Coaxial nanocables

Figure 9.7 Typical TEM images (a) and (b) of the as-prepared gold/platinum hybrid NPs supported coaxial nanocables at different magnifications.132 (Reprinted with permission from S. Guo et al., J. Phys. Chem. C. 2008,112, 2389-2393. Copyright 2008 American Chemical Society.)...

Zhang, Y - Suenaga, K. Coiiiex. C. lijima. S. Coaxial nanocable Silicon carbide and silicon oxide sheathed with boron nitride and carbon. Science 1998 281. 973,... 

The nanowires themselves can be used as templates to generate the nanowires of other materials. The template may be coated onto the nanowire (physically) forming coaxial nanocables [316a], or it may react with the nanowires forming a new material [317a,b]. In the physical (solution or sol-gel coating) approach, the surfaces of the nanowires could be directly coated with conformal sheaths made of a different material to form coaxial nanocables. Subsequent dissolution of the original nanowires could lead to nanotubes of the coated material. The sol-gel... 

Au/PANI-CSA coaxial nanocables have been successfully synthesized by the oxidation of aniline with chloroauric acid in the presence of CSA [397]. PANI-CSA nanotubes were obtained by dissolving the Au nanowire core of the Au/PANI-CSA nanocables. Purified flagella fibers displaying an anionic aspartate-glutamate loop peptide with 18 carboxylate groups were used to initiate formation of PANI-NTs [398]. 

Aniline HAuCU Direct oxidation-reduction Camphorsulfonate, H2O 50-60 nm diameter of coaxial nanocables 33... 

I-J) Reproduced with permission from reference Chen, A., Wang, H., Li, X., 2005. One-step process to fabricate Ag-polypyrrole coaxial nanocables. Chem. Common. 1863-1864. Copyright 2005, Royal Society of Chemistry. (K) Reproduced with permission from reference Yin, J., Chang, R., Shui, Y, Zhao, X., 2013. Preparation and enhanced electro-responsive characteristic of reduced graphene oxide/polypyrrole composite sheet suspensions Soft Matter 9, 7468-7478, Copyright 2013, Royal Society of Chemistry. (L-M) Reproduced with permission from reference Wang,... 

Chen, A., Wang, H., Li, X., 2005. One-step process to fabricate Ag-polypyrrole coaxial nanocables. Chem. Commun. 14,1863-1864. 

PPy coaxial nanocables. The inset is the TEM of Sn02 MWCNT Sn02 PPy. Panels are reproduced with permission [111]. Copyright 2011, Elsevier. 

As mentioned above, metal/CPs with core-sheath structure can be prepared by the template method. However, the approach based on the template technique is complicated and non-economical because of the need to remove the templates. In fact, metal/CPs with core-sheath structure can be fabricated via a one-step chemical polymerization [83-87]. Niu and co-workers demonstrated that Au/PANI coaxial nanocables could also be fabricated by the redox reaction between chloroauric acid and aniline in the presence of d-CSA [85]. In that case, CSA acted not only as a dopant, but also as a surfactant or a soft template. In addition to Ag/PPy and Au/PANI nanocables, cable-like Au/poly(3,4-ethylenedioxythiophene) (PEDOT) nanostructures have been synthesized in the absence of any surfactant or stabilizer through one-step interfadal polymerization of EDOT dissolved in dichloromethane solvent and HAuCl dissolved in water [86]. Microscopy studies showed (Figure 13.6) that the outer and inner diameters of Au/PEDOT nanocables were aroimd 50 and 30 nm, respectively. 

PPy-PMMA coaxial nanocable was fabricated through sequential polymerization of methyl methaaylate and pyrrole inside the channel of mesoporous SBA-15 sihca, followed by removal of the silica template [168]. In addition, a PPy nanofiber insulated within 1-D silicate channel was produced using the pyrrole-containing surfactant monomer. Dming the sol-gel process, pyrrole domain was segregated and insulated by 1-D silicate nanochannel, and then the chemical polymerization of pyrrole resulted in the formation of PPy nanofiber [231]. 

The first example is the work of Lu et al. [124] who fabricated polypyrrole (PPy)ATi02 coaxial nanocables, where the conductivity of PPy was integrated with the photocatalytic activity of Ti02 for applications in electrochromic devices, nonlinear optical systems, and photoelectrochemical devices. The synthetic approach consisted in (1) preparation of Ti02 fibers by sol-gel electrospinning and calcination of the polymer (PVP in the specific case), (2) physical adsorption of Fe " oxidant on the surface of Ti02 nanofibers, and (3) polymerization of pyrrole (from vapor) on the surface of Ti02 nanofibers. 

Lu X, Zhao Q, Liu X, Wang D, Zhang W, Wang C, Wei Y (2006) Preparation and characterization of polypyrrole/Ti02 coaxial nanocables. Macrranol Rapid Commun 27 430-434... 

Shen L, Yuan C, Luo H et al (2011) In situ growth of Li4Ti50i2 on multi-walled carbon nanotubes novel coaxial nanocables for high rate lithium ion batteries. J Mater Chem 21 761-767... 

Y. Yin, Y. Lu, Y. Sun and Y. Xia, Silver nanowires can be directly coated with amorphous silica to generate well-controlled coaxial nanocables of silver/silica, Nano Lett. 2(4), (2002). 

Si02 layers can be coated on the surface of multiwall carbon nanotubes (MWCNTs) and used as templates [27]. Stoichiometric amounts of MWCNTs Si02, lithium acetate dihydrate, and ferric oxalate are mixed to synthesize MWCNTs Li2peSi04 composite by solid-state reaction at 600°C for 5 h in an Ar atmosphere. The in situ produced Li2FeSi04 shell on the surface of the MWCNTs forms a coaxial nanocable. 

Cao FF, Guo YG, Zheng SF, Wu XL, Jiang LY, Bi RR, Wan LJ, Maier J (2010) Symbiotic coaxial nanocables facile synthesis and an efficient and elegant morphological solution to the lithium storage problem. Chem Mater 22 1908-1914... 

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