Polyaniline coated gold-aryl nanoparticles: Electrochemical synthesis and efficiency in methylene blue dye removal

Abstract

Synthesis of gold-carbon σ-bond nanoparticles was achieved by the electrochemical reduction of aryldiazonium tetrachloroaurate(III) salt [HOOC-4-C6H4N≡N]AuCl4 in the presence of polyaniline (PANI) emeraldine salt. The in situ electrochemical synthesis of PANI coated Au−COOH NPs was efficient in KNO3 supporting electrolyte at different potential values using two electrodes cell. The deposition potential was determined from the cyclic voltammetry study of aryldiazonium gold(III) salt. The nanocomposites were characterized with thermal gravimetric analysis (TGA), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The multi-branched nanoparticles display the strongest diffraction peak in the direction of (111) which implies the deposition occurred preferentially along this highly energetic facet. The results concluded the thermal stability of the gold nanocomposites and the gold percentage in the range 5−23 wt.%. Selected area electron diffraction pattern (SAED) analysis displayed typical rings of face centered cubic structure of crystalline gold(0) nanoparticles. Raman analysis supported the completeness of the reduction of the aryldiazonium cation and gold(III) supported by the absence of the diazonium and [AuCl4]− vibrations and the presence of the gold-carbon peak. Emeraldine coated gold-carbon nanoparticles soaked to nanosand showed high removal percentage for methylene blue. The adsorption kinetics follows a pseudo-second order. It may indicate that the prepared materials could be used to remove synthetic dyes in textile wastewater treatment.