Brunauer Emmett Teller Method Research Articles

Porous polyaniline/flower-like hybrid phase MoS2/phosphorus-doped graphene ternary nanocomposite for efficient room temperature ammonia sensors

Ammonia, a ubiquitous gas with diverse industrial applications, demands reliable and cost-effective sensing technologies for monitoring and control. In this context, this study presents the development of a novel ternary nanocomposite comprised of porous polyaniline (PANI), hybrid phase molybdenum disulfide (MoS2), and phosphorus-doped graphene (PGO) for the realization of highly efficient room temperature ammonia sensors. The synergistic combination of these three materials leverages their individual properties, such as high surface area, excellent electrical conductivity, and enhanced catalytic activity, to create a robust sensing platform. The PANI/1 T-2 H MoS2/PGO nanocomposites were synthesized by a combination of solvothermal processing and in-situ polymerization techniques. The morphological and structural characteristics of the PANI/1 T-2 H MoS2/PGO nanocomposites were conducted using advanced analytical techniques, that include, Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Raman spectroscopy, Transmission Electron Microscopy (TEM), and X-ray Photoelectron Spectroscopy (XPS), and Brunauer-Emmett-Teller method (BET). The enhanced surface area of PANI/1 T-2 H MoS2/PGO (54.72 m2/g) compared to PANI (31.8 m2/g) has a positive impact on the sensing characteristics of PANI/1 T-2 H MoS2/PGO. The PANI/1 T-2 H MoS2/PGO nanocomposite sensor has shown sensing response values of ∼1070 %, response time of 12 s, recovery time of 30 s towards 100 ppm of NH3, and detection limit is 0.01 ppm (10 ppb). A highly linear gas response of the PANI/1 T-2 H MoS2/PGO sensor is observed in a range of 10–100 ppm ammonia concentration. The development of the PANI/1 T-2 H MoS2/PGO nanocomposite sensor aims to meet the increasing need for temperature-efficient, cost-effective, and energy-efficient gas sensing technologies that can be used in various fields including environmental monitoring and industrial safety.

Metal-free adsorption and photodegradation methods for methylene blue dye removal using different reduction grades of graphene oxide

The release of organic pollutants and dyes into the environment by industries has had profound and harmful effects on both humans and ecosystems. Graphene oxide (GO) and its reduced form have been investigated for their effectiveness in removing pollutant dyes. GO nano-powder was synthesized using an improved version of Hummer's method and subsequently thermally reduced at various temperatures, including 125, 150, 175, and 200 °C, under vacuum conditions. In the X-ray diffraction spectra, an intense (001) diffraction peak was initially observed at 9.136° (2θ) for pristine GO. This peak gradually shifted towards higher angles as the reduction process took place and eventually disappeared when the GO was reduced at 200 °C. The intensity ratio of the D and G bands (ID/IG ratio) for GO nano-powder in the Raman spectra decreased from 0.94 to 0.76 due to the reduction process. The FTIR spectra of GO and reduced graphene oxide (rGO) also illustrated the reduction process. The bandgap of pristine GO significantly decreased from 2.31 to 0.73 eV, as determined by ultraviolet–visible (UV–Vis) diffuse reflectance spectrophotometry during the reduction process. The surface area and pore volume of both pristine GO and rGO-150 were determined using the BET (Brunauer-Emmett-Teller) and BJH (Barrett-Joyner-Halenda) methods. The results indicated an increase in the BET surface area from 6.61 to 7.86 m2/g and a corresponding enhancement in pore volume from 0.118 to 0.128 cc/g after reduction. The adsorption and photocatalytic degradation behavior of pristine GO and reduced graphene oxides (rGOs) were examined using methylene blue dye. The pristine GO demonstrated impressive adsorption capability, effectively removing the dye by 85.78 % within just 15 min and achieving nearly 97 % removal after 4 h. In contrast, the highest photocatalytic degradation of methylene blue, about 47.58 %, was attained for the rGO sample reduced at 150 °C under the illumination of visible light.

