Vol. 54 No. 6
June, 2005
Tomoaki Nishino1 and Yoshio Umezawa1
1 Department of Chemistry, School of Science, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033(Received 17 December 2004, Accepted 28 February 2005)
We describe herein the concept, principle, and experimental results of molecular tips for chemically selective STM. It has been shown that molecular tips allow chemically selective imaging based upon the hydrogen bond, metal coordination, and charge-transfer interactions between the sample and tip molecules. These chemical interactions result from facilitated electron tunneling through overlapped electronic wave functions between the sample and tip molecules. The selectivity can be tailored upon designing functional groups of the tip molecules. Although most of the molecular tips were prepared by utilizing self-assembled monolayers, polypyrrole or carbon nanotubes immobilized onto underlying STM tips also allowed chemically selective imaging. In addition, the molecular tips enabled the conformational analysis and detection of intermolecular electron transmission from a single molecule to another adjacent single molecule.
Keywords : scanning tunneling microscopy (STM); molecular tips; chemical selectivity.
Hiroharu Yui1,2 and Tsuguo Sawada1,3
1 Department of Advanced Materials Science, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5-401, Kashiwanoha, Kashiwa-shi, Chiba 277-8561(Received 22 December 2004, Accepted 22 March 2005)
A spectroscopic technique with high sensitivity and spatial resolution is crucial for the analyses of liquids in nano-spaces and at interfacial areas. Especially, new techniques have been desired that can be applied to analyses of the dynamic behavior of molecular assemblies in buried restricted environments, such as at oil/water interfaces and in living cells. Here, we present our new experimental techniques, namely “Time-Resolved Quasi Elastic Laser Scattering” and “Electron Enhanced Raman Scattering”, which are expected to meet such requirements. We show various investigations on the structures of liquids and the dynamic behaviors of molecular assemblies under restricted geometries with these new techniques.
Keywords : light scattering; laser; interface; nanospace; liquid.
Shoji Okuno1, Yukiyasu Shimomae2, Yoshinao Wada3 and Ryuichi Arakawa1,2
1 Japan Science and Technology Agency, Wada Proteomics Project, 3-1-10, Technostage, Izumi-shi, Osaka 594-1144(Received 17 December 2004, Accepted 4 March 2005)
Desorption ionization on silicon (DIOS) is a novel matrix-free variant of laser desorption/ionization (LDI) techniques for mass spectrometry. DIOS sample targets or DIOS chips are produced by the electrochemical etching of silicon wafers under light exposure. In the present report, the optimal conditions regarding the resistivity of a silicon wafer, the etching current density and the etching time, for making DIOS chips with good ionization performance are described. The DIOS mass spectra of various kinds of synthetic polymers are compared with the matrix-assisted LDI (MALDI) mass spectra. In the quantitative analysis of mixtures of diol and triol types of polypropyleneglycol (PPG), DIOS provides more reliable data than MALDI under the optimized conditions. The ionization process in DIOS was studied in terms of the redox reaction of the analytes. Copper(II) chloride, some organic dyes and riboflavin, were reduced and some ferrocene derivatives were oxidized as well as MALDI. These results indicated that electron transfer between the analytes and the chip surface occurred in DIOS. The reduction of riboflavin was accelerated using water as a solvent.
Keywords : desorption ionization on silicon; laser desorption mass spectrometry; synthetic polymer; redox.
Takahiko Nojima1, Kenichi Yamashita1, Taizo Hatta2, Otohiko Tsuge2, Toshio Iwase3, Naoko Makita3, Kenichi Yoshikawa3, Satoshi Fujii1 and Shigeori Takenaka4
1 Department of Applied Chemistry, School of Engineering, Kyushu University, 6-10-1, Hakozaki, Higashi-ku, Fukuoka-shi, Fukuoka 812-8581(Received 20 December 2004, Accepted 3 March 2005)
The physicochemical behaviors of cationic water-soluble fullerene derivatives 1a-c (alpha-, beta-, and gamma-isomers, respectively) were studied in the absence or presence of bacteriophage T4 DNA as a double-stranded DNA (dsDNA). In water, 1a and 1b formed similar assemblies with diameters of 330~340 nm, identified by dynamic light scattering (DLS) measurements, whereas 1c formed a larger assembly with a diameter of 1400 nm. DLS and fluorescence microscopic studies showed that these assemblies collapsed after the addition of dsDNA to form new assemblies with dsDNA. In these assemble, 1a-c were formed to be lying in the DNA grooves with stoichiometric ratio of their cationic site to the DNA phosphate anionic site by spectroscopic and Transmittion electron microscopic measurements. A molecular-dynamic calculation of their complex revealed that fullerene moiety of 1a-c interacts with the groove surface of dsDNA while keeping the electrostatic interaction of the cation of 1a-c with the DNA phosphate anion. The results thus obtained have a potential for use in the new nano-structure assembly by using a dsDNA backbone.
