共查询到20条相似文献,搜索用时 31 毫秒
1.
G. V. Mamontov V. V. Dutov V. I. Sobolev O. V. Vodyankina 《Kinetics and Catalysis》2013,54(4):487-491
The catalysts of silver supported on mesoporous silica modified with Co3O4, CeO2, and ZrO2 were prepared by an impregnation method; characterized by X-ray diffraction analysis, temperature-programmed reduction, and low-temperature nitrogen adsorption; and studied in a model reaction of CO oxidation. It was found that the Ag/SiO2 system exhibited high activity in the reaction of CO oxidation, and the addition of transition metal oxides led to reduction of the temperature of 50% CO conversion by 40°C. The modification of Ag/SiO2 with cerium dioxide was found most effective because of the interaction of silver particles and CeO2 on the surface of silica gel. 相似文献
2.
M. Gabrovska D. Nikolova J. Krstić M. Stanković P. Stefanov R. Edreva-Kardjieva D. Jovanović 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2009,83(9):1461-1467
Two series of silver modified Ni-Mg materials were synthesized by precipitation-deposition on SiO2 support derived from two silica sources: diatomite activated at 800°C (Series a; Mg/Ni = 0.1 and SiO2/Ni = 1.07) and synthetic water glass (Series b; Mg/Ni = 0.1 and SiO2/Ni = 1.15). The modification with silver was made at three molar Ag/Ni ratios, namely 0.0025, 0.025, and 0.1. The effects
of the source of the silica support and the silver presence and content on the nickel state in the silver modified reduced-passivated
NiMg/SiO2 precursors of the vegetable oil hydrogenation catalyst were established by X-ray diffraction and X-ray photoelectron spectroscopy
techniques. The passivation procedure was applied in order to protect the metallic nickel particles from further oxidation.
The crystallization of the formed nickel hydrosilicate phases depends on the source of the silica support, more expressed
in the diatomite supported samples. It was shown that the silver modification of the NiMg/SiO2 precursors enhances the reduction of the nickel hydrosilicates accompanied by formation of relatively smaller metallic nickel
particles, more pronounced in the water glass supported precursors. The increase of the silver content in the water glass
deposited samples is responsible for the metallic nickel dispersion increase. The higher content of the Ni0 particles on the surface of the diatomite deposited samples is in accordance with the higher stability of the larger metallic
nickel crystallites to oxidation during the passivation step. On contrary, higher dispersed Ni0 particles on the surface of the water glass supported samples are more susceptible to the oxida
The article is published in the original. 相似文献
3.
Marek Jasiorski Anna Leszkiewicz Stefan Brzeziński Gabriela Bugla-Płoskońska Grażyna Malinowska Beata Borak Iwona Karbownik Agnieszka Baszczuk Wiesław Stręk Włodzimierz Doroszkiewicz 《Journal of Sol-Gel Science and Technology》2009,51(3):330-334
The aim of this study was to investigate antimicrobial activity of textiles doped with silver in different forms. Three types
of textiles were prepared and examined: textiles doped with commercially available Ag nanoparticles, textiles doped with commercial
colloidal silver and textiles doped with silver silica SiO2/Ag spheres. The specimens of silica submicron spheres were synthesized by the sol–gel method as a matrix for biological active
silver. The results of microbiological tests revealed that among three kinds of Ag doped textiles only these doped with SiO2/Ag spheres are bacteriostatically active. During the experiments minimal inhibiting bacteria growth concentration of active
SiO2/Ag spheres added to textiles was determined. 相似文献
4.
