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Gold and platinum nanoparticles were prepared using a reverse micelle technique, creating products with several particle sizes. The stabilized metal nanoparticles can be deposited over long-range distances forming ordered arrays using supercritical carbon dioxide to remove the colloid solvent. The use of supercritical carbon dioxide creates uniformly deposited particle layers and can be removed without disturbing the precipitated particles. We also show that these nanoparticles can be deposited efficiently in nanometer trenches, which is not possible using conventional particle deposition by liquid evaporation.

Metal catalyst used in the production of single-walled carbon nanotubes (SWNTs) can be effectively removed from the as-grown nanotubes by an in situ chelation/supercritical fluid carbon dioxide extraction method. A pretreatment procedure using bulk electrolysis with ethylenediaminetetraacetic acid significantly improves the efficiency of supercritical fluid extraction probably by removing the amorphous carbon associated with the metal from the SWNTs. More than 98% of the iron impurity can be removed from the as-grown SWNTs using this two-step purification method without obvious damage to the nanotube structures according to our spectroscopic data.

The luminescence quenching of UO2(NO3)·2TBP in supercritical fluid (ScF) CO2 has been examined with time resolved laser induced fluorescence (TRLIF). Quenching mechanisms for the uranyl complex with respect to ScF composition, pressure and temperature have been identified. A description of pressure quenching in ScF has been shown to require both the bimolecular collisional dynamics associated with a gas phase as well as the viscosity effects expected from a liquid phase.

The supercritical fluid extraction (SFE) of metal ions was assessed in terms of the ability of the process to extract, solvate, transport and collect metal species. The extraction efficiency (per cent removed from the sample matrix), collection efficiency (per cent recovered in the collection solvent) and SFE residue (unextracted metal complex or metal ion recovered from the apparatus by flushing with an organic or acidic solvent, respectively) were determined to ascertain whether a mass balance for the metal could be achieved. Using this approach, it was demonstrated that the amount of metal extracted from the sample matrix did not necessarily correspond to the concentration of metal recovered in the collection solvent, as the chelated metal complex could partially degrade and/or dissociate in the supercritical fluid prior to collection. Typically, a discrepancy of 1 to 15% could be obtained. The non-fluorinated metal β-diketones and dithiocarbamates had a greater tendency to dissociate and/or degrade in a supercritical fluid (i.e., ca. 14 and 5%, respectively) than the corresponding fluorinated metal complex (i.e., ca. 6 and 1%, respectively). As for the collection solvents, a range of suitable fluids were found to be capable of obtaining quantitative metal complex recoveries, including methanol, chloroform, isobutyl methyl ketone or 10% nitric acid. A radioactive isotope, 177Lu, was used to trace the location of the metal residue in the SFE apparatus.

The Heck coupling of iodobenzene with olefins occurs with high efficiencies at low temperatures in imidazolium-based ionic liquids catalyzed by PdCl2/Et3N, and the catalyst can be recycled after extraction of the products by supercritical CO2. The coupling efficiency is dependent on water content of the ionic liquid. With a low water content (<50 ppm) in the ionic liquid, the Heck coupling reaction would proceed with >90% yield at room temperature using this catalytic system.

Strontium (Sr2+) can be selectively extracted from aqueous solutions into supercritical fluid CO2 at 60 °C and 100 atm with dicyclohexano-18-crown-6 (DC18C6) using CF3(CF2)6CO2– (PFOA–) or CF3(CF2)6CF2SO3– (PFOSA–) as a counter anion; at a mole ratio of Sr2+ : DC18C6 : PFOA– = 1:10:50, the extraction of Sr (5.6 × 10–5 M) from water at pH 3 is near quantitative whereas Ca2+ and Mg2+ at equal concentration are only extracted to a level of 7 and 1%, respectively; PFOSA– is an effective counter anion for selective extraction of Sr2+ from 1.3 M HNO3 with DC18C6 in supercritical CO2.

UO2(NO3)2·2TBP is highly soluble in supercritical CO2, with concentrations of 0.0025–0.4981 M attainable at modest temperatures and pressures, demonstrating that supercritical CO2 can provide a viable substitute for organic solvents used in nuclear fuel processing.

The binding properties of two ligands, 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis(carboxymethoxy)calix[4]arene 1 and 5,11,17,23,29,35-hexa-tert-butyl-37,38,39,40,41,42- hexakiscarboxymethoxy)calix[6]arene 2, which show high selectivity for 225Ac3+ (an α-emitter with t1/2 = 10 days) over Na+, K+, Mg2+, Ca2+ and Zn2+ are described.