(360a) Electrostatically Controlled Assembly of Colloidal Particles Into Densely Packed Films

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Solution-phase synthesis allows scalable and cost-effective synthesis of a wide variety of inorganic materials in nano-dimensions that are often accompanied by novel material properties. For practical applications (e.g. in electronic and optical devices), it is often desired that these particles could be applied as solid films (coatings) over large area substrates.

Dip-coating has been previously employed for coating sol-gel precursors of mainly oxide materials. We show that it can be applied successfully to build densely packed microns-thick films of ready-made inorganic nanoparticles. Because the films are formed in a layer-by-layer fashion as opposed to a single coating step, formation of cracks can be prevented. Using the example of oppositely charged silica nanoparticles and silver-silica core-shell nanoparticles we show that electrostatic interactions between the particles and with the substrate are crucial to the outcome. Unlike in conventional layer-by-layer assembly, where the deposited inorganic particles are layered between oppositely charged polyelectrolyte layers, using small molecules such as (3-aminopropyl)trimethoxysilane for nanoparticle surface charge modification produces densely packed nanoparticle films.