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1.
The physical mechanisms of metallic nanoparticles formation by laser technology were studied. The system air/Au film/glass
was irradiated by laser at the conditions of surface plasmon resonance. A surface electromagnetic wave was excited in Kretchmann
configuration by the fundamental and second harmonics of the Q-switched YAG/Nd +3 laser with pulse power density close to the threshold of melting. Nanostructuring of Au film was observed only for the second
harmonic ( λ = 0.532 μm) irradiation at the surface plasmon polariton resonance (SPR) conditions. Estimations were done using the interference
model of the differently directed plasmon polariton waves excited by a surface electromagnetic wave on the metal surface.
It was shown that a regular pattern of locally heated spots can be formed in a metallic film by pulsed laser irradiation.
The spatial distribution of this pattern is close to the period of interference. The observed effect of laser nanofragmentation
is explained by the self-organization of plasmon polariton subsystem in the process of Au nanoparticles formation at high
laser intensity levels. These methods open new possibilities for nanostructured surfaces formation utilizing simple self-organization
processes. 相似文献
2.
Nanocomposite (NC) thin films with noble metal nanoparticles embedded in a dielectric material show very attractive plasmonic
properties due to dielectric and quantum confinement effects. For single component nanoparticles (NPs), the plasmon resonance
frequency can only be tuned in a narrow range. Much interest aroused in bimetallic nanoparticles (BNPs), however many wet
chemical approaches do not allow large variation of the NP alloy composition and filling factor. Here, we report a vapor phase
co-deposition method to produce polymer–metal NCs with embedded Ag 1 − x
Cu
x
alloy particles. The method allows production of NPs with controlled alloy composition ( x), metal filling ( f) and nanostructure in a protecting Teflon AF matrix. The nanostructure size and shape were characterized by transmission
electron microscope. Energy dispersive X-ray spectroscopy was used to determine x and f. The optical properties and the position of surface plasmon resonances were studied by UV–Vis spectroscopy. The plasmon resonances
can be tuned over a large range of the visible spectrum associated with the change in x, f, and nanostructure. For low filling factors and small particle sizes, only one resonance peak was observed. This is attributed
to enhanced miscibility at the nanoscale. Double plasmon resonances were seen for larger particle sizes in accord with phase
separation expected from the bulk phase diagram and were explained in terms of the formation of core-shell structures with
Cu core and Ag shell. Changes upon annealing at 200 °C are also reported. 相似文献
3.
In hot water (50–60°C), polyvinyl alcohol (PVA) molecules have coordination reaction with Au 3+ cations, forming an Au 3+-PVA polymer complex. In the proposed model reaction in small templates, the complex converts to Au 0 capping in PVA molecules. Adding sucrose (5–10 times the PVA in mass) in a typical batch promotes Au 3+→Au 0 reaction, showing absorption coefficient α in Au 0 surface plasmon band to be enhanced as much as 28 times the value in reaction with PVA. The band shifts at 547 nm from 566 nm ( α = 21.4 cm −1 mol −1) in the PVA sample. Drying Au 0-PVA/sucrose (2–5 wt% Au 0) colloid at 60–70°C and then heating at 450°C in air burns off the organic part, leaving behind a light ash colored powder with Au 0 nanoprisms or nanofibrils (∼30 nm average width). X-ray diffractogram has six reflections, (111), (200), (220), (311), (222), and (400), of Fm3 m fcc Au 0 of lattice parameter a = 0.4080 nm. The powder has photoluminescence in transversal and longitudinal Au 0 plasmon bands of 535 and 585 nm, respectively. 相似文献
4.
Water dispersible zinc sulfide quantum dots (ZnS QDs) with an average diameter of 2.9 nm were synthesized in an environment
friendly method using chitosan as stabilizing agent. These nanocrystals displayed characteristic absorption and emission spectra
having an absorbance edge at 300 nm and emission maxima ( λ
emission) at 427 nm. Citrate-capped silver nanoparticles (Ag NPs) of ca. 37-nm diameter were prepared by modified Turkevich process.
