Colloidal suspensions in modulated light fields

Colloidal suspensions in modulated light fields

Periodically-modulated potentials in the form of light fields have previously been applied to induce reversible phase transitions in dilute colloidal systems with long-range interactions. Here we investigate whether similar transitions can be induced in very dense systems, where interparticle contacts are important. Using microscopy we show that particles in such systems are indeed strongly aff...

Light-regulated electrostatic interactions in colloidal suspensions.

The net charge of a colloidal particle was controlled using light and a new photocleavable self-assembled monolayer (SAM). The SAM contained a terminal ammonium group and a centrally located carboxylic acid group that was masked with an ortho-nitrobenzyl functionality. Once exposed to UV light, the 2-nitrobenzyl group was cleaved, therefore transforming the colloidal particle from a net positiv...

Structure and Dynamics of Equilibrium and Non-Equilibrium Systems: Colloidal Suspensions in Confining Light Fields

Destabilization of Colloidal Suspensions 3.1 COLLOIDAL SUSPENSIONS

Many impurities in waters and wastewaters are present as colloidal dispersions, i.e. they occur in particulate form within the approximate size range 1 to 10 -3 μm (refer Fig 1.3). Examples of this type of suspension include clays, substances of biological origin such as natural colour, proteins, carbohydrates and their natural or industrial derivatives. Invariably suspensions of this type poss...

Light transport and rotational diffusion in optically anisotropic colloidal suspensions

2 Magnetic and optical properties of liquid crystalline colloidal particles 33 2. Introduction This work is concerned with the solution of an important problem of influence of a magnetic field on rotational diffusion in anisotropic colloidal solutions. It describes the results of experimental investigations of the author carried out using the method of diffusing-wave spectroscopy and the method...