Right Bipyramids

Other Morphologies Prepared by the Polyol Process 3.4.3.1 Right Bipyramids 

---

Fig. 2 SEM images of right-bipyramids approximately (a) 150 nm and (b) 75 nm in edge length. The inset in (b) shows the electron diffraction pattern obtained from a single right-bipyramid, indicating that it is bounded by (100) facets, Reprinted with permission from B. I Wiley, Y. Xiong, Z.-Y, Li, Y Yin and Younan Xia, Nana Lett., 2006, 6, 765. C 2006 American Chemical Society.

The method yields dipods, tripods and tetrapods (nanocrystals with 2, 3 and 4 arms respectively, the one with 4 arms generally being tetrahedral). Icosahedral Au nanocrystals are obtained by the reaction of HAuCb with PVP in aqueous media." Right-bipyramid (75-150 nm in edge length) nanocrystals of Ag (Fig. 2) have been prepared by the addition of NaBr during the polyol reduction of AgNO., in the presence of PVP." Cu nanoparticles of pyramidal shape have been made by an electrochemical procedure. ... 

Pd nanospheres (1-3 nm) were reported by Teranishi et al. upon reduction of PdCl " precursor in alcoholic environment in the presence of PVP [163]. Xia and coworkers gave a fundamental contribution in detailing the shape-controlled synthesis of metal NCs and particularly in the case of Pd [34]. Based on experimental results they discussed the thermodynamic and kinetic pathways occurring at the synthesis nucleation stage monitoring a series of experimental parameters which can force the system in one direction or the other (see Fig. 10.1b). They could predict and experimentally verify all the possible Pd shapes as cuboctahedrons [164], nanocubes, bars and rods [18, 165], right bipyramids [166] and nanoplates [36]. 

Figure 11.11 SEM image of silver right bipyramids compared with computer-aided design (CAD) model. Reproduced with permission from Ref [102] 2006 American Chemical Society.

Fig. 10. Arrangement of 18 (left) and 24 (right) spherons about an inner core of five spherons with the configuration of a trigonal bipyramid.

Fig. 7. Structures of five-coordinate Cu2+ from first principles molecular dynamics. A Berry twist mechanism for the interconversion of the two structures is shown (from left to right) the reorientation of the main axis of a square pyramidal configuration by pseudo-rotations via a trigonal bipyramidal configuration. The grey atoms in the plane of the trigonal bipyramid are all candidates for becoming apical atoms in a square pyramid.

Figure 51 Transformation of the capped trigonal prism (left) to the pentagonal bipyramid (right) with retention of a twofold axis. The angular coordinates are defined as the angles between the metal—ligand bonds and the twofold axis along the M—A bond. The 6 angular coordinates are defined relative to 0p = 0 and 6q = 180°...

Fig. 15 Effective magnetic moment for nearly-octahedral d1 complexes. Left Figgis theory for 2T2g reference (k = 1, X > 0) solid line - v = 0 (octahedron) dashed - v = -10 (compressed bipyramid, Aax < 0) dot-dashed - v = +10 (elongated bipyramid, Aax > 0). Right calculation in a complete d1 space (level-6) for a Ti(III) complex on tetragonal distortion with F4(xy) = 5000 cm-1 dashed - compressed bipyramid with F4(z) = 6000 cnr1 solid - octahedron with F4(z) = 5000 cm-1 dot-dashed - elongated bipyramid with F4(z) = 4000 cm-1...

Fig. 17 Modeling the magnetic functions (level-6) for a nearly-octahedral Ti(III) complex F4(xy) = 5000 cm 1, F4(z) = 6000 cm 1 (compressed tetragonal bipyramid) dot-dashed -the parallel (z) component, dashed - the perpendicular (xy) component, solid - averaged. Right extrapolated temperature independent paramagnetism - dashed...

---