Novel self-organized carbon nanoropes consisting of three helically coiled multi-wall nanotubes with a remarkable constant pitch over several microns were grown by the lanthanide oxide-catalyzed decomposition of gaseous acetylene on aluminophosphate (AlPO 4 -5) support. Direct characterization by the stereo transmission electron microscope and scanning electron microscope has convincingly shown that these three strands entwine with each other helically, which are presumably kept together by both the spontaneous curvature and van der Waals (vdW) attraction.
{"title":"Self-organization of triple-stranded carbon nanoropes","authors":"C. Su, D. W. Hwang, S. Lin, Bih-Yaw Jin, L. Hwang","doi":"10.1039/B110151J","DOIUrl":"https://doi.org/10.1039/B110151J","url":null,"abstract":"Novel self-organized carbon nanoropes consisting of three helically coiled multi-wall nanotubes with a remarkable constant pitch over several microns were grown by the lanthanide oxide-catalyzed decomposition of gaseous acetylene on aluminophosphate (AlPO 4 -5) support. Direct characterization by the stereo transmission electron microscope and scanning electron microscope has convincingly shown that these three strands entwine with each other helically, which are presumably kept together by both the spontaneous curvature and van der Waals (vdW) attraction.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73613620","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 report on the adsorption of adenine as well as on the coadsorption of adenine/thymine and uracil/thymine on Au(111). Adenine is chemisorbed in two different states. Mutual interaction between adenine and thymine could be detected only at negative potentials where both molecules are oriented with their plane parallel to the surface. This interaction depends on the concentration of thymine, the pH value, the temperature and the roughness of the surface. At positive potentials where thymine/adenine are oriented perpendicular to the electrode surface, from our experiments no hints to their interaction could be found. Thymine prevents the uracil adsorption and no cocondensation signal between the noncomplementary bases thymine/uracil was found.
{"title":"Adsorption behaviour of DNA bases at the Au(111) electrode","authors":"A. P. M. Camargo, H. Baumgärtel, C. Donner","doi":"10.1039/B208139C","DOIUrl":"https://doi.org/10.1039/B208139C","url":null,"abstract":"We report on the adsorption of adenine as well as on the coadsorption of adenine/thymine and uracil/thymine on Au(111). Adenine is chemisorbed in two different states. Mutual interaction between adenine and thymine could be detected only at negative potentials where both molecules are oriented with their plane parallel to the surface. This interaction depends on the concentration of thymine, the pH value, the temperature and the roughness of the surface. At positive potentials where thymine/adenine are oriented perpendicular to the electrode surface, from our experiments no hints to their interaction could be found. Thymine prevents the uracil adsorption and no cocondensation signal between the noncomplementary bases thymine/uracil was found.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82925648","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}
A variety of ultrafast vibrational excitation and probing methods are first discussed and it is shown that various vibrational spectroscopies can be devised by combining multiple excitation and probing methods. A few ultrafast vibrational spectroscopic methods in condensed phases, which have already been demonstrated and used to study vibrational relaxation phenomena and structural analysis of small polypeptides, are briefly summarized. Then, a number of novel ultrafast vibrational spectroscopies that have been theoretically investigated are discussed by emphasizing their differences from other existing methods. Perspectives on how these ultrafast vibrational spectroscopies in centrosymmetric and non-centrosymmetric condensed phases can be applied to the investigations of chemical reaction dynamics, solvation dynamics, time-dependent structural evolutions of polyatomic molecules such as proteins will be mentioned.
{"title":"Ultrafast vibrational spectroscopy in condensed phases","authors":"M. Cho","doi":"10.1039/B110898K","DOIUrl":"https://doi.org/10.1039/B110898K","url":null,"abstract":"A variety of ultrafast vibrational excitation and probing methods are first discussed and it is shown that various vibrational spectroscopies can be devised by combining multiple excitation and probing methods. A few ultrafast vibrational spectroscopic methods in condensed phases, which have already been demonstrated and used to study vibrational relaxation phenomena and structural analysis of small polypeptides, are briefly summarized. Then, a number of novel ultrafast vibrational spectroscopies that have been theoretically investigated are discussed by emphasizing their differences from other existing methods. Perspectives on how these ultrafast vibrational spectroscopies in centrosymmetric and non-centrosymmetric condensed phases can be applied to the investigations of chemical reaction dynamics, solvation dynamics, time-dependent structural evolutions of polyatomic molecules such as proteins will be mentioned.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81407617","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}
Multi-wall carbon nanotubes (MWNT) were synthesized by a novel method using mesoporous MCM-41 and MCM-48 silicates as nanoreactors in the absence of any metal traces. Transmission electron microscopy (TEM) studies revealed that the quality of carbon nanotubes obtained was very promising, the diameter distribution is very narrow.