Keywords : fullerene; dynamic light scattering; fluorescence image; transmission electron microscopy.
Masashi Suzuto1, Hitoshi Ohnishi1, Yasuyuki Hirakawa1 and Tsutomu Masujima1
1 Graduate School of Biomedical Sciences, Hiroshima University, 1-2-3, Kasumi, Minami-ku, Hiroshima-shi, Hiroshima 734-8551(Received 20 December 2004, Accepted 23 March 2005)
A micro spot illumination for a single molecule was achieved by using a single optical fiber with a laser source under a microscope (pin-fiber video-scopic method). This system is suitable for observing the microscopic kinetics of colloidal particles, living cells and DNA molecules. In this paper, we discuss investigations of the DNA extension scheme and its photocleavage. Under optimum conditions, DNA twisted movements, followed by cleavage, were observed when the DNA molecule was intensely irradiated by laser radiation via a single optical fiber. It was suggested that DNA chain vibration is caused by thermal-energy transformation of the absorbed illumination; the following cleavage is achieved by active oxygen in the solution.
Keywords : DNA; photocleavage; YOYO-1; fluorescent microscope; stretching DNA.
Ayaka Nishikawa1, Satoshi Tsukahara1 and Terufumi Fujiwara1
1 Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1, Kagamiyama, Higashi-Hiroshima-shi, Hiroshima 739-8526(Received 17 December 2004, Accepted 16 March 2005)
A newly designed planar quadrupole microelectrode of gold (thickness, 50 nm) and chromium (5 nm) was fabricated by photolithography. The radius of its working area was 125 µm. Two kinds of large DNAs, lDNA (48 kbp; bp, base pair) and T4GT7DNA (166 kbp), labeled with cationic fluorophores, were taken as a sample DNA. The dielectrophoretic (DEP) behaviors of DNA in the quadrupole electrode were measured with a fluorescence microscope by applying an alternating current with a frequency of 1 kHz~15 MHz and a root-mean-square voltage of 7.1 V. All of the single DNAs migrated radially to the edge of the electrode in the whole frequency range, that is, positive DEP, caused by a dynamic ion cloud around DNA. The DEP behaviors of DNAs confirmed that the fabricated quadrupole electrode made an ideal nonuniform electric field in the working area. Some aqueous substances were added and their influence on the DEP of DNA was examined. The longer T4GT7DNA migrated a little faster than lDNA, and an intercalating fluorophore slightly enhanced the DEP velocity of DNA. Aqueous polyethylene glycol (PEG) at a high concentration was known to induce a globule transition of DNA, but the viscosity of the solution at the PEG concentration was about 60-times higher than that of water. The dominant effect of PEG on the DEP of DNA was not the globule transition but the enlarged friction force that DNAs underwent from the solution, that is, a slow DEP migration. Anionic and nonionic surfactants had only a small influence on the positive DEP of DNA. A cationic surfactant (hexadecyltrimethylammonium chloride, CTAC) was strongly bound to DNA with an electrostatic interaction, but the DEP behavior of DNA was not measured because CTAC eliminated the interaction of DNA with the cationic fluorophores. Nonionic O/W emulsions showed negative DEP, independent of the DNA of positive DEP.
Keywords : microscopic dielectrophoresis; planar quadrupole microelectrode; DNA; coil-globule transition; surfactant.
