Presence Of Organic Molecules Research Articles

Influence of viscosity on the phase transformation of amorphous calcium carbonate in fluids: An understanding of the medium effect in biomimetic mineralization

Biological mineral generation via an amorphous precursor is a topic of great current interest. Various factors such as the temperature, solution composition and presence of organic molecules can influence this important inorganic process. Here we demonstrate that this mineral transformation can actually readily be regulated by solution viscosity, a fundamental but often overlooked property. In our experiment, amorphous calcium carbonate (ACC), a key model compound in biomimetic mineralization studies, is synthesized and dispersed into inert dispersants with different viscosities and the crystallization process is examined by using FT-IR spectroscopy and XRD. It is found that the inhibition of the transformation of ACC becomes more significant with increasing fluid viscosity. This phenomenon can be explained by the differences in ion diffusion in different media. Furthermore, the resulting crystals always have different morphologies and size distributions although they all have the calcite structure. This study implies that the importance of the fluid medium cannot be ignored in building a complete understanding of biological control of biomimetic crystallizations.

Organic molecule directed synthesis of bismuth nanostructures with varied shapes in aqueous solution and their optical characterization

An aqueous synthesis approach has been developed for shape control of Bi nanostructures. Here, we demonstrate a work on the selective preparation of bismuth nanospheres and nanorods reduced by hydrazine hydrate in the presence of organic molecules as controlling agent. Bismuth nanotubes were also obtained by manipulating the reaction parameters in the system. On controlling the size and dispersibility of the project powders, Bi nanospheres with average diameter of 100 nm, Bi nanorods with length of 50 nm or 200 nm, and Bi nanotubes with length of 100–200 nm have been successfully synthesized. We also discussed the possible growth mechanisms of bismuth nanostructures by studying the influences of experimental parameters. The optical absorption spectra of the shape-controlled bismuth nanostructures show strong absorptions in the range of 200–400 nm. These Bi nanostructures are expected to find potential applications in a variety of areas due to their optical characteristics.

Nanoscale morphological design of ZnO crystals grown in aqueous solutions

In the past decade, a wide variety of ZnO crystals were prepared through wet chemical processing. However, the fundamentals of the nanoscale morphological variation of ZnO crystals on the crystal growth in aqueous solution systems have not been sufficiently studied. This paper is a review of the various morphologies of ZnO crystals in relation to the preparation conditions, including the source chemicals, the role of seeds or substrates, and the presence of organic molecules as a shape modifier. Versatile guidelines for controlling the nanoscaled morphologies of ZnO crystals in the forms of individual particles and films as assembly of nanocrystals are proposed on the basis of the classification of typical phenomena. The essential parameters, such as the growth rate, growth site, and growth direction of ZnO crystals, are successfully tuned by varying the degree of supersaturation, the presence of seeds or substrates, and the addition of specific organic molecules, respectively.

Uranium speciation in biofilms studied by laser fluorescence techniques

Biofilms may immobilize toxic heavy metals in the environment and thereby influence their migration behaviour. The mechanisms of these processes are currently not understood, because the complexity of such biofilms creates many discrete geochemical microenvironments which may differ from the surrounding bulk solution in their bacterial diversity, their prevailing geochemical properties, e.g. pH and dissolved oxygen concentration, the presence of organic molecules, e.g. metabolites, and many more, all of which may affect metal speciation. To obtain such information, which is necessary for performance assessment studies or the development of new cost-effective strategies for cleaning waste waters, it is very important to develop new non-invasive methods applicable to study the interactions of metals within biofilm systems. Laser fluorescence techniques have some superior features, above all very high sensitivity for fluorescent heavy metals. An approach combining confocal laser scanning microscopy and laser-induced fluorescence spectroscopy for study of the interactions of biofilms with uranium is presented. It was found that coupling these techniques furnishes a promising tool for in-situ non-invasive study of fluorescent heavy metals within biofilm systems. Information on uranium speciation and uranium redox states can be obtained.

Growth Mechanism and Surface Chemical Characteristics of Dicarboxylic Acid-Modified CeO2 Nanocrystals Produced in Supercritical Water: Tailor-Made Water-Soluble CeO2 Nanocrystals

Tailor-made surface-modified metal oxide nanocrystals enable various applications including medical, electronic, magnetic, and photovoltaic devices. Both the synthesis and application of surface-modified metal oxide nanocrystals rely on the interaction between organic molecules and the surface of metal oxides. From this viewpoint, we have focused on the synthesis of metal oxide nanocrystals using supercritical water in the presence of organic molecules as a surface modifier. Here, we describe the use of dicarboxylic acids with various chain lengths as the modifiers of CeO2 nanocrystals. The morphology and displayed crystallite plane of CeO2 nanocrystals could be controlled by the length of dicarboxylic acids. Long dicarboxylic acids produced cuboctahedral or cubic CeO2 nanocrystals, possibly because of the decreased growth rate of the {200} plane. The growth mechanism of the CeO2 nanocrystals is discussed in detail. Furthermore, dicarboxylic acids on the surface of the CeO2 nanocrystals changed the isoele...

