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The synergism caused by of six -diketones on the extraction of gallium(III) with di(2-ethylhexyl)phosphoric acid (D2EHPA or HA) from weak acidic solution into heptane and supercritical carbon dioxide (SC-CO2) was investigated. Thenoyltrifluoroacetone (Htta), benzoylacetone (Hbza), benzoyltrifluoroacetone (Hbfa), acetylacetone (Hacac), trifluoroacetylacetone (Htfa), and hexafluoroacetylacetone (Hhfa) were used as synergists. In the heptane extraction with 5.0 × 10 −3 M D2EHPA and 5.0 × 10 −4 M -diketone, synergism occurred in the presence of Htta, Hbza, Hhfa, Hbfa and Htfa, but not to any extent with Hacac or Hbza. The synergistic effect increased in the following order: Htfa < Hhfa < Hbfa  Htta. The synergistic extraction equilibrium of gallium(III) with D2EHPA and Htta in heptane was investigated. The results suggest that two types of complexes were extracted with D2EHPA and Htta, namely GaA2(tta)·HA and GaA2(tta)·2HA. This synergistic effect also occurred in SC-CO2 extraction. However, the degree of synergism in the SC-CO2 system is smaller than that in the heptane system.

An external reflection (ER) spectrometric device was developed to directly measure adsorbates at the supercritical carbon dioxide (SC-CO2)-water interface. The aggregation of diprotonated species of 5,10,15,20-tetraphenyl-21H,23H-porphinetetrasulfonic acid (H4tpps(2-)) at the positively charged SC-CO2-water interface, prepared by adsorption by the cetyltrimethylammonium ion (CTA(+)), was studied using this device. Orientations of the H4tpps(2-) monomers and J-aggregates at the SC-CO2-water interface were assessed using s- and p-polarized external reflection (ER) spectra. It appeared that the porphyrin plane of the H4tpps(2-) monomer was nearly parallel to the SC-CO2-water interface, and that the long axis of the rod-like H4tpps(2-) J-aggregate was also nearly parallel to the interface. Dependence of the ER spectra on CTA(+) concentration and CO2 pressure were investigated, and the interfacial CTA(+) concentration was found to cause changes in the interfacial H4tpps(2-) species present. Increasing the CO2 pressure changed the interfacial species from the H4tpps(2-) monomer to the H4tpps(2-) J-aggregate because the interfacial CTA(+) concentration increased as the pressure increased. This suggests that the interfacial chemical species can be changed by controlling the pressure and temperature of the SC-CO2. This is the first report of direct measurements of the chemical species at the SC-CO2-water interface, as far as we know.

The photoredox ability of a hexarhenium(III) cluster, [Re6(μ 3-S)8Cl6]4−, in acetonitrile was examined on the basis of the emission quenching experiments of the cluster by a series of neutral organic electron acceptors (A). The photoinduced electron transfer quenching rate constants and the relevant activation parameters demonstrated that the hexarhenium(III) cluster acted as a useful photoredox sensitizer towards various A and the system gave a high charge separation yield owing to electrostatic repulsion between the product ions: [Re6(μ 3-S)8Cl6]3− and A −. These results were proved explicitly by nanosecond transient absorption spectroscopy.

The synergistic effect of five 8-quinolinol derivatives (HQs) on the extraction of gallium(III) with di(2-ethylhexyl)-phosphoric acid (D2EHPA or HA) from weak nitric acid into supercritical carbon dioxide (SC-CO(2)) was investigated. 8-Quinolinol (Hq), 5-ethoxymethyl-8-quinolinol (HO(2)q), 5-hexyloxymethyl-8-quinolinol (HO(6)q), 5-(2,2,2-trifluoroethoxymethyl)-8-quinolinol (HFO(2)q), and 5-chloro-8-quinolinol (5-Cl-Hq) were used as synergists. Synergism was observed for all of the HQs. The synergistic effect increased in the following order: Hq < HO(2)q < HFO(2)q < 5-Cl-Hq ≍ HO(6)q. The extent of synergism can be related to both the distribution constant and the acid dissociation constant of the HQ. The synergistic extraction equilibrium of gallium(III) with D2EHPA and 5-Cl-Hq into SC-CO(2) was investigated; the results suggest that the composition of the extracted complex is as GaA(2)Q·HA. The synergistic extraction mechanism was the same for both SC-CO(2) and n-heptane. The synergistic extraction equilibrium constants in both cases were calculated based on the experimental results.

We have reported on a novel microfluidic mixer based on AC electroosmosis. To elucidate the mixer characteristics, we performed detailed measurements of mixing under various experimental conditions including applied voltage, frequency and solution viscosity. The results are discussed through comparison with results obtained from a theoretical model of AC electroosmosis. As predicted from the theoretical model, we found that a larger voltage (approximately 20 V(p-p)) led to more rapid mixing, while the dependence of the mixing on frequency (1-5 kHz) was insignificant under the present experimental conditions. Furthermore, the dependence of the mixing on viscosity was successfully explained by the theoretical model, and the applicability of the mixer in viscous solution (2.83 mPa s) was confirmed experimentally. By using these results, it is possible to estimate the mixing performance under given conditions. These estimations can provide guidelines for using the mixer in microfluidic chemical analysis.

