Z. Zheng, Y. Xi, P. Dong, H. Huang, J. Z. Zhou, L. L. Wu, Z. H. Lin
A novel nanomaterial, an array of zinc oxide (ZnO) and polyaniline (PANI) coaxial nanowires, was synthesized using an anodic aluminum oxide (AAO) membrane as the template. The morphology of these coaxial nanowires was observed with transmission electron microscope (TEM). The experiments on photoluminescence (PL) of coaxial nanowires and their array in AAO membrane show that the visible emission band of ZnO shifts from 530 to 400 nm for the coaxial nanowires array in AAO membrane, and to a lower wavelength (385 nm) for coaxial nanowires in NaOH solution. When compared with the PL spectrum of ZnO nanowires array in AAO membrane, an about 100 times PL enhancement was found in the PL spectrum of ZnO and PANI coaxial nanowires array in AAO membrane. The possible explanations for these two blue shifts of visible emission band of ZnO and the PL enhancement were presented.
{"title":"The enhanced photoluminescence of zinc oxide and polyaniline coaxial nanowire arrays in anodic oxide aluminium membranes","authors":"Z. Zheng, Y. Xi, P. Dong, H. Huang, J. Z. Zhou, L. L. Wu, Z. H. Lin","doi":"10.1039/B201201D","DOIUrl":"https://doi.org/10.1039/B201201D","url":null,"abstract":"A novel nanomaterial, an array of zinc oxide (ZnO) and polyaniline (PANI) coaxial nanowires, was synthesized using an anodic aluminum oxide (AAO) membrane as the template. The morphology of these coaxial nanowires was observed with transmission electron microscope (TEM). The experiments on photoluminescence (PL) of coaxial nanowires and their array in AAO membrane show that the visible emission band of ZnO shifts from 530 to 400 nm for the coaxial nanowires array in AAO membrane, and to a lower wavelength (385 nm) for coaxial nanowires in NaOH solution. When compared with the PL spectrum of ZnO nanowires array in AAO membrane, an about 100 times PL enhancement was found in the PL spectrum of ZnO and PANI coaxial nanowires array in AAO membrane. The possible explanations for these two blue shifts of visible emission band of ZnO and the PL enhancement were presented.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"58 1","pages":"63-65"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85929926","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study examined the liquid part of solid/liquid interfaces at the atomic level. By measuring distance tunnelling characteristics the height of the potential barrier between the tip and the sample, i.e., the potential energy field the tunnelling electrons are exposed to, can be obtained, and this provides direct access to double layer properties. We found exponential IS-characteristics for the bare and the oxidised Au(111) surface, while non-exponential behaviour was obtained in the presence of ordered adlayers. The influence of the local environment just within the Helmholtz layer is strong enough to perturb the tunnelling process significantly. The electrolyte properties in the Gouy region do not change with electrode potential, the liquid in the tunnelling gap has only an average effect by lowering the barrier height.
{"title":"Distance tunnelling characteristics of solid/liquid interfaces: Au(111)/Cu2+/H2SO4","authors":"G. Nagy, D. Mayer, T. Wandlowski","doi":"10.1039/B205720B","DOIUrl":"https://doi.org/10.1039/B205720B","url":null,"abstract":"This study examined the liquid part of solid/liquid interfaces at the atomic level. By measuring distance tunnelling characteristics the height of the potential barrier between the tip and the sample, i.e., the potential energy field the tunnelling electrons are exposed to, can be obtained, and this provides direct access to double layer properties. We found exponential IS-characteristics for the bare and the oxidised Au(111) surface, while non-exponential behaviour was obtained in the presence of ordered adlayers. The influence of the local environment just within the Helmholtz layer is strong enough to perturb the tunnelling process significantly. The electrolyte properties in the Gouy region do not change with electrode potential, the liquid in the tunnelling gap has only an average effect by lowering the barrier height.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"45 1","pages":"112-116"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88182861","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The femtosecond two-dimensional infrared (2D IR) spectroscopy that was recently developed shows great promise for determining the dynamics of molecular structure at ultrafast time scales that are hard to access by NMR and X-ray diffraction methods. This Perspective focuses on the IR-COSY and THIRSTY methods that are based on heterodyned three pulse photon echoes. The relationships of 2D spectral properties coupling, structure, correlated fluctuations, energy transfer, and orientational motions to experimental results on small peptides and molecules are described. The status of this exciting new field is also discussed.
