THE SIZE CONTROL OF UNIFORM NANOCRYSTALLINE Si GRAINS BY CONSTRAINED GROWTH MODEL

2005 ◽  
Vol 19 (15n17) ◽  
pp. 2751-2756 ◽  
Author(s):  
KUNJI CHEN ◽  
KAI CHEN ◽  
PEIGAO HAN ◽  
HECHENG ZOU ◽  
ZHONGYUAN MA ◽  
...  
Keyword(s):  
Size Control ◽  
Nanocrystalline Silicon ◽  
Annealing Conditions ◽  
Crystallization Method ◽  
Transmission Electron ◽  
Mean Size ◽  
Sublayer Thickness ◽  
The Mean ◽  
Size Controlled ◽  
Nanocrystalline Si

Size-controlled nanocrystalline silicon ( nc - Si ) has been prepared from a - SiN x / a - Si:H/a - SiN x ( 'a' standing for amorphous) sandwich structures by thermal annealing. Transmission electron microscope analyses show that the mean size and the grain size distribution (GSD) of the nc - Si are controlled by the annealing conditions and the a - Si sublayer thickness. Based on our theoretical model of constrained crystallization, we interpret the phenomena of the growth halt of nc - Si and higher crystallization temperature for the thinner a - Si sublayers. The experimental results show that constrained crystallization method is promising to achieve uniform and high density nc - Si array which can be used in the future nano-devices.

The Constrained Growth and Patterned Distribution of nc-Si from a-SiNx/a-Si:H/a-SiNx: Mechanism and Experiments

2004 ◽  
Vol 849 ◽  
Author(s):  
K. J. Chen ◽  
K. Chen ◽  
L. C. Wu ◽  
Z. Y. Ma ◽  
P. G. Han ◽  
...  
Keyword(s):  
Thermal Annealing ◽  
Laser Annealing ◽  
Single Layer ◽  
Nanocrystalline Silicon ◽  
Annealing Conditions ◽  
Transmission Electron ◽  
Device Applications ◽  
Mean Size ◽  
Sublayer Thickness ◽  
Size Controlled

ABSTRACTWe get size-controlled nanocrystalline silicon (nc-Si) from a-SiNx/a-Si:H/a-SiNx sandwich structures by thermal annealing. Transmission electron microscope analyses show that the mean size and the grain size distribution (GSD) of the nc-Si are controlled by the annealing conditions and the a-Si sublayer thickness. We build a theoretical model of constrained crystallization which can well interpret the phenomena of the growth halt of nc-Si and higher crystallization temperature for the thinner a-Si sublayer. The experimental results indicate that constrained crystallization method is promising to achieve uniform and high density nc-Si array either by thermal annealing or by laser annealing. Based on this investigation we employ the method of laser interference crystallization (LIC) to fabricate nanocrystal Si with the two-dimensional (2D) patterned distribution within 10 nm thick a-Si:H single layer. Si nano-crystallites are selectively located in the discal regions within the initial a-Si:H layer. The present method is promising to fabricate various patterned nc-Si arrays for device applications simply by changing the geometry of the mask.

Surface Modification and Preparation of High Purity Nanometer Magnesium Hydroxide Using Impinging Stream

2011 ◽  
Vol 675-677 ◽  
pp. 847-851
Author(s):  
Jian Hai Zhao ◽  
Yan Ping Lai
Keyword(s):  
Surface Modification ◽  
Magnesium Hydroxide ◽  
High Purity ◽  
X Ray Diffraction ◽  
Control Factors ◽  
Operation Conditions ◽  
Crystallization Method ◽  
Transmission Electron ◽  
Mean Size ◽  
The Mean

High purity nanometer magnesium hydroxide is produced by impinging stream reaction crystallization method using bischofite as feedstock. Effects of operation conditions on the impinging stream of Mg (OH)2 are reported and the control factors of purity are confirmed. The morphology of the powder was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Result shows that purity of Mg (OH)2 can reach 99% and the mean size of crystal is 13.5nm. Surface modification of nano-sized magnesium hydroxide using four surface modifiers such as sodium steatite, sodium laurylsulfonate, sodium oleate and sodium silicate were investigated in this paper. The modified magnesium hydroxide has smaller particle size, larger powder contact angle, slower sedimentation velocity, the less in-oil capacity than unmodified sample

scholarly journals Size-Controlled Synthesis of CoFe2O4Nanoparticles Potential Contrast Agent for MRI and Investigation on Their Size-Dependent Magnetic Properties

