Conference Agenda

Widefield O-PTIR is a novel multi-modal technique for super-resolution infrared chemical imaging and spectroscopy, enabling sub-500 nm spatial resolution, rapid widefield IR absorption imaging in seconds or less, and full hyperspectral image acquisition in minutes. It is a new chemical imaging mode built upon the optical photothermal infrared (O-PTIR) platform, which employs fluorescence-detected photothermal IR (FL-PTIR). FL-PTIR achieves its speed and resolution advantages by detecting changes in fluorescence emission induced by IR absorption, applicable to both fluorescently labeled samples and autofluorescent biological materials. FL-PTIR offers a spatial resolution by a factor of 10-30X better than conventional IR spectroscopy, utilizing a visible probe beam to monitor IR-induced thermal changes on length scales below the classical diffraction limit.

In FL-PTIR, a tunable pulsed IR laser selectively excites molecular vibrations, inducing localized heating where absorption occurs. This thermal effect decreases fluorescence emission efficiency in fluorescent regions of the sample due to reduced quantum yield. The changes in fluorescent emission are detected using an s-CMOS camera across a widefield area. Sequential acquisition at multiple IR wavelengths yields hyperspectral image stacks that can be processed to extract detailed IR absorption spectra from specific regions of interest, revealing the spatial distribution of chemical species. The high temperature dependence of fluorescence quantum yield (~1%/°C) offers ~100X greater sensitivity compared to the intrinsic photothermal sensitivity of most materials, significantly reducing integration times. Additionally, the simultaneously acquired fluorescence images provide specific molecular targeting for chemical analysis.

We present FL-PTIR chemical images and spectra of fluorescently labeled cells, brain tissue, and bacteria, as well as of autofluorescent samples such as collagen, diatoms, microalgae, and plant tissue – including measurements of living specimens in water. Spectra extracted from FL-PTIR hyperspectral datasets demonstrate sensitivity to subtle chemical heterogeneity within biological samples.

FL-PTIR represents a promising approach for rapid, super-resolution infrared chemical imaging of fluorescently labeled and autofluorescent biological materials. By exploiting the strong thermal dependence of fluorescence quantum yield, it enables detailed chemical characterization with submicron spatial resolution, offering new opportunities for dynamic and label-guided vibrational imaging in complex biological systems.

Preconcentration is a key enabling step in trace gas analysis, particularly when using mid-infrared (MIR) spectroscopy to detect volatile organic compounds (VOCs) in the low ppm range. Although MIR techniques provide inherent molecular selectivity, their sensitivity at such concentrations is often insufficient for reliable detection in miniaturized or field-deployable systems. Here, we present a modular sensing platform that combines thermally regulated multichannel preconcentration (muc-IPRECON) with substrate-integrated hollow waveguides (iHWGs) for enhanced MIR detection performance.

The muc-IPRECON module incorporates up to three independently addressable sorbent channels within a compact aluminum substrate, enabling thermoelectrically controlled low-temperature adsorption (e.g., at −10 °C) and subsequent thermal desorption. A Peltier element ensures active cooling while maintaining a compact and portable design footprint. This configuration allows for flexible and selective enrichment of target VOCs under dynamic sampling conditions. Enriched analytes are guided into an iHWG gas cell, which is coupled to a FTIR spectrometer for real-time MIR analysis. The system accommodates various sorbent materials and is adaptable to a wide range of analytes and application scenarios.

System performance was demonstrated using a variety of VOCs spanning different target molecules and concentration ranges relevant in medical, environmental, and industrial contexts. Examples include acetone (as a biomarker in breath) and methane (as an industrial and environmental contaminant). By combining optimized sorbent materials with controlled low-temperature adsorption and thermal desorption, enrichment factors of up to 150 were achieved, enabling significantly improved limits of detection and quantification compared to direct MIR analysis. Full enrichment and measurement cycles were completed within minutes, supporting rapid, selective, and repeatable trace gas monitoring under real-world conditions.

