Chemical Physics Letters (v.457, #1-3)

Contents (iii-xviii).

Arrays of various cubic and spherical PbTe and Pbs quantum dots are shown (colors are not true). The size and shape are controlled by the synthesis conditions. Close-packed arrays of PbSe QDs produced by chemical post-treatment of the original QD films have been shown to exhibit very good inter-QD electronic coupling with DC carrier mobilities above 1 cm2/s.A review is presented of recent work on (1) the origin of the concept of enhanced multiple electron–hole pair (i.e. exciton) production in semiconductor quantum dots (QDs), (2) various experiments based on time-resolved fs to ns spectroscopy (transient IR absorption, transient visible to near-IR bleaching due to state filling, terahertz spectroscopy, and time-resolved photoluminescence) that support the occurrence of highly efficient multiple exciton generation (MEG) in QDs, (3) thermodynamic analyses of the theoretical enhancement of the conversion efficiency in solar cells that are based on MEG in QDs, (4) MEG in QD arrays that can be used in QD solar cells, (5) theoretical models to explain MEG, and (6) some recent controversy about the evidence for MEG.

Sensitive THz-ATR spectroscopy with a novel analysis enables us to determine the total number of hydrated water molecules.We propose a novel method to characterize hydration states from dielectric responses of solutions in terahertz (THz) frequency region. Hydration states can be evaluated quantitatively from a complex dielectric function derived from a theory with a local field correction. We demonstrated this method in disaccharide (sucrose and trehalose) water solutions using the THz time-domain attenuated total reflection (TD-ATR) spectroscopy. The method successfully evaluates the hydration state and its concentration dependence, providing a new tool to investigate the picosecond dynamics of hydration directly.

Photoelectron spectra of benzophenone radical anions microsolvated with methanol have been measured for elucidation of the origin of solvatochromic shifts in the condensed phase.The 355 nm photoelectron spectra of bare and methanol-solvated radical anions of benzophenone were measured. Sequential shifts of the vertical detachment energy represent a similarity in shape to those of the photoabsorption spectrum reported previously, exhibiting near convergence for solvation with two methanol molecules. An analysis of the solvation energetics shows that the solvatochromic shifts in alcoholic media are essentially caused by a change of long-range interactions involving the excess charge delocalized over the anion, instead of a former explanation based on local hydrogen-bonding of solvents with the singly occupied molecular orbital in the ground state.

A molecular beam optical Stark study of nickel monohydride, NiH by Jinhai Chen; Timothy C. Steimle (23-25).
Nickel monohydride, NiH, molecule with dipole moment indicated.The optical Stark effect in the B2Δ5/2  ← X2Δ5/2(1–0)Qe/f(5/2) and Pe/f(7/2) lines of nickel monohydride, 58NiH, was recorded and analyzed to produce values for the permanent electric dipole moment, μ, of 2.44 ± 0.02 D and 0.36 ± 0.02 D for the X2Δ5/2 and B2Δ5/2 states, respectively. The values are in agreement with the previously determined values [J.A. Gray, S.F. Rice, R.W. Field, J. Chem. Phys. 82 (1985) 4717] and with the experimental error approximately a factor of five smaller. A comparison with theoretical predictions and other first-row transition metal monohydrides is given.

We present results on the N–NO2 bond dissociation in gas-phase DMNA and HMX. The results obtained in our calculations are in good agreement with other methodologies, which demonstrates that the umbrella sampling model implemented in FIREBALL is able to correctly predict the free energies changing along the reaction potential surface.We discuss implementation of the umbrella sampling technique using the weight histogram analysis method in FIREBALL, a density functional theory method based on local-orbitals and pseudopotential theory. With this implementation, we calculate free energy curves of chosen reaction pathways from quantum mechanical forces; therefore, the potential of mean force yields energetic evaluations which include the electronic rearrangements as the structure changes during molecular dynamics simulations. The free energy curve is calculated along the entire reaction pathway rather than the traditional approach of using static single-point calculations along a reaction potential surface. We present results on the N–NO2 bond dissociation in gas-phase DMNA and HMX. The results obtained in our calculations are in good agreement with other methodologies, which demonstrates that the umbrella sampling model implemented in FIREBALL is able to correctly predict the free energies changing along the reaction potential surface.

Among several covalently-bonded isomeric forms of C 2 S 4 - hitherto proposed, the cyclic C 2 v isomer is identified as the spectral carrier of as-yet-unassigned ( CS 2 ) 2 - photoelectron band. A trail of evidence for C 2 S 4 ( 1 A 1 ) ← C 2 S 4 - (2B1) transition is left as a vibrational progression newly observed in the photoelectron measurment.An intense beam of the dimer anion of CS2 was prepared by a pulsed-discharge nozzle, which enabled the measurement of the previously-reported 2.7-eV photoelectron band of C 2 S 4 - with higher spectral resolution at 355 nm. This measurement has revealed that the band consists of a vibrational progression with an average spacing of 0.13 ± 0.01 eV, indicating a bound electronic property of the residual C2S4 neutral. With the aid of molecular orbital calculations, the observed progression has been assigned to the transition from C 2 S 4 - (2B1) to the vibrationally-excited states of C2S4(1A1), both possessing cyclic C 2 v structures.

The reaction of methyl radical with nitrogen atom on the triplet potential energy surface: A CCSD(T)/CBS characterization by Tiago Vinicius Alves; Antonio Gustavo S. de Oliveira Filho; Fernando R. Ornellas (36-41).
Mechanistic model of the N (4S) + CH3 (2A″) reaction.CCSD(T)/cc-pVnZ (n  = D, T, Q) calculations followed by extrapolations to the CBS limit are used to characterize stationary states of species participating in the N(4S) + CH3 (2A′′) reaction on the triplet PES. A mechanistic model is investigated and reaction rates are computed for every step and the overall reaction. Our best CBS estimate (1.93 × 10−10  cm3  molecule−1  s−1) for the overall rate constant leading to the formation of H2CN + H compares well with the experimental values (8.5 × 10−11 and 1.3 × 10−10  cm3  molecule−1  s−1), thus reducing significantly the discrepancy of a previous theoretical result (9.1 × 10−12  cm3  molecule−1  s−1).

