共查询到20条相似文献,搜索用时 15 毫秒
1.
Olivier Véron Jean Philippe Blondeau Naas Abdelkrim Esidor Ntsoenzok 《Plasmonics (Norwell, Mass.)》2010,5(2):213-219
The photoluminescence of silver nanoparticles glasses obtained by ionic exchange and annealing is investigated for various
ionic exchange times. These glasses are prepared by immersion of silicate glass samples in a molten salt bath of molar concentration
10% AgNO3 in NaNO3 at T = 320 °C. Scanning electron microscopy measurement in electron diffraction scattering (EDS) configuration confirms the silver
presence in the various glasses, and the UV/visible absorption gives the evolution of the spectra after ionic exchange and
plasmon resonance apparition after annealing. After annealing at 450 °C, both diagnostics inform us about the particles’ formation
and the silver rediffusion. Silver nanoparticle growth after annealing prior leads to photoluminescence exaltation and quenching
for the longest exchange samples. Subsequently, we propose potential mechanisms of the nanoparticle formation with an initial
depolymerization of the silicate network during the ionic exchange and repolymerization during annealing. 相似文献
2.
Mohammad Oves Mohammad Saghir Khan Almas Zaidi Arham S. Ahmed Faheem Ahmed Ejaz Ahmad Asif Sherwani Mohammad Owais Ameer Azam 《PloS one》2013,8(3)
Biofabricated metal nanoparticles are generally biocompatible, inexpensive, and ecofriendly, therefore, are used preferably in industries, medical and material science research. Considering the importance of biofabricated materials, we isolated, characterized and identified a novel bacterial strain OS4 of Stenotrophomonas maltophilia (GenBank: ). At neutral pH, this Gram negative bacterial strain significantly reduced hexavalent chromium, an important heavy metal contaminant found in the tannery effluents and minings. Subsequently, even at room temperature the supernatant of log phase grown culture of strain OS4 also reduced silver nitrate (AgNO3) to generate nanoparticles (AgNPs). These AgNPs were further characterized by UV–visible, Nanophox particle size analyzer, XRD, SEM and FTIR. As evident from the FTIR data, plausibly the protein components of supernatant caused the reduction of AgNO3. The cuboid and homogenous AgNPs showed a characteristic UV-visible peak at 428 nm with average size of ∼93 nm. The XRD spectra exhibited the characteristic Bragg peaks of 111, 200, 220 and 311 facets of the face centred cubic symmetry of nanoparticles suggesting that these nanoparticles were crystalline in nature. From the nanoparticle release kinetics data, the rapid release of AgNPs was correlated with the particle size and increasing surface area of the nanoparticles. A highly significant antimicrobial activity against medically important bacteria by the biofabricated AgNPs was also revealed as decline in growth of Staphylococcus aureus (91%), Escherichia coli (69%) and Serratia marcescens (66%) substantially. Additionally, different cytotoxic assays showed no toxicity of AgNPs to liver function, RBCs, splenocytes and HeLa cells, hence these particles were safe to use. Therefore, this novel bacterial strain OS4 is likely to provide broad spectrum benefits for curing chromium polluted sites, for biofabrication of AgNPs and ultimately in the nanoparticle based drug formulation for the treatment of infectious diseases. JN247637.1相似文献
3.
The extensive use of nanometal-based products increases the chance of their release into aquatic environments, raising the
question whether they can pose a risk to aquatic biota and the associated ecological processes. Aquatic microbes, namely fungi
and bacteria, play a key role in forested streams by decomposing plant litter from terrestrial vegetation. Here, we investigated
the effects of nanocopper oxide and nanosilver on leaf litter decomposition by aquatic microbes, and the results were compared
with the impacts of their ionic precursors. Alder leaves were immersed in a stream of Northwest Portugal to allow microbial
colonization before being exposed in microcosms to increased nominal concentrations of nanometals (CuO, 100, 200 and 500 ppm;
Ag, 100 and 300 ppm) and ionic metals (Cu2+ in CuCl2, 10, 20 and 30 ppm; Ag+ in AgNO3, 5 and 20 ppm) for 21 days. Results showed that rates of leaf decomposition decreased with exposure to nano- and ionic metals.
