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1.
Jingjing Gao Rongjun Qu Bo Tang Chunhua Wang Qianli Ma Changmei Sun 《Journal of nanoparticle research》2011,13(10):5289-5299
By using N,N-dimethylformamide (DMF) as a solvent and reducing agent, and polyurethane (PU) as a structure-directing agent, flexible silver
nanochains are formed under mild conditions with mean diameter of 15.97 and 35.6 nm, respectively. Some linear chain-like
aggregates of silver nanoparticles with mean diameter of 6.69 nm are also formed by controlling the experimental condition.
In parallel experiment, silver nanospheres with mean diameters of 5.76 nm, instead of nanochains are generated when antioxidants
are added. After 3 days of aging, some nano clusters are transformed into triangular or hexagonal nanoplates. This aggregation
behavior was characterized by UV–Vis spectroscopy, TEM, and powder X-ray diffraction. The aggregation mechanism of silver
nanoparticles in the PU and ATPU was discussed. Our results provide potential application for new generation of nanodevice. 相似文献
2.
Xin Chen Jun Tao Gang Zou Qijin Zhang Pei Wang 《Applied Physics A: Materials Science & Processing》2010,100(1):223-230
Diacetylene monomer containing p-nitrophenyl azobenzene moiety (NADA) was synthesized. Silver nanoparticles with different
concentrations were adulterated in the above polymerized NADA (PNADA) films and the third-order nonlinear optical properties
were investigated in detail. UV–vis spectra and transmission electron microscopy were used to confirm the formation of PNADA/Ag
nanocomposite films. The silver nanoparticles (average size of 10 nm) were well dispersed in the polymer films. The value
of the nonlinear refractive index n
2 for PNADA films (8.48×10−15 cm2/W) was much higher than that of pure polydiacetylene films. Further, the introduction of silver nanoparticles into the PNADA
polymer films led to the further enhancement of nonlinear optical properties. The maximum value of n
2 for PNADA/Ag nanocomposite films could be 11.6×10−15 cm2/W. This enhancement should be ascribed to the surface plasmon resonance of silver nanoparticles. 相似文献
3.
I. V. Zolotukhin S. V. Spitsina L. I. Yanchenko L. N. Korotkov 《Physics of the Solid State》1999,41(11):1891-1893
Macroscopic fractal aggregates of KH2PH4 (KDP) measuring up to 500 μm have been obtained. The fractal structure forms as a result of the precipitation of KDP particles
from a supersaturated aqueous solution in the presence of a temperature gradient followed by a diffusioncontrolled mechanism
of aggregation. The electron-microscopic analysis performed has shown that the fractals are formed predominantly from crystallites
of the tetragonal modification measuring ∼1 μm. The dielectric constant (ɛ) of fractal KH2PO4 has been measured in the temperature range 80–300 K. A characteristic anomaly has been discovered on the ɛ(T) curve in the vicinity of 122 K, which attests to a ferroelectric phase transition. The absolute value of ɛ is significantly smaller than the components ɛ
11 and ɛ
33 for KH2PO4.
Fiz. Tverd. Tela (St. Petersburg) 41, 2059–2061 (November 1999) 相似文献
4.
Marcus Koch Silke Kiefer Christian Cavelius Annette Kraegeloh 《Journal of nanoparticle research》2012,14(2):646-11
For a detailed analysis of the biological effects of silver nanoparticles, discrimination between effects related to the nano-scale
size of the particles and effects of released silver ions is required. Silver ions are either present in the initial particle
dispersion or released by the nanoparticles over time. The aim of this study is to monitor the free silver ion activity {Ag+} in the presence of silver nanoparticles using a silver ion selective electrode. Therefore, silver in the form of silver
nanoparticles, 4.2 ± 1.4 nm and 2–30 nm in size, or silver nitrate was added to cell culture media in the absence or presence
of A549 cells as a model for human type II alveolar epithelial cells. The free silver ion activity measured after the addition
of silver nanoparticles was determined by the initial ionic silver content. The p {Ag+} values indicated that the cell culture media decrease the free silver ion activity due to binding of silver ions by constituents
of the media. In the presence of A549 cells, the free silver ion activity was further reduced. The morphology of A549 cells,
cultivated in DME medium containing 9.1% (v/v) FBS, was affected by adding AgNO3 at concentrations of ≥30 μM after 24 h. In comparison, silver nanoparticles up to a concentration of 200 μM Ag did not affect
cellular morphology. Our experiments indicate that the effect of silver nanoparticles is mainly mediated by silver ions. An
effect of silver on cellular morphology was observed at p {Ag+} ≤ 9.2. 相似文献
5.
