The seeded growth of calcium phosphates. Surface characterization and the effect of seed material

The kinetics of growth of calcium phosphate on seed materials hydroxyapatite, “amorphous” calcium phosphate, enamel, and dentine has been studied at 25°C and at constant physiological pH in stable supersaturated solutions of calcium phosphate. The grown material was characterized chemically, by x-ray powder diffraction and specific surface area measurements and by scanning electron microscopy. In addition, dissolution kinetic studies have been made of the material grown at different times in the crystal growth experiments and of “amorphous” calcium phosphate. The crystallization experiments were made over a range of initial supersaturation to obtain information about the nature of the calcium phosphate phases formed. The specific surface area of the grown phases show marked changes during the growth experiments. The results of the dissolution experiments indicate that the solid material formed in the early stages of crystallization has a stoichiometry corresponding to OCP.     

A thermodynamic interpretation of the behavior of higher fatty alcohols and acids upon the chromatographic paper

An idea was presented of treating the chromatographed substance as a “solute,” and the chromatographic system, composed of the stationary and the mobile phase as a “solvent.” Moreover the concept of “local equilibrium” was introduced, allowing to regard a given chromatographic spot as a “binary solution.” Thus a possibility arose to apply the classical thermodynamic approach, normally used for binary solutions, and namely: μ_i = μ_i + RT ln x_iƒ_i, where μ_i—chemical potential of the “i”-th compound in the solution, μ_i—chemical potential of the pure “i”-th compound, x_i-molar fraction of the “i”-th compound, ƒ_i—its activity coefficient, in a modified form, suitable for the chromatographic purpose.     

Amine groups functionalized gel-type resin supported Pd catalysts: Physicochemical and catalytic properties in hydrogenation of alkynes

Palladium catalysts (0.125–0.5 wt.% Pd) supported by amine groups—functionalized gel-type resin (FCN) were studied in the hydrogenation of alkynes reagents, 2-butyne-1,4-diol and phenylacetylene. The catalysts were prepared by two routes. The first, “OAc” is based on the immobilization of Pd-precursor in the pre-swollen resin from THF solution of Pd(OAc)₂, followed by chemical reduction of the Pd-centers. This method produces Pd particles of size in nano-scale. The second procedure, “aq” implies the deposition of Pd-species on dry resin beads using aqueous solution of PdCl₂. Reduction of these Pd-species gives relatively large Pd particles, dominating are 30–50 nm in size. The SEM studies performed over the cross-section of catalysts grains showed location of Pd in outer shell of polymer beads in both “OAc” and “aq” catalysts; however, thinner layer of Pd appears in “aq” series catalysts. In the presence of all catalysts, prepared by “OAc” and “aq” methods the selectivity towards alkenes is high, above 90%. The catalysts of “aq’ series are much more active and more selective than “OAc” analogues giving selectivity to alkene ca. 94% at almost complete conversion of alkynes. Moreover, catalytic performance of “aq’ series catalyst is unchanged under recycling use. The catalyst was recovered and reused 4 times, maintaining its catalytic efficiency.     

Investigation of the interactions between ginsenosides and amino acids by mass spectrometry and theoretical chemistry

In order to evaluate the essence of the interactions of ginsenosides and proteins which are composed by α-amino acids, electrospray ionization mass spectrometry was employed to study the noncovalent interactions between ginsenosides (Rb₂, Rb₃, Re, Rg₁ and Rh₁) and 18 kinds of α-amino acids (Asp, Glu, Asn, Phe, Gln, Thr, Ser, Met, Trp, Val, Gly, Ile, Ala, Leu, Pro, His, Lys and Arg). The 1:1 and 2:1 noncovalent complexes of ginsenosides and amino acids were observed in the mass spectra. The dissociation constants for the noncovalent complexes were directly calculated based on peak intensities of ginsenosides and the noncovalent complexes in the mass spectra. Based on the dissociation constants, it can be concluded that the acidic and the basic amino acids, Asp, Glu, Lys and Arg, bound to ginsenosides more strongly than other amino acids. The experimental results were verified by theoretical calculations of parameters of noncovalent interaction between ginsenoside Re and Arg which served as a representative example. Two kinds of binding forms, “head–tail” (“H–T”) and “head–head” (“H–H”), were proposed to explain the interaction between ginsenosides and amino acids. And the interaction in “H–T” form was stronger than that in “H–H” form.     

