Controllable Charge Transfer in Ag-TiO₂ Composite Structure for SERS Application

Area of Science:

• Materials Science
• Nanotechnology
• Spectroscopy

Background:

• Surface-enhanced Raman scattering (SERS) is a powerful technique for detecting molecules at low concentrations.
• Metal-semiconductor nanostructures offer unique properties for enhancing SERS signals.
• Controlling nanoparticle aggregation is crucial for optimizing SERS performance.

Purpose of the Study:

• To investigate the Surface-enhanced Raman scattering (SERS) properties of TiO₂/Ag nanocaps arrays.
• To explore the influence of silver thickness in TiO₂/Ag bilayers on SERS intensity.
• To examine the effect of TiO₂ content in co-sputtered TiO₂-Ag monolayers on SERS properties and nanoparticle morphology.

Main Methods:

• Fabrication of TiO₂/Ag bilayer and TiO₂-Ag monolayer nanocaps arrays on a two-dimensional colloidal array substrate.
• Systematic variation of silver thickness in the bilayer structure.
• Controlled co-sputtering of TiO₂ and Ag for monolayer fabrication.
• Characterization of SERS properties and nanoparticle morphology.

Main Results:

• SERS intensity in TiO₂/Ag bilayers decreased with increasing silver thickness.
• A significant SERS enhancement was observed for a 10 nm sublayer Ag compared to a pure Ag monolayer.
• The TiO₂/Ag bilayer exhibited a synergistic metal-semiconductor effect, combining electromagnetic (EM) and charge-transfer (CT) mechanisms.
• Co-sputtered TiO₂-Ag monolayers showed reduced Ag particle aggregation and smaller Ag particle sizes, indicating TiO₂'s role in inhibiting aggregation.

Conclusions:

• The metal-semiconductor synergistic effect in TiO₂/Ag nanostructures significantly enhances SERS properties.
• Optimizing silver thickness and incorporating TiO₂ are key strategies for improving SERS performance.
• TiO₂ acts as an effective agent to control silver nanoparticle size and prevent aggregation, leading to more stable and efficient SERS substrates.