Ordered Arrays of Nanorods Obtained by Solid−Liquid Reactions of LaOCl Crystals

Abstract

A new top−bottom approach is developed to prepare ordered arrays of nanorods, based on controlled etching, as exemplified by the case of LaOCl crystals. Molten-salt issued LaOCl was applied as a precursor, with highly anisotropic crystals oriented along the [001] axis. These LaOCl flat crystals are reactive toward aqueous solutions at room temperature, yielding ordered assemblies of rod-like crystals. Depending on the reaction mixture composition, nanorods of LaOCl itself or other La compounds can be obtained. The morphology of the products obtained in the solutions can be finely controlled by adding extraneous chemical species which modify the etching kinetics. Thus, LaOCl reacts with the acidic phosphate solutions, leading to the arrays of LaPO4 nanorods, oriented along the [001] axis of the initial solid. By contrast, reaction with aqueous HCl produced assemblies of perpendicular rods, oriented along the [100] and [010] axes. The catalytic properties of the nanorods as obtained were tested in the decomposition of isopropanol. Strong differences of acid−base properties of differently oriented LaOCl particles have been observed.

Fabrication of La2Ti2O7 Crystals Using an Alkali-Metal Molybdate Flux Growth Method and Their Nitridability To Form LaTiO2N Crystals under a High-Temperature NH3 Atmosphere

“…Similarly, anionic charged planes can also be favored. 37 We assume that the Burton−Cabrera−Frank (BCF)-type screw-dislocation process was probably involved in the growth of the La 2 Ti 2 O 7 platelet crystals. In the high-temperature melt, the growth rate of crystals is believed to be governed by the rate of ions diffusing to kinks in the steps of spirals.…”

Novel blue-emitting Eu2+-activated LaOCl:Eu materials

“…26 These results indicate that the pure LaOCl:Eu 2+ phase could be obtained even at very high temperature, 1300 C. Moreover, the LaOCl:Eu 2+ phases show the strongly enhanced intensity of (00l) planes compared to the JCPDS standard pattern (#08-0477), which means that the LaOCl:Eu 2+ phosphor particles are well oriented along the [001] axis as previously reported. 27 FE-SEM images represent rectangular sheets of 2-20 mm size with round edges as depicted in Fig. 2.…”

Paramecium-like α-MnO2hierarchical hollow structures with enhanced electrochemical capacitance prepared by a facile dopamine carbon-source assisted shell-swelling etching method

“…Hollow nano/microstructures with interior cavities and controlled shell architectures used as electrochemical capacitors have also been attracting lots of attention due to their high specic surface area, numerous active sites and inner accessible space. [43][44][45][46][47][48][49][50] Thus assemblies and hollow structures made up of MnO 2 crystal units such as urchin-like MnO 2 hollow spheres, 51,52 assembled MnO 2 nanowire owers, 53 and MnO 2 hierarchical structures 54 have been developed to enhance the capacitance and cycle stability of electrodes for electrochemical capacitors. Various hollow and hierarchical structures of MnO 2 previously reported display a specic capacitance range from 194 to 356 F g À1 with a specic surface area less than 253 m 2 g À1 at a scan rate lower than 2 A g À1 .…”