Chemical Physics Letters (v.484, #1-3)

Contents (iii-vii).

This paper explores an alternative possibility to density functional theory (DFT) for developing an effective one-particle correlated orbital theory (COT), and an associated correlation orbital potential (COP), based upon insisting that the equations provide the exact principal ionization potentials (I) and electron affinities (A) for molecules. Elements of coupled-cluster theory and its equation-of-motion extensions are used to define a frequency independent self-energy, ΣCC, so that g = f + ΣCC, g φ p  = ωp φ p , for orbitals, { φ p } , where ωp  = Ip for all the occupied levels and ωp  = Ap for the unoccupied ones. The satisfaction of the COT equations provide consistency conditions on chosen approximations for two-particle interactions, which enable COT calculations to be done at the cost of a Hartree-Fock or DFT calculation.The formal and computational attraction of effective one-particle theories like Hartree–Fock and density functional theory raise the question of how far such approaches can be taken to offer exact results for selected properties of electrons in atoms, molecules, and solids. Some properties can be exactly described within an effective one-particle theory, like principal ionization potentials and electron affinities. This fact can be used to develop equations for a correlated orbital theory (COT) that guarantees a correct one-particle energy spectrum. They are built upon a coupled-cluster based frequency independent self-energy operator presented here, which distinguishes the approach from Dyson theory. The COT also offers an alternative to Kohn–Sham density functional theory (DFT), whose objective is to represent the electronic density exactly as a single determinant, while paying less attention to the energy spectrum. For any estimate of two-electron terms COT offers a litmus test of its accuracy for principal Ip’s and Ea’s. This feature for approximating the COT equations is illustrated numerically.

Temperature dependence of the gas-phase reactions of Cl atoms with propene and 1-butene between 285 <  T  < 313 K by Antonio A. Ceacero-Vega; Bernabé Ballesteros; José Albaladejo; Iustinian Bejan; Ian Barnes (10-13).
Relative rate coefficients for the reactions of chlorine atoms with propene and 1-butene as a function of temperature.Relative rate coefficients for the reactions of chlorine atoms with propene and 1-butene have been measured as a function of temperature (285–313 K) at 1 bar total pressure of air using FTIR as detection technique. Such studies are necessary to model the atmospheric chemistry of these alkenes and their impact on the air quality in areas where Cl chemistry is potentially important such as maritime and heavily polluted environments. The temperature dependence can be adequately described by the simple Arrhenius relationship and the following expressions in units of cm3 molecule−1  s−1 have been obtained: k propene  = (1.43 ± 0.35) × 10−14  exp[(2886 ± 73)/T] and k 1-butene  = (1.60 ± 0.81)  × 10−13  exp[(2235 ± 152)/T] (errors are 2σ).

We have determined the temperature of (CO2) N clusters (nanoparticles) (N ⩾  102) in a beam using SF6 molecules as probe thermometers.The method is suggested and the experimental results are presented on the temperature determination of (CO2) N clusters (nanoparticles) (N ⩾  102 is a number of monomers in a cluster) in a beam using SF6 molecules from intersecting molecular beam as probe thermometers. The molecules are captured by clusters and, after a certain time, sublimate from the surface of clusters carrying information on the velocity and temperature (internal energy) of clusters. Using time-of-flight (TOF) method the kinetic energy (velocity) of sublimated SF6 molecules was measured and the temperature of clusters was determined to be T cl  = (105 ± 15) K.

Are In13M (M = Li, Na, K) magic clusters? – A comparison with Al13M by Yuzhen Liu; Chuanyun Xiao; Kaiming Deng; Yongbo Yuan; Xuan Chen; Decai Huang; Qunxiang Li (18-23).
In13Na and Al13Na clusters show very similar electronic features that are characteristic of magic clusters.Density functional study was performed on the stability of In n M (n  = 11–15, M = Li, Na, K) clusters. In13M are characterized by electronic shell closure with enhanced stability, larger HOMO–LUMO gap, higher ionization potential, and lower electron affinity as compared with clusters of adjacent sizes, while very similar size dependence was found between In n M and Al n M in their electronic properties, suggesting that In13M be magic clusters and promising as building blocks in developing cluster-assembled materials. The calculated AEA of In13 is close to that of iodine, implying it would behave like a halogen atom in ionic In13M molecule.

Luminescence spectrum from N+  + CO2 collisions at the 1000 eVlab energy was recorded. The bands of the B ∼ 2 Σ u + - X ∼ 2 Π g and A ∼ 2 Π u - X ∼ 2 Π g transitions can be notice. The presented spectrum was taken with a resolution of 1.0 nm FWHM.For the N+  + CO2 collisions in the 6–1000 eVlab energy range a charge transfer excitation was observed. Luminescent charge exchange processes lead to the formation of the CO 2 + (A, B) states. The relative chemiluminescence cross-sections for these reactions are measured. The cross-section value for the reactions leading to the CO 2 + (A + B) states is constant in the 400–1000 eVlab collision energy range and is estimated to be equal to 4 × 10−17  cm2.

