Infrared Laser Spectroscopy Research Articles

A hybrid learning approach to better classify exhaled breath's infrared spectra: A noninvasive optical diagnosis for socially significant diseases.

Early diagnosis is crucial for effective treatment of socially significant diseases, such as type 1 diabetes mellitus (T1DM), pneumonia, and asthma. This study employs a diagnostic method based on infrared laser spectroscopy of human exhaled breath. The experimental setup comprises a quantum cascade laser, which emits in a pulsed mode with a peak power of up to 150 mW in the spectral range of 5.3-12.8 μm (780-1890 cm-1), and a Herriott multipass gas cell with a specific optical path length of 76 m. Using this setup, spectra of exhaled breath in the mid-infrared range were obtained from 165 volunteers, including healthy individuals, patients with T1DM, asthma, and pneumonia. The study proposes a hybrid approach for classifying these spectra, utilizing a variational autoencoder for dimensionality reduction and a support vector machine method for classification. The results demonstrate that the proposed hybrid approach outperforms other machine learning method combinations.

Competition between O-H and S-H Intermolecular Interactions in Conformationally Complex Systems: The 2-Phenylethanethiol and 2-Phenylethanol Dimers.

Noncovalent interactions involving sulfur centers play a relevant role in biological and chemical environments. Yet, detailed molecular descriptions are scarce and limited to very simple model systems. Here we explore the formation of the elusive S-H···S hydrogen bond and the competition between S-H···O and O-H···S interactions in pure and mixed dimers of the conformationally flexible molecules 2-phenylethanethiol (PET) and 2-phenylethanol (PEAL), using the isolated and size-controlled environment of a jet expansion. The structure of both PET-PET and PET-PEAL dimers was unraveled through a comprehensive methodology that combined rotationally resolved microwave spectroscopy, mass-resolved isomer-specific infrared laser spectroscopy, and quantum chemical calculations. This synergic experimental-computational approach offered unique insights into the potential energy surface, conformational equilibria, molecular structure, and intermolecular interactions of the dimers. The results show a preferential order for establishing hydrogen bonds following the sequence S-H···S < S-H···O ≲ O-H···S < O-H···O, despite the hydrogen bond only accounting for a fraction of the total interaction energy.

Pt+(C2H2)n Complexes Studied with Selected-Ion Infrared Spectroscopy.

Platinum cation complexes with multiple acetylene molecules are studied with mass spectrometry and infrared laser spectroscopy. Complexes of the form Pt+(C2H2)n are produced in a molecular beam by laser vaporization, analyzed with a time-of-flight mass spectrometer, and selected by mass for studies of their vibrational spectroscopy. Photodissociation action spectra in the C-H stretching region are compared to the spectra predicted for different structural isomers using density functional theory. The comparison between experiment and theory demonstrates that platinum forms cation-π complexes with up to three acetylene molecules, producing an unanticipated asymmetric structure for the three-ligand complex. Additional acetylenes form solvation structures around this three-ligand core. Reacted structures that couple acetylene molecules (e.g., to form benzene) are found by theory to be energetically favorable, but their formation is inhibited under the conditions of these experiments by large activation barriers.

Formation of the C4Hn+ (n = 2-5) ions upon ionization of acetylene clusters in helium droplets.

Infrared (IR) spectroscopy using ultracold helium nanodroplet matrices has proven to be a powerful method to interrogate encapsulated ions, molecules, and clusters. Due to the helium droplets' high ionization potential, optical transparency, and ability to pick up dopant molecules, the droplets offer a unique modality to probe transient chemical species produced via photo- or electron impact ionization. In this work, helium droplets were doped with acetylene molecules and ionized via electron impact. Ion-molecule reactions within the droplet volume yield larger carbo-cations that were studied via IR laser spectroscopy. This work is focused on cations containing four carbon atoms. The spectra of C4H2+, C4H3+, and C4H5+ are dominated by diacetylene, vinylacetylene, and methylcyclopropene cations, respectively, which are the lowest energy isomers. On the other hand, the spectrum of C4H4+ ions hints at the presence of several co-existing isomers, the identity of which remains to be elucidated.