Nano- and ionic metals inhibited bacterial biomass (from 68.6% to 96.5% of control) more than fungal biomass (from 28.5% to
82.9% of control). The exposure to increased concentrations of nano- and ionic metals decreased fungal sporulation rates from
91.0% to 99.4%. These effects were accompanied by shifts in the structure of fungal and bacterial communities based on DNA
fingerprints and fungal spore morphology. The impacts of metal nanoparticles on leaf decomposition by aquatic microbes were
less pronounced compared to their ionic forms, despite metal ions were applied at one order of magnitude lower concentrations.
Overall, results indicate that the increased release of nanometals to the environment may affect aquatic microbial communities
with impacts on organic matter decomposition in streams. 相似文献
4.
Morphological and Proteomic Responses of Eruca sativa Exposed to Silver Nanoparticles or Silver Nitrate 总被引:1,自引:0,他引:1
Candida Vannini Guido Domingo Elisabetta Onelli Bhakti Prinsi Milena Marsoni Luca Espen Marcella Bracale 《PloS one》2013,8(7)
Silver nanoparticles (AgNPs) are widely used in commercial products, and there are growing concerns about their impact on the environment. Information about the molecular interaction of AgNPs with plants is lacking. To increase our understanding of the mechanisms involved in plant responses to AgNPs and to differentiate between particle specific and ionic silver effects we determined the morphological and proteomic changes induced in Eruca sativa (commonly called rocket) in response to AgNPs or AgNO3. Seedlings were treated for 5 days with different concentrations of AgNPs or AgNO3. A similar increase in root elongation was observed when seedlings were exposed to 10 mg Ag L1 of either PVP-AgNPs or AgNO3. At this concentration we performed electron microscopy investigations and 2-dimensional electrophoresis (2DE) proteomic profiling. The low level of overlap of differentially expressed proteins indicates that AgNPs and AgNO3 cause different plant responses. Both Ag treatments cause changes in proteins involved in the redox regulation and in the sulfur metabolism. These responses could play an important role to maintain cellular homeostasis. Only the AgNP exposure cause the alteration of some proteins related to the endoplasmic reticulum and vacuole indicating these two organelles as targets of the AgNPs action. These data add further evidences that the effects of AgNPs are not simply due to the release of Ag ions. 相似文献
5.
Noura El-Ahmady El-Naggar Nayera A. M. Abdelwahed 《Journal of microbiology (Seoul, Korea)》2014,52(1):53-63
Central composite design was chosen to determine the combined effects of four process variables (AgNO3 concentration, incubation period, pH level and inoculum size) on the extracellular biosynthesis of silver nanoparticles (AgNPs) by Streptomyces viridochromogenes. Statistical analysis of the results showed that incubation period, initial pH level and inoculum size had significant effects (P<0.05) on the biosynthesis of silver nanoparticles at their individual level. The maximum biosynthesis of silver nanoparticles was achieved at a concentration of 0.5% (v/v) of 1 mM AgNO3, incubation period of 96 h, initial pH of 9 and inoculum size of 2% (v/v). After optimization, the biosynthesis of silver nanoparticles was improved by approximately 5-fold as compared to that of the unoptimized conditions. The synthetic process of silver nanoparticle generation using the reduction of aqueous Ag+ ion by the culture supernatants of S. viridochromogenes was quite fast, and silver nanoparticles were formed immediately by the addition of AgNO3 solution (1 mM) to the cell-free supernatant. Initial characterization of silver nanoparticles was performed by visual observation of color change from yellow to intense brown color. UV-visible spectrophotometry for measuring surface plasmon resonance showed a single absorption peak at 400 nm, which confirmed the presence of silver nanoparticles. Fourier Transform Infrared Spectroscopy analysis provided evidence for proteins as possible reducing and capping agents for stabilizing the nanoparticles. Transmission Electron Microscopy revealed the extracellular formation of spherical silver nanoparticles in the size range of 2.15–7.27 nm. Compared to the cell-free supernatant, the biosynthesized AgNPs revealed superior antimicrobial activity against Gram-negative, Gram-positive bacterial strains and Candida albicans. 相似文献
6.
