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 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A novel method for duplicating the hierarchical structures of biological substances at nanometer resolution in manganese oxides has been developed. This innovation uses natural biomorphic specimens, such as butterfly wing, cotton, and wood as templates. The biotemplates were first treated with either HCl/NaOH or HCl/H2O2/NaOH and then mixed with an aqueous solution of KMnO4. The treated biological materials were then ultrasonically irradiated, and finally, the biological templates were removed by calcination in air at temperatures between 500 and 800 degrees C. The structures of the resulting manganese oxides were characterized by a combination of XRD, FE-SEM, TEM and EDS. It was found that the fine hierarchical structures of the biological templates down to the nanometer scale were faithfully duplicated, and the duplication was positive. A mechanism for the positive replication is proposed and discussed in terms of the effects of the sonochemical reaction as well as the surface modification prior to the sonochemical reaction. The same sonochemical method can be extended to the duplication of intricate hierarchical structures of other biological forms in a large range of metal oxides.
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PMID:Precision replication of hierarchical biological structures by metal oxides using a sonochemical method. 1848 91

Perovskite-type LaMnO3 catalysts were prepared by co-precipitation, and a series of precious metal-coating LaMnO3 catalysts were obtained by impregnation. The activity of catalysts on soot was tested by temperature-programmed reaction. Catalysts were characterized by techniques such as H2-TPR, BET, XRD, SEM and FT-IR. The activity of Pd/LaMnO3 coating 0.5% (weight) Pd is the optimal, and the maximum combustion rate temperature decreases about 40 degrees C , as compared with LaMnO3. When the coating amount is more or less than 0.5%, the ignition temperature is higher than that of pure LaMnO3. The activity of Pd/LaMnO3 is the highest among 5 precious metals-loading catalysts, and the sequence is Au,Ru,Pt and Rh. TPR experiments indicate precious metal can help the transformation of Mn4+ to Mn3+, but has less influence on reduction of Mn3+ to Mn2+ of LaMnO3. The downshift of diffraction angle of XRD indicates some precious metals enter crystal lattice of LaMnO3, the crystal sizes of catalysts become larger after precious metal loading; BET and SEM results show sintering happened to catalysts after catalytic reaction. No obvious changes occur in the IR spectra of catalysts between after and before reaction, indicating catalysts have good structural stability. In conclusion, proper amount precious metal coating on LaMnO3 effectively improve the catalytic activity of LaMnO3 on soot.
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PMID:[Effect of precious metal loaded on LaMnO3 on catalytic oxidation of soot]. 1864 10

Manganese-containing nanoscale metal-organic frameworks (NMOFs) with controllable morphologies were synthesized using reverse-phase microemulsion techniques at room temperature and a surfactant-assisted procedure at 120 degrees C with microwave heating. The nanoparticles were characterized using a variety of methods including SEM, TEM, TGA, PXRD, and ICP-MS. Although the nanoparticles gave a modest longitudinal relaxivity (r1) on a per Mn basis, they provided an efficient vehicle for the delivery of large doses of Mn2+ ions which exhibited very high in vitro and in vivo r1 values and afforded excellent MR contrast enhancement. The particle surface was also modified with a silica shell to allow covalent attachment of a cyclic RGD peptide and an organic fluorophore. The cell-targeting molecules on the Mn NMOFs enhanced their delivery to cancer cells to allow for target-specific MR imaging in vitro. The MR contrast enhancement was also demonstrated in vivo using a mouse model. Such core-shell hybrid nanostructures provide an ideal platform for targeted delivery of other imaging and therapeutic agents to diseased tissues.
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PMID:Manganese-based nanoscale metal-organic frameworks for magnetic resonance imaging. 1884 56

Multi-crystalline La0.5Ba0.5MnO3 Nanowires have been synthesized with cationic surfactant at 220 degrees C. The structure, composition and physical property of the as-prepared nanowires have been characterized by a series of techniques including XRD, SEM, HRTEM, electron energy-loss spectroscopy (EELS) and magnetic measurements. It is found that the La0.5Ba0.5MnO3 nanowire has the typical cubic perovskite structure, each nanowire is composed of many small crystalline grains with different orientations. Valance state of manganese ion in La0.5Ba0.5MnO3 nanowires is determined by EELS technique. A "multi-nuclei" growth mode is proposed based on the microstructure analysis. The temperature dependence of magnetization has been briefly discussed.
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PMID:Synthesis and structural characterizations of multi-crystalline La0.5Ba0.5MnO3 nanowires: a "multi-nuclei" growth mode. 1905 14

