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Local drug delivery based on conducting polymer carriers is an innovative approach of medical treatment joining the concept of regional release of biomolecules with ion-exchange properties of conjugated polymers. In this study, we have applied electrochemical quartz crystal microbalance (EQCM) to monitor the process of three-step immobilization and release of anti-cancer drug, disuccinyl derivative of betulin, in PEDOT matrix. Each step of this process has been carefully investigated, i.e. electrochemical polymerization of monomer in the absence of drug, removal of primary dopant during the process of matrix reduction and drug incorporation during the process of matrix oxidation. The release of drug from PEDOT matrix has been performed via three paths, i.e. spontaneous release with no application of external potential, active release under potentiostatic conditions and active release under potentiodynamic conditions. EDS elemental analysis, scanning electron microscopy, IR and Raman spectroscopies, have been used to analyze structural and surface properties of drug-loaded PEDOT matrices.

Poly(3,4-ethylenedioxypyrrole), PEDOP, is a versatile compound, which has attracted significant scientific interest in the recent years. The wide range of its actual and prospective applications underlines the need for a comprehensive study of this material and identification of factors, allowing the physicochemical properties of PEDOP and its derivatives to be tailored for specific purposes. In this paper, we present the results of our investigation of the physicochemical properties of PEDOP, involving electrochemical, spectroelectrochemical and microscopic analysis. The electrochemical synthesis of PEDOP was performed in solvents of varying polarity and protic/aprotic nature, i.e. H2O, CH3CN and CH2Cl2, by means of cyclic voltammetry. Raman spectroscopy was applied in order to investigate the chemical structure of PEDOP synthesised under varying conditions. ESR measurements allowed the observation of changes in spin concentration as a function of applied potential and analysis of the stability of formed radical anions. UV–vis spectroelectrochemistry was applied to determine the value of optical band gap of PEDOP. The surface morphology of fabricated PEDOP layers was investigated via scanning electron microscopy.

The selected group of four amine-derivatives of phenothiazine was covalently grafted to the glassy carbon surface in the four-step procedure consisting of the electrochemical reduction of the diazonium salt followed by the electrochemical and chemical post-modification steps. The proposed strategy involves the bonding of linker molecule to which the photosensitizer is attached. The synthesized organic layers were characterized by means of cyclic voltammetry, XPS and Raman Spectroscopy. It was shown that the phenothiazines immobilized via proposed strategy retain their photochemical properties and are able to generate 1 O 2 when activated by the laser radiation. The effectiveness of in situ singlet oxygen generation by those new solid photoactive materials was determined by means of UVVis spectroscopy. The reported, covalently modified solid surfaces may find their application as the singlet oxygen photogenerators in the fine chemicals’ synthesis or in the wastewater treatment.

Aligned carbon nanotube fibers are macroscopic materials with remarkable properties, such as high specific strength, stiffness, extreme flexibility as well as electrical and thermal conductivity. It is demonstrated that when subjected to negative potentials, these structures undergo the process of swelling in which the increase of their external dimension is observed. Swelling is believed to be caused by cation insertion in the process similar to intercalation. The efficiency of swelling was determined both in organic and aqueous solutions of different pH. Chronocoulometry was used as the technique to monitor the charging-discharging processes of swollen ACNT fibers in a presence of different electrolytes, i.e. LiCl, NaCl and KCl. The possibility of performing the charging-discharging cycles multiple times indicates that the swollen ACNT fibers can be considered as an advantageous material for electrodes in ion batteries and supercapacitors. Keywords: Aligned carbon nanotubes, Swelling, Intercalation, Charging, Discharging

Five selected amine-derivatives of phenothiazine were electropolymerized on an ITO/glass substrate and then used in the daylight-activated process to produce in situ singlet oxygen which degrades phenol in a solution. The phenothiazines were immobilized in a simple electrochemical procedure in an acidic solution which led to the formation of an ultrathin transparent polymeric film. All films obtained on the ITO substrate including azure A (AA), azure C (AC), methylene blue (MB), toluidine blue (TBO), and thionine (Th) had a comparable surface coverage at the level of picomoles/cm 2 . The activity of these materials was then compared and presented in terms of an efficiency of the phenol degradation process in an aqueous solution by photogenerated singlet oxygen. That efficiency was determined by the UV–vis spectroscopy employing a phenol/4-aminoantipyrine complex. All the phenothiazine ultrathin polymeric films were capable of generating the singlet oxygen in the aqueous solution under daylight activation, which was used in the consecutive process of phenol degradation. The highest efficiency at a level of 51.4% and 45.4% was found for the AC/ITO and MB/ITO layers, respectively.

