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1.
This article describes a method for silica coating of Co–Pt alloy nanoparticles prepared in the presence of poly(vinylpyrrolidone)
(PVP) as a stabilizer. The Co–Pt nanoparticles were prepared in an aqueous solution at 25–80 °C from CoCl 2 (3.0 × 10 −4 M), H 2PtCl 6 (3.0 × 10 −4 M), PVP (0–10 g/L), and NaBH 4 (4.8 × 10 −3–2.4 × 10 −2 M). The silica coating was performed for the Co–Pt nanoparticle colloid containing the PVP ([Co] = [Pt] = 3.0 × 10 −5 M) at 25 °C in (1/4) (v/v) water/ethanol solution with tetraethoxyorthosilicate (TEOS) (7.2 × 10 −5–7.2 × 10 −3 M) and ammonia (0.1–1.0 M). Silica particles, which had an average size of 43 nm and contained multiple cores of Co–Pt nanoparticles
with a size of ca. 8 nm, were produced at 1.4 × 10 −3 M TEOS and 0.5 M ammonia after the preparation of Co–Pt nanoparticles at 80 °C, 5 g/L PVP, and 2.4 × 10 −2 M NaBH 4. Their core particles were fcc Co–Pt alloy crystallites. Their saturation magnetization was 2.0-emu/g sample, and their coercive
field was 12 Oe. 相似文献
2.
A Ce(IV)-based reducing capacity (CERAC) assay was developed to measure the total antioxidant capacity (TAC) of foods, in
which Ce(IV) would selectively oxidize antioxidant compounds but not citric acid and reducing sugars which are not classified
as antioxidants. The method is based on the electron-transfer (ET) reaction between Ce(IV) ion and antioxidants in optimized
acidic sulphate medium ( i.e., 0.3 M H 2SO 4 and 0.7 M Na 2SO 4) and subsequent determination of the produced Ce(III) ions by a fluorometric method. The fluorescent product, Ce(III), exhibited
strong fluorescence at 360 nm with an excitation wavelength of 256 nm, the fluorescence intensity being correlated to antioxidant
power of the original sample. The linear concentration range for most antioxidants was quite wide, e.g., 5.0 × 10 −7–1.0 × 10 −5 M for quercetin. The developed procedure was successfully applied to the TAC assay of antioxidant compounds such as trolox,
quercetin, gallic acid, ascorbic acid, catechin, naringin, naringenin, caffeic acid, ferulic acid, glutathione, and cysteine.
The proposed method was reproducible, additive in terms of TAC values of constituents of complex mixtures, and the trolox
equivalent antioxidant capacities (TEAC coefficients) of the tested antioxidant compounds gave good correlations with those
found by reference methods such as ABTS and CUPRAC. 相似文献
3.
A selective fluorescent cesium optode on a chromoionophore consisting of anthracene covalently linked through an imine bond
to a 15-crown-5 derivative has been reported. In the present system, 15-crown-5 derivative including anthracene was used a
fluoroionophore. The fluorescence response mechanism is based on the photo-induced electron transfer (PET) from the lone pair
of electrons of the nitrogen to the anthracene group and inhibition of PET system by cesium binding while increasing the fluorescence
intensity. Emission intensity 15-crown-5 anthracene was measured at 500 nm with absorbance at 400 nm in CH 3CN–H 2O (1:1) media. The method shows a very good selectivity and sensitivity for cesium with respect to other cations such as K +, Na + and Li + with linear range and detection limit of 5.0 × 10 −5 to 5.0 × 10 −1M and 3.0 × 10 −6M respectively. 相似文献
4.
This paper explores an ultra-sensitive luminescence method for the determination of Ketoprofen (KP) in pharmaceutical formulations.
