bluuebunny/crossref_metadata_2025 huggingface dataset:
Fabrication and Up-Conversion Luminescence of Er3+:Y2O3 Nanoparticles
Authors: Jun-Ming Luo , Yong-Xiu Li , Li-Ping Deng , Yong-Rui Yuan , Wei-Fan Chen
Published: April 2020

Y2O3 nanoparticles doped with different concentrations of Er3+ were prepared by the co-precipitation method. X-ray diffraction and transmission electron microscopy results show that Er3+ dissolves completely in the Y2O3
cubic phase. The Er3+:Y2O3 nanoparticles are homogeneous in size and nearly spherical, and the average diameter of the particles after being calcined at 1,000 °C for 2 h is in the range of 40–60 nm. When Er3+:Y2O3
nanoparticles are excited under a 980 nm diode laser, there are two main emission bands: green emission centered at 562 nm corresponding to the 4S3/2/2H11/2 → 4I15/2 radiative transitions and red emission centered at 660
nm corresponding to the 4F9/2 ∼ 4I15/2 radiative transitions. By changing the doping concentration of Er3+ ions, the up-conversion luminescence can be gradually tuned from green to red.
White Luminescence by Up-Conversion from Thin Film Made with Ln3+-Doped NaYF4 Nanoparticles
Authors: Dong Biao , Song Hongwei , Qin Ruifei , Bai Xue , Wang Fang , Fan Libo , Pan Guohui , Lu Shaozhe , Ren Xinguang , Zhao Haifeng
Published: April 2020

White light-emitting thin films containing Ln3+-doped NaYF4 nanoparticles were prepared by a simple spin-coating method. White light was generated by two different lanthanide ions, Er3+ (red and green) and Tm3+ (blue), by upconversion process
under the excitation of a 980-nm laser diode. The ratio of the intensity of the three main emissions was tuned by controlling the concentration of the nanoparticles in the thin film and the concentration of the lanthanide ions in the nanoparticles. The color coordinates corresponding to emissions
of different nanoparticle concentrations and with the different pump powers were investigated. When the pump power was fixed at 900 mW, the thin film with a concentration ratio of 2.5:1 emitted pure white light with coordinates of (0.333, 0.339).
A Novel Approach from Infrared to Ultraviolet Emission Enhancement in Yb3+, Er3+:CaF2 Nanofilms
Authors: Zhang Jisen , Qin Weiping , Zhang Jishuang , Wang Yan , Cao Chunyan , Jin Ye , Wei Guodong , Wang Guofeng , Wang Lili
Published: April 2020

Under 978 nm excitation, we explored the infrared-to-ultraviolet upconversion properties in the nanofilms with the nanoparticles of Yb3+, Er3+ codoped calcium fluoride (CaF2:Yb3+, Er3+). The strong enhancement of ultraviolet emission
was observed. The result is attributed to the optical performance characteristics of the nanostructure materials. Furthermore, a novel upconversion approach explains well the UV-enhanced emission.
Photoluminescence of ZnO:Eu3+ Nanoflowers
Authors: Tanner Peter A. , Yu Lixin
Published: April 2020

The synthesis of ZnO:Eu3+ nanoflowers by a low-temperature hydrothermal route is described. Characterization of the materials was performed by ESEM, XRD and FTIR spectra. The 355 nm excited photoluminescence spectra at 10 K do not indicate the presence of Eu2+
or the ZnO defect states which give rise to green or red broadband emission. Excitation into the ZnO conduction band at low temperature does not give emission from Eu3+. Selective excitation of the Eu3+ emission shows that Eu3+ ions occupy a variety of different
sites, of which one of them is similar to Eu3+ in C-type Eu2O3.
Formation of Nanocrystalline Matrix of Sodium Rare Earth Fluoride Up-Conversion Phosphors
Authors: Zhou Xingping , Li Shanshan , Chen Xiaoli , Zhu Quan , Wang Zhiqiang , Zhang Jun
Published: April 2020

Until now, ytterbium and erbium co-doped sodium yttrium fluoride (NaYF4:Yb, Er) is among the most efficient up-conversion phosphors. Its potential for applications in biological and medical fields has interested many scientists. However, the formation mechanism of the co-doped
sodium yttrium fluoride nanoparticles is still unknown. Based on the similarity of rare earth elements, this work started with studying the formation mechanism of NaYF4 nanoparticles without doping in aqueous phase. Effects of reactant concentrations, pH, and reaction time on the
particle formation were investigated. As the reaction time increased, NaYF4 nanoparticles grew sporadically. Effect of seeding was also studied. The reaction was not accelerated and the particle size was not altered by seeding. The above investigations suggested that in aqueous
solution NaYF4 nanoparticles were formed by the aggregation model. The aggregation of the primary particles may play a key role for the formation and size control of the nanoparticles. Smaller particles were achieved by the presence of chelators of Na2-ethylenediaminetetraacetic
acid and sodium nitrilotriacetate. This probably resulted from the adsorption of chelators on the NaYF4 nanoparticles and increased the repulsive force between the primary particles, preventing primary particles to form large particles by aggregation.
Study on UV Excitation Properties of Y2O3:Ln3+ (Ln = Eu3+ or Tb3+) Luminescent Nanomaterials
Authors: Meng Qingyu , Chen Baojiu , Zhao Xiaoxia , Wang Xiaojun , Xu Wu
Published: April 2020

