Transmission Fourier Transform Infrared Research Articles

Determining aqueous deuterium detection limits via infrared spectroscopy to understand its capabilities for real-time monitoring of tritiated water

Tritiated water will be present in many demonstrator class fusion devices in a wide array of locations and concentrations. Accurate and fast measurement will be a key requirement to ensure suitable process monitoring, safety assurance and tritium tracking is in place. This work quantifies the deuterium detection limits achievable using a benchtop transmission Fourier transform infrared (FTIR) instrument and an industrialised attenuated total reflectance (ATR)-FTIR instrument to understand the capabilities of these techniques for real-time monitoring of aqueous tritium. Deuterium limits of detection of 4.62 × 10-5 mol mL-1 and 1.07 × 10-3 mol mL-1 were demonstrated with measurement times of 10s for the transmission FTIR and ATR-FTIR, respectively. These instruments are considered viable for the measurement of high concentration tritiated water and have many potential benefits associated with their deployment.

Antisense oligonucleotide conjugated gold nanoconstructs-based electrochemical biosensor for detection of SARS-CoV-2

Nanoconstructs of gold nanoparticles (AuNPs) conjugated with SARS-CoV-2 specific antisense oligonucleotides (ASO) have been utilized to develop sensitive electrochemical nucleic acid biosensor for the detection of SARS-CoV-2 RNA. AuNPs were prepared through a one-pot synthesis method by utilizing Poly-L-Lysine (PLL) biopolymer and as synthesised AuNP were characterized by various analytical techniques such as UV–Vis spectroscopy, X-ray Diffraction (XRD) analysis, Fourier Transform Infra-Red spectroscopy (FT-IR), zeta potential, and Transmission Electron Microscopy (TEM). Poly-L-Lysine functionalized AuNPs (PLL-AuNPs) nanoconstructs platform was employed for immobilization of SARS-CoV-2 specific antisense oligonucleotides (ASO-conjugated PLL-AuNPs) via electrostatic interactions. The PLL-AuNPs were drop casted on glassy carbon electrode (GCE) following immobilization of ASO for fabrication of electrochemical biosensor. The ASO-conjugated PLL-AuNPs nanoconstructs were characterized by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) techniques. The responsiveness of ASO-conjugated PLL-AuNPs nanoconstructs in presence SARS-CoV-2 RNA was monitored using the DPV, SWV and EIS technique, where methylene blue was employed as an electrochemical indicator for DNA-RNA hybridization detection. The biosensor exhibits a detection range for SARS-CoV-2 RNA infection ranging from 0 to 100 nM, with a limit of detection at 30.2 nM. The electrode, modified with ASO-conjugated PLL-AuNPs, was employed for the detection of SARS-CoV-2 RNA from clinical samples collected from COVID-19-positive individuals.

Physical properties of pectin edible film with kepok banana blossom filler as food packaging

Kepok banana blossom is a part of banana plants that provide high antioxidant content. An antioxidant is defined as a component that can reduce the microbial activity of edible film. This research aims to determine the effect of kepok banana blossom on the physical properties of edible film. The material used in this research is kepok banana blossom which is obtained from a local market in Medan, Sumatera Utara. Pectin edible film was made by using the casting solution method which includes 0 wt%, 1.wt%, 3 wt%, 5wt%, 7wt%, and 9 wt% of kepok banana blossom as fillers. The physical properties of the edible film are observed by using Scanning Electron Microscope (SEM), Fourier Transform Infra-Red (FTIR), density test, and water vapor transmission rate (WVTR). FTIR resulting from edible film indicates the decreased functional group along with the additional filler concentrations of 5%. The SEM result of the edible film shows the form of fibers and the fibers cover the cavity. To conclude kepok banana blossom as a filler has an influence on the value of the antimicrobial index on the edible film.