The fluorescence of ZnS QDs was significantly quenched in presence of Ag NPs in a concentration-dependent manner with K
sv value of 9 × 10 9 M −1. The quenching mechanism was analyzed using Stern–Volmer plot which indicated mixed nature of quenching. Static mechanism
was evident from the formation of electrostatic complex between positively charged ZnS QDs and negatively charged Ag NPs as
confirmed by absorbance study. Due to excellent overlap between ZnS QDs emission and surface plasmon resonance band of Ag
NPs, the role of energy transfer process as an additional quenching mechanism was investigated by time-resolved fluorescence
measurements. Time-correlated single-photon counting study demonstrated decrease in average lifetime of ZnS QDs fluorescence
in presence of Ag NPs. The corresponding F?rster distance for the present QD–NP pair was calculated to be 18.4 nm. 相似文献
5.
A subwavelength plasmonic laser structure based on a metal-dielectric-metal nanocavity is proposed and numerically simulated
by using the finite difference time domain method with perfectly matched layer absorbing boundary condition. The nanocavity
model and gain analysis are respectively given. The simulation results show that the losses within the nanocavity (including
surface plasmon losses) can be compensated by the gain material and the threshold gain of the laser is about 1.5 × 10 3 cm −1 with the peak wavelength around 1,550 nm. The new device would be an important step toward a fully integrated surface plasmon
circuits. 相似文献
6.
We experimentally demonstrate a large third-order nonlinear susceptibility for a nanocomposite made of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]
doped with silver nanoprisms at 1,550 nm, achieved based on nonlinearity enhancement associated with strong surface plasmon
resonance. The nonlinear refractive index reaches −1.37 × 10 −12 m 2/W, which is three orders of magnitude larger than that of pure poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene].
An ultrafast response time of 18.7 ps is reached using fast energy transfer from excited states of organic molecules to silver
nanoprisms. A low-power and ultrafast nanocomposite photonic crystal all-optical switching is also realized. 相似文献
7.
In this paper, we report on luminescence and absorbance effects of Er +3:Au-doped tellurite glasses synthesized by a melting-quenching and heat treatment technique. After annealing times of 2.5,
5.0, 7.5, and 10.0 h, at 300 °C, the gold nanoparticles (GNP) effects on the Er +3 are verified from luminescence spectra and the corresponding levels lifetime. The localized surface plasmon resonance around
800 nm produced a maximum fluorescence enhancement for the band ranging from 800 to 840 nm, corresponding to the transitions
4H 11/2 → 4I 13/2 (805 nm) and 4S 3/2 → 4I 13/2 (840 nm), with annealing time till 7.5 h. The measured lifetime of the levels 4H 11/2 and 4S 3/2 confirmed the lifetime reduction due to the energy transfer from the GNP to Er +3, causing an enhanced photon emission rate in these levels. 相似文献
9.
The oscillating drop surfactometer (ODS) measures surface tension (γ) and energy dissipation (damping constant b) of surfactant on a 1 μl sample. γ is obtained from the period of oscillation and b from its free decay or from the phase shift slope in resonance. After calibration with substances with different γ, corrections
were made for capillary fixation and loss of mass by evaporation. Surface active substances are delivered from liposomes in
the interior (subphase) or injected from outside, with microdrops (180 pl each) of solution. As an application example, we
have investigated surfactant extract and pure phospholipid. In minutes after formation of a drop containing a diluted Survanta
suspension, γ decreases by 20 mN/m, while b increases three-fold. This effect, assigned to spontaneous adsorption from liposomes to the surface, is not seen with pure
dipalmitoylphosphatidylcholine (DPPC) under our conditions. However, microdrop injection of DPPC triggers a rapid decrease
of γ and a delayed strong increase in b. The effect is modulated by DPPC in the subphase and by cholesterol. Investigations with l-α-lysophosphatidylcholine show the high sensitivity of the ODS technique in the determination of the energy dissipation at
air-liquid boundary surfaces. Although the ODS is limited to applications with γ > 15 mN m −1, it offers the advantage to give, with small samples and within seconds, a simultaneous readout of both surface tension γ
and the parameter b, as a measure of surface viscosity.
Received: 22 October 1999 / Revised version: 24 January 2000 / Accepted: 24 January 2000 相似文献
10.
