Synthesis of gold microstructures with surface nanoroughness using a deep eutectic solvent for catalytic and diagnostic applications.

We synthesized highly monodisperse gold microparticles (AuMPs) using a deep eutectic solvent (DES) which composed of choline chloride and malonic acid as both a reaction medium and structure-directing agent. These microparticles exhibit distinctive surface nanoroughness and highly defined diameters that can be precisely controlled over a range of a few micrometers under different reductive conditions. The internal and external structures of the particles are thoroughly investigated by electron microscopy, which is further analyzed in association with their optical properties. We also investigate the gold microparticle concentration-dependent catalytic property employing a reductive reaction of 4-nitrophenol to 4-aminopenol as a model system. Importantly, the gold microparticles are densely functionalized with DNA and reversibly assemble with DNA-gold nanoparticle conjugate probes for the colorimetric detection of target DNA sequences, demonstrating that these novel structures can be utilized as platforms that quickly regulate the optical properties of plasmonic nanoparticles for diagnostic applications.