Cuticle chemistry of the Cheirolepidiaceae Frenelopsis teixeirae from the Lower Cretaceous of Portugal. A case of study using ATR-FTIR spectroscopy

A Cheirolepidiaceae Frenelopsis teixeirae from the Lower Cretaceous of the Santa Susana Formation, near Torres Vedras locality (Estremadura region, western Portugal), is analyzed by means of Fourier Transform Infrared (FTIR) spectroscopy in Attenuated Total Reflection (ATR) mode at both micro and macro scales. This analytical technique (ATR-FTIR spectroscopy), which requires minimal sample preparation and a small amount of material, is used to evaluate the chemical composition of the F. teixeirae cuticles. For this, functional groups (i.e., specific groupings of atoms within molecules), that compose the complex chemical structure making up the F. teixeirae cuticles, are detected, analyzed, and interpreted from the resulting spectra. The Frenelopsis material comprises compressions of eighteen leafy axes with very well-preserved cuticles. Previously reported chemical information derived from transmission FTIR spectra of the foliar cuticle of the podocarp Squamastrobus tigrensis from the Lower Cretaceous of Argentina is used for comparison in order to assess the existence of a distinctive spectroscopic pattern for this Portuguese taxon. Semi-quantitative data derived from FTIR spectra of both fossil taxa were statistically analyzed using principal component analysis (PCA). The F. teixeirae cuticles have a lower contribution of C=O stretch and a lower degree of biopolymeric matrix cross-linking (higher CHal/C=O ratio) than those of S. tigrensis. Despite the existing differences between both conifers, spectroscopic patterns characterizing each fossil taxon are not fully distinctive from a chemotaxonomic perspective. This is mainly related to the relatively variable morphological cuticular features (e.g., trichomes) and to the biomacropolymeric chemistry among the leaves of each fossil taxon.

Serum infrared spectral profile is predictive of the degree of hepatic fibrosis in chronic hepatitis C patients

Assessment of liver fibrosis is crucial to guide the therapeutic strategy in patients with chronic liver disease. We investigated the potential of serum Fourier transform infrared (FTIR) spectroscopy for assessing the degree of hepatic fibrosis in patients with chronic hepatitis C (CHC). The study was conducted on dried serum samples from 94 CHC patients at different histological stages of hepatic fibrosis: METAVIR F0 (n = 20), F1 (n = 17), F2 (n = 20), F3 (n = 20) and F4 (n = 17). Transmission FTIR spectra were acquired in the 4000–400 cm−1 range. Wavenumbers were selected by genetic algorithm (GA) according to their diagnostic performance as assessed by a partial least squares discriminant analysis (PLS-DA) model using a training and a validation set to differentiate severe stages of fibrosis from mild or moderate ones. The GA procedure was applied 50 times on randomly selected sets. Furthermore, the best set of wavenumbers was re-tested in 1000 randomly selected validation sets. Wavenumbers selected by GA corresponded to functional groups present in lipids, proteins, and carbohydrates. This model allowed to identify patients with cirrhosis (METAVIR F4), patients with advanced fibrosis (METAVIR F3 and F4), and patients with significant fibrosis (METAVIR F2, F3 and F4), with AUROC (Area Under the Receiver Operating Characteristic) of 0.88, 0.85 and 0.85, respectively. Thus, serum FTIR spectroscopy appears to have a strong potential as a new diagnostic tool for assessing the degree of fibrosis in patients with chronic liver disease.

Rapid and sensitive detection of esophageal cancer by FTIR spectroscopy of serum and plasma

