Evaporation, sources laser ablation

Despite the frequent use of arc-discharge and laser ablation techniques, both of these two methods suffer from some drawbacks. The first is that both methods involve evaporating the carbon source, which makes it difficult to scale up production to the industrial level using these approaches. Second, vaporization methods grow CNTs in highly tangled forms, mixed with unwanted forms of carbon and/or metal species. The CNTs thus produced are difficult to purify, manipulate, and assemble for building nanotube-device architectures in practical applications. 

There are several sample introduction methods that are used in conjunction with ICP, including nebulization, electrothermal evaporation, gas chromatography, hydride generation, and laser ablation [30]. Laser ablation combined with ICP (LA-ICP) is useful for analysis of solids. In such a source the sample is positioned in a chamber prior to the ICP source, the ablation cell. Argon gas at atmosperic pressure flows through the cell towards the ICP source. The sample is irradiated by a laser beam and... 

The utilily of PLD for Ihin film synlhesis is due in large part to Ihe unique characteristics of Ihe laser ablation process. As indicated above, laser ablation is a nonequilibrium process that enables stoichiometric evaporation of elements from a target source. In addition, it is also possible to control the energy of evaporated species in PLD, and thus control film growlh on Ihe subslrale surface. The underlying basis for these features of laser ablation and their utihty in thin film synthesis are described below. 

Vacuum is effective in collecting ISF firom skin that has been mechanically penetrated or had the stratum comeum removed. As with blood collection studies, large site-to-site and person-to-person variability is observed. A large vacuum headspace in the collection devise results in a decrease in volume due to evaporation and an increase in analyte concentrations. Outgassing of dissolved gas in the ISF and leaks between the skin and vacuum source lead to the formation of bubbles in the ISF stream over time. The application of one-half atmosphere vacuum through a harvesting head with an aperture of 2.5 mm over a 1 mm pattern of micropores produced by laser ablation of a black dye yields straw-colored interstitial fiuid at fiow rates of 5-15 pL/h for several days [4]. Vacuum collection over a much larger area (about 1 cm ) is required to collect similar amounts of ISF from low-frequency ultrasound-treated skin [8]. 

The interaction of the radiation from high-power laser sources with solids can lead to evaporation. As this is independent of the electrical conductivity of the sample, laser ablation is increasingly important for solid analysis [140]-[142]. 

---