Published papers

The development of new magnetic materials in which magnetic properties are combined with optical properties has been extensively studied. So far, several photo-responsive molecular solids have been reported. However, the strategies that are necessary to achieve photoinduced switching in a solid state are yet to be clarified. Here, I have focused on composite materials as a novel strategy for realizing such photo-functional magnetic systems. These include the incorporation of organic photochromes into magnetic systems, e.g., photo-controllable magnetic vesicles and LB films containing Prussian blue or iron oxide nanoparticles and azobenzene. © 2006 The Chemical Society of Japan.

This work presents the construction and application of boron-doped diamond (BDD) thin film electrode as sensor for the determination of three β-agonists, viz. salbutamol, terbutaline and clenbuterol. Although well-known as a chemically inert material, BDD film however shows fouling in detection of these compounds using fixed-potential mode amperometry. A suitable waveform for pulsed amperometric detection (PAD) was developed and used to determine the agonist compounds. It was seen that the developed PAD significantly refreshed the BDD surface for long-term detection in flow injection analysis. Linear working ranges were 0.5-100 μM, 1.0-100 μM and 0.5-50 μM for salbutamol, terbutaline and clenbuterol, respectively. The developed PAD-BDD system was applied to successfully determine salbutamol and terbutaline in commercial pharmaceutical products. The methods were validated with a capillary electrophoresis method. © 2006 by MDPI.

New photo-controllable supramolecular system containing magnetic ionic liquid (iron(III) chloride with 1-butyl-3-methylimidazolium chloride) and azobenzene has been prepared. Reversible structural changes due to cis-trans photoisomerization of azobenzene could be observed by means of resonance Raman and electronic spectroscopy. Field dependence of magnetic moment at 298 K exhibited paramagnetic behavior similar to pure iron(III) magnetic ionic liquid. Alternate irradiation of UV and visible light at 298 K resulted in a monotonous increase of magnetic moment. In analogy with previous study, the novel behavior can be explained as irreversible aggregation of paramagnetic iron(III) complexes forming a short-range order in the supramolecular system. © 2006 Elsevier B.V. All rights reserved.

Preparations, crystal structures, and spectral and magnetic properties of two new chiral one-dimensional cyano-bridged coordination polymers, [Cu IIL2][MII(CN)4]·2H 2O (MII = NiII (1) and PtII (2), L = trans-cyclohexane-(1 R,2R)-diamine) have been presented. Complex 1 crystallizes in the monoclinic P21 space group with a = 9.864(4) Å, b = 15.393(8) Å, c = 7.995(4) Å, β = 110.32(3)°, V = 1138.4(10) Å3, and Z = 2, while 2 crystallizes in the monoclinic P2 1 space group with a = 9.899(3) Å, b = 15.541(4) Å, c = 8.102(2) Å, β = 111.02(2)°, V = 1163.6(5) Å3, and Z = 2. The unique zigzag cyano-bridged chains along the crystallographic b axis consist of alternate chiral [CuL2]2+ cations and square-planar [M(CN)4]2- anions. One side of the axial Cu-N(≡C) bond distances are 2.324(6) and 2.34(1) Å with Cu-N≡C angles of 137.8(6)° and 138.2(9)° for 1 and 2, respectively. On the other hand, the opposite side of the axial Cu-N(≡C) bond distances are 3.120(8) and 3.09(1) Å with significantly large bent Cu-N≡C angles of 97.9(5)° and 96.8(7)° for 1 and 2, respectively. The novel axial bonding features of extremely long semi-coordination Cu-N bonds are attributed to coexistence of pseudo-Jahn-Teller elongation and electrostatic interaction in the unique zigzag cyano-bridged chains. The characteristic bonding features with overlap between small 3d (NiII) or large 5d (PtII) and 3d (CuII) orbitals results in larger shifts in XPS peaks of not only Cu2p1/2 and Cu2p3/2 but also Ni2p1/2 and Ni2p3/2 for 1 than those of 2, which is also consistent with weak antiferromagnetic interactions with Weiss constants of -5.31 and -5.94 K for 1 and 2, respectively. The d-d, π-π*, and CT bands in the electronic, CD, and MCD spectra for 1 and 2 in the solid state at room temperature are discussed from the viewpoint of magneto-optical properties. © 2006 American Chemical Society.