{"title":"Femtosecond two-dimensional infrared spectroscopy: IR-COSY and THIRSTY","authors":"N. Ge, R. Hochstrasser","doi":"10.1039/B109935C","DOIUrl":"https://doi.org/10.1039/B109935C","url":null,"abstract":"The femtosecond two-dimensional infrared (2D IR) spectroscopy that was recently developed shows great promise for determining the dynamics of molecular structure at ultrafast time scales that are hard to access by NMR and X-ray diffraction methods. This Perspective focuses on the IR-COSY and THIRSTY methods that are based on heterodyned three pulse photon echoes. The relationships of 2D spectral properties coupling, structure, correlated fluctuations, energy transfer, and orientational motions to experimental results on small peptides and molecules are described. The status of this exciting new field is also discussed.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"174 1","pages":"17-26"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81562364","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
E. Heeley, Ariana C. Morgovan, W. Bras, I. Dolbnya, A. Gleeson, A. Ryan
Shear induced crystallization of commercial grade polyethylenes (PE) have been investigated using simultaneous SAXS and WAXS, enabling real time studies of the kinetics and structure development to be performed.
{"title":"Shear-induced crystallization of polyethylene studied by small- and wide-angle X-ray scattering (SAXS/WAXS) techniques","authors":"E. Heeley, Ariana C. Morgovan, W. Bras, I. Dolbnya, A. Gleeson, A. Ryan","doi":"10.1039/B206832J","DOIUrl":"https://doi.org/10.1039/B206832J","url":null,"abstract":"Shear induced crystallization of commercial grade polyethylenes (PE) have been investigated using simultaneous SAXS and WAXS, enabling real time studies of the kinetics and structure development to be performed.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"1 1","pages":"158-160"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89777624","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The role of anharmonic effects in the vibrational spectroscopy of small biological molecules and their 1 ∶ 1 complexes with water is discussed. The strengths and limitations of the vibrational self-consistent field (VSCF) method and its extensions as a computational tool for this purpose are examined. Anharmonic coupling between different vibrational modes is found to be very important for these systems, even for fundamental transitions, and incorporation of these effects seems essential for quantitative interpretation of experimental data. Both analytical, empirical force fields, and potential surfaces computed from electronic structure methods are used in VSCF calculations of several benchmark systems and compared with experimental spectroscopic data. Glycine in several conformers, the glycine–water complex, and N-methylacetamide are among the systems discussed. The main conclusions are: (1) Electronic structure methods such as MP2/DZP and density functional B97, give very good agreement with experimental data. Thus, MP2 and B97 clearly provide an accurate description of the anharmonic interactions. VSCF calculations, including all modes, with MP2, B97 and other successful methods are presently feasible for molecules with up to 15-20 atoms. (2) The electronic structure methods seem to give spectroscopic predictions in much better accord with experiment than standard empirical force fields such as AMBER or OPLS. The anharmonic couplings provided by these methods differ greatly, in the cases tested to date, from the ab initio ones. The implications of these results for future modeling of small biomolecules are discussed. Comments are provided on future directions in this subject, including extensions to large biomolecules.
