UV-Vis Spectrophotometric Measurements Research Articles

Synthesis and Characterization of Ethycarbazole and Thiazole Containing Polymers

In this study bis (ethylcarbazole) diethylthiazole (ECzEBTECz) comonomer was synthesized by Stille coupling reaction and then electrochemically polymerized. The redox behaviour of resulting polymer, P [ECzEBTECz] was investigated by cyclic voltammetry at different scan rates. Polymeric film was further characterized by ATR-FTIR, UV-Visible and fluorescence spectrophotometric measurements. The capacitive behaviour of polymer was investigated by electrochemical impedance spectroscopic (EIS) measurements. Electrical equivalent circuit was applied to the experimental data to correlate the results, obtain the parameter of each element and explain the interface between the glassy carbon/P[ECzEBTECz]/Bu4NPF6 system. Voltammetry results show that the redox behaviour of the polymeric film is quite reversible and stable even at high scan rates. Fluorescence measurements suggest that the emission of the bithiazole moiety allows access to full visible spectrum so the color of polymer expected to suit to the need of optical applications such as LED.

Synthesis and characterization of CdSe nanocrystalline thin films deposited by chemical bath deposition

Cadmium selenide (CdSe) nanocrystalline thin films were prepared by chemical bath deposition (CBD) using ammonia and triethanolamine (TEA) as complexing agents, cadmium chloride and sodium selenosulphate as the sources of Cd2+ and Se2− ions, respectively. The structural and optical properties of CdSe nanocrystalline thin films were investigated as a function of the sodium selenosulphate concentrations or ammonia concentrations in precursors using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD) measurements, transmission electron microscopy (TEM) and UV–visible spectrophotometer measurements. The results reveal that the CdSe thin films are in the pure cubic phase, which composed of a large number of uniform spherical particles. Each spherical particle contains many nanocrystals 3–10nm in crystallite size. An increase in both the average diameter of the spherical particles and the crystallite size of the nanocrystals occurs with an increase in ammonia concentrations. The Se/Cd atom ratios of CdSe thin films firstly increase and then decrease with an increase in ammonia concentration or sodium selenosulphate concentration. The optical band gap of CdSe thin films decrease with an increase in ammonia concentrations. The kinetics and reaction mechanism of the CdSe nanocrystalline thin films during deposition are discussed.

The promising and potential role of IVF in cattle and beef industry

Background and Objective : In this work, dissociation of nano drug 5-Fluorouracil derivatives was studied theoretically.Methodology : For this purpose, Gibbs free energy values for neutral and deprotonated forms of 5-Fluorouracil were calculatedat gas and aqueous phases by using density functional theory (DFT) method. Solvent effects are taken into account by means ofpolarizable continuum model (PCM). Result : It was shown that, theoretically calculated pKa values are in good agreement withthe existing experimental pKa values, which are determined from capillary electrophoresis, potentiometric titration and UV–visible spectrophotometric measurements.

Photodegradation of dimethyldisulfide by heterogeneous catalysis using nanoCdS and nanoCdO embedded on the zeolite A synthesized from waste porcelain

Photodegradation of dimethyldisulfide (DMDS) was examined using nanoCdS and nanoCdO loaded on zeolite A as a heterogeneous catalyst under UV irradiation. Zeolite A was prepared from waste porcelain. Cadmium sulfide nanoparticles were prepared by a precipitation method using zeolite A as a template. Finally, CdO/A was prepared by wet impregnation of parent zeolite NaA with Cd(NO3)2 solution. Fourier transformation infrared, X-ray diffraction, and scanning electron microscopy methods were applied for the characterization of samples. UV–Vis spectrophotometric measurements were performed to determine the extent of decolorization and mineralization. Considering the influence of experimental parameters such as catalyst concentration, DMDS concentration, and pH of the test solutions, the contaminant photoelimination process was studied. The optimal operation parameters were found as follows: pH 1, 0.3g L−1 of catalyst loading, and 8 ppm of DMDS concentration. Based on the obtained results in the photodegradation process of DMDS, the most efficiency was detected in the presence of nanoCdS/A, while no remarkable activity was perceived when bulkCdS was used as the photocatalyst. CdO/A and nanoCdS particles also showed relatively good activities in the photodegradation extent of the contaminate. The degradation process obeyed first-order kinetics.

