Fourier-transform Spectroscopy Research Articles

Gas-phase Conformational Landscape and Ring-puckered Structure of 1-aminoindane.

Indane-based molecules are effective scaffolds for different pharmaceutical products, so it is relevant to analyze the relation between structure and functionality in indane derivatives. Here, we have characterized the conformational landscape and molecular structure of 1-aminoindane in the gas phase using chirped-excitation Fourier-transform microwave spectroscopy and computational methods. The rotational spectrum confirmed the presence of two conformers, which were identified based on their rotational constants and 14N nuclear quadrupole coupling tensor elements. The observed conformers share the cyclopentane puckering and amino equatorial configuration but differ in the orientation of the amino group hydrogens. The spectral analysis further allowed the observation of all monosubstituted 13C and 15 N isotopologues in natural abundance for the most stable isomer, allowing a precise structural determination for this species. Structural information was derived using the substitution ( ) and effective vibrational ground state ( ) methods, revealing that the structure of 1-aminoindane is very similar to that of indane. A calculation of the potential energy surface along the pathway for the conversion between the most stable equatorial species permitted to rationalize the non-observation of additional conformers via molecular relaxation during the adiabatic expansion. The computational results include ab initio (MP2) and DFT methods (B3LYP, ωB97X-D and M06-2X).

The Effect of Zeolite Na-X and Clinoptilolite as Functional Fillers on the Mechanical, Thermal and Barrier Properties of Thermoplastic Polyurethane.

To obtain sustainable food packaging materials, alternatives to traditional ones must be researched. In this work, two different kinds of zeolites, i.e., a natural one, Clinoptilolite, and a synthetic one, Zeolite Na-X, were mixed with thermoplastic polyurethane for the fabrication of composites. Composite films were prepared via a hot mixing stage and then by means of a hot compression molding process. Several TPU/zeolite composites were produced with a filler concentration ranging from 5% to 10%wt. Finally, the obtained films were characterized by Fourier Transform Spectroscopy (FT-IR, ATR), thermal analysis (TGA and DSC), frequency sweep test, scanning electron microscopy (SEM), mechanical tensile test and oxygen permeability test. For both fillers and at all concentrations, the inclusion of zeolites significantly influenced the analyzed properties. In the TPU/zeolite composites, an overall enhancement was observed compared to the neat polymer, attributed to improved processability, superior barrier properties and the potential to create active materials by loading zeolite combined with various chemicals for specific applications. These findings suggest that the resulting composites hold considerable promise for applications in the food packaging sector.

Broadband coherent Fourier scatterometry: A two-pulse approach.

We demonstrate a broadband implementation of coherent Fourier scatterometry (CFS) using a supercontinuum source. Spectral information can be resolved by splitting the incident field into two pulses with a variable delay and interfering them at the detector after interaction with the sample, bearing similarities with Fourier-transform spectroscopy. By varying the time delay between the pulses, a collection of diffraction patterns is captured in the Fourier plane, thereby obtaining an interferogram for every camera pixel. Spectrally resolved diffraction patterns can then be retrieved with a per-pixel Fourier transform as a function of the delay. We show the physical principle that motivates the two-pulse approach, the experimental realization, and results for a silicon line grating. The presented implementation using a supercontinuum source offers a cost-effective way to acquire multi-wavelength CFS data over a wide wavelength range, with the potential to improve reconstruction robustness and sensitivity in applications such as dimensional metrology.

Symmetric Non-Monochromatic Light as Reference in Fourier Transform Spectrometers.

Fourier transform spectrometers typically use a presumed monochromatic reference source to track and correct errors in optical path difference changes. This paper will conduct a theoretical analysis to show that non-monochromatic light sources with symmetric spectral profiles can also be used as reference sources without adding errors. An experiment was carried out using a symmetric broadband superluminescent diode (SLED) as reference light to measure the spectrum of some other SLED light sources to experimentally demonstrate this finding.

Investigation of Sn Promoter on Ni/CeO2 Catalysts for Enhanced Acetylene Semihydrogenation to Ethylene.

