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A new modified tetrapyridylporphyrin symmetrically coordinated to four [Ru(phen)₂Cl]⁺ groups has been synthesized and its structural and electrochemical properties have been investigated by means of ₁H and COSY NMR, UV-vis and luminescence spectroscopy, cyclic voltammetry and spectroelectrochemistry. The presence of the phenanthroline ligands has improved the stability of the molecular films generated on the surface of conventional solid electrodes in comparison with the analogous bipyridine derivative. The performance of the modified electrodes has been evaluated for the detection of dopamine, with excellent results.

A series of derivatives M₂P₂ (M₂ ≡ H₄, Co₂, Ni₂, Cu₂, Zn₂, Pd₂, Pt₂, Co/Ni, Ni/Cu, Ni/Zn) of the ligand meso,meso′-bis(octaethylporphyrinyl)butadiyne has been prepared and characterized by ¹H NMR, FT Raman and visible absorption spectroscopies as well as by cyclic and a.c. voltammetry in CH₂Cl₂ solution at 20 and −40 °C. The electronic spectra exhibit multiple Soret bands and the voltammetry reveals successive one-electron reductions indicating the accessibility of ‘mixed valence’ π-radical anions and π-dianions. Using in situ thin layer spectroelectrochemistry, the UV to near-IR spectra of [M₂P₂]¹⁻ and [M₂P₂]²⁻ (M as above) were recorded at ≤ −40 °C. Apart from the Co complexes (reduced at the metal ion), the bis(porphyrin) anions have spectra which include sharp, intense near-IR bands (ε = 50 000–200 000 M⁻¹cm⁻¹) at c. 4500 and 11 500 cm⁻¹([M₂P₂]¹⁻) and 9500 cm⁻¹([M₂P₂]²⁻). An empirically constructed semiquantitative frontier orbital model explains the observed electronic absorption bands. Inter-porphyrin conjugation, mediated by the butadiyne bridge, is responsible for the Soret band multiplicity. The near-IR bands of the anions are assigned to long-axis polarized π → π* transitions within the newly occupied upper manifold of the two-porphyrin eight-orbital framework. The small comproportionation constants found for the diporphyrin monoanions contradict the usual assumption that electronically coupled dimers should have a large voltammetric separation between the first and second redox steps.

Competing styles in statistical mechanics have been introduced to investigate physico-chemical systems displaying complex structures, when one faces difficulties to handle the standard formalism in the well-established Boltzmann–Gibbs statistics. After a brief description of the question, we consider the particular case of Renyi statistical approach, which is applied to the study of the "anomalous" (non-Fickian) diffusion that is involved in experiments of cyclic voltammetry in electro-physical chemistry. In these experiments, one is dealing with the fractal-like structure of the thin film morphology present in electrodes in microbatteries. Fractional-power laws are evidenced in the voltammetry measurements and in the analysis of the interphase width obtained using atomic force microscopy. The resulting fractional-powers are related to each other and to the statistical fractal dimension, and can be expressed in terms of the index on which Renyi's statistical approach depends. The important fact that this index, which is restricted to a given interval, provides a measure of the micro-roughness of the electrode surface, and is related to the dynamics involved, the nonequilibrium thermodynamic state of the system, and to the experimental protocol is clarified.

A new family of pyrrole substituted metallophthalocyanine complexes, namely cobalt(II), iron(II), manganese(III), nickel(II) and zinc(II) tetrakis-4-(pyrrol-1-yl)phenoxy phthalocyanines (noted as M(TPhPyrPc), where M is the metallic cation) have been synthesized and fully characterized. In particular, the UV-visible spectra of the iron and nickel complexes showed extensive aggregation even at low concentrations. The cyclic voltammetry of the cobalt, iron and manganese complexes showed three to four redox couples assigned to metal and ring based processes. Spectroelectrochemistry of the manganese derivative confirmed that the synthesized complex is Mn^III(TPhPyrPc^-2) and that the reduction of Mn^II(TPhPyrPc^-2) to be centred on the ring and rather than on the metal, forming the Mn^II(TPhPyrPc^-4) species. Also, the electrochemical polymerization of these newly synthesized pyrrole-substituted phthalocyanines has been demonstrated in the case of the cobalt complex and the electrocatalytic activity of the obtained film has been tested towards the oxidation of L-cysteine.

