摘要:
A process for making cerium dioxide nanoparticles containing at least one transition metal (M) utilizes a suspension of cerium hydroxide nanoparticles prepared by mechanical shearing of an aqueous mixture containing an oxidant in an amount effective to enable oxidation of cerous ion to ceric ion, thereby forming a product stream that contains transition metal-containing cerium dioxide nanoparticles, Ce1-xMxO2, wherein “x” has a value from about 0.3 to about 0.8. The nanoparticles thus obtained have a cubic fluorite structure, a mean hydrodynamic diameter in the range of about 1 nm to about 10 nm, and a geometric diameter of less than about 4 nm. The transition metal-containing crystalline cerium dioxide nanoparticles can be used to prepare a dispersion of the particles in a nonpolar medium.
摘要:
A method of making cerium dioxide nanoparticles includes: a) providing an aqueous reaction mixture having a source of cerous ion, a source of hydroxide ion, a nanoparticle stabilizer, and an oxidant at an initial temperature no higher than about 20° C.; b) mechanically shearing the mixture and causing it to pass through a perforated screen, thereby forming a suspension of cerium hydroxide nanoparticles; and c) raising the initial temperature to achieve oxidation of cerous ion to eerie ion and thereby form cerium dioxide nanoparticles having a mean diameter in the range of about 1 nm to about 15 nm. The cerium dioxide nanoparticles may be formed in a continuous process.
摘要:
This invention comprises a photographic element comprising a support and at least one blue sensitive silver halide emulsion layer containing a tabular grain silver halide emulsion, or an emulsion in which the halide content is at least 50% chloride and no more than 5% iodide, wherein the emulsion is spectrally sensitized with at least one dye providing a peak sensitization between 446 and 500 nm and at least one dye providing a peak sensitization between 400 and 445 nm and additionally sensitized with a fragmentable electron donor of the formula: X—Y′. or an electron donor which contains an —XY′ moiety; wherein X is an electron donor moiety, Y′ is a leaving proton H or a leaving group Y, with the proviso that if Y′ is H a base, &bgr;−, is covalently linked directly or indirectly to X. and wherein: 1) X—Y′ has an oxidation potential between 0 and about 1.4 V; and 2) the oxidized form of X—Y′ fragments to give the radical X• and the leaving fragment Y′; and, optionally, 3) the radical X• has an oxidation potential ≦−0.7V (that is, equal to or more negative than about −0.7 V).
摘要:
A color photographic element comprises a support and at least one dye image forming layer unit comprising gelatin-peptized radiation-sensitive silver halide grains, a fragmentable electron donating compound; and an electron transfer agent releasing compound.
摘要:
A photographic emulsion is disclosed containing for enhanced imaging speed high bromide {111} tabular grain emulsion peptizer with a cationic starch and sensitized with a fragmentable electron donating sensitizer. The photographic emulsion is disclosed for use in black-and-white and color photographic elements.
摘要:
A process of preparing a photographic emulsion having radiation-sensitive silver iodohalide grains. Iodide is introduced into the grains by releasing iodide ions from iodate (IO.sub.3.sup.-). Release of iodide ions from the IO.sub.3.sup.- is employed to enhance the uniformity of iodide availability during emulsion preparation, either during grain precipitation or subsequent halide conversion. The process of the invention is in one preferred form directed to the partial halide conversion of tabular grains. A speed-granularity advantage is demonstrated.
摘要:
A photographic element which has a blue sensitive emulsion with broad blue spectral coverage and yet, good speed and low fog. The element has a blue sensitive silver halide tabular grain emulsion which has a tabularity of at least 25 sensitized with a dye of formula (I) and a dye of formula (II), wherein the formula (I) dye on the emulsion has a peak sensitization of between 400-445 nm and the formula (II) dye on the emulsion has a peak sensitization of between 446-500 nm: ##STR1## wherein: Z.sub.1, Z.sub.2, Z.sub.3 and Z.sub.4 independently represent the atoms necessary to complete a substituted or unsubstituted benzene or naphthylene;X, Y, X.sub.1 and Y.sub.1 are independently O, S, Se or MR.sub.5, provided that at least X or Y is O or NR.sub.5, where R.sub.5 is a substituted or unsubstituted alkyl or aryl;R.sub.1, R.sub.2, R.sub.3 and R.sub.4 independently represent H or a substituted or unsubstituted alkyl or aryl.
摘要:
The present process provides a method for synthesizing difficult to make oxide-free nanometals and such as Zn, Sn and Ti and alloys of the period 4 and 5 transition metal elements in a free and reduced state using a solution phase synthesis process. Also provided is a method for stabilizing their associated colloidal metal and alloy dispersions under kinetic control at modest temperatures (
摘要:
A process for making cerium-containing oxide nanoparticles includes providing an aqueous reaction mixture containing a source of cerous ion, optionally a source of one or more metal ions (M) other than cerium, a source of hydroxide ion, at least one monoether carboxylic acid nanoparticle stabilizer wherein the molar ratio of said monoether carboxylic acid nanoparticle stabilizers to total metal ions is greater than 0.2, and an oxidant at an initial temperature in the range of about 20° C. to about 95° C. Temperature conditions are provided effective to enable oxidation of cerous ion to ceric ion, thereby forming a product dispersion of cerium-containing oxide nanoparticles, optionally containing one or more metal ions (M), Ce1-xMxO2-δ, wherein “x” has a value from about 0.0 to about 0.95. The nanoparticles may have a mean hydrodynamic diameter from about 1 nm to about 50 nm, and a geometric diameter of less than about 45 nm.
摘要:
A process for replacing the continuous phase of a nanoparticle dispersion with a less polar phase, includes filtering the dispersion through a semi-permeable membrane filter to remove the continuous phase, and introducing a less polar phase.