The paper describes the fabrication and chemical applications of polymer microchannel chips, with special reference to in situ observations of the chemical/physical processes occurring in polystyrene microchannel chips, including those in microchannel-microelectrode/microheater chips. On the basis of absorption/fluorescence microspectroscopy and microelectrochemistry techniques, we show some characteristic features of liquid/liquid extraction, electrochemical responses, and photochemical/electrochemical/thermal synthetic reactions in microchannel chips.

The solubilities of several cobalt(III) chelates (CoL3) with in supercritical carbon dioxide (SC-CO2) were investigated in the presence of fluorine- and trifluoromethyl-substituted phenols (PhOH) using UV–vis spectrophotometry. Solubility enhancement of CoL3 complexes in SC-CO2 was accomplished by adding PhOH. The association constants for tris(pentane-2,4-dionato)cobalt(III) (Co(acac)3) with various PhOH in SC-CO2 were determined from the relationship between the solubility enhancement and the PhOH concentration for each corresponding phenol. For compounds with no fluorine or trifluoromethyl groups in the ortho position, the association constants decreased as the pKa values of the PhOH compounds increased. In addition, the association constants for the PhOH compounds bearing a fluorine or trifluoromethyl group in the ortho position were less than the values expected based on their pKa values. These results are ascribed to the occurrence of the steric hindrance of the ortho-fluorine or trifluoromethyl group. Furthermore, the association constants for various CoL3 complexes and 3,5-bis(trifluoromethyl)phenol (BTMP) increased as the basicity of the chelating ligand increased. Finally, the thermodynamic parameters and the numbers of CO2 molecules released upon association of Co(acac)3 and BTMP were calculated using data for the dependence of the association constant on the pressure and temperature.

We developed a novel flow control system for a nanofluidic chemical process. Generally, flow control in nanochannels is difficult because of its high-pressure loss with very small volume flow rate. In our flow control method, liquid pressure in a microchannel connected to the nanochannels is regulated by utilizing a backpressure regulator. The flow control method was verified by using simple structured microchip, which included parallel nanochannels. We found that the observed flow rate was three times lower than the value expected from Hagen-Poiseuille's equation. That implied a size-dependent viscosity change in the nanochannels. Then, we demonstrated mixing of two different fluorescent solutions in a Y-shaped nanochannel and also a proton exchange reaction in the Y-shaped nanochannel. The flow control method will contribute to further integration of nanochemical systems.

We developed a fabrication method and a liquid filling method for a nano chemical reactor that used Y-shaped nanochannels specially designed for mixing and reacting. In order to reduce the pressure loss and to utilize the characteristics of the nanochannel, inlet microchannels were fabricated just beside the nanochannels. We investigated an initial liquid filling method into the nanochannels that ensured there were no air bubbles that could cause a flow stack due to the capillary pressure. In our method, the micro- and nanochannels were filled with carbon dioxide and any remaining air during the initial liquid introduction was dissolved utilizing the high solubility of carbon dioxide. We propose that chemical reactions in nanospaces can be realized by utilizing these fabrication and liquid introduction techniques.

A titania-modified microchannel chip (TMC) was fabricated to implement an efficient photocatalytic synthesis of l -pipecolinic acid from l -lysine. The conversion rate in the chip was 70 times larger than that in a cuvette using nm-sized titania particles with almost the same selectivity and enantiomeric excess. The results showed that TMC had satisfactory potential to allow its application to photocatalytic synthesis as well as photodegradation.

We have developed spectroelectrochemical detection using thermal lens microscopy (EC-TLM) with a microelectrode-microchannel chip (EMC). TLM has both high sensitive and spatial resolution comparable to fluorometry, while it can be applied to non fluorescent analytes. EMC provides an efficient electrolysis of the analyte and a controlled distribution of the redox product in the microchannel. Therefore, a combination of TLM and EMC enhance both the sensitivity and selectivity. To show the performance of EC-TLM, we fabricated a glass substrate EMC and constructed the detection system. Experiments showed that the potential dependence of the EC-TLM signal of o-tolidine agreed very well with the current signal obtained simultaneously. The EC-TLM signal depended on the detection point in the microchannel and was compared with distribution profiles of the oxidized species predicted by computer simulation. Under the present experimental conditions, EC-TLM could detect of the order of 10−6 mol dm−3 o-tolidine in μm-sized space with both signal-to-background and signal-to-noise ratios of 10. The results clearly showed that EC-TLM worked as expected and had adequate potential for use in sub-nano molar detection in micrometer-sized space.

Plastic microchannel-microheater chips were fabricated on the basis of imprinting and photolithography/etching techniques. Knowing the temperature-dependent fluorescence lifetime of Rhodamine B in water, the temperature profile of the solution phase in the microchannel in the vicinity of the heater was evaluated by space- and time-resolved fluorescence microspectroscopies. The fabricated chip was then applied to control the thermal phase transition of an aqueous poly(N-isopropylacrylamide) (PNIPAM) solution. PNIPAM particle formation by the phase transition was controlled by both the applied voltage to the heater and the solution-flow rate. The temperature profile showing below or above the phase-transition temperature (i.e., 32 °C) and solution-flow profile in the microchannel were visualized successfully on the basis of the PNIPAM particle formation. The continuous and automated concentration of a hydrophobic solute by the PNIPAM particles produced by the phase transition was also explored under solutio...

