Determination of solvation layer thickness by a magnetophotonic approach.

Department of Chemistry, University of California, Riverside, California 92521, USA.
ACS Nano (Impact Factor: 12.03). 04/2012; 6(5):4196-202. DOI: 10.1021/nn3007288
Source: PubMed

ABSTRACT Derjaguin-Landau-Verwey-Overbeek (DLVO) theory fails in explaining the superior stability of colloid particles in aqueous suspensions under conditions of high ionic strengths where electrostatic forces are effectively screened. Accumulating evidence shows that the formation of a thin rigid layer of solvent molecules in the vicinity of a colloidal particle surface provides an additional repulsive interaction when the interparticle distance is reduced to several nanometers. The effective determination of the thickness of the solvation layer however remains a challenge. Here, we demonstrate a simple yet powerful magnetophotonic technique that can be used to study the thickness of the solvation layers formed on the colloidal silica surface in various polar solvents. A relationship between the hydrogen-bonding ability of the solvents and the thickness of solvation layer on colloidal silica surfaces has been identified; this observation is found to be consistent with the previously proposed hydrogen-bonding origin of the solvation force.

  • [Show abstract] [Hide abstract]
    ABSTRACT: The effects of two amphiphiles, DBSA and LA, on the associating state and viscosity of three heavy oils with different resin/asphaltene (R/A) mass ratios were investigated through DSC analysis, rheological test and electrical conductivity measurement. The wax appearance temperatures of the three heavy oils are lower than 40 °C. The viscosity of heavy oils at temperature range 50~70 °C increases with increasing DBSA concentration but decreases with increasing LA concentration. Addition of DBSA increases the electrical conductivity of heavy oils, which implies that the DBSA acts as asphaltene dispersants; the electrical conductivity of heavy oils decreases after LA addition, which implies that the LA acts as asphaltene flocculants. The addition of DBSA decreases the size of asphaltene particles and generates new solvation layers, both of which favor the increase of heavy oil viscosity; the addition of LA increases the size of asphaltene particles and releases some liquid oils bounded by asphaltene particles, both of which favor the decrease of heavy oil viscosity. With the increase of R/A mass ratio, the stability of heavy oils increases while the viscosity enhancing/reducing efficiency of DBSA/LA decreases.
    Journal of Petroleum Science and Engineering 12/2014; · 1.10 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Simultaneous integration of multifunctional properties from different components into a hybrid nanostructure with hierarchical organization is attractive to construct new materials sought for diverse useful applications. This review highlights recent advances in the fabrication of multicomponent organic-conjugated inorganic nanoarchitectures and their potential uses in optical sensing and diagnostic tools. The similarity of the particle sizes, between inorganic hybrids and biomolecules, is the reason they can integrate into new bioconjugated nanocomposites. These multifunctional properties enable such materials to function as dual diagnostic and therapeutic agents in imaging-guided therapy. Deoxyribonucleic acid (DNA)-templated replica approaches for fabricating DNA-functionalized plasmonic nanoarchitectures are discussed to show how incorporation of metal clusters onto helical DNA structures occurs. The resulting helix plasmonic assemblies response enhanced plasmonic properties and circular dichroism signals to external environments, means they can function as highly selective bioprobes. Nanocrystal superlattices are prepared by assembling the uniform colloids by guiding the external magnetic field and solvent evaporation. The highly organized superlattices with long-range ordering exhibit optical properties tuned by external stimuli and, consequently they can be useful for desirable optical sensors and photoswitchable patterns. The efforts discussed in this review are expected to present the structural diversity of promising multifunctional nanoarchitectures for the design of efficient optical sensing and diagnostic tools.
    RSC Advances 01/2014; 4(2):916. · 3.71 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Understanding nanoparticle diffusion within non-Newtonian biological and synthetic fluids is essential in designing novel formulations (e.g. nanomedicines for drug delivery, shampoos, lotions, coatings, paints, etc.), but is presently poorly defined. This study reports the diffusion of thiolated and PEGylated silica nanoparticles, characterized by small angle neutron scattering, in solutions of various water-soluble polymers such as poly(acrylic acid) (PAA), poly(N-vinyl pyrrolidone) (PVP), poly(ethylene oxide) (PEO) and hydroxyethylcellulose (HEC), probed using NanoSight nanoparticle tracking analysis. Results show that the diffusivity of nanoparticles is affected by their dimensions, medium viscosity and in particular by specific interactions between nanoparticles and the macromolecules in solution; strong attractive interactions such as hydrogen bonding hamper diffusion. The water-soluble polymers retarded diffusion of thiolated particles in the order: PEO > PVP > PAA > HEC whereas for PEGylated silica particles retardation was in the order: PAA > PVP = HEC > PEO. In the absence of specific interactions with the medium, PEGylated nanoparticles exhibit enhanced mobility compared to their thiolated counterparts despite some increase in their dimensions.
    Langmuir 12/2013; · 4.38 Impact Factor