共查询到20条相似文献,搜索用时 31 毫秒
1.
Pratima Parashar 《Journal of Materials Science: Materials in Electronics》2012,23(6):1169-1173
Results of the structural studies of silver particulate films deposited at a rate of 0.4 nm/s on polymeric blends of polystyrene/poly
(2-vinyl pyridine), PS/P2VP held at a temperature 457 K by evaporation in a vacuum of 8 × 10−6 Torr are reported here. The morphology of silver particulate films, characterized by their size, size distribution, shape
and inter-particle separation, was observed to modify due to blending of PS with P2VP and amount of silver deposited. The
red shift in the plasmon resonance indicates the effect of blending P2VP with PS. Scanning electron microscopy was used to
study the change in morphology of the silver nanoparticles in correlation with the optical properties of silver particulate
films on PS/P2VP blends. The silver nanoparticles on the thin layers of polymer blends exhibited much smaller, narrower dispersion
and wide size distribution due to blending of PS with P2VP. 相似文献
2.
Shi M Lin CC Wu L Holt CM Mitlin D Kuznicki SM 《Journal of nanoscience and nanotechnology》2010,10(12):8448-8451
Titanium based molecular sieves, such as ETS-10, have the ability to exchange silver ions and subsequently support self assembly of stable silver nanoparticles when heated. We report that a high surface area sodium titanate (resembling ETS-2) displays a similar ability to self template silver nanoparticles on its surface. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show high concentrations of silver nanoparticles on the surface of this sodium titanate, formed by thermal reduction of exchanged silver cations. The nanoparticles range in size from 4 to 12 nm, centered at around 6 nm. In addition to SEM and TEM, XRD and surface area analysis were used to characterize the material. The results indicate that this sodium titanate has a high surface area (>263 m2/g), and high ion exchange capacity for silver (30+ wt%) making it an excellent substrate for the exchange and generation of uniform, high-density silver nanoparticles. 相似文献
3.
The catalytic properties of silver nanoparticles supported on silica and the relation between catalytic activity of silver particles and the support (silica) size are investigated in the present article. The silver nanoparticles with 4 nm diameters were synthesized and were attached to silica spheres with sizes of 40, 78, 105 nm, respectively. The reduction of Rhodamine 6G (R6G) by NaBH4 was designed by using the SiO2/Ag core-shell nanocomposites as catalysts. The experimental results demonstrated that the catalytic activity of silica/silver nanoparticles depends on not only the concentration of catalysts (silver) but also the support silica size. Silver particles supported on small SiO2 spheres (approximately 40 nm) show high catalytic activity. Moreover, by making a comparison between the UV-vis spectra of the catalyst before and after the catalytic reaction, we found that the position of surface plasma resonance (SPR) peak of Ag nanoparticles changes little. The above results suggested that the size and morphology of silver particles were probably kept unchanged after the reduction of R6G and also implied that the catalytic activity of silver particles was hardly lost during the catalytic reaction. 相似文献
4.
Suchita Kalele Aparna C. Deshpande Shashi Bhushan Singh S. K. Kulkarni 《Bulletin of Materials Science》2008,31(3):541-544
The photoluminescence (PL) from rhodamine (RHO6G) dye dispersed in ethanol has been studied in the presence of different amounts
of citrate stabilized silver nanoparticles of size, ∼10 nm. Enhancement as well as quenching of luminescence intensity has
been observed and it was found that luminescence intensity can be tuned by adding various amounts of silver nanoparticles
to the RHO6G dye dispersion. The luminescence spectra of dye consist of two peaks at 440 nm and 550 nm. Peak at 440 nm shows
an enhancement in intensity at all the concentrations of added silver nanoparticles with the maximum intensity for dye with
0.25 ml silver nanoparticles (82% enhancement in the luminescence intensity). PL intensity of intense peak at 550 nm of dye
molecules was found to be quenched in presence of silver nanoparticles and maximum quenching was found to be 41% for the dye
with 1 ml silver nanoparticles. However, for lowest concentration of silver nanoparticles viz. (0.01 ml), enhancement in intensity
was observed (13% enhancement than the dye molecules). The quenching as well as enhancement in the intensity can be understood
by considering the possibility of three different phenomena. It has been reported earlier that when metal nanoparticles are
in close proximity to the fluorophores, quenching of luminescence occurs, whereas when metal nanoparticles are located at
certain distance, enhancement in luminescence is observed. This effect has been explained by coupling of surface plasmon resonance
from metal nanoparticles with fluorophore, resulting in the increase of excitation and emission rate of the fluorophore in
the localized electromagnetic field. The quenching and enhancement of luminescence intensity of the dye molecules can also
be explained as the transfer of electrons from dye to the silver nanoparticles and to an extent it can be attributed to the
aggregation of dye molecules upon addition of silver nanoparticles. 相似文献
5.
