共查询到20条相似文献,搜索用时 46 毫秒
1.
Gold-Containing Nanocomposition Materials on the Basis of Homo- and Copolymers of Methylmethacrylate
N. O. Yakimovich N. V. Sapogova L. A. Smirnova A. P. Aleksandrov T. A. Gracheva A. V. Kirsanov N. M. Bityurin 《Russian Journal of Physical Chemistry B, Focus on Physics》2008,2(1):128-134
Films of polymethyl methacrylate and methyl methacrylate copolymers with ethylhexyl acrylate doped with HAuCl4 were subjected to UV irradiation followed by thermal treatment at various temperatures. The films were studied by absorption spectroscopy and small-angle X-ray scattering. The photolysis of HAuCl4 was found to result in the formation of gold nanoparticles, whose size depended on the structure of the polymeric matrix. An increase in the free volume of polymers caused the formation of larger particles. 相似文献
2.
T. A. Gracheva T. A. Kuz’micheva V. N. Perevezentsev A. E. Mochalova L. A. Smirnova E. V. Salomatina 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2011,5(3):426-430
The kinetics of UV-induced formation of gold nanoparticles in polymethylmethacrylate films doped with chloroauric acid HAuCl4 is studied. The films are investigated by the absorption spectroscopy and smallangle X-ray scattering methods. The changing size and polydispersity of gold nanoparticles are analyzed during their formation. The growth of gold nanoparticles is determined by the properties of a polymeric matrix and the rate of diffusion fluxes of matter. 相似文献
3.
The sonochemical formation of Au seeds and their autocatalytic growth to Au nanorods were investigated in a one-pot as a function of concentration of HAuCl4, AgNO3, and ascorbic acid (AA). The effects of ultrasonic power and irradiation time were also investigated. In addition, the formation rate of Au nanorods was analyzed by monitoring the extinction at 400 nm by UV–Vis spectroscopy and compared with the growth behavior of Au seeds to nanorods. Most of the reaction conditions affected the yield, size, and shape of Au nanorods formed. It was confirmed that the concentration balance between HAuCl4 and AA was important to proceed the formation of Au seeds and nanorods effectively. The formation rate became faster with increasing AA concentration and dog-bone shaped nanorods were formed at high AA concentration. It was also confirmed a unique phenomenon that the shape of Au nanorods changed even after the completion of the reduction of Au(I) in the case of short-time ultrasonic irradiation for Au seed formation. 相似文献
4.
The processes of laser-assisted formation of elongated Au nanoparticles and their subsequent agglomeration and fragmentation have been experimentally investigated. Elongated gold nanoparticles were formed by laser ablation of a solid target in water. IR radiation of ytterbium-doped fiber laser with a pulse width of 200 ns and a pulse energy of 0.5 to 1 mJ was used to this end. The extinction spectra and transmission electron microscopy images indicate the formation of elongated gold nanoparticles. The interaction of laser radiation with aqueous colloids of elongated nanoparticles in dependence of the pulse energy and exposure time has been analyzed. Possible processes of laser-assisted formation of elongated Au nanoparticles and their subsequent transition from agglomeration to fragmentation of gold nanoparticles, induced by laser irradiation are discussed. 相似文献
5.
We report on the synthesis of a metal–polymer composite material using an interfacial polymerization approach. The advantage of this approach is to form an intimate contact be‐tween the metal and polymer, which is an important param‐ eter for the synthesis of a nanocomposite material. It was found that polymerization of o‐phenylenediamine (PDA) us‐ing HAuCl4 as an oxidizing agent leads to the formation of poly‐PDA with a fiber‐like morphology, while the reduction of HAuCl4 results in the formation of well dispersed and sta‐bilized gold nanoparticles within the polymer matrix. The synthesis was carried out at the organic–aqueous interface. The resultant composite material was purely hydrophilic in nature and deposited at the aqueous fraction of the reaction medium. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
6.