Relativistic effects on the hexafluorides of group 10 metals by Jorge David; Patricio Fuentealba; Albeiro Restrepo (42-44).
Dilemma for the MF6 (M = Pd, Pt, Ds) structures: Non-relativistic calculations predict singlet e g 4 , D 4 h geometries; Crystal Field Theory predicts triplet t 2 g 4 , O h geometries; four component relativistic calculations predict singlet f g 4 , O h geometries.We present relativistic and non-relativistic ab initio treatments of the hexafluorides of group 10 metals. Non-relativistic equilibrium geometries belong to the D 4 h point group while relativistic calculations afford O h geometries. Relativistic effects yield singlet ground states for all complexes, the stabilization energy coming from the spin–orbit coupling. We used Time Dependent Density Functional Theory at the ZORA two component Regular Approximation to calculate the excitation spectra of the complexes. The predicted spectra correctly reproduce the experimental results. Relativistic effects in conjunction with spin–orbit coupling stabilize the O h geometry and are important in the prediction of spectra and properties of the hexafluorides of the group 10 metals.

Experimental observation of relativistic effects on electronic wavefunction for iodine lone-pair orbital of CF3I by Zhongjun Li; Xiangjun Chen; Xu Shan; Xinxia Xue; Tao Liu; Kezun Xu (45-48).
The different intensity of experimental momentum profiles for the spin-orbit splitting components 5e3/2 and 5e1/2 shows relativistic effects on electron wavefunctions.The binding energy spectra of CF3I in the energy range 9–15 eV have been measured by a newly developed high resolution (e, 2e) spectrometer with 0.5 eV energy resolution. The two spin-orbit splitting components 5e3/2 and 5e1/2 of iodine lone-pair orbital have been partially resolved and their individual electron momentum distributions have been obtained, together with their branching ratio as a function of momentum. The experimental results show the obvious relativistic effects on the wavefunctions for 5e3/2 and 5e1/2 orbitals.

Dominant role of the interstitial 4d transition-metal in TM@Zr 12 Z (TM = Y–Cd, Z  = 0, ±1) icosahedral cages by Chuan-Lu Yang; Mei-Shan Wang; Mei-Yu Sun; De-Hua Wang; Xiao-Guang Ma; Yu-Bing Gong (49-53).
One doped 4d transition-metal atom can stabilize the icosahedral Zr12 cage which contains 12 zirconium atoms but is not stable by itself.The atomic geometries, energetic stabilities and electronic properties of TM@Zr 12 Z (TM = Y–Cd, Z  = 0, ±1) clusters are investigated with density-functional theory and relativistic all-electron basis sets. Optimization calculations and frequency analyses show that all the 45 considered icosahedral geometries are stable. It is also found that the bond lengths, binding energies and the gaps between the highest occupied molecular orbitals and the lowest unoccupied molecular orbitals of the clusters obviously change with the interstitial atoms. The adiabatic ionization potentials and electron affinities are also relationship with the interstitial atoms. The role of the interstitial atoms on stabilizing the Zr12 cage is examined.

A number of excited states was characterized by the MRCI/CBS method.The X  2B1, 1  2A1, 2  2A1, 1  2B2, 1  2A2 states of NF2, the X  1A1, 1  3B1, 1  3A2, 1  1A2, 1  1B1, 1  3B2, 1  1B2 states of NF 2 + , and the X  1A1, 1  3B1, 1  3A2, 1  1B1, 2  1A1 1  1A2 states of NF 2 - were characterized by the MRCI calculations. The adiabatic excitation energies were extrapolated to their complete basis set limits. The electronic states of NF 2 - were studied for the first time and the electron affinity of NF2 was revisited. The results may serve as reliable input parameters in modeling the plasmochemical processes involving NF2 and its ions.

Laser-induced fluorescence spectra of jet-cooled thioanisole were measured to investigate the molecular structure. High-level MO calculations suggests that frequencies of mode 15 and δ(CSC), the deformation of the thiomethyl group, were very sensitive to orientation of the thiomethyl group. Analysis of the vibrational mode of the DF spectrum demonstrates that the most stable structure is planar.Laser-induced fluorescence (LIF) excitation and dispersed fluorescence (DF) spectra of jet-cooled thioanisole were measured for the first time. The DF spectrum was obtained by pumping the origin band to investigate the molecular structure in the S0 state. High-level MO calculations suggest that frequencies of mode 15 and δ(CSC), the deformation of the thiomethyl group, were very sensitive to orientation of the thiomethyl group. Analysis of the vibrational mode of the DF spectrum demonstrates that the most stable structure is planar. Analysis of low-frequency vibrational modes is found to be important to determine the flappy structures.

The ratio of the fluorescence decay in the presence of electric field relative to the one at zero field.Electric field effects on absorption and emission spectra and emission decay have been examined for tris(8-hydroxyquinoline)aluminum (Alq3) doped in a poly(methyl methacrylate) film. Emission spectra as well as absorption spectra of Alq3 exhibit the so-called Stark shift in the presence of external electric field, and a significant change in electric dipole moment takes place following the optical transition. Fluorescence of Alq3 also shows the electric-field-induced quenching, which is confirmed to originate from the field-induced increase in intramolecular non-radiative decay at the emitting state by the direct measurements of the field-induced change in fluorescence decay profile.

