Chemical Physics Letters (v.646, #C)

Contents (iii-xi).

Morphology evolution of MoS2: From monodisperse nanoparticles to self-assembled nanobelts by Ting Yu; Xingfang Luo; Shuming Han; Yingjie Cao; Cailei Yuan; Yong Yang; Qinliang Li (1-5).
The MoS2 nanobelts were successfully synthesized on SiO2/Si substrates using a vapor phase sulfurization process. Atomic force microscopy (AFM) techniques are employed to comprehensively study the morphology evolution of MoS2 from monodisperse nanoparticles to self-assembled nanobelts on the SiO2/Si substrates. A possible three-step morphology evolution process, which includes initial nucleation process, self-assembly process, and subsequent crystal growth process (Ostwald ripening), is proposed to explain the formation of MoS2. Moreover, MoS2 nanobelts are characterized by Raman spectroscopy and photo-luminescence (PL). These results provide the possibility to develop an easier-to-cooperate and morphology-controllable approach to fabricate novel architectures.

Electron density profile at the interfaces of bulk heterojunction solar cells and its implication on the S-kink characteristics by Abhay Gusain; Surendra Singh; A.K. Chauhan; Vibha Saxena; P. Jha; P. Veerender; Ajay Singh; P.V. Varde; Saibal Basu; D.K. Aswal; S.K. Gupta (6-11).
The efficiency of a bulk heterojunction (BHJ) solar cell critically depends upon quality of its interfaces. The imperfect interfaces can lead to S-kink in the current–voltage characteristics that reduce the efficiency of BHJ solar cells. In this letter, using PCDTBT:PCBM based BHJ solar cells, we demonstrate that non-destructive X-ray reflectivity is powerful technique to estimate the electron density profile across the BHJ solar cells. A direct correlation is observed between the enhanced electron density at PEDOT:PSS/PCDTBT:PCBM interface and appearance of S-kink in JV characteristics, which is also supported by X-ray photoelectron spectroscopy and Kelvin probe measurements.

Highly sensitive alcohol sensor based on a single Er-doped In2O3 nanoribbon by Zhaojun Qin; Yingkai Liu; Weiwu Chen; Peng Ai; Yuemei Wu; Shuanghui Li; Dapeng Yu (12-17).
The response of the sensors to 100 ppm CO, NO2, H2S, HCHO, C2H5OH at 220 °C are measured, as provided in Figure (a). At the same condition, both of the devices possess high response to alcohol. What is more, the response of Er-doped sensor to alcohol is twice more than that of its pure counterpart at optimal temperature. The response (recovery) time of the Er-doped In2O3 NB sensor to different concentration is surveyed, as displayed in Figure (b). The response (recovery) time is quite short and remains stable with an increase of alcohol concentration.Pure In2O3 NBs and Er-In2O3 NBs have been successfully synthesized by carbon thermal reduction. The doping of Er leads the optimal temperature of the In2O3 to decrease. The response of the Er-In2O3 sensor to 100 ppm of alcohol is 4.8 at 220 °C, which is twice larger than that of the pure In2O3 sensor. It is also found that the doping of Er has increased the performance of the sensors. Moreover, Er-In2O3 sensor has a fast response (recovery) time to different concentration of alcohol at 220 °C. In addition, the mechanism of pure In2O3 sensor and Er-In2O3 sensor are discussed.

Investigating the micellization of the triton-X surfactants: A non-invasive fluorometric and calorimetric approach by Sunidhi Jaiswal; Ramakanta Mondal; Deena Paul; Saptarshi Mukherjee (18-24).
Using intrinsic and extrinsic fluorescence approaches, we have studied the Critical Micelle Concentration (CMC) of three non-ionic surfactants namely, Triton X-114 (TX-114), Triton X-100 (TX-100) and Triton X-165 (TX-165) which differ in number of polyethylene oxide (PEO) groups. We have established that for TX-114 and TX-100, the external fluorophores C-153 and ANS support our intrinsic approach, whereas, for TX-165, the same is perhaps not true. This has been attributed to the different numbers of PEO groups constituting the surfactant systems. We have also studied the CMC using Isothermal Titration Calorimetry (ITC) which is in excellent harmony with our intrinsic approach.

