We present molecular dynamics (MD) simulations of water-filled silica nanopores such as those that occur in ordered oxide ceramics (MCM-41, SBA-15), controlled pore glasses (such as Vycor glass), mesoporous silica, bioglasses, and hydrous silica gel coatings of weathered minerals and glasses. Our simulations overlap the range of pore diameters (1–4 nm) where confinement causes the disappearance of bulk-liquid-like water. In ≥2 nm diameter pores, the silica surface carries three statistical monolayers of density-layered water, interfacial water structure is independent of confinement or surface curvature, and bulk-liquid-like water exists at the center of the pore (this last finding contradicts assumptions used in most previous neutron diffraction studies and in several MD simulation studies of silica nanopores). In 1 nm diameter pores, bulk-liquid-like water does not exist and the structural properties of interfacial water are influenced by confinement. Predicted water diffusion coefficients in 1–4 nm dia...
{"title":"Molecular dynamics simulations of water structure and diffusion in silica nanopores","authors":"I. Bourg, C. Steefel","doi":"10.1021/JP301299A","DOIUrl":"https://doi.org/10.1021/JP301299A","url":null,"abstract":"We present molecular dynamics (MD) simulations of water-filled silica nanopores such as those that occur in ordered oxide ceramics (MCM-41, SBA-15), controlled pore glasses (such as Vycor glass), mesoporous silica, bioglasses, and hydrous silica gel coatings of weathered minerals and glasses. Our simulations overlap the range of pore diameters (1–4 nm) where confinement causes the disappearance of bulk-liquid-like water. In ≥2 nm diameter pores, the silica surface carries three statistical monolayers of density-layered water, interfacial water structure is independent of confinement or surface curvature, and bulk-liquid-like water exists at the center of the pore (this last finding contradicts assumptions used in most previous neutron diffraction studies and in several MD simulation studies of silica nanopores). In 1 nm diameter pores, bulk-liquid-like water does not exist and the structural properties of interfacial water are influenced by confinement. Predicted water diffusion coefficients in 1–4 nm dia...","PeriodicalId":58,"journal":{"name":"The Journal of Physical Chemistry ","volume":"14 1","pages":"11556-11564"},"PeriodicalIF":2.781,"publicationDate":"2012-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87091610","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}
Gérald Lelong, R. Heyd, G. Charalambopoulou, T. Steriotis, A. Brandt, K. Beck, M. Vayer, D. Price, J. Brady, M. Saboungi
The microstructure evolution of confined glucose solutions in silica gels can provide insights into the effect of sugars in protecting living organisms under extreme dehydration conditions. Aqueous silica gels with relatively small pore sizes capable of deforming under changes in environmental conditions are used here as a model system. In situ monitoring of the dehydration process – with and without the presence of sugar molecules – by optical photography, gravimetric measurements, small-angle neutron scattering, and atomic force microscopy reveals that sugar plays a crucial role in the mechanics and protection of the gel. In the absence of sugar, dehydration leads to considerable degradation, whereas the incorporation of large doses of glucose maintains the stability and robustness of the structure. A model is proposed to explain the time dependence of the dehydration process.
