Doubly localized surface plasmon resonance in bimodally distributed silver nanoparticles

Area of Science:

• Materials Science
• Nanotechnology
• Surface Science

Background:

• Controlling nanoparticle size distribution is crucial for tuning their optical properties.
• Physical vapour deposition (PVD) is a common technique for nanoparticle synthesis.
• Bimodal size distributions can lead to unique optical phenomena like double plasmon resonance.

Purpose of the Study:

• To report a novel method for growing bimodally distributed silver nanoparticles.
• To investigate the influence of deposition time on nanoparticle size distribution.
• To analyze the optical properties, specifically localized surface plasmon resonance (LSPR), of these nanoparticles.

Main Methods:

• Sequential physical vapour deposition (PVD) involving substrate heating, atmospheric exposure, vacuum annealing, and silver re-deposition.
• Varying deposition times to control nanoparticle growth.
• Characterization of nanoparticle optical properties using LSPR spectroscopy.

Main Results:

• Successful synthesis of bimodally distributed silver nanoparticles.
• Observation of double plasmon resonance peaks in LSPR spectra, correlating with two distinct nanoparticle populations.
• Demonstration that LSPR spectra can be modeled using a double Lorentz oscillator model, confirming non-interacting resonant nanoparticles.

Conclusions:

• The sequential PVD method effectively produces silver nanoparticles with bimodal size distributions.
• Atmospheric exposure and subsequent vacuum annealing induce nanoparticle re-shaping, driven by oxygen physisorption and surface energy changes, leading to bimodal distribution.
• The resulting bimodal nanoparticles exhibit distinct LSPR characteristics, offering potential for tailored optical applications.