Time-resolved EPR study on photoreduction of sodium anthraquinone-2-sulfate in liposomes by Shinya Moribe; Tadaaki Ikoma; Kimio Akiyama; Shozo Tero-Kubota (66-68).
Photolysis of amphiphilic anthraquinone-2-sulfonic acid (2-AQS) in liposome buffer solution shows transient electron spin polarization consisting of a net emissive polarization attributable to hydrogen abstraction in a lipid bilayer and a net absorptive pattern caused by electron transfer via the triplet exciplex 3(2-AQS–Cl) in an aqueous phase.Laser pulse photolysis of amphiphilic anthraquinone-2-sulfonic acid (2-AQS) in liposome buffer solution shows transient electron spin polarization consisting of a net emissive polarization attributable to hydrogen abstraction in a lipid bilayer and a net absorptive pattern caused by electron transfer via the triplet exciplex 3(2-AQS-Cl) in an aqueous phase. The diffusion rate of the neutral semiquinone radical from the interior of the lipid bilayer to a bulk water region is determined to be 7 × 105  s−1, suggesting that the rate is slower compared with the micellar system.

Initial adsorption mechanisms of TiCl4 on OH/Si(1 0 0)-2 × 1 by Manik Kumer Ghosh; Cheol Ho Choi (69-73).
H–Cl Trapped intermediate of initial TiCl4 adsorption on OH/Si(1 0 0)-2 × 1 surface.The initial adsorption mechanisms of TiCl4 on OH/Si(1 0 0)-2 × 1 surface were theoretically investigated with the help of ab initio theories. Four reaction channels were identified. The penta-coordinated Ti, which effectively blocks the surface adsorption sites, plays a significant role in all processes.

Superconductivity of C60 fullerite intercalated with Ca by means of shock-wave pressure technique by Yu.A. Ossipyan; N.S. Sidorov; A.V. Palnichenko; O.M. Vyaselev; M.V. Kartsovnik; M. Opel; V.V. Avdonin; D.V. Shakhrai; N.V. Biktimirova; A.A. Golyshev (74-77).
High pressure shock-wave setup for C60 fullerite Ca-intercalation (1—sample, 2—copper chamber, 3—steel guard ring, 4—aluminum impactor).C60 fullerite has been Ca-intercalated under high pressure up to 240 kbar induced by a shock-wave. Conductance of the samples exposed to shock-wave pressure has been measured. Magnetometric measurements have revealed superconductivity of the intercalated samples at 4.7, 9.9, and 30 K.

Behavior of molecular oxygen at the liquid–liquid interface: A molecular dynamics simulation study by Árpád Vincze; Pál Jedlovszky; Lívia B. Pártay; George Horvai (78-81).
No adsorption of O2 was observed at the liquid–liquid interface of water with DCE and with CCl4.Molecular dynamics simulations of O2 solvated at the vicinity of water/1,2-dichloroethane (DCE) and water/CCl4 liquid–liquid interfaces are reported. The distribution of oxygen along the interface normal is investigated. The results show that the choice of the algorithm used to keep the temperature of the system constant has a non-negligible effect on this distribution, the Nosé–Hoover thermostat being superior over the Berendsen thermostat in this respect. No adsorption of O2 at the interface has been observed, even if its molecular scale roughness is taken into account by means of the novel method for identification of truly interfacial molecules (ITIM).

Multiphotonic excitation and solvation dynamics effects on the femtosecond transient absorption of O-hexamethoxyhypericin by Christian Ley; Johanna Brazard; Fabien Lacombat; Pascal Plaza; Monique M. Martin; George A. Kraus; Jacob W. Petrich (82-86).
Effect of the excitation fluence on the transient absorption kinetics of O-hexamethoxyhypericin at 565 nm.The hypothesis of a photoinduced intramolecular H-atom transfer in hypericin is reexamined by comparison with O-hexamethoxyhypericin, a derivative bearing no labile proton. In both cases, femtosecond transient absorption spectroscopy reveals an additional picosecond rising component in the kinetics under high excitation fluences. For the hexamethoxy derivative this effect is mixed with solvation dynamics but we succeeded in decoupling it. The delayed rise is ascribed to bi/multiphotonic excitation to upper excited states, followed by internal conversion to a hot S 1 state that subsequently cools down. The present observations are not consistent with the intramolecular H-atom transfer interpretation.

On the chromism of polyenes by J. Catalán (87-90).
The solvatochromic behaviour differs from the thermochromic one for polyene molecules, and their cause is not only based on the medium polarizability.At a constant temperature, the change in energy of the 1Ag → 1Bu electronic transition of a polyene with the solvent depends on solvent polarizability. For the same solvent and polyene, as the temperature varies, however, the energy of the 1Ag → 1Bu electronic transition not only depends on polarizability but also quite strongly on alterations of the chemical structure of the polyene.

Modelling the acidochromism of pyridylazulenes by Denis Jacquemin; Alexandre Lewalle; Eric A. Perpète (91-95).
The auxochromic and acidochromic effects are investigated for a series of ptridylazulenes.The structure of six recently synthesised neutral or charged 1-pyridylazulenes and 1,3-dipyridylazulene have been investigated with the PCM–PBE0/6-311++G(2d,2p) approach. Our calculations demonstrate that several conformers of similar energies might coexist in the experimental conditions. The absorption spectra of all derivatives have also been simulated with TD-DFT, and a very good agreement between the experimental and theoretical shifts is attained for both acidochromic and auxochromic phenomena. The origin of colour changes upon pH modification is rationalized.

The first step towards a direct link between diffraction experiments and computer simulations.A protocol for finding the applicability limits of interaction potential models, used in molecular dynamics (MD) computer simulations, is presented. The essence of the approach is to combine experimental structure factors and radial distribution functions from MD simulations in one single structural model, generated by Reverse Monte Carlo modeling. This way, it becomes possible to tell which parts of the structure are represented by the potential model in question. As an example, we use aqueous rubidium bromide solutions. We show that a great deal of structural information from MD may be consistent with neutron diffraction experiments at lower concentrations.