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Fujun Liu ◽  
Sophie Laurent ◽  
Alain Roch ◽  
Luce Vander Elst ◽  
Robert N. Muller
Keyword(s):  
Magnetic Layer ◽  
Size Control ◽  
Correlation Spectroscopy ◽  
Local Concentration ◽  
Long Term Stability ◽  
Size Dependent ◽  
Transmission Electron ◽  
Size Controlled ◽  
Size Of Nuclei

Cobalt ferrite nanoparticles (CoFe2O4NPs) were synthesized by coprecipitation followed by treatments with diluted nitric acid and sodium citrate. Transmission electron microscope (TEM) and photon correlation spectroscopy (PCS) characterization showed that the size distributions of these nanoparticles were monodisperse and that no aggregation occurred. This colloid showed a long-term stability. Through adjustment of the concentrations of reactants and reaction temperature, the size of the NPs can be tuned from 6 to 80 nm. The size-control mechanism is explained by a nucleation-growth model, where the local concentration of monomers is assumed to decide the size of nuclei, and reaction temperatures influence the growth of nuclei. Magnetization and relaxivityr1,2measurements showed that the NPs revealed size-dependent magnetization and relaxivity properties, which are explained via a “dead magnetic layer” theory where reductions of saturation magnetization (Ms) andr1,2are assumed to be caused by the demagnetization of surface spins.

scholarly journals MicroRNA Profiling of Exosomes Derived from Red Blood Cell Units: Implications in Transfusion-Related Immunomodulation

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Haobo Huang ◽  
Jinfeng Zhu ◽  
Liping Fan ◽  
Qiuyan Lin ◽  
Danhui Fu ◽  
...  
Keyword(s):  
Blood Cell ◽  
Red Blood Cell ◽  
Storage Time ◽  
Bioinformatic Analysis ◽  
Mirna Microarray ◽  
Qrt Pcr ◽  
Transmission Electron ◽  
Mean Size ◽  
The Mean ◽  
Polymerase Chain

Purpose. To elucidate the microRNAs existent in exosomes derived from stored red blood cell (RBC) unit and their potential function. Materials and Methods. Exosomes were isolated from the supernatant derived from stored RBC units by sequential centrifugation. Isolated exosomes were characterized by TEM (transmission electron microscopy), western blotting, and DLS (dynamic light scattering). MicroRNA (miRNA) microarray was performed to detect the expression of miRNAs in 3 exosome samples. Results revealed miRNAs that were simultaneously expressed in the 3 exosome samples and were previously reported to exist in mature RBCs. Functions and potential pathways of some detected miRNAs were illustrated by bioinformatic analysis. Validation of the top 3 abundant miRNAs was carried out by qRT-PCR (quantitative reverse transcription‐polymerase chain reaction). Results. TEM and DLS revealed the mean size of the exosomes (RBC-derived) as 64.08 nm. These exosomes exhibited higher abundance of short RNA than the long RNA. 78 miRNAs were simultaneously detected in 3 exosome samples and mature RBCs. Several biological processes might be impacted by these miRNAs, through their target gene(s) enriched in a particular signalling pathway. The top 3 (abundant) miRNAs detected were as follows: miR-125b-5p, miR-4454, and miR-451a. qRT-PCR revealed higher abundance of miR-451a than others. Only miR-4454 and miR-451a abundance tended to increase with increasing storage time. Conclusion. Exosomes derived from stored RBC units possessed multiple miRNAs and, hence, could serve various functions. The function of exosomes (RBC-derived) might be implemented partly by the predominantly enriched miR-451a.

