Fabrication and characterization of a NiO-ZnO/PANI-CNTs composite for sensing of methanol in an aqueous environment.

In this study, we fabricated a composite of NiO-ZnO/PANI-CNTs on a fluorine tin oxide (FTO) electrode and examined the electrochemical sensing behavior of the modified electrode to detect methanol in aqueous solution. The structural, morphological, and electrochemical properties of the composite were characterized using various methods such as X-ray diffraction (XRD), EDS, FTIR, X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and electrochemical techniques such as cyclic voltammetry (CV) and chronoamperometry (CA). The composite-based electrode showed excellent electrocatalytic activity and selectivity for methanol oxidation. The calibration equation obtained was ΔI = 0.0003 × CMeOH + 0.02811, with a high correlation coefficient of 0.9993, over a wide detection range of 0 to 500 mM. The material exhibits great potential for the fabrication of sensors to detect methanol in commercial products. Real gasoline samples have been selected to evaluate the practical performance and feasibility of this as-prepared sensor. The experimental data indicated that the recovery of gasoline samples is about 98%, indicating this to be an appropriate detection procedure for effective electrochemical determination of MeOH in real gasoline samples.

Atmospheric concentrations of sulfur dioxide, nitrogen oxides, ammonia, hydrogen chloride, nitric acid, formic and acetic acids in the south of Vietnam measured by the passive sampling method.

A passive sampling method was applied to measure the concentrations of air pollutants, such as sulfur dioxide, nitrogen oxides, ammonia, hydrogen chloride, and nitric, formic and acetic acids, in the ambient air at four test sites in the southern region of Vietnam. The monthly averages and the average concentrations of air pollutants during the period from July 2001 to September 2002 are reported here. The concentrations of air pollutants varied widely, depending on the test sites and the sampling periods. The average concentrations of sulfur dioxide in the air during the period from July 2001 to September 2002 at the four test sites were 3.3-16.9 ppb, and those of nitrogen dioxide were 5.4-12.8 ppb. The concentrations of nitrogen monoxide and hydrogen chloride were very low at all of the test sites. The observed concentrations of all of the above-mentioned pollutants were lower than those of the Vietnamese standards of air pollutants.