The conditions under which an oxide surface in aqueous solution will obey the Nernst equation with respect to H+/OH– as potential-determining ions are investigated and a modified form of the Nernst equation is derived. This is combined with a model of the inner part of the double layer involving adsorption of both anions and cations of a supporting uni-univalent electrolyte and a discreteness-of-charge correction in their adsorption isotherms. Theoretical total differential capacities at the interface are compared with experimental data for TiO2 and SiO2.
{"title":"Theory of the differential capacity of the oxide/aqueous electrolyte interface","authors":"S. Levine, A. L. Smith","doi":"10.1039/DF9715200290","DOIUrl":"https://doi.org/10.1039/DF9715200290","url":null,"abstract":"The conditions under which an oxide surface in aqueous solution will obey the Nernst equation with respect to H+/OH– as potential-determining ions are investigated and a modified form of the Nernst equation is derived. This is combined with a model of the inner part of the double layer involving adsorption of both anions and cations of a supporting uni-univalent electrolyte and a discreteness-of-charge correction in their adsorption isotherms. Theoretical total differential capacities at the interface are compared with experimental data for TiO2 and SiO2.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"112 1","pages":"290-301"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76541707","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}
Dark conductivity and photovoltaic effects have been investigated in thin film samples of chlorophyll a. Samples were fabricated by depositing monomolecular layers of chlorophyll a on to conducting glass and metal substrates. The dependence of the dark current on temperature and voltage in 10 monolayer samples at low voltages (< 500 mV) is consistent with a conductivity tunnelling process. At higher voltages the conductivity characteristics are consistent with conductivity tunnelling, Schottky emission and the Frenkel-Poole effect. An enhanced photovoltaic effect is found in chlorophyll a films (100 monolayers) composited with electron acceptor and donor materials. The results are discussed in terms of energy migration in photosynthetic units.
{"title":"Electrical characteristics of chlorophyll a films","authors":"P. J. Reucroft, W. H. Simpson","doi":"10.1039/DF9715100202","DOIUrl":"https://doi.org/10.1039/DF9715100202","url":null,"abstract":"Dark conductivity and photovoltaic effects have been investigated in thin film samples of chlorophyll a. Samples were fabricated by depositing monomolecular layers of chlorophyll a on to conducting glass and metal substrates. The dependence of the dark current on temperature and voltage in 10 monolayer samples at low voltages (< 500 mV) is consistent with a conductivity tunnelling process. At higher voltages the conductivity characteristics are consistent with conductivity tunnelling, Schottky emission and the Frenkel-Poole effect. An enhanced photovoltaic effect is found in chlorophyll a films (100 monolayers) composited with electron acceptor and donor materials. The results are discussed in terms of energy migration in photosynthetic units.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"1 1","pages":"202-211"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79498809","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}
Phonon modes in aromatic hydrocarbon crystals are classified to guide discussion of the electron-phonon interaction. The principal qualitative electron-phonon effects on charge carrier transport arise from the exchange integral variations due to lattice modes and from the binding energy due to frequency changes in out-of-plane molecular modes; other lattice and molecular modes have quantitative effects. The use of linear-response theory to calculate the conductivity for the two principal interactions is described. Each calculation embodies results applicable in the region intermediate between hopping and band transport, but as yet neither is completely analyzed in this region. Nevertheless, the fundamental processes governing charge carrier transport in these crystals now appear to be understood.
{"title":"Theory of electron-phonon interactions in organic crystals. Effect on charge carrier transport","authors":"R. Munn, W. Siebrand","doi":"10.1039/DF9715100017","DOIUrl":"https://doi.org/10.1039/DF9715100017","url":null,"abstract":"Phonon modes in aromatic hydrocarbon crystals are classified to guide discussion of the electron-phonon interaction. The principal qualitative electron-phonon effects on charge carrier transport arise from the exchange integral variations due to lattice modes and from the binding energy due to frequency changes in out-of-plane molecular modes; other lattice and molecular modes have quantitative effects. The use of linear-response theory to calculate the conductivity for the two principal interactions is described. Each calculation embodies results applicable in the region intermediate between hopping and band transport, but as yet neither is completely analyzed in this region. Nevertheless, the fundamental processes governing charge carrier transport in these crystals now appear to be understood.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"105 1","pages":"17-23"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75396459","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}
Since Eugene Houdry discovered some clays to be excellent catalysts for the “cracking” of heavy oils, the surface properties of silica-alumina combinations have been studied in various places and from various angles. The surface properties of silica-alumina-combinations differ in many ways from those of silica or of alumina, as such. Three different procedures for preparing the silica-aluminas may be mentioned, viz., (a) adsorption (chemisorption) of aluminium hydroxide on a wet silica surface, (b) precipitation of aluminium hydroxide on a wet silica gel, (c) co-gelling of a silica acid-and an aluminium salt solution. The influence of the alumina adsorption on the specific surface area, as measured with the B.E.T.-method and with the lauric acid method will be discussed. An attempt is made to give a picture of the binding of aluminium hydroxide on the silica, which leads to three possibilities, depending on the relative amount of both constituents. One of these possibilities leads to preparations with an acid character.