Ethylene, as an important chemical raw material, could be produced through the coal-based acetylene hydrogenation route. Nickel-based catalysts demonstrate significant activity in the semihydrogenation reaction of acetylene, but they encounter challenges related to catalyst deactivation and overhydrogenation. Herein, the effect of Sn promoter on Ni/CeO2 catalysts has been comprehensively explored for acetylene semihydrogenation. The optimized Ni/8%Sn-CeO2 catalytic performance was significantly improved, with 100% acetylene conversion and 82.5% ethylene selectivity at 250 °C, and the catalyst maintained high catalyst performance within a 1000 min stability test. A series of characterization tests show that CeO2 modified by moderate Sn4+ doping is more conducive to modulating the charge structure and geometry of the Ni active center. Additionally, the in situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy and density functional theory results indicated that catalysts doped with Sn4+ facilitated more efficient desorption of ethylene from the catalyst surface compared to Ni/CeO2 catalysts, thus improving ethylene selectivity and yield. This study highlights an effective strategy for improving the catalytic performance of rare-earth-based catalysts through the incorporation of effective metal promoters.

In-situ analysis of methane plasmas with mid-infrared supercontinuum-based Fourier-transform spectroscopy

The conversion of methane (CH4) into the hydrocarbons ethane (C2H6) and acetylene (C2H2) in plasma is investigated in the first in-situ study using a mid-infrared supercontinuum source and a Fourier transform spectrometer. Due to the spatial coherence of the supercontinuum source, it is possible to probe the plasma over a path length of 3.5 m and observe CH4, C2H6, and C2H2 with concentrations below percent level at a few mbar pressure. The broad spectral range of the supercontinuum source (1.4–4.1 μm) covers entire rovibrational bands of molecules, allowing simultaneous detection of the rotational and vibrational temperature of CH4 and C2H2. The ability to study these experimental parameters in situ opens new possibilities for understanding and optimizing plasma-based chemical conversions.

Derivation of the carbon dioxide total column in the atmosphere from satellite-based infrared fourier-transform spectrometer IKFS–2 measurements: analysis and application experience

The paper discusses the use of a new version of the regression technique for derivation the total content of carbon dioxide in the atmosphere XCO2 (column-averaged dry-air mole fraction) from measurements of the infrared Fourier-transform spectrometer IKFS–2 installed on board Russian meteorological satellite Meteor-M No. 2. To evaluate the accuracy of satellite-based XCO2 estimates the retrospective comparison was made with data from ground-based spectroscopic measurements at Peterhof site of St. Petersburg State University as well as with aircraft measurements of the V. E. Zuev Institute of Atmospheric Optics (IOA) in the area of the Novosibirsk Reservoir conducted in 2019-2022. A brief description of the regression technique modifications is given made to improve the accuracy of satellite – based XCO2 estimates. In particular, to compensate for the effect of changes in the IKFS-2 characteristics during a long flight, the XCO2 estimates calibration is realized using ground - based XCO2 measurements at the NOAA Observatory on Mauna Loa volcano (island of Hawaii). After calibration and cloud scenes filtering, the discrepancy between satellite estimates and ground-based / aircraft measurements is characterized by root mean square deviation of ~4 ppm or 1% of the CO2 total content. In order to accelerate the adjustment of the regression technique, used for estimating XCO2, to IKFS-2 data on new satellites, it is reasonable to use XCO2 observations at the TCCON terrestrial network in addition to conventional contact measurements of CO2 concentrations. Along with this, it seems rational to use the cryogenic film thickness on the glass of the IKFS-2 photodetector, characterizing the state of the instrument, as additional predictor in the regression model.

Hydrogen Production from Formic Acid Using KIT-6 Supported Non-NobleMetal-Based Catalysts.