Efficient wastewater decontamination using magnetic bentonite-alginate beads: A comprehensive study of adsorption dynamics, regeneration, and molecular interactions

This study enhances wastewater treatment methodologies by developing magnetic bentonite-alginate beads (MBent-A beads) for adsorbing methylene blue (MB) from aqueous solutions. Experimental and computational analyses were employed to evaluate the beads' adsorption efficiency, utilizing characterization techniques including Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), point of zero charge (pHpzc), Brunauer-Emmett-Teller method (BET), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) to examine the composite’s morphology and chemistry. Findings reveal a significant adsorption capacity with the beads' specific surface area at 3.94 m2/g and a maximum adsorption capacity of 774.32 mg/g. Adsorption kinetics adhered closely to the pseudo-second-order model, indicating a rapid adsorption process, while Langmuir isotherm analysis confirmed a uniform monolayer adsorption and temperature-dependent capacities. Thermodynamic analysis showed the adsorption process to be spontaneous and exothermic, reflecting a strong affinity between MB molecules and the bead surface. The beads demonstrated durability with more than 90% removal efficiency after five regeneration cycles, highlighting a minimal decrease from 98.54% to 90.60%. In-depth theoretical investigations using density functional theory (DFT), frontier molecular orbital (FMO), reduced density gradient (RDG), and quantum theory of atoms in molecules (QTAIM) analyses identified van der Waals forces and hydrogen bonding as primary interactions driving the adsorption. The synthesis of MBent-A beads and their confirmed efficacy in dye adsorption integrates experimental research with theoretical modeling, offering a robust solution for treating dye-contaminated wastewater and underlining the potential of MBent-A beads in environmental remediation.

Synthesis of Cu-MOF-derived complex copper–chromium oxides and their catalytic study on the thermal decomposition of ammonium perchlorate

In this work, a series of complex copper-chromium oxides were prepared by adjusting the molar ratio of Cr3+/Cu2+ using MOF-199 as a template. X-ray diffraction (XRD), scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) were used to characterize the structure, microscopic morphology and valence information of the samples. The specific surface area of the sample was estimated by the Brunauer-Emmett-Teller method (BET), and the pore size parameters of the sample were obtained by using the Barrett-Joyner-Halenda (BJH) model. The effect of the samples on the thermal decomposition process of ammonium perchlorate (AP) was investigated by differential scanning calorimetry-thermogravimetric analysis. The results show that the copper and chromium oxides in the complex exhibit good catalytic effects. Among them, CuCr(0.8) had the best catalytic effect, reducing the peak pyrolysis temperature of AP by 95.7 °C, increasing the heat release by 817 J/g, and reducing the reaction activation energy by 62.4 kJ/mol. Real-time FTIR was used to characterize the gas products during the thermal decomposition of AP, and the gas products of AP with CuCr(0.8) catalyst were different from those of pure AP, which may also be the reason for the increase of AP heat release after adding CuCr(0.8) catalyst.

Electrochemical determination of theophylline using a nickel ferrite/activated carbon-modified electrode

In this work, a nanocomposite based on nickel ferrite/activated carbon (NiF/AC) was used to modify a highly sensitive electrochemical sensor for the quantification of theophylline (TPL) in pharmaceutical tablets. The synthesized materials were characterized using x-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive x-ray spectroscopy-elemental mapping and surface area analysis via the Brunauer–Emmett–Teller method. Cyclic voltammetry was employed to study the electrocatalytic properties of the NiF/AC-GCE toward the oxidation of TPL. The dependence of the electrochemical response on the scan rate and pH was also investigated, and the working parameters were optimized. The linear range of the established electrochemical biosensor was from 0.5 to 5 μM (R2 = 0.997), with a detection limit of 0.21 μM. The present method was tested using three pharmaceutical formulation standard samples with good accuracy and acceptable recovery. Thus, it is a promising candidate for the determination of TPL in pharmaceutical formulations.

