| Thesis Name：Hydrogen storage in molecular compounds |
| Country：[CN] |
Usage：[Hydrogen storage] |
| Remarks： |
At low temperature (T) and high pressure (P), gas molecules can be held in ice cages to form crystalline molecular compounds that may have application for energy storage. We synthesized a hydrogen clathrate hydrate, H2(H2O)2, that holds 50 g/liter hydrogen by volume or 5.3 wt %. The clathrate, synthesized at 200–300 MPa and 240–249 K, can be preserved to ambient P at 77 K. The stored hydrogen is released when the clathrate is warmed to 140 K at ambient P. Low T also stabilizes other molecular compounds containing large amounts of molecular hydrogen, although not to ambient P, e.g., the stability field for H2(H2O) filled ice (11.2 wt % molecular hydrogen) is extended from 2,300 MPa at 300 K to 600 MPa at 190 K, and that for (H2)4CH4 (33.4 wt % molecular hydrogen) is extended from 5,000 MPa at 300 K to 200 MPa at 77 K. These unique characteristics show the potential of developing low-T molecular crystalline compounds as a new means for hydrogen storage.
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| Thesis Name：Effect of TiO2 nanoparticles on the electropolymerization of polypyrrole |
| Country：[CN] |
Usage：[Electrochemical polymerization] |
| Remarks： |
We report here the first electrochemical polymerization of polypyrrole (PPy) on gold substrates in aqueous solutions containing additives of 1 mM rutile TiO2 nanoparticles under the irradiation of UV light. As a result, PPy/TiO2 composites were prepared with an increased conductivity of 135 Scm−1, raising one order as compared with that of pure PPy. Furthermore, the thermal stability of the PPy-based composites was improved, as shown from thermogravimetric analysis (TGA). The effects of TiO2 on the PPy electropolymerization under UV irradiation were examined by its nucleation and growth mechanism and the onset potential of polymerization. The results indicate that the nucleation and growth are instantaneous two-dimensional and three-dimensional processes before and after nuclei overlapping, respectively, for the composite electropolymerization, which are distinguishable from those of pure PPy electropolymerization before nuclei overlapping.
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| Thesis Name：Supramolecular dendritic liquid quasicrystals. |
| Country：[CN] |
Usage：[A new mode of organization] |
| Remarks： |
A large number of synthetic and natural compounds self-organize into bulk phases exhibiting periodicities on the 10-8–10-6 metre scale as a consequence of their molecular shape, degree of amphiphilic character and, often, the presence of additional non-covalent interactions. Such phases are found in lyotropic systems (for example, lipid–water, soap–water), in a range of block copolymers and in thermotropic (solvent-free) liquid crystals. The resulting periodicity can be one-dimensional (lamellar phases), two-dimensional (columnar phases) or three dimensional ('micellar' or 'bicontinuous' phases). All such two- and three-dimensional structures identified to date obey the rules of crystallography and their symmetry can be described, respectively, by one of the 17 plane groups or 230 space groups. The 'micellar' phases have crystallographic counterparts in transition-metal alloys, where just one metal atom is equivalent to a 103 - 104-atom micelle. However, some metal alloys are known to defy the rules of crystallography and form so-called quasicrystals, which have rotational symmetry other than the allowed two-, three-, four- or six-fold symmetry. Here we show that such quasiperiodic structures can also exist in the scaled-up micellar phases, representing a new mode of organization in soft matter.
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| Thesis Name：Sweet success: ionic liquids derived from non-nutritive sweeteners |
| Country：[CN] |
Usage：[Sweet to ionic] |
| Remarks： |
When paired with a variety of organic cations, anions of the sweeteners, saccharin and acesulfame form ionic liquids.
The new ionic liquids were prepared by metathesis. The cations — an onium halide salt — were mixed with salts (Na, K or Au) of the sweetener in acetone or acetone/water. The ionic liquids are miscible with polar organic solvents and several of them are liquid at room temperature.
The new ionic liquids were characterized by 1H- and 13C-NMR along with FAB-MS (fast-atom bombardment mass spectrometry).
The use of these non-toxic anions subsequently with non-toxic cations provides the possibility to produce new ionic liquids that are truly benign. |
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| Thesis Name：Microbial polysaccharides template assembly of nanocrystal fibers |
| Country：[CN] |
Usage：[Nanocrystal fibres] |
| Remarks： |
Biological systems can produce extraordinary inorganic structures and morphologies. The mechanisms of synthesis are poorly understood but are of great interest for engineering novel materials. We use spectromicroscopy to show that microbially generated submicrometer-diameter iron oxyhydroxide (FeOOH) filaments contain polysaccharides, providing an explanation for the formation of akaganeite pseudo–single crystals with aspect ratios of 1000:1. We infer that the cells extrude the polysaccharide strands to localize FeOOH precipitation in proximity to the cell membrane to harness the proton gradient for energy generation. Characterization of organic compounds with high spatial resolution, correlated with mineralogical information, should improve our understanding of biomineralization mechanisms.