In this study, silver nanoparticles were prepared using silver nitrate as the metal precursor, starch as protecting agent, and sodium borohydride (NaBH4) as a reducing agent by the chemical reduction method. The formation of the silver nanoparticles was monitored using ultraviolet-visible absorption spectroscopy, cyclic voltammetry, and particle size analyzer and characterized by transmission electron microscopy (TEM) and x-ray diffraction (XRD). Synthesis of nanoparticles were carried out by varying different parameters, such as reaction temperature, concentration of reducing agent, concentration of silver ion in feed solution, type and concentration of the stabilizing agent, and stirrer speed expressed in terms of particle size and size distribution. Dispersion destabilization of colloidal nanoparticles was detected by Turbiscan. It was observed that size of the starch stabilized silver nanoparticles were lower than 10 nm. The microbial activity of synthesized silver nanoparticles was examined by modified Kirby-Bauer disk diffusion method. Silver nanoparticles were tested for their antibacterial activity against Gram negative bacteria such as Escherichia coli, Pseudomonas aeruginosa, and Gram positive bacteria such as Staphylococcus aureus and Staphylococcus epidermidis. High bacterial activity was observed at very low concentrations of silver (below 1.39 μg/ml). The antifungal activity of silver nanoparticles has been assayed against Candida albicans. 相似文献
6.
SERS-active silver nanoparticle aggregates produced in high-iron float glass by ion exchange process
L. Karvonen Y. ChenA. Säynätjoki K. TaiviolaA. Tervonen S. Honkanen 《Optical Materials》2011,34(1):1-5
Silver nanoparticles were produced in iron containing float glasses by silver-sodium ion exchange and post-annealing. In particular, the effect of the concentration and the oxidation state of iron in the host glass on the nanoparticle formation was studied. After the nanoparticle fabrication process, the samples were characterized by optical absorption measurements. The samples were etched to expose nanoparticle aggregates on the surface, which were studied by optical microscopy and scanning electron microscopy. The SERS-activity of these glass samples was demonstrated and compared using a dye molecule Rhodamine 6G (R6G) as an analyte. The importance of the iron oxidation level for reduction process is discussed. The glass with high concentration of Fe2+ ions was found to be superior in SERS applications of silver nanoparticles. The optimal surface features in terms of SERS enhancement are also discussed. 相似文献
7.
Di Corato R Palumberi D Marotta R Scotto M Carregal-Romero S Rivera Gil P Parak WJ Pellegrino T 《Small (Weinheim an der Bergstrasse, Germany)》2012,8(17):2731-2742
A versatile method for decorating magnetic nanobeads (being composite materials from polymers and superparamagnetic nanoparticles) with silver nanoparticles of 3-6 nm size is presented. Control over the silver nanoparticle coverage at the nanobead surface is achieved by changing the reaction parameters. Moreover, the silver-decorated magnetic nanobeads (Ag-MNBs) are studied with respect to their in vitro cytotoxicity on two distinct tumour cell lineages under different parameters, i.e., dose, incubation time, magnetic field applied during the culturing, silver ion leakage, and colloidal stability. It is found that enhanced magnetically mediated cellular uptake and silver ion leakage from the Ag-MNBs surface are the main factors which affect the toxicity of the Ag-MNBs and allow the half-maximal inhibitory dose of silver to be reduced to only 32 μg mL(-1) . Furthermore, a synergic cytotoxicity induced by photo-activation of silver nanoparticles was also found. 相似文献
8.