Adsorption of methyl blue, dichromate, and copper on ettringite under various pH values

Ettringite is a hydrous calcium aluminum sulfate mineral present in cement. In this study, ettringite was synthesized via co-precipitation to remove methyl blue, dichromate, and copper ions from solutions with various pH values. The synthesized ettringite was characterized using scanning electron microscopy, X-ray photoelectron spectrometry, Fourier transform infrared spectroscopy, zeta potential analysis, and the Brunauer–Emmett–Teller method. Equilibrium adsorption experiments were performed using methyl blue and dichromate at pH values ranging from 5 to 11. To avoid precipitation, equilibrium adsorption experiments were performed on copper ions in solutions with pH values of 3, 4, and 5. The adsorption kinetics experiments for each contaminant were performed at pH 5. The results showed that ettringite was successfully synthesized, and calcite might have precipitated during the synthesis process. The point of zero charge was at pH 8.6. The maximum adsorption capacities for methyl blue, dichromate, and copper ions at pH 5 were 406, 321, and 365 mg/g, respectively. The adsorption kinetics fitted the pseudo-second-order model well. The properties of the contaminants affect their equilibrium and rate constants. Ion exchange is regarded as the primary adsorption mechanism, whereas the other mechanisms include complexation, hydrogen bonding, surface precipitation, π-interaction, and van der Waals forces. This study revealed a new adsorbent, ettringite, for the removal of contaminants from wastewater, which is a promising alternative adsorbent that can be used under specific conditions.

Solvothermal synthesis and adsorption performance of layered boehmite using aluminum chloride and high-alumina fly ash

High alumina fly ash (FAHAl) is a kind of bulk solid waste unique to China, whose availability of high-value aluminum and the threat to the environment make its high-value utilization urgent. In this work, the alumina containing leaching solution obtained from Na2CO3 roasting and HCl leaching of FAHAl was used as the mother liquor to prepare layered boehmite in situ. The preparation process with AlCl3 as the raw material was also compared. The formation process and mechanism of boehmite, the choice of solvent, along with the adsorption capability of Congo red were analyzed by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller method and adsorption experiments. Results showed that during the preparation of layered boehmite, the precursor Al(OH)3 from the reaction of Al3+ and OH– is transformed into boehmite γ-AlOOH. The existence of ethanol is beneficial to regulate and promote the growth of boehmite crystal effectively. When water and ethanol is mixed with a volume ratio of 2:1 and used as the solvent, the maximum specific surface area of the boehmite is obtained of 135.7 m2·g–1, and 99.16% of Congo red can be absorbed after 10 min when AlCl3 is used as raw material. As purified leaching solution is used as the mother liquid, the crystallinity of boehmite decreases slightly when the pH value decreases from 12.5 to 11. When pH is 11, the removal efficiency of Congo red reaches a maximum of 72.25%. This process not only achieves the extraction of aluminum and high-value utilization of FAHAl, but also provided a thought to prepare layered boehmite with adsorption properties.

Sn‐MFI and Fe‐MFI zeolites for fructose conversion to levulinic and lactic acids by the one‐pot method

AbstractThis paper presents the results of the use of MFI zeolite as a catalyst modified with tin and iron. Sn‐MFI and Fe‐MFI catalysts were obtained by ion exchange under hydrothermal conditions with and without ammonium exchange. Catalytic materials were characterized with the use of analytical techniques such as X‐ray diffraction (XRD), Brunauer–Emmett–Teller method (BET), diffuse reflectance spectroscopy in the ultraviolet‐visible range (DRS UV–visible), hydrogen temperature programmed reduction (H2‐TPR), or Fourier transform infrared (FTIR) spectroscopy. The one‐pot catalytic conversion of fructose was performed at 220 °C for 1–5 h. Based on the results, the influence of time and material selection on the products obtained can be seen. Lactic acid (LAC) was obtained with a yield of 68.7% (after 2 h) and levulinic acid (LA) with a yield of 70.9% (after 5 h) with the participation of MFI. In turn, formic acid with a yield of 28.5% (after 5 h) was obtained with the participation of Fe‐MFI.

