Brunauer-Emmitt-Teller Research Articles

Antibacterial, antifungal and photocatalytic evaluation of Gd2O3-Fe2O3-CoO heterostructured photocatalyst

ABSTRACT In the present work, the tri-phase of Gd2O3-Fe2O3-CoO heterostructured ternary nanocomposite was synthesised via a facile co-precipitation method to investigate the antimicrobial and photocatalytic potential. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), and BET (Brunauer-Emmitt-Teller) analysis were used to examine the functional group detection, phase purity, surface morphology elemental detection and surface area of synthesised nanocomposite. The antibacterial study against Staphylococus aureus, Pseudomonas aeruginosa, Escherichia coli, and Bacillus subtilis bacterial strains was evaluated. The results showed higher activity against Pseudomonas aeruginosa with ZOI 26 mm. The antifungal test against Aspergillus flavus and Aspergillus niger was evaluated. The results showed higher activity against Aspergillus flavus with less growth of fungi around the composite. Methylene blue (MB) dye and Ciprofloxacin (CIP) drug were used as target pollutants to evaluate the photocatalytic performance of catalyst under solar light irradiation. The ternary composite exhibited 93% and 96% degradation efficiency towards MB and CIP at pH = 11, and pH = 7, respectively in 120 min which is higher than pure Gd2O3, Fe2O3 and CoO. Furthermore, active species trapping tests with various scavengers elucidate a possible mechanism, indicating that •O2 _and •OH radicals play a critical part in photodegradation reaction.

Development and Characterization of Functionalized Titanium Dioxide-Reinforced Sulfonated Copolyimide (SPI/TiO2) Nanocomposite Membranes with Improved Mechanical, Thermal, and Electrochemical Properties

Sulfonated polyimide (SPI) membranes are regarded as the potential alternative to Nafion as a polymer electrolyte membrane (PEM) for fuel cells. Herein, sulfonated copolyimide is synthesized through a direct polymerization method using 1,4,5,8-naphthalene tetra carboxylic dianhydride (NDTA), and sulfonated diamine 4,4′-diamino diphenyl-2,2′-disulfonic acid (BDSA). Sulfonated copolyimide is re-dissolved in dimethyl sulfoxide for the fabrication of thin films. The nanocomposites of both 1.0 and 2.0% of the functionalized TiO2-reinforced (SPI/TiO2) are fabricated by blending and casting method. TiO2 nanoparticles are surface-functionalized using (3-aminopropyl)triethoxysilane (APTES). Scanning electron microscopy (SEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared FTIR), and Brunauer-Emmitt-Teller (BET) techniques are used to reveal the distinctive characteristics of the newly synthesized SPI/TiO2 nanocomposite membranes. The as-synthesized SPI/TiO2 membranes are used to investigate their physicochemical and electrochemical parameters, including water uptake, ion exchange capacity (IEC), swelling property, oxidation stability, and dimensional change stability. The SPI and SPI/TiO2 composite membranes exhibit an ion-exchange value of 1.412 to 1.286 mmol/g. The SPI/TiO2 composite membranes show excellent H2O stability at room temperature. Overall, the results indicate that the SPI/TiO2 membranes exhibit the potential as PEM for direct methanol fuel cell applications. These nanocomposite membranes are also applicable in clean energy production from environment-friendly sources.