{"title":"Role of Glucose in Enhancing Stability of Aqueous Silica Gels Against Dehydration","authors":"Gérald Lelong, R. Heyd, G. Charalambopoulou, T. Steriotis, A. Brandt, K. Beck, M. Vayer, D. Price, J. Brady, M. Saboungi","doi":"10.1021/JP208377T","DOIUrl":"https://doi.org/10.1021/JP208377T","url":null,"abstract":"The microstructure evolution of confined glucose solutions in silica gels can provide insights into the effect of sugars in protecting living organisms under extreme dehydration conditions. Aqueous silica gels with relatively small pore sizes capable of deforming under changes in environmental conditions are used here as a model system. In situ monitoring of the dehydration process – with and without the presence of sugar molecules – by optical photography, gravimetric measurements, small-angle neutron scattering, and atomic force microscopy reveals that sugar plays a crucial role in the mechanics and protection of the gel. In the absence of sugar, dehydration leads to considerable degradation, whereas the incorporation of large doses of glucose maintains the stability and robustness of the structure. A model is proposed to explain the time dependence of the dehydration process.","PeriodicalId":58,"journal":{"name":"The Journal of Physical Chemistry ","volume":"36 1","pages":"1"},"PeriodicalIF":2.781,"publicationDate":"2012-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89206207","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. C. Reyes, Adam Slabon-Turski, C. Mensing, R. Nesper
The electronic structure and properties of LiEu2Si3 are investigated, using ab initio methods and experimental techniques. All europium ions are found in a 8S7/2 configuration. The system is metallic. We found evidence of competing exchange interactions between Eu moments which may result in the onset of a spin-glass behavior below 70 K. The electronic structures of LiEu2Si3 and the isostructural (inexistent) LiSr2Si3 are compared. The ambiguous role of lithium is discussed. The fact that LiEu2Si3 and LiSr2Si3 crystallize in different structure types is justified here, considering their relative thermodynamical stability and the difference between the effective charges of europium and strontium.
{"title":"Spin-Glass Behaviour and Electronic Structure of LiEu2Si3","authors":"E. C. Reyes, Adam Slabon-Turski, C. Mensing, R. Nesper","doi":"10.1021/JP205861X","DOIUrl":"https://doi.org/10.1021/JP205861X","url":null,"abstract":"The electronic structure and properties of LiEu2Si3 are investigated, using ab initio methods and experimental techniques. All europium ions are found in a 8S7/2 configuration. The system is metallic. We found evidence of competing exchange interactions between Eu moments which may result in the onset of a spin-glass behavior below 70 K. The electronic structures of LiEu2Si3 and the isostructural (inexistent) LiSr2Si3 are compared. The ambiguous role of lithium is discussed. The fact that LiEu2Si3 and LiSr2Si3 crystallize in different structure types is justified here, considering their relative thermodynamical stability and the difference between the effective charges of europium and strontium.","PeriodicalId":58,"journal":{"name":"The Journal of Physical Chemistry ","volume":"158 1","pages":"1158-1164"},"PeriodicalIF":2.781,"publicationDate":"2012-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85345572","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}
Lauren E. Polander, L. Pandey, S. Barlow, S. P. Tiwari, C. Risko, B. Kippelen, J. Brédas, S. Marder
2,2′-(Benzo[c][1,2,5]thiadiazol-4,7-diyl)-4,4′-dialkyl-bis(4H-dithieno[3,2-b:2′,3′-d]pyrrole) (DTP-BTD-DTP) donor–acceptor–donor (D-A-D) and 4-alkyl-2,6-bis(benzo[c][1,2,5]thiadiazol-4-yl)-4H-dithieno[3,2-b:2′,3′-d]pyrrole (BTD-DTP-BTD) acceptor–donor–acceptor (A-D-A) triads, with or without additional alkylation in the DTP 6- or BTD 7-positions, respectively, have been synthesized using Stille coupling reactions, characterized using UV–vis absorption spectroscopy and electrochemistry, modeled using density functional theory calculations, and used as charge-transport materials in field-effect transistors. The choice of alkyl substitution pattern has only minor effects on the optical and redox behavior but can be used to modify the thermal properties and solubility of these compounds. The D-A-D and A-D-A triads show long-wavelength absorption maxima at 566–588 and 517–521 nm, respectively, in solution. These transitions are attributed to excitation from a delocalized HOMO to a BTD-localized LUMO and, accor...
