On-line column preconcentration for the determination of cobalt in sea water by flow-injection chemiluminescence detection

A flow-injection method for the determination of dissolved cobalt(II) in sea water has been studied based on a combination of column preconcentration using 8-quinolinol immobilized on silica gel, fluoride containing metal alkoxide glass (8HQ-MAF) and chemiluminescence detection with a gallic acid-hydrogen peroxide system. Co(II) is selectively recovered from an acidified sample with 8-quinolinol immobilized on silica gel. After elution with dilute hydrochloric acid the resultant eluent is mixed with the reagent solutions, heated to 60^°C and then introduced into the CL cell. The analysis time including the 2-min sample load was 8 min per sea water sample with a corresponding detection limit of 0.62 ngl^-1 (3). The average standard deviation calculated for 10 replicate measurements of artificial sea water samples with a concentration of 10 ngl^-1 cobalt was ±2.1%. The method has been tested with the standard reference sea waters NASS and CASS.     

Synthesis of poly(diallyl phthalate) and silica gel polymer hybrids utilizing π–π interactions

We report here the synthesis of homogeneous polymer hybrids of poly(diallyl phthalate) (PDAP) and silica by utilizing π–π interactions. Use of arylalkoxysilanes such as phenyltrimethoxysilane (PhTMOS), phenethyltrimethoxysilane (PhenethylTMOS) and mesityltrimethoxysilane (MesTMOS) as sources for inorganic phases resulted in optically transparent PDAP-silica polymer hybrids in a wide range of organic and inorganic content ratios. On the other hand, alkoxysilanes such as tetramethoxysilane (TMOS), methyltrimethoxysilane (MTMOS) and i-butyltrimethoxysilane (iBuTMOS) resulted in phase separated, turbid solids. A mixture of tetramethoxysilane (TMOS) and PhTMOS was also studied for the synthesis of PDAP-silica gel polymer hybrids to control the cross-linking density in the inorganic phase. Homogeneity was found to be improved with an increase in PhTMOS content. These homogeneous PDAP polymer hybrids were found to have high thermal stability which wasachieved by nano-scale dispersion of PDAP in silica through extensiveinterface interactions. The homogeneity of the polymer hybrids was confirmed by SEM and TEM, which demonstrate a nanometer level integration of the organic polymer and the inorganic phase.     

Determination of rare earth elements in seawater by on-line column preconcentration inductively coupled plasma mass spectrometry

A home made column of commercially available iminodiacetate resin, Muromac A-1 (50–100 mesh) was used to concentrate rare earth elements (REEs) (15 elements: Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) in seawater. An automated low pressure flow analysis method with on-line column preconcentration/inductively coupled plasma mass spectrometry (ICP-MS) is described for the determination of REEs in seawater. Sample solutions (adjusted to pH of 3.0) passed through the column. After washing the column with water, the adsorbed elements were subsequently eluted into the plasma with 0.7 M nitric acid. Calibration curves were accomplished by means of purified artificial seawater with a sample loading time of 120 s. Detection limits (DLs) of the on-line column preconcentration/ICP-MS by eight replicate operations were between 0.040 and 0.251 pg ml⁻¹ for REEs in the artificial seawater. The precision was less than 8.9% for REEs and one sample can be processed in 7 min using a 7 ml of sample. The proposed method was applied to determine REEs in coastal seawater of Hiroshima Bay, Japan.     

Charge separation versus recombination in dye-sensitized nanocrystalline solar cells: the minimization of kinetic redundancy

In this paper we focus upon the electron injection dynamics in complete dye-sensitized nanocrystalline metal oxide solar cells (DSSCs). Electron injection dynamics are studied by transient absorption and emission studies of DSSCs and correlated with device photovoltaic performance and charge recombination dynamics. We find that the electron injection dynamics are dependent upon the composition of the redox electrolyte employed in the device. In a device with an electrolyte composition yielding optimum photovoltaic device efficiency, electron injection kinetics exhibit a half time of 150 ps. This half time is 20 times slower than that for control dye-sensitized films covered in inert organic liquids. This retardation is shown to result from the influence of the electrolyte upon the conduction band energetics of the TiO2 electrode. We conclude that optimum DSSC device performance is obtained when the charge separation kinetics are just fast enough to compete successfully with the dye excited-state decay. These conditions allow a high injection yield while minimizing interfacial charge recombination losses, thereby minimizing "kinetic redundancy" in the device. We show furthermore that the nonexponential nature of the injection dynamics can be simulated by a simple inhomogeneous disorder model and discuss the relevance of our findings to the optimization of both dye-sensitized and polymer based photovoltaic devices.     

