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1.
B. G. Ershov 《Russian Chemical Bulletin》1998,47(10):1905-1909
The radiation-chemical reduction of Co2+ ions in an aqueous solution of Co(ClO4)2 containing sodium formate was studied. Stable metal sols containing spherical particles with a diameter of 2–4 nm are formed
under γ-irradiation in the presence of polyacrylate as the stabilizing additive. An aqueous solution of colloidal cobalt has
an optical absorption that increrases smoothly in the UV region without a maximum to 200 nm (ɛ200=1.3·104 mol-1 L cm-1). It is established that the radiation-chemical reduction of the Co2+ ions occursvia an autocatalytic mechanism. The metal sols catalyze the reduction of the Co2+ ions by Co2
− radical ions formed under irradiation. The properties of the sols were studied, and it is shown that they are readily oxidized
by hydrogen peroxide and other oxidants. The mechanism of chemical reactions involving the sols is discussed.
Tranalated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1959–1964, October, 1998. 相似文献
2.
G. F. Novikov M. V. Gapanovich E. V. Rabenok L. M. Bogdanova L. I. Kuzub 《Russian Chemical Bulletin》2011,60(3):419-425
Sols of silver nanoparticles in toluene were studied by broadband dielectric spectroscopy (10−3–105 Hz). The frequency dependences of the specific alternating current (ac) conductivity and the complex electric modulus were
used to estimate the temperature/frequency intervals of long- and short-range charge transfer occurs, respectively. A considerable
increase (by more than 30 °C) in the Vogel temperature T
0 and the glass transition temperature T
g in sols compared with the pure solvent was found. It can be hypothesized that these cooperative effects reflect the initial
stage of the superlattice formation. Although the dielectric characteristics of sols are generally controlled by the conductivity
relaxation, the dielectric response was observed in the high-frequency range (1–103 Hz) at low temperatures (from −50 to +10 °C). This response results from the presence of nanoparticles in solution. It is
supposed that the relaxation is caused by the motion of ion impurities on the Ag nanoparticle surface within the carboxylate
ligands shell. The dielectric properties of films strongly depend on both the characteristics of nanoparticles and the conditions
of the film preparation. Like in sols, the direct current (dc) conductivity and the dielectric response of Ag nanoparticles
in films are due to ion impurities. 相似文献
3.
Silver nanoparticles preparation and the aggregation stability of the particles was investigated in lamellar liquid crystalline
systems. A liquid crystal of HDTABr/pentanol/water was first prepared. The water content was next increased while keeping
the mass ratio of HDTABr and pentanol constant. Silver nanoparticles were produced by replacing the aqueous phase by Ag sols
of various concentrations (0.5–5×10–3 mol/l) or by an in situ preparation method, i.e., interlamellar reduction of Ag+ ions in the liquid crystalline phase. The stability of the silver nanoparticles was monitored by UV-VIS spectroscopy and
TEM. The particle size ranged from 5 to 44 nm. The kinetic of silver nanoparticle aggregation was investigated. The effect
of nanoparticles on structural ordering in liquid crystals was studied by XRD measurements and it was established that the
lamellar distance (dL) was only slightly altered.
Electronic Publication 相似文献
4.
Control of Semiconductor Particle Size in Sol-Gel Thin Films 总被引:4,自引:0,他引:4
M. Guglielmi A. Martucci E. Menegazzo G.C. Righini S. Pelli J. Fick G. Vitrant 《Journal of Sol-Gel Science and Technology》1997,8(1-3):1017-1021
Thin silica and silica-titania films containing CdS and PbS quantum size particles were obtained by separate preparation of
the matrix and the colloidal sols and successive mixing. Sulfide particles were obtained by reaction of metal acetates with
thioacetamide and control of particle size was achieved by surface capping agents. Powders and thin films deposited on soda-lime
slides were prepared and characterized by XRD. Absorption spectra were recorded on films. The nonlinear refractive index was
measured by anm-line technique on a CdS-doped sample. The nonlinear effect was found to be reversible and an
2 value of −3 10−9 cm2/kW was measured. 相似文献
5.
