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Abstract: This paper describes the electrocatalytic activity of layer-by-layer self-assembled copper tetrasulfonated phthalocyanine (CuPcTS) on carbon nanotube (CNT)-modified glassy carbon (GC) electrode. CuPcTS is immobilized on the negatively charged CNT surface by alternatively assembling a cationic poly(diallyldimethylammonium chloride) (PDDA) layer and a CuPcTS layer. UV–vis absorption spectra and electrochemical measurements suggested the successive linear depositions of the bilayers of CuPcTs and PDDA on CNT. The surface morphology was observed using scanning electron microscopy. The viability of this CuPcTS/PDDA/CNT modified GC electrode as a redox mediator for the anodic oxidation and sensitive amperometric determination of 2-mercaptoethanol (2-ME) in alkaline conditions is described. The effect of number of bilayers of CuPcTS/PDDA and pH on electrochemical oxidation of 2-ME was studied. The proposed electrochemical sensor displayed excellent characteristics towards the determination of 2-ME in 0.1M NaOH; such as low overpotentials (−0.15V vs Ag/AgCl), linear concentration range of 3×10−5 M to 6×10−3 M, and with a detection limit of 2.5×10−5 M using simple amperometry. [Copyright &y& Elsevier]

Abstract: Ricin is a scheduled chemical warfare agent and biological warfare agent. Attempts were made for the detection of ricin in water samples by utilizing amperometric immunosensors. These electrodes were made by mixing Paraffin oil with graphite powder and multiwalled carbon nanotubes. The graphite paste electrode (CPE) and multiwalled carbon nanotubes paste electrode (MWCNTPE) were tested for their ability to detect 1-naphthol. A sandwich enzyme linked immunosorbent assay system was used to detect ricin. The detection limit for both electrodes was compared. It was found that the response of amperometric sensor is proportional to the ricin concentration in both the cases and is linear in the range 0.625–25ng/ml for MWCNTPE and 2.5–25ng/ml for CPE. The SEM showed that the MWCNTPE has revealed crevices/voids in which the antibodies may get trapped. Spectroscopic experiments proved that MWCNTPE adsorbs antibodies better than CPE. The high sensitivity of MWCNTPE was attributed to its better electrochemical properties rather than to its efficiency to adsorb antibodies. [Copyright &y& Elsevier]