Bovine-Hemoglobin Detection by Single-Particle Plasmon-Coupled Circular Dichroism.

Area of Science:

• Plasmonics
• Nanotechnology
• Spectroscopy

Background:

• Plasmon-coupled circular dichroism (PCD) detects chiral molecules using plasmonic sensors.
• Coupled nanoparticles enhance sensitivity but ensemble measurements suffer from signal averaging and structural interference.
• Existing methods struggle to isolate molecular signals from sensor artifacts.

Purpose of the Study:

• To develop a method for unambiguous single-particle PCD measurements of chiral analytes.
• To overcome ensemble averaging and structural chirality limitations in PCD sensing.
• To elucidate the mechanism of PCD at the single-nanostructure level.

Main Methods:

• Combining single-particle dark-field scattering with electron microscopy.
• Utilizing individual gold nanosphere dimers as plasmonic sensors.
• Analyzing the plasmon response to hemoglobin as a chiral analyte.

Main Results:

• Individual gold nanosphere dimers exhibited clear PCD signals for hemoglobin.
• Single gold nanosphere monomers showed no detectable signal.
• Electrodynamic simulations supported the observed differences in refractive index sensitivity.

Conclusions:

• Single-particle PCD analysis provides unambiguous detection of chiral molecules like hemoglobin.
• This approach effectively isolates molecular signals, avoiding ensemble averaging and sensor structural interference.
• The study clarifies PCD mechanisms by examining individual nanostructures.