Fabrication of Thorny Au Nanostructures on Polyaniline Surfaces for Sensitive Surface-Enhanced Raman Spectroscopy

Here we demonstrate, for the first time, the fabrication of Au nanostnictures on polyaniline (PANI) membrane surfaces for surface enhanced Raman spectroscopy (SERS) applications, through a direct chemical reduction by PANI. Introduction of acids into the HAuCl4 solution leads to homogeneous Au structures on the PANI surfaces, which show only sub-ppm detection levels toward the target analyte, 4-mercaptobenzoic acid (4-MBA), because of limited surface area and lack of surface roughness. Thorny Au nanostructures can be obtained through controlled reaction conditions and the addition of a capping agent poly (vinyl pyrrolidone) (PVP) in the HAuCl4 solution and the temperature kept at 80 degrees C in an oven. Those thorny Au nanostructures, with higher surface areas and unique geometric feature, show a SEAS detection sensitivity of 1 x 10(-9) M (sub-ppb level) toward two different analyte molecules, 4-MBA and Rhodamine B, demonstrating their generality for SEAS applications. These highly sensitive SERS-active substrates offer novel robust structures for trace detection of chemical and biological analytes.