Molecular precursor-mediated tuning of gold mesostructures: synthesis and SERRS studies

Abstract

This article describes the high yield synthesis of a range of anisotropic gold mesostructures such as flowers, cubes, plates, and quasispherical mesostructures using a seed-mediated approach. These structures were formed from precursor seed nanoparticles of gold stabilized by the template, 1,2-phenylenediamine (1,2-PDA). We demonstrated that control of the morphologies from mesoflowers to quasispherical structures is possible with the molecular precursors used in the synthesis of seeds. It was found that concentration of the template, 1,2-PDA added during seed preparation played an important role in the conversion of mesoflowers to quasispherical and cube-like structures. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis spectroscopy and energy dispersive analysis of X-rays (EDAX) were used for the determination of physical and chemical composition of the nano/mesostructures formed. The seed nanoparticles responsible for the formation of these various anisotropic structures were further characterized and analyzed using laser desorption ionization mass spectrometry (LDI MS) and TEM. We demonstrated high surface-enhanced resonance Raman scattering (SERRS) activity of the mesoflowers using crystal violet (CV) as the analyte molecule. The shape-dependent SERRS activity of various meso/nanostructures was also studied. A ~0.8×10² decrease in the SERRS intensity was observed in quasispherical structures compared to mesoflowers. The increased SERRS activity is attributed to the unique shape and nanofeatures present on the mesoflowers, which were absent in the quasispherical mesostructures. We believe that the high SERRS activity exhibited by the mesoflowers may be utilized for developing novel sensors.