Hydrophobic Platinum Research Articles

Hydrogen Isotope Fractionation in Aqueous Alkaline Earth Chloride Solutions

The D/H ratio of hydrogen gas in equilibrium with aqueous alkaline earth (Mg, Ca, Sr or Ba) chloride solutions measured at 25◦C using a hydrophobic platinum catalyst, was found to be higher than the D/H ratio equilibrated with the applied pure water. The hydrogen isotope effect between such solutions and pure water changes with the molality of the solutions. The order of the D/H ratios in alkaline earth chlorides is found to be BaCl2 > SrCl2 ≥ CaCl2 ≥ MgCl2. The hydrogen isotope effect in the aqueous chloride solutions of Mg, Ca, Sr or Ba ions is significantly larger than that in the aqueous chloride solutions of Li, Na, K or Cs ions. For MgCl2 and CaCl2 solutions, the hydrogen isotope effect is opposite to the oxygen isotope effect. The results are compared with the free energy change of transfer from H2O to D2O, and are discussed for the vapour pressure ratio of H2O and D2O of CaCl2 solutions.

Preparation of hydrophobic platinum catalysts using a water-in-CO 2 microemulsion

The hydrophobic platinum catalyst for the chemical exchange reaction between water and hydrogen was prepared by the two-step reduction of 1,5-cyclooctadiene dimethyl platinum (II): A reduction using the reducing agent of sodium tetraborohydrate solution in a water-in-CO 2 microemulsion and the auto-catalytic reduction using hydrogen gas. The platinum particles were locally dispersed on the nano-textured hydrophobic layer formed on the gauze. Their average size was about 50 nm in diameter using a scanning electron microscope and energy dispersive X-ray spectroscopy. The hydrophobicity of the gauze did not decrease even after the deposition of the platinum nano-particles based on a measurement of the amount of water absorbed on the gauze. The hydrophobic platinum catalyst developed in this study was found to be effective for the isotopic exchange reaction of hydrogen atoms between hydrogen and deuterium even in the presence of water. The hydrogen and deuterium atoms were dissociated and exchanged with each other on the surface of the platinum particles and HD was generated. The HD/D 2 ratio increased from 0.012 to 0.050.

Apoptosis and inhibition of gap-junctional intercellular communication induced by LA-12, a novel hydrophobic platinum(IV) complex

A new hydrophobic platinum(IV) complex, LA-12, a very efficient anticancer drug lacking cross-resistance with cisplatin (CDDP), is now being tested in clinical trials. Here we investigated the apoptogenic activity of LA-12 and its effect on gap-junctional intercellular communication (GJIC) in the rat liver epithelial cell line WB-F344. LA-12 induced apoptosis much more efficiently than did CDDP due to a combination of rapid penetration into the cell and attack on DNA, leading to fast activation of p53 and caspase-3. Exposure of WB-F344 cells to LA-12 led to rapid induction of the time- and dose-dependent decrease in GJIC. On the molecular level, loss of GJIC induced by LA-12 was mediated by activation of extracellular signal-regulated kinase (ERK)-1 and ERK-2, as demonstrated by the use of inhibitors of ERK activation. Inhibition of GJIC was linked to rapid hyperphosphorylation of connexin-43 and disappearance of connexon clusters from membranes, which was not observed in the case of CDDP.

Kolbe Electrolysis of Carboxylates on a Hydrophobic Platinum Electrode Composite-plated with PTFE Particles

Kolbe Electrolysis of Carboxylates on a Hydrophobic Platinum Electrode Composite-plated with PTFE Particles

Preparation of Hydrophobic Platinum Electrodes by Composite-Plating

Preparation of Hydrophobic Platinum Electrodes by Composite-Plating

Hydrogen Isotope Fractionation in Aqueous Alkali Halide Solutions

Abstract The D/H ratios of hydrogen gas in equilibrium with aqueous alkali halide solutions were deter-mined at 25 °C, using a hydrophobic platinum catalyst. The hydrogen isotope effect between the solution and pure water changes linearly with the molality of the solution at low concentrations, but deviates from this linearity at higher concentration for all alkali halide solutions. The magnitude of the hydrogen isotope effect is in the order; Kl > Nal > KBr > CsCl ≧ NaBr > KCl > NaCl > LiCl, at concentrations up to a molality of 4 m. The sign and trend of the hydrogen isotope effect is different from that of oxygen. In aqueous alkali halide solutions, the hydrogen isotope effect is influenced by both the cation and the anion species, while the oxygen isotope effect is mainly caused by the cation species. This suggests that the mechanism of hydrogen isotope fractionation between the water molecules in the hydration spheres and the free water molecules differs from the mechanism of the oxygen isotope fractionation. The hydrogen and oxygen isotope effects for alkali halides, except LiCl and NaCl, may be influenced by changes in energy of the hydrogen bonding in free water molecules.

