Abstract: Superabsorbent polymers (SAPs) or hydrogels with three-dimensional hydrophilic network structure are high-performance water absorbent and retention materials. The in situ synthesis of metal nanoparticles within polymeric network as antibacterial agents for bio-applications is an approach that takes advantage of the existing free-space into networks, which not only acts as a template for nucleation of nanoparticles, but also provides long term stability and reduces their toxicity by delaying their oxidation and release. In this work, SAP/nanosilver nanocomposites were successfully developed by a unique green process at room temperature, which involves in situ formation of silver nanoparticles (AgNPs) within hydrogels as a template. The aim of this study is to investigate whether these AgNPs-loaded hydrogels are potential candidates for antimicrobial applications. Firstly, the superabsorbents were prepared through radical copolymerization via grafting and crosslinking of acrylamide (AAm) onto chitosan backbone (Cs) using potassium persulfate as initiator and N,N’-methylenebisacrylamide as the crosslinker. Then, they were hydrolyzed to achieve superabsorbents with ampholytic properties and uppermost swelling capacity. Lastly, the AgNPs were biosynthesized and entrapped into hydrogels through a simple, eco-friendly and cost-effective method using aqueous silver nitrate as a silver precursor and curcuma longa tuber-powder extracts as both reducing and stabilizing agent. The formed superabsorbents nanocomposites (Cs-g-PAAm)/AgNPs were characterized by X-ray Diffraction (XRD), UV-visible Spectroscopy, Attenuated Total reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), Inductively Coupled Plasma (ICP), and Thermogravimetric Analysis (TGA). Microscopic surface structure analyzed by Transmission Electron Microscopy (TEM) has showed spherical shapes of AgNPs with size in the range of 3-15 nm. The extent of nanosilver loading was decreased by increasing Cs content into network. The silver-loaded hydrogel was thermally more stable than the unloaded dry hydrogel counterpart. The swelling equilibrium degree (Q) and centrifuge retention capacity (CRC) in deionized water were affected by both contents of Cs and the entrapped AgNPs. The nanosilver-embedded hydrogels exhibited antibacterial activity against Escherichia coli and Staphylococcus aureus bacteria. These comprehensive results suggest that the elaborated AgNPs-loaded nanomaterials could be used to produce valuable wound dressing.
Abstract: A considerable amount of lignocellulosic by-product could be obtained from olive pulp during olive oil extraction industry. The major constituents of the olive pulp are husks and seeds. The separation of each portion of olive pulp (seeds and husks) was carried out by water flotation where seeds were sediment in the bottom. Both seeds and husks were dignified by 15% NaOH followed by complete lignin removal by using sodium chlorite in acidic medium. The isolated holocellulose, α-cellulose, hydrogel and CMC which prepared from cellulose of both seeds and husk fractions were characterized by FTIR and SEM. The present study focused on the investigation of the chemical components of the lignocellulosic fraction of olive pulp. Biofunctionlization of hydrogel was achieved through loading of silver nanoparticles AgNPs in to the prepared hydrogel. The antimicrobial activity of the loaded silver hydrogel against G-ve, and G+ve, and candida was demonstrated.
Abstract: Despite the rapid nanotechnology progress and recognition, its potential impact in ecosystems and health of humans is still not fully known. In this paper, the study of ecotoxicological dangers of nanomaterials is presented. By chemical reduction method, silver (AgNPs) and gold (AuNPs) nanoparticles were synthesized, characterized and used in experiments to examine their impact on microorganisms (Escherichia coli, Staphylococcus aureus and Candida albicans) and terrestrial flora (Phaseolus vulgaris and Lepidium sativum). The results collected during experiments with terrestrial flora show tendentious growth stimulations caused by gold nanoparticles. In contrast to these results, silver nanoparticle solutions inhibited growth of beans and garden cress, compared to control samples. The results obtained from experiments with microorganisms show similarities with ones collected from experiments with terrestrial plants. Samples treated with AuNPs of size 13 nm showed stimulation in the growth of the colonies compared with 3,5 nm size nanoparticles.
Abstract: The abiotic elicitation is one of the methods for
increasing the secondary metabolites production in plant tissue
cultures and it seems to be more effective than traditional strategies.
This study verified the use of silver nitrate as elicitor to enhance
flavonolignans and flavonoid taxifolin production in suspension
culture of Sylibum marianum (L.) Gaertn. Silver nitrate in various
concentrations (5.887.10-3 mol/L, 5.887.10-4 mol/L, 5.887.10-5
mol/L) was used as elicitor. The content of secondary metabolites in
cell suspension cultures was determined by high performance liquid
chromatography. The samples were taken after 6, 12, 24, 48, 72 and
168 hours of treatment. The highest content of taxifolin production
(2.2 mg.g-1) in cell suspension culture of Silybum marianum (L.)
