(7da) The Crystal Quality and Structure of AM-6

Vanadosilicate AM-6 products with different crystal quality (i.e., disorder, or average length of the V-O-V chains in the AM-6 framework), as determined from the FWHM of ~868 cm^-1 Raman band, but with identical crystallinity/long range order and purity, as determined from the XRD data, were hydrothermally synthesized at 448-503 K using tetramethylammonium (TMA⁺) ions. The combined SEM, EDX, XRD, Raman, TGA, XPS, and nitrogen adsorption isotherm data showed that by treating these as-synthesized materials in gaseous ammonia at 673 K it is possible to completely remove TMA⁺ ions from the AM-6 pores without adversely affecting product crystallinity and the micropore structure of AM-6, and with only minimal degradation of crystal quality of the resulting products. However, the success in a complete removal of TMA⁺ ions without affecting other crystalochemical characteristics of the product depended on its initial crystal quality. TMA⁺ ions could not be completely removed from the lowest crystal quality product (FWHM=20.3 cm^-1) without completely decomposing the V-O-V chains. The intermediate crystal quality product (FWHM=15.0 cm^-1) could be successfully ammonia-treated only at 673 K to remove TMA⁺ ions, but higher temperatures resulted in a complete decomposition of the V-O-V chains. The highest crystal quality product (FWHM=12.7 cm^-1) retained the integrity of V-O-V chains as well as the long range order and the micropore structure when ammonia-treated up to 748 K.

Research Interests:

Molecularly selective photocatalysis is a potential method for using solar energy to destroy environmental pollutants and simultaneously recover useful products. However, commonly investigated photocatalysts are activated by ultraviolet (UV) irradiation because of their wide bandgaps, and UV light accounts only for a small fraction (~4-5%) of solar energy compared to visible light (~45%). In addition, common photocatalysts like TiO2, tend to completely oxidize organic pollutants, and thus preclude the recovery of desirable intermediate products. A novel nanostructured microporous vanadosilicate material, AM-6, with its 3-D pore structure and its ability to be photocatalytically active in the visible range provides a unique opportunity to investigate rate improvements through improved visible light activity, and selectivity through structure and electronic properties of the material for a potentially new and novel photocatalyst.

Postdoctoral Project: Synthesis and characterization of vanadosilicate AM-6 for photocatalytic applications.

During my tenure as a postdoc at the Texas Tech University under Albert Sacco Jr. and Juliuzs Warzywoda, I have broadened my skill set in the areas of materials synthesis and characterization working with a variety of inorganic porous materials. The majority of my work has focused on the quality of AM-6 crystals as well as the development of new synthesis methods and improvement of the crystal quality for photocatalysis applications. Utilization of zeolite and zeo-type materials as thin films has attracted significant relevance as an alternative way in many device applications such as membranes and sensors. In parallel with this purpose, I have worked on the growth of AM-6 thin films for advanced applications. Overall, my postdoctoral work has resulted in the filing of an article published in Microporous and Mesoporous Materials Journal.

I have also collaborated on projects including the investigation of catalytically active zeolites such as ZSM-5 and MCM-22 to improve the yield to the desired chemical products.

PhD Dissertation: Encapsulation of fragrance molecules in microcapsules and nanoporous zeolites.

Nanotechnological approach has recently been introduced into fragrance applications. One of these processes involves microencapsulation of fragrances in polymeric microcapsules, and the other is encapsulation of fragrances in nanoporous zeolites to tailor products with controlled release properties. My Ph.D. work at the Yeditepe University under the supervision of Nurcan Bac, focused on the encapsulation of fragrance using both polymeric microcapsules and zeolites as fragrance carriers. I produced microcapsules, containing fragrance for textile applications. This study was an industry funded project conducted in collaboration with EPS Fragrances Co. I also worked as a Quality Control Engineer in Yeditepe University Cosmetic Research and Production Facility, which provided me an opportunity to develop and transfer into practice various applications of nanotechnology to cosmetics.

