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The chlorite ion is an unavoidable by-product of the disinfection of drinking water by means of chlorine dioxide. The maximum concentration values of chlorite accepted in many countries' regulations range from 0.2 to 1.0 mg L(-1). A simple, inexpensive and quickly set up voltammetric procedure for the on-site determination of chlorite in drinking water networks is described. This procedure is suitable for the whole range of applications in drinking water plants. A useful cell for on-field analysis has been developed. Surface morphology and behaviour of carbon-based working electrodes have been investigated by voltammetry and atomic force microscopy (AFM). Actual samples of different types of water networks have been analysed for chlorite concentration.

Lead sulfide (PbS) thin films were grown on a single crystal Ag(111) substrate by Electrochemical Atomic Layer Epitaxy (ECALE) method, i.e., by alternated underpotential deposition (UPD) of lead and sulfur. The electrochemical analysis includes the investigation of the underpotential deposition processes of both Pb and S, and the characterization of deposits obtained with different deposition cycles to confirm the attainment of the right stoichiometric ratio between Pb and S. The morphological analysis has been performed by Atomic Force Microscopy (AFM) for deposits formed with 50 and 75 deposition cycles and at different times of exposition to the atmosphere. [ABSTRACT FROM AUTHOR]

Ternary compound semiconductors such as CdxZn1−xS (with 0.75>x>0.31) and CdxZn1−xSe (with 0.74>x>0.34) were grown on Ag (1 1 1) by the electrochemical atomic layer epitaxy (ECALE) method. The interest in ternary compounds arises from the possibility of varying the bandgap with composition. The elements forming the ternary cadmium and zinc sulfide were, at first, deposited in the sequence: S/Cd/S/Zn…, the order being one cycle of CdS and one cycle of ZnS. However, the quantitative analysis of the compound obtained revealed a very high percentage of Cd, roughly 75%. This means that the presence of cadmium somehow hinders Zn deposition. The most effective way to increase the amount of Zn is to deposit more cycles of ZnS. As an example, the compound with 50% of Cd and 50% of Zn is obtained by performing 3 deposition cycles of ZnS per deposition cycle of CdS. Therefore, the stoichiometry of the ternary sulfides depends on the ZnS/CdS deposition sequence. An analogous result was obtained for CdxZn1−xSe. The stoichiometry of the compounds obtained with different deposition sequences was determined by classical quantitative analysis after dissolving the deposits. The composition measurements were confirmed by ex situ X-ray photoelectron spectroscopy (XPS) in ultra-high vacuum. The right 1:1 ratio between cations and anions was found for all compounds examined, whatever the stoichiometry. A systematic electrochemical investigation was carried out with ZnS/CdS deposition sequences equal to 1, 2, 5. [Copyright &y& Elsevier]

Abstract: The attainment of ultrathin films of well ordered II–VI and III–V compound semiconductors is an active research area of the electrochemistry group at the University of Florence. The method employed is the electrochemical atomic layer epitaxy (ECALE) which is based on self limiting reactions such as underpotential deposition (UPD). Recently, the possibility of combining the electrodeposition at nanometer scale and the self assembly phenomena has been investigated. In particular, the ECALE method was used to deposit CdS on Ag(111) covered by a patterned hexadecanthiol (HDT) self assembled monolayer (SAM). In fact, the deposition of CdS only takes place on the uncovered silver substrate, whereas it is not possible on the thiols monolayers. The deposits have been characterized by electrochemical techniques and AFM measurements. [Copyright &y& Elsevier]