scholarly journals Biomineralization of Monohydrocalcite Induced by the Halophile Halomonas smyrnensis WMS‐3

Minerals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 632 ◽  
Author(s):  
Pan ◽  
Zhao ◽  
Tucker ◽  
Zhou ◽  
Jiang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Carbon Isotope ◽  
Extracellular Polymeric Substances ◽  
Salt Lake ◽  
Stable Carbon Isotope ◽  
Ion Concentration ◽  
Molar Ratios ◽  
Transmission Electron ◽  
Halomonas Smyrnensis

The halophilic bacterium Halomonas smyrnensis from a modern salt lake used in experiments to induce biomineralization has resulted in the precipitation of monohydrocalcite and other carbonate minerals. In this study, a Halomonas smyrnensis WMS‐3 (GenBank:MH425323) strain was identified based on 16S rDNA homology comparison, and then cultured in mediums with 3% NaCl concentration to induce monohydrocalcite at different Mg/Ca molar ratios of 0, 2, 5, 7, and 9. The growth curve of WMS‐3 bacteria, pH values, NH4+ concentration, HCO3− and CO32− concentration, carbonic anhydrase (CA) activity, and the changes in Ca2+ and Mg2+ ion concentration were determined to further explore the extracellular biomineralization mechanism. Moreover, the nucleation mechanism of monohydrocalcite on extracellular polymeric substances (EPS) was analyzed through studying ultrathin slices of the WMS‐3 strain by High resolution transmission electron microscopy (HRTEM), Selected area election diffraction (SAED), Scanning transmission electron microscopy (STEM), and elemental mapping, besides this, amino acids in the EPS were also analyzed. The results show that pH increased to about 9.0 under the influence of ammonia and CA activity. The precipitation ratio (%, the ratio of the mass/volume concentration) of the Ca2+ ion was 64.32%, 62.20%, 60.22%, 59.57%, and 54.42% at Mg/Ca molar ratios of 0, 2, 5, 7, and 9, respectively, on the 21st day of the experiments, and 6.69%, 7.10%, 7.74%, 8.09% for the Mg2+ ion concentration at Mg/Ca molar ratios 2, 5, 7, and 9, respectively. The obtained minerals were calcite, Mg‐rich calcite, aragonite, and hydromagnesite, in addition to the monohydrocalcite, as identified by X-ray diffraction (XRD) analyses. Monohydrocalcite had higher crystallinity when the Mg/Ca ratio increased from 7 to 9; thus, the stability of monohydrocalcite increased, also proven by the thermogravimetry (TG), derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC) analyses. The C=O and C–O–C organic functional groups present in/on the minerals analyzed by Fourier transform infrared spectroscopy (FTIR), the various morphologies and the existence of P and S determined by scanning electron microscope-energy dispersive spectrometer (SEM‐EDS), the relatively more negative stable carbon isotope values (−16.91‰ to −17.91‰) analyzed by a carbon isotope laser spectrometer, plus the typical surface chemistry by XPS, all support the biogenesis of these mineral precipitates. Moreover, Ca2+ ions were able to enter the bacterial cell to induce intracellular biomineralization. This study is useful to understand the mechanism of biomineralization further and may provide theoretical reference concerning the formation of monohydrocalcite in nature.

Study of the preparation and properties of CeO2single/multiwall hollow microspheres

2007 ◽  
Vol 22 (6) ◽  
pp. 1472-1478 ◽  
Author(s):  
Youjin Zhang ◽  
Tao Cheng ◽  
Qixiu Hu ◽  
Zhiyong Fang ◽  
Kaidong Han
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Reaction Time ◽  
Reaction Temperature ◽  
Hollow Microspheres ◽  
X Ray ◽  
Molar Ratios ◽  
Preparation Conditions ◽  
Transmission Electron ◽  
Absorption Edges

