Seeing, Counting, Identifying, and Distinguishing Single Molecules from Their Mixtures via Raman Spectroscopy

Area of Science:

• Molecular Spectroscopy
• Nanotechnology
• Chemical Sensing

Background:

• Distinguishing individual molecules in mixtures is a significant challenge in molecular science.
• Current methods often struggle with sensitivity and specificity at low concentrations.

Purpose of the Study:

• To develop a novel single-molecule surface-enhanced Raman spectroscopy (SM-SERS) strategy.
• To achieve high-credibility identification and distinction of individual molecules in dilute mixtures.

Main Methods:

• Employing a synergistic SM-SERS approach combining giant electromagnetic enhancement (EME) from plasmonic nanogaps and giant chemical enhancement (CME) from monolayer WS2.
• Utilizing 785 nm near-infrared laser excitation for rapid (50 ms acquisition) spectral analysis.
• Analyzing dilute mixtures of rhodamine B, rhodamine 6G, and crystal violet down to 10^-16 M concentrations.

Main Results:

• Successful sighting, counting, identification, and distinction of individual molecules in a dilute mixture.
• Demonstration of rapid and high-credibility spectral acquisition and analysis.
• Validation of the EME-CME synergy for ultra-sensitive molecular detection.

Conclusions:

• The developed EME-CME synergy SM-SERS strategy offers a powerful new capability for optical probing of molecular properties.
• This technique enables the monitoring of spatial-temporal evolution of molecular characteristics.
• The findings open new frontiers in molecular science for real-time analysis of physical, chemical, and biological processes.