Chemical Physics Letters (v.668, #C)

Contents (iii-vi).

First-principles investigation of Cu-doped ZnS with enhanced photocatalytic hydrogen production activity by Ming Dong; Peng Zhou; Chuanjia Jiang; Bei Cheng; Jiaguo Yu (1-6).
Display OmittedThe band structure and electronic properties of Cu-doped wurtzite ZnS were investigated by density functional theory calculations. According to the formation energies, the substitutional Cu and S vacancy defects are stable among the examined doping species. Particularly, the hybridization of substitutional Cu 3d and S 3p orbitals narrows the band gap of substitutional Cu-doped ZnS (CuZn-ZnS), while the high effective mass ratio of photogenerated holes and electrons (mh /me ) in the CuZn-ZnS is beneficial for the separation and migration of the photogenerated charge carriers. Lab-synthesized CuZn-ZnS sample exhibited enhanced visible-light absorption and photocatalytic hydrogen production activity compared to pure ZnS.
Keywords: Substitutional Cu; Doped ZnS; Visible light response; Effective mass; Photocatalytic hydrogen production;

Stacking with the unnatural DNA base 6-ethynylpyridone by Douglas J. Gibson; Tanja van Mourik (7-13).
Display OmittedIt was previously reported that the incorporation of 6-ethynylpyridone (E) into a DNA duplex (replacing T in a T:A base pair) leads to DNA duplexes that are more stable than the T:A-containing duplexes. DFT calculations at the M06-2X/6-31+G(d) and BLYP-D3/6-31+G(d) levels on various base pairs, stacked bases and stacked base pairs in continuum solvation water suggest that the observed increased stability of E:A-containing duplexes is due to the combined effects of stronger base pairing and enhanced stacking of the E:A base pair.
Keywords: Unnatural base pair; 6-Ethynylpyridone; Density functional theory; Stacking; M06-2X; BLYP-D3;

Dynamic self-assembly of ‘living’ polymeric chains by Binghui Deng; Yunfeng Shi (14-18).
Display OmittedWe report a dynamic self-assembly system of ‘living’ polymeric chains sustained by chemistry using reactive molecular dynamics simulations. The linear polymeric chains consist of self-assembled nanoparticles connected by metastable linker molecules. As such, the polymeric chains, once assembled, undergo spontaneous dissociation driven by thermodynamics. However, with a continuous supply of linker molecules and the stored chemical energy therein, the polymeric chains can survive and maintain a steady state averaged chain length. These dynamically self-assembled polymeric chains are analogous to biological systems that both are thermodynamically metastable, yet dynamically stable upon continuous influx of matter and energy.
Keywords: Molecular dynamics; Polymeric chains; Dynamic self-assembly;

Synthesis of Cu0.95V2O5/polypyrrole core/sheath nanobelts and its electrochemical property by Shaoyan Zhang; Weirong Han; Yongfang Chang; Yan Sun; Chunsheng Li (19-22).
Display OmittedA novel heterogeneous Cu0.95V2O5/polypyrrole core/sheath nanobelts have been synthesized via in-situ oxidative polymerization of pyrrole monomers on the surface of hydrothermally synthesized Cu0.95V2O5 nanobelts. The composite are several micrometers in length and 100–200 nm in width. The electrochemical performance of the composites for use as anode materials in lithium-ion batteries were investigated and compared with bare Cu0.95V2O5 nanobelts. It was found the electrochemical performance of Cu0.95V2O5/PPy was significantly enhanced. The remarkable electrochemical performance is mainly attributed to the heterogeneous core/sheath structure, the conductive PPy nanolayer coating help to preserve high capacity, maintain high electrochemical stability, and reduce charge transfer resistance during cycling performance.
Keywords: Copper vanadates; Polypyrrole; Lithium-ion battery; Nanocomposites; Functional;

Display OmittedNew adiabatic potential energy surfaces (PESs) for 2 A ′ and 2 A ″ states of SiH(X 2 Π )-He( 1 S ) complex have been calculated at the restricted coupled cluster level of theory including single, double and triple excitation [RCCSD(T)]. The RKHS method was used for the analytic fit of these PESs. The resulting PESs were employed later in the close-coupling approach for the computation of the inelastic integral cross sections which take into account the fine-structure of the SiH radical. Scattering calculations, are done on a grid of collision energies large enough to ensure converged state-to-state rate coefficients for the temperature ranging from 8 K up to 300 K.
Keywords: Open-shell; Potential energy surface; Inelastic rotational collision; Cross sections; Close-coupling; Rccsd(t);

