Abstract: Dielectric ceramic samples in the BaO-Re2O3-TiO2
ternary system were synthesized with structural formula Ba2-
xRe4+2x/3Ti8O24 where Re= rare earth metal and Re= Sm and La where
x varies from 0.0 to 0.6 with step size 0.1. Polycrystalline samples
were prepared by the conventional solid state reaction technique. The
dielectric, electrical and impedance analysis of all the samples in the
frequency range 1KHz- 1MHz at room temperature (25°C) have been
done to get the understanding of electrical conduction and dielectric
relaxation and their correlation. Dielectric response of the samples at
lower frequencies shows dielectric dispersion while at higher
frequencies it shows dielectric relaxation. The ac conductivity is well
fitted by the Jonscher law. The spectroscopic data in the impedance
plane confirms the existence of grain contribution to the relaxation.
All the properties are found out to be function of frequency as well as
the amount of substitution.
Abstract: The effect of N2 pretreatment on the catalytic activity
of tungsten-based catalysts was investigated in the metathesis of
ethylene and trans-2-butene at 450oC and atmospheric pressure. The
presence of tungsten active species was confirmed by UV-Vis and
Raman spectroscopy. Compared to the WO3-based catalysts treated
in air, higher amount of WO4 2-tetrahedral species and lower amount
of WO3 crystalline species were observed on the N2-treated ones.
These contribute to the higher conversion of 2-butene and propylene
selectivity during 10 h time-on-stream. Moreover, N2 treatment led to
lower amount of coke formation as revealed by TPO of the spent
catalysts.
Abstract: Poly vinyl acetate (PVA)-based titania (TiO2)–carbon
nanotube composite nanofibers (PVA-TCCNs) with various
PVA-to-solvent ratios and PVA-based TiO2 composite nanofibers
(PVA-TN) were synthesized using an electrospinning process,
followed by thermal treatment. The photocatalytic activities of these
nanofibers in the degradation of airborne monocyclic aromatics under
visible-light irradiation were examined. This study focuses on the
application of these photocatalysts to the degradation of the target
compounds at sub-part-per-million indoor air concentrations. The
characteristics of the photocatalysts were examined using scanning
electron microscopy, X-ray diffraction, ultraviolet-visible
spectroscopy, and Fourier-transform infrared spectroscopy. For all the
target compounds, the PVA-TCCNs showed photocatalytic
degradation efficiencies superior to those of the reference PVA-TN.
Specifically, the average photocatalytic degradation efficiencies for
benzene, toluene, ethyl benzene, and o-xylene (BTEX) obtained using
the PVA-TCCNs with a PVA-to-solvent ratio of 0.3 (PVA-TCCN-0.3)
were 11%, 59%, 89%, and 92%, respectively, whereas those observed
using PVA-TNs were 5%, 9%, 28%, and 32%, respectively.
PVA-TCCN-0.3 displayed the highest photocatalytic degradation
efficiency for BTEX, suggesting the presence of an optimal
PVA-to-solvent ratio for the synthesis of PVA-TCCNs. The average
photocatalytic efficiencies for BTEX decreased from 11% to 4%, 59%
to 18%, 89% to 37%, and 92% to 53%, respectively, when the flow
rate was increased from 1.0 to 4.0 L min1. In addition, the average
photocatalytic efficiencies for BTEX increased 11% to ~0%, 59% to
3%, 89% to 7%, and 92% to 13%, respectively, when the input
concentration increased from 0.1 to 1.0 ppm. The prepared
PVA-TCCNs were effective for the purification of airborne aromatics
at indoor concentration levels, particularly when the operating
conditions were optimized.
Abstract: Thin ZnO films are deposited on glass substrates via
sol–gel method and dip-coating. The films are prepared from zinc
acetate dehydrate as a starting reagent. After that the as-prepared
ZnO sol is aged for different periods (0, 1, 3, 5, 10, 15 and 30 days).
Nanocrystalline thin films are deposited from various sols. The
effect ZnO sols aging time on the structural and photocatalytic
properties of the films is studied. The films surface is studied by
Scanning Electron Microscopy. The effect of the aging time of the
starting solution is studied in the photocatalytic degradation of
Reactive Black 5 (RB5) by UV-vis spectroscopy. The experiments
are conducted upon UV-light illumination and in complete darkness.
