سال:1398 | دوره: | شماره: |تعداد مقالات:8

Recently, mixed metal aluminate as a highly active, stable, and reusable nanocatalyst was extremely used in chemical reactions such as esterification. The preparation of the samples via a simple, rapid, and cost-effective method is one of the main problems on the front of the industrial application of these materials. For this purpose, the solution combustion method (SCM) was assessed for the fabrication of spinel CoAl2O4, and the effects of fuel-to-oxidizer (F/O) ratio on crystalline structure, surface functional groups, surface area, morphology, and porosity were analyzed. The activity of the samples, which was impregnated by the sulfate group was evaluated in the esterification reaction. Morphology and texture properties of the samples indicated the crystallinity, surface area, and pore diameter of CoAl2O4 were enhanced by increasing the F/O ratio. It can be related to increasing the combustion reaction time and temperature. However, at F/O ratios above two, due to limited diffusion of oxygen into the reaction medium, the reaction terminated immaturely. Sulfated cobalt aluminate fabricated at F/O ratio of two was successfully synthesized in nanoscale with same particle size. Moreover, it did not show impurity in its structure that is related to the ability of the combustion method for the fabrication of pure nanocatalyst. Evaluation of the catalytic activity of the SO4 2− /CoAl2O4 nanocatalysts in the esterification reaction confirmed the results of physicochemical studies. For instance, the sample prepared at F/O ratio of two presented the highest conversion (96. 7%) at methanol/oleic acid molar ratio of nine, catalyst amount of 3 wt. %, and reaction temperature and time of 120 ° C and 4 h, respectively. In addition to preserving its activity for four runs (conversion > 85%), its activity was simply recovered upon regeneration by sulfate group, making it a promising alternative for industrial production of biodiesel.

The current work investigated the green and low-cost preparation of silver nanoparticles (AgNPs) using the aqueous extract from Launaea taraxacifolia leaf and studied its antimicrobial effects. The leaf extract was analysed in a gas chromatogram– mass spectrometer to assess the phytochemicals present. UV– Vis spectrophotometer was used to monitor the formation of AgNPs, the morphological assessment was performed by a scanning electron microscope, energy dispersive X-ray analysis was used to determine the elemental composition, the particle size and shape were studied using transmission electron microscopy, and the vibrational modes of bonds in the AgNPs were assessed by Fourier transformed infrared spectroscopy. The AgNPs produced were spherical and in a size range of 9– 15. 5 nm, monodispersed with a large surface area. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the AgNPs against Pseudomonas aeruginosa and Proteus mirabilis were very low. Against P. aeruginosa, the MIC was 0. 10 mg/mL and the MBC was 0. 15 mg/mL, while the MIC and MBC against P. mirabilis were 0. 05 and 0. 25 mg/mL, respectively. Therefore, the AgNPs prepared using L. taraxacifolia leaf extract showed high antibacterial activities and could be a candidate antimicrobial agent for biomedical applications.

Uses of nanocatalysts have become more useful in optimizing catalytic reactions. They are known to enhance the rate of reaction by offering a greater number of active sites by possessing a high surface-to-volume ratio. In the present work, calcium oxide nanocatalysts were synthesized through the sol– gel method. The particle size of the nanocatalyst prepared ranged up to 8 nm. Soybean oil was used as the raw material for the synthesis of biodiesel. The synthesized nano-CaO was characterized through scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and BET (Brunauer– Emmett– Teller). Average BET surface area analysis of the nanocatalyst was calculated to be 67. 781 m2/g and pore diameter was 3. 302 nm. Nano-CaO catalyst was used to synthesize biodiesel and optimize the reaction variables through optimization processes to achieve a high yield of biodiesel. The reaction variables that were optimized were catalyst amount, oil to methanol molar ratio and reaction temperature. Upon optimization, the conversion of biodiesel was found to be 97. 61%. The optimized value of the reaction variables was: catalyst amount of 3. 675 wt% with respect to oil, molar ratio (alcohol to oil) of 11: 1, and reaction temperature of 60 ° C for 2 h.

Highly effective novel adsorbent [ CoFe2O4-humic acid(HA)] was synthesized by co-precipitation technique at pH 6 (H6) and pH 8 (H8). XRD, SBET and Zeta-potential measurements were used to study the physicochemical properties of the prepared nanoparticles. XRD results showed that the chemical treatment of CoFe2O4 by HA causes the appearance of carbon as new active sites for adsorption process. Batch adsorption tests were achieved to eliminate anionic remazole-red (RR-133) and cationic methylene blue (MB) dyes. The obtained data showed that H6 and H8 solids calcined at 300 and 500 ° C have higher adsorption rate for removing of dye than unmodified cobalt iron mixed oxide. The removal reached 100% after a period of dye contact time 2 min and 30 min for RR and MB, respectively. The uptake of RR and MB was much affected by the pH of dye solution. The pseudo-second-order kinetic model was the most fitted well and the adsorption process followed the Langmuir isotherm model. The adsorption of dye on adsorbent was chemisorption process. The as-prepared adsorbents can be regenerated and reused four times for both dyes. The efficiency of the prepared nano-samples and durability as adsorbent were accomplished.

