Partitioning sample collection/solvent extraction cartridge packed with octadecyl‐derivatized macroporous silica particles for the analysis of sesquiterpenes in air samples

A novel sampling device based on the partition of target analytes to the extraction medium was developed for the determination of sesquiterpenes in air samples. The extraction medium was prepared by the chemical derivatization of a specially prepared macroporous silica, with a specific surface area of 2.0 m²/g. Taking advantage of the sample extraction, which was mainly based on the partition of sesquiterpenes between air and a C₁₈‐bonded phase, the extracted analytes were rapidly and quantitatively desorbed just by passing a small amount of desorption solvent for subsequent analysis by gas chromatography with mass spectrometry. Several experimental conditions, such as the sampling volume and temperature, were systematically evaluated. Under optimized conditions, desorption of the extracted analytes was completed within 1 min with a desorption efficiency of more than 99.9%, achieved using 5 mL of acetone for all the evaluated sesquiterpenes. The applicability of the developed device was confirmed by the determination of several sesquiterpenes from coniferous trees. Although further improvements of the device are required for collecting large volumes or high‐temperature air samples, the potential of the developed sampling device was confirmed by determining traces of semivolatile organic compounds in air samples.     

Characteristics of granular boehmite and its ability to adsorb phosphate from aqueous solution

In this study, we investigated the surface properties of granulated boehmite with vinyl acetate (G-BE20) and measured the amount of phosphate it adsorbed and the effect of contact time and solution pH on the adsorption process. The specific surface area (144.9?m²/g) and the number of surface hydroxyl groups (0.88?mmol/g) of G-BE20 were smaller than those of virgin boehmite (BE), which gave a specific surface area and number of surface hydroxyl groups of 297.0?m²/g and 1.08?mmol/g, respectively. The amount of phosphate adsorbed increased with the temperature. The isotherm model of Langmuir was used to fit experimental adsorption equilibrium data for phosphate adsorption onto G-BE20. The calculated thermodynamic parameters show the spontaneous and endothermic nature of the adsorption process. The equilibrium adsorption onto G-BE20 was reached within 16?h and the amount of phosphate adsorbed was 8.4?mg/g. The kinetic mechanism of phosphate uptake was evaluated with two different models: the Largergren pseudo first- and pseudo second-order models. The data obtained showed a better fit to the pseudo second-order model (0.991) than to the pseudo first-order model (0.967), as indicated by the r values. The rate constants for the adsorption of phosphate onto G-BE20 were calculated as 0.481?1/h and 0.029?g/mg?h. The adsorption of phosphate onto G-BE20 was the maximum in the pH range 3.0-4.0.     

Gold-Titanium(IV) Oxide Plasmonic Photocatalysts Prepared by a Colloid-Photodeposition Method: Correlation Between Physical Properties and Photocatalytic Activities

Colloidal gold (Au) nanoparticles were prepared and successfully loaded on titanium(IV) oxide (TiO(2)) without change in the original particle size using a method of colloid photodeposition operated in the presence of a hole scavenger (CPH). The prepared Au nanoparticles supported on TiO(2) showed strong photoabsorption at around 550 nm due to surface plasmon resonance (SPR) of Au and exhibited a photocatalytic activity in mineralization of formic acid in aqueous suspensions under irradiation of visible light (>ca. 520 nm). A linear correlation between photocatalytic activity and the amount of Au loaded, that is, the number of Au nanoparticles, was observed, indicating that the activity of Au/TiO(2) plasmonic photocatalysts can be controlled simply by the amount of Au loading using the CPH method and that the external surface area of Au nanoparticles is a decisive factor in mineralization of formic acid under visible light irradiation. Very high reaction rates were obtained in samples with 5 wt % Au or more, although the rate tended to be saturated. The CPH method can be widely applied for loading of Au nanoparticles on various TiO(2) supports without change in the original size independent of the TiO(2) phase. The rate of CO(2) formation also increased linearly with increase in the external surface area of Au. Interestingly, the TiO(2) supports showed different slopes of the plots. The slope is important for selection of TiO(2) as a material supporting colloidal Au nanoparticles.     

Quantitative determination of singlet oxygen generated by excited state aromatic amino acids, proteins, and immunoglobulins

Singlet oxygen quantum yields generated by excited state aromatic amino acids (tryptophan, tyrosine, phenylalanine), N-acetylated amino acids (N-acetyl-tryptophan, N-acetyl-tyrosine, N-acetyl-phenylalanine), and from selected proteins and immunoglobulins have been quantified by time-resolved phosphorescence measurements. A small, but significant, quantum yield found for proteins and immunoglobulins demonstrates that molecular oxygen can diffuse through the polypeptide matrix and can be sensitized by residues buried within the folds of protein structure.     

