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Fatty acids (oils) from the seeds of oilseed crops such as soybeans, sunflower and etc. are processed into vegetable oil for consumption and food preparation. Seeds of other plants naturally contain specialty fatty acids, called "modified fatty acids" ("mFAs"), that are useful as chemical feedstocks, replacing chemicals otherwise obtained from petroleum. Unfortunately seeds of these plants are not amenable to being grown and harvested in commercially relevant amounts. Thus, there has been considerable effort devoted to developing altered oilseed crops that efficiently produce modified fatty acids. The present technology provides means to produce fatty acids having a cyclopropane ring, which makes the oil extremely useful for chemical processing into such products as plastics, paints, dyes, coatings and the like. This technology exemplifies how normal oilseed crops can be modified to produce valuable chemicals. In addition to being renewable, production of such chemicals in plant seeds is environmentally safe and clean.
The present technology provides modified oilseed crops having increased amounts of a non-native, modified fatty acid compound of interest. The system involves transformation of a crop plant with a gene encoding a synthase or encoding a fatty acid modifying enzyme specific for the mFA of interest and an acyltransferase gene and expressing both genes in the transformed plant. Specific embodiments include synthase genes or fatty acid modifying genes isolated from source plants that normally accumulate elevated amounts of the particular mFA. Preferred embodiments of the technology include acyltransferases that transfer either the substrate for the synthase enzyme or transfer the modified fatty acid of interest to, for example, monoacyl- or diacylglycerol. Preferably, acyltransferase genes are obtained from source plants that normally accumulate elevated amounts of the mFA of interest. Manipulation of the accumulation of the proper substrate for the synthase or FA modifying enzyme was useful in preferred embodiments. Enzymes that compete for the synthase or modifying enzyme substrates are suppressed by genotypic and phenotypic mutation of genes encoding the competing enzymes. A particular embodiment of the invention focuses on generating transformed plants accumulating elevated amounts of cyclopropane fatty acids (CPFAs). CPFAs are of particular interest because the presence of the cyclopropane ring creates a reaction center for facile synthesis of branched chain fatty acids. The optimal CPFA synthase may depend on the targeted crop plant. In some embodiments, an Escherichia coli cyclopropane fatty acid synthase was a preferred choice. Acyltransferase genes were selected from the group consisting of lysophosphatidic acid acyltransferase (LPAT), Phospholipid Diacyl Glycerol Acyl Transferase acyltransferase (PDAT) and diacylglycerol acyltransferase (DGAT) genes. A Sterculia foetida LPAT gene provided a particularly preferred embodiment.
Platinum is the most efficient electrocatalyst for accelerating the oxygen reduction reaction in fuel cells. It is also expensive. Palladium-cobalt particles have been used to replace platinum to catalyze this reaction, leading to a much lower cost electrocatalyst.
Ternary alloys of palladium, cobalt, and a third transition metal are formed into nanoparticles, bound to a conducting medium, and applied as the anode in a fuel cell to reduce oxygen. Palladium-cobalt alloys may also incorporate two additional transition metals to make a four-component, or quaternary, alloy. These alloys are deployed on the anode of fuel cells as electrocatalysts for the oxygen reduction reaction. Nickel and iron are preferred transition metal components.
Anisotropic growth of palladium nanoparticles on high surface area carbon supports is encouraged by the choice of surface preparation and electrochemical deposition parameters. The resultant nanorods and nanowires have extremely smooth surfaces, improving their catalytic activity for the oxygen reduction reaction in fuel cells, as well as for other reactions. These ultra-smooth surfaces can be used as-grown, or may be subjected to further processing, such as deposition of monolayers of platinum or gold, to further enhance catalytic activity. These materials are well suited to heterogeneous catalysis and electrocatalysis, especially at fuel cell electrodes.
