Site-selective doping

Further modification of the above nanostructures is useful for obtaining new functional materials. Thirdly, we apply the dopant-induced laser ablation technique to site-selectively doped thin diblock copolymer films with spheres (sea-island), cylinders (hole-network), and wormlike structures on the nanoscale [19, 20]. When the dye-doped component parts are ablated away by laser light, the films are modified selectively. Concerning the laser ablation of diblock copolymer films, Lengl et al. carried out the excimer laser ablation of diblock copolymer monolayer films, forming spherical micelles loaded with an Au salt to obtain metallic Au nanodots [21]. They used the laser ablation to remove the polymer matrix. In our experiment, however, the laser ablation is used to remove one component of block copolymers. Thereby, we can expect to obtain new functional materials with novel nanostmctures. 

Nanoscale Morphological Change of PS-b-P4VP Block Copolymer Films Induced by Site-Selective Doping of a Photoactive Chromophore... 

As aforementioned, diblock copolymer films have a wide variety of nanosized microphase separation structures such as spheres, cylinders, and lamellae. As described in the above subsection, photofunctional chromophores were able to be doped site-selectively into the nanoscale microdomain structures of the diblock copolymer films, resulting in nanoscale surface morphological change of the doped films. The further modification of the nanostructures is useful for obtaining new functional materials. Hence, in order to create further surface morphological change of the nanoscale microdomain structures, dopant-induced laser ablation is applied to the site-selectively doped diblock polymer films. 

Wang, Z., Masuo, S., Machida, S. and Itaya, A. (2007) Site-selective doping of dyes into polystyrene-fclock-Poly(4-vinyl pyridine) diblock copolymer films and selective laser... 

A very nice example of the power of Mossbauer spectroscopy was the demonstration [37] of site selective doping of compound 111-V semiconductors such as GaAs, where it was concluded from the measured Sn isomer shift that implanted In and Sb radioactive parent ions selectively populate 111 and V sites respectively. 

Laser ablation of polymer films has been extensively investigated, both for application to their surface modification and thin-film deposition and for elucidation of the mechanism [15]. Dopant-induced laser ablation of polymer films has also been investigated [16]. In this technique ablation is induced by excitation not of the target polymer film itself but of a small amount of the photosensitizer doped in the polymer film. When dye molecules are doped site-selectively into the nanoscale microdomain structures of diblock copolymer films, dopant-induced laser ablation is expected to create a change in the morphology of nanoscale structures on the polymer surface. 

Site-Selective Modification of the Nanoscale Surface Morphology of Dye-Doped Copolymer Films Using Dopant-Induced Laser Ablation... 

For symmetric PS-fo-P4VP (20 000 19 000) diblock copolymer films with the wormlike phase separation structures, the TCPP-doped films were irradiated using one laser shot with a fluence of 150 mJ cm in air. The ablation phenomenon is observed for this irradiation fluence (Figure 12.5c and f), but it is difficult to conclude that this is a selective ablation of the doped-P4VP parts. We cannot deny the possibility that the decomposition of the P4VP parts affects the PS parts because of the existence of large interfaces between the two symmetric blocks in wormlike structures. Thus, for the site-selective ablation of diblock copolymer films, the surface morphology of the phase separation structures is one of the most important parameters. 

Ideally, lanthanide ions occupy site with C3V symmetry when incorporated into the GaN lattice by substituting the Ga3+. However the actual site symmetry is often found lower than C3V due to strain and defects. So far no crystal field analysis has ever been reported for lanthanide-doped III-V QDs, due to the co-existence of multi-sites which complicates the energy level structure and makes crystal field analysis difficult. Site selective spectroscopy is a very useful tool thus proposed to investigate the different crystal field environments of lanthanide ions doped in III-V QDs. 

Site Selective Photochemical Change in Anthracene Crystals Doped with 2-Hydroxyanthracene. 

For our purposes, the relevant point to emphasize is that electrocatalytic processes can involve different catalytically active sites and/or different catalytic mechanisms. These features are of considerable interest for sensing because they enhance the possibilities of obtaining highly selective responses for selected analytes by modulating the structural environment and concentration of catalytic sites in doped materials. This matter will be treated in more detail in Chapter 9. 

Domenech, A., and Alarcon, J. 2003. Vanadium-doped zircon and zirconia materials prepared from gel precursors as site-selective electrochemical sensors. Instrumentation, Science Technology 31, 121-139. 

Domenech, A., Torres, EJ., and Alarcon, J. 2004c. Electrochemistry of vanadium-doped ZrSiO,. Site-selective electrocatalytic effect on nitrite oxidation. Electrochimica Acta 49, 1623 4632. 

In the course of a study of the luminescence properties of uranium-doped sodium fluoride single crystals, the complicated uranate luminescence spectra have been unraveled, using chemical variation of the crystal compositions and by applying site selective laser excitation techniques Using the results from both luminescence and electrical conductivity experiments a model was deduced for the configurations of the uranium centres ). 

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