Sensing and structure analysis by in situ IR spectroscopy: from mL flow cells to microfluidic applications

Abstract

In situ mid-infrared (MIR) spectroscopy in liquids is an emerging field for the analysis of functional surfaces and chemical reactions. Different basic geometries exist for in situ MIR spectroscopy in milliliter (mL) and microfluidic flow cells, such as attenuated total reflection (ATR), simple reflection, transmission and fiber waveguides. After a general introduction of linear optical in situ MIR techniques, the methodology of ATR, ellipsometric and microfluidic applications in single-reflection geometries is presented. Selected examples focusing on thin layers relevant to optical, electronical, polymer, biomedical, sensing and silicon technology are discussed. The development of an optofluidic platform translates IR spectroscopy to the world of micro- and nanofluidics. With the implementation of SEIRA (surface enhanced infrared absorption) interfaces, the sensitivity of optofluidic analyses of biomolecules can be improved significantly. A large variety of enhancement surfaces ranging from tailored nanostructures to metal-island film substrates are promising for this purpose. Meanwhile, time-resolved studies, such as sub-monolayer formation of organic molecules in nL volumes, become available in microscopic or laser-based set-ups. With the adaption of modern brilliant IR sources, such as tunable and broadband IR lasers as well as frequency comb sources, possible applications of far-field IR spectroscopy in in situ sensing with high lateral (sub-mm) and time (sub-s) resolution are considerably extended.

Label-Free Physical Techniques and Methodologies for Proteins Detection in Microfluidic Biosensor Structures

“…MIR spectroscopy is an indispensable tool for the experimental research of protein structure, conformations, and interactions [ 163 , 164 ]. Some of the IR techniques, e.g., FTIR ATR, time-resolved IR spectroscopy, or more sophisticated plasmonics based surface enhanced IR spectroscopy are suitable for integration in microfluidic platforms [ 165 ].…”

Surface Functionalization with Polymer Membrane or SEIRA Interface to Improve the Sensitivity of Chalcogenide-Based Infrared Sensors Dedicated to the Detection of Organic Molecules

“…Indeed, there is a growing demand for portable monitoring systems with high stability, high sensitivity, wide detection range, and short response times. − A number of chemical sensors are commercially available for field measurements (e.g., portable gas chromatographs, surface acoustic wave sensors, optical instruments). ,− However, in situ chemical sensors suitable for contaminant-monitoring applications are still lacking due to cost, multiple detection failures, actual portability, and/or reliability for long-term detection in a complex aquatic environment. , Infrared spectroscopy is a powerful tool: a simple, reliable, fast, cost-efficient, and nondestructive method for detecting and determining the composition of complex samples . Due to the intrinsic characteristics of optical sensors, the evanescent field is sensitive to the changes induced by the analyte on the sensor surface such as scattering, fluorescence, and notably absorption.…”

Infrared spectroscopic monitoring of solid-state processes

“…Although the various applications of IR spectroscopy to monitor solid-state processes are covered by numerous reviews, 1-10 the author's intention is to bring to focus some specific applications and perspectives, that have so far remained somewhat out of focus. Numerous recent excellent reviews on the specific applications of IR spectroscopy are available, for example on the applications of IR spectroscopy in monitoring liquids 2,[11][12][13] or gaseous systems, [14][15][16] as well as interfaces. 2,9,[17][18][19][20][21][22][23] Infrared spectroscopy…”