FTIR Spectroscopic Studies Research Articles

Optimizing sensitizer concentration from senna tora leaves for enhanced interfacial interactions in dye-sensitized solar cells

A novel approach is adopted for the determination of the optimum concentration of natural dye powder extracted from the leaves of Senna Tora in the solvent ethanol and soak the TiO2 coated FTO substrate to be used as photoanode of dye sensitized solar cell (DSSC). Various concentration (0.5 g/15 ml, 0.75 g/15 ml, 1 g/15 ml and 1.5 g/15 ml) of the dye powder in ethanol is subjected for UV–Visible, FTIR and PL Spectroscopic studies. Solar cells are fabricated with the sensitizer in Photoanode, I-/I3- electrolyte and counter electrode of graphite coated FTO are subjected for JV characterization to determine the best concentration of dye to give good photoconversion efficiency. From the study, it is found that, among the four concentrations of the dye in ethanol for the extraction of the dye, 1.5 g in 15 ml of ethanol has shown higher efficiency of 2.29 % with fill factor, short circuit current density and open circuit voltage of 0.84, 2.64 mA/cm2 and 1.03 V.

A homobimetallic nickel(II) complex for discriminative chromogenic recognition of aqueous cyanide and silver(I) from medicinal products: Role of end-on thiocyanate bridging

Herein, a homobimetallic azomethine-functionalized nickel(II) complex, [Ni2L2(van)(μ1,1-NCS)] (AMR-1, where L = 2-[(2-Hydroxy-1,1-dimethyl-ethylimino)-methyl]-6-methoxyphenol, molecular weight = 788.20 (found)) has been judiciously synthesized with N-coordinated end-on thiocyanate. AMR-1 exhibited promising chromogenic variation from pale green to colourless with hypochromic shifting in the visible region in the presence of silver(I). Herein, the exposed sulfur site of the co-ligand acts as chemodosimetric recognition site for highly selective detection of a soft metal pollutant, silver ion (Ag+) with the limit of detection (LOD) of 0.37 ppm. Along with this, aqueous cyanide (CN−) recognition was accomplished in a mutually independent way with distinct chromogenic variation from pale green to yellowish color within ∼5 s. This led to the LOD of 0.46 ppm, which is much lower than the safe limit, set by the World Health Organization (WHO). The stability constant value for cyanide interaction with AMR-1 is obtained to be 1.49 × 103 M−1 as per 1:1 binding stoichiometry. Experimental findings, obtained from UV–Vis, HR-MS, FT-IR, and 1H NMR spectroscopic studies in conjugation with the decreased HOMO-LUMO energy gap from 3.40 eV to 2.07 eV, obtained from density functional theory studies, support the mechanistic pathway of interaction. Implementing molecular logic platforms benefits from fabricating three-input-two-output logic circuits by imitating variable spectroscopic outcomes. Real-time multifarious applications of AMR-1 have been accomplished with paper strip-based solid-state assay and recognition of the target-specific analytes from targeted medicinal specimens and from both cyanogenic as well as non-cyanogenic food sources. To the best of our knowledge, this is probably the first nickel(II) complex derived sensory receptor that is effectually implemented towards recognition of another metal ion, silver (I) along with CN− from aqueous as well as from real specimens.

Study of thermally induced interactions between active substances from the sartans class and various excipients

AbstractSartans, also known as angiotensin receptor blockers, comprise a category of antihypertensive medications designed to inhibit the actions of angiotensin II (Ang II) in the body, ultimately reducing blood pressure levels. This class of compounds is derived from 2-(1-benzyl-1H-imidazol-5-yl)-acetic acid, with its origin characterized by an imidazole core that underwent various substitutions at specific positions within the heterocyclic nucleus. We investigated the behavior of Losartan, Valsartan and Irbesartan and their compatibility with various excipients used in pharmaceutical tablet formulations by FTIR spectroscopic studies, thermal behavior by thermogravimetry and differential scanning calorimetry. The aim of the study was to determine the excipients to be used in pharmaceutical formulations containing drugs from the class of sartans as active ingredients. Our study concludes by recommending precautionary measures in elaborating new solid formulations containing lactose in the case of Losartan.

