Fourier-transform Spectroscopy Research Articles

Accurate calibration spectra for precision radial velocities

Astronomical spectrographs require calibration of their dispersion relation, for which external sources like hollow-cathode lamps or absorption-gas cells are useful. Laser frequency combs (LFCs) are often regarded as ideal calibrators because they provide the highest accuracy and dense sampling, but LFCs are facing operational challenges such as generating blue visual light or tunable offset frequencies. As an example of an external source, we aim to provide a precise and accurate frequency solution for the spectrum of molecular iodine absorption by referencing to an LFC that does not cover the same frequency range. We used a Fourier Transform Spectrometer (FTS) to produce a consistent frequency scale for the combined spectrum from an iodine absorption cell at 5200– 6200 Å and an LFC at 8200 Å. We used 17 807 comb lines to determine the FTS frequency offset and compared the calibrated iodine spectrum to a synthetic spectrum computed from a molecular potential model. In a single scan, the frequency offset was determined from the comb spectrum with an uncertainty of ∼1 cms−1. The distribution of comb line frequencies is consistent with no deviation from linearity. The iodine observation matches the model with an offset of smaller than the model uncertainties of ∼1 m s−1, which confirms that the FTS zero point is valid outside the range covered by the LFC, and that the frequencies of the iodine absorption model are accurate. We also report small systematic effects regarding the iodine model’s energy scale. We conclude that Fourier Transform Spectrometry can transfer LFC accuracy into frequency ranges not originally covered by the comb. This allows us to assign accurate frequency scales to the spectra of customized wavelength calibrators. The calibrators can be optimized for individual spectrograph designs regarding resolution and spectral bandwidth, and requirements on their long-term stability are relaxed because FTS monitoring can be performed during operation. This provides flexibility for the design and operation of calibration sources for high-precision Doppler experiments.

Mixed Bio-based Surfactant-Templated Mesoporous Silica for Supporting Palladium Catalyst

The study aimed on the synthesis of bio-based surfactant-templated mesoporous silica for supporting palladium catalyst using mixed bio-based templating agents namely cashew nut shell liquid (CNSL) and castor oil for pore direction purposes. The materials prepared through co-condensation of 3-aminopropyltriethoxysilane (APTS) and tetraethyl orthosilicate (TEOS) in a 1:4 molar ratio using 1:1, 4:1 and 9:1 ratio of CNSL and castor oil. The resulting porous materials were utilized to support the palladium(II) chloride catalyst, resulting in a heterogeneous catalyst-a better and more environmentally friendly catalyst than a homogeneous one. Different instruments were used to characterized the prepared materials such as nitrogen porosimeter, Powder X-ray Diffraction, Diffuse Reflectance Infrared Fourier Transform Spectroscopy and Inductively coupled plasma optical emission spectroscopy. Physisorption studies of the prepared materials indicated that the largest pore diameter of 43.84 nm could be obtained by using a 1:1 molar ratio of CNSL and castor oil. On the other hand, the largest surface area of 209 m2/g was obtained from a 9:1 whereas the largest pore volume was 1.55 cm3/g from a 4:1. Diffuse Reflectance Infrared Fourier Transform Spectroscopy analysis confirmed the presence of N-H group, the bending vibration bands at around 1640 and 1543 cm-1 indicating that the reaction of organoaminesilanes and tetraethyl orthosilicate had occurred. The palladium content of the supported catalyst was determined by ICP-OES which confirmed the attachment of palladium to the synthesized materials. The highest palladium loading was obtained from the adsorbent prepared by using 1:1 ratio of surfactants mixture which gave the adsorption value of 2.16 mmol/g. Powder X-ray Diffraction indicated that the synthesized organosilica materials are amorphous with improved crystallinity upon attachment of palladium catalyst. The incorporation of palladium in the synthesized materials using the mixed bio-based surfactant was successful.

