A space-tunable gold nanoparticle arrays and investigation on their SERS performance

Abstract

Studies on two dimensional gold nanoparticle (2D Au NPs ) arrays evidence that intense electricmagnetic fields (‘hot spots’) generated within the gaps between adjacent Au NPs could promote the Surface-Enhanced Raman scattering (SERS) performance a lot. To achive these ‘hot spots’, tightly arrayed metallic nanostructures are required, however, fabricaton of these arrays with a facile method still poses as a challenge. In this work, a new strategy of preparing novel Au NPs arrays with UV-light tunable space between adjacent Au NPs was proposed. Photosensitive films of polyionic films containing poly[1-[4-(3-carboxy-4-hydroxyphenylazo)benzenesulfonamido]-1,2-ethanediyl,sodium salt] (PAZO)/poly(diallyldimethyl ammonium chloride) (PDDA) on Si substrate were first prepared by implementing a Layer-by-Layer adsorption technique. Then, large-area and uniform arrays of Au NPs were tranferred onto the PAZO/PDDA films by the Langmuir-Blodgett method. SERS performance of the prepared substrate was evaluated by using 4-mercaptobenzoic acid (4-MBA) as the Raman reporter under a 785-nm laser excitation. The experimental results indicate that Raman signal can be significantly improved as the time of UV irradiating on the substrate increases. More specifically, the signal intensity at the peak of 1078 cm−1 is 1.6 times higher than that of the initial value. In consideration of the mechanism of the above observation, it is ascribed to the UV-light induced inter space shrinking between Au NPs and providing enhanced ‘hot spots’.