Nanoparticles

We perform colloidal synthesis and measurements of CdS, CdS-ZnS core-shell nanoparticles for understanding mechanism of particle formation and for making stable, size controlled (2-10 nm) nanoparticle dispersions. These dispersions are subsequently tried for thin film formation by electrophoresis for coating applications. We also make iron-oxide nanoparticles for the possibility of using it as a contrast agent in magnetic resonance imaging, related to medical diagnosis. Control of mean particle size and size distribution is crucial in all these applications.

To gain further insight in the control variables, in parallel, we have developed population balance equation based mathematical models and performed Monte Carlo simulation of nanoparticle formation in self-assembled colloids - like microemulsions, di-block copolymers etc. This is done in conjunction with our and others' experimental data to come up with predictive calculations for both spherical nanoparticles and anisotropic nanostructures, like nanorods.

Mesoporous materials

We carry out experiments in making mesoporous materials (like MCM-41, SBA-15) of controlled pore-size (5-20 nm) for understanding structure and related adsorption and diffusion issues in these small pores as a function of pore diameter. We further utilize such porous silica matrices for making silver nanoparticles for water purification (killing bacteria) and filtration studies, or make pores functionalized to make them hydrophobic for water-organic mixture separation. Sometimes, the porous silica is impregnated with dyes to use them for detection of pH sensitive aqueous and gaseous mixtures. We are working on extending these studies to make chemical sensors.

Nanocomposites

Polymers (like PEPEG, Polyester, PS etc.) have been used to make composites with our own (synthesized) mesoporous materials or commercially available nanotubes. We try to explain the enhanced mechanical strength, Young's modulus and damping properties (in structural vibration) of these composites from detailed microstructural studies, supplementing it with empirical calculations.

Oil-water interfaces

Mesoporous thin films at oil-water interface have been made with differential wetting characteristics across two surfaces of the film. Thus one surface can selectively manifest itself as a superhydrophobic one, whereas the other is hydrophilic in nature. In some cases, we change the subphase composition to switch the behaviour from hydrophilic to hydrophobic and vice versa. We want to take this work further towards developing smart membranes or surfaces.

Aerosols

We sample both outdoor (ambient) and indoor (smoke) aerosols for studying formation and dynamics of particulate matter, suspended in air or gas. On the other hand knowledge of particle/aerosol formation mechanism is combined with our MC simulation background to explain formation of useful particulate additives (like TiO₂) and reinforcing materials by aerosol-based reactors.