{"title":"Mesoporous silicates as nanoreactors for synthesis of carbon nanotubes","authors":"M. Urbán, Z. Kónya, D. Mehn, Ji Zhu, I. Kiricsi","doi":"10.1039/B203767J","DOIUrl":"https://doi.org/10.1039/B203767J","url":null,"abstract":"Multi-wall carbon nanotubes (MWNT) were synthesized by a novel method using mesoporous MCM-41 and MCM-48 silicates as nanoreactors in the absence of any metal traces. Transmission electron microscopy (TEM) studies revealed that the quality of carbon nanotubes obtained was very promising, the diameter distribution is very narrow.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76490276","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}
Visible light emission from metal–water interfaces at laser-induced breakdown (LIB) has been observed for aluminium, titanium and platinum. The spectra are found to consist of broadband continuum without any discrete atomic lines, which may be useful as a pulsed light source for spectroscopy. A simple thermal diffusion model combined with blackbody radiation is described, the numerical result of which agrees fairly well with the observed spectra.
{"title":"Laser-induced breakdown spectroscopy at metal–water interfaces","authors":"Honoh Suzuki, H. Nishikawa, I.‐Yin Sandy Lee","doi":"10.1039/B202597C","DOIUrl":"https://doi.org/10.1039/B202597C","url":null,"abstract":"Visible light emission from metal–water interfaces at laser-induced breakdown (LIB) has been observed for aluminium, titanium and platinum. The spectra are found to consist of broadband continuum without any discrete atomic lines, which may be useful as a pulsed light source for spectroscopy. A simple thermal diffusion model combined with blackbody radiation is described, the numerical result of which agrees fairly well with the observed spectra.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85555272","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}
K. Izawa, T. Ogasawara, H. Masuda, H. Okabayashi, C. O'Connor, I. Noda
Two-dimensional correlation gel permeation chromatography (2D GPC) was used to elucidate intricate details of the initial ten minutes of the sol–gel transition of n-octyltriethoxysilane (OTES), catalysed by 0.5 and 2.0 M HCl·H 2 O. The results demonstrate that the features of 2D GPC correlation spectra directly reflect the dynamic variation of reactions or interactions present during the polymerization process.
利用二维相关凝胶渗透色谱(2D GPC)分析了0.5和2.0 M HCl·h2o催化下正辛基三乙氧基硅烷(OTES)的溶胶-凝胶转变过程的复杂细节。结果表明，二维GPC相关光谱的特征直接反映了聚合过程中反应或相互作用的动态变化。
{"title":"Two-dimensional correlation gel permeation chromatography (2D correlation GPC) study of the sol–gel polymerization of octyltriethoxysilane. HCl-concentration dependence","authors":"K. Izawa, T. Ogasawara, H. Masuda, H. Okabayashi, C. O'Connor, I. Noda","doi":"10.1039/B107635C","DOIUrl":"https://doi.org/10.1039/B107635C","url":null,"abstract":"Two-dimensional correlation gel permeation chromatography (2D GPC) was used to elucidate intricate details of the initial ten minutes of the sol–gel transition of n-octyltriethoxysilane (OTES), catalysed by 0.5 and 2.0 M HCl·H 2 O. The results demonstrate that the features of 2D GPC correlation spectra directly reflect the dynamic variation of reactions or interactions present during the polymerization process.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89047520","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}
AlCl 3 crystallizes as an ionic solid but melts to form a molecular liquid consisting of Al 2 Cl 6 units. In order to see if this transition involves a major change in electronic structure, the dimer and crystal of AlCl 3 are examined with the aid of generalized gradient corrected density functional theory (GGC-DFT) calculations and the electronic wavefunctions examined with the aid of a Wannier localisation transformation of the Kohn–Sham eigenfunctions. The change from octahedral to tetrahedral coordination of Al which is observed on melting has been induced by simply rescaling the unit cell parameters, and the variations in the hybridization of the Wannier orbitals across the transition have been analysed thoroughly. The predominantly ionic character of the interactions across the ionic to molecular transition is confirmed, validating the use of ionic interaction potentials to represent AlCl 3 and related systems. Dipole moments of the single ions have been estimated from the position of the Wannier function centres and they are found to reproduce with remarkable accuracy the values predicted by a polarizable ionic interaction potential. A similar analysis has been carried over to the AlBr 3 –Al 2 Br 6 system, which is known to consist of molecular units in both crystal and gas phase.