The aim of this study is to investigate the activity of KIT-6 supported nickel (Ni) and cobalt (Co) catalysts, and the effect of Co incorporation to the Ni@KIT-6 catalyst in the formic acid (FA) dehydrogenation. Ni and Co are inexpensive and readily available non-noble transition metals that are considered ideal for dehydrogenation reactions due to their high activity against C-C and C-H bond breaking. In this study, KIT-6 supported catalysts were tested for hydrogen production from FA in a conventionally heated packed-bed continuous-flow system. N2 adsorption-desorption isotherms of the samples were found to be consistent with Type-IV according to the International Union of Pure and Applied Chemistry (IUPAC) classification. The introduction of metal loading resulted in the preservation of the mesoporous structure of the support material. X-ray diffraction (XRD) patterns of the catalysts exhibited the characteristic amorphous silica structure. Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFT) analysis, Lewis acidity of Co-based catalysts was found to be higher than the Ni-based catalysts. The complete formic acid conversion was observed at 200-350 °C. The highest H2 selectivity was obtained with the 3Ni@KIT-6 catalyst. The Co-based catalysts exhibited relatively lower catalytic activity, which was linked to increased coke formation within these catalysts.

Highly efficient CO2 capture on acid-treated sepiolite impregnated with mixed polyethyleneimine and diethanolamine

Amine-functionalized solid adsorbents exhibit broad prospects in CO2 capture from flue gases due to their high adsorption capacity and selectivity. However, reported adsorbents are still facing challenges, including high costs, the easy agglomeration of polyamines, and limited adsorption temperature ranges. In this study, sepiolite-based mixed amine adsorbents are prepared by synergistically impregnating acid-treated sepiolite with a mixture of polyethyleneimine (PEI) and diethanolamine (DEA). Results show that at a PEI/DEA loading ratio of 1:1 and a mixture loading of 60wt%, the CO2 adsorption capacity of the resulting adsorbent increases from 0.58mmol/g for acid-treated sepiolite to 2.89mmol/g at 60°C, and remains above 2.50mmol/g after 10 cycles. Meanwhile, the optimized adsorbent maintains a capacity of over 2.44mmol/g within the temperature range of 30–70°C. Additionally, the CO2 selectivity and maximum heat of adsorption for the optimized adsorbent are calculated to be 1184 and 60.08kJ/mol, respectively. An improved CO2 adsorption capacity is obtained, an increase from 0.052mmol/g for acid-treated sepiolite to 1.60mmol/g. Furthermore, an in-situ diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS) analysis reveals that the introduction of DEA into PEI helps in polyamine dispersion, thereby enhancing CO2 adsorption capacity. The CO2 capture mechanism follows a zwitterionic reaction, where CO2 is ultimately converted into carbamate and carbamic acid. Overall, the as-prepared sepiolite-based mixed amine adsorbents, which are characterized by high CO2 adsorption capacity and selectivity, low cost, broad adsorption temperature range, moderate heat of adsorption, and good cycle stability, show promising potential for industrial applications.

Nondestructive Control of Macrolides in Tableted Pharmaceuticals Using Near-IR Fourier-Transform Spectrometry and Digital Colorimetry

Nondestructive Control of Macrolides in Tableted Pharmaceuticals Using Near-IR Fourier-Transform Spectrometry and Digital Colorimetry

Sodium cation exchanged zeolites for direct air capture of CO2

Direct air capture technology requires investigating materials that can capture carbon dioxide inexpensively and efficiently, considering their performance under real atmospheric conditions. This study systematically investigated the CO2 adsorption-desorption performance of the representative zeolites (ZSM-5, Beta, Mordenite and Y) in H- and Na-forms using various analytical methods, including in-situ Diffuse Reflectance Infrared Fourier Transform spectroscopy. Compared to the corresponding H-zeolites, the enhancement of CO2 adsorption capacity by Na+ ions was observed for all the structure-type zeolite adsorbents. The Na-ZSM-5 showed excellent performance in the direct air capture of CO2 (DAC) due to its relatively smaller pore size and stronger acid-basic properties. The effective adsorption capacity of Na-ZSM-5 was pronounced at lower Si/Al ratios, making it the most efficient low-concentration CO2 adsorbent. The low silica Na-ZSM-5 exhibited a durable adsorption-desorption capacity after multiple cycles, indicating its practical reusability. When applied to real atmospheric air conditions, this low silica Na-ZSM-5 effectively adsorbed CO2 in the presence of oxygen and moisture, emphasizing its potential for a direct air capture adsorbent. This study provides insights into the properties of zeolites for CO2 capture from air, highlighting their potential as effective DAC sorbents that can be produced on a large scale.

