Journal of the American Chemical Society, Jan 6, 2005
Stable Pd(0) and Rh(0) nanoparticles with small and narrow size distribution can be prepared from... more Stable Pd(0) and Rh(0) nanoparticles with small and narrow size distribution can be prepared from relative large and agglomerated transition-metal particles dispersed in 1-n-butyl-3methylimidazolium hexafluorophosphate ionic liquid by simple laser irradiation. The laser irradiation is a complementary method for the generation of stable metal colloids in ionic liquids and also for the regeneration of small-size nanoparticles that may result from their agglomeration after different applications.
Transition metal-containing membrane films of 10, 20, and 40 μm thickness were obtained by the co... more Transition metal-containing membrane films of 10, 20, and 40 μm thickness were obtained by the combination of irregularly shaped nanoparticles with monomodal size distributions of 4.8 ± 1.1 nm (Rh(0)) and 3.0 ± 0.4 nm (Pt(0)) dispersed in the ionic liquid (IL) 1-n-butyl-3-methylimidazolium bis(trifluoromethane sulfonyl)imide (BMI·(NTf)(2)) with a syrup of cellulose acetate (CA) in acetone. The Rh(0) and Pt(0) metal concentration increased proportionally with increases in film thickness up to 20 μm, and then the material became metal saturated. The presence of small and stable Rh(0) or Pt(0) nanoparticles induced an augmentation in the CA/IL film surface areas. The augmentation of the IL content resulted in an increase of elasticity and decrease in tenacity and toughness, whereas the stress at break was not influenced. The introduction of IL probably causes an increase in the separation between the cellulose macromolecules that results in a higher flexibility, lower viscosity, and be...
Dalton transactions (Cambridge, England : 2003), Jan 21, 2007
Rh(0) nanoparticles (ca. 4 nm) dispersed in an ionic liquid (1-n-butyl-3-methylimidazolium tetraf... more Rh(0) nanoparticles (ca. 4 nm) dispersed in an ionic liquid (1-n-butyl-3-methylimidazolium tetrafluoroborate) were immobilized within a silica network, prepared by the sol-gel method. The effect of the sol-gel catalyst (acid or base) on the encapsulated ionic liquid and Rh(0) content, on the silica morphology and texture, and on the catalyst alkene hydrogenation activity was investigated. The Rh(0) content in the resulting xerogels (ca. 0.1 wt% Rh/SiO(2)) was shown to be independent of the sol-gel process. However, acidic conditions afforded higher contents of encapsulated ionic liquid and xerogels with larger pore diameters, which in turn might be responsible for the higher catalyst activity in hydrogenation of the alkenes.
Hydrogen reduction of cationic or neutral Ir(i) compounds, namely [Ir(COD)(2)]BF(4) and [Ir(COD)C... more Hydrogen reduction of cationic or neutral Ir(i) compounds, namely [Ir(COD)(2)]BF(4) and [Ir(COD)Cl](2)respectively. in the ionic liquid (IL) 1-alkyl-3-methylimidazolium tetrafluoroborate affords either irregularly sized spherical (from 1.9 +/- 0.4 to 3.6 +/- 0.9 nm) or worm-like metal nanoparticles, depending on the nature of the imidazolium alkyl group and the type of iridium precursor. The ionic Ir(i) precursor tends to be dissolved and concentrated on the IL polar domains (populated by the imidazolium nucleus and tetrafluoroborate anions) while the neutral precursor dissolves preferentially in the non-polar region of the IL (populated mainly by N-alkyl side chains). The size, or volume, of the nano-region where the Ir(i) precursor is dissolved and reduced, determines the size and, probably, the shape of the formed nanoparticles. The HR-TEM image shows that the Ir(0) with worm-like shape are polycrystalline and formed from aggregation individual "spherical" nanoparticles of around 1.9 nm. The catalytic activity of Ir(0) NPs on the hydrogenation of cyclohexene (0.01 mol L(-1) of Ir atoms in IL, 75 degrees C, 8 bar of H(2), 500 rpm stirring, 1/1000 Ir(0)/cyclohexene ratio) is always greater in C(1)C(10)I.BF(4) than C(1)C(4)I.BF(4), regardless of the nature of Ir(i) precursor. Moreover, the cyclohexene hydrogenations performed with Ir(0) nanocatalysts made from ionic Ir(i) precursor are approximately twice faster than those NPs obtained from the neutral Ir(i) precursor, in the same IL.
The hydroformylation of 1-alkenes can be performed in solventless conditions using ligand-modifie... more The hydroformylation of 1-alkenes can be performed in solventless conditions using ligand-modified or unmodified Rh(0) nanoparticles prepared in imidazolium ionic liquids as catalyst precursors. There is a strong influence of the nanoparticle size on the hydroformylation reaction. Aldehydes are generated when 5.0nm Rh(0) nanoparticles are used in the hydroformylation of 1-alkenes and l/b selectivities up to 25 can be achieved
Rh(0) nanoparticles (ca. 4 nm) dispersed in an ionic liquid (1-n-butyl-3-methylimidazolium tetraf... more Rh(0) nanoparticles (ca. 4 nm) dispersed in an ionic liquid (1-n-butyl-3-methylimidazolium tetrafluoroborate) were immobilized within a silica network, prepared by the sol-gel method. The effect of the sol-gel catalyst (acid or base) on the encapsulated ionic liquid and Rh(0) content, on the silica morphology and texture, and on the catalyst alkene hydrogenation activity was investigated. The Rh(0) content in the resulting xerogels (ca. 0.1 wt% Rh/SiO(2)) was shown to be independent of the sol-gel process. However, acidic conditions afforded higher contents of encapsulated ionic liquid and xerogels with larger pore diameters, which in turn might be responsible for the higher catalyst activity in hydrogenation of the alkenes.