We report the deposition of highly uniform thin silver films on plastic materials using a wet-chemistry method, suitable for
surface plasmon-coupled emission (SPCE). This approach is reproducible for diverse low-cost applications and versatile to
generate silver surfaces on various plastics substrates. An oxygen plasma pretreatment of the plastic provides for rapid silvering,
leading to a 47-nm-thick continuous film for SPCE applications. The surface smoothness and thickness of the films have been
estimated using atomic force microscope. The higher refractive index of polycarbonate, resulted in an SPCE angle of θ
F = 47 0 for Rhodamine B, compared to glass ( θ
F = 50 0). The current study presents details on film deposition conditions, appropriate choice of index matching fluids, substrates,
and light sources that play a vital role to augment SPCE emission intensity. 相似文献
11.
Creatinine-functionalized AuNPs (CreAuNPs) were prepared via a facile one-pot reaction of sodium borohydride and the mixture solution of gold(III) chloride trihydrate and creatinine. The morphology and surface state of as-prepared CreAuNPs were characterized by transmission electron microscopy and Fourier transform infrared spectroscopy. All the results demonstrated that CreAuNPs were spherical with an average diameter of about 4.2 nm, and creatinine existed on the surface of AuNPs via Au-N interaction. The as-prepared CreAuNPs exhibited a weak surface plasmon resonance (SPR) absorption owing to their small size, while the addition of Ag+ could induce the aggregation of spherical CreAuNPs, producing a strong SPR absorption and apparent color change from colorless to purple owing to the surface plasmon coupling. On this basis, a colorimetric assay for Ag+ was established. The assay could selectively detect Ag+ as low as 1 μM with a good linearity in the range of 5–40 μM. Additionally, the assay was successfully applied to the determination of Ag+ in tap water, lake water, and river water samples. 相似文献
12.
Human FcγRI (CD64) is an integral membrane glycoprotein functioning as a high-affinity receptor binding to monomeric IgG.
In this study, the extracellular region of FcγRI, which is the actual part that interacts with IgG, was expressed as aglycosylated
recombinant human FcγRI (rhFcγRI) in Escherichia coli. The soluble form of aglycosylated rhFcγRI was expressed in the periplasm of E. coli. The production of soluble aglycosylated rhFcγRI was increased by low induction levels. Furthermore, this production was
increased by low translational efficiency, controlled by modification of the putative region between the ribosome binding
site and initiation codon of rhFcγRI fusing signal peptide (MalE, PelB, or TorT) of the expression vector. By the optimization
of induction and translational efficiency, the production of soluble aglycosylated rhFcγRI was up to approximately 0.8 mg/l
of culture medium. Surface plasmon resonance analysis revealed that the binding affinities of aglycosylated rhFcγRI for human
IgG1 (equilibrium dissociation constant K
D = [1.7 ± 0.2] × 10 −10 M) and IgG3 ( K
D = [1.1 ± 0.2] × 10 −10 M) were similar to those of glycosylated rhFcγRI. 相似文献
13.
The influence of substrate, light intensity, temperature and growth phase on the dry weight per unit biovolume of both living
Phormidium autumnale trichomes and living single cells was investigated microinterferometrically. With a Mach–Zehnder Interference Microscope,
both the interference-stripe-field method and the phase-shift method were used to measure the optical path differences (OPD)
of cells and trichomes. To calculate the cellular dry weight of trichomes, the trichome diameters have to be measured. Widths
between 4 and 7 μm were determined. Thick trichomes are characteristic for growth on agar-solidified medium, whereas this
was observed in single cases only from trichomes growing on soil surfaces. A reliable prediction of trichome width from growth
conditions is not possible. The dry weights per unit biovolume (fg μm −3) are independent of the studied parameters during the exponential growth phase (296 ± 22 fg μm −3) with exception of the agar-based cultures growing at low light intensity (259 ± 16 fg μm −3). During the stationary phase, dry weights per unit biovolume increase independently of growth conditions (353 ± 39 fg μm −3). Two separate factors of 0.14 and 0.17 for converting biovolume (mm 3) of cells to milligrams carbon could be determined by comparing the growth phase and stationary phase-dependent average values
of dry weights per unit biovolume, respectively. These conversion factors could be used as species-specific factors for Phormidium growing on soil surfaces. Irrespective of the method, both the stripe-field and phase-shift method gave similar results.
