Coupling a rapid-scan FT-IR spectrometer with quantum cascade

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Coupling a rapid-scan FT-IR spectrometer with quantum cascade lasers within a single setup: an easy way to reach microsecond time resolution without losing spectral information Josefine Schnee, Philippe Bazin, Benoît Barviau, Frederic Grisch, Bruno J. Beccard, and Marco Daturi Anal. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.analchem.8b04621 • Publication Date (Web): 26 Feb 2019 Downloaded from http://pubs.acs.org on February 27, 2019

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Analytical Chemistry

Coupling a rapid-scan FT-IR spectrometer with quantum cascade lasers within a single setup: an easy way to reach microsecond time resolution without losing spectral information Josefine Schnee,1* Philippe Bazin,1 Benoît Barviau,2 Frédéric Grisch,2 Bruno J. Beccard,3 Marco Daturi,1* 1Normandie 2CORIA

Université, ENSICAEN, UNICAEN, CNRS, Laboratoire Catalyse et Spectrochimie, 14000 Caen, France – UMR 6614, Normandie Université, CNRS, INSA et Université de Rouen, Campus Universitaire du Madrillet, 76800 Saint-Etienne du Rouvray, France 3Thermo Fisher Scientific, 16 Avenue du Québec, BP 30210, F – 91941 Courtaboeuf Cedex

*Corresponding authors. E-mail addresses: [email protected], [email protected].

Abstract For the first time, a standard rapid-scan Fourier-transform infrared (FT-IR) spectrometer was coupled with quantum cascade lasers (QCLs) tunable within the 1876 – 905 cm-1 spectral range, within one single setup, by keeping one single sample compartment. The aim was to extend the time resolution of absorption measurements by several orders of magnitude thanks to the fast pulsed QCL technology without losing the spectral information provided by standard FT-IR spectroscopy, both probing the same sample. By slightly modifying the optical bench arrangement, the spectrometer now enables a fast and easy switch between the standard FT-IR mode, used for classical broadband scans from 6000 to 650 cm-1, and the new QCL-irradiation mode, used for ultrafast recording at specific wavenumbers (the two diagnostics have superimposed beam paths). So, one can study a sample (in condensed or gaseous state) during a physical or chemical transformation first as a whole in a broadband configuration, and then immediately switch to the QCL mode to monitor a selected absorption feature (associated to an intermediate, a structural change, a diffusing substance, ... for example) versus time. The QCL mode then drastically boosts the time resolution from tens of milliseconds (in rapid-scan FTIR) to a few microseconds, as demonstrated here in the case of ammonia diffusion into a commercial zeolite ZSM-5.

Keywords: Time-resolved FT-IR spectroscopy; Quantum cascade laser; In situ monitoring; Operando; Kinetics; Uptake curves; Diffusion Infrared (IR) spectroscopy is one of the most important analytical techniques nowadays available. Nearly any sample in nearly any state may be studied.1 An IR spectrum can be seen as the identity card of a solid, liquid or gaseous sample, each absorption band being associated1 to the vibration of a given molecular bond. This is largely exploited among others in the field of biology, for example, to examine the structure and/or dynamics of proteins, or to screen cancer cells and monitor their behavior.2,3,4,5 In contrast to dispersive spectrometers, Fourier-transform infrared (FT-IR) spectrometers are able to measure all wavelengths in the IR beam at the same time, and therefore allow much faster acquisition times/a higher throughput. Moreover, as they do not use diffraction gratings, more energy is available to illuminate the sample and detector, leading to higher signal-to-noise ratios.1,6,7 Nevertheless, as we demonstrate in the present paper, moving from dispersive to FT spectrometers should not be the ultimate step on the evolution scale of IR spectrometers. Indeed, we show that it is