The variation of the absorption spectra shows the degradation of RB5
dissolved in water, as a result of the reaction, occurring on the surface
of the films and promoted by UV irradiation. The initial
concentrations of dye (5, 10 and 20 ppm) and the effect of the aging
time are varied during the experiments. The results show, that the
increasing aging time of starting solution with respect to ZnO
generally promotes photocatalytic activity. The thin films obtained
from ZnO sol, which is aged 30 days have best photocatalytic
degradation of the dye (97,22%) in comparison with the freshly
prepared ones (65,92%). The samples and photocatalytic
experimental results are reproducible. Nevertheless, all films exhibit
a substantial activity in both UV light and darkness, which is
promising for the development of new ZnO photocatalysts by sol-gel
method.
Abstract: Alkylated silicon nanocrystals (C11-SiNCs) were
prepared successfully by galvanostatic etching of p-Si(100) wafers
followed by a thermal hydrosilation reaction of 1-undecene in
refluxing toluene in order to extract C11-SiNCs from porous silicon.
Erbium trichloride was added to alkylated SiNCs using a simple
mixing chemical route. To the best of our knowledge, this is the first
investigation on mixing SiNCs with erbium ions (III) by this
chemical method. The chemical characterization of C11-SiNCs and
their mixtures with Er3+(Er/C11-SiNCs) were carried out using X-ray
photoemission spectroscopy (XPS). The optical properties of C11-
SiNCs and their mixtures with Er3+ were investigated using Raman
spectroscopy and photoluminescence (PL). The erbium mixed
alkylated SiNCs shows an orange PL emission peak at around 595
nm that originates from radiative recombination of Si. Er/C11-SiNCs
mixture also exhibits a weak PL emission peak at 1536 nm that
originates from the intra-4f transition in erbium ions (Er3+). The PL
peak of Si in Er/C11-SiNCs mixture is increased in the intensity up to
three times as compared to pure C11-SiNCs. The collected data
suggest that this chemical mixing route leads instead to a transfer of
energy from erbium ions to alkylated SiNCs.
Abstract: Carbon nanotube is one of the most attractive materials
for the potential applications of nanotechnology due to its excellent
mechanical, thermal, electrical and optical properties. In this paper we
report a supercapacitor made of nickel foil electrodes, coated with
multiwall carbon nanotubes (MWCNTs) thin film using
electrophoretic deposition (EPD) method. Chemical vapor deposition
method was used for the growth of MWCNTs and ethanol was used as
a hydrocarbon source. High graphitic multiwall carbon nanotube was
found at 750oC analyzing by Raman spectroscopy. We observed the
electrochemical performance of supercapacitor by cyclic
voltammetry. The electrodes of supercapacitor fabricated from
MWCNTs exhibit considerably small equivalent series resistance
(ESR), and a high specific power density. Electrophoretic deposition
is an easy method in fabricating MWCNT electrodes for high
performance supercapacitor.
Abstract: In the present study, we have synthesized Cr and Fe
doped zinc oxide (ZnO) nanostructures (Zn1-δCraFebO; where δ = a +
b = 20%, a = 5, 6, 8 & 10% and b = 15, 14, 12 & 10%) via sol-gel
method at different doping concentrations. The synthesized samples
were characterized for structural properties by X-ray diffractrometer
and field emission scanning electron microscope and the optical
properties were carried out through photoluminescence and UVvisible
spectroscopy. The particle size calculated through field
emission scanning electron microscope varies from 41 to 96 nm for
the samples synthesized at different doping concentrations. The
optical band gaps calculated through UV-visible spectroscopy are
found to be decreasing from 3.27 to 3.02 eV as the doping
concentration of Cr increases and Fe decreases.
Abstract: Multiwall carbon nanotubes, prepared by chemical
vapor deposition, have an average diameter of 60-100 nm as shown
by High Resolution Transmittance Electron Microscope, HR-TEM.
The Multiwall carbon nanotubes (MWCNTs) were further
characterized using X-ray Diffraction and Raman Spectroscopy.
Mercury uptake capacity of MWCNTs was studied using batch
adsorption method at different concentration ranges up to 150 ppm.
Mercury concentration (before and after the treatment) was measured
using cold vapor atomic absorption spectroscopy. The effect of time,
concentration, pH and adsorbent dose were studied. MWCNT were
found to perform complete absorption in the sub-ppm concentrations
(parts per billion levels) while for high concentrations, the adsorption
efficiency was 92% at the optimum conditions; 0.1 g of the adsorbent
at 150 ppm mercury (II) solution. The adsorption of mercury on
MWCNTs was found to follow the Freundlich adsorption isotherm
and the pseudo-second order kinetic model.
