Sensing and structure analysis byin situIR spectroscopy: from mL flow cells to microfluidic applications

Area of Science:

• Optics and Photonics
• Spectroscopy
• Materials Science

Background:

• In situ mid-infrared (MIR) spectroscopy is crucial for analyzing functional surfaces and chemical reactions in liquids.
• Existing geometries include attenuated total reflection (ATR), reflection, transmission, and fiber waveguides for MIR spectroscopy in flow cells.

Purpose of the Study:

• To present the methodology of ATR, ellipsometric, and microfluidic applications in single-reflection geometries for in situ MIR spectroscopy.
• To highlight selected examples in optical, electronic, polymer, biomedical, sensing, and silicon technologies.
• To discuss the development of optofluidic platforms and surface-enhanced infrared absorption (SEIRA) for enhanced sensitivity.

Main Methods:

• Review of linear optical in situ MIR techniques, focusing on single-reflection geometries (ATR, ellipsometry, microfluidics).
• Development of an optofluidic platform integrating IR spectroscopy with microfluidics.
• Implementation of SEIRA interfaces using nanostructures and metal-island films for enhanced sensitivity.
• Utilization of advanced IR sources (tunable lasers, frequency combs) for time-resolved and spatially resolved measurements.

Main Results:

• Demonstration of in situ MIR spectroscopy applications in various technological fields.
• Significant sensitivity improvement in optofluidic analyses of biomolecules via SEIRA.
• Enabling time-resolved studies of molecular formation in nanoliter volumes.
• Extension of far-field IR spectroscopy applications for in situ sensing with high spatial and temporal resolution.

Conclusions:

• In situ MIR spectroscopy, particularly with optofluidic platforms and SEIRA, offers powerful capabilities for analyzing liquid-phase systems.
• Advanced IR sources and techniques enable high-resolution, time-resolved sensing relevant to diverse scientific and technological domains.