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1.
A. Venkateswara Rao Uzma K. H. Bangi Sunetra L. Dhere Hiroaki Imai Hiroshi Hirashima 《Journal of Sol-Gel Science and Technology》2011,57(1):95-100
The effect of iron acetylacetonate on the physico-chemical properties of waterglass based silica aerogels by ambient pressure
drying has been investigated. Doping the gels with iron acetylacetonat (FeAA) facilitates in the diminution of the density
of the aerogels. The well established silica network provides effective confinement of FeAA nanoparticles which resists the
collapse of silica network during ambient pressure drying. Therefore, in the present paper, the effects of FeAA on the physico-chemical
properties of the aerogels have been studied by varying the FeAA:Na2SiO3 molar ratio from 3 × 10−4 to 6 × 10−4. The aerogels were prepared via ambient pressure drying and characterized by the bulk density, thermal conductivity and water
contact angle. The aerogel’s surface morphology, elemental analysis and pore structure were characterized by means of EDAX
and FTIR, TEM and N2 adsorption- desorption analyzer. The high temperature hydrophobicity of these aerogels was checked by heating them in temperature
controlled furnace. Silica aerogels with low density ~0.050 g/cc have been obtained using the molar ratio of Na2SiO3:H2O:FeAA:Citric acid:TMCS at 1:146.67:3 × 10−4:0.54:9.46, respectively. EDAX and FTIR studies show that the iron species are entrapped in the mesoporous framework and not
took part in the bonding with silica. 相似文献
2.
Y. Kobayashi H. Kakinuma D. Nagao Y. Ando T. Miyazaki M. Konno 《Journal of Sol-Gel Science and Technology》2008,47(1):16-22
This paper describes a method for fabrication of silica-coated Co–Pt alloy nanoparticles in a liquid phase process. The Co–Pt
nanoparticles were prepared from CoCl2 (4.2 × 10−5 M), H2PtCl6 (1.8 × 10−5 M), citric acid (4 × 10−4 M) and NaBH4 (1.2 × 10−2 M) with a Co:Pt mole ratio of 7:3. The silica coating was performed in water/ethanol solution with a silane coupling agent,
3-aminopropyltrimethoxysilane (8 × 10−5 M), and a silica source, tetraethoxyorthosilicate (7.2 × 10−4 M) in the presence of the Co–Pt nanoparticles. Observations with a transmittance electron microscope and a scanning transmission
electron microscope revealed that the Co-rich and Pt-rich nanoparticles were coated with silica. According to X-ray diffraction
measurements, core particles were crystallized to metallic Co crystallites and fcc Co–Pt alloy crystallites with annealing
in air at 300–500 °C. Magnetic properties of the silica-coated particles were strongly dependent on annealing temperature.
Maximum values of 11.4 emu/g-sample for saturation magnetization and 365 Oe for coercive field were obtained for the particles
annealed at 300 and 500 °C, respectively. Annealing at a temperature as high as 700 °C destroyed the coating structures because
of crystallization of silica shell, resulting in reduction in saturation magnetization and coercive field. 相似文献
3.
Yoshio Kobayashi Takuya Nozawa Tomohiko Nakagawa Kohsuke Gonda Motohiro Takeda Noriaki Ohuchi Atsuo Kasuya 《Journal of Sol-Gel Science and Technology》2010,55(1):79-85
This paper describes a method for direct coating of fluorescent semiconductor nanoparticles with silica shell. The fluorescent
semiconductor nanoparticles used were CdSe
x
Te1–x
nanoparticles coated with ZnS and succeedingly surface-modified with carboxyl groups, or quantum dots (Q-dots). The Q-dots
were silica-coated by performing sol–gel reaction of tetraethyl orthosilicate (TEOS) using NaOH as a catalyst in the presence
of the Q-dots. Quasi-perfect Q-dots/silica core-shell particles were formed at 5.0 M H2O and 4.0 × 10−4 M NaOH. Under these concentrations of H2O and NaOH, the particle size of Q-dots/silica particles could be varied from 20.1 to 38.1 nm as the TEOS concentration increased
from 2.5 × 10−4 to 50 × 10−4 M. The Q-dots/silica particles showed fluorescence as well as the uncoated Q-dots. 相似文献
4.