Localization-dependent charge separation efficiency at an organic/inorganic hybrid interface by Laura Foglia; Lea Bogner; Martin Wolf; Julia Stähler (25-30).
By combining complementary optical techniques, photoluminescence and time-resolved excited state absorption, we achieve a comprehensive picture of the relaxation processes in the organic/inorganic hybrid system SP6/ZnO. We identify two long-lived excited states of the organic molecules of which only the lowest energy one, localized on the sexiphenyl backbone of the molecule, is found to efficiently charge separate to the ZnO conduction band or radiatively recombine. The other state, most likely localized on the spiro-linked biphenyl, relaxes only by intersystem crossing to a long-lived, probably triplet state, thus acting as a sink of the excitation and limiting the charge separation efficiency.

Wide range double photoionisation spectra of N2 and CO2 by J.H.D. Eland; S. Plogmaker; P. Lablanquie; F. Penent; J. Palaudoux; C. Nicolas; E. Robert; C. Miron; R. Feifel (31-35).
Using a magnetic bottle time-of-flight electron spectrometer we have measured double photoionisation spectra of N2 and CO2 covering the range from threshold up to the triple ionisation energies. The experiments demonstrate the use of a new asynchronous chopper in eight-bunch mode of the synchrotron radiation source SOLEIL. For CO2 2+ some broad bands in the Auger spectra are found to have multiple resolved counterparts in the photoionisation spectrum. All the bands in the Auger spectra have counterparts in the photoionisation spectra, where extra bands attributed to triplet states are present. In the spectrum of N2 2+ we suggest reassignment of one band.

Molecular dynamics study of the formation mechanisms of ionic SDS and nonionic C12E8 micelles and n-dodecane droplets by Shinji Kawada; Mika Komori; Kazushi Fujimoto; Noriyuki Yoshii; Susumu Okazaki (36-40).
In order to clarify the early-stage kinetics of micelle formation in concentrated surfactant solutions, all-atom molecular dynamics (MD) calculations of the aggregation of surfactant molecules dispersed in water were performed for ionic sodium dodecyl sulfate (SDS), nonionic octaethyleneglycol monododecyl ether (C12E8), and n-dodecane. The relationship between aggregate domain length and elapsed time from the beginning of the MD calculation obeyed the well-known Lifshitz–Slyozov (LS) law for C12E8 and n-dodecane. In contrast, the aggregation rate of SDS did not obey the LS law. This difference is likely due to the differences in strength of the electrostatic interactions between the aggregates.

Nickel antimony oxide (NiSb2O6): A fascinating nanostructured material for gas sensing application by Archana Singh; Ajendra Singh; Satyendra Singh; Poonam Tandon (41-46).
Display OmittedFabrication of nanocrystalline NiSb2O6 thin films via sol–gel spin coating method towards the development of liquefied petroleum gas (LPG) sensor operable at room temperature (25 °C) is being reported. Nanostructural, surface morphological and optical properties of trirutile-type NiSb2O6 have been investigated in order to explore the parameters of interest. The crystallite size has been found to be 19 nm. A detailed sensing performance (sensitivity, sensor response, response and recovery times, reproducibility and long term stability) of NiSb2O6 nanostructures grown on alumina substrate has been investigated.

Ab-initio molecular treatment of the symmetric Mg2+–Mg charge transfer process by M. Amami; A. Moussa; A. Zaidi; S. Lahmar; M.C. Bacchus-Montabonel (47-51).
Potential energy curves of the MgMg2+ molecular system in the lowest electronic states as well as radial and rotational couplings between these states are obtained from ab-initio calculations at the CASSCF/MRCI level of theory using large basis sets. These data are used to investigate, via the semi-classical molecular close coupling method, the single symmetric charge transfer processes of Mg2+–Mg collisions in the [1.0–650] keV laboratory energy range. Total and partial cross sections for the expected capture channels are calculated and compared with the available experimental and theoretical results.

