Three-layered nanoparticles

Fig. 10.10 Zeta potential of three-layered nanoparticles (3LNPs)...

Some time ago, we investigated the behavior PEO-containing PE terpolymer PS-PVP-PEO in aqueous solutions [88, 89], The micellization of this copolymer is strongly pH-dependent because PVP is protonized and therefore soluble in acidic solutions at pH lower than 4.8, but is deprotonized and therefore water-insoluble at higher pH. The PS-PVP-PEO micelle is a three-layer nanoparticle in which the PVP blocks form a middle layer between the rigid PS core and the PEO shell. The PVP layer is either collapsed at high pH, so that PS-PVP-PEO micelles resemble onion micelles formed in mixtures of PS-PVP and PVP-PEO diblock copolymers, or it is partially protonized, swollen, and flexible in acid aqueous media, so that the PVP layer becomes a soluble inner shell between the core and the outer PEO shell. 

Three-layered nanoparticles containing an hbPG core and cross-linked block copolymers based on N-isopropyl acrylate and N,N-dimethylaminoethyl acrylate as the respective arms were synthesized and proved to be thermoresponsive. ° Chu and co-workers" reported electrically conductive core-shell nanoparticles based on poly(n-butylacrylate-b-polystyrene) multiarm star polymers. The PS segments were converted to poly(p-styrenesulfonate) (PSS), thus generating amphiphilic tmimolecular micelles. Then the oxidative propagation of 3,4-ethylenedioxythiophene (EDOT) on the PSS chains was carried out by counterion-induced polymerization to produce a stable aqueous dispersion of the respective PEDOT complex. 

Fig. 7.12 SEM images ofthe diatomite substrate through sequential assembly of positively-at low (A) and high (B) magnification. The di- charged PDDA and negatively-charged zeolite atomite has a disk-like shape about 1.2 pm in nanocrystals (C). The inset in (C) shows an thickness and 20-40 pm in diameterwith a nearly enlarged view of the nanoparticle-modified sur-regular array of submicrometer-sized pores face. (Reprinted from [129] with permission of (about 300-500 nm). SEM images of diatomite Wiley-VCH.) coated with three layers of zeolite ( nanocrystals...

Time courses of rate of hydrogen generated from decalin with carbon-supported platinum catalyst at various feed rates in bench-scale continuous operation. Catalyst platinum nanoparticles supported on ACC (5 wt-metal%), 0.29 g (one layer, ), 0.58 g (two layers, A), and 0.87 g (three layers, O). Feed rate of decalin 1.5, 2.0, 2.5, 3.0, and 5.0 mL/min. Reaction conditions boiling and refluxing by heating at 280°C and cooling at 25°C. 

Figure 10. (A) Schematic illustration of PEI-mediated self-assembly of FePt nanoparticles by alternately adsorbing a layer of PEI and a layer of nanoparticles on a solid surface and TEM images of PEI-mediated assembly of 4 nm Fe58Pt42 nanoparticles on silicon oxide surface (B) one layer of assembly and (C) three layers of assembly [56].

Fig. 4 a, b. TEM micrographs of hollow silica spheres produced by calcining PS particles coated with (a) one and (b) three Si02 nanoparticle/PDADMAC layer pairs at 450°C. The wall thickness of the hollow capsules is approximately three times greater for those shown in (b) compared with those shown in (a), c, d Cross-sections of the hollow silica spheres of the same composition as those shown in (b). The hollow silica spheres retain the spherical shape of the original PS particle templates (see Fig. 3). (Adapted from [22,62] by permission of the American Association for the Advancement of Science and the American Chemical Society)...

The above three layers form what is collectively referred to as the "ink-receptive formulation". Critical to the success of this product is the COLORCAST technology embodied by the cationic polymer additives called "mordants" that are designed to bind and fix the dye molecules, along the ceramic nanoparticle in the protective overcoat. The exact choice, concentration, and location of the mordants are critical to achieving the best balance of image stabUity across the four main environmental factors hght, heat, humidity, and ozone. Equally important is incorporation of the proprietary ceramic nanoparticles present in the overcoat layer. 