The technique is indirect and exploits the luminescence enhancement of terbium (Tb 3+) by complexation with KP (Tb 3+–KP), which was monitored at respective excitation and emission wavelengths of λ
ex = 258 nm and λ
em = 549 nm. The effect of varying the Tb 3+ concentration and using multiple solvents was examined to determine optimal experimental conditions. Maximum sensitization
was accomplished in the presence of methanol where the most favourable condition for the formation of the complex was recorded
at a level of 1.0 × 10 −5 M of Tb 3+. Under these optimum experimental conditions, linear calibration curve was obtained in the range of 2.8 × 10 −7–3.1 × 10 −6 M with a detection limit of 8.7 × 10 −8 M. The technique was validated with ‘working’ reference standards and produced relative standard deviations < 2% indicating
that the reproducibility was highly acceptable. The proposed method was successfully applied to assays of KP in pharmaceutical
formulations with average recoveries of 92–98%. The results were found to be in good agreement with those obtained by HPLC.
The method is highly suited for general applications of this nature. 相似文献
5.
In this study, the optical properties as well as mechanical and electrical degradation of low-density polyethylene (LDPE)/polypropylene
fiber (PP fiber) (10–50% PP fiber), polypropylene (PP)/PP fiber (10–50% PP fiber), and LDPE/diamond (0.1–3% diamond) blends,
which are prepared by hot pressing method, with changing thicknesses ranging from 30 to 225 μm, are compared. The spectra,
in the wavelength range 200–2500 nm, are examined. Based on optical absorption spectra obtained, Tauc graphs are plotted.
Determined values of the direct optical energy gap (E
d
opt
), the indirect optical energy gap (E
i
opt
), the width of the band (ΔE), and ultraviolet transmittance (T UV) are listed. The direct E
d
opt
and indirect E
i
opt
values for organic blends are in the range of 3.10–3.17 eV and 1.52–2.99 eV; for inorganic blends they are 1.80–4.13 eV and
1.55–4.7 eV respectively. The electrical strength (ε) and the mechanical tension (σ) have been investigated, and graphs (the
dependence of the electrical life time log τ ε on ε) are given. The experimental results are analyzed from the viewpoint of the validity of the thermofluctuation theory.
LDPE and LDPE/0.5% diamond composite parameters consecutively changed: σ from 68 to 82 MPa, ε from 60·10 6 to 85·10 6 V/m, mechanical lifetime τ σ from 10 to 1.5·10 5 sec, electrical lifetime τ ε from 2· 10 3 to 2·10 5 sec, and structure-sensitive parameters γ and χ — from 1.48 to 1.18 (J)MPa/mole and from 0.97 to 0.70 (J)Vm −1/mole respectively. The values of mechanical and electrical durability were observed to increase by 20 and 41%, respectively,
for LDPE/0.5% diamond composite.
Published in Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 5, pp. 677–683, September–October, 2007. 相似文献
6.
A highly sensitive method is proposed to determine copper(II) ions by forming a stable complex through their interaction with
4-(2′-benzothiazolylazo)-salicylic acid (BTAS) at room temperature and pH of about 5.0. The complex gave a maximum absorption
at λ = 485 nm with a molar absorptivity coefficient of 2.35·10 4 l/(mol·cm). The linear range for the copper determination is 0.63–5.04 mg/l. The method can be applied to determine copper
ions in different biological specimens like some drugs and water samples. 相似文献
7.
A sensitive time- resolved luminescence method for the determination of meloxicam (MX) in methanol and in aqueous solution
is described. The method is based on the luminescence sensitization of europium (Eu 3+) by formation of ternary complex with MX in the presence of 1,10- phenanthroline as coligand, Tween-80 as surfactant and
gadolinium ion as a co-luminescence reagent. The signal for Eu- MX-1, 10- phenanthroline is monitored at λ ex = 360 nm and λ em = 620 nm. Optimum conditions for the formation of the complex in aqueous system were 0.01 M TRIS buffer, pH 8.0, 1,10- phenanthroline
(6.0 × 10 −6 M) , Gd 3+ (7.0 × 10 −6 M), Tween-80 (0.28%) and 1.75 mM of Eu 3+ which allows the determination of 20–800 ppb of MX with limit of detection (LOD) of 7 ppb. The relative standard deviations
of the method range between 0.1 and 1.1% indicating excellent reproducibility of the method. The proposed method was successfully
applied for the assay of MX in pharmaceutical formulations, plasma and in urine samples. Average recoveries of 99.8 ± 1.1%,
100.2 ± 0.9% and 100.9 ± 1.1% were obtained for MX in tablet, plasma and urine sample respectively. 相似文献
8.