Liyan Yin Benjamin P. Colman Bonnie M. McGill Justin P. Wright Emily S. Bernhardt 《PloS one》2012,7(10)
The increasing commercial production of engineered nanoparticles (ENPs) has led to concerns over the potential adverse impacts of these ENPs on biota in natural environments. Silver nanoparticles (AgNPs) are one of the most widely used ENPs and are expected to enter natural ecosystems. Here we examined the effects of AgNPs on germination and growth of eleven species of common wetland plants. We examined plant responses to AgNP exposure in simple pure culture experiments (direct exposure) and for seeds planted in homogenized field soils in a greenhouse experiment (soil exposure). We compared the effects of two AgNPs–20-nm polyvinylpyrrolidine-coated silver nanoparticles (PVP-AgNPs) and 6-nm gum arabic coated silver nanoparticles (GA-AgNPs)–to the effects of AgNO3 exposure added at equivalent Ag concentrations (1, 10 or 40 mg Ag L−1). In the direct exposure experiments, PVP-AgNP had no effect on germination while 40 mg Ag L−1 GA-AgNP exposure significantly reduced the germination rate of three species and enhanced the germination rate of one species. In contrast, 40 mg Ag L−1 AgNO3 enhanced the germination rate of five species. In general root growth was much more affected by Ag exposure than was leaf growth. The magnitude of inhibition was always greater for GA-AgNPs than for AgNO3 and PVP-AgNPs. In the soil exposure experiment, germination effects were less pronounced. The plant growth response differed by taxa with Lolium multiflorum growing more rapidly under both AgNO3 and GA-AgNP exposures and all other taxa having significantly reduced growth under GA-AgNP exposure. AgNO3 did not reduce the growth of any species while PVP-AgNPs significantly inhibited the growth of only one species. Our findings suggest important new avenues of research for understanding the fate and transport of NPs in natural media, the interactions between NPs and plants, and indirect and direct effects of NPs in mixed plant communities. 相似文献
7.
The Actinomycete Gordonia amicalis HS-11 produced orange pigments when cultivated on n-hexadecane as the sole carbon source. When cells of this pigmented bacterium were incubated with 1 mM chloroauric acid (HAuCl4) or silver nitrate (AgNO3), pH 9.0, at 25 °C, gold and silver nanoparticles, respectively, were obtained in a cell associated manner. It was hypothesized that the pigments present in the cells may be mediating metal reduction reactions. After solvent extraction and High Performance Liquid Chromatography, two major pigments displaying UV–vis spectra characteristic of carotenoids were isolated. These were identified on the basis of Atmospheric Pressure Chemical Ionization Mass Spectrometry (APCI-MS) in the positive mode as 1′-OH-4-keto-γ-carotene (Carotenoid K) and 1′-OH-γ-carotene (Carotenoid B). The hydroxyl groups present in the carotenoids were eliminated under alkaline conditions and provided the reducing equivalents necessary for synthesizing nanoparticles. Cell associated and carotenoid stabilized nanoparticles were characterized by different analytical techniques. In vitro free radical scavenging activities of cells (control, gold and silver nanoparticle loaded), purified carotenoids and carotenoid stabilized gold and silver nanoparticles were evaluated. Silver nanoparticle loaded cells and carotenoid stabilized silver nanoparticles exhibited improved nitric oxide (NO) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activities compared to their control and gold counterparts. This paper thus reports cell associated nanoparticle synthesis by G. amicalis, describes for the first time the role of carotenoid pigments in metal reduction processes and demonstrates enhanced free radical scavenging activities of the carotenoid stabilized nanoparticles. 相似文献
8.