A novel, selective methodology is derived based on the difference between the diffusion processes at microelectrodes (i.e., hemispherical diffusion) and the macroelectrode (i.e., linear diffusion) in a metal-implanted boron-doped diamond electrode (metal-BDDs). As an example, the selective detection of glucose in a solution containing interference species such as ascorbic acid and uric acid is demonstrated. The electrochemical properties of BDD, which are low background current, extremely high stability, and (especially) inactivity toward glucose, play an important role in realizing these differences in the diffusion characteristics. The present methodology can be applied not only to selective glucose detection by the metal-BDD system but also to other selective detection systems. © 2006 American Chemical Society.

The development of new magnetic materials in which magnetic properties can be controlled by optical stimuli has been extensively studied. So far, several photo-responsive molecular solids have been reported. First, in this review, several photo-magnetic molecular solids are introduced briefly. Then, a new strategy for realizing photo-functional magnetic systems such as photo-chromic magnets is also introduced in detail. © 2006 Elsevier B.V. All rights reserved.

The title chiral photochromic Schiff base compound, C15H 14BrNO, was synthesized from (R)-1-phenylethylamine and 5-bromosalicylaldehyde. The molecule is the phenolimine tautomer, the C=N and N-C bond distances being 1.261(7) and 1.482 (7) Å, respectively. There is an intramolecular O-H⋯N hydrogen bond with an O⋯N distance of 2.593 (7) Å. © 2006 International Union of Crystallography. All rights reserved.

Indium-modified, boron-doped diamond electrodes fabricated by an ion implantation method have been developed for electrochemical detection of arsenite (As(III)). Ir+ ions were implanted with an energy of 800 keV and a dose of 1015 ion cm-2. An annealing treatment at 850 °C for 45 min in H2 plasma (80 Torr) was required to rearrange metastable diamond produced by an implantation process. Characterization was investigated by SEM, AFM, Raman, and X-ray photoelectron spectroscopy. Cyclic voltammetry and flow injection analysis with amperometric detection were used to study the electrochemical reaction. The electrodes exhibited high catalytic activity toward As(III) oxidation with the detection limit (S/N = 3), sensitivity, and linearity of 20 nM (1.5 ppb), 93 nA μM -1 cm-2, and 0.999, respectively. The precision for 10 replicate determinations of 50 μM As(III) was 4.56% relative standard deviation. The advantageous properties of the electrodes were its inherent stability with a very low background current. The electrode was applicable for analysis of spiked arsenic in tap water containing a significant amount of various ion elements. The results indicate that the metal-implanted method could be promising for controlling the electrochemical properties of diamond electrodes. © 2006 American Chemical Society.

The influence of support electrolyte on the electrochemical degradation of formic acid was studied on boron-doped diamond (BDD) electrodes. Experimental data are compared with a theoretical model, which is based on organic degradation via hydroxyl radicals under current or mass transport controlled regimes depending on the difference between the applied and limiting current. The kinetics of the different reactions involved in the process is also briefly studied. It is shown that when sulfuric acid is used as support electrolyte, the reactions involving electro-generated peroxodisulfate anions during the degradation of formic acid are highly dependent on temperature. For this reason, the influence on the overall process of the chemical reaction between these anions and formic acid tends to increase with increasing temperatures and when the electrolysis becomes controlled by mass transport. However, it is proven that degradation of formic acid in the bulk occurs under current controlled regime as well. Furthermore, it is shown that the use of sulfuric acid as support electrolyte enhances the degradation of formic acid at high temperatures and when the process is controlled by mass transfer compared to other inert support electrolytes. © 2013 The Chemical Society of Japan.