Takanori Inoue1, Hirotoshi Nishi1, Toshiyuki Kitauira1, Yoshiaki Kurauchi1 and Kazuya Ohga1
1 Department of Applied Chemistry, Oita University, 700, Dannoharu, Oita-shi, Oita 870-1192(Received 17 December 2004, Accepted 4 April 2005)
A laser multi-photon ionization technique has been applied to an interface region in two-phase systems (n-octane/water). The Laser irradiated the interface under total reflection condition from the oil phase, and the photo-ionization signal was caused by water region. Pyrene stayed at the oil/water interface, and the amount of Pyrenesulfonic acid at the interface was very small. Other aromatic molecules, naphthalene derivatives and benzene derivatives, were also applied to this technique. The pH and the surfactant dependence also exhibited that the non-ionic molecules stayed at the oil/water interface. Upon lower the pH, the protonated aromatic molecules increased and overall dissolving process decelerated. With increasing the anionic and cationic surfactant concentrations, the photo-ionization current gradually decreased. The surfactant and aromatic molecules formed into micelles in the bulk water region. Photo-ionization is a potential tool for investigating the phenomena of a two-phase system.
Keywords : multi photon ionization; oil/water interface; aromatic molecule; surfactant.
Shoji Ishizaka1, Takeshi Araki1, Yoshiaki Nishijima1 and Noboru Kitamura1
1 Division of Chemistry, Graduate School of Science, Hokkaido University, Kita 10-Nishi 8, Kita-ku, Sapporo-shi, Hokkaido 060-0810(Received 20 December 2004, Accepted 5 March 2005)
The excited-state proton-transfer dynamics of 6-hydroxypyrene-1-sulfonic acid (HPSA) at a water/1,2-dichloroethane (DCE) interface was studied by using time-resolved total internal reflection (TIR) fluorometry. The TIR fluorescence spectrum of HPSA observed at a water/DCE interface with the maximum wavelength at around 495 nm was assigned to that from the base-form of HPSA, produced by the excited-state proton-transfer reaction with water. However, the relative fluorescence intensity of the base-form (495 nm) to that of the acid-form (435 nm) observed at the interface was weaker than that in water. Furthermore, the excited-state proton-transfer rate constant (kf) of HPSA at a water/DCE interface (5.0×108 s-1), determined by the TIR fluorescence dynamics, was slower than that in water (9.8×108 s-1). On the other hand, the kf value of HPSA in a water-ethanol mixture depended on the forth power of the water concentration. This result suggested that the excited singlet state of HPSA transferred a proton to a water cluster composed of four molecules. The structures of the water cluster and the hydrogen bond at a water/DCE interface were suggested to reflect on the proton-transfer rate constant.
Keywords : liquid-liquid interface; excited-state proton transfer; total internal reflection fluorometry.
Hiroshi Kakizaki1 and Kiyoharu Nakatani1
1 Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1, Tennodai, Tsukuba-shi, Ibaraki 305-8571(Received 27 December 2004, Accepted 6 March 2005)
The sorption of phenol blue (PB), known as a solvatochromic dye, from an alcohol (methanol, ethanol, butanol or pentanol)-water mixture solvent into single spherical octadecylsilyl (ODS)-silica gel microparticles {particle diameter (d) of 20~60 µm, pore diameter of 12 nm} was investigated by absorption microspectroscopy. For ~0.5 vol% pentanol, ~0.5 vol% butanol or 1 vol% ethanol, the adsorption coefficient of PB in a single microparticle (Kads), determined on the basis of the Langmuir isotherm, was much smaller than that for water although the relative permittivity of the mixture solvent was almost the same as that of water. Furthermore, the absorption maximum of PB in the microparticle (λmax) for the mixture solvent was slightly shifted from that for water. For 1 vol% methanol, both λmax and Kads did not change compared with those for water. The results showed that for a mixture solvent of pentanol, butanol or ethanol the microscopic polarity in the ODS phase was larger and the polarity and hydrogen bonding in the vicinity of the ODS/solution interface were smaller than those for water because the alcohol molecules with the long alkyl chain length distributed in the ODS phase. Concerning the volume percentage of alcohol greater than ~5 vol%, on the other hand, λmax and Kads significantly decreased with the increasing volume percentage of alcohol, revealing a decrease in the relative permittivity of the mixture solvent as well as changes in the microscopic polarity and hydrogen bonding.
Keywords : ODS silica gel; absorption microspectroscopy; adsorption; microscopic polarity; single microparticle.
