共查询到20条相似文献,搜索用时 15 毫秒
1.
In this work, the fungus Penicillium was used for rapid extra-/intracellular biosynthesis of gold nanoparticles. AuCl4
− ions reacted with the cell filtrate of Penicillium sp. resulting in extracellular biosynthesis of gold nanoparticles within 1 min. Intracellular biosynthesis of gold nanoparticles
was obtained by incubating AuCl4
− solution with fungal biomass for 8 h. The gold nanoparticles were characterized by means of visual observation, UV–Vis absorption
spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy-dispersive
X-ray spectroscopy (EDX). The extracellular nanoparticles exhibited maximum absorbance at 545 nm in UV–Vis spectroscopy. The
XRD spectrum showed Bragg reflections corresponding to the gold nanocrystals. TEM exhibited the formed spherical gold nanoparticles
in the size range from 30 to 50 nm with an average size of 45 nm. SEM and TEM revealed that the intracellular gold nanoparticles
were well dispersed on the cell wall and within the cell, and they are mostly spherical in shape with an average diameter
of 50 nm. The presence of gold was confirmed by EDX analysis. 相似文献
2.
Uğur Tamer İsmail H. Boyacı Erhan Temur Adem Zengin İlker Dincer Yalçın Elerman 《Journal of nanoparticle research》2011,13(8):3167-3176
The preparation and application of rod-shaped core–shell structured Fe3O4–Au nanoparticles for immunomagnetic separation and sensing were described for the first time with this study. To synthesize
magnetic gold nanorod particles, the seed-mediated synthetic method was carried out and the resulting nanoparticles were characterized
with transmission electron microscopy (TEM), ultraviolet visible spectroscopy (UV–Vis), energy-dispersive X-ray (EDX), and
X-ray diffraction (XRD). Magnetic properties of the nanoparticles were also examined. Characterization of the magnetic gold
nanorod particles has proven that the resulting nanoparticles were composed of Fe3O4 core and the gold shell. The rod-shaped gold-coated iron nanoparticles have an average diameter of 16 ± 2 nm and an average
length of about 50 ± 5 nm (corresponding aspect ratio of 3). The saturation magnetization value for the magnetic gold nanorod
particles was found to be 37 emu/g at 300 K. Rapid and room temperature reaction synthesis of magnetic gold nanorod particles
and subsequent surface modification with E. coli antibodies provide immunomagnetic separation and SERS application. The analytical performance of the SERS-based homogenous
sandwich immunoassay system with respect to linear range, detection limit, and response time is also presented. 相似文献
3.
Metallic gold nanoparticles have been synthesized by the reduction of chloroaurate anions [AuCl4]− solution with hydrazine in the aqueous starch and ethylene glycol solution at room temperature and at atmospheric pressure.
The characterization of synthesized gold nanoparticles by UV–vis spectroscopy, high resolution transmission electron microscopy
(HRTEM), electron diffraction analysis, X-ray diffraction (XRD), and X-rays photoelectron spectroscopy (XPS) indicate that
average size of pure gold nanoparticles is 3.5 nm, they are spherical in shape and are pure metallic gold. The concentration
effects of [AuCl4]− anions, starch, ethylene glycol, and hydrazine, on particle size, were investigated, and the stabilization mechanism of Au
nanoparticles by starch polymer molecules was also studied by FT-IR and thermogravimetric analysis (TGA). FT-IR and TGA analysis
shows that hydroxyl groups of starch are responsible of capping and stabilizing gold nanoparticles. The UV–vis spectrum of
these samples shows that there is blue shift in surface plasmon resonance peak with decrease in particle size due to the quantum
confinement effect, a supporting evidence of formation of gold nanoparticles and this shift remains stable even after 3 months. 相似文献
4.
Extracellular biosynthesis of monodispersed gold nanoparticles by a SAM capping route 总被引:1,自引:0,他引:1
Li Wen Zhonghua Lin Pingying Gu Jianzhang Zhou Bingxing Yao Guoliang Chen Jinkun Fu 《Journal of nanoparticle research》2009,11(2):279-288
Monodispersed gold nanoparticles capped with a self-assembled monolayer of dodecanethiol were biosynthesized extracellularly
by an efficient, simple, and environmental friendly procedure, which involved the use of Bacillus megatherium D01 as the reducing agent and the use of dodecanethiol as the capping ligand at 26 °C. The kinetics of gold nanoparticle
formation was followed by transmission electron microscope (TEM) and UV-vis spectroscopy. It was shown that reaction time
was an important parameter in controlling the morphology of gold nanoparticles. The effect of thiol on the shape, size, and
dispersity of gold nanoparticles was also studied. The results showed that the presence of thiol during the biosynthesis could
induce the formation of small size gold nanoparticles (<2.5 nm), hold the shape of spherical nanoparticles, and promote the
monodispersity of nanoparticles. Through the modulation of reaction time and the use of thiol, monodispersed spherical gold
nanoparticles capped with thiol of 1.9 ± 0.8 nm size were formed by using Bacillus megatherium D01. 相似文献
5.
