Mehmet Lütfi Yola

A novel magnetic Fe@Au core–shell nanoparticles anchored graphene oxide recyclable nanocatalyst for the reduction of nitrophenol compounds

In this study, a novel catalyst based on Fe@Au bimetallic nanoparticles involved graphene oxide was prepared and characterized by transmission electron microscope (TEM), and x-ray photoelectron spectroscopy (XPS). The nanomaterial was used in catalytic reductions of 4-nitrophenol and 2-nitrophenol in the presence of sodium borohydride. The experimental parameters such as temperature, the dosage of catalyst and the concentration of sodium borohydride were studied. The rates of catalytic reduction of the nitrophenol compounds have been found as the sequence: 4-nitrophenol>2-nitrophenol. The kinetic and thermodynamic parameters of nitrophenol compounds were determined. Activation energies were found as 2.33 kcal mol(-1) and 3.16 kcal mol(-1) for 4-nitrophenol and 2-nitrophenol, respectively. The nanomaterial was separated from the product by using a magnet and recycled after the reduction of nitrophenol compounds. The recyclable of the nanocatalyst is economically significant in industry.

Development of molecular imprinted nanosensor for determination of tobramycin in pharmaceuticals and foods

In this study, we developed quartz crystal microbalance (QCM) nanosensor for the real-time detection of tobramycin (TOB). Firstly, the modification of gold surface of QCM chip was performed by self-assembling monolayer formation of allyl mercaptane to introduce polymerizable double bonds on the chip surface. Then, TOB imprinted poly(2-hydroxyethyl methacrylate-methacryloylamidoglutamic acid) [p(HEMA-MAGA)] film was generated on the gold surface. The nonmodified and TOB-imprinted p(HEMA-MAGA) surfaces were characterized by using atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectroscopy, ellipsometry and contact angle measurements. The proposed method was validated according to the ICH guideline. The linearity range and the detection limit (S/N=3) were obtained as 1.7×10(-11)-1.5×10(-10) M and 5.7×10(-12) M, respectively. The developed method was applied to pharmaceuticals, and food samples such as chicken egg white and milk extract for the determination of TOB. In addition, association kinetics analysis and isotherm models were applied to the data to explain the adsorption process that took place.

A novel electrochemical sensor based on calixarene functionalized reduced graphene oxide: Application to simultaneous determination of Fe(III), Cd(II) and Pb(II) ions

A glassy carbon electrode (GCE) modified by calixarene functionalized reduced graphene oxide (CA/RGO) has been fabricated and utilized in this study for simultaneous voltammetric detection of several metal ions, Fe(II), Cd(II) and Pb(II), in aqueous solution. The CA/RGO nanocomposite was characterized in surface and electrochemical properties using scanning electron microscopy (SEM), infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), Raman spectroscopy and electrochemical impedance spectroscopy (EIS). The CA/RGO coating significantly improves the sensitivity of electrochemical responses and separation of heavy metals. The electrochemical oxidation of Fe(III), Cd(II), and Pb(II) was performed by square wave voltammetry (SWV). The metal ions, Fe(III), Cd(II), and Pb(II), gave a linear relationship with their concentrations at 1.0×10-10-1.0×10-8M on the CA/RGO/GCE. The detection limits of the metal ions were found to be similar at 2.0×10-11M. A good recovery was also obtained for practical use of the CA/RGO/GCE in pharmaceutical formulation.

Adsorptive stripping voltammetric methods for determination of ezetimibe in tablets

Abstract In this study, square-wave adsorptive stripping voltammetry (SWAdSV) and differential pulse adsorptive stripping voltammetry (DPAdSV) were used for determination of ezetimibe (EZE) in the presence of 0.1 m K2HPO4–Na2B4O7 (1:1) supporting electrolyte. The well-defined peaks for SWAdSV were observed at accumulation time of 15 s, accumulation potential of -0.80 V, frequency of 15 Hz, pulse amplitude of 25 mV, potential increment of 4 mV. For DPAdSV, accumulation time of 15 s, accumulation potential of -0.85 mV, scan rate of 20 mV/s and pulse amplitude of 50 mV were found as the best apparatus parameters. EZE gave rise to a single voltammetric peak in the potential interval from -1236 to -1252 mV for SWAdSV and interval from -1190 to -1210 mV for DPAdSV. The developed methods were validated according to the ICH guideline and were found to be linear, sensitive, specific, precise and accurate. The linearity ranges of EZE for SWAdSV and DPAdSV are 33–596 ng/ml and 66–400 ng/ml, respectively. The developed method was applied successfully for the determination of EZE in tablet dosage form.

