Complexation and adsorption of thiourea in sulphate medium on electrochemically roughened silver electrodes

Adsorption and oxidation pathways of thiourea at polycrystalline platinum electrodes

“…Usually, a parallel orientation on the surface is proposed in alkaline solutions, but in acidic medium either a tilt or vertical adsorption through the sulphur atom has been suggested [11][12][13][14][15]. On the other hand, TU solutions are able to reduce transition metal ions to form complexed species [7,[16][17][18][19][20]. Therefore, it is quite important to obtain information about the interaction between TU and metal surfaces for a better understanding of its additive function on metal electrodeposition and corrosion inhibition.…”

“…Several electrochemical methods as well as in situ and ex situ spectroscopic techniques have been employed to investigate the adsorption and oxidation reactions of TU on different metals [7,13,[18][19][20][21][22][23][24][25][26][27][28][29]. Voltamperometric studies have shown the formation of residual sulphur on the surface after TU molecule oxidation [20,21,30,31].…”

Spectroscopic Investigation of the Adsorption and Oxidation of Thiourea on Polycrystalline Au and Au(111) in Acidic Media

“…Specifically, TU is used to enhance the morphology of copper and silver electrodeposits, − refining the deposit grain size by adsorption on active nucleation sites . TU in solution is able to reduce transition metals, like copper, silver, and gold, with formation of complex species, ,− with the remarkable production of linear bidentate gold complexes when the metal acts with an oxidation state of +1 . The crystal and molecular structure of different TU−metal complexes has been determined by X-ray. , …”

“…In situ vibrational spectroscopies were also used to investigate these reactions. ,,,,− Surface-enhanced Raman spectroscopy has shown that TU adsorbs strongly on the metal surface via the sulfur atom in a wide potential range and desorbs at sufficiently negative potentials. ,,,− On the other hand, the combination of Fourier transform infrared spectroscopy (FTIRS) with electrochemical techniques enables the acquisition of molecular information concerning the direct interaction of the adsorbate at the metal/electrolyte interface. , Consequently, in situ FTIRS appears also to be a useful technique to study the interaction of organic plating additives.…”

Effect of Ion Complexation on Transport Selectivity in Gold-, and -Silver-Thiourea-Water/Nafion Membrane Systems

“…(33) As a result of the polar saucture of -s-Q=NH~NH~, thiourea usually coordinates to metal ions via the sulfur at0rn.W- 38) Gold and silver belong to the IB group and both Au(l) and Ag(1) have the electronic configuration of dlo. It is known that in aqueous solutions AuO is only stable in the presence of complexing ligands such as CN-and it generally exhibits a linear two-fold coordination.…”