Four amine-derivative phenothiazines were converted to the corresponding diazonium salt forms prior to their electrochemical grafting on the GC electrode with the aim to assess their ability to generate singlet oxygen. It was demonstrated by cyclic voltammetry and XPS spectroscopy that the molecular layers were effectively bound to the GC surface by applying the reductive potential in situ in the reaction diazo-mixture. The chosen procedure without the product separation step, appears to be especially useful due to the high solubility of the resulted phenothiazine diazonium salts. The effectiveness of singlet oxygen generation was measured for all of the grafted surfaces by UVVis spectra monitoring of the adjacent solution phase of 1,3-diphenylisobenzofuran (DPBF), which is well known trapping molecule used in detection of singlet oxygen. The data presented in the work prove that all of the molecular layers are effective singlet oxygen generators that might be used for various areas of applications where a highly oxidative reactant is required.

The purpose of this study is to develop biocompatible and conducting coating being carrier of biologically active compounds with the potential use in neuroprosthetics. Conducting polypyrrole matrix has been used to immobilize and release model drugs, quercetin and ciprofloxacin. Two routes of immobilization are described: drugs have been incorporated in the polymer matrix in the course of the electropolymerization process or after polymerization, in the course of polymer oxidation. Using UV/Vis spectroscopic detection we demonstrate that both immobilization approaches display different drug-loading efficiencies. In the case of ciprofloxacin, drug incorporation following synthesis is a more efficient immobilization approach (final drug concentration: 43.3 (± 9.5) μM/cm2), while for quercetin the highest loading is accomplished by drug incorporation during synthesis (final drug concentration: 29.1 (± 5.9) μM/cm2). The process of drug incorporation results in the variation of surface morphology with respect to the method of immobilization as well as the choice of drug. The results prove that electrochemical methods are efficient procedures for making multifunctional polymer matrices which might be perspective bioactive coatings for implantable neuroprosthetic devices.

Thionine (Th) was electrochemically grafted to the glassy carbon (GC) surface from its corresponding diazonium salt to investigate it as a singlet oxygen source under light excitation. As confirmed by cyclic voltammetry data the Th molecules may form a monolayer structure in the reduction process carried out directly from the diazotization reaction mixture without a time-consuming separation step. It was found that illuminated grafted Th at a level of monolayer coverage on GC surface is able to generate singlet oxygen at a constant rate. To determine efficiency of the photogeneration process a singlet oxygen selective trap, 1,3-diphenylisobenzofuran (DPBF), was employed, which was monitored using UVVis spectroscopy. The progress of the trap decay was determined in terms of its half-life. Keywords: Singlet oxygen, Phenothiazines, Photosensitizers, Photochemical generation, Electrografting

The process of conjugated polymer deposition on the surface of horizontally aligned multi-walled carbon nanotube, HA-CNT, electrode is described. Poly(3,4-ethylenedioxythiophene), PEDOT, was grown electrochemically under variable conditions in both aqueous and non-aqueous solutions of selected electrolytes. It is shown that the mechanism of nucleation highly depends on the reaction environment. The presence of a surfactant or non-aqueous medium favors the process of progressive nucleation in which the polymer growth is uniform and a homogeneous film of PEDOT is formed. It is demonstrated that the conditions make it is possible to cover the outer walls of individual HA-CNTs instead of forming thick polymer layer. The application of overpotential is proven to be a necessary condition to generate radical cations and cause relatively fast growth of polymer layer.

The effect of the functionalization of multi-walled carbon nanotubes (MWCNTs) on the process of electrochemical co-deposition of MWCNTs and polypyrrole (PPy), as well as the morphology of obtained composites have been demonstrated. As the nanotube components of the hybrids, three types of MWCNT were used, namely c-CVD derived (pristine) MWCNTs, their oxidized counterparts MWCNT-Ox and pyrrole-modified MWCNT-Py. The stability of pristine and functionalized MWCNTs (f-MWCNT) dispersions in tetrahydrofuran and water was studied together with the description of the process of formation PPy/(f-)MWCNT hybrid materials via electrochemical co-deposition. The structural and morphological properties of the hybrids were characterized by Raman spectroscopy, scanning electron microscopy and atomic force microscopy revealing substantial differences among hybrid materials in their surface morphology and the influence of MWCNT functionalization on the orientation of growing PPy chains.

The selected group of five amine-derivative phenothiazines was used to form their electropolymerized films in aqueous acidic solution with the aim to assess their ability to generate singlet oxygen. The films were characterized using cyclic voltammetry, UVVis spectroelectrochemistry, and Raman spectroscopy. The data of all the films were compared with properties of their monomer analogs. It was demonstrated that the electrochemically prepared films similarly to the known process of the corresponding monomers in solution phase are able to generate singlet oxygen in a photochemical surface process activated by laser radiation. These photogeneration process of the short-living species was monitored using the selected trap, which is detectable using UVVis spectroscopy. The effectiveness of the surface photogeneration reaction for each polymeric structure was determined in terms of half-life of the trap decay. The presented heterogeneous process of singlet oxygen photogeneration is believed to extend the area of applications of that highly oxidative reactant as compared to known homogeneous systems employing unbounded active species.