Preparation and characterization of cellulose/flaxseed gum composite hydrogel and its hemostatic and wound healing functions evaluation

The composite hydrogel was prepared with cellulose and flaxseed gum and characterized by fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Brunauer–Emmitt–Teller (BET) and thermogravimetric analysis (TGA). The swelling property, drug adsorption, biocompatibility and hemostatic function of composite hydrogel were investigated. The composite hydrogel had the pore structure and exhibited high stability with a thermal decomposition temperature of 332.66 °C. And the composite hydrogel showed excellent swelling capability with a moisture expansivity of over 200%, and with a drug adsorption capacity of 7.27 ± 0.15 mg/g. Mechanical properties tests showed that as the proportion of flaxseed gum increased, the ability to withstand pressure of hydrogel was improved. In addition, MTT assay, flow cytometry analysis, and in vivo toxicological evaluation suggested that composite hydrogel had good biocompatibility. Moreover, hemostatic potential assay and wound healing were made in order to evaluate the effect of hemostasis and wound healing of composite hydrogel and our results indicated that the composite hydrogel with cellulose and flaxseed gum could be effective to promote hemostatic and wound healing function. All in all, the great properties exhibited by the composite hydrogel could make it a potential candidate as biomaterial in bleeding and wound treatment.

Photocatalytic Degradation of Congo Red Dye from Aqueous Environment Using Cobalt Ferrite Nanostructures: Development, Characterization, and Photocatalytic Performance

Highly efficient and effective treatments of hazardous dye-based color effluents are a major problem in the industrial sector. In this research, the cobalt ferrite (CoFe2O4) catalyst was produced and used for the degradation of Congo red (CR) as a model dye from aqueous solution. For a said purpose, cobalt ferrite (CoFe2O4) nanostructures with photocatalytic degradation potential were engineered via co-precipitation method using Fe2(SO4)3, CoO2, and triethylene glycol (as a stabilizing agent). As prepared, CoFe2O4 nanostructures were further surface-functionalized with 3-APTES and tested for CR degradation. The prepared CoFe2O4 nanostructures were characterized by X-ray diffraction, Fourier transform infra-red (FT-IR), scanning electron microscopy (SEM), and Brunauer-Emmitt-Teller (BET) analysis. UV-visible absorption was used to measure the optical band gap of prepared CoFe2O4 nanostructures through Tauc plots. The as-prepared CoFe2O4 nanostructure bandgap was found to be 2.71 EV while using an acidic medium. The degradation rates of CR dye for bs-CoFe2O4, as-CoFe2O4, and fs-CoFe2O4 nanostructures at pH 9 were 84, 87, and 92%, respectively. Furthermore, the influences of various process parameters, i.e., the effect of catalyst dose, contact time, dye dose/concentration, pH effect, and effect of different acids, were checked for the prepared three types of nanostructures, i.e., bs-CoFe2O4, as-CoFe2O4, and fs-CoFe2O4. The kinetics models properly explained that the reaction of degradation following pseudo-first-order kinetics.

Fabrication of hierarchically mesoporous NiO nanostructures and their role in heterogeneous photocatalysis and sensing activity

The exposure of high surface area with NiO mesoporous material and assembling hetero-structures by incorporating TiO2 nanoparticles represent a valuable way for producing high-performance photocatalysts and sensitive electrochemical sensor. Acid base free modified sol–gel route was used to synthesize highly porous and photoactive NiO, NiO/TiO2 and NiO/TiO2/Dextran catalysts. Powder X-ray diffraction analysis, UV–Vis spectroscopy, Energy dispersive X-ray (EDX) spectroscopy, Scanning electron microscopy, Transmission electron microscopy, Atomic force microscopy, Thermo-gravimetric analysis and Brunauer-Emmitt- Teller (BET) adsorption isotherm techniques were used to characterize the materials. The as-synthesized mesoporous NiO/TiO2/Dextran is crystalline, pure and highly porous with the surface area of 225 m2g− 1. The mesoporous NiO/TiO2/Dextran exhibited significant photochemical degradation capability for Malachite Green Oxalate (MG-Oxalate) dye. It was found that MG-Oxalate dye of 20 ppm concentration has been completely degraded and decolorized with the optimum NiO/TiO2/Dextran catalyst dose of 0.8 g/L in 60 min at pH 8.0. The reaction kinetics revealed that the photocatalytic degradation of MG-Oxalate dye follows pseudo-first-order reaction kinetics with the rate constant, k of 0.049 min− 1 and can be recycled up to 10 cycles. An electrochemical sensor was developed based on NiO/TiO2/Dextran modified Glassy carbon electrode (GCE) for sensitive and selective sensing of dye. The differential pulse voltammetry response of NiO/TiO2/Dextran/GCE for MG-Oxalate shows linear dependence in the concentration range of 1–25 ppm with a limit of detection 0.0056 µM and Sensitivity 0.16 µA mM− 1 cm− 2.