{"title":"Constitution and properties of silica-alumina-catalysts","authors":"J. Boer","doi":"10.1039/DF9715200109","DOIUrl":"https://doi.org/10.1039/DF9715200109","url":null,"abstract":"Since Eugene Houdry discovered some clays to be excellent catalysts for the “cracking” of heavy oils, the surface properties of silica-alumina combinations have been studied in various places and from various angles. The surface properties of silica-alumina-combinations differ in many ways from those of silica or of alumina, as such. Three different procedures for preparing the silica-aluminas may be mentioned, viz., (a) adsorption (chemisorption) of aluminium hydroxide on a wet silica surface, (b) precipitation of aluminium hydroxide on a wet silica gel, (c) co-gelling of a silica acid-and an aluminium salt solution. The influence of the alumina adsorption on the specific surface area, as measured with the B.E.T.-method and with the lauric acid method will be discussed. An attempt is made to give a picture of the binding of aluminium hydroxide on the silica, which leads to three possibilities, depending on the relative amount of both constituents. One of these possibilities leads to preparations with an acid character.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"15 1","pages":"109-112"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72784318","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}
Adsorption and catalysis at the surface of metal oxides is directly related to the electronic constitution in the vicinity of the surface not merely in terms of the predominant electronic character but more importantly the complex assembly of trapping electronic states. Experimental techniques have been developed using both thermally stimulated electron current measurements and thermal glow curves to establish in detail the complex distribution of electronic states. They can lead to quantitative information on both the position and occupancy of trapping states. Preliminary correlation has also been established between trapping states and simple adsorption phenomena. Detailed characteristics have been established for various samples of very high purity zinc oxide and TiO2 including a study of the effect of controlled impurities at a level of a few p.p.m. and variations due to particle size. Direct correlation is made with the adsorption of gases, simple catalytic reactions, the interaction with binders used in electron photography and general characteristics of electron photographic coatings.
{"title":"Surface electronic structure of oxides as established by thermally stimulated electron current measurements","authors":"T. J. Gray, N. Lowery","doi":"10.1039/DF9715200132","DOIUrl":"https://doi.org/10.1039/DF9715200132","url":null,"abstract":"Adsorption and catalysis at the surface of metal oxides is directly related to the electronic constitution in the vicinity of the surface not merely in terms of the predominant electronic character but more importantly the complex assembly of trapping electronic states. Experimental techniques have been developed using both thermally stimulated electron current measurements and thermal glow curves to establish in detail the complex distribution of electronic states. They can lead to quantitative information on both the position and occupancy of trapping states. Preliminary correlation has also been established between trapping states and simple adsorption phenomena. Detailed characteristics have been established for various samples of very high purity zinc oxide and TiO2 including a study of the effect of controlled impurities at a level of a few p.p.m. and variations due to particle size. Direct correlation is made with the adsorption of gases, simple catalytic reactions, the interaction with binders used in electron photography and general characteristics of electron photographic coatings.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"15 1","pages":"132-139"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74910876","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}
Streaming potential data for the vitreous silica/aqueous electrolyte interface have been obtained to yield the ζ potential variation with pH as a function of the concentration of KNO3, Ba(NO3)2 and La(NO3)3 solutions. The results have been interpreted in terms of the Gouy-Chapman-Stern theory, modified to include discreteness of charge effects, to account for the observed maxima in |ζ| with pH for adsorbed Ba2+ and La3+. For satisfactory agreement between theory and experiment it was necessary to add a term to account for the change in the free energy of solvation as the multicharged cations adsorb at the silica/water interface.
{"title":"Discreteness of charge and solvation effects in cation adsorption at the oxide/water interface","authors":"G. Wiese, R. James, T. Healy","doi":"10.1039/DF9715200302","DOIUrl":"https://doi.org/10.1039/DF9715200302","url":null,"abstract":"Streaming potential data for the vitreous silica/aqueous electrolyte interface have been obtained to yield the ζ potential variation with pH as a function of the concentration of KNO3, Ba(NO3)2 and La(NO3)3 solutions. The results have been interpreted in terms of the Gouy-Chapman-Stern theory, modified to include discreteness of charge effects, to account for the observed maxima in |ζ| with pH for adsorbed Ba2+ and La3+. For satisfactory agreement between theory and experiment it was necessary to add a term to account for the change in the free energy of solvation as the multicharged cations adsorb at the silica/water interface.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"45 1","pages":"302-311"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82211529","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 review is given of some advances since 1967 in this field as it applies to homomolecular crystals of the anthracene type. The topics discussed include carrier generation and recombination, carrier motion and trapping, and the relationship between these processes and the observed current-voltage dependence in the crystal.