Basic Research Needs on Physical Chemistry of Radionuclides in the Nuclear Fuel Cycle

AbstractFrom uranium-ore treatment to spent fuel recycling, waste treatment and conditioning and to final storage of waste packages, radionuclides are involved in numerous chemical and physical reactions. The understanding of their chemical forms (speciation) and behavior as well (retention, complexation,...), as a function of the environment conditions (T, P, solid/liquid/gas interfaces), are key issues for the development of the industrial nuclear activities. Dedicated analytical tools are needed to determine the radionuclide concentrations and speciation in the liquids, solids and gas, over a wide range of concentrations and matrixes. The obtained experimental data on radionuclide speciation are integrated in dedicated data bases, supporting various models used to simulate the system behavior (i.e. RN migration under geological disposal, RN contamination in the primary fluids of nuclear power plants, RN behavior in the PUREX process, etc.). There are several needs in the following domains of the fuel cycle :♦ The development of innovative methods to enhance analytical performances of isotopic composition of elements in irradiated fuels or waste streams arising from processed spent fuels. Isobaric interferences may be suppressed by specific ion-molecules reactions in collision/cell coupled with Mass Spectrometer, instead of preliminary chromatographic separations.♦ The thermo chemistry at high temperature and pressure of the coolant fluids of the nuclear power plants, to model the solid/liquids interactions controlling its contamination by the activated products and hideout processes.♦ The development of scientific and operational models of the radiolysis of organic molecules and materials, under extreme conditions (γ and α radiolysis), to understand the controlling long-term degradation phenomena ( i.e. H2 degassing in the waste packages).♦ The fundamental understanding of sorption processes of redox sensitive elements such as U on specific mineral surfaces, in the presence of organic molecules, to develop dedicated tools for radionuclide monitoring and measurement in the environment.

The effect of some amines and alcohols on the organized structure of [bmim][BF4] investigated by 1H NMR spectroscopy

The effect exerted by some amines and alcohols on the 1 H NMR spectra of 1-butyl-3methylimidazolium tetrafluoroborate [bmim][BF4] has been studied. This ionic liquid, which is one of the most widely used, is characterized by a high structural order degree, as a consequence of the symmetry and the coordination ability of the anion. In order to have information about the dependence of the detected effects on the alcohol or amine structure, some different primary, secondary and tertiary amines and alcohols have been considered. Furthermore, in the case of amines, their basicity has been also taken into account. Both amines and alcohols induce variation in chemical shifts values and signal multiplicity of imidazolium protons. Collected data show that, among imidazolium protons, the aromatic ones are the most affected by the presence of organic molecule. Cross-correlations among chemical shift values relevant to these protons allow us to explain how 1 H NMR spectrum variations depend on probe structural properties.

Study of the Crystallization of Nanoporous Mixed Metal Oxide Phases

A systematic study of the synthesis and characterization of pristine ceria and of mixed cerium/metal oxides has been undertaken. Various synthetic routes were explored, with the crystallization process being examined via thermal analysis, XRD and electron microscopy. It was shown that even when multiple phases were generated upon heat treatment, mixed phases were also generated. However, the presence of organic molecules during the syntheses, as matrices, solvents or precipitating bases, had a profound effect upon the surface texture of the samples prepared.

Gas-Phase Photodegradation of Decane and Methanol onTiO2: Dynamic Surface Chemistry Characterized by Diffuse Reflectance FTIR

Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was used to study illuminatedTiO2surfaces under both vacuum conditions, and in the presence of organic molecules (decane and methanol). In the presence of hole scavengers, electrons are trapped at Ti(III)–OH sites, and free electrons are generated. These free electrons are seen to decay by exposure either to oxygen or to heat; in the case of heating, reinjection of holes into the lattice by loss of sorbed hole scavenger leads to a decrease in Ti(III)–OH centers. Decane adsorption experiments lend support to the theory that removal of surficial hydrocarbon contaminants is responsible for superhydrophilicTiO2surfaces. Oxidation of decane led to a mixture of surface-bound organics, while oxidation of methanol leads to the formation of surface-bound formic acid.

Selective synthesis and thin-film formation of α-cobalt hydroxide through an approach inspired by biomineralization

An approach inspired by biomineralization leads to the selective formation of highly crystalline α-Co(OH)2 and its oriented thin films in the presence of organic molecules under mild conditions.