Yasunobu Iwami1, Masahiro Yamamoto1, Naoya Nishi1 and Takashi Kakiuchi1
1 Department of Energy and Hydrocarbon Chemistry, Kyoto University, Nishikyo-ku, Kyoto-shi, Kyoto 615-8510(Received 30 December 2004, Accepted 5 March 2005)
The sub-ps solvation dynamics in a water|Aerosol OT (AOT)|1,2-dichloroethane (DCE) reverse micelle system has been investigated by fluorescence lifetime measurements of coumarin 343. From absorption spectroscopic measurements, the fluorescence dye molecules were found to be located at the outer side of the reverse micelle interface. The diffusive part of the sub-ps solvation became slower for smaller micelles with the radius of 2~4 nm. This may be due to the interaction between water and AOT molecules in the smaller micelles.
Keywords : solvation dynamics; reverse micelle; fluorescence lifetime; up-conversion method; aerosol OT; 1,2-dichloroethane.
Mihoko Ui1, Akiyo Yamauchi1 and Iwao Suzuki1
1 Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3, Aoba, Aramaki, Aoba-ku, Sendai-shi, Miyagi 980-8578(Received 13 December 2004, Accepted 3 February 2005)
A novel fluorescent derivative of α-cyclodextrin (α-CD), possessing a pyrenylmethylamino moiety (1), was synthesized to investigate its chiral discrimination ability for N-octanoyltrptophan (D-Trp-C8 and L-Trp-C8). From the pH-dependent fluorescence variations, the pKa of 1 was determined to be 6.95. Under a weakly acidic condition (pH 5.9), although an ammonium form prevailed for 1 and, as a result, photo-induced electron transfer should be absent, the fluorescence of 1 was markedly quenched, probably due to electron or energy transfer between the pyrene residue of 1 and the indole moiety of the guests. A simple 1 : 1 host-guest complexation model was successfully applied to the guest concentration-dependent fluorescence variations, yielding 1 : 1 host-guest association constants for D-Trp-C8 and L-Trp-C8 as 2160 and 1200 M-1, respectively, while the values were decreased to 790 and 557 M-1, respectively, at pH 4.0, where the carboxy groups of the guests protonated. In 1H-NMR spectra measured with a mixture of D-Trp-C8 and 1, significant upfield shifts were observed for the aromatic signals of both D-Trp-C8 and 1, indicating that the two aromatic groups existed close to each other. On the other hand, no such significant upfield shifts were observed for a mixture of L-Trp-C8 and 1. These results indicate that the pyrene residue and the ammonium group of 1 provided effective recognition sites to 1 in addition to the α-CD cavity when 1 complexed with D-Trp-C8, but not with D-Trp-C8.
Keywords : cyclodextrin; pyrene; tryptophan; chiral recognition; host-guest.
Tetsuo Kuwabara1, Kazuya Suzuki1, Naoya Miyajima1 and Yasutada Suzuki1
1 Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, 4-3-11, Takeda, Kofu-shi, Yamanashi 400-8511(Received 21 December 2004, Accepted 22 April 2005)
Two p-methyl red-modified cyclodextrins, each being different only in the cavity size of cyclodextrins with α- and β- type (p-MR-α-CD and p-MR-β-CD), were prepared to investigate their molecular-recognition abilities, accompanied with color changes, as well as to investigate their conformations in aqueous solutions. The difference in the cavity size of cyclodextrins caused a marked difference in their conformations, in which p-MR-α-CD and p-MR-β-CD adopted a face-to-face dimmer form and a intramolecular self-inclusion complex monomer one, respectively. This reflected the different acid-base equilibrium behaviors, as shown by the fact that the protonation occurred on the dimethylamino group of the dye unit for p-MR-α-CD and on the azo group for p-MR-β-CD when the pH of the solution was lowered, each revealing colorless and a red color of the solutions. At the pH of the solution near their pKa, they exhibited guest-induced color changes from yellow to red and from orange to red, respectively. Based on this, we evaluated the sensor ability of the modified cyclodextrins against various alcohols. p-MR-α-CD detected higher alcohols with a linear structure rather than a cyclic ones, while p-MR-β-CD showed a higher sensing ability for cyclic alcohols, especially for adamantine derivatives., rather than linear ones.
Keywords : cyclodextrin; dye; molecular recognition; color change.
