Laser ablation nanotube synthesis

Ka, I. Le Borgne, V. Ma, D. El Khakani, M. A., Pulsed laser ablation based direct synthesis of single-wall carbon nanotube/Pbs quantum dot nanohybrids exhibiting strong, spectrally wide and fast photoresponse. Adv. Mater. 2012, n/a-n/a. 

The past decade has led to the detection of new carbon allotropes such as fullerenes26 and carbon nanotubes,27 28 in which the presence of five-mem-bered rings allows planar polycyclic aromatic hydrocarbons to fold into bent structures. One notes at the same time that these structures are not objects of controlled chemical synthesis but result from unse-lective physical processes such as laser ablation or discharge in a light arc.29 It should be noted, on the other hand, that, e.g., pyrolytic graphitization processes, incomplete combustion of hydrocarbon precursors yielding carbon black, and carbon fibers30 are all related to mechanisms of benzene formation and fusion to polycyclic aromatic hydrocarbons. 

Kozlov G.I. (2003) Forming of carbon cobweb at the single walls nanotube synthesis in the stream of laser ablation products widening in an electric field. Pisma v JTF, 18, 88-94. (In Russian). 

The synthesis processes for the nanotubes have been continuously refined in the recent years and today, a number of methods are available to synthesize both single and multiwalled carbon nanotubes. These methods include high temperature evaporation using arc-discharge (28-30), laser ablation (31), chemical vapor deposition etc. (32-34). 

Stephan was the first to attempted direct synthesis of the B and N multi walled carbon nanotubes (BCN-MWNTs) in 1994 [15-17]. Since then, considerable progress has been made in the synthesis of BCN-MWNTs by different means of arc-discharge [16-18], laser ablation [18-20], piyolysis methods [18,21], and chemical vapor deposition [18,20-24]. Aligned BNC nanotubes have been sueeessfully fabricated by bias assisted hot filament chemieal vapor deposition [27,28]. Up to now, the only existing BCN-SWNTs synthesis was achieved via an... 

It occurs catalytically on the surface of Fe nanoparticles grown from Fe(CO)5. Also, the conventional synthesis of nanotubes by catalytic CVD from acetylene or methane can be formally considered as redox reaction. Nevertheless, the electrochemical model of carbonization (Sections 4.1.1 and 4.1.2) is hardly applicable for CVD and HiPco, since the nanotubes grow on the catalyst particle by apposition from the gas phase, and not from the barrier film (Figure 4.1). The yield and quality of electrochemically made nanotubes are usually not competitive to those of catalytic processes in carbon arc, laser ablation, CVD and HiPco. However, this methodology demonstrated that nanotubes (and also fullerenes and onions (Section 4.3)) can be prepared by soft chemistry" at room or sub-room temperatures [4,5,101]. Secondly, some electrochemical syntheses of nanotubes do not require a catalyst [4,5,95-98,100,101]. This might be attractive if high-purity, metal-free tubes are required. 

Although currently yields obtained in electrochemical synthesis of fullerenes and nanotubes are not yet competitive compared to those prepared via the usual processes (carbon arc, laser ablation, etc.), such procedures are of considerable interest (Kavan et al., 2004). 

MWNT can also be prepared by laser ablation. Contrary to the synthesis of single-walled nanotubes, no catalyst is added here, but a pure graphite target is vaporized by means of a focused laser beam. The resulting MWNT are precipitated at cooler positions within the reactor. Here as well, the operating temperature is about 1200 °C because the number of defects increases and the yields of MWNT decrease at lower temperatures. Below 200 °C then, no growth of carbon nanotubes is observed anymore. The process produces a considerable portion of amorphous carbon, fullerenes, and carbon nanoparticles besides the desired MWNT. These impurities have to be removed before further use. The yields of multiwalled nanotubes usually range about 40%. 

The mechanism of nanotube formation in chemical vapor deposition features characteristics rather distinct from those found for the synthesis by arc discharge or laser ablation. Contrary to the latter, a solution of small carbon clusters in and subsequent diffusion through catalyst particles play a minor role in the deposition from the gas phase. The employed hydrocarbons decompose directly on the surface of the catalytic particle. The carbon, therefore, becomes immediately available for nanotube growth. 

Dozens of methods to synthesize nanotubes, nanowires, and nanorods have been reported that can be found in the references included in Table 1. In addition to the most well known ones, such as hot plasmas, laser ablation, chemical vapor deposition, high temperature solid state and hydrothermal synthesis, fill-ing/coating of carbon nanotubes and similar types of materials, three methods have been developed that enable the synthesis of a wealth of new anisotropic nanoparticles. 

InP nanocrystals can be made by dehalosilylation of InCls and (MesSi) 3P with subsequent thermolysis at 200 - 400 Monodisperse and soluble InP nanocrystals are obtained by thermolysis reactions in trioctylphosphine oxide. InP nanoparticles can also be obtained by the decomposition of organometallic precursors. A novel route has been developed to prepare nanocrystalline InP by the reaction of InCls, P4, and KBH4 at temperatures as low as 80°C, which is the lowest temperature reported for InP nanocrystals. The synthesis of InP nanotubes by laser ablation is also reported. 

BN and B cCj,N2 nanotubes and fullerene-like structures have been synthesized by various laboratories in recent years. The most popular methods are the plasma arc and laser ablation techniques. The first report on the synthesis of BN nanotubes, using the arc-discharge technique, was by the Zettl group [85, 86]. Because... 

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