Decay times of 4-(dimethylamino)benzonitrile in acetonitrile and conclusions on entropy of activation by Klaas A. Zachariasse; Sergey I. Druzhinin; Peter Mayer; Sergey A. Kovalenko; Tamara Senyushkina (28-32).
Picosecond fluorescence decay times of 4-(dimethylamino)benzonitrile in acetonitrile provide reliable information on the charge transfer reaction.From picosecond decay times of 4-(dimethylamino)benzonitrile (DMABN) and 4-(dimethylamino)benzoic acid ethyl ester (DMABE) in acetonitrile (Ref. ), a conclusion on entropy effects cannot be made because of large uncertainties of the data. The planarized 1-tert-butyl-6-cyano-1,2,3,4-tetrahydroquinoline (NTC6) as a model for a planar intramolecular charge transfer (ICT) state and the influence of pretwist and size of the amino group is also discussed. For DMABE excited state absorption spectra show a decay of the locally excited (LE) and a rise of the ICT state of 1.0 ps, posing the question whether the lowest excited singlet state is of Lb or La character.

Layer-by-layer films from tartrazine dye with bovine serum albumin by Nara C. de Souza; Júlio C. Johner Flores; Josmary R. Silva (33-36).
Atomic force microscopy image of BSA/Tart LbL film with scan size of 10 × 10 μm2. The top layer is of tartrazine.We report on the preparation and study of the adsorption process of layer-by-layer films of tartrazine alternated with bovine serum albumin. UV–Vis spectroscopy indicated that the films form J-aggregates of tartrazine. Adsorption kinetics was fitted by the Johnson–Mehl–Avrami equation and surface morphological analyses by atomic force microscopy suggested that the J-aggregates were column-shaped, which was attributed to the column-like symmetry of the tartrazine molecules. The columnar structures that formed probably arose from the juxtaposition of smaller aggregates that were already present at the beginning of film growth.

STEM image for nanoparticle clusters diameter-selected at 20 nm composed of outer surface-deposited Ag nanoparticles and the inner core composed of C60 molecules.We demonstrate production of nanoparticle clusters, namely clusters composed of nanoparticles, using a combination of surface-active Ag nanoparticles and surface-inactive C60 nanoparticles. The produced clusters, after diameter-selection by a differential mobility analyzer, were analyzed by field-emission scanning electronic microscopy and X-ray photoelectron spectroscopy. The produced clusters are found to be composed of outer surface-deposited Ag nanoparticles with ∼3 nm diameters that are distinctly isolated from one another and with an inner core composed of C60 molecules. The number of constituent Ag nanoparticles is adjustable by selection of the diameters of the clusters.

Organic photovoltaic cells based on tetrathia[22]annulene[2,1,2,1]/PCBM heterojunction by Hongxia Xi; Zhongming Wei; Wei Xu; Zhishan Bo; Wenping Hu; Daoben Zhu (41-43).
Organic photovoltaic cells based on tetrathia[22]annulene[2,1,2,1]/PCBM heterojunction were fabricated and investigated.Organic photovoltaic cells (OPVs) based on tetrathia[22]annulene[2,1,2,1] (TTA)/[6,6]-phenyl-C61 butyric acid methyl ester (PCBM) heterojunction were fabricated and investigated. The optimized device performance displayed a power conversion efficiency (η) of 0.23% with open-circuit voltage (V oc) of 0.16 V, short-circuit current density (J sc) of 3.1 mA/cm2 and the fill factor (FF) of 0.46.

Structural, electronic properties and stability of metatitanic acid (H2TiO3) nanotubes by A.N. Enyashin; T.A. Denisova; A.L. Ivanovskii (44-47).
The atomic models for nanotubes of recently prepared metatitanic acid (H2TiO3) are designed and their cohesive and electronic properties are predicted.Quite recently, metatitanic acid (H2TiO3) has been successfully prepared, which extended the family of known titanic acids H2Ti n O2 n +1 (n  = 2, 3 and 4). Here the atomic models for nanotubes (NTs) of metatitanic acid are designed and their cohesive and electronic properties are considered depending on their chirality and radii by means of density-functional theory-tight-binding (DFTB) method.Our main findings are that the proposed H2TiO3 tubes are stable and that all these NTs will be the insulators (independently from their chirality and the diameters) with forbidden gaps at about ∼4.6 eV. We have found also that aforementioned properties of predicted H2TiO3 NTs are very similar with those of recently prepared fabricated nanotubes of polytitanic acids; thus, it is possible to expect that the proposed H2TiO3 tubular materials may be fabricated.