Y2O3:Ln3+ (Ln = Eu or Tb) nanocrystals with different Ln3+ doping concentrations and average sizes were prepared by chemical self-combustion. The corresponding bulk materials with various doping concentrations were obtained by annealing the
nanomaterials at high temperature. The emission spectra, excitation spectra, and X-ray diffraction spectra were used in this study. It was found that the charge transfer band of Y2O3:Eu3+ red-shifted as particle size decreased, and the charge transfer band
in the 5-nm particles obviously broadened toward the long wavelength. It was also found that the profile of excitation spectra corresponding to the 4f5d (4f8 → 4f75d1) transition changed a lot with the variation of the
particle size. The dependence of the excitation spectra of Y2O3:Ln3+ on particle size was investigated.
SWNT-DNA and SWNT-polyC Hybrids: AFM Study and Computer Modeling
Authors: Karachevtsev M. V. , Lytvyn O. S. , Stepanian S. G. , Leontiev V. S. , Adamowicz L. , Karachevtsev V. A.
Published: April 2020

Hybrids of carbon single-walled nanotubes (SWNT) with fragmented single or double-stranded DNA (fss- or fds-DNA) or polyC were studied by Atom Force Microscopy (AFM) and computer modeling. It was found that fragments of the polymer wrap in several layers around the nanotube, forming
a strand-like spindle. In contrast to the fss-DNA, the fds-DNA also forms compact structures near the tube surface due to the formation of self-assembly structures consisting of a few DNA fragments. The hybrids of SWNT with wrapped single-, double- or triple strands of the biopolymer were
simulated, and it was shown that such structures are stable. To explain the reason of multi-layer polymeric coating of the nanotube surface, the energy of the intermolecular interactions between different components of polyC was calculated at the MP2/6-31++G** level as well as the
interaction energy in the SWNT-cytosine complex.
Cross-Sectional STEM Observation of Nanoparticle-Attached Silicon Wafer: Specimen Prepared by Focused Ion-Beam
Authors: Yonezawa Tetsu , Yamanoi Yoshinori , Nishihara Hiroshi
Published: April 2020

A thermal hydrosilylation process could successfully immobilize 5-heptene-1-thiol-stabilized gold nanoparticles onto hydrogen-terminated silicon surfaces. In order to understand the immobilization structures, it is very important to observe the linkage between the nanoparticles and
the substrate surface. For this purpose, a cross-sectional observation of gold nanoparticle-attached silicon substrate was carried out by using a high resolution scanning transmission electron microscopy (HR-STEM). The specimens were prepared by using a focused ion-beam (FIB) machine. According
to the Ga ion-beam irradiation, many single-nano-sized nanoparticles were fused to grow up to larger particles and amorphous Si layers were generated.
Solvothermal Growth of Flower-Like Morphology from Nanorods of Copper Sulfides
Authors: Roy Poulomi , Srivastava Suneel Kumar
Published: April 2020

The present work reports the effect of reaction time on solvothermal synthesis of copper sulfides from CuCl2·2H2O and thiourea with various compositions and morphologies using ethylenediamine as solvent at 120 °C. X-ray diffraction patterns of the products
at different durations shows the development of different stoichiometric composition of copper sulfides in where Cu:S ratio increases from 1.39 to 1.79 indicating transformation of Cu39S28 to Cu7S4. As inferred by EDX and XPS studies of the final
products. SEM shows the growth of bundles of nanorods of length ≈1 μm and diameter in nanometer range are observed after 6 h. On increasing the reaction duration to 9 h, nanorods tends to combines with each other and growth occurs in six directions and after 12 h leads to the
formation of flower-like morphology of copper sulfide. The optical properties of these products also have been studied.
Polymeric Nanocomposites: Compounding and Performance
Authors: Utracki L. A.
Published: April 2020

Polymeric nanocomposites (PNC) are binary mixtures of strongly interacting, inorganic platelets dispersed in a polymeric matrix. For full exfoliation, the thermodynamic miscibility is required. There are three basic methods of organically-modified clay dispersion that might result in
PNC: (1) in polymer solution (followed by solvent removal), (2) in a monomer (followed by polymerization), and (3) in molten polymer (compounding). Most commercial PNC are produced by the second method, but it is the third one that has the greatest promise for the plastics industry. Similarly
as during the manufacture of polymer blends, the layered silicates must be compatibilized by intercalation with organic salts and/or addition of functionalized macromolecules. Compounding affects the kinetics of dispersion process, but rarely the miscibility. Melt compounding is carried out
either in a single-screw (SSE) or a twin-screw extruder (TSE). Furthermore, an extensional flow mixer (EFM) might be attached to an extruder. Two versions of EFM were evaluated: (1) designed for polymer homogenization and blending, and (2) designed for dispersing nano-particles. In this review,
the dispersion of organoclay in polystyrene (PS), polyamide-6 (PA-6) or in polypropylene (PP) is discussed. The PNC based on PS or PA-6 contained two components (polymer and organoclay), whereas those based on PP in addition had a compatibilizer mixture of two maleated polypropylenes. Better
dispersion was found compounding PNC's in a SSE + EFM than in TSE with or without EFM. The mechanical performance (tensile, flexural and impact) was examined.
Shape Memory Polymers and Their Nanocomposites: A Review of Science and Technology of New Multifunctional Materials
Authors: Gunes I. Sedat , Jana Sadhan C.
Published: April 2020

This paper aims to present a review of recent progress made on shape memory polymers (SMPs) and their nanocomposites. Developments in allied fields are also presented in an effort to identify the current and future trends in this area. A new classification of SMP—rubberlike
and mesomorphic systems—is suggested. The underlying physical mechanisms of shape memory actions, polymer-nanofiller interactions, and the resultant properties of SMP nanocomposites are discussed. Examples are presented to highlight the influence of processing conditions, filler
geometry and filler surface characteristics, and the nature of matrix polymers on shape memory properties. A short description of current and potential applications is also presented.
Thermal and Thermomechanical Properties of Poly(butylene succinate) Nanocomposites
Authors: Makhatha Mamookho E. , Sinha Ray Suprakas , Hato Joseph , Luyt Adriaan S.
Published: April 2020