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worth going one step further, namely by combining FT-IR spectrometers with additional well-chosen monochromatic IR sources allowing them to operate also in a single-wavelength mode. The core part of FT-IR spectrometers consists of an interferometer combining a beam splitter and two mirrors, which split and recombine the signal of the light source before sending it through the sample till the detector. One of the mirrors is stationary while the other one is moved at a constant velocity during data acquisition.6,7 To study the kinetics of dynamic phenomena that are not reversible (typically because the material can get modified under working conditions), the interferometer must be handled in the so-called “rapid-scan” mode. The latter consists of moving the mobile mirror in a continuous way, in contrast to the “step-scan” mode which consists of moving the mirror to a fixed position, triggering a reversible phenomenon, recording the evolution of the IR signal as a function of time at that position, then stepping the mirror to the next position, and repeating the procedure.8,9 While in step-scan the time resolution is limited only by the response time of the detector and acquisition electronics (and is also limited to perfectly reproducible phenomena, thus to very stable materials), in rapid-scan, it is achieved via the scan rate, the latter being itself limited by the mechanical movement/physical mass of the scanning mirror.8,10 To overcome the above limitations, extend the fast analysis to non-reproducible phenomena, and boost the time resolution of our standard rapid-scan FT-IR spectrometer, we used quantum cascade lasers (QCLs). Invented in 1994, QCLs are electrically pumped unipolar semiconductor lasers. They emit light through “intersubband” optical transitions, in contrast to bipolar semiconductor lasers being “interband” lasers. As the photon energy resulting from intersubband transitions is independent of the band gap of the material in the active region, it can be tuned by adapting the so-called quantum well thickness.11,12 So, as shown in the present paper, we combined our FT-IR spectrometer with an optical bench containing four QCLs emitting in different (but slightly overlapping) wavenumber ranges within 1876 – 905 cm-1. Within the latter ranges, each of the QCLs was tunable to one single chosen wavenumber. By properly adapting the mirrors arrangement, we enabled the spectrometer to easily switch from the full standard rapid-scan FT-IR to a QCL-irradiation mode tuned to one of the wavenumbers of interest. This is typically of interest when wishing to measure the evolution of one single species among others within an interesting spectral region which contains several molecular/structural fingerprints. Then, we used the QCL-irradiation mode to follow the IR absorbance versus time with a time resolution not achievable with rapid-scan FT-IR, namely depending only on the response time of the detector (here 50 MHz), the QCL pulse rate (settable up to 1 MHz) and the data acquisition system (operating here with a best time resolution of 3 µs, see Experimental section). So, while still providing the whole qualitative and quantitative information for which rapid-scan FT-IR spectrometers are usually used, our QCL – FT-IR combined spectrometer drastically pushes the limits in monitoring dynamic phenomena at an unprecedented time resolution (for a spectrometer initially designed for rapid-scan FT-IR), and with a very large operating flexibility. Compared to another recently presented spectrometer based on dual-frequency-comb spectroscopy using mid-IR frequency combs generated by QCLs (not being coupled to any other system), which allows recording absorption spectra covering 55 cm-1 in the fingerprint region of proteins with a spectral resolution of 0.3 cm-1 and submicrosecond time resolution,13 the advantages of the present QCL – FT-IR combined spectrometer are 1) the possibility to acquire spectra over a significantly broader range of wavenumbers (6000 – 650 cm1), and 2) the fact that our spectrometer is based on a standard model already widely available in the community of analytical chemists, and which is very easy to upgrade with the QCLs. On the other hand, the dual-frequency-comb spectrometer provides particularly high spectral and temporal resolutions,


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simultaneously, but only in a narrow range of wavenumbers, therefore restraining its use for specific targets. So, the two approaches are somehow complementary. In the present paper, we validate the new QCL – FT-IR combined setup, and demonstrate its superior performance in monitoring dynamic phenomena compared to standard FT-IR spectrometers, by taking the example of the diffusion of gaseous ammonia into the protonated Zeolite Socony Mobil-5 (H-ZSM-5, commercially available). Zeolites are microporous aluminosilicate minerals with a threedimensional framework. They are commonly used as catalysts and adsorbents, in particular to take up gaseous ammonia that is emitted14 from livestock operations and fertilizer production and can harm15 living organisms.