We report on the use of poly(allylamine) hydrochloride (PAH) as a reducing agent for the controlled formation of gold nanoparticles
(AuNPs) in the size range of 5–50 nm. The formation of AuNPs using this polymer matrix allows for the AuNPs to be imbedded
in the polymer matrix, once formed. The kinetics of AuNP formation are shown to be pseudo first-order in [HAuCl4] at room temperature. The kinetics of AuNP formation are controlled by the ratio of reducing agent to HAuCl4 as well as the overall concentration of the PAH and HAuCl4. Additionally, at low PAH:HAuCl4 mole ratios, the plasmon resonance wavelength can be controlled through the ratio of the reactants. This plamson resonance
shift is shown to be related to AuNP size by means of TEM imaging data on the AuNPs. 相似文献
7.
A facile synthesis route is described for the preparation of a poly-(o-aminophenol)-gold nanoparticle composite material by polymerization of o-aminophenol (AP) monomer using HAuCl4 as the oxidant. The synthesis was carried out in a methanol medium so that it could serve a dual solvent role, a solvent
for both the AP and the water solution of HAuCl4. It was found that oxidative polymerization of AP leads to the formation of poly-AP with a diameter of 50±10nm, while the
reduction of AuCl4
- results in the formation of gold nanoparticles (∼ 2nm). The gold nanoparticles were uniformly dispersed and highly stabilized
throughout the macromolecular chain that formed a uniform metal-polymer composite material. The resultant composite material
was characterized by means of different techniques, such as UV-vis, IR and Raman spectroscopy, which offered the information
about the chemical structure of polymer, whereas electron microscopy images provided information regarding the morphology
of the composite material and the distribution of the metal particles in the composite material. 相似文献
8.
E. Jimnez Kamal Abderrafi Juan Martínez-Pastor Rafael Abargues Jos Luís Valds Rafael Ibez 《Superlattices and Microstructures》2008,43(5-6):487
Metal nanoparticles can be prepared by a novel technique that consists of the laser ablation of a solid target immersed in a water solution of a metal salt. Silicon was chosen as the most adequate target to synthesize silver and gold nanoparticles from a water solution of either AgNO3 or HAuCl4. The influence of both the silver nitrate concentrations and the irradiation time of the Si target on the optical properties of the Au and Ag nanoparticles have been investigated. The crystalline nature of the metal nanoparticles has been determined by X-ray diffraction (XRD). Average size and particle size distribution have been measured by means of TEM. The absorbance spectra show the characteristic band of the surface resonant plasmon of silver and gold nanoparticles. 相似文献
9.
Jian Zhang Baohui Zhao Linghui Meng Hongying Wu Xudong Wang Chenxi Li 《Journal of nanoparticle research》2007,9(6):1167-1171
Narrow-dispersed gold nanospheres, regular single-crystal nanoplates and nanobulks were prepared, respectively, by reducing
HAuCl4 within a hydrogel system under UV irradiation. The formation of gold products with different geometric shape and size was
found to depend on both the microenvironment of the gel matrix and the initial concentration of HAuCl4. The resultant gold particles were investigated by UV–vis spectroscopy, X-ray diffraction, transmission electron microscopy,
scanning electron microscopy, and energy-dispersion X-ray spectroscopy.
Electronic Supplementary Material The online version of this article at (doi: ) contains supplementary material, which is available to authorised users. 相似文献
10.