This article describes the thermal and thermomechanical properties of poly(butylene succinate) (PBS) and its nanocomposites. PBS nanocomposites with three different weight ratios of organically modified synthetic fluorine mica (OMSFM) have been prepared by melt-mixing in a batch mixer
at 140 °C. The structure and morphology of the nanocomposites were characterized by X-ray diffraction (XRD) analyses and transmission electron microscopy (TEM) observations that reveal the homogeneous dispersion of the intercalated silicate layers into the PBS matrix. The thermal properties
of pure PBS and the nanocomposite samples were studied by both conventional and temperature modulated differential scanning calorimetry (DSC) analyses, which show multiple melting behavior of the PBS matrix. The investigation of the thermomechanical properties was performed by dynamic mechanical
analysis. Results reveal significant improvement in the storage modulus of neat PBS upon addition of OMSFM. The tensile modulus of neat PBS is also increased substantially with the addition of OMSFM, however, the strength at yield and elongation at break of neat PBS systematically decreases
with the loading of OMSFM. The thermal stability of the nanocomposites compared to that of the pure polymer sample was examined under both pyrolytic and thermooxidative environments. It is shown that the thermal stability of PBS is increased moderately in the presence of 3 wt% of OMSFM, but
there is no significant effect on further silicate loading in the oxidative environment. In the nitrogen environment, however, the thermal stability systematically decreases with increasing clay loading.
Preparation and Properties of Fluorine-Containing Colorless Polyimide Nanocomposite Films with Organo-Modified Montmorillonites for Potential Flexible Substrate
Authors: Park Jin-Ho , Kim Jin-Hoe , Park Jin-Woo , Chang Jin-Hae , Ha Chang-Sik
Published: April 2020

We prepared transparent polyimide (PI) and organo-modified montmorillonite (OMMT) nanocomposite films from the solution of poly(amic acid) and various amounts (0.5–2 wt%) of OMMT in N,N-dimethylacetamide (DMAc). The Poly(amic acid) was prepared from the reaction of 4,4′-(hexafluoroisopropylidene)diphthalic
anhydride (6FDA) and 2,2′-bis (trifluoromethyl)-4,4′-diamino phenyl (TFDB). Dodecylamine (C12-) and dodecyltriphenylphosphonium chloride (C12PPh-Cl–) were used as organic modifiers in OMMT. The PI/OMMT nanocomposite films were characterized
by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscope (TEM), UV-Vis transmission spectra, thermomechanical analysis (TMA), and rheometric dynamic analysis (RDA). As the OMMT contents is increased, PI/OMMT nanocomposites generally show
better properties compared to pristine PI films, although the transparency of the PI/OMMT nanocomposite films is sacrificed slightly. However, it is concluded that these nanocomposite films are good candidates for potential flexible substrates.
Morphological, Rheological and Mechanical Characterization of Polypropylene Nanocomposite Blends
Authors: Rosales C. , Contreras V. , Matos M. , Perera R. , Villarreal N. , García-López D. , Pastor J. M.
Published: April 2020

In the present work, the effectiveness of styrene/ethylene-butylene/styrene rubbers grafted with maleic anhydride (MA) and a metallocene polyethylene (mPE) as toughening materials in binary and ternary blends with polypropylene and its nanocomposite as continuous phases was evaluated
in terms of transmission electron microscopy (TEM), scanning electron microscopy (SEM), oscillatory shear flow and dynamic mechanical thermal analysis (DMA). The flexural modulus and heat distortion temperature values were determined as well. A metallocene polyethylene and a polyamide-6 were
used as dispersed phases in these binary and ternary blends produced via melt blending in a corotating twin-screw extruder. Results showed that the compatibilized blends prepared without clay are tougher than those prepared with the nanocomposite of PP as the matrix phase and no significant
changes in shear viscosity, melt elasticity, flexural or storage moduli and heat distortion temperature values were observed between them. However, the binary blend with a nanocomposite of PP as matrix and metallocene polyethylene phase exhibited better toughness, lower shear viscosity, flexural
modulus, and heat distortion temperature values than that prepared with polyamide-6 as dispersed phase. These results are related to the degree of clay dispersion in the PP and to the type of morphology developed in the different blends.
Organophilic Boehmite Nanoparticles by ATRP Methacrylates Polymerization: Synthesis, Characterization and Dispersion in Polypropylene
Authors: Coiai Serena , Passaglia Elisa , Augier Sylvain , Narducci Piero , Ciardelli Francesco
Published: April 2020

Boehmite nanoparticles covered with a polymer shell enhancing the organophilicity of the surface were prepared by physical adsorption of a polyelectrolyte atom transfer radical polymerization (ATRP) macroinitiator followed by graft-polymerization of methyl methacrylate or 2-hydroxyethyl
methacrylate. The presence of polymer chains adsorbed/grafted on the Boehmite was confirmed by attenuated total reflection infrared (ATR-IR) spectroscopy and by thermo-gravimetric analysis (TGA), which showed a significant amount of polymer covering the particles. The methodology of polymerization
and the kinetics suggested the possibility to modulate the amount, type and thickness of grafted polymer shell. These organic–inorganic hybrid materials were melt compounded in a Brabender mixer with isotactic polypropylene in the presence of functionalized polypropylene. The dispersion
degree of Boehmite nanoparticles in the polypropylene matrixas well as their reinforcing effect were studied by morphology characterization [scanning electron microscopy (SEM) and X-ray diffraction (XRD)], whereas thermal and thermo-mechanical properties were assessed by differential scanning
calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA).
Hybrid Carbon Nanotube/Nanodiamond Structures as Electron Emitters for Cold Cathodes
Authors: Fiori A. , Orlanducci S. , Sessa V. , Tamburri E. , Toschi F. , Terranova M. L. , Ciorba A. , Rossi M. , Lucci M. , Barnard A. S.
Published: April 2020