TamilSelvi Selvam Chao-Ming Chiang Kai-Ming Chi 《Journal of nanoparticle research》2011,13(8):3275-3286
Amphiphilic gold nanoclusters with the diameter of 1.8 ± 0.2 nm were prepared by decomposition of organometallic gold precursor
CH3AuPPh3 in the presence of mercaptoacids in o-xylene. Self-assembly of the 16-mercaptohexadecanoic acid protected gold clusters led to the formation of the nanosheets
consisted of aligned gold clusters. The hydrogen bonding between the carboxylic groups attached on the adjacent gold clusters
likely drives the self-assembly. This phenomenon was cross-verified by employing the preheated mercaptoacid-amine surfactant
system where a part of the mercaptoacids and amines were converted into –NH3
+–−OOC– ion pair and interrupting a part of the hydrogen bonding sites to lead to the reduction in the size of the structures
from nanosheets to nanobelts. Interestingly, we found the dependency of the luminescent properties on the extent of maintaining
the self-assembly of the clusters intern dictated by the surfactants. 相似文献
6.
Aihui Liang Yueyuan Liang Zhiliang Jiang Hesheng Jiang 《Journal of fluorescence》2009,19(6):1009-1015
The AucoreAgshell (Au@Ag) nanoparticles in size of 30 nm were prepared using 10 nm gold nanoparticles as seeds at 90°C, and were purified by
high-speed centrifugation to remove the excess trisodium citrate to obtain Au@Ag nanoprobe. In the medium of pH 4.0 acetate
buffer solution—7.2 μmol/L H2O2–67 μmol/L Fe(II), Au@Ag nanoparticles exhibited a resonance scattering (RS) peak at 538 nm. Upon addition of Catalase (Ct),
the system produced hydroxyl radical that oxidized the Au@Ag nanoprobe to form the AuAg nanoparticles with partly bare nanogold.
Those AuAg nanoparticles aggregated to large nanoclusters that led to the RS peak wavelength red-shift and its RS peak intensity
enhanced. The catalase activity (C) is linear to the enhanced RS intensity (ΔI) in the range of 6 to 2,800 U/L, with regression equation of ΔI = 0.168 C-0.2, the correlation coefficient of 0.9952, and detection limit of 2.8 U/L. This method was applied to the detection of serum
samples, and the results were agreement with that of the spectrophotometry. A new catalytic mechanism of catalase was proposed
with oxywater principle that was agreement with the results of resonance scattering spectroscopy, absorption spectrophotometry,
transmission electron microscopy and laser scattering. 相似文献
7.
Composite Au–SnO2 nanoparticles (NPs) are synthesized by nano-soldering of pure Au and SnO2 NPs. The multi-step process involves synthesis of pure Au and SnO2 NPs separately by nanosecond pulse laser ablation of pure gold and pure tin targets in deionized water and post-ablation
laser heating of mixed solution of Au colloidal and SnO2 colloidal to form nanocomposite. Transmission Electron Microscopy (TEM) and High-Resolution Transmission Electron Microscopy
(HRTEM) were used to study the effect of laser irradiation time on morphology of the composite Au–SnO2 NPs. The spherical particles of 4 nm mean size were obtained for 5 min of post-laser heating. Increased mean size and elongated
particles were observed on further laser heating. UV–vis spectra of Au–SnO2 nanocomposites show red shift in the plasmon resonance absorption peak and line shape broadening with respect to pure Au
NPs. The negative binding energy shift of Au 4f7/2 peak observed in X-ray Photoelectron Spectra (XPS) indicates charge transfer in the nano-soldered Au–SnO2 between gold and tin oxide and formation of soldered nanocomposite. 相似文献
8.
Fatma K. Canitez Mustafa S. Yavuz Ramazan Ozturk 《Journal of nanoparticle research》2011,13(12):7219-7228
In this study, the meso-tetra (p-hydroxyphenyl) porphyrin and meso-tetra (m-hydroxyphenyl) porphyrin were coated on to gold nanoparticles (AuNPs) via thioacetate anchors which easily dissociate to
form S–Au bonds. 4-tert-butyl phenyl thioacetate-AuNPs were prepared and used as a monodentate passivant to control the size of the tetradentate
porphyrin-AuNPs. The porphyrin-coated AuNPs were characterized by UV–Vis, TEM, XRD, and XPS analyses. The tetradentate porphyrin-AuNPs
size is within a range of 5–15 nm in diameter with exotic shapes. The plausible network formation for AuNP@p-TPP-SAc and the capping structure of the AuNP@m-TPP-SAc have been suggested. 相似文献
9.