Energy transfer and enriched emission spectrum in Cr and Ce co-doped Y3Al5O12 yellow phosphors by Wendong Wang; Jinke Tang; Sheng Teng (Victor) Hsu; Jing Wang; B. Patrick Sullivan (103-105).
We report energy transfer in Cr/Ce co-doped Y3Al5O12 that has direct implication on the science and technology of white LED phosphors.Ce/Cr co-doped Y3Al5O12 (Ce/Cr:YAG) exhibits enriched emission spectrum in the red region due to a non-radiative energy transfer from the Ce3+(2E) level to Cr3+(4T) level. Excitation spectra collected at Cr3+ red emission show an intense excitation broad band at 458 nm confirming the energy transfer, which is responsible for the two orders of magnitude increase in the intensity of the red emission compared to YAG doped with Cr alone. The huge increase in the Cr red emission in Ce/Cr:YAG compared to Cr:YAG suggests that the former is an efficient red and yellow phosphor and has potential in white LEDs and laser applications.

Three-pulse photon echo peak shift in optically dense samples by N. Christensson; B. Dietzek; T. Pascher; A. Yartsev; T. Pullerits (106-109).
We have measured the dependence of the three-pulse photon echo peak shift signal on sample optical density and thickness.We have investigated the dependence of the three-pulse photon echo peak-shift (3PEPS) signal on solute concentration and sample path length. The most prominent effect is an increase of the amplitude of the long decay component of the 3PEPS at high optical densities, but signal distortions are observed for all timescales in the experiments. The distortions of the peak shift signal are more severe for longer path lengths. These observations are assigned to pulse propagation effects. At low concentrations interference between the solute signal and the non-resonant solvent response severely distort the peak profiles at short population times.

At higher temperatures the H-atom in the very strong F–H–F hydrogen bond is essentially centred between the two fluorine atoms, while upon cooling it shifts closer to F(2).The crystal of [C6H13N2]+[HF2] is built of ionic pairs tied by strong N–H···F hydrogen bonds. A very strong F–H···F hydrogen bond linking the anion is symmetric at higher temperatures, while upon cooling the H-atom shifts continuously to a clearly non-centred site. This first observation of the thermally induced proton migration in the strongest known hydrogen bond is explained by the potential-energy fluctuations due to the large-amplitude motions of the fluorine atoms. The crystal undergoes a continuous phase transition at 150.6 K, accompanied by the symmetry change from Cmc21 to P1. The transition mechanism involves an order–disorder contribution related to the behaviour of the hydrogen difluoride anion.

Interference and electro-optical Kerr effects responsible for electroabsorption spectra of transparent Parylene-C films by Y. Harima; T. Hashiguchi; Y. Fujikawa; K. Komaguchi; Y. Ooyama; I. Imae (115-118).
Electroabsorption spectra of Parylene-C films are found to exhibit several peaks whose wavelengths depend on the thickness of the film.Electroabsorption spectra of Parylene-C films are found to exhibit several peaks whose wavelengths depend on the thickness of the film. The spectral feature is well correlated to the first derivative of the transmission spectrum of the Parylene-C film sandwiched between two reflective metal layers, and the peak intensities are in proportion to the square of the magnitude of a modulation voltage. The electroabsorption spectra observed in a transparent region of the electrically insulating films are accounted for in terms of the interference effect coupled with the electro-optical Kerr effect of the Parylene-C films.

The n–π and π–π electronic transitions of mesoionic compounds in gas-phase and in DMSO have been calculated using the TD-DFT approach in combination with B3LYP and PBE1PBE hybrid functionals. The solvent effects have been included using the PCM method.Using the TD-DFT approach in combination with B3LYP and PBE1PBE hybrid functionals we have calculated the n–π and π–π electronic transitions of sulfur-bearing mesoionic compounds in gas-phase and in DMSO. The solvent effects have been included using the PCM method. The calculations show large hypsochromic shifts for these two lowest transitions in going from gas-phase to DMSO, specially for the weak n–π transition. For the compound 4-phenyl-5-(p-chlorophenyl)-1,3,4-thiadiaolium-2-thiolate the TD-B3LYP/6-311+G(2d,p) and [TD-PBE1PBE/6-311+G(2d,p)] models predict for the intense π–π transition in DMSO absorption wavelengths of 413.50 nm and [394.59 nm] in good agreement with the available experimental result around of 408 nm.

The SiC fullerene structures are distorted and open unlike their C20 fullerene counterpart.Stability of SiC fullerene type structures is still an unsolved issue as no experimental confirmation has been reported so far regarding its existence. However, theoretical reports are available in the literature where carbon fullerenes were taken as base models for SiC fullerene structures. In this present Letter we show by a systematic study on the C20 fullerene that this approach may not always produce the ground state structure in fullerene form. Instead, the energetically favorable structure could be highly distorted and open structure. However, we observed a very systematic linear trend in the evolution of binding energies of SiC clusters from the carbon fullerene.

Generation of multiple circular walls on a thin film of nematic liquid crystal by laser scanning by M. Kojima; J. Yamamoto; K. Sadakane; K. Yoshikawa (130-133).
Target pattern is generated through a spiral scanning of IR laser on a nematic liquid crystal.We found that multiple circular walls (MCW) can be generated on a thin film of a nematic liquid crystal through a spiral scanning of a focused IR laser. The ratios between the radii of adjacent rings of MCW were almost constant. These constant ratios can be explained theoretically by minimization of the Frank elastic free energy of nematic medium. The director field on a MCW exhibits chiral symmetry-breaking although the elastic free energies of both chiral MCWs are degenerated, i.e., the director on a MCW can rotate clockwise or counterclockwise along the radial direction.

Post-calcination with nitrogen is effective for improving the activity of (Zn1+ x Ge)(N2O x ) for photocatalytic overall water splitting under visible light.The activity of Rh y Cr2− y O3-loaded (Zn1+ x Ge)(N2O x ) photocatalyst for overall water splitting under visible light is enhanced by N2 calcination of (Zn1+ x Ge)(N2O x ) at 673 K, achieving an apparent quantum efficiency of 2.0% at 420–440 nm. The enhancement in activity is attributable to a decrease in the density of defects acting as recombination centers for photogenerated electrons and holes.