Theoretical investigation on the molecular inclusion process of prilocaine into p-sulfonic acid calix[6]arene by Sara M.R. de Sousa; Sergio A. Fernandes; Wagner B. De Almeida; Luciana Guimarães; Paula A.S. Abranches; Eduardo V.V. Varejão; Clebio S. Nascimento Jr. (52-55).
The present letter reports, for the first time, results from a theoretical analysis of the inclusion process involving the prilocaine into the p-sulfonic acid calix[6]arene. Structure and stabilization energies were calculated, in both gas and aqueous phases, using a sequential methodology based on semiempirical and Density Functional Theory (DFT) calculations. From the results, a qualitative structure property relationship could be established with some main structural features being relevant for inclusion complex stabilization: (i) the hydrogen bonds established between guest and host molecules, (ii) the dispersion effect and (iii) the inclusion mode of guest molecule into the host cavity.

Palladium clusters on graphene support: An ab initio study by Miroslav Rubeš; Junjie He; Petr Nachtigall; Ota Bludský (56-63).
CCSD(T) calculations with an energy-consistent scalar relativistic pseudopotential have been performed on a series of Pd–PAH complexes. The CCSD(T)//CBS interaction energies for Pd–ethylene and Pd–PAH (PAH = benzene, naphthalene, pyrene, coronene and ovalene) are −32.3, −25.3, −21.0, −22.5, −23.1 and −24.0 kcal mol−1, respectively. A DFT/CC interaction model based on the Pd–PAH calculations has been proposed for a reliable and accurate description of Pd–cluster interaction with graphene support. PBE/CC and PBEh/CC calculations for Pd n –PAH and Pd n –graphene (n  ≤ 4) are reported. The PBEh/CC value of −27.7 kcal mol−1 is our best estimate of the Pd–graphene interaction energy.

By using optical electric-field-induced second-harmonic generation (EFISHG) technique, we studied carrier behavior caused by contact electrification (CE) in an organic double-layer element. This double-layer sample was half suspended in the open air, where one electrode (anode or cathode) was connected with a Cu foil for electrification while the other electrode was floated. Results showed two distinct carrier behaviors, depending on the (anode or cathode) connections to the Cu foil, and these carrier behaviors were analyzed based on the Maxwell–Wagner model. The double-layer sample works as a simple solar cell device. The photovoltaic effect and CE process have been proved to be two paralleled effects without strong interaction with each other, while photoconductivity changing in the sample can enhance the relaxation of CE induced charges. By probing the carrier behavior in this half-suspended device, the EFISHG technique has been demonstrated to be an effective non-contact method for clarifying the CE effect on related energy harvesting devices and electronics devices. Meanwhile, the related physical analysis in this letter is also useful for elucidating the fundamental characteristic of hybrid energy system based on solar cell and triboelectric nanogenerator.

ZnS nanoparticles (NPs) have been synthesized by the facile chemical route with a narrow size distribution in the MA/octene-1 copolymer matrix and effect of reaction time has been discussed. X-ray diffraction pattern confirms the pure cubic phase of ZnS with 5–7 nm average crystal sizes which are in good agreement with the AFM and UV–vis measurements. Absorption spectra exhibit a strong blue shift from the bulk with the 3.98 eV optical band gap which clearly indicates the strong size confinement effect. Thermogravimetric analyses show increased thermal stability of the nanocomposite compared to the copolymer. The possible growth mechanism of the particles formation and stabilization has been discussed.