Boris Mahltig Dirk Fiedler Anja Fischer Paul Simon 《Journal of Sol-Gel Science and Technology》2010,55(3):269-277
Antimicrobial textile materials were produced by sol–gel coatings with embedded biocidal compounds. For preparation a sol–gel
procedure was used, starting from pure silica sols and 3-glycidyloxypropyltriethoxysilane (GLYEO) containing silica sols.
These sols were modified with silver compounds, hexadecyltrimethyl-ammonium-p-toluolsulfonat (HTAT) and copper compounds, respectively. The investigations were performed on viscose fabrics as function
of the concentration of biocidal compounds and of thermal treatment of textile after dip-coating between 80 up to 180 °C.
The use of modified silica coatings leads to a decreased growth of fungi (Aspergillus niger) and bacteria (Bacillus subtilis and Pseudomonas putida) with increasing amount of the biocide embedded in the coating. The addition of GLYEO supports the biocidal effect of the
coatings and enhances the stability of the coating solutions. For preparation of antimicrobial silica coatings the biocides
silver, copper or HTAT can be used alone but the combination of these compounds leads to enhanced results against both fungi
and bacteria. Therefore silica sols containing a combination of different types of biocides may be used for antimicrobial
modification of textiles in some practical applications. For industrial applications the here presented coating solutions
are especially advantageous, because of 90% water content in the solvent. 相似文献
6.
The complex formation of soluble poly (N-vinylimidazole) (PVIm) with trivalent metal ions in aqueous solution was studied by using UV–vis spectroscopy. Formation
constants of PVIm–metal complexes were calculated by applying the “molar ratio” method. It was found that the interaction
between PVIm and trivalent metal ions follows 4(base unit):1(metal ion) stoichiometry. The stability constants for the complexes
of PVIm with trivalent transition-metal ions were in agreement with the Irving– William series. The biggest formation constant
was found for the PVIm–Fe3+ complex system. The capacity of adsorption for these metal ions was investigated using cross-linked PVIm. Cross-linked PVIm
hydrogels were prepared by irradiating binary mixture of N-vinylimidazole–water with a 60Co γ-ray source having a dose rate of 4.5 kGy/h. Adsorption studies were performed at different pH and metal ion concentrations
at room temperature. It was observed that the same sequence for the metal ions was verified by adsorption studies.
Received: 28 May 2001 Accepted: 29 July 相似文献
7.
B. G. Ershov 《Russian Chemical Bulletin》2000,49(10):1715-1721
Radiation-chemical reduction of Ni2+ ions in aqueous solutions of Ni(ClO4)2 containing sodium formate or isopropyl alcohol was studied, γ-Irradiation of deaerated solutions in the presence of polyethyleneimine,
polyacrylate, or polyvinyl sulfate gives stable metal sols containing spherical particles 2–4 nm in diameter. The optical
absorption spectra of nickel nanoparticles exhibit a band with a maximum at 215±5 nm (ε215=4.7·103 L mol−1 cm−1) and a shoulder at 350 nm. A mechanism for the radiation-chemical reduction of Ni2+ ions by hydrated electrons and organic radicals (CO2- radical anions in the case of HCOONa and Me2C·OH radicals in the case of PriOH). The redox potentials of the Ni2+/Ni0 and Ni+/Ni0 pairs (Ni0 is a nickel atom) are approximately −2.2 and −1.7 V, respectively. The nanoparticles are readily oxidized by O2, H2O2, and other oxidants. The reactions of these species with silver ions yield relatively stable nanoaggregates containing both
nickel and silver in addition to silver nanoparticles.
Published inIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 1733–1739, October, 2000. 相似文献
8.
B. G. Ershov 《Russian Chemical Bulletin》1994,43(1):16-21
Colloidal copper has been obtained by -irradiation of aqueous solutions of copper (II) perchlorate in the presence of alcohol and polyethyleneimine (PEI). The sols are spherical particles about 4 nm in diameter, which are quickly oxidized by oxygen or other oxidants. When CuII is not entirely incorporated into the complex with PEI, disproportionation of CuI aqua complexes formed affords the metal, along with Cu2O. Reduction of the PEI complex of CuI by hydrated electrons gives only colloidal copper. The copper ions can be reduced on the surface of silver sols. Optical parameters of the resulting bimetallic particles have been studied. The presence of copper ions leads to broadening of the absorption band associated with the silver sols and shifts it to the UV region, which is due to the transfer of electrons from copper to silver. Three copper monolayers are enough to cause plasmon absorption of colloidal copper.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 25–30, January, 1994. 相似文献
9.