Facile synthesis of CuCo2O4@CdS nanoheterostructure for asymmetric supercapacitor

The abundant active sites, high theoretical capacitance, and cost-effective synthesis of transition metal oxides@sulfides (TMOs@TMSs) have made them a highly desirable choice as active electrode materials for supercapacitors. This study demonstrated the successful fabrication of a CuCo2O4@CdS nanoheterostructure electrode using a simple and economical co-precipitation method The morphology, physicochemical properties, and electrochemical behavior of this electrode were subsequently studied. The synthesized CuCo2O4@CdS nanoheterostructure was characterized using Infrared Fourier-transform spectroscopy, X-ray diffraction, Raman spectroscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, High-resolution transmission electron microscopy, N2 adsorption/desorption isotherms and atomic force microscopy. The electrochemical performance was studied using cyclic voltammetry, impedance spectroscopy, and galvanostatic charge-discharge (GCD) measurements with a 6 Molar KOH aqueous electrolytic solution. Results from powder X-ray diffraction pattern and energy dispersive X-ray revealed the formation of CuCo2O4@CdS nanoheterostructure. Furthermore, SEM images showed the formation of more spherical structures in nanoheterostructure. The results of optical measurements of thin films were analyzed, which showed an increase in the energy gap (Eg) of CuCo2O4 nanoparticles when combined with cadmium sulfide (CdS). Additionally, the intensity of photoluminescence of the CuCo2O4@CdS nanoheterostructure was lower compared to the pure nanoparticles. Moreover, the newly synthesized CuCo2O4@CdS nanoheterostructure showed a specific capacitance of 257.5 F g−1 at a current density of 0.5 A g−1 via a three-electrode galvanostatic charge-discharge system, respectively. In the asymmetric device, the supercapacitor yielded an optimum energy density and power density of 19.6 Wh kg−1 and 700 W kg−1 at 1 A g−1 current density, respectively. Although the capacitance retention was maintained at nearly 85.2 % after 4000 cycles at a current density of 3 A g−1.

Very low Ru loadings boosting performance of Ni-based dual-function materials during the integrated CO2 capture and methanation process

Herein, the effect of the Ru:Ni bimetallic composition in dual-function materials (DFMs) for the integrated CO2 capture and methanation process (ICCU-Methanation) is systematically evaluated and combined with a thorough material characterization, as well as a mechanistic (in-situ diffuse reflectance infrared fourier-transform spectroscopy (in-situ DRIFTS)) and computational (computational fluid dynamics (CFD) modelling) investigation, in order to improve the performance of Ni-based DFMs. The bimetallic DFMs are comprised of a main Ni active metallic phase (20 wt%) and are modified with low Ru loadings in the 0.1–1 wt% range (to keep the material cost low), supported on Na2O/Al2O3. It is shown that the addition of even a very low Ru loading (0.1–0.2 wt%) can drastically improve the material reducibility, exposing a significantly higher amount of surface-active metallic sites, with Ru being highly dispersed over the support and the Ni phase, while also forming some small Ru particles. This manifests in a significant enhancement in the CH4 yield and the CH4 production kinetics during ICCU-Methanation (which mainly proceeds via formate intermediates), with 0.2 wt% Ru addition leading to the best results. This bimetallic DFM also shows high stability and a relatively good performance under an oxidizing CO2 capture atmosphere. The formation rate of CH4 during hydrogenation is then further validated via CFD modelling and the developed model is subsequently applied in the prediction of the effect of other parameters, including the inlet H2 concentration, inlet flow rate, dual-function material weight, and reactor internal diameter.