Novel slight yellow CeO2single/multiwall hollow microspheres were synthesized by the hydrothermal method without any surfactant and characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), field-emission scanning electron microscopy (FESEM), and x-ray photoelectron spectra (XPS). The results showed that the products were CeO2single/multiwall hollow microspheres, the shells of which were composed of CeO2nanoparticles with a mean size of 70 nm. The effect of the preparation conditions, the reaction temperature, the reaction time, and the molar ratios of urea to Ce(NO3)3·6H2O on the morphology of the products, was investigated. The optimal preparation conditions are determined as follows: the reaction temperature of 230 °C, the reaction time of 6 to 10 h, and the molar ratios of urea to Ce(NO3)3·6H2O of 3:1 to 6:1. The formation mechanism of CeO2single/multiwall hollow microspheres was proposed. The ultraviolet-visible (UV-VIS) diffuse reflectance spectra of the samples were measured. The results showed that the absorption edges of the samples were red-shifted compared with that of bulk CeO2, and that the red-shift of the absorption edges and the yellow of the samples enhanced with increasing the yield of CeO2single/multiwall hollow microspheres. The catalytic activity and the recycling performance of the sample on CO oxidation were tested and theT100%(the temperature at which CO 100% conversion) was 230 °C in the first run and decreased by 270 and 205 °C compared with that of bulk CeO2and CeO2nanocrystal, respectively.

Convenient Route to Cu-Ag Bimetallic Nanoleaflets with High Content of Cu and their Electrochemical Properties

2017 ◽  
Vol 727 ◽  
pp. 395-402
Author(s):  
Zi Run Wang ◽  
Xin Liu ◽  
Gui Qi Xie ◽  
Yi Wu ◽  
Ming Nie ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Reduction Method ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
X Ray ◽  
Molar Ratios ◽  
Phase Reduction ◽  
Transmission Electron ◽  
Convenient Route

Cu-Ag alloy nanoparticles were synthesized by a liquid phase reduction method. Using sodium formaldehyde sulfoxylate (SFS) as reducing agents, copper-silver bimetallic nanoleaflets with high content of Cu were prepared. The obtained Cu-Ag bimetallic nanocrystal were characterized by powder X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), field emission scanning electron microscope (FESEM), high resolution transmission electron microscopy (HRTEM) and transmission electron microscopy (TEM). Different molar ratio of Cu-Ag bimetallic nanomaterials could produce different morphologies. The surfactant β-CD plays a crucial role on the structure of the products. The different molar ratios of Cu-Ag were also investigated. The electrochemical activity was evaluated using cyclic voltammetry (CV), electrochemical hydrogen evolution reaction (HER) in a 0.5M Na2SO4 electrolyte.

scholarly journals Facile synthesis of nanoscaled α-Fe2O3, CuO and CuO/Fe2O3 hybrid oxides and their electrocatalytic and photocatalytic properties

2013 ◽  
Vol 11 (5) ◽  
pp. 763-773 ◽  
Author(s):  
Lu Pan ◽  
Jing Tang ◽  
Fengwu Wang
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Photoelectron Spectroscopy ◽  
Basic Solution ◽  
X Ray Diffraction ◽  
Methyl Orange Degradation ◽  
X Ray ◽  
Molar Ratios ◽  
Transmission Electron ◽  
Nitrophenol Reduction

AbstractA facile and easily controlled route was designed to synthesize nano-structured Fe2O3, CuO, and CuO/Fe2O3 hybrid oxides with different Cu/Fe molar ratios via a hydrothermal procedure. The samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM) and field-emission scanning electron microscopy (FE-SEM). The results showed that the morphologies of the samples changed with different Cu/Fe ratios. The electrocatalytic properties of the samples modified on a glassy carbon electrode for p-nitrophenol reduction in a basic solution were investigated. The results indicated that CuO/Fe2O3 hybrids with lower Cu/Fe ratio exhibited higher electrocatalytic activity. The photocatalytic performances of the samples for methyl orange degradation with assistance of oxydol under irradiation of visible light were studied. The results revealed that CuO/Fe2O3 hybrids with higher Cu/Fe ratio showed efficient photocatalytic activity.