Ali Safaei 《Journal of nanoparticle research》2010,12(3):759-776
The size dependency of the cohesive energy of nanocrystals is obtained in terms of their averaged structural and energetic
properties, which are in direct proportion with their cohesive energies. The significance of the effect of the geometrical
shape of nanoparticles on their thermal stability has been discussed. The model has been found to have good prediction for
the case of Cu and Al nanoparticles, with sizes in the ranges of 1–22 nm and 2–22 nm, respectively. Defining a new parameter,
named as the surface-to-volume energy-contribution ratio, the relative thermal stabilities of different nanoclusters and their
different surface-crystalline faces are discussed and compared to the molecular dynamic (MD) simulation results of copper
nanoclusters. Finally, based on the size dependency of the cohesive energy, a formula for the size-dependent diffusion coefficient
has been presented which includes the structural and energetic effects. Using this formula, the faster-than-expected interdiffusion/alloying
of Au(core)–Ag(shell) nanoparticles with the core–shell structure, the Au-core diameter of 20 nm and the Ag-shell thickness of 2.91 nm, has been
discussed and the calculated diffusion coefficient has been found to be consistent with its corresponding experimental value. 相似文献
10.
U?ur?Tamer Yusuf?Gündo?du ?smail?Hakk??Boyac? Kadir?Pekmez 《Journal of nanoparticle research》2010,12(4):1187-1196
The production of monodispersed magnetic nanoparticles with appropriate surface modification has attracted increasing attention
in biomedical applications including drug delivery, separation, and purification of biomolecules from the matrices. In the
present study, we report rapid and room temperature reaction synthesis of gold-coated iron nanoparticles in aqueous solution
using the borohydride reduction of HAuCl4 under sonication for the first time. The resulting nanoparticles were characterized with transmission electron microscopy
(TEM), electron spectroscopy for chemical analysis (ESCA), ultraviolet visible spectroscopy (UV–Vis), and X-ray diffraction
(XRD). Surface charges and magnetic properties of the nanoparticles were also examined. The pattern of Fe3O4 nanoparticles is face centered cubic with an average diameter of 9.5 nm and the initial reduction of gold on the surface
of Fe3O4 particles exhibits uniform Fe3O4–Au nanoparticles with an average diameter of 12.5 nm. The saturation magnetization values for the uncoated and gold-coated
Fe3O4 nanoparticles were found to be 30 and 4.5 emu/g, respectively, at 300 K. The progression of binding events between boronic
acid terminated ligand shell and fructose based on the covalent bonding interaction was measured by absorbance spectral changes.
Immunomagnetic separation was also performed at different E. coli concentration to evaluate capturing efficiency of resulting nanoparticles. Immunomagnetic separation percentages were varied
in a range of 52.1 and 21.9% depend on the initial bacteria counts. 相似文献
11.
Takashi Ogi Norizoh Saitoh Toshiyuki Nomura Yasuhiro Konishi 《Journal of nanoparticle research》2010,12(7):2531-2539
Biosynthesis of spherical gold nanoparticles and gold nanoplates was achieved at room temperature and pH 2.8 when cell extract
from the metal-reducing bacterium Shewanella algae was used as both a reducing and shape-controlling agent. Cell extract, prepared by sonicating a suspension of S. algae cells, was capable of reducing 1 mol/m3 aqueous AuCl4
− ions into elemental gold within 10 min when H2 gas was provided as an electron donor. The time interval lapsed since the beginning of the bioreductive reaction was found
to be an important factor in controlling the morphology of biogenic gold nanoparticles. After 1 h, there was a large population
of well-dispersed, spherical gold nanoparticles with a mean size of 9.6 nm. Gold nanoplates with an edge length of 100 nm
appeared after 6 h, and 60% of the total nanoparticle population was due to gold nanoplates with an edge length of 100–200 nm
after 24 h. The yield of gold nanoplates prepared with S. algae extract was four times higher than that prepared with resting cells of S. algae. The resulting biogenic gold nanoparticle suspensions showed a large variation in color, ranging from pale pink to purple
due to changes in nanoparticle morphology. 相似文献
12.