This approach demonstrates how modular thermal preconcentration, combined with compact MIR photonic components, enables highly sensitive and selective VOC detection in practical, field-relevant applications.

Ref:

Kokoric V. et al., “IPRECON: An integrated preconcentrator for the enrichment of volatile organics in exhaled breath”, doi:10.1039/C5AY00627K

Kokoric V. et al., “muciPRECON: Multichannel preconcentrators for portable mid-infrared hydrocarbon gas sensors”, doi:10.1039/C6AY01236H

Barreto D. N. et al., “From light pipes to substrate-integrated hollow waveguides for gas sensing: A review”, doi:10.1021/acsmeasuresciau.1c00007

Barreto D. N. et al., “Mid-infrared acetone gas sensors using substrate-integrated hollow waveguides augmented by advanced preconcentrators”, doi:pending

Chemical analysis plays a vital role in numerous fields, where spectroscopic techniques serve as essential tools. However, the complexity of samples often necessitates the combination of multiple spectroscopic methods to achieve accurate and reliable results. Multispectral measurements offer a synergistic effect, especially for rapidly changing or heterogeneous media in chemical and biochemical reactions. Fiber optics helps to integrate different spectroscopic techniques within a single probe, providing simultaneous analysis of media composition at the same point and time.

A strong advantage of fiber optic spectroscopy is in its capability to enable chemical reaction monitoring or process-control in-line in various applications, including harsh environments, such as wide temperature ranges from -150°C to +250°C, high pressure up to 200 Bar or in vacuum, and where there are vibrations, aggressive liquids or gases, or electromagnetic fields, including microwave and hard radiation. This advantage permits remote process-control even in industry – in contrast with laboratory conditions – and this feature is highly requested to secure sustainable process control. Depending on the chemical process or materials to be analyzed, fiber probes can be based on 4 different fiber types selected for the required spectral range and used for Transmission, Reflection, ATR-absorption, Raman & Fluorescence spectroscopies. Advanced fiber optic combi probes can utilize two spectroscopic methods in the same probe shaft - such as Mid-FTIR+Fluorescence, Raman+Near-IR, Raman+Mid-FTIR and even combinations of three techniques as well. Spectral data fusion from complementary methods enables enhanced sensitivity and accuracy of the media composition analysis for automated process control in-line.

Here we present our latest development of a multispectral fiber probe capable of obtaining Raman spectra alongside attenuated total reflection (ATR) for Mid IR-absorption, and fluorescence spectroscopy. Raman scattering and fluorescence emission, despite their different physical nature, are often observed together, and their spectral signals can overlap. Example applications of this triple method combi-probe will be presented – to distinguish the cheapest rapeseed and a high-grade extra virgin olive oil. Wide variability of the chemical composition of the natural products due to the different growing conditions makes olive oil samples difficult specimens. Application of an appropriate mathematical processing to complementary spectral data fusion illustrates the advantage of having three different spectroscopy methods used with one combi-probe. Depending on the sample nature and the analytical problem being solved, various pairwise combinations of methods, and in some cases their triple combination, can result in a synergistic improvement.

Another interesting combi-probe application of the fusion of ATR-absorption and Fluorescence spectra will demo how to differentiate 3 types of chicken tissues when only 2 information rich wavelengths in the Mid IR and Visible ranges were selected. This allowed design of a simple low-cost spectral fiber sensor to replace expensive FTIR and Fluorescence spectrometers for this distinct application. The concept opens the way to develop a broad range of cost-effective IoT Spectral Fiber Sensors for customized process control and sustainable automation in food, biotech, chemical, pharma and other industries.

The latest development was made for Combi-probe which enable to collect Raman and Mid InfraRed absorption spectra from the same spot – combining all specific bands for molecular vibrations. Example of its application will be presented for 2 combinations of spectrometers Raman with FTIR-spectrometer and Raman with NLIR-spectrometer - super fast Non-Linear InfraRed spectrometer from Company NLIR, Denmark.