Experimental section Setting-up of the new spectrometer. The four QCLs were provided by Daylight Solutions Inc. (San Diego, USA) within a single MIRcat-QT system which was incorporated into a Thermo Scientific iS50 Research Module (left hand side annex bench on Figure 1). The QCLs had respectively a spectral tuning range from 1876.2 to 1675.0 cm-1, 1736.1 to 1310.6 cm-1, 1459.9 to 1175.1 cm-1 and 1225.5 to 905.0 cm-1. The associated spot size and wavelength accuracy were respectively < 2.5 mm and ≤ 1 cm-1. The linewidth was ≤ 1 cm-1 (FWHM). The laser beams were directed to the sample compartment of the FTIR spectrometer (Thermo Scientific Nicolet iS50) through the latter but without crossing the interferometer, as shown in the central part of Figure 1. The lasers were pulsed instead of continuously emitting, in order to avoid locally laser-induced sample heating. The spectrometer was equipped with a 50 MHz mercury cadmium telluride (MCT) cryo-detector suitable for both rapid-scan FT-IR analysis and QCL-time-resolved absorbance diagnostic. The data acquisition system for the QCL mode was provided by STYREL Technologies, partner of National Instruments (NI). It consisted of a NI PXIe-1073 chassis and a PXIe-5122 high resolution oscilloscope card (100 MHz bandwidth) controlled through a PCIe interface integrated within a Ci5 mini-PC configuration, as well as of a custom-made LabVIEW application. The LabVIEW application was designed in such a way that the data acquisition was triggered at each laser pulse (width of 300 ns here). So, the time resolution in our experiments corresponded to the time in-between two successive laser pulses. As the pulse rate was settable up to 1 MHz, corresponding to a time in-between two successive pulses of 1 µs, the best achievable time resolution was theoretically 1 µs. Although this time resolution agreed with the acquisition time (also typically 1 µs, as explained below), it was hindered by the acquisition trigger re-arm time of 3 µs. Due to this re-arm time, the best achievable time resolution became 4 µs (acquisition time of 1 µs + acquisition trigger re-arm time of 3 µs). So, although the laser pulse rate could have been set as high as 1 MHz, the bottle neck of our system were the electronics, making it senseless to use pulse rates above 250000 Hz (thus times in-between two successive pulses below 4 µs). Regarding the data acquisition in itself, the signal voltage (V) curve of each pulse took 1 µs to be measured as it consisted of 100 records acquired at 100 MHz (highest possible sampling rate achievable with our system). The number of records was chosen to enclose the whole signal increase and decrease (see scheme on Supplementary Figure 1). The data treatment then consisted of calculating the amplitude (= maximum – minimum) of each signal curve, and of exporting the values to a text file vs time. So, each laser pulse corresponded to one line in the text file (with the time in the first column, and the “max – min” of the recorded signal curve in the second column), and the difference in time from one line to another in the text file corresponded to the time resolution in the experiment. Notice that the data acquisition and data treatment corresponded to two parallelized functions in the LabVIEW code, so that the data 3 ACS Paragon Plus Environment


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treatment could be initiated separately from the data acquisition. This was done to avoid unwanted delays in the data acquisition. A circular buffer was used to overcome memory limitations. Furthermore, after a desired acquisition time (thus after having already recorded the signal of a desired number of pulses), the application allowed triggering the introduction of a probe molecule into the IR cell through an external device, namely an automatic fast pneumatic valve (provided by VAT as “Fast closing valve Series 75”) positioned at the entrance of the cell. The latter function was also available from a separate LabVIEW box independent of the main application in order to be able to open and close the valve even when the MIRcat was off, namely in standard FT-IR experiments (as the application cannot start without laser input). In the presence of a probe molecule in the IR cell, the absorbance of the QCL beam was always calculated following Equation 1. “Amplitude under probe molecule” means the amplitude of the IR signal as measured when the probe was inside the volume of the cell. “Amplitude under vacuum” means the amplitude of the signal when the analysis cell was under vacuum. Equation 1


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Figure 1. Picture of the Thermo Scientific Nicolet iS50 FT-IR spectrometer coupled with the MIRcat-QT system. In (a), the setup works in the standard FT-IR mode. The MIRcat is off, whereas the standard IR source is on. In (b), the setup works in the QCL-irradiation mode. The MIRcat is on, whereas the standard IR source is off. In both (a) and (b), the respectively orange and green lines represent the pathway of the IR beam from the source till the detector. To make the IR beam reach the annex bench for gas analysis instead of the sample compartment of the spectrometer, the mobile mirror marked with “5” must be moved to the right into the beam pathway. In (b), the laser beam does not cross the interferometer. Its first reflection within the spectrometer is ensured by a small mirror of about 0.5 cm diameter, namely small enough to not disturb when the setup works in the standard FT-IR mode.

