Leonid M. Goldenberg

Chemosensor devices: voltammetric molecular recognition at solid interfaces

This article reviews progress in modifying electrode surfaces with functional organic molecules which act as signalling units upon molecular recognition of a guest molecule or ion. This process triggers a change in the physicochemical properties of the host assembly which can be monitored by an electrochemical response. Topics covered include: molecular recognition in conjugated polymers; molecular recognition in monolayers formed by Langmuir-Blodgett and self assembly techniques; incorporation of recognition sites (‘molecular gates’) in otherwise passivating monolayers; ion channel sensors. Representative redox moieties include: polythiophene and polypyrrole derivatives, paraquat, ferrocene, tetrathiafulvalene, metalloporphyrins, C 60 , Ru(NH 3 ) 6 3+ and Fe(bpy) 2 (CN) 2 0 . Issues relevant to the development of practical, commercially-viable sensors are considered.

A Comparative Study of the Electrochemical Properties of Dip‐Coated, Spun, and Langmuir‐Blodgett Films of Polyaniline

Polyaniline (PAn) via solution processing has been formed into thin films using dip coating, spin coating, and the Langmuir-Blodgett (LB) technique on ITO electrodes to facilitate both cyclic voltammetry and spectroelectrochemical analysis. We find that the LB technique yields films which display the most defined voltammetric properties, although in all cases electroactivity is observed. Effects due to the residual solvent contained in the films are seen

Anodic synthesis of poly(p-phenylene)

Abstract This paper describes studies carried out on poly( p -phenylene) obtained by anodic polymerization of benzene and other aromatic compounds. It coatains over 100 refereces concerning electrochemical polymerization, polymerization mechanism, physical, spectroscopic and electrochemical properties, film morphology and applications. The aim of this report is to provide an exhaustive survey of this subject and to try and extract new research trends in this field.

Electrochemical properties of Langmuir—Blodgett films

Abstract Electrochemical properties of thin films of electroactive materials formed on the electrode surface by the Langmuir—Blodgett (LB) technique are reviewed. The focus is on charge transfer materials which form electroconductive films (tetrathiafulvalene, tetracyanoquinodimethane, fullerenes, phthalocyanines, conjugated polymers etc.) and other LB redox materials such as porphyrins, ferrocenes, metal bipyridine complexes and viologens. Structure—property relationships in experimental voltammetry of LB films and their agreement with theoretical models are examined. Specially organized structures, formed by the LB technique, of different materials for the study of the mechanism of electron transfer and for possible application in molecular electronics are considered as well. Potential applications of the electroactive LB films in electrocatalysis, electrochromic displays, information storage devices and molecular electronic devices are envisaged.

Single Step Optical Fabrication of a DFB Laser Device in Fluorescent Azobenzene‐Containing Materials

Distributed feedback (DFB) lasers are produced directly in fluorescent azobenzene-containing materials using a single holographic optical step. Surface relief grating capable of producing images in fluorescence microscopy can be holographically formed in a number of materials.

New materials with detachable azobenzene: effective, colourless and extremely stable surface relief gratings

New detachable azobenzene-containing materials produced via solid state reaction of urea formation were used for the inscription of effective, colourless and stable surface relief gratings.

Synthesis and electrochemistry of new tetrathiafulvalene (TTF) dendrimers : X-ray crystal structure of a tetrafunctionalised TTF core unit

A new synthetic approach to tetrathiafulvalene (TTF) dendrimers is reported. Tetrakis(4-chloromethylbenzylthio)tetrathiafulvalene7 is a functionalised core unit which reacts with four equivalents of the thiolate ion generated from compound 16 to afford the trisdeca-TTF derivative 3. Compound 3 is a shelf-stable solid which has been characterised by elemental analysis, MALDI-TOF mass spectrometry, 1 H NMR spectroscopy and solution electrochemistry. Thin layer cyclic voltammetry studies on pentakis-TTF and trisdeca-TTF derivatives 11 and 3 in dichloromethane solution in the presence of 2,3-dichloronaphthoquinone as an internal reference, show that all the TTF units undergo two single-electron oxidations. The single crystal X-ray structure of compound 7 is reported: the molecules have crystallographic C i symmetry and form chair-like stacks parallel to the crystallographic y axis.