A method has been developed to obtain good quality Langmuir-Blodgett (LB) films of mixtures of lutetium bisphthalocyanine and carbon nanotubes. The π-A isotherms exhibit high monolayer stability and the compressed monolayers are easily transferred to solid substrates by Y-type deposition. The electronic absorption spectra of the composite LB films show the characteristic bands of both compounds; the bands appear broader and shifted to higher wavelengths than those observed in solutions or in disordered films prepared by the casting method. The films are sensitive to oxidant or reducing vapors, whose presence cause modifications in the electronic absorption spectra of the films. These fast and reversible changes can be the basis of optical sensors based on thin films of lutetium bisphthalocyanine and carbon nanotubes. LB film electrodes immersed in KCl and KClO₄ solutions show electroactivity associated to the oxidation and reduction of the phthalocyanine ring. Important changes in the UV-vis-NIR spectra registered in situ simultaneously to the application of the electrical potential have been observed. The electrochromism observed opens the possibility of using such thin films in electrochromic devices. Composite films show characteristic electrochemical responses when exposed to solutions of antioxidants, where a certain degree of electrocatalytic effect is observed. The enhanced degree of selectivity can be used in the development of voltammetric sensors.

Thymoquinone, a significant component in medicine and the spice industry due to its potent antioxidant properties, is the focus of this paper. The development of a titanium oxide-modified graphite paste electrode is presented for the detection of thymoquinone in black cumin. The electrochemical characteristics of the thymoquinone molecule were explored in a 0.1 M phosphate buffer solution of pH of 6. The modified graphite paste electrode exhibits excellent linearity across the concentration range of 0.1-200 $\mu$M with limit of detection is 0.02 $\mu$M. The developed electrode exhibits commendable repeatability, reproducibility and exceptional sensitivity towards thymoquinone. The separation of various concentrations of thymoquinone samples such as Mousumi, Priya Gold, Sunrise and DNV using Principal Component Analysis (PCA) with the Separability Index (SI) of 67.89 utilized to differentiate between different thymoquinone concentrations.

This study presents an intelligent voltammetric system consisting of a personal computer and a digital voltammeter with VXIbus architecture of system control board, voltammetric measurement board and electrode evaluation board. System is designed to provide superior, comprehensive, versatile and convenient storage, analysis and display of electrochemical and voltammetric waveforms. Voltammeter is capable of stand-alone operation or direct PC control through a Labview program and serial communication interface. Stand-alone offers several general voltammetric functions such as electrochemical treatment and evaluation of electrodes and experimental voltammetry. PC connection gives additional functions such as automatic scanning of oxidation potential, expanded storage and processing of experimental data, arbitrary voltammetric waveform parameters, etc. Standalone uses microcontroller and three-bus structure, with EEPROM storing waveform parameters, experimental data and machine code program downloaded from PC. Electrode evaluation board tests electrode quality by measuring electrode equivalent resistance and capacitance, requiring only one button to perform the entire procedure. Minimum potential unit is 1 mV, at which setting the voltage range is −2.05 to +2.05 V. At a minimum unit of 4.9 mV, the voltage range is −10 to +10V. Experimental results are presented using carbon fiber electrode to measure the dopamine concentration in PBS solution, showing minimum oxidation current can be measured to less than 10 pA, with a minimum detectable bulk concentration of less than 10 ppb. The combination of PC with stand-alone voltammeter offers high-speed, precision, automation, versatility and portability, while the VXIbus architecture allows easy expansion capability.

Nowadays tools based on Scanning Probe Methods (SPM) have become indispensable in a wide range of applications such as cell imaging and spectroscopy, profilometry, or surface patterning on a nanometric scale. Common to all SPM techniques is a typically slow working speed which is one of their main drawbacks. The SPM speed barrier can be improved by operating a number of probes in parallel mode. A key element when developing probe array devices is a convenient read-out system for measurements of the probe deflection. Such a read-out should be sufficiently sensitive, resistant to the working environment, and compatible with the operation of large number of probes working in parallel. In terms of fabrication, the geometrical uniformity i.e. the realisation of large numbers of identical probes, is a major concern but also the material choice compatible with high sensitivity, the detection scheme and the working environment is a challenging issue. Examples of promising applications using parallel SPM are dip-pen-nanolithography, data storage, and parallel imaging.