Diffusion tests. The ZSM-5 samples (CBV 8014 from Zeolyst International, Si/Al = 40) were pressed into a self-supported disc (2 cm2 area, 10 mg cm-2). The resulting pellets were placed into a homemade IR cell equipped with KBr windows and a heating system, and positioned in the sample compartment of the spectrometer. Before experiment, to get converted from their ammoniated to protonated form (respectively NH4-ZSM-5 to H-ZSM-5), the samples were pre-treated16 in situ in the cell at 450 °C for 6 hours under vacuum (10-6 Torr). A 1 °C min-1 ramp was used to heat from room temperature to 450 °C. To check whether the transformation proceeded well, an FT-IR spectrum (400 – 4000 cm-1 range) was 5 ACS Paragon Plus Environment


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measured before and after the pre-treatment (128 scans, 4 cm-1 resolution, 1.89 cm s-1 scan rate). The identity of the H-ZSM-5 samples was reflected by the presence of two bands at 3740 cm-1 and 3610 cm-1 respectively associated to Si-OH and Si-OH-Al groups, and by the absence of the band at 1435 cm-1 associated to NH4+ ions.16 Typically, a diffusion test was launched by 1) closing the IR cell (still under vacuum at 10-6 Torr since the pre-treatment), i.e. closing the fast pneumatic valve fixed at the entrance, 2) equilibrating a given pressure of ammonia upstream the latter valve, and 3) opening the valve while acquiring data, in other words triggering the entrance of ammonia into the IR cell. Such tests were performed not only in the presence of a sample in the IR cell but also with the empty cell. In the presence of a sample, the IR band of interest was that at 1435 cm-1 characteristic of surface NH4+ ions17 appearing along with the diffusion of ammonia through H-ZSM-5. In the absence of zeolitic sample, the IR band at 929 cm-1 was followed, namely one of the bands characteristic of gaseous ammonia. This allowed among others checking that the time needed for ammonia to diffuse into the IR cell was negligible compared to the time of diffusion into H-ZSM-5. In the rapid-scan FT-IR mode, the data acquisition consisted of measuring spectra continuously and as rapidly as possible (1 “optimized” scan, 32 cm-1 resolution, 6.32 cm s-1 scan rate) from the start to the end of the experiment. It was launched through the “series” option in the Thermo Scientific OMNIC software, always a few seconds before the valve at the entrance of the IR cell was opened. Afterwards, the whole series of spectra was processed using the same background measured before experiment (in the presence or not of a sample, depending on the type of experiment). Choice of the current to apply to the QCLs. In order to get a measurable IR absorbance upon performing the diffusion tests under ammonia in the QCL mode, the current (mA) applied to the QCLs had to be properly selected. At the wavenumbers of interest (929 and 1435 cm-1), the QCL signal voltage (V) was measured under vacuum (10-6 Torr) at room temperature over 20 seconds with different values of current applied. The resulting mean amplitudes were plotted against the current (Supplementary Figure 2). After a steep initial increase within a narrow range of currents (700 to 740 mA at 929 cm-1, Supplementary Figure 2a; 260 to 300 mA at 1435 cm-1, Supplementary Figure 2b), the signal amplitude reached a plateau. As the diffusion of ammonia into the empty cell (initially under vacuum, 10-6 Torr) was followed at 929 cm-1 with currents within the plateau (750 to 950 mA on Supplementary Figure 2a), nearly no absorbance of the QCL beam was measured. With currents comprised within the increasing region, absorbance values always around 0.9 were obtained, with a level of noise increasing with decreasing current (see examples on Supplementary Figure 3). Actually, the best signal was measured at 740 mA (Supplementary Figure 3c), so just before the plateau started on Supplementary Figure 2a. Based on this, the diffusion tests through H-ZSM-5 for which the QCL was tuned to 1435 cm-1 were also performed with a current just before start of the plateau on Supplementary Figure 2b, namely 300 mA.

