Nanometer-sized Crystals Research Articles

Synchrotron Radiation Microbeam X-ray Analysis of Microstructures and the Polymorphic Transformation of Spherulite Crystals of Trilaurin

Using synchrotron radiation X-ray microbeam diffraction, we investigated microstructures and molecular arrangements during solid-state β′ → β polymorphic transformation in two-dimensional spherulites of trilaurin grown within thin spaces between polyethylene terephthalate (PET) films. The two-dimensional spherulites of β′ were composed of nanometer-sized crystals in which the lamellar planes were oriented parallel to the radial direction of the spherulites. It was verified that, following solid-state transformation from β′ to β, the orientations of the long-chain axes of the β form remained unchanged with respect to those of the β′ form. This suggests that the molecular arrangements of trilaurin during the β′ → β polymorphic transformation occurred through template effects of the lamellar structures of the mother phase of β′.

Disorder-induced phase coexistence in bulk doped manganites and its suppression in nanometer-sized crystals: The case ofLa0.9Ca0.1MnO3

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Germania Nanoparticles and Nanocrystals at Room Temperature in Water and Aqueous Lysine Sols

Facile synthesis of nanometer-sized germania crystals and amorphous germania nanoparticles (ca. 1 nm) is investigated through hydrolysis of germanium tetraethoxide and subsequent condensation of germania in both pure water and aqueous lysine solutions. Germanium tetraethoxide rapidly hydrolyzes in pure water, leading to solvated germanate species at lower germania concentrations and the onset of nanometer-sized germania crystals at room temperature with increasing germania content. In the presence of the basic amino acid L-lysine, amorphous germania nanoparticles (ca. 1 nm) spontaneously form with increasing germania content and coexist with nanometer-sized germania crystals at higher germania concentrations. Lysine and germania concentration both influence crystallite size and morphology (i.e., polyhedral, cubic). The facile, room-temperature crystallization of germania in the presence and absence of lysine is striking. The fact that the crystal morphology shows no signs of nanoparticle aggregative assembly, as has been observed in the formation of other oxide crystals, suggests that crystal growth takes place by addition of dissolved species rather than nanoparticles, and could have implications for other oxide systems.

Hydroxyapatite Grown on a Native Extracellular Matrix: Initial Interactions with Human Fibroblasts

Proteins are known to modulate the physical properties of minerals, and thus we anticipate that they will strongly influence the structure and the biological properties of biomimetically prepared carbonate-containing hydroxyapatite. This study was designed to learn more about the main morphological characteristics of hydroxyapatite layer grown on different substrates coated with an extracellular matrix, a biological matrix that was produced by cultured osteoblast-like cells. The hydroxyapatite growth was carried out in a simulated body fluid, a solution that resembles the human blood plasma. It was found that the extracellular matrix may serve as a template for the mineralization of biomimetic hydroxyapatite on the surface of materials like stainless steel, silicon, and silica glass, leading to the formation of a homogeneous layer. The latter was consisting of nanometer-sized hydroxyapatite crystals grouped in particles with regular sphere shape and with a significantly higher average diameter in comparison to samples without extracellular matrix coating. Subsequent in vitro studies with living fibroblasts showed that the cellular behavior depended on the type of underlying substrate used for the hydroxyapatite growth, as well as on the immersion time of the samples in the simulated body fluid. Increasing the thickness of the hydroxyapatite layer altered visibly the cellular response, and the fibroblasts developed stellate morphology on the samples with a hydroxyapatite-extracellular matrix coating. Preadsorption with fibronectin significantly improved the initial cell adhesion and spreading to all surfaces. Thus, such an approach may contribute to the development of surfaces with better tissue compatibility.

Molecular Mechanisms of Magnetosome Formation

Magnetotactic bacteria are a diverse group of microorganisms with the ability to use geomagnetic fields for direction sensing. This unique feat is accomplished with the help of magnetosomes, nanometer-sized magnetic crystals surrounded by a lipid bilayer membrane and organized into chains via a dedicated cytoskeleton within the cell. Because of the special properties of these magnetic crystals, magnetotactic bacteria have been exploited for a variety of applications in diverse disciplines from geobiology to biotechnology. In addition, magnetosomes have served as a powerful model system for the study of biomineralization and cell biology in bacteria. This review focuses on recent advances in understanding the molecular mechanisms of magnetosome formation and magnetite biomineralization.