{"title":"Benzothiadiazole-Dithienopyrrole Donor–Acceptor–Donor and Acceptor–Donor–Acceptor Triads: Synthesis and Optical, Electrochemical, and Charge-Transport Properties","authors":"Lauren E. Polander, L. Pandey, S. Barlow, S. P. Tiwari, C. Risko, B. Kippelen, J. Brédas, S. Marder","doi":"10.1021/JP208643K","DOIUrl":"https://doi.org/10.1021/JP208643K","url":null,"abstract":"2,2′-(Benzo[c][1,2,5]thiadiazol-4,7-diyl)-4,4′-dialkyl-bis(4H-dithieno[3,2-b:2′,3′-d]pyrrole) (DTP-BTD-DTP) donor–acceptor–donor (D-A-D) and 4-alkyl-2,6-bis(benzo[c][1,2,5]thiadiazol-4-yl)-4H-dithieno[3,2-b:2′,3′-d]pyrrole (BTD-DTP-BTD) acceptor–donor–acceptor (A-D-A) triads, with or without additional alkylation in the DTP 6- or BTD 7-positions, respectively, have been synthesized using Stille coupling reactions, characterized using UV–vis absorption spectroscopy and electrochemistry, modeled using density functional theory calculations, and used as charge-transport materials in field-effect transistors. The choice of alkyl substitution pattern has only minor effects on the optical and redox behavior but can be used to modify the thermal properties and solubility of these compounds. The D-A-D and A-D-A triads show long-wavelength absorption maxima at 566–588 and 517–521 nm, respectively, in solution. These transitions are attributed to excitation from a delocalized HOMO to a BTD-localized LUMO and, accor...","PeriodicalId":58,"journal":{"name":"The Journal of Physical Chemistry ","volume":"81 1","pages":"23149-23163"},"PeriodicalIF":2.781,"publicationDate":"2011-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75354521","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 examine the conductometric CO sensing of TiO2 nanoparticle films prepared with a recently developed flame technique. Porous films of crystalline TiO2 nanoparticles were grown directly on interdigitated electrodes by repeatedly translating electrodes over a premixed stagnation flame doped with titanium tetraisopropoxide as the titanium precursor. Flame-deposited electrodes with particle diameter around 9 nm show enhanced sensitivity to CO by up to an order of magnitude compared to sensing films prepared using a commercial TiO2 powder with the particle diameter around 25 nm. A gas-surface model is used to examine chemical kinetic and equilibrium behaviors and explain the sensor responses. The analysis shows that the nature of the gas-surface reactions is similar between these films. The desirable feature of flame-deposited sensing film is attributed to the smaller particle size which provides a greater surface area and a more electrically sensitive conduit.
{"title":"Nanoporous Titania Gas Sensing Films Prepared in a Premixed Stagnation Flame","authors":"E. Tolmachoff, S. Memarzadeh, Hai Wang","doi":"10.1021/JP206061H","DOIUrl":"https://doi.org/10.1021/JP206061H","url":null,"abstract":"We examine the conductometric CO sensing of TiO2 nanoparticle films prepared with a recently developed flame technique. Porous films of crystalline TiO2 nanoparticles were grown directly on interdigitated electrodes by repeatedly translating electrodes over a premixed stagnation flame doped with titanium tetraisopropoxide as the titanium precursor. Flame-deposited electrodes with particle diameter around 9 nm show enhanced sensitivity to CO by up to an order of magnitude compared to sensing films prepared using a commercial TiO2 powder with the particle diameter around 25 nm. A gas-surface model is used to examine chemical kinetic and equilibrium behaviors and explain the sensor responses. The analysis shows that the nature of the gas-surface reactions is similar between these films. The desirable feature of flame-deposited sensing film is attributed to the smaller particle size which provides a greater surface area and a more electrically sensitive conduit.","PeriodicalId":58,"journal":{"name":"The Journal of Physical Chemistry ","volume":"39 1","pages":"21620-21628"},"PeriodicalIF":2.781,"publicationDate":"2011-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78741276","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 correlated disorder model (CDM) has been proposed as a theory of charge transport in molecularly doped polymers (MDPs). Recently a test of the CDM was proposed: it was predicted that the dipolar disorder energy can be obtained from the slope of the log of the mobility versus square root of the electric field (the Poole-Frenkel or PF slope). We find that the dipolar disorder energy obtained from the experimental PF slopes are almost always larger than the theoretical predictions, especially for MDPs made from dopants with low dipole moments. In addition, the theory relates the dipolar disorder energy to the temperature T0 at which the electric field dependence of the mobility vanishes. We find that the observed T0 does appear to increase as the dipolar disorder increases but is in quantitative agreement (within 25 K) with the theoretical predictions for only a limited set of the measurements. We conclude that it appears that the CDM needs further development to be consistent with charge transport in or...