A mixed character involving both metal and pyridines has been proposed for the reduction process of An py NH via relativistic DFT calculations, but a metal-based reduction mechanism suggested for thf-coordinated complexes. The solvent polarity and equatorial coordination environment play a significant role in calculating the reduction potentials (E 0). The marked E 0 shift for the thf-coordinated actinyl silylamides is elucidated by the different electron-donating ability of equatorial NSiH3 and NSiMe3 groups.Relativistic density functional theory was used to explore the structural and redox properties of 18 prototypical actinyl silylamides including a variation of metals (U, Np and Pu), metal oxidation states (VI and V) and equatorial ligands. A theoretical approach associated with implicit solvation and spin–orbit/multiplet corrections was proved to be reliable. A marked shift of reduction potentials of actinyl silylamides caused by changes of equatorial coordination ligands and implicit solvation was elucidated by analyses of electronic structures and single-electron reduction mechanism.

Pressure-driven-flow of a dilute aqueous solution in a microchannel with charged walls generates streaming currents (ionic current) and streaming potentials across the microchannel. While generation of streaming currents can be performed in network of parallel circular microchannels or unstructured porous media, accurate measurements of such currents remain a challenge. In this study a gigantic amount of streaming current was successfully generated and measured using a glass microchannel array with special gold sputtered coatings on both its ends. Streaming current as high as 0.7 mA was obtained with moderate pressure drop (124 kPa) across the glass microchannel array that consists of approximately 11 250 000 parallel microchannels with radii of 2.5 μm. Higher streaming currents are also possible to generate (scaled to 142 μA/cm2 of frontal area at a flow rate of 12 cm3/s) with potential applications in surface charge characterizations and electrokinetic power generation. In addition, apparent ζ potential of glass microchannel array surface was estimated with the aid of streaming current data and Levine–Olivare theories and an apparent ζ potential of −65 mV (0 M KCl, κa  = 8) is reported.

Photochemical functionalization of diamond films using a short carbon chain acid by Chun Wang; Nan Huang; Hao Zhuang; Bing Yang; Zhaofeng Zhai; Xin Jiang (87-90).
Diamond is recognized as a promising semiconductor material for biological applications, because of its high chemical stability and biocompatibility. Here, we report an acid with only three carbon chain, acrylic acid (AA), for the functionalization of H-terminated diamond film via photochemical method. The successfully modified surfaces were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy and contact angle analyzer. Our functionalization approach was proven to be simple and facile, which shows a new potential opportunity for the photochemical modification of diamond surface with short carbon chain acid.

Strain distribution of confined Ge/GeO2 core/shell nanoparticles engineered by growth environments by Wenyan Wei; Cailei Yuan; Xingfang Luo; Ting Yu; Gongping Wang (91-94).
The strain distributions of Ge/GeO2 core/shell nanoparticles confined in different host matrix grown by surface oxidation are investigated. The simulated results by finite element method demonstrated that the strains of the Ge core and the GeO2 shell strongly depend on the growth environments of the nanoparticles. Moreover, it can be found that there is a transformation of the strain on Ge core from tensile to compressive strain during the growth of Ge/GeO2 core/shell nanoparticles. And, the transformation of the strain is closely related with the Young's modulus of surrounding materials of Ge/GeO2 core/shell nanoparticles.

Single atom (B, N or P) doping zigzag single-walled carbon nanotubes (SWCNTs) evolve from semiconducting to metallic by using density functional theory. The energy gaps of (8,0) tubes significantly narrow as a result of B/N and B/P pair co-doping. Especially, B/P pair co-doping makes the bottom of conduction band move to the Fermi level direction, and the top of valence band barely shift. With the increasing concentration of B/P pair, the bottom of conduction movement becomes stronger and the energy gaps decrease. Moreover, B or N-rich doping significantly changes the semiconducting character of pure B/N pairs co-doped models.