Can Ag+ Permeate through a Potassium Ion Channel? A Bottom-Up Approach by Infrared Spectroscopy of the Ag+ Complex with the Partial Peptide of a Selectivity Filter.

Silver and silver ions have a long history of antimicrobial activity and medical applications. Nevertheless, the activity of Ag+ against bacteria, how it enters a cell, has not yet been established. The K+ channel, a membrane protein, is a possible route. The addition of a channel inhibitor (4-aminopyridine) to modulate the Ag+ uptake could support this view. However, the inhibitor enhances the uptake of Ag+, the opposite result. We have applied cold ion trap infrared laser spectroscopy to complexes of Ag+ and Ac-Tyr-NHMe (a model for GYG) which is a portion of the selectivity filter in the K+ channel to consider the question of permeation. With support from quantum chemical calculations, we have determined the stable conformations of the complex. The conformations strongly suggest that Ag+ would not readily permeate the K+ channel. The mechanism of the unexpected enhancement by the inhibitor is discussed.

HPB P08 Exploring Carbon-13 breath delta value and other biomarkers of infection following Liver Transplantation and Hepatopancreatobiliary Surgery

Abstract Background Sepsis and infection are the leading cause of morbidity and mortality after surgery, but the inflammatory response to the trauma of surgery can make diagnosis challenging. Carbon-13 breath delta value (13C BDV) has been shown to be discriminant as a novel diagnostic marker for sepsis and infection. We aim to assess biomarkers including BDV following major hepatopancreatobiliary (HPB) surgery to diagnose postoperative infection/sepsis. Methods 20 participants undergoing HPB surgery were recruited prospectively. Breath samples were collected from baseline preoperatively, and on postoperative days (POD) 1–9, with plasma and peripheral blood mononuclear cell (PBMC) samples preoperatively, POD1, 4 and 8. Breath samples were analysed using infrared laser spectroscopy to generate BDV (per mil). Plasma was analysed for cytokines using MesoScale Discovery immunoassay, Procalcitonin (PCT) using ELISA, and Cell surface marker expression on monocytes was phenotyped using flow cytometry. Differences between groups who did and did not develop infective complications was analysed using two-way ANOVA and Mann Whitney U test. Results 5/20 participants developed infective complications, with a mean day of diagnosis POD5. There was no difference between BDV in patients with or without infection. Monocyte count was increased in infected participants at all timepoints, and monocyte expression of PD-L1 on POD1, and CD155 and HLA-DR on POD4 was upregulated, +13.09% (95%CI 1.59 to 24.61, p&amp;lt;0.05), +422.5 MFI (95% CI -770.9 to -73.68, p&amp;lt;0.05), and +19.02% (95% CI 37.58 to 0.45, p&amp;lt;0.05) respectively. Conclusions Monocyte expression of PD-L1, HLA-DR and CD155 is associated with infection, +13.09% (p&amp;lt;0.05), +422.5 MFI (p&amp;lt;0.05), and +19.02% (p&amp;lt;0.05) respectively. The innate immune system is dysregulated in infection following major HPB surgery. In this cohort BDV did not predict infection. Further investigation of novel biomarkers including BDV and soluble monocyte markers is required.

Deep Learning for Type 1 Diabetes Mellitus Diagnosis Using Infrared Quantum Cascade Laser Spectroscopy.

An estimated 10.5% of the world’s population aged 20–79 years are currently living with diabetes in 2021. An urgent task is to develop a non-invasive express-diagnostics of diabetes with high accuracy. Type 1 diabetes mellitus (T1DM) diagnostic method based on infrared laser spectroscopy of human exhaled breath is described. A quantum cascade laser emitting in a pulsed mode with a peak power of up to 150 mW in the spectral range of 5.3–12.8 μm and Herriot multipass gas cell with an optical path length of 76 m were used. We propose a method for collecting and drying an exhaled human air sample and have measured 1200 infrared exhaled breath spectra from 60 healthy volunteers (the control group) and 60 volunteers with confirmed T1DM (the target group). A 1-D convolutional neural network for the classification of healthy and T1DM volunteers with an accuracy of 99.7%, recall 99.6% and AUC score 99.9% was used. The demonstrated results require clarification on a larger dataset and series of clinical studies and, further, the method can be implemented in routine medical practice.