{"title":"Charge Transport in Molecularly Doped Polymers: Tests of the Correlated Disorder Model","authors":"L. Schein, A. Tyutnev","doi":"10.1021/JP112290T","DOIUrl":"https://doi.org/10.1021/JP112290T","url":null,"abstract":"The correlated disorder model (CDM) has been proposed as a theory of charge transport in molecularly doped polymers (MDPs). Recently a test of the CDM was proposed: it was predicted that the dipolar disorder energy can be obtained from the slope of the log of the mobility versus square root of the electric field (the Poole-Frenkel or PF slope). We find that the dipolar disorder energy obtained from the experimental PF slopes are almost always larger than the theoretical predictions, especially for MDPs made from dopants with low dipole moments. In addition, the theory relates the dipolar disorder energy to the temperature T0 at which the electric field dependence of the mobility vanishes. We find that the observed T0 does appear to increase as the dipolar disorder increases but is in quantitative agreement (within 25 K) with the theoretical predictions for only a limited set of the measurements. We conclude that it appears that the CDM needs further development to be consistent with charge transport in or...","PeriodicalId":58,"journal":{"name":"The Journal of Physical Chemistry ","volume":"77 1","pages":"6939-6947"},"PeriodicalIF":2.781,"publicationDate":"2011-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75839125","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}
Michael Busby, A. Devaux, C. Blum, V. Subramaniam, G. Calzaferri, L. Cola
Supramolecularly organized host guest systems have been prepared by inserting three perylene dyes with differing end substituents into the nanosized channels of zeolite L (ZL) by gas-phase adsorption under vacuum conditions. The end substituents allowed controlling the core-to-core distances of the molecules in the channels. The three perylene dyes investigated have very similar absorption and fluorescence spectra in diluted solutions, as well as fluorescence lifetimes ∼ 4 ns. Large ZL crystals in the size range of 1500−3000 nm in length and about 1000 nm in diameter as well as nanosized NZL crystals of about 30 nm in length and diameter were used as hosts. Different loadings have been investigated. The photophysical properties of the materials were analyzed as suspensions in refractive index matching solvents, such as toluene or ethyl benzoic acid ester; as bulk materials in glass ampules; and by means of time-, space-, and spectrally resolved single-crystal fluorescence microspectrocopy techniques. The inserted dyes can form J-aggregates if the structure of the perylene derivative allows for short distances between the electronic transition moments in an in-line arrangement. J-coupling was not seen for the molecules with substituents that keep them further apart. Aligned and stabilized J-aggregates in one-dimensional channels provide new options for preparing optical devices, where coherent exciton delocalization over nanometer-to-micrometer scales may result in efficient photonic wires. The exciton coupling can be controlled by varying the molecular tail groups.