scholarly journals One-Pot Microwave-Assisted Synthesis of Graphene-Supported PtCoM (M = Mn, Ru, Mo) Catalysts for Low-Temperature Fuel Cells

Catalysts ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1431
Author(s):  
Antanas Nacys ◽  
Teofilius Kilmonis ◽  
Virginija Kepenienė ◽  
Aldona Balčiūnaitė ◽  
Raminta Stagniūnaitė ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Microwave Assisted Synthesis ◽  
Electrochemical Characteristics ◽  
One Pot ◽  
Molar Ratios ◽  
Microwave Assisted ◽  
Transmission Electron ◽  
Low Temperature Fuel Cells ◽  
A Current

In this study, one-pot microwave-assisted synthesis was used to fabricate the graphene (GR)-supported PtCoM catalysts where M = Mn, Ru, and Mo. The catalysts with the molar ratios of metals Pt:Co:Mn, Pt:Co:Ru, and Pt:Co:Mo equal to 1:3:1, 1:2:2, and 7:2:1, respectively, were prepared. Catalysts were characterized using Transmission Electron Microscopy (TEM). The electrocatalytic activity of the GR-supported PtCoMn, PtCoRu, and PtCoMo catalysts was evaluated toward methanol oxidation in an alkaline medium employing cyclic voltammetry and chrono-techniques. The most efficient electrochemical characteristics demonstrated the PtCoMn/GR catalyst with a current density value of 144.5 mA cm−2, which was up to 4.8 times higher than that at the PtCoRu(1:2:2)/GR, PtCoMo(7:2:1)/GR, and bare Pt/GR catalysts.

Preparation of Size Controllable BaTiO3 Nanoparticles in Microemulsion at Low Temperature

2014 ◽  
Vol 1004-1005 ◽  
pp. 63-68 ◽  
Author(s):  
Zhao Deng ◽  
Ying Dai ◽  
Hua Xiao ◽  
Meng Jun Zhou
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Low Temperature ◽  
Atmospheric Pressure ◽  
Tetrabutyl Titanate ◽  
X Ray Diffraction ◽  
X Ray ◽  
Molar Ratios ◽  
Transmission Electron ◽  
Barium Titanate Nanoparticles

Size controllable Barium titanate nanoparticles were synthesized in microemulsion consisting of water, OP-10, hexanol and cyclohexane under atmospheric pressure and low temperature, with Ba (OH)2·8H2O and tetrabutyl titanate used as starting reactants. Products were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX). The results show that 65°C is the proper temperature for the synthesis. The particle size can be controlled by varying the reactants’ concentration, ω value (molar ratios of water to surfactant) and aging time.

Structural Defects in Ion Implanted 4H-SiC Epilayers

2000 ◽  
Vol 640 ◽  
Author(s):  
P. O. Å. Persson ◽  
W. Skorupa ◽  
D. Panknin ◽  
A. Kuznetsov ◽  
A. Hallén ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Annealing Process ◽  
Ion Concentration ◽  
Electrical Activation ◽  
Structural Defects ◽  
Dislocation Loops ◽  
Transmission Electron ◽  
Residual Damage ◽  
Vacancy Concentrations

ABSTRACTTransmission electron microscopy (TEM) was used to investigate Al, Ar, C and Si ionimplanted 4H-SiC epilayers. After the implantation the samples were thermally annealed for 30 minutes at 1700°C. During the annealing process dislocation loops are formed and the generation of such dislocation loops upon annealing, is investigated with respect to dopant electrical activation, peak ion concentration and calculated interstitial/vacancy concentrations. It is concluded that the dislocation loops are generated as the result of a combination of residual damage and excess interstitials generated in a “plus one” (+1) process.