R. W. Horne E. Matijević R. H. Ottewill J. W. Weymouth 《Colloid and polymer science》1958,161(1):50-59
Summary Examination of the influence of dodecylpyridinium iodide on the formation of silver iodide sols (conc. 5 × 10−4 M), by turbidimetric measurements, revealed the presence of four coagulation regions with intermediate regions in which stable
sols were formed. The form of the sol particles and the structure of the coagula, formed under these conditions, has been
investigated in detail using the electron microscope. Selected area microelectron-diffraction and X-ray diffraction examination
of the various regions showed that the silver iodide particles generally had a hexagonal structure but under some conditionsγ-cubic silver iodide was also present. It was found that at low concentrations of surface active agent (10−6M) the rate of sol particle growth was enhanced but at higher concentrations (10−3M) it was greatly retarded. The phenomena observed were interpreted on the basis of the strong adsorption of dodecylpyridinium
ions onto the negatively charged silver iodide surface.
On leave of absence from Faculty of Science, University of Zagreb (Yugoslavia).
We wish to thank the Governing Body of Trinity Hall for a Consolidated Zinc Corporation grant to one o f us (E. M.). 相似文献
Zusammenfassung Prüfung des Einflusses von Dodecylpyridinium-Iodid auf die Bildung von Silberiodidsolen (Konzentration 5 · 10−4 M) durch Lichttrübungsmessung zeigt die Anwesenheit von vier Koagulationsgebieten mit Zwischengebieten, in denen stabile Sole gebildet werden. Die Form der Solteilchen und die Struktur der unter diesen Bedingungen gebildeten Koagulate wurden exakt mit dem Elektronenmikroskop untersucht. Elektronenbeugungs- und R?ntgenstrahlen-Interferenzuntersuchungen bestimmter Fl?chen der Abbildungen aus den verschiedenen Zustandsgebieten zeigen, da? die Silberiodidteilchen gew?hnlich hexagonale Struktur besitzen, da? jedoch unter gewissen Bedingungen auch gammakubisches Silber anwesend ist. Ferner wurde gefunden, da? bei niedrigen Konzentrationen von oberfl?chenaktiven Medien (10−6 M) die Geschwindigkeit des Solteilchenwachstums erh?ht wird, aber bei h?heren Konzentrationen (10−3 M) stark verz?gert wird. Die beobachteten Ph?nomene werden auf der Basis starker Adsorption von Dodecylpyridinium-Ionen auf der negativ geladenen Silberiodid-Oberfl?che gedeutet.
On leave of absence from Faculty of Science, University of Zagreb (Yugoslavia).
We wish to thank the Governing Body of Trinity Hall for a Consolidated Zinc Corporation grant to one o f us (E. M.). 相似文献
10.
A. Sarkar Shweta Hegde T. Mukherjee S. Kapoor 《Research on Chemical Intermediates》2010,36(3):309-318
The effect of silver ions and silver nanoparticles on the rate of polymerization of acrylamide and N-isopropylacylamide was investigated. Composites of silver particles of diameter around 30 nm and polyacrylamide were prepared
by the photochemical method in the absence of any photosensitizer. The particles formed were characterized by UV–visible spectrophotometry,
XRD, and TEM. It was shown that the presence of metal ions such as Ag+, Co2+, and Ni2+ in the acrylamide monomer is essential for photoinduced polymerization. 相似文献
11.
The effects of variant counterions with ionic strength of 0.05, 0.10, 0.20 and 0.25 mol·kg^-1 on the stability and particle size of silica sols have been studied using the traditional methods of Ubbelohde viscosity measurement, TEM and titration respectively, finding that the stability and particle size of the silica sols are all concerned with the acidic, positively electric properties and the sizes of the counterions, as well as the attraction between the counterions and surface silicon hydroxyl groups of the silica sols. The small positively charged counterions lead to the decrease in particle sizes, making the silica sol the most stable. But the larger weakly acidic counterions can restrict the particle sizes of the silica sols and easily make the sols coagulate. It was also found that there existed a linear relationship between log r and log η, which has not ever been reported. The effect of temperature on the stability and particle sizes was also discussed. 相似文献
12.
