A novel method for monitoring heavy metals in seawater is presented. The method is based on the electrochem. codeposition of metal hydroxides driven by the change of pH at the surface of a gold electrode. Altering the pH is achieved by applying a neg. potential or current that reduces the water and thereby increases the concn. of hydroxyl ions. This, in turn, causes metals to coppt. with Mg(OH)2. The continuous deposition enriches the ppt. with the metals (as compared with their concn. in the aq. phase) and allows their detn. by ICP-MS upon dissolving the deposit. A set of expts. in which seawater was spiked with 1-10 ppm of Cu, Cr, Co, Zn and Pb, was conducted. It was obsd. that metals were accumulated in the ppt. as a function of time and their concn. in seawater. The ppts. were analyzed by SEM, EDS and XPS indicating that the metal hydroxides formed a sep. phase from Mg(OH)2 and even water electroreducible metals, e.g., Cu2+, preferentially pptd. as hydroxides. Distribution consts. correlating the concns. of the metals in the deposited salts to their concns. in seawater were calcd. These calcns. imply that the mechanism governing the pptn. of the metal hydroxides by the electrochem. induced process is likely to be kinetically and mass-transport driven rather than thermodynamically controlled. [on SciFinder(R)]

Milk is one of the most fundamental ingredients in our diet. It is a complex biol. fluid, which contains numerous substances, ranging from metal ions to enzymes. There is a const. search for an improved way of monitoring its quality and freshness. These are highly affected by the redox state of milk, which is governed by different species. In this study, we investigated the redox state and capacity of milk. Specifically, milk was potentiometrically titrated using different redox mediators, which enabled facilitation of electron transfer between different oxidizable species and the electrode. We found that the iodine/iodide redox couple was superior for measuring the redox capacity of milk. These measurements revealed that milk is not a well-poised system due to the presence of at least two different oxidizable species, one of which is hydrophobic while the other is hydrophilic and therefore could be sepd. by phase sepn. of milk. [on SciFinder(R)]

The deposition and characterization of Langmuir-Blodgett (LB) layers of polyaniline (PAN) on solid supports is described. Langmuir films were spread as a mixt. of PAN and dodecylbenzenesulfonic acid (DBSA) at the water/air interface and deposited on either glass or indium tin oxide (ITO). Mono- and multi-layer films of PAN/DBSA were characterized by XPS, at. force microscopy (AFM), absorption spectroscopy and cyclic voltammetry (CV). The ultrathin films produced are highly uniform and very stable. Further characterization of the films was accomplished by scanning electrochem. microscopy (SECM) in the feedback mode. The cond. depended strongly on the pH of the soln. and the no. of layers deposited. Values for the pH-dependent lateral cond. of PAN LB films are reported. [on SciFinder(R)]

The deposition and characterisation of Langmuir-Blodgett (LB) layers of polyaniline (PAN) on solid supports is described. Langmuir films were spread as a mixture of PAN and dodecylbenzenesulfonic acid (DBSA) at the water/air interface and deposited on either glass or indium tin oxide (ITO). Mono- and multi-layer films of PAN/DBSA were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), absorption spectroscopy and cyclic voltammetry (CV). The ultrathin films produced were found to be highly uniform and very stable. Further characterisation of the films was accomplished by scanning electrochemical microscopy (SECM) in the feedback mode. It was found that the conductivity depended strongly on the pH of the solution and the number of layers deposited. Values for the pH-dependent lateral conductivity of PAN LB films are reported.[on SciFinder (R)]

Drug-eluting stents (DESs) have been associated with adverse clinical effects. Moreover, recent publications have shown that the coating of DESs suffers from defects. The purpose of this contribution is to examine a three-step process for surface modification as a means of improving the durability of DESs. In the first step, 4-(2-bromoethyl)benzenediazonium tetrafluoroborate was electrografted onto a stainless steel (SS) stent. X-ray photoelectron spectroscopy (XPS) of the modified stent confirmed the formation of the organic layer. In the second step, methyl methacrylate was polymerized onto the grafted surface by atom-transfer radical polymerization. XPS, electrochemical impedance spectroscopy, and contact-angle measurements were used to characterize the polymer brushes. The last step involved spray-coating of the stent with a drug-in-polymer matrix [poly(n-butyl methacrylate)/poly(ethylene-co-vinyl acetate) + paclitaxel]. Scanning electron microscopy confirmed the considerably improved durability of the drug-in-polymer matrix. Bare controls showed greater cracking and delamination of the coating than did the two-step modified stents after incubation under physiological (37 degrees C) and accelerated (60 degrees C) conditions. Finally, paclitaxel controlled release from the modified SS DESs was moderate compared with that of nontreated samples. In conclusion, the proposed method significantly improves the durability of drug-in-polymer matrixes on a SS DESs.[on SciFinder (R)]

