Nanosheet solutions

Terpyridine, N N N ligands (245-249) and their N C N and N N C analogues (250-257) have been successfully coordinated to Pt(II), leading to neutral, mono- or doubly charged species, which in some cases display bright luminescence, both in degassed fluid solutions and frozen matrices. In particular, it has been shown by Che et al. that they can form supramolecular structures, such as nanowires, nanosheets, and polymeric mesophases, with interesting optical properties (214—216,258). 

Weng et al. [113] studied the effect of tetramethylammonium cations (TMA"") on HO2 crystal morphology under hydrothermal conditions. The as-synthesized samples were characterized by XRD, TEM and SEM methods (see Table 2). The observed morphologies include besom-like particle, nanosheet and nanotubes. The mechanism to accelerate the formation of nanotube in the base of NaOH/TMAOH mixture is illustrated in Eigure 7. Bulk HO2 is first exfoliated to be layered protonic titanate by the mineralization effect of Na". In the presence of TMA"" cations, the separation of layered protonic titanate is accelerated by intercalating TMA"" cations in layered titanate. As a result of the presence of more layered titanate in the hydrothermal solution, nanotubes are formed ahead of schedule by curliness of layered titanate. Thus, the mechanism through which TMA cations affect crystal growth in the conditions of this study is different. 

Conversions of nanosheets into nanorods have been possible for metal oxides such as ZnO (44). The self-assembled nanosheets arc first prepared by a solution phase hydrothermal synthesis. The reactant solution eontains zine nitrate, hexamethylene tetra-mine and hydrazine, whieh helps in the fonnation of precursor nanosheets in an orderly fashion. At shorter time seales ( 46), nanosheets are formed and after 8 h, hollow microspheres arc formed. The nanosheets arc calcined at 400°C to get ZnO nanorods, as depicted in Figure 7.6. This is an example where one nanostmcture transforms to a completely different morphology. 

By using an exfoliation and flocculation technique, Prasad et al. were able to prepare a polyaniline/NbWOe hybrid material [74]. Dispersed nanosheets of HNbWOe were obtained by treating HNbWOe with tetrabutyl ammonium hydroxide. The suspension of the exfoliated layers was then added to an alcoholic solution of aniline, followed by addition of a few drops of 1M HCl, and overnight sonication in order to induce flocculation of the aniline-NbWOe nanocomposite. The nanocomposite was isolated by centrifugation, and dried. Treatment of the nanocomposite with O2 at 130 °C for several weeks resulted in the formation of intercalated PANI. 

Figure 7.6 Schematic illustration of nucleation and growth mechanism of PANi nanowires (a) heterogeneous nucleation on GO nanosheets (b) homogeneous nucleation in bulk solution. Reprinted with permission from Ref. [84], Copyright 2010, American Chemical Society.

PANI/graphene nanosheets (GNs) films were prepared by mixing the PANl powder and GNs in NMP solution [29]. High-magnification field-emission... 

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