{"title":"Interactions of Perylene Bisimide in the One Dimensional Channels of Zeolite L","authors":"Michael Busby, A. Devaux, C. Blum, V. Subramaniam, G. Calzaferri, L. Cola","doi":"10.1021/JP1108625","DOIUrl":"https://doi.org/10.1021/JP1108625","url":null,"abstract":"Supramolecularly organized host guest systems have been prepared by inserting three perylene dyes with differing end substituents into the nanosized channels of zeolite L (ZL) by gas-phase adsorption under vacuum conditions. The end substituents allowed controlling the core-to-core distances of the molecules in the channels. The three perylene dyes investigated have very similar absorption and fluorescence spectra in diluted solutions, as well as fluorescence lifetimes ∼ 4 ns. Large ZL crystals in the size range of 1500−3000 nm in length and about 1000 nm in diameter as well as nanosized NZL crystals of about 30 nm in length and diameter were used as hosts. Different loadings have been investigated. The photophysical properties of the materials were analyzed as suspensions in refractive index matching solvents, such as toluene or ethyl benzoic acid ester; as bulk materials in glass ampules; and by means of time-, space-, and spectrally resolved single-crystal fluorescence microspectrocopy techniques. The inserted dyes can form J-aggregates if the structure of the perylene derivative allows for short distances between the electronic transition moments in an in-line arrangement. J-coupling was not seen for the molecules with substituents that keep them further apart. Aligned and stabilized J-aggregates in one-dimensional channels provide new options for preparing optical devices, where coherent exciton delocalization over nanometer-to-micrometer scales may result in efficient photonic wires. The exciton coupling can be controlled by varying the molecular tail groups.","PeriodicalId":58,"journal":{"name":"The Journal of Physical Chemistry ","volume":"40 1","pages":"5974-5981"},"PeriodicalIF":2.781,"publicationDate":"2011-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81942904","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 finite element method (FEM) was used to solve the time-harmonic Maxwell equations to calculate full infrared (IR) absorption spectra of organic substances near particles adsorbed to a silicon/air interface mimicking a surface-enhanced infrared absorption spectroscopy (SEIRAS) experiment in internal reflection geometry. An enhancement factor attributed to the presence of the metal has been defined, and its dependence on the particle size and arrangement has been studied. The enhancement factor was found to increase with increasing particle size. Contributions of parts of the surface to the overall absorbance has been analyzed through the electric field patterns and by placing a probe material in the region to be analyzed. For isolated particles, the gap between particle and surface has a large contribution to the overall spectrum. Further, large contributions were found from the regions between touching particles. An experiment probing gold particles on a silicon surface using attenuated total internal...
{"title":"Computation of surface-enhanced infrared absorption spectra of particles at a surface through the Finite Element Method","authors":"G. Vasan, Ying Chen, A. Erbe","doi":"10.1021/JP108667K","DOIUrl":"https://doi.org/10.1021/JP108667K","url":null,"abstract":"The finite element method (FEM) was used to solve the time-harmonic Maxwell equations to calculate full infrared (IR) absorption spectra of organic substances near particles adsorbed to a silicon/air interface mimicking a surface-enhanced infrared absorption spectroscopy (SEIRAS) experiment in internal reflection geometry. An enhancement factor attributed to the presence of the metal has been defined, and its dependence on the particle size and arrangement has been studied. The enhancement factor was found to increase with increasing particle size. Contributions of parts of the surface to the overall absorbance has been analyzed through the electric field patterns and by placing a probe material in the region to be analyzed. For isolated particles, the gap between particle and surface has a large contribution to the overall spectrum. Further, large contributions were found from the regions between touching particles. An experiment probing gold particles on a silicon surface using attenuated total internal...","PeriodicalId":58,"journal":{"name":"The Journal of Physical Chemistry ","volume":"39 1","pages":"3025-3033"},"PeriodicalIF":2.781,"publicationDate":"2011-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74945249","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}
Xi Chen, Wanhong Ma, Jing Li, Zhaohui Wang, Chungcheng Chen, Hongwei Ji, Jincai Zhao
A red iron(II) 4,4′-dicarboxy-2,2′-bipyridine complex ([FeII(dcbpy)3]) was investigated as an extraordinary Fenton catalyst capable of activating much more molecular O2 to mineralize organic pollutants in water at biocompatible pH values under visible irradiation. Eight representative organic pollutants were effectively degraded in the presence of this catalyst with high turnover number (368−2000). The flexible bifunctional coordination mode (N donor for ferrous ion and O donor for ferric form) devoted by the ligand dcbpy should be responsible for the preservation of iron(II/III) catalysis in such a neutral pH condition, whereas any substitution of the 4,4′-carboxylic groups in dcbpy by other groups such as ether, alcohol, nitroyl, or methyl groups resulted in nearly total loss of catalytic stability. More important, the present [FeII(dcbpy)3] catalyst can dramatically change the traditional role ofH2O2 as main oxidant in the general Fenton reaction and make molecular O2 become the main oxidant in the min...
