Nanoparticles of yellow gold and grey silicon ..

T1 - Synthesis of Silicon Nanoparticles in Nonthermal Capacitively-Coupled Flowing Plasmas

Role of ammonia in silica nanoparticle synthesis?

N2 - Control of the size and material properties of silicon nanoparticles plays a critical role in optimizing applications using those nanoparticles, such as photovoltaics and biomedical devices. While synthesis of silicon nanoparticles in low temperature plasmas has many attractive features, the basic mechanisms leading to formation of nanoparticles in these plasmas are poorly understood. A two-dimensional numerical model for synthesis of silicon nanoparticles (4 gas mixtures. Algorithms for the kinetics of nanoparticle formation were self-consistently embedded into a plasma hydrodynamics simulation to account for nucleation, growth, charging, and transport of nanoparticles. We found that with RF excitation in narrow tubes at pressures of a few Torr, the electric field does not fully confine charged nanoparticles in the axial direction, which then results in a finite residence time of particles in the plasma. We found that because of the high neutral nanoparticle density, coagulation plays a significant role in growth. The model predicts the possibility of synthesizing crystalline silicon nanoparticles under these conditions. Trends in the growth of nanoparticles as a function of power are discussed.

T1 - Synthesis and characterization of manganese-doped silicon nanoparticles

Journal | Nanoparticle | Silicon

The novel thiourea-functionalized silicon nanoparticles (SiNPs) have been successfully synthesized using allylamine and sulforaphane, an important anticancer drug, followed by a hydrosilylation reaction on the surface of hydrogen terminated SiNPs. Their physiochemical properties have been investigated by photoluminescence emission, Fourier transform infrared spectroscopy (FTIR) and elemental analysis. The MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay has been employed to evaluate toxicity in human colorectal adenocarcinoma (Caco-2) cells and human normal colon epithelial (CCD) cells. The results show significant toxicity of thiourea SiNPs after 72 h of incubation in the cancer cell line, and the toxicity is concentration dependent and saturated for concentrations above 100 μg/mL. Confocal microscopy images have demonstrated the internalization of thiourea-functionalized SiNPs inside the cells. Flow cytometry data has confirmed receptor-mediated targeting in cancer cells. This nanocomposite takes advantage of the epidermal growth factor receptor (EGFR) active targeting of the ligand in addition to the photoluminescence properties of SiNPs for bioimaging purposes. The results suggest that this novel nanosystem can be extrapolated for active targeting of the receptors that are overexpressed in cancer cells such as EGFR using the targeting characteristics of thiourea-functionalized SiNPs and therefore encourage further investigation and development of anticancer agents specifically exploiting the EGFR inhibitory activity of such nanoparticles.

AB - Control of the size and material properties of silicon nanoparticles plays a critical role in optimizing applications using those nanoparticles, such as photovoltaics and biomedical devices. While synthesis of silicon nanoparticles in low temperature plasmas has many attractive features, the basic mechanisms leading to formation of nanoparticles in these plasmas are poorly understood. A two-dimensional numerical model for synthesis of silicon nanoparticles (4 gas mixtures. Algorithms for the kinetics of nanoparticle formation were self-consistently embedded into a plasma hydrodynamics simulation to account for nucleation, growth, charging, and transport of nanoparticles. We found that with RF excitation in narrow tubes at pressures of a few Torr, the electric field does not fully confine charged nanoparticles in the axial direction, which then results in a finite residence time of particles in the plasma. We found that because of the high neutral nanoparticle density, coagulation plays a significant role in growth. The model predicts the possibility of synthesizing crystalline silicon nanoparticles under these conditions. Trends in the growth of nanoparticles as a function of power are discussed.


A new model for silicon nanoparticle synthesis - …

Crystalline semiconductor nanoparticles are of interest for a variety of electronic and opto-electronic applications. We report experimental studies of the synthesis and characterization of crystalline silicon nanoparticles using a constricted-mode capacitive RF plasma in continuation of results reported earlier from an RF inductively coupled plasma [1]. The constricted-mode discharge is based on a thermal plasma instability yielding a high-density plasma filament, which rotates at a high frequency. Silane is dissociated, leading to particle nucleation and growth. Particles are extracted by passing the particle-laden gas through an orifice to form a beam and collected by inertial impaction. We are able to reproducibly synthesize highly oriented freestanding single-crystal silicon nanoparticles. Monodisperse particle size distributions centered at a 35nm particle diameter with a geometric standard deviation of 1.3 are obtained. Transmission electron microscope (TEM) studies show uniformly shaped cubic particles. Selected-area electron diffraction patterns indicate the particles have the diamond-cubic silicon structure. To study the electrical properties of these particles, metal-semiconductor-metal structures were fabricated and analyzed.

Silicon Nanoparticles - nanogloss

We have shown the utility of quantum dot (QD)-siRNA complexes in maintaining the integrity of the blood brain barrier (BBB) (see Figure ). The matrix-degrading metalloproteinases (MMPs), particularly MMP-9, are involved in neuroinflammation processes leading to disrupting of the BBB, thereby exacerbating neurological diseases such as HIV-1 AIDS dementia and cerebral ischemia.[] We evaluated the specificity and efficiency of QD complexed with MMP-9-siRNA (nanoplex) in downregulating the expression of MMP-9 in brain microvascular endothelial cells (BMVECs) that constitute the BBB. Silencing MMP-9 gene expression in BMVECs and other cells such as leukocytes may help prevent breakdown of the BBB and inhibit subsequent invasion of the central nervous system (CNS) by infected and inflammatory cells, as well as circulating neurotoxins. Several other groups have also demonstrated the significance of QD/QR mediated delivery of siRNA molecules for the treatment of a variety of ailments, particularly cancer.