Browsing by Subject "TNT"
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Item Open Access Fluorescent paper strips for highly sensitive and selective detection of nitroaromatic analytes in water samples(Wiley - V C H Verlag GmbH & Co. KGaA, 2017) Daglar, B.; Demirel, G. B.; Bayındır, MehmetA portable, low-cost, flexible, sensitive and selective paper-based sensor was proposed for nitroaromatic explosive detection in water samples. The sensor was designed to achieve π-π stacking formation between emaraldine base polyaniline (PANI) and pyrene (Py) molecules. This π-π stacking formation enables a sensitive turn-off fluorescence quenching under the principle of photo-induced electron transfer (PET) mechanism. PANI−Py absorbed paper strips were immersed into the aqueous mediums of analytes and the fluorescence quenching was observed under a simple UV lamp by naked-eye. Paper strips exhibited∼ 96 % quenching efficiency and the limit of detection was calculated about 9.59 ng/ml. Self-quenching efficiency test showed that the sensor can be used for several weeks under the adequate storing conditions. In addition, experimental findings revealed that the paper-based PANI−Py strips work with high precision in real-samples such as tap water with∼ 85 % quenching efficiency. Moreover the reusability investigations showed that PANI−Py paper-based sensor can be reused 5 times with 54 % sensitivity.Item Open Access Highly fluorescent pyrene-functional polystyrene copolymer nanofibers for enhanced sensing performance of TNT(American Chemical Society, 2015) Senthamizhan, A.; Celebioglu A.; Bayir, S.; Gorur, M.; Doganci, E.; Yilmaz, F.; Uyar, TamerA pyrene-functional polystyrene copolymer was prepared via 1,3-dipolar cycloaddition reaction (Sharpless-type click recation) between azide-functional styrene copolymer and 1-ethynylpyrene. Subsequently, nanofibers of pyrene-functional polystyrene copolymer were obtained by using electrospinning technique. The nanofibers thus obtained, found to preserve their parent fluorescence nature, confirmed the avoidance of aggregation during fiber formation. The trace detection of trinitrotoluene (TNT) in water with a detection limit of 5 nM was demonstrated, which is much lower than the maximum allowable limit set by the U.S. Environmental Protection Agency. Interestingly, the sensing performance was found to be selective toward TNT in water, even in the presence of higher concentrations of toxic metal pollutants such as Cd2+, Co2+, Cu2+, and Hg2+. The enhanced sensing performance was found to be due to the enlarged contact area and intrinsic nanoporous fiber morphology. Effortlessly, the visual colorimetric sensing performance can be seen by naked eye with a color change in a response time of few seconds. Furthermore, vapor-phase detection of TNT was studied, and the results are discussed herein. In terms of practical application, electrospun nanofibrous web of pyrene-functional polystyrene copolymer has various salient features including flexibility, reproducibility, and ease of use, and visual outputs increase their value and add to their advantage.Item Open Access Novel biological materials for food and environmental applications(Bilkent University, 2012) Umu, Özgün Candan OnarmanProbiotics are microorganisms that have many health benefits to their host, such as promoting normal intestinal microflora, inhibiting the growth of pathogenic microorganisms, improving digestion and stimulation of gastrointestinal immunity. Probiotic microorganisms include bacteria, fungi and yeast, and they are highly desirable to be used as animal feed supplements. For this application, Bacillus species are preferred since they are resistant to extreme environmental conditions due to their spore-forming capacity in addition to having other important probiotic characteristics. In the first chapter of this study, 84 independent bacterial colonies were obtained from different bovine chyme samples and among them 29 were determined as belonging to genus Bacillus. These isolates were principally screened for their antimicrobial activity against a group of selected bacteria including pathogenic organisms such as Salmonella enterica, Klebsiella pneumoniae, Pseudomonas aeruginosa and Staphylococcus aureus. 7 strains (STF4, STF8, STF9, STF10, STF15, STF25 and STF26) with highest antimicrobial activity were further tested for other probiotic properties. They were resistant to the gastrointestinal conditions and most of the antibiotics tested. In addition, they were checked for the presence of plasmids and performed cytotoxicity tests. We propose novel Bacillus strains that have potential to be used as probiotic organisms. TNT is a hazardous nitroaromatic compound that can be found in soil, sediment and water due to extensive contamination from military munitions after the World War II. It has many negative health effects on almost all of the living organisms (e.g. bacteria, fungi, algae, animal and human). So far, bacteria, fungi and plants are commonly used for biodegradation process but only a little is known about effect of algae on this issue. However, algae can be used as a good alternative for bioremediation and biosensor purposes as they do not require advance technology and are effective in terms of cost. 5 different microalgae strains (STA1, STA2, STA3, STA4 and STA5) were tested in terms of survival in different TNT concentration and biodegradation capability of TNT. These strains were isolated from water contaminated with TNT obtained from the Brass Factory affiliated with Mechanical and Chemical Industry Corporation (MKE) located in Kırıkkale, Turkey. Even though these strains did not use TNT as carbon source for growth; they utilize it at different degrees for other metabolic activities. Moreover, the growth of STA2 strain was not inhibited by high TNT concentrations (up to 50 mg/L TNT).Item Open Access Reusable and flexible heterogeneous catalyst for reduction of TNT by Pd nanocube decorated ZnO nanolayers onto electrospun polymeric nanofibers(Wiley-Blackwell, 2017-10) Arslan, O.; Eren, H.; Bıyıklı, Necmi; Uyar, TamerAn effective method for the fabrication of well designed nanocomposite for the catalytic reduction of 2,4,6-trinitrotoluene (TNT) was developed. Here, cubic palladium (Pd) nanoparticles were utilized for enhancing the interface properties, attachment quality, catalytic yield and stability after the catalysis reactions. Ligand controlled facet growth by the Br- anions during thermal decomposition of the palladium-precursor resulted with cubic shaped average ∼13 nm palladium nanocubes (Pd NC). The anisotropic Pd NC were utilized to decorate the surface of the zinc oxide (ZnO) nanolayers deposited by atomic layer deposition (ALD) technique on the electrospun polyacrylonitrile (PAN) nanofibers. Due to the polymeric nature of the electrospun PAN nanofibers, Pd NC decorated nanoweb is highly flexible and has a high surface area. For the sustainable Pd NC decoration on the ZnO surfaces coated on PAN nanofibers, anchor points were formed by the functional thiol groups which can facilitate the Pd NC attachment and stability on the ZnO surface. The -OH and alkyl thiol groups obtained via sol-gel reactions positioned on the ZnO layer providing a better interface between ZnO and Pd NC which cannot be obtained by pristine PAN nanofibers. Additionally, due to the increased surface interaction, geometrical positioning on fibers for a better intermediate complex formation and stability via soft-soft interaction, Pd NC decorated flexible polymeric electrospun nanoweb provided enhanced catalytic reduction of TNT in aqueous medium.