation dynamics of 2,6-p-toluidinonaphthalene sulfonate (TNS) is studied in an aggregate containing human serum albumin (HSA) and sodium dodecyl sulfate (SDS). Solvation dynamics of TNS bound to HSA displays two components, 90 and 4000 ps. When SDS binds to HSA the solvation dynamics becomes faster and a significant portion is missed in a picosecond setup. This is attributed to the displacement of the bound water molecules by SDS in the immediate vicinity of TNS in the HSA–SDS aggregate.

Template-based melting-recrystallization route to organic nanotubes by Liyun Zhao; Wensheng Yang; Guangjin Zhang; Tianyou Zhai; Jiannian Yao (479-483).
A facile template-based melting-recrystallization route has been developed to fabricate organic nanotubes from a low molecular weight compound, dibenzoylmethane. It is found that the diameters of the nanotubes correspond well to the membrane pores sizes and the wall thicknesses of the nanotubes can be controlled by the experimental conditions such as the immersion time. The compactness of the nanotubes is about 1 × 109 cm−2. The fluorescence emission of the nanotubes is improved greatly compared to that of bulk crystal.

Synthesis of CoFe2O4 nanowire arrays by sol–gel template method by Guangbin Ji; Shaolong Tang; Baolong Xu; Benxi Gu; Youwei Du (484-489).
CoFe2O4 nanowire arrays with an average diameter of about 40 nm were prepared in porous anodic aluminum oxide (AAO) template using sol–gel process. Transmission electron microscopy (TEM) diffraction pattern and X-ray diffraction (XRD) showed that the nanowires were polycrystalline phase. Magnetic measurements showed the arrays of nanowires did not show a preferential magnetic orientation, the reason was briefly discussed. The effect of heating rate on the structure and magnetic properties of CoFe2O4 nanowire arrays was investigated. The result showed that the coercivity decreased with the increase of the heating rate.

Electronically excited states and transport properties of thermal plasmas: the viscosity by M. Capitelli; A. Laricchiuta; D. Pagano; P. Traversa (490-494).
The viscosity of a partially ionized thermal hydrogen plasma has been calculated by taking into account electronically excited states with their abnormal transport cross-sections. The results show a strong dependence of viscosity on the presence of electronically excited states especially at high pressure. The insensitivity of viscosity respect to the choice of cross-sections of excited states at atmospheric pressure is explained on the basis of a compensation between diagonal and off-diagonal elements in the viscosity equation.

The data on the ‘coordination number’ n and on the nearest-neighbor distance R nn in liquid CF4 within a broad range of experimental conditions were obtained by the analysis of the profiles of (ν 1+ν 3) and of (ν 3+ν 4) IR-absorption bands. The pronounced linear increase on density of n was observed whereas value of R nn=4.40(5) Å was practically invariable. We consider that the variation of vacancies number is mainly responsible for the change of the density of the liquid on the alteration of its thermodynamic conditions, and it is not due to a simple dilation or contraction of the medium.

Thermochemical stability of the HO2–HClO4 complex by Abraham F Jalbout; M Solimannaejad; J.K Labanowski (503-506).
The thermochemical stability of the HO2–HClO4 complex is studied using both second-order Møller–Plesset perturbation theory (MP2) and the B3LYP density functional theory (DFT) method. Our calculations reveal stabilization energies of 11.1 and 13.2 kcal mol−1 at the MP2/6-311++G(3df, 3pd) and B3LYP/6-311++G(3df, 3pd) levels, respectively.

Light-induced luminescent enhancement and structural change in cubic nanocrystallineY2O3:Tb by Jiwei Wang; Hongwei Song; Baojuan Sun; Xinguang Ren; Baojiu Chen; Wu Xu (507-511).
Light-induced spectral change and its restore process in the dark of nanocrystalline Y2O3:Tb were studied. It was observed that the intensity in 4f5d band increased by ultraviolet and visible irradiation. The smaller the particle size and the shorter the wavelength is, the larger the light-induced luminescent enhancement is. Two restore components were observed, corresponding to two defects, the internal and the surface. The studies on electron spin resonance (ESR) spectra indicate that optical irradiation eliminated the dangling Y–O bonds in the surface.