Fourier transform infrared (FTIR) spectroscopy, as a platform technology for cancer detection, must be up to the challenge of clinical transformation. To this end, detection of esophageal squamous cell carcinoma (ESCC) was hereby explored using serum and plasma scrape-coated on barium fluoride (BaF2) disk by transmission FTIR method, and the classification model was built using six multivariate statistical analyses, including support vector machine (SVM), principal component linear discriminant analysis (PC-LDA), decision tree (DT), k-nearest neighbor (KNN) classification, ensemble algorithms (EA) and partial least squares for discriminant analysis (PLS-DA). All statistical analyses methods demonstrated that late-stage cancer could be well classified from healthy people employing either serum or plasma with different anticoagulants. Resulting PC-LDA model differentiated late-stage cancer from normal group with an accuracy of 99.26%, a sensitivity of 98.53%, and a specificity of 100%. The accuracy and sensitivity reached 97.08% and 91.43%, respectively for early-stage cancer discrimination from normal group. This pilot exploration demonstrated that transmission FTIR provided a rapid, cost effective and sensitive method for ESCC diagnosis using either serum or plasma.

Visualizing Hydrophobic and Hydrophilic Enzyme Interactions during Immobilization by Means of Infrared Microscopy

A novel Fourier transform infrared (FT-IR) microscopy method was developed and used to analyze the diffusion of lipase CalB in two different resins during immobilization. The method consisted of a streamlined sample preparation process and an automated transmission FT-IR microscopic measurement using a commercial benchtop device. The immobilization of CalB was performed on a hydrophobic resin containing aromatic groups (ECR1030M based on divinylbenzene) and on a hydrophilic resin containing ester groups and thus oxygen (ECR8204M based on methacrylate) and FT-IR revealed that the kinetic of immobilization and the distribution of the enzyme on the two resins were completely different. Furthermore, the technique revealed that CalB was immobilized on the external surface only in the case of the hydrophobic ECR1030M in a layer of about 50–70 µm, whereas when immobilized on the hydrophilic carrier ECR8204M the interaction of the enzyme with the carrier was uniform over the full diameter of the polymer bead. The enzyme activity however was higher on the hydrophobic support ECR1030M.

Preparation of sulfobutylether-β-cyclodextrin bonded Fe3O4/SiO2 core-shell nanoparticles and its application in enantioselective liquid-liquid extraction

The surface of SiO2 coated magnetic nanoparticles (NMPs) was modified by bonding with sulfobutylether-β-cyclodextrin (SBE-β-CD) via carbodiimide activation for the first time. The magnetic nanoparticles were synthesized by chemical coprecipitation method under alkaline condition, and the magnetic particles were modified by citric acid. Then the surface of obtained magnetic nanoparticles was coated with SiO2, and SBE-β-CD modified by citric acid was bonded to the surface of Fe3O4/SiO2 MNPs under carbodiimide activation method. The synthesized functionalized magnetic nanoparticles were characterized by X-ray Diffraction, Fourier Transform Infra-Red spectroscopy, thermogravimetric analyses and transmission electron microscopy. These functional nano-sized particles were scrutinized for enantioselective liquid-liquid extraction of five racemic drugs/intermediates, including trans-paroxol, N-methyl duloxetine, fluoxetine, tropic acid and acetyltropic acid, and it was found that compared with traditional SBE-β-CD, the present magnetic silica nanoparticles bonded with SBE-β-CD showed higher enantiorecognition with some racemates using enantioselective liquid-liquid extractions. To our knowledge, this is the first-time report on preparation and application of magnetic nanoparticles bonded with SBE-β-CD in enantioselective liquid-liquid extraction for chiral separations.

Know What You Don’t Know: Assessment of Overlooked Microplastic Particles in FTIR Images

Assessing data analysis routines (DARs) for microplastics (MP) identification in Fourier-transform infrared (FTIR) images left the question ‘Do we overlook any MP particles in our sample?’ widely unanswered. Here, a reference image of microplastics, RefIMP, is presented to answer this question. RefIMP contains over 1200 MP and non-MP particles that serve as a ground truth that a DAR’s result can be compared to. Together with our MatLab® script for MP validation, MPVal, DARs can be evaluated on a particle level instead of isolated spectra. This prevents over-optimistic performance expectations, as testing of three hypotheses illustrates: (I) excessive background masking can cause overlooking of particles, (II) random decision forest models benefit from high-diversity training data, (III) among the model hyperparameters, the classification threshold influences the performance most. A minimum of 7.99% overlooked particles was achieved, most of which were polyethylene and varnish-like. Cellulose was the class most susceptible to over-segmentation. Most false assignments were attributed to confusion of polylactic acid for polymethyl methacrylate and of polypropylene for polyethylene. Moreover, a set of over 9000 transmission FTIR spectra is provided with this work, that can be used to set up DARs or as standard test set.

