Inorganic colloids and hybrid materials

Members

Research thematics

Organized nanoparticles

Recent developments in “green chemistry” allow the elaboration of stable colloidal suspensions of anisotropic nanoparticles which self-organize into liquid crystalline phases with very rich behavior :

• A nematic phase of goethite nanorods has a collective diffusion coefficient that decreases at large space scales [1].
• The aqueous suspensions of some natural clays exhibit a nematic liquid-crystalline phase that aligns easily under electric field [2].

The self-assembly properties of semi-conducting nanoplatelets in solution is very sensitive to their thickness : thin platelets curl up into multi-walled tubes, while thicker ones form stacks [3]. These anisotropic nanoparticles exhibit exceptional optical properties that may be useful in opto-electronic devices such as LEDs or for building photo-voltaic cells.

Doped mesophases

Mineral nanoparticules have also been used to formulate organic/inorganic hybrid systems (doped mesophases). The aim is to control the distribution and orientation of the nano-objects within a matrix with tunable mechanical behavior by using self-organized systems.

The inclusions are chosen as a functionof their specific properties (catalytic, photo-reductive, photo-catalytic, optical etc.) or to probe the physical properties of the host phases :

• Small inorganic and hydrophobic particles inserted within surfactant bilayers repel one another [4] [5], in contrast with the predictions of simplified elastic theories. This interaction renders gold nanoparticles easier to stabilize within these matrices [5] and may have profound consequences for the interaction of membrane proteins [6].
• By inserting goethite nanorods in a lamellar phase we obtain a system with composite nematic/smectic symmetry, easy to align and responsive to an external magnetic field [7].