Hybrid density functional theory (DFT) calculations are performed to study AuX2 (X=Cl, Br, and I) clusters in the neutral and anionic charge states. The equilibrium geometries of AuX2 and AuX2 are linear structures. The ground states of AuX2 and AuX2 are doublet ( 2 Π g ) and singlet ( 1 Σ g ), respectively. Time-dependent DFT is used to calculate the low-lying excited states. The theoretical assignment for the features in the experimental photoelectron spectra is given. All results obtained are in good agreement with the available experimental data.

Density functional theory investigations of geometries and electronic spectra of lithium phthalocyanines by Xia Liu; Lian-Cai Xu; Tian-Jing He; Dong-Ming Chen; Fan-Chen Liu (517-525).
The ground-state geometries of dilithium and monolithium complexes of phthalocyanine (Li2Pc and LiPc) and three reduced/oxidized species of LiPc (i.e., [LiPc], [LiPc]2− and [LiPc]+) have been studied with the density functional theory. It was shown that Li2Pc has a stable D4h structure with the two lithium atoms bonded symmetrically up and below the Pc plane. Both LiPc and [LiPc] have a planar D4h structure whereas [LiPc]+ has a significantly saddle-distorted D2d structure. [LiPc]2− has a planar D2h structure with a rectangular distortion due to the ground state Jahn–Teller effect. Electronic absorption spectra of Li2Pc and LiPc were calculated with the time-dependent DFT method, and the results are in good agreement with the experiments.

The CAS calculations with the ANO-L basis were performed for eight electronic states of the vinylidene anion (H2CC). The results (CASPT2/ANO-L vertical excitation energies and CASSI oscillator strengths) suggest that the observed absorption band of H2CC at 374 nm is attributed to the X2B2  → 22B2 transition and do not support the previous assignment to the X2B2  → 12A1 transition. The CAS excited-state calculations were also performed for a temporary anion, trans-HCCH, and the CASPT2/ANO-L results were used for assignment of observed absorption bands of trans-HCCH. When an ANO-L+ basis (including more diffuse functions) was used, CASSCF wavefunctions for some of the calculated states of the two anions described ‘composed’ systems (neutral species plus free electron) and the results were not reliable.

We report on the observation of a strong KrF laser-induced ultraviolet absorption and refractive index changes from germanium-doped and boron co-doped silica (Ge–B–SiO2) planar waveguides. The Ge–B–SiO2 planar waveguides on a pure silica substrate with optical propagation-loss of ∼0.2 dB/cm at 1.55 μm have been deposited by a new approach namely inductively coupled plasma-enhanced chemical vapor deposition. We have noticed that samples when annealed at 1000 °C are exhibiting very limited ultraviolet absorption at ∼240 nm, however, an enhancement has been found with the ∼240 nm absorption band due to the hydrogenation treatments. KrF laser has partially bleached the absorption at ∼240 nm and that has generated new paramagnetic site such as GeE centers with significant changes in the ultraviolet related absorption and refractive index of Ge–B–SiO2 waveguides.

Detection of pentazolate anion (cyclo-N5 ) from laser ionization and decomposition of solid p-dimethylaminophenylpentazole by Henric Östmark; Sara Wallin; Tore Brinck; Peter Carlqvist; Rob Claridge; Emma Hedlund; Larisa Yudina (539-546).
Laser desorption ionization (LDI) time-of-flight (TOF) mass spectroscopy of solid p-dimethylaminophenylpentazole (1) gives strong peaks of m/z −42 and −70. The −70 peak was identified by 15N labeling of 1 to be the pentazolate anion (cyclo-N5 ). The pentazolate anion is formed by an electron attachment to 1 forming the corresponding radical anion followed by a decomposition into 4-N(CH3)2-C6H4 and (cyclo-N5 ). The LDI TOF experimental study also revealed that the (cyclo-N5 ) is very stable. These conclusions are supported by QM calculations at the B3LYP/6-311+G(2df,p) level.