Betul Akkopru Akgun Nathan P. Mellott Caner Durucan 《Journal of Sol-Gel Science and Technology》2012,62(2):240-251
Silver containing silica (Ag–SiO2) thin films with and without aluminum (Al) were prepared on soda-lime-silica glass by spin coating of aqueous sols. The coating
sol was formed through mixing tetraethyl orthosilicate [Si(OC2H5)4]/ethanol solution with aqueous silver nitrate (AgNO3) and aluminum nitrate nonahydrate [(AlNO3)3·9H2O] solutions. The deposited films were calcined in air at 100, 300 and 500 °C for 2 h and characterized using x-ray diffraction,
UV-visible and x-ray photoelectron spectroscopy. The effect of Al incorporation and calcination treatment on microstructure
and durability of the films, and chemical/physical state of silver in the silica thin film have been reported. The bactericidal
activity of the films was also determined against Staphylococcus aureus via disk diffusion assay studies before and after chemical durability tests. The investigations revealed that the optical,
bactericidal properties and chemical durability of Ag–SiO2 films can be improved by Al addition. The Al-modified Ag–SiO2 thin films do not exhibit any coloring after calcination in the range of 100–500 °C, illustrating that silver is incorporated
within the silica gel network in ionic form (Ag+). Al incorporation also improved the overall durability and antibacterial endurance of Ag–SiO2 thin films. 相似文献
5.
D. O. Martynova L. S. Kibis O. A. Stonkus O. V. Vodyankina T. I. Izaak E. M. Slavinskaya A. I. Boronin 《Kinetics and Catalysis》2013,54(4):492-496
The Ag/SiO2 composites were synthesized based on porous blocked silica with a pore size of 30–50 nm and a specific surface area of 99 m2/g. Silver particles were introduced into the pores of the support by its impregnation with a solution of an ammonium complex of silver followed by reduction with hydrogen. The liquid-phase reduction of silver ions in pores was performed in the absence of stabilizing agents with the use of ethylene glycol (a polyol method) or formamide as a reducing agent. The methods used in the preparation of composites made it possible to vary the particle size of silver. The greatest size that is almost comparable with the pore size was achieved with the use of formamide. The catalytic activity of the Ag/SiO2 composites was studied in the reaction of CO oxidation. It was found that the catalysts obtained upon the reduction of Ag+ ions by formamide exhibited considerable low-temperature activity. A necessary condition for the manifestation of low-temperature activity is redox treatment, in the course of which the particle size of silver considerably decreases. 相似文献
6.
B. Mahltig E. Gutmann M. Reibold D. C. Meyer H. Böttcher 《Journal of Sol-Gel Science and Technology》2009,51(2):204-214
Ag and Ag/SiO2 sols containing nanocrystalline silver particles can be advantageously prepared by solvothermal methods using an autoclave
with conventional thermal or microwave heating. In this process, the reduction of silver salts can be realized with alcohols
like ethanol in the presence of polyvinylpyrrolidone at temperatures of more than 120 °C. Furthermore a combination of silver
salt reduction with hydrolysis of alkoxysilanes during the solvothermal process can yield Ag/SiO2 composite sols. Particle size and crystallinity of as-prepared particles are analyzed by means of X-ray diffraction and high-resolution
transmission electron microscopy. Nanosized silver particles gained by this process exhibit antimicrobial properties that
are investigated in detail after application on textile fabrics. 相似文献
7.
Water-borne raspberry-like PMMA/SiO2 nanocom-posite particles were prepared via free radical copolymerization of methyl methacrylate (MMA) with 1-vinylimidazole
(1-VID) in the presence of ultrafine aqueous silica sols. The acid-base interaction between hydroxyl groups (acidic) of silica
surfaces and amino groups (basic) of 1-VID was strong enough for promoting the formation of long-standing stable PMMA/SiO2 nanocomposite particles when 10 mol% or more 1-VID as auxiliary monomer was used. The average particle sizes and the silica
contents of the nanocomposite particles were in the ranges from 120–330 nm and 15%–20%, respectively. TEM and SEM observations
indicated a raspberry-like morphology of the obtained nanocomposite particles.
__________
Translated from Chemical Journal of Chinese Universities, 2005, 26(7) (in Chinese) 相似文献
8.