{"title":"Ionic to molecular transition in AlCl3: an examination of the electronic structure","authors":"L. Bernasconi, P. Madden, M. Wilson","doi":"10.1039/B107715E","DOIUrl":"https://doi.org/10.1039/B107715E","url":null,"abstract":"AlCl 3 crystallizes as an ionic solid but melts to form a molecular liquid consisting of Al 2 Cl 6 units. In order to see if this transition involves a major change in electronic structure, the dimer and crystal of AlCl 3 are examined with the aid of generalized gradient corrected density functional theory (GGC-DFT) calculations and the electronic wavefunctions examined with the aid of a Wannier localisation transformation of the Kohn–Sham eigenfunctions. The change from octahedral to tetrahedral coordination of Al which is observed on melting has been induced by simply rescaling the unit cell parameters, and the variations in the hybridization of the Wannier orbitals across the transition have been analysed thoroughly. The predominantly ionic character of the interactions across the ionic to molecular transition is confirmed, validating the use of ionic interaction potentials to represent AlCl 3 and related systems. Dipole moments of the single ions have been estimated from the position of the Wannier function centres and they are found to reproduce with remarkable accuracy the values predicted by a polarizable ionic interaction potential. A similar analysis has been carried over to the AlBr 3 –Al 2 Br 6 system, which is known to consist of molecular units in both crystal and gas phase.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79865633","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 reflects on several recent advances in the studies of structure and dynamics of cluster anions, bridging the gap between ‘cluster’ and condensed phases. Applications involving photofragment and photodetachment spectroscopy, as well as femtosecond time-resolved experiments, are described. Special emphasis is given to the effects of microscopic solvation on the electronic structure and reactivity of negative ions in heterogeneous and homogeneous cluster environments. Some recent breakthroughs in experimental methodology are also outlined, in particular the application of photofragment and photoelectron methods and the imaging technique to the studies of molecular cluster anions.
{"title":"Dynamics of cluster anions: a detailed look at condensed-phase interactions","authors":"A. Sanov, W. C. Lineberger","doi":"10.1039/B209239E","DOIUrl":"https://doi.org/10.1039/B209239E","url":null,"abstract":"This Perspective reflects on several recent advances in the studies of structure and dynamics of cluster anions, bridging the gap between ‘cluster’ and condensed phases. Applications involving photofragment and photodetachment spectroscopy, as well as femtosecond time-resolved experiments, are described. Special emphasis is given to the effects of microscopic solvation on the electronic structure and reactivity of negative ions in heterogeneous and homogeneous cluster environments. Some recent breakthroughs in experimental methodology are also outlined, in particular the application of photofragment and photoelectron methods and the imaging technique to the studies of molecular cluster anions.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80614322","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 article explores the correlation between the ultra-violet circular dichroism of chirally substituted benzene molecules in solution, and their absolute configurations determined on the basis of infrared (or ultraviolet) spectroscopy, coupled with ab initio computation, in the gas phase. New results for isolated and solvated molecules in the ephedra class of drugs are presented. They lead to a revision of the current ‘sector rules’ associated with excitation into the 1 L b state of the benzene ring and suggest a new strategy for bridging the gap between isolated molecular and solvated cluster structures determined in the gas phase and the structures adopted in condensed media.