A polymer microchannel chip with a symmetrical or unsymmetrical zigzag-side-walled structure was fabricated by an imprinting method, and applied to study shape effects on solution flow characteristics as well as on the liquid/liquid extraction efficiency of an aluminium(III) chelate complex (Al-DHAB: DHAB = o,o'-dihydroxyazobenzene) in a microchannel chip. In an unsymmetrical zigzag-side-walled channel chip (us-channel), an oil/water interface was sinusoidal, while that in a symmetrical zigzag-side-walled channel chip (s-channel) was flat as long as the observation was made under an optical microscope. It was demonstrated that the efficiency of the water-to-oil (1-butanol) extraction of Al-DHAB in the microchannel was governed by the contact time between the two phases. As the most important results, furthermore, the extraction efficiency was higher in the us-channel, as compared with that in the s-channel, owing to the sinusoidal liquid/liquid interfacial structure and, therefore, to the high interfacial area between the two phases.

We have fabricated nanometer-sized channels, demonstrated a technique for the introduction of liquid into the channels, and carried out time-resolved fluorescence measurements of aqueous solutions. In this study, 330-nm- and 850-nm-sized channels were fabricated on fused-silica substrates by fast atom beam etching and hydrofluoric acid bonding methods. A liquid introduction method utilizing capillary action was demonstrated. The liquid introduction was observed under an optical microscope, and the liquid velocity during the introduction was analyzed by surface energy and macroscale hydrodynamics. The liquid velocity due to capillary action in the nanometer-sized channel seemed more than four times slower than the estimation. Then, aqueous solutions of rhodamine 6G (R6G), sulforhodamine 101 (SR101), and rhodamine B (RB) in the channels were measured by time-resolved fluorescence spectroscopy; spectra of the same solution in a 250-microm-sized channel were also measured as a reference for the macrospace. Although the fluorescence spectra in the 330-nm-, 850-nm- and 250-microm-sized channels agreed with one another, the fluorescent decays in the nanometer-sized channels were faster for R6G and SR101 and slower for RB than the respective decays in the 250-microm-sized channels. The results suggested the solutions had lower dielectric constants and higher viscosities in the nanometer-sized channels.

A CS4−:(RuB32+)2 hybrid complex as a new class of a chemosensor was prepared by an ion-exchange reaction, where CS4− and RuB32+ were calix[4]arenetetrasulfonate and a tris(2,2′-bipyridine)ruthenium(II) dication, respectively. In the solid state, one RuB32+ was shown to bury partly in the cavity of CS4− from the upper rim, while other RuB32+ sits near the CS4−:RuB32+ ion-pair to balance the total electric charge of the hybrid. In methanol, on the other hand, two RuB32+ molecules in the hybrid complex located in the vicinity of a CS4− molecule at analogous microenvironments as suggested by 1 H -NMR. Spectroscopic and excited-state properties of RuB32+ in the hybrid were influenced by CS4− through the ion-excited dipole interaction and photoinduced electron transfer quenching. In the presence of a foreign cation as a guest, the emission intensity and lifetime of RuB32+ increased, demonstrating that CS4−:(RuB32+)2 hybrid complex acted as a luminescent chemosensor. The mechanism of ion recognition was discussed in terms of changes in the photophysical properties of the hybrid complex.

A case of eosinophilic pseudotumor of the liver due to Ascaris (A) suum is described in a 34-year-old-man with a high serum level of immunoglobulin E and hypereosinophilia ascribed to a history of atopic dermatitis since childhood. Multiple hepatic hypoechoic nodules detected by ultrasound were confirmed as low-density nodules on computed tomography (CT), and as low and high signal intensity lesions on T1-and T2-weighted magnetic resonance imaging (MRI), respectively. CT during arteriography (CTA) and arterial portography revealed multiple nodules with ring-shaped enhancement and perfusion defect, respectively. Biopsied liver tissue specimens did not contain tumor cells or atypical cells; instead, they showed marked infiltration of eosinophils with necrosis and Charcot-Leyden crystals in the portal tracts and hepatic sinusoides, suggesting parasitic infection, although neither larvae nor eggs were detected. The diagnosis of visceral larva migrans (VLM) due to A. suum was based on immunoserological tests. The patient was a habitual consumer of raw bovine liver, which may explain the A. suum infection. After drug therapy with albendazole, the hypoechoic nodules disappeared. Differential diagnoses and the possible transfection route of A. suum are discussed.

A microspectroscopy system combined with a fluid manifold was developed to manipulate and analyze "single" living cells. A sample buffer solution containing living cells was introduced into a flow cell set on a thermostated microscope stage and a few cells were allowed to attach to the bottom wall of the flow cell. With these living cells being attached to the wall, other floating cells were pumped out by flowing a buffer solution. These procedures made it possible to keep a few cells in the flow cell and to analyze single cells by fluorescence microspectroscopy. The technique was applied to study the time course of staining processes of single living yeast (Saccharomyces cerevisiae) cells by using two types of a fluorescent probe. The present methodology was shown to be of primary importance for obtaining biochemical/physiological information on single living cells and also for studying cell-to-cell variations in several characteristics.