However, the phase-shift method measured lower variances of values. Additionally, detailed quantifying investigations of structures
within cells are possible. Thus, the phase-shift method could be a powerful analytical tool in, e.g., ecotoxicological monitoring
analyses. 相似文献
14.
Potential uptake and clearance rates of fluorescent microspheres (FM) from 0.25 to 4.05 μm diameter were determined for the
non-loricate ciliate Pseudocohnilembus sp. from Antarctic sea ice. The percentage of ciliate cells that ingested FM after 20 min incubation decreased with increasing
particle diameter. Pseudocohnilembus sp. ingested FM between 0.25 and 4.05 μm in diameter. We offered FM at concentrations less than natural concentrations for
plankton plus detrital material and obtained clearance rates less than those previously reported for bactivorous ciliates.
Clearance rates were 3.6–5.4 nl cell −1 h −1 for FM 0.5 and 1 μm diameter, respectively, but decreased to 1.1 nl cell −1 h −1 for 1.97 μm diameter and 1.4 nl cell −1 h −1 for 4.05-μm-diameter FM. Clearance and uptake rates of FM 0.5 and 1 μm diameter indicate that Pseudocohnilembus sp. principally grazes on bacteria-sized particles. However, it can also ingest organisms as large as nanoplankton and may
graze particles as small as femtoplankton and colloids. This suggests a feeding strategy that may suit the temporal and spatial
changes in food availability in the sea-ice habitat.
Accepted: 13 August 2000 相似文献
15.
The present research work was aimed to formulate clotrimazole encapsulated Cavamax W7 composite ethosomes by injection method
for improved delivery across epidermis. 3 2 factorial design was used to design nine formulations (F1-F9) and compared with ethosomal formulations (F10-F12). F9 with
vesicle size of 202.8 ± 4.8 nm, highest zeta potential (−83.6 ± 0.96 mV) and %EE of 98.42 ± 0.15 was selected as optimized
composite ethosome and F12 as reference ethosomal formulation. As revealed by transmission electron microscopy F9 vesicles
were more condensed, uniformly spherical in shape than F12 vesicles. Vesicular stability studies indicated F9 to be more stable
as compared to F12. Both F9 and F12 were incorporated in carbopol 934 gel base to get G1–G8 gel formulations and evaluated
for in vitro skin permeability. Cavamax W7 composite ethosomal optimized gel (G5) showed higher in vitro percent cumulative drug permeation (88.53 ± 2.10%) in 8 h and steady state flux ( J
ss) of 3.39 ± 1.45 μg/cm 2/min against the J
ss of 1.57 ± 0.23 μg/cm 2/min for ethosomal gel (G1) and 1.13 ± 0.06 μg/cm 2/min for marketed formulation. The J
ss flux of G5 was independent of amount of drug applied/unit area of skin. In vivo confocal laser scanning microscopic study of G5 depicted uniform and deeper penetration of rhodamine B (marker) in epidermis
from Cavamax W7 composite ethosomal gel in comparison to G1. Finally, G5 demonstrated better ( p < 0.05) antifungal activity against Candida albicans and Aspergillus niger than G1 thus, signifying that Cavamax W7 composite ethosomes present a superior stable and efficacious vesicular system than
ethosomal formulation for topical delivery of clotrimazole. 相似文献
16.
