A new approach for designing a voltammetric selective electrode is presented. The approach is based on the formation of a disorganised inert self-assembled monolayer (SAM), in which an amphiphilic molecule is incorporated. The latter serves as the selectivity factor, which extracts the analyte. The purpose of these experiments is to study the parameters that affect the capability of a monolayer to host amphiphiles. As model systems we focused on the incorporation of simple amphiphilic molecules (quaternary alkyl ammonium salts), electroactive amphiphiles (dialkylviologens) and a macrocycle ligand (tetramethylcyclam) into octadecyl silane monolayers formed on indium tin oxide (ITO) and purposely made disorganised alkanethiols on gold. We find that basically, the incorporation of amphiphiles into a hydrophobic inert SAM resembles a reversed stationary phase in liquid chromatography and this configuration can be used for designing selective electrodes.[on SciFinder (R)]

Different approaches for increasing the sensitivity and selectivity of voltammetric probes for heavy metals were examd. These have involved adsorbed monolayers of host mols., functionalized self-assembled monolayers and thin polymeric films. Two systems are presented that focus on the selective anal. of Hg(II) and Fe(II). The electrode for Hg(II) is based on a macrocyclic ligand, i.e., Kryptofix-222, while that for Fe(II) relies on the selective complexation by ferroin ligands, such as 1,10-phenanthroline. The monomeric and polymeric approaches were examd. and compared for both systems. The principal aim of this manuscript is to highlight the ability of fine-tuning the selectivity characteristics of the solid-liq. interface as a result of considering and optimizing analyte-interface interactions. Basically, an interface comprising a monolayer, which is capable of forming a strong and selective complex with the analyte, is likely to exhibit sensitivity that is at least as good as a polymeric film. However, the stability and durability of the latter usually makes it a superior interface for repetitive anal. and will therefore be the preferred choice for flow anal. systems. [on SciFinder(R)]

A new approach for designing a voltammetric selective electrode is presented. The approach is based on the formation of a disorganized inert self-assembled monolayer (SAM), in which an amphiphilic mol. is incorporated. The latter serves as the selectivity factor, which exts. the analyte. The purpose of these expts. is to study the parameters that affect the capability of a monolayer to host amphiphiles. As model systems the authors focused on the incorporation of simple amphiphilic mols. (quaternary alkyl ammonium salts), electroactive amphiphiles (dialkylviologens) and a macrocycle ligand (tetramethylcyclam) into octadecyl silane monolayers formed on In Sn oxide (ITO) and purposely made disorganized alkanethiols on Au. Basically, the incorporation of amphiphiles into a hydrophobic inert SAM resembles a reversed stationary phase in liq. chromatog. and this configuration can be used for designing selective electrodes. [on SciFinder(R)]

A disposable heating unit for use for heating the contents of a container, includes a first region contg. a combination of at least two solid substances which undergo an exothermic chem. reaction which is not spontaneous at room temp. Adjacent to the first region is a second region contg. at least a first reagent. A storage cell is configured for releasing the liq. contg. a second reagent into the second region. The first and second reagents undergo a spontaneous exothermic chem. reaction when brought into contact, thereby initiating the exothermic chem. reaction of the solid substances. [on SciFinder(R)]

A review with refs. of self-heating beverage containers. [on SciFinder(R)]

The scanning electrochem. microscope was applied in the feedback mode to deposit Au microstructures on n-Si(111) and indium-tin oxide. This was accomplished by the anodic dissoln. of Au at the microelectrode followed by the subsequent redeposition of the Au on the substrate. The influence of pH, substrate potential, and deposition time on the cryst. nanometer structure of the micrometer Au deposits was studied. The effect of these parameters on deposition could be explained by the band structure of the silicon. Also, understanding the role played by the different parameters allows depositing predefined nanocryst. structures. [on SciFinder(R)]

A highly flexible, automatic sequential-injection stripping anal. (SISA) system was developed and applied for monitoring the levels of Hg in aq. solns. using a chem. modified electrode. The prepn. of the modified electrode comprises spin coating of an EtOH soln. of poly(4-vinylpyridine) and Kryptofix-222 onto a glassy C electrode (GCE) followed by crosslinking the polymer. The anal. is based on the anodic stripping voltammetry of Hg using differential pulse voltammetry. A sequence of 36 operations was needed to complete a full cycle of cleaning, calibration and anal. [on SciFinder(R)]

A monolayer of conducting polymer, polyaniline (PAN), was assembled on hydroxyl-terminated surfaces, such as quartz, glass, indium-tin oxide, and native oxide on Si. The approach for assembling two-dimensional monolayers of PAN is based on a chem. or electrochem. surface polymn. of electrostatically bound anilinium. The latter was bound to the neg. charged sulfonate group of mercaptoethanesulfonate that was previously coupled by an SN2 reaction to an iodopropyl self-assembled monolayer. The consecutive assembling steps were followed by XPS, UV-vis-NIR spectroscopy, variable angle spectroscopic ellipsometry, contact angle, and at. force microscopy measurements. The characteristic electronic properties of the PAN monolayers were studied by UV-vis-NIR spectroscopy and cyclic voltammetry. [on SciFinder(R)]

The prepn. and characterization of octadecylsilane, C18, monolayers on indium-tin oxide (ITO) were studied carefully. A reproducible procedure was developed for the formation of C18/ITO employing octadecyltrimethoxysilane (OTMS) as a monomer. The films were studied by electrochem., wettability, IR and at. force microscopy. All these measurements provide evidence for the formation of a disorganized, 'brush-type' monolayer with a max. surface fractional coverage of 0.90 ± 0.04. The surface coverage can be controlled through the silanization time. The applications and implications of such disorganized monolayers in electroanal. chem. are discussed. [on SciFinder(R)]

Different approaches for increasing the sensitivity, selectivity and stability of a voltammetric probe for mercury ions were probed. These involve the application of adsorbed monolayers of a host mol., i.e., 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane (Kryptofix-222) and thin polymeric films. The stability, reproducibility and durability of the sensors in the anal. of Hg2+ from different sources were examd. and compared. A monolayer of the macrocyclic ligand, which is capable of forming a strong and selective complex with the mercury, is superior to polymeric films in terms of sensitivity and ease of regeneration. However, the stability and durability of polymeric films, in which Kryptofix-222 is incorporated, will eventually dictate their use as preferred interfaces for repetitive analyses esp. in flow anal. systems. An application of a polymer-Kryptofix-222 modified electrode for monitoring mercury in a bioremediation pilot was examd. using an automatic sequential-injection stripping anal. (SISA) system. [on SciFinder(R)]

A review is given on scanning electrochem. microscopy (SECM) as a tool for surface modification. It is distinguished between the direct mode and the feedback mode of the SECM. In the direct mode, the substrate serves as the auxiliary electrode, while, in the feedback mode, the substrate is unibiased, and a mediator is used that shuttles between the ultramicroelectrode and the surface. The etching of semiconductors, the metal deposition and etching, the deposition of conducting polymers, and the patterning of org. and biomols. are treated for both the direct- and the feedback mode technique of the SECM. The achievable resoln. and the patterning rate are addressed. [on SciFinder(R)]