Plasmonic and Electrostatic Interactions Enable Uniformly Enhanced Liquid Bacterial Surface-Enhanced Raman Scattering...

Area of Science:

• Nanotechnology
• Spectroscopy
• Microbiology

Background:

• Surface-enhanced Raman spectroscopy (SERS) is a powerful technique for molecular detection.
• Performing SERS in liquid environments while maintaining cell viability is essential for biological applications.
• Understanding nanoparticle-bacteria interactions is key to optimizing SERS sensitivity and uniformity.

Purpose of the Study:

• To investigate bacterial liquid-SERS using gold nanorods.
• To study the plasmonic and electrostatic interactions influencing SERS enhancement.
• To establish a foundation for bacterial identification and drug susceptibility testing in biological fluids.

Main Methods:

• Synthesis of gold nanorods with varying plasmon resonances (670-860 nm).
• Characterization of SERS signatures for Gram-negative and Gram-positive bacteria in water.
• Analysis of bacterial and nanorod concentrations, cryo-electron microscopy, and zeta potential measurements.

Main Results:

• Achieved large-area SERS enhancement independent of nanorod resonance and bacteria type.
• Demonstrated significantly higher SERS signals for bacteria with higher surface charge density.
• Identified electrostatic attraction between positively charged nanorods and negatively charged bacteria as the cause of enhanced signals.

Conclusions:

• Robust liquid-SERS measurements were established for bacterial analysis.
• Electrostatic interactions play a critical role in uniform SERS enhancement.
• This work supports the development of SERS for bacterial diagnostics in biological samples.