Aqueous pathways for formation of zinc oxide particles in the presence of carboxymethyl inulin

In this study, zinc oxide (ZnO) crystals were obtained by a simple wet chemical method using zinc nitrate hexahydrate (Zn(NO₃)₂·6H₂O) and hexamethylenetetramine as the starting materials in the presence of the water-soluble biopolymer carboxymethyl inulin (CMI). We investigated the effect of reaction temperature and CMI concentration on the morphology, surface area, particle size, and size distribution of zinc oxide. X-ray diffraction analysis showed the XRD patterns for all the samples were similar to that of ZnO with the wurtzite structure, irrespective of the geometric shape of the particle. The ZnO rod grows preferentially along the [001] direction in the absence of the CMI. The biopolymer affects the ZnO crystals in a concentration-dependent manner by altering the growth rate of the particles along the c-axis and a-axis. The vast majority of the crystals have a central grain boundary in the presence of CMI. The precipitate consisted of micrometer-sized hexagonally shaped bipyramidal ZnO crystals and nanocrystals.     

A rapid way to synthesize Brønsted acidic ionic liquid and its application as an efficient catalyst for esterification

A novel and time-saving method to prepare a Brønsted acidic ionic liquid, 1-carboxymethyl-3-methylimidazolium hydrogen sulfate ([CMI][HSO₄]), in high yield and purity was performed under microwave irradiation. The ionic liquid showed an incomparable catalytic efficiency in the microwave-accelerated esterification of arenecarboxylic acids. Moreover, its ability of being recovered and reused many times without loss of activity has made [CMI][HSO₄] more favorable from the viewpoint of green chemistry.     

The role of the Czech Metrology Institute in the field of metrology in chemistry

 The main role of a national metrological institute is to assure metrological traceability in the country. Metrology in chemistry is a developing field with specific features quite different from physical metrology and it is very difficult to establish a metrological system in chemistry based on the work of a single national institute, especially in small countries. For this reason the Czech Metrology Institute (CMI) has helped to establish the Association of National Reference Laboratories (METROCHEM) which is responsible for ensuring the traceability of chemical measurements in the Czech Republic. CMI is expected to carry out reference material certification (according to the Law on metrology) and develop special fields (electrochemistry, moisture and protein in grains).     

Fluorescent coronene monoimide gels via H-bonding induced frustrated dipolar assembly

Two stage self-assembly of novel coronene monoimide (CMI) based gels that results in resurfacing of monomer emission in the aggregated state is reported. This process is attributed to a frustrated head-head dipolar assembly forced by hydrogen bonding.     

Two-body Coulomb explosion in methylacetylene in intense laser fields: double proton migration and proton/deuteron exchange

Two-body decomposition processes of methylacetylene (CH(3)CCH) and its isotopomer methyl-d(3)-acetylene (CD(3)CCH) in intense laser fields (790 nm, 40 fs, 5.0 × 10(13) W cm(-2)) are investigated by the coincidence momentum imaging (CMI). In methyl-d(3)-acetylene, a total of six decomposition pathways in which one of the C-C bonds is broken and a total of six pathways in which an atomic hydrogen ion (H(+) or D(+)) or a molecular hydrogen ion (H(2)(+), HD(+), D(3)(+), or HD(2)(+)) is ejected are identified. It is revealed from the analysis of the CMI data that the migration of two deuterons as well as the exchange between a proton and a deuteron occurs prior to the two-body decomposition of a doubly charged parent molecule.     

Comparison of activity measurements in nuclear medicine services in the Czech Republic

Radionuclide calibrator used in nuclear medicine is the radiation detection equipment for measuring radiopharmaceutical activity. This instrument consists of an ionization chamber with an electrometer. This paper examines the variation in the amounts of radioactivity that is associated with dose calibration. The amount of radioactivity in each sample was measured by CMI and compared with values obtained from radionuclide calibrators over a year period. Measurements of serum bottles were within 10 % for ¹⁸F and ⁹⁰Y, 10–15 % for ¹³¹I and ⁵¹Cr, 10–20 % for ^99mTc, 15–20 % for ⁶⁷Ga, 10–25 % for ¹¹¹In, 15–30 % for ²⁰¹Tl and 15–45 % for ¹²³I.     