Preparation of alpha-elastin nanoparticles by gamma irradiation

Nanoparticles were prepared by utilizing the thermosensitive aggregation of alpha-elastin and gamma ray crosslinking. Three different heating process, “Slow heating”, “Fast heating”, and “Heat shock”, were applied for the aggregation of the alpha-elastin and examined to yield nanoparticles by gamma rays crosslinking. As a result, only “Slow heating” process yielded nanoparticles with diameters of about ca. 300 nm above cloud point (CP) and about ca. 100 nm below CP, and a narrow size distribution above 1.0 mg/ml concentration (exclude 1.0 mg/ml).     

Adsorption of NOM onto Activated Carbon: Effect of Surface Charge, Ionic Strength, and Pore Volume Distribution

Adsorption of natural organic matter (NOM) onto seven activated carbons with a wide range of surface properties was studied at high and low ionic strength over a range of pH values. From adsorption isotherm studies it was found that, for six of seven carbons, at low surface concentrations, increased ionic strength decreased NOM adsorption. As the surface concentration increased, the adsorption isotherms converged and intersected, after which the addition of salt resulted in increased adsorption. This “crossover point” marked a change in the adsorption mechanism from the “screening reduced” to the “screening enhanced” adsorption regimes. The adsorption mechanisms are extremely complicated and appear attributable to various factors, including electrostatic forces, pore volume distribution, and chemical interactions between the NOM and the surface functionalities on the carbon surfaces.     

Supramolecular edifices and switches based on metals

Our studies allowed to unravel at least partially, the “so-called” spontaneous self-assembly processes of supramolecular edifices based on metals. The formation of a tricuprous double-stranded helix in solution was found to be driven by thermodynamics via highly distorted intermediates. Dinuclear europium(III) triple-stranded helices were built in solution via alternative “braiding” and “keystone” mechanism. The overall process was also dominated by thermodynamics. Moreover, multipodal ligand with the appropriate binding sites can operate as Cu(II)/Cu(I) molecular switches. Recently, we examined ligands with neighboring binding functionalities (N,N) and (N,O) which confer to the corresponding divalent metal complexes new properties. They could operate as proton-driven multistage molecular switching devices based on region-selective metal binding.     

Comparison of chemometric methods for brand classification of cigarettes by near-infrared spectroscopy

The combinations of NIR spectroscopy and three classification algorithms, i.e., multi-class support vector machine (BSVM), k-nearest neighbor (KNN) and soft independent modeling of class analogies (SIMCA), for discriminating different brands of cigarettes, were explored. The influence of the training set size on the relative performance of each algorithm was also investigated. A NIR spectral dataset involving the classification of cigarettes of three brands was used for illustration. Three performance criteria based on “correctly classified rate (CCR)”, i.e., “Average CCR”, “95 percentile of CCR” and “S.D. of CCR”, were defined to compare different algorithms. It was revealed that BSVM is significantly better than KNN or SIMCA in the statistical sense, especially in cases where the training set is relatively small. The results suggest that NIR spectroscopy together with BSVM could be an alternative to traditional methods for discriminating different brands of cigarettes.     