Ru(bpy)2(CE-bpy)2+ was prepared where bpy and CE-bpy were 2,2'-bipyridine and bpy having a crown-ether moiety at the 3,3'-positions, respectively. Although Ru(bpy)2(CE-bpy)2+ showed only very weak emission in acetonitrile, recognition of Na+, Li+, or K+ by the crown-ether moiety in CE-bpy resulted in increases in both the emission intensity and the lifetime of the complex, demonstrating that it acted as a photoreceptor. The results were discussed in terms of a steric hindrance between the 3,3'-substituents on CE-bpy and structural changes in both CE-bpy and the complex upon ion recognition, as studied by variable-temperature 1H-NMR and steady-state/dynamic emission spectroscopy of the complex.

A series of the octahedral hexarhenium(III) complexes containing a variable number of diphosphine (diphos) or diphosphine-monoxide (diphosO) ligands have been prepared by the substitution of the diphosphine Ph2P(CH2)nPPh2 (n = 1 to 5) for the iodide ions in the parent octahedral hexarhenium cluster compound [Re6Se8I6]3-. The diphosphine Ph2P-(CH2)nPPh2 ligands adopt an eta1-bonding mode with the Re6(mu3-Se)8 core, and the P donor atom in the pendant arm is noncoordinated and oxygenated in most cases. The series of new hexarhenium(III) complexes have been well-defined by 1H, 13C, and 31P NMR spectroscopic and FAB-MS data. Four compounds among the series were characterized by X-ray structural determination. Geometrical isomers were identified by NMR spectroscopy as well as by the structural determinations. The apical ligand substitution induces significant change in the redox potentials and the photophysical properties of the Re6(mu3-Se), core. The E1/2 value of the reversible process ReIII6/ReIII5ReIV becomes more positive with the increasing number of the coordinated P donors. The phosphine-substituted hexarhenium(III) derivatives are highly luminescent, with microsecond scale emissive lifetime at ambient temperature, and the fully substituted derivatives with the formula [Re6Se8-(eta1-diphosO)6]2+ display the strongest luminescence with the longest emission lifetimes.

The polarity of a water/oil (oil: cyclohexane, carbon tetrachloride, toluene, chlorobenzene, o-dichlorobenzene, or 1,2-dichloroethane) interface was investigated by means of time-resolved total-internal-reflection (TIR) fluorescence spectroscopy of a polarity-sensitive probe: sulforhodamine B (SRB). In bulk solutions, the nonradiative decay rate constant of SRB increased with an increase in a solvent polarity parameter [ET(30)], and this relationship was used to estimate the polarities of water/oil interfaces. For the oil having a relatively low solvent polarity [ET(30)35 kcal/mol], the polarity of the water/ oil interface agreed with that of the arithmetic average of the polarities of the two phases [ET(30)calc]. For water/odichlorobenzene and water/1,2-dichloroethane interfaces [ET(30) of the oil35 kcal/mol], on the other hand, the interfacial polarity determined by TIR spectroscopy was lower than the ET(30)calc. The results are discussed in terms of thickness/roughness of the water/oil interface.

Polymer microchips, possessing a minute channel(s) on the substrate with its width and depth of 100 and 20μm, respectively, were fabricated on the basis of photolithography and imprinting methods. Microelectrodes were also introduced successfully onto the microchannels by applying vacuum deposition and lithography/etching of metal thin films. Fabricated polymer microchannel chips were demonstrated to be potential enough for various chemical applications.

The structures of water, partitioned in cation-exchange resin particles, were studied on the basis of fluorescence dynamics of Nile Blue A (NB). The fluorescence lifetime of NB in the resin was longer than that in water and increased with increasing cross-linking density of the resin (rho). The results demonstrated that the water structures in the resin were significantly different from those in water and dependent on rho. A study on solvation dynamics of NB in the resin, reflecting structured water around the ion-exchange group, revealed the roles of "bound water" molecules in the water structures, since the solvent relaxation time (tauS) in the resin was much longer than that in water and depended on p; tauS increased from 34 to 55 ps with increasing rho from 2 to 8%. The origin of the rho dependence of tauS was discussed in terms of the separation distance between the ion-exchange groups, and the effects of the counterion of the ion-exchange group on the solvation processes were also discussed.

A microinjection-microspectroscopy system combined with a fluid manifold was developed to manipulate and analyze ‘single’ micro-oil-droplets in water. Water was poured into a flow cell set on a microscope stage through a microcapillary tube. A single tributyl phosphate (TBP) microdroplet was then pushed out to the water phase in the cell through an another tiny capillary tube and held on the top end of the tube. These procedures made it possible to inject a single microdroplet exclusively into the cell. The technique was applied to study a time course of liquid/liquid extraction processes of an Al-DHAB chelate (DHAB=2,2′-dihydroxyazobenzene) from water to single TBP microdroplets. The extraction rate of Al-DHAB was determined for individual microdroplets and the results were discussed in terms of the solution flow rate and the droplet diameter.