Lee H Sung D Veerapandian M Yun K Seo SW 《Analytical and bioanalytical chemistry》2011,400(2):535-545
The present paper reports the utilization of hybrid nanocomposite particles consisting of PEI25k-PEG5k copolymer grafted silica
nanoparticles (SiO2NPs) for enhanced cellular uptake and siRNA delivery. High-resolution transmission electron microscopy and dynamic light scattering
measurements ensured the average particle size of the final hybrid component as 45 nm (core SiO2, 28–30 nm and shell PEI25k-PEG5k, 12–15 nm). Surface morphology from atomic force microscopy analysis showed the significant
relationship between the particle size and shape. 29Si and 13C cross-polarization–magic angle spinning solid state nuclear magnetic resonance (NMR), 1H-NMR, and Fourier transform infrared spectroscopy were used to obtain the relevant structural information (such as Q3, silanol;
Q4, siloxane functional groups of SiO2NPs; resonance shifts and bending vibrations of PEI25k, –CH2–CH2–NH–; and PEG5k, –CH2–CH2–O–) from copolymer nanoparticle. Stable complexation of siRNA and nanocomposite particle (wt.%:wt.%) was achieved from 1:5
to 1:15 ratio. Nanocomposite particle (N/P) ratio and siRNA concentration determine the stability and knockdown efficiency
of the PEI25k-PEG5k-graft-SiO2NPs–siRNA complexes. It was shown that highly positively charged (zeta potential, +66 mV) PEI25k-PEG5k-graft-SiO2NPs result in strong affinity with negatively charged siRNA. Confocal microscopy showed intensified cellular uptake of siRNA
into cytoplasm of A549 cancer cell utilized for in vitro study. In conclusion, the coherence, graft density of copolymer-SiO2NPs, and siRNA concentration were found to strongly influence the stability, and hence determine the knockdown efficiency,
of PEI25k-PEG5k-graft-SiO2NPs–siRNA complexes. 相似文献
9.
UV-photocatalytic oxidation of 2,4-dichlorophenoxyacetic acid (2,4-d) was studied on Silver–TiO2 semiconductors prepared by co-gelling silver acetylacetonate and titanium butoxide (TiO2–Ag) or by incipient impregnation with silver acetylacetonate (0.5 wt% Ag) of bare TiO2 sol–gel and TiO2–P25 supports. The comparative study shows that only a slight modification on the specific surface area was obtained on the
TiO2–Ag sample (60 m2/g) as compared to the TiO2 sol–gel bare support (65 m2/g). XRD patterns of the samples show anatase as the crystalline phase present in the sol–gel TiO2 preparations. By means of HRTEM and HAADF-STEM electron microscopy techniques, silver nanoparticles (<12.0 nm) were identified
which are very small to be detected by XRD. The photocatalytic oxidation of the herbicide 2,4-d used as a model of contaminant show for the kinetic parameter t1/2 values of 45 min for the TiO2–Ag sample, while for the impregnated Ag/TiO2 and Ag/P25 nanomaterials t1/2 was 124 and 66 min, respectively. The higher photoactivity of the TiO2–Ag photocatalyst is attributed to a combined effect of the silver nanoparticles in interaction with the titania semiconductor. 相似文献
10.
Two sol-gel fabrication processes were investigated to make silica spheres containing Ag nanoparticles: (1) a modified Stöber method for silica spheres below 1 m size, and (2) a SiO2-film formation method on spheres of 3–;7 m size. The spheres were designed to incorporate silver nanoparticles of high (3) in a spherical optical cavity structure for the resonance effect. For the incorporation, interaction between [Ag(NH3)2]+ ion and Si-OH was important. In the Stöber method, the size of the silica spheres was determined by a charge balance of plus and minus ions on the silica surface. In the film formation method, the capture of Ag complex ion on the silica surface depended on whether the surface was covered with OH groups or not. After doping [Ag(NH3)2]+ into silica particles or SiO2 films on the spheres, these ions w ere reduced by NaBH4 to form silver nanoparticles. From plasma absorption at around 420 nm wavelength and TEM photographs of nanometer-sized silver particles, their formation inside the spherical cavity structures was confirmed. 相似文献
11.
K. V. Katok V. A. Tertykh V. V. Yanishpolskii A. V. Ragulya V. P. Klimenko D. O. Klymchuk 《Journal of Thermal Analysis and Calorimetry》2010,101(2):725-728
Matrix isolation of ferroelectric BaTiO3 nanoparticles was executed by formation of protective silica shell (via hydrolysis and polycondensation of tetraethyl orthosilicate)
on particles of precursor—barium titanyl oxalate. Synthesized BaTiO3–SiO2 composites have been characterized by IR spectroscopy, XRD, TEM, DTA/DTG methods. 相似文献
12.