Water Sorption Isotherm of Pea Starch Edible Films and Prediction Models.

The moisture sorption isotherm of pea starch films prepared with various glycerol contents as plasticizer was investigated at different storage relative humidities (11%–96% RH) and at 5 ± 1, 15 ± 1, 25 ± 1 and 40 ± 1 °C by using gravimetric method. The results showed that the equilibrium moisture content of all films increased substantially above aw = 0.6. Films plasticized with glycerol, under all temperatures and RH conditions (11%–96%), adsorbed more moisture resulting in higher equilibrium moisture contents. Reduction of the temperature enhanced the equilibrium moisture content and monolayer water of the films. The obtained experimental data were fitted to different models including two-parameter equations (Oswin, Henderson, Brunauer–Emmitt–Teller (BET), Flory–Huggins, and Iglesias–Chirife), three-parameter equations Guggenhiem–Anderson–deBoer (GAB), Ferro–Fontan, and Lewicki) and a four-parameter equation (Peleg). The three-parameter Lewicki model was found to be the best-fitted model for representing the experimental data within the studied temperatures and whole range of relative humidities (11%–98%). Addition of glycerol increased the net isosteric heat of moisture sorption of pea starch film. The results provide important information with estimating of stability and functional characteristics of the films in various environments.

Combustion synthesized La2O3and La(OH)3: recyclable catalytic activity towards Knoevenagel and Hantzsch reactions

Combustion synthesized La2O3 and subsequently produced La(OH)3 are characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and Brunauer–Emmitt–Teller (BET) methods. The basicity of La2O3 and La(OH)3 is utilized for Knoevenagel and Hantzsch reactions. Reaction of aldehydes with suitable substrates containing active methylene groups led to Knoevenagel and Hantzsch products in good to excellent yields in organic solvents, water and under dry or solvent free conditions. Catalytic activity remains unchanged even after multiple (nine) cycles. Detailed mechanistic investigation using the simple adsorption reveals the prevalence of Eley–Rideal type adsorption where only one of the reactants is adsorbed for the reaction.

Preparation of monolithic oxynitride glasses by sol–gel method

Monolithic aerogels and xerogels were obtained by drying gels at super critical condition and ambient pressure after aging at room temperature for various lengths of time. Heat treatment of porous xerogels at low temperature (≤1000°C) in air and flowing ammonia resulted dense, homogeneous oxide and oxynitride glasses, respectively. The chemical bonding state and properties of gels and glasses were investigated employing Fourier transform infrared spectroscopy (FTIR), dilatometry, and Brunauer–Emmitt–Teller (BET) methods. Nitrogen content of oxynitride glasses were determined by oxygen nitrogen analyzer. Based on the compressive strength measurement, the strength of gels was increased from 0.73 to 1.5 (Mpa) with aging time. The pore size distribution was also changed significantly during aging process via hydrolysis and condensation reactions; the latter is confirmed by the FTIR spectra. The dilatometric softening point temperature of glasses and their micro-hardness were increased after nitridation process. Spectroscopic evidence indicated that nitrogen was chemically dissolved in the network of glass and its content was increased from 0.67 to 2.08 (wt.%) after nitridation for 5 and 15h, respectively .