{"title":"Photocatalytic Oxidation of Organic Pollutants Catalyzed by an Iron Complex at Biocompatible pH Values: Using O2 as Main Oxidant in a Fenton-like Reaction","authors":"Xi Chen, Wanhong Ma, Jing Li, Zhaohui Wang, Chungcheng Chen, Hongwei Ji, Jincai Zhao","doi":"10.1021/JP110277K","DOIUrl":"https://doi.org/10.1021/JP110277K","url":null,"abstract":"A red iron(II) 4,4′-dicarboxy-2,2′-bipyridine complex ([FeII(dcbpy)3]) was investigated as an extraordinary Fenton catalyst capable of activating much more molecular O2 to mineralize organic pollutants in water at biocompatible pH values under visible irradiation. Eight representative organic pollutants were effectively degraded in the presence of this catalyst with high turnover number (368−2000). The flexible bifunctional coordination mode (N donor for ferrous ion and O donor for ferric form) devoted by the ligand dcbpy should be responsible for the preservation of iron(II/III) catalysis in such a neutral pH condition, whereas any substitution of the 4,4′-carboxylic groups in dcbpy by other groups such as ether, alcohol, nitroyl, or methyl groups resulted in nearly total loss of catalytic stability. More important, the present [FeII(dcbpy)3] catalyst can dramatically change the traditional role ofH2O2 as main oxidant in the general Fenton reaction and make molecular O2 become the main oxidant in the min...","PeriodicalId":58,"journal":{"name":"The Journal of Physical Chemistry ","volume":"61 1","pages":"4089-4095"},"PeriodicalIF":2.781,"publicationDate":"2011-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79846042","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}
T. Kar, S. Patnaik, H. Bettinger, A. Roy, S. Scheiner
Vibrational frequencies of functionalized groups (−COOH, −CONH2, and −COOCH3) of tip-modified single-wall carbon nanotubes are estimated using density functional theory. Both metallic (5,5) and semiconducting (10,0) nanotubes are considered with single and multiple functional groups at their tip. Several differences in frequency and intensity of the characteristic C═O band between (5,5) and (10,0) tubes are observed, which might help experimentalists to identify different tubes. For example, (5,5) tubes exhibit higher C═O frequencies than (10,0) tubes for all groups, and these bands are more intense in the latter tubes. These differences persist within a narrow range of diameter. To understand the effect of nanotubes on the spectra, fragment models containing parts of tube attached to functional groups are also studied. Such a computationally inexpensive model (compared to full tube) faithfully reproduces IR spectra and may be used for a wide range of end-modified tubes.
{"title":"IR Characterization of Tip-Functionalized Single-Wall Carbon Nanotubes","authors":"T. Kar, S. Patnaik, H. Bettinger, A. Roy, S. Scheiner","doi":"10.1021/JP104883E","DOIUrl":"https://doi.org/10.1021/JP104883E","url":null,"abstract":"Vibrational frequencies of functionalized groups (−COOH, −CONH2, and −COOCH3) of tip-modified single-wall carbon nanotubes are estimated using density functional theory. Both metallic (5,5) and semiconducting (10,0) nanotubes are considered with single and multiple functional groups at their tip. Several differences in frequency and intensity of the characteristic C═O band between (5,5) and (10,0) tubes are observed, which might help experimentalists to identify different tubes. For example, (5,5) tubes exhibit higher C═O frequencies than (10,0) tubes for all groups, and these bands are more intense in the latter tubes. These differences persist within a narrow range of diameter. To understand the effect of nanotubes on the spectra, fragment models containing parts of tube attached to functional groups are also studied. Such a computationally inexpensive model (compared to full tube) faithfully reproduces IR spectra and may be used for a wide range of end-modified tubes.","PeriodicalId":58,"journal":{"name":"The Journal of Physical Chemistry ","volume":"452 1","pages":"20955-20961"},"PeriodicalIF":2.781,"publicationDate":"2010-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86992829","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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