A Simple Dilution Method for Preparation of Different Aggregates from Oleic Acid/CHAPSO Bicelles

2021 ◽  
Vol 21 (12) ◽  
pp. 5993-5999
Author(s):  
Shogo Taguchi ◽  
Yasuaki Tachibana ◽  
Yuta Kimura ◽  
Takuji Yamamoto ◽  
Hiroshi Umakoshi
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Oleic Acid ◽  
Fatty Acid ◽  
Light Scattering ◽  
Packing Density ◽  
Dilution Method ◽  
Molar Ratios ◽  
Transmission Electron ◽  
Functional Membrane

We evaluated the effect of dilution on both the size and packing density of aggregates prepared from a fatty acid (oleic acid, OA)/detergent (3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxypropane sulfonate (CHAPSO)) bicelle as a parent for functional membrane materials. The sizes of the aggregates formed at different molar ratios, XOA(= [OA]/([OA]+[CHAPSO])), of 0.3 and 0.7 and their parent bicelles were measured by dynamic light scattering and transmission electron microscopy; their packing density was evaluated by deconvolution of the fluorescence spectrum, where Laurdan molecules were used as a probe. The experimental results showed that the bicelles formed aggregates upon dilution because of the hydration of CHAPSO. The packing density of the nano-ordered aggregate formed at XOA = 0.3 was much greater than that of the aggregate formed at XOA = 0.7, implying the formation of an ordered aggregate under the condition of XOA = 0.3

Techniques for Transmission Electron Microscopy of Fiber-Matrix Interfaces in Aluminum Alloy-Boron Composites by Ion Erosio

1971 ◽  
Vol 29 ◽  
pp. 204-205
Author(s):  
G. G. Shaw
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Aluminum Alloy ◽  
Electron Beam ◽  
Pure Aluminum ◽  
Ion Milling ◽  
Transmission Electron ◽  
Fiber Matrix ◽  
Ion Erosion ◽  
Row Of Fibers

The morphology and composition of the fiber-matrix interface can best be studied by transmission electron microscopy and electron diffraction. For some composites satisfactory samples can be prepared by electropolishing. For others such as aluminum alloy-boron composites ion erosion is necessary.When one wishes to examine a specimen with the electron beam perpendicular to the fiber, preparation is as follows: A 1/8 in. disk is cut from the sample with a cylindrical tool by spark machining. Thin slices, 5 mils thick, containing one row of fibers, are then, spark-machined from the disk. After spark machining, the slice is carefully polished with diamond paste until the row of fibers is exposed on each side, as shown in Figure 1.In the case where examination is desired with the electron beam parallel to the fiber, preparation is as follows: Experimental composites are usually 50 mils or less in thickness so an auxiliary holder is necessary during ion milling and for easy transfer to the electron microscope. This holder is pure aluminum sheet, 3 mils thick.

Direct Observation of Heat Exchanger Deposits by Cross Sectioning

1967 ◽  
Vol 25 ◽  
pp. 364-365
Author(s):  
R. W. Anderson ◽  
D. L. Senecal
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Heat Exchanger ◽  
Direct Observation ◽  
Cross Sections ◽  
Preparation Method ◽  
Specimen Preparation ◽  
Flowing Water ◽  
Transmission Electron ◽  
Deposit Layer

A problem was presented to observe the packing densities of deposits of sub-micron corrosion product particles. The deposits were 5-100 mils thick and had formed on the inside surfaces of 3/8 inch diameter Zircaloy-2 heat exchanger tubes. The particles were iron oxides deposited from flowing water and consequently were only weakly bonded. Particular care was required during handling to preserve the original formations of the deposits. The specimen preparation method described below allowed direct observation of cross sections of the deposit layers by transmission electron microscopy.The specimens were short sections of the tubes (about 3 inches long) that were carefully cut from the systems. The insides of the tube sections were first coated with a thin layer of a fluid epoxy resin by dipping. This coating served to impregnate the deposit layer as well as to protect the layer if subsequent handling were required.

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