3D Nanoscale Morphology Characterization of Ternary Organic Solar Cells

It is highly desired to develop advanced characterization techniques to explore the 3D nanoscale morphology of the complicated blend film of ternary organic solar cells (OSCs). Here, ternary OSCs are constructed by incorporating the nonfullerene acceptor perylenediimide (PDI)-diketopyrrolopyrrole (DPP)-PDI and their morphology is characterized in depth to understand the performance variation. In particular, photoinduced force microscopy (PiFM) coupled with infrared laser spectroscopy is conducted to qualitatively study the distribution of donor and acceptors in the blend film by chemical identification and to quantitatively probe the segmentation of domains and the domain size distribution after PDI-DPP-PDI acceptor incorporation by PiFM imaging and data processing. In addition, the energy-filtered transmission electron microscopy with energy loss spectra is utilized to visualize the nanoscale morphology of ultrathin cross-sections in the configuration of the real ternary device for the first time in the field of photovoltaics. These measurements allow to "view" the surface and cross-sectional morphology and provide strong evidence that the PDI-DPP-PDI acceptor can suppress the aggregation of the fullerene molecules and generate the homogenous morphology with a higher-level of the molecularly mixed phase, which can prevent the charge recombination and stabilize the morphology of photoactive layer.

A LabVIEW based virtual instrument system for mid infrared laser spectroscopy measurements

The development of a virtual instrument (VI) interface to acquire spectroscopic measurements using a quantum cascade laser-based on LabVIEWTM is presented. The interface can enable mid-infrared laser spectroscopic data acquisition using a fast response mercury-cadmium-telluride (MCT) detector. The MCT is connected to an analog/digital converter card, and the data is displayed in a virtual high-speed oscilloscope. The VI processes the acquired data, displays the information, and saves it to a file through several operations using a “state machine” architecture. Transmission measurements of a polystyrene film were used to calibrate the system. They were compared to the National Institute of Standards and Technology-based FT-IR reference spectrum, showing excellent agreement. The system was tested with four different optical setups for IR Transmission, Diffuse Reflectance Infrared Spectroscopy, Reflection Absorption Infrared Spectroscopy, and Attenuated Total Reflection. The VI can be easily customized, allowing users to adapt it according to their specific laboratory needs.

Femtosecond Infrared Laser Spectroscopy of Characteristic Molecular Vibrations in Bacteria in the 6-µm Spectral Range

Femtosecond Infrared Laser Spectroscopy of Characteristic Molecular Vibrations in Bacteria in the 6-µm Spectral Range

Carbon Monoxide Emissions from Corn Silage

Carbon monoxide (CO) emissions from corn silage were observed using Fourier Transform Infrared (FTIR) spectroscopy and laser spectroscopy. In the first experiment, corn silage was produced using laboratory bucket silos. Air samples were collected from the bucket silos during the first week of ensiling and analyzed using a low-resolution Bruker FTIR spectrometer coupled with a long optical path length White Cell. The CO concentration in the bucket silo gas, derived from the FTIR spectra using the LINEFIT program, was as high as 48.0 ppm. In the second experiment, air samples were collected through a flux chamber from an Ag-Bag silage pile on a commercial dairy that was opened several months after ensiling. The Ag-Bag air samples were analyzed using a high-resolution Bruker FTIR spectrometer, and CO concentrations were retrieved to be 6.83 ppm, corresponding to an area emission rate of 33.7 mg/(hour ·m2). An LGR N2O/CO gas analyzer based on infrared laser spectroscopy was also used to measure the CO concentrations from the same flux chamber. Elevated CO concentrations were observed from these silage sources. The present study revealed that CO was emitted by corn silage during different phases of ensiling. Annual CO emissions from the corn silage were estimated to be much lower than those from the well-known emission categories in San Joaquin Valley (SJV) and California, but comparable to those from food and agricultural sources in the SJV. It is also confirmed that FTIR spectroscopy is a viable method for measuring CO concentrations in complex gas mixtures, such as silage gas.