《Materials Letters》2006,60(17-18):2256-2260
Silver nanoparticles were synthesized by using amphiphilic block copolymer Polyacrylonitrile-block-poly(ethylene glycol)-blcok-Polyacrylonitrile (PAN-b-PEG-b-PAN, PEA) based on the flexibility of the copolymer chains and the complex effect of –CN in the polyacrylonitrile with Ag+ ion and Ag under ultrasonic irradiation. The product was characterized by X-ray Diffraction (XRD), Fourier Transfer Infrared Spectrometer (FTIR), Transmission Electron Microscope (TEM), UV–Vis spectrum and Thermal Gravity Analysis (TGA). The results revealed that the size and size distribution of the resulting silver nanoparticles prepared basing on the copolymer were strongly dependent on the initial concentration of the silver ion solution and the irradiation conditions. Low initial silver ion concentration allowed for yielding silver nanoparticles with a small size and the size of the silver nanoparticles increased with increasing of silver ion concentration. The silver crystal was polycrystalline with a cubic structure, as confirmed by XRD. This work provides a simple route for the in situ synthesis of Ag nanoparticles. 相似文献
9.
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11.
Polypyrrole–silver (PPy–Ag) nanocomposites with various silver contents have been synthesized via a kinetically favorable one-step chemical oxidative polymerization process. The oxidant, ammonium persulfate, was used to oxidize pyrrole monomer for growing chains of PPy. And AgNO3 was used as a precursor for metallic silver nanoparticles. The detailed characterization techniques, UV–Vis–NIR, fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction spectroscopy, field-emission scanning electron microscopy, and transmission electron microscopy (TEM), have been used to reveal electronic environment, structure, and morphology of composites as well as as-synthesized PPy. The synthesis environment prior to polymerization has also been investigated by absorption spectroscopy. The TEM images of PPy–Ag nanocomposites reveal that silver nanoparticles are deeply embedded into the polymer matrix in addition to surface adsorption. It is observed that the size distribution of inorganic nanoparticles (ca. 4–10 nm, depending on the metal ion concentrations) as well as structural morphology is altered by the initial concentrations of silver ions. 相似文献
12.
We have developed a novel microgravimetric immunosensor using a WO(3) nanoparticle-modified immunoassay and a silver enhancement reaction. When the nanoparticles in silver ion solution (i.e. AgNO(3)) are exposed to visible light, the silver ions are photocatalytically reduced and form a metallic silver coating on the nanoparticles. This silver coating consequently induces changes in the mass and light absorption spectrum. Although photocatalytic reduction reactions can be achieved using ultraviolet (UV) light and TiO(2) nanoparticles as described in our previous publication (Seo et al 2010 Nanotechnology 21 505502), the use of UV light in biosensing applications has drawbacks in that UV light can damage proteins. In addition, conventional quartz crystal substrates must be passivated to prevent undesirable silver ion reduction on their gold-coated sensing surfaces. We addressed these problems by adopting a visible light-induced photocatalytic silver enhancement method using WO(3) nanoparticles and lateral field excited (LFE) quartz crystals. As a proof-of-concept demonstration of the technique, streptavidin was adsorbed onto an LFE quartz crystal, and its mass was enhanced with biotinylated WO(3) nanoparticles, this being followed by a photocatalytic silver enhancement reaction. The mass change due to the enhancement was found to be > 30 times greater than the mass change obtained with the streptavidin alone. 相似文献
13.
Choi JH Jung CH Hwang IT An MY Lee BM Kim DK Lee JS Nho YC Huh KM Hong SK 《Journal of nanoscience and nanotechnology》2010,10(10):6879-6882
A convenient and effective method to pattern polymer-embedded metal nanoparticles by ion irradiation has been developed. The thin Pluronic films containing silver nitrate as a precursor of silver nanoparticles were irradiated through a pattern mask with accelerated proton (H+) ions. It was found from the UV-Vis measurement that the formation of silver nanoparticles in the Pluronic matrix was dependant on the amount of silver nitrate. The 50 microm line (pitch 150 microm) patterns of the Pluronic containing silver nanoparticles were obtained with the thin film irradiated to 1 x 10(16) ions/cm2. The heat treatment effect on the morphology of the patterns was investigated by using a scanning electron microscope with an energy dispersive X-ray spectrometer. The results confirmed that the silver nanoparticles were successfully embedded in the Pluronic patterns and the patterns were changed into large silver particles by a heat treatment above 350 degrees C. 相似文献
14.