Conjugated polymers due to their reversible transition between the redox states are potentially able to immobilise and release ionic species. In this study, we have successfully developed a conducting polymer system based on poly(3,4-ethylenedioxythiophene) (PEDOT) for electrically triggered, local delivery of an ionic form of ibuprofen (IBU), a non-steroidal anti-inflammatory, and analgesic drug. It was shown that by changing the electropolymerisation conditions, the polymer matrix of specified IBU content can be synthesised. The electrochemical synthesis has been optimised to obtain the conducting matrix with the highest possible drug content. The process of electrically stimulated drug release has been extensively studied in terms of the dynamics of the controlled IBU release under varying conditions. The maximum concentration of the released IBU, 0.66 (±0.10) mM, was observed at the applied potential E = −0.5 V (vs. Ag/AgCl). It was demonstrated that the immobilisation-release procedure can be repeated several times making the PEDOT matrix promising materials for controlled drug release systems applied e.g. in neuroprosthetics.

The work describes the in situ Raman spectroelectrochemical studies on polyaniline (PANi) thin films covalently bound to the modified gold surface. The PANi thin films were synthesized via surface-initiated electrochemical polymerization on gold substrates initially modified by the formation of self-assembled monolayer of 4-aminothiophenol, or comparatively by the electrografting of 4-nitrobenzenediazonium salt followed by the electrochemical reduction of aromatic nitro-groups to form aniline-containing monolayer. Due to the defined surface-chain bonding and the ordered polymer structure, the obtained thin PANi films exhibit a narrow peak separation of the polymer redox transitions and negatively shifted potential of its full oxidation, as revealed by the PANi Raman spectra recorded at controlled potentials and cyclic voltammetry measurements.

The work describes the formation of poly(3,4-ethylenedioxythiophene) (PEDOT) brushes attached to thienyl-modified glassy carbon surface (GC) via surface-initiated electrochemical polymerization. The initial modification of the GC electrode was performed by using of three different thienyl-derivatives of aniline that were first converted to the form of diazonium salts. These salts were then electrochemically reduced creating the organic monolayer covalently bound to GC. The surface layer was investigated electrochemically and identified using XPS. The structural conjugation of the resulting monolayer made it possible to initiate the electrochemical polymerization of EDOT from the modified surface. The polymeric structure formed on the thienyl-modified surface reveals a better redox peak separation as compared to the classical polymer film on a bare electrode that can be assigned to its more ordered and uniform structure.

We report on electronic and spectroscopic properties of a new synthesized bicarbazole monomer and its electroactive polymer. In the monomer a branching of the carbazole conjugation occurs through N-linked, conjugated bridge between two carbazole units. That extended conjugation path adds rigidity to the large molecule, which leads in electropolymerization to the formation of ordered polymeric structure. That result is supported by an evident hypsochromic shift in both the absorption and fluorescence spectra measured for the monomer and its polymer. The effect of broadening of the band gap of the created polymer demonstrates a new route in designing of monomers that may lead to stable polymeric materials emitting blue light. The ex situ IR spectra of the polymer and the course of the electropolymerization monitored using in situ IR measurements confirm the assumed structure of the obtained polymer. Electrochemical, UVVis-, and EPR-spectroelectrochemical data have been provided to discuss the properties of the system and to support the proposed reaction mechanism.

Hybrid systems composed of the reduced-graphene-oxide supported gold, iridium or bimetallic (AuIr) nanoparticles (at loadings typically below 5 µg cm-2) have been considered as active matrices for platinum catalysts utilized at low loadings (-2) during the reduction of oxygen in mostly acid but also alkaline media. Comparison is made to the analogous systems based on conventional Vulcan carbon carriers. Gold nanoparticles are prepared both by the electrochemical and chemical reductionapproaches in which the pre-reduced Keggin-type phosphomolybdate heteropolyblue species act as the reducing agent for the HAuCl4 precursor. Polyoxmetallate (PMo12O40 3-) adsorbates or “capping ligands” tend to stabilize gold (iridium or bimetallic) nanoparticle deposits, facilitate their dispersion and attachment to carbon supports. Indeed, it is apparent from the independent diagnostic voltammetric experiments (in 0.5 mol dm-3 H2SO4) that heteropolymolybdates form readily stable adsorbates on nanostructures of gold, irridium and carbon (reduced graphene oxide and Vulcan). It is reasonable to expect that the polyoxometallate-assisted nucleation of gold has occurred in the proximity of oxygenated defects existing on carbon substrates. Under conditions of the electrochemical experiments performed in 0.1 mol dm-3 KOH) the phosphomolybdate adsorbates are removed from the interface because they undergo dissolution and decomposition in alkaline medium. High electrocatalytic activity of the reduced-graphene oxide-supported catalytic systems toward the reduction of oxygen is demonstrated using chronoamperometry and gas-diffusion electrode, in addition to the conventional and rotating ring-disk electrode (RDE) voltammetry. Among important issues is the presence of structural defects existing on poorly organized graphitic structure of reduced graphene oxide (as evident from Raman spectroscopy). When using the reduced graphene oxide carriers for Au (Ir or AuIr) nanostructures together with Pt nanoparticles, the resulting catalytic systems have exhibited typically higher (certainly not lower) O2-reduction currents (relative to those recorded at conventional Vulcan-supported Pt at the same loading) in acid medium (0.5 M H2SO4). The RDE data are consistent with the lower formation of the hydrogen peroxide intermediate (

