Trioctyl phosphine

The growth or agglomeration of nanoparticles can be decreased by electrostatic stabilization or steric stabilization. Electrostatic stabilization can be achieved by targeted adsorption of ions (H, OH , S04, etc.) on the particle surface. Steric stabilization is achieved by adsorption of long-chain organic molecules (e.g., oleyl amine, oleic acid, trioctyl phosphine, trioctyl phosphine oxide, etc.). ... 

In an attempt to create particles with different sizes and properties, ligands other than dodecanethiol were used to create polydispersed colloids from the SMAD method. Thus, dodecylamine, trioctyl phosphine, and dodecyl alcohol were used in addition to dodecanethiol. The results of these studies led to nearly monodispersed stable colloids for the phosphine protected particles at 6.3 nm in diameter (Figure 13). 

Figure 13. TEM micrograph of trioctyl phosphine (TOP)-stabilized Ag nanoparticles.

The extractant is di(2-ethylhexyl) phosphoric acid (DEHPA) in conjuction with trioctyl phosphine oxide (TOPO). Stripping is by ammonium carbonate, and uranium precipitates as ammonium uranyl tricarbonate. The mixture shows a synergistic effect. The mixture is stable, and extracts uranium in hexavalent state. 

Formation of trioctyl phosphine complex, ether extraction... 

Korkisch and Koch [106,107] determined low concentrations of uranium in seawater by extraction and ion exchange in a solvent system containing trioctyl phosphine oxide. Uranium is extracted from the sample solution (adjusted to be 1 M in hydrochloric acid and to contain 0.5% of ascorbic acid) with 0.1 M trioctylphos-phine oxide in ethyl ether. The extract is treated with sufficient 2-methoxyethanol and 12 M hydrochloric acid to make the solvent composition 2-methoxyethanol-0.1 M ethereal trioctylphosphine acid-12 M hydrochloric acid (9 10 1) this solution is applied to a column of Dowex 1-X8 resin (Cl" form). Excess of trioctylphosphine oxide is removed by washing the column with the same solvent mixture. Molybdenum is removed by elution with 2-methoxyethanol-30% aqueous hydrogen peroxide-12 M hydrochloric... 

Fig. 4.5 Relative increase, DIDo in extraction of hexafluoroacetylacetone (HFA) into hexane from O.IM NaC104 at pH = 2, at different concentrations of the adduct trioctyl-phosphine oxide (TOPO) in the organic phase. The fitted curve is D D = 1 H- 10 [TOPO] g + 10 [TOPO] g. (From Ref. 9.)... 

Fig. 4.12 Enhancement of Zn(ll) extraction, D Do, from 1 M NaC104 into carbon tetrachloride containing the complexing extractants acetylacetone (O), trifluoroacetone (A), or hexafluoroacetone ( ) as a function of the concentration of the adduct former trioctyl phosphine oxide (B). The curves are fitted with Eq. (4.50) using the constants log Km = 3.01 (AA), 6.70 (TEA), 7.0 (TEA), and Km = 4.66 (AA), nil (TEA), 11.6 (HEA). (Erom Ref. 24.)...

Limited laboratory tests to explore the feasibility of substituting T0P0 (trioctyl phosphine oxide) for DBBP were performed. Advantages cited by Bruns (lj>) for use of 0.15M T0P0-CC1 for DBBP in the americium extraction scheme would not eliminate the need for a difficult-to-control feed acidity adjustment step. Primarily for this latter reason, further consideration of T0P0 as an alternative americium extractant was not actively pursued. 

Such experiments show that oxalate, tartrate, and citrate give fairly strong complexes, and indeed these mixtures do not suffer quite such rapid oxidation as the other systems (57, 70). Stability constants for the complexing of U(III) by acetate, 2-hydroxy-2-methylpropionate, nitriloacetate, trans-cyclohexyl-1,2-diaminotetraacetate, ethylenedi-amine tetraacetate, and diethylenetriamine pentaacetate have been reported, but no pure compounds have been isolated (71). Thiocyanate also accelerates oxidation of the uranium, but the blue complex that is formed can be extracted with triethyl phosphate, tributyl phosphate, or better, trioctyl phosphine oxide the organic extract decomposes only slowly (45, 72). 

In both reactions, some of the driving force comes from the removal of the volatile product RCl. This first of the two methods has been employed by Colvin and coworkers [63] to prepare capped Ti02 nanoparticles in refiuxing heptadecane with trioctyl phosphine oxide as the capping agent ... 

The particles formed clear solutions in non-polar solvents, from which they could be precipitated through the addition of a polar solvent such as acetone. When trioctyl phosphine oxide was not taken with the starting materials, insoluble precipitates were obtained. 

Guo and co-workers have synthesized trioctyl phosphine oxide (TOPO) stabilized iron nanoparticles by the microemulsion method with an average diameter of 3 nm [192]. The amorphous particles are known to effectively catalyze reactions such as the decomposition of H2O2. A specific advantage of this method is that the presence of O2 does not hamper the electrocatalytic currents obtained for H2O2. Gold colloids capped with a mixed monolayer of alkylthiol and amidoferrocenyl-... 

Amorphous aluminum oxide has recently been proved to extract lithium from brines and bitterns having lithium concentrations of 0.83 and 13.1 mg/1, respectively. The sorption may be explained by the formation of hydrous lithium aluminum oxide. The sorption capacity of amorphous hydrous aluminum oxide was found to be 4.0 mmol/g. For brines and bitterns the lithium concentration factors on the sorbent attained values of 370 and 130, respectively equilibrium was reached after 7 days. The desorption of lithium ions was carried out with boiling water yielding a maximum concentration factor of lithium in the eluate of 46 in reference to the initial lithium concentration of the brines. Lithium was separated from the eluates by solvent extraction with cyclohexane containing thenoyltrifluoracetone and trioctyl-phosphine oxide, subsequent back extraction with hydrochloric acid, and precipitation of lithium phosphate by addition of K3P04. The purity of the precipitate amounted to at least 95% I7 21). 

The polarographic reduction of triphenylphosphine oxide and trioctyl-phosphine oxide at low concentration in nitroethane has been studied. The estimation of phosphate insecticides by polarography has been reported, and the rearrangement of a-hydroxyphosphinates has been followed by conductance. ... 

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