The field emission properties of hybrid carbon nanotubes/nanodiamond structures produced by one-step chemical vapor deposition (CVD) process have been investigated in order to assess their application as electron emitters for cold cathodes. The electron emission properties of a series
of samples have been investigated by current–pressure, current–voltage and current–time measurements with the aim of testing the emission stability under working conditions relevant to technological applications. Stable emission, high values of current density and lack of
arcing have been observed during prolonged working cycles, and without degradation of the material structure.
In Vitro Cellular Uptake and Cytotoxic Effect of Functionalized Nickel Nanoparticles on Leukemia Cancer Cells
Authors: Guo Dadong , Wu Chunhui , Li Xiaomao , Jiang Hui , Wang Xuemei , Chen Baoan
Published: April 2020

Nickel nanoparticles (Ni NPs) have been applied in a wide range of areas because of their unique structure and properties such as catalysts, high-density magnetic recording media and others. However, little effort has been paid to their biological application and the concrete effect
of Ni NPs on biological systems is still unknown. In this study, the possibility of the utilization of the magnetic Ni NPs in cancer cell studies was explored and the effects of the Ni NPs capped with positively charged tetraheptylammonium on leukemia K562 cells in vitro were investigated.
Our observations of optical microscopy, atomic force microscopy (AFM) and scanning electron microscopy (SEM) studies indicate that the morphological changes of cancer cells induced by Ni NPs could be apparently observed. The results of 3-(4,5-dimethylthiazol-2-yl)2,5-diphenyl-tetrazolium bromide
(MTT) assay, DNA fragmentation and flow cytometry studies demonstrate that the Ni NPs could exert cytotoxicity to leukemia K562 cells at high concentration, and subsequently induce both apoptosis and necrosis of target cancer cells, whilst it had little impact on target cells when at low concentration.
Meanwhile, functionalized Ni NPs with positively charged groups could enhance the permeability of cell membrane and facilitate the cellular uptake of outer target molecules into cancer cells. These findings reveal the potential mechanism of Ni NPs to target cancer cells which could induce
the cytotoxicity to leukemia cancer cells and suggest the possibility for applications of the Ni NPs in related clinical and biomedical areas.
Basic Fibroblast Growth Factor Loaded Biodegradable PCL-PEG-PCL Copolymeric Nanoparticles: Preparation, In Vitro Release and Immunogenicity Study
Authors: Gou Maling , Dai Mei , Gu Yinchun , Li Xingyi , Wen Yanjun , Yang Li , Wang Ke , Wei Yuquan , Qian Zhiyong
Published: April 2020

In this article, human basic fibroblast growth factor (bFGF) loaded PCL-PEG-PCL (PCEC) nanoparticles were prepared by modified W1/O/W2 double emulsion solvent evaporation method. The bFGF encapsulated in PCEC nanoparticles could be released in sustained release
behavior in vitro. After subcutaneous single-dose injection of bFGF loaded PCEC nanoparticles at 20 μg of bFGF per dose in mice, the anti-bFGF special autoantibodyIgG continued to grow until 8 weeks after the immunization and was still kept at high level at week 11. At the same time,
HK293 cell viability assay in vitro indicated that the cytotoxicity of blank PCEC nanoparticles was low but dose dependent. For some success in controlling tumor growth had been met by neutralizing bFGF reported previously, the bFGF loaded PCEC nanoparticles prepared in this paper might
have potential application as anti-tumor vaccine.
Imaging Breast Cancer Cells and Tissues Using Peptide-Labeled Fluorescent Silica Nanoparticles
Authors: Wu Ping , He Xiaoxiao , Wang Kemin , Tan Weihong , Ma Ding , Yang Wanhua , He Chunmei
Published: April 2020

The imaging of tumor cells and tumor tissue samples is very important for cancer detection and therapy. We have taken advantages of fluorescent silica nanoparticles (FSiNPs) coupled with a molecular recognition element that allows for effective in vitro and ex vivo imaging
of tumor cells and tissues. In this study, we report on the targeting and imaging of MDA-MB-231 human breast cancer cells using arginine-glycine-aspartic acid (RGD) peptide-labeled FSiNPs. When linked with RGD peptide using the cyanogen bromide (CNBr) method, the FSiNPs exhibited high target
binding to αvβ3 integrin receptor (ABIR)-positive MDA-MB-231 breast cancer cells in vitro. Further study regarding the ex vivo imaging of tumor tissue samples was also carried out by intravenously injecting RGD peptide-labeled FSiNPs into
athymic nude mice bearing the MDA-MB-231 tumors. Tissue images demonstrated that the high integrin αvβ3 expression level of the MDA-MB-231 tumors was clearly visible due to the special targeting effects of the RGD peptide-labeled FSiNPs, and the tumor
fluorescence reached maximum intensity at 1 h postinjection. Our results break new ground for using FSiNPs to optically image tumors, and may also broaden the applications of silica nanoparticles in biomedicine.
Red Shift for CdTe Nanoparticle Thin Films and Suspensions During Heating
Authors: Dunn S. , Gardner H. C. , Bertoni C. , Gallardo D. E. , Gaponik N. , Eychmüller A.
Published: April 2020