Gaertn. was detected after silver nitrate (5.887.10-4 mol/L) treatment
and 72 h application. Flavonolignans such as silybinA, silybin B,
silydianin, silychristin, isosilybin A, isosilybin B were not produced
by cell suspension culture of S. marianum after elicitor treatment.
Our results show that the secondarymetabolites could be released
from S. marianum cells into the nutrient medium by changed
permeability of cell wall.
Abstract: Nanofibers are defined as fibers with diameters less
than 100 nanometers. In this study, behaviours of activated carbon
nanofiber (ACNF), carbon nanofiber (CNF), polyacrylonitrile/ carbon
nanotube (PAN/CNT), polyvinyl alcohol/nanosilver (PVA/Ag) in
proton exchange membrane (PEM) fuel cells are investigated
experimentally. This material was used as gas diffusion layer (GDL)
in PEM fuel cells. In this study, the electrical conductivities of
nanofiber and nanofiber/nanoparticles have been studied to
understand their effects on PEM fuel cell performance. According to
the experimental results, the maximum electrical conductivity
performance of the fuel cell with nanofiber was found to be at
PVA/Ag (at UConn condition). The electrical conductivities of CNF,
ACNF, PAN/CNT are lower for PEM. The resistance of cell with
PVA/Ag is lower than the resistance of cell with PAN/CNT, ACNF,
CNF.
Abstract: Highly stable and homogeneously dispersed amino
acid coated silver nanoparticles (ANP) of ≈ 10 nm diameter, ranging
from 420 to 430 nm are prepared on AgNO3 solution addition to gum
of Azadirachta indica solution at 373.15 K. The amino acids were
selected based on their polarity. The synthesized nanoparticles were
characterized by UV-Vis, FTIR spectroscopy, HR-TEM, XRD, SEM
and 1H-NMR. The coated nanoparticles were used as catalyst for the
reduction of methylene blue dye in presence of Sn(II) in aqueous,
anionic and cationic micellar media. The rate of reduction of dye was
determined by measuring the absorbance at 660 nm,
spectrophotometrically and followed the order: Kcationic > Kanionic >
Kwater. After 12 min and in absence of the ANP, only 2%, 3% and 6%
of the dye reduction was completed in aqueous, anionic and cationic
micellar media respectively while, in presence of ANP coated by
polar neutral amino acid with non-polar -R group, the reduction
completed to 84%, 95% and 98% respectively. The ANP coated with
polar neutral amino acid having non-polar -R group, increased the
rate of reduction of the dye by 94, 3205 and 6370 folds in aqueous,
anionic and cationic micellar media respectively. Also, the rate of
reduction of the dye increased by three folds when the micellar media
was changed from anionic to cationic when the ANP is coated by a
polar neutral amino acid having a non-polar -R group.
Abstract: In this paper, we calculate the two-photon ionization
(TPI) cross-section for pump-probe scheme in Ag neutral cluster. The
pump photon energy is assumed to be close to the surface plasmon
(SP) energy of cluster in dielectric media. Due to this choice, the
pump wave excites collective oscillations of electrons-SP and the
probe wave causes ionization of the cluster. Since the interband
transition energy in Ag exceeds the SP resonance energy, the main
contribution into the TPI comes from the latter. The advantage of Ag
clusters as compared to the other noble metals is that the SP
resonance in silver cluster is much sharper because of peculiarities of
its dielectric function. The calculations are performed by separating
the coordinates of electrons corresponding to the collective
oscillations and the individual motion that allows taking into account
the resonance contribution of excited SP oscillations. It is shown that
the ionization cross section increases by two orders of magnitude if
the energy of the pump photon matches the surface plasmon energy
in the cluster.
Abstract: At the present work, highly transparent strip type
quasi-solid state dye-sensitized solar cells (DSSCs) were fabricated
through inkjet printing using nanocomposite TiO2 inks as raw
materials and tested under outdoor illumination conditions. The cells,
which can be considered as the structural units of large area modules,
were fully characterized electrically and electrochemically and after
the evaluation of the received results a large area DSSC module was
manufactured. The module design was a sandwich Z-interconnection
where the working electrode is deposited on one conductive glass and
the counter electrode on a second glass. Silver current collective
fingers were printed on the conductive glasses to make the internal
electrical connections and the adjacent cells were connected in series
and finally insulated using a UV curing resin to protect them from the
corrosive (I-/I3-) redox couple of the electrolyte. Finally, outdoor tests
were carried out to the fabricated dye-sensitized solar module and its
performance data were collected and assessed.