The fluorescence dynamics of Rhodamine 6G (R6G) in ethylene glycol/water (EG/W) microdroplets dispersed in a polydimethylsiloxane (PDMS) solid matrix were studied by picosecond time-resolved microspectroscopy. The large decrease in the fluorescence lifetime of R6G was observed for the droplets with the diameter (d) below 10 μm and at the R6G concentrations ([R6G]) above 0.1 mM. Absorption microspectroscopy revealed that the dimer formation of R6G in EG/W microdroplets was facilitated with decreasing d and increasing [R6G]. The size-dependent fluorescence lifetime of R6G was related to quenching of the monomer excited state by the R6G dimer. The origin of size-dependent dimer formation and, thus, the size-dependent fluorescence lifetime of R6G in micrometer-sized droplets in the PDMS matrix was discussed in detail.

Preparations of a series of face-capped octahedral hexarhenium(III) clusters having two N-heterocyclic ligands, [Bu4N]2[trans-[Re6(mu 3-S)8Cl4(L)2]] (Bu4N+ = tetra-n-butylammonium cation; L = pyrazine (1a), 4,4'-bipyridine (3a), 4-methylpyridine (5a), 4-(dimethylamino)pyridine (6a)) and their cis analogues (1b, 3b, 5b, and 6b, respectively), and their electrochemical and photophysical properties have been reported. An X-ray crystal structure determination has been carried out for 1a to confirm the trans configuration (C40H80N6S8Cl4Re6, orthorhombic, space group Cmca (No. 64), a = 19.560(5) A, b = 19.494(4) A, c = 18.592(4) A, beta = 115.76(2) degrees, Z = 4). The redox potential of the reversible ReIII6/ReIII5ReIV process of these complexes and previously reported [Bu4N]2[trans- and cis-[Re6(mu 3-S)8Cl4(4-cyanopyridine)2]] (2a and 2b, respectively) and [Bu4N]2[trans- and cis-[Re6(mu 3-S)8Cl4(pyridine)2]] (4a and 4b, respectively) in acetonitrile depends linearly on the pKa of the N-heterocyclic ligands, with the potentials being more negative with basic ligands. The ligand-centered-redox waves for 1a, 1b, 2a, and 2b were observed as split waves (delta E1/2 = 90-140 mV), the extent of the splitting being larger for the cis isomer and largest for the pyrazine complexes. Electronic interaction between the two ligands through the [Re6(mu 3-S)8]2+ core has been suggested. The second ligand-reduction wave was also observed for 3a and 3b, the potential being shifted positively to coalesce with the first reduction wave on addition of the weak proton donor imidazole. This is accounted for by the proton-coupled redox reaction at the free pyridyl site of the 4,4'-bipyridine ligands. All of the complexes show luminescence in acetonitrile at room temperature. While the complexes of pyridine and 4-methylpyridine show photophysical characteristics (lambda em 740-750 nm, phi em 0.031-0.057, tau em 4.2-6.2 microseconds) similar to those (770 nm, 0.039, and 6.3 microseconds, respectively) of [Re6(mu 3-S)8Cl6]4-, emissions of other complexes are significantly weak with lambda em, phi em, and tau em values in the ranges 763-785 nm, 0.0010-0.0017, and 0.013-0.029 microsecond, respectively. Suggestions are given for the excited states localized on the cluster core and the ligand pi* orbitals.

Space- and time-resolved microspectroscopies have been developed and applied to the study of inhomogeneous structures in two-dimensional (microtubes and microchannels) and three-dimensional samples (polymer microspheres and microdroplets). In this particular technique, an optical trapping method was applied successfully to elucidate the chemical and physical characteristics of individual microparticles in solution. Confocal fluorescence microspectroscopy was also shown to have sufficient potential to observe directly the ion-exchange–diffusion processes of an ion in single ion-exchange polymer microparticles. The important roles of space- and time-resolved microspectroscopy in analysing several minute samples having different sizes and shapes are described in detail.

A laser trapping-microspectroscopy system combined with a fluid manifold was developed to manipulate and analyze "single" microparticles. A sample solution containing microparticles was introduced to a flow cell set on a microscope stage, and a single particle was trapped by a 1064-nm laser beam. With the particle being trapped, the other particles were pumped out by flowing water to hold the unique microparticle in the flow cell. Under solution-flow conditions, a single microparticle was laser trapped in balance with the gradient (F(g)) and Stokes forces (F(s)) experienced by the particle, and thus, the trapped position was shifted to the downstream side of the 1064-nm laser beam focus. Flow rate and particle size dependencies of this particular positional displacement of the particle were discussed in terms of F(g) and F(s). On the basis of these studies, optical requirements to conduct absorption microspectroscopy of a laser-trapped particle were optimized, and the technique was applied to study a time course of dye adsorption processes in single microparticles. The adsorption rate of Rhodamine B was determined for individual microparticles for the first time.

The fluorescence dynamics of Rhodamine B (RhB) and excitation energy transfer from RhB to Malachite Green (MG) in cation-exchange resin particles were studied with special reference to elucidating effects of the cross-linking density of the resin on the fluorescence dynamics. In the cation-exchange resin, the fluorescence lifetime and rotational relaxation time of RhB were very slow compared to those determined in an aqueous solution, suggesting strong binding of the dye to the ion-exchange group of the resin. Therefore, the spatial distribution characteristics of the dye in the resin particle was used as a measure for that of the ion-exchange group. The apparent structural dimension determined by the fractal dimension analysis of energy-transfer quenching of RhB by MG, representing the distribution characteristics of the dye in the resin, was smaller than Euclidean dimension (3) and decreased from 2.8 to 2.6 with decrease in the cross-linking density of the resin from 8 to 2%. The origin of the fractal-l...