Construction of ZnO/Cu2O composites for enhanced antibacterial activity and analysis of antibacterial mechanism

Composite antibacterial materials were prepared by loading ZnO with good stability and biocompatibility on Cu2O. Cu2+ was released slowly due to the loading of ZnO, so the ZnO-Cu2O composites achieved lasting antibacterial effect. The basic form of the resulting ZnO/Cu2O composites, chemical composition, and crystal structure analyses were carried out by scanning electron microscopy (SEM), electron diffraction spectroscopy, Brunauer–Emmett–Teller method, X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, and X-ray phosphorescence. The optical properties of ZnO/Cu2O composites were determined by UV–vis spectroscopy and photoluminescence spectroscopy. E. coli and S. aureus were used to detect the antibacterial properties of the ZnO/Cu2O composites. The antibacterial mechanism of ZnO/Cu2O composites was investigated through ion dissolution, reactive oxygen species (ROS), and mechanical damage experiments. The results show that the increase in specific surface area, slow release of Cu2+ and increase in ROS lead to better antibacterial activity of ZnO/Cu2O composites. The antibacterial mechanism of these ZnO/Cu2O composites involves ion release, active oxygen and mechanical damage. The internal damage of bacteria was further analyzed by lipid peroxidation, protein leakage, respiratory chain dehydrogenase activity and bacteria in vitro fluid ion to thoroughly understand the inactivation mechanism of bacteria by the composite antibacterial material.

Tailored synthesis of SnSe/SnO2@rGO composites with synergistic properties for photodegradation

SnSe/SnO2@rGO composite photocatalyst was prepared using a simple in-situ selenization method. The structure, morphology, and properties of the material were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and Brunauer–Emmett–Teller method. Moreover, the photocatalytic efficiency of the catalyst was evaluated on the aqueous solution of methylene blue under simulated natural light irradiation (wavelength >300 nm). After 120 min of degradation, the photocatalytic activity of SnSe/SnO2@rGO exceeded 90%. These results indicate that the heterojunction structure of SnSe/SnO2@rGO effectively promoted interfacial electron transfer and reduced the self-radiative recombination of charges, thereby improving the performance of the photocatalyst. Hence, the synthesized SnSe/SnO2@rGO possesses potential applications in the photocatalytic degradation of wastewater.

Complex microwave processing of high-ash brown coal in relation to the energy and metallurgical industries

Relevance. The need of the Tomsk region for valuable energy resources obtained from local low-grade resources to develop iron ore deposits available in the region and cover energy needs. Aim. To study gaseous and solid products obtained from low-grade brown coal of the Talovsky deposit (Tomsk region) under microwave pyrolysis conditions in relation to the energy and metallurgical industries. Objects. Brown coal of the Talovsky deposit (Tomsk region). Methods. Certified SS methods to determine thermal characteristics and elemental composition of coal organic and mineral parts, the "transmission-reflection" method for measuring imaginary (ε'') and real (ε') components of the complex dielectric permittivity, physical experiment, gas analysis, Brunauer–Emmett–Teller method for measuring texture characteristics. Results. Brown coal of the Talovsky deposit has high values of moisture and ash contents for operating conditions, which leads to a low calorific value. Such characteristics make it possible to classify coal as a low-grade fuel, which indicates the inexpediency of its use as a raw material for the energy and metallurgical industries. Thermal processing by means of microwave pyrolysis makes it possible to obtain a high-calorie (heat of combustion over 21 MJ/m3) and environmentally friendly (hydrogen content over 29%) gaseous fuel from the low-grade brown coal of the Talovsky deposit. The resulting solid carbonaceous residue has an ash content of over 48%, which required its chemical treatment in a solution of HF and HCl. As a result of the solid carbonaceous residue treatment, its ash content decreased by more than 38%, the sulfur content – by more than 1.5 times. According to its characteristics, the resulting product corresponds to the currently available carbonaceous products – semi-coke, coke and carbon reducing agent for ferroalloy production.