Carrier Transport and Lateral Conductivity in Nanocrystalline Silicon Layers

2000 ◽  
Vol 638 ◽  
Author(s):  
H. B. Kim ◽  
L. Montes ◽  
R. Krishnan ◽  
P. M. Fauchet ◽  
L. Tsybeskov
Keyword(s):  
Electrical Properties ◽  
Direct Current ◽  
Coulomb Blockade ◽  
Carrier Transport ◽  
Nanocrystalline Silicon ◽  
Conductivity Measurements ◽  
Si Nanocrystals ◽  
Ac Conductivity Measurements ◽  
Size Controlled ◽  
Nanocrystalline Si

AbstractWe have studied carrier transport and lateral electrical properties of nanocrystalline Si layers containing size controlled Si nanocrystals. Using results from direct current (dc) and alternating current (ac) conductivity measurements, the charging of Si nanocrystals and Coulomb blockade effect are discussed.

Stress and Crystallization of Plasma Enhanced Chemical Vapour Deposition Nanocrystalline Silicon Films

2008 ◽  
Vol 8 (5) ◽  
pp. 2693-2698 ◽  
Author(s):  
S. B. Milne ◽  
Y. Q. Fu ◽  
J. K. Luo ◽  
A. J. Flewitt ◽  
S. Pisana ◽  
...  
Keyword(s):  
Film Growth ◽  
Chemical Vapour ◽  
Nanocrystalline Silicon ◽  
Film Structure ◽  
Intrinsic Stress ◽  
Plasma Power ◽  
Annealing Conditions ◽  
Si Films ◽  
Gas Ratio ◽  
Nanocrystalline Si

Nanocrystalline Si films were prepared with a RF-PECVD system using different SiH4/H2 ratios, plasma powers, substrate temperatures and annealing conditions. The film's intrinsic stress was characterized in relation to the crystallization fraction. Results show that an increasing H2 gas ratio, plasma power or substrate temperature can shift the growth mechanism across a transition point, past which nanocrystalline Si is dominant in the film structure. The film's intrinsic stress normally peaks during this transition region. Different mechanisms of stress formation and relaxation during film growth were discussed, including ion bombardment effects, hydrogen induced bond-reconstruction and nanocomposite effects (nanocrystals embedded in an amorphous Si matrix). A three-parameter schematic plot has been proposed which is based on the results obtained. The film structure and stress are presented in relation to SiH4 gas ratio, plasma power and temperature.

scholarly journals Bio-Based Nanoparticles as a Carrier of β-Carotene: Production, Characterisation and In Vitro Gastrointestinal Digestion

Molecules ◽  
2020 ◽  
Vol 25 (19) ◽  
pp. 4497
Author(s):  
Beatriz S. Afonso ◽  
Ana G. Azevedo ◽  
Catarina Gonçalves ◽  
Isabel R. Amado ◽  
Eugénio C. Ferreira ◽  
...  
Keyword(s):  
Encapsulation Efficiency ◽  
In Vitro Digestion ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Mean Size ◽  
Average Size ◽  
Size Controlled ◽  
Β Carotene

β-carotene loaded bio-based nanoparticles (NPs) were produced by the solvent-displacement method using two polymers: zein and ethylcellulose. The production of NPs was optimised through an experimental design and characterised in terms of average size and polydispersity index. The processing conditions that allowed to obtain NPs (<100 nm) were used for β-carotene encapsulation. Then β-carotene loaded NPs were characterised in terms of zeta potential and encapsulation efficiency. Transmission electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction analysis were performed for further morphological and chemical characterisation. In the end, a static in vitro digestion following the INFOGEST protocol was performed and the bioaccessibility of β-carotene encapsulated in both NPs was determined. Results show that the best conditions for a size-controlled production with a narrow size distribution are lower polymer concentrations and higher antisolvent concentrations. The encapsulation of β-carotene in ethylcellulose NPs resulted in nanoparticles with a mean average size of 60 ± 9 nm and encapsulation efficiency of 74 ± 2%. β-carotene loaded zein-based NPs resulted in a mean size of 83 ± 8 nm and encapsulation efficiency of 93 ± 4%. Results obtained from the in vitro digestion showed that β-carotene bioaccessibility when encapsulated in zein NPs is 37 ± 1%, which is higher than the value of 8.3 ± 0.1% obtained for the ethylcellulose NPs.