Efficient Singlet‐State Deactivation of Cyano‐Substituted Indolines in Protic Solvents via CN?HO Hydrogen Bonds

The photophysical properties of indoline (I) and three of its derivatives, namely, N‐methylindoline (MI), 5‐cyanoindoline (CI), and 5‐cyano‐N‐methylindoline (CMI), are studied in H‐donating solvents of varying polarity. Based on measurements of fluorescence yield and lifetime, and of triplet yield and hydrated‐electron formation, two distinct mechanisms of solvent‐induced fluorescence quenching are evidenced. The first mechanism involves the cyano substituent and leads to an increase in the rate constant of internal conversion of one order of magnitude in ethanolic solution and of more than two orders of magnitude in water, as compared to solutions in n‐hexane or acetonitrile. A similar trend had previously been observed in the case of 4‐N,N‐dimethylaminobenzonitrile (DMABN). The second mechanism reduces the fluorescence lifetimes of the non‐cyanated derivatives in aqueous solution by one order of magnitude and is related to the formation of hydrated electrons. Neither of these mechanisms is influenced by methylation at the ring nitrogen. Quantum chemical calculations are performed on the ground and excited states of the hydrogen‐bonded complexes between protic solvents and MI as well as CMI. Stable hydrogen‐bonded configurations involving the CN substituent and a solvent OH group are found; these configurations are stable both in the ground and the first excited singlet states, whereas the corresponding complex at the ring amino nitrogen is stable in the ground state only. The CN? HO configuration is therefore a prime candidate for a mechanistic explanation of the observed quenching by the first mechanism. These findings may have useful applications for the design of fluorescence probes for water in biological systems.     

Prediction and measurement of pollutant emissions in CNG fired internal combustion engine

In the present study, the detailed reaction mechanisms were developed and Chemkin 4.1.1 was implemented to predict the formation of pollutant species in compressed natural gas (CNG) fired internal combustion (IC) engine. The proposed mechanisms were developed by coupling the EXGAS (an automatic mechanism generation tool for alkane oxidation) mechanisms with the Leed's NOx mechanism (version 2.0). The simulation results of each proposed mechanism were validated by the experimental measurements for profiles of temperature, pressure and pollutant species (CO, NOx). The rate of production analysis of each mechanism identified the important reactions in each mechanism which contributed to the formation of pollutant species. In spite of some discrepancies, the experimental measurements indicate that Mechanism-IV (consisting of 208 reactions and 78 species) showed closer agreement for each of the predicted profiles of temperature, pressure and pollutant species (CO, NOx).     

Trigonelline and other betaines in species of Laminariales

A collection of Laminariales species was made with examples in each of the presently recognized families of the order. Extracts of each species were examined for betaines, using primarily 'H NMR spectroscopy for their identification. Glycinebetaine was detected in all species tested and would appear to be a consistent feature of the Laminariales. Gamma-Aminobutyric acid betaine was found in all species of Laminaria examined and in three of the five Saccharina species (family Laminariaceae), but was not detected in species of either other genera of the family or in those of other Laminariales families. Trigonelline was found in some Laminaria and Saccharina species, as well as in the north Pacific species Postelsia palmaeformis (Laminariaceae), Pseudochorda nagaii (Pseudochordaceae) and Akkesiphycus lubricus (Akkesiphycaceae).     

Study on the mineral extraction of legume and grass species from various soil types, by instrumental neutron activation analysis

Instrumental neutron activation analysis (INAA), followed by gamma-ray spectrometry, was used to determine the concentration of K, Ca, Mg, Na, Zn, Fe, Mn, Mo, Co, Cr, La, Eu and Th in six species of legumes and three species of grasses. Each species of forage was cultivated on two differet oxisols, that is, a red yellow Latossol and a dark red Latossol, with the aim of comparing the influence of the soils in the mineral extraction. Besides, on each kind of soil, two different limestone concentrations were used in order to verify how the soil pH correction could influence the elemental absorption in each species, and at the same time; to search for an optimum value of limestone concentration for each soil.     

Characterization of 10 species ofMahonia by capillary electrophoresis

Summary A simple, rapid and effective capillary electrophoresis method was developed for the characterization of 10 different species ofMahonia. A fingerprint of the extract of each species was constructed using a mixed buffer of borate and phosphate, containing methanol, pH 8.0. The effective electrophoretic mobility and % normalized area of each peak in electrophoregrams were evaluated to characterize various species. Three alkaloids: berberine, palmatine and jatrorrhizine were found in all 10 species. The CE technique appears to provide a powerful tool for the identification and quality control of plant drugs.     