Newly synthesised diglycolamide functionalised silica gel with terminal 2-ethylhexyl alkyl chain, Silica-DGA (2EH) having high ligand density for adsorption of trivalent actinide and lanthanide from acidic medium

A novel diglycolamide resin with 2-ethylhexyl terminal alkyl chain functionalised to silica gel was synthesised and characterised by ATR-FTIR, SEM, TG/DSC, &13C (CP/MAS) solid state NMR techniques. Effective functionalization of the organic ligand upon silica gel was confirmed from the two carbonyl stretching frequencies at 1735 cm−1 and 1619 cm−1 in the FTIR spectrum and carbonyl carbon atom signal at 170 ppm in 13C (CP/MAS) solid state NMR spectrum. Thermo gravimetric measurement showed 17.3 ± 0.2 % (W/W) weight loss corresponding to the ligand loading value of 425 µmol/g. The resin showed very high uptake of trivalent lanthanide and actinide ions from 4.0 M HNO3 medium and very low distribution of Cs & Sr; Kd ∼ 1.1×103 mL/g for Am(III), ∼ 1.41×103 mL/g for Eu(III), ∼2.5 mL/g for Sr and 1.53 mL/g for Cs. FTIR spectroscopic study of the Eu3+ adsorbed resin showed single carbonyl stretching frequency at 1654 cm−1, instead of the two carbonyl stretching frequencies in fresh silica-DGA(2EH) resin indicating complexation through carbonyl oxygen. Very low Kd of ∼1.2–5.1 mL/g for lanthanides/actinides from 4.0 M HNO3 containing water soluble DGA namely N, N, N, N, Tetraethyldiglycolamide (TEDGA) in the concentration range 0.3–0.1 M indicates 99 % back adsorption feasibility.

Synthesis, characterization, in vitro and in silico biological studies of 3d transition metal(II) chelates of a Schiff base derived from sulfamethazine and 3,5-diiodosalicylaldehyde

A Schiff base (imine) ligand, (E)-4-((2-hydroxy-3,5-diiodobenzylidene)amino)-N-(4,6-dimethylpyrimidin-2-yl)benzenesulfonamide (HL), was synthesized by condensation of 3,5-diiodosalicylaldehyde with sulfamethazine. The ligand was then complexed with Zn(II), Cu(II), Ni(II), Co(II) and Fe(II) employing a metal to ligand ratio of 1:2 to form chelates (1-5), [M(L)2(H2O)2]. Characterization was done by UV-visible, FTIR, 1H and 13C NMR spectroscopy, elemental analysis, magnetic moments, thermogravimetric analyses (TGA) and conductance studies. The Schiff base behaved as a bidentate ligand and metal chelates assumed octahedral geometry. MOE-docking was employed to assess binding of the Schiff base (HL) and its chelates (1-5) with 1T2P, 1VVQ, 2W61, 3U2D, 4H8E and 5K18 proteins. Results indicated that Zn(II) chelate (1) and Fe(II) chelate (5) are the most potent compounds. Antibacterial and antibiofilm activities were executed against Enterococcus faecalis, Staphylococcus aureus, Proteus mirabilis and Klebsiella pneumoniae. Antifungal activities were performed against Candida albicans and Aspergillus niger. The Schiff base exhibited moderate antibacterial/antifungal activities that were enhanced on chelation with metal ions. Zinc(II) chelate (1) and Fe(II) chelate (5) show excellent antibacterial/antifungal activities. Complex 2 exhibited good antibiofilm activity.

A multi-stimuli-responsive fluorescence material based on 1,8-naphthalimide.

A pair of 1,8-naphthalimides (NPIs) were designed and successfully synthesized through embellishing amino-containing NPI with 4-diethylaminosalicyladehyde and 4-diethylaminobenzaldehyde, respectively. Their structures were fully confirmed by 1H/13C NMR, HR-MS and FT-IR spectroscopic studies. Their photophysical properties were systematically investigated in different solvents of varied polarity, in THF/water mixtures with varying water fractions (fw), and in THF solvent with varying concentrations of NPIs. It inferred that the distinct differences in emission between two NPIs during self-assembled process could be ascribed that the hydroxyl-containing NPI allowed the excited-state intramolecular proton transfer process between -OH and CH=N units in the aggregation state. Interestingly, the solid of 4-diethylaminosalicyladehyde-functionalized NPI exhibited multi-stimuli-responsive fluorescence changes involving mechanofluorochromism and HCl/NH3 vapor stimulus-induced conversion. However, no remarkable change was observed in the photoluminescence (PL) spectra for the solid of 4-diethylaminobenzaldehyde-functionalized NPI under the stimuli of mechanical force and organic solvent.