Spatially Resolved Product Formation in the Reaction of Formic Acid with Calcium Carbonate (101̄4): The Role of Step Density and Adsorbed Water-Assisted Ion Mobility

The reaction of calcium carbonate (1014) single-crystal surfaces with formic acid (HCOOH) vapor was investigated using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). AFM images indicate the reaction produces rather well-defined crystallites, preferentially at step edges and at distinct angles to one another and mirroring the rhombohedral structure of the calcite surface, while exposing unreacted carbonate surface. The size and surface density of the crystallites depend upon substrate step density, exposure time, and relative humidity. XPS data confirmed the crystallite composition as the expected calcium formate product. The AFM images show erosion and pit formation of the calcite surface in the vicinity of the product crystallites, clearly providing the spatially resolved characterization of the source of Ca ions. AFM experiments exploring the effects of water vapor on the reacted surface show that the calcium formate crystallites are mobile under conditions of high relative humidity, combining to form larger crystallites and nanometer-sized crystals with an orthorhombohedral habit consistent with the alpha form, as confirmed by X-ray diffraction. The implications for the reactions described here are discussed.

Inclusions of nanocrystalline hydrous aluminium silicate “Phase Egg” in superdeep diamonds from Juina (Mato Grosso State, Brazil)

Inclusions in alluvial diamond from Juina (Mato Grosso, Brazil) have been investigated by TEM methods (electron diffraction, HRTEM, AEM, HAADF, EELS) and Raman spectroscopy. The inclusion paragenesis of Juina diamonds is dominated by ultrahigh-pressure (“superdeep”) phases. One of these diamonds, sample #1.1/4, contains several micrometer-sized (approximately 200 μm by 50–70 μm) inclusions, which have been studied. TEM foils prepared applying Focused Ion Beam (FIB) technique revealed that these inclusions consist of a porous, nanocrystalline groundmass, which is composed of nanometre-sized crystals of a hydrous aluminium silicate phase with Al:Si approximately 1:1 and chemical composition of phase “Egg” (AlSiO 3(OH)), a minor volume fraction of nanocrystalline stishovite and pore space, which was originally filled with a fluid or gas. The nanocrystalline hydrous aluminium silicate phase is idiomorphic, randomly oriented (approximately 20–30 nm in size) predominantly with tetragonal crystal structure ( a 0 = 0.743 nm, c 0 = 0.706 nm). The monoclinic structure of synthetic phase “Egg” determined at ambient conditions [M.W. Schmidt, L.W. Finger, R.J. Ross, R.E. Dinnebier, Synthesis, crystal structure, and phase relations of AlSiO 3OH, a high-pressure hydrous phase, American Mineralogist 83 (1998) 881 – 888] is only occasionally observed. The fluid filling in the porosity has been released into the vacuum of the FIB during TEM specimen preparation. Quench products of the fluid containing minor concentrations of F- P- S- Cl- K- Ca and Ba were detected at the walls of the pores. In addition phase “Egg” is identified by μ-Raman spectroscopy within a second sample (RS 43a) from the same location. The presence of Phase “Egg” in the inclusions in diamond may suggest that crustal material has been subducted to a depth of the lower Transition Zone. Although, metastable growth of nanocrystalline high-pressure phases or extension of their respective stability fields to lower pressure can not ruled out completely.

On structural and high temperature electrochemical properties of ZrO2 thin film coating on Zr metal produced by carbonate melt

Melt of NaCO3 can favor oxidation of Zr to form ZrO2 thin film on Zr surface, which is used to make Zr/ZrO2 oxidation/reduction electrode of pH sensor for testing elevated temperature aqueous solutions. Using SEM, EPMA, XPS, EXAFS and HRTEM, we found that ZrO2 film is tightness and solid with 20 μm thickness composed by nanometer-sized monoclinic crystals. Zr/ZrO2 interface is characterized of zoning structure according to topography and chemical composition in five zones: oxygen-rich ZrO2, ZrO2, oxygen-rich Zr metal, oxygen-bearing Zr and Zr from outmost to center. Melt oxidation process of Zr involved oxidation time, air and temperature. The air is important effect on structural and electrochemical properties of ZrO2 thin film for making elevate temperature electrochemical sensor. If oxygen air largely presented in carbonate melting process, ZrO2 thin film is not tightness and not for oxidation/reduction electrode.