Analytical Techniques for the Authenticity Evaluation of Chokeberry, Blackberry and Raspberry Fruit Wines: Exploring FT-MIR Analysis and Chemometrics

The modern analytical technique of Fourier-transform mid-infrared spectroscopy (FT-MIR) has found its place in routine wine quality control. It allows rapid and nondestructive analysis, with easy sample preparation and without the need for chemical pretreatment or expensive reagents. The objective of this research was to apply these advantages to fruit wines in order to create a tool for the authentication of fruit wines produced from different fruit species (chokeberry, blackberry, and raspberry). The aim of this work was to establish a chemometric model from FT-MIR spectra and to find a “fingerprint” of specific fruit wines, enabling the classification of fruit wines by plant species. Physicochemical analysis of 111 Croatian fruit wine samples (38 liqueur fruit wines and 73 fruit wines) revealed content levels of the following parameters: alcoholic strength (5.0–15.2% vol.), total dry extract (60.4–253.3 g/L), total sugars (1.2–229.9 g/L), pH (3.13–4.98), total acidity (4.2–18.3 g/L) and volatile acidity (0.2–1.5 g/L). For statistical data processing, spectral ranges between 926 and 1450 cm−1 and between 1801 and 2951 cm−1 were used. The first principal component (PC1) explained 70.4% of the observed variation, and the second component (PC2) explained 16.7%, clearly separating chokeberry fruit wines from blackberry and raspberry fruit wines. Soft Independent Modeling Class Analogy (SIMCA) was performed following the development of a PCA model showing that the chokeberry and blackberry wine samples form clearly separated clusters. Key discriminators for classifying chokeberry vs. blackberry wines were identified at 1157, 1304, and 1435 cm−1, demonstrating high discrimination power (DP 26, 17, and 14, respectively). FT-MIR spectroscopy, in combination with chemometric methods, has shown promising potential for the authenticity assessment of fruit wines.

Colorimetric approach based on iron oxide magnetic molecularly imprinted nanozyme for sensitive determination of antipyrine and benzocaine: Application to environmental water samples and pharmaceutical dosage form

Nanozymes provide the required enzymatic activity however, they lack the selectivity to target a certain drug during analysis. Herein, a novel polydopamine molecularly imprinted polymer (MIP) was fabricated onto Fe3O4 nanozymes surface for sensitive and selective determination of antipyrine (ANT) and benzocaine HCl (BEN). Synthesized Fe3O4 nanozyme with peroxidase like activity catalyzed the oxidation of ortho phenylenediamine by the aid of H2O2 to produce intense yellow color that can be measured via colorimetric assay. The MIPs were prepared and characterized using field-emission scanning electronic microscopy, Fourier-transform IR spectroscopy, surface area analysis, and X-ray diffraction spectrum. Two Fe3O4 @ MIP NPs nanozyme with peroxidase like activity of two drugs were prepared. Upon binding of the target drug with its respective MIP, an inhibition in the Fe3O4 enzymatic activity occurred and thus a decrease in the yellow color produced. This quantitative decrease in the color intensity represents the drug concentration. Factors affecting the enzymatic colorimetric reaction have been investigated and optimized. The formed MIPs increased the sensitivity of the proposed method with LOD 1.405, 0.658 ng mL−1, LOQ 4.259, 1.993 and recovery percentage of 100.07, 100.57 for ANT and BEN, respectively. The reusability of the Fe3O4 @ MIP NPs was assessed for six cycles without significant loss in enzymatic oxidase activity. Furthermore, the method was validated following ICH guidelines. Then, it was successfully applied for determination of the two drugs in spiked environmental water samples and pharmaceutical formulation.