Ion-exchange processes of a cationic dye (Malachite Green, MG) are studied for individual polymer particles (diameter of 20 or 13 μm) by laser trapping microspectroscopy. When a cation-exchange resin, preadsorbed homogeneously with Rhodamine B (RhB), is soaked in an aqueous MG solution, MG is adsorbed in the surface layer of the particle in the initial stage and then diffuses into the inner volume with time. In the MG-diffused layer, RhB fluorescence is quenched by excitation energy transfer from the excited state of RhB to the ground-state MG, as revealed by fluorescence microspectroscopy of individual resin particles in the dye solution. On the basis of the time dependence of the quenching efficiency, the thickness of the MG-diffused layer at a given soaking time is estimated, and the diffusion coefficient of the dye in the particle is determined to be 8 × 10(-)(11) cm(2) s(-)(1). This method is shown to be very useful for determining the diffusion coefficient of a nonfluorescent ion in individual ion-exchange resin microparticles.

Diffuse reflectance spectroscopy on polymer particles and silica gels adsorbing tris(2, 2′-bipyridine)ruthenium(II), Ru(II), was conducted to elucidate the shape and size effects of an adsorbent on the spectrum. The diffuse reflectance light intensity (f(r∞)) was linearly correlated with the amount of the complex ([Ru(II)]) adsorbed on spherical polymer beads, amorphous-, or spherical-shaped silica gels as low as [Ru(II)]=10-8mol/cm3. However, the slope of a f(r∞) vs. [Ru(II)] plot was different between the adsorbents. The results were explained in terms of the different light scattering coefficient between the adsorbents, originating primarily from the different shape and size of the adsorbent., This study was partly supported by a Grant-in-Aid from the Ministry of Education, Science, Sports and Culture (08404051).

Laser trapping-microspectroscopy and confocal laser fluorescence microspectroscopy have been applied to analyze inhomogeneous structures in single microparticles. In the case of melamine-resin microcapsules containing a toluene solution of a tetraphenylporphyrine derivative, the capsules showed an extraordinary diameter dependence of dye absorbance, and the results were explained in terms of the size-dependent distribution of the dye between the inner tolune and melamine resin phases. Single particle measurements were shown to be absolutely necessary to elucidate characteristic features of the chemistry of microparticles.

We explored optical trapping-spectrophotometry of ion-exchange polymer microparticles in water and, determined the dye (tris(2, 2′-bipyridine)ruthenium(II) complex; Ru2+) concentration adsorbed on an individual particle (diameter (d)=20-140μm). The absorbance of Ru2+ on the particle increased with an increase of the dye concentration in the aqueous phase, while it was essentially independent of d. The results indicate that adsorption of the complex takes place in the surface layer of the particle, but not homogeneously in the entire particle. A possible role of the optical trapping- spectrophotometry method in direct analyses of trace amounts of molecules concentrated on single microparticles in olution is discussed.

Molecular association of malachite green (MG) in single micrometer-sized water droplets dispersed in di-n-butyl phthalate was studied by means of scanning laser manipulation and absorption spectroscopy to elucidate characteristic features of chemical processes at the droplet/oil interface. At a high MG concentration, the droplet showed a new absorption band around 580 nm in addition to the monomer band at 615 nm. Analyses of the concentration-dependent absorption spectrum of MG in the droplet indicated that the band at 580 nm could be assigned to that of the MG dimer. The dimer formation of MG in the water droplet was shown to be facilitated with decreasing the droplet diameter, demonstrating the micrometer size effect on dye association. A role of the water/oil interface for the MG dimer formation is discussed.

Electron transfer between ferrocene in a single oil droplet and hexacyanoferrate(III) in the surrounding water phase was studied by laser trapping, spectroscopic, and electrochemical techniques. We determined the rate of interfacial electron transfer for an individual droplet and found for the first time that the rate increased with a decreased in the droplet diameter. This particular micrometer size dependence was discussed on the basis of kinetic analysis of the electron transfer rate.

We report measurements of the kinetics of polymer diffusion in latex films prepared from pairs of poly(butyl methacrylate) [PBMA] latex particles. One set contains only a small amount of sulfate groups; the others contain significant amounts of carboxylic acid groups at the surface. Neutralization of these acid groups with sodium and barium hydroxide retards the interdiffusion rate but does not suppress it. In these experiments, we employ pairs of particles identical in size, with very similar molecular weights, molecular weight distributions, and surface charge densities, that differ only in the fluorescent chromophore (phenanthrene [Phe] or anthracene [An]) used to label the polymer. Each pair of latexes allows us to use direct nonradiative transfer [DET] experiments to follow polymer interdiffusion in films prepared from their dispersions. Acid group neutralization in the latex converts an acid-rich phase at the interparticle boundary in the film into an ionomer phase. Ba 2+ salts are more effective than Na + at slowing down the polymer diffusion rate, and their influence increases in proportion to the amount of polar groups present. We follow an approach developed by Eisenberg (Macromolecules 1871, 4, 125) to estimate the T g values of the ionomer phase in each film and show that there is a linear relationship between the mean apparent diffusion coefficient of the polymer determined from the DET experiment and T-T g , where T is the annealing temperature of the film