Humic Substances from Waste-Based Fertilizers for Improved Soil Fertility

This research explores how different organic waste transformation methods influence the production of humic substances (HSs) and their impact on soil quality. Using olive and orange wastes as substrates, the study compares vermicomposting, composting, and anaerobic digestion processes to determine which method produces the most humic-substance-rich products. The characterization of HSs in each product included analyses of total organic carbon (TOC), humic and fulvic acid content, humification rate, humification degree, and E4/E6 ratio, with HSs extracted using potassium hydroxide (KOH) and analyzed via Diffuse Reflectance Infrared Fourier-Transform (DRIFT) spectroscopy to assess structural complexity. The results revealed that the chemical composition of the input materials significantly influenced the transformation dynamics, with orange by-products exhibiting a higher humification rate and degree. Vermicomposting emerged as the most efficient process, producing fertilizers with superior humic content, greater microbial biodiversity, and enhanced cation exchange capacity, thus markedly improving soil quality. Composting also contributed to the stabilization of organic matter, albeit less effectively than vermicomposting. Anaerobic digestion, by contrast, resulted in products with lower levels of HSs and reduced nutrient content. Aerobic processes, particularly vermicomposting, demonstrated the most rapid and effective transformation, producing structurally complex, stable humus-like substances with pronounced benefits for soil health. These findings underscore vermicomposting as the most sustainable and efficacious approach for generating HS-rich organic fertilizers, presenting a powerful alternative to synthetic fertilizers. Furthermore, this study highlights the potential of organic waste valorization to mitigate environmental pollution and foster circular economy practices in sustainable agriculture.

Enhancement of mechanical properties of natural rubber latex sheets by incorporating allyl-modified microcrystalline cellulose (AMCC)

Microcrystalline cellulose (MCC) was chemically modified with allyl bromide through the hydroxyl groups of cellulose to obtain allyl-modified microcrystalline cellulose (AMCC). To enhance the curing and mechanical properties of natural rubber latex, this AMCC was then compounded with a natural rubber latex formulation to produce rubber sheets. Unmodified MCC was also compounded and prepared into rubber sheets, which served as a reference. The formation of AMCC was confirmed using Fourier Transform Spectroscopy (FTIR). Furthermore, the thermal behavior of AMCC was examined by thermogravimetric analysis (TGA), and the degree of crystallinity before and after modification was evaluated by X-ray diffraction (XRD). The results of the rubber sheets showed that overall, maximum torque (MH), degree of crosslinking density, vulcanization rate (cure rate index), and tensile strength increased in AMCC-loaded rubber compared to MCC-loaded sheets. On the other hand, optimum cure time (t90) and elongation at break were lower in the AMCC-loaded rubber than in the MCC-loaded sheets. In overall, this method outlines a successful incorporation of modified cellulose into natural rubber-based products to obtain enhanced mechanical properties.

Role of Hydroxyl Groups in Zn-containing Nanosized MFI Zeolite for the Photocatalytic Oxidation of Methane.

The effective conversion of methane to a mixture of more valuable hydrocarbons and hydrogen under mild conditions is a significant scientific and practical challenge. Here, we synthesized Zn-containing nanosized MFI zeolite for direct oxidation of methane in the presence of H2O and air. The presence of the surface hydroxyl groups on nanosized MFI-type zeolite and their significant reduction in the Zn-containing nanosized MFI zeolite were confirmed with Infrared Fourier Transform (FTIR) spectroscopy. Incorporation of zinc atoms into the framework of nanosized MFI zeolite is revealed by Nuclear Magnetic Resonance, X-ray Diffraction and UV-Vis Spectroscopy. Unexpectedly, pure silica MFI zeolite exhibited the highest photocatalytic performance. Our findings demonstrated that large number of isolated silanol groups and silanol nests increase the formation of ⋅OH, and enhance the productivity of oxygenate compounds and C2H6, while the Zn incorporated into the zeolite framework or attached to the silanol nests of the nanosized zeolites are less efficient. A mechanism of photocatalytic methane oxidation is proposed. These findings provide insights into the development of active nanosized zeolite photocatalysts with an extended amount of surface hydroxyl groups that can play a key role in photocatalytic methane conversion.