Results and Discussion Validation of the new spectrometer. To prove the relevance of our QCL-acquired data, we first monitored phenomena which were slow enough to get properly time-resolved through both standard rapid-scan FT-IR and QCL diagnostics. For example, as observed by following the IR band at 1435 cm-1 characteristic17 of surface NH4+ ions, the diffusion of ammonia (1.5 Torr) into H-ZSM-5 took 4 s at 350 °C. As shown on Figure 2a, this was slow enough for rapid-scan FT-IR to yield the full ammonia uptake curve, provided that it was performed in the fastest possible conditions (1 “optimized” scan, 32 cm-1 resolution, 6.32 cm s-1 scan rate). This uptake curve (20 ms time resolution) then overlapped with the 6 ACS Paragon Plus Environment

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corresponding QCL-measured one (50 kHz pulse rate, leading to 20 µs time resolution), thereby validating our QCL mode. Actually, as shown on Figure 2b, the curve followed the well-known Fickian model for intracrystalline diffusion,18,19,20 with an effective diffusivity (De) of 8.5 10-11 cm² s-1.

Figure 2. (a) IR absorbance at 1435 cm-1 through QCL diagnostic (left axis) and standard rapid-scan FT-IR spectroscopy (right axis) as a function of time upon diffusion of ammonia (1.5 Torr) into H-ZSM-5 at 350 °C. (b) Comparison of the QCLmeasured absorbance curve with the Fickian model for intracrystalline diffusion, fitted with an effective diffusivity (De) of 8.5 10-11 cm² s-1. Mt is the total amount of ammonia within the sample at a time t; Meq is the corresponding amount at equilibrium.

Performance of the new spectrometer. To illustrate the superior capability of our QCL – FT-IR combined setup compared to standard rapid-scan FT-IR spectrometers, we performed further ammonia diffusion tests through the same zeolite at pressures higher than 1.5 Torr. Figure 3 compares some of the observed uptake curves (at 8, 60, 80 and 110 Torr) in the FT-IR versus QCL modes. Already at 8 Torr (Figure 3a), the uptake curves do no longer match with the Fickian model for intracrystalline diffusion. Indeed, equilibrium is reached after only 700 ms (versus 4 s at 1.5 Torr), what reflects20 that the effective diffusivity is now concentration-dependent. More precisely, it increases with the concentration, while it remained constant at 1.5 Torr, as required by Fick’s model. Nevertheless, the uptake still remains slow enough to get properly time-resolved through rapid-scan FT-IR spectroscopy. In contrast, at 60 Torr (Figure 3b), when the uptake is as fast as 100 ms, FT-IR resolves the whole curve only through 6 points, what is insufficient to be reliable. Then, at 80 and 110 Torr (Figures 3c and 3d), when the uptake takes only 75 and 60 ms, respectively, FT-IR truly misses information. In contrast to the QCL mode, it catches only the slowest period of the uptake, namely the end. It does no longer allow observing the initial period. However, this period here reflects an important change in the uptake kinetics, namely a change in the initial rate-limiting step. Indeed, as shown through the QCL mode (20 µs time resolution, sufficient here), the initial slope becomes linear exactly as upon ammonia diffusion into the empty cell (see Supplementary Figure 3). This reflects that the intracrystalline diffusion becomes so fast that the transport from the outer gas phase towards the crystals takes over as the rate-limiting step.21 In a later stage of the uptake, the situation then reverses again, as reflected by the slow tailing of the uptake curves. Indeed, as the concentration gradient within the crystals decreases, the intracrystalline diffusion slows down again, finally becoming slower again than the intercrystalline diffusion.21



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Figure 3. IR absorbance at 1435 cm-1 through QCL diagnostic (left axis) and standard rapid-scan FT-IR spectroscopy (right axis) as a function of time upon diffusion of 8 Torr (a), 60 Torr (b), 80 Torr (c) and 110 Torr (d) of ammonia into H-ZSM-5 at 350 °C.