Preparation and catalytic activity of titanium silicalite-1 zeolite membrane with TPABr as template

The preparation of the supported titanium silicalite-1 (TS-1) zeolite membrane with inexpensive tetrapropylammonium bromide (TPABr)/weak base synthesis system was studied by three methods, and the catalytic activity of the obtained TS-1 zeolite membrane was evaluated with the oxidation of 2-propanol (IPA) under pervaporation condition. It was found that TS-1 zeolite membrane could be successfully prepared with “seeding” or “seeding in situ” method, but could not be achieved with “in situ” method. Adding a little amount of promoter ions of PO₄³⁻ into the synthesis gel was of benefit to the catalytic activity of the prepared TS-1 zeolite membrane, but had no obvious effect on the membrane layer formation on the mullite porous support. For “seeding” method, the membrane prepared with the synthesis gel having molar composition of SiO₂:0.1TPABr:0.9Et₂NH:0.03TiO₂:80H₂O:0.06H₃PO₄ at 150 °C for 48 h showed the highest oxidation conversion of IPA of 72% accompanied by a flux of 0.35 kg/m² h. Further more, much higher IPA oxidation conversion of 76% accompanied by a flux of 0.65 kg/m² h was obtained for the TS-1 zeolite membrane prepared with the same synthesis gel by “seeding in situ” method at 150 °C for 72 h.     

Photoresist Modification of Sol–Gel Solutions for Texturing of Bi<Subscript>4</Subscript>Ti<Subscript>3</Subscript>O<Subscript>12</Subscript> and Bi<Subscript>3</Subscript>TiNbO<Subscript>9</Subscript> Thin Films

Bismuth titanate (Bi₄Ti₃O₁₂) and bismuth titanium niobate (Bi₃TiNbO₉) c-axis textured thin films were fabricated using the sol–gel processing technique. Chemical modification of precursor solutions was performed using a proprietary photosensitive chemical (photoresist). Increases in crystallinity and texture of resulting films were seen over films that were made from unmodified solutions. Analysis by X-ray diffraction (XRD) revealed c-axis orientation factors for Bi₄Ti₃O₁₂ near 88% and Bi₃TiNbO₉ near 63% in “modified” films. Atomic force microscopy images of films show microstructural improvement between “modified” and “unmodified” films. Images generally show smaller randomly oriented grains in “unmodified” films, and larger oriented platelet structures related to growth due to crystal habit in “modified” films. Light scattering experiments show the addition of photoresist to the precursor solution initiates accelerated particle growth. AFM imaging of soft-baked films also suggests an enhancement of texture.     

New Method of Analysis of Intermolecular Contacts in the Crystal Structure: π-Complexes

A new method for analysis of intermolecular contacts in the crystal structure based on characteristics of the Voronoi-Dirichlet polyhedra (VDP) is considered using metal π-complexes as examples. The crystal data of the compounds were used to determine the surface area of the VDP faces corresponding to all intermolecular contacts in one π-complex, the total volume of the pyramids with VDP faces as bases and the nuclei of atoms involved in the intermolecular contacts at the vertices, and the total solid angle at which the “intermolecular” VDP faces are seen from the corresponding nuclei of the molecule. A common linear correlation between the enthalpy of sublimation of π-complexes and saturated or unsaturated hydrocarbons and the molecular VDP characteristics was elucidated. On the basis of the results, the enthalpies of sublimation were calculated for some iron π-complexes (for which data on the crystal structure were available) and C₆₀ and C₇₀ fullerenes.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 7, 2005, pp. 495–505.Original Russian Text Copyright © 2005 by Serezhkin, Shevchenko, Serezhkina.     

On the ionic conductivity and phase transitions in the Li2SO4---Li2WO4 system and their relation to ion transport mechanism

Secco et al. have performed several measurements of ionic conductivity, which they have considered as “convincing evidence” that the “paddle-wheel” mechanism does not contribute significantly to ion conductivity in Li₂SO₄-based compositions. However, a comparison of their results in the high-conductivity range with those of other investigators suggests that their data are artifacts. The cause of this is that the resistance of their sulfate-rich samples is about 0.1 ohm at high temperatures. Thus, their results are reliable only for “normal,” i.e., low, conductivities. It is briefly summarized why the “paddle-wheel” mechanism for ion transport is superior to a percolation-type mechanism for a few high-conducting phases.     