A theoretical study of properties and reactions involving arsenic and selenium compounds present in coal combustion flue gases

Species of arsenic and selenium thought to be present in coal combustion flue gases were studied using density functional theory and a broad range of ab initio methods. At each level of theory, the calculated geometries and vibrational frequencies of each species as well as the reaction enthalpies of anticipated reactions were compared with experimental data where available. Comparisons between each calculation are given along with a discussion of the better performance of some theoretical calculations for a given species/reaction.     

Spectroscopic and Potentiometric Investigation of a Diprotic Acid: An Experimental Approach to Understanding Alpha Functions

A laboratory experiment suitable for second- or higher-year chemistry students uses thymol blue, an organic dye, for investigating the fraction of each colored species present as a function of pH. Visible color changes in the vivid, highly absorbing dye permit students to see relative amounts of acid, base, and ampholyte species during the titration, while potentiometric measurement of pH and spectroscopic determination of concentrations permit quantitation of the species present. A standard Beers law calibration curve is constructed for known concentrations of the pure forms of each species at a pH where that species is present as nearly 100% of the total analytical concentration of the dye. Using the molar absorptivities of the three species computed from the calibration curves, simultaneous determination of concentration by species is performed on a set of solutions having constant total concentration of dye such that each solution represents one point in the range pH 0 to pH 13. A mathematical software application is used to solve the simultaneous equations and determine the fraction of each species present. Students then use a spreadsheet application to plot the fractions as functions of pH (the alpha functions). The significance of the isosbestic points in the spectra is also explored.     

Phasor transform to extract glucose and ascorbic acid data in an amperometric sensor

A method for separating the signals from glucose and ascorbic acid on a single recognition surface using an ac immittance technique is presented. It is proposed that each oxidation process can be represented by a unique vector based on psi and YO, and that the concentration of each analyte can be determined by monitoring the change in the admittance magnitude in the direction of the characteristic angle for that particular species. The total Faradaic admittance (YF,total) for all electroactive species present is given by a linear combination of the independent vectors from the different species. In the system tested, the analytes are glucose and ascorbic acid, the former being estimated via the measurand, hydrogen peroxide. Thus, one of the electroactive species (hydrogen peroxide) is not a bulk solution species, but is 'generated' in the enzyme matrix. The admittance measurements from ascorbic acid and the enzyme-generated hydrogen peroxide showed the characteristic phase angles of each oxidation signal, allowing for good spatial resolution. The behaviour of each of these analytes is presented and calibration curves tested. Based on the calibration curves and the basis vectors, samples containing both glucose and ascorbic acid were measured by transforming the measured total admittance from the complex Cartesian space into 'analyte space', where the X-Y axes are given by the basis vectors ?EGHP,GOD and ?AA,GOD, respectively.     

Speciation and biosynthetic variation in four dictyoceratid sponges and their cyanobacterial symbiont, Oscillatoria spongeliae

Four species of marine sponges (Phylum Porifera, Order Dictyoceratida), which contain the filamentous cyanobacterial symbiont Oscillatoria spongeliae, were collected from four locations in Palau. The halogenated natural products associated with the symbiont were characterized from each sample, revealing that each species contained either chlorinated peptides, brominated diphenyl ethers, or no halogenated compounds. Analysis of the host sponges and the symbionts indicated that each species of sponge contained a distinct strain of morphologically similar cyanobacteria. Although cospeciation may be present in this group, we have identified that at least one host switching event has occurred in this symbiosis. Only the strain of O. spongeliae in the sponge containing the chlorinated compounds possessed genes involved in the biosynthesis of chlorinated leucine precursors, indicating that the chemical variation observed in these animals has a genetic foundation.     

A novel kinetic method for the speciation of cadmium in river water by micro solvent extraction with dithizone.

Cadmium species in river water were kinetically extracted with dithizone by varying the extraction time. The obtained extraction curve showed a three-stage stepwise profile that reflected the rate of the ligand substitution reaction between the dithizone and cadmium species. Corresponding to each stage, we divided these extracted cadmium species into three groups: "highly labile", "moderately labile" and "slowly labile" species.     