Platinum is an excellent catalyst for many reactions. However, it is also easily poisoned by carbon monoxide and very expensive. Tolerance to carbon monoxide can be increased by using a particle composite consisting of clusters or an atomically thin layer of the platinum on a ruthenium particle. When used as an electrocatalyst for the oxidation of fuel at a fuel cell anode, this structure exhibits low platinum loading and elevated tolerance to carbon monoxide when compared to commercially available platinum/carbon electrocatalysts. These structures can be used in fuel cells and other electrocatalytic or heterogeneous catalytic applications.
Ruthenium nanoparticles are deposited on a conductive support and exposed to hydrogen at elevated temperature. The hydrogen-exposed nanoparticles are then cooled and placed in contact with a solution of Group VIII noble metal compound(s), such as platinum. The noble metal is deposited on the surface of the nanoparticles as clusters or an atomically thin layer, forming an active electrocatalyst.
Platinum is the most efficient electrocatalyst for accelerating the oxygen reduction reaction in fuel cells. Under operating conditions, though, platinum catalysts can dissolve. When used in place of pure platinum, platinum-metal oxide composites can spare the precious metal when used as fuel cell catalysts.
Metal oxides are not typically conductive enough to be good substrates for electrochemical deposition of metals. In the inventive method, non-noble metal cations are first adsorbed onto the surface of a metal oxide core. The cation adsorbate is then reduced to provide an appropriate surface for the subsequent deposition of noble metal from a solution of metal salts.
Platinum is a very good, albeit expensive, electrocatalyst. In order to increase the catalytic activity of an electrocatalyst per mass platinum (the platinum mass activity), nanoparticles of less expensive materials are coated with atomically thin layers of platinum. The nanoparticles have a core-shell structure and include palladium, gold, and their alloys with other transition metals. The platinum-coated composite can be used as an electrocatalyst in place of pure platinum, for example, in fuel cells.
A particle composite includes a nanoparticle having a core at least partially encapsulated by a shell of a different composition, the resulting core-shell nanoparticle at least partially encapsulated by an atomically thin layer of platinum. Particularly useful composites include platinum-encapsulated core-shell nanoparticles in which the core is a first-row transition metal and the shell is a noble metal other than platinum. The core-shell nanoparticles may be formed by subjecting a homogeneous allow of a noble metal and a non-noble metal to a heat treatment during which segregation of elements occurs, resulting in a core highly enriched in the non-noble metal and a shell highly enriched in the noble metal.
Semiconducting nanowires rarely develop a protective coating in situ, leaving the surface vulnerable to defects and contaminants. By encapsulating them in the growth chamber with a stable compound, not only is the surface protected from environmental contaminants, but deleterious surface electronic states are minimized.
The invention involves a method for encapsulating semiconductor nanowires with inert carbon shells without modifying the nanowires’ electrical and optical properties, and the resulting structures. Key to the formation of ordered graphite shells is the presence of nanoclusters of metal on the surface of the nanowires. These metal clusters induce local formation of graphitic carbon in well-defined layers. The local carbon nuclei then continue to grow, spreading to uniformly cover the entire nanowire. The process takes place at moderate temperatures, 400?500°C, in the presence of sufficient carbon.
Homogeneous catalysts are usually more selective than heterogeneous catalysts, but they are often difficult to recycle. This organometallic complex containing molybdenum or tungsten and not containing a precious metal can be used to catalyze the hydrogenation and/or hydrosilylation of an organic compound. At the end of the reaction, the molybdenum or tungsten precipitates and can be recovered. Mild process conditions can be used to generate the catalyst, in line with the objectives of “green chemistry.”
An organometallic complex contains Mo or W and does not contain a precious metal. The complex is capable of catalyzing hydrogenation and/or hydrosilylation of an organic compound. The catalyst precipitates from solution at the end of the reaction and can be recovered by decanting. The process of preparing the organometallic complex uses mild conditions: about 1 atm pressure and 100°C or less. The process may be performed under a range of conditions from about 1 atmosphere to about 5000 psi and between -95°C and 120°C.
