Copper, colloidal

Savinova ER, Chuvilin AL, Parmon VN. 1988. Copper colloids stabilized by water-soluble polymers Part 1. Preparation and Properties. J Mol Catal 48 217-229. 

Fig. 9.4.25 Optical absorption spectra of copper colloid prepared by the gas flow-solution trap method as a function of lime development. The numbers in the figure are the time after the preparation of Lhe sample. The spectrum of sodium eihoxidc in ethanol (authentic sample) is also shown in the same figure, marked by b. The insertion is the expansion of the region of the isosbestic point. The deviation from the isosbestic point at 10 h after the preparation of colloids is shown by a in the insert. (From Ref. 26.)...

Hirai. H., Wakabayashi, H. and Komiyama, M. (1983). Polymer-protected copper colloids as catalysis for selective hydration of acrylonitrile. Chemistry Letters. 1047-1050. 

Creighton et al estimated the enhancement of the scattering of pyridine from a copper colloid at 647.1 nm excitation to be... 

The possibility of detecting a vibrational band associated with a surface-molecule bond was already discussed. In this context we mention the silver-thiourea bond seen by Macomber and Furtak and the copper-N vibrations seen on copper colloids. ... 

The spectral features of copper colloids prepared by laser ablation in water (Fig. 2) in the UV region around 275 nm can be assigned to the metal interband transitions and, perhaps, because copper is reactive to produce some compounds such as copper oxide and hydroxide. Owing to the high reactivity of copper, it was practically impossible to observe the copper plasmon band near 560 nm [5]. 

Turbidity may appear in bottled white wines containing free SO2 and no air. The precipitate gradually settles out to form a brownish-red deposit. This is a two-stage reaction, with the initial formation of an unstable copper colloid, followed by the flocculation and precipitation of this colloid on contact with proteins in the wine. 

S.S. Pesetskii and O.N. Alexandrova. Effect of dicarbonic acids on adhesive interaction of polyamide hhns with copper. Colloidal J., 1990, Vol. 52, No. 2, pp. 302-308. 

Copper colloids protected by PVPD with a 3240 degree of polymerization, most effectively catalyze the selective (100%) hydration of acrylonitrile (AN) to acrylamide in water at 80 °C at a molar Cu/AN ratio of 0.017. The acrylamide yield reaches 25.4 mole % within 2h [46]. The reaction is first order with respect to the acrylonitrile concentration down to 47% conversion. The catalytic activity of all other protected colloidal dispersions is also much higher (2.5-8.6 mole % in 2h) than the activity of the copper precipitate which forms by the reduction of copper sulphate by NaBH4 in the absence of a copolymer (0.3 mole % in 2 h). Hirai and Toshima [46] have reviewed the preparation and characterization of polymer-protected colloidal metal catalysts together with their characteristic properties and some of their applications. 

Gold, copper and silver surfaces have the d band lower than the Fermi level which means that they enhance the vibrational signals. In the case of copper colloidal solutions or metal deposited as islands, the band corresponding to the surface plasmons is observed in the near infrared. ". The metal colloids are preferentially prepared by following the method reported by Lee and Meisel. Reducing agents normally used are boronhydride, citrate or hydroxylamine , depending on the required physical and electronic characteristics of the surface. 

Apparently, the simplest solution-based approach to produce copper colloids is the direct reduction of a precursor in an appropriate aqueous solution. Most frequently, an alkaline medium and complexing additives are employed this is necessary in order to sequester Cu ions and to prevent the undesired formation of insoluble CuP hydroxides, eventually evolving into CU2O or CuO NPs. In contrast, the formation of cuprate ions or other soluble Cu complexes makes possible the synthesis of Cu NPs, due to the following reaction scheme [99] ... 

The elements are obtainable in a state of very high purity but some of their physical properties are nonetheless variable because of their dependence on mechanical history. Their colours (Cu reddish, Ag white and Au yellow) and sheen are so characteristic that the names of the metals are used to describe them. Gold can also be obtained in red, blue and violet colloidal forms by the addition of vtirious reducing agents to very dilute aqueous solutions of gold(III) chloride. A remarkably stable example is the Purple of Cassius , obtained by using SnCla as reductant, which not only provides a sensitive test for Au but is also used to colour glass and ceramics. Colloidal silver and copper are also obtainable but are less stable. 

Brom-jod, n. iodine bromide, -kalium, n. potassium bromide, -kalzium, n., kalk, tn. calcium bromide, -kampher, tn. bromo-camphor, Pharm.) monobromated camphor, -kohlenstoff, tn. carbon (tetra)bromide. -korper, tn. Colloids) "bromide body (bromide ion), -kupfer, n. copper bromide, lauge, /. bromine lye (solution of sodium hypobromite and bromide made by passing bromine into sodium hydroxide solution), -lithium, n. lithium bromide. -Idsung, /. bro-nune solution, -magnesium, n. magnesium bromide. -metall, n. metallic bromide. 

Chemical reduction is used extensively nowadays for the deposition of nickel or copper as the first stage in the electroplating of plastics. The most widely used plastic as a basis for electroplating is acrylonitrile-butadiene-styrene co-polymer (ABS). Immersion of the plastic in a chromic acid-sulphuric acid mixture causes the butadiene particles to be attacked and oxidised, whilst making the material hydrophilic at the same time. The activation process which follows is necessary to enable the subsequent electroless nickel or copper to be deposited, since this will only take place in the presence of certain catalytic metals (especially silver and palladium), which are adsorbed on to the surface of the plastic. The adsorbed metallic film is produced by a prior immersion in a stannous chloride solution, which reduces the palladium or silver ions to the metallic state. The solutions mostly employed are acid palladium chloride or ammoniacal silver nitrate. The etched plastic can also be immersed first in acidified palladium chloride and then in an alkylamine borane, which likewise form metallic palladium catalytic nuclei. Colloidal copper catalysts are of some interest, as they are cheaper and are also claimed to promote better coverage of electroless copper. 

Discussion. Sodium diethyldithiocarbamate (B) reacts with a weakly acidic or ammoniacal solution of copper(II) in low concentration to produce a brown colloidal suspension of the copper(II) diethyldithiocarbamate. The suspension may be extracted with an organic solvent (chloroform, carbon tetrachloride or butyl acetate) and the coloured extract analysed spectrophotometrically at 560 nm (butyl acetate) or 435 nm (chloroform or carbon tetrachloride). 

Consequently, when selecting and blending the various raw materials used in all-polymer/all-organic formulations, the questions of thermal and hydrolytic stability and ability to transport or otherwise control colloidal iron oxides (in addition to possible adverse effects such as copper corrosion) become increasingly important at higher boiler temperatures and pressures. 

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