Dispersed Molecular Aggregates

Panda, Amiya Kumar; Moulik, Satya P.; Bhowmik, B. B.; Das, Anindita

doi:10.1006/jcis.2000.7323

Cited by 36 publications

(16 citation statements)

References 29 publications

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“…In Table I, the $\overline R_{\rm h(m)}$ , $\overline R_{\rm h(a)}$ , $\overline D_{\rm m}$ , $\overline D_{\rm a}$ , and the polydispersity index (PDI) values are presented for different inulin concentrations. The PDI is the ratio between the standard error in $\overline R_{\rm h}$ (σ) and $\overline R_{\rm h}$ , i.e., σ/$\overline R_{\rm h}$ 34–36. A PDI value of ≤ 0.1 identifies a dispersion to be monodisperse.…”

Section: Resultsmentioning

confidence: 99%

Physicochemical studies on the biopolymer inulin: A critical evaluation of its self‐aggregation, aggregate‐morphology, interaction with water, and thermal stability

2009

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Physicochemical properties viz., aggregation, molar mass, shape, and size of chicory inulin in solution were determined by fluorimetry, DLS, SLS, TEM, and viscometry methods. The thermal stability of the biopolymer was examined by TGA, DTA, and DSC measurements. The water vapor adsorption of desiccated inulin was also studied by the isopiestic method, and the data were analyzed in the light of the BET equation. On the basis of the obstruction to ion conductance by the inulin aggregates in solution and analysis of the data, the extent of hydration of inulin in solution was estimated. The result was coupled with the intrinsic viscosity, [eta], of inulin to ascertain the shape of the biopolymer aggregates in aqueous solution. The critical aggregation concentration (cac) of inulin in aqueous as well as in salt solution was assessed by fluorimetry. The weight average molar mass, Mw , of inulin monomer and its aggregate was found to be 4468 and 1.03 x 10(6) g/mol, respectively, in aqueous solution. This aggregated mass was 2.4 x 10(6) g/mol in 0.5M NH(4)SCN solution. The [eta] values of the soft supramolecular aggregates in solution (without and with salt) were small and comparable with globular proteins evidencing spherical geometry of the biopolymer aggregates as supported by the TEM results. In DMSO, rod-like aggregates of inulin was found by the TEM study. The [eta] of the biopolymer in the DMSO medium was therefore, higher than that in the aqueous medium. Unlike aqueous medium, the aggregation in DMSO was not associated with a cac.

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Section: Resultsmentioning

confidence: 99%

Physicochemical studies on the biopolymer inulin: A critical evaluation of its self‐aggregation, aggregate‐morphology, interaction with water, and thermal stability

2009

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“…In another route, the rigidity of the glass, membrane [12] and polymersurfactant gel templates [13] restrict rapid molecular diffusion and thereby prevent particle growth. The mostly explored route is, however, the microemulsion route [14][15][16][17][18] where the tiny water droplets are used as the microreactor and the continuous oil medium resists coagulation. Sodium polyphosphate [19,20] and phosphotungstic acid [21] have been widely used as stabilizers of nano-dispersions in solution.…”

Section: Introductionmentioning

confidence: 99%

Studies on ZnS Nanoparticles Prepared in Aqueous Sodium Dodecylsulphate (SDS) Micellar Medium

2005

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ZnS, a large band gap material, is useful in electro-luminescence and optoelectronic devices. We herein report a method for preparation of nanosized ZnS particles in micellar medium of anionic surfactant sodium dodecylsulphate. The optical properties of the prepared ZnS nanoparticles have been studied by absorption and fluorescence methods. Electron microscopic characterization has evidenced triangular particles, an uncommon observation in the synthesis of nanomaterials. PVC membrane containing nano ZnS dispersions has been prepared and its response as Zn 2+ ion-selective membrane has been reported.

