1,720,993 research outputs found
Synthesis, analysis, and characterizations to investigate the influence of ni dopant on the structural and magnetic properties of Co Fe 2 O4 nanoparticles confined within the mesoporous silica SBA-15 matrix
No full textThis study designates the synthesis and characterization of undoped and Ni-doped CoFe2O4 nanoparticles within the highly ordered nanoscale channels of mesoporous silica SBA-15 matrix by using two-step nanocasting process. The impact of Ni doping in the structural and magnetic properties of CoFe2O4/SBA-15 nanocomposite was investigated by XRD, FT-IR, FESEM/EDX, N-2-adsorption/desorption, and VSM techniques. XRD studies have depicted that Ni doping results in pure ferrite phase with crystallite size decreasing from 11.8 to 10.2 nm and lattice constant's reduction due to smaller ionic radii of the nickel ions as against cobalt ions. The formation of metal-oxygen complexes located in the spinel lattice was proved by FT-IR spectroscopy which exhibits two main absorption bands belonging to the tetrahedral and octahedral sites. Compared with CoFe2O4/SBA-15, Ni0.5Co0.5Fe2O4/SBA-15 nanocomposite possesses higher BET surface area and pore volume due to creation of additional porosity in the mixed ferrite sample. The surface morphology of the CoFe2O4/SBA-15 and Ni0.5Co0.5Fe2O4/SBA-15 nanocomposites, as measured by FESEM, indicates the fiber-like aggregates consisting of relatively uniform short rod-shaped grains. Ni doping is observed to influence the ferromagnetic behavior significantly, while the saturation magnetization gets reduced from 18.12 to 12.74 emu/g which is associated with the lower orbital contribution to magnetic moment of Ni2+ ions in as against Co2+ ions, conversely, the coercivity gets increased from 158 to 249 Oe, which suggests the hardening of the magnetic material, which may be due to the increase in surface anisotropy resulted from the matrix effect. Therefore, the present study notifies the potential magneto-electronic applications of Ni0.5Co0.5Fe2O4/SBA-15 nanocomposite, with the realization of controllable size and magnetic properties along with SBA-15 matrix
Cationic surfactant templated synthesis of magnetic mesoporous nanocomposites for efficient removal of Light Green
No full textFe3O4-SiO2-NH2, Fe3O4-CTABSiO(2)-NH2 and Fe3O4-SiO2-CTABSiO(2)-NH2 magnetic adsorbents were successfully prepared and could be used effectively for the adsorption of Light Green from aqueous solutions. Unlike the first sample, mesoporous silica coatings were created using cetyltrimethylammoniumbromide micelles as molecular templates on superparamagnetic iron oxide in one sample, and on silica-coated iron oxide in the other sample to improve the adsorptive properties of the nanocomposites. The characterization by FT-IR, SEM/EDX, Zeta-potential, XRD, VSM, and N-2-adsorption/desorption confirmed the production of mesoporous silica layer. Although coating processes with both silica and mesoporous silica layers led to a vaguely decrease in saturation magnetization of the Fe3O4-SiO2-CTABSiO(2)-NH2, the nanoparticles were protected with silica coatings for environment conditions and made more suitable for subsequent amino functionalization. The results determined from Batch adsorption experiments fitted to Langmuir isotherm model with maximum adsorption capacity (q(max)) equal to 56.18, 196.08 and 227.27 mg g(-1), for Fe3O4-SiO2-NH2, Fe3O4-CTABSiO(2)-NH2 and Fe3O4-SiO2-CTABSiO(2)-NH2, respectively, and it was seen from the kinetic results, the LG adsorption was identified by pseudo-second-order kinetics, revealing that LG adsorption process is homogeneous, monolayer and based on chemical interactions. According to the results, both silica and mesoporous silica coating strategy can play crucial role in improving the adsorptive properties of nanocomposites
Ph-responsive magnetic mesoporous silica based bimodal drug delivery system for both anionic and cationic drugs
Full text linkIn this study, pH-responsive drug delivery system was prepared by magnetic mesoporous silica synthesis through hydrothermal method followed by post-synthetic amino modification. The structure of the synthesized nanocomposite was characterized by XRD, FT-IR, VSM, XPS, TEM, SEM, N2-adsorption/desorption, and surface charge density analyses. The nanocomposite, which was determined to have a remarkably stable mesostructure and superparamagnetic character, was used as drug carrier for both anionic character Indomethacin (IND) and cationic character Doxorubicin (DOX). IND, an anti-inflammatory drug, and DOX, an anticancer drug used in chemotherapy, must be used in high doses due to their low water solubility and lack of targeting ability, respectively. The loading capacities determined according to the adsorption equilibrium are quite high for both drugs (106.96 and 134.10 mg/g, for IND and DOX, respectively) due to electrostatic attraction and hydrogen bond formation. For IND, the release study was realized in phosphate buffer solutions (pH 7.4, 6.8 and 2.2) by mimicking the gastrointestinal tract; for DOX, human blood pH (7.4) and cancer cell pH (5.5) were selected as the release medium. IND exhibited increased release behavior at neutral pH (7.4, 39.5% release), while DOX exhibited increased release behavior at acidic pH (5.5, 39.7% release). Peppas-Sahlin and Korsmeyer-Peppas kinetic models effectively described the IND and DOX release behavior from the nanocomposite. Both IND and DOX could be loaded with high loading efficiency (85.36% and 88.88% for IND and DOX, respectively) onto the nanocomposite and pH-controlled release can be achieved, which may be inspiring for a bimodal nanomedical treatment approach
Adsorption of light green and brilliant yellow anionic dyes using amino functionalized magnetic silica (Fe 3 O 4 @SiO 2 @NH 2) nanocomposite
No full textFe3O4@SiO2@NH2 nanocomposite was prepared for highly effective adsorption of two anionic dyes one of which is triarylmethane dye (light green, LG) and the other is azo dye (brilliant yellow, BY). The characterization results demonstrated that superparamagnetic Fe3O4 nanoparticles were covered with silica and functionalized with amino groups successfully without losing magnetic character. The effects of adsorbent dosage, contact time, pH, temperature, and dye molecular structure on the adsorption were investigated. Acidic pH was better for both LG and BY, on the other hand, alkaline pH was favorable to some extent for LG in comparison with BY due to the contribution of stacking effect in addition to electrostatic attraction. Kinetic data demonstrated that the driving force for adsorption process could be explained by pseudo-second order mechanism in both systems. The equilibrium data were more compatible with Langmuir isotherm than those of Freundlich isotherm and the maximum adsorption capacities of Fe3O4@SiO2@NH2 calculated from Langmuir isotherm model for LG and BY at 30 degrees C and natural pH of the solution were 40.2 and 35.5 mg g(-1). Thermodynamic calculations related to temperature dependence demonstrated that the adsorption process was spontaneous and exothermic
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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