Ken Hosoya1, Mitsuko Bendo1, Nobuo Tanaka1, Keiko Wada2, Ryoji Kose3 and Yoshimasa Sugai3
1 Department of Polymer Science & Engineering, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto-shi, Kyoto 606-8585(Received 16 December 2004, Accepted 28 March 2005)
We have to develop an adsorbent for the sake of removing nitric acid and phosphoric acid from natural river water to reduce this environmental problem. Although only a small amount of the adsorbent was applied to a river, 81% of nitric acid and 52% of phosphoric acid were removed from the natural river water continuously for 3 months.
Keywords : nano-interface; molecular recognition region; adsorption; polyester; environmental water; biodegradable.
Takahito Kawano1, Yukichi Horiguchi2, Yasuro Niidome2,3, Takuro Niidome2,3 and Sunao Yamada2,3
1 Department of Materials Science, Nagasaki University, 1-14, Bunkyo-cho, Nagasaki-shi, Nagasaki 852-8521(Received 24 December 2004, Accepted 28 February 2005)
Cationic gold nanoparticles were obtained by chemical reduction of tetrachloroaurate (AuCl4-) in the presence of the 2-aminoethanethiol (AET). Formation of colloidal gold nanoparticles was monitored by absorption spectroscopy, light scattering, and zeta potential measurements. Colloidal gold nanoparticles were obtained when the ratio of AuCl4- and AET was about 1 : 1.5. The mean size and the zeta potential of the nanoparticles was 34±6 nm and +44±24 mV, respectively. The polyethyleneoxide compound terminated with a SH group (PEG-SH) increased the mean size of the nanoparticles (49±18 nm), but decreased zeta potentials of the gold nanoparticles (+16±7 mV). The PEG-SH was effective to stabilize the colloidal dispersion of the gold nanoparticles.
Keywords : gold nanoparticles; aminoethanethiol; zeta potential; cationic nanoparticles.
Yoshie Iwane1, Setsuko Yajima1, Eisaku Nomura2, Hisaji Taniguchi2 and Keiichi Kimura1
1 Faculty of Systems Engineering, Wakayama University, 930, Sakaedani, Wakayama-shi, Wakayama, 640-8510(Received 20 December 2004, Accepted 28 April 2005)
The surface plasmon absorption of silver colloid, which was formed by the reduction of silver ion with a calixarene derivative bearing a gallate ester group in ethanol, was observed by absorption spectroscopy. The time-dependent absorption of silver colloid was found, which shows that the silver colloid is unstable and easy to aggregate. In order to prevent the silver colloid aggregation, poly(N-vinylpirrolidone) (PVP) was added into the solution at a constant time after preparing of sample solutions. The addition of PVP was effective for the stabilization of silver colloid, and the absorbance change with time was depressed. In the calibration graph, the absorbance increased with increasing silver-ion concentration, especially in the concentration range of 2.00×10-6~1.00×10-5 M. It is feasible to determine silver-ion concentrations using this method.
Keywords : silver colloid; calixarene gallate ester; silver-ion reduction; surface plasmon absorption; quantitative determination.
Takahide Nishiyama1, Fumihiro Endo1, Hiroko Eguchi1, Tatsuro Nakagama1, Nobuko Seino2, Masaki Shinoda2, Takuya Shimosaka1,3, Toshiyuki Hobo1 and Katsumi Uchiyama1
1 Department of Applied Chemistry, Graduate School of Engineering, Tokyo Metropolitan University, 1-1, Minamiohsawa, Hachioji-shi, Tokyo 192-0397(Received 21 December 2004, Accepted 21 March 2005)
We have developed an ultra micro sample injector for a gas chromatography (GC). An ink-jet chip, originally used for industrial recorder, was modified at the edge near the orifice and fixed into the GC. To evaluate the characteristics of this injector, a sample injector and a thermal conductive detector (TCD) were connected directly and water was used as the sample. The volume of the droplet, the interval time and the back pressure to the ink-jet chip were investigated. Within a range of 1~5 nl of sample injection, the TCD response according to the amount of the sample volume (about the volume of 1 drop from the ink-jet micro chip: about 1 nl) was obtained. The reproducibility of the peak area was obtained to be about 1.0% of the RSD value. To compare the injection method of the ink-jet chip with that of the usual micro syringe, a method using the ink-jet chip could introduce 1/1000 amount of the sample and give reproducible result.