In this work we prepared the hybrid material (SG) by the sol–gel method through the reaction between tetraethylortosilicate
(TEOS) and acetylacetonatepropyltrimethoxysilane (ACACSIL). We also immobilized the acetylacetonate on silica surface (GR)
by the grafting method through the reaction between a commercial silica and ACACSIL. Infrared thermal analysis showed that
these materials were thermally stable until 200 °C. SG is a microporous material and has surface area of 500 m2 g−1, average porous volume of 0.09 cm3 g−1 and organic content of 1 mmol g−1. GR is a mesoporous material and has surface area of 300 m2 g−1, average porous volume of 0.7 cm3 g−1 and organic content of 0.4 mmol g−1. Iron(III) was coordinated to SG and GR resulting in the SG–Fe and GR–Fe silicas which were tested as catalysts on the aerobic
epoxidation of cis-cyclooctene. SG–Fe yielded 100% of conversion and 94% of selectivity in epoxide whereas GR–Fe silica led
to a maximum conversion of 50% and 100% of selectivity. 相似文献
5.
Silver nanoparticles are prepared by reducing Ag+ ions with sodium borohydride in aqueous solutions containing carbonate ions (5 × 10−5−1 × 10−2 mol l−1). It is established that carbonate ions represent an efficient stabilizer that provides nanoparticles with electrostatic
protection via the formation of an electrical double layer. The maximum stability of a silver dispersion is observed at a
carbonate ion concentration of 1 × 10−3 mol l−1. The average size of silver nanoparticles is 10.0 ± 2.5 nm. The formation kinetics of silver nanoparticles is described by
an equation for a first-order reaction with a rate constant of 2.3 × 10−3 s−1 (±20%). 相似文献
6.
We have developed a circular-dichroism thermal lens microscope for UV wavelengths (UV-CD-TLM), for the first time, to realize
sensitive chiral analysis on a microchip. Quasi-continuous-wave phase modulation of a pulsed UV laser was used to generate
left-circularly polarized light and right-circularly polarized light and to detect the generated TL signal amplitude and phase
with a lock-in amplifier. The amplitude and phase were used to determine the concentration and chirality, respectively, of
a sample. The basic principle of UV-CD-TLM for chiral analysis on a microchip was verified by measuring aqueous solutions
of optically active camphorsulfonic acids (CSA). Lower limits of detection (LOD) were calculated at S/N = 2 and were 8.7 × 10−4 mol L−1 (ΔA = 5.2 × 10−6 Abs.) for (+)-CSA and 8.4 × 10−4 mol L−1 (ΔA = 5.0 × 10−6 Abs.) for (−)-CSA. In terms of number of molecules, LODs for UV-CD-TLM were calculated to be 8.7 fmol and 8.4 fmol, respectively.
This is at least three orders of magnitude lower than previously obtained. The applicability of UV-CD-TLM for chiral analysis
on a microchip was verified.
Figure Sensitive chiral analysis by thermal lens microscope (TLM) 相似文献
7.
Bangfa Ni Caijing Xiao Donghui Huang Hongchao Sun Guiying Zhang Cunxiong Liu Pingsheng Wang Haiqing Zhang Weizhi Tian 《Journal of Radioanalytical and Nuclear Chemistry》2012,291(2):313-319
China Advance Research Reactor (CARR) at China Institute of Atomic Energy (CIAE), with a non-perturbed maximum thermal neutron
flux of 1 × 1015 cm−2 s−1 at the center of active area, is one of the most powerful research reactors in the world. Three neutron channels have been
allocated for conventional neutron activation analysis (NAA), thermal neutron prompt gamma activation analysis (PGAA) and
cold neutron PGAA, respectively. Two irradiation tube systems are installed in the conventional NAA channel. One of them is
for short irradiation with the rabbit size of diameter (Φ)19 × 40 mm, the other one is for long irradiation with the rabbit
size of Φ39 × 70 mm. The medium temperature is about 45 °C and the thermal neutron flux is about 3 × 1014 cm−2 s−1 at sample positions. The flux gradient is expected to be very small according to the designed neutron flux distribution.