Controlled synthesis of efficient NiWS active phases derived from lacunary polyoxometalate and the application in hydrodesulfurization

Efficient catalysts with abundant NiWS active phases for hydrodesulfurization (HDS) were prepared based on structural diversity as well as unique electrostatics property of lacunary Keggin polyoxometalates (POMs). Owing to super nucleophilicity and coordinative ability, the trivacant Keggin [PW9O34]9- (PW9) can accurately capture and anchor Ni2+ promoters into its skeleton to form nanosized Nix@PW9 molecule in impregnating solution, thereby achieving ultra-dispersion of Ni promoters, high Ni/W ratio, and atomic-scale Ni–W proximity. The superior structure of Nix@PW9 promoted the simultaneous reduction and sulfuration of Ni and W species, thus obtaining shorter slab length, less stacking number, highly efficient synergism, and high concentration of NiWS active phases. Therefore, the resulted S-NiPW9/Al2O3 catalyst exhibits efficient HDS activity for dibenzothiophene (DBT) removal compared to that of reference catalysts prepared from monovacant [PW11O39]7- (PW11), saturated [PW12O40]3- (PW12), and conventional oxide precursors. The structure-directing effects of oxidic POM precursors on the texture and performance of HDS active phases were revealed by employing a variety of characterization methods, including transmission Fourier transform infrared (TS-FTIR), attenuated total reflectance Fourier transform infrared (ATR-FTIR), ultraviolet–visible spectroscopy (UV–Vis), single crystal X-ray diffraction, H2 temperature programmed reduction (H2-TPR), CO adsorbed Fourier transform infrared spectroscopy (IR/CO), X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM). This POMs-based molecular methodology opens a new avenue to better understand the evolution behavior of precursors and the formation mechanism of active species during the preparation of catalysts.

Collagen stabilization by natural cross-linkers: A qualitative and quantitative FTIR study on ultra-thin dentin collagen model.

Due to its low tolerance to external factors such as enzymes, dentin collagen often requires stabilization, which can be achieved through cross-linking. In this study, qualitative and quantitative Fourier transform infrared (FTIR) analyses were used to assess dentin collagen stabilization effects of three structurally-different flavonoids -A-type linkage proanthocyanidins (A-PA), B-type linkage proanthocyanidins (B-PA), and epigallocatechin gallate (EGCG), all from natural extracts. Particularly, transmission FTIR spectroscopy was used for the first time to quantitatively assess the biodegradation of fresh ultra-thin (10 µm) dentin collagen films caused by collagenase digestion. Two traditional analytical methods, namely the hydroxyproline assay and weight loss analysis, were also used for comparison purposes. The results from all three methods showed consistently that A-PA and B-PA provide better collagen stabilization than EGCG at concentrations of 0.65% and 1.3% (p<0.01). FTIR is demonstrated to be a valuable and reliable analytical tool for qualitative and quantitative evaluation of ultra-thin collagen films.

In Vitro Assessment of Sunscreen Efficacy Using Fourier Transform Infrared (FTIR) Spectroscopy on Synthetic Skin.