Polydimethylsiloxane‐coated partitioning sample collection device for the precise quantification of polycyclic aromatic hydrocarbons in air

A novel partitioning collection device comprising a glass cartridge packed with poly(dimethylsiloxane)‐coated macroporous silica particles was developed for the precise quantification of polycyclic aromatic hydrocarbons in air. The analyte collection and elution performances achieved using different amounts of poly(dimethylsiloxane) coating were quantitatively evaluated. The sample retention power increased with increasing the coating, and more than 250 L of air could be collected without analyte breakthrough at a sampling temperature of 35°C. During the air collection, the moisture in the air was not retained on the particles due to the hydrophobic surface of the sorbent. A complete and rapid elution of the collected analytes from the device was accomplished by the passage of only 10 mL of acetone with ultrasonication for 1 min. The proposed method was successfully applied for the determination of airborne polycyclic aromatic hydrocarbons in tunnel air.     

Vibrational spectroscopy of Cs+ solvated by methylamine

We report the vibrational spectra of the cluster ions Cs⁺(CH₃NH₂)_N, N=3–22. Bands in the 1015–1050 cm^?1 region of the infrared are due to the v8 mode (CN stretch) of methylamine molecules displaying different degrees of interaction with the central ion. Monte Carlo simulations of the solvated Cs⁺ ion indicate that nine methylamine molecules fill the first solvation shell of Cs⁺ and that possible rearrangements in cluster structure occur at N=14?15. No absorptions due to bulklike methylamine molecules are observed through N=22.     

Preparation,Functionality, and Application of Metal Oxide‐coated Noble Metal Nanoparticles

With their remarkable properties and wide‐ranging applications, nanostructures of noble metals and metal oxides have been receiving significantly increased attention in recent years. The desire to combine the properties of these two functional materials for specific applications has naturally prompted research in the design and synthesis of novel nanocomposites, consisting of both noble metal and metal‐oxide components. In this review, particular attention is given to core–shell type metal oxide‐coated noble metal nanostructures (i.e., metal@oxide), which display potential utility in applications, including photothermal therapy, catalytic conversions, photocatalysis, molecular sensing, and photovoltaics. Emerging research directions and areas are envisioned at the end to solicit more attention and work in this regard.

     

Excimer radiation from Na—Noble-gas and K—Noble-gas molecules

Emission bands from Na-noble-gas (and K-noble-gas) molecules, due to transitions between the 4sσ (and 5sσ) bound excited states and dissociating ground states, are observed. The noble gases used are Ar, Kr and Xe. The red shift of the emission band from the forbidden atomic s-s transition is largest for NaXe, for which it is 3055 cm^?1. This NaXe band may be useful as an excimer laser source, tunable from 4280 Å to 4500 Å.     

Radiometric detection in flow-injection analysis (Radiometric Flow-Injection Analysis)

A single line system with a detector of radioactivity was used for the determination of⁶⁰Co. In the determination, no additional chemistry is involved and limited dispersion is desirable. For this application, the FIA system is used only as a transport system for the sample up to the detector.     

Structural aspects, IR study, and molecular photophysics of the cumulene-bridged complexes with rhenium(I), ruthenium(II), and osmium(II) centers

The synthesis of a series of ReI, RuII, and OsII complexes that contain rigid polyphosphine/cumulene spacers is reported here. These cumulenic ligands, namely, 1,1',3,3'-tetrakis(diphenylphosphino)allene (C3P4) and 1,1',4,4'-tetrakis(diphenylphosphino)cumulene (C4P4), utilize diphenylphosphino linkage components to coordinate to the metal-polypyridyl or metal-carbonyl units. Characterization of all mono-, homo-, and heterobimetallic complexes is achieved using 31P(1H) NMR, IR, and fast atom bombardment mass spectroscopy (FAB/MS) and elemental analysis. The two ReI homobimetallic complexes were also characterized by single-crystal X-ray structure determination, which provided the structural evidence of a 90 degrees rotation between the C3 and C4 adducts causing a change in the electrochemical behavior. The ground-state electronic absorption and redox interactions, along with the excited-state photophysical characteristics, are also explored. Electrochemical studies showed that an increase in the carbon chain length resulted in a greater amount of sigma-donation from the ligand to the metal centers, as well as a greater amount of electronic communication between the metal termini of the bimetallic species. The electronic absorption and emission spectra of the new complexes were also determined and characterized. The lifetimes of the excited-state luminescence of the ReI mono- and homobimetallic complexes were found to be an order of magnitude shorter than the lifetimes of the heterobimetallic complexes containing the RuII and OsII moieties. Excited-state energy transfer was observed from the higher MLCT excited state of the ReI centers to the lower energy MLCT excited state of the RuII and OsII centers on the following basis: no ReI-based emission was detected in the steady-state emission measurements, the time-resolved decay traces were fitted to only single-exponential decays, and the quantum yields were identical for each compound at two different excitation wavelengths where different percentages of the metal-based chromophores were excited.