Hierarchic patterning: architectures beyond ‘giant molecular wheels’

Müller, Achim; Diemann, E.; Kuhlmann, Christoph; Eimer, Wolfgang; Serain, Claire; Tak, Taehyun; Knöchel, A.; Pranzas, P. Klaus

doi:10.1039/b103639b

Cited by 86 publications

(82 citation statements)

References 5 publications

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“…24 We used FlFFF to monitor the evolution of molybdate nanoparticles in a {Mo 132 } suspension prepared by Müller's procedure. 7,15,16 Under our FlFFF conditions, 25 soluble species and particles smaller than 3 nm are swept to the waste stream by the cross-flow, while larger particles are separated and eluted through a UV-visible detector. FlFFF fractograms monitoring the absorbance of the eluate at 455 nm are shown in Figure 1b.…”

mentioning

confidence: 99%

Monitoring the Growth of Polyoxomolybdate Nanoparticles in Suspension by Flow Field-Flow Fractionation

et al. 2005

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Reduction reactions of molybdate in acidic, aqueous solution lead to colored, mixed-valent Mo V/VI polyoxomolybdate (POM) species. [1][2][3][4][5] The two-century-old mystery of the "molybdenum blues" 6 exemplifies the difficulty in characterizing suspensions of POM particles. Müller, Liu, and co-workers revealed the fundamental compositions of the related "molybdenum browns", including I h symmetrical keplerates. In general, reduced molybdates assemble into nanometric species (Figure 1a). Light-scattering, small-angle X-ray scattering (SAXS), and microscopy show slow aggregation of Na 15 The key methodology of our study is field-flow fractionation (FFF), a flow-based, chromatography-like separation and sizing technique that can monitor changes in the particle-size distribution of a suspension in situ. FFF is conducted in a thin, empty channel, with separation based on relative hydrodynamic behavior. [21][22][23] In flow field-flow fractionation (FlFFF), a cross-flow perpendicular to the direction of laminar channel flow forces dissimilar particles to different levels in the channel, where they are eluted at different flow velocities. FlFFF fractionates particles between 1 and 1000 nm and allows analysis of the eluate. 24 We used FlFFF to monitor the evolution of molybdate nanoparticles in a {Mo 132 } suspension prepared by Müller's procedure. 7,15,16 Under our FlFFF conditions, 25 soluble species and particles smaller than 3 nm are swept to the waste stream by the cross-flow, while larger particles are separated and eluted through a UV-visible detector. FlFFF fractograms monitoring the absorbance of the eluate at 455 nm are shown in Figure 1b.The particle-size distributions calculated 26 from the data in Figure 1b have diameters ranging from 3 to 75 nm, roughly distributed in three populations with maxima about 3.4, 12, and 25 nm. The mean diameter is 31((1) nm (confidence level 95%), averaged over 24 FFF runs from 8 days. The baseline fractogram at 10 min indicates that no particles over ca. 3 nm had yet formed. At 2 h, the 3.4-nm population is largest. The total area under the fractogram increases rapidly from 2 to 8 h, at which time the 12-and 25-nm populations are larger. We suggest that the 3.4-nm particles, decreasing after 2 h but observed consistently throughout the entire period, are the {Mo 132 } with their associated counterions and solvation shell. The overall particle population reaches a maximum at ca. 8 h, decreases rapidly for about 2 days and more slowly thereafter (Figure 1b). The decrease parallels the precipitation of large particles that are not sampled by FlFFF shown in the SEM 27 image in Figure 2a. The precipitate is in dynamic equilibrium with species still in solution or suspension, yielding after several days ca. 0.1-mm octahedral crystals of {Mo 132 }, Fm3 with a ≈ 46 Å, 15 shown in Figure 2b.The particle-size distribution of the molybdate suspension was corroborated by AFM, SEM, and HRTEM. Good agreement between particle-size distributions obtained by FFF and microscopy suggests t...

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Monitoring the Growth of Polyoxomolybdate Nanoparticles in Suspension by Flow Field-Flow Fractionation

et al. 2005

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“…Thus upon photoreduction, a molybdenum blue dispersion is generated. [49,50] The blue colour is attributed to an intervalence charge transfer between Mo V and Mo VI centres of the Mo 154 -type molybdenum blue units generated in the dispersion following photoreduction in the molybdenum blue dispersion. Because of the small volume fraction of these SOMs, coupled with their large size, a detailed spectroscopic determination of the chemical nature of these SOMs was not possible.…”

Section: Topological Transformation From Rod To Sphere: Reasons Of Chmentioning

confidence: 99%

“…Such photochemical transformation would provide a system of SOM nanorods with ring-shaped building units such as that of [Mo 154 ] generated in the course of photochemical reduction in molybdenum blue, [32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50] which, in turn, can be centres of C 5 dislocations and can tile a spherical surface. [34,49,50] In this work we used heptamolybdate-based SOMs to show that such topological transformation into SOM spheres is possible. We also demonstrate intermediate stages of sphero-cylinders as the transformation proceeds from rods to spheres.…”

Section: Introductionmentioning

confidence: 99%

Photoinduced Topological Transformation in Mesoscopic Inorganic Nanoparticles: Application as a UV Sensor

2014

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“…Liu's group has made prominent contributions in studies of aggregation behaviors about polyoxometalate and POM-based complexes. Many of the nanometer-scaled giant polyoxometalate macroanions usually do not exist as single ions even in dilute solution [21]. Instead, they tend to self-associate into a more stable, hollow, spherical, single-layer ''blackberry'' structure [22,23].…”

Section: Self-assembly Of Modified Polyoxometalate Complexesmentioning

confidence: 99%

Assembly of Polyoxometalate-Based Composite Materials

Fan

Hao

Wei

2012

J Inorg Organomet Polym

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This paper is a review the polyoxometalatebased composite materials, including polyoxometalate incorporated Langmuir and Langmuir-Blodgett, layerby-layer multilayers and novel honeycomb films, selfassembly structures of modified polyoxometalate complexes (e.g., onion-like structures, new inorganic-organic-inorganic vesicles, thermotropic and lyotropic liquid crystalline structures, gels), and amino acid-and protein-polyoxometalate nanorods and nanoparticles. Polyoxometalate-embedded layer-by-layer multilayer films show electrocatalytic or photochemical activity; and, novel photoluminescent honeycomb films templated by microwater droplets are reviewed. Inorganic-organic-inorganic hybrid vesicles display the potential as nano-switches. In addition, amino acid-and proteinpolyoxometalate composite nanostructures indicate potential antimicrobial applications. Therefore, the polyoxometalatebased composite materials have promising applications in electrochemistry, photochemistry and biomedicine.

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Hierarchic patterning: architectures beyond ‘giant molecular wheels’

Cited by 86 publications

References 5 publications

Monitoring the Growth of Polyoxomolybdate Nanoparticles in Suspension by Flow Field-Flow Fractionation

Monitoring the Growth of Polyoxomolybdate Nanoparticles in Suspension by Flow Field-Flow Fractionation

Photoinduced Topological Transformation in Mesoscopic Inorganic Nanoparticles: Application as a UV Sensor

Assembly of Polyoxometalate-Based Composite Materials

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