Browsing by Subject "Silica Nanoparticles"

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Open Access
A droplet-based microfluidic reactor for silica nanoparticle synthesis and post processing of quantum dots
(2017-07) Nikdoost, Arsalan
The unique properties of nanoparticles mainly depend on their size and morphology; thus, it is of the utmost importance to synthesize them monodispersely to be useful in an application. Micro uidic reactors enable a monodisperse nanoparticle synthesis through a precise control over the reaction conditions such as temperature, residence time, and reactant concentrations. Droplet-based microreactors facilitate the rapid mixing of reactants with a reduced diffusion length, while maintaining a uniform residence time because of the circulating ow profile in contrast to the parabolic ow profile in continuous ow microreactors. In this thesis, a droplet-based silicon microreactor was fabricated and used for silica nanoparticle synthesis. Silica nanoparticles were obtained with a size range of 25:0 2:7 nm. Considering the shorter processing time and the decreased amount of materials used alongside the comparable size range and monodispersity, this method was later implemented to be used for silica coating of quantum dot semiconductors. Silica coating of quantum dots maintain their photostability and preserve their optical properties. This thesis is the first attempt to coat CdSe/CdS core/shell quantum dots with a silica layer inside a microreactor. The accurate control over the reaction could enable the adjustable size and size distribution of the synthesized nanoparticles. The initial results are presented as part of this thesis.
Open Access
Synthesis of silica-based nanomaterials and their applications in fluorescent, biological and chemical sensing
(2018-06) Beyazkılıç, Pınar
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.