Silicone nanoparticles

In view of the above, instead of avoiding powder formation regimes in discharges, careful powder management involving optimization of the ratio of radicals and silicon nanoparticles arriving on the substrate has been proposed [379]. 

Zhou, X.S., et al., Self-assembled nanocomposite of silicon nanoparticles encapsulated in graphene through electrostatic attraction for lithium-ion batteries. Advanced Energy Materials, 2012. 2(9) p. 1086-1090. 

In order to overcome these problems, hybridization of both materials (C and Si) in one electrode material by HTC seemed to be a promising option [75]. For this purpose, pre-formed silicon nanoparticles were dispersed into a dilute solution of glucose followed by hydrothermal treatment at 180 °C. The carbon-coated particles were then further treated at 750 °C in order to improve the conductivity and structural order of the carbon layer. It was shown that the hydrothermal treatment, following by high temperature carbonization, resulted in formation of a few nanometer thin layer of SiOx layer on the Si nanoparticles, effectively leading to a Si/SiOx/C nanocomposite. Some TEM micrographs of these materials are shown in Fig. 7.8. 

Fig. 7.8 TEM images of the Si SiOx/C nanocomposite nanoparticles produced by hydrothermal carbonization of glucose and Si and further carbonization at 750 °C under N2. (a) Overview of the Si SiOx/C nanocomposites and a TEM image at higher magnification (in the inset) showing uniform spherical particles (b) HRTEM image clearly showing the core/shell structure (c), (d) HRTEM image displaying details of the silicon nanoparticles coated with SiOxand carbon.

D. Hill, T. Jawhari, J.G. Cespedes, J.A. Garcia and E. Bertran, In-situ monitoring of laser annealing by micro-Raman spectroscopy for hydrogenated silicon nanoparticles produced in radio frequency glow discharge, Phys. Status SolidiA, 203, 1296-1300 (2006). 

Fig. 4.1. Schematic structure of a silicon nanoparticle with a thin Si02 passivating layer and of mesoporous silica (MCM-41 material).

Figure 7 Schematic diagram of microplasma reactor for the synthesis of silicon nanoparticles. A microdischarge forms at the cathode tip and extends a short distance toward the anode (Sankaran et al, 2005 reproduced with permission).

Currently silicon is still one of the most important semiconductors as it is the basis of any computer chip. It exhibits an indirect band gap of 1.1 eV at room temperature in the microcrystalline phase. Similar to Ge, silicon nanoparticles show a size-dependent photoluminescence. It was reported by Katayama el al. that a thin Si layer can be electrodeposited in l-ethyl-3-methylimidazolium hexafluorosilicate at 90 °C [44], However, upon exposure to air the deposit reacted completely to SiC>2, which makes it difficult to decide whether the deposit was semiconducting or not. Recently, we showed for the first time that silicon can be well electrodeposited from SiCU in the air and water stable ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([BMPJTfiN) [45, 46]. This ionic liquid can be... 

Hydrofluoric acid — (HF) A solution of hydrogen fluoride in water. The pure hydrogen fluoride is characterized by Mw of 20.0063 gmol-1 m.p. -83.55 °C (1 atm) b.p. 19.5 °C (latm). When concentrated, this colorless fuming liquid is extremely corrosive and can dissolve almost all inorganic oxides such as silicate compounds or oxides of metals like stainless steel, aluminum, and uranium however, it can be stored in casted iron bottles because a corrosion-resistant iron fluoride layer protects the metal. It is used for several purposes such as the preparation of titanium oxide nano tube arrays [i], silicon nanoparticles [ii] and electrochemical etching of silicon [iii], electrochemical deposition of lithium [iv], etc. 

Keywords Cyclodextrin silicone nanoparticle spontaneous emulsification drug... 

Electron hole transport composites consisting of poly(aniline-co-2-acrylami-do-2-methyl-propanesulfonic acid), (V), and silicon nanoparticles were prepared by Hsu [4] and then used to prepare light-emitting diodes and electrodes for thin film field effect transistors. 

Kapaklis V, Politis C, Poulopoulos P, Schweiss P. Photoluminescence from silicon nanoparticles prepared from bulk amorphous silicon monoxide by the disproportionation reaction. Appl. Phys. Lett. 2005 87. 

Wang L, Reipa V, Blasic J. Silicon nanoparticles as a luminescent label to DNA. Bioconj. Chem. 2004 15 409-412. 

Finally, there have been reports that deal with other forms of spectral detection. A platinum (Il)-coproporphyrin reagent has been evaluated for phosphorescent labelling of oligonucleotides. The presence of the label had little effect on conjugation, and labelled primers were effective in PCR reactions. A silicon nanoparticle conjugated to ODNs acted as a luminescent label, and a molecular beacon (see later) has been prepared which contains a photoluminescent dye (Ru(II)(bpy)3) and the luminescent quencher Black Hole Quencher-2 . ... 