Ice nucleation activity of bacteria isolated from snow compared with organic and inorganic substrates

Environmental context. Biological ice nucleators have been found to freeze water at very warm temperatures. The potential of bio-aerosols to greatly influence cloud chemistry and microphysics is becoming increasingly apparent, yet detailed knowledge of their actual role in atmospheric processes is lacking. The formation of ice in the atmosphere has significant local, regional and global influence, ranging from precipitation to cloud nucleation and thus climate. Ice nucleation tests on bacteria isolated from snow and laboratory-grown bacteria, in comparison with those of known organic and inorganic aerosols, shed light on this issue. Abstract. Ice nucleation experiments on bacteria isolated from snow as well as grown in the laboratory, in comparison with those of known organic and inorganic aerosols, examined the importance of bio-aerosols on cloud processes. Snow samples were collected from urban and suburban sites in the greater Montreal region in Canada (45°28′N, 73°45′W). Among many snow bacterial isolates, eight types of bacterial species, none belonging to known effective ice nucleators such as Pseudomonas or Erwinia genera, were identified to show an intermediate range of ice nucleation activity (–12.9 ± 1.3°C to –17.5 ± 2.8°C). Comparable results were also obtained for molten snow samples and inorganic suspensions (kaolin and montmorillonite) of buffered water solutions. The presence of organic molecules (oxalic, malonic and succinic acids) had minimal effect (<2°C) on ice nucleation. Considering experimental limitations, and drawing from observation in snow samples of a variety of bacterial populations with variable ice-nucleation ability, a shift in airborne-species population may significantly alter glaciation processes in clouds.

A systematic study of chromium solubility in the presence of organic matter: consequences for the treatment of chromium‐containing wastewater

AbstractThe treatment objective for wastewater containing Cr(VI) and/or Cr(III) is the reduction of Cr(VI) to the less toxic Cr(III) and the sequestering of Cr(III) from the water streams. The presence of organic matter in the wastewater and in a bioreactor environment may alter the solubility behavior of Cr(III), resulting in poor sequestering and Cr(III) removal from the soluble phase. Systematic experimental solubility results for Cr(III) were obtained in the presence of organic molecules often encountered in industrial effluents containing chromium as well as in biological treatment systems. Chromium solubility curves were determined experimentally from synthetic solutions of Cr(III) in contact with organic acids (acetic, oxalic, citric and ascorbic), amino acids (alanine and aspartic), proteins (albumin and casein) and synthetic nutrient media (yeast extract, nutrient broth and peptones). Experimental data sets were generated for each one of the above organics at three different initial organics concentrations in order to quantify the role of the relative abundance of organic matter in the solubility behavior of Cr(III). A progressive increase of trivalent chromium solubility was systematically observed when the relative abundance of organic ligands to Cr(III) exceeds 10, indicating the existence of a threshold above which the solubility of Cr(III) increases significantly. The hexacoordinate and octahedral character of Cr(III) complexes may explain the need for ligand excess also pointing to a treatment strategy suggesting the relative abundance of organic moieties should be kept below the above threshold. Copyright © 2007 Society of Chemical Industry

Water Behavior Revisited at the Air/Ionic Solution and Silica/Ionic Solution Interfaces. Extension to Coadsorption of Ions and Organic Molecules

This paper reports on investigations about the adsorption at the air-water surface, and for the sake of comparison at the silica-solution interface, of two 1-2 electrolytes, Pb(NO(3))(2) and PbCl(2), at first alone and then from a mixture with carbofuran or with benzene; all of them were at concentrations below 10(-2) M. The limited domain, where the Debye and Hückel formalism for solutions and the Wagner-Onsager-Samaras (WOS) model for surfaces are correct, is then respected. This study was aimed at trying to identify the part played in the surface by the different particles of the system components and in particular the role of water. When aqueous solutions of nonorganic salts are dilute enough, their surface tensions are known to be salt concentration-independent; however, the zero value of the resulting relative adsorption has never been the subject of analysis about water behavior. By combining experimental relative adsorptions and Gibbs excesses calculated from the WOS theory, we will show that, in well-known solutions such as KCl ones, where the negative excess in salt can be very precisely modeled by the WOS theory, the resulting water excess Gamma(W) is negative. The same result can be obtained by taking into account the Ray-Jones effect. This observation drove us to wonder about the results of a similar analysis done on solutions of unsymmetrical electrolytes and on mixtures of salt and organic molecules. Experiments showed that, for all of the systems, Gamma(W) was negative. For a given salt, Gamma(W) was more negative in the presence of organic molecules, and carbofuran was a more efficient water repellent than benzene; water repulsion was greater with nitrates than with chlorides. From these data, it seems that water was repelled toward the solution bulk, whereas ions probably took place between the bulk and a layer of organic molecules. These observations called for a more detailed modeling.