The electrochemical detection of dissolved ozone in water was examined using boron-doped diamond (BDD) electrodes. A well-defined reduction peak was observed at ∼380 mV for H-terminated BDD, whereas it was observed at ∼200 mV in the case of O-terminated BDD for an ozone solution in a 0.1 M phosphate buffer solution at pH 7. The peak potential for ozone reduction was selective with respect to oxygen reduction at both H- and O-terminated BDD electrodes, whereas it occurred at approximately the same potential as oxygen reduction at other types of solid electrodes, including glassy-carbon, platinum, and gold electrodes. Interference from chlorine was not observed in lower concentration than 300 μM ClO-. Furthermore, in order to apply the detection technique to electrolyte-free media, BDD microelectrodes were also used. A linear calibration curve for dissolved ozone in water could be achieved between concentrations of 0.49 and 740 μM, with an estimated detection limit (S/N = 3) of 0.185 μM (S/N = 3). Excellent stability was demonstrated for repetitions of these calibration curves performed in 3 consecutive days. © 2013 American Chemical Society.

The electrochemical detection of lipophilic antioxidants, α-tocopherol (vitamin E, VE) and ubiquinone (coenzyme Q10, CoQ10), in methanol and in methanol/hexane mixture solutions, respectively, at boron-doped diamond (BDD) electrodes was investigated by cyclic voltammetry (CV) and flow-injection electrochemical measurements. CV measurements revealed that the overpotential for electrochemical reaction of VE and CoQ10 was larger at an oxidized BDD electrode surface than at that of a hydrogenated BDD (H-BDD) electrode. The slope of the CV calibration curve used to determine the VE and CoQ10 concentrations was larger at a glassy carbon (GC) electrode than at the H-BDD electrode; however, the signal-to-background ratio was larger at the H-BDD electrode than at the GC electrode, due to the low background feature of the H-BDD electrode. The limit of detection (LOD), defined by a signal-to-noise ratio of three for flow-injection electrochemical detection, was much smaller at the H-BDD electrode (VE: 41 nM and CoQ10: 17 nM) than at the GC electrode (VE: 263 nM and CoQ10: 71 nM). These results confirm that the H-BDD electrode is reliable for the electrochemical detection of lipophilic antioxidants, especially at low concentrations. © 2013 Elsevier Ltd. All rights reserved.

Individual and simultaneous electrochemical detection of iodide and iodine has been performed via cyclic voltammetry on boron doped diamond (BDD) electrodes in a 1 M NaClO4 (pH 8) solution, representative of typical environmental water conditions. It is feasible to compute accurate calibration curve for both compounds using cyclic voltammetry measurements by determining the peak current intensities as a function of the concentration. A lower detection limit of about 20 μM was obtained for iodide and 10 μM for iodine. Based on the comparison between the peak current intensities reported during the oxidation of KI, it is probable that iodide (I-) is ?rst oxidized in a single step to yield iodine (I2). The latter is further oxidized to obtain IO3 -. This technique, however, did not allow for a reasonably accurate detection of iodate (IO3 -) on a BDD electrode. © 2012 Elsevier B.V. All rights reserved.

Selective anodic stripping voltammetry of trace metal ions in a mixture solution with another interfering metal was developed based on Fick's law concerning the diffusion profile of interfering metals at the electrode surface after electrolysis treatment. A boron-doped diamond film was used as the sensing electrode, while a perforated carbon sheet was used for the interference-depleting electrode. The influence of the electrode distance and the time of electrolysis on the formation of the diffusion profile was studied. As a working model, the detection of cadmium with copper interference was investigated. The advantage of the method in comparison to general electrolysis was also discussed. The method offers a new perspective for improving the selective detection of metal ions by analyzing the diffusion profiles of the interfering species at the surface of electrodes. © the Owner Societies 2013.

The in vitro and in vivo electrochemical detection of the reduced form of glutathione (L-γ-glutamyl-L-cysteinyl-glycine, GSH) using boron doped diamond (BDD) microelectrode for potential application in the assessment of cancerous tumors is presented. Accurate calibration curve for the determination of GSH could be obtained by the in vitro electrochemical measurements. Additionally, it was shown that it was possible to separate the detection of GSH from the oxidized form of glutathione (GSSG) using chronoamperometry measurements. In vivo GSH detection measurements have been performed in human cancer cells inoculated in immunodeficient mice. These measurements have shown that the difference of GSH level between cancerous and normal tissues can be detected. Moreover, GSH detection measurements carried out before and after X-ray irradiation have proved that it is possible to assess in vivo the decrease in GSH concentration in the tumor after a specific treatment.

