Nanocomposite silicasurfactant microcapsules by evaporation induced self assembly: tuning the morphological buckling by modifying viscosity and surface charge

Abstract

Nanocomposite microcapsules of silica and surfactants have been synthesized using evaporation induced self-assembly through spray drying. It was established using electron microscopy and smallangle neutron/X-ray scattering experiments that the viscosity of the virgin dispersion and surface charge of colloidal components play a significant role in the buckling of spray droplets during drying. Hollow spherical grains are realized at relatively low viscosity and higher surface charge while mushroom like grains manifest at higher viscosity and lower surface charge. In the intermediate conditions, deformed doughnut shaped microcapsules are obtained. Scattering experiments establish the presence of the organization of micelle like aggregates of surfactants in the dried grains and also corroborate with the observations from electron microscopy. A plausible mechanism regarding the chronological pathways of morphological transformation is illustrated. Computer simulation, based on buckling of an elastic shell using a surface evolver, has been attempted in order to corroborate the experimental results.

Liquid phase exfoliation and crumpling of inorganic nanosheets

“…56,57 As the water evaporates, capillary forces compress the shell; consequently, the nanosheet shell yields and buckles due to strong compression forces, in accordance with elastic shell deformation theory. 33,61 Depending on the moduli of the shell itself, dimpled structures form as the interior volume is reduced. 29,59,60 Again this process, particularly the balance between convective and diffusive mass transfer, is discussed in detail in the previous report.…”

Porous nano-structured micro-granules from silica-milk bi-colloidal suspension: Synthesis and characterization

“…This indeed indicates the significant role of inter-particle interaction in morphological transformation. It should be mentioned that in some of the previous works [24][25]27,[29][30][31][47][48][49][50][51][52][53][54], using single-component colloidal suspension, it was indicated that the spherical shape of droplet is retained even in the granule because of isotropic drying at slow drying rate. It has also been discussed that the formation doughnut shape is a consequence of anisotropic drying and shell buckling when drying rate is fast enough.…”

E. coli imprinted nano-structured silica micro-granules by spray drying: Optimization of calcination temperature

“…These include spray drying [3], freeze-drying [4], porogenation [5,6], micro-emulsion formation [7], gas-blowing techniques [8], phase separation [9] etc. Synthesis of micro-granules through drying of suspension-droplets is a well established process that can produce micrometric composite granules in a single step through evaporation-induced assembly [10][11][12][13][14][15]. Such assembly process is a quick and efficient bottom-up approach for realizing multi-functional composite micro-granules.…”