Phosphorus–nitrogen compounds: part 30. Syntheses and structural investigations, antimicrobial and cytotoxic activities and DNA interactions of vanillinato-substituted NN or NO spirocyclic monoferrocenyl cyclotriphosphazenes

The gradual Cl replacement reactions of NN (1–3) or NO spirocyclic monoferrocenyl cyclotriphosphazenes (4 and 5) with the potassium salt of 4-hydroxy-3-methoxybenzaldehyde (potassium vanillinate) resulted in the mono (1a–5a), geminal (gem-1b–5b), non-geminal (cis-5b and trans-1b–4b), tri (1c, 3c–5c) and tetra-vanillinato-substituted phosphazenes (1d–5d). All the phosphazene derivatives have stereogenic P-center(s), except tetra-substituted ones. The vanillinatophosphazenes have reversible voltammograms with one-electron anodic and cathodic peaks which are attributed to ferrocenyl redox probe. The structures of the new phosphazene compounds were determined by FTIR, MS, 1H, 13C{1H} and 31P{1H} NMR spectral data. The solid-state structure of cis-5b was examined by single-crystal X-ray diffraction techniques. In addition, the compounds were tested in HeLa cancer cell lines using MTT assay. The 12 phosphazene derivatives were screened for antimicrobial activity, and 3c was very effective against S. aureus even at 4.88xa0µM concentration, taking into account the MIC values. Besides, interactions between the phosphazenes and pBR322 plasmid DNA were also investigated.Graphical AbstractThe vanillinato cyclotriphosphazenes containing pendant monoferrocenyl arms were obtained. Some of the phosphazenes were tested against HeLa cancer cells. The new phosphazenes were screened for antimicrobial activity, and interactions between the phosphazenes and pBR322 plasmid DNA were evaluated. The spectral characterizations of all the phosphazenes were presented.

Phosphorus-Nitrogen Compounds: Part 25. Syntheses, Spectroscopic, Structural and Electrochemical Investigations, Antimicrobial Activities, and DNA Interactions of Ferrocenyldiaminocyclotriphosphazenes

Abstract The condensation reactions of hexachlorocyclotriphosphazene (N3P3Cl6) with mono (1 and 2) and bisferrocenyldiamines (3–5 and 7) resulted in the formation of tetrachloro mono- (8 and 9) and bisferrocenylspirocyclotriphosphazenes (10–13). In addition the tetramorpholino mono- (8a and 9a) and bisferrocenylphosphazenes (10a–12a) were obtained from the reactions of the corresponding tetrachlorophosphazenes (8–12) with excess morpholine. The structures of all the phosphazenes were determined using FTIR, MS, 1H, 13C, and 31P NMR and 2-dimensional NMR techniques. The structures of 9a and 13 were determined by single crystal X-ray diffraction techniques. Cyclic voltammetric investigations of compounds 8a, 9a, and 11a revealed that ferrocene redox centers undergo reversible oxidation. These ferrocenylphosphazenes appear to be quite robust electrochemically. Interactions between the compounds 8a, 9a, 11a, and 12a and pBR322 plasmid DNA were investigated by agarose gel electrophoresis. [Supplementary materials are available for this article. Go to the publishers online edition of Phosphorus, Sulfer, and Silicon and the Related Elements for the following free supplemental files: Additional text and figures.] GRAPHICAL ABSTRACT

Synthesis, In Vitro Antimicrobial and Antioxidant Activities of Some New 4,5-Dihydro-1H-1,2,4-triazol-5-one Derivatives

A series of compounds derived from 4,5‐dihydro‐1H‐1,2,4‐triazol‐5‐one were synthesized and characterized by spectral data. The 12 new compounds were analyzed for their potential in vitro antioxidant activities by three different methods. Compound 4f showed the best activity for the iron binding. In addition, the compounds 4 were titrated potentiometrically with tetrabutylammonium hydroxide in non‐aqueous solvents. The RP‐HPLC capacity factors (k′) of the series were also determined on a C18 column, with methanol/water as the mobile phase. The correlation between logu2009k′ with the percentage of methanol in the mobile phase was used for the determination of the logu2009kw values for these compounds. The antimicrobial activities of these compounds were also screened against bacteria and yeast.