A new method is proposed for the accurate and reproducible detection of dopamine using cyclic voltammetry on boron-doped diamond (BDD) electrode. It is shown that reproducible voltammograms can be obtained when applying a relatively high scan rate (100Vs -1) during the detection measurements. For lower scan rates (1Vs -1), it is proven that electrode fouling occurs due do the deposition of a polymer at the electrode surface arising from the oxidation of aminochrome. Cyclic voltammetry measurements of the [Fe(CN) 6] 3-/[Fe(CN) 6] 4- couple performed before and after dopamine detection on BDD and glassy carbon electrodes have shown that the electrochemical activity of the electrode decreases only at low scan rates for BDD dopamine (DA) detection, which leads to electrode poisoning whereas the activity remains unchanged for higher scan rates. However, on glassy carbon electrodes, the electrochemical activity of the material decreases after DA detection measurements independently of the scan rate applied. Therefore, this study shows that electrode fouling during the detection of dopamine by cyclic voltammetry can be avoided only when using BDD electrode but also only for high applied scan rates. © 2012 The Chemical Society of Japan.

Gold-modified boron doped diamond (BDD) electrodes were examined for the amperometric detection of oxygen as well as a detector for measuring biochemical oxygen demand (BOD) using Rhodotorula mucilaginosa UICC Y-181. An optimum potential of -0.5 V (vs Ag/AgCl) was applied, and the optimum waiting time was observed to be 20 min. A linear calibration curve for oxygen reduction was achieved with a sensitivity of 1.4 μA mg-1 L oxygen. Furthermore, a linear calibration curve in the glucose concentration range of 0.1-0.5 mM (equivalent to 10-50 mg L-1 BOD) was obtained with an estimated detection limit of 4 mg L-1 BOD. Excellent reproducibility of the BOD sensor was shown with an RSD of 0.9%. Moreover, the BOD sensor showed good tolerance against the presence of copper ions up to a maximum concentration of 0.80 μM (equivalent to 50 ppb). The sensor was applied to BOD measurements of the water from a lake at the University of Indonesia in Jakarta, Indonesia, with results comparable to those made using a standard method for BOD measurement. © 2012 American Chemical Society.

Electrochemical detection of Cr 6+ has been performed by cyclic and linear scan voltammetry on boron doped diamond (BDD) electrode. This method is based on the electrochemical reduction of Cr 6+ to Cr 3+. The resulting voltammograms exhibited a clear peak at 0.03 V vs. AgCl related to this reduction and highly accurate (r 2 = 0.99) calibration curves could be obtained for a chromium concentration range between 10 ppb and 5 ppm. The influence of other metals dissolved in solution (Cu, Cd, Pb, B and Se) has been investigated as well and it was found that the Cr 6+ calibration curves remained unaltered. For all the experiments performed, a detection limit around 3 ppb was achieved. The high accuracy and reproducibility of the results as well as the excellent stability of the electrode material proves the excellent capabilities of this system for chromium detection. © 2012 Elsevier Ltd.

57Fe Mössbauer spectroscopy was applied to an iron-based layered compound CeFePO. At temperatures from 9.4 to 293 K, no magnetic splitting was observed in the Mössbauer spectra of CeFePO indicating a paramagnetic phase of the Fe magnetic sublattice. All the spectra were fitted with a small quadrupole splitting, and the Debye temperature of CeFePO was found to be ∼448 K. The isomer shift at room temperature, 0.32 mm/s, was almost equal to those of LnFeAsO (Ln = La, Ce, Sm). Comparing s-electron density using the isomer shifts and unit cell volumes, it was found that the Fe of CeFePO has a similar valence state to other layered iron-based quaternary oxypnictides except LaFePO. © 2012 The Physical Society of Japan.

Direct evidence: The existence of methoxy radical species formed during an anodic oxidation in MeOH on a boron-doped diamond (BDD) electrode was confirmed by ESR spectroscopy. Effective production of a neolignan, licarinA, was accomplished by the BDD-mediated anodic oxidation protocol (see picture). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.