The effect of SiO2 crystallization in enhancing the luminescence of Dy3+-Sm3+ co-doped glass ceramics for cool white light application.

The present work investigates the structural and luminescence behaviour of Dy3+-Sm3+ co-doped glass ceramics obtained through heat treatment of precursor glasses. The growth of SiO2 polycrystalline particles and evolution of these crystallites in the glass domain are witnessed via XRD and FESEM study. The presence of network vibrational bands, hydroxyl groups and the increased quantity of bridging oxygens (BOs) in glass ceramics are analysed through FTIR spectroscopy study. The absorption study (UV-Visible-NIR) showed the possible electronic transitions of Dy3+ and Sm3+ ions. The red shift in the absorption band edges and the lower bandgap values are obtained as a result of improved heat treatment in glass ceramics. Emission studies show the enhanced luminescence intensity of glass ceramics under 350 and 402 nm excitations. Decay measurement of glass ceramics showed the improved lifetimes of Dy3+ and Sm3+ ions to have appeared in microseconds (×10-6s). The colour characteristics of glass ceramics analysed using CIE colour chromaticity diagram and correlated colour temperature (CCT) values suggest the neutral to cool white light emissions. Therefore, prepared glass ceramics with SiO2 polycrystalline phase are considered to be suitable materials in cool white LEDs applications.

Influence of oxygen pressure during deposition on the microwave dielectric tunability of Ba0.5Sr0.5TiO3 thin films in PLD process

Thin films of Ba0.5Sr0.5TiO3 (BSTO) were pulsed laser deposited on platinized silicon substrates with varying oxygen pressure from 5 × 10−1 mbar to 5 × 10−6 mbar. A strong correlation between the oxygen partial pressure during the PLD process and the structural and microwave dielectric properties of the PLD-grown BSTO thin films is observed. The structural properties of the PLD-grown BSTO films were analyzed by XRD, Raman spectroscopy, FTIR spectroscopy, and XPS studies, and it is observed that oxygen vacancies are formed in low oxygen pressure deposited films. Dielectric studies at microwave frequencies show that high oxygen pressure deposited BSTO films show good microwave dielectric properties and crystallinity. At 1 GHz frequency, the BSTO film grown at 5 × 10−2 mbar oxygen pressure exhibits a dielectric constant ∼470 and dielectric loss ∼0.15. The oxygen vacancies change the nature of metal-oxide bonding (Ti-O bond), affect the polarizabilities, and, as a result, reduce the dielectric constant. A maximum dielectric tunability of 71 % is observed in microwave frequencies for the BSTO films grown at 5 × 10−2 mbar oxygen pressure.

Encapsulation of three different types of polyphenols in casein using a customized pH-driven method: Preparation and characterization

Phenolic compounds represent natural compounds endowed with diverse biological functionalities. However, their inherent limitations, characterized by poor water solubility and low oral bioavailability, limit their broader applications. Encapsulation delivery systems are emerging as a remedy, able to ameliorate these limitations by enhancing the stability and solubility of phenolic compounds. In this study, a novel, customized pH-driven approach was developed by determining the optimal deprotonation and protonation points of three different types of polyphenols: ferulic acid, resveratrol, and rhein. The polyphenols were successfully encapsulated in a casein carrier. The solubility, stability, LogD, and LogS curves of the three polyphenols at different pH values were analyzed to identify the optimal deprotonation points for ferulic acid (pH 9), resveratrol (pH 11), and rhein (pH 10). Based on these findings, three different nanoparticles were prepared. The encapsulation efficiencies of the three phenolic compounds were 95.86%, 94.62%, and 94.18%, respectively, and the casein nanoparticles remained stable at room temperature for seven days. FTIR spectroscopy, fluorescence spectroscopy, and molecular docking study substantiated the encapsulation of phenolic compounds within the hydrophobic core of casein-based complexes, facilitated by hydrogen bonding interactions and hydrophobic interactions. Furthermore, the analysis of antioxidant activity elucidated that casein nanoparticles heightened both the water solubility and antioxidant efficacy of the phenolic compounds. This customized encapsulation technique, by establishing a transitional pH value, resolves the challenges of chemical instability and facile degradation of polyphenols under alkaline conditions in the application process of pH-driven methods. It presents novel insights for the application of polyphenols in the domains of food and biomedical fields.

