Surface free energy and wettability of silyl layers on silicon determined from contact angle hysteresis

Using the literature data of the advancing and receding contact angles for water, diiodomethane and hexadecane measured on various hydrophobic silyl layers (mostly monolayers) produced on silicon wafers the apparent surface free energies gamma(s)(tot) were calculated by applying new model of the contact angle hysteresis interpretation. It was found that, for the same silyl layer, the calculated gamma(s)(tot) values to some degree depended on the probe liquid used. Therefore, thus calculated the surface free energies should be considered as apparent ones. Moreover, also the values of the dispersion component gamma(s)(d) of these layers depend on the probe liquid used, but to a less degree. This must be due to the strength of the force field originating from the probe liquid and the spacing between the interacting molecules. The relationships between gamma(s)(tot) and gamma(s)(d) are discussed on the basis of the equations derived. It may be postulated that applying proposed model of the contact angle hysteresis and calculating the apparent total surface free energies and the dispersion contributions better insight into wetting properties of the silyled silicon surface can be achieved.     

Synthesis and optical properties of new polyurethane cationomers with anchored stilbene chromophores

An ionic diol bearing a one‐sided urethane‐stilbene group located on the ammonium quaternary structure was prepared and proposed as an intermediate for polyurethane ionomer synthesis. Polyurethane cationomers with stilbene ionic groups based on poly(tetramethylene oxide) diols, 4,4′‐diphenylmethane diisocyanate and the aforementioned ionic diol, were synthesized and characterized. Some aspects of the trans–cis photoisomerism and fluorescent emission of the stilbene chromophore in polyurethane cationomers were studied comparatively with the urethane‐stilbene diol. The stilbene polycations absorbed at λ_A = 316 nm and emitted violet‐blue light with an emission maxima at λ_F = 444 nm (dimethylformamide solution) and λ_F = 465 nm (film). These polymers are known for their elastomeric properties and are assumed to be of great interest for some future applications. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1918–1928, 2002     

Mass spectral identification of isomeric fluoronitroanilines

The electron impact and methane chemical ionization mass spectra of 2-fluoro-5-nitroaniline and 4-fluoro-3-nitroaniline have been investigated. Similar fragment ions were observed for both compounds under electron impact conditions, but the difference in the relative ion intensities of two key fragment ions allowed the positive identification of these two isomers. The difference can be attributed to an ortho effect involving fluorine and the amino substituent. A fragmentation pathway consistent with this observation is suggested.     

Investigation of Medium Power Radiofrequency Capacitively Coupled Plasmas and Their Application to Atomic Emission Spectrometry for the Determination of Aluminium in Water Samples

A medium power radiofrequency capacitively coupled plasma (275W, 27.12MHz) with low argon consumption (0.5Lmin^–1) was investigated to be used for the determination of aluminium in water samples pneumatically nebulised by atomic emission spectrometry. The plasma torch was operated in two geometric configurations, coaxial and coaxial-annular with single (SRTr.f.CCP) or double ring electrodes (DRTr.f.CCP), respectively. The optimum experimental parameters (observation height, Ar flow rate, distance between ring electrodes, matrix interference of Na⁺ and Ca²⁺ and anion nature) for Al 396.152nm emission were established. Under optimum operating conditions of the DRTr.f.CCP torch (6cm distance between annular electrodes), a detection limit of 70ngmL^–1 aluminium was found. Both operating parameters and several figures of merit of the investigated plasmas were compared to those of microwave plasmas and inductively coupled plasma used in atomic emission spectrometry. The method was used to control the quality of drinking and industrial water. Samples were mineralised with 2mL of 1+1 HNO₃ and 10mL of 1+1 HCl. In the range of 0.15–3.5mgL^–1 Al³⁺ the relative standard deviation varied between 3.7 and 8.6% (n=3). For two certified drinking water samples containing 0.206 and 0.218mgL^–1 Al³⁺ the recovery (n=5) was 97.6±6.8% and 98.6±7.3%, respectively.     

Voltammetry of Osmium End‐Labeled Oligodeoxynucleotides at Carbon,Mercury, and Gold Electrodes

Voltammetric behavior of oligodeoxynucleotide (ODN) 5′‐T₄₀ (GAA)₇–3′ end‐labeled with osmium tetroxide,2,2‐bipyridine [Os(VIII)bipy] was compared with Os(VIII)bipy‐base‐ and with Os(VI)bipy‐sugar‐modified thymine ribosides. Cyclic voltammograms of Os(VIII)bipy‐modified ODN at mercury and carbon electrodes were similar but not identical to those of Os(VIII)bipy‐modified thymine riboside. Treatment of the ODN with Os(VI)bipy did not result in the ODN modification, in agreement with the known specificity of the reagent to the sugar cis‐diols. We show that in addition to mercury and carbon electrodes, the gold electrode can be used to detect Os(VIII)bipy‐labeled ODN. Comparison of voltammetric behavior of end‐labeled ODN using three types of electrodes most frequently used in DNA analysis may help to optimize electrochemical DNA sensors.     

