Single bacteria identification with second-harmonic generation in MoS₂

Area of Science:

• Materials Science
• Nanotechnology
• Biophotonics

Background:

• Transition-metal dichalcogenides, like monolayer MoS₂, possess significant nonlinear optical properties.
• These properties make them attractive for photonic devices and sensing applications.
• Microbial interactions with 2D materials are an emerging area of research.

Purpose of the Study:

• To investigate the impact of single bacteria on second-harmonic generation (SHG) in monolayer MoS₂.
• To explore SHG imaging for label-free bacterial detection, identification, and stress monitoring.
• To demonstrate UV-induced bacterial removal and characterization using SHG.

Main Methods:

• Utilizing monolayer MoS₂ as a substrate for bacterial deposition.
• Analyzing anisotropic polarization responses in SHG signals induced by bacteria.
• Employing SHG imaging to monitor biomaterial strain and bacterial rupture.
• Investigating UV-induced bacterial removal and species-specific rupture time analysis.

Main Results:

• Bacteria deposited on MoS₂ alter SHG signals, showing anisotropic polarization dependent on bacterial orientation.
• SHG imaging effectively detects biomaterial strain as low as 0.1% due to bacterial presence.
• Transient SHG signals reveal species-specific bacterial rupture times after UV exposure.
• Label-free identification of single bacterial cells, including *E. coli* and *L. casei*, is achieved.

Conclusions:

• Monolayer MoS₂ can be used to monitor bacterial-induced strain and facilitate label-free pathogen identification.
• SHG imaging offers a sensitive method for single-cell bacterial analysis and differentiation.
• This approach holds promise for developing advanced diagnostic tools for microbial detection.