Au core/Au-Ag alloy shell nanorods: composition- and shape-tailored optical responses

Area of Science:

• Nanotechnology
• Materials Science
• Plasmonics

Background:

• Gold nanorods (Au NRs) are crucial in plasmonics.
• Developing alloy nanostructures offers tunable optical and electronic properties.

Purpose of the Study:

• To develop a method for synthesizing gold core/gold-silver alloy shell nanorods (Au@Au(x)Ag(1-x) NRs).
• To investigate the effect of composition on morphology, localized surface plasmon resonance (LSPR), and dielectric sensitivity.
• To evaluate the surface-enhanced Raman spectroscopy (SERS) activity of the alloy shells.

Main Methods:

• Co-reduction of gold and silver ions using Au NRs as templates.
• Composition tuning by varying the Ag+/Au3+ ratio (x from 0 to 1).
• Characterization of morphology, LSPR, dielectric sensitivity, and SERS activity.

Main Results:

• Successfully synthesized Au@Au(x)Ag(1-x) NRs with a wide tunable composition range.
• Observed that Ag+/Au3+ ratio influences endcap morphology, causing an abnormal red-shift in LSPR.
• Demonstrated that dielectric sensitivity is primarily determined by the LSPR band maximum.
• Found that alloy shells have lower SERS activity than pure silver shells due to altered electron structure.

Conclusions:

• A feasible method for preparing tunable Au@Au(x)Ag(1-x) NRs was established.
• Morphology-composition-plasmon resonance relationships were elucidated.
• The study provides insights into the plasmonic and SERS properties of bimetallic nanorods.