The interaction between peptide and silver nanoparticle surfaces has been increasingly of interest for bionanotechnology applications. To fully understand how to control such interactions, we have studied the optical properties of peptide-modified silver nanoparticles. However, the impacts of peptide binding motif upon the surface characteristics and physicochemical properties of nanoparticles remain not yet fully understood. Here, we have prepared sodium citrate-stabilized silver nanoparticles and coated with peptide IVD (ID3). These nanomaterials were characterized by UV-visible, transmission electron microscopy (TEM), and z-potential measurement. The results indicate that silver nanoparticles (AgNP)-peptide interface is generated using ID3 peptide and suggested that the reactivity of peptide is governed by the conformation of the bound peptide on the nanoparticle surface. The peptide-nanoparticle interactions could potentially be used to make specific functionality into the peptide capped nanomaterials and antibacterial applications. 相似文献
9.
In the present research silver nanoparticle was fabricated by chemical reduction of silver salt (Silver nitrate, AgNO3) solution. Sodium citrate was used as a reducer. The formation of silver nanoparticle was observed visually by color change
(greenish yellow). The surface plasmon resonance peak in absorption spectra of silver nanoparticle showed an absorption maximum
at 420 nm in UV-VIS spectrometry. The X-ray diffraction pattern showed the presence of sharp reflections at 111, 200, 220,
and 311. This would indicate the presence of silver nanoparticle. The scanning electron micrograph revealed that the average
size of silver nanoparticle was 21.22 ± 5.17 nm. Silver nanoparticle exhibited better antimicrobial activity against Staphylococcus aureus than the other bacterial pathogens. The correlation coefficient between silver nanoparticles and selected bacterial pathogens
revealed that there is a strong negative correlation with Escherichia coli, S. aureus and Klebsiella pneumonia (r = −0.975, −0.993, and −0.998, respectively). 相似文献
10.
Non-tuberculous mycobacteria are a threat to human health, gaining entry to the body through contaminated water systems, where they form persistent biofilms despite extensive attempts at disinfection. Silver is a natural antibacterial agent and in nanoparticle form activity is increased by a high surface area. Silver nanoparticles (AgNPs) have been used as alternative disinfectants in circulating water systems, washing machines and even clothing. However, nanoparticles, like any other antibiotic that has a pervasive durable presence, carry the risk of creating a resistant population. In this study Mycobacterium smegmatis strain mc2155 was cultured in AgNP enriched agar such that only a small population survived. Surviving cultures were isolated and re-exposed to AgNPs and AgNO3 and resistance to silver was compared to a negative control. After only a single exposure, mutant M. smegmatis populations were resistant to AgNPs and AgNO3. Further, the silver resistant mutants were exposed to antibiotics to determine if general resistance had been conferred. The minimum inhibitory concentration of isoniazid was four times higher for silver resistant mutants than for strain mc2155. However, core resistance was not conferred to other toxic metal ions. The mutants had lower resistance to CuSO4 and ZnSO4 than the mc2155 strain. 相似文献
11.
Werther Guidi Nissim Frederic E. Pitre Hafssa Kadri Dominic Desjardins Michel Labrecque 《International journal of phytoremediation》2014,16(7-8):660-670
This is a preliminary hydroponic study to test willow sensitivity to silver nitrate, a highly toxic chemical compound. We grew willow cuttings for a period of three weeks in the presence of increasing AgNO3 concentrations and assessed the response in terms of growth and physiology. We found that AgNO3 is generally extremely harmful to willow. AgNO3 concentration as high as 0.027 μM may result in a significant reduction of biomass productivity and a decrease in stomatal conductance over the first week of exposure. However, willows seem able to adapt to high AgNO3 concentrations on a longer timeline. 相似文献
12.
