Physical aspects of photochemistry and radiation chemistry of molecules adsorbed on silica, .gamma.-alumina, zeolites, and clays

Thomas, J. K.

doi:10.1021/cr00017a014

Cited by 334 publications

(262 citation statements)

References 43 publications

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“…Good examples of this are photochemical studies of polycyclic aromatic hydrocarbons, ketones, and dyes, among others, on solid powdered substrates, such as hydrophobic or hydrophilic zeolites, 4 silicas with different porosities, 1a aluminas, and silica-aluminas. 5 Supramolecular studies of probes within cavities of cyclodextrins 6 or calixarenes 7,8 should also be mentioned, among other supramolecular studies.…”

Section: Introductionmentioning

confidence: 99%

Luminescence Lifetime Distributions Analysis in Heterogeneous Systems by the Use of Excel's Solver

Branco¹,

Rego²,

Machado³

et al. 2005

J. Phys. Chem. B

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A detailed study of the luminescence decay curves of pyrene included within p-tert-butylcalix [4]arene cavities and benzophenone into silicalite channels is reported. A new methodology for a lifetime distribution analysis of the decay curve of probes onto heterogeneous surfaces is presented, which allows for asymmetric distributions and uses Voigt profiles (Gaussian and Lorentzian mixture) instead of pure Gaussian or Lorentzian distributions. Our approach uses a very simple and widely available tool for fitting, the Microsoft Excel Solver. In the case of the pyrene/tert-butylcalix[4]arene sample, the room temperature luminescence detected in the microsecond time scale was not only the phosphorescence of pyrene but also monomer delayed fluorescence, crystal phosphorescence, and excimer delayed fluorescence. In the benzophenone/silicalite case, three emissive forms of benzophenone could be assigned, one of benzophenone included into the silicalite circular zigzag channels, another for emplacement into the elliptical straight channels and finally when benzophenone is placed at the crossing points of those silicalite channels, where smaller spatial restrictions for benzophenone exist.

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Section: Introductionmentioning

confidence: 99%

Luminescence Lifetime Distributions Analysis in Heterogeneous Systems by the Use of Excel's Solver

Branco¹,

Rego²,

Machado³

et al. 2005

J. Phys. Chem. B

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“…2, 3)34 ( 2 ) ( 3 ) Table 2 summarizes the effect of saponite clay, in comparison with other additives, on the photodimerization of the cyclic enones. The product ratio of HH-to HT-dimers in photolysis of 2a intercalated on saponite clay layers was as high as 17 (run 1), in stark contrast to the reaction in bulk solution (run 8) which proceeded only about one-tenth as fast as that on clay layers and predominantly affording anti-HT dimer.…”

Section: Photocyclodimerization Of Olefins In Claymentioning

confidence: 99%

The Photochemistry and Stereochemical Control of Clay-Intercalated Compounds.

