Study of the Thermal Decompositions on N,N-Dialkyl-N'-Benzoylthiourea Complexes of Cu(II), Ni(II), Pd(II), Pt(II), Cd(II), Ru(III) and Fe(III)

The thermal decompositions of the complexes of N,N-dialkyl-N'-benzoylthioureas with Cu(II), Ni(II), Pd(II), Pt(II), Cd(II), Ru(III) and Fe(III) were studied by TG and DTA techniques. These metal complexes decompose in two stages: elimination of dialkylbenzamide, and total decomposition to metal sulphides or metals. The influence of the alkyl substituents in these benzoylthiourea chelates on the thermal behaviour of the metal complexes was investigated.This revised version was published online in November 2005 with corrections to the Cover Date.     

The ranks of certain semigroups of partial isometries

Let \(I_{n}\) be the symmetric inverse semigroup on \(X_{n}=\{1,\ldots ,n\}\), and let \(DP_{n}\) and \(ODP_{n}\) be its subsemigroups of partial isometries and of order-preserving partial isometries on \(X_{n}\) under its natural order, respectively. In this paper we find the ranks of the subsemigroups \(DP_{n,r}=\{ \alpha \in DP_{n}:|\mathrm {im\, }(\alpha )|\le r\}\) and \(ODP_{n,r}=\{ \alpha \in ODP_{n}: |\mathrm {im\, }(\alpha )|\le r\}\) for \(2\le r\le n-1\).     

Control of specific attachment of proteins by adsorption of polymer layers

This study concerns the design of protein-resistant polymer adsorbed layers for the control of surface binding of biospecific recognition entities. Polymer surface layers were prepared using the adsorption of poly(allylamine hydrochloride) (PAH), poly(l-lysine) (PL), and branched and linear polyethyleneimine (PEI) and further modified by the covalent attachment of biotin for specific avidin attachment. The adsorption of PAH, PL, and PEI on silicon substrates was studied as a function of pH and ionic strength using ellipsometry. Average dry layer thicknesses of approximately 10, approximately 5, approximately 9, and approximately 3 A (+/-1 A) were obtained when polymer adsorption occurred from solutions at pH 9.5 that contained 0.5 M NaCl for PAH, PL, branched PEI, and linear PEI, respectively. These polymers showed significant differences in their efficiency to suppress nonspecific avidin adsorption. At low ionic strength, avidin adsorption occurred on all polymer-coated surfaces at basic pH values, despite the same positive electrostatic charge for protein globules and the surface. Though the net electrostatic repulsion between avidin molecules and branched PEI was efficiently screened in a protein solution of pH 7 and 0.15 M NaCl, branched-PEI coatings of high molecular weight were unique in their ability to provide avidin-resistant surfaces as a result of steric hindrance from the branched architecture of adsorbed polymer chains. All polymers studied were effective in suppressing avidin adsorption at pH 3 as a result of protonation of the avidin surface functional groups at this pH. Branched-PEI-coated surfaces were also effective for the suppression of smaller positively charged proteins such as lysozyme and ribonuclease A at pH 7 and 0.15 M NaCl. They were also resistant to the adsorption of negatively charged proteins such as BSA and fibrinogen at pH 7 and 0.75 M NaCl. Furthermore, by using PEI-modified protein-repellent surfaces, selective binding of avidin was achieved to surface-bound silver nanoparticles, which should provide a promising application for the label-free detection of biological species using surface-enhanced Raman scattering (SERS).     

Biosorption of uranium (VI) and thorium (IV) onto Ulva gigantea (K��tzing) bliding: discussion of adsorption isotherms, kinetics and thermodynamic

Ulva gigantea (Kützing) bliding (UGB) obtained from sea inlet of Izmir-Turkey has been studied as a biosorbent for removal of radioactive metals from water. In this study, unmodified UGB and modified UGB with glutaraldehyde (GUGB) characterized by FTIR spectroscopy were used as biosorbents for removal of U(VI) and Th(IV) ions from aqueous solution. Adsorption experiments performed under batch process with initial pH, contact time, adsorbent mass and temperature as variables. In order to determine the adsorption characteristics, Langmuir, Freundlich and Dubinin-Raduschkevich adsorption isotherms were applied to the adsorption data. Adsorption experiments showed that the adsorption isotherms correlated well with the Freundlich model. The sorption followed pseudo-second-order kinetics. The thermodynamic parameters such as variations of ??H°, ??G° and ??S° were estimated as a function of temperature. The thermodynamics of the adsorption of U(VI) and Th(IV) onto UGB and GUGB indicates that the spontaneous and exothermic nature of the process. The results showed that UGB and GUGB were potential for application in removal of U(VI) and Th(IV) from aqueous solution.     

Synthesis of Polyacrylamide Flocculants with Polyethylene Glycol Segments by Photopolymerization

Abstract

Macro photoinitiators possessing polyethylene glycol(PEG) segments were used for radical polymerization of acrylamide(AAm) to yield high molecular weight block copolymers (PAAm-b-PEG-b-PAAm) composed of PEG and polyacrylamide(PAAm) as the inner segment and outer segment respectively. The block copolymers were used as flocculates to clear a saturated borax solution prepared from tincal concentrate and showed good flocculating properties.     

