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Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A natural bentonite modified with a cationic surfactant, cetyl trimethylammonium bromide (CTAB), was used as an adsorbent for removal of phenol from aqueous solutions. The natural and modified bentonites (organobentonite) were characterized with some instrumental techniques (FTIR, XRD and SEM). Adsorption studies were performed in a batch system, and the effects of various experimental parameters such as solution pH, contact time, initial phenol concentration, organobentonite concentration, and temperature, etc. were evaluated upon the phenol adsorption onto organobentonite. Maximum phenol removal was observed at pH 9.0. Equilibrium was attained after contact of 1h only. The adsorption isotherms were described by Langmuir and Freundlich isotherm models, and both model fitted well. The monolayer adsorption capacity of organobentonite was found to be 333 mg g(-1). Desorption of phenol from the loaded adsorbent was achieved by using 20% acetone solution. The kinetic studies indicated that the adsorption process was best described by the pseudo-second-order kinetics (R(2) > 0.99). Thermodynamic parameters including the Gibbs free energy (DeltaG degrees), enthalpy (DeltaH degrees), and entropy (DeltaS degrees) were also calculated. These parameters indicated that adsorption of phenol onto organobentonite was feasible, spontaneous and exothermic in the temperature range of 0-40 degrees C.
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PMID:Removal of phenol from aqueous solutions by adsorption onto organomodified Tirebolu bentonite: equilibrium, kinetic and thermodynamic study. 1965 23

A highly efficient monoclinic BiVO(4) photocatalyst (C-BVO) was synthesized by an aqueous method with the assistance of cetyltrimethylammonium bromide (CTAB). The structure, morphology and photophysical properties of the C-BVO were characterized by XRD, FE-SEM and diffuse reflectance spectroscopy, respectively. The photocatalytic efficiencies were evaluated by the degradation of rhodamine B (RhB) under visible-light irradiation, revealing that the degradation rate over the C-BVO was much higher than that over the reference BiVO(4) prepared by aqueous method and over the one prepared by solid-state reaction. The efficiency of de-ethylation and that of the cleavage of conjugated chromophore structure were investigated, respectively. The chemical oxygen demand (COD) values of the RhB were measured after the photocatalytic degradation over the C-BVO and demonstrated a 53% decrease in COD. The effects of CTAB on the synthesis of C-BVO were investigated, which revealed that CTAB not only changed the reaction process via the formation of BiOBr as an intermediate, but also facilitated the transition from BiOBr to BiVO(4). Comparison experiments were carried out and showed that the existence of impurity level makes significant contribution to the high photocatalytic efficiency of the C-BVO.
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PMID:CTAB-assisted synthesis of monoclinic BiVO4 photocatalyst and its highly efficient degradation of organic dye under visible-light irradiation. 1973 35

The effect of cationic template on the adsorption of chromium (VI), furfural and copperphthalocyanine-3,4',4'',4'''-tetrasulfonic acid tetrasodium salt (CuPc) in MCM-41 and MCM-48 mesoporous materials was investigated in this work. We used cetyltrimethylammonium bromide (CTAB) as the cationic template and sodiummetasilicate (for MCM-41) and tetraethyl-orthosilicon (for MCM-48) as the silica source for the synthesis of mesoporous materials. The properties of synthesized samples were characterized with XRD-low angle, SEM, N(2) adsorption-desorption and TG-DT analysis. The extent of adsorption was investigated as a function of solution pH, shaking speed, contact time, analyte concentration, reaction temperature and supporting electrolyte (sodium chloride) concentration. Langmuir and Freundlich isotherms were used to model the adsorption equilibrium data. The as-synthesized mesoporous samples showed very high adsorption capacity for the analytes and adsorption uptakes were rapid on the adsorbents reaching equilibrium in less than 2 h. The materials without surfactant did not show significant affinity for the analytes.
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PMID:Fast and efficient mesoporous adsorbents for the separation of toxic compounds from aqueous media. 2002 25

We have studied the effect of Cr(III)(phen)3 [(tris(1,10-phenanthroline) chromium(III) chloride)] on lymphocytes in order to find out if metallothioneins (MTs) are produced in the process. We also investigated whether zinc pretreatment is able to protect cells from apoptosis reported to occur for this compound. Our results indicate that MT synthesis is induced by Cr(III)(phen)3, and it has been identified as the MT-3 isoform through RT-PCR which has not been reported earlier. By zinc pretreatment, this apoptosis is reversed as inferred from cytotoxicity studies, Annexin-V/PI staining, ethidium bromide/acridine orange staining and DNA fragmentation pattern and ultrastructural investigations using TEM and SEM. The zinc pretreatment reduces the amount of ROS produced by Cr(III)(phen)3. The MT-1a and 1b synthesized by zinc (also evidenced through RT-PCR experiments) is possibly able to scavenge ROS which is one of the early signaling molecules that lead to apoptosis. Zinc pretreatment also reverses the changes in downstream signaling events such as mitochondrial membrane potential, ATP levels and the activation of caspase-3. This is the first report on the induction of MT-3 in lymphocytes due to a metal stress or any other stimuli. Even though MT-3 is synthesized here, apoptosis still occurs due to ROS production on Cr(III)(phen)3 exposure when the cells have not been primed with zinc.
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PMID:Zinc protects human peripheral blood lymphocytes from Cr(III)(phenanthroline)3-induced apoptosis. 2004 34