Petr ?mejkal Ji?í Pfleger Blanka Vl?ková 《Applied Physics A: Materials Science & Processing》2010,101(1):37-40
Laser ablation of a silver (Ag) and/or gold (Au) target was performed in liquid ammonia (l-NH3) at 233 K using nanosecond laser pulses of 1064, 532 and 355 nm wavelengths. An “in situ” monitoring of the ablation process
by UV/vis/NIR spectroscopy has shown the evolution of the surface plasmon extinction band of silver or gold nanoparticles
and thus confirmed their formation. While sols of Au nanoparticles in l-NH3 are quite stable in air, those of Ag nanoparticles undergo oxidation to Ag(I) complexes with NH3 ligands. On the other hand, formation of solvated electrons, namely of the (e−)NH3 solvates, has not been unequivocally confirmed under the conditions of our laser ablation/nanoparticle fragmentation experiment,
since only very weak vis/NIR spectral features of these solvates were observed with a low reproducibility. Reference experiments
have shown that the well-known chemical production of these solvates is hindered by the presence of Ag and Au plates. Ag and
Au targets can thus possibly act as electron scavengers in our ablation experiments. 相似文献
11.
Optical properties and ultrafast electron dynamics in gold–silver alloy and core–shell nanoparticles
Silver and gold are the two most popular metals used for many nanoparticle applications, such as surface enhanced Raman scattering
or surface enhanced fluorescence, in which the local field enhancement associated with the excitation of the localized surface-plasmon–polariton
resonance (SPR) is exploited. Therefore, tunability of the SPR over a wide energy range is required. For this purpose we have
investigated core–shell nanoparticles composed of gold and silver with different shell thicknesses as well as the impact of
alloying on these nanoparticles due to a tempering process. The nanoparticles were prepared by subsequent deposition of Au
and Ag atoms or vice versa on quartz substrates followed by diffusion and nucleation. Their linear extinction spectra were
measured as a function of shell thickness and annealing temperature. It turned out that different gold shell thicknesses on
silver cores allow a tuning of the SPR position from 2.79 to 2.05 eV, but interestingly without a significant change on the
extinction amplitude. Heating of core–shell nanoparticles up to only 540 K leads to the formation of alloy nanoparticles,
accompanied by a back shift of the SPR to 2.60 eV. Calculations performed in quasi-static approximation describe the experimental
results quite well and prove the structural assignments of the samples. In additional experiments, we applied the well-established
persistent spectral hole burning technique to the alloy nanoparticles in order to determine the ultrafast dephasing time T
2. We obtained a dephasing time of T
2=(8.1±1.6) fs, in good agreement with the dephasing time of T
2,∞=8.9 fs, which is already included in the dielectric function of the bulk. 相似文献
12.
In this work, micro plasma-induced non-equilibrium liquid chemistry was utilized to synthesize and controlled formation of gold metallic nanoparticles (Au MNPs) by governing the concentration of (HAuCl4). These new approaches based on both plasma and liquid electrolytes contain charged species, and the interactions between the two phases represent a unique combination of physics, chemistry, and materials science. Continuous and stable DC glow discharge was done in home–made cavity to synthesize the definite sizes of (Au MNPs) by means of (3 kV) discharge voltage and (2 mA) discharge current for a period of (7 min) in aqueous solution of HAuCl4 with four different concentrations of about 1 mM, 5 mM, 10 mM and 20 mM at room temperature. The atmospheric pressure plasma discharge between stainless steel capillary tube cathode electrode over the (HAuCl4) solution and platinum plate as an anode dipped in solution for rapid formation of colloidal Au MNPs. Morphology aspects of the synthesized Au MNPs layer were studied by examining the (FE-SEM), HR-TEM images and X-ray difraction (XRD) pattern. Optical features of (Au MNPs) were considered via a UV–Vis beam spectrophotometer. These measurements showed that Au MNPs were organized by governing the concentration of HAuCl4, and uniform Au MNPs with specific exclusive sizes were acquired. Grain size, specific surface area and optical stability of Au MNPs strongly be affected by the HAuCl4 concentrations. 相似文献
13.
