Toward a Thermally Robust Operando Surface-Enhanced Raman Spectroscopy Substrate

Abstract

The work presented here describes the first steps toward designing a thermally robust surface-enhanced Raman spectroscopy (SERS) substrate with the potential to conduct in situ monitoring of catalytic reactions. Nanosphere lithography (NSL) fabricated SERS substrates were coated with thin (0.2-1.0 nm) films of atomic layer deposited (ALD) Al 2 O 3 . The thermal stability of these substrates was examined at various temperatures (100-500 °C) and over time (up to 6 h) in nitrogen. The results showed that ALD Al 2 O 3 coated nanoparticles maintained their original geometry significantly better than the bare Ag nanoparticles. While experiments showed that thicker ALD Al 2 O 3 coatings resulted in the most stable nanoparticle structure, ALD Al 2 O 3 coatings as thin as 0.2 nm resulted in thermally robust nanostructures as well. Additionally, the ALD Al 2 O 3 coated nanoparticles were heated under propane to mimic reaction conditions. These experiments showed that while the nanoparticle geometries were not as stable under reducing atmosphere conditions, they were much more stable than uncoated nanoparticles and therefore have the potential to be used for SERS monitoring of reactions conducted at elevated temperatures.

ZnO/Ag heterogeneous structure nanoarrays: Photocatalytic synthesis and used as substrate for surface-enhanced Raman scattering detection

“…Various methods for the preparation of SERS substrates have been reported, such as atomic layer deposition (ALD) [15], chemical reduction [16], lithography [17] and ion-beam-sputtered technique [18]. However, more work is still needed to simplify the synthesis method and to improve the sensitivity.…”

Use of atomic layer deposition to improve the stability of silver substrates for in situ, high‐temperature SERS measurements

“…Consequently, the ALD technique can simultaneously control the surface layer composition, the distance from the silver to the surface and the dielectric constant of the medium surrounding the SERS substrate. [27 -30] As an example, Whitney et al [31] recently reported the improved thermal stability of lithographic silver substrates using ALD, though no SERS measurements were acquired.…”

Surface- and Tip-Enhanced Raman Spectroscopy in Catalysis

“…(c) UV–vis absorption spectra of gold nanoparticles at elevated temperatures indicate that their LSPR shifts above temperatures of 100 °C. 94 (d) UV–vis absorption spectra of gold nanoparticles coated with 1 nm alumina at elevated temperatures indicate that stability is maintained up to 400 °C. 94 Adapted from ref (94).…”