Isolation of lignan glucosides and neolignan sulfate from the leaves of Glochidion zeylanicum (Gaertn) A. Juss

Six lignan and neolignan derivatives (1-6) were isolated from the n-BuOH-soluble fraction of a MeOH extract of the leaves of Glochidion zeylanicum. On the basis of spectral data, their structures were elucidated to be (+)-isolarisiresinol 3a-O-beta-glucopyranoside (1), dihydrodehydrodiconiferyl alcohol 4-, 9- and 9'-O-beta-D-glucopyranosides (2-4, respectively), (+)-isolarisiresinol 2a-O-beta-D-glucopyranoside (5), and dihydrodehydrodiconiferyl alcohol 9-O-sulfate (6), and 5 and 6 were new compounds.     

Photoluminescence enhancement of PEG-modified YAG:Ce3+ nanocrystal phosphor prepared by glycothermal method

Y3Al5O12:Ce3+ (YAG:Ce3+) nanocrystals were synthesized in 1,4-butylene glycol (BG) with and without poly(ethylene glycol) (PEG) by the glycothermal method. The internal quantum efficiency of the photoluminescence (PL) corresponding to the 5d --> 4f transition of Ce3+ in the YAG:Ce3+ nanocrystal increased from 21.3 to 37.9% by addition of PEG, while no appreciable change in the primary particle size, the crystallite size, and the lattice distortion was recognized by transmission electron microscopy and X-ray diffractometry. The thermogravimetry-differential thermal analysis, Fourier transform infrared absorption spectroscopy and 1H --> 13C cross-polarization magic angle spinning nuclear magnetic resonance (CP-MAS NMR) confirmed the preferential coordination of PEG to the YAG:Ce3+ nanocrystal. 27Al single-pulse excitation MAS NMR reveals that the ratio of the 4-fold coordination site to the 6-fold coordination site increased from 0.53 to 0.72 by addition of PEG. We conclude that the surface modification of the YAG:Ce3+ nanocrystal by PEG induces the surface passivation, the prevention of the oxidation of Ce3+ to Ce4+, the promotion of the incorporation of Ce3+ into YAG and the local structural rearrangement, resulting in the PL enhancement.     

Rhodium-catalyzed isomerization of alpha-arylpropargyl alcohols to indanones: involvement of an unexpected reaction cascade

A rhodium-catalyzed isomerization of alpha-arylpropargyl alcohols to indanones has been developed under mild conditions. Considering the ease of preparation of these propargyl alcohols (terminal alkynes + aromatic aldehydes), this method provides a new way of constructing indanones with high efficiency. By the mechanistic investigations using deuterium-labeled substrates, it has also been demonstrated that the reaction goes through an unexpected cascade, with a 1,4-hydrogen shift being the turnover-limiting step of the catalytic cycle.     

Highly active, immobilized ruthenium catalysts for oxidation of alcohols to aldehydes and ketones. Preparation and use in both batch and flow systems

A novel, highly active immobilized ruthenium catalyst, which can be successfully used in oxidation of alcohols to aldehydes and ketones, has been developed. In contrast to most immobilized catalysts, the Ru catalyst has activity that is higher than that of the original non-immobilized catalyst. In a batch system, the Ru catalyst was recovered and reused several times without loss of activity. The catalyst was also applied to a flow system, in which excellent conversions and yields were demonstrated. No leaching of Ru was observed in both cases.     

Self-oscillation of polymer chains induced by the Belousov-Zhabotinsky reaction under acid-free conditions

A novel self-oscillating polymer was prepared by utilizing the Belousov-Zhabotinsky (BZ) reaction. In this study, a sulfonic acid group was newly introduced as a pH-control site into the copolymer of N-isopropylacrylamide, and the ruthenium complex was introduced as a catalyst site. By introducing the pH-control site, we succeed in causing the soluble-insoluble self-oscillation of the polymer solution under acid-free conditions in which only two BZ substrates, malonic acid and sodium bromate, were present as added agents. The self-oscillating behavior was remarkably influenced by the temperature and polymer concentration, which reflects the intermolecular aggregative capacity of the polymer chains in the reduced state to change the lower critical solution temperature. This achievement of self-oscillation of polymer chains under acid-free conditions may lead to their practical use as novel biomimetic materials under biological conditions.