Rapid Colorimetric Assays to Qualitatively Distinguish RNA and DNA in Biomolecular Samples

Biochemical experimentation generally requires accurate knowledge, at an early stage, of the nucleic acid, protein, and other biomolecular components in potentially heterogeneous specimens. Nucleic acids can be detected via several established approaches, including analytical methods that are spectrophotometric (e.g., A(260)), fluorometric (e.g., binding of fluorescent dyes), or colorimetric (nucleoside-specific chromogenic chemical reactions).(1) Though it cannot readily distinguish RNA from DNA, the A(260)/A(280) ratio is commonly employed, as it offers a simple and rapid(2) assessment of the relative content of nucleic acid, which absorbs predominantly near 260 nm and protein, which absorbs primarily near 280 nm. Ratios < 0.8 are taken as indicative of 'pure' protein specimens, while pure nucleic acid (NA) is characterized by ratios > 1.5(3). However, there are scenarios in which the protein/NA content cannot be as clearly or reliably inferred from simple uv-vis spectrophotometric measurements. For instance, (i) samples may contain one or more proteins which are relatively devoid of the aromatic amino acids responsible for absorption at ≈280 nm (Trp, Tyr, Phe), as is the case with some small RNA-binding proteins, and (ii) samples can exhibit intermediate A(260)/A(280) ratios (~0.8 < ~1.5), where the protein/NA content is far less clear and may even reflect some high-affinity association between the protein and NA components. For such scenarios, we describe herein a suite of colorimetric assays to rapidly distinguish RNA, DNA, and reducing sugars in a potentially mixed sample of biomolecules. The methods rely on the differential sensitivity of pentoses and other carbohydrates to Benedict's, Bial's (orcinol), and Dische's (diphenylamine) reagents; the streamlined protocols can be completed in a matter of minutes, without any additional steps of having to isolate the components. The assays can be performed in parallel to differentiate between RNA and DNA, as well as indicate the presence of free reducing sugars such as glucose, fructose, and ribose (Figure 1).

Rapid Colorimetric Assays to Qualitatively Distinguish RNA and DNA in Biomolecular Samples

Biochemical experimentation generally requires accurate knowledge, at an early stage, of the nucleic acid, protein, and other biomolecular components in potentially heterogeneous specimens. Nucleic acids can be detected via several established approaches, including analytical methods that are spectrophotometric (e.g., A260), fluorometric (e.g., binding of fluorescent dyes), or colorimetric (nucleoside-specific chromogenic chemical reactions).1 Though it cannot readily distinguish RNA from DNA, the A260/A280 ratio is commonly employed, as it offers a simple and rapid2 assessment of the relative content of nucleic acid, which absorbs predominantly near 260 nm and protein, which absorbs primarily near 280 nm. Ratios < 0.8 are taken as indicative of 'pure' protein specimens, while pure nucleic acid (NA) is characterized by ratios > 1.53. However, there are scenarios in which the protein/NA content cannot be as clearly or reliably inferred from simple uv-vis spectrophotometric measurements. For instance, (i) samples may contain one or more proteins which are relatively devoid of the aromatic amino acids responsible for absorption at ≈280 nm (Trp, Tyr, Phe), as is the case with some small RNA-binding proteins, and (ii) samples can exhibit intermediate A260/A280 ratios (~0.8 < ~1.5), where the protein/NA content is far less clear and may even reflect some high-affinity association between the protein and NA components. For such scenarios, we describe herein a suite of colorimetric assays to rapidly distinguish RNA, DNA, and reducing sugars in a potentially mixed sample of biomolecules. The methods rely on the differential sensitivity of pentoses and other carbohydrates to Benedict's, Bial's (orcinol), and Dische's (diphenylamine) reagents; the streamlined protocols can be completed in a matter of minutes, without any additional steps of having to isolate the components. The assays can be performed in parallel to differentiate between RNA and DNA, as well as indicate the presence of free reducing sugars such as glucose, fructose, and ribose (Figure 1).