Ab initio and DFT investigation of the mean dipole polarizabilities and the polarizability anisotropies of stoichiometric Al n P n (n  = 2–9) clusters.The mean dipole polarizabilities and the polarizability anisotropies of stoichiometric Al n P n (n  = 2–9) clusters are investigated and presented for the first time. Basis set augmentation effects on the 6-31+G substrate are studied and discussed. The electron correlation contributions to the polarizability were studied for clusters up to 12 atoms at MP2 and CCSD(T) levels of theory, and the performance of the widely used B3LYP, B3PW91, mPW1PW91 functionals are assessed. From the methodological standpoint, our results show that for clusters where the ionic contribution to the bonding is strong the MP2 method yields polarizability values in very good agreement with the more accurate CCSD(T) approximation.

Small Au clusters on a defective MgO(1 0 0) surface by Giovanni Barcaro; Alessandro Fortunelli (143-147).
Fluxional behavior of the Au8 cluster on a defective MgO(1 0 0) terrace.The lowest energy structures of small Au N clusters (N  = 4, 6, 8, 10) adsorbed on an MgO(1 0 0) terrace presenting a double vacancy (DV) neutral defect are investigated via a density-functional basin-hopping (DF-BH) approach. Gas-phase gold clusters in this size range exhibit planar structures, while a crossover from planar to cage structural motifs takes place between size 8 and 10 when the clusters are adsorbed on the defected surface. A fluxional behavior is found with different structural motifs very close in energy, in agreement with the co-existence of different epitaxies observed in Molecular Beam Epitaxy experiments on larger clusters. Au6, that is energetically favored in the gas-phase with respect to neighboring sizes thanks to an electronic shell-closure effect, presents a reduced HOMO–LUMO gap, and its stability is comparable to that of other even clusters.

The C-modified film prepared at the oxygen partial pressure of 0.05 Pa presented round island-like structure and wettability conversion from high hydrophobicity to super-hydrophilicity under UV light irradiation.C-modified TiO2 films have been deposited on slide glass substrates by magnetron reactive co-sputtering using titanium and graphite as targets. The influence of different oxygen partial pressures on the phase transition, microstructure and surface wettability of C-modified TiO2 films was investigated. The films were characterized by XPS, XRD, Raman spectra, SEM and AFM. Sample structure transferred from composite rutile-anatase to anatase with increasing oxygen partial pressure. The wettability transformation of different films under UV light irradiation was also discussed.

Modelling organic molecular crystals by hybrid quantum mechanical/molecular mechanical embedding by Juan Torras; Stefan Bromley; Oscar Bertran; Francesc Illas (154-158).
QM/MM embedding with one DT–TTF molecule in the QM zone and 479 DT–TTF molecules in the MM zone.Detail of the quantum mechanical/molecular mechanical (QM/MM) embedding with one DT-TTF molecule in the QM zone and 479 DT-TTF molecules in the MM zone.We present a hybrid quantum mechanical/molecular mechanical (QM/MM) embedding scheme to model organic molecular materials. The method employs specialist QM and MM codes as modules in an integrated way that enables the dynamic simulation of large numbers of molecules at a MM level with a smaller fraction treated at a higher QM level of theory. In this preliminary study our QM/MM methodology is applied to the high performance organic (opto)electronic material dithiophene–tetrathiafulvalene (DT–TTF). The QM/MM methodology is tested and confirmed with respect to experiment and previous cluster calculations. The effects of the more realistic treatment of the molecular environment are highlighted.

Optical limiting performances of multi-walled carbon nanotubols and [C60]fullerols by Qi Wang; Yujun Qin; Yunji Zhu; Xu Huang; Yuxi Tian; Pu Zhang; Zhi-Xin Guo; Yilin Wang (159-162).
The optical limiting performances of the aqueous dispersions of multi-walled carbon nanotubols and [C60]fullerols were investigated using the Z-scan measurements.The optical limiting performances of the aqueous dispersions of multi-walled carbon nanotubols and [C60]fullerols were investigated using the Z-scan measurements at 532 nm. In addition, the optical limiting properties of nitric-sulfuric processed multi-walled carbon nanotubes and surfactant-assisted multi-walled carbon nanotubes in water, and C60 in toluene were also measured to make comparison. All the carbon nanotube materials used in our experiments, especially multi-walled carbon nanotubols, showed much better optical limiting performances than [C60]fullerols and C60. The mechanisms of the optical limiting performances of the samples were also proposed and discussed.

Size-dependence of stability and optical properties of lead sulfide clusters by Jiangang He; Caiping Liu; Fujun Li; Rongjian Sa; Kechen Wu (163-168).
The structural evolutions, size-dependent stabilities and optical properties of (PbS) n clusters (n=  1–16) have been systematically studied.The geometries, stabilities, and optical properties of lead sulfide (PbS) n clusters (n=  1–16) have been studied by using density functional theory method in order to exposit the structural evolutions and size-dependent stabilities and optical properties. The clusters favor the galena structures and follow a simple cubic growth pattern. The even number clusters show higher stabilities than the odd ones do and the magic numbers appear at n  = 4, 8, 10, and 14. The mean static polarizabilities of the lowest-energy structures exhibit a linearly increased tendency while the largest mean second hyperpolarizabilities of each size present the exponentially increased character.

Magnetism in germanium-doped boron-nitride nanotubes by Jianbao Wu; Weiyi Zhang (169-173).
Charge distribution of the in-gap states for the S N case is more extend than that of for the S B case.The magnetic property of the pristine and germanium-doped (10, 0) boron-nitride (BN) nanotube has been studied using a DFT-LSDA method. The germanium substitution for either a single boron or single nitrogen atom yields a spin-polarized, almost dispersionless π bands within the original band gap and net magnetic moment is 1 μ B . The flat band originates from the local structural deformation in the vicinity of germanium atom. Contrast to the theoretical models based on carbon or silicon-doped BN nanotubes, substituting a nitrogen atom with germanium atom results in three pairs of in-gap states which indicates more extended nanotube deformation than those previously studied.

