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.