Covalent Hybrid Materials Based on Nanolatex Particles and Dawson Polyoxometalates

Abstract

and a ring are seen, respectively. In some areas, bilayers are formed, and most of the particles seem to be registered with the underlying particles. It is also interesting to note that the mean particle size in the disordered region is slightly smaller than that in the ordered region, while the size dispersion in the disordered region is high compared to that in the ordered region. This observation is consistent with the general trend found in the literature that the degree of local order of deposited particles is strongly dependent on the average particle size, and that larger nanoparticles tend to form ordered structures more easily than their smaller counterparts. [19] This phenomenon is hallmarked by a smaller size distribution in the ordered region. We also see a sharp transition between the ordered monolayer region and the bare substrate region, suggesting that the lateral diffusion is mainly driven by the existence of a relatively stronger interaction between the nanoparticles than between the particles and the carbon substrate.In conclusion, we have successfully demonstrated that the incoherent electron imaging technique has great potential in characterizing the growth of ultrafine-nanoparticle thin films. It offers the possibility of directly visualizing the 3D topography of colloidal thin films at the nanometer scale. The relative simplicity of HAADF image interpretation compared with, say, conventional TEM or electron tomography [20] would be particularly welcome to non-specialists. Using the HAADF technique, we have identified an interesting growth mode of ultrafine Ag/Au bimetallic nanoparticles on an amorphous carbon film in ambient conditions, in which particles with different size or shape are segregated into ordered and disordered regions during the dewetting process. We show that the ordering of the first layer of nanoparticles is important to the subsequent layer growth. Further work is in progress to understand the possible kinetic and thermodynamic factors behind this observation. ExperimentalThe Ag/Au nanoparticles (with an average diameter of ∼4 nm) used in this study were prepared using the inverse-micelle method to form the Ag core and heterogeneous deposition of the Au shell atoms [21]. The particles were passivated by C 12 H 25 SH chain molecules and dispersed at 0.01 M concentration in toluene for storage. The thin film was prepared by the droplet-evaporation method: A droplet (1 lL) of the solution containing the nanoparticle dispersion was deposited on a Cu grid covered with an amorphous carbon film. The solvent was evaporated in ambient conditions. The grid with the nanoparticle thin film formed on it was then transferred into an FEI Tecnai F20 electron microscope with a field-emission gun. The system has a specially designed chamber with an additional cryogenic pump so as to approach an ultrahigh-vacuum environment around the specimen. Hybrid organic-inorganic systems have attracted widespread attention in the domain of materials science. The interest lies in the synergy between...

Syntheses, Characterization, and X‐ray Crystal Structures of Mono‐Lacunary Dawson Polyoxometalate‐Based Organosilyl Complexes

“…n-[T (isomer) = Si (α), Ge (α), Ga (a mixture of α and β); X = COOH, COOCH 3 , CONH 2 , CN; n = 5, 6]; [2] and organosilyl derivatives such as [α-SiW 11 O 40 (SiR) 2 ] 4-[R = C 2 H 5 , CH=CH 2 , C 10 H 21 , Ph, NC(CH 2 ) 3 , C 3 H 5 ], [12] [α 2 -P 2 W 17 O 61 {O(SiR) 2 }] 6-{R = C 6 H 5 , 4-[(C 2 H 5 O) 2 P(=O)-CH 2 ]-C 6 H 4 , C 3 H 6 SH}, [13,14] [γ-PW 10 O 36 (tBuSiOH) 2 ] 3-, [15] [γ-PW 10 O 36 (tBuSiO) 2 (SiMe 2 )] 3-, [15] [γ-SiW 10 3 ], [16] [α-A-PW 9 O 34 (tBuSiO) 3 [17,18] [α-A-TW 9 O 34 -(R 2 Si) 3 ] n-(T = Si, P; R = Me, Ph; n = 3,4), [18] [α-A-PW 9 O 34 (tBuSiOH) 3 ] 3-, [18] [α-B-AsW 9 O 33 (tBuSiOH) 3 ] 3-, [18] [α-B-AsW 9 O 33 (tBuSiO) 3 (RSi)] 3-, [18] [α-A-TW 9 O 34 (RSiO) 3 -(RSi)]…”

Design of Hydrophobic Polyoxometalate Hybrid Assemblies Beyond Surfactant Encapsulation

“…[3] Polyoxometalate clusters cover an enormous size range and comprise conserved/transferable building blocks; it is this feature that means they hold considerable promise for the controlled assembly of large nanostructures and framework materials. [4] The synthesis of organic-inorganic hybrid POMs has attracted widespread attention in the domain of materials science since the nanoscale clusters, which are highly anionic, are perfect scaffolds for the development of hybrid assemblies, though direct covalent modification of POMs is rare and only a few POM clusters including [Mo 6 O 19 ] 2À , [5] a 1 /a 2 -[P 2 W 17 O 61 ] 10À , [6][7] some organophosphoryl [8] and organosilyl [9] derivatives of lacunary POM clusters have been covalently functionalized to date. [10] As these hybrid materials will combine not only the advantages of or-A C H T U N G T R E N N U N G ganic components and inorganic clusters, but also the close interaction and synergistic effect between them, it is of great interest to develop such organic-inorganic hybrids through covalent functionalization.…”

In Quest of a Systematic Framework for Unifying and Defining Nanoscience

“…Core-shell-type nanolatex: polyoxometalates (POM) compounds have been readily synthesized in aqueous solvents by the covalent attachment of thiol- Schmid et al (2000), , Srivastava et al (2005), Shi et al ( , 2007, Wilcoxon and Abrams (2006), and Knecht and Crooks ( Superscript numbers for nanocompounds [S-n:H-n] 1-15 above are keyed to literature references and correspond to the bold numbers noted in the nanocompound grid (Table 4) J Nanopart Res (2009Res ( ) 11:1251Res ( -1310Res ( 1281 functionalized POMs to chlorobenzyl-functionalized [S-2]-type nanolatex element surfaces (Cannizzo et al 2005). Solutions of these nanocompounds did not exhibit significant aggregation even after several months.…”