Constructing organic-inorganic woven hybrid membrane for highly-selective catalytic conversion of lignin-based phenolic molecule to value-added products

Addressing the global need for sustainable chemical processes, this study introduces an innovative Woven Hybrid Membrane (WHM) specifically designed for the efficient oxidation of vanillyl alcohol (VAA) to vanillin (VLN). This transformation is crucial for converting lignocellulosic biomass into valuable chemical products, aligning with sustainable development goals. Utilizing a novel catalytic system that combines 2,2,6,6-tetramethylpiperidine 1-oxyl (TMP) and copper on a unique mesh-like structure, the WHM enhances both the economic and environmental viability of the process. This design not only overcomes the limitations of powdered catalysts, which are challenging to recover and reuse, but also promotes high catalytic efficiency and selectivity. By employing oxygen as the oxidant, our system maintains near 100% selectivity for VLN, demonstrating high conversion rates across multiple cycles without significant degradation in performance. Advanced analytical techniques, including electrochemical analysis and Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), were used to explore the catalyst's functionality and the reaction mechanism. The results confirm the stability and effectiveness of the WHM, showcasing its potential as a reusable, highly efficient, and environmentally friendly catalyst. This research represents a significant step forward in the field of sustainable industrial chemistry, offering a robust solution for the bio-refinery industry's push towards greener processes.

Signal-to-Noise Ratio Analysis of Bandpass Sampling Time-Modulated Fourier Transform Spectroscopy

In Bandpass Sampling Fourier Transform Spectroscopy, a comprehensive method for evaluating signal-to-noise ratio (SNR) has not yet been established. This paper employs an energy conservation approach to analyze the relationship of SNR between interferogram and spectra in Bandpass Sampling Time-Modulated Fourier Transform Spectroscopy (BPS-FTS). It systematically presents models for the average SNR of the system interferogram and the average SNR of reconstructed spectra under different parameters. These models are compared with SNR models in traditional Fourier transform spectroscopy (FTS) and are mutually validated through theoretical modeling and simulation analysis. It provides a theoretical basis and simulation verification for the design and implementation of the system.

Engineering Lewis-Acid Defects on ZnO Quantum Dots by Trace Transition-Metal Single Atoms for High Glycerol-to-Glycerol Carbonate Conversion.

Efficient conversion of biomass wastes into valuable chemicals has been regarded as a sustainable approach for green and circular economy. Herein, a highly efficient catalytic conversion of glycerol (Gly) into glycerol carbonate (GlyC) by carbonylation with the commercially available urea is presented using low-cost transition metal single atoms supported on zinc oxide quantum dots (M1-ZnO QDs) as a catalyst without using any solvent. A facile one-step wet chemical synthesis allows various types of metal single atoms to simultaneously dope and introduce Lewis-acid defects in the ZnO QD structure. It is found that doping with a trace amount of isolated metal atoms greatly boosts the catalytic activity with Gly conversion of 90.7%, GlyC selectivity of 100.0%, and GlyC yield of 90.6%. Congruential results from both Density Functional Theory (DFT)and in situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (in situ DRIFTS) studies reveal that the superior catalytic performance can be attributed to the enriched Lewis acid sites that endow optimal adsorption, formation of the intermediate for coupling between urea and Gly, and desorption of GlyC. Moreover, the tiny size of ZnO QDs efficiently promotes the accessibility of these active sites to the reactants.

Rapid detection and spectroscopic feature analysis of mineral content in camel milk using fourier-transform mid-infrared spectroscopy and traditional machine learning algorithms

Camel milk is rich in nutrients and bioactive factors, with mineral content generally higher than that of cow milk, but there is currently no internationally established, rapid, batch-testing method for the mineral content. This study collected samples of camel milk from 113 locations in Xinjiang, China. For the first time internationally, based on the true mineral values determined by ICP-OES (Inductively Coupled Plasma Optical Emission Spectroscopy) and the extracted mid-infrared spectra data, a quantitative prediction model for 10 key minerals (Ca, Fe, K, Mg, Mn, Na, P, Sr, Zn, and Se) was established using Fourier-Transform Mid-Infrared Spectroscopy (FT-MIRS) and the traditional machine learning algorithm Partial Least Squares Regression. The Rt2 of the test set ranged from 0.61 to 0.91, RMSEt ranged from 2.21ug/kg(Se) to 197.08 mg/kg(K) and the RPDt from 1.59 to 3.28. In addition, the distribution, patterns, and correlations of mineral-related characteristic wavenumbers in camel milk were summarized. This study opens a new avenue for the rapid detection of minerals in camel milk and fills the research gap in in using FT-MIRS to detect mineral content in camel milk.