Keywords : ink-jet; sample injection methods; thermal conductive detector; water; gas chromatography.
Shuji Matsuo1 and Hisanobu Wakita1,2
1 Advanced Materials Institute, Fukuoka University, 8-19-1 Nanakuma, Jonan-ku, Fukuoka-shi, Fukuoka 814-0180(Received 25 February 2005, Accepted 8 April 2005)
For investigating the effect of the boundary structure on spectral shapes of an X-ray absorption near-edge structure (XANES), Br L3-edge XANES spectra were analyzed using electronic state calculations by the discrete variational (DV)-Xa molecular-orbital method. Analyses of the spectral shape for crystalline LiBr with the Coulomb force were performed by calculations using four models: the bulk LiBr model, the surface model, the surface-hydration model with Madelung potential, and the bulk LiBr model without Madelung potential. Each spectral shape that was calculated for the four models was characteristic of each model, and the spectral shape calculated for the bulk LiBr model with Madelung potential was in satisfactory agreement with the experimental Br L3-edge XANES spectral shape for the crystalline LiBr. An analysis of the spectral shape of Br L3-edge XANES for a 0.1 M aqueous solution of KBr was performed by the calculations using models consisting of a pair of hydrated K and Br ions. The spectral shapes calculated for all models can prove that hydrated K ions in a 0.1 M aqueous solution of KBr only little affected the experimental XANES spectral shape.
Keywords : XANES; DV-Xa MO method; simulation; surface; hydration
Takuya Shimosaka1,2, Kaori Nakamura1, Katsumi Uchiyama1 and Toshiyuki Hobo1
1 Tokyo Metropolitan University, School of Engineering, 1-1, Minamiosawa, Hachioji-shi, Tokyo 192-0397(Received 12 January 2005, Accepted 11 April 2005)
When a phospholipids bilayer with a metallochromic indicator was measured by total internal reflection with thermal lens spectrometry, the signal was more fluctuated than that of a dye solution. To clarify the difference of the signal fluctuation for the bilayer and the dye solution, power spectra of the results were obtained by a Fourier transform. In a lower frequency region, the intensity of the power spectrum for the phospholipid bilayer measurement was higher than that for the dye solution measurements. We supposed that the fluctuation was caused by the heterogeneity of the bilayer, or aggregation of the dye molecules in the bilayer, or both. Signals at different temperatures were obtained, and these power spectra were compared with each other. The spectra lower than 0.05 Hz increased as the temperature became higher, and agreed with the expected result.
Keywords : total internal reflection with thermal lens spectroscopy; phospholipid bilayer; signal fluctuation; power spectrum; heterogeneity.
Kotaro Morita1, Tatsuya Uchida2, Chizuru Sakurai1 and Norio Teramae1
1 Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki, Aoba-ku, Sendai-shi, Miyagi 980-8578(Received 15 December 2004, Accepted 18 February 2005)
The adsorption and desorption processes of 5'-thiolated DNA oligomers onto a gold electrode were investigated using a quartz crystal microbalance (QCM). The morphology of the DNA layer adsorbed on the gold surface was observed and characterized using scanning tunneling microscopy (STM) and electrochemical measurements. The results of QCM experiments showed that the surface coverage of tholated DNA was estimated to be ca. 30%. The STM observation and electrochemical measurements revealed the flexibility of the immobilzied DNA on the gold electrode surface.
Keywords : DNA; quartz crystal microbalance; scanning tunneling microscopy; reductive desorption; differential pulse voltammetry.
Kin-ichi Tsunoda1, Ken-ichi Shimosakai1, Yasuyuki Hashimoto1, Tomonari Umemura1 and Tamao Odake1
1 Department of Chemistry, Gunma University, 1-5-1, Tenjin-cho, Kiryu-shi, Gunma 376-8515(Received 17 December 2004, Accepted 3 March 2005)
An ITO electrode slab optical waveguide spectroelectrochemical measurement system was built for simultaneous Visible attenuated total reflection (ATR) and electrochemical measurements and was applied to study the spectroelectrochemical behavior of iodine at the ITO electrode. The cyclic voltamogram and the potential-absorbance curve at 430 nm for the redox reaction of iodine were observed and the formation of iodine was confirmed by the Visible ATR spectra of iodine (λmax=430 nm) which showed blue-shift compared with those of gasous iodine as well as iodine in non-polar solvents (λmax=500~600 nm). Moreover, the linear responses of the peak current and the maximum absorbance for the oxidation reaction of iodide were obtained to the concentration of iodide in aqueous samples.