A novel visible-light-driven photocatalyst Sm2InNbO7 for H2 or O2 evolution by Xin-De Tang; Hong-Qi Ye; Hui Liu; Chen-Xia Ma; Zhi Zhao (48-53).
A new visible-light-driven photocatalyst Sm2InNbO7 with A2B2O7-type pyrochlore structure, which shows a higher activity for photocatalytic H2 evolution than that of InNbO4, was developed.A new visible-light-driven photocatalyst Sm2InNbO7 crystallized in a cubic system with the space group Fd3m was synthesized by a solid-state reaction method. Sm2InNbO7 showed high activities for photocatalytic H2 evolution from CH3OH aqueous solution and for photocatalytic O2 evolution from AgNO3 aqueous solution under visible-light irradiation, which was even better than that of InNbO4, a well-known visible-light-driven photocatalyst. Density functional theory (DFT) calculation indicated that strong dispersion from the hybridized In 5s and 5p orbitals at the bottom of the conduction band (CB) was considered to contribute to the high activity of photocatalyst Sm2InNbO7.

Exciplex emission at the interface of TAPC and BCP, and its application in white organic light-emitting diodes.By investigating the electroluminescence of bilayer organic light-emitting diodes based on 1,1-bis((di-4-tolylamino)phenyl) cyclohexane (TAPC) and 2,9-dimethyl-4,7-di(phenyl)-1,10-phenanthroline (BCP), a new emission maximized at 480 nm from TAPC/BCP interface was observed and it was confirmed to be an exciplex emission of [TAPCBCP]. We found that the emission intensity of this exciplex increases with only increasing the thickness of BCP layer from 10 nm to 30 nm in bilayer device ITO/TAPC(60 nm)/BCP/Al. Being the hole-blocking BCP layer in the bilayer devices, the combination of electromer emission and excimer emission from TAPC, as well as exciplex emission from TAPC/BCP interface, provides a simple way to obtain white light emission.

Spatial modulation of d states in a nanoscale Co island by T.G. Gopakumar; N. Néel; J. Kröger; R. Berndt (59-63).
Spatial map of differential conductance (left) and STM image revealing site-selective adsorption of FePc on trilayer Co island (right).A cryogenic scanning tunnelling microscope was used to probe the electronic properties of a moiré pattern observed from cobalt islands on Ag(1 1 1). Spatially resolved spectroscopy reveals that the moiré lattice gives rise to a periodic electronic pattern of cobalt d states. The arrangement of magnetic molecules on the moiré lattice suggests an electronic template effect.

Double proton transfer mechanism in the adenine–uracil base pair and spontaneous mutation in RNA duplex by José P. Cerón-Carrasco; Alberto Requena; Eric A. Perpète; Catherine Michaux; Denis Jacquemin (64-68).
We show how water molecules can assist double proton transfer in adenine–uracil base pair.We study the mechanism of double proton transfer (DPT) in the adenine–uracil (AU) base pair, both in gas phase and under the influence of surrounding water molecules. According to our ab initio calculations, no stable proton transfer product exists in gas phase, while in solution, the DPT process may occur only through the catalysis of water molecules. Nevertheless, a thermodynamic analysis confirms that AU does not contribute to spontaneous mutation in RNA duplex, and thus guanine–cytosine (GC) would be the only base pair contributing to spontaneous mutation.

The gas-phase decompositions of a thiazole-substituted dioxetanone were investigated at the CASSCF/CASPT2 level of theory.The gas-phase decompositions of a thiazole-substituted dioxetanone, in both the natural and anionic forms, were investigated theoretically in a CASSCF/CASPT2 study. The neutral conjugated thiazole (with or without a hydroxyl group) substitution on the dioxetanone has no evident effect on the dissociation; however, a subsequent deprotonation – invoking charge-transfer excitations from the thiazole to the dioxetanone moiety – will dramatically change the reaction mechanism from stepwise to concerted, and reduce the activation barrier by ∼8 kcal mol−1. These findings are helpful for the better understanding of dioxetanone chemiluminescence and the charge-transfer induced electron excitation in chemi- and bioluminescence processes.

When DC voltage was applied between cathode and anode in the colloidal solution, dilute/dense layers of colloidal particles separated out horizontally.A simple electrochemical scheme has been worked out to effectively concentrate Pt particles in a colloidal solution by application of a DC current of typically 40–80 V across the electrodes separated by 3 cm within 15 min. When the voltage was applied between the cathode and anode in the colloidal solution, the colloidal particles were separated horizontally into vacant and dense layers. The particles were finally concentrated below the bottom edge of the anode in the solution, and the boundary height of the vacant and dense layers was found to depend on the depth of the bottom edge of the anode.