The homogeneous reduction of diazonium salts by hypophosphorous acid, provides an easy methodology for the derivatisation of carbon powder. The resulting derivatised carbon was characterised electrochemically showing the behaviour expected of a surface bound species. This procedure provides an easy, inexpensive methodology for functionalising carbon which might find applications in ion-exchange resins or combinatorial chemistry.

The derivatisation of carbon powder by physical adsorption of N,N'-diphenyl-p-phenylenediamine (DPPD) onto the surface of graphite particles (1-2 microm diameter) results in usefully functionalised carbon. The derivatised carbon powders have been studied using cyclic voltammetry by (i) abrasive immobilisation of the powder onto a basal plane pyrolytic graphite electrode (bppg) and (ii) by the manufacture of carbon-epoxy electrodes containing the derivatised carbon. The electrochemical response of the DPPD modified carbon has been examined in the presence of sulfide and possible reactions identified for the behaviour of each electrode substrate. The analytical application of the carbon-epoxy electrode for the sensing of sulfide is reported.

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a b s t r a c tA new protocol toward the synthesis of cobalt nitroprusside (CoNP) coordination nanoparticles has been described based on drop-by-drop (DbD) method without using any additives. It was also prepared by sonication as well as bulk mixing methods for comparison purpose. The prepared complex was characterized by Infrared spectroscopy (FTIR), XRD and cyclicvoltammetry (CV) techniques. The CoNP complexes prepared by different synthetic approaches were used as modifier molecules to fabricate carbon paste electrodes (CPE's) toward electrochemical oxidation of sulfite. The experimental results revealed that the cobalt nitroprusside nanoparticles (n-CoNP) prepared by drop-by-drop method showed a considerable enhancement in the electrocatalytic activity when compared to its counterparts prepared by other approaches. Electrochemical behavior of the n-CoNP CPE was studied and used as an electrochemical sensor for the quantification of sulfite at trace level. It showed a linear response over the concentration range 1-5.9 × 10 −5 M and 2-8 × 10 −3 M of sulfite. The limit of detection and limit of quantification were found to be 0.4 × 10 −5 M and 2.29 × 10 −5 M respectively. The interference of various organic acids and inorganic ions commonly present in different food and water sample matrices were studied. The n-CoNP modified electrode was used for the quantification of sulfite in different food samples and the results were in good agreement with those obtained by the standard iodometric protocol.

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Peroxynitrite is a potent oxidizing and nitrating agent which has detrimental effects on cells by altering the structure and function of biomolecules present within. A fluorescent probe rhodamine B phenyl hydrazide (RBPH) has been proposed for peroxynitrite (ONOO(-)) imaging in MCF-7 cells based on its oxidation property, which converts RBPH to pink colored and highly fluorescent rhodamine B. The fluorescence emission intensity of the rhodamine B produced in the above process is linearly related to the concentration of peroxynitrite. The method obeys Beer's law in the concentration range 2-20 nM and the detection limit has been found to be 1.4 nM. The possible reaction mechanism of peroxynitrite with RBPH to produce rhodamine B has been discussed with spectroscopic evidence. The Probe is selective to the peroxynitrite in the pH range 6-8 which is near physiological pH. Fluorescence microscopic studies suggest that the probe is cell permeable and hence peroxynitrite was imaged in MCF-7 cells.

A new type of covalent bulk modified glassy carbon composite electrode has been fabricated and utilized in the simultaneous determination of lead and cadmium ions in aqueous medium. The covalent bulk modification was achieved by the chemical reduction of 2-hydroxybenzoic acid diazonium tetrafluroborate in the presence of hypophosphorous acid as a chemical reducing agent. The covalent attachment of the modifier molecule was examined by studying Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and the surface morphology was examined by scanning electron microscopy images. The electrochemistry of modified glassy carbon spheres was studied by its cyclic voltammetry to decipher the complexing ability of the modifier molecules towards Pb 2+ and Cd 2+ ions. The developed sensor showed a linear response in the concentration range 1-10 μM with a detection limit of 0.18 and 0.20 μM for lead and cadmium, respectively. The applicability of the proposed sensor has been checked by measuring the lead and cadmium levels quantitatively from sewage water and battery effluent samples.

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