Reduced graphene-oxide-supported the various metals analogue of polynuclear Prussian Blue are considered here together with traces of platinum as well as low loadings of platinum (10-15 mg cm-2) as catalytic materials for reduction of oxygen in acid media. Comparison is made to the analogous systems based on conventional Vulcan carbon carriers. Electrocatalysts based on graphene and graphene-oxide (GO) are more homogeneous and possess properties such as excellent conductivity, good chemical stability and can be functionalized in a controlled manner. Following the heat-treatment step at higher temperatures, some thermal decomposition of the cyanometallate network occurs and, consequently, metallic sites are generated. The resulting material has occurred to show highly potent electrocatalytic properties toward electroreductions of oxygen in acid solution (the highest currents and the most positive electroreduction potentials) using cyclic and rotating ring-disk electrode (RDE) voltammetric experiments. Among important issues are possible activating interactions between analogue of Prussian Blue, platinum nanoparticles and the support, as well as presence of structural defects existing on poorly organized graphitic structure of reduced graphene oxide (as evident from Raman spectroscopy). An electrocatalytic system, that utilizes metal hexacyanometallates nanoparticles with trace amount of Pt modified reduced graphene-oxide-supported is also characterized here by additional diagnostic experiments, namely galvanodynamic measurements with use of so called gas diffusion electrode (GDE) operating under conditions resembling those characteristic of the cathode in a real fuel cell.

The results of investigations of conductive polymers made of monomers built of five of six-membered systems (thiophene, furan or pyridine) and phenothiazine (Ph_Het) are reported. Electrochemical properties of the monomers used (Table 1 and 2, Fig. 1-3, 6, 7) and polymeric films, made of them via electro syntheses (Table 3, Fig. 4, 5, 8 - 11), were evaluated by cyclic voltammetry, UV-Vis spectroscopy and EPR spectroscopy coupled with electrochemical technique. The measurements showed the electro activity of materials. Two-stage oxidation of the monomers (first step - to cation-radical, the other one - to dication) took place in the measured potential range. Voltammetric scanning of the molecules containing heterocyclic thiophene or furan rings led to settling of conductive polymer layer on the surface of working electrode. The deposition of polymer film was not observed in the case of monomer with pyridine rings. Estimated values of (Eg) of conductive polymers layers formed were in the range 2.0 - 2.5 eV.

The group of 1,4-dialkoxy-2,5-bis[2-(thien-2-yl)ethenyl]benzene stereoisomers was synthesized in which methoxy- and ethoxy-groups were used as alkoxy-substituents. These isomers were characterized as solution species both electrochemically and spectroscopically. As expected, these compounds, having a stilben like structure, are the subject of photoisomerization, which is described and discussed. It is demonstrated how electrochemical process may cause isomerization of the double C C bonds in that group of compounds. An attempt of using electrochemical methods to monitor the process of photoisomerization of these compounds is presented. Mechanism of the oxidatively induced electrochemical isomerization has been proposed and discussed. The electrochemical isomerization mechanism is verified by digital simulation, which allowed estimating basic kinetic parameters of the processes.

Summary — Two compounds, 1,4-bis-(2(Z)-thienylenevinylene)-benzene (M1) and 1,4-bis-(2(Z)-thienylenevinylene)-2,5-dimethoxybenzene (M2) were synthesized and characterized using spectroscopic and electrochemical methods. Spectroscopic and photoluminescent properties of these compounds were found to be evidently dependent on their structure. Both M1 and M2 can be oxidized electrochemically producing forms of higher molecular weight. Intermediate products, which include stable oligomeric forms, were distinguished using spectroscopy during polymerization. In the final stage, oxidation of the oligomers at the electrode surface led to homogeneous, well adhering polymer films. The doping process of these polymers that also reflects their structure is discussed. Generally, polarons produced during oxidation do not undergo a process of recombination to bipolarons due to the block structure. Both polymers studied have photoluminescent properties. Effects of structure on the observed phenomena and parameters, like the wavelength position, the half width of the peak maximum are demonstrated and discussed.

Given the useful electroanalytical properties of carbon electrodes, having an optically transparent material could lead to new measurement paradigms that combine electrochemical and spectroscopic measurements.