Utility of Energy Technology Development in Environmentally Sustainable Development

Energy technology development, adoption, and deployment are featured in the national economic development plans of all countries. The success of such economic development plans has manifestations that go beyond just the provision of goods and services to citizens who increasingly demand an enhanced standard of living. It extends to the survival of political establishments themselves. Furthermore, the international geopolitics of energy systems and its complex web of possibilities, opportunities, and jconstraints drive, and are driven, by technology implementation. Thus, the construction of oil platforms in the North Sea reformatted international alignments on energy issues, and advances in horizontal drilling technologies for oil recovery from continental shelves increased the number of oil-producing countries. Today, basically all countries that border on oceans and large seas are oil-producing. Technology is the link between opportunity/ potential and harvest of benefits along the path to sustainable development, a status that must be defined in terms of the optional mix of economic development, environmental quality, and social equity. Energy as a natural resource is as bountiful as its demands for operational civil/industrial systems. Unfortunately, it is not always available in readily usable forms at locations of high demand. Geospatial factors climate, terrain, vegetation, and geology , socio-economic factors, and political factors e.g., international alliances determine the overall implementability and sustainability of a specific energy technology. The first set of factors merely determines the technical potential along with some associated cost factors, while the second and third set of factors determine the possibility and ease of translation from an acceptable level of technical potential to implementation. On the basis of geospatial factors, high feasibility can be assigned to geothermal energy as the primary energy source in the northwestern United States, solar energy in the tropics, wind energy in the desert and high-altitude terrains, biomass energy in luxuriantly vegetated zones around the world and in regions that produce significant amounts of organic wastes, and nuclear energy in countries endowed with uranium/plutonium. Such perfect matches between energy demand and indigenous energy sources qualify as highly desirable cases of the much sought-after “distributed energy system.” They can also minimize intercontinental and international transfers of energy in terms of electricity and fuel that have caused some costly conflicts. Unfortunately, the potential for such development is currently overridden by socioeconomic and sociopolitical factors, as well as the lack of technological capacity of some regions and countries. About half the people in the world, mostly within the tropics, still cook their food over open fires that are fueled by firewood, coal, animal dung, and crop residues. These fuels cause a high toll in mortality due to indoor air pollution that causes many acute and chronic pulmonary diseases. As many as 14% of urban households and 49% of rural households in the developing world did not have access to electricity in 2000. Developments in solar energy systems have not reached the stage that could take advantage of the relatively isolated regions where most developing countries are located, in order to produce affordable and efficient solar cells that can meet energy demand. However, recent developments in nanotechnology and fabrication methods are likely to improve the efficiency and affordability of solar energy systems to make them implementable in circumstances beyond highprofile applications. A variety of photovoltaic solar cell devices are at the research stage, although scale-up systems that convert more than 30% of incident sunlight into electricity would still be expensive. Among the promising materials for solar cells are nanometer-sized semiconductor crystals, dye-sensitized solar cells, lead selenide PbSe nanocrystals, and cadmium selenide CdSe nanocrystals. As more activities and instruments are extended to extreme environments such as space, deep sea, deserts, forests, Arctic zones, Antarctic zones, caves, and deep mines, remoteaccess equipment needs more efficient power sources that need little or no network connections. Improvements in battery and fuel-cell systems are needed. For some functions, such as the use of numerous but isolated sensors to monitor many environmental parameters in remote environments, appropriatelysized and efficient battery and fuel-cell systems are needed. In a bidirectional advance, microsensors, some of which are based on enzymes, are used to develop fuel cells for small devices while larger fuel cells are being developed to support wind energy systems. An acceleration of technological advances in energy systems is needed to support many sustainable development projects. In order to be sustainable, it is important that policymakers and technology developers seek the optimization of the three pillars of sustainable development economic development, environmental equity, and social equity with specification of minimum acceptable levels of each factor rather than seeking to maximize any of the factors to the detriment of others. The principal categories of options that are available for promoting the implementation of promising systems and technologies are engineering, communication/education, regulation, enforcement, market incentives, environmental management systems, and international cooperation.