We report the experimental results on temperature-dependent studies of interactions between a novel biocompatible thermosensitive
polymer hydrogel and different stabilizing agent capped gold nanoparticles (Au NPs) with particle size ranging from 5 to 20 nm.
Stabilizing agents such as thioglycolic acid, tryptophan, and phenylalanine have been used as capping agents for Au NPs. The
poly-N-isopropyl acrylamide-co-acrylic acid (pNIPAm-AAc) with 3.0 ± 0.7 μm in size was synthesized by radical polymerization of
a selected mixture of N-isopropyl acrylamide (NIPAm), methylene-bis-acrylamide and acrylic acid (AAc). The capped Au NPs were mixed with a solution
of pNIPAm-AAc hydrogel. The temperature-dependent properties of the mixture were studied by UV–vis spectroscopy, dynamic light
scattering based particle size analysis, and transmission electron microscopy (TEM). The observations indicated change in
the lower critical solution temperature (LCST) depending on the nature of the stabilizer, with hydrophobic ones lowering the
value while hydrophilic stabilizers increasing the same. Also, the optical absorption due to Au NPs, when stabilized with
hydrophobic groups, reduced significantly at above LCST along with significant blue shift of wavelength maximum. 相似文献
13.
Tiyaporn Luangpipat Isabel R. Beattie Yusuf Chisti Richard G. Haverkamp 《Journal of nanoparticle research》2011,13(12):6439-6445
An efficient biological route to production of gold nanoparticles which allows the nanoparticles to be easily recovered remains
elusive. Live cells of the green microalga Chlorella vulgaris were incubated with a solution of gold chloride and harvested by centrifugation. Nanoparticles inside intact cells were identified
by transmission electron microscopy and confirmed to be metallic gold by synchrotron based X-ray powder diffraction and X-ray
absorption spectroscopy. These intracellular gold nanoparticles were 40–60 nm in diameter. At a concentration of 1.4% Au in
the alga, a better than 97% recovery of the gold from solution was achieved. A maximum of 4.2% Au in the alga was obtained.
Exposure of C. vulgaris to solutions containing dissolved salts of palladium, ruthenium, and rhodium also resulted in the production of the corresponding
nanoparticles within the cells. These were surmised to be also metallic, but were produced at a much lower intracellular concentration
than achieved with gold. Iridium was apparently toxic to the alga. No nanoparticles were observed using platinum solutions.
C. vulgaris provides a possible route to large scale production of gold nanoparticles. 相似文献
14.
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
15.
Vladimir V. Tatarchuk Anastasiya P. Sergievskaya Irina A. Druzhinina Vladimir I. Zaikovsky 《Journal of nanoparticle research》2011,13(10):4997-5007
The kinetics of the growth of gold nanoparticles during the reduction of tetrachloroauric acid by hydrazine in dispersed aqueous
solution encapsulated by reverse micelles of Triton N-42 surfactant (with decane as dispersion medium) was studied by means
of spectrophotometry. According to DLS data, at a set value of solubilization capacity V
s/V
o = 0.005 initial micelles have an aqueous core hydrodynamic diameter d
c = 3.6±0.2 nm. The final particles obtained after full reduction of AuIII have a metallic core of defect-free single-crystalline gold with a narrow size distribution and average core diameter d
Au = 7.7 ± 1.4 nm as shown by TEM. The rate of the particle growth is limited by the rate of gold reduction. The process kinetics
corresponds to the model consisting of two stages of reduction AuIII → AuI → Au0. The stages involve the formation and redox decay of the intermediate complexes Au(N2H4)Cl3 and Au(N2H4)Cl, and each stage proceeds via two routes: (1) homogeneous in the dispersed aqueous phase, and (2) heterogeneous on the
particle surfaces. Reactions taking route (2) are autocatalytic because they proceed with participation of the surface atoms
of particles as the final products of AuIII reduction. The dependencies of observed rate constants on reagent concentrations, temperature, and solubilization capacity
of the micellar solution are studied. 相似文献
16.
Ivan I. Stoikov Elena A. Yushkova Igor S. Antipin Alexander I. Konovalov 《Journal of nanoparticle research》2011,13(12):6603-6611
The effect of solvent nature and temperature on the formation of 3D-dimensional SAM (self-assembled monolayers on nanoparticles)
based on synthetically available stereoisomers of p-tert-butyl thiacalix[4]arenes tetrasubstituted at the lower rim by pyrrolidide and octylamide groups (cone, partial cone, and 1,3-alternate) with lithium and silver nanoparticles were determined by dynamic light-scattering and transmission electron microscopy.