A green synthetic method for cobalt(II,III) oxide nanoparticles with high surface activity

Objectives. To develop a new green method for the synthesis of nanosized materials of cobalt(II,III) oxide, with improved surface activity, using environmentally friendly precursors and solvents.Methods. A green method was proposed, in order to isolate Co3O4 nanoparticles with high surface activity. Instead of the usual organic solvents, three different natural sugars, including glycogen, sucrose, and glucose were used for the first time as templates. Water as a green solvent was used in all the steps. The polymorphic composition of the synthesized samples was determined by means of X-ray phase analysis. The morphology of the obtained crystallites was studied from micrographs of the oxide phases. Image Pro Plus 6 software was used to measure the size of nanoparticles. The surface activity of the isolated samples was studied using the Brunauer–Emmett–Teller method and the Langmuir method. The Barret–Joyner–Halenda method was used to determine the diameter, volume, and distribution of pores.Results. The crystallite sizes of the samples are 23 nm, 36 nm, and 30 nm for glucose, glycogen, and sucrose templates, respectively. Adsorption–desorption isotherms for samples obtained from complexes of glucose and sucrose correspond to type IV, indicating a strong interaction between the adsorbent and the adsorbed sample. The isotherm for the sample isolated from the complex with glycogen is of a different type and most likely indicates that this sample is almost completely mesoporous. The pore radii are found in the interval 1.2–1.6 nm.Conclusions. A new green method for the synthesis of nanosized particles of Co(II,III) oxide using natural saccharides and deionized water was developed. The composition, morphology, structure, and surface activity of the samples obtained were studied. It was shown that due to the polymeric structure of their metal complexes and the ability to bind active carbon on the surface of nanoparticles, natural saccharides can be used as matrices in the synthesis of nanosized metal oxides with high surface activity.

Embedding and cross-sectioning as a sample preparation procedure for accurate and representative size and shape measurement of nanopowders

Reliable measurement of the size of polydisperse, complex-shaped commercial nanopowders is a difficult but necessary task, e.g., for regulatory requirements and toxicity risk assessment. Suitable methods exist for the accurate characterization of the size of non-aggregated, stabilized, spherical and monodisperse nanoparticles. In contrast, industrial nanoscale powders usually require dedicated sample preparation procedures developed for the analysis method of choice. These nano-powders tend to agglomerate and/or aggregate, a behavior which in combination with an innate broad particle size distribution and irregular shape often significantly alters the achievable accuracy of the measured size parameters. The present study systematically tests two commercially available nanoscale powders using different sample preparation methods for correlative analysis by scanning electron microscopy, dynamic light scattering, Brunauer–Emmet–Teller method and differential mobility analysis. One focus was set on the sample preparation by embedding nanoparticles in carbon-based hot-mounting resin. Literature on this topic is scarce and the accuracy of the data extracted from cross sections of these particles is unclearly stated. In this paper systematic simulations on the deviation of the size parameters of well-defined series of nanoparticles with different shapes from the nominal value were carried out and the contributing factors are discussed.

A facile method of treating spent catalysts via using solvent for recovering undamaged catalyst support.

The process of washing and removing crude oil from spent catalysts is a serious issue in both catalyst regeneration and precious metals recovery. In this work, five different solvents with various polar and aromatic properties were chosen to evaluate their impact on the catalyst support structure and crude oil recovery from oil-contaminated spent catalysts. After the deoiling process, the spent catalyst was analyzed by scanning electron microscopy, X-ray diffraction (XRD), Fourier transform-infrared spectroscopy, elemental analyzer, contact angle measurement, gas chromatography-mass spectrometry, inductively coupled plasma-atomic emission spectroscopy, and Brunauer Emmet Teller (BET) method. Our findings demonstrate that p-xylene and kerosene are more effective in removing oil than other solvents. This is due to crude oil's similar polarity and molecular nature with kerosene and p-xylene. Considering the economical reason, kerosene is a better choice for deoiling spent catalyst compared to p-xylene as it is more affordable than p-xylene. XRD data show that the structure of the catalyst support was unaltered by the solvent treatment process, while BET data reveals that the surface area and pore volume are significantly enhanced after the deoiling process. These results imply that deoiling is a very crucial step for the recycling, regeneration, and reuse of spent catalysts. Our work is significant in developing sustainable approaches for managing spent catalysts, and minimizing waste and environmental pollution.

