Impact of temperature-induced coalescence on SERS properties of Au nanoparticles deposited on GaN nano-columns

• Published in: Applied surface science 2016-08, Vol.378, p.30-36
• Main Authors: Dzięcielewski, Igor, Smalc-Koziorowska, Julita, Bańkowska, Małgorzata, Sochacki, Tomasz, Khachapuridze, Alexandr, Weyher, Jan
• Format: Article
• Language: English
• Subjects: Coalescence; Coalescing; Gold; Nanoparticles; Nanostructure; Platforms; Raman scattering; Spectra
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2016.03.200

[Display omitted] •The changes of gold nanoparticles morphology occurring during annealing.•The relation between crystallographic structure of gold nanoparticles and optimizing SERS signal.•Nature of SERS hot-spots on gold surface decrease upon coalescence.•The direct relation between annealing temperature and SERS signal quality.•Possibility to positively affect sensor structure via temperature annealing. Nanostructured GaN surfaces sputtered with Au provide very promising and reproducible platforms for surface enhanced Raman scattering (SERS). The enhancement factor (EF) in SERS is expected to depend strongly on the local metal (Au) surface structure (size, distribution and morphology). Herein we show how temperature-induced coalescence followed by recrystallization of Au on GaN nano-columns occurs well below the melting point of gold. This process is reflected in SEM, TEM images and SERS spectra of Au/GaN – bound p‐mercaptobenzoic acid (4-MBA), a model Raman scatterer. SERS signals of 4-MBA bound to Au/GaN reach minimum for platforms exposed to t=350°C before regaining the intensity when annealed in the range of 450–900°C. The results have been discussed in the light of the nature of SERS active sites – so called “hot spots” and structure of Au nanoparticles.