PREPARATION AND CHARACTERIZATION OF SOLID DISPERSION USEFUL IN MAKING SUBLINGUAL TABLETS OF PIROXICAM

This study aimed to investigate the usage of solid dispersion (SD) to enhance the dissolution rate of the poorly soluble drug piroxicam for sublingual formulation. Poloxamer grade 407 (Kolliphor® P-407), a commercially available polymer, was chosen, and various solid dispersions with different weight ratios of piroxicam and Poloxamer were prepared using the hot melt method. Compatibility tests using FTIR spectroscopy, DSC, and XRD were conducted to assess any chemical or physical interactions between the drug and polymer. In vitro dissolution tests were performed on the solid dispersions. The results of the FTIR spectroscopy study indicated no chemical interaction between the drug and the polymer. Similarly, the DSC and XRD analyses showed no physical interaction between the drug and the polymer. The maximum cumulative percentage release of the pure drug and the solid dispersion at 15 minutes were 40.90±1.83% and 99.56±3.25%, respectively. Based on these findings, it was concluded that the solid dispersion with a ratio of 2:1 (Drug: Poloxamer-407) showed a noteworthy upsurge in the dissolution rate in comparison to the pure drug.

Anthocyanins of Delonix Regia Floral Petals: A Novel Approach on Fluorescence Enhancement, Forster Resonance Energy Transfer Mechanism and Photostability Studies for Optoelectronic Applications.

In this work, we focused on extracting the anthocyanin dye in acetone, butanol, ethanol, and water solvents from Delonix regia flowers by a simple maceration extraction process. The identification of functional group analysis, vibrational studies, energy transfer mechanisms, optoelectronic properties, photostability studies, FRET-assisted potential light emissions and photometric properties of the anthocyanin dyes are successively investigated. FTIR spectroscopy and vibrational studies have confirmed the existence of polyphenolic groups in 2-phenyl chromenylium (anthocyanin) dyes. The optoelectronic results show the least direct bandgap (2.04eV), indirect bandgap (1.55eV), Urbach energy (0.380eV), high refractive index (1.20), dielectric constant (2.794), and high optical conductivity (1.954 × 103 S/m) for the anthocyanin dye extracted found in water solvent. The photoluminescence properties such as Stoke's shift, high quantum yield, and lifetime results show that anthocyanin dyes are promising candidates for red-LEDs and optical materials. The absorption and emission spectra of the anthocyanin dyes follow the mirror image rule and the Franck-Condon factor exists between vibrational energy levels corresponding to all the electronic transitions. The excellent correspondence between the absorption and emission spectra reinforces that the anthocyanins are efficient (46%) FRET probes. Further, photometric properties such as CIE, CRI, CCT and colour purity results of anthocyanins in all studied solvents revealed that this material exhibits orange to red shades (x = 0.48 → 0.54 and y = 0.36 →0.45) and is well suitable for have great potential in the manufacturing of Organic-LEDs and other optoelectronic device applications.

A Ratiometric Green Fluorescent Carbazole-Bis(hydrazinobenzothiazole) Probe for the Selective Detection of Toxic Hg2+ Ions in Real Water Samples.

A dyad Carbazolyl-bis(hydrazinobenzothiazole) was designed to form a symmetrical structure that containing two-arm active binding sites facilitates coordination with Hg2+ ion. This sensor has imparted a colorimetric and fluorometric changes in presence of Hg2+ ions. The ligand showed a selective blue shift in presence of Hg2+even in co-existence with heavy metal ions with luminescence change from colorless to blue and colorless to green under day light. Enhanced Intramolecular charge transfer process is responsible for fluorescence transformation when ligand interacts with Hg2+ ion. The emission spectra showed a ratiometric response to increasing addition of Hg2+ ions. The sensor is capable of detecting above the lower concentration of 6.8025×10-8 M. The fluorescence efficiency of CBT-2 with Hg2+ ion is quite stable under different co-metal ions and wide range of pH 6 to 9. The sensor CBT-2 forms a 1 : 1 stoichiometric complex with Hg2+ ions and the binding nature is confirmed from the 1H-NMR, FTIR, and mass spectroscopic studies. The sensor CBT-2 and its Hg2+ complex possess good binding nature to protein in Bovine Serum Albumin which could be good in biological applications. Additionally, wedevelop a practical application in real water sample analysis and electrochemical detection via oxidation potential discrimination.