Platinum 2,2′:6′,2′-terpyridine complexes as probes for CMC determination of sodium dodecyl sulfate solutions

The platinum complex [Pt(terpy)(OH)] + (terpy = 2,2′:6′,2′-terpyridine) is a molecular “light switch” for the determination of critical micelle concentration (CMC) in sodium dodecyl sulfate (SDS) micellar system in aqueous solution. No emission from [Pt(terpy)(OH)] + is observed when the complex is dissolved in water or in very dilute SDS solution but a strong luminescence with emission maximum at 605 nm and excited-state lifetime of 0.1 μs is observed once the SDS concentration reaches the CMC. The emission wavelength of the hydrophobic platinum complex [Pt(mpterpy)(OH 2)] 2+ (mpterpy = 4′-( p-methoxyphenyl)-2,2′:6′,2′-terpyridine) is also a sensitive parameter for CMC determinatin. Unlike [Pt(terpy)(OH)] +, [Pt(mpterpy)(OH 2)] 2+ has an emission at 720 nm in SDS solution with concentration below CMC. When the concentration of SDS reaches the CMC, there is a sudden, large hypochromic shift of the emission maximum from 720 nm to 610 nm. The emission maximum of [Pt(mpterpy)(OH 2)] 2+ stays at 610 nm as the SDS concentration increases further beyond the critical micelle concentration.

Temperature dependence of fractionation of hydrogen isotopes in aqueous sodium chloride solutions

The D/H ratios of hydrogen gas in equilibrium with aqueous sodium chloride solutions of 2, 4 and 6 molalities were determined within the range 10 to 95°C, using a hydrophobic platinum catalyst. With each of the different sodium chloride concentrations, the hydrogen isotope effect between the solution and pure water changes linearly with the square of the reciprocal temperature. On the basis of the results for hydrogen isotope fractionation observed in this study, and those of hydrogen isotope fractionation between pure water and vapor, it is concluded that the structure of the aqueous sodium chloride solution does not change significantly with temperature. The hydrogen isotope effect is evidently different from the results of vapor pressure isotope effects (VPIE) on sodium chloride solutions measured on separated isotopes. The difference between the present work and the VPIE studies is probably due to a non-ideal behavior in a mixture of isotopic water molecules and/or to a H2O-D2O disproportionation reaction in sodium chloride solutions. The distinction between the latter two mechanisms can not be differentiated at present.

New observation on thin discontinuous metal films

It is shown from the capacitance-voltage curves of metal-insulator-semiconductor structures that molecular species in an electrolyte interact with thin discontinuous, hydrophobic platinum films in a way similar to that in a gas phase. It is suggested that this is due to the presence of air volumes in the cracks of the discontinuous metal. This suggestion is supported by theoretical models for the wetting of thin films. The observation may have implications for the use of thin metal layers as the sensing material in chemical sensors for molecular species in solutions.

SYNTHESIS AND CHARACTERIZATION OF A SERIES OF HYDROPHOBIC ANTITUMOR BIS(CARBOXYLATO) (1,2-DIAMINOCYCLOHEXANE) PLATINUM(II) COMPLEXES

Abstract A series of hydrophobic platinum(II) complexes of the type (DACH)PtX2 (where DACH = various isomeric forms of 1,2-diaminocyclohexane and X = pentanoato, hexanoato, heptanoato, octanoato, nonanoato, decanoato, unidecanoato, laurato, tridecanoato, myristato, pentadecanoato, palmitato, heptadecanoato, or stearato) has been synthesized and characterized using elemental analysis, infrared spectra and nuclear magnetic resonance (13C{1H} and 195Pt{1H}). The complexes have been prepared as potential antitumor agents for liposome entrapment.

Synthesis and Characterization of a Series of Hydrophobic Antitumor Amine Platinum(II) Carboxylates

Abstract As part of a systematic study, a series of hydrophobic amine platinum(II) carboxylate complexes has been prepared as potential antitumor agents in a liposomal-entrapped form. These complexes have been characterized by elemental analysis, 1R, 13C and 195Pt NMR spectroscopic techniques. Effect of ligand donors on NMR chemical shift is briefly discussed.

Fractionation of Hydrogen Isotopes in Aqueous Lithium Chloride Solutions

The D/H ratio of hydrogen gas in equilibrium with water vapor over aqueous lithium chloride solutions was measured at 25 °C, using a hydrophobic platinum catalyst. Experimental details are described. The hydrogen isotope effect between the solution and pure water depends linearly on the LiCl concentration up to ca. 12 m, and at higher concentrations a marked deviation from linearity takes place, as was also observed for the oxygen isotope effect measured by Bopp et al. On the basis of these hydrogen and oxygen isotope effects it is concluded that H2 18O is enriched in the water molecules coordinated to Li+ ions and HD16O is enriched in the free water molecules of the solution. The observed deviation from linearity for concentrations higher than ca. 12m is interpreted in terms of structural changes in the hydration sphere of the Li+ ions.

Effective Method for Recovering and Enriching Tritium from Tritiated Water by Dual-Temperature H2O-H2Exchange Process

The composite packing with the hydrophobic platinum catalyst for the isotope exchange reaction in H/sub 2/O-H/sub 2/ system was improved to be appreciably active. Therefore, it became realistic to design a process for tritium recovery by the dual-temperature exchange method. The separation performance of dual-temperature 5stage cascade (S3-E2) was simulated. The process was designed to be operated under the condition of P = 0.1 MPa, T /sub H/ = 70/sup 0/C, T /sub c/ = 15 about 20 /sup 0/C. The cascade could attain tritium recovery ratio of 0.99 and enriching ratio larger than 10/sup 3/.

Rapid determination of heavy water concentration by isotopic exchange reaction between liquid water and hydrogen using hydrophobic platinum catalyst

Rapid determination of heavy water concentration by isotopic exchange reaction between liquid water and hydrogen using hydrophobic platinum catalyst