Abstract: In this paper, we study the optical nonlinearities of
Silver sulfide (Ag2S) nanostructures dispersed in the Dimethyl
sulfoxide (DMSO) under exposure to 532 nm, 15 nanosecond (ns)
pulsed laser irradiation. Ultraviolet–visible absorption spectrometry
(UV-Vis), X-ray diffraction (XRD), and transmission electron
microscopy (TEM) are used to characterize the obtained nanocrystal
samples. The band gap energy of colloid is determined by analyzing
the UV–Vis absorption spectra of the Ag2S NPs using the band
theory of semiconductors. Z-scan technique is used to characterize
the optical nonlinear properties of the Ag2S nanoparticles (NPs).
Large enhancement of two photon absorption effect is observed with
increase in concentration of the Ag2S nanoparticles using open Zscan
measurements in the ns laser regime. The values of the nonlinear
absorption coefficients are determined based on the local nonlinear
responses including two photon absorption. The observed aperture
dependence of the Ag2S NP limiting performance indicates that the
nonlinear scattering plays an important role in the limiting action of
the sample. The concentration dependence of the optical liming is
also investigated. Our results demonstrate that the optical limiting
threshold decreases with increasing the silver sulfide NPs in DMSO.
Abstract: This paper presents thermal annealing de-wetting
technique for the preparation of porous metal membrane for Thin
Film Encapsulation (TFE) application. Thermal annealing de-wetting
experimental results reveal that pore size formation in porous metal
membrane depend upon i.e. 1. The substrate at which metal is
deposited, 2. Melting point of metal used for porous metal cap layer
membrane formation, 3. Thickness of metal used for cap layer, 4.
Temperature used for formation of porous metal membrane. In order
to demonstrate this technique, Silver (Ag) was used as a metal for
preparation of porous metal membrane on amorphous silicon (a-Si)
and silicon oxide. The annealing of the silver thin film of various
thicknesses was performed at different temperature. Pores in porous
silver film were analyzed using Scanning Electron Microscope
(SEM). In order to check the usefulness of porous metal film for TFE
application, the porous silver film prepared on amorphous silicon (a-
Si) and silicon oxide was released using XeF2 and VHF, respectively.
Finally, guide line and structures are suggested to use this porous
membrane for robust TFE application.
Abstract: The use of engineered nanomaterials has increased as
a result of their positive impact on many sectors of the economy,
including agriculture. Silver nanoparticles (AgNPs) are now used to
enhance seed germination, plant growth, and photosynthetic quantum
efficiency and as antimicrobial agents to control plant diseases. In
this study, we examined the effect of AgNP dosage on the seed
germination of three plant species: corn (Zea mays L.), watermelon
(Citrullus lanatus [Thunb.] Matsum. & Nakai) and zucchini
(Cucurbita pepo L.). This experiment was designed to study the
effect of AgNPs on germination percentage, germination rate, mean
germination time, root length and fresh and dry weight of seedlings
for the three species. Seven concentrations (0.05, 0.1, 0.5, 1, 1.5, 2
and 2.5 mg/ml) of AgNPs were examined at the seed germination
stage. The three species had different dose responses to AgNPs in
terms of germination parameters and the measured growth
characteristics. The germination rates of the three plants were
enhanced in response to AgNPs. Significant enhancement of the
germination percentage values was observed after treatment of the
watermelon and zucchini plants with AgNPs in comparison with
untreated seeds. AgNPs showed a toxic effect on corn root
elongation, whereas watermelon and zucchini seedling growth were
positively affected by certain concentrations of AgNPs. This study
showed that exposure to AgNPs caused both positive and negative
effects on plant growth and germination.
