No abstract

Highly ordered pyrolytic graphite (HOPG) surfaces were modified by the adsorption of Pd molecular precursors from solution. Two palladium-containing molecular precursors were studied, a mononuclear one and a trinuclear one, to compare their affinities and distributions at substrate surfaces. To obtain Pd nanoparticles, these neutral molecular precursors were reduced under a hydrogen atmosphere. Thermogravimetric analysis was carried out to establish the behavior of these precursors at various temperatures. Understanding the thermal stability of these compounds is very important to establish the appropriate conditions to form metallic Pd. The modified surface has been characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy; also, the reductive process was monitored by XPS. Remarkable differences were observed between the mononuclear and trinuclear compounds in terms of dispersion, particle size, and homogeneity. The preference of the trinuclear compound was to deposit at HOPG defects, in contrast to that of the mononuclear one, which was agglomeration on all surfaces. After the application of this technique, not only Pd nanoparticles but also Pd nanowires were obtained.

The detection of ethanol concentration is very important for different applications such as food industry, medicine, beverage, traffic safety and other health related analysis in blood, urine, and saliva. Recently, Pd nanoparticles (PdNP) have been of interest because exhibit interesting properties such as electrocatalytic activity towards alcohols oxidation in alkaline media, more abundant, and lower costs compared to Pt. In this work, we synthesized palladium nanoparticles with an organic-thiol ligand by chemical reduction method using sodium borohydride as reducing agent. The organic thiol ligands avoid the agglomeration and controlled particle sizes. The electrochemical detection of ethanol in KOH solution with PdNP with the organic thiol ligand on glassy carbon electrodes was done by cyclic voltammetry (CV). The morphology of PdNP nanoparticles with the organic thiol group was studied using SEM, XPS and TEM. The TEM do not demonstrated agglomeration of the nanoparticles and showed a particles size distribution of 2-10 nanometers. XPS spectra confirmed the presence of metallic palladium and sulphur peaks in the nanoparticles. The electrochemical results proved that the palladium nanoparticles with organic-thiol ligand had an excellent electrocatalytic activity for ethanol oxidation in alkaline media. The palladium nanoparticles are a promising material for ethanol sensors.

No abstract