Praveen Joseph Santhosh Acharya Ganesh Sanjeev N. N. Bhat Y. Narayana 《Journal of Radioanalytical and Nuclear Chemistry》2011,290(1):209-214
In the case of sparsely ionizing radiation such as electron, the dose rate and the pattern of energy deposition of the radiation
are the important physical factors which can affect the amount of damage in living cells. In the present study, the differences
in the cell survival efficiency and dose rate effect in diploid yeast strains Saccharomyces cerevisiae X2180 and Saccharomyces cerevisiae D7 under euoxic and hypoxic condition have been quantified. Irradiation was carried out using 8 MeV pulsed electron beam
from Microtron accelerator. The dose per pulse and pulse width of the beam used was 0.6 Gy and 2.3 μs, respectively, which
correspond to an instantaneous dose rate of 2.6 × 105 Gy s−1. For survival studies doses were delivered at a rate of 50 pulses per second (an average dose rate of 1,800 Gy s−1). Fricke and alanine dosimeters were used to measure the dose delivered to the sample. A significant difference in the dose
response has been observed under euoxic and hypoxic condition. Dose rate effect has been studied by changing the pulse repetition
rate of the Microtron and the dose rate used was from 180 to 1800 Gy min−1. A significant dose rate effect was observed under euoxic condition for Saccharomyces cerevisiae X2180 but the same was absent under hypoxic condition. The dose rate effect was absent for Saccharomyces cerevisiae D7 under both irradiation condition. The survival curves are found to be sigmoidal in shape under both condition but with
a wider shoulder under hypoxic condition. The D0 value and the Oxygen Enhancement Ratio (OER) at that point have been derived. 相似文献
13.
A polystyrene-based membrane of 7,8:16,17-dibenzo-6,9,15,18-tetraoxo-1,5,10,14-tetrathiacyclooctadeca-7,16-diene [Bz2Oxo4(18)dieneS4] was fabricated using sodium tetraphenylborate (NaTPB) and dioctyl phthalate (DOP) as anion excluder and plasticizing agent.
The best performance was obtained from the membrane with the composition ionophore [Bz2Oxo4(18)dieneS4]:polystyrene:DOP:NaTPB, 5:100:150:10 (w/w). The response of the electrode was linear over a wide range of concentration, 1.26×10–6–1.00×10–1 mol L−1 for silver ion with a Nernstian slope of 58.4±0.1 mV per decade and a detection limit of 1.0×10−6 mol L−1. The electrode was found to be chemically inert and of adequate stability with a response time of 10 s and could be used
for a period of 3 months without change of potential. It worked satisfactorily in mixtures containing up to 35% (v/v) non-aqueous content. The proposed membrane sensor had good selectivity for Ag+ over a wide variety of metal ions in the pH range 2.2–8.5. It was successfully used as an indicator electrode in potentiometric
titration of silver ion. The electrode was also useful for determination of Ag+ in waste from photographic films. 相似文献
14.
Silver colloids of well-defined shape, size were synthesized by γ-ray irradiating silver salt in reversed microemulsions, and then pure silver dry powders were obtained. The sols were studied by absorption spectroscopy, and the silver powders were characterized by Transmission Electron Micrographs (TEM) and X-ray Diffraction (XRD). The effect of radiation dose and aging time was discussed. 相似文献
15.
The dissociation constants of 3-methyl-1-phenyl-{p-[N-(pyrimidin-2-yl)sulfamoyl]phenylazo}-2-pyrazolin-5-one and metal-ligand stability constants of its complexes with some transition
metal ions have been determined potentiometrically in 0.1 M-KCl and ethanol—water mixture (30 vol. %). The order of the stability
constants of the formed complexes increases in the sequence Mn2+, Co2+, Ni2+, Cu2+, La3+, Hf3+, UO
2
2+
, Zr4+. The effect of temperature was studied and the corresponding thermodynamic parameters (ΔG, ΔH, and ΔS) were derived and discussed. The dissociation process is nonspontaneous, endothermic, and entropically unfavourable. The
formation of the metal complexes was found to be spontaneous, exothermic, and entropically favourable.