The work that we have conducted shows that temperature affects the wavelength of light emitted from CdTe nanoparticle clusters that are in a suspension or deposited into thin films via a layer-by-layer process. Compared with the stock suspension, the films show an initial photoluminescent
shift, of circa 6–8 nm to the red, when the particles are deposited. A shift of circa 6–8 nm is also seen when the suspensions are first heated to 85 °C from room temperature (20 °C) having been stored in a fridge at 5 °C. This shift is non-recoverable.
With continual cycling from room temperature to 85 °C the suspensions show a slight tendency for the emission to move increasingly to the red; whereas the films show no such tendency. In both cases, the range in emission is ca 10 nm from the room temperature state to 80 °C.
The intensity of the emission from the film drops abruptly (ca 50% reduction) after one cycle of heating; in the suspension there is an initial increase (ca 3–5% increase) in intensity before it decays. We see that the shift towards the red has been attributed to energy
transfer or a rearrangement of the packing of the particles in the thin films. After conducting analysis of the films using scanning probe microscopy we have determined that a change in the morphology is responsible for the permanent shift in emission wavelength associated with prolonged heating.
The influence of traps has not been ruled out, but the morphological change in the samples is very large and is likely to be the dominating mechanism affecting change for the red shift at room temperature.
TiO2 Array Films with Controllable Morphology
Authors: Pan Feng , Zhang Junying , Zhang Weiwei , Cai Chao , Wang Tianmin
Published: April 2020

Titanium dioxide films with large-area 2D ordered pore structure were prepared on glass substrate via a sol dip-coating latex template method. By simply controlling the concentration of the precursor sol, TiO2 array films with different morphologies, such as hollow sphere
shell, bowl, pot, and ring arrays were obtained. Such films have large-scale periodic feature and large specific areas, which is promising to be useful in the optical, gas-sensing, catalysis applications.
Transverse Susceptibility Method in Nanoparticulate Magnetic Media
Authors: Cimpoesu Dorin , Spinu Leonard , Stancu Alexandru
Published: April 2020

Transverse susceptibility (TS) method is a reliable method for the determination of anisotropy in nanoparticulate media. To correctly evaluate the value of anisotropy in various modern nanostructured materials, a number of theoretical problems related to the method have to be well understood
to avoid significant systematic errors. This paper presents the state of the art in the TS method which includes the expression for single domain particles with any type of anisotropy, the theoretical and micromagnetic, using Landau-Lifshitz-Gilbert (LLG) equation and stochastic LLG equation
studies of the effects of ac field amplitude, inter-particle interactions, and magnetic relaxation. The problem of both real and imaginary parts of the TS signal is also discussed.
Probing Arrays of Circular Magnetic Microdots by Ferromagnetic Resonance
Authors: Kakazei G. N. , Mewes T. , Wigen P. E. , Hammel P. C. , Slavin A. N. , Pogorelov Yu. G. , Costa M. D. , Golub V. O. , Guslienko K. Yu. , Novosad V.
Published: April 2020

X-band ferromagnetic resonance (FMR) was used to characterize in-plane magnetic anisotropies in rectangular and square arrays of circular nickel and Permalloy microdots. In the case of a rectangular lattice, as interdot distances in one direction decrease, the in-plane uniaxial anisotropy
field increases, in good agreement with a simple theory of magnetostatically interacting uniformly magnetized dots. In the case of a square lattice a four-fold anisotropy of the in-plane FMR field Hr was found when the interdot distance a gets comparable to the dot diameter
D. This anisotropy, not expected in the case of uniformly magnetized dots, was explained by a non-uniform magnetization m(r) in a dot in response to dipolar forces in the patternedmagnetic structure. It is well described by an iterative solution of a continuous variation
procedure. In the case of perpendicular magnetization multiple sharp resonance peaks were observed below the main FMR peak in all the samples, and the relative positions of these peaks were independent of the interdot separations. Quantitative description of the observed multiresonance FMR
spectra was given using the dipole-exchange spin wave dispersion equation for a perpendicularly magnetized film where in-plane wave vector is quantized due to the finite dot radius, and the inhomogenetiy of the intradot static demagnetization field in the nonellipsoidal dot is taken into account.
It was demonstrated that ferromagnetic resonance force microscopy (FMRFM) can be used to determine both local and global properties of patterned submicron ferromagnetic samples. Local spectroscopy together with the possibility to vary the tip-sample spacing enables the separation of those
two contributions to a FMRFM spectrum. The global FMR properties of circular submicron dots determined using magnetic resonance force microscopy are in a good agreement with results obtained using conventional FMR and with theoretical descriptions.
Microwave Properties of Ferromagnetic Nanostructures
Authors: Valenzuela R. , Alvarez G. , Mata-Zamora M. E.
Published: April 2020

A review of the dynamic properties of nanostructured ferromagnetic materials at microwave frequencies (1–40 GHz) is presented. Since some confusion has recently appeared between giant magnetoimpedance (GMI) and ferromagnetic resonance (FMR), a detailed analysis is made in order
to establish their differences. A brief review of a novel microwave absorption mode, the low-field microwave absorption (LFA) is then presented, together with a discussion about its similarities with GMI. Recent results on high-frequency measurements on nanogranular thin films and FMR in nanowire
arrays are finally addressed.
Design of Spintronic Materials with Simple Structures
Authors: Fong C. Y. , Qian M. C. , Liu Kai , Yang L. H. , Pask J. E.
Published: April 2020

A brief comparison of conventional electronics and spintronics is given. The key features of half metallic binary compounds with the zincblende structure are presented, using MnAs as an example. We discuss the interactions responsible for the half metallic properties. Special properties
of superlattices and a digital ferromagnetic heterostructure incorporating zincblende half metals are also discussed.
Non-Equilibrium Molecular Dynamics Simulation of Nanojet Injection with Adaptive-Spatial Decomposition Parallel Algorithm
Authors: Shin Hyun-Ho , Yoon Woong-Sup
Published: April 2020

