Colloids are ubiquitous and it forms an interesting branch of soft matter science owing to the nature of interactions among the constituent phases. Such interactions are amalgamation of various effects, namely, electro-static, van der Waal, excluded volume, etc. As soon as the continuous medium of a colloidal dispersion i.e., the solvent, starts disappearing, as by evaporation, the interaction among the particles gets altered. The extent of modification depends on the competitive dominance of the aforementioned factors. In fact, the phenomenon of evaporation of suspension droplets is widely used in various industries including food and pharmaceutical industries and this process is known as spray drying. Fast evaporating droplets exhibit spectacular behavior due to sudden transition from liquid to powder state associated with assembly of the nanostructures as drive by evaporation. Since last decade, the above mentioned spray drying process has re-embellished itself in nano-science and nano-technology. Using such evaporative technique, we have synthesized various hierarchically structured micro/meso/macro-porous granules. We have demonstrated sphere to doughnut like shape transformation during spray drying and quantified the role of various physicochemical factors responsible for effecting such transformation through buckling. Potential application of such spray dried micro-granules in filtration and bioremediation has also been indicated. Understanding the mesoscopic structure and correlation among the constituent nanostructures in a granule is crucial. In this regard, small-angle neutron scattering (SANS), X-ray scattering (SAXS) and scanning electron microscopy (SEM) have been found effective tools in probing such nano-structured granules. In this presentation, we will discuss some of our recent results on such spray dried micro-granules and will touch upon a few potential applications of such porous granules.
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