In the 5^th semester of my Ph.D., I was accepted to the Research Fellowship Program at Texas Tech University and worked under Albert Sacco Jr. and Juliuzs Warzywoda. During my visit, I focused on synthesis and characterization of zeolite X crystals for adsorption and desorption applications and improved my instrumental skills by learning XRD, SEM, EDX, and TGA/DSC. In addition to adsorptive properties of zeolites, I studied on the ion-exchanged zeolites in collaboration with the Genetics and Bioengineering Department to understand the antimicrobial behavior of zeolites. My Ph.D. work resulted in publications (4 first-authored papers and 1 book chapter).

Publications

• Tekin, R., Warzywoda, J., and Sacco, A. (2017). The effect of gaseous ammonia treatment of AM-6 crystallized in the presence of tetramethylammonium cations on their removal from crystal pores, and the crystal quality and structure of AM-6, 251, 94-104.

• Tekin, R., Bac, N., and Erdogmus, H. (2017). Assessment of Zeolites as Antimicrobial Fragrance Carriers, Antimicrobial Research: Novel bioknowledge and educational programs (Accepted).

• Tekin, R. and Bac, N. (2016). Antimicrobial behavior of ion-exchanged zeolite X containing fragrance. Microporous and Mesoporous Materials, 234, 55-60.

• Tekin, R., Bac, N., Warzywoda, J., and Sacco, A. (2015). Encapsulation of a fragrance molecule in zeolite X. Microporous and Mesoporous Materials, 215, 51-57.

• Tekin, R., Bac, N., Warzywoda, J., and Sacco, A. (2015). Effect of reaction mixture composition and silica source on size distribution of zeolite X crystals. Journal of Crystal Growth, 411, 45-48.

• Tekin, R., Bac, N., and Erdogmus, H. (2013). Microencapsulation of Fragrance and Natural Volatile Oils for Application in Cosmetics, and Household Cleaning Products. In Macromolecular Symposia (Vol. 333, No. 1, pp. 35-40).

Teaching Interests:

I have considerable teaching experience and previously served as a teaching assistant for Design of Chemical & Biological Processing Units and Experimental Chemical and Bioprocess Engineering courses in the Chemical Engineering Department at Yeditepe University, Istanbul. I delivered several lectures and led tutorial and review sessions. I was praised by the students for the clarity of my presentation and conveyance of learning objectives, and my empathy for student advancement. I believe, I have the credentials to make significant contributions to teaching in the Chemical Engineering or Material Science Department. My research and teaching expertise has prepared me to teach Design of Chemical Processing Units as well as Mass Transfer. I can also teach any course in the core chemical engineering curricula and technical electives such as Materials Science and Instrumental Analysis. Students will be given the opportunity to work in project teams to investigate a topic of their choosing. Over the course of the semester, they will teach their classmates, using the educational tools, and give a presentation on their chosen topic. In addition to enhancing their understanding through peer instruction, they will gain valuable practice giving presentations. My goal is to help students identify important problems and to arrive at intelligent solutions by teaching critical thinking skills.

I am currently a Research Associate in the Materials Characterization Center at College of Engineering, Texas Tech University and conduct comprehensive hands on training for the users of X-ray powder diffractometers (XRD); transmission electron microscopy (TEM); field emission scanning electron microscopy (FE-SEM); TGA/DSC; XPS, FTIR, Raman, UV-Vis, EDX and GC.MS spectrometers; confocal microscopy; particle size analyzers; zeta potential analyzer; gas sorption analyzer for characterization of surface area, pore volume, and pore size distribution of microporous and mesoporous solids. I have mentored several undergraduate and graduate students in Texas Tech and Yeditepe University. I found each of these experiences to be very rewarding and believe they have helped prepare me for future mentorship and teaching roles. I have obtained Global Scholarship for the 21st Century Award in recognition of the distinguished academic achievements during my tenure as a visiting international scholar at Texas Tech University.