Abstract: The detection of environmental gases, 12CO2, 13CO2,
and CH4, using near-infrared semiconductor lasers with a short
laser path length is studied by means of wavelength-modulation
spectroscopy. The developed system is compact and has high
sensitivity enough to detect the absorption peaks of isotopic 13CO2
of a 3-% CO2 gas at 2 μm with a path length of 2.4 m, where
its peak size is two orders of magnitude smaller than that of the
ordinary 12CO2 peaks. In addition, the detection of 12CO2 peaks of
a 385-ppm (0.0385-%) CO2 gas in the air is made at 2 μm with a
path length of 1.4 m. Furthermore, in pursuing the detection of an
ancient environmental CH4 gas confined to a bubble in ice at the
polar regions, measurements of the absorption spectrum for a trace
gas of CH4 in a small area are attempted. For a 100-% CH4 gas
trapped in a ∼ 1 mm3 glass container, the absorption peaks of CH4
are obtained at 1.65 μm with a path length of 3 mm, and also the
gas pressure is extrapolated from the measured data.
Abstract: This study was conducted to evaluate the manganese
removal from aqueous solution using Banana peels activated carbon
(BPAC). Batch experiments have been carried out to determine the
influence of parameters such as pH, biosorbent dose, initial metal ion
concentrations and contact times on the biosorption process. From
these investigations, a significant increase in percentage removal of
manganese 97.4% is observed at pH value 5.0, biosorbent dose 0.8 g,
initial concentration 20 ppm, temperature 25 ± 2°C, stirring rate 200
rpm and contact time 2h. The equilibrium concentration and the
adsorption capacity at equilibrium of the experimental results were
fitted to the Langmuir and Freundlich isotherm models; the Langmuir
isotherm was found to well represent the measured adsorption data
implying BPAC had heterogeneous surface. A raw groundwater
samples were collected from Baharmos groundwater treatment plant
network at Embaba and Manshiet Elkanater City/District-Giza,
Egypt, for treatment at the best conditions that reached at first phase
by BPAC. The treatment with BPAC could reduce iron and
manganese value of raw groundwater by 91.4% and 97.1%,
respectively and the effect of the treatment process on the
microbiological properties of groundwater sample showed decrease
of total bacterial count either at 22°C or at 37°C to 85.7% and 82.4%,
respectively. Also, BPAC was characterized using SEM and FTIR
spectroscopy.
Abstract: One- and two-dimensional carbon nanostructures with
sp2 hybridization of carbon atoms (single walled carbon nanotubes
and graphene) are promising materials in future electronic and
spintronics devices due to specific character of their electronic
structure. In this paper we present a comparative study of graphene
and single-wall carbon nanotubes by Raman spectro-microscopy in
strong magnetic field. This unique method allows to study changes in
electronic band structure of the two types of carbon nanostructures
induced by a strong magnetic field.
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: Pollution of the Klip River has caused
microorganisms inhabiting it to develop protective survival
mechanisms. This study isolated and characterized the heavy metal
resistant bacteria in the Klip River. Water and sediment samples were
collected from six sites along the course of the river. The pH,
turbidity, salinity, temperature and dissolved oxygen were measured
in-situ. The concentrations of six heavy metals (Cd, Cu, Fe, Ni, Pb
and Zn) of the water samples were determined by atomic absorption
spectroscopy. Biochemical and antibiotic profiles of the isolates were
assessed using the API 20E® and Kirby Bauer Method. Growth
studies were carried out using spectrophotometric methods. The
isolates were identified using 16SrDNA sequencing. The uppermost
part of the Klip River with the lowest pH had the highest levels of
heavy metals. Turbidity, salinity and specific conductivity increased
measurably at Site 4 (Henley on Klip Weir). MIC tests showed that
16 isolates exhibited high iron and lead resistance. Antibiotic
susceptibility tests revealed that the isolates exhibited multitolerances
to drugs such as Tetracycline, Ampicillin, and
Amoxicillin.