Optical Transitions in Light-Emitting Nanocrystalline Silicon Thin Films

1999 ◽  
Vol 557 ◽  
Author(s):  
T. Toyama ◽  
Y. Kotani ◽  
A. Shimode ◽  
S. Abo ◽  
H. Okamoto
Keyword(s):  
Thin Films ◽  
Crystal Size ◽  
Nanocrystalline Silicon ◽  
Optical Transitions ◽  
Direct Transition ◽  
Light Emitting ◽  
Silicon Thin Films ◽  
Peak Energy ◽  
The Mean ◽  
Nanocrystalline Si

AbstractOptical transitions in nanocrystalline Si (nc-Si) thin films with different mean crystal sizes ranging from < 2 nm to ~3 nm have been studied by electroreflectance (ER) spectroscopy. At 293 K, ER signals are observed at 1.20-1.37 eV to be corresponding to fundamental gap in bulk crystalline Si. With a decrease in the mean crystal sizes of nc-Si, the transition energy of the fundamental gap is increased and the ER signal is intensified. The bandgap widening would be due to quantum confinement (QC) in nc-Si, and the increased signal indicates appearance of direct transition nature. The ER signals are also observed at 2.2 eV and at E1 (E0’) direct gap of 3.1-3.4 eV, while photoluminescence (PL) peak energies are located at 1.65-1.75 eV and at 2.3 eV. With the reduced mean crystal size, the 1.7-eV PL peak energy is also increased, suggesting that QC is also responsible for the increased PL peak energy.

Preparation of Paclitaxel-Loaded Microspheres with Fe3O4 Nanoparticles and Study of their Target-Orientation and Sustained-Release Property

2012 ◽  
Vol 535-537 ◽  
pp. 521-524
Author(s):  
Sheng Cui ◽  
Ben Lan Lin ◽  
Xiao Dong Shen
Keyword(s):  
Sustained Release ◽  
Loading Rate ◽  
Drug Loading ◽  
Target Orientation ◽  
Mtt Method ◽  
Transmission Electron ◽  
Release Property ◽  
Mean Size ◽  
Magnetic Fe3o4 Nanoparticles ◽  
The Mean

Paclitaxel-loaded microspheres with magnetic Fe3O4 nanoparticles were synthesized with albumin as carrier. The morphology was characterized by high-resolution transmission electron microscopy (HRTEM). The drug-loading rate and entrapment rate of the microspheres were researched by ultraviolet and visible spectrophotometer. The inhibition action of taxol microspheres to growth of esophagus cancer Eca109 cell were examined by MTT method. The result shows that it is regular spherical. The mean size and size distribution of microspheres are 275.6nm and 144.3nm by Zetasizer3000. The drug-loading rate is 3.013% and the entrapment rate is 35.26%. It has excellent target-orientation and sustained-release property which can prevent the growth of Eca109 cell.

scholarly journals Fluctuation relations and fitness landscapes of growing cell populations

2020 ◽  
Author(s):  
Arthur Genthon ◽  
David Lacoste
Keyword(s):  
Fitness Landscape ◽  
Size Control ◽  
Phenotypic Trait ◽  
Symmetry Relation ◽  
General Symmetry ◽  
Fluctuation Relations ◽  
Growing Cell ◽  
Fluctuation Relation ◽  
The Mean ◽  
Size Controlled

AbstractWe construct a pathwise formulation of a growing population of cells, based on two different samplings of lineages within the population, namely the forward and backward samplings. We show that a general symmetry relation, called fluctuation relation relates these two samplings, independently of the model used to generate divisions and growth in the cell population. Known models of cell size control are studied with a formalism based on path integrals or on operators. We investigate some consequences of this fluctuation relation, which constrains the distributions of the number of cell divisions and leads to inequalities between the mean number of divisions and the doubling time of the population. We finally study the concept of fitness landscape, which quantifies the correlations between a phenotypic trait of interest and the number of divisions. We obtain explicit results when the trait is the age or the size, for age and size-controlled models.

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