CdHgTe nanoparticles (NPs) with the emission in the near-infrared regions were prepared in aqueous solution, and were characterized
by transmission electron microscopy, X-ray diffraction spectrometry, spectrofluorometry and ultraviolet-visible spectrometry.
Based on the fluorescence quenching of CdHgTe NPs in the presence of proteins, a novel method for the determination of proteins
with CdHgTe NPs as a near-infrared fluorescence probe was developed. Maximum fluorescence quenching was observed with the
excitation and emission wavelengths of 500 and 693 nm, respectively. Under the optimal conditions, the calibration graphs
were linear in the range of 0.04 × 10 −6–5.6 × 10 −6 g ml −1 for lysozyme (Lyz) and 0.06 × 10 −6–6.1 × 10 −6 g ml −1 for bovine hemoglobin (BHb), respectively. The limits of detection were 13 ng ml −1 for Lyz and 27 ng ml −1 for BHb, respectively. Four synthetic samples were determined and the results were satisfied. 相似文献
9.
In this work, a new simple and sensitive flow injection method is developed for the determination of homocysteine with spectrofluorimetric
detection technique. This method is based on the oxidation of homocysteine with Tl (III) in acidic media, producing fluorescence
reagent, TlCl 32- (λ ex = 237 nm, λ em = 419 nm). The effects of chemical parameters (including pH of the solutions, the buffer, Tl (III) and potassium chloride
concentrations), instrumental parameters (such as flow rate of the solutions, reaction coil length, and sample loop volume)
and temperature on the fluorescence intensity as an analytical signal are studied and optimized. In the optimum conditions
of the above variables, homocysteine can be determined in the range 4.0 × 10 -7–40.0 × 10 -6 M with the LDR from 4.0 × 10 -7 to 25.0 × 10 -6 M. The detection limit (with S/N = 3) is 6.0 × 10 -8 M of homocysteine and precision for the injection of 5.0, 10.0 and 15.0 μM of homocysteine are 0.8%, 1.5% and 2.5% ( n = 10) respectively. The rate of analysis is 90 samples per hour. The influence of potential interfering substances, including
amino acids and carbohydrates is also studied. The proposed method has been successfully used for the determination of homocysteine
in the real sample (blood serum and tap water) matrix. 相似文献
10.
Gold nanoparticles have been precipitated on the surface of quartz slides covered with titanium (IV) butoxide. UV irradiation
of modified quartz slides immersed into water solutions of hydrogen tetrachloroaurate of different concentrations (2.5 × 10 −4–1.0 × 10 −2 M) has been used for this purpose. Properties of produced samples have been investigated by UV–Vis spectroscopy, IR spectroscopy,
SEM-EDX, TGA, and AFM. According to the obtained data, produced gold particles are distributed on modified quartz surface
very uniformly and the average size of gold particles is about 30–50 nm. 相似文献
11.
A new spectrofluorimetric method has been developed and validated for the quantification of ceftriaxone in bulk powder, pharmaceutical
formulations and spiked human plasma. The developed method is reproducible, accurate, sensitive and cost effective. In this
method, ceftriaxone was converted into a fluorescent compound by reacting with 0.8 M ethyl acetoacetate and 25% formaldehyde
in a buffered medium (pH = 4.2) at 90 °C. The excitation and emission wavelengths of the fluorescent reaction product are
316 nm and 388 nm respectively. Optimization of the experimental conditions affecting the condensation reaction were carefully
carried out and the optimum experimental conditions were incorporated in the procedure. The developed method has a broad linear
range (0.2–20 μg mL −1) with a correlation coefficient of 0.9992. The limit of detection (LOD) and limit of quantification (LOQ) was found to be
1.94 × 10 −2 μg mL −1 and 6.47 × 10 −2 μg mL −1 respectively. The common excipients and co-administered drugs were investigated for their interferences effect in the assay.
