Dope dyeing

Doped silicon, conductivity in, 23 35 Doped/undoped electrochromic organic films, 6 580-582 Dope-dyeing, 9 197 Dope-making process, in acrylic fiber solution spinning, 11 204 Dope solids, in air gap spinning, 11 209 Doping, 23 838—839 calcium, 23 842-844 conducting polymers, 7 528-529... 

Methods of Doping Dye Molecules into Silica Nanoparticles. 234... 

In this chapter, the first section will focus on the designs of different structures of DDSNs. The basic synthesis methods of pure silica nanoparticles will be briefly summarized at the beginning. The general methods for doping dye molecules into a silica matrix will then be covered followed by the introduction of several DDSN designs. The second section will be a major focus of this chapter. Various advantageous properties of DDSNs will be discussed. These discussions will involve reaction kinetics, solubility, photostability, and fluorescence intensity including quantum yield and lifetime, as well as toxicity. With the rapid development of DDSNs, more features and functionalities of DDSNs are expected in the near future. 

In a reverse microemulsion, the hydrolysis and polymerization of the silicate precursor occur in the water droplet, therefore, to dope dyes in the silica nanoparticles they must be water soluble. However, a number of organic dye molecules are hydrophobic, requiring modifications prior to doping. Several methods are available to link a hydrophobic dye molecule to a water soluble group. A simple and effective example is to link a hydrophilic dextran to the dye molecules [8]. This modification can greatly enhance the water solubility of hydrophobic dye molecules, but will increase the cost of resultant DDSNs. 

Montalti and co-workers studied dansyl [27] and pyrene [28] derivatives and found the fluorescence quantum yields and excited-state lifetime of these two dyes increased in DDSNs. They attributed the enhancements to the shielding effect from the quenchers or polar solvent in the suspension. Their studies also demonstrated that the lifetime of the doped dye molecules was also dependent on the size of the DDSNs. Small DDSNs had a larger population of the short-living moieties that were more sensitive to the environment outside the DDSN. In contrast, the large DDSN had a larger population of the long-living moieties that were not sensitive to the environment. 

The amorphous silica matrixes are porous network structures that allow other species to penetrate [44]. Thus, the doped dye molecules have the ability to react with targets. However, the reaction kinetics is significantly different than the molecules in a bulk solution. In the synthesis of DDSNs, commonly used silicon alkoxides including TEOS and TMOS have tetrahedron structures, which allow compact polycondensation. As a result, the developed silica nanomatrix can be very dense. The small pore sizes provide limited and narrow pathways for other species to diffuse into the silica matrix. 

In conclusion it can be stated that the p- and -type dark conductivity of doped dyes and a number of undoped dyes is the result of differences in the densities of holes and electrons. Thus, in -type dyes we have p n, and in n-... 

However, there are many other chemicals and additives that a producer may be required to add to the solution, including (1) a few parts per million of a tracer element for later identification of the product (2) coloring pigments for dope dyed rayon ( dope dyeing ... 

On the other hand, liquid phase deposition (LPD) has been demonstrated as a flexible wet chemical method for preparing metal oxide nanostructured films on electrode surfaces. By the LPD process, electroactive titanium dioxide (Ti02) films were prepared on graphite, glassy carbon and ITO. The electrochemical properties of such LPD Ti02 films were dependent upon the film thickness controlled by the deposition time. The LPD technique was easily combined with other techniques, e.g., seed-mediated growth, which could provide metal/metal oxide composite nanomaterials. Moreover, hybrid nanostructured films were facilely obtained by doping dyes, surfactants and other... 

Photochemical hole burning spectroscopy is applied to estimate the low-temperature relaxation properties of polymers. Methacrylate polymers, polyethylene derivatives, and polymers with aromatic groups were studied. Both slight and large changes of microenvironments around doped dye molecules are detected by temperature cycling experiment. Relaxation behavior of the polymers is discussed in relation to their diemical structures. The low-energy excitation mode of each polymer is also estimated and... 

The changes of microenvironments around the doped dye molecules have a strong correlation with the characters of matrix polymers such as steric hindrance for segmental motion, amount of free volume, and interchain hydrogen bonds. By the PHB measurements, we can detect both slight and large environmental change around the dyes doped in polymers at low temperatures. The PHB spectroscopy is expected to be extended to other polymer systems to study low-temperature relaxation properties of them. 

Figure 19 NP samples with diffa-ent doping dye combinations under 300-nm UV illumination. Dye doping ratio (in order) 1 0 0, 0 1 0, 1 0 1, 4 1.5 3, 0.5 0.5 0.5, 2 2 2, 0 1 1, 0.5 0.5 4. (Reproduced with pamission from Ref. 40. 2005, American Chanical Society.)...

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