An Adaptive-Spatial Decomposition parallel algorithm was developed to increase computation efficiency for molecular dynamics simulations of nano-fluids. Injection of a liquid argon jet with a scale of 17.6 molecular diameters was investigated. A solid annular platinum injector was also
solved simultaneously with the liquid injectant by adopting a solid modeling technique which incorporates phantom atoms. The viscous heat was naturally discharged through the solids so the liquid boiling problem was avoided with no separate use of temperature controlling methods. Parametric
investigations of injection speed, wall temperature, and injector length were made. A sudden pressure drop at the orifice exit causes flash boiling of the liquid departing the nozzle exit with strong evaporation on the surface of the liquids, while rendering a slender jet. The elevation of
the injection speed and the wall temperature causes an activation of the surface evaporation concurrent with reduction in the jet breakup length and the drop size.
An Atomistically Enriched Continuum Model for Nanoscale Contact Mechanics and Its Application to Contact Scaling
Authors: Sauer Roger A. , Li Shaofan
Published: April 2020

This work provides a comprehensive exposition and extension of an atomistically enriched contact mechanics model initially proposed by the present authors. The contact model is based on the coarse-graining of the interaction occurring between the molecules of the contacting bodies.
As these bodies may be highly compliant, a geometrically nonlinear kinematical description is chosen. Thus a large deformation continuum contact formulation is obtained which reflects the attractive and repulsive character of intermolecular interactions. Further emphasis is placed on the efficiency
of the proposed atomistic-continuum contact model in numerical simulations. Therefore three contact formulations are discussed and validated by lattice statics computations. Demonstrated by a simple benchmark problem the scaling of the proposed contact model is investigated and some of the
important scaling laws are obtained. In particular, the length scaling, or size effect, of the contact model is studied. Due to its formal generality and its numerical efficiency over a wide range of length scales, the proposed contact formulation can be applied to a variety of multiscale
contact phenomena. This is illustrated by several numerical examples.
Preparation of Platinum Nanoparticles in Heterogeneous Solid-Liquid System by Ultrasound and Microwave Irradiation
Authors: Ishikawa Dai , Hayashi Yamato , Takizawa Hirotsugu
Published: April 2020

Pt nanoparticles and Pt/spherical carbon (SC) were prepared in a heterogeneous (PtO2/SC, water/ethanol) solid-liquid system without dispersant using ultrasound and microwave irradiation. The Pt nanoparticles and Pt/SC were characterized using X-ray diffraction (XRD), transmission
electron microscopy-energy-dispersive X-ray spectroscopy (TEM-EDX), and dynamic light scattering method for particle size determination. The average size of the Pt nanoparticles prepared by only ultrasound irradiation was smaller than that prepared by microwave irradiation. Pt nanoparticles
were successfully prepared by microwave irradiation with a reaction time of several minutes at a specific concentration of diluted ethanol. Pt/SC prepared by combined ultrasound and microwave irradiation resulted in fine particles with good homogeneous distribution.
Removal of Metal Catalyst in Multi-Walled Carbon Nanotubes with Combination of Air and Hydrogen Annealing Followed by Acid Treatment
Authors: Li Quanlong , Yuan Dongxing , Guan Bin , Lin Qingmei , Wang Xuefeng
Published: April 2020

Multi-walled carbon nanotubes (MWCNTs) prepared by the decomposition of CH4 on a Ni-MgO catalyst were treated with air and hydrogen annealing, and the combination of air and hydrogen annealing, respectively, followed by acid reflux. The treated MWCNTs were characterized by
the techniques of transmission electron microscopy, thermogravimetric analysis and flame atomic absorption spectrometry. The results showed that hydrogen annealed MWCNTs were more air stable than air annealed ones. Followed by acid treatment, the combination of air and hydrogen annealing was
more efficient than either air annealing or hydrogen annealing for the removal of catalyst in MWCNTs. For the treatment with 2 h of hydrogen annealing followed by 2 h of air annealing, the catalyst Ni remained in the purified sample was 10.8 μg/g, and the yield rate was 82.3%. With
2 h of air annealing followed by 2 h of hydrogen annealing, the data were 5.8 μg/g and 61.9%, respectively. The different functions of air and hydrogen during annealing were discussed.
High-Aspect Ratio Nano-Noodles of Alumina and Titania
Authors: Friedman Adam L. , Panaitescu Eugen , Richter Christiaan , Menon Latika
Published: April 2020

We report the formation of high-aspect ratio rod-like structures or 'nano-noodles' of alumina or titania. Such structures are formed either by rapid anodization of aluminum/titanium foil or by long-term post-anodization treatment of porous templates. Specifically, the nano-noodle structures
form during anodization in highly acidic electrolytes and/or at high anodization voltages, or when porous templates are etched for long periods of time in an acid. Growth mechanism for such structures is also proposed.
Micro-Brillouin Study of the Eigenvibrations of Single Isolated Polymer Nanospheres
Authors: Li Yi , Lim Hock Siah , Wang Zhi Kui , Ng Ser Choon , Kuok Meng Hau
Published: April 2020

The localized acoustic modes of single isolated polymethyl methacrylate (PMMA) and polystyrene nanospheres have been studied by micro-Brillouin light scattering. The measured mode frequencies are analyzed on the basis of the Lamb theory formulated for a sphere under free boundary conditions.
By measuring light scattering from single isolated particles, placed atop a piece of polished silicon wafer, the free-surface conditions are almost experimentally realized. The observed spectral peaks are attributed to localized eigenvibrations whose frequencies scale as inverse sphere diameter,
in accordance with Lamb's theory. The Young's moduli and Poisson ratios of the polymer spheres studied have been evaluated from fits to the experimental data. We have demonstrated that micro-Brillouin spectroscopy is a powerful technique for probing the acoustic dynamics and mechanical properties
of nanostructures.
Nanomachining with a Mechanical Manipulation System
Authors: Chang M. , Deka J. R. , Lin C. H.
Published: April 2020