Semi-empirical quantum evaluation of peptide – MHC class II binding by Ronald González; Carlos F. Suárez; Hugo J. Bohórquez; Manuel A. Patarroyo; Manuel E. Patarroyo (29-34).
Display OmittedPeptide presentation by the major histocompatibility complex (MHC) is a key process for triggering a specific immune response. Studying peptide-MHC (pMHC) binding from a structural-based approach has potential for reducing the costs of investigation into vaccine development. This study involved using two semi-empirical quantum chemistry methods (PM7 and FMO-DFTB) for computing the binding energies of peptides bonded to HLA-DR1 and HLA-DR2. We found that key stabilising water molecules involved in the peptide binding mechanism were required for finding high correlation with IC50 experimental values. Our proposal is computationally non-intensive, and is a reliable alternative for studying pMHC binding interactions.
Keywords: FMO-DFTB; PM7; HLA-DR; Receptor-ligand interactions;

Effective capture and release of circulating tumor cells using core-shell Fe3O4@MnO2 nanoparticles by Liang Xiao; Zhao-Bo He; Bo Cai; Lang Rao; Long Cheng; Wei Liu; Shi-Shang Guo; Xing-Zhong Zhao (35-41).
Display OmittedCirculating tumor cells (CTCs) have been believed to hold significant insights for cancer diagnosis and therapy. Here, we developed a simple and effective method to capture and release viable CTCs using core-shell Fe3O4@MnO2 nanoparticles. Fe3O4@MnO2 nanoparticles bioconjugated with anti-EpCAM antibody have characteristics of specific recognition, magnetic-driven cell isolation and oxalic acid-assisted cell release. The capture and release efficiency of target cancer cells were ∼83% and ∼55%, respectively. And ∼70% of released cells kept good viability, which could facilitate the subsequent cellular analysis.
Keywords: Circulating tumor cells; Core-shell Fe3O4@MnO2 nanoparticles; Cell capture and release; Cancer diagnosis and therapy;

Atom-triatom rigid rotor inelastic scattering with the MultiConfiguration Time Dependent Hartree approach by Steve Ndengué; Richard Dawes; Fabien Gatti; Hans-Dieter Meyer (42-46).
Display OmittedThe inelastic scattering between a rigid rotor triatomic molecule and an atom is described within the frame of the MultiConfiguration Time dependent Hartree (MCTDH) method. Sample calculations are done on the H2O-Ar system for which a flexible 6D PES (used here in the rigid rotor approximation) has been recently computed in our group and will be presented separately. The results are compared with corresponding time independent calculations using the Arthurs and Dalgarno approach and confirm as expected the equivalence of the two methods.
Keywords: Quantum dynamics; Inelastic scattering; Time-dependent; Close-coupling;

Display OmittedWe have developed a simple ammonium ion-assisted hydrothermal method for the fast preparation of high quality Zinc Oxide (ZnO) nanorod arrays. Ammonium salts were introduced into typically hydrothermal growth solutions formed from Zinc acetate (ZnAc2) and hexamethylenetetramine (HMTA). Scanning electron microscope (SEM), X-ray diffractometer (XRD), High resolution transmission electron microscopic (HRTEM) and photoluminescence (PL) measurements revealed that the growth rate of ZnO nanorods was promoted by adding ammonium salts and the as-grown ZnO nanostructure arrays showed remarkably low defect density. Upon addition of ammonium salt to the hydrothermal reaction solution, complex Zn(NH3)4 2+ was formed by Zn2+ capturing NH3 molecules dissociated from HMTA. The improvement of growth rate and optical property of the ZnO nanostructure arrays was attributed to positively charged Zn(NH3)4 2+ attracting oxygen rich OH- in the growth sites of ZnO for hydrolysis reaction and simultaneously inhibiting the defect. Our results demonstrated that ammonium salt can act as a new paradigm to control morphology and quality of the ZnO microstructures.
Keywords: ZnO nanorods; Growth rate; Defect density; Ammonium salt; Hydrothermal route;

