Nupur Biswas

Radiation-induced synthesis of self-organized assemblies of functionalized inorganic–organic hybrid nanocomposites

We demonstrate a unique single-pot synthesis of self-organized structures of CdS/dendrimer nanocomposites having long-range correlation by adopting a radiation-induced technique. The present method has been able to produce long-range chain-like networks of CdS nanoparticles of high stability within the dendrimer matrix with particle size monodispersity ∼6%, as visualized with atomic force microscopy, while individual particles are characterized by transmission electron microscopy, photoluminescence, absorption spectroscopy and dynamic light scattering. Results point to a possible mechanism of long-range self-organization from the nanometer to micrometer length scales, where the self-organization is controlled by surface functionality of the dendrimer molecule, solvent and crystal phase of the CdS nanocrystals. The present investigation opens up new potential routes to manipulate semiconductor nanocomposites for optical diagnostics and for applications that require dendrimer nanocomposites with a long-range order.

“Coffee-ring” patterns of polymer droplets

Dried droplets of polymer solutions carries the self-assembly behavior of polymer molecules by forming various patterns. Pattern formation is a consequence of deposition of molecules depending on motion of the contact line during the drying process. The contact line motion depends on initial polymer concentrations and hence entanglement. Thus depending on entanglement the patterns represent the ‘particle’ like or ‘collective’ behavior of polymer molecules.

Counterion effects on nano-confined metal–drug–DNA complexes

Summary We have explored morphology of DNA molecules bound with Cu complexes of piroxicam (a non-steroidal anti-inflammatory drug) molecules under one-dimensional confinement of thin films and have studied the effect of counterions present in a buffer. X-ray reflectivity at and away from the Cu K absorption edge and atomic force microscopy studies reveal that confinement segregates the drug molecules preferentially in a top layer of the DNA film, and counterions enhance this segregation.

Surface correlation in a nano-confined DNA film

Molecules of natural polyelectrolyte DNA, fully neutralized in brine water, show formation of well defined thin films under nano-confinement. The X-ray scattering studies reveal film thickness ∼ 1.5 times of DNA chain width, indicating lateral entanglement whereas the film has self-affine correlation in plane when probing scale is small (with Atomic Force Microscopy) but when probed at large length scale (with diffuse X-ray scattering) they show liquid like correlation due to quasi-equilibrium condition.