Browsing by Author "Sopubekova, Eliza"
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Item Open Access Directed assembly of charged nanoparticles by using electrostatic forces in a fluidic medium(2019-02) Sopubekova, ElizaDeposition of nanoparticles in a controlled manner is suitable for the application of unique properties of nanoparticles in designing novel electronic devices. Printing different types of nanoparticles on the same surface generates multifunctional surfaces and opens up possibilities to elaborate future devices. Electrostatic forces can potentially be utilized to manipulate different types of materials such as magnetic, insulating, conducting, semiconducting, organic and inorganic materials. Moreover, chemistry of materials and the surface is not altered. Herein, we applied these forces to direct and position charged nanoparticles on desired areas of the surface from nonpolar and aqueous dispersions. Assemblies of particles are obtained on both nonconductive surface with charged patterns and on metallic nano- and microstructured electrodes. Arrays of gold electrodes of sizes from 500 nm to 50 μm were prepared by using the conventional fabrication techniques such as photolithography, electron beam lithography, thermal evaporation and lift off. Charge patterns are formed on 100 nm PMMA surface which is coated on the electrodes to provide electrical contact. An external voltage was applied and substrate was immersed into desired aqueous negatively charged colloidal gold dispersion to direct nanoparticles on aforementioned charge patterns. The next step was to attract two different charged nanoparticles towards different locations on the same substrate by means of electrophoretic deposition. Assemblies formed from positively charged silver nanoparticles and negatively charged fluorescent latex and silica nanoparticles are demonstrated. Last but not least, composite structures were obtained with similar techniques in order to increase the functionality of the structured surface. To achieve this goal, different types of nanoparticles were coated on top of each other without changing the location of electrodes. The shape of these composite structures is controlled by the electrode geometry.Item Open Access Single, binary and successive patterning of charged nanoparticles by electrophoretic deposition(Springer, 2021-11-19) Sopubekova, Eliza; Kibar, G.; Yegan Erdem, EmineDeposition of nanoparticles on a substrate in a controlled manner leads to the formation of multifunctional surfaces and therefore devices. Electrostatic forces can be utilized to manipulate different types of materials such as magnetic, insulating, conducting, semiconducting, organic and inorganic, without altering the chemistry of the surface. However, simultaneous and successive electrophoretic deposition (EPD) methods are not fully utilized for nanoparticles with different characteristics. In this work, electrostatic forces are applied to direct and position charged nanoparticles suspended in aqueous dispersions on desired areas of the surface. Assemblies of particles are obtained by electrostatic attraction generated by gold electrodes of sizes from 500 nm to 50 µm that are fabricated by thermal evaporation. Different types of charged nanoparticles were simultaneously attracted towards different locations of the surface by means of EPD; as a result, alternating nanoparticle patterns and particle deposition on the same designated areas for forming composite areas are obtained. Assemblies formed from positively charged silver nanoparticles and negatively charged fluorescent latex and silica nanoparticles are demonstrated. The position of metallic-, polymeric- and inorganic-based nanoparticles is controlled by the design of electrode geometry.