Ismail Boz

Square-wave stripping voltammetric determination of caffeic acid on electrochemically reduced graphene oxide–Nafion composite film

An electrochemical sensor composed of Nafion-graphene nanocomposite film for the voltammetric determination of caffeic acid (CA) was studied. A Nafion graphene oxide-modified glassy carbon electrode was fabricated by a simple drop-casting method and then graphene oxide was electrochemically reduced over the glassy carbon electrode. The electrochemical analysis method was based on the adsorption of caffeic acid on Nafion/ER-GO/GCE and then the oxidation of CA during the stripping step. The resulting electrode showed an excellent electrocatalytical response to the oxidation of caffeic acid (CA). The electrochemistry of caffeic acid on Nafion/ER-GO modified glassy carbon electrodes (GCEs) were studied by cyclic voltammetry and square-wave adsorption stripping voltammetry (SW-AdSV). At optimized test conditions, the calibration curve for CA showed two linear segments: the first linear segment increased from 0.1 to 1.5 and second linear segment increased up to 10 µM. The detection limit was determined as 9.1×10(-8) mol L(-1) using SW-AdSV. Finally, the proposed method was successfully used to determine CA in white wine samples.

Photocatalytic decomposition of 4-chlorophenol over oxide catalysts

4-Chlorophenol in the presence of catalysts was decomposed in aqueous solution by a 125 W medium pressure mercury lamp in a thermostated quartz batch photoreactor, and the organic bound chlorine was catalytically converted into the environmentally less harmful inorganic chloride. Differences in the concentration of 4-chlorophenol and of the intermediates, such as hydroquinone and quinone, are followed by HPLC. The best catalyst among a homolog series for the photo-decomposition of 4-chlorophenol was selected as finely dispersed platinum oxide on a TiO2 semiconductor support, and kinetic parameters of the Langmuir-Hinshelwood type decomposition reaction were reported for the selected catalyst. A simple mechanism of substrate degradation in accord with the chosen kinetic model was postulated. The developed process may serve photooxidative removal of chlorophenols in wastewater without using costly oxidants.

Higher Alcohol Synthesis over a K-Promoted Co2O3/CuO/ZnO/Al2O3 Catalyst

Higher alcohol synthesis over a K2O-promoted Co2O3/CuO/ZnO/Al2O3 catalyst has been studied in an internal recycle reactor under steady-state conditions using hydrogen to carbon monoxide inlet ratios between 0.5 and 3.3 and inlet carbon dioxide concentrations between 0 and 10%. The selectivity of hydrocarbons and alcohols with 1-8 carbon atoms was obtained as a function of exit carbon dioxide content, exit hydrogen to carbon monoxide ratio, and operating temperature (498-578 K), using space velocities between 1500 and 15 000 h-1 (STP). These experiments, combined with information obtained from active catalyst characterization using XPS, indicated that the chain growth probability factor of higher alcohols was independent of conversion, whereas that of hydrocarbons was dependent on conversion.

Composition of Turkish Lemon and Grapefruit Peel Oils

Abstract Lemon [Citrus limon (L.) Burm. f.] and grapefruit (Citrusparadisi Macf.) peel oils were obtained by cold-pressing lemon and grapefruit peels. The oils were analyzed by high-resolution gas chromatograph (HRGC) and high-resolution gas chromatography/mass spectrometer (HRGC/MS). In total, 42 and 27 components have been identified in lemon and grapefruit oils, respectively. Lemon oil showed a high content of monoterpene hydrocarbons (89.9%) with limonene (61.8%), γ-terpinene (10.6%) and β-pinene (8.1%) being the first three major components. Similarly, grape-fruit oil was characterized by its higher content of monoterpene hydrocarbons (96.4%) of which limonene (92.5%) and myrcene (2.6%) were the first two major components. Grapefruit oil contained a lower amount of sesquiterpene hydrocarbons, aldehydes, alcohols and esters than that in lemon oil.

Photodegradation of Methylene Blue with Ag2O/TiO2 under Visible Light: Operational Parameters

Ag2O modified TiO2 nanoparticles were synthesized by precipitation and wet impregnation method. They were characterized by X-ray diffraction technique, UV-vis diffuse reflectance spectrophotometry and Fourier transform infrared spectroscopy. Inductively coupled plasma mass spectrometry was performed to quantify Ag amount in the photocatalysts. The photocatalysts occurred in the concentration range of 0.05%–2% in the Ag/Ti molar ratio. The photocatalytic activity was investigated for the degradation of methylene blue as a model organic dye. Optimum reaction conditions were determined to provide maximum dye degradation efficiencies under visible light. Under visible light illumination, C2-Ag2O/TiO2 (Ag/Ti = 0.1/100) showed the highest activity. Reaction rate constants were calculated and compared for various reaction conditions.

Nafion-graphene composite film modified glassy carbon electrode for voltammetric determination of p-aminophenol

A Nafion-graphene (Nafion-GR) nanocomposite film modified glassy carbon electrode was fabricated by a simple drop-casting method, and used in the electrochemical detection of p-aminophenol (4-AP). Owing to the large surface area, good conductivity of GR and good affinity of Nafion, the sensor exhibited excellent electrocatalytic activity for the oxidation of 4-AP. The electrochemical behaviors of 4-AP on Nafion/GR film modified glassy carbon electrodes were investigated by cyclic voltammetry and differential pulse voltammetry. A calibration curve is constructed in the same matrix, urine, as the unknown samples to be analyzed. The Nafion-GR film modified electrode was linearly dependent on the 4-AP concentration and the linear analytical curve was obtained in the ranges of 0.5–200 μM with differential pulse voltammetry (DPV) and the detection limit was 0.051 μM. The Nafion-graphene nanocomposite modified electrode exhibited good reusability than pure graphene modified GCE. This procedure can be used for the determination of p-aminophenol in the presence of its degradation products and paracetamol. Finally, the proposed method was successfully used to determine p-aminophenol in local tap water samples in urine samples and pharmaceutical preparations.