Efficient Methanol Electro-oxidation on Ni, S Dual Doped Reduced Graphene Layer Catalyst

Energy crisis is the most popular issue in the world, which must be overcome with the development of alternative energy sources. Among them, methanol is a promising fuel when used in direct methanol fuel cells. However, the mentioned cell needs highly electroactive and stable anode materials toward MeOH. Ni has gained attention as it is an alternative to noble atoms. In this study, Ni was deposited on reduced graphene layer which functionalized with S atoms via the hydrothermal method. The fabricated sample was characterized by using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), mapping, X-ray Powder Diffraction (XRD), and Brunauer–Emmett–Teller method (BET). Two samples as called Ni/GCE and Ni@s-rGO/GCE were examined for methanol oxidation reaction in alkaline media. For methanol oxidation, due to the higher surface area, and small particle size of Ni, the mass activity of Ni@s-rGO/GCE is two times higher than Ni/GCE

Iron-TiO2 pillared clay nanocomposites: Eco-friendly solutions for photocatalytic removal of organic and pathogen contaminants

The synthesis of modified natural bentonite by TiO2 nanoparticles and their photocatalytic and antibacterial applications were studied. The natural bentonite (NB) used in this work has been purified by acid treatment to obtain activated bentonite (AB). Then, the intercalation of AB by Fe3+ noted, as FeAB was prepared. TiO2 and the three nanocomposites (TiO2/NB, TiO2/AB and TiO2/FeAB) were synthesized via a sol–gel and hydrothermal process. TiO2 pillared clays showed an important photocatalytic properties compared to TiO2 nanoparticles alone for the degradation of Metoprolol tartrate (MET). Therefore, TiO2/FeAB were found to be the most effective photocatalyst. The materials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) with energy dispersive spectroscopy (EDS) and BET (Brunauer-Emmett-Teller) method. The results of FTIR spectra was consistent with the DRX patterns. The SEM pictures reveal significantly larger particle aggregates, which correspond to bentonite and small particles, which belong to TiO2. The antibacterial activities of all samples was evaluated by using Escherichia coli (Gram-negative bacteria) and Staphylococcus aureus (Gram-positive bacteria). A considerably high bacterial inactivation was achieved within 1 h of visible light irradiation for E. coli colonies. However, in dark all the colonies of S. aureus were killed in the first 30 min.

Electrochemical Performances of PtCrCo Alloy/Nitrogen-Doped Activated Carbon for Proton Exchange Membrane Fuel Cell Catalyst

Proton Exchange Membrane Fuel Cell is a promising green energy conversion machine. However, some drawbacks, such as Pt corrosion on the cathode side, the high price of Pt, Nafion membrane, and the need for the high precision assembly process, limit their commercialization. In this study, PtCrCo alloy which is supported by nitrogen-doped activated carbon was synthesized by facile method to increase electrochemical performance as a cathode catalyst and reduce Pt catalyst usage. Nitrogen-doped Activated Carbon/PtCrCo/Nitrogen-doped Carbon (NAC/PtCrCo/N) catalyst was investigated to analyze the effect of increasing the composition of nitrogen-doped activated carbon in the synthesis process on the morphology and electrochemical performances of the catalyst. Polyaniline (PANI) as Nitrogen precursor was added to Activated Carbon (AC) powder with ratio of AC to PANI; 1:0, 3:1, 1:1, 1:3, as called AC, NAC1, NAC2, and NAC3 respectively. The catalyst synthesis process is carried out with the four activated carbon supports. Material characterizations were carried out using X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Brunauer-Emmett-Teller (BET), Cyclic Voltametry (CV), and Linear Sweep Voltametry (LSV). The XRD measurement shows that the addition of nitrogen doping tends to reduce the diffraction peak intensity of nitrogen-doped activated carbon compared to the pristine carbon. The doping also increases the surface area of the activated carbon as measured by the BET method. Nitrogen doping increases the conductivity and the addition of alloys can add better stability and catalytic activity for cyclic voltammetry results of the four catalysts cannot be calculated. The NAC3/Pt-Cr-Co/N electrocatalyst exhibited the highest initial potential at ~1 mAcm-2 of 0.997 V compared to the other four samples. On the other hand, AC/Pt-Cr-Co/N catalyst has the highest current density value of 22.156 mAcm-2.