Some important physical processes represented by the shape of voltammograms of polyaniline in the phase of oxidation are identified and modelled. The main process, i.e. an angular diffusion by which the motion of conducting polymer subunits take place is described and modelled. To fit a molecular picture of the oxidation process a nontrivial random walk of polymer subunits in configurational space of angles has been performed. A very good agreement between theoretical predictions and experimental data has been obtained.

Since the majority of anticancer pharmacological agents affect not only cancer tissue but also normal cells, chemotherapy is usually accompanied with severe side effects. Regional chemotherapy, as the alternative version of conventional treatment, leads to the enhancement of the therapeutic efficiency of anticancer drugs and, simultaneously, reduction of toxic effects to healthy tissues. This paper provides an insight into different approaches of local delivery of chemotherapeutics, such as the injection of anticancer agents directly into tumor tissue, the use of injectable in situ forming drug carriers or injectable platforms in a form of implants. The wide range of biomaterials used as reservoirs of anticancer drugs is described, i.e. poly(ethylene glycol) and its copolymers, polyurethanes, poly(lactic acid) and its copolymers, poly(ɛ-caprolactone), polyanhydrides, chitosan, cellulose, cyclodextrins, silk, conducting polymers, modified titanium surfaces, calcium phosphate based biomaterials, silicone and silica implants, as well as carbon nanotubes and graphene. To emphasize the applicability of regional chemotherapy in cancer treatment, the commercially available products approved by the relevant health agencies are presented.

As numerous therapeutic agents are not well tolerated when administrated systemically, localized and controlled delivery can help to decrease their toxicity by applying an optimized drug concentration at extended exposure time. Among different types of drug delivery systems, conjugated polymers are considered as promising materials due to their biocompatibility, electrical conductivity and ability to undergo controllable redox reactions. In this work poly(3,4-ethylenedioxypyrrole), PEDOP, matrix is described for the first time as a reservoir of a model drug, ibuprofen (IBU). Drug immobilization process is performed in situ, during the electrochemical polymerization of 10 mM EDOP in the presence of 5-50 mM IBU. The loading efficiency of polymer matrix is dependent on IBU concentration and reaches 25.0±1.3 μg/cm2. The analysis of PEDOP-IBU chemical structure based on Raman spectroscopy, energy dispersive spectroscopy and surface morphology data provided by scanning electron microscopy shows that IBU is accumulated in the structure of matrix and evidently influences its morphology. IBU is then released in a controlled way under the influence of applied potential (-0.7 V vs. Ag/AgCl). It is demonstrated that the judicious choice of the synthesis conditions leads to a tailored loading efficiency of PEDOP matrix and to a tunable drug release.

Four new compounds: 1,4-dimetoxy-2,5-bis[2-(tien-2-yl)ethenyl]benzene), 1,4-dietoxy-2,5-bis[2-(tien-2-yl)ethenyl]benzene), 1,4-isopropyloxy-2,5-bis[2-(tien-2-yl)ethenyl]benzene) and 1,4-dietoksy-2,5-bis[2-(5-methylthiophen-2-yl)ethenyl]benzene are synthesized. Three steroisomers ZZ, EZ and EE are isolated from the reaction mixture for the first two of them. Third compound is fully converted to the most stable EE form. Polymerization of all isomers leads to identical polymeric product. Mechanism of polymerization is recognized by using model molecule with methyl substituents blocking α-, α′-sites. All seven stereoisomers have photoluminescent properties. Detailed spectral and electrochemical studies reveal isomerization phenomena during oxidation or at light exposure.

An existence of a new, stable oligomer state of the solid film is reported, which is produced under electrochemical conditions. In this state, a formal charge exchanged in the redox process is about one-half of electron per oligomer molecule. The procedure, which allows controlling precisely the amount of oligomer on the electrode surface, is proposed that together with the coulometric evaluation of the electric charge provides the number of electrons involved in a redox process. This is demonstrated for a case of α-monochloro-substituted regioregular sexi (3-octylthiophene) oligomer (6OTCl). The electrochemical results are discussed together with UV–Vis–NIR spectroelectrochemical data obtained for both solution and solid phase that support the proposed interpretation.

In this work we report on the electrochemical and spectroelectrochemical characterization of the series of α-monochloro substituted regioregular 3-alkylthiophene consisting of 4–8 units of (3-octylthiophene) in solution. The shortest in the series tetramer molecules undergo a fast dimerization process, whereas longer oligomers are not subject to consecutive reactions when oxidized to form the radical cation. Each oxidation stage corresponds to one-electron process; single radical cation and dication are initially produced, which in turn are doubled within each oligomer molecule. Studies of these compounds in solution species were carried out in the thin layer cell on optically transparent electrodes. Clear tendencies are observed with increasing number of thiophene units for the peak potential of the redox reactions and positions of maximum absorbance. Formation of additional electronic bands within the band gap, shifted to the lower energies, has been also observed.

