Investigation of Semiconductor Nanoparticle?s Desiccation Pattern Formation Dynamics

Semiconductor nanoparticles and their assemblies are considered as building blocks of next generation nanoscale electronic devices. Many researchers reported the self-assembly of colloidal nanoparticles which yield different types of desiccation patterns such as dendrites, stripes, 2D arrays etc. and explained the structures mainly using diffusion limited aggregation and Mullins-Sekerka instability. Through this proposal, we aim to investigate the dynamics of the nanoparticle drying process on a solid substrate macroscopically using optical video microscopy methods. The open questions are (a) does the solidification domain appear always at the edge of the drop? (b) Are they multiple solidification domains? (c) During the drying process, does the solidification front propagate with different velocities? (d) Do the solidification fronts overlap? To answer these questions, various optical measurements such as bright-field and dark- field video microscopy will be developed. Further, SnO2 colloidal nanoparticle?s desiccation patterns will be formed on various smooth substrates such as glass, Teflon and metals. The evaporation rate will be controlled by adjusting the substrate temperature.

Semiconductor nanoparticles and their assemblies are considered as building blocks of next generation nanoscale electronic devices. Many researchers reported the self-assembly of colloidal nanoparticles which yield different types of desiccation patterns such as dendrites, stripes, 2D arrays etc. and explained the structures mainly using diffusion limited aggregation and Mullins-Sekerka instability. Through this proposal, we aim to investigate the dynamics of the nanoparticle drying process on a solid substrate macroscopically using optical video microscopy methods. The open questions are (a) does the solidification domain appear always at the edge of the drop? (b) Are they multiple solidification domains? (c) During the drying process, does the solidification front propagate with different velocities? (d) Do the solidification fronts overlap? To answer these questions, various optical measurements such as bright-field and dark- field video microscopy will be developed. Further, SnO2 colloidal nanoparticle?s desiccation patterns will be formed on various smooth substrates such as glass, Teflon and metals. The evaporation rate will be controlled by adjusting the substrate temperature.

Evaporation driven desiccation pattern formation is a natural phenomenon originating from the self-assembly of colloidal nanoparticles. In comparison to other pattern formation methods, evaporation driven self-assembly is a low-cost and easy technique. The mechanisms, which drive the organization of particles, are electrostatic, van der Waals and dipolar interactions [1]. Researchers produced variety of patterns such as ring, dendritic, 2D arrays and layers [2, 3, 4, 5, 6]. Several models are proposed for the pattern formation out of which diffusion limited aggregation and Mullins-Sekerka instability are generally discussed [7-12]. Coupling of excitonic states [13] or plasmonic states [14] or magnetic moments [15] of individual nanoparticles in the self-assembly provides distinct properties that are beneficial for optoelectronic devices such as wavegudes, magnetic data storage devices and photonic crystals [16, 17]. Recently, we report the application of SnO2 nanoparticles desiccation pattern as a template for organizing dye molecules [18] that is promising for display applications.