Although there are several methods for assessing the sun protection factor (SPF) of sunscreen products, there is no standard and reliable in vitro method. Each test entails limitations and drawbacks. Therefore, this study aimed to assess the employability of FTIR as an alternative and quick method to evaluate the efficacy of various sunscreen formulations, their concentrations, and the timing of their application. Infrared radiation has longer wavelengths than ultraviolet, penetrates deeply into the skin, and hence enables the understanding of sunscreens' ability to block the transmission of radiation. The FTIR transmission using synthetic skin to study the effect of sunscreen agents (oxybenzone, octyl methoxycinnamate, titanium dioxide (TiO2), and zinc oxide (ZnO)) was conducted in the range 450-4000cm-1. Comparison studies were made at the peak of 805cm-1. After 2 h of sunscreen application, using the maximum concentrations, the FTIR peak at wavenumber 805cm-1 demonstrated a significant reduction of transmission from 96.55 to 60.09%, 57.59%, 32.02%, and 37.1% for oxybenzone, octyl methoxycinnamate, TiO2, and ZnO respectively (P<0.05). A significant reduction in transmission was observed (P<0.05) with increasing sunscreen concentrations after 2 h of application. Nevertheless, the upper limit of concentration showed no appreciable change from the middle level of concentration, and hence it is cost-effective to employ the middle concentration. Inorganic sunscreens showed a higher protection level than organic. Fixed-dose combinations of sunscreens showed an enhanced effect yet were not synergistic. In conclusion, the use of FTIR spectroscopy with synthetic skin is a quick and user-friendly technique that enables the assessment of the efficacy of sunscreen formulations.

OPTICAL STUDY OF SOL-GEL SPIN-COATING TiO2/Si3N4 MULTILAYERS ON GLASS SUBSTRATES

In this work, we have adopted a sol-gel spin-coating technique and prepared alternative TiO2/Si3N4 multilayers on glass substrates. These alternating layers of TiO2/Si3N4 thin film samples were calcinated at two different temperatures and studied for their optical performance. The optical properties of fabricated thin films were investigated by UV-Visible spectrophotometer, X-ray diffractometer (XRD), Fourier transform infrared (FTIR), and Raman spectroscopy. UV-visible spectra showed broader and higher optical reflectance in the visible spectral region. FTIR transmission spectra show Ti-O-Ti and Si-N stretching modes at around 600 and 881 cm-1. XRD pattern confirmed the presence of anatase-TiO2 and α-Si3N4 phases. Finally, Raman spectra revealed the presence of anatase-TiO2 and N-Si vibration modes.

Infrared optical properties of SiO2 films on silicon substrate under different temperatures

SiO2 is a very important low refractive index film material that can operate in the UV to mid-IR regions. The SiO2 films used were deposited on Si substrates by different deposition techniques. We designed and manufactured a high-temperature infrared spectrum measuring equipment connected with a Fourier transform infrared (FTIR) spectrometer; the measuring temperature could range from room-temperature to 600°C. The FTIR transmission spectra of SiO2 films under different working temperatures were measured in the wavenumber region from 4000 to 400 cm − 1. From the measured spectra, it can be seen that IBS-SiO2 and IAD-SiO2 films are more stable and operating temperature can reach 400°C. EB-SiO2 film is worse and operating temperature is only 300°C. Complex dielectric functions of SiO2 films under different temperature conditions were calculated from FTIR transmittance spectra, and the best fitted method was obtained for calculating optical constants of dielectric materials in the high temperature condition. The results show that the structure of the Si-O-Si network in IBS-SiO2 films was the most stable structure. The experimental results were of great significance to practical application.

SYNTHESIS AND CHARACTERIZATION OF PEG-CINNAMON ESSENTIAL OIL NANOPARTICLES AND THEIR APPLICATION AS AN INSECTICIDAL AGENT

