Absorption of nanoparticles

As with the uptake of other types of active species discussed in this chapter, microgel particle/nanoparticle composite materials show a large range of potential applications, making this whole field of microgel particle uptake and release a rapidly developing area. 

2 Saunders, B.R. and Vincent, B. (1999) Advances in Colloid and Interface Science, 80, 1. 

5 Femandez-Nieves, A, Femandez-Barbero. A. and Vincent, B. (2003) Journal of Chemical Physics, 119, 10383. 

and Zhou, S. (1996) Journal of Polymer Scknce Part B Polymer Physks, 34, 1597. 

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The oral administration of peptides and proteins by means of PACA nanoparticles is another interesting perspective. Although the oral absorption of nanoparticles... 

Link S and El-Sayed M A 1999 Size and temperature dependence of the plasmon absorption of colloidal gold nanoparticles J. Phys. Chem. B 103 4212... 

Overall the results led to the conclusion that acetylated nanoparticles of both starch and cellulose offer potential eco-friendly substitutes for the conventional filler carbon black upto 40 phr. They imparted high mechanical strength and elasticity with minimum compromise in themal stability and moisture absorption of the resulting bionanocomposites. Cellulose acetate nanoparticles afforded effective reinforcement even upto loadings as high as 50 phr. 

The purpose of this section is to describe recent achievements in time-resolved X-ray diffraction from liquids. Keeping the scope of the present chapter in mind, neither X-ray diffraction from solids nor X-ray absorption will be discussed. The majority of experiments realized up to now were performed using optical excitation, although some recent attempts using infrared excitation were also reported. The main topics that have been studied are (1) visualization of atomic motions during a chemical reaction, (2) structure of reaction intermediates in a complex reaction sequence, (3) heat propagation in impulsively heated liquids, and (4) chemical hydrodynamics of nanoparticle suspensions. We hope that the actual state-of-the-art will be illustrated in this way. 

Figure 8. TEM and optical absorption of the sample implanted with 5 x 10 Au /cm (a) TEM cross-sectional micrograph (dashed lines represent the free surface and film-substrate interface) (b) nanoparticles size distribution (c) simulated optical spectra (1) Au cluster in a non-absorbing medium with n = 1.6 (2) Au cluster in polyimide (absorbing) (3) Au(core)-C(shell) cluster in a nonabsorbing medium with n = 1.6 (4) the experimental spectrum of Au-implanted polyimide sample, (d) X-ray diffraction patterns as a function of the implantation fiuence.

Figure 5.33 Electron micrographs of nanoparticle helices inside tubules of DC8,nPC+ 2% DCgj9PEOH after sequential absorption of charged polymers followed by treatment with 45-nm silica spheres. Reprinted with permission from Ref. 141. Copyright 2000 by the American Chemical Society.

Measurements of the optical properties in this range of wavelengths can probe the fundamental electronic transitions in these nanostructures. Some of the aforementioned effects have in fact been experimentally revealed in this series of experiments (90). As mentioned above, the IF nanoparticles in this study were prepared by a careful sulfidization of oxide nanoparticles. Briefly, the reaction starts on the surface of the oxide nanoparticle and proceeds inward, and hence the number of closed (fullerene-like) sulfide layers can be controlled quite accurately during the reaction. Also, the deeper the sulfide layer in the nanoparticle, the smaller is its radius and the larger is the strain in the nanostructure. Once available in sufficient quantities, the absorption spectra of thin films of the fullerene-like particles and nanotubes were measured at various temperatures (4-300 K). The excitonic nature of the absorption of the nanoparticles was established, which is a manifestation of the semiconducting nature of the material. Furthermore, a clear red shift in the ex-citon energy, which increased with the number of sulfide layers of the nanoparticles, was also observed (see Fig. 21). The temperature dependence of the exciton... 

It is difficult to predict the effect of surface functionalization on the optical properties of nanoparticles in general. Surface ligands have only minor influence on the spectroscopic properties of nanoparticles, the properties of which are primarily dominated by the crystal field of the host lattice (e.g., rare-earth doped nanocrystals) or by plasmon resonance (e.g., gold nanoparticles). In the case of QDs, the fluorescence quantum yield and decay behavior respond to surface functionalization and bioconjugation, whereas the spectral position and shape of the absorption and emission are barely affected. 

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