Dielectric colloidal micro-/nanospheres (CMNS) are promising candidates for different applications. In this thesis, colloidal spheres are either used for light management in photonic devices such as solar cells or surface enhanced Raman scattering (SERS) substrates. CMNS arrays can direct the broad incident radiation into a set of tighter foci, at which light intensity becomes considerably concentrated, enabling higher conversion efficiency. Furthermore, the CMNS arrays acting as an effective medium on the device surface can reduce reflection and facilitate improved forward scattering and hence the utilization of light within the device. Therefore, uniform arrays of CMNS located on top of the photonic devices can behave as antireflection coatings or as micro-lenses which can be regarded as a surface distributed concentrator within the framework of concentrated photovoltaics (CPV). Fabrication of such a lighttrapping structure is low-cost and less complicated than common alternatives such as vacuum evaporated multilayer antireflection coatings. In this thesis, experimental demonstration and computational support of the optimal size and shape of such CMNS arrays are illustrated. Besides, thin metallic film coated dielectric nanospheres are demonstrated to have a high potential for fabrication of cost-effective SERS substrates. In addition to the morphological advantages that nanospheres offer for attaining a high density of hotspots, possessing shape adjustability by uncomplicated thermal treatment make them an attractive platform for tuneable SERS substrates. Furthermore, when combined with oblique angle metal deposition technique, adjustable gaps at a high density and adjustable shape of metal films, such as silver (Ag) films, can be achieved on nanospheres. Applying small changes in deposition angle can provide means for fine adjustment of the SERS enhancement factor (EF), resulting in EF up to 108 measured using crystal violet dye molecule as a Raman analyte. This practice paves the way for the fabrication of high EF SERS substrates at a reasonable cost using a monolayer of self-organized nanosphere pattern. An ultra-thin Ag film coated at 5o tilt is shown to be an excellent substitute for a film deposited at 0o with double the thickness. There is a strong agreement between the experimental results and finite element method based simulations exhibiting expected field enhancements up to 109 at a tilt angle of 5o. In summary, the demonstration of several ordered colloidal mask applications in light management for photonic devices is aimed at this thesis.


Designing heat-exchanger networks for energy savings in chemical plants
Özgen, Canan; Baç, Nurcan; Gürkan, Türker; Tosun, İsmail (Elsevier BV, 1989-12)
The pinch-design method is applied to the evaluation of heat-exchanger networks for an existing monomer plant. The problem resulting from partially condensed multicomponent vapor streams possessing variable CP () values is solved by applying a novel technique. The rigorous design obtained is further revised by the consideration of plant constraints.
A facile one-step synthesis of polymer supported rhodium nanoparticles in organic medium and their catalytic performance in the dehydrogenation of ammonia-borane
Karahan, Senem; Zahmakıran, Mehmet; Özkar, Saim (2012-01-01)
A new type of supported rhodium nanoparticles were reproducibly prepared from N(2)H(4)BH(3) reduction of [Rh(mu-Cl)(1,5-cod)](2) without using any solid support and pre-treatment technique. Their characterization shows the formation of well dispersed rhodium(0) nanoparticles within the framework of a polyaminoborane based polymeric support. These new rhodium(0) nanoparticles were found to be the most active supported catalyst in the catalytic dehydrogenation of ammonia-borane in water at room temperature.
Immobilization of dioxomolybdenum(VI) complex bearing salicylidene 2-picoloyl hydrazone on chloropropyl functionalized SBA-15: A highly active, selective and reusable catalyst in olefin epoxidation
Bagherzadeh, Mojtaba; Zare, Maryam; Salemnoush, Taghi; Özkar, Saim; Akbayrak, Serdar (Elsevier BV, 2014-04-05)
A novel organic-inorganic hybrid heterogeneous catalyst system was obtained from the reaction of the molybdenum(VI) complex of salicylidene 2-picoloyl hydrazone with mesoporous silica containing 3-chloropropyl groups prepared by a direct synthetic approach involving hydrolysis and co-condensation of tetraethylorthosilicate (TEOS) and 3-chloropropyltrimethoxysilane in the presence of the triblock copolymer P123 as template under acidic conditions. Characterization of the functionalized materials by X-ray dif...
IDER, YZ; SAKI, MC (1993-09-08)
Use of notch filters in signal averaged ECG applications is avoided because they introduce ringing following the QRS. The authors therefore studied the use of a line interference subtraction (LIS) filter by which a scaled and shifted version of a signal at line frequency (line reference signal, LRS) is subtracted from the ECG signal in order to reduce the level of line interference. The frequency of the LRS must be the same as that of the line interference. For this, hardware is developed such that line fre...
Synthetic Design of Polyester Electrolytes Guided by Hydrophobicity Calculations
Yıldırım, Erol; Peretic, Matthew J.; Pasquinelli, Melissa A.; Mathers, Robert T. (American Chemical Society (ACS), 2016-10-25)
Partition coefficients (LogP) help to quantify hydrophobicity, which can be used to guide the design of polymer electrolytes with properties. Thus, this study combined synthetic experiments and modeling to produce polyester electrolytes that solubilize lithium salts. These polyester electrolytes were derived from natural sources and polymerized with different ratios of polyols (diglycerol, glycerol, and diethylene glycol) and citric acid in the presence of lithium salts (LiTf and LiTFSI). The Fisher esterif...
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