Nilda Vanesa Ayala-Núñez Humberto H. Lara Villegas Liliana del Carmen Ixtepan Turrent Cristina Rodríguez Padilla 《NanoBioTechnology》2009,5(1-4):2-9
Silver nanoparticles, which are being used increasingly as antimicrobial agents, may extend its antibacterial application to methicillin-resistant Staphylococcus aureus (MRSA), the main cause of nosocomial infections worldwide. To explore the antibacterial properties of silver nanoparticles against MRSA, the present work includes an analysis of the relation between nanosilver effect and MRSA’s resistance mechanisms, a study of the size dependence of the bactericidal activity of nanosilver and a toxicity assessment of nanoparticles against epithelial human cells. Minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and MBC/MIC ratio of silver nanoparticles were quantified by using a luciferase-based assay. The cytotoxic effect (CC50 and CC90) of three different nanosilver sizes (10, 30–40, and 100 nm) were assessed in HeLa cells by a similar method. The therapeutic index was used as an indicator of nanosilver overall efficacy and safety. Silver nanoparticles inhibited bacterial growth of both MRSA and non-MR S. aureus in a bactericidal rather than a bacteriostatic manner (MBC/MIC ratio?≤?4). Silver nanoparticle’s therapeutic index varied when nanoparticle’s size diminished. At the same dose range, 10 nm nanoparticles were the most effective since they did not affect HeLa’s cell viability while inhibiting a considerable percentage of MRSA growth. Silver nanoparticles are effective bactericidal agents that are not affected by drug-resistant mechanisms of MRSA. Nanosilver size mediates MRSA inhibition and the cytotoxicity to human cells, being smaller nanoparticles the ones with a better antibacterial activity and nontoxic effect. 相似文献
13.
Yu Juan Zhang 《Plasmonics (Norwell, Mass.)》2011,6(2):393-397
Efficient conversion of absorbed light to heat energy and strong scattering by gold and silver nanoparticles suggest these
nanoparticles as the agents of heating and imaging. Absorption efficiency and scattering efficiency of gold and silver nanoparticles
were studied through numerical simulation using the discrete dipole approximation method. This study shows that the size of
gold and silver nanoparticles can effect gold and silver nanoparticles’ absorption efficiency and scattering efficiency. The
gold nanoparticle is found to possess the maximum absorption efficiency when the size of gold nanoparticle is 50 nm and the
incident wavelength is 540 nm, and the increasing scattering efficiency with the increasing size of gold nanoparticle in the
medium, and refractive index of the medium is around 1.33. However, the silver nanoparticle owns the maximum absorption efficiency
when the size of silver nanoparticle is 20 nm and the incident wavelength is 396 nm, and the maximum scattering efficiency
when the size of silver nanoparticle is 30 nm and the incident wavelength is 410 nm in the same medium. The conditions for
achieving the maximum adsorption efficiency and scattering efficiency of gold and silver nanoparticle can be used for heating
and imaging using visible and near-infrared light. 相似文献
14.
In this paper, the enhancement of thermal properties of polymer-coated silver nanoparticles by the addition of plasmid DNA is described. Nanoparticles of noble metals such as gold and silver possess specific characteristics by virtue of their quantum size effects. Therefore, noble metal nanoparticles are used for chemical sensing and biosensing applications based on their localized surface plasmon resonance absorption that can be measured in the visible region. The polyvinylpyrrolidone (PVP)-coated noble metal nanoparticles, in particular, with high dispersion ability in water, offer several advantages for sensing applications. However, some difficulties are encountered in the use of these PVP-coated noble metal nanoparticles for sensing applications due to their poor thermal properties. To improve the thermal properties of PVP-coated noble metal nanoparticles, we found that the addition of plasmid DNA to PVP-coated silver nanoparticles enhances their thermal properties due to good thermal stability of DNA. The introduction of plasmid DNA into PVP-coated silver nanoparticle dispersion enhanced the thermal properties through the formation of a complex between the nanoparticles and plasmid DNA. Furthermore, other polymers such as proteins and polyethylene glycol did not enhance the thermal properties of PVP-coated silver nanoparticles. Thus, the PVP-coated silver nanoparticle–plasmid DNA complex with enhanced thermal properties has a great potential for use in medical and drug delivery applications. 相似文献
15.