Yawei Zhou Linfeng Gao Guofei An Chaoshun Yang Xiaopeng Zhao 《Journal of Materials Science: Materials in Electronics》2013,24(6):2156-2160
We report a facile method for the fabrication of polystyrene/silver composite nanoparticles with core–shell nanostructures. First, polystyrene (PS) nanoparticles with carboxyl acid groups on their surfaces were prepared via the dispersion polymerisation of styrene in water with the assistance of acrylic acid. Second, with the addition of [Ag(NH3)2]+ to the PS dispersion, [Ag(NH3)2]+ was absorbed onto the surfaces of the modified PS nanoparticles. Finally, the [Ag(NH3)2]+ complex ions were reduced to Ag to form the PS/Ag nanocomposites upon heating. The resulting PS/Ag composite nanoparticles were characterized via scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, and dynamic light scattering. 相似文献
15.
A new method for the preparation of silver nanoparticles (AgNPs) on silver chloride discs was developed to integrate the unique properties of plasmonic nanoparticles into infrared optical sensing technologies. AgNP layers exhibiting strong infrared surface enhancement were prepared by reacting silver chloride discs in a solution containing hydrazine, which acts as a reducing agent. The silver ions in the outer layer of the disc could be reduced under proper conditions and the reduced silver coagulated to form suitable AgNPs for surface-enhanced infrared absorption (SEIRA) measurements. To examine the influences of the reaction solution composition and also to optimize preparation of SEIRA substrates, factors such as pH value, reaction time, and concentration of reducing agent were examined. Results indicated that both the concentrations of hydrazine and hydroxide strongly influenced the SEIRA signals. The strongest signals were observed when AgNPs on a AgCl substrate were prepared by using a reducing solution of 20 mM NaOH with 0.75 mM hydrazine. Using the optimized substrates, intense SEIRA spectra were observed with an enhancement factor around two orders of magnitude compared to measurements made using conventional sampling techniques. 相似文献
16.
A model alkane molecule, triacontane, is used to assess the effects of condensed gold and silver nanoparticles on the molecular ion yields upon atomic (Ga(+) and In(+)) and polyatomic (C60(+) and Bi3(+)) ion bombardment in metal-assisted secondary ion mass spectrometry (MetA-SIMS). Molecular films spin-coated on silicon were metallized using a sputter-coater system, in order to deposit controlled quantities of gold and silver on the surface (from 0 to 15 nm equivalent thickness). The effects of gold and silver islets condensed on triacontane are also compared to the situation of thin triacontane overlayers on metallic substrates (gold and silver). The results focus primarily on the measured yields of quasi-molecular ions, such as (M - H)(+) and (2M - 2H)(+), and metal-cationized molecules, such as (M + Au)(+) and (M + Ag)(+), as a function of the quantity of metal on the surface. They confirm the absence of a simple rule to explain the secondary ion yield improvement in MetA-SIMS. The behavior is strongly dependent on the specific projectile/metal couple used for the experiment. Under atomic bombardment (Ga(+), In(+)), the characteristic ion yields an increase with the gold dose up to approximately 6 nm equivalent thickness. The yield enhancement factor between gold-metallized and pristine samples can be as large as approximately 70 (for (M - H)(+) under Ga(+) bombardment; 10 nm of Au). In contrast, with cluster projectiles such as Bi3(+) and C60(+), the presence of gold and silver leads to a dramatic molecular ion yield decrease. Cluster projectiles prove to be beneficial for triacontane overlayers spin-coated on silicon or metal substrates (Au, Ag) but not in the situation of MetA-SIMS. The fundamental difference of behavior between atomic and cluster primary ions is tentatively explained by arguments involving the different energy deposition mechanisms of these projectiles. Our results also show that Au and Ag nanoparticles do not induce the same behavior in MetA-SIMS of triacontane. The microstructures of the metallized layers are also different. While metallic substrates provide higher yields than metal islet overlayers in the case of silver, whatever the projectile used, the situation is reversed with gold. 相似文献
17.