V. N. Panchenko V. A. Pozimenko E. A. Paukshtis V. A. Zakharov 《Russian Journal of Inorganic Chemistry》2009,54(11):1798-1803
The aminated silica gels SiO2/SOCl2/NH3 (I), SiO2/SiCl4/NH3 (II), SiO2/BCl3/NH3 (III), and SiO2/γ-aminopropyltriethoxysilane (SiO2/APTES, IV) have been synthesized. According to DRIFT spectroscopy and chemical analysis data, the surface amino groups of I–III are “free,” while those of IV interact with the surface OH groups of the silica gel and with one another. The strength of basic sites has been measured
on the proton affinity (PA) scale as the shift of the ν(CD) band of adsorbed deuterochloroform. The basicity of an aminated
silica gel depends on its chemical composition. Silica gel IV (PA = 938 kJ/mol) is a stronger base than I–III (PA = 829 kJ/mol). As the basicity of the NH2 group decreases, the N-H stretching band shifts to higher frequencies. 相似文献
13.
T. I. Izaak D. O. Martynova O. A. Stonkus E. M. Slavinskaya A. I. Boronin 《Journal of Sol-Gel Science and Technology》2013,68(3):471-478
Porous monolithic gels based on silica with pore size from 16 nm to 3–5 μm have been synthesized using sol–gel technology. Parameters of porous structure are determined by the components molar ratio in the reaction mixture. The reduction processes of silver ions by formamide in the synthesized porous gel were studied. It has been shown that at the initial stage of the reaction, silver particles with size up to 10 nm are formed in the absence of any stabilizers. The composites Ag/SiO2 were synthesized by means of the threefold impregnation of porous monoliths using the solution of silver nitrate in the mixture of methanol and formamide. Their catalytic activity in the CO oxidation was studied. It was discovered that after activation in oxygen and hydrogen the samples display a low temperature activity, which depends on the number of Si–O-nonbridging oxygen groups on the surface of silica porous monoliths. 相似文献
14.
N. A. Sadokhina A. F. Prokhorova R. I. Kvon I. S. Mashkovskii G. O. Bragina G. N. Baeva V. I. Bukhtiyarov A. Yu. Stakheev 《Kinetics and Catalysis》2012,53(1):107-116
The activity of 0.25–5% Ag/Al2O3 catalysts in the selective catalytic reduction of nitrogen oxides with n-hexane under the conditions of promotion with a small amount of H2 was studied. It was found that, upon the introduction of ∼1000 ppm of H2 into the reaction mixture, the Ag/Al2O3 samples containing 1–2% Ag exhibited optimum activity and selectivity. It was established that, in the presence of 1000 ppm
of H2, the rate of the selective catalytic reduction of NO
x
was higher by a factor of 10–13, and the onset temperature of the reaction was lower by approximately 100°C. It was found
by X-ray photoelectron spectroscopy, temperature-programmed reduction, and UV spectroscopy that the high activity of 1–2%
Ag/Al2O3 catalysts was due to the presence of small Ag
n
δ+ and Ag
m
0 clusters on their surface. A decrease in the concentration of Ag below the optimum value resulted in the predominance of
an inactive ionic form on the catalyst surfaces. As the concentration of Ag was increased (>2%), large particles of Ag2O and Ag0, which facilitate the oxidation of n-C6H14, were formed to lead to a decrease in selectivity and in the degree of reduction of nitrogen oxides. 相似文献
15.
Gennady I. Ostapenko 《Journal of Solid State Electrochemistry》2002,6(2):139-141
The electrochemical behaviour of the Ag(Hg)/Ag4RbI5 interface is investigated by a potentiostatic pulse method. It is found that the rate-determining step of the electrode reaction
is electron transfer with an exchange current density of 68 mA cm–2 and a transfer coefficient of approximately 0.45. The order of the electrochemical reaction for silver oxidation is estimated
from polarization investigations of silver amalgam in various concentrations. From this it is deduced that the mercury is
ionized and is implanted in the electrolyte together with silver under anodic polarization: 15Ag+85Hg–100e–→15Ag++85Hg+. From comparison of the electrochemical behaviour of the Ag(Hg)/Ag4RbI5 and Ag/Ag4RbI5 interfaces it is concluded that the rate of anodic silver dissolution on the Ag/Ag4RbI5 interface is limited by crystallization effects.
