A seed-less method for synthesis of ultra-thin gold nanosheets by using a deep eutectic solvent and gum arabic and their electrocatalytic application

Abstract

Ultra-thin and large gold nanosheets were easily synthesized by using a deep eutectic solvent (DES) as a reducing and directing agent with gum arabic (GA) as a stabilizer and shape-controlling agent through a seed-less protocol at room temperature. The applied reducing and stabilizing agents are nontoxic, cheap and biodegradable. The low amount of DES enables a kinetically controlled growth of gold nanosheets. Also, the strong binding of GA onto the surface of gold has a critical role in the formation of gold nanosheets. Large-scale glittering ultra-thin gold nanosheets can be obtained in the presence of GA. Without GA, the obtained products were thick plates and quasi-microspheres with rough surfaces. The formation of gold nanosheets depended on a number of factors, such as initial reactant concentrations and reaction temperature. The obtained products in different conditions were characterized by different techniques including field emission scanning electron microscopy, atomic force microscopy, X-ray diffraction and UV-Vis spectroscopy. Synthesized gold nanosheets were used for modification of a carbon ionic liquid electrode (CILE). A high electrocatalytic effect of gold nanocomposite CILE was observed toward hydrazine oxidation. The high conductivity and sharp edges of the gold nanosheets are responsible for this electrocatalytic activity.