Page 27 - Synthesis of Functional Nanoparticles Using an Atmospheric Pressure Microplasma Process - LiangLiang Lin
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1) Catalysis
Introduction - Plasma and Microplasma-assisted Nanofabrication
Figure 1.7 Applications of nanomaterials in various fields
Nano-sized inorganic particles, especially metal nanoparticles, are widely used as catalysts in various reactions. For example, Ni and Fe nanoparticles show excellent catalytic activity for CNTs growth.128 Chiang et al. used plasma-generated Ni and Fe nanoparticles to catalyze the CNTs growth. The results showed that the reduction of an averaged Ni nanoparticles size from 3.1 nm to 2.2 nm, caused an improvement for the rate of CNTs growth by 13 times. Moreover, Ni nanoparticles with different dimensions could control precisely the CNTs’ inner and outer diameter as well as wall numbers.129 Afterwards, they studied the catalytic activity of the bimetallic nanoparticles, and found that NixFe1-x could significantly increase the catalytic activity and lower the activation energies for CNTs growth compared with monometallic nanoparticles.92 For example, with Ni0.67Fe0.33 nanoparticles, the CNTs could grow at 300 °Cwith activation energy as low as 37 kJ/mol, while CNTs only grew at 400 °C with Ni nanoparticles and the activation energy was estimated to be 73 kJ/mol.
2) Optical applications
The optical properties of nanoparticles are interdependent to a great extent. For instance, noble metal nanoparticles have size dependent optical properties, where the absorbance onset and emissions shift to higher energy with decreasing size due to the quantum size effect. Thus, different colors can be obtainedby controlling the particle size. Nowadays they have been are chosen as ideal materials for bio-imaging applications, primarily because of their biocompatibility, low short-term toxicity as well as high absorption coefficient for electromagnetic radiation and physical density.130 For example, gold/silver nanoparticles show promising prospects in cancer treatment due to their unique characteristics such as the high surface to volume ratio, facile surface chemistry, excellent optical properties as well as the ability to convert radio frequencies or light into heat.131 They can extravasate into tumor stroma and accumulate at tumor sites, and be tracked directly by optical microscopy because
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