Browsing by Author "Budunoglu, H."
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Item Open Access Flexible and mechanically stable antireflective coatings from nanoporous organically modified silica colloids(Royal Society of Chemistry, 2012) Budunoglu, H.; Yildirim, A.; Bayındır, MehmetWe report the preparation of flexible and mechanically stable antireflective organically modified silica (ormosil) coatings at ambient conditions. Thin films are obtained from colloidal suspensions of ormosil gels which are prepared using methyltrimethoxysilane (MTMS) and tetraethyl orthosilicate (TEOS) monomers. The ormosil suspensions are directly applicable and suitable for the large-area deposition of nanoporous ormosil thin films. The nanoporosity of the films can be tuned by changing the monomer ratio of the starting solution. Thin films on flexible substrates retain their antireflective properties even after 100 cycles of excessive bending without a significant change in transmission. Furthermore, the films remained intact after water dripping and adhesive tape tests. In addition, thin films on glass substrates are found to exhibit antifogging properties after annealing at 600 °C for 30 min. The ease of fabrication and multifunctionality of these films make them ideal coatings for flexible electronic and optoelectronic devices, sensors, and solar cells. © 2012 The Royal Society of Chemistry.Item Open Access Highly transparent, flexible, and thermally stable superhydrophobic ORMOSIL aerogel thin films(American Chemical Society, 2011) Budunoglu, H.; Yildirim, A.; Güler, Mustafa O.; Bayındır, MehmetWe report preparation of highly transparent, flexible, and thermally stable superhydrophobic organically modified silica (ORMOSIL) aerogel thin films from colloidal dispersions at ambient conditions. The prepared dispersions are suitable for large area processing with ease of coating and being directly applicable without requiring any pre- or posttreatment on a variety of surfaces including glass, wood, and plastics. ORMOSIL films exhibit and retain superhydrophobic behavior up to 500 °C and even on bent flexible substrates. The surface of the films can be converted from superhydrophobic (contact angle of 179.9°) to superhydrophilic (contact angle of <5°) by calcination at high temperatures. The wettability of the coatings can be changed by tuning the calcination temperature and duration. The prepared films also exhibit low refractive index and high porosity making them suitable as multifunctional coatings for many application fields including solar cells, flexible electronics, and lab on papers. © 2011 American Chemical Society.Item Open Access One-pot preparation of fluorinated mesoporous silica nanoparticles for liquid marble formation and superhydrophobic surfaces(American Chemical Society, 2011) Yildirim, A.; Budunoglu, H.; Daglar, B.; Deniz, H.; Bayındır, MehmetOne-pot synthesis of fluorinated mesoporous silica nanoparticles (FMSNs) is reported. Uniform mesoporous nanoparticles are prepared by condensation of tetraethyl orthosilicate (TEOS) and fluoroalkyl containing organotriethoxy silane monomers, respectively. The method enables selective deposition of fluorine atoms on the surface of the particles. FMSNs are used to prepare stable liquid marbles with water. An organo-modified silica sol is used with FMSNs to prepare mechanically stable superhydrophobic surfaces (water contact angle of 161 degrees). The mechanical stability of the surface is investigated with water dripping and adhesive tape tests. The prepared FMSNs are promising building blocks for robust, large-area, and multifunctional self-cleaning surfaces.Item Open Access Superhydrophobic and omnidirectional antireflective surfaces from nanostructured ormosil colloids(American Chemical Society, 2013-02-13) Yildirim, A.; Khudiyev, T.; Daglar, B.; Budunoglu, H.; Okyay, Ali Kemal; Bayındır, MehmetA large-area superhydrophobic and omnidirectional antireflective nanostructured organically modified silica coating has been designed and prepared. The coating mimics the self-cleaning property of superhydrophobic lotus leaves and omnidirectional broad band antireflectivity of moth compound eyes, simultaneously. Water contact and sliding angles of the coating are around 160 and 10, respectively. Coating improves the transmittance of the glass substrate around 4%, when coated on a single side of a glass, in visible and near-infrared region at normal incidence angles. At oblique incidence angles (up to 60) improvement in transmission reaches to around 8%. In addition, coatings are mechanically stable against impact of water droplets from considerable heights. We believe that our inexpensive and durable multifunctional coatings are suitable for stepping out of the laboratory to practical outdoor applications.Item Open Access Template free preparation of nanoporous organically modified silica thin films on flexible substrates(Royal Society of Chemistry, 2011) Yildirim, A.; Budunoglu, H.; Yaman, M.; Güler, Mustafa O.; Bayındır, MehmetWe report the preparation and characterization of nanoporous organically modified silica (ormosil) thin films at room temperature and neutral pH conditions from homogeneous methyl silsesquioxane (MSQ) gels. Universally applicable and stable colloidal ormosil suspensions are prepared from the gels by sonication and coated to the substrates including glass, paper and plastics. The nanoporosity and thickness of the films can be tuned, which makes them suitable for certain applications including sensing, functional coatings, and low-dielectric materials. We demonstrate the antireflection property of the films on glass, cellulose acetate (CA) and polyetherimide (PEI) substrates. The films on CA and PEI retain their antireflection property after multiple bending cycles. Furthermore, films are intrinsically hydrophobic, over a wide pH range, with static contact angles up to 143 degrees on paper and 123 degrees on glass and CA. Producing nanoporous ormosil thin films on flexible substrates may expand their use in low cost electronic, optical devices and sensors, and lab-on-paper applications.Item Open Access Template-free synthesis of organically modified silica mesoporous thin films for TNT sensing(American Chemical Society, 2010) Yildirim, A.; Budunoglu, H.; Deniz, H.; Güler, Mustafa O.; Bayındır, MehmetIn this paper, we present a facile, template-free sol−gel method to produce fluorescent and highly mesoporous organically modified silica (ORMOSIL) thin films for vapor phase sensing of TNT. An alkyltrifunctional, methyltrimethoxysilane MTMS precursor was used to impart hydrophobic behavior to gel network in order to form the spring back effect. In this way, porous films (up to 74% porosity) are obtained at ambient conditions. Fluorescent molecules are physically encapsulated in the ORMOSIL network during gelation. Fluorescence of the films was found to be stable even after 3 months, proving the successful fixing of the dye into the ORMOSIL network. The functional ORMOSIL thin films exhibited high fluorescence quenching upon exposition to TNT and DNT vapor. Fluorescence quenching responses of the films are thickness-dependent and higher fluorescence quenching efficiency was observed for the thinnest film (8.6% in 10 s). The prepared mesoporous ORMOSIL thin films have great potential in new sensor and catalysis applications.