Keywords : slab optical waveguide; ITO electrode; spectroelectrochemistry; iodine.
Yusuke Hiejima1, Mitsuhiro Kanakubo1, Takafumi Aizawa1, Yoshiaki Kurata1 and Yutaka Ikushima1
1 National Institute of Advanced Industrial Science and Technology (AIST), 4-2-1, Nigatake, Miyagino-ku, Sendai-shi, Miyagi 983-8551(Received 17 December 2004, Accepted 19 February 2005)
High-pressure NMR spectroscopy is applied for Xe (129Xe) and SF6 (19F) confined in nanopore in a wide range of the fluid phase. Two distinct signals due to bulk and confined fluids are observed. The mean fluid density in nanopore is estimated from the ratio of the integrated signal intensities of bulk and confined fluids. The variation in the chemical shift of the confined fluid is correlated with that of the mean density in nanopore.
Keywords : 129Xe and 19F NMR; high pressure; confined fluid; density; chemical shift.
Tamio Kamidate1, Yoshiki Ishida1, Hirofumi Tani1 and Akihiko Ishida1
1 Division of Molecular Chemistry, Graduate School of Engineering, Hokkaido University, Kita 13-Nishi 8, Kita-ku, Sapporo-shi, Hokkaido 060-8628(Received 14 December 2004, Accepted 17 March 2005)
Fluorescein (FL) and H2O2 rapidly permeated into the inner phase of liposome which trapped horseradish peroxidase (HRP), to initiate HRP-catalyzed FL chemiluminescence (CL) with H2O2. The CL intensity was dependent on the concentration of H2O2. The optimum conditions of charge-type, composition and diameter of liposome in the assay of H2O2 were determined by measuring the CL intensity, to be maximal under optimum conditions. Anionic liposome containing phosphatidylcholine, dimyristoyl-glycero-phosphocholine and cholesterol (Chol) was effective for enhancing the CL intensity and stability of liposome. The CL intensity decreased with an increase in the content of Chol in liposome. The optimal content of Chol was thus determined to be 10 mol%. The effect of the liposome size on the CL intensity was examined by preparing liposomes with a different diameter. The CL intensity increased with an increase in the diameter of liposome. The optimal diameter of liposome was thus determined to be 1000 nm. The logarithmic calibration curve of H2O2 was linear over the range from the detection limit of 4.0×10-8 M up to 1.0×10-5 M. When HRP trapped in liposome was used as a catalyst, the CL intensity was greater than that observed by using HRP dissolved in the bulk solution in the range of 4.0×10-7 M up to 1.0×10-5 M of H2O2.
Keywords : chemiluminescence; liposome; peroxidase; hydrogen peroxide; fluoresein.
Naoya Kimura1,2, Ken-ichi Ohno1,3, Toshihiro Nakamura2 and Masaaki Yamada1
1 Department of Applied Chemistry, Graduate School of Engineering, Tokyo Metropolitan University, 1-1, Minami-Ohsawa, Hachioji-shi, Tokyo 192-0397(Received 20 December 2004, Accepted 27 January 2005)
Aggregates (mixed micelles, bilayer membranes, vesicles) formed from aqueous mixtures of dodecyltrimethylammonium chloride (DTAC) and sodium dodecyl sulfate (SDS) were evaluated for chemiluminescence (CL) reaction media by means of a batch method. The uranine CL based on oxidation by hypochlorous acid was chosen as a model CL system. The uranine CL intensity was enhanced by a factor of 91 in mixed micelles ([DTAC]/[SDS]=1.5) compared with that in other aggregates (bilayer membranes and vesicles). This enhancement is thought to be caused by the increased CL quantum yield, which results from stabilization of the emitter (uranine) on the interface of the rigid mixed micelles.
Keywords : chemiluminescence; surfactant mixtures; mixed micelles; uranine; hypochlorous acid.
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