Direct ab initio study of the C6H6  + CH3/C2H5  = C6H5  + CH4/C2H6 reactions by Tam V.-T. Mai; Artur Ratkiewicz; Minh v. Duong; Lam K. Huynh (102-109).
A kinetic study of the reactions C6H6  + CH3/C2H5  = C6H5  + CH4/C2H6 was carried out in the temperature range of 300–2500 K using high levels of electronic structure theory, namely, CCSD(T)/CBS//BH&HLYP/cc-pVDZ, and canonical variational transition state theory (CVT) with corrections for small curvature tunneling (SCT) and hindered internal rotation (HIR) treatments. It is found that variational effect is not important and both SCT and HIR corrections noticeably affect the rate constants. Being in good agreement with literature data, the calculated results provide solid basis information for the investigation of the polyaromatic hydrocarbon (PAH) + alkyl radical reaction, an important class in combustion and soot formation.

Computational analysis of hydrogenated graphyne folding by Christopher Lenear; Matthew Becton; Xianqiao Wang (110-118).
This letter employs molecular mechanics simulations to analyze the geometric changes of foreign-atom-doped graphyne. Simulation results show that higher the density of dopant and the greater area covered by the dopant correlates to a greater folding angle of the graphyne sheet. Compared to graphene, graphyne folding could prove to be more effective for various nanodevices based on its unique band gap, especially when doped, and its tunable interactions with and absorption of foreign molecules. Therefore, our findings may offer unique perspectives into the development of novel graphyne-based nanodevices and stimulate the community's research interest in graphene-related origami.

The present letter extricates the chemical physics behind non-covalent interaction between fullerenes (C60 and C70) and a designed chiral monoporphyrin molecule (1) in toluene. Steady state fluorescence studies on complex formation reveal higher binding constant (K) for C70/1 complex, i.e., K  = 16,020 dm3  mol−1, and very good selectivity of binding, viz., K C70/1 /K C60/1  ∼ 10.0. Time-resolved fluorescence study elicits role of static quenching mechanism behind photoexcited decay of 1 * in presence of fullerene. Density functional theoretical calculations in vacuo validates the strong complexation between C70 and 1 and establishes the side-on binding motif of C70 towards 1 during complexation.

X-ray photoelectron spectroscopy (XPS) is used as a probe of the interaction between rhodium acetate ([Rh2(OAc)4]) and ionic liquids. Due to the impact of the anion of ionic liquids on the electronic environment of the rhodium centre, the measured Rh 3d binding energies of [Rh2(OAc)4] dissolved in a series of ionic liquids were found to decrease along with the increasing of the basicity of anions. The reduction of Rh(II) to Rh(0) in 1-octyl-3methylimidazolium acetate ([C8C1Im][OAc]) under UHV condition was monitored by XPS. The intensity of the new formed metallic Rh(0) peak was found increased along with time. The surface enrichment of the new formed Rh(0) species in the system was also concluded.

On the hierarchical parallelization of ab initio simulations by Sergi Ruiz-Barragan; Kazuya Ishimura; Motoyuki Shiga (130-135).
Display OmittedA hierarchical parallelization has been implemented in a new unified code PIMD-SMASH for ab initio simulation where the replicas and the Born–Oppenheimer forces are parallelized. It is demonstrated that ab initio path integral molecular dynamics simulations can be carried out very efficiently for systems up to a few tens of water molecules. The code was then used to study a Diels–Alder reaction of cyclopentadiene and butenone by ab initio string method. A reduction in the reaction energy barrier is found in the presence of hydrogen-bonded water, in accordance with experiment.

First-principles calculations of Raman spectra in Li-doped Si nanocrystals by N. Scott Bobbitt; James R. Chelikowsky (136-141).
Display OmittedWe examine the vibrational and Raman spectra for Li doped Si nanocrystals using real-space pseudopotentials constructed within density functional theory. We calculate differences in the Raman spectra using the Placzek approximation. The insertion of Li atoms into Si nanocrystals disrupts the Si crystal structure forming a region of Li–Si alloy in which the regular crystal structure is significantly disrupted. The Raman spectrum for this alloy exhibits a Li induced peak at 440–480 cm−1. We find an accompanying reduction in the size of the dominant bulk-like Si peak at 520 cm−1. Both of these results are consistent with experiment. Our analysis of the calculated spectrum confirms the utility of using Raman spectroscopy, coupled with first principle computations, to predict the structural and electronic properties of Li doped Si nanocrystals.