Based on anti-idiotypic network theory in light of the need for new antifungal drugs, we attempted to identify biologically
active fragments from HM-1 yeast killer toxin and its anti-idiotypic antibody and to compare their potency as an antifungal
agent. Thirteen overlapping peptides from HM-1 killer toxin and six peptides from its anti-idiotypic single-chain variable
fragment (scFv) antibodies representing the complementarity determining regions were synthesized. The binding affinities of
these peptides were investigated and measured by Dot blot and surface plasmon resonance analysis and finally their antifungal
activities were investigated by inhibition of growth, colony forming unit assay. Peptide P6, containing the potential active
site of HM-1 was highly capable of inhibiting the growth of Saccharomyces cerevisiae but was less effective on pathogenic fungi. However, peptide fragments derived from scFv antibody exerted remarkable inhibitory
effect on the growth of pathogenic strains of Candida and Cryptococcus species in vitro. One scFv-derived decapeptide (SP6) was selected as the strongest killer peptide for its high binding affinity
and antifungal abilities on both Candida and Cryptococcus species with IC 50 values from 2.33 × 10 −7 M to 36.0 × 10 −7 M. SP6 peptide activity was neutralized by laminarin, a β-1,3-glucan molecule, indicating this peptide derived from scFv
anti-idiotypic antibody retains antifungal activity through interaction with cell wall β-glucan of their target fungal cells.
Experimental evidence strongly suggested the possibility of development of anti-idiotypic scFv peptide-based antifungal agents
which may lead to improve therapeutics for the management of varieties of fungal infections. 相似文献
18.
In the medium of H 2SO 4 and in the presence of TiO 2+, gold nanoparticles in size of 10 nm exhibited a weak surface plasmon resonance scattering (SPRS) peak at 775 nm. Upon addition
of trace H 2O 2, the yellow complex [TiO(H 2O 2)] 2+ formed that cause the gold nanoparticles aggregations to form bigger gold nanoparticle clusters in size of about 900 nm,
and the SPRS intensity at 775 nm ( I) enhanced greatly. The enhanced intensity Δ I was linear to the H 2O 2 concentration in the range of 0.025–48.7 μg/mL, with a detection limit of 0.014 μg/mL H 2O 2. This SPRS method was applied to determining H 2O 2 in water samples with satisfactory results. 相似文献
19.
Photodynamic inactivation is a new promising approach to treat bacterial infections. Usually, the evaluation of the efficacy
of this method is done through time-consuming and labor-intensive microbiological test methods. This paper describes the development
and implementation of an optical method to evaluate the photodynamic inactivation of bacteria based on non-invasive diffuse
reflectance measurements. Five Staphylococcus aureus cultures and 15 mice have been used in this study. A skin lesion was created on the back of all animals, and it was contaminated
with S. aureus (5.16 ± 0.013 log CFU/ml). Toluidine Blue O ( c = 8.67 × 10 − 3 M) has been used as a photosensitiser agent. The bacterial cultures and animals were exposed to laser radiation ( λ = 635 nm, P = 15 mW, DE = 8.654 J/cm 2) for 20 min. The photodynamic inactivation of bacteria was monitored by acquiring the wounds’ reflection spectra at different
time points and by microbiological exams on the bioptical material. The good correlation between the diffuse reflectance and
colony-forming units demonstrates the value of this optical method based on diffuse reflectance measurements as a rapid technique
to monitor photodynamic bacterial inactivation. 相似文献
20.
It has been demonstrated that inhaled fine ( d < 2.5 μm) and ultrafine ( d < 100 nm) particles produce more severe toxicity than coarse particles. Some recent data support the concept that the central
nervous system (CNS) may be a target for the inhaled fine particulates. This work describes initial observation of the transport
of intranasally instilled fine ferric oxide (Fe 2O 3) particles in animal brain. The iron micro-distribution and chemical state in the mice olfactory bulb and brain stem on day
14 after intranasal instillation of fine Fe 2O 3 particle (280 ± 80 nm) suspension at a single dose of 40 mg/kg body weight were analyzed by synchrotron radiation x-ray fluorescence
and x-ray absorption near-edge structure (XANES). The micro-distribution map of iron in the olfactory bulb and brain stem
shows an obvious increase of Fe contents in the olfactory nerve and the trigeminus of brain stem, suggesting that Fe 2O 3 particles were possibly transported via uptake by sensory nerve endings of the olfactory nerve and trigeminus. The XANES
results indicate that the ratios of Fe (III)/Fe (II) were increased in the olfactory bulb and brain stem. The further histopathological
observation showed that the neuron fatty degeneration occurred in the CA3 area of hippocampus. Such results imply an adverse
impact of inhalation of fine Fe 2O 3 particles on CNS. 相似文献
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