Sol–gel films and monoliths were prepared by hydrolysis of tetraethyl orthosilicate (TEOS) or tetramethyl orthosilicate (TMOS) in the presence of 1,3-bis(9-anthryl)propan-1-ol (BAP), bis(9-anthrylmethyl)amine (BAA) and the intramolecular photodimer of BM (DBAA). The intramolecular photodimerization of these dianthryl compounds as photoprobes was examined in sol–gel glasses and compared with those in solutions as well as in poly(methyl methacrylate)(PMMA) films. The intramolecular photodimerization of both BAP and BAA was severely suppressed in sol–gel glasses and PMMA films to lead to exclusive photo-oxidization, indicating the steric restriction of these matrices. A marked difference in the matrix effect between the two solids was found in the reversible photodimerization of DBAA. Photogenerated anthryl units of DBAA disappeared upon exposure to 365 nm light faster in PMMA than in sol–gel silica, suggesting that the face-to-face conformation of photodissociated DBAA is more readily relaxed rather than in the inorganic matrix. This was supported by the fact that further exposure to 285 nm light gave a lower regeneration of anthryl units in the silica bulk material than in the PMMA matrices.

マイクロメートルサイズの微粒子を非接触・非破壊に自由に操ることのできるレーザー捕そく法と,空間分解能を持つ顕微分光法を組み合わせたレーザー捕そく・顕微分光法を用いることにより,微粒子1粒ごとの分光分析が可能である.これを用い,水中に分散した油滴の油水界面で起こる反応の解析,油滴の融合,マイクロカプセル調製時に生じる内包物質の不均一(濃度)分布,イオン交換過程の直接測定に応用した例について紹介する.微粒子1粒ごとの分光分析を行い,その粒径依存性を検討することにより,従来の分散系や微粒子集合系の測定では知り得なかった粒ごとの濃度の違いや微粒子内での分布状態を明らかにすることができる.空間配置を意識した測定・反応の重要性についても合わせて述べる.

The mixing of fluids using AC electrothermal flow (AC-ETF) is presented. A pair of coplanar electrodes with a sinusoidal interelectrode gap was used to enhance the mixing in a microchannel. To demonstrate the performance of the mixer, conventional dilution experiments were conducted using Texas Red-labeled dextran. The dependence of mixing on the salt concentration (10(-3) ∼ 10(-1) mol dm(-3) ) of the solutions and frequency (100 kHz ∼ 5 MHz) of the applied voltage were investigated. AC-ETF was responsible for the mixing at salt concentrations10(-2) mol dm(-3) , whereas the effect of AC-EOF was suggested to play a role at concentrations10(-2) mol dm(-3) in the low-frequency region. The fluorogenic reaction of human serum albumin (HSA) with SYPRO Red in the mixer was also examined, and results showed that enrichment of fluorescence intensity and an almost uniform distribution of stained HSA were achieved. The present mixer can be employed as a powerful tool to facilitate efficient chemical and biomedical analysis on microfluidic devices.

The surface of colloidal silica particles was chemisorbed with spirobenzopyran molecule having a long hydrocarbon chain. The spiropyran silica particles (SP-CS) displayed normal photochromism. When SP-CS were dispersed in carbon tetrachloride, UV irradiation induced flocculation of the particles to bring about markedly enhanced sedimentation. Subsequent visible irradiation recovered the dispersed state again.

Electron transfer between ferrocene (FeCp) and Fe(III) across the droplet/water interface was studied by an optically transparent thin-layer electrode method. A time dependence of the FeCp concentration in the droplets caused by the interfacial electron transfer was discussed on the basis of coulometric analysis of Fe(II) or Fe(III) in the water phase and fluorometric analysis of FeCp in the droplets.

The preparation and characterization are described of a series of core-shell poly(butyl methacrylate) latex particles containing varying amounts of carboxylic acid groups. Matched pairs of particles, labelled with either donor (phenanthrene) or acceptor (anthracene) groups, were prepared by three-stage emulsion polymerization under monomer-starved conditions in which varying amounts of methacrylic acid were introduced into the third-stage polymerization. Films were prepared from the latex. The rate of polymer interdiffusion in the films, as followed by energy transfer measurements, decreased as the carboxyl content of the latex shell increased.