Dynamics of coordination of H3O+ and NH4+ in crown ether cavities.

Crown ethers stand out for their ability to form inclusion complexes with metal cations and positively charged molecular moieties. Hydronium and ammonium interact strongly with crown ethers and potentially modulate their ionophoric activity in protic solvents and physiological environments commonly involved in (bio)technological applications. In this work, Born-Oppenheimer molecular dynamics (BOMD) computations are employed to gain insights into the coordination arrangements of H3O+ and NH4+ in the complexes with the native crown ethers 15-crown-5 (15c5) and 18-crown-6 (18c6). Both cations display dynamic changes in coordination inside the cavities of the crown ethers. On the one hand, hydronium explores different coordination arrangements, through rotation around its C3 axis in the 15c5 complex, and through breathing motions, involving rapid inversions of the O atom along the C3 axis in the 18c6 complex. On the other hand, ammonium undergoes a facile rotation in three dimensional space, leading to frequent changes in the NH bonds involved in the coordination with the crown ether. The reduced host-guest symmetry matching of the 15c5 macrocycle enhances the reorientation dynamics and, in the case of H3O+, it promotes short H-bonding distances yielding events of proton transfer to the crown ether. The infrared vibrational spectra predicted by the BOMD computations within this dynamic framework reproduce with remarkable accuracy the action spectra of the isolated complexes obtained in previous infrared laser spectroscopy experiments. The experimentally observed band positions and broadening can then be rationalized in terms of orientational diffusion of the cations, changes in the coordinating H-bonding pairs sustaining the complex and eventual proton bridge formation.

Infrared laser spectroscopy of the ν3-ν4 difference band and detection of the ν3 band of NO3

The infrared diode laser spectrum of the ν3-ν4 difference band of 14NO3 has been observed in the 690 cm−1 region. By fixing the lower state (v4 = 1) constants to the previously determined values, molecular constants in v3 = 1 have been determined for the first time : the vibrational energy E3 = 1054.13679(69) cm−1, the rotational constants B3 = 0.4562291(41), C3 = 0.2274567(53) cm−1, the first-order Coriolis coupling constant Cζ3 = 0.0032073(99) cm−1, and the spin–orbit interaction constant aeff = –0.03979(70) cm−1, with one standard deviation in parentheses. The ν3 fundamental band has been detected with weaker intensity than the ν3 + ν4 band by a factor of ~ 2000.

A rapid, spatially dispersive frequency comb spectrograph aimed at gas phase chemical reaction kinetics

This New Views article will highlight some recent advances in high sensitivity gas detection using direct infrared absorption frequency comb laser spectroscopy, with a focus on frequency comb use in chemical reaction kinetics and our own contribution to this field. Our recently implemented detection technique uses a combination of a 12.9 GHz free spectral range virtually imaged phased array and diffraction grating to spatially disperse the mid-infrared frequency comb onto a camera. Individual frequencies or ‘comb teeth’ of a 250 MHz repetition-rate frequency comb are able to be resolved. High molecular sensitivity is achieved by increasing the interaction path length using a Herriott multipass cell. High spectral resolution, broadband spectral coverage, and high molecular sensitivity are all achieved on an adjustable 1–50 µs timescale, making this frequency comb apparatus ideal for measuring chemical reaction kinetics where multiple absorbing species can be monitored simultaneously. This New Views article will also discuss some of the challenges and decisions that chemists might face in implementing this advanced physics technology in their own laboratory. Spatially dispersed 250 MHz mid-infrared frequency comb laser, with absorption of some frequencies by a dilute sample of methane.