Theoretical characterization of vanadyl and VO3+ cations in gas phase by S. Almenia; M. Mogren Al Mogren; D. Ben Abdallah; R. Linguerri; M. Hochlaf (142-147).
We investigate VO2+ and VO3+ ions theoretically. The electronic computations are performed using multi reference configuration interaction approaches in conjunction with the aug-cc-pV5Z basis set. VO2+ potential possesses a Morse-like shape instead of the common volcanic shape since both the charge retaining (V2+  + O) and charge separating (V+  + O+) dissociation channels are almost coinciding in energy. Its intense blue color is due to the A2Π–X2Δ transition. We predict VO3+ as metastable. For bound states, we derived a set of accurate spectroscopic parameters. We estimate the adiabatic double and triple ionization energies of VO to be 22.5 eV and 50.9 eV.

The magnetic and transport properties of edge passivated silicene nanoribbon by Mn atoms by Changpeng Chen; Ziqing Zhu; Dace Zha; Meilan Qi; Jinping Wu (148-152).
The effect of chemical doping on the ZSiNRs with Mn as passivating element replacing H atoms at one edge are investigated by first-principles calculations. The structures optimized in the typical ferromagnetic and antiferromagnetic coupling show that the system leads to an AFM state and achieve half-metallic properties. Also, our first principle approach based on the Keldysh non-equilibrium Green's function method gives the spin-dependent transport properties of the device. When the system changes from parallel to antiparallel configuration. The spin-up current increases rapidly while the spin-up current is still depressed. Further, it is found that the system is a quite good spin filtering device with nearly 80% spin filtering efficiency at a wide bias voltage region and therefore suitable for applications. The mechanisms for these phenomena are proposed in detail.

Tunneling effect in 1,5 H-migration of a prototypical •OOQOOH by Yuan Sha; Theodore S. Dibble (153-157).
Propane is the smallest molecule that can serve as a model of the chemistry of diesel autoignition. Diesel autoignition requires H-migration reactions of the type •OOCH2CH2CH2OOH → HOOCH2CH2C•HOOH. Previous studies of this type of H-migration reaction accounted for tunneling (through-barrier processes) using 1-D models of the reaction coordinate, namely, the Eckart or Wigner approximations. Here we present the first study to use multi-dimensional approaches, specifically, small- and large-curvature tunneling, to treat through-barrier processes. Calculations are carried out using the Polyrate program and make use of the M05-2X/6-31+G(d,p) level of theory.

Graphene as a diffusion barrier for isomorphous systems: Cu–Ni system by Apurba Roy; M.K. Punith Kumar; Chandan Srivastava (158-161).
Electrochemical exfoliation technique using the pyrophosphate anion derived from tetra sodium pyrophosphate was employed to produce graphene. As-synthesized graphene was then drop dried over a cold rolled Cu sheet. Ni coating was then electrodeposited over bare Cu and graphene–Cu substrates. Both substrates were then isothermally annealed at 800 °C for 3 h. WDS analysis showed substantial atomic diffusion in annealed Ni–Cu sample. Cu–graphene–Ni sample, on the other hand, showed negligible diffusion illustrating the diffusion barrier property of the graphene coating.

IRMPD signature of protonated pantothenic acid, an ubiquitous nutrient by Davide Corinti; Luisa Mannina; Barbara Chiavarino; Vincent Steinmetz; Simonetta Fornarini; Maria Elisa Crestoni (162-167).
Intrinsic properties of pantothenic acid, an essential nutraceutical, are examined. The effect of protonation on the energetic and geometric features of pantothenic acid, generated as gaseous protonated species, are investigated by infrared multiple photon dissociation (IRMPD) spectroscopy over an extended frequency range (800–2000 cm−1 and 2800–3700 cm−1). DFT calculations are exploited to identify the possible structures and predict the absorption spectra at the B3LYP/6-311++G(d,p) level. Two amide-protonated structures, characterized by the most stable binding motifs, account well for the experimental spectrum, thus revealing structurally diagnostic features of potential benefit for the development of highly sensitive and selective nutrient screening.

