Self-Assembly of Silica Nanoparticles on Glass Surface

Abstract

In this work, silica nanoparticles were synthesised using Stöber Method. Compared to other synthesis techniques like, Stöber Method is regarded as one of the simplest and most effective route for silica nanoparticle synthesis. Low temperature stabilises the nanosilica suspension, and low ratio of NH3/TEOS avoids coagulation of particles. These nanoparticles (average size less than 1 ?m) were self-assembled on a glass surface using sodium carboxymethyl cellulose (CMCNa) and oxalic acid template. The silica nanoparticle self-assembly was validated by the observed fractal-pattern in a sessile drop. For preparing superhydrophilic film, sequential adsorption (layer-by-layer coating) of a polyelectrolyte and silica nanoparticle suspension on the surface was done for appropriate number of cycles. Layer-by-Layer assembly is an economical, easy and a fast technique for coating of substrates with alternate layers. It is known that superhydrophilicity (and superhydrophobicity) increases with increase in surface roughness. By this technique, two different coatings with equal number of depositions were created – one consisting of polyelectrolyte and silica nanoparticles and other consisting of polyelectrolyte and silica nanoparticle with sodium carboxymethyl cellulose and oxalic acid. Contact angle measurement done on these two coating validated the superhydrophilic property of the films. The second-type coating had a lower contact angle (less than 10°) while the first-type coating had a contact angle slightly greater than 10°.