Electronic Publication 相似文献
16.
Betul Akkopru Akgun Caner Durucan Nathan P. Mellott 《Journal of Sol-Gel Science and Technology》2011,58(1):277-289
Titanium dioxide (TiO2) thin films, with and without silver (Ag), were prepared on float glass via sol–gel processing. The float glass substrates
were pre-coated with a silica-barrier layer prior to the deposition of TiO2-based thin films. Silver nanoparticle incorporation into the TiO2 matrix was achieved by thermal reduction of Ag ions dissolved in a titanium-n-butoxide (Ti[O(CH2)3CH3]4) based sol during calcination in air at 250, 450 and 650 °C. Thin films were characterized using glancing incidence X-ray
diffraction, UV–visible spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. The effects of Ag concentration
and calcination temperature on microstructure and on chemical and physical properties of the thin films have been reported.
The size and chemical state of Ag particles, as well as the phase characteristics of the titania matrix were strongly influenced
by Ag concentration and calcination temperature. Results from this study can be utilized in both processing and structure-functional
property optimization of sol–gel based Ag-TiO2 thin films by aqueous routes. 相似文献
17.
《应用有机金属化学》2017,31(7)
A heterogeneous catalyst (FeSi/Ag/VO) based on silver and vanadyl as active sites and mesoporous silica‐coated nanospheres of magnetite (Fe3O4@m‐SiO2) as support was successfully prepared by deposition of Ag nanoparticles and the covalent grafting of vanadyl(IV) acetylacetonate on Fe3O4@m‐SiO2. The catalyst exhibited excellent activity for the oxidation of alkanes, benzene and alkylaromatics using green oxidant H2O2 and oxalic acid in acetonitrile at 60 °C. 相似文献
18.
E. A. Kononova I. I. Mikhalenko V. D. Yagodovskii 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2008,82(4):669-674
The influence of the low-temperature treatment of Ag hydrosol on the properties of silver particles was studied by electron
absorption spectroscopy over the temperature range 77–230 K. Low-temperature treatment caused the aggregation of particles
because of an increase in the number of defects on the surface of Ag observed as an increase in the damping coefficient of
electron plasma oscillations. These processes depended on the temperature and initial concentration of disperse silver. Defect
formation is explained taking into account the tunnel mechanism of the interaction of low-atomic mobile H+(H2O)
n
and OH−(H2O)
n
clusters with the surface of silver particles at low temperatures.
Original Russian Text ? E.A. Kononova, I.I. Mikhalenko, V.D. Yagodovskii, 2008, published in Zhurnal Fizicheskoi Khimii, 2008,
Vol. 82, No. 4, pp. 774–779. 相似文献
19.
Composite materials of Ag species embedded in SiO2 matrix were prepared by the sol-gel method. Two kinds of sample preparation were used. In the first one, the Ag aggregates
were synthesized using two different reduction solutions, obtaining fine particles with a quasi-spherical shape and particles
with a dendrite-like form, that were later added to the SiO2 matrix. In the second one, the Ag aggregates were formed in the SiO2 matrix from silver nitrate solutions. The prepared samples were annealed in air at different temperatures. By using uv-visible
spectroscopy, X-ray diffraction, EDS, DTA, TGA and SEM, the structures of all the samples were studied. It was found that
the embedded species and the heat treatments modify strongly the optical properties of the samples. 相似文献
20.
G. V. Krylova A. M. Eremenko N. P. Smirnova S. Eustis 《Theoretical and Experimental Chemistry》2005,41(2):105-110
Stable nanoparticle colloids of silver were obtained by irradiation of aqueous-alcoholic solutions of AgNO3 in the presence of mesoporous SiO2 powder and films modified with benzophenone (BP/SiO2). Colloidal solutions of Ludox silica were used to stabilize the photochemically produced nanoparticles of silver in solution. Formation of nanoparticles of Ag on the surface of mesoporous silica occurred on irradiation of SiO2 modified with silver ions (Ag+/SiO2) in the presence of benzophenone solution.__________Translated from Teoreticheskaya i Eksperimental’naya Khimiya, Vol. 41, No. 2, pp. 100–104, March–April, 2005. 相似文献