Fabrication and Characterization of Narrow-Wavelength Phosphors of Tb-Doped Yttrium-Silicon-Aluminum Oxynitride Using Spray Pyrolysis

Selective emission of green light phosphor powder Y4SiAlO8N as the host material and Tb3+ as the activator was successfully achieved using spray pyrolysis (SP). Samples synthesized with various calcination temperatures and precursor concentrations indicated that the most suitable parameter for the synthesized powder is the calcination of 0.05 M Y3.92SiAlO8N:0.08Tb3+ at a temperature of 1600 °C. The effect of the selected parameters was substantiated by the high purity of the Y3.92SiAlO8N:0.08Tb3+ phase, as confirmed by X-ray diffraction (XRD) analysis. The Scherrer equation was used to calculate grain size. In addition, scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometry (EDS) confirmed the presence of micron-sized particles, which matched well with the theoretical chemical composition. The specific surface area of the phosphor powder was determined using the Brunauer–Emmett–Teller method. Finally, fluorescence spectrometry was used to determine the luminescence properties. The correlation between the crystallinity of the phosphor powder and narrowing emission is also discussed.

Azide Thermolysis Frameworks: Self‐inflating, Porous, and Lightweight Materials

AbstractPorous organic materials have received increasing attention due to their potential applications, such as gas storage, gas separation, and catalysis. In this work, we present a series of aromatic, polyazide‐containing building blocks that enable the formation of a new class of amorphous porous organic materials. The azide precursors are obtained in moderate to good yields following an easy synthesis procedure. By thermal decomposition, self‐inflating porous structures named Azide Thermolysis Frameworks (ATFs) can be obtained. Modified thermogravimetric analysis is used to determine the onset temperature at which the azides decompose and the frameworks are formed. The frameworks are further investigated via infrared (IR) spectroscopy, elemental analysis, scanning electron microscopy (SEM), and gas adsorption measurements. Specific surface areas and pore sizes are determined by nitrogen adsorption measurements at 77 K using the Brunauer–Emmett–Teller method (BET) to give surface areas of up to 677 m2/g for the ATF resulting from the thermolysis of TPB‐Azide at 450 °C, which can compete with early Covalent Organic Frameworks (COFs). The specific surface area can be tuned by varying the thermolysis temperature.

A Fluidizable Catalyst for N-Butane Oxidative Dehydrogenation under Oxygen-Free Reaction Conditions

This study evaluates the effectiveness of fluidizable VOx/MgO-γAl2O3 catalysts for C4-olefin production via n-butane oxidative dehydrogenation (BODH). Catalysts were prepared via vacuum incipient wetness impregnation and then characterized by employing several techniques such as BET (Brunauer–Emmett–Teller) method, XRD (X-ray diffraction), LRS (laser Raman spectroscopy), XPS (X-ray photoelectron spectroscopy), TPR/TPO (temperature-programmed reduction/temperature-programmed oxidation), NH3-TPD (temperature-programmed desorption), NH3 -desorption kinetics and pyridine-FTIR. The BET analysis showed the prepared catalysts’ mesoporous structure and high surface areas. The XRD, LRS and XPS established the desirable presence of amorphous VOx phases. The TPR/TPO analyses corroborated catalyst stability over repeated reduction and oxidation cycles. The NH3-TPD and NH3 desorption kinetics showed that the catalysts had dominant moderate acidities and weak metal-support interactions. In addition, Pyridine-FTIR showed the critical influence of Lewis acidity. The VOx/MgO-γAl2O3 catalysts were evaluated for BODH using a fluidized CREC Riser Simulator, operated under gas-phase oxygen-free conditions, at 5 to 20 s reaction times, and at 450 °C to 600 °C temperatures. The developed VOx/MgO-γAl2O3 catalysts demonstrated performance stability throughout multiple injections of butane feed. Catalyst regeneration was also conducted after six consecutive BODH runs, and the coke formed was measured using TOC (Total Organic Carbon). Regarding the various BODH catalyst prepared, the 5 wt% V-doped MgO-γAl2O3 yielded in a fluidized CREC Riser Simulator the highest selectivity for C4-olefins, ranging from 82% to 86%, alongside a butane conversion rate of 24% to 27%, at 500 °C and at a 10 s reaction time.