V2O5 ribbons

Another way of obtaining suspensions of anisotropic mineral moieties is by the spontaneous condensation of dissolved molecular species. A typical example of this process is the synthesis of V2O5 ribbons by using chimie douce (soft chemistry) techniques (Fig. 6) [35,36]. At pH=2, V(V) species exist in an octahedral coordination with a V=0 bond pointing along the Oz axis, three V-OH bonds in the xOy plane, and two bonded H2O molecules to fill the coordination sphere. Beyond a concentration threshold of 10 mol 1 , these vanadate species spontaneously condense in the xOy plane by two different reactions respectively called olation and oxolation reactions (olation V-0H-l-V-0H2 V-0H-V-i-H20 oxola-tion V-OH-l-V-OH—>V-0-V-i-H20) to form ribbons 1 nm thick, about 25 nm... 

Fig. 6. a The molecular species that condense through olation and oxolation reactions into V2O5 ribbons b whose molecular structure is shown in c. (Reprinted from [4b], copyright (2000) from John Wiley and Sons)... 

Molecular Ribbons V2O5, a MLC that Can be Readily Aligned... 

Figure 8.6 Transmission eiectron micrograph of a V2O5 aerogel iiiustrating the characteristic ribbon morphology. (Reproduced with permission from D. R. Roiison and B. Dunn, J. Mater. Chem. 2001, 11, 963. Copyright 2001 The Royal Society of Chemistry.)...

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