The Characteristics of Milk Fatty Acid Profile Predicted by Fourier-Transform Mid-Infrared Spectroscopy (FT-MIRS) in Chinese Holstein Cows

The Characteristics of Milk Fatty Acid Profile Predicted by Fourier-Transform Mid-Infrared Spectroscopy (FT-MIRS) in Chinese Holstein Cows

Characterization of the Dielectric Parameters of Monophase Polycrystalline Bismuth Titanate Pyrochlore (Bi2Ti2O7) Ceramics and Glass-Ceramics

Pyrochlore compounds have a number of technological applications, such as dielectrics for high-frequency and magnetoelectric devices. In bulk materials, they exhibit stimulated cation arrangement and good long-distance order within the pyrochlore framework. Bismuth titanate ceramics containing SiO2 and Nd2O3 were synthesized in the Bi2O3-TiO2-SiO2-Nd2O3 system using the melt-quenching method. In a previous study, the phase composition of selected samples was determined by X-ray diffraction (XRD) analysis and the microstructure was studied by scanning electron microscopy (SEM). The preparation of monophase polycrystalline materials was concluded. Infrared Fourier-transformed spectroscopy (FTIR) was applied in order to identify the structure. The electrical conductivity, as well as the dielectric losses and dielectric constants of selected samples were determined, and the influence of the phase composition on the dielectric characteristics was evaluated. The combination of the pyrochlore phase with the amorphous phase represented by the structural groups Bi-O-Si and Si-O-Si exerts a grain boundary strengthening effect.

Role of hydroxyl groups in Zn-containing nanosized MFI zeolite for the photocatalytic oxidation of methane.

Effective conversion of methane to a mixture of more valuable hydrocarbons and hydrogen under mild conditions is a great 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 a UV-Vis Spectroscopy. Unexpectedly, pure silica MFI zeolite exhibited the highest photocatalytic performance. Our finds 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 developing active nanosized zeolite photocatalysts with extended amount of surface hydroxyl groups that can play a key role in photocatalytic methane conversion.

Emergence of meta-methylbenzyl alcohol in novel pathway of ethanol with methacrolein catalyzed by hydroxyapatite

Bioethanol, a renewable resource, can be converted into high value-added chemicals. Methylbenzyl alcohol in its ortho- and para-isomers has been successfully synthesized from ethanol upgrading over metal-modified hydroxyapatite (HAP). However, meta-methylbenzyl alcohol (3-MB-OH), a particularly valuable fine chemical, has yet to be produced from ethanol. Herein, we present a novel reaction pathway for the selective synthesis of 3-MB-OH over HAP by co-feeding ethanol with methacrolein. Notably, the selectivity of 3-MB-OH reached up to 36.2 % in our tests. Experiments using intermediates as reactants proved that the introduction of methacrolein definitively led to the production of 3-MB-OH, which was also confirmed by in-situ diffuse reflectance infrared Fourier-transform spectroscopy. Moreover, we inferred the co-conversion reaction pathway of ethanol and methacrolein. Density functional theory calculations indicated that ethanol preferentially underwent Meerwein-Ponndorf-Verley hydrogen transfer with methacrolein, resulting in acetaldehyde formation and subsequently promoting the synthesis of aromatic compounds.

Effect of Light Irradiance and Curing Duration on Degree of Conversion of Dual-Cure Resin Core in Various Cavities with Different Depths and Diameters.

(1) Background: To compare the degree of conversion of resin cores in various types of cavities and determine an effective irradiation method for achieving a higher degree of conversion. (2) Methods: Four different-sized cavities (narrow-shallow, narrow-deep, wide-shallow, and wide-deep) were simulated using a Teflon mold. The light irradiance reaching the bottom of each mold was measured by positioning a radiometer. The degree of conversion of the dual-cure resin core after irradiation (400 mW/cm2 for 20 s, 400 mW/cm2 for 40 s, and 800 mW/cm2 for 20 s) was measured using Fourier-transform near-infrared spectroscopy. (3) Results: The highest light irradiance was found at the bottom of wide-shallow cavities, followed by wide-deep, narrow-shallow, and narrow-deep ones (p < 0.001). In narrow cavities, irradiation at 800 mW/cm2 for 20 s led to a significantly higher degree of conversion (p < 0.001). In wide cavities, irradiation at 400 mW/cm2 for 40 s and 800 mW/cm2 for 20 s both led to a significantly higher degree of conversion (p < 0.001). (4) Conclusions: Less curing light reaches the bottom of cavities with a smaller diameter and greater depth. Providing a higher irradiance of light can induce a higher degree of conversion of resin composites in narrower cavities.