It was found that the variation of the temperature of the system and the nature of the solvent leads to the formation discrete
or extended particles (CH2Cl2) (98–110 nm), nanostructures (CH3CN) (120–295 nm) or three-dimensional SAM (DMF) (1–13 nm; 46–622 nm). 相似文献
17.
Abstract
Essentially, biomolecule assisted synthesis of inorganic nanoparticles can be divided into two categories. One uses multi-domain protein cages (template) and other relies on the self-assembly of the biomolecules including small peptides, DNA, and denatured protein. Protein templated synthesis of various nanomaterials is relatively well understood as the cages of the biological macromolecules and their specific interaction with inorganic ions ultimately dictate the size and crystallinity of the nanomaterials. On the other hand formation of nanoparticles using protein in the cost of the native structural integrity for the self-assembly is not well understood till date. In the present work we report a protein-assisted synthesis route to prepare highly crystalline 3–5 nm gold nanoparticles, which relies systematic thermal denaturation of a number of proteins and protein mixture from Escherichia coli in absence of any reducing agent. By using UV–vis, circular dichroism spectroscopy, and high-resolution transmission electron microscopy we have explored details of the associated biochemistry of the proteins dictating kinetics, size, and crystallinity of the nanoparticles. The kinetics of nanoparticles formation in this route, which is sigmoidal in nature, has been modelled in a simple scheme of autocatalytic process. Interestingly, the protein-capped as prepared Au nanoparticles are found to serve as effective catalyst to activate the reduction of 4-nitrophenol in the presence of NaBH4. The kinetic data obtained by monitoring the reduction of 4-nitrophenol by UV/vis-spectroscopy revealing the efficient catalytic activity of the nanoparticles have been explained in terms of the Langmuir–Hinshelwood model. The methodology and the details of the protein chemistry presented here may find relevance in the protein-assisted synthesis of inorganic nanostructures in general. 相似文献18.
We report a straightforward approach to prepare multifunctional manganese–gold nanoparticles by attaching Mn(II) ions onto
the surface of 20 nm citrate-capped gold nanoparticles. In vitro MRI measurements made in agarose gel phantoms exhibited high
relaxivity (18.26 ± 1.04 mmol−1 s−1). Controlled incubation of the nanoparticles with mesenchymal stem cells (MSCs) was used to study cellular uptake of these
particles and this process appeared to be controlled by the size of the nanoparticle aggregates in the extracellular solution.
SEM images of live MSCs showed an increased concentration of particles near the cell membrane and a distribution of the size
of particles within the cells. Survivability for MSCs in contact with Mn–Au NPs was greater than 97% over the 3-day period
and up to the 1 mM Mn used in this study. The high relaxivity and low cell mortality are suggestive of an enhanced positive
contrast agent for in vitro or in vivo applications. 相似文献
19.
Xin Chen Jun Tao Gang Zou Qijin Zhang Pei Wang 《Applied Physics A: Materials Science & Processing》2010,100(1):223-230
Diacetylene monomer containing p-nitrophenyl azobenzene moiety (NADA) was synthesized. Silver nanoparticles with different
concentrations were adulterated in the above polymerized NADA (PNADA) films and the third-order nonlinear optical properties
were investigated in detail. UV–vis spectra and transmission electron microscopy were used to confirm the formation of PNADA/Ag
nanocomposite films. The silver nanoparticles (average size of 10 nm) were well dispersed in the polymer films. The value
of the nonlinear refractive index n
2 for PNADA films (8.48×10−15 cm2/W) was much higher than that of pure polydiacetylene films. Further, the introduction of silver nanoparticles into the PNADA
polymer films led to the further enhancement of nonlinear optical properties. The maximum value of n
2 for PNADA/Ag nanocomposite films could be 11.6×10−15 cm2/W. This enhancement should be ascribed to the surface plasmon resonance of silver nanoparticles. 相似文献
20.
Spatial inhomogeneities of the indium distribution in In
x
Ga1–x
N epitaxial layers grown on sapphire substrate with a GaN buffer layer were investigated using photoluminescence (PL) in addition
to confocal scanning Raman spectroscopy (RS) and PL. Broad emission bands from In-enriched InGaN nanoclusters (700–900 nm)
and from the volume outside the clusters (about 460 nm) were observed in PL spectra of an epitaxial InGaN layer with an average
In content of 25.7%. It was established that larger micro-PL intensities corresponded to energetically shallower clusters.
The observed broadly asymmetric A1(LO) RS band of InGaN confirmed that the In concentration in the layer was highly variable. Modeling the LO phonon band by
two Lorentzian curves gave an average In concentration of 21% in the volume outside the clusters and 37% in the nanoclusters,
which was considerably higher than the average concentration in the layer and agreed well with their PL band positions. 相似文献