Nanoembossed gold nanoshell with a fluorescence-like strong SERS signal

Abstract

We present a nanoembossed nanoshell with a new internal location for the formation of strong electromagnetic fields. The internally nanoembossed gold nanoshell (AuNS) is fabricated by electrostatically assembling smaller silica nanoparticles (∼15.7 nm) around the silica core (∼123.6 nm) followed by growing gold nanoseeds on the core in a wet process. FDTD calculations reveal the creation of a strong electromagnetic field (|E/Ein|max = 55 at 633 nm) at sharp edges formed by the contact between the nanoembosses and the silica core. The field formation is supported by measuring the SERS signal of Ru(bpy) encapsulated in the nanoembossing silica nanoparticles. SERS signals as strong as the corresponding fluorescence are obtained. The Raman enhancement factor (EF) is estimated to be up to 1010 at 633 nm excitation, in addition to a comparable EF at 785 nm laser excitation. The SERS intensity of the nanoembossed nanoshell layer is sufficiently high compared to the outer or the core of the nanoshell. Finally, we fabricate all-in-one nanoparticles with all the three places where the reporter dyes are loaded and acquire the highest SERS intensity to potentially enable bio-medical applications of the nanoembossed AuNS as a sensitive and reliable labeling particle.