{"title":"Calculation of anharmonic vibrational spectroscopy of small biological molecules","authors":"R. Gerber, B. Brauer, S. Gregurick, G. Chaban","doi":"10.1039/B208000A","DOIUrl":"https://doi.org/10.1039/B208000A","url":null,"abstract":"The role of anharmonic effects in the vibrational spectroscopy of small biological molecules and their 1 ∶ 1 complexes with water is discussed. The strengths and limitations of the vibrational self-consistent field (VSCF) method and its extensions as a computational tool for this purpose are examined. Anharmonic coupling between different vibrational modes is found to be very important for these systems, even for fundamental transitions, and incorporation of these effects seems essential for quantitative interpretation of experimental data. Both analytical, empirical force fields, and potential surfaces computed from electronic structure methods are used in VSCF calculations of several benchmark systems and compared with experimental spectroscopic data. Glycine in several conformers, the glycine–water complex, and N-methylacetamide are among the systems discussed. The main conclusions are: (1) Electronic structure methods such as MP2/DZP and density functional B97, give very good agreement with experimental data. Thus, MP2 and B97 clearly provide an accurate description of the anharmonic interactions. VSCF calculations, including all modes, with MP2, B97 and other successful methods are presently feasible for molecules with up to 15-20 atoms. (2) The electronic structure methods seem to give spectroscopic predictions in much better accord with experiment than standard empirical force fields such as AMBER or OPLS. The anharmonic couplings provided by these methods differ greatly, in the cases tested to date, from the ab initio ones. The implications of these results for future modeling of small biomolecules are discussed. Comments are provided on future directions in this subject, including extensions to large biomolecules.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"5 1","pages":"142-150"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81741241","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
G. Louit, A. Hocquet, M. Ghomi, M. Meyer, J. Sühnel
Following a previous publication (M. Meyer, M. Brandl and J Suhnel, J. Phys. Chem. A, 2001, 105, 8223–8225) on quantum mechanical calculations of guanine tetrads where the issue of the difference between bifurcated and Hoogsteen conformations was addressed geometrically and energetically, we tackle the problem from the Atoms in Molecules (AIM) point of view of the topological analysis of the electronic density. We provide electronic argumentation to discuss the bifurcated or Hoogsteen issue, from the analysis of density and laplacian at the bond critical point criteria, and from the integration of atomic properties. The Hoogsteen hydrogen bonding network appears to be stronger than the bifurcated one, and benefits more from cooperativity.
继先前的出版物(M. Meyer, M. Brandl和J. Suhnel, J. Phys。化学。在鸟嘌呤四分体的量子力学计算中，我们从几何和能量上解决了分叉构象和Hoogsteen构象之间的差异问题，我们从分子中的原子(AIM)的电子密度拓扑分析的角度来解决这个问题。我们提供了电子论证来讨论分岔或Hoogsteen问题，从密度和拉普拉斯在键临界点准则的分析，并从原子性质的整合。Hoogsteen氢键网络似乎比分叉的网络更强，并且从协同性中获益更多。
{"title":"Are guanine tetrads stabilised by bifurcated hydrogen bonds? An AIM topological analysis of the electronic density","authors":"G. Louit, A. Hocquet, M. Ghomi, M. Meyer, J. Sühnel","doi":"10.1039/B204736E","DOIUrl":"https://doi.org/10.1039/B204736E","url":null,"abstract":"Following a previous publication (M. Meyer, M. Brandl and J Suhnel, J. Phys. Chem. A, 2001, 105, 8223–8225) on quantum mechanical calculations of guanine tetrads where the issue of the difference between bifurcated and Hoogsteen conformations was addressed geometrically and energetically, we tackle the problem from the Atoms in Molecules (AIM) point of view of the topological analysis of the electronic density. We provide electronic argumentation to discuss the bifurcated or Hoogsteen issue, from the analysis of density and laplacian at the bond critical point criteria, and from the integration of atomic properties. The Hoogsteen hydrogen bonding network appears to be stronger than the bifurcated one, and benefits more from cooperativity.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"59 1","pages":"94-98"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80520503","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This perspective reviews experiments in which spectroscopy rather than scattering is used to probe reactive potential energy surfaces. The application of negative ion photodetachment to the transition state spectroscopy of benchmark reactions is described, followed by a brief description of recent transition state spectroscopy experiment starting from clustered precursor anions that probe the effects of solvation on transition state spectroscopy and dynamics. Experiments on the spectroscopy of open-shell “pre-reactive” complexes are also discussed.