Infrared laser spectroscopy measurement of the electron affinity of thallium

SynopsisThe electron affinity of thallium, Tl, has been measured using tunable infrared laser photodetachment threshold spectroscopy. The relative cross section for neutral atom production following photodetachment from Tl− was measured with a crossed laser-ion beam apparatus over the photon energy range 300 - 900 meV. A single s-wave threshold was observed near 320 meV due to the opening of the ground state phodetachment channel, yielding a preliminary value for the electron affinity of thallium. The present results are compared to previous experimental and theoretical results.

The influence of stabilization efficiency on skin–core structure and properties of polyacrylonitrile fibers

In this paper, we report the efficient preparation of polyacrylonitrile-based carbon fibers (CFs) by increasing the stabilization temperature and shortening the stabilization time. The oxidized fibers (OFs) were firstly prepared from precursor fibers (PFs) with different diameters at high stabilization efficiency. The skin–core structure of the obtained OFs was studied by optical microscopy, scanning electron microscopy, atomic force microscopy and nanoscale infrared laser spectroscopy, which revealed that fine denier PFs were more suitable for high-efficient stabilization treatment. Moreover, fine denier PFs were stabilized using four different temperature profiles, and then carbonized under stationary processing conditions to fabricate CFs with different stabilization efficiencies. The skin–core structure, crystallite thickness and mechanical properties of the obtained CFs were tested by scanning electron microscopy, Raman spectra, wide-angle X-ray diffraction and tensile testing methods. Noteworthily, T400-grade CFs were achieved and the manufacturing time was reduced by increasing stabilization efficiency, thus lowering the production costs of CFs.

1422P - Molecular fingerprinting in breast cancer (BC) screening using Quantum Optics (QO) technology combined with an artificial intelligence (AI) approach applying the concept of “molecular profiles at n variables (MPnV)”: A prospective pilot study

BackgroundBC screening by mammography is associated with a significant reduction in mortality (19 % overall reduction of the relative risk), however with significant limitations and debatable cost-effectiveness. Screening individuals for cancer using liquid biopsies (LB) represents an unmet need. We report the first prospective “proof of concept” study using the QO technology combined with an AI approach using the concept of “MPnV” applied to BC detection. MethodsQO (femto/atto-second infrared laser spectroscopy) on LB is a simple, non-invasive and reproducible method allowing to identify individualized molecular spectra (MS). These highly detailed MS can be correlated to physiological or pathological changes allowing detection and translation of differences. Integrated into a super-computational approach using a non-hierarchical deep data mining strategy (MPnV concept), MS could discriminate individuals with and without BC. The plasma of 68 controls and 27 BC patients, accrued at the King Saud University BC screening program, Riyadh, Saudi Arabia (KSA), were studied by QO (Max Planck Institute of Quantum Optics /Ludwig Maximillian University Munich, Garching, Germany). The MS were analysed on the Shaheen II supercomputer at King Abdallah University for Science and Technology (KAUST), KSA, in order to generate comparative algorithms. ResultsThe use of special feature selection, followed by class analysis allowed to differentiate profiles between the two groups with a sensitivity of 97% and a specificity of 72% (variables n=1,100). A more in-depth analysis led to 99% sensitivity, but with a lower specificity of 64%. Further analysis of the series, using an age-matched approach led to 97% sensitivity with 98% specificity in differentiating women with or without BC. ConclusionsThese results warrant a large scale prospective validation BC screening trial (ongoing) and “proof of concept trials” in other frequent cancers, in particular those without existing screening programs. Editorial acknowledgementProf. Ferenc Krausz, Director, and Dr. Mihaela Zigman, Leader of the Broadband Infrared Diagnostics, Max Planck Institute of Quantum Optics (MPQ), Faculty of Physics at Ludwig-Maximilians Universität München (LMU), Garching, Germany. Legal entity responsible for the studyJean Marc Nabholtz, Oncology Centre, King Saud University, Riyadh, Saudi Arabia. Funding1. Oncology Centre, King Saud University Medical City, King Saud University, Saudi Arabia. 2. Max-Planck-Institut für Quantenoptik and Faculty of Physics at Ludwig-Maximilians Universität München, Garching, Germany. 3. Computational Bioscience Research Centre, King Abdallah University for Science and Technology (KAUST), Thuwal, Saudi Arabia. DisclosureM.R.K. Bahadoor: Travel / Accommodation / Expenses, ASCO Participation Funded: Pfizer; Advisory / Consultancy, Pancreas Expert Opinion Advisory: Baxter. All other authors have declared no conflicts of interest.