Abstracted from his M.Sc. Thesis. 相似文献
16.
The dependence of the stability of SiO2 and Al2O3 sols on the pH of their medium has been studied. Vapor adsorption isotherms on powders were prepared from acidic and basic
sols, the immersion enthalpy (heat) of samples containing preadsorbed water have been determined and, also, the reversibility
of the sol ⇌ xerogel transformation, i.e. the peptizability of the powders, has been investigated.
Based on the flocculation values determined with KCl, the sols have been classified into three groups. The stability of highly
hydrophilic sols (acidic SiO2- and Al2O3-sols) is ensured by a thick continuous diffuse lyosphere formed around the particles, as the continuity principle by Ostwald–Buzágh
suggests. In this case, no electric charge is needed for ensuring stability. These sols are thermodynamically stable (group
1). Sols with medium stability are stabilized by the electrical double layer around the particles and by 1–2 layers of adsorbed
water. The flocculation value of these sols is determined by the electrostatic interaction, whereas the peptizability of the
flocs is related to formation of water layers. Such sols are the basic SiO2- and Al2O3-sols (group 2). Sols of low stability are of hydrophobic nature. Their flocculation value with 1:1 electrolytes is smaller
than 0.1 molkg-1. The transformation process sol ⇒ floccule ⇒ xerogel is mostly irreversible. There are a lot of such sols (group 3). The
existence of a hydrosphere is proved by the almost identical value of the hydration energy for both the acidic and the basic
SiO2 sols, in spite of an order of magnitude difference in the flocculation value. The remnants of adsorbed water after drying
hinders sintering of the particles and ensures the peptizability of powders.
The highly hydrophilic sols (sequence of hydrophilicity: SiO2> Al2O3>FeO OH ⋅ 0.5 H2O) are all oxides which are formed in acidic media.
Received: 25 May 1997 Accepted: 13 October 1997 相似文献
17.
Summary The stability of Thorium dioxide sols at pH=3.5 was examined as a function of anionic surface active agents spectrophotometrically. At low concentrations of surface
active agents, the stability of the sol decreases and attains a minimum value at concentrations 10−4 to 10−3 M. With increasing concentration the stability increases and attains a maximum at concentrations 10−3 to 10−2 M. The effect of the PH-value, the chain length and the head groups of the surface active agents are also studied. The results were explained on
the basis of strong adsorption of these ions at the Stern plane. 相似文献
18.
It is shown that, in silver hydrosols that are produced by the reduction of metal cations under the action of borohydride and do not contain electron-donor additives, the photoinduced reduction of Ag+ ions and photoinduced oxidation of nanoparticles occur at pH 9.0 and 4.0, respectively. The effect of ionic composition of sols on the direction of the photoinduced process makes it possible to assume that OH? anions reduce silver cations on the surface of nanosized nuclei. 相似文献
19.
The radiation-chemical reduction of silver, copper, cadmium, thallium, lead, cobalt, and nickel ions to form stable metal nanoparticles was studied in the presence of PW11O39
7- and P2W17O61
10- heteropoly anions in aqueous solutions containing sodium formate or isopropanol. The heteropoly anions were found to be efficient stabilizing agents for the resulting sols. The optical characteristics of the sols were determined. 相似文献
20.
Summary When silver iodide, silver bromide and silver chloride solsin statu nascendi are coagulated by thorium nitrate in the presence of potassium nitrate, three coagulation maxima appear. Two of them are
identical with maxima that are found in absence of KNO3, denoted with (II) and (IV) in fig. 1. The new maximum appears in the stability region of recharged sols (III). It is believed
that this maximum is also—as maximum (IV)—caused by the coagulation of recharged silver halide sols by nitrate ions. Appearance
of two nitrate coagulation maxima is explained by different charge densities on sol particles at various concentrations of
Th(NO3)4 where they are formed. The new maximum indicates a lower charge density of sol particles. The possibility that the new maximum
could have been caused by ionic complex species between thorium and nitrate ions has been rejected for data are available
that the equilibrium constant for such complexes is small.
