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Nearly monodisperse BaTiO3hollow nanoparticles were prepared through a one-pot template-free route in molten hydrated salt medium. The composition and morphologies of the time-dependent products were investigated in detail, and Ostwald ripening is concluded to be responsible for the hollowing evolvement of the BaTiO3particles. The size of the initial solid particles is proposed to play an important role in determining the evacuation manner of the solid in the ripening-induced hollowing process, that is, evacuating from the center region or underneath the surface layer of the solid aggregates, and could result in the morphology variation (i.e., hollow geometry or core−shell one) of the final products. Our study also points out that a highly active precursor is crucial to improve the uniformity of the products, and elevated reaction temperature is a prerequisite to activate the hollowing evolvement of solid aggregates. Second-harmonic-generation and Raman analyses revealed the ferroelectric tetragonal characteristic of the obtained BaTiO3hollow nanoparticles, and the tetragonality (c/a) was quantified to be about 1.005 according to the Rietveld refinement of the X-ray diffraction pattern. [ABSTRACT FROM AUTHOR]

Abstract: Platinum–copper bimetallic alloy nanoparticles were synthesized in water-in-oil (w/o) microemulsions of water/cetyltrimethyammonium bromide (CTAB)/isooctane/n-butanol by the co-reduction of H2PtCl6 and CuCl2 with hydrazine at room temperature. The samples were characterized by high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and X-ray photoelectron spectrum (XPS). XRD results show that there is only one peak in the pattern of bimetallic nanoparticles, corresponding to the (111) plane of the PtCu3 bulk alloy. XPS illustrates that both elements in the nanoparticles are in zero-valence and possess the characteristic metallic binding energy. HRTEM analyses confirm the formation of the PtCu3 alloy nanoparticles with a mean diameter of about 1.6nm, where the corresponding lattice spacing of 1.87Å is consistent with that of the (200) plane of PtCu3 bulk alloy. Moreover, the factors influencing the size of PtCu3 nanoparticles had also been investigated and discussed. [Copyright &y& Elsevier]

Single crystal of hydrated sodium borate Na2B5O8(OH)∙2H2O has been grown with sizes up to 5 × 5 × 3 mm3 under mild hydrothermal conditions at 180°C. The structure is determined by single-crystal X-ray diffraction and further characterized by IR and TG analyses. It crystallizes in the orthorhombic space group Pna21, with a =11.967(2) Å, b = 6.5320(13) Å, c = 11.126(2) Å, Z = 4, R1 = 0.0183, and wR2 = 0.0483. The crystal structure of Na2B5O8(OH)∙2H2O is made up of Na—O polyhedra, and [B5O8(OH)]2- polyborate anions. Transmittance spectrum is performed on the Na2B5O8(OH)∙2H2O crystal, which shows an absorption edge less than 190 nm in the UV region. The powder second-harmonic generation intensity measured by Kurtz—Perry method indicates that Na2B5O8(OH)∙2H2O is about half that of KH2PO4(KDP). [ABSTRACT FROM AUTHOR]

Many biological surfaces in both the plant and animal kingdom possess unusual structural features at the micro- and nanometre-scale that control their interaction with water and hence wettability. An intriguing example is provided by desert beetles, which use micrometre-sized patterns of hydrophobic and hydrophilic regions on their backs to capture water from humid air. As anyone who has admired spider webs adorned with dew drops will appreciate, spider silk is also capable of efficiently collecting water from air. Here we show that the water-collecting ability of the capture silk of the cribellate spider Uloborus walckenaerius is the result of a unique fibre structure that forms after wetting, with the ‘wet-rebuilt’ fibres characterized by periodic spindle-knots made of random nanofibrils and separated by joints made of aligned nanofibrils. These structural features result in a surface energy gradient between the spindle-knots and the joints and also in a difference in Laplace pressure, with both factors acting together to achieve continuous condensation and directional collection of water drops around spindle-knots. Submillimetre-sized liquid drops have been driven by surface energy gradients or a difference in Laplace pressure, but until now neither force on its own has been used to overcome the larger hysteresis effects that make the movement of micrometre-sized drops more difficult. By tapping into both driving forces, spider silk achieves this task. Inspired by this finding, we designed artificial fibres that mimic the structural features of silk and exhibit its directional water-collecting ability. [ABSTRACT FROM AUTHOR]

A new nonlinear optical crystal, Na3VO2B6O11, has been grown by the top-seeded solution growth method using a Na2CO3−V2O5flux. The structure of the compound was determined by single-crystal X-ray diffraction. It crystallizes in the noncentrosymmetric orthorhombic system, space group P212121, with cell parameters a= 7.7359(9) Å, b= 10.1884(12) Å, c= 12.5697(15) Å, V= 990.7(2) Å3, and Z= 4. Na3VO2B6O11has a three-dimensional structure consisting of hexaborate groups connected by VO4tetrahedra with the sodium atoms distributed in channels through out the three-dimensional network. The refractive indices have been measured by the minimum deviation technique and fit to the Sellmeier equations. Nonlinear optical measurements on the compound demonstrate that the material has second harmonic generation properties, with an efficiency approximately the same as that of KH2PO4. [ABSTRACT FROM AUTHOR]