Monodispersed platinum (Pt) nanoparticles were synthesized from reducing hydrated hydrogen hexachloroplatinic acid (H2PtCl6·nH2O) with ethanol in the presence of polyvinylpyrrolidone (PVP) as a steric stabilizer. Concentration of both PVP and ethanol
influenced the aggregate structure and crystallite size of the nanoparticles. When the molar ratio of monomeric unit of PVP
to Pt, i.e., [PVP]/[Pt], was one, the synthesized Pt particles coagulated pronouncedly into an inter-connected particulate
network or self-organized into spherical superstructures with an apparent diameter ranging from 60 to 80 nm, depending on
the ethanol concentration. The geometry and structure of these complex aggregates were characterized by fractal analysis.
Fractal dimensions of 2.13–2.23 in three dimensions were determined from the Richardson’s plot, which suggests that a reaction-limited
cluster–cluster aggregation model (RCLA) was operative. The Pt colloids became apparently more stable when the [PVP]/[Pt]
ratio was increased greater than 20. Crystallite size of the Pt nanoparticles was found to increase linearly with the ethanol concentration as the [PVP]/[Pt] was held at one. This suggests that the reduction rate of PtCl6
2− ions in solution is critically important to the synthesized crystallite size. 相似文献
6.
The aggregation behaviour of a hydrotrope, sodiumn-butyl benzene sulfonate (Na-NBBS), in aqueous solutions is investigated by small-angle neutron scattering (SANS). Nearly
ellipsoidal aggregates of Na-NBBS at concentrations well above its minimum hydrotrope concentration were detected by SANS.
The hydrotrope seems to form self-assemblies with aggregation number of 36–40 with a substantial charge on the aggregate.
This aggregation number is weakly affected by the hydrotrope concentration. 相似文献
7.
U. Busolt E. Cottancin L. Socaciu H. Röhr T. Leisner L. Wöste 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):297-300
The diffusion and aggregation of preformed Agn-clusters (
n
= 2-9) deposited onto a highly oriented pyrolytic graphite (HOPG) substrate is studied by two-photon-photoemission (2PPE). The sample
is irradiated with ultrashort laser pulse pairs and the kinetic energy of the emitted photoelectrons is analyzed in a magnetic
bottle type time-of-flight spectrometer. During annealing of the sample from 100 K up to room temperature, nanoparticles are
formed on the surface by diffusion and aggregation of the silver clusters. A steep increase of the total photoelectron yield
at a sample temperature of about 150 K is explained by the excitation of plasmons in the silver nanoparticles. From the kinetic
energy distribution of the photoelectrons we deduce a strong variation of the work function of the sample during the formation
of the nanoparticles, which is attributed to a quantum size effect. 相似文献
8.
Xiang Lin Wu‐Li‐Ji Hasi Xiu‐Tao Lou Shuang Lin Fang Yang Bao‐Shen Jia Yu Cui De‐Xin Ba Dian‐Yang Lin Zhi‐Wei Lu 《Journal of Raman spectroscopy : JRS》2014,45(2):162-167
Surface‐enhanced Raman spectroscopy (SERS) was used for rapid detection of sodium thiocyanate in milk employing silver aggregates as active substrate. Silver nanoparticles were induced to silver aggregates by trichloroacetic acid (TCA). The limit of detection (LOD) for sodium thiocyanate was 10−2 µg ml−1 in water with an analytical enhancement factor of 5.4 × 106. The silver aggregates represent good reproducibility and stability. Good linear relationship was obtained for sodium thiocyanate in milk at concentration ranges from 0.1 to 10 µg ml−1 (R2 = 0.995). Using TCA as protein precipitator, silver colloid would aggregate spontaneously when mixing with samples during SERS measurement without the need of additional aggregating agent. The simple pretreatment procedures and analytical methods are less time consuming (<10 min) and environmentally friendly, making the proposed method much practical for in situ detection of sodium thiocyanate in market milk. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
9.