Pneumatic systems are used for samples transfer. The speed of rabbits is designed to be about 20 m/s, and it takes 3 s to
travel from irradiation position to detector. Three sets of gamma counting systems and one delayed neutron counting system
are being equipped for routine analysis. They are designed for running continuously and automatically. And all the functions
can be operated at laboratory or office through remote controlled computer. Software has been made domestically for spectrum
peak search, concentration calculation with relative method and k0 method with interference corrections and some other functions for the convenience of users. 相似文献
8.
Barbora Drtinová Milan Pospíšil 《Journal of Radioanalytical and Nuclear Chemistry》2010,286(3):631-636
Behavior of cadmium(II) in aqueous solutions irradiated by accelerated electrons was studied. A concentration of 8.8 × 10−4 mol L−1 of cadmium dissolved from Cd(NO3)2 requires dose of 15 kGy to be effectively removed from the system containing 1 × 10−2 mol L−1 of HCOOK as a scavenger of OH radicals. The positive effect of deaeration with N2O or N2 was observed in the range of lower doses. The addition of solid modifiers (bentonite, active carbon, zeolite, Cu2O, NiO, TiO2 and CuO) reduced the effectivity of radiation removal of cadmium. Product of irradiation is CdCO3. On the contrary, in the system with cadmium dissolved from CdCl2 radiation reduction takes place. Systems contained organic complexants (ethylene diamine tetraacetic acid–EDTA, citric acid)
were also studied. The solutions of Cd(NO3)2 containing initial concentration 2.37 × 10−4 mol L−1 of CdII were mixed with 3 × 10−4 mol L−1 EDTA. In this system the efficient degradation proceeds up to 90% at a dose of 45 kGy with addition of 5 × 10−3 mol L−1 carbonate (pH 10.5). The product of irradiation is CdCO3. The presence of 1 × 10−2 mol L−1 of HCOOK in the solution is necessary for radiation removal of cadmium complexed with citric acid (1 × 10−3 mol L−1) at pH 8. With increasing concentration of HCOOK (up to 5 × 10−2 mol L−1) decreases the pH value necessary for the radiation induced precipitation of cadmium. The best result was obtained in the
system containing zeolite as a solid modifier. 相似文献
9.
This work reported for the first time the use of flow injection electrochemiluminescence (FI-ECL) sensor for the determination
of durabolin in an aqueous system based on CdTe quantum dot (QD) films. Aqueous CdTe colloidal solutions were prepared using
thioglycolic acid as a capping agent. Zetasizer Nano ZS (Malvern, UK) was employed to characterize the size of CdTe QDs. The
UV–vis and photoluminescence spectra of samples were systematically characterized. Indium tin oxide (ITO) slide glass was
modified with CdTe QDs by layer-by-layer self-assembly. CdTe QD films were packed into a homemade cell and used as a recognizer
of the FI-ECL sensor to determine durabolin. The intensive anodic ECL emission was obtained at a starting potential of +1.3 V
(vs. Ag/AgCl) in a carbonate bicarbonate buffer solution with a pH of 9.93 at an ITO electrode. The ECL intensity was correlated
linearly with the concentration of durabolin over the range of 1.0 × 10−8–1.0 × 10−5 g mL−1, and the detection limit was 2.5 × 10−9 g mL−1. The relative standard deviation for the determination of 1.0 × 10−6 g mL−1 durabolin was 1.04% (n = 11). This simple and sensitive sensor revealed good reproducibility for ECL analysis. As a result, the new FI-ECL sensor
had been successfully applied to the determination of durabolin in food samples. This strategy could be easily realized and
opened new avenues for the applications of QDs in ECL biosensing. 相似文献
10.
Electrical conductivity of some dibenzoylmethane arylhydrazones (DBMAH) were measured during heating and reheating runs. The
observed variation of the conductance of the polycrystalline sample during thermal agitation was found to depend on the ordering
and disordering of molecules which in turn cause the lattice dipole to distort. A semiconducting behavior was detected for
these systems as it was deduced from their conductance values (1.7 × 10−6 − 8.25 × 10−7 ohm−1 cm−1). The presence of substituents affects markedly the measured electrical conductivity and calculated activation energy values. 相似文献
11.