Transformative Dynamics: Self-Assembly of Iron Oxide Hydroxide Nanorods into Iron Oxide Microcubes for Enhanced Perfluoroalkyl Substance Remediation.

We report the controlled synthesis of iron oxide microcubes (IOMCs) through the self-assembly arrays of ferric oxide hydroxide nanorods (NRs). The formation of IOMCs involves a complex interplay of nucleation, self-assembly, and growth mechanisms influenced by time, thermal treatment, and surfactant dynamics. The self-assembly of vertically aligned NRs into IOMCs is controlled by dynamic magnetism properties and capping agents like cetyltrimethylammonium bromide (CTAB), whose concentration and temperature modulation dictate growth kinetics and structural uniformity. These controlled structural growths were obtained via a hydrothermal process at 120 °C at various intervals of 8, 16, 24, and 32 h in the presence of CTAB as the capping agent. In this hydrothermal method, the formation of vertically oriented NR arrays was observed without the presence of ligands, binders, harsh drying techniques, and solvent evaporation. The formation of the self-assembly of NRs to IOMCs is obtained with an increase in saturated magnetization to attain the most stable state. The synthesized IOMCs have a uniform size, quasi-shape, and excellent dispersion. Due to its excellent magnetic and catalytic properties, IOMCs were employed to remove the various emerging pollutants known as per- and polyfluorinated substances (PFAS). Various microscopic and spectroscopic techniques were employed for the characterization and interaction studies of IOMCs with various PFAS. The interaction between IOMCs and perfluoroalkyl substances (PFAS) was investigated, revealing strong adsorption tendencies facilitated by electrostatic interactions, as evidenced by UV-vis and FT-IR spectroscopic studies. Furthermore, the higher magnetic and positive surface charge of IOMCs is responsible for an effective remediation eliminating any secondary pollution with ease of recovery after the sorption interaction studies, thereby making it practically worthwhile.

Synthesis, Characterization and Antioxidant Activity of some New Antipyrine derived Schiff Bases

Synthesis, characterization of a series of some new antipyrine derived Schiff bases 5(a-f) have been carried out and evaluated for their antioxidant activity. The newly synthesized compounds were characterized by physical and spectral data. The compounds 5(a-f) were measured for physical parameters and enlisted. The completion of the reaction, the progress of the reaction, and the purity of all newly produced compounds were monitored by TLC. Compounds in series 5(a-f) have yields that vary from 70 to 93%. Based on a review of the literature, there were no antipyrine derivatived Schiff bases reported till now, hence they were synthesized and characterized in this work. It was found that these moieties were useful in the field of pharmaceutical chemistry and that they demonstrated a variety of pharmacological actions. In the current work, six synthetic compounds 5(a-f) were prepared, and characterized by FTIR, 1HNMR and Mass spectroscopy studies. Melting points were determined and TLC was used to verify the purity of each compound. In an effort to produce new therapeutic compounds these compounds are tested for antioxidant properties and reported.

Crystal chemistry, Raman and FTIR spectroscopy, optical absorption, and luminescence study of Fe-dominant sogdianite

Abstract Fe-dominant sogdianite, a cyclosilicate compound with the chemical formula (Fe3+ 0.74Zr0.64Ti0.46 Al0.15)(□1.02Na0.98)K[Li3Si12O30], was studied. The investigation involved a comprehensive analysis of the mineral sample, including crystal-chemical analysis, Raman and FTIR spectroscopy, optical absorption, and luminescence study. Crystallographic site populations were determined through single crystal structure refinement and electron probe microanalysis. The thermoelastic behavior of a powder was studied using in situ high-temperature X-ray diffraction (30–750 °C). Notably, no phase transition was detected; sogdianite exhibited anisotropic thermal expansion. The first time study of vibrational spectra and spectral bands assigning were performed. The electronic transitions in d 5-ion impurities of sogdianite were studied using optical absorption and luminescence spectroscopy. The origin of pink color and luminescence of sogdianite was clarified. The broad spectral bands in the visible UV spectral region are responsible for the pink color exhibited by sogdianite and could be attributed to d–d transitions occurring in Fe3+ ions.