Mehmet Kozan 《Journal of Quantitative Spectroscopy & Radiative Transfer》2008,109(2):327-336
The morphology of WO3 aggregates formed by irregular nanoparticles (D∼40 nm) and nanowires of different aspect ratios (2, 4, 6, and 10 μm nominal lengths) dispersed in commonly used polar solvents without dispersant agents is investigated using a small-angle light scattering technique and by means of fractal theory. Nanoparticles form compact spherical aggregates (Df∼2.6), whereas 2 μm nanowires with low aspect ratio (L/D∼10) follow a slow cluster-cluster aggregation mechanism with no discernable change in fractal dimension (Df=2.1) monitored in an extended period of 6 months, despite a notable growth in size (Rg=2.3-3.1 μm). For higher aspect ratio nanowires, scattered intensity profiles, which migrate towards the Porod regime, qualitatively obey the Lorenz-Mie theory predictions. The 10 μm nanowires with very high aspect ratio (L/D∼250) are observed to form stable dispersions in a time span of 6 days. Analytical methods based on spherical primary particle formulations predict Df=1.9, 1.7, and 1.4 for 4, 6, and 10 μm nanowires, respectively. 相似文献
10.
The aggregation behavior of silver nanoparticles (AgNPs) prepared by a green synthesis procedure using starch as the stabilizer
was studied by the small angle X-ray scattering (SAXS) technique. The protecting ability of starch was affected by the presence
of NaOH leading to different aggregation behaviors. In all the samples, mass as well as surface fractal regimes were observed.
Assuming spherical form, the radii of nanoparticles were in the range of 11–17 nm. 相似文献
11.
S. Padovani F. D'Acapito E. Cattaruzza A. De Lorenzi F. Gonella G. Mattei C. Maurizio P. Mazzoldi M. Montagna S. Ronchin C. Tosello M. Ferrari 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,25(1):11-17
Composite silica films containing metal nanoclusters were prepared by the rf- sputtering technique, in which SiO2 was co-deposited with gold+copper, gold+silver, or copper+silver. The formation of either pure or alloy clusters was studied
by extended X-ray absorption fine structure spectroscopy and transmission electron microscopy. For all systems, the presence
of alloy aggregates was evidenced. Moreover, small amounts of pure metal aggregates as well as dispersed or oxidized dopants
were observed.
61.46.+w Nanoscale materials: clusters, nanoparticles, nanotubes, and nanocrystals – 61.10.Ht X-ray absorption spectroscopy:
EXAFS, NEXAFS, XANES, etc. – 81.05.Pj Glass-based composites, vitroceramics
Received 29 June 2001 相似文献
12.
R. Brazis L. Safonova R. Narkowicz 《International Journal of Infrared and Millimeter Waves》1997,18(8):1575-1584
Non-transmission bands of electromagnetic waves propagating along the layers in periodic structures are studied in the steady
magnetic field perpendicular both to the uniaxis and the direction of propagation. The band control range (36÷75 GHz) inn-InSb/Al2O3 structures with the carrier densities 4 1013 ≤n ≤ 8 1014 cm−3 in magnetic fieldsB
o ≤ 2 T at temperatures 77 ≤T ≤ 200 K is found to agree with the calculated in the effective medium approximation. Attenuation down to −50 dB within the
band is observed. The band lineshape is found to indicate additional effects related to the finite layer thickness and periodicity
termination predicted by a more rigorous theory of dispersion. 相似文献
13.
Teresa L. Barone Anshuman Amit Lall Yifang Zhu Rong-Chung Yu Sheldon K. Friedlander 《Journal of nanoparticle research》2006,8(5):669-680
Nanoparticle chain aggregates (NCAs) are often sized and collected using instruments that rely on inertial transport mechanisms. The instruments size segregate aggregates according to the diameter of a sphere with the same aerodynamic behavior in a mechanical force field. A new method of interpreting the aerodynamic diameter of NCAs is described. The method can be used to calculate aggregate surface area or volume. This is useful since inertial instruments are normally calibrated for spheres, and the calibrations cannot be directly used to calculate aggregate properties. A linear relationship between aggregate aerodynamic diameter and primary particle diameter based on published Monte-Carlo drag calculations is derived. The relationship shows that the aggregate aerodynamic diameter is independent of the number of primary particles that compose an aggregate, hence the aggregate mass. The analysis applies to aggregates with low fractal dimension and uniform primary particle diameter. This is often a reasonable approximation for the morphology of nanoparticles generated in high temperature gases. An analogy is the use of the sphere as an approximation for compact particles. The analysis is applied to the collection of NCAs by a low-pressure impactor. Our results indicate the low-pressure impactor collects aggregates with a known surface area per unit volume on each stage. Combustion processes often produce particles with aggregate structure. For diesel exhaust aggregates, the surface area per unit volume calculated by our method was about twice that of spheres with diameter equal to the aerodynamic diameter. Measurements of aggregates collected near a major freeway and at Los Angeles International Airport (LAX) were made for two aerodynamic cutoff diameter diameters (d
a,50), 50 and 75 nm. (Aerodynamic cutoff diameter refers to the diameter of particles collected with 50% efficiency on a low-pressure impactor stage.) Near-freeway aggregates were probably primarily a mixture of diesel and internal combustion engine emissions. Aggregates collected at LAX were most likely present as a result of aircraft emissions. In both measurements, the aggregate aerodynamic diameters calculated from the primary particle diameter were fairly close to the stage cutoff diameter. The number of primary particles per aggregate varied one order of magnitude for particles depositing on the same stage. The average aggregate surface area per unit volume was 2.41 × 106 cm−1 and 2.59 × 106 cm−1 (50 nm d
a,50) and 1.81 × 106 cm−1 and 1.68 × 106 cm−1 (75 nm d
a,50) for near-freeway and LAX measurements, respectively. These preliminary measurements are consistent with values calculated from theory. 相似文献
14.