Uzma K. H. Bangi M. S. Kavale Seungsu Baek Hyung-Ho Park 《Journal of Sol-Gel Science and Technology》2012,62(2):201-207
The successful incorporation of multiwalled carbon nanotubes (MWCNTs) into silica aerogels prepared by sol–gel method is reported
herein. Pure silica aerogels prepared using sodium silicate precursor by ambient pressure drying are so fragile that they
cannot be used easily. MWCNTs were used as reinforcements to improve the mechanical properties of silica aerogels. Results
show that inserting small amounts of MWCNTs in the gels causes enhanced dimensional stability of silica aerogels. The silica
aerogels were prepared by doping MWCNTs in silica matrix before gelation. The influence of MWCNTs on some microstructural
aspects of silica matrix has been studied using nitrogen adsorption–desorption isotherms. From SEM study it is confirmed that
the silica particles get capped on the surface of MWCNTs suggesting an enhanced toughness. Further, FTIR, Raman, EDAX, thermal
conductivity and hydrophobicity studies of these doped aerogels were carried out. By addition of MWCNTs, silica aerogels were
formed with 706 m2/g BET and 1,200 m2/g Langmuir surface areas and 149o contact angle. Low density (0.052 g/cc) and low thermal conductivity (0.067 W/m K) MWCNTs doped silica aerogels were obtained
for the molar ratio of Na2SiO3::H2O::MWCNTs::citric acid::TMCS at 1::146.67::2.5 × 10−3::0.54::9.46 respectively with improved mechanical strength. 相似文献
12.
Junzhi Zhang Jinyan Wang Linghua Wang Xiuyou Han Mingshan Zhao Xigao Jian 《Journal of Sol-Gel Science and Technology》2010,56(2):197-202
Colorless and transparent polysilisiquioxane was synthesized using non-hydrolytic sol–gel process. A high degree of poly-condensation
and a lower remnant ratio of Si–OCH3 were calculated by 29Si NMR and 1H NMR, respectively. After spin-coating, subsequently UV and thermal curing, free-cracked thin films were obtained. The properties
of the free-cracked thin films were measured by a prism coupler and thermal analysis system. The refractive index increased
to 1.5495 (1,310 nm TE) and 1.5468 (1,550 nm TE), respectively, with the increasing of phenyltrimethoxysilane content to 20 mol%.
Birefringence was below 0.0005. The thermo-optic coefficient was about −2.8 × 10−4 °C−1. The optical loss was 0.20 dB cm−1 at 1,310 nm and 0.75 dB cm−1 at 1,550 nm, which was very important for core layer material of optical waveguide. The results of Thermo-Gravimetric Analysis
indicated an excellent thermal stability. All of these properties imply that it will be a promising core layer material of
optical waveguide. 相似文献
13.
Jinglong Wang Yifei Jiang Dekun Huang Tingyu Wen Jinzhou Du Jing Zhang 《Journal of Radioanalytical and Nuclear Chemistry》2012,292(3):1297-1301
Through placement in a few hours after collecting radioaerosol samples (in Shanghai) after Fukushima nuclear power plant (NPP)
accident, radionuclides with gamma-emitting rays can be found to be nuclides (132I/132Te, 129I/129Te) other than 131I, 134,137Cs because of the decrease in background baseline after the daughter nuclides (i.e. 214Bi, 214Pb and etc.) of radon makes decay sharply. Based on aerosol sample collected by passing through 1,300 M3 air in 24 h, the lower limit of detection (LLD) of 132I/132Te, 129I/129Te can be decreased from 6.11 × 10−5, 3.46 × 10−4 Bq m−3 after half an hour sampling to 1.64 × 10−5, 8.19 × 10−5 Bq m−3 after sampling 48 h sampling. Similarly, LLD can be decreased from 9.63 × 10−5 to 1.41 × 10−5 Bq m−3 for 131I, 7.72 × 10−5 to 9.96 × 10−6 Bq m−3 for 134Cs and 9.67 × 10−5 to 1.45 × 10−5 Bq m−3 for 137Cs after the same time sampling. In the same time, the activities of daughter nuclides such as 214Pb and 212Bi from the decay of their parent nuclides 222Rn and 220Rn can sharply decrease from 2.45 × 10−2, 2.57 × 10−2 Bq m−3 to be ~10−4 Bq m−3 while the activities of the concerned nuclides 132I/132Te, 129Te, 131I, 134,137Cs were almost constant. As our knowledge, it is the first time to report such case which is very helpful to monitor the leaked
nuclides from NPP by aerosol sampling in both normal operation case and emergency case. 相似文献
14.
