Overtone photothermal microscopy for high-resolution and high-sensitivity vibrational imaging

Area of Science:

• Optics and Photonics
• Chemical Imaging
• Biomedical Engineering

Background:

• Photothermal microscopy uses thermal gradients for nanostructure and molecule mapping.
• Existing visible and mid-infrared techniques have limitations in chemical specificity and water absorption.
• A need exists for a sensitive, chemically specific imaging method that overcomes these limitations.

Purpose of the Study:

• To introduce overtone photothermal (OPT) microscopy, a novel technique for high-resolution chemical imaging.
• To demonstrate OPT microscopy's capability in diverse applications, including polymer nanostructures and biological tissues.
• To establish OPT microscopy as a complementary modality for multiscale chemical investigations.

Main Methods:

• Development of overtone photothermal (OPT) microscopy using a visible probe.
• Detection of local heat in the C-H overtone region for enhanced sensitivity.
• Application of OPT microscopy to polymer nanostructures, cancer cells, C. elegans, and brain tissues.

Main Results:

• Achieved high chemical specificity, detection sensitivity, and spatial resolution.
• Demonstrated high-fidelity chemical imaging of polymer nanostructures.
• Enabled depth-resolved intracellular chemical mapping of cancer cells and imaging of scattering tissues.

Conclusions:

• OPT microscopy bridges the gap between visible and mid-infrared photothermal methods.
• This technique provides a new modality for high-resolution, high-sensitivity chemical imaging.
• OPT microscopy facilitates multiscale structural and chemical investigations, complementing existing imaging approaches.