Bhupendra Chudasama Anjana K. Vala Nidhi Andhariya R. V. Mehta R. V. Upadhyay 《Journal of nanoparticle research》2010,12(5):1677-1685
In this article, we describe a simple one-pot rapid synthesis route to produce uniform silver nanoparticles by thermal reduction
of AgNO3 using oleylamine as reducing and capping agent. To enhance the dispersal ability of as-synthesized hydrophobic silver nanoparticles
in water, while maintaining their unique properties, a facile phase transfer mechanism has been developed using biocompatible
block co-polymer pluronic F-127. Formation of silver nanoparticles is confirmed by X-ray diffraction (XRD), transmission electron
microscopy (TEM) and UV–vis spectroscopy. Hydrodynamic size and its distribution are obtained from dynamic light scattering
(DLS). Hydrodynamic size and size distribution of as-synthesized and phase transferred silver nanoparticles are 8.2 ± 1.5 nm
(σ = 18.3%) and 31.1 ± 4.5 nm (σ = 14.5%), respectively. Antimicrobial activities of hydrophilic silver nanoparticles is tested
against two Gram positive (Bacillus megaterium and Staphylococcus aureus), and three Gram negative (Escherichia
coli, Proteus
vulgaris and Shigella
sonnei) bacteria. Minimum inhibitory concentration (MIC) values obtained in the present study for the tested microorganisms are
found much better than those reported for commercially available antibacterial agents. 相似文献
15.
Rati Ranjan Nayak Nilotpala Pradhan Debadhyan Behera Kshyama Madhusikta Pradhan Srabani Mishra Lala Behari Sukla Barada Kanta Mishra 《Journal of nanoparticle research》2011,13(8):3129-3137
An eco-friendly microbial method for synthesis of silver colloid solution with antimicrobial activity is developed using a
fungal strain of Penicillium purpurogenum NPMF. It is observed that increase in concentration of AgNO3 increases the formation of silver nanoparticle. At 5 mM concentration highly populated polydispersed nanoparticles form.
Furthermore, change in pH of the reaction mixture leads to change in shape and size of silver nanoparticles. At lower pH two
peaks are observed in the absorption spectra showing polydispersity of nanoparticles. However, highly monodispersed spherical
nanoparticles of 8–10 nm size form with 1 mM AgNO3 concentration at pH 8. Antimicrobial activity of nanoparticles is demonstrated against pathogenic gram negative bacteria
like Escherichia coli and Pseudomonas aeruginosa, and gram positive bacteria like Staphylococcus aureus. The antimicrobial activity of silver nanoparticles obtained at different initial pH show strong dependence on the surface
area and shape of the nanoparticles. 相似文献
16.
Suspensions of oligophenylenevinylene (nPV) nanoparticles withn = 2 vinylene units are doped with nPVs of longer chainlengths,n = 3–5. Absorption and fluorescence spectroscopy and steady-state and time-resolved fluorescence anisotropy measurements
are used to determine the photo-physical properties of the suspensions. Undoped nanoparticles form highly oriented H-aggregates
with low fluorescence quantum yields (ΦF ≈ 0.1). Introduction of bulky substituents into the particle constituting molecules perturbs the intermolecular orientation.