Prebiotic chemistry: A fuzzy field

If prebiotic chemistry is defined as the study of the chemical steps, which lead to the first organisms, a clear-cut definition of “living organism” is needed. Unfortunately, no unambiguous and universally accepted definition exists for the concept “living”. Under these conditions, fuzzy logic is probably the methodological tool that can best be used to handle questions pertaining to “the origin of life”. A conventional scale must, however, be defined which interestingly enough, depends necessarily on our present-day scientific knowledge.     

Effect of nanobubbles on friction forces between hydrophobic surfaces in water

Micro- and nanoscale combined hierarchical polymer structures were fabricated by UV-assisted capillary force lithography. The method is based on the sequential application of engraved polymer molds with a UV-curable resin of polyurethane acrylate (PUA) followed by surface treatment with a trichloro(1H,1H,2H,2H-perfluorooctyl) silane in vapor phase. Two distinct wetting states were observed on these dual-roughness structures. One is “Cassie–Wenzel state” where a water droplet forms heterogeneous contact with microstructures and homogeneous contact with nanostructures. The other is “Cassie–Cassie state” where a droplet makes heterogeneous contact both with micro- and nanostructures. A simple thermodynamic model was developed to explain static contact angle, hysteresis, and wetting transition on dual-roughness structures.     

“In situ” ESR and UV-visible spectroscopic studies of iron phthalocyanine films deposited on gold electrodes

The electrochemical behaviour of iron phthalocyanine (Fe^IIPc) films, supported on gold substrates, was studied in 3.5 M NaOH solution, using cyclic voltammetry and coupled “in situ” ESR and UV-visible spectroscopic techniques. Two types of electron transfer were observed in the potential range from −0.45 to −1.0 V vs. Hg/HgO. According to the “in situ” spectroscopy investigations, these two processes were assigned respectively to electron transfers involving first the ligand ring, and then the centre iron ion.     

An infrared spectroscopic study of hydrogen bonding in ethyl phenol: A model system for polymer phenolics

A detailed analysis of the bands appearing in the OH stretching region of the infrared spectrum of ethyl phenol solutions is presented. In cyclohexane solutions, the band due to “free” (non-hydrogen-bonded groups) contains overlapping contributions from both monomeric and end-group species. Other assignments are made on the basis of whether the proton and oxygen in a particular OH group are both involved in hydrogen bonds (as “donors” and “acceptors”, respectively), or if only the proton is acting as a donor. The strongest band in the spectra obtained at the highest concentration of ethyl phenol is due to OH groups present in linear chains of hydrogen-bonded OH groups (as recognized in numerous other studies), but a band due to cyclic trimers has also been identified. The assignment of other modes is more uncertain and various possibilities are discussed. In toluene solutions, assignments are more complicated, because bands due to OH–π hydrogen bonds are observed instead of free groups. Finally, the data from cyclohexane solutions was used to calculate equilibrium constants capable of describing the distribution of species present. A new methodology for determining the equilibrium constant describing association in the form of dimers is described.     

Chemodosimeters and 3D inorganic functionalised hosts for the fluoro-chromogenic sensing of anions

We report here recent examples developed in our research group on the development of novel chemodosimeters for fluoro-chromogenic anion sensing. For instance, squaridine, pyrylium and pent-2-en-1,5-dione dye scaffoldings have been used to obtain highly specific chromo-fluorogenic responses for anions such as cyanide, sulfide or certain carboxylates in water or mixed aqueous solutions. We will also report new examples on the use of “smart sensory materials” based on nanoscopic inorganic structures as bio-mimetic hosts for anion sensing. These systems combine molecular ideas and 3D solid pre-organised features as new design concepts for the development of organic/inorganic hybrid materials for recognition/sensing protocols. For instance, the functionalisation of siliceous mesoporous materials with ureas, thioureas, guanidinium groups or saccharides and suitable dyes has resulted in enhanced fluoro-chromogenic sensing of anionic species such as fatty acids, citrate or borate.     