Synthesis of Magnetite Nanoparticles for Bio‐ and Nanotechnology: Genetic Engineering and Biomimetics of Bacterial Magnetosomes

Magnetotactic bacteria (MTB) have the ability to navigate along the Earth's magnetic field. This so-called magnetotaxis is a result of the presence of magnetosomes, organelles which comprise nanometer-sized intracellular crystals of magnetite (Fe(3)O(4)) enveloped by a membrane. Because of their unique characteristics, magnetosomes have a high potential for nano- and biotechnological applications, which require a specifically designed particle surface. The functionalization of magnetosomes is possible either by chemical modification of purified particles or by genetic engineering of magnetosome membrane proteins. The second approach is potentially superior to chemical approaches as a large variety of biological functions such as protein tags, fluorophores, and enzymes may be directly incorporated in a site-specific manner during magnetosome biomineralization. An alternative to the bacterial production of magnetosomes are biomimetic approaches, which aim to mimic the bacterial biomineralization pathway in vitro. In MTB a number of magnetosome proteins with putative functions in the biomineralization of the nanoparticles have been identified by genetic and biochemical approaches. The initial results obtained by several groups indicate that some of these proteins have an impact on nanomagnetite properties in vitro. In this article the key features of magnetosomes are discussed, an overview of their potential applications are given, and different strategies are proposed for the functionalization of magnetosome particles and for the biomimetism of their biomineralization pathway.

Elastic deformation of nanometer-sized metal crystals in graphitic shells

The elastic deformation of nanometer-sized metal crystals is achieved by encapsulating them in carbon nanotubes or carbon onions. Electron irradiation of these core-shell particles leads to high pressure in their center due to a shrinkage of the graphitic shells. Pressures in the range of 10–30GPa are found by measuring the decrease in lattice spacings in the encapsulated metal crystals. Hence, it is quantitatively shown how closed graphitic shells can be applied as compression cells on the nanoscale.

Oxygen and silver diffusion into float glass

In the float glass process, molten glass is floated on a molten metallic tin bath, such that tin penetrates the glass surface. Consequently, the glass has distinctly two different faces; the tin-penetrated face (bottom face) and the opposite face (top face). In this paper, the effects of tin on oxygen and silver diffusion into the top and bottom faces of a soda–lime–silica float glass are reported. It was revealed that oxygen diffusion from the atmosphere into the bottom face at temperatures above glass transition temperature was extremely suppressed near the surface region of the glass. This was not observed for the top face. This effect was ascribed to chemical reactions between the diffused oxygen and Sn2+ near the surface of the glass. Silver diffusion was also influenced by the tin due to chemical reactions of Ag+ ions with Sn2+, leading to the precipitation of nanometer-sized Ag crystals. As a result, the coloration due to the surface plasmon resonance of the Ag crystals was significantly different between the top and bottom faces because of differences in the nucleation and growth processes associated with the Ag crystals.

Core/shell ZrTiO4/LiAlSi2O6 nanocrystals: A synchrotron X-ray diffraction study of high-pressure compression

In situ synchrotron X-ray diffraction studies have been performed on an optically transparent lithium-aluminosilicate glass-ceramic composite with nanometer-sized LiAlSi2O6 crystals embedded in a host matrix. The pressure-induced evolution of X-ray diffraction patterns was followed in compression up to 50 GPa and in subsequent decompression to ambient conditions. In the low-pressure range, the diffraction patterns illustrated a progressive shift and broadening of the diffraction lines consistent with a gradual densification of the LiAlSi2O6 phase. The unit cell volume of the LiAlSi2O6 nanocrystalline phase calculated for the compression sequence between ambient pressure and 12.5 GPa decreased by about 13.5%. At higher pressures, the diffraction patterns displayed considerable line broadenings indicating a partial amorphization of the nanocrystalline phase. Additionally, the patterns revealed the increasing presence of the ZrTiO4 phase which was nucleated in the host matrix prior to the crystallization of the LiAlSi2O6 main nanocrystalline phase. The diffraction pattern of the composite quenched from 50 GPa to ambient pressure conditions did not show full reversibility of pressure-induced changes. Despite the dominating presence of the broad diffraction bands, the diffraction pattern of the pressure-quenched material suggested that the decompressed structure carries at least a partial signature of the initial ambient LiAlSi2O6 phase.