Investigation on the structure and optical properties of chemically deposited ZnSe nanocrystalline thin films

ZnSe thin films are deposited onto glass substrates by the chemical bath deposition (CBD) method at different hydrazine hydrate concentrations and different zinc sulfate concentrations using the precursors of zinc sulfate, sodium selenosulphate, hydrazine hydrate, ammonia and de-ionized water. The morphology, structural and optical properties of ZnSe nanocrystalline thin films were investigated as a function of hydrazine hydrate concentration or zinc sulfate concentration using scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV–visible spectrophotometer measurements. The results reveal that the ZnSe thin films are composed of a large number of uniform spherical particles. The crystal structure of ZnSe nanocrystalline thin films is the zinc-blende structure. Both the average diameter of the spherical particles and the grain size of the nanocrystals increase with an increase in hydrazine hydrate concentration and/or zinc sulfate concentration. The optical band gap of the ZnSe thin films decrease with an increase in hydrazine hydrate concentration and/or zinc sulfate concentration due to the quantum-size effects. The kinetics and reaction mechanism of the ZnSe nanocrystalline thin films during deposition are discussed.

Speciation of nickel (II) chloride complexes in hydrothermal fluids: In situ XAS study

In situ XAS data of Ni(II) chloride solutions with various salinities (0–7.68m) were collected to investigate the stoichiometry and geometry of Ni(II) chloride complexes from room temperature up to 369°C at 400bar, and to 434°C at 600bar. Increasing temperature and/or salinity results in a change in the coordination of the Ni(II) chlorocomplexes from octahedral to (distorted) tetrahedral. Octahedral species predominate within the whole salinity range at room temperature and up to ~200°C, and tetrahedral species become significant beyond this temperature. At 369°C and 400bar, octahedral species remain in equilibrium with tetrahedral species, and the number of chloride ligands in the first coordination shell depends on the Cl:Ni molar ratio. EXAFS refinements and ab initio XANES calculations show that the highest order chlorocomplex present over the investigated pressure, temperature and composition ranges is the distorted tetrahedral complex [NiCl3(H2O)]−, which predominates in the highest Cl concentration (7.68m) solution at 434°C and 600bar. A quantitative thermodynamic analysis of the XANES and EXAFS data reveals that the XAS data are consistent with the speciation models derived from recent UV-Vis spectrophotometric measurements (25°C–250°C, 100bar; Liu et al., 2012b) and the high temperature, high pressure solubility experiments of Lin and Popp (1984) and Fahlquist and Popp (1989), if the NiCl2(aq) species exists in both octahedral ([NiCl2(H2O)4](aq)) and tetrahedral ([NiCl2(H2O)2](aq)) forms, with the ratio of octahedral to tetrahedral decreasing at high temperature (>200°C). The new XAS data show that the octahedral to tetrahedral transition in Ni(II) chloride complexes occurs at higher temperature and/or salinity than the corresponding Co(II) complexes (Liu et al., 2011).