Cyclotrimerization of Acetylene in Gas Phase V+(C2H2)n Complexes: Detection of Intermediates and Products with Infrared Spectroscopy

Infrared laser spectroscopy and mass spectrometry were used to determine the structures of intermediates and products in the single-atom-catalyzed trimerization of acetylene to form benzene. Complexes of the form V+(C2H2)n were produced in the gas phase via laser ablation in a pulsed-nozzle source, size-selected with a mass spectrometer, and studied with infrared laser photodissociation spectroscopy. Density functional theory calculations were performed in support of the experiments. Single- and double-acetylene complexes form V+(C2H2)n metallacycle structures. Three-acetylene complexes exhibit a surprising dependence on the acetylene concentration, forming V+(C2H2)3 and (C2H2)V+(C4H4) tri- and dimetallacycle ion structures at low concentrations and eventually V+(benzene) at higher concentrations. These observations reveal intermediates along the reaction path of acetylene cyclotrimerization to benzene.

A global database of water vapor isotopes measured with high temporal resolution infrared laser spectroscopy

The isotopic composition of water vapour provides integrated perspectives on the hydrological histories of air masses and has been widely used for tracing physical processes in hydrological and climatic studies. Over the last two decades, the infrared laser spectroscopy technique has been used to measure the isotopic composition of water vapour near the Earth’s surface. Here, we have assembled a global database of high temporal resolution stable water vapour isotope ratios (δ18O and δD) observed using this measurement technique. As of March 2018, the database includes data collected at 35 sites in 15 Köppen climate zones from the years 2004 to 2017. The key variables in each dataset are hourly values of δ18O and δD in atmospheric water vapour. To support interpretation of the isotopologue data, synchronized time series of standard meteorological variables from in situ observations and ERA5 reanalyses are also provided. This database is intended to serve as a centralized platform allowing researchers to share their vapour isotope datasets, thus facilitating investigations that transcend disciplinary and geographic boundaries.

Rovibrational laser jet-cooled spectroscopy of the NH3–Ar complex in the ν2 umbrella region of NH3: comparison between new infrared data and an ab initio calculated spectrum

ABSTRACTFive ortho and para bands of the ν2 umbrella mode of the NH3–Ar van der Waals complex have been recorded at high resolution using jet-cooled infrared laser spectroscopy. A rovibrational analysis provides accurate band centres and upper state rotational constants for the Πs(j = 1,k = 0) ← Σa(j,k = 0) and Σs(j = 1,k = 0) ← Σa(j,k = 0) ortho bands. The puzzling para bands observed in the region of the lower and upper components of the inversion splitting doublet have been assigned by comparison with rovibrational and tunnelling levels and transitions calculated ab initio. The latter calculations are based on the four-dimensional potential energy surface reported by Loreau et al. [J. Chem. Phys. 141, 224303 (2014)], which takes explicitly into account the umbrella motion of the ammonia molecule. The very good agreement found between Πs/a,lower(j = 1,k = 1) ← Σa(j = 1,k = 1) and Πs/a,upper(j = 1,k = 1) ← Σs(j = 1,k = 1) experimental and calculated transitions has been exploited to determine precisely two different inversion splittings in the ν2 state (32.003(1) and 36.008(1) cm−1) from extrapolated Q(0) line frequencies and to obtain a qualitative picture of Coriolis couplings present in both the ν2 = 0 and ν2 = 1 states.