The high-resolution molecular portrait of coffee: A gateway to insights into its roasting chemistry and comprehensive authenticity profiles

The direct-infusion of 130 coffee samples into a Fourier-transform ion cyclotron mass spectrometer (FT-ICR-MS) provided an ultra-high resolution perspective on the molecular complexity of coffee: The exceptional resolving power and mass accuracy (± 0.2 ppm) facilitated the annotation of unambiguous molecular formulas to 11,500 mass signals.Utilizing this molecular diversity, we extracted hundreds of compound signals linked to the roasting process through guided Orthogonal Partial Least Squares (OPLS) analysis. Visualizations such as van Krevelen diagrams and Kendrick mass defect analysis provided deeper insights into the intrinsic compositional nature of these compounds and the complex chemistry underlying coffee roasting.Predictive OPLS-DA models established universal molecular profiles for rapid authentication of Coffea arabica versus Coffea canephora (Robusta) coffees. Compositional analysis revealed Robusta specific signals, indicative of tryptophan-conjugates of hydroxycinnamic acids. Complementary LC-ToF-MS2 confirmed their compound class, building blocks and structures. Their water-soluble nature allows for application across raw and roasted beans, as well as in ready-made coffee products.

Efficient dye removal using manganese oxide-modified nanocellulosic films from sugarcane bagasse

Removing toxic dyes from industrial wastewater is crucial for environmental protection. This research introduced novel composite films of manganese oxide (MnO2)-modified nanocellulose (MCel) and unmodified nanocellulose (Cel) derived from sugarcane bagasse for dye removal. Nanocellulose was extracted from sugarcane bagasse and subsequently transformed into MCel through in-situ MnO2 synthesis. The MCel/Cel composites, with various MCel to Cel ratios, were fabricated into films and evaluated for their efficiency in removing methylene blue (MB). The films were characterized using Fourier Transform Spectroscopy for functional group analysis, X-ray diffraction for crystallinity, (X-Ray Photoelectron Spectroscopy) for chemical state analysis, Field Emission Scanning Electron Microscopy-Energy Dispersive Spectroscopy for morphology and elemental composition, and Thermogravimetric Analysis for thermal behaviors. Adsorption results showed that all MCel/Cel composite films achieved over 97 % removal of MB (initial concentration 100 mg L−1) within 24 h, with convenient adsorbent retrieval after adsorption. The adsorption process followed a pseudo-second order kinetic model and Langmuir adsorption isotherm. The optimal 95:5 MCel/Cel film exhibited a rate constant of 6.16 × 10−4 g mg−1 min−1 and the calculated adsorption capacity of 181.85 mg g−1. These results demonstrate significant potential for wastewater treatment and sustainable waste valorization by converting sugarcane bagasse cellulose into environmentally friendly adsorbents for contaminant removal.

A detailed characterization study of Ni/CeO2 catalysts identifies Ni availability as the primary factor affecting CO2 methanation performance

The structure of a catalyst has a strong impact on its performance. Here we investigate the physicochemical properties of Ni/CeO2 in an attempt to draw structure–activity relationships for CO2 methanation. A combination of characterisation methods (X-ray diffraction (XRD), 4D Scanning Transmission Electron Microscopy (4D-STEM), CO chemisorption and oxygen storage capacity study etc.) clearly demonstrates the effect of Ni particle size, Ni availability (i.e. catalytically accessible Ni) and oxygen vacancies at the Ni-CeO2 interface in Ni/CeO2 during CO2 methanation. Among them, the role of exposed Ni active sites is highlighted, and two possible optimisation schemes i.e. changing the support calcination temperature and the final calcination atmosphere are proposed to obtain a better dispersal of Ni NPs on CeO2. Both modification methods do not affect the reaction route, and the activity differences of Ni/CeO2 can be explained by the various hydrogenation rate of formate species, as confirmed by in situ diffuse-reflectance infrared Fourier-transform spectroscopy (DRIFTS) measurements.