Revision of iron(III)–citrate speciation in aqueous solution. Voltammetric and spectrophotometric studies

A detailed study of iron (III)–citrate speciation in aqueous solution (θ=25°C, Ic=0.7molL−1) was carried out by voltammetric and UV–vis spectrophotometric measurements and the obtained data were used for reconciled characterization of iron (III)–citrate complexes. Four different redox processes were registered in the voltammograms: at 0.1V (pH=5.5) which corresponded to the reduction of iron(III)–monocitrate species (Fe:cit=1:1), at about −0.1V (pH=5.5) that was related to the reduction of FeL25−, FeL2H4− and FeL2H23− complexes, at −0.28V (pH=5.5) which corresponded to the reduction of polynuclear iron(III)–citrate complex(es), and at −0.4V (pH=7.5) which was probably a consequence of Fe(cit)2(OH)x species reduction. Reversible redox process at −0.1V allowed for the determination of iron(III)–citrate species and their stability constants by analyzing Ep vs. pH and Ep vs. [L4−] dependence. The UV–vis spectra recorded at varied pH revealed four different spectrally active species: FeLH (logβ=25.69), FeL2H23− (logβ=48.06), FeL2H4− (logβ=44.60), and FeL25− (logβ=38.85). The stability constants obtained by spectrophotometry were in agreement with those determined electrochemically. The UV–vis spectra recorded at various citrate concentrations (pH=2.0) supported the results of spectrophotometric–potentiometric titration.

Ab initio studies on acidity and tautomeric equilibrium constants of some benzoxa-, benzothia-, benzoselena-zolinone derivatives

This paper presents ab initio procedure to calculate aqueous-phase acid dissociation constants (pKa) values, accurately. In this work, dissociation and tautomeric equilibrium constants (KT) of some benzoxa-, benzothia-, benzoselena-zolinone derivatives were studied theoretically. For this purpose, Gibbs free energy values for neutral and deprotonated forms of investigated compounds were calculated at gas and aqueous phase by using Hartree–Fock (HF) and density functional theory (DFT) calculation methods. For both calculation methods it was found that 6-311G(d) basis set is the most convenient method. Solvent effects are taken into account by means of conductor-like polarizable continuum model (CPCM). It was shown that, theoretically calculated pKa values are in good agreement with the existing experimental pKa values, which are determined from capillary electrophoresis, potentiometric titration and UV–visible spectrophotometric measurements. Calculated pKa values also revealed that the DFT method (R2=0.92) gave much closed results to experimental values in comparison to Hartree–Fock method (R2=0.86). Due to the all investigated compounds have keto-enol tautomerism, KT and pKT values were calculated without need to form model compounds. Theoretically calculated KT values indicated that, keto forms are predominant for all the investigated compounds.

Complex Stability and Molecular Structure Studies of Divalent Metal Ion with l-Norleucine and Vitamin B3

The stability constants of l-norleucine (Nle) and nicotinic acid (NA) with divalent metal ion (Cu2+, Ni2+, and Co2+) binary and mixed ligand systems at 298 K and ionic strength 0.15 mol·dm–3 NaNO3 water solutions were determined using pH-potentiometry. The stability constants data were estimated using the HYPERQUAD 2008 program, and each complex species was shown graphically using the HySS program. UV–visible spectrophotometric measurements were performed to prove the complex species formation. In addition, the possible binding sites of the ligands Nle and NA to bind metal ions and the Gibbs free energy of some complex species were predicted and evaluated by using the Gaussian 09 program.

Sunlight assisted photodecolorization of crystal violet catalyzed by CdS nanoparticles embedded on zeolite A

Zeolite A was prepared from waste porcelain as a cheap source of Si. Cadmium sulfide nanoparticles were prepared by a precipitation process after ion exchange of Cd 2+ into the zeolite A. Fourier Transformation Infrared (FT-IR), X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) methods were applied for the characterization of samples. The prepared composite was used as a catalyst in the photodecolorization process of crystal violet dye in aqueous solution under sunlight radiation. UV–vis spectrophotometric measurements were performed to determine the extent of decolorization and mineralization. The extent of mineralization was also confirmed by Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) concentration determination and High Performance Liquid Chromatography (HPLC) methods. Considering the influence of experimental parameters such as catalyst concentration, dye concentration, solution pH, and temperature, the dye photoelimination process was studied. The optimal operation parameters were found as follows: pH 9, 1 g L −1 of catalyst loading and 20 ppm of the dye concentration. Zeolite A and naked CdS nanoparticles did not show a remarkable decolorization efficiency. The decolorization process obeyed first-order kinetics.

