Tahir Tilki

Investigation of electrorheological properties of biodegradable modified cellulose/corn oil suspensions

Considerable scientific and industrial interest is currently being focused on a class of materials known as electrorheological (ER) fluids, which display remarkable rheological behaviour, being able to convert rapidly and repeatedly from a liquid to solid when an electric field (E) is applied or removed. In this study, biodegradable cellulose was modified and converted to their carboxyl salts. Modified cellulose is characterised by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, energy dispersive spectroscopy (EDS), thermogravimetric analysis (TGA) and conductivity measurements. Suspensions of cellulose (C) and modified cellulose (MC) were prepared in insulated corn oil (CO). The effects of electric field strength, shear rate, shear stress, temperature, etc. of these suspensions onto ER activity were determined. Rheological measurements were carried out via a rotational rheometer with a high-voltage generator to investigate the effects of electric field strength and particle concentration on ER performance. The results show that the ER properties are enhanced by increasing the particle concentration and electric field strength. Also the cellulose-based ER fluids exhibit viscoelastic behaviour under an applied electric field due to the chain formation induced by electric polarization between particles.

Synthesis and Characterization of Some N-substituted Polypyrrole Derivatives: Towards Glucose Sensing Electrodes

Synthesis and chemical oxidative polymerization of some N-substituted pyrroles ((N-Py)s) were carried out using Clauson-Kaas method and FeCl3 in CHCl3 medium, respectively. The produced polymers, N-(p-benzoic acid)polypyrrole (NpbPPy); N-(o-aminophenyl)polypyrrole (NoaPPy); N-(m-nitrophenyl) polypyrrole (NmnPPy), were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analysis. An enzymatic glucose biosensor is fabricated through immobilizing glucose oxidase (GOX) into N-substitued polypyrrole matrixes. The parameters affecting the fabrication and experimental conditions of biosensors were optimized. The best biosensor results were obtained for NpbPPy matrix. The sensitivity of the proposed biosensor permitted the determination of glucose in the concentration range of 0–9.2 M with a detection limit of 1× 10− 6. The apparent Michaelis–Menten constant (KM app) for the sensor was found to be 25.95 mM.

Some Novel Conducting Polythiophene Derivatives: Theoretical Analysis, Synthesis, Characterization and Electroreological Properties

A series of alternating phylene and symmetrically bithiophene containing repeat units and the respective homopolymers have been synthesized and characterized by combining FTIR, UV-Vis spectroscopy, four probe conductivity measurement, TGA and SEM analysis. Quantum mechanical calculations of the structures and infrared spectra of the monomers and respective dimers were compared with experimental results. The polymers are soluble in N-methyl-pyrrolidone (NMP). The samples have conductivities of 10−5 S/cm levels. Thermal degradation analysis results indicated that poly-bithiophene derivatives have higher thermal stabilities than poly-monothiophene derivatives. All samples exhibited different surface morphologies. The electrorheological (ER) properties of polymer suspensions in silicone oil were prepared and ER behavior was investigated as a function of shear rate, electric field strength and frequency.

Antimicrobial pyrazole dyes: synthesis, characterization, and absorption characteristics

Twenty-one novel pyrazole azo compounds were synthesized by coupling 3-amino-5-hydroxy-1H-pyrazole and 3-amino-1-phenyl-2-pyrazoline-5-one with diazonium salts derived from aniline, o, m, and p-nitroaniline, o and p-methoxyaniline, o, m, and p-chloroaniline, and o, m, and p-methylaniline. Spectroscopic data for these dyes, dissolved in six solvents, were measured. The effects of acid and base on the visible absorption spectra of the dyes are also reported. The structures of all the compounds were confirmed by Fourier-transform infrared spectroscopy, mass spectroscopy, ultraviolet and visible electronic absorption spectroscopy, nuclear magnetic resonance spectroscopy, and elemental analysis. In addition, the antimicrobial activity of the dyes against six pathogenic bacteria were examined in detail.

Antimicrobial activities and absorption properties of disazo dyes containing imidazole and pyrazole moieties

ABSTRACT The newly synthesized thirteen disazo dyes containing imidazole and pyrazole cycles (3a-3m) were carried out by diazotization reaction of 5-amino-4-arylazo-3-methyl-1H-pyrazoles (2a-2m) and coupling reaction with 1-methyl imidazole. Structures of synthesized azo dyes were characterized by UV–Vis, FT-IR, 1H-NMR, elemental analysis and their solvatochromic properties were studied in DMSO, DMF, methanol, acetic acid and chloroform. In addition, the antimicrobial activities of dyes against twelve pathogenic bacteria were examined in detail and all dyes showed antimicrobial activity against different bacterial strains.

