let us use correct words, correct terms: a dispersion is a composition of at least 2 materials and this composition has at least 2 separate phases, i.e., 2 phases which have a completely different composition, one of which is the continuous phase, the other one is the dispersed phase, usually in nano size (10 to 100 nm, rarely below 10 nm, sometimes above 100 nm but should be below 1 µm).

In your case, the Ag nanoparticles are the dispersed phase, i.e., the nanoparticles have a phase boundary only with the continuous phase; at that phase boundary, the composition suddenly changes from Ag to H2O (or whatever is the continuous phase).

Such a *dispersion* is the contrary of *solution*, therefore one can not say "homogeneous solution of silver nanoparticles".

A solution is a composition of at least 2 materials which shows only one single phase: the solvent and the other material which is dissolved; *dissolved* means, it is present in molecular scale, and every molecule is surrounded ("solvated") by the solvent.

here dispersion means to form an homogenous solution of silver nanoparticles. nanoparticles have high surface area hence it tends to get agglomerated. Citrate act has capping agent, which caps the silver nanoparticles to prevent agglomeration and forms homogenous suspension.

let us use correct words, correct terms: a dispersion is a composition of at least 2 materials and this composition has at least 2 separate phases, i.e., 2 phases which have a completely different composition, one of which is the continuous phase, the other one is the dispersed phase, usually in nano size (10 to 100 nm, rarely below 10 nm, sometimes above 100 nm but should be below 1 µm).

In your case, the Ag nanoparticles are the dispersed phase, i.e., the nanoparticles have a phase boundary only with the continuous phase; at that phase boundary, the composition suddenly changes from Ag to H2O (or whatever is the continuous phase).

Such a *dispersion* is the contrary of *solution*, therefore one can not say "homogeneous solution of silver nanoparticles".

A solution is a composition of at least 2 materials which shows only one single phase: the solvent and the other material which is dissolved; *dissolved* means, it is present in molecular scale, and every molecule is surrounded ("solvated") by the solvent.

The dispersion of silver nanoparticles with physical dispersal procedures

Hung-WenLinaWen-HwaHwubMing-DerGer

Journal of Materials Processing Technology

Volume 206, Issues 1–3, 12 September 2008, Pages 56-61

Abstract

Dispersion degree strongly influences the rheological properties of nanosized particles containing suspension and, as a consequence, the quality of the deposited film. Furthermore, their applications will be rigorously restricted if the bad dispersion cannot be solved effectively. In this investigation, two physical dispersal processes, mechanical mixing with a three-roller mill and sonication, are used to disperse the nanosized silver particles in ethylene glycol and their effectiveness in dispersion are compared. The particle size distributions after dispersion with various procedures are observed by field emission scanning electron microscope (FE-SEM) and measured by image analysis technique. The measurement results show that mixing with a three-roll mill is an effective tool to break the agglomerates of silver nanoparticles in solvent, resulting in a better dispersion. The dispersion degree effect on the rheological properties and thixotropic characteristics of these suspensions are also elucidated. In addition, the film deposited from suspension with Ag nano particles mixed by three-roller mill has the lowest resistivity of approximately 3.64 × 102 μΩ cm.

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Dispersion of functionalized silver nanoparticles in polymer matrices: Stability, characterization, and physical properties

Uma Chatterjee, Suresh K. Jewrajka†* and Suparna Guh

Polymer Composites

Volume 30, Issue 6, pages 827–834, June 2009

Abstract

Three types of silver/polymer nanocomposite films were prepared: (1) silver/polymethyl methacrylate, (2) silver/polystyrene, and (3) silver/polyt-butyl methacrylate by mixing colloidal solution of functionalized Ag nanoparticles with solution of pre-made polymers. The nanoparticles are randomly dispersed into the matrices. The desired surface functionality of Ag nanoparticle was achieved by using specific amphiphilic block copolymer (specific hydrophobic block part) as stabilizer. The stability of nanoparticles in these host hydrophobic polymer matrices was determined after annealing the nanocomposite films at high temperature. The nanoparticles remained stable and no agglomeration occurred upon annealing up to 120°C. Up to 20 wt% of block copolymer stabilized Ag nanoparticles (11% Ag) was successfully loaded in the polymer matrix. Such a dispersion of Ag nanoparticles into a hydrophobic polymer matrix significantly enhances the mechanical properties of the nanocomposite films. The storage and loss modulus increase with increasing Ag nanoparticles content. Compared with a polymer matrix, the polymer/Ag nanocomposites film (containing 0.65% of Ag) prepared by this method displayed storage modulus that are up to 130% higher. This is attributed to the high surface area of the polymer coated Ag nanoparticles in the polymer matrix and van der Waal's attraction force between surface of Ag nanoparticles (polymer brush) and host polymer matrix. Comparison of thermal properties of polymer and polymer/Ag nanocomposite films showed that the thermal stability of nanocomposites increases by about 20°C. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers

interesting contribution, in this context (rheology, viscosity) please look at this as well:

Chapter Rheological Phenomena and Structure Formation in Multiphase ...

Article On turbulence in dilatant dispersions