Controlling charge migration and CO2 conversion through surface decoration of 2D-hydrotalcite on bismuth oxybromide for enhanced artificial photosynthesis

Photocatalytic reduction of CO2 in pure H2O media to produce chemicals presents an appealing avenue for simultaneously alleviating energy and environmental crises. However, the rapid recombination of photogenerated charge carriers presents a significant challenge in this promising field. Heterojunction engineering has emerged as an effective approach to address this dilemma. Here, by decorating 2D NiAl-layered double hydroxides (NAL) onto bismuth oxybromide (BOB), we have created a S-scheme heterojunction (N1B1 composite). This catalyst affords CO2-to-CO yields of 102.30 μmol g−1 with a selectivity of 100 %. Ultraviolet photoelectron spectroscopy (UPS) and in-situ irradiated X-ray photoelectron spectroscopy (ISI-XPS) reveal that charge transfer occurs efficiently from BOB to 2D-NAL upon light irradiation. The designed N1B1 heterojunction achieves 7.3-fold and 2.1-fold increase in the internal electric field strength compared to bare 2D-NAL and BOB, respectively, which should be accountable for the improved charge migration. Additionally, pulsed chemisorption and in-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) show the presence of multiple carbonate intermediates with activated OCO bonds upon N1B1 composite, with *CO2− being identified as the most crucial species for CO production.

Calcium Acetate Drug Produced from Rapana venosa Invasive Gastropod Shells: Green Process Control Assisted by Raman Technology.

The highly demanded calcium acetate (Ca(CH3COO)2) for biomedicine and various industries constantly requires green and low-cost methods of synthesis. In the present work, a sustainable approach to produce Ca(CH3COO)2 is reported as a proof of concept, processing for the first time as a starting material the worldwide highly abundant Rapana venosa shells, which is a neglected biogenic waste with high economical potential due to the rich mineral and organic pigmentary content. A green synthesis involving an eco-friendly acetic acid has been optimized at room temperature, without any additional energy consumption, and the resulting saturated Ca(CH3COO)2 solution was further slowly evaporated in three stages to obtain white Ca(CH3COO)2 crystalline powder, without impurity traces. Raman spectroscopy provided efficient structural information for every step of the process control, during demineralization as well as end product validation. Yields as high as 87.5% of highly pure Ca(CH3COO)2 mass have been achieved from raw R. venosa shells, proving the uniqueness and economic viability of the method. X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDX), and Fourier-Transform IR spectroscopy (FTIR) analyses validated the final product identity, hydration status, crystalline morphology, and composition. The purity of the resulting product suggests a high valorization potential of the abundant R. venosa shell in the context of the blue bioeconomy and offers a cleaner and efficient method of Ca(CH3COO)2 production with important applications in relevant industries.

Evaluation of Sentinel-5P TROPOMI Methane Observations at Northern High Latitudes