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“…[30][31][32] In a single step, about 100 ultrasmall (1-2 nm) WO x NPs were encased within circa 40 nm silica nanospheres (Figure 1 a) at metal loadings of about 20 wt % when using a nonionic Brij-L4/n-heptane/water RME system (Supporting Information, Figures S3-S7 and S9-S18). High-angle annular dark field scanning transmission electron microscopy (STEM) images show that controlled temperature treatments of the encapsulated WO x NPs with sequential oxidizing (air, 450 8C), reducing (21 % CH 4 /H 2 mixture, 590 8C), and carburizing (21 % CH 4 /H 2 mixture, 835 8C) conditions result in the formation of carbide NPs in the 1-4 nm range (Figure 1 b).…”

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confidence: 99%

Engineering Non‐sintered, Metal‐Terminated Tungsten Carbide Nanoparticles for Catalysis

2014

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Transition-metal carbides (TMCs) exhibit catalytic activities similar to platinum group metals (PGMs), yet TMCs are orders of magnitude more abundant and less expensive. However, current TMC synthesis methods lead to sintering, support degradation, and surface impurity deposition, ultimately precluding their wide-scale use as catalysts. A method is presented for the production of metal-terminated TMC nanoparticles in the 1-4 nm range with tunable size, composition, and crystal phase. Carbon-supported tungsten carbide (WC) and molybdenum tungsten carbide (Mo x W 1Àx C) nanoparticles are highly active and stable electrocatalysts. Specifically, activities and capacitances about 100-fold higher than commercial WC and within an order of magnitude of platinumbased catalysts are achieved for the hydrogen evolution and methanol electrooxidation reactions. This method opens an attractive avenue to replace PGMs in high energy density applications such as fuel cells and electrolyzers.Early transition-metal carbides (TMCs) are earth-abundant materials with established commercial use in a variety of applications owing to their favorable optical, electronic, mechanical, and chemical properties. [1][2][3] Tungsten carbide (WC) has garnered much attention for its catalytic similarities to the platinum group metals [4] (PGMs) in several thermoand electrocatalytic reactions, such as biomass conversion, [2,5,6] hydrogen evolution and oxygen reduction, [7][8][9][10][11] and alcohol electrooxidation. [12,13] The reactivity of WC has been partially attributed to the intercalation of C to the W lattice, which gives rise to a "Pt-like" d-band electronic density states (DOS). [14] Peppernick et al. demonstrated that WC À ions exhibit isoelectronic correspondence with Pt À ions.[15] Because WC exhibits high thermal and electrochemical stability while resisting common catalyst poisons such as carbon monoxide and sulfur, [1][2][3] it has been identified as a suitable candidate to replace PGM catalysts in emerging renewable energy technologies, such as fuel cells and electrolyzers. [7][8][9][10][11][16][17][18] While there are many methods to synthesize WC nanoparticles (NPs), none of the current methods can simultaneously prevent sintering of the WC nanoparticles while also mitigating surface impurity deposition. Thus, despite the promising catalytic properties of model WC surfaces, the lack of synthesis methods to produce metal-terminated WC NPs of controlled sizes has prevented its wide-spread use as an earthabundant catalyst. [1,2,7,19] The high carburization temperatures (> ca. 700 8C) required to overcome the thermodynamic and kinetic barriers for carbon incorporation into the metal lattice induce uncontrollable particle sintering, generating particles with exceedingly low surface areas that are not suitable for commercial applications (Supporting Information , Figure S1). [1,2] Although alternative synthesis methods with unconventional heating [20][21][22][23] and carbon sources [11,17,19,24,25] have been developed to mitiga...

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Dispersed Molecular Aggregates

Cited by 36 publications

References 29 publications

Physicochemical studies on the biopolymer inulin: A critical evaluation of its self‐aggregation, aggregate‐morphology, interaction with water, and thermal stability

Physicochemical studies on the biopolymer inulin: A critical evaluation of its self‐aggregation, aggregate‐morphology, interaction with water, and thermal stability

Studies on ZnS Nanoparticles Prepared in Aqueous Sodium Dodecylsulphate (SDS) Micellar Medium

Engineering Non‐sintered, Metal‐Terminated Tungsten Carbide Nanoparticles for Catalysis

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