Titania with nanocavities offers improved blocking of light in the ultraviolet range of the electro¬magnetic spectrum. It transmits about 25 percent less light than do traditional bulk titanium dioxide or titanium dioxide nanoparticles. Theoretically, by controlling the size of the nanocavities the transmission of the titania with nanocavities can be four times less than titanium dioxide or titanium dioxide nanoparticles.
Titania nanorods with nanocavities are produced by heat treatment of an intermediate hydrogen titanate. The intermediate hydrogen titanate is prepared by alkali treatment of TiO2 particles inside an autoclave at temperatures ranging from about from about 150ºC to about 190ºC. The intermediate hydrogen titanates are then heat treated at a temperature from about 55 ºC to about 750ºC under an atmosphere of oxygen or ammonia, resulting in nanorods with polyhedral nanocavities dispersed throughout. The typical diameter of the nanocavities is about 10 nm.
Many properties of materials depend on their structural symmetry—for example, piezoelectricity is simply not observed in high-symmetry configurations. When the building blocks of a lattice are isotropic (perfectly uniform), they rarely form a low-symmetry crystal system. Now, by controlling the interlinking of isotropic nanoparticles, it is possible to custom-design the symmetry of a self-assembled lattice and enhance the desired properties in the full nanomaterial.
Lattice Design via Multivalent Linkers (LDML) is based on specially synthesized linkers with multiple attachment points, which determine connections between isotropic DNA-coated particles. Such linkers possess a specific symmetry that, analogously to atomic bonds, will result in the formed lattice displaying a designed symmetry. By introducing linkers with a specific architecture of linker-particle connecting sites determined by molecular bonds (for example DNA, hydrogen bonds etc.), the correspondence between linker symmetry and packing of particles into superstructures emerges during the self-assembly process.
A new method of growing high-temperature superconductors controls hydrogen fluoride gas pressure and creates larger, more uniform crystal structures in these versatile materials. Superconductors offer extreme efficiency by transmitting electric current without any dc resistive loss, and high-temperature versions further reduce cost by requiring less extreme cooling. This process of growing the crystalline structures in cuprate superconductors promises higher quality fabrication for a broad range of applications.
Accumulation of hydrogen fluoride (HF) gas creates a significant obstacle in the uniform growth of high-temperature superconductors, which operate at temperatures higher than the boiling point of liquid nitrogen. HF restricts the growth area of crystalline structures and can be dangerous if uncontrolled. Precisely controlling the HF vapor pressure during growth produces crystalline superconductors with highly-oriented atomic structures. The barium ?uoride or “ex situ process” is being applied to the growth of YBa2Cu3O7 (YBCO) layers on flexible metallic substrates. But HF, a product of the conversion of the YBCO ?uorinated precursor to crystalline YBCO, can quickly accumulate in an ex situ reactor and stop the growth of YBCO. This solution to the problem of HF build-up and subsequent nonuniformity relies on the removal of HF by chemical absorption using a solid absorber. A solid HF absorber allows for the implementation of a one-dimensional solution to the hydrodynamic problem of achieving HF partial pressure uniformity.
A novel structure design for thin film organic photovoltaic (OPV) devices provides a system for increasing the optical absorption in the active layer. The waveguided structure permits reduction of the active layer thickness, resulting in enhanced charge collection and extraction, leading to improved power conversion efficiency compared to standard OPV devices.
High optical absorption in OPV devices demands an active layer thickness of about 150 nm, a thickness that results in inefficient charge collection. To decrease the thickness of the active layer a new structure has been designed that increases the optical absorption in very thin film OPV devices. The structure makes use of a slot-waveguide approach to confine the electromagnetic field in the thin active layer. The invention enables a stronger optical absorption in the active layers that are thin enough to have electrical transport gain leading to a significant increase in internal quantum efficiency (IQE) and a higher overall power conversion efficiency.