In the presence of K2SO4 the coagulation effects of thorium nitrate on silver halide sols are markedly different. In acidified solutions only one
coagulation maximum appears at rather high thorium nitrate concentrations [∼ 10−3
N Th (NO3)4] and the sol remains negatively charged [up to ∼ 10−2
N Th (NO3)4] This is explained by complex formation of Th-ions and sulfate ions whereby ionic species of lower charge are formed, which
exert a weaker coagulation effect. In neutral solutions another maximum at lower concentration of Th (NO3)4 is formed which appears to be the usual coagulation maximum produced by hydrolyzed thorium ions.
The antagonistic effects of the salt pair Th (NO3)4-K2SO4 upon the coagulation of silver halides has been discussed and we have concluded that the large effects repeatedly reported
can be explained not by simple electrostatic effects of ions in solution but rather by the formation of complexes between
Th- and SO4-ions.
Supported in part by U.S. Atomic Energy Commission Contract No. AT (30-1)-1801. 相似文献
Zusammenfassung Die Koagulationseffekte des Thoriumnitrats in Anwesenheit von Kaliumnitrat und Kaliumsulfat an Silberhalogenid-Solenin statu nascendi wurden ausführlich untersucht. Wenn Silberhalogenid-Sole durch Thoriumnitrat-L?sungen koaguliert werden, bilden sich zwei Koagulationsmaxima (II und IV, Abb. 1). Bei sehr niedrigen Konzentrationen des Thoriumnitrats koaguliert das Thorium-Ion (oder Komplex) die negativen Silberhalogenid-Sole, w?hrend bei h?heren Thoriumnitrat-Konzentrationen die ungeladenen Sole durch die NitratIonen koaguliert werden. Zwischen den zwei Maxima besteht ein weites Gebiet der stabilen umgeladenen Sole (III). Unter dem Zusatz von konstanten Mengen des Kaliumnitrats wird in diesem Gebiet ein neues (drittes) Maximum gebildet (Abb. 2–5), das auch als Koagulationsmaximum identifiziert wurde. Es wird angenommen, da? dieses Maximum wieder eine Koagulation der umgeladenen Silberhalogenid-Sole durch Nitrat-Ionen darstellt. Das Auftreten von zwei Koagulationsmaxima, verursacht durch Nitrat-Ionen, wird durch die verschiedenen Ladungsdichten an Solteilchen in Gebieten der Thoriumnitrat-Konzentrationen, in denen Maxima erscheinen, erkl?rt. Die M?glichkeit eines Koagulationseffektes der komplexen Ionen zwischen Thorium und Nitrat wurde ausgeschlossen, da die Gleichgewichtskonstante solcher Komplexe ziemlich niedrig ist. In Anwesenheit von Kaliumsulfat sieht die Koagulationskurve für Silberhalogenid Sole sehr unterschiedlich aus (Abb. 6–8). In den mit Salpeters?ure (0,001N) versetzten Solen erscheint nur ein Maximum bei ziemlich hohen Thoriumnitrat-Konzentrationen [∼ 10−3 N Th (NO3)4], wobei die Solteilchen noch immer negativ sind. Da Thorium- und Sulfat-Ionen sehr stabile Ionen-Komplexe bilden, die eine niedrigere Valenz aufweisen, kann das Maximum als Folge der Koagulationseffekte solcher Komplexe an die Silberhalogenid-Sole angesehen werden. In neutralen L?sungen zeigt sich neben dem beschriebenen Maximum noch ein anderes Maximum bei niedrigerer Thoriumnitrat-Konzentration. Dieses Maximum, hervorgerufen durch die hydrolysierten Thorium-Ionen, scheint das „normale“ Koagulationsmaximum zu sein. Dieantagonistischen Effekte des Salzpaares Th (NO3)4-K2SO4 bei der Koagulation der Silberhalogenide wurden diskutiert, und es wurde geschlossen, da? die gro?en Effekte, die wiederholt ver?ffentlicht worden waren, sehr schwer nur durch die elektrostatischen Anziehungen zwischen den Ionen erkl?rt werden k?nnen. Die Komplexbildung zwischen Thorium- und Sulfat-Ionen wird für den sogenannten antagonistischen Effekt in diesem Falle als verantwortlich angesehen.
Supported in part by U.S. Atomic Energy Commission Contract No. AT (30-1)-1801. 相似文献