In this work we study the effect of zigzag single walled nanotubes (ZNT’s) of varying sizes on the dimerization of simple polar molecules by either absorption or adsorption. The results show that in the larger case the stability of the dimmers increases.In this work we study the effect of zigzag single walled nanotubes (ZNT’s) of varying sizes on the complexation of simple polar molecules by adsorption. We have considered two ZNT’s (with constant lengths of 13.5 Å), the (8, 0) which corresponds to 6.3 Å and the (14, 0) species that has a diameter of 11.4 Å. This was performed in order to compare the relative complexation energies of the polar molecules adsorbed on the inside and on the surface of the nanotube structures.

A ‘Scorpion’ like SWNT/carbon sheet molecular trap by Aned de Leon; Abraham F. Jalbout (179-184).
In this work we have devised a ‘Scorpion’ like system composed of a zigzag (8,0) single walled carbon nanotube (SWNT) bound to a 20 ring carbon sheet by a two molecule glycine chain. The results suggest that one can cause expulsion of small polar molecules from the cavities of SWNT species.In this work we have devised a ‘Scorpion’ like system composed of a zigzag (8,0) single walled carbon nanotube (SWNT) bound to a 20 ring carbon sheet by a two molecule glycine chain. DFT-BLYP/DND calculations were performed to analyze the ability of such a system to trap simple polar molecules in the cavities of the SWNT species as well as on the surface of the carbon sheet.

SWNT–amino acid interactions: A theoretical study by Aned de Leon; Abraham F. Jalbout; Vladimir A. Basiuk (185-190).
This work encompasses a detailed discussion of the interactions between an armchair (5, 5) single walled carbon nanotube (SWNT) and amino acids. After multiple configurations and test calculations we have deduced that the highest dissociation energies are obtained when metallic SWNT systems interact with biological molecules. The implications of such findings are discussed according to biochemical properties of the amino acids.In the present work we discuss the interactions between an armchair (5, 5) single walled carbon nanotube (SWNT) and amino acids. After multiple configurations and test calculations we have deduced that the highest dissociation energies are obtained when metallic SWNT systems interact with biological molecules. The DFT–BLYP/DND calculations reveal that the most favorable interactions of the SWNT system is with arginine, cysteine, alanine and asparagine which is related to the backbone structure of the corresponding amino acids.

Phonon characterization of nano-crystals by Raman spectroscopy by Pier Carlo Ricci; Marcello Salis; Alberto Anedda (191-193).
It is proposed a numerical method to retrieve an approximated average phonon dispersion curve from Raman spectra of nano-sized crystals.Proposed herein is a method based on the Levenberg–Marquadt technique to retrieve an approximated average phonon dispersion curve from Raman spectra of nano-sized crystals. To this end we deal with a modified form of the well-known phonon confinement model in which the intrinsic linewidth Γ 0 is replaced by an effective linewidth Γ. An application to experimental results obtained on TiO2 nano-crystals is presented as a test of the method.

Enhanced photoluminescence of a tetranuclear neodymium complex: Fluorescent resonance energy transfer analysis by Xiaoming Qiu; Kehan Yu; Chao Gao; Chaoqi Hou; Junfang He; Zhiwei Zhou; Wei Wei; Bo Peng (194-197).
A novel tetranuclear neodymium complex was synthesized and fluorescent resonance energy transfer theory was applied to investigate the optical properties.A novel tetranuclear neodymium complex was synthesized and dissolved into N,N-dimethylformamide. The molecular structure of the complex was characterized by single-crystal X-ray diffraction. Fluorescent resonance energy transfer theory was applied to investigate the optical properties of the sample. It was found that the quenching of Nd3+ excited state via O–H vibrational excitation could be nearly neglected and the cross-relaxation or excitation migration rate of the tetranuclear complex was only 1/16 times of the traditional mononuclear one.

The response of the senor and the control samples upon steam pulses and the SEM image of the nanowires grown on polycrystalline ZnSe. Resistive humidity sensor with interesting linear response has been achieved.A resistive-type relative humidity sensor based on one-dimensional ZnSe nanostructures is reported. The sensor is fabricated by a two-step thermal evaporation – first the growth of a polycrystalline ZnSe substrate and then the growth of ZnSe nanowires. Ohmic contacts have been made to the sensor by simple silver painting. The sensor has a linear response of relative humidity over the range of 11.3–97.3%, which offers better sensitivity than the commonly reported exponential response, particularly at low relative humidity below 20%. A model based on capillary condensation is given to explain this feature.

Efficient visible light-sensitive photocatalysts: Grafting Cu(II) ions onto TiO2 and WO3 photocatalysts by Hiroshi Irie; Shuhei Miura; Kazuhide Kamiya; Kazuhito Hashimoto (202-205).
TiO2 and WO3 powders with Cu(II) ion grafts have led to the development of novel photocatalysts that are sensitive to visible light. Their reaction is triggered by photo-induced interfacial charge transfer (IFCT).We have designed and fabricated efficient photocatalysts sensitive to visible light, Cu(II)-grafted TiO2 (Cu(II)/TiO2) and WO3 (Cu(II)/WO3), after the suggestions made in the literature as to the photo-induced interfacial charge transfer from a semiconductor to an adsorbed molecular species and the catalytic multi-electron reduction of oxygen by Cu(I) ions. In fact, Cu(II)/TiO2 and Cu(II)/WO3 photocatalysts decomposed 2-propanol to CO2 via acetone under visible light (>400 nm) with quantum efficiencies of 8.8% and 17%, respectively. The turnover numbers of this reaction exceeded 4.1 for Cu(II)/TiO2 and 51 for Cu(II)/WO3, indicating that both function catalytically.

In situ Raman studies of single-walled carbon nanotubes grown by local catalyst heating by S. Dittmer; N. Olofsson; J. Ek Weis; O.A. Nerushev; A.V. Gromov; E.E.B. Campbell (206-210).
In situ Raman studies of SWNT grown using a local catalyst heating technique.Using in situ Raman spectroscopy we investigate single wall carbon nanotube growth on Mo electrodes, using a highly localized resistive heating technique. Small diameter semiconducting single wall nanotubes grow very rapidly when the catalyst support is heated to a temperature of 800 °C. The G/D ratio shows an interesting time-dependent behaviour. It first decreases, indicating the presence of amorphous carbon and then significantly increases again after ca. 5 min growth while retaining the position and shape expected for predominantly semiconducting carbon nanotubes.

