Nanorods

Martin B R efa/1999 Orthogonal self-assembly on colloidal gold-platinum nanorods Adv. Mater. 11 1021... 

Yu Y efa/1997 Gold nanorods electrochemical synthesis and optical properties J. Phys. Chem. B 101 6661... 

Silver nitrate (AgN03) is a compound that fulfills the precedent requirements (Till = 212°C), and also it can be easily decomposed into pure silver by thermal treatment at 400 °C. As mentioned before, the basic characterisation technique for this studies is transmission electron microscopy (TEM) the atoms with rather high atomic number would facilitate the detection of the nanorods. 

Enclosed nitrate filaments can be thermally decomposed to silver by a simple heat treatment. In opposition to electron irradiation that fragments the filaments, the simple heating yields continuous metal nanorods (see Fig. 6 for a silver filament generated by a 60 min. treatment at 400°C, pressure lO Torr). 

Fig. 6. HREM picture of a CNT enclosing a silver nanorod generated by thermal treatment of silver nitrate filled CNTs.

Fig. 7. Silver nanorod enclosed in a CNT generated by thermal treatment of silver nitrate and close CNTs. See text for explanations.

Deng, D. W. Qin, Y. B. Yang, X. Yu, J. S. and Pan, Y. (2006). The selective synthesis of water-soluble highly luminescent CdTe nanoparticles and nanorods The influence of precursor Cd/Te molar ratio.. Cryst. Growth, 296,141-149. 

The same approach with Ni-thiolate precursor has also successfully produced rhombohedral NiS (millerite) nanorods and triangular nanoplates with a nearly 1 1 ratio (Fig. 20.2) [5]. The lengths of nanorods are controllable through different heating conditions and range from 15 to 50 nm with aspect ratios of approximately 4. The pyrolysis temperature and the reactant concentration, when the precursor was prepared, mainly influence the rod or triangle proportions. 

Although random and irregular type GaN nanorods have been prepared by using transition metal nanoparticles, such as Ni, Co, and Fe as catalysts and carbon nanotubes as the template, the preparation of controllable regular array of strai t GaN nanorods has not yet been reported. Fabrication of well-ordered nano-structures with high density is very important for the application of nano-structures to practical devices. 

In this study, we report on the GaN nanorod growth by HOMVPE technique with or without using a new precursor, tris(N,N-dimethyldithiocarbamato)gallium(III) (Ga(mDTC)3). The structural and optical properties of GaN nanorods were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL). 

Fig. 4. SEM image of the GaN nanorods grown by HOMVPE technique without using Ga(mDTC)3...

Within the scope of thermoelectric nanostructures, Sima et al. [161] prepared nanorod (fibril) and microtube (tubule) arrays of PbSei. , Tej by potentiostatic electrodeposition from nitric acid solutions of Pb(N03)2, H2Se03, and Te02, using a 30 fim thick polycarbonate track-etch membrane, with pores 100-2,000 nm in diameter, as template (Cu supported). After electrodeposition the polymer membrane was dissolved in CH2CI2. Solid rods were obtained in membranes with small pores, and hollow tubes in those with large pores. The formation of microtubes rather than nanorods in the larger pores was attributed to the higher deposition current. 

Kang Y, Kim D (2006) WeU-ahgned CdS nanorod/conjugated polymer solar cells. Sol Energy Mater Sol Cells 90 166-174... 

Sima M, Enculescu I, Visan T, Spohr R, Trautmann C (2004) Electrochemical deposition of PbSei j Tej nanorod arrays using ion track etched membranes as template. Mol Cryst Liq Cryst 418 749-755... 

Huynh WU, Dittmer JJ, Ahvisatos AP (2002) Hybrid nanorod-polymer solar cells. Science 295 2425-2427... 

This process of crystalHzation using charges was extended to other systems using as an alternative mixtures of amines and long chain carboxylic acids. In this way, super-lattices of nanorods of cobalt and of nanocubes of iron were prepared (vide infra). 

Thus, the decomposition of Ni(COD)2 by dihydrogen in the presence of HDA yields nanoparticles, the aspect ratio of which depends upon the ligand concentration. Thus for one or less equivalent HDA, the reaction produces isotropic Ni particles whereas using ten equivalent HDA, nanorods, monodis-perse in diameter, are obtained [74]. The formation of nanowires can also be promoted by a rapid decomposition process. This is illustrated by the decom-... 

Fig. 12 Cobalt nanorods synthesized in the presence of a mixture of oleic acid and a octylamine b dedecylamine c hexadecylamine d octadecylamine...

Fig. 13 Super-lattice of cobalt nanorods a Top view hexagonal b vue de cote c image k haute resolution...

The lower symmetry of nanorods (in comparison to nanoshells) allows additional flexibility in terms of the tunability of their optical extinction properties. Not only can the properties be tuned by control of aspect ratio (Figure 7.4a) but there is also an effect of particle volume (Figure 7.4b), end cap profile (Figure 7.4c), convexity of waist (Figure 7.4d), convexity of ends (Figure 7.4e) and loss of rotational symmetry (Figure 7.4f). 

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