Spectral characterization and antimicrobial activity of 2-(5-chloro/nitro-1H-benzimidazol-2-yl)-4-bromo/nitro-phenols and their zinc(II) complexes.

2-(5-Chloro/nitro-1H-benzimidazol-2-yl)-4-bromo/nitro-phenols (HL(x); x=1-4) and their complexes with zinc(II)nitrate have been synthesized and characterized. In the tetrahedral mononuclear complexes, the ligands are bidentate, via the imine nitrogen and the phenolate oxygen atoms. The structures of the complexes were confirmed on the basis of elemental analysis, molar conductivity, TGA, FT-IR, NMR, mass and UV-vis spectroscopy. The optimized geometry of the complexes was derived from theoretical calculation in DGauss/DFT level on CACHE program. From theoretical calculations it was found that bromo derivatives of the ligands (HL(1) and HL(3)) have higher stability than the other ligands and similarly, their Zn(II) complexes have higher stability than the other complexes. The antimicrobial activities of the compounds were evaluated using the disk diffusion method against six bacteria and Candida albicans. All of the complexes exhibited selective antibacterial activity on Staphylococcus epidermidis. HL(3) and [Zn(L(1))(2)].H(2)O are more active than Ciprofloxazin and, [Zn(L(2))(2)] has antibacterial activity as potent as Ciprofloxazin against S. epidermidis.

Spectral characterization and antimicrobial activity of Cu(II) and Fe(III) complexes of 2-(5-Cl/NO2-1H-benzimidazol-2-yl)-4-Br/NO2-phenols

The compounds of 2-(5-chloro/nitro-1H-benzimidazol-2-yl)-4-bromo/nitrophenols (HLX : X = 1–4) and their copper(II) nitrate and iron(III) nitrate complexes have been synthesized and characterized. The structures of the complexes were confirmed on the basis of elemental analysis, thermal gravimetric analysis, molar conductivity and magnetic moment measurements, FT-IR, mass, and UV-Vis spectroscopy techniques. The complexes show high-thermal stability with >350°C m.p. In all complexes, the ligands are bidentate via one imine nitrogen and a phenolate oxygen. Cu(II) complexes having 1 : 2 M : L ratio are classified as non-electrolytes, whereas 1 : 1 M : L ratio is observed in Fe(III) complexes except [Fe(L3)2(H2O)2](NO3) ⋅ 3H2O. The antimicrobial activities of the ligands and the complexes were evaluated using the disc diffusion method in DMSO as well as minimum inhibitory concentration dilution method against Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Proteus mirabilis. Antifungal activities were reported for Candida albicans. The complexes [Fe(L3)2(H2O)2](NO3) ⋅ 3H2O and [Cu(L3)2] ⋅ 2H2O are more effective against S. epidermidis than ciprofloxacin.

FTIR spectroscopic and quantum chemical studies on hydantoin

In this study the geometry optimization of monomeric and dimeric forms (D1, D2, and D3) of hydantoin molecule were done using DFT method employing 6–31++G(d, p) basis set. Harmonic and anharmonic wavenumbers and infrared intensities were computed at the same theory level. Experimental IR spectrum was recorded in the region 400–4000 cm−1. It has also been characterized by 1H and 13C NMR spectrum. The hydrogen bond (HB) interaction of hydantoin was analyzed via dimers of hydantoin. Detailed vibrational wavenumber shifts and all vibrational mode analyses were reported. Total energy distributions (TED, %) calculations were done to characterize the fundamentals.

Synthesis and Optical Properties of Sb-Doped CdS Photocatalysts and Their Use in Methylene Blue (MB) Degradation

Abstract Sb-CdS catalysts with good crystalline structure were prepared by chemical precipitation and hydrothermal method. The results showed that hydrothermal treatment is an effective method to prepare CdS based catalysts of hexagonal structure. Single Sb2S3 catalyst has spherical and Sb doped CdS catalysts have hexagonal structure. Sb doped CdS which is prepared by Na2S with chemical precipitation, has cubic structure. The band gap energies of Sb doped CdS photocatalysts were estimated using UV-visible reflectance spectra to be about the range of 2.35–2.57 eV. In particular, the photoluminescence (PL) spectra show enhancing emission peaks that strongly decrease with a doping Sb where the catalyst was prepared with ethylenediamine (EDA) and thioacetamide (TAA), has shown the lowest luminescence intensity. Photocatalytic degradation of methylene blue was carried out using Sb doped and Sb2S3-CdS binary catalysts under a 400 W medium-pressure mercury lamp of visible light irradiation (λ>420 nm). Higher photocatalytic degradation was achieved by adding Sb to CdS catalyst with using hydrothermal method and EDA as coordinating agent compare with the other catalysts. In this case the photocatalytic degradation of the Sb-CdS-EDA-TAA photocatalyst after 4 h irradiation time was about 84 %.