Abstract: The use of engineered nanomaterials has increased as
a result of their positive impact on many sectors of the economy,
including agriculture. Silver nanoparticles (AgNPs) are now used to
enhance seed germination, plant growth, and photosynthetic quantum
efficiency and as antimicrobial agents to control plant diseases. In
this study, we examined the effect of AgNP dosage on the seed
germination of three plant species: corn (Zea mays L.), watermelon
(Citrullus lanatus [Thunb.] Matsum. & Nakai) and zucchini
(Cucurbita pepo L.). This experiment was designed to study the
effect of AgNPs on germination percentage, germination rate, mean
germination time, root length and fresh and dry weight of seedlings
for the three species. Seven concentrations (0.05, 0.1, 0.5, 1, 1.5, 2
and 2.5 mg/ml) of AgNPs were examined at the seed germination
stage. The three species had different dose responses to AgNPs in
terms of germination parameters and the measured growth
characteristics. The germination rates of the three plants were
enhanced in response to AgNPs. Significant enhancement of the
germination percentage values was observed after treatment of the
watermelon and zucchini plants with AgNPs in comparison with
untreated seeds. AgNPs showed a toxic effect on corn root
elongation, whereas watermelon and zucchini seedling growth were
positively affected by certain concentrations of AgNPs. This study
showed that exposure to AgNPs caused both positive and negative
effects on plant growth and germination.
Abstract: Surface modification and functionalization has been
an important tool for scientists in order to open new frontiers in
nanoscience and nanotechnology. Desired surface characteristics for
the intended applications can be achieved with surface
functionalization.
In this work, the effect of water soluble ligands on the adsorption
capabilities of silver nanoparticles onto AC which was synthesized
from German beech wood was investigated. Sodium borohydride
(NaBH4) and polyvinyl alcohol (PVA) were used as the ligands.
Silver nanoparticles with different surface coatings have average
sizes range from 10 to 13 nm. They were synthesized in aqueous
media by reducing Ag (I) ion in the presence of ligands. These
particles displayed adsorption tendencies towards AC when they
were mixed together and shaken in distilled water.
Silver nanoparticles (NaBH4-AgNPs) reduced and stabilized by
NaBH4 adsorbed onto AC with a homogenous dispersion of
aggregates with sizes in the range of 100-400 nm. Beside, silver
nanoparticles, which were prepared in the presence of both NaBH4
and PVA (NaBH4/PVA-Ag NPs), demonstrated that NaBH4/PVA-Ag
NPs adsorbed and dispersed homogenously but, they aggregated with
larger sizes on the AC surface (range from 300 to 600 nm). In
addition, desorption resistance of Ag nanoparticles were investigated
in distilled water. According to the results AgNPs were not desorbed
on the AC surface in distilled water.
Abstract: The temperature dependence of wettability (wetting
angle, Θ (T)) for Ag-based melts on graphite and Al2O3 substrates is
compared. Typical alloying effects are found, as the Ag host metal is
gradually replaced by various metallic elements. The essence of
alloying lies in the change of the electron/atom (e/a) ratio. This ratio
is also manifested in the shift of wetting angles on the same substrate.
Nevertheless, the effects are partially smeared by other
(metallurgical) factors, like the interaction between the oxygenalloying
elements and by the graphite substrate-oxygen interaction. In
contrast, such effects are not pronounced in the case of Al2O3
substrates. As a consequence, Θ(T) exhibits an opposite trend in the
case of two substrates. Crossovers of the Θ(T) curves were often
found. The positions of crossovers depend on the chemical character
and concentration of solute atoms. Segregation and epitaxial texture
formation after solidification were also observed in certain alloy
drops, especially in high concentration range. This phenomenon is
not yet explained in every detail.
Abstract: The present work aims to throw light on the effects of
arcing in air on the surface state of contact pastilles made of silvernickel
Ag-Ni (60/40). Also, the photoelectric emission from these
electrical contacts has been investigated in the spectral range of 196-
256 nm. In order to study the effects of arcing on the EWF, the
metallic samples were subjected to electrical arcs in air, at
atmospheric pressure and room temperature, after that, they have
been introduced into the vacuum chamber of an experimental UHV
set-up for EWF measurements. Both Fowler method of isothermal
curves and linearized Fowler plots were used for the measurement of
the EWF by the photoelectric effect.
It has been found that the EWF varies with the number of applied
arcs. Thus, after 500 arcs in air, the observed EWF increasing is
probably due to progressive inclusion of oxide on alloy surface.
Microscopic examination is necessary to get better understandings on
EWF of silver alloys, for both virgin and arced electrical contacts.
Abstract: A Silver (Ag) thin film is introduced as a template and
doping source for vertically aligned p–type ZnO nanorods. ZnO
nanorods were grown using an ammonium hydroxide based
hydrothermal process. During the hydrothermal process, the Ag thin
film was dissolved to generate Ag ions in the solution. The Ag ions can
contribute to doping in the wurzite structure of ZnO and the (111)
grain of Ag thin film can be the epitaxial temporal template for the
(0001) plane of ZnO. Hence, Ag–doped p–type ZnO nanorods were
successfully grown on the substrate, which can be an electrode or
semiconductor for the device application. To demonstrate the
potentials of this idea, p–n diode was fabricated and its electrical
characteristics were demonstrated.