Results of corrosion resistance tests of Ti6Al4V ELI alloy after electropolishing and anodic oxidation in new baths were presented in the paper. As a result of the electropolishing and anodic oxidation significant growth of corrosion resistance was obtained. The alloy was also crevice corrosion-proof. Chemiluminescence investigation proved low chemical activity of the passive layer and AFM test showed that the layer is uniform. The main component of the passive layer of the specimens that has the highest corrosion resistance was titanium dioxide TiO 2 . In the layer, lower concentration of aluminum and vanadium was observed, which is beneficial for the implants. The aluminum and vanadium occurred in oxide form.

The spectroelectrochemical responsiveness of an optically transparent diamond electrode (OTE) toward ferrocene was investigated. A freestanding, mechanically polished, boron-doped diamond disk (0.38 mm thick and 8 mm in diameter) served as the OTE for UV-Vis transmission spectroelectrochemical measurements. A specially designed, thin-layer spectroelectrochemical cell was constructed for the measurements in which ferrocene was electrooxidized to ferricinium ion via a one-electron redox reaction. The oxidation reaction product was spectroscopically monitored in the ultraviolet ( λ =252, 285 nm) region of the electromagnetic spectrum. Well-defined and highly stable spectroelectrochemical responses were observed for this type of diamond OTE. The results indicate that diamond is a useful OTE material for spectroelectrochemically studying nonaqueous redox reactions.

No other material shows as much versatility as an electrode as does electrically conducting, chemical vapor deposited (CVD) diamond. The material can be used in electroanalysis to provide low detection limits for analytes with superb precision and stability; for high-current density electrolysis (1-10 A/cm2) in aggressive solution environments, without any microstructural or morphological degradation; as a corrosion-resistant electrocatalyst support; and as an optically transparent electrode (OTE) for spectroelectrochemical measurements.

Exemplifying the synergy of anticancer properties of triterpenoids and ion retention qualities of conjugated polymers, we propose a conducting matrix to be a reservoir of anticancer compounds. In this study, poly(3,4-ethylenedioxythiophene), PEDOT, based matrix for electrically triggered and local delivery of the ionic form of anticancer drug, oleanolic acid (HOL), has been investigated. An initial, one-step fabrication procedure has been proposed, providing layers exhibiting good drug release properties and biological activity. Investigation of obtained systems and implementation of modifications revealed another route of fabrication. This procedure was found to yield layers possessing a significantly greater storage capacity of OL(-), as evidenced by the 52% increase in the drug concentrations attainable through electro-assisted release. Examination of the biological activity of immobilised and released OL(-) molecules proved that electrochemical treatment has negligible impact on the anticancer properties of OL(-), particularly when employing the three-step procedure, in which the range of applied potentials is limited. PEDOT/OL(-) composite has been demonstrated to be a robust and cost-effective material for controlled drug delivery.

The electrochemical properties of solid phase α-monochloro substituted regioregular 3-alkylthiophene consisting of six units of 3-octylthiophene (6OT) were studied in nonaqueous electrolyte solutions using cyclic voltammetry and electrochemical atomic force microscopy (EC AFM). As confirmed by voltammetry, the 6OT molecules in an oxidized form of monocation radical are not subject to consecutive reactions, due to the presence of the α-substituent. In situ AFM images of the thin films of 6OT cast on metal substrates revealed reversible, drastic changes of the film morphology while applied potential was switched between values corresponding to the particular redox state. Dimerization of the oligomers and π-stacks formation is postulated to explain the observed morphology changes in the 6OT films.

Electrochemical atomic force microscopy (EC AFM) studies of copper stripping/deposition processes under potentiostatic control were carried out on boron doped diamond thin-film electrodes in solutions of different ability to form copper complexes. Careful analysis of the electrode surface profiles taken at the potentials switched between oxidative and reductive values reveals the nucleation state and the early stages of complex formation when cations are released from the deposited metal. An unusual increase of the deposit-layer thickness is observed in sulfate- and phosphate-solutions at the positive potentials in contrast to an expected decrease of the surface adlayer thickness accompanying its stripping. The last effect takes place in the case of copper stripping in the presence of nitrates when no complex is formed. Similar behavior is observed on the HOPG electrode used in these studies as a reference surface.

This note describes the results of a comparative study of the reductive desorption characteristics of alkanethiolate monolayers at single crystal Au(111) and Au(110) electrodes. The voltammetric data reveal that the reductive desorption potential is dependent on the surface crystallinity of the underlying gold substrate. The observed difference in potential between these two substrates is indicative of a difference in binding strength of the monolayer at different binding sites in which the gold-sulfur bonding is stronger at the Au(110) than at the Au(111) single crystal. Spectroscopic data (X-ray photoelectron and infrared reflection spectroscopies) provide additional comparisons for the monolayer structures at the two substrates. These findings substantiate our recent study on the voltammetric differences between the atomically smooth surfaces of annealed Au(111) films and the micro-topographically rougher as-evaporated Au(111) films.