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| Thesis Name： new oligosaccharide synthesis using special hydroxy protecting group. |
| Country：[CN] |
Usage：[Protecting groups] |
| Remarks： |
A new hydroxy protecting group for the convenient preparation of oligosaccharides has been developed using the uni-chemo protection (UCP) concept.
The UCP group comprises polymerized amino acid derivatives that protect each hydroxyl group by an ester linkage. With different degrees of polymerization, the hydroxyl groups were characterized and controlled.
Using this protecting group, two kinds of sialyl-T analogues were successfully synthesized from the same sugar units merely by repeating Edman degradation and coupling. |
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| Thesis Name：Thick film miniaturized HCl gas sensor |
| Country：[CN] |
Usage：[HCl gas sensor] |
| Remarks： |
Planar miniaturized HCl sensors were fabricated using thick films of the proton conducting solid electrolyte of strontium cerate doped with 10mol% Nd2O3 interfaced with chloride ion conducting SrCl2. The proton conducting film was fabricated by screen-printing using an ink of the doped strontium cerate on an alumina substrate which was then fired at 1773K. SEM and EDAX analysis showed that the film is dense and bonds closely to the substrate, although some reactions were observed at the interface between the strontium cerate film and the alumina substrate. Results from impedance spectroscopy showed that conductivity of the thick film is similar to that of bulk strontium cerate. SrCl2 was applied on the cerate film as a slurry from an aqueous solution which was then subsequently heated to 1153K. Sensors based on forming an electrochemical chain with the two electrolytes showed fairly good HCl sensing properties in the 830–973K temperature range. The emf values obtained were linear with respect to the logarithm of HCl concentration over a wide range (from several to 1000ppm). The tubular sensors were also tested under similar conditions. The results given by film sensors are qualitatively comparable to the bulk tubular sensors, although not in complete quantitative agreement.
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| Thesis Name：An operational supramolecular nanovalve. |
| Country：[CN] |
Usage：[ A nanovalve] |
| Remarks： |
Nanovalves were created by tethering pseudorotaxanes as gates at the entrances of ca. 2 nm cylindrical pores in mesostructured silica.
The pseudorotaxane gatekeeper comprises a gatepost (a tethered 1,5-dioxynapthalene (DNP)-containing derivative (DNPD)) and a gate (cyclobis-(paraquat-p-phenylene) , CBPQT4+) that recognises DNP units. Tris(2,2'-phenylpyridyl)iridium(III), Ir(ppy)3, that fluoresces at 506 nm was used as the trapped molecule.
Sol-gel technology was used to prepare films that were derivatized with the DNPD gateposts. The pores of the mesostructure were diffusion-filled with Ir(ppy)3. The gate was closed by immersing the film in an aqueous solution of CBPQT•4Cl.
The system was placed in a solution of PhMe/EtOH before adding an external reducing agent (NaCNBH3) to open the valve and release the luminescent molecules. |
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| Thesis Name：High-mobility ultrathin semiconducting films prepared by spin coating |
| Country：[CN] |
Usage：[Put a spin on it] |
| Remarks： |
The ability to deposit and tailor reliable semiconducting films (with a particular recent emphasis on ultrathin systems) is indispensable for contemporary solid-state electronics. The search for thin-film semiconductors that provide simultaneously high carrier mobility and convenient solution-based deposition is also an important research direction, with the resulting expectations of new technologies (such as flexible or wearable computers, large-area high-resolution displays and electronic paper) and lower-cost device fabrication. Here we demonstrate a technique for spin coating ultrathin (50 Å), crystalline and continuous metal chalcogenide films, based on the low-temperature decomposition of highly soluble hydrazinium precursors. We fabricate thin-film field-effect transistors (TFTs) based on semiconducting SnS2-xSex films, which exhibit n-type transport, large current densities (>105 A cm-2) and mobilities greater than 10 cm2 V-1 s-1—an order of magnitude higher than previously reported values for spin-coated semiconductors. The spin-coating technique is expected to be applicable to a range of metal chalcogenides, particularly those based on main group metals, as well as for the fabrication of a variety of thin-film-based devices (for example, solar cells, thermoelectrics and memory devices).
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| Thesis Name：Electrical or photocontrol of the rotary motion of a metallacarborane. |
| Country：[CN] |
Usage：[electron transfer or photoexcitation processes to control rotary motion in a metal complex is described] |
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Rotary motion around a molecular axis has been controlled by simple electron transfer processes and by photoexcitation. The basis of the motion is intramolecular rotation of a carborane cage ligand (7,8-dicarbollide) around a nickel axle. The Ni(III) metallacarborane structure is a transoid sandwich with two pairs of carbon vertices reflected through a center of symmetry, but that of the Ni(IV) species is cisoid. The interconversion of the two provides the basis for controlled, rotational, oscillatory motion. The energies of the Ni(III) and Ni(IV) species are calculated as a function of the rotation angle.
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