Au nanoparticle embedded Poly(methyl-methacrylate) and Poly(styrene) free-standing films for wettability and surface enhanced Raman scattering applications

Abstract

In the present work, free-standing films of Au nanoparticle embedded in Poly(methyl-methacrylate-PMMA) and Poly(styrene – PS) are prepared using biomimetic templates of black plum and lemon grass leaves. The nanoparticles of gold are spherical on the black plum template whereas they form nanotriangles on the lemon grass template. Water contact angle measurements of the leaf surfaces show that the black plum leaf is hydrophilic while lemongrass is hydrophobic in nature. The films fabricated using these templates exhibit hydrophilic water contact angles that can be controlled by changing surface roughness and concentration of the Au precursor (HAuCl4). The water contact angle decreases from 72.7° to 41.7° for Au-PMMA and 78.0° to 52.7° for Au-PS on the black plum leaf template. The range is 87.7–71.4° for Au-PMMA and 86.6–77.7° for Au-PS on lemongrass leaf template. The surface roughness of the free-standing films is strongly dependent on the template and precursor concentration. Furthermore, the application of these films as surface enhanced Raman scattering (SERS) substrates is demonstrated. The detection of bio-molecules such as 4-aminothiophenol, L-Aspartic acid and Chebulinic acid with enhancement factors of ~104, ~103 and ~101 respectively, is reported. There is significant enhancement in the SERS signals on Au-polymer surfaces in comparison to their pristine counterparts.