The study deals with the EO-NPs encapsulated cinnamon essential oil for insecticidal activity. The prepared nanoparticles were subjected to characterization studies using Dynamic Light Scattering (DLS) analysis, Fourier Transform Infra-Red spectroscopy (FTIR) and Transmission Electron Microscopy (TEM) analysis. The DLS analysis revealed that the size of the nanoparticles had a slight increase in diameter after three months of storage. Similarly, the characterization with TEM showed that the prepared nanoparticles were of round or spherical shape with clear morphology without any crack in the external surface. Considerable mortality was observed from the insecticidal bioassay carried out by contact with cinnamon essential oil nanoparticles encapsulated with PEG (EO-NPs) against adult Oryzaephilus surinamensis (Linnaeus) (Coleoptra : Silvanidae). Further, the cinnamon EO-NPs also produced significant repellency effect on the adult insects. About 85% mortality (Contact Toxicity) was observed with 0.025 mg x cm2 concentration of EO-NPs. The results indicate that the cinnamon essential oil encapsulated with PEG nanoparticles could be an effective alternative to chemical pesticides for the control of stored product grain pests. Further this is the first report on the insecticidal efficacy of PEG encapsulated cinnamon essential oil against Oryzaephilus surinamensis.

Attenuated Total Reflection Fourier Transform Infrared (ATR FT-IR) Spectroscopy for the Quantitative Analysis of Deuterium in Plasma: Application to Total Body Water Determination in Humans and Other Animals.

Conventional methods for measuring the concentration of deuterium in body fluids are by either isotope ratio mass spectrometry or Fourier transform infrared transmission (FT-IR) spectroscopy. The latter method is often preferred as it is less expensive and time consuming; however, having a lower sensitivity means a larger sample volume is required. This study investigated an alternative FT-IR spectroscopic method, attenuated total reflection Fourier transform infrared spectroscopy (ATR FT-IR), which has the potential to provide shorter analysis times while requiring smaller sample volumes. Deuterium was assayed using ATR FT-IR in plasma in the concentration range 0.5 to 2.5 mg mL-1, typical of those observed in tracer dilution measurements of total body water. Minimal sample preparation was required and analysis time was substantially decreased compared to transmission FT-IR. Samples were analyzed with high precision (coefficient of variation (CV) < 0.5%). Precision of assay was maintained when assaying plasma volumes of only 10 µL. The application of the method to the determination of total body water in humans and animals (horses) was demonstrated. A rapid and simple method for the measurement of deuterium in plasma is described that only requires very small sample volumes, rendering the method suitable for use in pediatrics where blood sampling is required to be kept to a minimum.

Fourier Transform Infrared (FTIR) Spectroscopic Analyses of Microbiological Samples and Biogenic Selenium Nanoparticles of Microbial Origin: Sample Preparation Effects.

To demonstrate the importance of sample preparation used in Fourier transform infrared (FTIR) spectroscopy of microbiological materials, bacterial biomass samples with and without grinding and after different drying periods (1.5–23 h at 45 °C), as well as biogenic selenium nanoparticles (SeNPs; without washing and after one to three washing steps) were comparatively studied by transmission FTIR spectroscopy. For preparing bacterial biomass samples, Azospirillum brasilense Sp7 and A. baldaniorum Sp245 (earlier known as A. brasilense Sp245) were used. The SeNPs were obtained using A. brasilense Sp7 incubated with selenite. Grinding of the biomass samples was shown to result in slight downshifting of the bands related to cellular poly-3-hydroxybutyrate (PHB) present in the samples in small amounts (under ~10%), reflecting its partial crystallisation. Drying for 23 h was shown to give more reproducible FTIR spectra of bacterial samples. SeNPs were shown to contain capping layers of proteins, polysaccharides and lipids. The as-prepared SeNPs contained significant amounts of carboxylated components in their bioorganic capping, which appeared to be weakly bound and were largely removed after washing. Spectroscopic characteristics and changes induced by various sample preparation steps are discussed with regard to optimising sample treatment procedures for FTIR spectroscopic analyses of microbiological specimens.