Shichi

Takagi

2002

J. Syn. Org. Chem., Jpn.

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This article surveys investigations on stereospecific organic photoreactions utilizing well-organized aggregated structures of molecules formed in the interlayer spaces of inorganic layered host compounds. In the beginning sections, the chemical compositions and structural features of the layered hosts and their unique adsorption properties are described, as well as the aggregated structures of the guest molecules. The later sections describe various organic photoreactions, including [2+2] photocycloadditions, photopolymerization and the photopinacolization of aromatic olefins and/or aromatic ketones, while the stereochemistry of the photoreactions is discussed in relation to the aggregated structures of the guest molecules. Table 1. A representative LDH clay is hydrotalcite, which is naturally produced and consists only of octahedral unit cell sheets of magnesium hydroxide accompanied by differing amounts of aluminum (normally one-fourth of Mg(OH)2), as depicted in Figure 2. Divalent anions such as CO22-intercalated in LDH have difficulty being exchanged with foreign anions. Therefore, it can be dehydrated to magnesium aluminium oxide by heating at 450 t, losing the carbon dioxide. Then, it can be rapidly rehydrated, adsorbing various anions and reconstructing the hydrotalcite structure.1°'11 The simple structure of this LDH enables the artificial synthesis of various kinds of LDH with lattice metal ions such as Zn-Al, Co-Al, and Fe-Al, and can be applied to catalytic systems. ' However, appropriate treatment enables the intercalation reactions to proceed also in these clay minerals. The anisotropic nature of intercalated guest molecules has been observed since the beginning of clay chemistry. The adsorption property in clays permits the mutual interaction of the incorporated guests which form self-assembling molecular aggregates due to the two-dimensional layer surface in contrast to silica colloidal surfaces.15 The efficiency of the self-assembly interaction depends on the structure of the clay minerals and guest organic compounds, the kind and amount of exchangeable metallic ions, and the amount of intercalated water in the interlayers. Detailed information on the high dimensional structure of the guest molecules has been obtained by various spectroscopic analytical methods such as X-ray diffraction, neutron scattering or high-resolution electron microscopy, nuclear magnetic resonance (NMR),16 electron spin resonance (ESR),17 as well as polarized spectroscopies which are able to clarify the orientations of the guests within the layers.18 In addition, Messbauer spectroscopic analysis and ESCA have been employed to further elucidate the structures.19The pioneering work of Weiss has shown that a long alkyl chain containing ammonium ions is intercalated as an antiparallel oriented monolayer between the layers, which could then be changed to a bilayer by the dispersion of higher alcohol, similar to the case of LB film.2° Moreover, the bis (long chained alkyl) ammonium ions themselves form extremely sta...

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“…My approach toward efficient artificial LHSs is based on method (c), in which clay nanosheets are used as the host material to build the 2D dye assembly using host (nanosheet)-guest (molecule) interactions. A clay nanosheet [27][28][29][30][31], saponite, is an attractive material characterized by (1) nanostructured flat sheets that can be formed by elements with large Clarke numbers (expressing the average content of the chemical elements in the earth), (2) negatively charged surfaces, (3) exfoliation or stacking ability of individual nanosheets in water, and (4) optical transparency in the visible light region in the exfoliated state when the particle size is small (ca. < 200 nm).…”

Section: Introductionmentioning

confidence: 99%

Manipulation of supramolecular 2D assembly of functional dyes toward artificial light-harvesting systems

Ishida

2014

Pure and Applied Chemistry

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Abstract:In recent years, excellent research has revealed that light-harvesting systems (LHSs) are composed of beautifully aligned chlorophyll molecules; the regulated alignment of chlorophylls is responsible for the efficient and selective light-harvesting energy transfer processes in purple bacteria. This finding led to the construction of a regularly arranged assembly of functional dyes as a step toward fabricating artificial LHSs. While most approaches toward the construction of dye assemblies have depended on molecular interactions such as covalent, coordination, and hydrogen bonds, my approach involves guest-host interactions using an inorganic nanosheet as the host material. This short review presents the construction of a 2D dye assembly and its effective utilization in artificial light-harvesting applications. Owing to the highly stable and uniform 2D alignment of functional dyes on inorganic nanosheets, nearly 100 % singlet-singlet energy transfer and efficient light-harvesting were achieved. I believe that the results presented herein will contribute to the construction of efficient photochemical reaction systems in supramolecular host-guest assemblies, which may facilitate the realization of artificial photosynthesis.

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Physical aspects of photochemistry and radiation chemistry of molecules adsorbed on silica, .gamma.-alumina, zeolites, and clays

Cited by 334 publications

References 43 publications

Luminescence Lifetime Distributions Analysis in Heterogeneous Systems by the Use of Excel's Solver

Luminescence Lifetime Distributions Analysis in Heterogeneous Systems by the Use of Excel's Solver

The Photochemistry and Stereochemical Control of Clay-Intercalated Compounds.

Manipulation of supramolecular 2D assembly of functional dyes toward artificial light-harvesting systems

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