Synthesis of large-scale transparent gold nanosheets sandwiched between stabilizers at a solid–liquid interface

Abstract

Micrometer-sized gold nanosheets (Au-NSs) were directly deposited on a large-scale at a solid–liquid interface using a modified solid matrix (SM) method. The reducing agent and the stabilizer were in the solid phase, and the oxidizing agent (HAuCl₄) with an acetate ion as an additional stabilizer was in the aqueous phase. The deposited Au-NSs had either a definite geometric shape or a highly branched 2D dendritic nanosheet-like (Au-DS) morphology. Au-NSs of definite shape were formed on the solid surface from solutions of pH 4 or less. The formation of Au-DSs were observed in solutions of higher pH (5 to 8.4) because of rapid reactions. The deposited Au-NSs were optically transparent and exhibited preferential growth along the {111} crystal facet. The acetate ion acted as a stabilizer and selectively adsorbed onto the Au{111} crystal facet limiting the growth of the Au-NSs in the {111} direction. Hence, the formed Au-NSs were sandwiched between stabilizers in the solid and liquid phases in the presence of acetate ions in the solution phase. However, in the absence of acetate ions, a rapid reaction generates highly branched 3D gold microcrystals with a dendritic morphology. Nano/microcrystals with a highly branched morphology were deposited on a large scale onto the SM without introducing any template or surfactant into the solution phase. A thiol-based epoxy resin immobilized with natural or synthetic tannin was used as the SM.