Xiaoying Liu Yonghong Li Xinsheng Liu Xiandong Zeng Bo Kong Shenglian Luo Wanzhi Wei 《Journal of Solid State Electrochemistry》2012,16(3):883-889
A simple sensor based on bare carbon ionic liquid electrode was fabricated for simultaneous determination of dihydroxybenzene
isomers in 0.1 mol L−1 phosphate buffer solution (pH 6.0). The oxidation peak potential of hydroquinone was about 0.136 V, catechol was about 0.240 V,
and resorcinol 0.632 V by differential pulse voltammetric measurements, which indicated that the dihydroxybenzene isomers
could be separated absolutely. The sensor showed wide linear behaviors in the range of 5.0 × 10−7–2.0 × 10−4 mol L−1 for hydroquinone and catechol, 3.5 × 10−6–1.535 × 10−4 mol L−1 for resorcinol, respectively. And the detection limits of the three dihydroxybenzene isomers were 5.0 × 10−8, 2.0 × 10−7, 5.0 × 10−7 mol L−1, respectively (S/N = 3). The proposed method could be applied to the determination of dihydroxybenzene isomers in artificial wastewater and
the recovery was from 93.9% to 104.6%. 相似文献
15.
Thongthai Witoon Metta Chareonpanich Jumras Limtrakul 《Journal of Sol-Gel Science and Technology》2009,51(2):146-152
In this study, the formation of silica–chitosan hybrid materials via sol–gel process under pH values of 2–6 were investigated
using N2 sorption analysis, scanning electron microscopy, transmission electron microscopy, thermal analysis and zeta potential analyzer.
The hierarchical structure consisting of meso- and macropore was formed when pH value was higher than 2. Mesopores were formed
as the interparticle channels of silica nanoparticles aggregates, whereas macropores were the void between the aggregates
(clusters). The clusters size was decreased with increasing the pH value, resulting in the increase of the macroporosity.
The thermal conductivity of the products was controlled in the range of 0.06 and 0.13 W m−1 K−1 by varying the product porosity between 88 and 69% (pH 6 and pH 2, respectively). 相似文献
16.
D. M. Ortega-Sotelo J. G. Gonzalez-Rodriguez M. A. Neri-Flores M. Casales L. Martinez A. Martinez-Villafañe 《Journal of Solid State Electrochemistry》2011,15(9):1997-2004
The corrosion inhibition of X-70 pipeline steel in saltwater saturated with CO2 at 50 °C with carboxyamido imidazoline has been evaluated by using electrochemical techniques. Techniques included polarization
curves, linear polarization resistance, electrochemical impedance, and electrochemical noise measurements. Inhibitor concentrations
were 0, 1.6 × 10−5, 3.32 × 10−5, 8.1 × 10−5, 1.6 × 10−4, and 3.32 × 10−4 mol l−1. All techniques showed that the best corrosion inhibition was obtained by adding 8.1 × 10−5 mol l−1 of carboxyamido imidazoline. For inhibitor concentrations higher than 8.1 × 10−5 mol l−1 a desorption process occurs, and an explanation has been given for this phenomenon. 相似文献
17.
Neetu Bansal 《Transition Metal Chemistry》2010,35(4):483-490
A kinetic method for the determination of organosulfur compounds by UV spectrophotometry is described. Organosulfur compounds
have been shown to inhibit the Hg(II)-catalyzed substitution of cyanide in hexacyanoferrate(II) by 2-methylpyrazine (2-Mepz).
The inhibitory effect is proportional to the concentration of inhibitor and can be used as the basis for the determination
of trace amounts of organosulfur compounds such as cysteine, 2,3-dimercaptopropanol (DMP) and thioglycolic acid (TGA). Both
the influence of the reaction variables and interference of a variety of ions have been studied. A mechanism for the inhibition
process is proposed. The determination range depends on the amount of Hg(II) added and stability of the Hg(II)–ligand complex.
