Template-free methods

There are many experimental techniques for the preparation of nanowires from the liquid phase. A considerable research effort has been expended in developing template-free methods for the deposition of one-dimensional nanostructures in a liquid environment the most important procedures are hydrothermal methods, electrospinning,sonochemical and surfactant assisted. 

According to this formula, for a given oxidant the resultant nanofiber diameter can be predicted. The dopant-free template-free method not only provides a quantitative way of controlling the diameter of the PANI-NFs, but also simplifies the reagents. PANI-NFs were successfully prepared by using the dopant-free template-free method through the... 

Miscellaneous Template-Free Methods Self-assembled PANI-NFs have been prepared by the oxidative polymerization of aniline with APS in an acidic aqueous solution in the presence of HCl [172,204—206], HCl and ethanol [207], HCl and colloidal Au particles... 

Dopant-Free Template-Free Method PANI-NTs have been prepared by the oxidative polymerization of anihne with APS in water without added acid (Figure 2.18) [199,350,380,381]. This is a facile and efficient approach to synthesize PANI-NTs because it not only omits hard templates and post-treatment template removal, but also simplifies reagents. A modification of the dopant-free template-free method of PANI-NTs synthesis... 

Figure 2.18 Typical (a) SEM and (b) TEM of PANI-NTs prepared by dopant-free template-free method. (Reprinted with permission from Macromolecular Chemistry and Physics, Formation mechanism of polyaniline nanotubes by a simplified template-free method by H. Ding,]. Shen, M. Wan andZ. Chen, 209, 8, 864-871. Copyright (2008) Wiley-VCH)...

Miscellaneous Template-Free Methods PANI-NTs, having cavities of various diameters, have been found as by-products of PANI-NF synthesis through the oxidation of aniline with silver nitrate in aqueous solutions of HNO3 [225]. Ag was obtained as nanopartieles accompanying macroscopic Ag flakes in the resulting PANI/Ag composite. 

Four-probe pressed-pellet conductivities for PANI emeraldine hydrochloride nanofibers are in the range 2-10 S cm [51], similar to conventional PANI emeraldine hydrochloride powder [1]. Maximum conductivities of PANI-NFs prepared by various template and template-free methods are given in Tables 2.1 and 2.2, respectively. 

Table 2.2 Maximum conductivity of PANI- NFs prepared by template-free methods ...

Y. Yang and M. Wan, Chiral nanotubes of polyaniline synthesized by a template-free method, J. Mater. Chem., 12, 897-901 (2002). 

Y. F. Huang and C. W. Lin, Exploration of the formation mechanisms of polyaniline nanotubes and nanofibers through a template-free method, Synth. Met., 159,1824-1830 (2009). 

J. Wang, J. Wang, Z. Wang, and F. Zhang, A template-free method toward urchin-like polyaniline microspheres, Macromol. Rapid Commun., 30, 604—608 (2009). 

M.X. Wan, A template-free method towards conducting polymer nanostmetures, Adv. Mater., 20(15), 2926-2932 (2008). 

Y. Zhu, H. He, M. Wan, and L. Jiang, Rose-hke microstmetures of polyaniline by using a simplified template-free method under a high relative humidity, Macromol. Rapid Commun., 29(21), 1705-1710(2008). 

Composites with one-dimensional structure can also be fabricated by template-free method. They are formed via an in situ synthetic process. For instance, Ag/PPy nanocables have been prepared through the redox reaction between pyrrole and silver nitrite in aqueous solution in the presence of polyvinylpyrrolidone. During the reaction process, the formation of Ag nanowires and the polymerization of a pyrrole sheath were proceeded simultaneously. The as-synthesized Ag/PPy nanocables displayed a coaxial nanostructure with a dark core and a lighter sheath (Fig. 4.3I-J) (Chen et al., 2005). The diameter of the Ag nanowire core was about 20 nm, while the outer diameter of PPy sheath reached about 50 nm. 

Template-Free Methods for Conducting Polymer Nono-Architecture 21... 

The deposition of parylene nanofibers by template-based and template-free methods has been studied... 

ID assemblies of nanopaiticles refer to the controlled assembly of nanoparticles into wires, rods, belts, rings, and tubes, which have become the focus of intensive research owing to their unique application in mesoscopic physics and fabrication of nanoscale devices. The basic method for ID assemblies can be divided into template-directed method and template-free method which will be introduced in the following text. 

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