Gold-coated silver dendrites as SERS substrates with an improved lifetime

Area of Science:

• Materials Science
• Nanotechnology
• Spectroscopy

Background:

• Nanostructured silver offers high signal enhancement for surface-enhanced Raman spectroscopy (SERS).
• Chemical instability of silver, particularly oxidation, limits the operational lifetime of SERS substrates.
• Developing stable SERS substrates is crucial for reliable and long-term chemical sensing applications.

Purpose of the Study:

• To investigate the long-term stability of silver dendrites as SERS substrates.
• To evaluate the effectiveness of a gold coating in preventing silver oxidation and enhancing substrate lifetime.
• To explore a new method for creating durable SERS-active nanostructures.

Main Methods:

• Fabrication of silver dendrites as SERS substrates.
• Coating silver dendrites with a monolayer-thin gold film using immersion plating.
• Long-term monitoring of SERS spectra of 1,2-benzenedithiol monolayers on coated and uncoated silver dendrites over one year.
• Analysis using X-ray photoelectron spectroscopy (XPS) to confirm chemical stability.

Main Results:

• Uncoated silver dendrites showed significant degradation in SERS signal over time due to oxidation.
• Gold-coated silver dendrites exhibited no degradation in SERS spectra, indicating enhanced chemical stability.
• XPS analysis confirmed oxidation of uncoated silver but no chemical changes in gold-coated silver structures.

Conclusions:

• Galvanic displacement of gold onto preformed silver nanostructures is an effective strategy to create stable SERS substrates.
• This method significantly improves the operating and shelf lifetimes of silver-based SERS substrates.
• The gold coating protects the underlying silver from oxidation, ensuring consistent SERS performance.