Kinetic parameters were determined from Lineweaver–Burk plots, obtained in the absence and presence of the inhibitor. Excellent
linearity is observed for all analytes over their respective concentration ranges with correlation coefficient >0.9. The condition
calibration curves were linear in the range of 5 × 10−6–15 × 10−6 M for cysteine, 1 × 10−7–7 × 10−7 M for DMP and 1 × 10−6–10 × 10−6 M for TGA. The detection limits were 1.18 × 10−7 M for cysteine, 4.16 × 10−8 M for DMP and 1.30 × 10−7 M for TGA. The effects of amino acids that can interfere in the determination of cysteine were studied. 相似文献
18.
Abstract
The effect of sodium benzoate (SB) and sodium 4-(phenylamino)benzenesulfonate (SPABS) on the corrosion behavior of low carbon steel has been investigated using gravimetric method in the temperature range of 30–80 °C, velocity range of 1.44–2.02 m s−1 and concentration range of 6.94 × 10−4 to 4.16 × 10−3 mol dm−3 SB and 3.69 × 10−4 to 2.06 × 10−3 mol dm−3 SPABS. Optimization of temperature, fluid velocity, and inhibitors concentration has been made. The obtained results indicate that the inhibition efficiency (w IE %) at 1.56 m s−1 is not in excess of 81.5% at 4.16 × 10−3 mol dm−3 SB and 84.4% at 2.06 × 10−3 mol dm−3 SPABS. The inhibitive performance of these compounds showed an improvement with increasing concentration up to critical values of SB and SPABS; beyond these concentrations no further effectiveness is observed. These inhibitors retard the anodic dissolution of low carbon steel by protective layer bonding on the metal surface. The adsorption of SB and SPABS on the low carbon steel surface was found to obey the Freundlich isotherm model. The FT-IR spectroscopy was used to analyze the surface adsorbed film. 相似文献19.
R. Venkata Krishnan Hrudananda Jena K. V. Govindan Kutty K. Nagarajan 《Journal of Thermal Analysis and Calorimetry》2010,101(1):371-377
Rare earth uranates Nd6UO12, Gd6UO12 and Eu6UO12 were prepared by combustion synthesis and characterized by XRD. Single-phase rhombohedral structure was observed for all
the above compounds. Heat capacity measurements were carried out on Nd6UO12 and Gd6UO12 with differential scanning calorimetry in the temperature range 298–800 K. Enthalpy, entropy and Gibbs energy functions were
computed. Heat capacity values of Nd6UO12 and Gd6UO12 at 298 K are 436 and 400 J K−1 mol−1, respectively. Thermal expansion characteristics were studied using high temperature X-ray diffraction (HTXRD) in the temperature
range 298–873 K. The coefficients of thermal expansion measured for Eu6UO12 are 10.5 × 10−6 and 7.3 × 10−6 K−1 along a- and c-axis, respectively. Similarly, the coefficients of thermal expansion of Gd6UO12 along a-axis are 10.0 × 10−6 K−1 and along c-axis is 9.7 × 10−6 K−1. 相似文献
20.
Shanmugam Sreedaran Kuppannan Shanmuga Bharathi Aziz Kalilur Rahiman Raju Prabu Raman Jagadesh Nanjian Raaman Vengidusamy Narayanan 《Transition Metal Chemistry》2009,34(1):33-41
A series of trinuclear Cu(II) complexes have been prepared by Schiff base condensation of 1,8-[bis(3-formyl-2-hydroxy-5-methyl)benzyl]-l,4,8,11-tetraazacyclotetradecane
and 1,8-[bis(3-formyl-2-hydroxy-5-bromo)benzyl]-l,4,8,11-tetraazacyclotetradecane with aromatic and aliphatic diamines, Cu(II)
perchlorate and triethylamine. The complexes were characterized by elemental and spectroscopic analysis. Electrochemical studies
of the complexes in DMF solution show three irreversible one-electron reduction processes around Epc
1 = −0.73 to −0.98 V, Epc
2 = −0.91 to −1.20 V and Epc
3 = −1.21 to −1.33 V. ESR spectra and magnetic moments of the trinuclear Cu(II) complexes show the presence of antiferromagnetic
coupling. The rate constants for hydrolysis of 4-nitrophenylphosphate by the Cu(II) complexes are in the range of 3.33 × 10−2 to 7.58 × 10−2 min−1. The rate constants for the catecholase activity of the complexes fall in the range of 2.67 × 10−2 to 7.56 × 10−2 min−1. All the complexes were screened for antifungal and antibacterial activity. 相似文献