Polymer diffusion in latex films prepared from two pairs of poly(butyl methacrylate) (PBMA) latex particles is investigated. One set contains only a small amount of sulfate groups at the surface; the other contains a significant amount of carboxylic acid groups at the surface. Neutralization of these acid groups with ammonium, sodium, and barium hydroxide retards the interdiffusion rate at 100°C but does not suppress it. In these experiments, we employ pairs of particles identical in size, with very similar molecular weights, molecular weight distributions, and surface charge densities, that differ only in the fluorescent chromophore [phenanthrene (Phe) or anthracene (An)] used to label the polymer

A measuring method for the distribution behavior between supercritical carbon dioxide and water by a microchip was developed. A surface modification of the microchannel by dichlorodimethylsilane induced a spontaneous phase separation of the supercritical carbon dioxide and aqueous phases in the microchip. The maximum contact time of the aqueous phase to the supercritical carbon dioxide phase was obtained as 0.58 s. This device withstood pressure up to 12.8 MPa. The distribution of tris(acetylacetonato)cobalt(III) (Co(acac)(3)) from the supercritical carbon dioxide phase to the aqueous phase in a microchannel could be measured. The concentration of Co(acac)(3) distributed into the aqueous phase was increased by lengthening the contact time of both phases. These demonstrations showed that the method developed in this study could be used to measure the distribution behavior between supercritical carbon dioxide and water.

The distribution characteristics of a dye in single melamine resin wall microcapsules containing a dye/toluene solution are studied by a laser trapping-absorption microspectroscopy technique. In the case of Disperse Orange 13 as a dye, the molar absorptivity determined from the slope of a dye absorbance-capsule diameter (d) plot agrees well with that observed in a homogeneous toluene solution, indicating that the dye is solubilized homogeneously in the inner toluene solution of the capsule. For tetraphenylporphyrins (MTPP: Zn(II)TPP, Co(II)TPP, or H(2)TPP), however, the d dependence of absorbance shows a sigmoidal curve. Since absorbance of a ZnTPP/toluene droplet before polymerization of the melamine resin increases linearly with an increase in the droplet diameter, the sigmoidal d dependence of the absorbance is concluded to originate from distribution of the dye into the resin wall. Detailed analyses of the data indicate that the partitioning ratio of the dye between the toluene and resin phases is dependent on the capsule diameter. Size-dependent distribution of MTPP in single microcapsules is discussed on the basis of a proposed model and the d dependence of the dye absorbance, and it is concluded that the distribution of MTPP to the melamine resin wall is facilitated for larger microcapsules.

Models and the relevant equations giving optical absorbance of an analyte (i.e., dye) confined in a small volume with different shapes and sizes (sample dimension, D) are given, and factors governing absorbance are discussed. Dye absorbance is shown to be dependent on the three-dimensional sample structure: films (1-D), tubes (2-D), and spheres (3-D). The magnitude of the dimension effect on absorbance is determined by the size of both the sample and the probe beam. Furthermore, dye distribution characteristics in 2-D and 3-D systems also affect absorbance; a dye distributed exclusively to the surface layer of a 2-D or 3-D sample gave an absorbance 0.50- or 0.33-fold of that homogeneously distributed, respectively. If a dye is distributed in the inner volume of the sample alone, absorbance increases over that for homogeneous distribution. Effects of sample dimension, dye distribution characteristics, and the size of the probe beam in absorption microspectroscopy are discussed on the basis of the proposed models, and an experimental check of the models is presented.

Ion-exchange processes of a cationic dye (Rhodamine B; RhB) were studied for individual polymer particles (diameter of 16-20 μm) by laser trapping microspectroscopy and confocal fluorescence laser microspectroscopy. The absorbance of RhB at 565 nm adsorbed on a cation-exchange particle increased linearly with the concentration of RhB in the aqueous phase, while it was independent of the particle diameter. Fluorescence intensity profile measurements of RhB along the particle diameter by confocal fluorescence microspectroscopy directly proved that ion exchange took place in the surface layer (∼2-μm thickness) of the particle in the initial stage (1 h). Diffusion of RhB in the particle was very slow, and ion exchange proceeded gradually to the inner volume in the order of days. The ion-exchange processes were analyzed on the basis of simulation of the time course of the concentration profile of RhB in the particle, and the diffusion coefficient of RhB was determined to be (2-4) × 10(-11) cm(2)·s(-1).

Sol-gel glass thin films were prepared from tetraethyl orthosilicate in the presence of 4-methoxy-4′-(2-hydroxyethoxy)azobenzene (MHAB), 4-methoxy-4′-(N-(3-triethoxysilylpropyl)carbamoylmethoxy)azobenzene (MTAB) and 4,4′-bis(N-(3-triethoxysilylpropyl)carbamoylmethoxy)azobenzene (DTAB). The optical absorption spectra of the three azobenzenes entrapped in the films were investigated. The trans-cis photoisomerization and the thermal reversion of the azobenzene moiety were studied in the glass films and compared with those in solutions as well as in polymethyl methacrylate (PMMA) thin films. Triethoxysilyl groups linked with the azobenzene moiety had no effect on isomerization reactions. The cis fraction of the three azobenzenes in a photostationary state in PMMA was quite similar to that in solution whereas the photoisomerization was strongly suppressed in sol-gel films due to the rigidity of the matrix. The introduction of one triethoxysilyl group has a slight effect on both photoisomerization and thermal reversion in sol-gel films. Photoisomerization of DTAB with two silylating units was depressed in a sol-sol film because both sides of the azobenzene moiety were fixed to the sol-gel glass matrix.

Single micrometer-sized oil droplets formed at the end of a capillary tube in an aqueous surfactant solution were shown to exhibit vigorous auto-oscillated vibrations. The frequency and amplitude of the vibration were dependent on the droplet size, the concentration of the surfactant, and the nature of the oil used. The possible mechanism was discussed.