F. Ruffino V. Torrisi G. Marletta M. G. Grimaldi 《Applied Physics A: Materials Science & Processing》2012,107(3):669-683
The morphology evolution of nano-grained Ag and Au films deposited on polystyrene (PS) and poly(methyl methacrylate) (PMMA) polymeric layers were studied, using the atomic force microscopy technique, when annealed above the polymers glass transition temperature. The main effects on the morphology changes were identified with those concerning the embedding kinetics of the Ag and Au nanoparticles in the PS or PMMA layers. The embedding process of the nanoparticles follows as a consequence of the long-range mobility of the polymeric chains above the glass transition temperature. In particular, the dependence of the nanoparticles mean height and surface density on the annealing time at various temperatures was quantified. The analyses of these behaviors allowed us: (1) to distinguish the overall embedding process in a first stage in which a thin wetting layer of the polymer coats the nanoparticles followed by a true embedding process of the nanoparticles into the polymer layer; (2) to evaluate the characteristic coating time for the Ag and Au nanoparticles in the PS and PMMA in the first stage; (3) to evaluate the characteristic embedding velocity for the Ag and Au nanoparticles in the PS and PMMA in the second stage; (4) to derive the activation energies for the embedding process of the Ag and Au nanoparticles in PS and PMMA; (5) to identify the embedding statistics of the Ag and Au nanoparticles in PS and PMMA with a “failure” Weibull statistics. 相似文献
14.
Jordi Llorca Albert Casanovas Montserrat Domínguez Ignasi Casanova Inmaculada Angurell Miquel Seco Oriol Rossell 《Journal of nanoparticle research》2008,10(3):537-542
Catalytically active gold nanoparticle films have been prepared from core-shell nanoparticles by plasma-activation and characterized
by high-resolution transmission electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. Methane
can be selectively oxidized into formic acid with an O2–H2 mixture in a catalytic wall reactor functionalized with plasma-activated gold nanoparticle films containing well-defined
Au particles of about 3.5 nm in diameter. No catalytic activity was recorded over gold nanoparticle films prepared by thermal
decomposition of core-shell nanoparticles due to particle agglomeration. 相似文献
15.
A novel approach to pattern nanocrystalline gold (Au) octahedra is presented based on electron irradiation combined with thermal
treatment and post-cleaning process using HAuCl4-loaded poly(styrene-b-2-vinyl pyridine) (PS-b-P2VP) block copolymer (BCP) as a precursor material. The BCP tends to cross-link
under electron irradiation, and thus a patterned film can be prepared by selectively irradiating an electron beam onto a precursor
film using a shadow mask. A post-thermal treatment leads to the formation of crystalline Au nano-octahedra inside the patterned
film with a help of the BCP acting as a capping agent. Subsequently, the BCP can be removed by O2 plasma etching combined with oxidative degradation, with the Au nanoparticles remaining. As a result, a patterned film consisting
of high-purity nanocrystalline Au octahedra is fabricated. The sizes of the Au octahedral nanoparticles can be readily controlled
from 49 to 101 nm by changing the thickness of the precursor film. The patterned Au nano-octahedra films exhibit excellent
surface-enhanced Raman scattering behavior with the maximum enhancement factor of ~106. 相似文献
16.
T. A. Gracheva T. A. Kuz’micheva V. N. Perevezentsev L. A. Smirnova A. E. Mochalova E. B. Salomatina 《Technical Physics》2017,62(8):1228-1232
Using methods of optical spectroscopy and small-angle X-ray scattering, the kinetics of the UV radiation-induced formation of gold nanoparticles in HAuCl4-doped water–acid solutions of chitosan has been studied from the very beginning of the reaction. It has been shown that, during synthesis, as the mean size of nanoparticles grows from 2.9 to 6.3 nm, the maximum of the plasmon resonance shifts toward shorter waves (535–523 nm), whereas for a fully formed ensemble of nanoparticles, the reverse trend is observed. It has been found experimentally that the particle size distribution curve changes during synthesis. Based on the inverse problem analysis, conclusions have been drawn regarding the dominant mechanisms behind nanoparticle growth. 相似文献
17.