Drug-eluting stents (DESs) have been assocd. with adverse clin. effects. Moreover, recent publications have shown that the coating of DESs suffers from defects. The purpose of this contribution is to examine a three-step process for surface modification as a means of improving the durability of DESs. In the first step, 4-(2-bromoethyl)benzenediazonium tetrafluoroborate was electrografted onto a stainless steel (SS) stent. XPS of the modified stent confirmed the formation of the org. layer. In the second step, Me methacrylate was polymd. onto the grafted surface by atom-transfer radical polymn. XPS, electrochem. impedance spectroscopy, and contact-angle measurements were used to characterize the polymer brushes. The last step involved spray-coating of the stent with a drug-in-polymer matrix [poly(Bu methacrylate)/poly(ethylene-co-vinyl acetate) + paclitaxel]. SEM confirmed the considerably improved durability of the drug-in-polymer matrix. Bare controls showed greater cracking and delamination of the coating than did the two-step modified stents after incubation under physiol. (37°) and accelerated (60°) conditions. Finally, paclitaxel controlled release from the modified SS DESs was moderate compared with that of nontreated samples. In conclusion, the proposed method significantly improves the durability of drug-in-polymer matrixes on a SS DESs. [on SciFinder(R)]

The inhibition of Mg (AZ91D) corrosion by thin sol-gel films was studied. The sol-gel films were prepd. by the traditional acid or base-catalyzed hydrolysis and condensation, and finally deposited by dip coating. Two different sol-gel monomers were used: phenyltrimethoxysilane (PTMOS) and Zr(IV) tetra-1-propoxide (ZrTPO). Films were made of each of the individual monomers and by depositing 1st a PTMOS film followed by ZrTPO-based film. The corrosion inhibition of the films and their characterization were examd. by different methods including potentiodynamic polarization, contact angle measurement, adhesion test, XPS, SEM and electrochem. impedance spectroscopy (EIS). While the ZrTPO-based film did not show a significant corrosion inhibition, the PTMOS-based film provided moderate protection. The combined film exhibited superior corrosion inhibition as compared with the other films. [on SciFinder(R)]

Local and bulk deposition of gold particles was accomplished by the spontaneous reaction between chem. reduced polyaniline (PAN) thin films and AuCl4-. PAN layers were deposited on glass, ITO, and glassy C (GC) by the Langmuir-Blodgett method and spin-coating. Characterization of the PAN films was carried out by microscopy, UV-vis spectroscopy, and electrochem. The nature of the Au deposit was greatly affected by the thickness of the PAN. Scanning electrochem. microscopy was used as a means of locally depositing Au nanoparticles on an unbiased PAN film by anodically dissolving a Au microelectrode. This represents a generic approach whereby a variety of metal micro- and nanoparticles can be locally deposited on insulating supports. [on SciFinder(R)]

This work describes attempts to develop a new type of modified electrode with high selectivity for uranyl ions, UO22+. The goal was addressed by binding derivs. of calix[6]arene, a macrocyclic mol. composed of 6 phenol units known as a super uranophile, to the electrode surface. Selective extn. of UO22+ onto the electrode surface, followed by a voltammetric measurement provides a quant. uranyl anal. The initial approach to binding calix[6]arene mols. onto electrodes involved an ionic deriv., 4-sulfonic-calix[6]arene, electrostatically attached to a pos.-charged, self-assembled monolayer of cysteamine (2-aminoethanethiol) on a Au electrode. Attachment of the 4-sulfonic-calix[6]arene to the cysteamine monolayer was verified by XPS, IR spectroscopy, and capacitance measurements. Voltammetric expts. showed UO22+ can be pre-concd. and measured using these modified electrodes. [on SciFinder(R)]

The invention provides a new method for the electrochem. co-deposition of sol-gel and one or more additives selected amongst a great variety of agents such as monomers, oligomers, polymers, metals and others. The method affords continuous films of high stability and precision. [on SciFinder(R)]

A single-step method for the prepn. of thin sol-gel/Cu mixed films is described, which is based on a novel electrochem. sol-gel methodol., resulting in nanocomposite coating. The method combines electrochem. with the acceleration of sol-gel hydrolysis and condensation processes. While sol-gel is deposited of increasing the pH in the vicinity of the electrode surface, Cu ions are electrochem. reduced. Characterization of the deposited films was accomplished by SEM, XPS, tunneling at. force microscopy, and other surface techniques. The different parameters that affect the structure and compn. of the deposited films were examd. The morphol. and grain size of the films are strongly affected by the ratio between the sol-gel monomer and Cu ions. Also, the potential of deposition affects also the compn. of the films as it controls the kinetics of sol-gel and Cu deposition. [on SciFinder(R)]

The application of 1,9-nonanedithiol (NDT) self-assembled monolayer (SAM) on gold for the electrochem. detn. of Cd2+ was studied. A NDT SAM strongly affects the stripping wave of Cd, resulting in a sharp peak that was used for electroanal. detn. of Cd2+ in aq. solns. The different parameters, such as potential and time of deposition of Cd, were examd. Also, polarization-modulated IR reflection absorption spectroscopy (PM IRRAS) and XPS were used for exploring the interaction between the deposited Cd and the thiol groups on Au. FTIR measurements clearly indicate that NDT is assembled in a disordered liq. type monolayer interacting with the Au electrode via both thiol moieties. XPS reveals that Cd is stripped at two different potentials and that the signal of sulfur is almost unchanged by deposition and desorption of Cd. All these finding allude to the interesting conclusion that Cd is deposited on Au lifting to some extent the thiol groups. [on SciFinder(R)]