《Materials Letters》2007,61(14-15):3048-3051
Silver nanoparticles were prepared by the reduction of silver salts with sodium borohydride and capped with a copolymer of styrene sulfonate and maleic monomers. The synthesized nanoparticles were then deposited on a glass substrate using the layer-by-layer deposition technique in alternance with polycationic poly(diallyl-dimethylammonium chloride) PDADMAC. The synthesis of the silver nanoparticles as well as the layer-by-layer deposition with PDADMAC was easily monitored by UV–Vis spectroscopy due to the strong plasmon absorbance at 400 nm of the silver nanoparticles. Our study shows that increasing the concentration ration between the co-polyelectrolyte and silver nitrate has a negative effect on the size distribution of the resulting silver nanoparticles. For the layer-by-layer assembly, the PSS-co-Maleic was found to be a good capping agent since it allows later the formation of uniform thin films when deposited with PDADMAC. A linear increase in absorbance as a function of the number of deposited layers was observed. 相似文献
18.
M. Motamedi JuibariS. Abbasalizadeh Gh. Salehi Jouzani M. Noruzi 《Materials Letters》2011,65(6):1014-1017
The microflora of Ramsar geothermal hot springs located in Mazandaran province, Iran was screened for native thermophilic bacteria that are capable of biosynthesis of silver nanoparticles. One isolate identified as “Ureibacillus thermosphaericus” showed high potential for silver nanoparticle biosynthesis with extracellular mechanism and selected for the biosynthesis optimization. Biosynthesis reactions were conducted using the culture supernatant at different temperatures (60-80 °C) and silver ion concentrations (0.001-0.1 M). The results obtained showed that pure spherical nanoparticles in the range of 10-100 nm were produced, and the maximum nanoparticle production was achieved using 0.01 M Ag-NO3 at 80 °C. In conclusion, the findings of this study confirmed the great biocatalyzing potential of the extremophilic U. thermosphaericus supernatant for intensified biosynthesis of silver nanoparticle at elevated temperatures and high silver ion concentrations. 相似文献
19.
Despite the fact that polystyrene (PS) spheres have been developed as polymeric carriers or matrices for various biomedical applications, the synthesis of PS spheres is time-consuming. This work describes the fabrication of a uniform PS sphere, coated with silver nanoparticles (Ag-PS), by simultaneous photoinduced polymerization and reduction fabricated using x-rays in aqueous solution without any initiator. The solution contains only styrene, silver ions (Ag(+)), and poly(vinyl pyrrolidone) (PVP) as a stabilizer. The proposed mechanism of the formation of the Ag-PS nanocomposite spheres involves the generation of radicals in the aqueous solution to induce PS polymerization and the reduction of Ag. The distribution of the sizes of the core PS spheres in the Ag-PS nanocomposite spheres was systematically examined as a function of irradiation time, concentration of styrene, and amount of PVP. Ag-PS nanocomposite spheres exhibit antimicrobial activity against bacteria (Escherichia coli and Staphylococcus aureus). Additionally, the cationic (vinylbenzyl)trimethylammonium (TMA) monomer was photopolymerized to form positively charged TMA-PS spheres as gene carriers with uniquely low cytotoxicity. Given these design advantages, the method proposed herein is simpler than typical approaches for synthesizing PS spheres with functionalized groups and PS spheres coated with Ag nanoparticles. 相似文献
20.
The Taguchi method of experimental design is very well suited to improving the production process of synthetic nanoparticles.
The current application of the Taguchi method was successful in optimizing the experimental parameters affect on synthesis
procedure of silver chromate nanoparticles. Ultrafine silver chromate particles were synthesied by precipitation method using
addition of silver ion solution to the chromate reagent. The effect of reaction conditions such as: silver and chromate concentrations,
flow rate of reagent addition and temperature on the particle size of synthesized silver chromate particles were investigated.
The effect of these factors on the diameter of silver chromate particles were quantitavely evaluated by the analysis of variance
(ANOVA). The results showed that silver chromate particles can be synthesized by controlling silver concentration, flow rate
and temperature. Finally, the optimum conditions for synthesis of silver chromate particles by this simple and fast method
were proposed. The results of ANOVA showed that 0.001 mol/l silver ion concentration, 40 ml/min flow rate for addition of
silver reagent to the chromate solution and 0°C temperature are optimum conditions for producing silver chromate particles
with 100 ± 33 nm width. On the other hand, the Ag2CrO4 nano-superstructures were synthesized by electrosynthesis method. The results showed that Ag2CrO4 nanoparticles synthesized by this method have 75 nm average diameter. 相似文献