Addition of GeO2to Reduce the Viscosity of Parent Glasses for Low-Expansion, Transparent Glass?Ceramics Containing High-Quartz Solid Solutions

Parent glasses for fabricating glass–ceramics with nanometer-sized crystals usually have high viscosities, resulting in high processing temperatures. In this study, GeO2 was added to a transparent, near-zero thermal-expansion Li2O–Al2O3–SiO2 glass–ceramic to reduce the viscosity of the parent glass. The effects of this compositional modification on the viscosity and crystal-nucleation rate of the parent glasses, and on the crystal size, thermal expansion, and optical transparency of the resulting glass–ceramics were investigated. It was found that addition of GeO2 was useful in reducing the glass viscosity. Owing to the reduced nucleating rate with the increase in the GeO2 content, the nucleating times required for reaching the smallest crystal size, the lowest coefficient of thermal expansion, and the highest transparency were all increased. With increasing GeO2 content, the lowest coefficient of thermal expansion that can be reached for glass–ceramics increased (0.14–2.9 × 10−6 K−1). The highest transparency of the GeO2-containing glass–ceramics is almost as good as that of the GeO2-free glass–ceramic and is almost independent of GeO2 content when the crystal size is smaller than about 65 nm.

Combined magnetic and structural investigation of nano crystalline iron oxides: The interplay between crystal size and phase composition during FeS 2 oxidation

The oxides that form during thermal oxidation of natural FeS 2 (pyrite and marcasite) consist of nanometer-sized crystals of α-Fe 2O 3 and γ-Fe 2O 3. This is shown with heating experiments that were made up to 650 °C, which resembles temperatures used in metallurgical processes. It is shown that magnetic measurements can play a key role in the investigation of this reaction, due to the unwanted blurring effects associated with finite crystal sizes if other methods are used. According to Mössbauer spectra combined with pXRD, many α-Fe 2O 3 crystals are in a stable magnetic state only due to the formation of bridging superexchange interactions in between them, but the γ-Fe 2O 3 experiences super-paramagnetic relaxation ceasing first at 20 K. Magnetisation measurements were used for two main purposes (1) determination of the amounts of γ-Fe 2O 3 in the products, and (2) for characterization of γ-Fe 2O 3 with respect to crystal size and possible magnetic surface effects such as spin-glass. It is proven that fine FeS 2 grains produce more γ-Fe 2O 3 than coarse. At 500 °C the fine FeS 2 grains oxidised into c. 30% γ-Fe 2O 3 and ca. 70% α-Fe 2O 3. At 525 °C, the γ-Fe 2O 3 amounts were also estimated in coarse oxidised FeS 2, and results were ca. 20% and 10% γ-Fe 2O 3 for the fine and coarse FeS 2 respectively. The γ-Fe 2O 3 crystal sizes were a function of both temperature and grain size, and it decreased with decreasing grain size, and upon rising the temperature from 450 to 550 °C. It is argued that the estimated errors during γ-Fe 2O 3 amount determination are due mainly to disordered magnetic sublattices at the crystal faces of γ-Fe 2O 3, giving an error of ca. 15% for those samples that have the smallest crystals.

Carbon Nanotubes as High-Pressure Cylinders and Nanoextruders

Closed-shell carbon nanostructures, such as carbon onions, have been shown to act as self-contracting high-pressure cells under electron irradiation. We report that controlled irradiation of multiwalled carbon nanotubes can cause large pressure buildup within the nanotube cores that can plastically deform, extrude, and break solid materials that are encapsulated inside the core. We further showed by atomistic simulations that the internal pressure inside nanotubes can reach values higher than 40 gigapascals. Nanotubes can thus be used as robust nanoscale jigs for extruding and deforming hard nanomaterials and for modifying their properties, as well as templates for the study of individual nanometer-sized crystals under high pressure.