Measurement of soil water using Compton scattering

Compton scattering method has been used as a possible tool in the study of the properties of soil for agricultural purposes. In this study, the soil water is determined by using Compton scattering method. The soil sample was collected from Erzurum and a 2 × 2 in. NaI (Tl) scintillation detector measured Compton scattered radiation from the soil sample. The radioactive source used in the experiment was a ¹³³Ba. The soil samples were irrigated by adding known quantities of water and a standard curve was constructed with the amount of water added versus Compton scattering intensity. It was observed that Compton scattering method in measurement of the soil water has advantages such as practical, inexpensive, non‐destructive and fast analysis. Copyright © 2011 John Wiley & Sons, Ltd.     

Solid phase extractive preconcentration of trace metals using p-tert-butylcalix[4]arene-1,2-crown-4-anchored chloromethylated polymeric resin beads

5,11,17,23-Tetrakis(1,1-dimethylethyl)-25,26-dihydroxy-27,28-crown-4-calix[4]arene in the cone conformation was synthesized. This p-tert-butylcalix[4]arene-1,2-crown-4 compound was then anchored with Merrifield chloromethylated resin beads. The modified polymeric resin was characterized by ¹H NMR, FT-IR and elemental analysis and used successfully for the separation and preconcentration of Cu(II), Cd(II), Co(II), Ni(II) and Zn(II) prior to their determination by FAAS. Effective extraction conditions were optimized in both batch and column methods. The resin exhibits good separating ability with maximum between pH 6.0-7.0 for Cu(II), pH 6.0 for Cd(II), pH 5.0 for Co(II), pH 4.0-4.5 for Ni(II), and pH 4.5 for Zn(II). The elution studies were carried out with 0.5 mol L⁻¹ HCl for Cu(II), Co(II) and Co(II), 1.0 mol L⁻¹ HCl for Cd(II) and Zn(II). The sorption capacity, preconcentration factor and distribution coefficient of each metal ion were determined. The detection limits were 1.10, 1.25, 1.83, 1.68 and 2.01 μg L⁻¹ for Cu(II), Cd(II), Co(II), Ni(II) and Zn(II). The influence of several ions on the resin performance was also investigated. The validity of the proposed method was checked for these metal ions in NIST standard reference material 2709 (San Joaquin Soil) and 2711 (Montana Soil).     

Salicylate Ion‐Selective Electrode Based on a Calix[4]arene as Ionophore

A salicylate‐selective electrode based on calix[4]arene derivative was developed and its response characteristics were investigated. The optimum membrane composition was 1 % ionophore, 30 % PVC, 69 % DOS. The electrode exhibited a Nernstian slope of 58.8±0.5 mV/pSal in the range of 1.0×10^?5–1.0×10^?1 M with a detection limit of 4.3×10^?6 M at pH 4.0, 20±1 °C. The potentiometric response of the electrode in the presence of different anions was investigated by the separate solution method. The lifetime was found at least 4 months, and its response time was 5–10 s. It was successfully used for the potentiometric determination of salicylate in pharmaceutical preparations.     

Absorption and fluorescence properties of aryl substituted porphyrins in different media

Absorption and fluorescence properties of aryl substituted porphyrins, 5,10,15,20-tetra-4-oxy(aceticacid)phenylporphyrin (TAPP), 5,10,15,20-tetra-(4-phenoxyphenyl) porphyrin (TPPP), 5,10,15,20-tetra-(3-bromo-4-hydroxyphenyl) porphyrin (TBHPP), and 5,10,15,20-tetra-p-chloromethylphenyl porphyrin (CMPP) were investigated. The UV/vis absorption, fluorescence and excited spectra as the fluorescence quantum yields and fluorescence lifetimes for the compounds were measured in organic solvents (chloroform (CHCl₃), tetrahydrofuran (THF)) and immobilized media (PVC film, sol–gel matrix). The fluorescence quantum yields of TAPP and TPPP were higher than the others. The fluorescence lifetimes of all studied porphyrin derivates were found to be fifty percent lower and their fluorescence intensities were increased fifty percent more in both of immobilized mediums, as compared to organic solvents.     

In vitro bioactivity and crystallization behavior of bioactive glass in the system SiO2-CaO-Al2O3-P2O5-Na2O-MgO-CaF2

In this study, bioactivity of glass in the system SiO₂-CaO-Al₂O₃-P₂O₅-Na₂O-MgO-CaF₂ was investigated. For this purpose, a glass sample was prepared by the traditional melting method. Crystallization behavior of bioactive glass was also investigated using differential thermal analyses. The Avrami constant of bioactive glass sample calculated according to the Ozawa equation was 3.72 ± 0.4, which indicates bulk crystallization. Using the Matusita-Sakka and the Kissinger equations, activation energy of crystal growth was determined as (394 ± 17) kJ mol⁻¹ and (373 ± 12) kJ mol⁻¹, respectively. These results indicate that the crystallization activation energy data of bioactive glass obtained in this study are accurate and reliable. Bioactivity of the resultant glass sample was analyzed by immersion in simulated body fluid. Scanning electron microscopy, thin film X-ray diffraction, ultraviolet spectroscopy and inductively coupled plasma techniques were used to monitor changes in the glass surface and the simulated body fluid composition. The results revealed that a hydroxyapatite layer was formed on the glass surface after 21 days of immersion in SBF. Formation of the hydroxyapatite layer confirmed the bioactivity of the glass in the system SiO₂-CaO-Al₂O₃-P₂O₅-Na₂O-MgO-CaF₂. In addition, physical and mechanical properties of the sample were measured to determine changes in the properties with the immersion time. The results show that bioactive glass maintained its strength during the immersion in a simulated body fluid solution.