The effects of calcium ions (Ca(2+)) on the surface characteristics and adsorptive properties of hydrous manganese dioxide (deltaMnO(2)), taking arsenic and humic acid as model pollutants, were systematically investigated. The FTIR spectra and SEM/EDX analyses indicate coordination between Ca(2+) and the surface hydroxyls ([triple bond]Mn-OH) of deltaMnO(2), which leads to an increase of the surface zeta potential. Ca(2+) can facilitate deltaMnO(2) aggregation, as indicated by the particle size distribution (PSD) and on-line flocculating index (FI). The variation of deltaMnO(2) surface characteristics that is induced by Ca(2+) enhances the adsorption of humic acid (HA) and arsenic onto deltaMnO(2). The adsorption of HA is enhanced more significantly by Ca(2+) than that of arsenic, which is positively related to the coordination strength between Ca(2+) and individual pollutants. The SEM/EDX analysis shows the formation of Ca-HA complexes, which have a higher affinity for deltaMnO(2) than HA. The bridging effect of Ca(2+) plays a major role in enhancing HA adsorption onto deltaMnO(2). Due to different interactions between Ca(2+) and pollutants, the adsorption mechanism is pollutant-dependent in the presence of Ca(2+).
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PMID:Effects of calcium ions on surface characteristics and adsorptive properties of hydrous manganese dioxide. 1913 83

A novel hydrous-manganese-oxide-coated alumina (HMOCA) material was prepared through a redox process. The adsorbent was characterized by SEM, BET surface area measurement, XRD, pH(PZC) measurement, FTIR spectroscopy, and XPS. The manganese oxides were amorphous and manganese existed mainly in the +IV oxidation state. Batch and column experiments were carried out to investigate the adsorption potential of the adsorbent. Fluoride adsorption onto HMOCA followed the pseudo-second-order equation well with a correlation coefficient greater than 0.99. Both external and intraparticle diffusion contributed to the rate of transfer and removal. The adsorption of fluoride was thought to take place mainly by ion-exchange. Optimum removal of fluoride occurred in a pH range of 4.0-6.0. The maximum adsorption capacity calculated from the Langmuir model was 7.09 mg/g. The presence of HCO(3)(-), SO(4)(2-) and PO(4)(3-) had negative effects on the adsorption of fluoride. The adsorbed fluoride can be released by alkali solution. Column studies were performed and 669 bed volumes were treated with the effluent fluoride under 1.0mg/L at an influent F(-) concentration of 5.0mg/L and flow rate of 2.39 m(3)/(m(2)h) (empty bed contact time=7.5 min).
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PMID:Removal of fluoride by hydrous manganese oxide-coated alumina: performance and mechanism. 1932 49

This paper presented the synthesis of a novel composite adsorbent silica gel microspheres encapsulated with 5-sulfosalicylic acid functionalized polystyrene (SG-PS-azo-SSA). It was characterized by titration method, FT-IR (Fourier transform infrared spectrometer), SEM (scanning electron microscope), EDXAS (energy dispersive X-ray analysis system), etc. SG-PS-azo-SSA has been used to investigate the adsorption of Mn(II), Fe(III), Co(II), Ni(II), Zn(II), Cd(II), Hg(II), Pd(II), Cu(II), Ag(I) and Au(III) from aqueous solutions. The research results revealed that SG-PS-azo-SSA has the better adsorption capacity for Cu(II), Ag(I) and Au(III). Langmuir and Freundlich isotherm models were applied to analyze the experimental data and the adsorption of Cu(II), Ag(I) and Au(III) on SG-PS-azo-SSA fitted well to the Langmuir isotherm equation. The obtained maximum adsorption capacity for Cu(II), Ag(I), and Au(III) is 0.472 mmol/g, 0.822 mmol/g and 0.810 mmol/g, respectively. Thus, silica gel encapsulated by 5-sulfosalicyclic acid functionalized polystyrene (SG-PS-azo-SSA) is favorable and useful for the removal of Cu(II), Ag(I) and Au(III) metal ions.
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PMID:Removal of transition metal ions from aqueous solutions by adsorption onto a novel silica gel matrix composite adsorbent. 1938 Jan 93

