Vanadia−Silica Sol−Gel Derived Glass:  Factors Affecting Homogeneity and Morphology

Curran, Matthew D.; Pooré, Duke D.; Stiegman, A. E.

doi:10.1021/cm9802292

Cited by 21 publications

(31 citation statements)

References 24 publications

(37 reference statements)

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“…To obtain homogeneous materials reproducibly, conditions were optimized for the amount of water and the concentration and molar ratio of Co II and ferricyanide by following previously developed procedures 8. 9 In the optimized preparation, Co II nitrate was dissolved in methanol and added to tetramethylorthosilicate. Aqueous potassium ferricyanide was added to this solution to give a 1:1 Co:Fe molar ratio.…”

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confidence: 99%

Transparent, Superparamagnetic K${{{\rm I}\hfill \atop x\hfill}}$Co${{{\rm II}\hfill \atop y\hfill}}$[Fe^III(CN)₆]–Silica Nanocomposites with Tunable Photomagnetism

et al. 2003

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There has been considerable interest in molecular magnets based on the Prussian blue class of transition-metal cyanide complexes.[1] Pioneering work on these materials has realized a broad range of ferro-and ferrimagnetic solids with Curie points ranging from cryogenic to above room temperature. [2,3] A parallel interest also exists in the development of nanocomposite structures containing nanoscale magnetic particles exhibiting single-domain magnetic behavior. [4][5][6] Investigations of magnetic nanocomposites is driven by their novel properties and their potential as new magnetic, optical, and electronic materials. With one exception, [7] however, the Prussian blue class of magnetic materials has not been produced as nanoparticles, and, to the best of our knowledge, there have been no reports of their incorporation into composite structures. Herein we report the fabrication of a new nanocomposite material containingferromagnetic analogue of Prussian blue, in a porous silica matrix. This material is made by a controlled multicomponent sol-gel synthesis in which the precipitation of the Prussian blue analogue is arrested at nanoscale dimensions by gelation of the silica network. The resulting materials are homogeneous, optically transparent, and exhibit superparamagnetic and tunable photomagnetic behavior. We believe that this study suggests a new approach for utilizing the Prussian blue class of magnetic materials in advanced optical and magnetic applications.Homogeneous silica xerogels containing cyanide-bridged Co II /Fe III centers were made by incorporation of both transition-metal components during the solution phase of the synthesis. To obtain homogeneous materials reproducibly, conditions were optimized for the amount of water and the concentration and molar ratio of Co II and ferricyanide by following previously developed procedures. [8,9] In the optimized preparation, Co II nitrate was dissolved in methanol and added to tetramethylorthosilicate. Aqueous potassium ferricyanide was added to this solution to give a 1:1 Co:Fe molar ratio. Upon mixing, the solution turns dark purple, which suggests the formation of the mixed-valence complex. At concentrations up to 0.03 mol % total-metal to silicon (Fe + Co/Si), the solution remained transparent through gelation, aging, and drying, and ultimately yielded a homogeneous, optically transparent xerogel (Figure 1, inset). The spectrum of this glass (Figure 1) is qualitatively similar to that of the bulk materials, with a broad intervalence charge-transfer band in the visible region between 450 and 650 nm and a sharp, higher energy peak around 400 nm. However, the maximum of the intervalence band lies at 452 nm (22 124 cm À1 ) which is blue-shifted by approximately 2900 cm À1 from that of the bulk materials. To determine whether the magnetic behavior was singular, the magnetic susceptibility of these materials was measured as a function of temperature and field strength.[10] Bulk M

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Transparent, Superparamagnetic K${{{\rm I}\hfill \atop x\hfill}}$Co${{{\rm II}\hfill \atop y\hfill}}$[Fe^III(CN)₆]–Silica Nanocomposites with Tunable Photomagnetism

et al. 2003

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“…For the aerogel samples, the incorporation of silicon into the alumina network was demonstrated in a previous paper [10], leading to a more homogeneous material with better resistance to sintering and transformation into a-alumina. Homogeneous multicomponent systems are known, e.g., tetrahedrally coordinated silicon atoms are substituted by vanadium atoms (with reduction from V V to V IV ) in vanadia-silica sol-gel-derived materials prepared by co-condensation of the respective alkoxides, [18][19][20][21]. The similar coordination environments favor the formation of a homogeneous xerogel, which is not the case for the Si-doped boehmite sol-gel in which Si is in a tetrahedral environment and Al an octahedral one.…”

Section: Discussionmentioning

confidence: 99%

Platinum supported on doped alumina catalysts for propulsion applications. Xerogels versus aerogels