Abstract: The paper presents the results of clusterization by
Kohonen self-organizing maps (SOM) applied for analysis of array of
Raman spectra of multi-component solutions of inorganic salts, for
determination of types of salts present in the solution. It is
demonstrated that use of SOM is a promising method for solution of
clusterization and classification problems in spectroscopy of multicomponent
objects, as attributing a pattern to some cluster may be
used for recognition of component composition of the object.
Abstract: In this study, a comparative analysis of the approaches
associated with the use of neural network algorithms for effective
solution of a complex inverse problem – the problem of identifying
and determining the individual concentrations of inorganic salts in
multicomponent aqueous solutions by the spectra of Raman
scattering of light – is performed. It is shown that application of
artificial neural networks provides the average accuracy of
determination of concentration of each salt no worse than 0.025 M.
The results of comparative analysis of input data compression
methods are presented. It is demonstrated that use of uniform
aggregation of input features allows decreasing the error of
determination of individual concentrations of components by 16-18%
on the average.
Abstract: Bioreduction of silver nanoparticles (AgNPs) from silver ions (Ag+) using water extract of Thai basil leaf was successfully carried out. The basil leaf extract provided a reducing agent and stabilizing agent for a synthesis of metal nanoparticles. Silver nanoparticles received from cut and uncut basil leaf was compared. The resulting silver nanoparticles are characterized by UV-Vis spectroscopy. The maximum intensities of silver nanoparticle from cut and uncut basil leaf were 410 and 420, respectively. The techniques involved are simple, eco-friendly and rapid.
Abstract: The porous silicon (PS), formed from the anodization
of a p+ type substrate silicon, consists of a network organized in a
pseudo-column as structure of multiple side ramifications. Structural
micro-topology can be interpreted as the fraction of the interconnected
solid phase contributing to thermal transport. The
reduction of dimensions of silicon of each nanocristallite during the
oxidation induced a reduction in thermal conductivity. Integration of
thermal sensors in the Microsystems silicon requires an effective
insulation of the sensor element. Indeed, the low thermal conductivity
of PS consists in a very promising way in the fabrication of integrated
thermal Microsystems.In this work we are interesting in the
measurements of thermal conductivity (on the surface and in depth)
of PS by the micro-Raman spectroscopy. The thermal conductivity is
studied according to the parameters of anodization (initial doping and
current density. We also, determine porosity of samples by
spectroellipsometry.
Abstract: The deposition of diamond films on a Si3N4 substrate
is an attractive technique for industrial applications because of the
excellent properties of diamond. Pretreatment of substrate is very
important prior to diamond deposition to promote nucleation and
adhesion between coating and substrate. Deposition of
nanocrystalline diamonds films on silicon nitride substrate have been
carried out by HF-CVD technique using mixture of methane and
hydrogen gases. Different pretreatment of substrate including
chemical etching consists of hot acid etching and basic etching and
mechanical etching were used to study the quality of diamond formed
on the substrate. The structure and morphology of diamond coating
have been studied using X-ray Diffraction (XRD) and Scanning
Electron Microscope (SEM) while diamond film quality has been
characterized using Raman spectroscopy. AFM was used to
investigate the effect of chemical etching and mechanical
pretreatment on the surface roughness of the substrates and the
resultant morphology of nanocrystalline diamond. It was found that
diamond film deposited on as-received, basic etched and grinded
substrate shows the morphology of cauliflower while blasted and
acidic etched substrates produce smooth, continuous diamond film.
However, the Raman investigation did not show any deviation in
quality of diamond film for any pretreatment.
Abstract: ZnO nanostructure were synthesized via microwave
method using zinc acetate as starting material, guanidinium as
structure directing agents, and water as solvent.. This work
investigates the photodegradation of azo dyes using the ZnO Flowerlike
in aqueous solutions. As synthesized ZnO samples were
characterized using X-Ray powder diffraction (XRD), scanning
electron microscopy (SEM), and FTIR spectroscopy.In this work
photodecolorization of congored azo dye under UV irradiation by
nano ZnO was studied.
Abstract: The state and stability of hemoglobin adsorbed on the
glass surface was investigated using slab optical waveguide (SOWG)
spectroscopy. The peak position of the absorption band of hemoglobin
adsorbed on the glass surface was same as that of the hemoglobin in
solution. This result suggests that no significant denaturation occurred
by adsorption. The adsorption of hemoglobin is relatively strong that
the hemoglobin molecules even remained adsorbed after rinsing the
cell with buffer solution. The peak shift caused by the reduction of
adsorbed hemoglobin was also observed.