The developed method was validated statistically through recovery studies and successfully applied to ceftriaxone determination
in bulk powder, pharmaceutical formulations and spiked human plasma samples. The percent recoveries were found to be in the
range of 99.04–100.26% for bulk powder, 98.88–99.92% for pharmaceutical formulations and 94.22–98.48% for spiked human plasma.
The results were verified by comparing with reference literature HPLC method and were found in good agreement. 相似文献
12.
A novel, simple, sensitive and selective spectrofluorimetric method was developed for the determination of trace amounts of
chlorzoxazone and Ibuprofen in pharmaceutical tablets using optical sensor Eu-Tetracycline HCl doped in sol–gel matrix. The
chlorzoxazone or Ibuprofen can remarkably enhance the luminescence intensity of Eu-Tetracycline HCl complex doped in a sol–gel
matrix in dimethylformamide (DMF) at pH 9.7 and 6.3, respectively, λ ex = 400 nm. The enhancing of luminescence intensity peak of Eu-Tetracycline HCl complex at 617 nm is proportional to the concentration
of chlorzoxazone or Ibuprofen a result that suggested profitable application as a simple optical sensor for chlorzoxazone
or Ibuprofen assessment. The dynamic ranges found for the determination of chlorzoxazone and Ibuprofen concentration are 5 × 10 −9–1 × 10 −4 and 1 × 10 −8–7 × 10 −5 mol L −1, and the limit of detection (LOD) and quantitation limit of detection (LOQ) are 3.1 × 10 −10 , 9.6 × 10 −10 and 5.6 × 10 −10, 1.7 × 10 −9 mol L −1, respectively. 相似文献
13.
A new, simple and accurate spectrofluorimetric method for the determination of metoclopramide hydrochloride was developed.
The metoclopramide hydrochloride can remarkably enhance the luminescence intensity of the Tb 3+ ion doped in PMMA matrix at λ ex = 360 nm in methanol at pH 6.9. The intensity of the emission band at 545 nm of Tb 3+ ion doped in PMMA matrix is increased due to the energy transfer from metoclopramide hydrochloride to Tb 3+ in the excited stated. The effect of different parameters, e.g., pH, temperature, Tb 3+ concentration, foreign ions that control the fluorescence intensity of the produced ion associate was critically investigated.
The calibration curve of the emission intensity at 545 nm shows linear response of metoclopramide over a concentration range
of 5 × 10 −5–5.0 × 10 −8 M with detection limit of 8.7 × 10 −10 M. The method was used successfully for the determination of metoclopramide in pharmaceutical preparations and human serum.
The average recovery of 99.48% with standard deviation of 0.32% and 96.98% with standard deviation of 0.4%, of pharmaceutical
preparations and human serum respectively, were obtained which compared will with the results obtained from standard LC method
of average recovery 99.04% and standard deviation of 0.6% and average recovery of 98.19% with standard deviation of 0.6% of
pharmaceutical preparations and human serum, respectively. 相似文献
14.
We report a technique for the efficient generation of tunable coherent deep UV radiation and its application in studies of
RDX and TNT at the ppm level on the basis of their absorption characteristics. The obtained experimental absorption data are
compared with conventional spectrophotometric data. The UV radiation in the range 200–260 nm has been generated by the type-I
noncollinear third harmonic of the dye laser radiation (600–700 nm) and also by sum frequency mixing (SFM) of Nd:YAG output
(1064 nm) with the second harmonic of the dye laser in β-barium borate (BBO) crystal. The maximum conversion efficiency of
the generated signal is estimated to be 57.5% at λ = 218.9 nm wavelength. Apart from measurements of the absorbance of RDX
and TNT at different concentrations in their respective solutions, the minimum detection concentrations have also been ascertained.
The estimated minimum detectable concentration of RDX is 8.47·10 −9 M, whereas that for TNT is 35.7·10 −9 M. The data were obtained using only ∼100 μJ/pulse of laser energy.