Effects of Annealing Treatment and Buffer Layer on Properties of ZnMgO Films Prepared on Diamond Substrates

ZnMgO films were prepared at room temperature on freestanding diamond (FSD) substrates with and without ZnO buffer layers by radio-frequency (RF) reactive magnetron sputtering method. The effects of annealing treatment and ZnO buffer layers on the structural, optical, and electrical properties of the ZnMgO films were studied by X-ray diffraction (XRD), UV-visible spectrophotometer, and electrical measurements. The experimental results suggested that the annealing treatment and buffer layer were helpful to improve the crystalline quality of ZnMgO/diamond heteroepitaxial films.

Synthesis and characterization of electrically conductive composite films of polypyrrole/poly(acrylonitrile-co-styrene)

Homogeneus Polypyrrole (PPy)/poly(acrylonitrile-co-styrene) (SAN) composite thin films were prepared by chemical polymerization of pyrrole on poly(acrylonitrile-co-styrene) matrix. Ce (IV) is used as an oxidant for in-situ polymerizion of pyrrole on SAN matrix, having an advantageous over the impregnation method. The formation and incorporation of PPy in the copolymer matrix were confirmed by FTIR-ATR and UV-Visible spectrophotometric measurements. Thermal analyses showed that after polymerization of Py in copolymer matrix, thermal behavior of SAN was changed and derivative of weight loss at this temperature was increased by increasing of PPy content. XPS and FTIR-ATR analysis of composite films indicated cerium salt with nitrate ion acted as a dopant. The increase in the AC electrical conductivity of the PPy/SAN composites over pure SAN was observed. At lower frequency up to 105 Hz, conductivity was shown an independent behavior from frequency; but at high frequencies (105–107 Hz), dependence on frequency was explained by polaron and bipolaron formations of PPy. The dispersion of PPy particles in copolymer matrix was proven by SEM, AFM and digital camera. By the increase of PPy content in the composite films, increase in AC conductivities, and decrease in dielectric constants and loss were observed.

Growth of ZnS Films and Application in Heterojunction

ZnS films were prepared by radio-frequency (RF) magnetron sputtering method. The effects of substrate temperature and annealing treatment on the properties of ZnS films were studied. The ZnS films were characterized by X-ray diffraction (XRD), UV-visible spectrophotometer, and electrical measurements. The results showed that the higher substrate temperature and post-deposition annealing treatment was helpful in improving the crystalline quality of the films, and the film had an n-type conductivity. N-type ZnS films were also deposited on p-type single-crystalline silicon (Si) substrates to fabricate ZnS/ Si heterojunction. The current-voltage (I-V) characteristic of the heterojunction was examined, which showed a rectifying behavior with turn-on voltage of about 2V.

Effect of the Hydrodynamic Conditions on the Electrochemical Degradation of Phenol on a BDD Anode

The influence of the hydrodynamics of the system on the extent of the electrochemical degradation of phenol, using a boron doped diamond (BDD) anode was investigated. Two different electrochemical cells were used: a batch stirred cell (A), with a volume of 200 mL and a BDD anode of 17.5 cm 2 , and a batch with recirculation cell (B), with a BDD anode of 70 cm 2 and connected to a tank of 30 L. Assays were performed at different stirring speeds and applied current density of 300 A m -2 , for cell A, and various flow rates, with an imposed current density of 100 A m -2 , for cell B. Chemical oxygen demand (COD) and total organic carbon (TOC) tests were performed to the samples collected throughout the assays, as well as UV-Vis spectrophotometric measurements. For cell A, after 2 h assay, COD removals between 84 and 94% and TOC removals ranging from 54 and 86 % were attained. For the assays run with cell B, during 10 h, COD and TOC removals varied from 27 to 51% and from 23 to 46%, respectively. The influence of the turbulence near the electrode’s surface in the combustion efficiency was also analysed.

