Biyosensör ve biyomedikal uygulamalar için zeolit nanokristalleri kullanılarak fonksiyonel yüzeylerin oluşturulması.

Zeolites are crystalline aluminosilicates which have highly ordered pore structures and high surface area. Also the tailorable surface properties, high ion-exchange capability, high chemical, thermal, and mechanical strength make these particles an important candidate for various application such as sensors, catalysis, dielectric materials, separation, and membrane technologies. Although zeolites have these unique properties, applications where zeolites are integrated into devices according to their application areas, are limited due to the powder form of the material. The purpose of the current study was to investigate the effect of zeolite nanoparticles on conductometric biosensor performance and cell viability measurements. Firstly, zeolite attachment on silicon surfaces was investigated by attaching silicalite and zeolite A nanoparticles onto the silicon substrates by direct attachment methodology in a closely packed monolayer form with perfect orientation and full coverage without using any chemical linker. Furthermore, the ability to pattern these zeolite crystals on silicon substrates with electron beam lithography and photolithography techniques was investigated. With the combination of electron beam lithography and direct attachment methodology, zeolite patterns were produced with feature sizes as small as a single silicalite nanoparticle thick line, that is approximately 500 nm. This approach has the ability of patterning very small features on silicon substrate, but the drawback is the long patterning time and lack of electron beam stability during long pattern formation process. Accordingly, it is almost impossible to form large patterns with electron beam lithography systems. Afterwards, to have full control on surfaces with differentiated areas on solid substrates, patterns of one type of zeolite crystals was formed on the monolayer of another type of zeolite layer with electron beam lithography for the first time. The same closed packed and highly oriented silicalite patterns were successfully formed on zeolite A monolayers and vice versa. Then photolithography technique was combined with direct attachment methodology to overcome the problem of the lack of total patterned area. With this technique, it was possible to pattern the whole silicon wafer in a couple of seconds, however the feature size of the zeolite patterns was limited with the infrastructures of the mask fabricated for photolithography studies. In this particular study, zeolite lines patterns with a minimum of 5 µm thickness were prepared and the total patterned area was kept constant at 1 cm2. Similar to what was obtained by electron beam lithography study, zeolite A patterns were formed on silicalite monolayers with the minimum feature size of 5 µm and vice versa. In the second part of the study, zeolite films were prepared on the transducers of conductometric biosensors using dip coating technique and named as Zeolite Coated Transducers (ZCT). Electrodes prepared using a mixture of zeolite and enzyme solution and then subjected to casting using glutaraldehyde were called Zeolite Membrane Transducers (ZMT). The operational and storage stabilities were determined to be in an acceptable range using ZCTs for conductometric urea biosensors. It was observed that using electrodes fabricated by the ZCT technique enhanced the biosensor signals up to two times and showed a rapid response after the addition of urea to the medium when it was compared with Standard Membrane Transducers (SMT). This enhancement can be explained by the lack of GA layer on top of the film, which acts as a diffusion barrier and inhibits the activity of the enzyme. On the second part of this conductometric biosensor study, effect of zeolite modification with methyl viologen (MV) and silver nanoparticles (Ag+ and Ag0), as well as the effect of changing Si/Al ratio was investigated with three different zeolite Beta particles which have Si/Al ratios of 40, 50, and 60. There were no significant effect of MV modification on ZMTs and there was no response observed with Ag+ and Ag0 modified zeolites. However, it was observed that conductometric responses increased with increasing Si/Al ratio for ZMTs. This behavior can be due to an increased hydrophobicity and/or the increasing acidic strength with the increasing Si/Al ratio within the zeolite crystals. Also ZCTs showed higher responses with respect to both SMTs and ZMTs. When compared with SMTs and ZMTs, ZCTs had higher reproducibility due to the controlled thickness of zeolite thin film by dip coating, and the controlled amount of enzyme adsorbed on this film. In the third part of the study, effect of zeolites on cell proliferation with MG63 osteoblast cells and NIH3T3 fibroblast cells were investigated. For that purpose, zeolite A, silicalite, and calcined forms of these zeolites were patterned with photolithography technique onto silicon wafers. Three different patterns prepared for this particular study, which has 0.125cm2, 0.08825cm2, and 0.04167cm2 zeolite patterned areas on 1 cm2 samples. In that way, not only the zeolite type and effect of calcination of zeolites, but also the effect of zeolite amount on MG63 osteoblast cells and NIH3T3 fibroblast cells were investigated. Silicalite coated samples were observed to have higher amount of cells than zeolite A coated samples after 24, 48, and 72 hours of incubation. This may be referred to the hydrophilic/hydrophobic properties, surface charge, and/or particle size of zeolites. Also it is observed that higher zeolite amount on samples resulted in an increase in the number of cells attached to the samples. There was also a significant increase in the number of cells upon using calcined silicalite samples. Accordingly, it can be hypothesized that zeolite pores result in an enhancement of protein adsorption and proliferation, even if this only occurs at the pore openings. On the other hand, there was no positive effect of calcining zeolite A. This result was expected since there is no structure directing agent used in synthesis procedure of zeolite A, which again supports the fact that pores might have some role in cell attachment.M.S. - Master of Scienc