The effect of torsional motion on the thermodynamic and kinetic properties of propiolic acid has been studied using density functional theory in conjugation with second order vibrational perturbation theory (VPT2) and semiclassical transition state theory (SCTST). In order to compute the partition functions, the density of states which forms the essential link between the properties of system and the partition functions, were determined by using Wang–Landau algorithm. By using the density of states and the partition functions, the thermodynamic and kinetic properties of the system have been determined.The conformational isomerization of propiolic acid and its H/D isotopic counterparts are studied by using high-level quantum chemistry in conjugation with semiclassical transition state theory and second order vibrational perturbation theory. The electronic structure calculations were carried at DFT and MP2 levels of theory. The vibrational anharmonicity coefficients including the fully coupled vibrational modes of the reaction coordinate of the transition state, used in semiclassical transition state theory, are computed at hybrid functional B3LYP in conjugation with aug-cc-pVTZ and SNSD basis sets. The corresponding solutions give rate as well as the equilibrium constants between the isomers and the isotopic analogs.

The pure rotational spectrum of the organozinc halide, ClZnCH3 (X 1A1), has been measured using Fourier-transform microwave (FTMW) and millimeter-wave direct-absorption methods in the frequency range 10–296 GHz. This work is the first study of ClZnCH3 by gas-phase spectroscopy. The molecule was created in a DC discharge from the reaction of zinc vapor, produced either by a Broida-type oven or by laser ablation, with chloromethane in what appears to be a metal insertion process. Rotational and chlorine quadrupole constants were determined for three zinc isotopologues. The Zn―Cl bond was found to be partly ionic and significantly shorter than in EtZnCl.

We performed dye-assisted two-photon-excitation imaging of plasmon modes in single gold nanoplates using a scanning near-field optical microscope. We observed that the fluorescence from the dye molecules was excited by the two-photon process and was enhanced several-fold on the nanoplate compared to the bare substrate. Two-photon excitation images of the single nanoplate show unique spatial features that differ from the morphology of the sample. Using electromagnetic simulations, we assigned the observed spatial features to the plasmon mode resonantly excited by the dye fluorescence.

Well-developed hexagonal ZnO nanorods and morphology-controlled nanostructures were synthesized at low temperatures using a simple solution method without the assistance of any templates or catalysts.Well-developed hexagonal ZnO nanorods and morphology-controlled nanostructures were synthesized at low temperatures using a simple solution method without the assistance of any templates or catalysts. Uniform conical nanorods with an average diameter of 35 nm and the aspect ratio of 14 could be obtained at a near-room temperature, while nanoplatelets with the planar aspect ratio of 2.4–4.8 were produced at higher temperatures. It was revealed that the morphology, dimensions, and the crystallinity of ZnO nanostructures could be controlled by elaborately adjusting experimental conditions such as the molar ratio of Zn2+ to OH, EDA concentration, and temperature.

Theoretical studies of the vibrational frequencies of C6n 2H6n (n  = 2–12) coronenes, show that, despite full conjugation, delocalization and aromaticity, the stability of the planar geometry rapidly decreases with size. A switch to a nonplanar geometry can be expected at around n  = 9–12; any larger gas-phase coronene, including graphene, should be nonplanar. When applied to coronenes, popular quantum chemical methods, including Hartree–Fock and density functional theory, are shown to produce anomalous imaginary frequencies suggesting unrealistic geometry distortions; this reveals a serious methodological problem in calculations on extended systems which needs to be resolved through further basis set development.