NiO nanoparticles: Facile route synthesis, characterization and potential towards third generation solar cell

Abstract In this work, nickel oxide nanoparticles (NiO NPs) have been synthesized through highly versatile and cost-efficient chemical precipitation process using polyvinylpyrrolidone (PVP) as a surfactant. The X-ray diffraction (XRD), UV–Visible (UV–Vis), Thermogravimetric analysis (TGA), and Fourier transform infrared (FTIR) techniques were employed to characterize the synthesized NiO NPs. The XRD pattern studies revealed that the NiO NPs have a face-centered cubic (FCC) structure and the mean crystallite size of about 7 nm. The optical band gap of 2.88 eV estimated from the tauc plot of thin film UV–vis absorption spectra. FTIR transmission spectra display a prominent band at ∼433 cm−1, which coincides with the bending vibration of Ni–O bond. The prepared NiO NPs retain the prodigious potential as a transparent electrode towards the solar photovoltaic (PV) cell.

Ga speciation in Ga/H-ZSM-5 by in-situ transmission FTIR spectroscopy

H-ZSM-5 supported Ga (Ga/H-ZSM-5) has long been recognized as a promising catalyst for nonoxidative dehydrogenation and dehydroaromatization of alkanes. However, Ga speciation under reaction conditions remains controversial. In this work, in-situ transmission Fourier Transform infrared (FTIR) spectroscopy is employed to systematically investigate Ga speciation in Ga/H-ZSM-5 with three Si/Al ratios (15, 28 and 39) and a wide range of Ga/Al ratios (0–1.7). Quantitative FTIR spectroscopy with pyridine reveals that one Ga atom roughly replaces one Brønsted acid site (BAS) at Ga/BAS ratio up to 0.7, however, only up to ~80% of the BAS on the H-ZSM-5 can be exchanged even with excess amounts of Ga. At a low Si/Al ratio of 15, the intensity of GaHx bands on reduced Ga/H-ZSM-5 at 550 °C increases almost linearly at low Ga loadings (Ga/Al < 0.13), and then levels off. In contrast, no detectable GaHx bands are observed on Ga/H-ZSM-5 with a high Si/Al ratio of 39, with Ga/Al ratios up to 1.3. The dependence of GaHx bands on both the Si/Al ratios and the Ga/Al ratios shows that Ga speciation varies with BAS density in the zeolite. We hypothesize that paired BAS sites are preferentially exchanged with Ga+, leading to the formation of Ga+−H+ pair sites, while the exchange of isolated BAS form isolated Ga+ species. Using water as a probe molecule, we show that isolated Ga+ and Ga+−H+ pair sites have distinct properties, i.e., the former can be easily oxidized by water at 150 °C to form GaOOH species, while the latter is inactive under the same conditions. These results provide direct experimental evidence for the existence of two types of Ga species on reduced Ga/H-ZSM-5, highlighting the possibility that they have different catalytic activities in alkane dehydrogenation reactions.

Water adsorption on silica and calcium‐boroaluminosilicate glass surfaces—Thickness and hydrogen bonding of water layer

AbstractAdsorption isotherm of water on silica (modeled with fused quartz) and calcium‐boroaluminosilicate (Ca‐BAS) glass surfaces as a function of relative humidity (RH) was studied using Fourier transform infrared (FTIR) spectroscopy. The effective thickness of the adsorbed water layer and the distribution of hydrogen bonding interactions of water molecules in the adsorbed layer were determined by comparing the transmission FTIR spectra collected at the Brewster incidence angle with the theoretically calculated spectra. In the sub‐monolayer regime (&lt;30% RH), differences between the water spectra on fused quartz and Ca‐BAS glass could be related to the areal density of hydroxyl groups as well as the elemental composition of the surface determined with x‐ray photoelectron spectroscopy. In the transition regime (30%–60% RH), multilayers start growing and the difference between the fused quartz and Ca‐BAS surfaces diminishes as the humidity increases. In the multilayer regime (&gt;60% RH), the total amount as well as the hydrogen bonding interactions of adsorbed water layers become insensitive to the surface chemistry and are governed mostly by the phase transition (vapor condensation) behavior. Overall, this study reveals how the water layer thickness and structure on the multicomponent silicate glass surface in ambient conditions are different from those on the pure silica surface.