Conventional and unconventional infrared spectrometry and their quantitative interpretation

In condensed matter, optical properties can be described by a dielectric function (DF), and the structures observed in spectra are then related to the poles and zeros of the DF. As an example, model functions are calculated by a fit to measured spectroscopic data for polystyrene and silica. The first material shows weak, narrow bands and the latter strong, broad bands and a negative real part of the DF.Based on these model DFs, spectra are simulated which are expected to be obtained by “conventional” methods such as transmittance or reflectance measurements, or by “unconventional” methods such as reflectance at oblique incidence, diffuse reflectance, photoacoustic spectroscopy and attenuated total reflectance. A variety of simulated, typical spectra are plotted as a small “atlas”. Conditions are discussed that allow a straightforward procedure for interpreting the spectra quantitatively, i.e., the evaluation of the resonance frequency and the concentration of the oscillators under consideration.It is shown that for systems characterized by weak, narrow oscillator lines, mostly an intuitive interpretation is possible, looking only at the position and strength of “lines” in the spectra. Materials showing strong polar vibrations, however, require more sophisticated procedures for interpreting the spectra.     

On the formation and structure of self-assembling monolayers. I. A comparative atr-wettability study of Langmuir—Blodgett and adsorbed films on flat substrates and glass microbeads

Organized oleophobic monolayers of several long chain compounds and steroid derivatives produced on flat solid substrates by spontaneous adsorption from organic solutions are compared with Langmuir—Blodgett (LB) monolayers transferred on identical substrates from the water-air interface. Quantitative infrared ATR and polarized ATR spectroscopy, and wettability measurements are used to correlate the various films and to determine their molecular density and orientation, mode of film-to-surface binding, and other structural characteristics. Formation of oleophobic adsorbed monolayers on a model powder substrate—smooth glass microbeads—is also investigated. It is concluded that, irrespective of the mode of film-to-surface binding (ionic, covalent, or hydrogen bonding), and the nature of the substrate (Ge, Si, ZnSe, glass slides, glass microbeads), saturation of the adsorption leads in all studied systems to the formation of tightly packed and highly oriented monolayers, structurally equivalent to LB monolayers of same or similar compounds deposited on the bare surfaces of the respective substrates. These findings are interpreted in terms of a cooperative surface process leading to aggregation of molecules into a characteristic “monolayer phase.” Significant structural differences may develop in LB built-up films thicker than one monolayer. A mechanism for the formation of covalently bonded silane monolayers is proposed.     

Probably counterfeit in Roman Imperial Age: Pattern recognition helps diagnostic performed with inductive coupled plasma spectrometry and thermogravimetry analysis of a torso and a head of Roman Age marble statue

This work deals with the attempt to classify marbles, coupling chemometry and two different instrumental techniques, such as inductive coupled plasma atomic emission spectroscopy (ICP-AES) and thermogravimetry analysis (TGA). Chemometrics have been hyphenated, firstly to obtain variables selection on weight loss vs temperature in TGA and after for unsupervised classification of 22 samples (5 ancient marble and 17 single samples from quarries) obtaining a well recognisable classification. The objects in “test set” are the body and the head of one statue and a Torso Virile statue; the “evaluation set” are two well-known ancient finds; the “training set” is constituted by 17 samples coming from marble assigned to Italian, Greek and Turkish quarries.22 elements (Ca, Si, Na, K, Mg Ti, Al, Fe, Pb, Zn, Sr, Zr, Cu, Mn, Rb, Y) are taken into consideration; with TGA 951 values of mass-residual vs temperature are considered. After selection 8 variables from ICP-AES and 4 from TG compose the matrix.We obtain a separation of Italian marbles cluster from marbles of other countries and recognise the different provenience of the body and head and classify the unknown one. This methodology can be applied to classification study of similar ancient artefacts as pottery, ceramics, glass and stones.Counterfeit, or substitution of parts such as head, legs, and hands was a current practice in the late Roman Age, and also in the Renaissance a lot of statues were “rebuilt” with spare parts, so this word describes an historical restoration practice and not just depreciative.