X.B. Yan T. Xu G. Chen X.B. Wang H.W. Liu S.R. Yang 《Applied Physics A: Materials Science & Processing》2005,81(1):197-203
Amorphous hydrogenated carbon (aC:H) films containing Au nanoparticles have been successfully prepared by heat-treatment of the precursors including poly(phenylcarbyne) polymer and HAuCl4 at 600 °C in Ar atmosphere. The microstructure and morphology of the obtained films were investigated by means of Raman, XPS, XRD, TEM, and AFM. The sheet resistivity of the films was measured by a four-point probe method. Moreover, a ball-on-disc test was employed to obtain information about the frictional properties and sliding wear resistance of the films. The results show that heat-treatment of the precursors at 600 °C causes the change of the polymer into amorphous hydrogenated carbon phase, and the reduction of AuCl4- anions into zero-valence Au. All of the AuaC:H films exhibit smooth morphologies, with the RMS roughness smaller than 0.80 nm. Au nanoparticles are well dispersed in the amorphous carbon matrix, with size ranging from several to tens of nanometers, and the particle size increases with increasing gold content. The incorporation of Au in the carbon matrix can drastically decrease the resistivity and the resistivity of composite films gradually decreases with increasing Au concentration. AuaC:H films with the Au concentration of 2% and 4% show much better friction-reduction and wear-resistance than aC:H film. PACS 81.15.Np; 81.07.-b; 81.40.Pq 相似文献
18.
N. Bityurin A. Alexandrov A. Afanasiev N. Agareva A. Pikulin N. Sapogova L. Soustov E. Salomatina E. Gorshkova N. Tsverova L. Smirnova 《Applied Physics A: Materials Science & Processing》2013,112(1):135-138
UV irradiation of materials consisting of a polymer matrix that possesses precursors of noble metals followed by annealing results in creation of metal nanoparticles within the irradiated domains. Such photoinduced nanocomposites are promising for photonics applications due to the strong alteration of their optical properties compared to initial nonirradiated materials. We report our results on the synthesis and investigation of two kinds of these materials:
- Photoinduced Au nanocomposites based on PMMA matrices, including bulk materials prepared by means of the polymerization technique;
- photoinduced Ag nanocomposites with an organic–inorganic hybrid matrix based on TiO2 gels.
19.
We studied the kinetics of the reduction of a gold precursor (HAuCl4) and the effect of the molar ratio (R) of sodium citrate, which was introduced from a seed solution, and the gold precursor
on the shape evolution of gold nanomaterials in the presence of preformed 13 nm gold nanoparticles as seeds. The reduction
of the gold precursor by sodium citrate was accelerated due to the presence of gold seeds. Nearly single-crystalline gold
nanowires were formed at a very low R value (R = 0.16) in the presence of the seeds as a result of the oriented attachment of the growing gold nanoparticles. At a higher
R value (R = 0.33), gold nanochains were formed due to the non-oriented attachment of gold nanoparticles. At a much higher R value (R = 1.32), only larger spherical gold nanoparticles grown from the seeds were found. In the absence of gold seeds, no single-crystalline
nanowires were formed at the same R value. Our results indicate that the formation of the 1D nanostructures (nanochains and
nanowires) at low R values is due to the attachment of gold nanoparticles along one direction, which is driven by the surface energy reduction,
nanoparticle attraction, and dipole–dipole interaction between adjacent nanoparticles. 相似文献
20.
Highly stable colloidal gold nanoparticles are obtained in a pseudo-template system using a specific polyhydrosilane copolymeric structure. This process takes place in situ by microwaves activation of the polymer solution in a non-polar solvent followed by stirring with solid HAuCl4 in natural light. The experimental procedure is very simple and the resulted colloidal gold solution is indefinitely stable. The specific surface plasmon resonance absorption band of the gold nanoparticles is strongly red shifted and is strictly related to their size. AFM correlated with DLS analysis showed flattened round shaped colloidal polymer-gold nanoparticles with large diameters. SEM-EDX combined analysis reveals that the polysilane-gold nanoparticles show a natural tendency to auto-assemble in close packed structures which form large areas over the polymer film surface. 相似文献