Synthesis, Structural, and Optical Properties of 2-(2-methyl 8-hydroxyquinoline) Magnesium Nanorods for Optical Display Systems.

Organic semiconductors find widespread applications in the realm of organic light-emitting diodes (OLEDs) as well as organic photovoltaic cells. In the domain of OLED devices, it is plausible for nano-based Mg metal complexes to play a role as electron and hole-transport layers. In the present investigation, we synthesized 2(2-methyl 8-hydroxyquinoline) magnesium [Mg(mq)2] nanorods through the employment of the precipitation method, using 2-methyl 8- hydroxyquinoline and magnesium acetate. We employed various techniques to characterize the Mg(mq)2 nanorods, including powder XRD, FTIR spectroscopy, SEM, EDX, UV-Vis, and PL spectroscopy studies. The structural aspects of Mg(mq)2 were ascertained through P-XRD analysis. The elemental composition of Mg(mq)2 and its surface texture were established via EDX and HR-SEM analyses. FTIR spectroscopy confirmed the existence of functional groups within the sample. UV-Vis spectroscopy was utilized to evaluate the optical absorbance, bandgap, and Urbach energy of Mg(mq)2. The luminescence properties of the Mg(mq)2 nanorods were determined from the photoluminescence study. The characterization results were compared with the Zn(mq)2 nano samples. The experimental results presented herein serve to demonstrate the practicality of employing Mg(mq)2 nanorods in OLED devices.

Comparative physicochemical and FTIR spectroscopic studies of exudate and purified forms of Moringa oleifera gum and Jhingan gum

Comparative physicochemical and FTIR spectroscopic studies of exudate and purified forms of Moringa oleifera gum and Jhingan gum

Evaluation of Antibacterial, Antioxidant and Immunomodulatory Potential of Mitragyna parvifolia Leaves-Assisted Fe2O3 Nanoparticles

This work includes the use of leaves of Mitragyna parvifolia for green synthesis of [Formula: see text] nanoparticles ([Formula: see text] NPs), which offers a sustainable eco-friendly approach. Characterization of synthesized [Formula: see text] NPs was done by UV-visible, FTIR spectroscopy, XRD and FESEM studies. FTIR exhibited the existence of Fe-O, O–H and COO–Fe stretching owing to the occurrence of the carboxylic group. FESEM analysis revealed that the average size of [Formula: see text] NPs was 92 nm, which varies in their shape. The study also includes the determination of antibacterial, in vitro antioxidant and immunomodulatory efficacy of synthesized [Formula: see text] NPs. Results suggested that [Formula: see text] NPs exhibit potent antibacterial efficacy against B. subtilis and S. aureus, gram-positive as well as E. coli and P. aureginosa, gram-negative bacterial strains used in this study. The study exhibited significant ([Formula: see text] < 0.01) in vitro antioxidant and immunomodulatory potential of synthesized [Formula: see text] NPs against concanavalin-A activated Wistar albino rat’s splenocytes. The green synthesized [Formula: see text] NPs using M. parvifolia leaves may offer a novel approach in the medicinal and immunological field to overcome oxidative stress as well as enhance immune responses for potential health benefits of human beings.

Interactions between Ethyl Lactate and Substituted Ethanols or Ethyl Acetate: Thermodynamic, FT-IR Spectroscopic, DFT Method, and PC-SAFT EoS Studies

Interactions between Ethyl Lactate and Substituted Ethanols or Ethyl Acetate: Thermodynamic, FT-IR Spectroscopic, DFT Method, and PC-SAFT EoS Studies

Silver-Loaded Chabazite in Ethanol-to-Hydrocarbon Process-Operando FT-IR and UV-Vis Spectroscopic Studies.

The ethanol dehydration process is studied regarding protonic and Ag-loaded chabazite zeolite in advanced FT-IR and UV-vis operando spectroscopic studies with simultaneous mass spectroscopy and gas chromatography analyses of products. The spectroscopic investigation provides information on the species formed on the surface of catalysts, while mass spectrometry and gas chromatography methods identify the desorbed products. These studies are also supported by spectroscopic, chromatographic, and thermogravimetric analyses of coke species formed over the catalyst's surface during ethanol conversion. The Ag-chabazite catalyst shows higher selectivity for ethylene and propylene; the slower formation of coke species; and, thus, a longer lifetime.