Nanocrystalline ZrO 2 thin films as electrode materials using in high temperature–pressure chemical sensors

The nature of the ZrO 2 thin films in the Zr/ZrO 2 electrode plays a vital role to build Zr/ZrO 2 high temperature–pressure chemical sensors, when the electrode is utilized to be in situ measuring electro-chemical properties of hydrothermal fluids. Zr metal was oxidized with a NaCO 3 melt to form a thin film of ZrO 2 on the surface of Zr, then an oxidation–reduction electrode was performed. The electro-chemical properties of the Zr/ZrO 2 electrode were tested from room temperature to high temperatures and high pressures. By using SEM, EPMA and HRTEM, analyses of topography, chemical composition and structure of the ZrO 2 thin films revealed that Zr/ZrO 2 interface is divided in to 5 zones from the outmost zone to the center: 1) prismatic and oxygen-rich ZrO 2, 2) ZrO 2; 3) oxygen-rich Zr; 4) oxygen-bearing Zr; 5) Zr metal. Especially, the outmost oxygen-rich ZrO 2 zone of the thin films is composed of nanometer-sized monoclinic crystals with high oxygen content, when Zr/ZrO 2 electrode is conducted to make a good high temperature chemical sensor.

Nanoceramic Matrices: Biomedical Applications

Natural bone consisted of calcium phosphate with nanometer-sized needle-like crystals of approximately 5-20 nm width by 60 nm length. Synthetic calcium phosphates and Bioglass are biocompatible and bioactive as they bond to bone and enhance bone tissue formation. This property is attributed to their similarity with the mineral phase of natural bone except its constituent particle size. Calcium phosphate ceramics have been used in dentistry and orthopedics for over 30 years because of these properties. Several studies indicated that incorporation of growth hormones into these ceramic matrices facilitated increased tissue regeneration. Nanophase calcium phosphates can mimic the dimensions of constituent components of natural tissues; can modulate enhanced osteoblast adhesion and resorption with long-term functionality of tissue engineered implants. This mini review discusses some of the recent developments in nanophase ceramic matrices utilized for bone tissue engineering.

C201 抗HER2抗体標識量子ドットを用いたマウス腫瘍内での単粒子イメージング

Quantum dot (Qdot) is nanometer-sized crystals which improved brightness, resistance against photobleaching compared with organic dyes and fluorescent proteins. Therefore, Qdot is thought to become new adjuncts of fluorescent bioprobes for medical applications, especially for cancer imaging 1, 2. We have used Qdot conjugated with, monoclonal anti-HER2 (human epithelial growth factor type 2 ) antibody (Trastuzumab) for molecular imaging of breast cancer cells. We utilized poly ethylene glycol (PEG) coated Qdot-Trastuzumab complex to label a cell membrane of the HER2 overexpressing breast cancer cells. Using this complex, we established the in vivo fluorescent cancer imaging method. After injection of the Qdot-Trastuzumab complex to the human breast cancer xenograft mouse model, the accumulation of Qdot to the tumor tissue was clearly observed at subcellular resolution with the original 3D intravital microscopic system. Furthermore, We report the tracking of single particles of quantum dots conjugated with trastuzumab in living mice. This suggests that we can eventually develop a novel cancer imaging and drug tracking system.

Zero-birefringence optical polymers by nano-birefringent crystals for liquid crystal displays

We report a method for compensating the birefringence of optical polymers by doping them with nanometer-size inorganic birefringent crystals. In this method, an inorganic birefringent crystal is chosen that has the opposite birefringence to the polymer and a rod like shape which is oriented when the polymer chains are oriented. As a result, the birefringence of the polymer is compensated by the opposing birefringence of the crystal. Positive orientational birefringence of poly(methylmethacrylate (MMA)-co-benzylmethacrylate (BzMA)) = 78/22 (wt/wt) was compensated by doping with 0.3 wt.% of the smaller strontium carbonate (SrCO 3) crystals with a length of about 200 nm and a width of about 20 nm. The birefringence of the copolymer containing SrCO 3 was almost zero with any draw ratio between 1.0 and 2.2. The polarization state was almost maintained when it passed through the film. On the other hand, we concluded that the size of the larger crystals (about 3.0 μm × about 300 nm) is too large to form an optically isotropic medium with the polymer. In spite of doping with 0.3 wt.% of the smaller SrCO 3 crystal, the transmittance of the doped film with a thickness of 30 μm was almost the same as the undoped one in the visible region. The increase in haze by doping with 0.3 wt.% of the smaller SrCO 3 crystal was 0.1%. Furthermore, the negative birefringence of PMMA was enhanced by the SrCO 3 crystal.