Electrooxidation of benzyl alcohol and benzaldehyde on a nickel oxy-hydroxide electrode in a filter-press type cell

The electrooxidation of benzyl alcohol and benzaldehyde in alkaline medium was carried out in a filter-press type cell on a nickel oxy-hydroxide electrode under different experimental conditions. An overpotential occurs in the presence of organic molecules in the solution shifting oxygen evolution towards higher potentials. The results obtained were conclusive that benzyl alcohol and benzaldehyde electrooxidation on NiOOH layers yielded benzoic acid as the main final reaction product. Chromatographic analysis of the bulk solution showed that the electrocatalytic oxidation of harmful molecules was carried out until the formation of acid compounds (benzoic acid) as an ultimate stage, suggesting that a Ni anode can be used successfully for waste remediation.

A novel paramagnetic polymeric sensor material sensitive to organic molecules

Utilizing the Diels-Alder reaction between cyclopentadiene groups attached on the linear polystyrene in the presence of nitroxide free radicals, a novel cross-linked network containing nitroxide free radicals is prepared. The signals of the electron spin resonance (ESR) from the resultant paramagnetic polymeric material contacting with organic molecules are different from uncontacting with organic molecules obviously. And the response from the organic molecules to organic molecules free or vice versa was reversible. Therefore, the resultant material is a novel paramagnetic polymeric sensor material sensitive to organic molecules and can be used for detecting the presence of organic molecules or the absence of organic molecules.

Layered Tungsten Oxide-Based Organic−Inorganic Hybrid Materials: An Infrared and Raman Study

Tungsten oxide-organic layered hybrid materials have been studied by infrared and Raman spectroscopy and demonstrate a difference in bonding nature as the length of the interlayer organic "spacer" molecule is increased. Ethylenediamine-tungsten oxide clearly displays a lack of terminal -NH3(+) ammonium groups which appear in hybrids with longer organic molecules, thus indicating that the longer chains are bound by electrostatic interactions as well as or in place of the hydrogen bonding that must be present in the shorter chain ethylenediamine hybrids. The presence of organic molecules between the tungsten oxide layers, compared with the layered tungstic acid H2WO4, shows a decrease in the apical W=O bond strength, as might be expected from the aforementioned electrostatic interaction.

Anisotropic lattice distortions in biogenic aragonite

Composite biogenic materials produced by organisms have a complicated design on a nanometre scale. An outstanding example of organic-inorganic composites is provided by mollusc seashells, whose superior mechanical properties are due to their multi-level crystalline hierarchy and the presence of a small amount (0.1-5 wt%) of organic molecules. The presence of organic molecules, among other characteristics, can influence the coherence length for X-ray scattering in biogenic crystals. Here we show the results of synchrotron high-resolution X-ray powder diffraction measurements in biogenic and non-biogenic (geological) aragonite crystals. On applying the Rietveld refinement procedure to the high-resolution diffraction spectra, we were able to extract the aragonite lattice parameters with an accuracy of 10 p.p.m. As a result, we found anisotropic lattice distortions in biogenic aragonite relative to the geological sample, maximum distortion being 0.1% along the c axis of the orthorhombic unit cell. The organic molecules could be a source of these structural distortions in biogenic crystals. This finding may be important to the general understanding of the biomineralization process and the development of bio-inspired 'smart' materials.

Fabrication of Calcium Carbonate with Exquisite Morphologies and Colors through a New Controlled Precipitation Approach

Abstract A new approach involving the in situ hydrolysis of diethyl carbonate in calcium-containing solution was proposed for the controlled precipitation of CaCO3. CaCO3 crystals with exquisite morphologies and colors have been fabricated through this approach in the presence of organic molecules.

Unusual Crystallization Behavior of Selenium in the Presence of Organic Molecules at Room Temperature

Abstract Amorphous Se was converted into fibrous crystals of hexagonal Se or polyhedral crystals of α-monoclinic Se when exposed to organic fluids at room temperature for several days. The growth phase was dependent upon the dielectric constant of the organic liquids. It is notable that hexagonal Se and α-monoclinic Se formed under vapors of d- and l-camphor, respectively. It is proposed that the organic compounds do not act as solvents, but play a catalytic role in the reactions.

Extension of the stability range of the reconstructed Au(1 0 0) surface in the presence of organic molecules

The impact of γ-butyrolactone and cyclohexanone on the stability of the reconstructed Au(1 0 0) surface was investigated by cyclic voltammetry. Moreover, it was noticed that in an appropriate range of cyclohexanone concentration, the current peak due to the lifting of the thermally induced reconstruction changes its shape while the peak due to the lifting of the charge-induced reconstruction does not.