Courthéoux¹,

Popa²,

Gautron³

et al. 2004

Journal of Non-Crystalline Solids

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“…Alkoxides of various metals and metalloids (Si, Al, Ti, Zr, V, Ta, etc.) [116][117][118][119][120][121][122][123][124][125][126][127][128] have been used as sol-gel precursors to create a wide variety of sol-gel materials. Among them, silicon alkoxides are by far the most commonly used sol-gel precursors.…”

Section: Methodsmentioning

confidence: 99%

Advances in sol‐gel based columns for capillary electrochromatography: Sol‐gel open‐tubular columns

Malik

2002

Electrophoresis

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The development of sol-gel open-tubular column technology in capillary electrochromatography (CEC) is reviewed. Sol-gel column technology offers a versatile means of creating organic-inorganic hybrid stationary phases. Sol-gel column technology provides a general approach to column fabrication for microseparation techniques including CEC, and is amenable to both open-tubular and monolithic columns. Direct chemical bonding of the stationary phase to the capillary inner walls provides enhanced thermal and solvent stability to sol-gel columns. Sol-gel stationary phases inherently possess higher surface area, and thus provide an effective one-step alternative to conventional open-tubular column technology. Sol-gel column technology is applicable to both silica-based and transition metal oxide-based hybrid stationary phases, and thus, provides a great opportunity to utilize advanced material properties of a wide range of nontraditional stationary phases to achieve enhanced selectivity in analytical microseparations. A wide variety of stationary phase ligands can be chemically immobilized on the capillary inner surface using a single-step sol-gel procedure. Sol-gel chemistry can be applied to design stationary phases with desired chromatographic characteristics, including the possibility of creating columns with either a positive or a negative charge on the stationary phase surface. This provides a new tool to control electroosmotic flow (EOF) in the column. Column efficiencies on the order of half a million theoretical plates per meter have been reported for sol-gel open-tubular CEC columns. The selectivity of sol-gel stationary phases can be easily fine-tuned by adjusting the composition of the coating sol solution. Open-tubular columns have significant advantages over their packed counterparts because of the simplicity in column making and hassle-free fritless operation. Open-tubular CEC columns possess low sample capacity and low detection sensitivity. Full utilization of the analytical potential of sol-gel open-tubular columns will require a concomitant development in the area of high-sensitivity detection technology.

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Vanadia−Silica Sol−Gel Derived Glass: Factors Affecting Homogeneity and Morphology

Cited by 21 publications

References 24 publications

Transparent, Superparamagnetic K${{{\rm I}\hfill \atop x\hfill}}$Co${{{\rm II}\hfill \atop y\hfill}}$[Fe^III(CN)₆]–Silica Nanocomposites with Tunable Photomagnetism

Transparent, Superparamagnetic K${{{\rm I}\hfill \atop x\hfill}}$Co${{{\rm II}\hfill \atop y\hfill}}$[Fe^III(CN)₆]–Silica Nanocomposites with Tunable Photomagnetism

Platinum supported on doped alumina catalysts for propulsion applications. Xerogels versus aerogels

Advances in sol‐gel based columns for capillary electrochromatography: Sol‐gel open‐tubular columns

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Vanadia−Silica Sol−Gel Derived Glass: Factors Affecting Homogeneity and Morphology

Cited by 21 publications

References 24 publications

Transparent, Superparamagnetic K${{{\rm I}\hfill \atop x\hfill}}$Co${{{\rm II}\hfill \atop y\hfill}}$[FeIII(CN)6]–Silica Nanocomposites with Tunable Photomagnetism

Transparent, Superparamagnetic K${{{\rm I}\hfill \atop x\hfill}}$Co${{{\rm II}\hfill \atop y\hfill}}$[FeIII(CN)6]–Silica Nanocomposites with Tunable Photomagnetism

Platinum supported on doped alumina catalysts for propulsion applications. Xerogels versus aerogels

Advances in sol‐gel based columns for capillary electrochromatography: Sol‐gel open‐tubular columns

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Product

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Transparent, Superparamagnetic K${{{\rm I}\hfill \atop x\hfill}}$Co${{{\rm II}\hfill \atop y\hfill}}$[Fe^III(CN)₆]–Silica Nanocomposites with Tunable Photomagnetism

Transparent, Superparamagnetic K${{{\rm I}\hfill \atop x\hfill}}$Co${{{\rm II}\hfill \atop y\hfill}}$[Fe^III(CN)₆]–Silica Nanocomposites with Tunable Photomagnetism