Figure 18 Illustration of a three-layer arrangement of CoPt3 nanoparticles...

To solve this problem, Shen and coworkers developed a three-layered pH-responsive nanoparticle (3LNP) that had a neutral corona at the physiological pH, but the corona became positively charged at the tumor extracellular pH, which resulted in rapid cellular internalization (Scheme 10.2) [165, 166]. 

Scheme 10.3 Fabrication of drug-loaded pH-responsive three-layered onion-structured nanoparticles (3LNPs) via pH-controUed hierarchical self-assembly...

Zhan, Y Van Kirk, E. Xu, P Murdoch, W. J. Radosz, M. Shen, Y. pH-responsive three layer onion-structured nanoparticles for drug delivery. Polym. Mater. Sci. Eng. Prepr. 2006, 94, 139-140. 

We find that a layer model analysis can adequately describe the Pt NMR spectrum of nanoscale electrode materials. The shifts of the surface and sub-surface peaks of Pt NMR spectra correlate well with the electronegativity of various adsorbates, while the Knight shift of the adsorbate varies linearly with the f-LDOS of the clean metal surface. The Pt NMR response of Pt atoms from the innermost layers of the nanoparticles does not show any influence of the adsorbate present on the surface. This provides experimental evidence, which extends the applicability of the Friedel-Heine invariance theorem to the case of metal nanoparticles. Further, a spatially-resolved oscillation in the s-like E( -LDOS was observed via Pt NMR of a carbon-supported Pt catalyst sample. The data indicate that much of the observed broadening of the bulk-like peak in Pt NMR spectra of such systems can be attributed to spatial variations of the A( f). The oscillatory variation in A(A) beyond 0.4 nm indicates that the influence of the metal surface goes at least three layers inside the particles, in contrast to the predictions based on the Tellium model. 

Fig. 7a shows a schematic of the arrangement for the spectro-electrochemical experiment performed by Su et al. The lowest layer is the bulk Pt substrate on which a thin layer of Pt nanoparticles is deposited. In this case, CO is adsorbed on the Pt nanoparticles and the system is immersed in water. The adsorbed CO molecules and water are treated as the mixed phase. In the absence of CO, the mixed phase is simply water, and CO adsorption only adds a component to Bmag- In the theoretical study of Su el al, a three-layer model was used to simulate the experimental system in which the first layer is water, the third layer is the substrate, and the layer between them is an effective layer composed of Pt nanoparticles, adsorbed CO and water, as shown in Fig. 7b. For each layer, an optical constant obtained from the literature was given to describe its optical property and the dielectric constant was calculated as the square of refractive index. Since the size of the Pt nanoparticles is much smaller than the wavelength of the incident IR radiation, EMT could be used to calculate the effective dielectric constant of the second layer. Although this layer consists of three phases, namely Pt nanoparticles, adsorbed CO molecules and water, inclusion of the three phases separately in these calculations led to an excessively complicated computation, so CO molecules and water were treated as a mixed phase and Pt nanoparticles were immersed in this mixed phase.

Figure 4.12 Schematic outline illustrating the concept of the three-layer oversaturation technique used for the crystallization of monodisperse FePt and CoPtS nanoparticles.

A further group of nanocomposites are the well-known bentonites, revitalized at the end of the 1980s by Toyota Research. Bentonites are swellable, three-layer silicates consisting mainly of montmorillonite. The new organophilic bentonite Nanofil product family from Siid Chemie AG is based partly on the Bavarian calcium bentonites, which are activated by acid leaching [see Table 27 [77]], and do without cationic exchange. (Author s remark With a mean particle size of 4 pm, these are by no means nanoparticles ). 

The composite of PbTe and polymer is generally formed by in situ fabrication [20,22]. Wang et al. fabricated PbTe-PANI composite with PbTe/PANi/ PbTe three-layer sphere-like nanostructures [22]. Although the electrical conductivity of the PbTe/PANI/PbTe composite is lower than that of the PbTe nanoparticle, the Seebeck coefficient reached 578-626 pV/K, which is much higher than those of both the PbTe nanoparticle and PANI, resulting in a high power factor of 63.5-86.2 pW/mK (Table 6.5). These results... 

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