Abstract: Energy consumption and users’ satisfaction were
compared in three LEED certified office buildings in turkey and an
office building in Egypt. The field studies were conducted in summer
2012. The measured environmental parameters in the four buildings
were indoor air temperature, relative humidity, CO2 percentage and
light intensity. The traditional building is located in Smart Village in
Abu Rawash, Cairo, Egypt. The building was studied for 7 days
resulting in 84 responds. The three rated buildings are in Istanbul;
Turkey. A Platinum LEED certified office building is owned by
BASF and gained a platinum certificate for new construction and
major renovation. The building was studied for 3 days resulting in 13
responds. A Gold LEED certified office building is owned by BASF
and gained a gold certificate for new construction and major
renovation. The building was studied for 2 days resulting in 10
responds. A silver LEED certified office building is owned by
Unilever and gained a silver certificate for commercial interiors. The
building was studied for 7 days resulting in 84 responds.
The results showed that all buildings had no significant difference
regarding occupants’ satisfaction with the amount of lighting, noise
level, odor and access to the outdoor view. There was significant
difference between occupants’ satisfaction in LEED certified
buildings and the traditional building regarding the thermal
environment and the perception of the general environment (colors,
carpet and decoration. The findings suggest that careful design could
lead to a certified building that enhances the thermal environment and
the perception of the indoor environment leading to energy
consumption without scarifying occupants’ satisfaction.
Abstract: Metal-enhanced Luminescence of silicon nanocrystals
(SiNCs) was determined using two different particle sizes of silver
nanoparticles (AgNPs). SiNCs have been characterized by scanning
electron microscopy (SEM), high resolution transmission electron
microscopy (HRTEM), Fourier transform infrared spectroscopy
(FTIR) and X-ray photoelectron spectroscopy (XPS). It is found that
the SiNCs are crystalline with an average diameter of 65 nm and FCC
lattice. AgNPs were synthesized using photochemical reduction of
AgNO3 with sodium dodecyl sulphate (SDS). The enhanced
luminescence of SiNCs by AgNPs was evaluated by confocal Raman
microspectroscopy. Enhancement up to x9 and x3 times were
observed for SiNCs that mixed with AgNPs which have an average
particle size of 100 nm and 30 nm, respectively. Silver NPs-enhanced
luminescence of SiNCs occurs as a result of the coupling between the
excitation laser light and the plasmon bands of AgNPs; thus this
intense field at AgNPs surface couples strongly to SiNCs.
Abstract: A phase diagram of the Ag2SO4 - CaSO4 (Silver sulphate – Calcium Sulphate) binaries system using conductivity, XRD (X-Ray Diffraction Technique) and DTA (Differential Thermal Analysis) data is constructed. The eutectic reaction (liquid -» a-Ag2SO4 + CaSO4) is observed at 10 mole% CaSO4 and 645°C. Room temperature solid solubility limit up to 5.27 mole % of Ca 2+ in Ag2SO4 is set using X-ray powder diffraction and scanning electron microscopy results. All compositions beyond this limit are two-phase mixtures below and above the transition temperature (≈ 416°C). The bulk conductivity, obtained following complex impedance spectroscopy, is found decreasing with increase in CaSO4 content. Amongst other binary compositions, the 80AgSO4-20CaSO4 gave improved sinterability/packing density.
Abstract: Polymer composite nano-fibers including (1, 3 wt %)
silver nano-particles have been produced by electrospinning method.
Polyacrylonitrile/N,N-dimethylformamide (PAN/DMF) solution have
been prepared and the amount of silver nitrate have been adjusted to
PAN weight. Silver nano-particles were obtained from reduction of
silver ions into silver nano-particles by chemical reduction by
hydrazine hydroxide (N2H5OH). The different amount of silver salt
was loaded into polymer matrix to obtain polyacrylonitrile composite
nano-fiber containing silver nano-particles. The effect of the amount
of silver nano-particles on the properties of composite nano-fiber web
was investigated. Electrical conductivity, mechanical properties,
thermal properties were examined by Microtest LCR Meter 6370
(0.01 mΩ-100 MΩ), Tensile tester, Differential scanning calorimeter
DSC (Q10) and SEM respectively. Also antimicrobial efficiency test
(ASTM E2149-10) was done against to Staphylococcus aureus
bacteria. It has been seen that breaking strength, conductivity,
antimicrobial effect, enthalpy during cyclization increase by use of
silver nano-particles while the diameter of nano-fiber decreases.