We have studied the consequence of different functionalization types onto the decoration of multi-wall carbon nanotubes (MWCNTs) surface by nanoparticles of bismuth and nickel oxides. Three organic molecules were considered for the functionalization: 5-amino-1, 2, 3-benzenetricarboxylic acid, 4-aminobenzylphosphonic acid and sulfanilic acid. Nanotubes modification with in situ created diazonium salts followed by their impregnation with suitable salts [ammonium bismuth citrate and nickel (II) nitrate hexahydrate] utilizing infrared (IR) irradiation was found the crucial stage in the homogeneous impregnation of functionalized CNTs. Furthermore, calcination of these samples in argon environment gave rise to controlled decorated MWCNTs. The currently used technique is simple as well as effective. The synthesized materials were characterized by XPS, PXRD, FESEM, EDX, HRTEM and Raman spectroscopy. Bismuth oxide decorations were successfully performed using 5-amino-1, 2, 3-benzenetricarboxylic acid (particle size ranges from 1 to 10 nm with mean diameter ~ 2. 4 nm) and 4-aminobenzylphosphonic acid (particle size ranges from 1 to 6 nm with mean diameter ~ 1. 9 nm) functionalized MWCNTs. However, only 4-aminobenzylphosphonic acid functionalized MWCNTs showed strong affinity towards oxides of nickel nanoparticles (mainly in hydroxide form, particles size ranging from 1 to 6 nm with mean diameter ~ 2. 3 nm). Thus, various functions arranged in the order of their increasing anchoring capacities are as follows: sulfonic < carboxylic < phosphonic. The method is valid for large-scale preparations. These advanced nanocomposites are potential candidates for various applications in nanotechnology.

In this work, the interactions between adenine– adenine di-nucleotide (DA2N) and carbon nanotube (CNT) in the presence of Lysyllysine (LL) was studied by the molecular dynamics simulation. Different carbon nanotubes including (5. 5), (6. 6) and (7. 7) were used to investigate the effect of CNT type. The binding energies were calculated using the molecular mechanics-Poisson Bolzmann surface area method. The results showed that the contribution of the van der Waals interactions between DA2N and CNT was greater than that of the electrostatic interactions. The LL significantly enhanced the electrostatic interactions between the DA2N and CNT (6. 6). The quantum calculations revealed that the sensor properties of the DA2N were not significantly affected by the CNT and LL. However, the five-membered ring of adenine played a more important role in the sensing properties of the DA2N. The obtained results are consistent with the previous experimental observations that can help to understand the molecular mechanism of the interaction of DA2N with CNT.

The present work considers an adsorptive removal of Indigo carmine (IC) dye onto nanotube carbon (CNTs). The pure CNTs were prepared via chemical vapor deposition (CVD) method utilizing methane gas as a carbon source at 1000 ° C in a quartz tube. The morphology and surface chemical structure of the adsorbents were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), nitrogen adsorption/desorption technique, and thermal gravity analysis (TGA). The parameters of the IC dye adsorption, such as initial concentration, contact time, pH, and mass-loaded adsorbent, were evaluated. The kinetic study confirmed that a pseudo-second-order model was best fitted to the adsorption data. The removal efficiency of adsorption onto pure and COOH-functionalized CNTs was 84% and 98. 7% at 15 min, respectively. The equilibrium results were fitted well to the Langmuir isotherm model. The adsorption capacity of the CNT and COOH– CNT was 88. 5 and 136 mg/g, respectively. The reusability of the adsorbents was studied, and after eight cycles, the efficiency decreased to 70%. Moreover, the density functional theory calculations confirmed that the functionalization of CNTs with COOH groups improves the adsorption properties of IC due to the formation of hydrogen-bonding interactions.

In this work, the specimen of the fabrics (polyester/viscose blend) was prepared. At first, the samples were placed under microwave radiation at different times, and then the optimum condition of treated fabrics (8 min) was selected for treatment. The physical properties and surface morphology of Cu nanoparticle and multi-wall carbon nanotubes (MWCNTs) with different percentages were measured using dispersing agent, washing performance, stability, and physical properties of the fabric. The image of surface morphology’ s specimens was also photographed by scanning electron microscopy (SEM). Afterwards, we measured the specimens’ electrical conductivity properties, according to AATCC 2005-76 standards, and subsequently, K/S, %R, and Lab value of specimens was analyzed using reflection spectrophotometer. In fact, the results indicated that optimum electrical resistivity, which was also the aim of the study, is 9% one weight of fabric (o. w. f. ) nanoparticles on the fabric and that electrical resistivity for the values of 9% o. w. f. for CNT is slightly greater than Cu.