Single-molecule detection with enhanced Raman scattering of tungsten oxide nanostructure

Area of Science:

• Materials Science
• Nanotechnology
• Spectroscopy

Background:

• Raman scattering is a powerful technique for molecular analysis.
• Achieving single-molecule detection in Raman spectroscopy remains a significant challenge.
• Tungsten oxide nanostructures are being explored for their unique optical and electronic properties.

Purpose of the Study:

• To investigate the Raman scattering enhancement effect of tungsten oxide nanorods.
• To demonstrate single-molecule detection using these nanorods.
• To elucidate the structural basis for the observed enhancement.

Main Methods:

• Preparation of tungsten oxide nanorods.
• Adsorption of isotopically labeled carbon monoxide (¹²CO and ¹³CO) onto nanorods.
• Raman mapping and spectroscopy.
• Density Functional Theory (DFT) calculations.

Main Results:

• Tungsten oxide nanorods exhibited a very large enhancement effect on Raman scattering.
• Distinct Raman images for ¹²CO and ¹³CO were obtained, confirming single-molecule sensitivity.
• The characteristic blinking phenomenon associated with single-molecule detection was observed.
• DFT calculations revealed that the {001}CS structure of tungsten oxide nanorods possesses two-dimensional electrical conduction properties.

Conclusions:

• Tungsten oxide nanorods are highly effective SERS substrates.
• The {001}CS crystal facet is responsible for the significant Raman enhancement.
• This work paves the way for ultrasensitive detection of molecules at the single-molecule level.