Aryl ester dendrimers incorporating tetrathiafulvalene units: convergent synthesis, electrochemistry and charge-transfer properties

The convergent synthesis of a range of aryl ester dendrimers with peripheral tetrathiafulvalene (TTF) units is reported.4-(Hydroxymethyl)-TTF and 4,5-(2-hydroxymethylpropane-1,3-diyldithio)-TTF have been used as the starting TTF reagents. The core reagents are benzene-1,3,5-tricarbonyl trichloride, terephthaloyl chloride, biphenyl-4-4′-dicarbonyl chloride and 4,4′-oxybis(benzenecarbonyl chloride). Dendrimers comprising up to 12 TTF units have been characterised by elemental analysis, plasma desorption mass spectrometry,1H NMR spectroscopy and solution electrochemistry. Cyclic voltammetry (CV) and ultra microelectrode CV studies show that the TTF dendrimers display nearly ideal redox behaviour for the TTF system with no significant interaction between the TTF units. Thin layer cyclic voltammetric studies show that all the TTF units of these systems undergo two, single-electron oxidations. The dendrimers form charge-transfer complexes upon reaction with iodine in solution. Intermolecular interactions of the TTF radical cations are observed in the UV–VIS spectra of some of the oxidised derivatives.

Synthesis and intramolecular charge-transfer properties of new tetrathiafulvalene–σ-tetracyanoanthraquinodimethane diad (TTF–σ-TCNAQ) and triad (TTF–σ-TCNAQ–σ-TTF) molecules

We report the use of functionalised electron acceptor tetracyanoanthraquinodimethane (TCNAQ) units in the synthesis of novel diad D–σ-A compounds 6 and 7 [D=tetrathiafulvalenyl (TTF) and ferrocenyl] and the triad TTF–σ-TCNAQ–σ-TTF assembly 8. Compounds 6–8 display a very weak, broad, low-energy intramolecular charge-transfer band in the UV–VIS spectra. Nanosecond laser flash photolysis of compound 6 did not lead to any new transient absorptions in the 300–800 nm region, suggesting that if a charge-separated species is formed upon excitation, then back electron transfer occurs very rapidly to regenerate the ground state. Cyclic voltammetry of compounds 6–8 shows that reversible oxidation processes occur for the TTF and ferrocene moieties, and a reversible two-electron reduction occurs for the TCNAQ moiety. Spectroelectrochemical studies on compound 6 have enabled the redox processes to be assigned to the sequential formation of the TTF radical cation and dication upon oxidation, and the TCNAQ dianion upon reduction. Simultaneous electrochemistry and EPR (SEEPR) experiments provide further evidence for intramolecular interaction between the TTF and TCNAQ moieties in compound 6. Quantum mechanical calculations on compound 6, performed by the AM1 method, predict that in its minimum energy conformation the TTF and TCNAQ moieties are approximately orthogonal to one another, with the TCNAQ unit folded into a butterfly conformation.

Reversible structuring of photosensitive polymer films by surface plasmon near field radiation

We report on the fabrication and characterisation of a novel type of hybrid azo-modified photosensitive polymer film with a nanoscale metallic structuring integrated into the substrate. The metal structures permit to generate surface plasmon near fields when irradiated by UV-light from the rear without directly illuminating the polymer. This allows establishment of a localized, complex-shape intensity distribution at sub-wavelength resolution with a corresponding impact on the photosensitive polymer. The possibilities of exploiting this setup are manifold. We find that just by using the change of polarization of the incident light as means of control, the topography can be driven to change between various patterns reversibly. These results are confirmed by numerical simulations and compared with in situ recorded topography changes.