Published in Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 6, pp. 516–521, July–August, 2007. 相似文献
15.
A new, simple, sensitive and selective spectrofluorimetric method for the determination of Hydrochlorothiazide was developed
in acetonitrile at pH 6.2. The Hydrochlorothiazide can remarkably enhance the luminescence intensity of the Tb 3+ ion doped in sol–gel matrix at λ ex = 370 nm. The intensity of the emission band of Tb 3+ ion doped in sol–gel matrix was increased due to the energy transfer from the triplet excited state of Hydrochlorothiazide
to ( 5D 4) excited energy state of Tb 3 ion. The enhancement of the emission band of Tb 3+ ion doped in sol–gel matrix at ( 5D 4→ 7 F 5) 545 nm was directly proportion to the concentration of Hydrochlorothiazide with a dynamic ranges of 5.0 × 10 −10—5.0 × 10 −6 mol L −1 and detection limit of 2.2 × 10 −11 mol L −1. 相似文献
16.
A sensitive, simple, and reproducible method was developed in this study for the determination of pramipexole, and in doing that, a glassy carbon electrode modified with –COOH-functionalized multi-walled carbon nanotube was utilized. The modified electrode was compared with a bare glassy carbon electrode in order to prove the sensitivity of the developed sensor. Cyclic, differential pulse, and adsorptive stripping differential pulse voltammetric techniques were used to investigate the oxidation behavior and stripping techniques were used for the determination of pramipexole. Based on optimum experimental conditions, calibration and partial validation studies were realized for bare and modified electrodes. As a result, the values of limit of detection and quantification were determined as be 2.38 × 10−10 and 7.93 × 10−10 M for bare and 1.06 × 10−10 and 3.52 × 10−10 M for modified glassy carbon electrodes, respectively. The applicability of the bare and modified electrodes was demonstrated for the determination of pramipexole in pharmaceutical dosage forms. The selectivity of the developed method was considered in the presence of Ca2+, Na+, K+, and glucose, ascorbic acid, uric acid, and dopamine. Interfering agents except uric acid did not affect pramipexole determination considerably. 相似文献
17.
Building activities are recognised to produce coarse particulate matter but less is known about the release of airborne ultrafine
particles (UFPs; those below 100 nm in diameter). For the first time, this study has investigated the release of particles
in the 5–560 nm range from three simulated building activities: the crushing of concrete cubes, the demolition of old concrete
slabs, and the recycling of concrete debris. A fast response differential mobility spectrometer (Cambustion DMS50) was used
to measure particle number concentrations (PNC) and size distributions (PNDs) at a sampling frequency of 10 Hz in a confined
laboratory room providing controlled environment and near–steady background PNCs. The sampling point was intentionally kept
close to the test samples so that the release of new UFPs during these simulated processes can be quantified. Tri–modal particle
size distributions were recorded for all cases, demonstrating different peak diameters in fresh nuclei (<10 nm), nucleation
(10–30 nm) and accumulation (30–300 nm) modes for individual activities. The measured background size distributions showed
modal peaks at about 13 and 49 nm with average background PNCs ~1.47 × 10 4 cm −3. These background modal peaks shifted towards the larger sizes during the work periods (i.e. actual experiments) and the
total PNCs increased between 2 and 17 times over the background PNCs for different activities. After adjusting for background
concentrations, the net release of PNCs during cube crushing, slab demolition, and ‘dry’ and ‘wet’ recycling events were measured
as ~0.77, 19.1, 22.7 and 1.76 (×10 4) cm −3, respectively. The PNDs were converted into particle mass concentrations (PMCs). While majority of new PNC release was below
100 nm (i.e. UFPs), the bulk of new PMC emissions were constituted by the particles over 100 nm; ~95, 79, 73 and 90% of total
PNCs, and ~71, 92, 93 and 91% of total PMCs, for cube crushing, slab demolition, dry recycling and wet recycling, respectively.