Estimation of Silica Species’ Concentrations in Lithium and Magnesium Chloride Solutions from the Peak Intensities Observed by FAB-MS

The concentrations of dissolved silica species in electrolyte solutions were derived from the relative intensities of silica species, obtained from FAB-MS measurements (fast atom bombardment mass spectrometry), and the total concentration of dissolved silica. Generally, silica species in aqueous solutions form various complexes with cations such as sodium (Na⁺) or calcium (Ca²⁺), and it has been difficult to determine the concentration of each species. From the observed results from FAB-MS, the chemical species of silica dissolved in lithium chloride (LiCl) and magnesium chloride (MgCl₂) solutions do not include complexes with these cations, and thus Li⁺ and Mg²⁺ do not replace protons of the silanol groups in silica. Therefore, in LiCl and MgCl₂ solutions, all of the simple structures of silicate species can be identified. The concentration of each silica species was estimated on the basis of its mass spectra peak intensities and the total concentration of silica as determined by colorimetry. This study yields the concentration of each silica species within small errors, whereas conventional methods (such as ²⁹Si-NMR) have not yielded the concentrations of individual silica species. From these results, dimers and cyclic tetramers are concluded to be the main species in silica solutions with concentrations of at most 0.1 to 0.2 μmol⋅dm⁻³. This tendency should also occur in NaCl and CaCl₂ solutions, which are major electrolytes in natural waters.     

Multivariate statistical analysis of non‐mass‐selected ToF‐SIMS data

Cluster LMIGs are now regarded as the standard primary ion guns on time‐of‐flight secondary ion mass spectrometers (ToF‐SIMS). The ToF‐SIMS analyst typically selects a bombarding species (cluster size and charge) to be used for material analysis. Using standard data collection protocols where the analyst uses only a single primary bombarding species, only a fraction of the ion‐beam current generated by the LMIG is used. In this work, we demonstrate for the first time that it is possible to perform ToF‐SIMS analysis when all of the primary ion intensity (clusters) are used; we refer to this new data analysis mode as non‐mass‐selected (NMS) analysis. Since each of the bombarding species has a different mass‐to‐charge ratio, they strike the sample at different times, and as a result, each of the bombarding species generates a spectrum. The resulting NMS ToF‐SIMS spectrum contains contributions from each of the bombarding species that are shifted in time. NMS spectra are incredibly complicated and would be difficult, if not impossible, to analyze using univariate methodology. We will demonstrate that automated multivariate statistical analysis (MVSA) tools are capable of rapidly converting the complicated NMS data sets into a handful of chemical components (represented by both spectra and images) that are easier to interpret since each component spectrum represents a unique and simpler chemistry. Copyright © 2008 John Wiley & Sons, Ltd.     

Time-resolved vibrational spectroscopy of a molecular shuttle

Time-resolved vibrational spectroscopy is used to investigate the inter-component motion of an ultraviolet-triggered two-station molecular shuttle. The operation cycle of this molecular shuttle involves several intermediate species, which are observable in the amide I and amide II regions of the mid-IR spectrum. Using ab initio calculations on specific parts of the rotaxane, and by comparing the transient spectra of the normal rotaxane with that of the N-deuterated version, we can assign the observed vibrational modes of each species occurring during the shuttling cycle in an unambiguous way. The complete time- and frequency-dependent data set is analyzed using singular value decomposition (SVD). Using a kinetic model to describe the time-dependent concentrations of the transient species, we derive the absorption spectra associated with each stage in the operation cycle of the molecular shuttle, including the recombination of the charged species.     

Deconvolution of Complex Absorption Spectra Recorded in the Pulse Radiolysis of Aqueous Solutions of 3,5-Dihydroxytolyene

The optical absorption spectra of short-lived species generated in aerated aqueous solutions of 3,5-dihydroxytoluene, a representative of alkylhydroxybenzenes, by the action of single electron beam pulses were recorded. The decay curves recorded at different wavelengths differ from each other, thus suggesting that the transient species react with one another and with water via a complex mechanism and making it possible to discriminate between individual bands characterizing each particular species in the overall spectrum. Two procedures for analyzing complex absorption spectra were employed: (i) with the use of spectra observed at different time delays after the electron pulse and (ii) with deconvolution into a sum of Gaussians.