Silver in various forms has long been recognized for antimicrobial properties, both in biomedical devices and in eyes. However,
soluble drugs used on the ocular surface are rapidly cleared through tear ducts and eventually ingested, resulting in decreased
efficacy of the drug on its target tissue and potential concern for systemic side effects. Silver nanoparticles were studied
as a source of anti-microbial silver for possible controlled-release contact lens controlled delivery formulations. Silver
ion release over a period of several weeks from nanoparticle sources of various sizes and doses was evaluated in vitro against
Pseudomonas aeruginosa strain PAO1. Mammalian cell viability and cytokine expression in response to silver nanoparticle exposure is evaluated using
corneal epithelial cells and eye-associated macrophages cultured in vitro in serum-free media. Minimal microcidal and cell
toxic effects were observed for several silver nanoparticle suspensions and aqueous extraction times for bulk total silver
concentrations commensurate with comparative silver ion (e.g., ) toxicity. This indicates that (1) silver particles themselves in these size ranges (20–60 nm diameter) are not microcidal
under conditions tested, and (2) insufficient silver ion is generated from these particles at these silver ion-equivalent
loadings to produce observable biological effects compared to silver ions in these in vitro assays. This is consistent with
confounding literature describing both efficacy and lack of microcidal effects for silver nanoparticles, depending on milieu,
surface oxide properties, and size. If dosing allows substantially increased silver particle loading in the lens to produce
sufficient pathogen-toxic silver ions and/or particle-microbe direct contact, the bactericidal efficacy of silver nanoparticles
in vitro could possibly limit bacterial colonization problems associated with extended-wear contact lenses. 相似文献
16.
Jose?Luis?Elechiguerra Justin?L?Burt Jose?R?Morones Alejandra?Camacho-Bragado Xiaoxia?Gao Humberto?H?Lara Miguel?Jose?Yacaman
The interaction of nanoparticles with biomolecules and microorganisms is an expanding field of research. Within this field,
an area that has been largely unexplored is the interaction of metal nanoparticles with viruses. In this work, we demonstrate
that silver nanoparticles undergo a size-dependent interaction with HIV-1, with nanoparticles exclusively in the range of
1–10 nm attached to the virus. The regular spatial arrangement of the attached nanoparticles, the center-to-center distance
between nanoparticles, and the fact that the exposed sulfur-bearing residues of the glycoprotein knobs would be attractive
sites for nanoparticle interaction suggest that silver nanoparticles interact with the HIV-1 virus via preferential binding
to the gp120 glycoprotein knobs. Due to this interaction, silver nanoparticles inhibit the virus from binding to host cells,
as demonstrated in vitro. 相似文献
17.
Mostafa Khajeh 《Biological trace element research》2010,138(1-3):337-345
In this study, silver nanoparticles were prepared and used for separation and preconcentration of manganese from biological samples. The technical feasibility of silver nanoparticles for manganese removal was investigated under batch studies. The effects of different parameters such as pH of solution, time (t), amounts of PAN (E), and silver nanoparticles (N) on the adsorption of manganese by silver nanoparticle were investigated using factorial design and response surface methodology based on Box–Behnken design. Thermodynamic parameters indicate the adsorption process to be exothermic. The limit of detection of the proposed method followed by inductively coupled plasma was found to be 0.08?µg L?1. The method was applied to determine of manganese in biological samples. 相似文献
18.
We discovered that Yeast Extract Mannitol (YEM) medium possessed immense potential to generate silver nanoparticles from AgNO3 upon autoclaving, which was evident from (i) alteration in color of the medium; (ii) peak at ∼410 nm in UV-Vis spectrum due to surface plasmon resonance specific to silver nanoparticles; and (iii) TEM investigations. TEM coupled with EDX confirmed that distinct nanoparticles were composed of silver. Yeast extract and mannitol were key components of YEM medium responsible for the formation of nanoparticles. PXRD analysis indicated crystalline geometry and Ag/Ag2O phases in nanoparticles generated with YEM medium, yeast extract and mannitol. Our investigations also revealed that both mannitol and yeast extract possessed potential to convert ∼80% of silver ions in 0.5 mM AgNO3 to nanoparticles, on autoclaving for 30 min at 121°C under a pressure of 1.06 kg/cm2. Addition of filter sterilized AgNO3 under ambient conditions to pre-autoclaved YEM medium and yeast extract brought about color change due to the formation of silver nanoparticles, but required prolonged duration. In general, even after 72 h intensity of color was significantly less than that recorded following autoclaving. Silver nanoparticles formed at room temperature were more heterogeneous compared to that obtained upon autoclaving. In summary, our findings demonstrated that (i) YEM medium and its constituents promote synthesis of silver nanoparticles; and (ii) autoclaving enhances rapid synthesis of silver nanoparticles by YEM medium, yeast extract and mannitol. 相似文献
19.