Two novel crown ether compounds, N,N`-bis(2-hydroxy-5-nitrobenzyl)-4, 13-diazadibenzo-18-crown-6 (CCE) and N, N`-bis(7-hydroxy-4-methylcoumarin-8-methylene)-4, 13-diazadibenzo-18-crown-6 (FCE), have been synthesized as potential reagents for the selective extraction and determination of heavy metal ions. Characterizations of the acid-base reactivity and the heavy metal ion extraction capabilities are reported. Both CCE and FCE undergo four-step ionization processes with associated tautomeric transformations and form stable complexes with divalent metal cations that can be extracted into 1,2-dichloroethane. Extraction constants for Ba(II), Ca(II), Cd(II), Cu(II), Hg(II), Pb(II), and Sr(II) have been determined for both reagents. For CCE, the extraction order is Hg(II) > Pb(II) > Cu(II) > Cd(II) > Ca(II) > Sr(II) > Ba(II), whereas the order for FCE is Hg(II) > Cu(II) > Pb(II) > Cd(II) > Ca(II) > Sr(II) > Ba(II). The selectivity of CCE for Hg(II) over the next-best-extracted cation, Pb(II), is nearly 2 x 10{sup 7} and that of FCE for Hg(II) over next-best-extracted cation, Cu(II), is nearly 5 x 10{sup 6}. Potential applications to chemical analysis, based on the unprecedented selectivity of both reagents for Hg(II), are briefly examined. 54 refs., 7 figs., 3 tabs.

The radical cation of carbon-sulfur [7]helicene is configurationally stable in solution at room temperature. In contrast to the radical cations of alpha-oligothiophenes, which form diamagnetic pi-dimers at low temperature, the radical cation of this helical, cross-conjugated beta-oligothiophene shows a low propensity toward dimerization.

A new analytical spectroelectrochemical methodology is reported on that utilizes an optically transparent boron-doped diamond thin film. The film was deposited on undoped Si by microwave-assisted chemical vapor deposition using a 4-h growth with a 0.5% CH4/H2 source gas mixture and 2 ppm B2H6 added for boron doping. The thin-film electrode possessed a transparency of 40-60% in the mid- and far-IR regions of the electromagnetic spectrum. The physical, electrical, optical, and electrochemical properties of the electrode were characterized by scanning electron microscopy, Raman spectroscopy, X-ray diffraction, four-point probe electrical resistance measurements, IR spectroscopy, and cyclic voltammetry. The film's electrochemical behavior was evaluated using both aqueous (Fe(CN)(6)3-/4-, methyl viologen, Ru(NH3)(6)3+/2+, and IrCl(6)2-/3-) and nonaqueous (ferrocene) redox systems. The film exhibited a low and stable background current and a nearly reversible voltammetric response for all these redox systems. The diamond/Si optically transparent electrode (OTE) and a thin-layer transmission cell were used to record the spectroelectrochemical response for 10 mM Fe(CN)(6)3-/4- in 1 M KCl. Difference IR spectra (oxidized minus reduced), recorded at various applied potentials, showed that the CN vibrational mode at 2039 cm-1 for Fe(CN)(6)4- reversibly shifted to 2116 cm-1 upon oxidation to Fe(CN)(6)3-, as expected. Difference IR spectra (oxidized minus reduced) were also recorded for 20 mM ferrocene in 0.1 M TBABF4/CH3CN. A shift of the C-H bending mode of the cyclopentadienyl ring from 823 to 857 cm-1 occurred upon oxidation of ferrocene to ferricenium. The key finding from the work is that the diamond OTE provides sensitive, reproducible, and stable spectroelectrochemical responses for aqueous and nonaqueous redox systems in the mid- and far-IR.

The optical and electrochemical properties of transparent, boron-doped diamond thin film, deposited on quartz, are discussed. The films were deposited by microwave-assisted chemical vapor deposition, for 1-2 h, using a 0.5% CH4/H2 source gas mixture at 45 Torr and 600 W of power. A high rate of diamond nucleation was achieved by mechanically scratching the quartz. This pretreatment leads to the formation of a continuous film, in a short period of time, which consists of nanometer-sized grains of diamond. The thin-film electrode was characterized by cyclic voltammetry, atomic force microscopy, and UV-visible absorption spectrophotometry. The film's electrochemical response was evaluated using Ru(NH3)6(3+/2+) in 1 M KCl, Fe(CN)6(3-/4-) in 1 M KCl, and chlorpromazine (CPZ) in 10 mM HClO4. The film exhibited a low voltammetric background current and a stable and active voltammetric response for all three redox systems. The optical transparency of the polycrystalline film in the visible region was near 50% and fairly constant between 300 and 800 nm. The optical and electrical properties were extremely stable during 48-h exposure tests in various aqueous (HNO3, NaOH) solutions and nonaqueous (e.g., chlorinated) solvents. The properties were also extremely stable during anodic and cathodic potential cycling in harsh aqueous environments. This stability is in stark contrast to what was observed for an indium-doped tin oxide thin film coated on quartz. The spectroelectrochemical response (transmission mode) for CPZ was studied in detail, using a thin-layer spectroelectrochemical cell. Thin-layer voltammetry, potential step/ absorption measurements, and detection analytical figures of merit are presented. The results demonstrate that durable, stable, and optically transparent diamond thin films, with low electrical resistivity (approximately 0.026 omega x cm) laterally through the film, can be deposited on quartz.