FEN BİLİMLERİ ENSTİTÜSÜ/LİSANSÜSTÜ TEZ PROJESİ

ZEOLİT 4A VE ZEOLİT 13X'İN YEREL VE DOĞAL KAYNAKLARDAN SENTEZLENMES

ZEOLİT 4A, ZEOLİT 13X VE ZEOLİT Y KRİSTALLERİNİN ÜLKEMİZ DOĞAL KAYNAKLARINDA OLAN KAOLİN VE TRONA İLE ÜRETİMİNİN GELİŞTİRİLMESİ

ZEOLİT 4A, ZEOLİT 13X VE ZEOLİT Y KRİSTALLERİNİN ÜLKEMİZ DOĞAL KAYNAKLARINDA OLAN KAOLİN VE TRONA İLE ÜRETİMİNİN GELİŞTİRİLMES

Fabrication of nano- to micron-sized patterns using zeolites: Its application in BSA adsorption

Nano to micron-sized zeolite A (Z-A) and silicalite (Z-SIL) patterns were generated using the combinations of electron beam lithography (EBL) or photolithography (PL) with direct attachment method to be able to generate differentiated areas on a single surface in a cheap and facile way. The possibility to generate minimum sized zeolite patterns on top of zeolite monolayers was investigated by using EBL to understand the capability of the system for the first time. Also generation of large scale zeolite patterns on top of a different zeolite monolayer was investigated by using PL allowing the generation of differentiated surfaces for various potential applications such as selective adsorption studies. With this combination, it was shown that creating 3D zeolite architectures of different types with a perfect control in all dimensions was possible without the using any chemical linker. In order to test the potential different behaviors that zeolites of different properties are offering in the adsorption of biomolecules, zeolite patterned surfaces developed by PL were subjected to adsorption studies with bovine serum albumin (BSA). Irrespective of zeolite type, BSA always preferred the patterned regions rather than the underlying zeolite monolayers. It can be speculated that the obtained difference in roughness values facilitates the protein to be selectively adsorbed onto surfaces with increased roughness, i.e., the patterned regions. Moreover, we observed similar to 2-fold fluorescence intensity difference between Z-SIL and Z-A patterns, which were subjected to FITC-BSA solution. Hydrophobic interactions and charge repulsion are considered as two critical forces responsible for the observed adsorption differences

Development of antibacterial powder coatings using single and binary ion-exchanged zeolite A prepared from local kaolin

Antibacterial electrostatic powder paint coating with intended esthetic criteria was specially formulated for industrial applications using single (Ag+) and binary exchanged (Ag+ and Zn2+) zeolite A, which was prepared from local kaolin resources. Optimization studies on reaction parameters were conducted to obtain the most crystalline zeolite A from kaolin. The Ag+ and Zn2+ exchanged zeolite A samples prepared from kaolin were introduced as filler into the paint matrix during the electrostatic powder coating process. The antibacterial efficacy of the coatings was evaluated against E. coli and S. aureus based on Japanese Industrial Standard JIS Z 2801 method. Color analysis was also performed on these coatings in order to meet the least discoloration criteria, which is relevant to judge the quality of the coatings for industrial use. Single ion-exchanged coatings with Ag+ resulted in discoloring effect, which was diminished by adding Zn2+. The results indicated that the coatings containing both 2 wt% Ag+ and 12 wt% Zn2+ exchanged zeolite A exhibited 99.99% and 99.96% reduction for E. coli and S. aureus, respectively. This was of special interest for zeolite A samples that were prepared from local kaolin resources with more significant discoloration due to using natural kaolin as raw material. In conclusion, a low cost and antibacterial powder paint formulation with desired esthetic criteria using zeolites was achieved for the first time using a combination of Ag+ and Zn2+ ions

Critical analysis of zeolite 4A synthesis through one-pot fusion hydrothermal treatment approach for class F fly ash

In this study, ‘‘One-pot fusion assisted hydrothermal synthesis’’ approach was employed to understand the nucleation and crystallization behaviour of the fusion product of Class F fly ash for zeolite 4A synthesis. Two sets of experiments were conducted by tailoring the control parameter of H2O/Na2O molar ratio (L/S) to investigate the nucleation and crystallization behaviour of zeolite 4A. The molar ratios of SiO2/Al2O3 and Na2O/SiO2 were tuned before alkali fusion by adding different amounts of Al(OH)3 to the fly ash along with the alkali agent, Na2CO3. Under the conditions of 12h aging at 47 °C and 7h crystallization at 90 °C, the sample with high L/S ratio (3.1 Na2O: 2.2 SiO2: 1.0 Al2O3: 79.2 H2O) yielded pure phase of Zeolite 4A with 94% relative crystallinity, while the sample with low L/S ratio (3.1 Na2O: 2.2 SiO2: 1.0 Al2O3: 42.2 H2O) resulted in the highest sodalite impurity. In general, the alkalinity level was observed to be the most dominant factor among all synthesis parameters. Nevertheless, low L/S ratio led to rapid crystallization in just 2.5h at 75 °C. Because of the dependency on the alkalinity level, the dissolution of low-carnegieite (LC) was determined as the decisive factor in the formation of zeolite 4A from the fusion product. The total time of hydrothermal treatment and aging temperature were the other main factors. The crystal growth of zeolite 4A was more sensitive to changes induced by crystallization time and temperature at high L/S ratio. Relative crystallinity of zeolite 4A varied in an expanded range in terms of crystallization time (36%–86%) and temperature (25%–73%) at high L/S ratio