The N-particle random walk in the presence of a trap at the origin is applied to the geminate recombination of hemeprotein-ligand dynamics within the diffusion approximation in one dimension. Analytical expressions for the survival probabilities of the unbound heme are procured in terms of the span 〈S N (t)〉 of the multiparticle walk. The behaviour of the span is studied in the asymptotic limit of t→∞. When N is large 〈S N (t)〉 depends linearly on t 1/2 with no dependence on N, but when N is small, 〈S N (t)〉 varies linearly with N and has a logarithmic dependence on t.

This Letter reports studies of the lateral diffusion of the WALP16 peptide incorporated in phospholipid bilayers. Pulsed field gradient (PFG) NMR experiments in combination with Magic angle sample spinning (MAS) were performed to observe the diffusion of all membrane components. The observed spin–echo decays are described using a two-dimensional diffusion model that allows the calculation of the lateral diffusion coefficient of the peptide.

We present a simple and feasible method based on ab initio principle for studying the partly deformed quantum dot with a three-dimensional confinement potential of finite depth, which relies on the unrestricted Hartree–Fock–Roothaan equation. The results show that the electronic filling spectra can reconstruct due to the deformation effect in few-electron quantum dots. This method can solve few-body problem of the deformed quantum dot and study the geometry effect on the excess electron filling spectra.

We have studied the influence of up to fifth-nearest neighbor interactions on thermal desorption, using a novel kinetic Monte Carlo simulation scheme. It is shown that in many cases the long-range components of the adsorbate–adsorbate attractions can be reduced to an effective pairwise nearest neighbor interaction, which is much easier to handle, both, in theory and simulation. A criterion for the relevance or negligibility of long-range interaction components will be given. Special attention is devoted to the presence of kinetically limited surface diffusion for adsorbates exhibiting long-range lateral interaction. Such systems are shown to be much more sensitive to kinetic influences than systems governed by nearest neighbor interactions, only.

Perturbation theory is used to predict the light-induced spin polarization associated with the quartet state of rigid, strongly coupled triplet–doublet spin pairs. It is shown that spin–orbit coupling mixes the trip–doublet and trip–quartet states and that if the mixing determines the rate of ISC, it leads to net and multiplet spin polarization of the quartet state. Analytical expressions for the contributions to the spin polarization are derived using first-order perturbation theory. Using these expressions, the sign, magnetic field dependence and orientation dependence of the spin polarization are discussed in terms of the exchange coupling, zero-field splitting and spin–orbit coupling within the system.

Preferential solvation and elasticity of the hydrogen bonds network in tertiary butyl alcohol–water mixture by Michael Kiselev; Dmitry Ivlev; Yurii Puhovski; Teerakiat Kerdcharoen (581-587).
Molecular dynamics simulations have been performed for water–tertiary butyl alcohol (TBA) mixtures in the water rich region. Examination of the Kirkwood–Buff integrals, local composition, and potential mean force for concentration in the range 0.05–0.07 TBA mole fraction leads to insight into the unexpected behaviors of some thermodynamics properties. Hydrophobic hydration phenomena and solvent–solute association are discussed at the molecular level. Since the hydrogen bond network elasticity modulus is a quantitative measure of the resistance of the water hydrogen bonds network to external perturbation arising from solvent–solute interactions, a first principle calculation of the elasticity modulus was carried out.

Recently, experimental evidence for an oxygen isotope anomaly in surface-assisted ozone dissociation has been published by Chakraborty and Bhattacharya [Chem. Phys. Lett. 369 (2003) 662]. The authors claim that product oxygen from dissociation of ozone on glass and quartz surfaces is depleted in both heavy oxygen isotopes by about equal amounts. The evidence presented, however, is by no means conclusive. Earlier measurements and even the control experiments of Chakraborty and Bhattacharya suggest that ozone decomposition on glass and quartz surfaces actually follows a normal mass-dependent relationship.

Author Index (595-605).