Synthesis of silica-based nanomaterials and their applications in fluorescent, biological and chemical sensing

This thesis describes development of nanoparticle-based liquid sensors and coatings for droplet-based bioassays. Liquid sensors were produced from mesostructured (2-50 nm) hybrid silica nanoparticles. Detection of trace trinitrotoluene (TNT) and dopamine in aqueous phase was shown based on uorescence of nanoparticles. Silica nanoparticles were synthesized using a facile one-pot solgel method. Pyrene molecules were hybridized with hydrophobic parts of cetyltrimethylammonium micelles followed by silica growth around micelles. Nanoparticles showed good dispersibility and colloidal stability in water. Pyrene exhibited bright and highly stable emission. Pyrene emission exhibited a rapid, sensitive and visual uorescence quenching against TNT and dopamine. For droplet-based assays, robust superhydrophilic patterned superhydrophobic coatings were developed. Biomolecular adsorption and droplet mixing were shown on coatings which were prepared using sol-gel method followed by ultraviolet/ ozone (UV/O) treatment. Droplet-based biomolecular detection platforms were developed using superhydrophilic patterned superhydrophobic surfaces. Bene tting from con nement and evaporation-induced shrinkage of droplets on wetted patterns, sensitive glucose and DNA detection was demonstrated. Glucose was detected based on enhancement of polydopamine (PDA) emission by hydrogen peroxide (H2O2) produced in glucose oxidation reaction. Detection in evaporating droplets resulted with bright uorescence and high sensitivity for analyte molecules. This was due to droplet evaporation which concentrated molecules and increased reaction rates. Surfaces and nanoparticles developed in this thesis hold great potential for biological and chemical analysis with low sample volumes owing to their simple production, sensitive detection responses and versatility.