Composite particles nanoparticles

All the examples gathered here demonstrate the possibility to control the growth of metallic and oxide nanoparticles using biological templates. A wide variety of chemical composition, particle size and assemblage can be obtained via these approaches. Moreover, due to the biological nature of the template, applications in fields related to biotechnology and medicinal science can be envisioned. 

This construction results in signal enhancement when the composite particles are employed as optical nanosensors due to the possibility to exploit to this scope the Surface Enhanced Raman Scattering (SERS) by the embedded Au nanoparticles. 

Figure 5 A schematic illustration of a multistep continuous-flow synthesis system for making ZnS-coated CdSe composite particles. Luminescence spectra of uncoated CdSe from CdSe portion and coated particles from the outlet at different flow rates. Labels denote the flow volume of the two syringes for the CdSe and ZnS raw feedstock. Uncoated CdSe nanoparticles were obtained using a flow rate of 100 pi min 1 images reproduced, with permission, from Wang et al, 2004).

Figure 16. TEM images of binary nanoparticle assemblies of (A) Fe304(4 nm) Fe58Pt42(4 nm) nanoparticles and (B) one sintered FePt-Fe3Pt composite particle [75].

Keywords. Polymer latex, Miniemulsion, Heterophase polymerization, Polymer nanoparticles, Composite particles... 

Here, we review the use of microgel particles as reactors for the immobilization of catalytically active metal nanoparticles or enzymes. The composite particles of microgels and the metal nanoparticles can be used for catalysis in aqueous media, that is, under very mild conditions [24-28], Thus, the composite systems allow us to do green chemistry [29] and conduct chemical reactions in a very efficient way. 

Investigations by DLS measurements of composite particles indicated that the original thermosensitive properties of the PNIPA network are not suppressed by the incorporation of metal particles into the network. That is, the shrinking and re-swelling of microgel is not hampered by the incorporation of metal nanoparticles into the network. The metal composite particles show similar volume transition temperature as the carrier particle at 32°C, which is in excellent agreement with previous findings on these systems as shown in Fig. 7 [64, 65], This indicates... 

Fig. 8 Composite particles consisting of thermosensitive core-shell particles in which metallic nanoparticles are embedded. Left The composite particles are suspended in water, which swells the thermosensitive network attached to the surface of the core particles. In this state, the reagents can diffuse freely to the nanoparticles, which act as catalysts. Right At higher temperatures (T > 32°C) the network shrinks and the catalytic activity of the nanoparticles is strongly diminished...

Fig. 10 Rate constant app as function of the surface area S of metal nanoparticles normalized to the unit volume of the system squares SPB-Ag composite particles, circles microgel-Ag composite particles, triangles microgel-Pd composite particles, and diamonds SPB-Pt composite particles [72]. T = 20°C, [4-nitrophenol] = O.lmmolL-1, [NaBPLj] = lOmmolL-1 [24]...

Fig. 11 Dependence of the rate constant k on the temperature T for different systems Arrhenius plot of k measured in the presence of the composite particles SPB-30-Pd9 (filled squares, [Pd composites] = 0.00063 gL-1). In the case of the Microgel-1-Pd9 system (open squares, [Pd composites] = 0.00128 gL-1), we obtained an 5-curve that is similar to that of silver nanoparticles (filled circles, data taken from [59], [Ag composites] = 0.0063 gL-1). The concentrations of the reactants were [4-nitrophenol] = O.lmmolL-1 and [NaBIE] = lOmmolL-1 [24]...

All results reviewed herein demonstrate that the microgel particles may serve as nanoreactors for the immobilization of catalytically active nanostructures, namely for metal nanoparticles and enzymes. In both cases, the resulting composites particles are stable against coagulation and can be easily handled. Moreover, the catalytic activity of metal nanoparticles can be modulated through the volume transition that takes place within the thermosensitive microgel carrier system. Similar behavior has been also observed for the temperature dependence of enzymatic activity. Thus, the microgel particles present an active carrier system for applications in catalysis. 

Future measurements should greatly increase our knowledge of the chemical composition of nanoparticles. The recent development of a novel laser desorption/ionization single-particle mass spectrometer (RSMS-II) (Carson et al. 1997 Ge et al. 1998 Phares... 

The compositions of nanoparticles in Houston differ markedly from those observed in Atlanta. In particular, the dominant composition in Houston is a Si-based particle rather than an organic type (Phares et al. 2001b). The Si particle type is also prevalent... 

We demonstrated that a naturally derived polysaccharide, chitosan, is capable of forming composite nanoparticles with silica. For encapsulated particles, we used silicification and biosilicification to encapsulate curcumin and analyzed the physicochemical properties of curcumin nanoparticles. It proved that encapsulated curcumin nanoparticles enhanced stability toward ultraviolet (UV) irradiation, antioxidation and antitumor activity, enhanced/added function, solubility, bioactivities/ bioavailability, and control release and overcame the immunobarrier. We present an in vitro study that examined the cytotoxicity of amorphous and composite silica nanoparticles to different cell lines. These bioactives include curcumin mdAntrodia cinnamomea. It is hoped that by examining the response of multiple cell lines to silica nanoparticles more basic information regarding the cytotoxicity as well as potential functions of silica in future oncological applications could become available. 

Fig. 10 Processing pathway for obtaining nanocomposite material. (1) Colloidal dispersion of y-Fe203 nanoparticles in hexane. (2) Initial sol with silicon precursor, water, solvents, and iron oxide NPs at ambient conditions, (i) Expanded sol under supercritical conditions with gel composite particles. (4) Dry composite particles. V volume, P pressure, T temperature...

CuInSe2XTe2(i-x) nanoparticles incorporated into silicate glass reveal complicated photoluminescence with the above-than-band gap excitation. It depends on composition of nanoparticles. The secondary heat treatment differently affects the selenides and tellurides. Defect states within the particles and excitons are proposed as possible sources of the luminescence. 

When metal particles are isolated in a polymer so that the interaction between them can be neglected, the conductivity of a composite is determined by that of a polymer matrix. In such composites, metal nanoparticles can only inject carriers into a polymer but do not influence substantially the conductivity process [59], This is the case of metal-PPX films prepared by the cryochemical vapor deposition teclmique if such films contain metal or semiconductor nanocrystals in amounts less than 4—5 vol. % [30]. The conductivity of such composites follows classical olmfic current-voltage relationship [30] and Arrheiuus dependence on temperature [57]. At higher metal contents the mechaiusm of conductivity in synthesized composite films changes under influence of the interparficle interaction. In PPX films containing Pb nanoparficles in amounts from 5 to 10 vol. %, the dependence of current I on voltage U looks like In / [30]. This dependence is characteristic for a... 

Yan F, Li J, Zhang J, et al. (2(X)9) Preparation of Fe304/polystyrene composite particles from monolayer oleic acid modified Fe304 nanoparticles via miniemulsion polymerization. J Nanopart Res 11 289-296... 

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