A differential pulse adsorptive cathodic stripping voltammetric (DPAdCSV) method for the determination of lead levels in water sample by using pairs of ligands (complexing agents) / – nitrite and 1,10 phennanthroline - nitrite were investigated. Variables affecting the response such as pH, supporting electrolyte, deposition potential, deposition time, stirring speed, drop size, sweep rate, pulse amplitude and ligand concentration were studied. Under optimized conditions the relationship between peak current and lead concentration with 2,2ʹ-bipyridine - nitrite and 1,10 phennanthroline - nitrite were linear in the range of 10 - 500 ng mL-1 and 7–500 ng mL-1 with limit of detection of 0.48 ng mL-1 and 0.36 ng mL -1 respectively . The relative standard deviations (RSD) for 9 determinations of 25 ng mL−1 Pb (II) using 2,2ʹ-bipyridine - nitrite and 1,10 phennanthroline - nitrite were 1.74% and 1.84%, respectively. The values obtained for the proposed technique correlated well with those of atomic absorption spectrometry (AAS) as the standard method with correlation coefficient (R2 ) of 0.9991 and 0.9986. The method was applied for the determination of lead in sea, lake and tap waters. The interferences of other metals and major salts present were negligible except iron (III) and Aluminum (III)
The formation of nano pores on aluminum at 30oC- 38oC, employing a one step anodization technique which does not require removing the oxide layer formed is presented. A 20% phosphoric acid electrolyte (concentration higher than the normal anodization concentration of 5 to 10%) at a cell potential of 60 volts was used. A platinum electrode was used as the cathode electrode while the aluminum substrate as the anode electrode. A dc powered electrochemical cell to provide the required amount of current density (without the use of temperature controlled water bath) suitable or necessary for pore formation at room temperature was employed. The results obtained show that pore formation at room temperature is achievable and the pore diameter ranged between 80-120 nm.
The effect of microwaves on the functionalization of single-walled carbon nanotubes (SWNTs) by the diazonium method was studied. The usage of a new approach led to the identification of the strength of the interaction (physical or chemical) between the functional groups and the carbon nanotube surface. Moreover, the nature (chemical formula) of the adsorbed/grafted functional groups was determined. According to thermogravimetric analysis coupled with mass spectrometry and Raman spectroscopy, the optimal functionalization level was reached after 5 min of reaction. Prolonged reaction times can lead to undesired reactions such as defunctionalization, solvent addition and polymerization of the grafted functions. The strength (chemi- vs physisorption) of the bonds between the grafted functional groups and the SWNTs is discussed showing the occurrence of physical adsorption as a consequence of defunctionalization after 15 min of reaction under microwaves. Several chemical mechanisms of grafting could be identified, and it was possible to distinguish conditions leading to the desired chemical grafting from those leading to undesired reactions such as physisorption and polymerization.