Page 28 - Synthesis of Functional Nanoparticles Using an Atmospheric Pressure Microplasma Process - LiangLiang Lin
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Chapter 1
of their special optical and imaging properties. Microplasma electrochemical method may become an attractive and reliable way to prepare metal nanoparticles for biological application, since it is environment friendly without any stabilizers, the products are smaller with narrower size distribution compared with the products achieved by other methods.
In addition to noble metal nanoparticles, lanthanide-doped nanophosphors have attracted considerable interest for bio-imaging applications owing to their sharp emission/absorption bands, long fluorescence lifetimes and particle size independent emission wavelengths. Therefore, tunable emissions can be achieved by choosing proper color-center elements. A representive example is the Y2O3:Eu3+ nanophosphor, which is a well-known red luminescent material and can exhibit excellent luminescence efficiency under ultraviolet excitation. This in conjunction with their superior photo-stability, narrow line-width emission bands and high quantum yields makes them attractive for various fields including field emission displays, cathode ray tubes, plasma display panels and optoelectronic devices. As a perfect host matrice for luminescent material, the green synthesis of high quality of Y2O3 nanoparticles are now attracting increasing interests.
Metal nitrides, as an emerging plasmonic material, have also attracted much attention for their silimar optical properties to noble metal nanoparticles but being considerably more cost- effective for production.141 Being similar to Au, titanium nitride (TiN) and zirconium nitride (ZrN) have a zero cross-over wavelength in the visible range (dielectric permittivity), rendering them plasmonic resonances in the visible and near infrared range. Additionally, their superior thermal stability, with melting points being close to refractory metals such as molybdenum, tungsten and tantalum, makes them suitable candidates for high temperature applications. Among metal nitrides nanoparticles, TiN is of higher interest due to potential applications in the microelectronics industry. Optical properties of TiN nanostructured films have been widely studied via SPP experiments. Recently, it was shown that epitaxially grown TiN nanoparticles exhibit better plasmonic properties and enable exciting applications such as plasmonic interconnects and hyperbolic metamaterials. Optical properties of TiN nanoparticles were studied numerically in 2003 by Quinten et al., where it was found what extinction peaks are similar to Au, but with broader widths. Later in 2004, Reinholdt et al. fabricated TiN nanoparticles via a laser ablation method and demonstrated their plasmonic behavior at slightly longer wavelengths (400-500 nm). In 2010, Cortie et al. examined the optical properties of TiN semi-shell structures and reported resonance peaks in the near infrared region for these geometries (700-750 nm). Recently, it is demonstrated that TiN nanoparticles produced by lithographical method provide a better heating efficiency in the biological transparency window compared to Au nanoparticles with identical geometries.
3) Hyperthermia and drug delivery
Magnetic nanoparticles are of great interests for investigators from various disciplines, especially for the bio-application purpose. One promising field is the hyperthermia. By placing magnetic nanoparticles (e.g. iron oxide, Ni) in altering current (AC) fields, they are driven to flip the magnetization direction between the parallel and antiparallel orientations. This allows the transfer of magnetic energy to heat. Since tumor cells are more sensitive to temperature increase than normal cells, the increase of temperature can destroy the tumor

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