Wet-chemical dip-coating preparation of highly oriented copper–aluminum oxide thin film and its opto-electrical characterization

Transparent p-type semiconducting copper aluminum oxide thin film has been synthesized by a wet-chemical route. CuCl and AlCl 3, dissolved in HCl, are taken as starting materials. pH value of the solution is controlled by adding a measured amount of NaOH into it. Films are deposited by dip-coating technique on glass and Si substrates followed by annealing in air at 500 °C for 3 h. XRD pattern confirms the crystalline CuAlO 2 phase formation in the film and also indicates a strong (0 0 6) orientation. UV–vis spectrophotometric measurements show high transparency of the film in the visible region with a direct allowed bandgap of 3.94 eV. Electrical measurements depict the thermally activated conduction within the films. Thermoelectric measurements confirm the p-type nature of the films. Compositional analysis shows the presence of excess (nonstoichiometric) oxygen within the material, which is incorporated during the air-annealing of the film. According to defect equilibrium, this excess oxygen is predicted to cause the p-type conductivity of the film. This type of cost-effective solution-based technique is very useful for volume production of this kind of technologically important material for transparent electronic and other diverse applications.

Ni2+ cation and imidazole as corrosion inhibitors for carbon steel in sulfuric acid solutions

The effect of Ni2+ cation, imidazole, and mixtures of them on the corrosion behavior of carbon steel in 0.5 M H2SO4 solution was studied by using galvanostatic polarization, potentiodynamic anodic polarization, and weight-loss techniques. Ni2+ cation, imidazole, and mixtures of them provide a good protection to carbon steel against pitting corrosion in chloride-containing solutions. The inhibiting solutions were analyzed by using UV–Vis spectrophotometry. The inhibition was explained on the basis of formation of a complex between the two components. The inhibition mechanism was discussed in terms of the results derived from corrosion and UV–Vis spectrophotometric measurements as well as conductometric investigations.

Inhibitive properties, thermodynamic and quantum chemical studies of alloxazine on mild steel corrosion in H 2SO 4

Alloxazine (ALLOX) was tested as corrosion inhibitor for mild steel in 0.5 M H 2SO 4 solution using non-electrochemical technique (gravimetric and UV–Visible spectrophotometric measurements) at 303–333 K. ALLOX acts as inhibitor for mild steel in acidic medium. Inhibition efficiency increases with increase in concentration of ALLOX but decrease with rise in temperature. The adsorption of ALLOX was found to follow Temkin adsorption isotherm model. Both the activation and thermodynamic parameters governing the adsorption process were calculated and discussed. The adsorption follows a first-order kinetics. DFT study gave further insight into the mechanism of inhibition action of ALLOX.

The effect of calibration equations on the uncertainty of UV–Vis spectrophotometric measurements

The effect of adequateness of the calibration equations on measurement uncertainty was not mentioned by EURACHEM. In this work, we investigate the sources of uncertainty when measuring glucose concentration with a UV–Vis spectrophotometer. The effect of two calibration equations on the uncertainty was compared. The sources of the glucose concentration measurement uncertainty include purity, volume of flasks, mass and the calibration equations. The effects of two calibration equations, linear and polynomial equation, on the uncertainty source were evaluated using the inverse calibration equation. The results indicated that the uncertainty components from purity were the smallest. The volumes of the volumetric flasks had only modest effect on the uncertainty, while the mass was an important source of the uncertainty. The contribution of the calibration equation to the total relative measurement uncertainty was 59.39% for the linear equation and 30.34% for the polynomial equation. With the selection of the adequate equation, the uncertainty source of the calibration equation could be reduced significantly.