Synthesis and Characterization of Hydrophobic Silica Aerogel by Two Step(Acid-Base) Sol-Gel Process

The silica aerogel was prepared by the acid–base sol–gel polymerization of tetraethylorthosilicate precursor followed by ambient pressure drying. The prepared silica aerogels were characterized by Fourier transform infrared (FT-IR), Thermogravimetric and differential thermal analysis (TG/DTA), X-ray diffractometer (XRD), Energy dispersive X-ray microanalysis (EDX), Brunauer–Emmitt–Teller (BET) and Scanning electron microscopy (SEM). The result silica aerogel is a light and crack-free solid with very low bulk density 0.027 g /cm 3 , high specific surface area 655.58 m 2 / g and large pore volume 0.4831 cm 3 / g. The average size of particles was calculated using a Microstructure Measurement program and Minitab statistical software.

Magnetic Nanoparticles: Magnetic Cores with Porous Coatings: Growth of Metal‐Organic Frameworks on Particles Using Liquid Phase Epitaxy (Adv. Funct. Mater. 9/2013)

Nanoparticles with a magnetic core are coated with highly porous metal organic frameworks (MOFs) using liquid phase epitaxy. As demonstrated using X-ray diffraction (XRD), transmission electron microscopy (TEM), and Brunauer–Emmitt–Teller (BET) analysis, a well-defined number of layers is deposited. On page 1210, Christof Wöll and co-workers report that such magnetic MOF particles can be used for catalysis, as chromatographic media, and for the fabrication of core/shell/shell particles.

A comparative study of pyrolyzed and doped cobalt-polypyrrole eletrocatalysts for oxygen reduction reaction

The pyrolyzed carbon supported cobalt polypyrrole (Co-PPy/C) catalysts were prepared without or with three selected dopants, namely, sodium dodecylbezene sulfonate (DBSNa), sodium paratoluene sulfonate (TSNa) and sodium bezene sulfonate (BSNa), respectively, through chemical oxidation with ferric chloride as an oxidant. The structure, surface and electrochemical properties of the obtained catalysts were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, Brunauer–Emmitt–Teller (BET) analysis, cyclic voltammetry, rotating disc electrode technique and Raman spectroscopy. The introduction of dopants increased the surface concentrations of nitrogen and cobalt which would provide more active sites for oxygen reduction reaction (ORR), and enhanced the graphitization degree of carbon support which would improve the electron conductivity. The electron numbers of ORR for the non-doped and doped Co-PPy/C were evaluated to be 2.7–3.1, respectively. The pyrolyzed BSNa-doped Co-PPy/C exhibited the best electrocatalytic activity toward ORR due to its higher surface areas, larger amounts of micropores, as well as relatively higher nitrogen and cobalt contents.

The influence of alkali metal cations in substituted nanostructured LaCoO3 on oxidation catalytic activity

Perovskite-type oxides La 0.9 M 0.1 CoO 3 (M=K/Na/Li) were prepared by a citrate sol–gel method. These oxides were characterized by x-ray diffraction analysis (XRD), a scanning electron microscope (SEM) and the N 2 physisorption Brunauer–Emmitt–Teller (BET) method. Their catalytic activity was studied by a constant microflow method for CO- and C 3 H 6-oxidation and by thermal decomposition of diesel soot. The results show that the obtained perovskite materials have a sphere shape, particles size of about 40–50 nm and surface area from 12.0 to 14.9 m 2 g −1. They have high catalytic activities decreasing in the sequence K > Na > Li on conversion CO, C 3 H 6 and diesel soot. The total conversion temperature of CO, C3H6 and diesel soot is 325 °C, 340 °C and 430 °C, respectively. Thus, these catalysts have high applicability in the removal of exhaust gas, especially from diesel engines.