The Arctic and boreal regions are experiencing a rapid increase in temperature, resulting in a changing cryosphere, increasing human activity, and potentially increasing high-latitude methane emissions. Satellite observations from Sentinel-5P TROPOMI provide an unprecedented coverage of a column-averaged dry-air mole fraction of methane (XCH4) in the Arctic, compared to previous missions or in situ measurements. The purpose of this study is to support and enhance the data used for high-latitude research through presenting a systematic evaluation of TROPOMI methane products derived from two different processing algorithms: the operational product (OPER) and the scientific product (WFMD), including the comparison of recent version changes of the products (OPER, OPER rpro, WFMD v1.2, and WFMD v1.8). One finding is that OPER rpro yields lower XCH4 than WFMD v1.8, the difference increasing towards the highest latitudes. TROPOMI product differences were evaluated with respect to ground-based high-latitude references, including four Fourier Transform Spectrometer in the Total Carbon Column Observing Network (TCCON) and five EM27/SUN instruments in the Collaborative Carbon Column Observing Network (COCCON). The mean TROPOMI–TCCON GGG2020 daily median XCH4 difference was site-dependent and varied for OPER rpro from −0.47 ppb to 22.4 ppb, and for WFMD v1.8 from 1.2 ppb to 19.4 ppb with standard deviations between 13.0 and 20.4 ppb and 12.5–15.0 ppb, respectively. The TROPOMI–COCCON daily median XCH4 difference varied from −26.5 ppb to 5.6 ppb for OPER rpro, with a standard deviation of 14.0–28.7 ppb, and from −5.0 ppb to 17.2 ppb for WFMD v1.8, with a standard deviation of 11.5–13.0 ppb. Although the accuracy and precision of both TROPOMI products are, on average, good compared to the TCCON and COCCON, a persistent seasonal bias in TROPOMI XCH4 (high values in spring; low values in autumn) is found for OPER rpro and is reflected in the higher standard deviation values. A systematic decrease of about 7 ppb was found between TCCON GGG2014 and GGG2020 product update highlighting the importance of also ensuring the reliability of ground-based retrievals. Comparisons to atmospheric profile measurements with AirCore carried out in Sodankylä, Northern Finland, resulted in XCH4 differences comparable to or smaller than those from ground-based remote sensing.

Fourier-transform near-infrared spectroscopy first application to age determination in European fish species: the case of the Atlantic horse mackerel from the central Mediterranean Sea

Fourier-transform near-infrared spectroscopy (FT-NIRS) has recently been used to reduce the processing time for estimates of annual age in several fish species. The present study represents the first application of this technique to marine organisms from the European waters. Atlantic horse mackerel (Trachurus trachurus) from the central Mediterranean Sea was selected for its ecological role, its socioeconomic value, and because its age is regularly estimated by otolith reading under a stereomicroscope for stock assessment purposes. Absorption spectra of the whole otoliths were acquired by FT-NIRS across a multiyear dataset, obtained during acoustic surveys carried out in different regions of the central Mediterranean Sea. The acquired spectra were processed to optimize calibration models to predict age. The best linear models obtained by the optimizing procedure predicted age successfully with a coefficient of determination of 0.95–0.96, mean squared error of 0.5 years, and bias &amp;lt;0.03 years. Although regional calibration models were also obtained separately, the models with all regions combined appeared much more robust and encompassing the whole age range, suggesting its usefulness for the entire spatial distribution range considered in the preset study. The use of FT-NIRS allowed to successfully predict age for horse mackerel between the ages 1 and 14, with similar or better precision (and bias) of the traditional methods, also increasing the standardization by repeatability of age assignments. The preliminary results obtained by this study encourage further effort to fine-tune the calibration model for new species, in order to apply a precise, rapid, cost-effective method for stock assessment purposes of Mediterranean fish resources.

High-precision detection of dibutyl hydroxytoluene in edible oil via convolutional autoencoder compressed Fourier-transform near-infrared spectroscopy

The quality of edible oils is closely related to their chemical compositions. Antioxidants have widespread application in edible oil production. In this study, a pioneering detection approach involving the use of a one-dimensional convolutional autoencoder (1D-CAE) was introduced to compress spectral data for assessing antioxidant levels in edible oils. Fourier-transform near-infrared (FT-NIR) characterisation of edible oil samples with varying antioxidant concentrations was also conducted. An 1D-CAE model was developed to compress different pre-processed spectra into a condensed representation. These compressed features were then integrated with a support vector machine and partial least squares regression models to establish correlations for each target. The study examined the influence of pre-processing steps and feature engineering methods on near-infrared spectral analysis through independent or combined model analysis. The findings revealed that features derived from the 1D-CAE model demonstrated remarkable repeatability and can be utilised to construct robust detection models. The experimental results showed that the optimal detection model derived based on the 1D-CAE compression features has an average R2, RPD and RMSE of 0.9953, 15.1664 and 1.2035, respectively, on the prediction set. FT-NIR spectroscopy can be used to accurately detect butylated hydroxytoluene in edible oils. Therefore, autoencoders are an effective tool in spectroscopic analysis, offering promising avenues for future research and application.