Recent investigations in the anti-microbial properties of the functional polymers are predominantly focused on the structure of the cationic moieties. In the present study, we investigated that the nature of the anion present in polysulfobetaines affects activity against certain microorganisms and their anti-microbial properties have been rationalized in terms of the structure-activity relationship. Vinyl imidazolium-based polysulfobetaines were prepared by the quaternization of poly(N-vinyl imidazole) with sodium salt of 2-bromo ethanesulfonic acid. The bromide counter anion of the resulting polymer was exchanged with different anions to generate a series of polymers. These were characterized by FTIR, DSC, XRD, SEM, elemental analysis (C, H, N and S) and viscosity measurements. The anti-microbial activity studies were carried against three fungi (Aspergillus niger, Byssochlamys fulva and Mucor circenelliods) and two bacteria (Bacillus coagulans BTS-3 and Pseudomonas aeruginosa BTS-2). The nature of the anion affects the structure of polysulfobetaine by realignment of polymer chains. The anion-dependent anti-microbial properties of polysulfobetaines result from the interaction of the microbes at the polymer interface.
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PMID:Anion effects on anti-microbial activity of poly[1-vinyl-3-(2-sulfoethyl imidazolium betaine)]. 2006 Jan 20

A novel biocompatible composite film based on a water-insoluble surfactant, didodecyldimethylammonium bromide (DDAB), and a hydrophobic room-temperature ionic liquid (RTIL), 1-hexyl-3-methyl-imidazolium hexafluorophosphate (HIMIMPF(6)), for the immobilization of biocatalytical proteins was reported. Differential scanning calorimetry (DSC) showed that the DDAB-HIMIMPF(6) composite film has higher thermal stability than the DDAB film alone. SEM images indicated that different microstructures existed between the DDAB film and the composite film, indicating the interaction between DDAB and RTILs. This composite can be used as the immobilization matrix of proteins and other biomacromolecules. Heme-proteins, including hemoglobin (Hb), myoglobin (Mb) and horseradish peroxidase (HRP), were used as model proteins for studying the electrochemical behaviors of the resulting biocatalytical composite films. In the case of Hb, a pair of well-defined quasi-reversible redox peaks was obtained when the composite film containing Hb was modified on a glassy carbon electrode. The formal potential (E degrees '), the surface coverage (Gamma(*)) and the electron transfer rate constant (k(s)) were calculated as -0.308V, 1.32x10(-11)molcm(-2) and 11.642s(-1), respectively. While, these parameters for Hb on DDAB films alone were -0.309V, 7.20x10(-12)molcm(-2) and 2.748s(-1), respectively. Therefore, the composite are more suitable for the direct electron transfer between Hb than DDAB alone. The native conformation and bioactivity of Hb adsorbed on the composite film was proved to be maintained, reflected by the unchanged ultraviolet-visible (UV-vis) as well as the catalytic activity toward hydrogen peroxide (H(2)O(2)) and nitric oxide (NO) compared with the free Hb molecules. Furthermore, Hb on the composite film are more sensitive for the detection of hydrogen peroxide (H(2)O(2)) and nitric oxide (NO) than that on DDAB film alone. The linear range of H(2)O(2) on Hb/DDAB-RTILs/GC electrode is from 0.5 to 57.5microM with linear regression equations I(microA)=0.149+0.00904C(microM), while, the linear range of H(2)O(2) on Hb/DDAB/GC electrode is from 0.5 to 57.5microM with linear regression equations I(microA)=0.0938+0.00553C(microM). For NO, its linear range on Hb/DDAB-RTILs/GC electrode is from 1.8 to 21.6microM with linear regression equations I(microA)=0.0937+0.0232C(microM). But its linear range on Hb/DDAB/GC electrode is from 1.8 to 21.6microM with linear regression equations I(microA)=0.0285+0.0167C(microM). Similar results were observed for Mb and HRP in the DDAB-HIMIMPF(6) composite film.
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PMID:Electrochemical behavior of biocatalytical composite based on heme-proteins, didodecyldimethylammonium bromide and room-temperature ionic liquid. 2017 91