Synthesis of 2,4-dihalogenofluorobenzenes and their antimicrobial and antifungal activity studies

The aim of this study was to synthesize and identify 2,4-dihalogenofluorobenzene (or trihalogenobenzene) derivatives by spectroscopic means, 1H-NMR and 19F-NMR. The 2,4-dihalofluorobenzene derivatives considered were 2,4-dichlorofluorobenzene (1), 2-bromo-4-chlorofluorobenzene (2), 2-iodo-4-chlorofluorobenzene(3), 2,5-dichlorofluorobenzene (4), 2-bromo-5-chlorofluorobenzene (5), 2-iodo-5-chlorofluorobenzene (6).The in vitro antibacterial and antifungal activities of trihalogenobenzene derivatives were studied against the bacteria Staphylococcus aureus ATCC 25923 Gram(+), Bacillus cereus ATCC 6633 Gram(+), Micrococcus flavus (clinical isolate) Gram(+), Morgenella morganii (clinical isolate) Gram(-), Escherichia coli ATCC 27853 Gram(-) and fungus Candida albicans (clinical isolate), obtained from the biology departments of the Pamukkale and Gazi Universities. The antibacterial and antifungal activities were measured by minimum inhibition concentration (MIC) method and the disc-diffusion method used to measure zone diameter against Gram-positive and Gram-negative bacteria and fungi. All these bacteria and fungi were studied against antibiotics to compare the zone diameters with the results from our treatments.

Disazo dyes containing pyrazole and benzothiazole moieties: synthesis, characterization, absorption characteristics and tautomeric structures

Eight newly synthesized disazo disperse dyes containing benzothiazole and pyrazole moieties were prepared by diazotization of 2-aminobenzothiazole, coupling with 3-aminocrotononitrile as active methylene, cyclization reactions with hydrazine hydrate and phenyl hydrazine, diazotization again and finally coupling with dimedone, dioxane, 1-methyl imidazole and 2-methyl imidazole, respectively. Their structures were characterized with spectroscopic methods (FT-IR, 1H-NMR, 13C-NMR) and solvatochromic properties were studied with UV–Vis spectroscopy in different solvents. Tautomeric structures of synthesized dyes were also examined in detail.

Synthesis of a Series of Disperse Disazo Dyes and Investigation of Absorption Properties / Bir Seri Dispers Disazo Boyarmaddelerin Sentezi ve Absorpsiyon Özelliklerinin İncelenmesi

In our study, we aimed to synthesize diazo dyes containing heterocyclic compounds and obtain more batocromic colors. Ethyl 2-cyano-2-(2-phenylhydrazono)acetate (1a-1c) was obtained.with coupling reaction of the diazonium salts of o-, m- and p-NO2 aniline with ethyl cyanoacetate. 5-amino-4-(phenyldiazenyl)-1H-pyrazol-3-ol (2a-2c) mono azo dyes which are containing pyrazole ring were obtained with the ring closure of the obtained results with hydrazine hydrate. Synthesis of new disazo dyes (3a-3c)(4a-4c) were carried out with diazotized again to the obtained mono azo dye and coupling with 4-methyl-1-phenyl-2-pyrazoline and 3-methyl-1H-5-pyrazolone which we were synthesized. Structures of synthesized disazo dyes were characterized by spectroscopic methods. The effects of solvent on the visible absorption spectra of the dyes were also investigated. Calismamizda heterosiklik bilesenler iceren disazo boyarmaddelerin sentezlenmesi ve daha batokromik renklerin elde edilmesi amaclanmistir. o -, m - ve p -NO 2 anilinlerin diazonyum tuzlarinin etilsiyanoasetat ile kenetlenmesi ile etil-2-siyano-2-(2-fenilhidrazono)asetat (1a-1c) elde edilmistir. Elde edilen bu urunlerin hidrazin hidrat ile halka kapanmasi sonucu pirazol halkasi iceren 5-amino-4-(fenildiazenil)-1H-pirazol-3-ol (2a-2c) mono azo boyalari elde edilmistir. Elde edilen mono azo boyalarin tekrar diazolanip sentezledigimiz 4-metil-1-fenil-2-pirazolon ve 3-metil-1H-5-pirazolon bilesikleri ile kenetlenmesi sonucu yeni disazo boyarmaddelerinin (3a-3c)(4a-4c) sentezi gerceklestirilmistir. Sentezlenen disazo sinifi boyarmaddelerin yapilari spektroskopik yontemlerle aydinlatilmistir. Ayrica bilesiklerin absorpsiyon spektrumlari uzerine cozucu etkisi incelenmistir.