Conclusions We developed a new kind of rapid-scan FT-IR spectrometer which for the first time combines the standard working mode with an additional one consisting of irradiating the sample through QCLs at selected wavenumbers. This spectrometer is easily flexible and reproducible, can monitor both samples in condensed and gaseous states, and reaches an unprecedented time resolution (for a spectrometer that was initially designed for rapid-scan FT-IR) upon monitoring dynamic phenomena, namely a few microseconds. Of course, the detection region can be extended below and above the tested 1876 – 905 cm-1 interval by implementing different QCL lasers when eventually available. Performing FT-IR spectroscopy and QCL absorbance diagnostic within a single setup rather than separately from each other has the advantage of allowing to establish truly accurate relationships between the spectral information provided by FT-IR over a wide range of wavenumbers (6000 to 650 cm-1) and the temporal information provided by the quantum cascade laser diagnostic at a specific wavenumber. Indeed, both techniques are applied in exactly the same operating conditions, thanks to a fast and easy switch from the one to the other. We demonstrated the reliability and superior performance of the new device compared to conventional FT-IR spectrometers through the measurement of kinetic uptake curves of ammonia by a zeolite H-ZSM-5. In this case study, we showed that our spectrometer was able to measure a change in the rate-limiting step which is crucial to be considered in order to fully understand and optimize the process, but was impossible to observe with a standard rapid-scan FT-IR spectrometer. This opens the way to a better understanding of fast dynamic phenomena in general (e.g formation of reaction intermediates, drugs delivery in living organisms, protein conformational changes, ligand binding to proteins, etc.), whatever the field of application, and notably when operando monitoring catalytic phenomena.22,23 In particular, there might be applications in which the QCLs could be used both to monitor the chemical events (as in the present work) and to trigger them. The availability of FT-IR 8 ACS Paragon Plus Environment

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within the same setup would then allow directly correlating the time-resolved curves obtained through the QCL absorbance diagnostic with the spectral changes occurring due to the same chemical events.

References 1. Stuart, B. Infrared Spectroscopy: Fundamentals and Applications; Wiley, 2004. 2. Baker, M. J.; Trevisan, J.; Bassan, P.; Bhargava, R.; Butler, H. J.; Dorling, K. M.; Fielden, P. R.; Fogarty, S. W.; Fullwood, N. J.; Heys, K. A.; Hughes, C.; Lasch, P.; Martin-Hirsch, P. L.; Obinaju, B.; Sockalingum, G. D.; Sulé-Suso, J.; Strong, R. J.; Walsh, M. J.; Wood, B. R.; Gardner, P.; Martin, F. L. Using Fourier transform IR spectroscopy to analyze biological materials. Nat. Protoc. 2014, 9 (8), 1771-1791. 3. Slayton, R. M.; Anfinrud, P. A. Time-resolved mid-infrared spectroscopy: methods and biological applications. Curr. Opin. Struct. Biol. 1997, 7 (5), 717-721. 4. Lee, S. Y.; Yoon, K.-A.; Jang, S. H.; Ganbold, E. O.; Uuriintuya, D.; Shin, S.-M.; Ryu, P. D.; Joo, S.-W. Infrared spectroscopy characterization of normal and lung cancer cells originated from epithelium. J. Vet. Sci. 2009, 10 (4), 299-304. 5. Schwaighofer, A.; Alcaráz, M. R.; Araman, C.; Goicoechea, H.; Lendl, B. External cavityquantum cascade laser infrared spectroscopy for secondary structure analysis of proteins at low concentrations. Sci. Rep. 2016, 6, 33556. 6. Blum, M. M.; John, H. Historical perspective and modern applications of Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR). Drug Test. Anal. 2012, 4 (3-4), 298302. 7. Griffiths, P. R.; De Haseth, J. A. Fourier transform infrared spectrometry; Wiley, 2007. 8. Johnson, T. J.; Simon, A.; Weil, J. M.; Harris, G. W. Applications of Time-Resolved Step-Scan and Rapid-Scan FT-IR Spectroscopy: Dynamics from Ten Seconds to Ten Nanoseconds. Appl. Spectrosc. 1993, 47 (9), 1376-1381. 9. Thibault-Starzyk, F.; Seguin, E.; Thomas, S.; Daturi, M.; Arnolds, H.; King, D. A. Real-Time Infrared Detection of Cyanide Flip on Silver-Alumina NOx Removal Catalyst. Science 2009, 324 (5930), 1048-1051. 10. Wasylenko, W.; Frei, H. Direct Observation of Surface Ethyl to Ethane Interconversion upon C2H4 Hydrogenation over Pt/Al2O3 Catalyst by Time-Resolved FT-IR Spectroscopy. J. Phys. Chem. B 2005, 109 (35), 16873-16878. 11. Waried, H. H. Synchronization of quantum cascade lasers with mutual optoelectronic coupling. Chinese J. Phys. 2018, 56 (3), 1113-1120. 12. Tittel, F. K.; Bakhirkin, Y.; Kosterev, A. A.; Wysocki, G. Recent Advances in Trace Gas Detection Using Quantum and Interband Cascade Lasers. Rev Laser Eng 2006, 34 (4), 275-282. 13. Klocke, J. L.; Mangold, M.; Allmendinger, P.; Hugi, A.; Geiser, M.; Jouy, P.; Faist, J.; Kottke, T. Single-Shot Sub-microsecond Mid-infrared Spectroscopy on Protein Reactions with Quantum Cascade Laser Frequency Combs. Anal. Chem. 2018, 90 (17), 10494-10500. 14. Ro, K. S.; Lima, I. M.; Reddy, G. B.; Jackson, M. A.; Gao, B. Removing Gaseous NH3 Using Biochar as an Adsorbent. Agriculture 2015, 5, 991-1002. 15. Zhou, L.; Boyd, C. E. Total ammonia nitrogen removal from aqueous solutions by the natural zeolite, mordenite: A laboratory test and experimental study. Aquaculture 2014, 432, 252-257. 16. Sadowska, K.; Góra-Marek, K.; Datka, J. Hierarchic zeolites studied by IR spectroscopy: Acid properties of zeolite ZSM-5 desilicated with NaOH and NaOH/tetrabutylamine hydroxide. Vib. Spectrosc 2012, 63, 418-425. 17. Rasmussen, S. B.; Portela, R.; Bazin, P.; Ávila, P.; Bañares, M. A.; Daturi, M. Transient operando study on the NH3/NH4+ interplay in V-SCR monolithic catalysts. Appl. Catal., B 2018, 224, 109-115.