Transfer of selected heavy metals and radionuclides from calcareous peat to saw sedge (Cladium mariscus) in eastern Poland

Summary The level of artificial and natural radionuclide concentration as well as heavy metal content were determined in samples of saw sedge and peat collected in the Special Protection Area of peat bogs near Chelm (Poland). Gamma- and alpha-spectrometry with proper sample preparation were used to determine natural gamma-emitters, artificial ¹³⁷Cs and alpha-radiating plutonium (²³⁸Pu and ^239,240Pu). Non radioactive elements were determined by AAS. Rather low level of heavy metal concentration in all samples was found, however, the transfer factors were significant. Peat contamination with artificial radionuclides (¹³⁷Cs and plutonium) was low. Contrary, the concentration of these isotopes in saw sedge was higher than normally observed in non contaminated areas, what is a result of a significant transfer factor.     

Zirconium sandwich complexes with eta(9) indenyl ligands: well-defined precursors for zirconocene-mediated coupling reactions

A family of isolable, well-defined bis-indenyl zirconium sandwich complexes, (eta(5)-C(9)H(5)-1,3-R(2))(eta(9)-C(9)H(5)-1,3-R(2))Zr (R = silyl, alkyl), have been prepared by either alkane reductive elimination or alkali metal reduction of a suitable zirconium(IV) dihalide precursor. Crystallographic characterization of two of these derivatives, R = SiMe(2)CMe(3) and CHMe(2), reveals unprecedented eta(9) coordination of one of the indenyl ligands. Variable-temperature and EXSY NMR studies establish that the eta(5) and eta(9) rings are rapidly interconverting in solution. The sandwich complexes serve as effective sources of low-valent zirconium reacting rapidly with both olefins and alkynes at ambient temperature. In contrast to bis-cyclopentadienyl chemistry, the olefin adducts of the bis-indenyl zirconium sandwiches undergo preferential C-H activation to yield the corresponding allyl hydride compounds, although reaction with excess olefin proceeds through the eta(2)-olefin adduct, forming the corresponding zirconacyclopentane.     

12. Anil-Synthese. 17. Mitteilung. Über die Herstellung von styryl-derivaten des 2-phenyl-4H-1,2,4-triazolo [1,5-a]pyridins

Preparation of styryl derivatives of 2-phenyl-4H-1,2,4-triazolo [1,5-a]pyridine 7-Methyl-2-phenyl- and 2-(3-chloro-4-methylphenyl)-4H-1,2,4-triazolo[1,5-a]-pyridines react with anils of aromatic aldehydes in the presence of dimethyl-formamide and potassium hydroxide at 20–45° to yield the 2-phenyl-7-styryl- and 2-(2-chloro-stilben-4-yl)-4H-1,2,4-triazolo [1,5-a]pyridines respectively (‘Anil Synthesis’). Further, the Schiff's bases derived from o-chloroaniline and 2-(p-formyl-phenyl)- and 7-formyl-2-phenyl-4H-1,2,4-triazolo [1,5-a]pyridine yield, with methyl- and with p-tolyl-substituted heterocycles, the corresponding heterocyclic substituted styryl and stilbenyl derivatives.     

Effect of aminoacids on the surface free energy of nitrofurantoin

Changes in nitrofurantoin surface free energy components, Lifshitz-van der Waals, _s ^LW , electron donor, _s ^– , and electron acceptor, _s ⁺ , due to adsorption of the aminoacids: lysine, alanine and glutamic acid, were determined by means of the thin-layer wicking technique. It was found that the aminoacids slightly increase the _s ^– component already at 10^–4 M concentration. They reduce the _s ⁺ component practically to zero, and a very sharp increase of _s ^– was observed when the nitrofurantoin surface was precovered from the solutions at concentrations larger tan 10^–4 M. It is concluded that the adsorption of the aminoacids takes place via hydrogen bonding and electrostatic interactions between nitrofurantoin surface and aminoacid molecules. The increase in the _s ^– parameter is probably caused by the presence of carboxyl groups in the aminoacid molecules.     

Pulse-polarographic analysis of nucleic acids and proteins

Nucleic acids and proteins were studied by means of derivative and normal pulse polarography, and d.c. and a.c. polarography in connection with the dropping mercury electrode. It was shown that natural ribonucleic acids, as transfer, ribosomal and viral RNAs yield derivative pulse-polarographic peaks; from their heights and potentials conclusions can be made about their content of ordered structure in solution, similarly as in the case of deoxyribonucleic acids studied earlier. Synthetic single-stranded polyribo-cytidylic acid yields a well developed peak, whereas in the double-helical complex with polyriboguanylie acid it is inactive when using either derivative pulse polarography or d.c. polarography. Well developed peaks were obtained also with albumin (a protein containing reducible?S?S? groups), while only an inflex was observed on the d.c. polarogram. Proteins were also studied in media containing cobalt (Brdi?ka's solution) or nickel and it was shown that derivative pulse polarography due to its high sensitivity and accuracy enables us to carry out the measurements even in less common media than Brdi?ka's solution. This fact could be exploited in clinical chemistry as well as in the investigation of the nature of catalytic currents of proteins. The currents of double-helical polynucleotides obtained by means of normal pulse polarography exhibit a marked dependence on the initial potential and cannot represent a reliable indicator of structural changes of biopolymers in solution. They can however, be used in studies of the influence of the polynucleotide adsorption at different potentials on the subsequent reduction.