Gold Nanorods as Plasmonic Sensors for Particle Diffusion

Area of Science:

• Nanotechnology
• Physical Chemistry
• Surface Science

Background:

• Plasmonic gold nanoparticles typically detect analytes bound to their surface.
• Weak analyte-surface interactions lead to diffusion within the sensor's sensing volume.
• This diffusion causes minor shifts in plasmon resonance position.

Purpose of the Study:

• To develop a method for detecting and quantifying analyte diffusion near plasmonic nanoparticle sensors.
• To determine the diffusion coefficient of analytes with negligible surface binding.
• To establish a theoretical model for nanoscale diffusion measurements.

Main Methods:

• Utilizing a sensitive and fast detection scheme to monitor plasmon resonance fluctuations.
• Employing a theoretical model tailored to the experimental detection geometry.
• Implementing nanoscale plasmon correlation spectroscopy (NanoPCS).

Main Results:

• Successfully detected small temporal shifts in plasmon resonance position caused by analyte diffusion.
• Determined analyte diffusion coefficients using the NanoPCS method.
• Validated the method by observing expected trends with varying diffusor size and medium viscosity.
• Observed reduced diffusion effects near solid interfaces.

Conclusions:

• NanoPCS provides a reliable method to measure analyte diffusion coefficients near nanoparticles.
• The technique is effective even when analyte-surface interactions are minimal.
• This method has practical applications in studying diffusion dynamics in nanoscale environments.