Unique gold sponges: biopolymer-assisted hydrothermal synthesis and potential applicationas surface-enhanced Raman scattering substrates

Abstract

In this paper we describe a biopolymer-assisted hydrothermal approach to the synthesis ofgold sponges. This is carried out by transferring a hyaluronic acid potassiumsalt/HAuCl4 aqueous solution into a stainless steel autoclave with a Teflon liner and heating in an oven at180 °C for 6 h. Here, hyaluronic acid potassium salt plays three roles in the synthesis,namely, stabilization, reduction, and as a soft template. Field emission scanningelectron microscopy images, energy-dispersive x-ray spectroscopy, and x-raydiffraction reveal that the materials obtained consist of an interconnectedframework of face-centred cubic metallic gold filaments, which is approximately0.6 µm in width and composed of fused micrometre-sized particles that enclose pores1–4 µm in size. The test of surface-enhanced Raman scattering (SERS) from 4-mercaptobenzoicacid shows that the prepared gold sponges are an active SERS substrate. This is largelybecause they had an increased number of particle junctions, which are SERS active sites.This route can also be extended to the fabrication of silver sponges, which arecomposed of fused crystallites with diameters of 200–400 nm that enclosed pores0.4–2 µm in size. The test of SERS from Rhodamine 6G also reveals that the prepared silver spongesare likewise an excellent SERS substrate.