The standard nanofabrication toolkit includes techniques primarily aimed at creating 2D patterns in dielectric media. Creating metal patterns on a submicron scale requires a combination of nanofabrication tools and several material processing steps. For example, steps to create planar metal structures using ultraviolet photolithography and electron-beam lithography can include sample exposure, sample development, metal deposition, and metal liftoff. To create 3D metal structures, the sequence is repeated multiple times. The complexity and difficulty of stacking and aligning multiple layers limits practical implementations of 3D metal structuring using standard nanofabrication tools. Femtosecond-laser direct-writing has emerged as a pre-eminent technique for 3D nanofabrication.1,2 Femtosecond lasers are frequently used to create 3D patterns in polymers and glasses.3-7 However, 3D metal direct-writing remains a challenge. Here, we describe a method to fabricate silver nanostructures embedded inside a polymer matrix using a femtosecond laser centered at 800 nm. The method enables the fabrication of patterns not feasible using other techniques, such as 3D arrays of disconnected silver voxels.8 Disconnected 3D metal patterns are useful for metamaterials where unit cells are not in contact with each other,9 such as coupled metal dot10,11or coupled metal rod12,13 resonators. Potential applications include negative index metamaterials, invisibility cloaks, and perfect lenses.In femtosecond-laser direct-writing, the laser wavelength is chosen such that photons are not linearly absorbed in the target medium. When the laser pulse duration is compressed to the femtosecond time scale and the radiation is tightly focused inside the target, the extremely high intensity induces nonlinear absorption. Multiple photons are absorbed simultaneously to cause electronic transitions that lead to material modification within the focused region. Using this approach, one can form structures in the bulk of a material rather than on its surface.Most work on 3D direct metal writing has focused on creating self-supported metal structures.14-16 The method described here yields sub-micrometer silver structures that do not need to be self-supported because they are embedded inside a matrix. A doped polymer matrix is prepared using a mixture of silver nitrate (AgNO3), polyvinylpyrrolidone (PVP) and water (H2O). Samples are then patterned by irradiation with an 11-MHz femtosecond laser producing 50-fs pulses. During irradiation, photoreduction of silver ions is induced through nonlinear absorption, creating an aggregate of silver nanoparticles in the focal region. Using this approach we create silver patterns embedded in a doped PVP matrix. Adding 3D translation of the sample extends the patterning to three dimensions. 相似文献
20.
Bai Hong-Juan Yang Bin-Sheng Chai Chun-Jing Yang Guan-E. Jia Wan-Li Yi Zhi-Ben 《World journal of microbiology & biotechnology》2011,27(11):2723-2728
The use of microorganisms in the synthesis of nanoparticles emerges as an eco-friendly and exciting approach. In this study,
silver nanoparticles were successfully synthesized from AgNO3 by reduction of aqueous Ag+ ions with the cell filtrate of Rhodobacter sphaeroides. Nanoparticles were characterized by means of UV–vis absorption spectroscopy, X-Ray Diffraction (XRD), transmission electron
microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). Crystalline nature of the nanoparticles in
the fcc structure are confirmed by the peaks in the XRD pattern corresponding to (111), (200), (220) and (311) planes, bright
circular spots in the selected are a electron diffraction (SAED) and clear lattice fringes in the high-resolution TEM image.
Also, the size of silver nanoparticles was controlled by the specific activity of nitrate reductase in the cell filtrate. 相似文献