In this paper the dependence of the rate of chemical reactions in a nanoparticle on its size is considered using reaction of oxidation of the silicon nanoparticle as an example. 

It is known that the presence of oxygen in silicon microelectronic elements can considerably affect their electrophysical properties. Concentration of oxygen can decrease due to reaction between oxygen and silicon (oxidation of silicon). Let us consider a possible influence of the size on above-mentioned chemical reaction in a spherical silicon nanoparticle. We accept the model used in [2]. In this model it is supposed that oxidation of silicon by molecular oxygen takes place over the whole volume of silicon. Under this assumption the concentration of oxygen in the particle can be found from the following equation ... 

We assume that relation between the activation energy for diffusion of oxygen in silicon nanoparticle (Dj) and in bulk silicon (E ) by analogy with [1] reads... 

Figure 1. E)ependence of the dimensionless rate constant for oxidation of the silicon nanoparticle k,...

Consider the time dependence of oxygen concentration in the silicon nanoparticle. For simplicity the distribution of oxygen over the particle volume is supposed to be uniform. We assume also that concentration of silicon C2 is much higher than concentrations of oxygen and the reaction product (silicon dioxide) and that the value of C2 can be approximately considered to be constant, i.e. Cj = Cj(f = 0) = CjQ. Taking into account the above-mentioned assumptions and Eq. (I), the dimensionless concentration of oxygen in the nanoparticle 1 (0 = Cl (0 / c, (t = 0) can be written as... 

The effect of the nanoparticle size on chemical reactions in the particle was considered for oxygenation of the silicon nanoparticle. It is shown that, according to the considered model, the rate of chemical reaction in nanoparticles increases with a decrease in their size. 

In 1990, Canham reported the room-temperature luminescence of porous silicon.11111 This important discovery has attracted much attention towards an investigation in silicon with the quantum-size effect. Through chemical-vapor deposition, it is also possible to load silicon nanoparticles into zeolite channels and pores. First, disilane is treated with the protons in a zeolite and is grafted to the zeolite walls [Equation (9.13)] ... 

Silicon nanoparticles in a narrow range of sizes (25-50 nm) were obtained by mechanical attrition. ... 

Li ZF, Ruckenstein E (2004) Water-soluble poly(acrylic acid) grafted luminescent silicon nanoparticles and their use as fluorescent biological staining labels. Nano Lett 4 1463-1467... 

Lie LH, Patole SN, Pike AR, Ryder LC, Connolly BA, Ward AD, Tuite EM, Houlton A, Horrocks BR (2004) Immobilisation and synthesis of DNA on Si(l 11), nanocrystalline porous silicon and silicon nanoparticles. Faraday Discuss 125 235-249... 

Pettigrew KA, Liu Q, Power PP, Kauzlarich SM (2003) Solution synthesis of alkyl- and alkyl/alkoxy-capped silicon nanoparticles via oxidation of MgaSi. Chem Mater 15 4005-4011... 

Rogozhina EV, Eckhoff DA, Gratton E, Braun PV (2006) Carboxyl functionahzation of ul-trasmaU luminescent silicon nanoparticles through thermal hydrosilylation. 1 Mater Chem 16 1421-1430... 

Sato S, Swihart MT (2006) Propionic-acid-terminated silicon nanoparticles synthesis and optical characterization. Chem Mater 18 4083-4088... 

Reindl, A. et al.. Dispersing silicon nanoparticles with a stirred media mill and subsequent functionalization with phenyl acetylene. Colloids Sutf. A, 301, 382, 2007. 

Molecular dynamics (MD) computations of coalescence have been made for silicon nanoparticles ranging in size from. 30 to 480 atoms, corresponding to a maximum diameter smaller than. 3 nm (Zachariah and Cairier, 1999), The compulations were based on an interatomic potential developed for silicon atoms with covalent bonding. The particle structure was assumed to be amorphous. The MD simulations indicate that the transition between solid and liquid-state behavior occurs over a wide temperature range significantly lower than the melting point of bulk silicon (1740 K), a well-known effect for nanoparticics (Chapter 9), The broadest transition occurred for the smallest particles studied (30 atoms), probably becau.se the surface atoms make up a large fraction of the particle mass. 

Another remarkable synthetic effort has been made by the preparation of colloidal Q-particles of the technically more relevant IV-IV materials (i.e., silicon and germanium) [20-25]. Silicon nanoparticles, especially, are currently drawing a lot of attention, since it was found by Canham [26] that nanostructured silicon formed under anodic etching of silicon wafers (called porous silicon ) exhibits bright red fluorescence. Due to the indirect nature of the band transition, bulk silicon shows, by contrast, almost no fluorescence and thus cannot be utilized for optoelectronic devices. 

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