To investigate the effects of dietary iron (Fe) on manganese (Mn) metabolism, 24 weaned pigs (21 d old) were blocked by litter and weight and randomly assigned to the following treatments: 1) no supplemental Fe [low Fe (L-Fe)]; 2) 100 mg supplemental Fe/kg [adequate Fe (A-Fe)]; and 3) 500 mg supplemental Fe/kg [high Fe (H-Fe)]. The basal diet was analyzed to contain 20 mg Fe/kg. Tissues were harvested after 32 d of feeding. Daily gain (least square means +/- SEM) was greater in A-Fe pigs (328.3 +/- 29.9 g/d) than in L-Fe pigs (224.0 +/- 11.2 g/d). Hemoglobin concentrations on d 32 were lower in L-Fe pigs (62 +/- 3.5 g/L) than in A-Fe pigs (128 +/- 5.6 g/L) and did not differ between pigs fed A-Fe and H-Fe (133 +/- 12.0 g/L). Liver Fe increased with increasing dietary Fe. Relative hepatic hepcidin expression was greater in pigs fed A-Fe and H-Fe than in those fed L-Fe. Relative expressions of duodenal divalent metal transporter 1 (DMT1) and solute carrier family 39 member 14 (ZIP14) were increased in L-Fe pigs compared with H-Fe pigs. Liver copper (Cu) was higher in L-Fe (0.56 +/- 0.04 mmol/kg) and H-Fe (0.58 +/- 0.04 mmol/kg) pigs than in A-Fe pigs (0.40 +/- 0.04 mmol/kg). Liver Mn was lower in H-Fe pigs (0.15 +/- 0.01 mmol/kg) than in A-Fe (0.23 +/- 0.02 mmol/kg) or L-Fe pigs (0.20 +/- 0.02 mmol/kg). Duodenal Mn concentrations were greater in L-Fe pigs than in A-Fe or H-Fe pigs. Fe deficiency in pigs increased gene expression of duodenal metal transporters (DMT1 and ZIP14) and supplementation with H-Fe reduced expression of DMT1 and ZIP14, which may have decreased absorption of Mn.
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PMID:Iron transporters are differentially regulated by dietary iron, and modifications are associated with changes in manganese metabolism in young pigs. 1953 23

A new chitosan derivative has been synthesized by crosslinking a metal complexing agent, [6,6'-piperazine-1,4-diyldimethylenebis (4-methyl-2-formyl) phenol] (L), with chitosan (CTS). The resulting material (CCTSL) was characterized by elemental (CHN), spectral (FTIR and solid-state NMR), thermal (TGA and DTA), and structural (powder XRD and SEM) analyses. Adsorption experiments (pH dependency, kinetics, and equilibrium) of CCTSL toward various metal ions such as Mn(II), Fe(II), Co(II), Cu(II), Ni(II), Cd(II), and Pb(II) were carried out at 25 degrees C. The results showed that the adsorption was dependent on the pH of the solution, with a maximum capacity between pHs 6.5 and 8.5. The kinetics was evaluated by applying the pseudo-first-order and pseudo-second-order equation models and the equilibrium data were analyzed by Langmuir isotherm model. The maximum adsorption capacity was 1.21 mmol g(-1) for Cu(II) and the order of adsorption capacities for the metal(II) ions studied was found to be Cu(II)>Ni(II)>Cd(II)> or =Co(II)> or =Mn(II)> or =Fe(II)> or =Pb(II).
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PMID:Synthesis and characterization of a crosslinked chitosan derivative with a complexing agent and its adsorption studies toward metal(II) ions. 1954 61

Manganese nodule leached residue is a good adsorbent. Adsorption of phenol (PhOH) on water washed manganese nodule leached residue (WMNLR), waste materials from manganese nodules processing plant, has been investigated. The adsorbent (WMNLR) used for the removal of phenolic compounds were characterized by EDX, FTIR, SEM and BET surface area measurement before and after the adsorption process. Adsorption experiments were carried out to study the effect of various parameters like adsorbent dose, pH, adsorbate concentration, reaction time, temperature and calcination temperature. WMNLR calcined at 400 degrees C showed highest adsorption capacity. The equilibrium adsorption data for phenol was analyzed by using Langmuir isotherm model. The maximum adsorption of phenol was obtained at pH 3 (about 95% for adsorbent dose 1g/L and 30 mg/L adsorbate concentration). The increase in percentage of adsorption with increase in temperature indicates that adsorption is endothermic in nature. The pseudo-second-order kinetics was followed in the adsorption process.
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PMID:Removal of phenolic compounds from aqueous solutions by adsorption onto manganese nodule leached residue. 1983 80


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