At the room temperature, a novel and environmental friendly approach for synthesizing polyaniline (PANI) nanofibers on a large scale is presented firstly in the aqueous phase by ultraviolet (UV)-assisted polymerization using cetyltrimethylammonium bromide (CTAB) as the "soft-template." It is obvious that the polymerization process can be accelerated under the illumination of UV light and the preliminary mechanism has been pointed out. Furthermore, it also can be noted that the lower concentrations of CTAB and HCl are helpful for the fabrication of smooth and uniform PANI nanofibers. As observed with FE-SEM and TEM, the as-synthesized PANI nanostructures under the appropriate conditions are composed of uniform nanofibers with the average diameter of about 100 nm and the length of several micrometers. Subsequently, the synthesized PANI nanostructures are characterized with UV-vis, FT-IR, XRD spectra, and the typical physical and chemical properties of PANI are displayed. In addition, the conductivity of the synthesized PANI nanofibers was also measured with the four probe method and the excellent conductivity was presented. In summary, the procedure presented here only involving exposure of an acidic aqueous solution of aniline to UV light illumination is so simple and the needed equipment is so low cost, from the viewpoint of technological applications, that the large-scale UV-assisted polymerization of PANI nanofibers from the monomer solution is feasible and promising.
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PMID:Fabrication of one dimensional polyaniline nanofibers by UV-assisted polymerization in the aqueous phase. 2035 39

Asymmetric mono cationic 4,4'-bipyridiniums, 1-butyl-4,4'-bipyridinium bromide (BUBP) and 1-methyl-4,4'-bipyridinium iodide (MEBP) showed electrochromic properties from blue to transparent yellow. The electrochromic bipyridiniums, BUBP and MEBP, were introduced to solid state electrochromic cells by using a solution of the bipyridinium, TiO2, and polymer electrolyte composite. The 4,4'-bipyridinium derivatives was attached to TiO2 nanoparticles and decreased aggregation of TiO2 to afford EC dye-TiO2 nanoparticles with average diameter smaller than 20 nm, as determined by FE-SEM. An all solid state electrochromic cells prepared from the dye-TiO2 nanoparticles showed improved electrochromic response compared to that without TiO2. Thus the cell from the BUBP- TiO2 nanoparticles responded to a step potential of +/-2 V within 7 sec with coloration efficiency of 117. The redox cyclability of the bipyridinium-TiO2 nanoparticles cell was longer than that of the TiO2 free cells. The enhanced properties were attributed to the conductivity and the large surface area of TiO2 nanoparticles.
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PMID:Electrochromic properties of asymmetric 4,4'-bipyridinium nanocomposites with inorganic nanoparticles. 2035 44

Spherical-like Pt-MCM-41 meso-materials, including Pt-MCM-41, Pt-Al-MCM-41, and Pt-La-MCM-41, as well as MCM-41, were synthesized by a "one-step" approach with orthosilicate (TEOS) as silica source and cetyltrimethylammonium bromide (CTAB) as a template in the presence of suitable H(2)SO(4) (or HCl) at 0 degrees C. The samples were characterized by XRD, N(2) sorption, FTIR, SEM, TEM, ICP-AES, and XPS techniques. The results show that the metallic cations (such as Al(3+) and La(3+)) were hard to be incorporated into the synthesized samples under strong acidic conditions. However, H(2)PtCl(6) can be introduced almost 100% in the as-synthesized Pt-containing meso-materials, and H(2)PtCl(6) in the samples can be decomposed mostly into metallic Pt accompanied by part Pt(2)Si and few Pt oxides during the calcination at 550 degrees C to remove the template. In the catalytic hydrogenation of nitrobenzene, the calcined Pt-MCM-41 meso-materials, like the corresponding reduced samples, exhibit high catalytic activities with an excellent selectivity to aniline, which are much better than those of the reduced Pt/MCM-41 prepared by the incipient wetness method.
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PMID:Synthesis of spherical-like Pt-MCM-41 meso-materials with high catalytic performance for hydrogenation of nitrobenzene. 2038 12

A series of functionalized SBA-16 were synthesized and subsequently oxidized into sulfonic functionalized mesoporous silica mixing tetraethyl orthosilicate (TEOS) and 3-mercaptopropyltriethoxysilane (TMMPS), with triblock copolymers pluronic (F127) and cetyltrimethyl ammonium bromide (CTMABr) served as the mixing template by combination of hydrothermal and co-condensation method. The materials were characterized by X-ray diffraction, nitrogen gas sorption and SEM. The results show that the resulting functional materials belong to mesoporous materials when n(TEOS): n(TMMPS) is 3-8. The removal of Chrysoidine from water reaches the highest by functionalized mesoporous material when n(TEOS): n(TMMPS) is 7. Compared with different pH values, when the pH value ranges from 4-5 the adsorption reaches the highest.
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PMID:[Removal of chrysoidine from water by functionalized mesoporous material SBA-16]. 2069 69


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