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18. Möller, A.; Pessoa Guimaraes, A.; Gläser, R.; Staudt, R. Uptake-curves for the determination of diffusion coefficients and sorption equilibria for n-alkanes on zeolites. Microporous and Mesoporous Mater. 2009, 125 (1), 23-29. 19. Forni, L.; Magni, E. Temperature-programmed desorption study of ammonia desorptiondiffusion in molecular sieves: I. Theory. J. Catal. 1988, 112 (2), 437-443. 20. Xiao, J.; Wei, J. Diffusion mechanism of hydrocarbons in zeolites—II. Analysis of experimental observations. Chem. Eng. Sci. 1992, 47 (5), 1143-1159. 21. Schumacher, R.; Lorenz, P.; Karge, H. G. On the sorption of ethylbenzene in ZSM-5. Stud. Surf. Sci. Catal. 1997, 105, 1747-1754. 22. Vimont, A.; Thibault-Starzyk, F.; Daturi, M. Analysing and understanding the active site by IR spectroscopy. Chem. Soc. Rev. 2010, 39 (12), 4928-4950. 23. Bañares, M. A. Operando methodology: combination of in situ spectroscopy and simultaneous activity measurements under catalytic reaction conditions. Catal. Today 2005, 100 (12), 71-77.

Acknowledgements The present project was cofunded by the LabEx EMC3 via the contract “DRUID” and by the European Union in the frame of the operational program FEDER/FSE 2014-2020. The authors acknowledge Yoann Levaque (Laboratoire Catalyse et Spectrochimie, Université de Caen, France) for his technical support, and Dr. Vladimir L. Zholobenko (Keele University, England) for providing the ZSM-5 batch.

Author contributions P.B. and M.D. conceived the project and, with the help of B.J.B., modified the spectrometer so that it was operational in combination with the QCLs; J.S. designed and performed the experimental studies and wrote the manuscript; B.B. and F.G. provided scientific and technical support regarding the QCLs and helped setting up the data acquisition and treatment system for the QCL mode. All authors discussed the results and commented on the manuscript.

Competing interests The authors declare no competing interests.

Supporting Information. A scheme describing the data acquisition system, and some chosen results of experiments performed to properly set the QCL parameters.

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Coupling a rapid-scan FT-IR spectrometer with quantum cascade

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