Gold Nanoparticle Deposition on Silica Nanohelices: A New Controllable 3D Substrate in Aqueous Suspension for Optical Sensing

We describe new methods to prepare gold nanoparticle/silica nanohelix hybrid nanostructures which form a 3D network in the aqueous phase. Nanometric silica helices and tubules obtained by sol-gel polycondensation on organic templates of self-assembled amphiphilic molecules were further functionalized with (3-aminopropyl)-triethoxysilane (APTES) or (3-mercaptopropyl)triethoxysilane (MPTES). These helices interact strongly with gold nanoparticles (GNPs) of various diameters (1-15 nm). Small GNPs (1-2 nm) at the surface of silica nanohelices grew to about 5 nm when stored in the appropriate organic solvent, whereas this growth process was not observed in water, allowing the size of GNPs at the surface of silica to be controlled by a simple solvent exchange. Larger GNPs (more than 10 nm) at the surface of nano hybrid fibers were used to produce surface enhanced raman scattering (SERS) using benzenthiol as a probe. This provides a novel sustainable approach for designing nanohybrid systems with photonic applications such as ultrasensitive chemical and biological sensors using a simple aqueous suspension of a 3D network of nanohelices.