Direct Synthesis of Palladium Nanocrystals in Aqueous Solution with Systematic Shape Evolution.

Palladium octahedra, truncated octahedra, cuboctahedra, truncated cubes, and nanocubes with sizes of tens of nanometers have been synthesized in an aqueous mixture of H2PdCl4 solution, cetyltrimethylammonium chloride (CTAC) surfactant, KBr solution, dilute KI solution, and ascorbic acid solution at 35 °C for 30 min. By tuning the amount of dilute KBr solution introduced, particle shape control can be achieved. Adjusting the volumes of the Pd precursor and KBr solutions added, smaller and larger Pd nanocrystals were obtained with excellent shape control. Extensive structural and optical characterization of these nanocrystals has been performed. Two absorption bands in the ultraviolet region can be discerned for these Pd nanocrystals. Concave Pd cubes can also be prepared. Pd cubes were found to grow at a faster rate than that for the formation of octahedra. The concentrations of KBr and KI in the solution are so low that spectral shifts were not detected upon their addition to the solution. The Pd nanocrystals can readily be used for various applications after simple removal of surfactant.

Synthesis and photophysical properties of self-assembled metallogels of platinum(II) acetylide complexes with elaborate long-chain pyridine-2,6-dicarboxamides.

A series of platinum(II) acetylide complexes with elaborate long-chain pyridine-2,6-dicarboxamides was synthesized. These metal complexes are capable of immobilizing organic solvents to form luminescent metallogels through a combination of intermolecular hydrogen bonding, aromatic π-π, and van der Waals interactions. Fibrillar morphologies were identified by TEM for these metallogels. Unique photophysical properties associated with the sol-to-gel transition have been disclosed with luminescence enhancement at elevated temperatures, which is in sharp contrast to typical thermotropic organogels or metallogels reported in the literature. Such unusual luminescence enhancement is attributed to the increased degree of freedom at higher temperatures that results in the formation of favorable molecular aggregates in the excited state through enhanced aromatic π-π and metallophilic Pt(II)···Pt(II) interactions. Structurally similar Pt-bp3 is not able to gel any common organic solvents. The inability of Pt-bp3 to form gels illustrates the importance of gelation to the macroscopic photophysical properties; Pt-bp3 does not show emission enhancement at elevated temperatures due to its low tendency to form strong aggregates in the ground state.

Synthesis, optical, and mesomorphic properties of self-assembled organogels featuring phenylethynyl framework with elaborated long-chain pyridine-2,6-dicarboxamides.

A series of new organogelators with pi-conjugated phenylethynyl framework featuring long-chain carboxamides have been synthesized. These organgelators have shown great ability to gel a variety of organic solvents to form stable organogels with the minimum gelation concentration as low as 0.1 wt %. Gelation is completely thermoreversible, and it occurs due to the aggregation of the organogelators resulting in the formation of a fibrous network via a combination of intermolecular hydrogen bonding, pi-pi stacking, and van der Waals interactions that is observed for the xerogels by TEM. The influence of sol-to-gel transition has been explored in detail by variable-temperature 1H NMR, UV-vis absorption, and fluorescence spectroscopy. Aggregation-induced enhanced emission has been observed in these organogelator molecules with an order of higher fluorescence quantum yields from solution to gels. In addition, some molecules also exhibit unique liquid crystalline properties over a large temperature range as revealed by DSC and POM studies.

[Study on exploring for oil and gas using reflectance spectra of surface soils].

Reflectance spectra in the visible and near-infrared wavelength region provide a rapid and inexpensive means for determining the mineralogy of samples and obtaining information on chemical composition. Hydrocarbon microseepage theory sets up a cause-and-effect relation between oil and gas reservoirs and some special surface alterations. Therefore the authors can explore for oil and gas by determining the reflectance spectra of surface alterations. This determination can be fulfilled by means of field work and hyperspectral remote sensing. In the present paper, firstly a macroscopical feature of reflectance spectra of typical observation points in gas fields is presented. Then a method is proposed in order to provide surface distribution information (e.g., classification) of alterations based on the reflectance spectra determined from the field, and obtain anomaly zones of the special alterations. This method has been applied to the analysis of the reflectance spectra determined in the field of Qinghai X X area, and the classification results tally with the existent gas fields in this area. A robustness analysis of the method shows that good results can be obtained when different combinations of parameters, such as samples, study band regions and thresholds, have been chosen in the process of classification. The valid classification samples and algorithms can be provided for the oil and gas exploration in progress in this area using NASA experimental hyperion hyperspectral satellite.