Upon doping, efficient energy transfer to the dopants is found, changing the color and leading to enhancement of the fluorescence
quantum yields up to ΦF = 0.6. The intermolecular orientation is not changed upon doping. 相似文献
17.
The sizes, shapes, and growth rates of gold and silver nanoparticles stabilized with polyvinylpyrrolidone in water can be
controlled by using picosecond laser pulses. The nucleation of small metal clusters formed with NaBH4 addition to produce nanoparticles takes two months with aging but 30 min with laser irradiation. Laser pulses can also induce
nanoparticles to have narrow size and shape distribution or to undergo aggregation into much larger particles. The latter
process is more likely found when the metal is silver or the irradiation wavelength is short. Laser-induced growth and shape
transformation processes are explained in terms of BH4
− depletion, metal fusion, and electron ejection followed by disintegration. 相似文献
18.
J. García-Barrasa J. M. López-de-Luzuriaga M. Monge Katerina Soulantica Guillaume Viau 《Journal of nanoparticle research》2011,13(2):791-801
Abstract
Silver nanocrystal superlattices (NCSs) stabilized by hexadecanethiol have been prepared through reduction of [Ag(hexadecanethiolate)] n , formed in situ by reaction of the organometallic precursor [Ag(C6F5)] and hexadecanethiol. The nanostructures have been characterized by transmission electron microscopy (TEM) and X-ray diffractometry (XRD). Several reaction parameters such as solvent (anisole or toluene), reaction temperature (150 or 120 °C) or silver:thiol ratio (1:1 or 2:1) have been studied. The NCSs are formed by silver nanoparticles which sizes range from 3.7 to 5.1 nm, depending on the reaction conditions. The formation a of lamellar phase of di-n-hexadecyldisulfide by oxidation of the hexadecanethiolate ligands bonded to Ag(I) is detected by XRD. 相似文献19.
The dielectric function of yttrium in the range between 0.2 μm and 2 μm is composed of a harmonic oscillator contribution
due to a discrete interband transition and the contribution of free electrons. Hence, it is possible to discuss surface plasmon
polaritons as well as other electronic resonances in the optical extinction spectra of yttrium nanoparticles. For the latter,
we discuss the broadening of the resonance caused by the aggregation of particles. When particles are lumped into aggregates,
the color of the particle system also changes. Aggregation also affects the surface plasmon resonance in yttrium nanoparticles
in a way comparable to silver or gold nanoparticle aggregates. Comparison is made with the first experimental results on yttriumnanoparticles,
showing that aggregation is the dominant effect for the broad resonance in the measured extinction spectra.
Received: 2 July 2001 / Revised version: 10 September 2001 / Published online: 15 October 2001 相似文献
20.
Veronika Sutrov Ivana loufov Martina Nevoralov Blanka Vl
kov 《Journal of Raman spectroscopy : JRS》2015,46(6):559-565
Adsorbate‐containing, nanosponge Ag aggregates overlayed by a thin (~1.5 mm) liquid layer are reported as a new type of sample for Surface‐enhanced Raman scattering (SERS) microRaman spectral measurements and adsorbate (analyte) detection. Macroscopic Ag aggregates (of about 1.5 × 1.0 × 0.025 mm size) with the nanosponge internal morphology (revealed by Scanning electron microscopy (SEM)) were prepared by 3D assembling of fused fractal aggregates (D = 1.84 ± 0.04) formed in Ag nanoparticle hydrosol/HCl/adsorbate systems with 2,2’‐bipyridine (bpy) and/or a cationic free‐base tetrakis(2‐methyl‐4‐pyridiniumyl) porphine (H2TMPyP) as the testing adsorbates. For SERS microRaman measurements, the macroscopic aggregate was overlayed by a thin (~1.5 mm) layer of the residual liquid. Preparation procedure, nanoscale imaging, and SERS spectral probing including the determination of the detection limits of the adsorbates revealed the following advantages of the adsorbate‐containing, liquid‐overlayed 3D nanosponge aggregate as a sample for SERS microRaman spectral measurements: (1) localization of adsorbate (analyte) into hot spots and, simultaneously, prevention of the analyte decomposition during the spectral measurement (carried out without an immersion objective), (2) fast and simple sample preparation, and (3) minimization of sample volume and an efficient concentration of hot spots into the focus of the laser beam. The advantages of the nanosponge Ag aggregates are further demonstrated by the 40 fmol limit of detection of bpy as Ag(0)‐bpy surface complex, as well as by preservation of the native structure of the cationic free‐base porphyrin H2TMPyP. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献