QTAIM multicenter bond index analysis of amino acid’s aromaticity in the isolated and complexed states. Six-, two- and three-center bond indices are evaluated.In order to provide insight into the influence of metal cations on the aromaticity of amino acids, evaluation of six-center delocalization indices is accomplished in the context of quantum theory of atoms in molecules (QTAIM). Aromaticity of two amino acids, phenylalanine and tyrosine, is investigated as typical amino acids containing aromatic ring in their isolated state and complexed by some metal cations. The results showed that the metal cations affect the most important three connectivities differently. Also, it is shown that the existence of metal cations can increase two-center delocalization in certain parts of the aromatic rings.

Two state reactivity mechanism for the rearrangement of hydrogen peroxynitrite to nitric acid by Renato Contreras; Marcelo Galván; Mónica Oliva; Vincent S. Safont; Juan Andrés; Doris Guerra; Arie Aizman (216-221).
A triplet reactive intermediate 3HOONO has been located on a two state reactivity (TSR) potential energy surface for the isomerization of HOONO to nitric acid. This bi-radical is postulated as one of the possible activated species responsible for the potent oxidant activity attributed to H-peroxynitrite.For the isomerization of HOONO to nitric acid, a spin triplet reactive intermediate 3HOONO was identified on a two state reactivity (TSR) potential energy surface. This bi-radical is postulated as one of the possible activated species responsible for the potent oxidant activity attributed to H-peroxynitrite. A theoretical analysis based on spin density-dependent reactivity indices consistently explains the observed reactivity of this molecule in biological and model systems.

In neurosporene, coherent excitation to the closely-located 1 B u + (0) and 1 B u - (1) levels (‘diabatic levels’) generated short-lived stimulated emission from the 1 B u - (0) level and long-lived stimulated emission from the diabatic level.Excitation with ∼30 fs pulses to the 1 B u + (0) vibronic level of neurosporene and spheroidene (having n  = 9 and 10 double bonds) in tetrahydrofuran generated a single persistent stimulated emission with the 1 B u + (0) energy as well as the 1 B u - (0) stimulated emission; the measured energies agreed nicely with those determined by measurement of resonance-Raman excitation profiles [K. Furuichi, T. Sashima, Y. Koyama, Chem. Phys. Lett. 356 (2002) 547]. The observation is ascribed to simultaneous coherent excitation to the optically-allowed 1 B u + (0) and isoenergetic optically-forbidden 1 B u - (1) or 1 B u - (2) levels (‘diabatic levels’) followed by rapid vibrational relaxation.

Photophysical properties of an amino acid (tryptophan) have been studied in different aqueous micellar environments at various pH using steady-state emission spectroscopy. The sensory capability of tryptophan in biomimicking ionic micellar nanocage at various pH were also studied.Photophysical properties of an amino acid (tryptophan) have been studied in different aqueous micellar environments at various pH using steady-state emission spectroscopy. We report herein tuning of the sensory capability of tryptophan in biomimicking ionic micellar nanocage at various pH. In an un-buffered aqueous solution (or at pH 7) and pH 4 the fluorescence quenching efficiency of tryptophan in the presence of trace metal ion Cu2+ increases significantly around critical micelle concentration (CMC) of an anionic surfactant sodium dodecyl sulfate (SDS). At pH 11 fluorescence quenching efficiency of tryptophan increases significantly around CMC of a cationic surfactant cetyl trimethyl ammonium bromide (CTAB).

Thermally induced double proton transfer in GG and wobble GT base pairs: A possible origin of the mutagenic guanine by Adchara Padermshoke; Yukiteru Katsumoto; Ryuta Masaki; Misako Aida (232-236).
Double proton transfer in GG and wobble GT base pairs may be a potential pathway for the generation of the mutagenic amino-enol form of guanine.Double proton transfer (DPT) reactions in three guanine-guanine (GG) dimers, a guanine-thymine wobble (wGT) base pair, and a model compound 4(3H)-pyrimidinone (k-PP) dimer have been investigated using ab initio MO calculations and liquid-phase infrared (IR) spectroscopy. The calculations suggest that the DPT processes in these dimers are energetically accessible. Temperature-dependent IR measurements of the model compound reveal that slight thermal energy can induce the DPT reaction, and hence the enol tautomer can result. The present study demonstrates a potential pathway for the generation of the mutagenic amino-enol form of guanine.

The pulsed EPR spectra for a three-particle system with the uniform and staggered Dzyaloshinskii–Moriya interactions are distinguished by analyzing relaxation processes from the double to single quantum coherence.The Dzyaloshinskii–Moriya (DM) interaction is induced by the spin–orbit interaction with an antisymmetric component in the exchange coupling. We have examined a possibility to detect the DM interaction as well as the non-secular part of the dipolar interaction for weakly-coupled systems by analyzing relaxation processes from the double to single quantum coherence by pulsed EPR measurement. Numerical simulation for two and three spin-1/2 systems indicates that the proposed measurement has a capability to determine the signs of the DM interactions that are important to distinguish spins in a uniform field from in a staggered field.

Nuclear wave packet motion of the neutral adsorbate.We have applied the open-system treatment, recently developed by the authors, to a simple adsorbate-metal surface model potential. The open-system treatment is found to give a quasi-diabatic representation where the adsorbate electronic states cross the metal ones in the manifold consisting of the Born-Oppenheimer potential energy curves of the whole system. On the obtained quasi-diabatic curves, one can effectively follow time propagation of a nuclear wave packet. The computed propagation has revealed that the formation of a metastable adsorbate leads to the coherent vibrational motion of the neutral adsorbate as well as the desorption induced by electronic transitions.