{"title":"Spectroscopy of reactive potential energy surfaces","authors":"D. Neumark","doi":"10.1039/B202218D","DOIUrl":"https://doi.org/10.1039/B202218D","url":null,"abstract":"This perspective reviews experiments in which spectroscopy rather than scattering is used to probe reactive potential energy surfaces. The application of negative ion photodetachment to the transition state spectroscopy of benchmark reactions is described, followed by a brief description of recent transition state spectroscopy experiment starting from clustered precursor anions that probe the effects of solvation on transition state spectroscopy and dynamics. Experiments on the spectroscopy of open-shell “pre-reactive” complexes are also discussed.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"5 1","pages":"76-81"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81565564","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The electronic structures of a series of sodium chloride clusters (NaCl) n (n = 2–40) cut out from the NaCl solid have been investigated by means of ab initio calculations. The calculation results demonstrated a good correlation of the topologic parameters N d (the total amount of dangling bonds of a cut-out cluster) and β (the average dangling bonds on each in-cluster atom) with the stability of clusters as well as an evident convergence from clusters to the bulk solid. Particularly, we found that the effective charges on the Cl anions are more site dependent than size dependent.
用从头算方法研究了从NaCl固体中切出的一系列氯化钠簇(NaCl) n (n = 2-40)的电子结构。计算结果表明，拓扑参数N d(切出簇的悬垂键总数)和β(簇内原子上的平均悬垂键数)与簇的稳定性有良好的相关性，并且簇向固体有明显的收敛性。特别是，我们发现Cl阴离子上的有效电荷更多地依赖于位置而不是尺寸。
{"title":"Convergence from clusters to the bulk solid: an ab initio investigation of clusters NanCln (n=2-40)","authors":"Jinfeng Lai, Xin Lu, Lan-Sun Zheng","doi":"10.1039/B202278H","DOIUrl":"https://doi.org/10.1039/B202278H","url":null,"abstract":"The electronic structures of a series of sodium chloride clusters (NaCl) n (n = 2–40) cut out from the NaCl solid have been investigated by means of ab initio calculations. The calculation results demonstrated a good correlation of the topologic parameters N d (the total amount of dangling bonds of a cut-out cluster) and β (the average dangling bonds on each in-cluster atom) with the stability of clusters as well as an evident convergence from clusters to the bulk solid. Particularly, we found that the effective charges on the Cl anions are more site dependent than size dependent.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"38 1","pages":"82-87"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89935700","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this Perspective we briefly review our recent studies which prove unequivocally the existence of a quantum dynamical resonance in the F + HD → HF + D reaction. The signatures of the resonance in the integral and differential cross sections of this reaction are elucidated. The interplay between experiment and theory is crucial in establishing the existence of a resonance in a bimolecular reaction and in revealing its physical characteristics.
{"title":"Resonances in bimolecular reactions","authors":"Kopin Liu, R. T. Skodje, D. Manolopoulos","doi":"10.1039/B110570A","DOIUrl":"https://doi.org/10.1039/B110570A","url":null,"abstract":"In this Perspective we briefly review our recent studies which prove unequivocally the existence of a quantum dynamical resonance in the F + HD → HF + D reaction. The signatures of the resonance in the integral and differential cross sections of this reaction are elucidated. The interplay between experiment and theory is crucial in establishing the existence of a resonance in a bimolecular reaction and in revealing its physical characteristics.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"23 1","pages":"27-33"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84724087","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We apply the one-dimensional vibron model to compute energies and infrared intensities of CH vibrational modes (stretching and bending states) of n-paraffin molecules. We consider the possible onset of interactions between different kinds of bending motions as well as that of anharmonic resonances between CH stretching modes and CH bending overtone/combination vibrations.
{"title":"Vibrational modes of CH bonds in n-paraffin molecular chains: an algebraic description","authors":"Tijana Marinković, S. Oss","doi":"10.1039/B201553F","DOIUrl":"https://doi.org/10.1039/B201553F","url":null,"abstract":"We apply the one-dimensional vibron model to compute energies and infrared intensities of CH vibrational modes (stretching and bending states) of n-paraffin molecules. We consider the possible onset of interactions between different kinds of bending motions as well as that of anharmonic resonances between CH stretching modes and CH bending overtone/combination vibrations.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"27 1","pages":"66-75"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78162897","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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