A targeted drug delivery system based on dopamine functionalized nano graphene oxide by Elham Masoudipour; Soheila Kashanian; Nasim Maleki (56-63).
Display OmittedThe cellular targeting property of a biocompatible drug delivery system can widely increase the therapeutic effect against various diseases. Here, we report a dopamine conjugated nano graphene oxide (DA-nGO) carrier for cellular delivery of the anticancer drug, Methotrexate (MTX) into DA receptor positive human breast adenocarcinoma cell line. The material was characterized using scanning electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy and UV–vis spectroscopy. Furthermore, the antineoplastic action of MTX loaded DA-nGO against DA receptor positive and negative cell lines were explored. The results presented in this article demonstrated that the application of DA functionalized GO as a targeting drug carrier can improve the drug delivery efficacy for DA receptor positive cancer cell lines and promise future designing of carrier conjugates based on it.
Keywords: Dopamine; Functionalized graphene oxide; Methotrexate; Targeted drug delivery;

Energy level alignment at the interface of NPB/HAT-CN/graphene for flexible organic light-emitting diodes by Eonseok Oh; Soohyung Park; Junkyeong Jeong; Seong Jun Kang; Hyunbok Lee; Yeonjin Yi (64-68).
Display OmittedGraphene is highly promising as an electrode for flexible optoelectronic devices due to its excellent conductivity and transparency. However, it is necessary to tailor its work function with a charge injection layer in order to obtain favorable energy level alignment for efficient charge injection. An adequate charge injection layer can only be chosen with the understanding of the interfacial electronic structure between a charge transport layer and an electrode. In this study, we investigated the energy level alignment of N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB)/hexaazatriphenylene hexacarbonitrile (HAT-CN)/graphene using in situ ultraviolet and X-ray photoelectron spectroscopy measurements. The effective work function of graphene was significantly increased by 0.94 eV by the HAT-CN hole injection layer (HIL) due to the interface dipole formation. In addition, the charge generation barrier (CGB) between NPB and HAT-CN, which plays a decisive role in charge injection efficiency with a charge generation HIL, was measured to be 0.66 eV. This CGB on graphene is the same as the CGBs on other electrodes, and smaller than that of the widely-used MoO3 HIL. Therefore, HAT-CN could be a promising HIL for efficient flexible organic light-emitting diodes with a graphene anode.
Keywords: Graphene; HAT-CN; NPB; Energy level alignment; Hole injection layer;

Resonance methods in quadrupole ion traps by Dalton T. Snyder; Wen-Ping Peng; R. Graham Cooks (69-89).
Display OmittedThe quadrupole ion trap is widely used in the chemical physics community for making measurements on dynamical systems, both intramolecular (e.g. ion fragmentation reactions) and intermolecular (e.g. ion/molecule reactions). In this review, we discuss linear and nonlinear resonances in quadrupole ion traps, an understanding of which is critical for operation of these devices and interpretation of the data which they provide. The effect of quadrupole field nonlinearity is addressed, with important implications for promoting fragmentation and achieving unique methods of mass scanning. Methods that depend on ion resonances (i.e. matching an external perturbation with an ion’s induced frequency of motion) are discussed, including ion isolation, ion activation, and ion ejection.
Keywords: Quadrupole ion trap; Resonances; Quadrupole potential; Secular frequency; Nonlinear field;

Display OmittedThe extremely weak 2–0 O(14) electric quadrupole transition of N2 has been detected by very high sensitivity Cavity Ring Down spectroscopy near 4518 cm−1. It is the first N2 absorption line in the first overtone band reported so far from laboratory experiments. By combining a feedback narrowed Distributed Feedback laser diode with a passive cell tracking technique, a limit of detection of α min  ∼ 1.2 × 10−11  cm−1 was achieved after one day of spectra averaging. The N2 2–0 O(14) line position and line intensity (about 1.5 × 10−30  cm/molecule) agree with calculated values provided in the HITRAN2012 database.
Keywords: Nitrogen; Electric quadrupole; CW-CRDS; Cavity Ring Down Spectroscopy; HITRAN; Atmospheric window;