Stilbene, time-resolved emission spectra, emission anisotropy spectra, photoisomerization, intramolecular charge transfer.Steady-state absorption, emission, polarization spectra and time-resolved emission spectra (TRES) were used to study the spectroscopic properties of 4-dimethylamino-4′-methoxy-stilbene (DMS) in various solvents at 23 °C. The short time components of fluorescence (τ less than 100 ps) were found for DMS in polar solvents. The long time component shortens with decreasing viscosity of solvents. The maximum wavelength of emission spectra shifts for 15 nm within 200 ps after excitation which is accompanied by a change in the shape of spectra. The emission anisotropy r values increase in the vicinity of the 0–0 transition wavelength.

The s-cis and s-trans conformers are energetically nearly degenerate. Of the two rings appended to the phenazine nucleus, the phenyl ring is rigidly kept perpendicular whereas the aminophenyl ring is twisted and can easily oscillate. The electronic transitions responsible for the brilliant colour of the mauveine dyes are related to a modification of the π-bonding pattern within the diaminophenazine moiety.The equilibrium structure of the mauveines has been studied with the density functional theory. The molecular framework consists of a planar diaminophenazine with a centrally appended perpendicular phenyl ring and a laterally bound twisted aminophenyl group. Of the three aromatic fragments, it is only the aminophenyl part that exhibits a conformational flexibility around the C(phenazine)–N–C(phenyl) bonds. The electronic absorption spectra have been examined using hybrid time-dependent density functional theory. The π → π excitations, mainly occurring in the phenazine moiety, are the major contributors to the strong absorption bands. Intramolecular π-charge transfer from the appended phenyl rings to the phenazine nucleus give rise to weakly-allowed transitions.

Oscillation of a water surface in contact with a fixed camphor disk by Hiroyuki Kitahata; Kouhei Kawata; Yutaka Sumino; Satoshi Nakata (254-258).
When a fixed camphor disk is attached to water, oscillatory motion of a water surface is observed.The oscillatory motion of a water surface in contact with a fixed camphor disk was investigated. A periodic change in the contact length of the upheld water was synchronized with the changes in the force working on the disk. The period of the oscillation changed depending on the surface tension and the surface area of the water phase. The mechanism of oscillation is discussed in relation to the kinetics of the camphor molecular layer on the water surface and the change in the driving force working on the contact line due to the surface tension and the Marangoni flow.

Fluorescence emission anisotropy, two-component systems, forward and back excitation energy transfer, Green functions, Monte-Carlo simulations.Hybrid Monte-Carlo simulation algorithm of fluorescence anisotropy decay in the presence of forward and back energy transfer is presented for rigid disordered systems. The results of hybrid Monte-Carlo simulations are compared with the results of SCDM theoretical model and with Monte–Carlo step by step simulations. Very good agreement between theoretical and simulation data as well as Monte–Carlo simulations has been obtained. The hybrid Monte-Carlo simulation of emission anisotropy is characterized by much better accuracy and little time consumption, especially for long times and also for low donor and at the same time high acceptor concentrations.

The consistent charge equilibration (CQEq) method with optimized parameters is applied to MM calculations of guanidinium chloride ionic liquid systems.The consistent charge equilibration (CQEq) method is applied to guanidinium chloride ionic liquid systems. The QEq parameters are optimized for methyl substituted guanidinium chlorides to represent the atomic charges by quantum chemical calculations with six atom types for H, C, N and Cl atoms. The atomic charges and optimized structural parameters are compared with quantum chemical calculations.

The intermediate Hamiltonian Fock-space coupled cluster (IH-FS-CC) method with full inclusion of the connected triple excitations for excitation energies has been formulated and implemented.The newly formulated intermediate Hamiltonian Fock-space coupled cluster (FS-CC) method with full singles, doubles, and triples is applied to calculate benchmark excitation energies for the N2, C2, H2O molecules and Ne atom. The intermediate Hamiltonian formulation eliminates intruder states and divergence problems which occur via the traditional FS approach. For the 14 states available the MAE is 0.03 eV and the maximum deviation is 0.16 eV.

Single-shot near-field heterodyne transient grating method revealed the dynamics of photoreduction of chlorauric acid and subsequent nanoparticle formation.The dynamic processes of photoreduction of chloroauric acid and subsequent formation of gold nanoparticles were directly observed by means of the single-shot, near-field heterodyne transient grating method. For a polyvinylpyrrolidone (PVP) concentration of less than 0.5 mM, the observed transient responses consisted of four exponential functions that corresponded to thermal decay and the reaction and diffusion processes of three chemical species in the photoreduction processes. Another exponential component was found for PVP concentrations above 0.5 mM, and it was proposed that this component corresponds to the diffusion of gold nanoparticles from the decay time dependence on the pump intensity.

Electron correlation effects on the nonlinear optical properties of conjugated polyenes by Qingxu Li; Liping Chen; Qikai Li; Zhigang Shuai (276-278).
Hyperpolarizability as a function of chain length for linear push–pull polyenes evaluated with Hartree–Fock, MP2, and coupled cluster methods.We employ the coupled cluster method to calculate the nonlinear optical coefficients for conjugated polyenes and their push–pull forms. We find that the electron correlation always reduces the nonlinear optical responses. While MP2 can predict correct trend for properties like dipole moment and polarizability, it gives completely wrong trend for the hyperpolarizabilites for long polyenes. It is highly cautioned to use MP2 when benchmarking computational methods for nonlinear properties such as improving exchange-correlation functionals in DFT.

The influence of tip positions on the transmission spectra of a molecular wire.Using first order perturbation theory, we show that the bandwidth, intensity, and lineshape in transmission spectra of a single molecular junction calculated by the non-equilibrium Green’s function (NEGF) method can be rationalized by the one- and two-resonant state approximations. Particularly, we find that the lineshape of the transmission function is strongly influenced by the relative phases between the two nearest-neighbor resonant states. Finally, we utilize these results to examine two systems: a Hückel model system with five sites and a single fluoro-1,4-benzenedithiol molecule within the extended Hückel approximation.