This study describes about the development of a mechanical manipulation system that can perform three-dimensional nano-machining inside a scanning electron microscope (SEM). Experiments are carried out by constructing a precise machining platform integrated with pico-motors, linear
stages and monolithic-silicon-based tips which is generally used in atomic-force microscope (AFM). This integrated system can easily manipulate the atoms in a workpiece inside an SEM. The platform consists of three translational stages along XYZ axis direction and one rotational stage, with
a resolution of 30 nm. The system can be utilized to produce nanopattern such as nanolines, nanoscale characters on silicon substrate coated with gold (Au) and aluminum (Al). Molecular dynamics simulation model is used to analyze the machining mechanism from various machining parameters. The
same AFM tip can be utilized to scratch away the unwanted material from the workpiece surface.
Stability of Zinc Oxide Nanofluids Prepared with Aggregated Nanocrystalline Powders
Authors: Leonard J. P. , Chung S. J. , Nettleship I. , Soong Y. , Martello D. V. , Chyu M. K.
Published: April 2020

Aqueous zinc oxide (ZnO) suspensions were prepared using a two-step preparation method in which an aggregated nanocrystalline ZnO powder was dispersed in water using a polyelectrolyte. The fluid showed anomalously high thermal conductivity when compared with the Maxwell and Hamilton-Crosser
predictions. However, analysis of the particle size distribution showed that the fluid contained aggregated 20 nm crystallites of ZnO with a high volume fraction of particles larger than 100 nm. Sedimentation experiments revealed that particles settled out of the stationary fluid over times
ranging from 0.1 hours to well over 10,000 hours. The size of the particles remaining in suspension agreed well with predictions made using Stoke's law, suggesting flocculation was not occurring in the fluids. Finally, a new concept of nanofluid stability is introduced based on the height
of the fluid, sedimentation, Brownian motion and the kinetic energy of the particles.
Direct Interaction of Colloidal Nanostructured ZnO and SnO2 with NO and SO2
Authors: Velasco-Arias D. , Díaz D. , Santiago-Jacinto P. , Rodríguez-Gattorno G. , Vázquez-Olmos A. , Castillo-Blum S. E.
Published: April 2020

A novel and easy synthesis pathway of small SnO2 nanoparticles is reported. The method consists of the spontaneous hydrolysis of SnCl4·5H2O in dimethyl sulfoxide (DMSO), containing 3% water, at room temperature. The structure of the SnO2
nanocrystals corresponds to that of the cassiterite phase, as shown by powder X-ray diffraction and HR-TEM. The UV-visible electronic absorption and emission spectra of the SnO2 colloids are discussed. The reactions of NO(g) and SO2(g) with ZnO (wurtzite phase)
and SnO2 nanocolloids are studied. The interaction of NO with ZnO nanoparticles generates the dissolution of the particles and it is quite probable that NO−13, NO−12, N2O and N2 are formed; while its contact
with SO2 probably yields SO−24, SO−23 and also the dissolution of the particles is observed. When these gases are reacted with SnO2, then NO−13, NO−12, SO−23
and SO−24, were respectively obtained.
Simplified Route to Multi-Walled Carbon Nanotube Synthesis by Aerosol Assisted Chemical Vapor Deposition
Authors: Antúnez-Flores W. , Valenzuela-Muñiz A. M. , Amézaga-Madrid P. , Alonso-Nuñez G. , Verde Y. , Martínez-Sánchez R. , Miki-Yoshida M.
Published: April 2020

Uniform multi-walled carbon nanotubes (MWCNTs) were obtained decomposing toluene inside of fused silica tubing previously covered with Co oxide thin film. The two-step process, ruled successively in the same aerosol assisted chemical vapor deposition (AACVD) set up, constitutes a simplified
route to the synthesis of MWCNTs. First, Co oxide thin film was deposited inside of fused silica tubing at 723 K, using a precursor solution of Co acetate in absolute methanol. After Co oxide deposition, the covered tubing was heated up to 1173 K under Ar flow, then a mist of toluene was injected
inside the tubing, using also Ar as carrier gas, consequently MWCNTs were obtained in the internal wall of the tubing. The Co oxide film and the MWCNTs were analyzed by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and atomic force microscopy
(AFM). Uniform and very long MWCNTs (several tens of μm) with diameters around 20 to 100 nm were observed, with the advantage that the content of Co particles inside the nanotube was very low.
Optical Properties of Nanostructured Sol–Gel Thin Films Doped with Fe2O3 and Their Ferromagnetic Characterization by Mössbauer Spectroscopy
Authors: Garcia-Macedo Jorge , Valverde-Aguilar Guadalupe , Gómez Raúl W. , Pérez-Mazariego José L. , Marquina Vivianne
Published: April 2020

Sol–gel thin films containing Fe2O3 were deposited onto glass substrates by the dip-coating method at room temperature. Fe2O3 enriched with the isotope 57Fe was embedded in two kinds of matrices: zinc oxide (ZnO) and silica
(SiO2). X-ray diffraction (XRD) was used for morphology and structure determination of the nanostructures and showed that the ZnO exhibit a wurtzite form when the film is annealed at 450 °C for 20 min. SiO2 thin films at C16H33PEO20:Fe2O3
= 1:2.7 × 10−1 molar concentration exhibit a hexagonal nanophase produced by the diblock copolymer Brij58 (C16H33PEO20). Optical absorption and infrared spectroscopy techniques were used to evaluate the optical quality of the films. In
order to determine if the Fe2O3 was incorporated into the matrices, room temperature Mössbauer spectra of both samples were obtained. In both cases the hematite spectrum was obtained, corroborating that the incorporation of the Fe2O3 to the
matrices was done without chemical reaction whatsoever.
Effect of Water on the Electrical Properties of Carbon Nanotubes
Authors: Mendoza D. , Santiago P.
Published: April 2020