This paper describes preliminary results in the design, construction, and characterization of cobalt (II) porphyrins derivatized with alkanethiol appendages. The use of the thiol appendages leads to the formation of a chemisorbed monolayer of the corresponding thiolate at gold electrodes. Our findings suggest that this approach may serve as a beginning for fabricating electrocatalytic monolayers with a preselected architecture through the manipulation of the number and location of the appendages. Voltammetric data indicate that monolayers from both I(Co) and II(Co) catalyze the two-electron reduction of O[sub 2] to H[sub 2]O[sub 2]. The monolayer from I(Co), however, has a lower electrocatalytic activity. Infrared, X-ray photoelectron, and visible spectroscopic data are presented that argue the difference in reactivity arises from a difference in interfacial architecture. The results from attempts to metalate monolayers from I(H[sub z]) and II(H[sub z]) support this interpretation. Findings are also reported that indicate the preparation of mixed monolayers (e.g., two-component monolayers from I(Co) and CH[sub 3](CH[sub z])[sub 3]SH) may prove valuable to this area of research. 20 refs., 3 figs.

A new type of optically transparent electrode is reported on--an electrically conductive diamond thin film. The electrode was free-standing (0.38 mm thick and 8 mm in diameter), mechanically polished to a 7-nm rms roughness over a 10-microm linear distance, boron-doped (0.05% B/C in the reactant gas mixture), and mounted in a thinlayer transmission cell. The electrode has a short-wavelength cutoff of approximately 225 nm, which is the indirect band gap of the material, and transmits light out to at least 1,000 nm. In theory, the electrode has an optical window from 225 nm well out into the far-infrared, except for the boron acceptor band and the intrinsic multiphonon absorptions. The electrode was used to electrooxidize ferrocyanide to ferricyanide, and the absorbance change associated with the formation of the oxidized product (lambdamax = 420 nm) was spectroscopically monitored. The electrode was also used to electroreduce methyl viologen (MV2+) to the cation radical (MV+*) and the neutral (MV0). The depletion of MV2+ (lambdamax = 257 nm) and formation of MV+* (lambdama = 398 and 605 nm) were spectroscopically monitored.

In the paper an assessment of the usefulness of a method for the formation of a hard carbon coating on the working surface of metal slitting saws has been presented. Metal slitting saws were used to cut off the tips of non-ferrous metals in printed-circuit boards. The results o the authors' own investigations concerning the assessment of life of metal slitting saws with modified geometry of the cutting edge and a hard carbon coating have been presented. Conclusions on the practicability of the RF PCVD method used have been formulated.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Spectroelectrochemical and electrochemical quartz crystal microbalance studies of solid phase α-monochloro substituted regioregular 3-octylthiophene oligomers consisting 6,7 or 8 thiophene rings have been reported. Depending on redox state, these oligothiophenes undergo reversible morphology changes as we described earlier, presumably due to π-stacks formation. This is now supported by UV-Vis spectroelectrochemistry of thin films on transparent Au electrodes. A clear existence of diffused isobestic point has been found between two maximum in addition to some spectral effects in near IR region. QCM measurements evidently reveal mass changes of the film resulting from charge compensation by electrolyte ions.

Electrochemical properties of regioregular oligomers of 3-octylthiophene deposited as a film covering gold or platinum electrode are presented. In situ measurements of conductivity were carried out during oxidation process. These measurements revealed that tetramer is subject of consecutive dimerization reactions whereas hexamer produces a stable cation-radical. AFM in situ observations demonstrate a life of the oligomer film driven by phase transitions due to conformational changes of molecules stimulated by applied potential.

Three stereoisomers (EE, EZ, and ZZ) of 1,4-diethoxy-2,5-bis[2-(thien-2-yl)ethenyl]benzene were synthesized and characterized. It is shown that the electrochemical and optical properties depend on the configuration of themolecules. It is also shown that both electrochemical polymerization and photoactivation of the EZ and ZZ isomers cause transformation of the molecules to the most stable EE configuration.