{"title":"Molecular conformation in the gas phase and in solution","authors":"P. Butz, G. Tranter, J. Simons","doi":"10.1039/B203810B","DOIUrl":"https://doi.org/10.1039/B203810B","url":null,"abstract":"The article explores the correlation between the ultra-violet circular dichroism of chirally substituted benzene molecules in solution, and their absolute configurations determined on the basis of infrared (or ultraviolet) spectroscopy, coupled with ab initio computation, in the gas phase. New results for isolated and solvated molecules in the ephedra class of drugs are presented. They lead to a revision of the current ‘sector rules’ associated with excitation into the 1 L b state of the benzene ring and suggest a new strategy for bridging the gap between isolated molecular and solvated cluster structures determined in the gas phase and the structures adopted in condensed media.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75239358","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}
Jason D. Thompson, J. D. Xidos, Timothy M. Sonbuchner, C. Cramer, D. Truhlar
We present a method that alleviates some of the sensitivity to the inclusion of diffuse basis functions when calculating partial atomic charges from a Lowdin population analysis. This new method locally redistributes that part of the Lowdin population that comes from diffuse basis functions so that the final charges closely resemble those calculated without diffuse functions. We call this method the redistributed Lowdin population analysis (RLPA). The method contains one parameter for each atomic number, and we optimized the parameter for the 6-31+G(d) basis set. The method has been tested on compounds that contain H, Li, C, N, O, F, Si, P, S, Cl, and Br. For a test set of 398 compounds with experimental and high-level theoretical dipole moments, the dipole moments derived from the charges obtained by standard Lowdin population analysis have errors 35% larger than those obtained by the corresponding RLPA using the same basis set. In judging the quality of the RLPA with respect to the test set of dipole moments, we have also found that dipole moments derived from Mulliken population analysis have errors 120% larger than those derived from RLPA for the same basis set. The new method is particularly successful for the 207 systems containing only first row atoms (H, C, N, O, F) for which the errors in the dipole moments computed from the partial atomic charges obtained by standard Lowdin and Mulliken analysis are respectively 115 and 419% larger than those obtained by RLPA.
我们提出了一种方法，当从洛丁族分析计算部分原子电荷时，减轻了对包含扩散基函数的一些敏感性。该方法局部重新分配了由漫射基函数得到的部分洛丁种群，使最终电荷与没有漫射基函数的计算结果非常接近。我们称这种方法为再分布洛丁种群分析(RLPA)。该方法为每个原子序数包含一个参数，我们针对6-31+G(d)基集优化了该参数。该方法已在含有H、Li、C、N、O、F、Si、P、S、Cl和Br的化合物上进行了测试。对于398个具有实验偶极矩和高水平理论偶极矩的化合物的测试集，用标准洛丁种群分析得到的电荷偶极矩的误差比使用相同基集的相应RLPA得到的误差大35%。在判断RLPA相对于偶极矩测试集的质量时，我们还发现，在相同的基集上，由Mulliken总体分析得出的偶极矩比由RLPA得出的偶极矩误差大120%。新方法对只包含第一行原子(H, C, N, O, F)的207个体系特别成功，用标准洛丁和Mulliken分析得到的部分原子电荷计算的偶极矩误差分别比RLPA计算的误差大115和419%。
{"title":"More reliable partial atomic charges when using diffuse basis sets","authors":"Jason D. Thompson, J. D. Xidos, Timothy M. Sonbuchner, C. Cramer, D. Truhlar","doi":"10.1039/B206369G","DOIUrl":"https://doi.org/10.1039/B206369G","url":null,"abstract":"We present a method that alleviates some of the sensitivity to the inclusion of diffuse basis functions when calculating partial atomic charges from a Lowdin population analysis. This new method locally redistributes that part of the Lowdin population that comes from diffuse basis functions so that the final charges closely resemble those calculated without diffuse functions. We call this method the redistributed Lowdin population analysis (RLPA). The method contains one parameter for each atomic number, and we optimized the parameter for the 6-31+G(d) basis set. The method has been tested on compounds that contain H, Li, C, N, O, F, Si, P, S, Cl, and Br. For a test set of 398 compounds with experimental and high-level theoretical dipole moments, the dipole moments derived from the charges obtained by standard Lowdin population analysis have errors 35% larger than those obtained by the corresponding RLPA using the same basis set. In judging the quality of the RLPA with respect to the test set of dipole moments, we have also found that dipole moments derived from Mulliken population analysis have errors 120% larger than those derived from RLPA for the same basis set. The new method is particularly successful for the 207 systems containing only first row atoms (H, C, N, O, F) for which the errors in the dipole moments computed from the partial atomic charges obtained by standard Lowdin and Mulliken analysis are respectively 115 and 419% larger than those obtained by RLPA.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87617607","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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