The results of this study firmly elucidate the release of UFPs and raise a need for further detailed studies and designing
health and safety related exposure guidelines for laboratory workplaces and operational building sites. 相似文献
18.
A simple and sensitive spectrofluorimetric method for determination of trace amount of doxycycline hydrochloride (DC) in pharmaceutical
tablets and serum samples was developed. In ammonia buffer solution of pH 8.9 the doxycycline hydrochloride can remarkably
enhance the luminescence intensity of the Sm 3+ ion in Sm 3+- DC complex at λ ex = 400 nm. The produced luminescence intensity of Sm 3+- DC complex in DMSO is in proportion to the concentration of DC and used as optical sensor for its determination. The dynamic
range for the determination of DC is 1 × 10 −8 – 5 × 10 −6 mol L −1 and in case of quantum yield calculations is 7 × 10 −9 – 5 × 10 −6 mol L −1 with detection limit of 6.5 × 10 −10 mol L −1. The enhancement mechanism of the luminescence intensity in the Sm 3+- DC system has been also discussed. A comparison with other spectrofluorimetric methods for tetracycline derivatives in which
Eu 3+ ion is used instead of Sm 3+ ion is also studied. 相似文献
19.
The internal morphology and magnetic properties of layer-by-layer assembled nanofilms of polyaniline (PANI) and maghemite
(γ-Fe 2O 3—7.5-nm diameter) were probed with cross-sectional transmission electron microscopy (TEM) and magnetization measurements (magnetic
hysteresis loops, magnetization using zero-field cooled/field-cooled protocols, and ac magnetic susceptibility). Additionally,
simulations of the as-produced samples were performed to assess both the nanofilm’s morphology and the corresponding magnetic
signatures using the cell dynamic system (CDS) approach and Monte Carlo (MC) through the standard Metropolis algorithm, respectively.
Fine control of the film thickness and average maghemite particle–particle within this magnetic structure was accomplished
by varying the number of bilayers (PANI/γ-Fe 2O 3) deposited onto silicon substrates or through changing the concentration of the maghemite particles suspended within the
colloidal dispersion sample used for film fabrication. PANI/γ-Fe 2O 3 nanofilms comprising 5, 10, 25 and 50 deposited bilayers displayed, respectively, blocking temperatures ( T
B) of 30, 35, 39 and 40 K and effective energy barriers (Δ E/ k
B) of 1.0 × 10 3, 2.3 × 10 3, 2.8 × 10 3 and 2.9 × 10 3 K. Simulation of magnetic nanofilms using the CDS model provided the internal morphology to carry on MC simulation of the
magnetic properties of the system taking into account the particle–particle dipolar interaction. The simulated (using CDS)
surface–surface particle distance of 0.5, 2.5 and 4.5 nm was obtained for nanofilms with thicknesses of 36.0, 33.9 and 27.1 nm,
respectively. The simulated (using MC) T
B values were 33.0, 30.2 and 29.5 K for nanofilms with thicknesses of 36.0, 33.9 and 27.1 nm, respectively. We found the experimental
(TEM and magnetic measurements) and the simulated data (CDS and MC) in very good agreement, falling within the same range
and displaying the same systematic trend. Our findings open up new perspectives for fabrication of magnetic nanofilms with
pre-established (simulated) morphology and magnetic properties. 相似文献
20.
An anti-Stokes luminescence band with λ max = 515 nm of microcrystals of solid AgCl 0.95I 0.05 solutions excited by a radiation flux of density 10 13–10 15 quanta/cm 2·sec in the range 600–800 nm at 77 K was detected. It is shown that the intensity of this luminescence and the frequency of
its excitation depend on the prior UV-irradiation of samples. Analysis of the stimulated-photoluminescence spectra and the
anti-Stokes luminescence excitation spectra of the indicated microcrystals has shown that to the centers of anti-Stokes luminescence
excitation correspond local levels in the forbidden band of the crystals. These states are apparently due to the atomic and
molecular disperse silver particles that can be inherent in character or formed as a result of a low-temperature photochemical
process.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 6, pp. 738–742, November–December, 2005. 相似文献
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