Solution properties of iron(III) complexes with 5-fluorosalicylic acid — spectra,speciation, and redox stability

Iron(III)-5-fluorosalicylic acid systems were investigated in water by pH potentiometry combined with UV-VIS spectrophotometry. The data revealed that stable aquated mono-, bis-, and tris(5-fluorosalicylato) iron(III) complexes are formed together with their monohydroxo and dihydroxo analogues. The stability constants of all present iron(III) species were calculated. Based on pH and the metal: ligand ratio dependent distribution of the species, electronic absorption spectra of the complexes in the visible region were obtained. Redox stability was monitored as an ability to undergo both spontaneous and photoinduced reduction of iron(III) to iron(II). Complexes do not undergo any redox changes when in dark neither in methanol nor in water. While aqueous solutions of complexes are stable under the influence of incident visible radiation, steady-state irradiation of the methanolic systems by visible light led to photoreduction of iron(III) to iron(II), the quantum yield of iron(II) photoformation was determined. Dedicated to Professor Milan Melník on the occasion of his 70th birthday     

Structural and nanomechanical properties of sol–gel prepared (K,Na)NbO3 thin films

Perovskite (K, Na)NbO₃ (KNN) thin films (~100 nm) were prepared by sol–gel/spin coating process on Pt/SiO₂/Si substrates and annealed at 650 °C. The structural properties of KNN films were confirmed by X‐ray diffraction analysis (XRD), Raman spectroscopy and scanning electron, transmission electron and atomic force microscopy (SEM, TEM and AFM) analysis. Pure perovskite phase of K_0.65Na_0.35NbO₃ in nonstoichiometric composition with monoclinic symmetry in film was revealed. Uniform homogeneous microstructure of KNN film with the roughness (~6.9 nm) contained spherical particles (~50–90 nm). Nanoindentation technique was used to characterize the mechanical properties of KNN films. Elastic modulus and hardness of Pt, SiO₂ and KNN thin films were calculated from their composite values of KNN/Pt/SiO₂/Si film/substrate system. The modulus and hardness of KNN film (71 and 4.5 GPa) were lower in comparison with SiO₂ (100 and 7.5 GPa). Pt film (~30 nm) did not influence the composite modulus, but had effect on hardness of KNN film. Copyright © 2015 John Wiley & Sons, Ltd.     

Sintered composite materials on the basis of Fe/FePO4‐coated powders

Composite materials with a network microstructure of α‐Fe areas surrounded by continuous layer of iron phosphate compounds were prepared on the basis of Fe/FePO₄ precipitation coated powder. Spherically shaped particles of this powder were compacted and sintered at 912, 930, 980, 1075 and 1130 °C for 3 min in air. Sufficiently fast heating rate, rapid formation of a liquid phase and fast cooling suppress the development of diffusion processes and consequently the formation of Fe–Fe metallic connections. Microscopic observations showed that, after appropriate processing conditions, an even and continuous layer, comprising a mixture of ferrous orthophosphate and iron oxide compounds, was achieved. Sintering at 1130 °C and fast cooling at ~25 000 °C/min resulted in the formation of a phosphate layer consisting of very fine lamellar structure – graftonite. The phase composition of the phosphate layer was correlated with processing conditions. Corrosion resistance of the sintered composites was measured and related to microstructure and processing technique variants. Copyright © 2014 John Wiley & Sons, Ltd.     

Differentiation of selected blue writing inks by surface-enhanced Raman spectroscopy

Raman spectroscopy and surface enhanced Raman spectroscopy were used to examine 14 blue inks obtained from commercially available stationery. Standard colouring agents in the inks: β-phase of phtalocyanine blue PB15 and some homologues of the methyl violet class, were identified. Surface enhanced Raman spectra were recorded on a firm heterostructure of silver/nanocrystalline diamond/silicon constituting an active substrate providing the possibility to write directly on the surface. Based on the differences in traditional and surface enhanced Raman spectra, two inks were identified unambiguously, the remaining inks were categorised into three groups exhibiting common spectral features. Despite their similarity, surface enhanced Raman spectra exhibited soft variations enabling discrimination of the inks, thus proving the usefulness of the method.     

Universal bound for global positive solutions of a superlinear parabolic problem

We prove universal a priori estimates of global positive solutions of the parabolic problem in , on . Here is a bounded domain in , , and p < 5 if n=3. Received April 6, 2000 / Accepted September 21, 2000 / Published online February 5, 2001     

Peculiarities of the Interaction of Short Oligonucleotides with Supported Lipid Films and Langmuir Monolayers

 The method of electrostriction was applied to supported bilayer lipid membranes (sBLM) and Langmuir monolayers with the aim to study the peculiarities of the interaction of short oligonucleotides with lipid films and of the duplex formation between complementary oligonucleotides. The bilayer lipid membranes (sBLM) were formed on an agar support, whereas Langmuir monolayers were generated on the air-water interface. As an oligonucleotide, the 15-mer 5^′-cholesterolphosphoryl-dT15 (CHpdT15) was synthesized. We could show that the interaction of CHpdT15 with sBLM resulted in a considerable increase of the elasticity modulus perpendicular to the membrane plane (E _⊥) and an increase of the surface potential. Interaction of complementary oligodeoxyadenylate (dA15) with sBLM modified by CHpdT15 resulted in a slight increase of the surface potential whereas E _⊥ slightly decreased. CHpdT15 forms monomolecular layers on the air/water interface. Interaction of dA15 with such monolayers resulted in an increase of the surface pressure, probably due to an increase of the surface charge of the monolayer; similar effects were observed for lipid monolayers modified by CHpdT15. Prospects of using such interactions for detecting DNA hybridization are discussed.     

Approaching bulk limit for three‐dimensional solids via the cyclic cluster approximation: Semiempirical INDO study

The cyclic cluster method has been examined for a number of solids using a recently developed computer code, Solid 98. Calculations are based on the quasirelativistic (QR) INDO/1 (intermediate neglect of differential overlap) method that is simple enough to allow for a saturation of the (cyclic) clusters. Convergence toward the bulk limit (INDO/1) charge density with respect to the size of the model cyclic cluster is shown for diamond, silicon, germanium, boron nitride, gallium phosphide, gallium arsenide, and gallium antimonide. Results show that, as soon as the initial cluster size reaches 5 to 6 nm, one can safely use the obtained density matrix as a good approximation to the bulk limit. ©1999 John Wiley & Sons, Inc. J Comput Chem 20: 253–261, 1999     

Isolation,Purification, Characterization and Direct Conjugation of the Lipid A-Free Lipopolysaccharide of Vibrio cholerae O139

The lipopolysaccharide (LPS) of Vibrio cholerae O139, strain CIRS245, was isolated conventionally, and the lipid A was removed by mild acid hydrolysis (0.1 m NaOAc buffer containing 1 % SDS, pH 4.2, 95 °C, 8 h). The crude product was a complex mixture consisting mainly of constituent fragments of the O-specific polysaccharide-core (OSPc). The OSPc was only a minor component in the mixture. Two-stage purification of the crude OSPc by HPLC gave pure OSPc fragment of the LPS, as shown by NMR spectroscopy, analytical HPLC and ESI-MS. This material is the purest OSPc fragment of the LPS from Vibrio cholerae O139 reported to date. The purified OSPc was readily converted to the corresponding methyl squarate derivative and the latter was conjugated to BSA. The conjugate, when examined by ELISA, showed immunoreactivity with sera from patients in Bangladesh recovering from cholera caused by V. cholerae O139, but not O1.