In this work we present the electrical characterization of carbon nanotubes synthesized by a thermal chemical deposition method, using carbon disulfide as the precursor of carbon and iron as the catalyst. We found a broad maximum in the electrical resistance as a function of temperature
between 275–300 K and a hysteretic behavior when the measurements were made in a humid environment. We propose that the water molecules act as traps for charge carriers, and the overall behavior of the observed phenomenon is discussed in terms of the confinement of water inside the carbon
nanotubes.
Pressure-Induced Phase Transition in Thiol-Capped CdTe Nanoparticles
Authors: Wu Fanxin , Zaug Joseph M. , Young Christopher E. , Zhang Jin Z.
Published: April 2020

Phase transitions for CdTe nanoparticles (NPs) under high pressure up to 37.0 GPa have been studied using fluorescence measurements. The phase transition from cinnarbar to rocksalt phase has been observed in CdTe NPs solution at 5.8 GPa, which is much higher than the phase transition
pressure of bulk CdTe (3.8 GPa) and that of CdTe NPs in solid form (0.8 GPa). CdTe NPs solution therefore shows elevated phase transition pressure and enhanced stability against pressure compared with bulk CdTe and CdTe NPs in solid forms. The enhanced stability of CdTe NPs solution has been
attributed to possible shape change in the phase transition and/or inhomogeneous strains in nanoparticle solutions.
Photoconductivity for Silver Nitrate in Nanostructured Sol–Gel Materials
Authors: Franco Alfredo , Rentería Víctor , Valverde-Aguilar Guadalupe , García-Macedo Jorge A.
Published: April 2020

We report on the photoconductive response of nanostructured sol–gel films in function of the silver nitrate concentration (ions and colloids). Silver colloids were obtained by spontaneous reduction process of Ag+ ions to Ag0. 2-d hexagonal nanosructured sol–gel
thin films were prepared by dipcoating method using the non-ionic diblock copolymer Brij58 to produce channels into the film, which house the silver nanoparticles. An optical absorption band located at 430 nm was detected by optical absorption; it corresponds to the surface plasmon. A fit
to this band with modified Gans theory is presented. Photoconductivity studies were performed on films with silver ions and films with silver colloids to characterize their mechanisms of charge transport in the darkness and under illumination at 420 and 633 nm wavelengths. The films with silver
colloids exhibit a photovoltaic effect stronger than the films with silver ions. While a photoconductive behaviour is observed in the films with silver ions.
Convictions et croyances : que protège la liberté de conscience ?
Authors: Guichard Sylvie
Published: April 2020

La liberté de conscience est généralement présentée comme un principe fondamental des sociétés démocratiques. Pourtant, sa définition concrète et ses modalités d’exercice demeurent imprécises et incertaines. Par ailleurs, la protection qu’elle offre aux convictions non-religieuses est bien plus restreinte que celle qu’elle garantit aux croyances religieuses. Ce rapide constat induit plusieurs questions : pourquoi de nombreuses constitutions mentionnent-elles conjointement la liberté de conscience et la liberté de religion ? D’où vient ce couple formé par ces deux libertés ? Que signifie-t-il pour chaque liberté prise séparément ? Que protège spécifiquement la liberté de conscience et quel est son champ d’application ? Afin d’apporter un éclairage à ces questions, cet article propose un argument en trois parties. La première partie observe que la liberté de conscience est entrée dans les textes constitutionnels étroitement liée avec la liberté de religion. Dans de nombreux pays, les constituants ont ainsi introduit la liberté de conscience sans en clarifier le contenu. La deuxième partie met en évidence qu’en se laïcisant, l’idée de conscience a ouvert un champ d’application potentiellement très large avec des limites difficiles à définir. La troisième partie s’intéresse aux conséquences contemporaines de cette évolution : la différence avec laquelle les croyances religieuses et les convictions non-religieuses sont protégées. Cette différence est en effet injustifiable dans les États libéraux contemporains, mais nous n’arrivons pas à nous défaire de cet implicite chrétien selon lequel les croyances religieuses sont « spéciales » et ont droit à une protection particulière par rapport aux convictions non-religieuses.
Organisations laïques et résurgence du religieux dans l’espace public, entre concurrence et continuité axiologiques : le cas de la Ligue de l’enseignement
Authors: Lancien Anne
Published: April 2020

Cet article s’intéresse aux modalités et conséquences de la résurgence du religieux sur un acteur associatif laïque, la Ligue de l’enseignement. Deux temps articulent notre réflexion : d’une part, l’organisation met en avant la nécessité d’une morale laïque, afin de proposer une alternative au référentiel axiologique dont sont porteuses les institutions religieuses, de même qu’une charte de la laïcité, dont les principes se veulent suffisamment englobants pour pouvoir réunir l’ensemble des familles spirituelles qui compose la société française. D’autre part, la Ligue accepte de reconnaître l’acteur religieux et sa légitimité à intervenir au sein du débat public, en tant que composante, parmi d’autres, de la société civile et participant à ce titre à l’élaboration du socle commun constitutif de la Cité. Notons cependant que cette reconnaissance ne se veut pas institutionnelle, la Ligue acceptant l’expression des droits collectifs mais non une traduction institutionnelle du pluralisme. L’organisation souhaite la mise en place d’une charte de la laïcité, qui définirait, à partir du dialogue entre l’ensemble des acteurs du débat public, les valeurs constitutives de la société.