{"title":"Photoconductivity and semiconductivity in organic crystals","authors":"M. Pope, H. Kallmann","doi":"10.1039/DF9715100007","DOIUrl":"https://doi.org/10.1039/DF9715100007","url":null,"abstract":"A review is given of some advances since 1967 in this field as it applies to homomolecular crystals of the anthracene type. The topics discussed include carrier generation and recombination, carrier motion and trapping, and the relationship between these processes and the observed current-voltage dependence in the crystal.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"14 1","pages":"7-16"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80802683","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 surface chemistry of pure AlPO4 was studied by infra-red spectroscopy in an attempt to explain why this material shows low catalytic activity despite its high acidity. Two major bands (3680 and 3800 cm–1) in spectra of dry AlPO4 were shown to represent chemically distinct types of surface OH groups. The band at 3800 cm–1 is assigned to Al—OH and that at 3680 cm–1 to P—OH. Study of adsorbed NH3 and pyridine showed both Lewis and Bronsted acid sites on the surface. Chemisorption of NH3 also produced NH2 and OH groups, showing the presence of “strained” oxide links. Adsorption of CO2 and HCI revealed very few “α-sites” or reactive surface oxide ions. The evidence suggests that the surface largely resembles a prism face (10text-decoration:overline10) of tridymite-form AlPO4, holding vicinal pairs of OH groups, with one group attached to Al and the other to P. Condensation produces acidic Al—O—P links in which O is held primarily by the P atom. The inactivity of AlPO4 probably reflects the inadequacy of PO groups as base sites rather than a lack of suitable acid sites.
用红外光谱研究了纯AlPO4的表面化学性质，试图解释为什么这种材料在高酸度的情况下表现出低催化活性。干燥AlPO4光谱中的两个主要波段(3680和3800 cm-1)显示了化学上不同类型的表面OH基团。3800 cm-1的波段分配给Al-OH, 3680 cm-1的波段分配给P-OH。对吸附NH3和吡啶的研究表明，表面存在Lewis和Bronsted酸位点。NH3的化学吸附也产生了NH2和OH基团，显示出“张力”氧化键的存在。对CO2和HCI的吸附显示很少有α-位点或活性表面氧化离子。证据表明，其表面很大程度上类似于三聚体形式的AlPO4的棱柱面，含有相邻的OH对，其中一个基团与Al相连，另一个与P相连。缩合产生酸性的Al - O - P连接，其中O主要由P原子保持。AlPO4的不活性可能反映了PO基团作为碱基的不足，而不是缺乏合适的酸位。
{"title":"Surface chemistry of AlPO4—a mixed oxide of Al and P","authors":"J. Peri","doi":"10.1039/DF9715200055","DOIUrl":"https://doi.org/10.1039/DF9715200055","url":null,"abstract":"The surface chemistry of pure AlPO4 was studied by infra-red spectroscopy in an attempt to explain why this material shows low catalytic activity despite its high acidity. Two major bands (3680 and 3800 cm–1) in spectra of dry AlPO4 were shown to represent chemically distinct types of surface OH groups. The band at 3800 cm–1 is assigned to Al—OH and that at 3680 cm–1 to P—OH. Study of adsorbed NH3 and pyridine showed both Lewis and Bronsted acid sites on the surface. Chemisorption of NH3 also produced NH2 and OH groups, showing the presence of “strained” oxide links. Adsorption of CO2 and HCI revealed very few “α-sites” or reactive surface oxide ions. The evidence suggests that the surface largely resembles a prism face (10text-decoration:overline10) of tridymite-form AlPO4, holding vicinal pairs of OH groups, with one group attached to Al and the other to P. Condensation produces acidic Al—O—P links in which O is held primarily by the P atom. The inactivity of AlPO4 probably reflects the inadequacy of PO groups as base sites rather than a lack of suitable acid sites.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"2 1","pages":"55-65"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81892057","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}
{"title":"Catalytic activity of organic semiconductors and enzymes.","authors":"H Inokuchi","doi":"10.1039/df9715100183","DOIUrl":"https://doi.org/10.1039/df9715100183","url":null,"abstract":"","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"51 ","pages":"183-9"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1039/df9715100183","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"16224383","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 vibrating condenser method was applied for measurement of the contact potential difference with organic crystals. It gave work functions of reasonable values for aromatic hydrocarbon crystals. From the work function, combined with other observable parameters, an energy diagram for the crystals can be constructed, which indicates that the location of the Fermi level is slightly different from that of the intrinsic level. Supplementary experiments on the photoelectromotive force due to the Dember effect and the photovoltaic effect in violanthrene crystal, gave results consistent with the above conclusion, indicating the hole conduction.
{"title":"Contact potential difference and work function of organic crystals","authors":"M. Kotani, H. Akamatu","doi":"10.1039/DF9715100094","DOIUrl":"https://doi.org/10.1039/DF9715100094","url":null,"abstract":"The vibrating condenser method was applied for measurement of the contact potential difference with organic crystals. It gave work functions of reasonable values for aromatic hydrocarbon crystals. From the work function, combined with other observable parameters, an energy diagram for the crystals can be constructed, which indicates that the location of the Fermi level is slightly different from that of the intrinsic level. Supplementary experiments on the photoelectromotive force due to the Dember effect and the photovoltaic effect in violanthrene crystal, gave results consistent with the above conclusion, indicating the hole conduction.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"64 1","pages":"94-101"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77224842","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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