Adsorption of Protein from Model Wine Solution by Different Bentonites

The adsorption of protein from model wine was investigated under different temperatures, pH values, contact times, and concentrations of ethanol, by certain bentonites. The results showed that ethanol molecules could broaden the protein molecules' channel to the interlayer of bentonite, and the maximum protein adsorption amount occurred under an ethanol concentration of 12% (by volume) and a pH value of 3.56. The increased single point Brunauer-Emmitt-Teller (BET) surface area (S BET) and adsorption pore volume ( V Ads) suggested a larger amount of active adsorption sites of the bentonite surface and a wider protein channel from the surface to the inner adsorption sites of bentonite, respectively. At the same time, higher methylene blue test (MBT) and swelling index (Sw) indicated that it was easy for the entrance of water and the absorbance of protein. Higher temperature was found favorable to eliminate more proteins and it took about 20 to 40min to arrive at the maximum adsorption.

Sol–hydrothermal preparation and photocatalysis of titanium dioxide

Nanosized TiO 2 with controlled crystal phase/structure was prepared by a sol–hydrothermal process using titanium (IV) n-butoxide as a precursor of TiO 2. After hydrothermal processing at 200 °C for 1 h, the granulous anatase phase with average crystal size of 5 nm was formed. Upon increasing the heat treatment period to more than 5 h, the rod-like rutile phase with particle size of 19 × 70 nm became predominant. The structure evolution from X-ray diffraction (XRD), particle size/morphology from transmission electron microscopy (TEM), surface area from Brunauer–Emmitt–Teller (BET) analysis, and photocatalytic activity of TiO 2 products show strong correlation with the hydrothermal conditions.

Effect of peptization on phase transformation of TiO 2 nanoparticles

TiO 2 nanoparticles were prepared by direct hydrolysis method from metatitanic acid. After the resulting powders were peptized by hydrochloric acid, the results showed that peptization of the precipitate favored formation of the rutile phase and highly crystalline anatase. Particles of the 100% rutile phase with high specific surface areas were obtained at relatively low temperatures. The specimens were characterized by transmission electron microscopy (TEM), X-ray diffractometry, Brunauer-Emmitt-Teller (BET) surface area analysis, and differential thermal analysis. To evaluate the effects of different phases on the degradation efficiency, anatase/rutile mixtures exhibited the best catalytic efficiency for the degradation of sodium benzenesulfate (BS), while pure rutile was the poorest catalyst.

Hydrothermal Synthesis of Nanosized Titania Powders: Influence of Peptization and Peptizing Agents on the Crystalline Phases and Phase Transitions

Nanocrystalline TiO2 particles were prepared by hydrothermally treating three different titanium alkoxide species, which were derived from (i) the hydrolysis of Ti(OPr)4 and Ti(OBu)4 (PT and BT, respectively) in the presence of HNO3, tetraethylammonium hydroxide (TENOH), or NH3·H2O; (ii) water‐washed precipitates; or (iii) sols that were obtained from the precipitates by peptizing with HNO3 or TENOH. X‐ray diffractometry, Brunauer–Emmitt–Teller (BET) surface area analysis, differential thermal analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy were used to characterize the powders. The results showed that peptization of the precipitate favored formation of the rutile phase and highly crystalline anatase under hydrothermal treatment. Particles of 100% rutile phase with high specific surface areas were obtained at a relatively low temperatures: room temperature, for HNO3‐peptized ([H+]/[Ti] = 4) PT sample (BET surface area of 96 m2/g); 200°C, for the HNO3‐peptized ([H+]/[Ti] = 1) PT sample (BET surface area of 49 m2/g); and 240°C for the HNO3‐peptized ([H+]/[Ti] = 1) BT sample (BET surface area of 42 m2/g). Particles that contained highly crystalline anatase, together with a small portion of rutile, were formed in both TENOH‐peptized samples. However, rutile was difficult to form, both in the water‐washed precipitates and in the species that was hydrolyzed in the presence of HNO3, TENOH, and NH3·H2O. The peptization effect of the H+ ion mainly lies in the breakage of oxolation by attacking the electrophilic O atoms among Ti atoms, thus creating conditions for the formation of rutile or anatase nuclei, after structural rearrangement.