Non-Plasmonic SERS with Silicon: Is It Really Safe? New Insights into the Optothermal Properties of Core/Shell Microbeads

Abstract

Silicon is one of the most interesting candidates for plasmon-free surface-enhaced Raman scattering (SERS), because of its high-refractive index and thermal stability. However, here we demonstrate that the alleged thermal stability of silicon nanoshells irradiated by conventional Raman laser cannot be taken for granted. We investigated the opto-thermal behavior of SiO/Si core/shell microbeads (Si-rex) irradiated with three common Raman laser sources (λ = 532, 633, 785 nm) under real working conditions. We obtained an experimental proof of the critical role played by bead size and aggregation in heat and light management, demonstrating that, in the case of strong opto-thermal coupling, the temperature can exceed that of the melting points of both core and shell components. In addition, we also show that weakly coupled beads can be utilized as stable substrates for plasmon-free SERS experiments.

Surface‐Enhanced Raman Scattering Enabled by Metal‐Coated Dielectric Microspheres

“…However, an irreversible damage of the spherical shape was observed upon a harsh condition (power density of ≈2.6 × 10 7 mW cm −2 with a 100× objective lens for 1 min). This agrees with the previous studies about significantly modified morphologies upon a high‐intensity laser irradiation …”

Stimuli-Responsive Phase Change Materials: Optical and Optoelectronic Applications

“…In the following, different strategies will be illustrated according to the different types of involved materials. In general terms, the employment of PCMs represents an efficient alternative possibility to store optical information, which enriches the palette of strategies that can be found in the literature [ 25 , 26 , 27 , 28 , 29 , 30 , 31 ]. In particular, it entails some advantages: the possibility of achieving not only binary systems but multicolor devices with precise color depth modulation, the possibility of exploiting different stimuli (especially, laser and voltage), precise spatial control and very quick actuation.…”

Metal-free SERS: Where we are now, where we are heading

“…Hydrogen-doping-induced metal-like H x MoO 3 [38] has shown to possess ultrahigh free-carrier concentration (10 21 cm −3 ), leading to a vast and tunable plasmon resonance with an LOD of 1.1 × 10 7 and SERS EF of 1 nM. Bontempi et al [47] detected methylene blue in solution at a low concentration (∼1 nM) with SiO 2 /Si microbeads [40]. TiO 2 /SiO 2 microspheres enabled an LOD of 10 μM [48].…”