Boosted photo-Fenton-like process for selective degradation of emerging contaminants by dehydrated Fe-based metal–organic framework with thermodynamically-favorable center metal electron density and confinement effect

The Heterogeneous Fenton reaction has long stood out as a highly effective technology for water purification. However, it is nowadays facing challenges such as low selectivity, sluggish Fe(III) reduction, and limited H2O2 conversion efficiency. Herein, dehydrated MIL-100(Fe)-250 was synthesized through thermal treatment, demonstrating superior efficiency in removing emerging contaminants, with a three-fold efficiency higher than undehydrated sample. The dehydrated MIL-100(Fe)-250 exhibited selective acceleration in the removal of quinolones and phenolic organics, rendering the system resistant to interference from coexisting matter. Through in-situ diffuse reflectance infrared Fourier-transform spectroscopy and density functional theory calculation, it was manifested that dehydration process regulates the steric hindrance and local electron density of Fe ions. This adjustment enhances charge transfer, thereby facilitating Fe(III) reduction and promoting the H2O2 activation and conversion efficiency. Moreover, the quasi-steady-state concentrations of hydroxyl radical in MIL-100(Fe)-250 were found to be 2.2 times higher than that those in undehydrated sample. Impressively, the dehydrated MIL-100(Fe)-250 displayed adaptability across a broad pH range of 5.0–9.0. The present study underscores the significant potential of porous MIL-100(Fe)-250 with spatial confinement, which imparts a clear size exclusion effect. As a result, this catalyst emerges as a promising candidate for eliminating contaminants in real water matrices, offering a viable strategy for water pollution control.

A Large-Scan-Range Electrothermal Micromirror Integrated with Thermal Convection-Based Position Sensors.

This paper presents the design, simulation, fabrication, and characterization of a novel large-scan-range electrothermal micromirror integrated with a pair of position sensors. Note that the micromirror and the sensors can be manufactured within a single MEMS process flow. Thanks to the precise control of the fabrication of the grid-based large-size Al/SiO2 bimorph actuators, the maximum piston displacement and optical scan angle of the micromirror reach 370 μm and 36° at only 6 Vdc, respectively. Furthermore, the working principle of the sensors is deeply investigated, where the motion of the micromirror is reflected by monitoring the temperature variation-induced resistance change of the thermistors on the substrate during the synchronous movement of the mirror plate and the heaters. The results show that the full-range motion of the micromirror can be recognized by the sensors with sensitivities of 0.3 mV/μm in the piston displacement sensing and 2.1 mV/° in the tip-tilt sensing, respectively. The demonstrated large-scan-range micromirror that can be monitored by position sensors has a promising prospect for the MEMS Fourier transform spectrometers (FTS) systems.

Fast and low energy-consumption integrated Fourier-transform spectrometer based on thin-film lithium niobate

Abstract Integrated miniature spectrometers have impacts in industry, agriculture, and aerospace applications due to their unique advantages in portability and energy consumption. Although existing on-chip spectrometers have achieved breakthroughs in key performance metrics, such as, a high resolution and a large bandwidth, their scanning speed and energy consumption still hinder practical applications of such devices. Here, a stationary Fourier transform spectrometer is introduced based on a Mach–Zehnder interferometer structure on thin-film lithium niobate. Long and low-loss spiral waveguides with electro-optic tuning are adopted as the optical path scanning elements with a half-wave voltage of 0.14 V. A high resolution of 2.1 nm and a spectral recovery with a bandwidth of 100 nm is demonstrated under a high-speed and high-voltage scanning in the range of −100 V to +100 V at up to 100 KHz. A low energy consumption in the μJ scale per scan is also achieved.