Journal of the American Chemical Society, Jan 6, 2005
Stable Pd(0) and Rh(0) nanoparticles with small and narrow size distribution can be prepared from... more Stable Pd(0) and Rh(0) nanoparticles with small and narrow size distribution can be prepared from relative large and agglomerated transition-metal particles dispersed in 1-n-butyl-3methylimidazolium hexafluorophosphate ionic liquid by simple laser irradiation. The laser irradiation is a complementary method for the generation of stable metal colloids in ionic liquids and also for the regeneration of small-size nanoparticles that may result from their agglomeration after different applications.
Transition metal-containing membrane films of 10, 20, and 40 μm thickness were obtained by the co... more Transition metal-containing membrane films of 10, 20, and 40 μm thickness were obtained by the combination of irregularly shaped nanoparticles with monomodal size distributions of 4.8 ± 1.1 nm (Rh(0)) and 3.0 ± 0.4 nm (Pt(0)) dispersed in the ionic liquid (IL) 1-n-butyl-3-methylimidazolium bis(trifluoromethane sulfonyl)imide (BMI·(NTf)(2)) with a syrup of cellulose acetate (CA) in acetone. The Rh(0) and Pt(0) metal concentration increased proportionally with increases in film thickness up to 20 μm, and then the material became metal saturated. The presence of small and stable Rh(0) or Pt(0) nanoparticles induced an augmentation in the CA/IL film surface areas. The augmentation of the IL content resulted in an increase of elasticity and decrease in tenacity and toughness, whereas the stress at break was not influenced. The introduction of IL probably causes an increase in the separation between the cellulose macromolecules that results in a higher flexibility, lower viscosity, and be...
Dalton transactions (Cambridge, England : 2003), Jan 21, 2007
Rh(0) nanoparticles (ca. 4 nm) dispersed in an ionic liquid (1-n-butyl-3-methylimidazolium tetraf... more Rh(0) nanoparticles (ca. 4 nm) dispersed in an ionic liquid (1-n-butyl-3-methylimidazolium tetrafluoroborate) were immobilized within a silica network, prepared by the sol-gel method. The effect of the sol-gel catalyst (acid or base) on the encapsulated ionic liquid and Rh(0) content, on the silica morphology and texture, and on the catalyst alkene hydrogenation activity was investigated. The Rh(0) content in the resulting xerogels (ca. 0.1 wt% Rh/SiO(2)) was shown to be independent of the sol-gel process. However, acidic conditions afforded higher contents of encapsulated ionic liquid and xerogels with larger pore diameters, which in turn might be responsible for the higher catalyst activity in hydrogenation of the alkenes.
Hydrogen reduction of cationic or neutral Ir(i) compounds, namely [Ir(COD)(2)]BF(4) and [Ir(COD)C... more Hydrogen reduction of cationic or neutral Ir(i) compounds, namely [Ir(COD)(2)]BF(4) and [Ir(COD)Cl](2)respectively. in the ionic liquid (IL) 1-alkyl-3-methylimidazolium tetrafluoroborate affords either irregularly sized spherical (from 1.9 +/- 0.4 to 3.6 +/- 0.9 nm) or worm-like metal nanoparticles, depending on the nature of the imidazolium alkyl group and the type of iridium precursor. The ionic Ir(i) precursor tends to be dissolved and concentrated on the IL polar domains (populated by the imidazolium nucleus and tetrafluoroborate anions) while the neutral precursor dissolves preferentially in the non-polar region of the IL (populated mainly by N-alkyl side chains). The size, or volume, of the nano-region where the Ir(i) precursor is dissolved and reduced, determines the size and, probably, the shape of the formed nanoparticles. The HR-TEM image shows that the Ir(0) with worm-like shape are polycrystalline and formed from aggregation individual "spherical" nanoparticles of around 1.9 nm. The catalytic activity of Ir(0) NPs on the hydrogenation of cyclohexene (0.01 mol L(-1) of Ir atoms in IL, 75 degrees C, 8 bar of H(2), 500 rpm stirring, 1/1000 Ir(0)/cyclohexene ratio) is always greater in C(1)C(10)I.BF(4) than C(1)C(4)I.BF(4), regardless of the nature of Ir(i) precursor. Moreover, the cyclohexene hydrogenations performed with Ir(0) nanocatalysts made from ionic Ir(i) precursor are approximately twice faster than those NPs obtained from the neutral Ir(i) precursor, in the same IL.
The hydroformylation of 1-alkenes can be performed in solventless conditions using ligand-modifie... more The hydroformylation of 1-alkenes can be performed in solventless conditions using ligand-modified or unmodified Rh(0) nanoparticles prepared in imidazolium ionic liquids as catalyst precursors. There is a strong influence of the nanoparticle size on the hydroformylation reaction. Aldehydes are generated when 5.0nm Rh(0) nanoparticles are used in the hydroformylation of 1-alkenes and l/b selectivities up to 25 can be achieved
Rh(0) nanoparticles (ca. 4 nm) dispersed in an ionic liquid (1-n-butyl-3-methylimidazolium tetraf... more Rh(0) nanoparticles (ca. 4 nm) dispersed in an ionic liquid (1-n-butyl-3-methylimidazolium tetrafluoroborate) were immobilized within a silica network, prepared by the sol-gel method. The effect of the sol-gel catalyst (acid or base) on the encapsulated ionic liquid and Rh(0) content, on the silica morphology and texture, and on the catalyst alkene hydrogenation activity was investigated. The Rh(0) content in the resulting xerogels (ca. 0.1 wt% Rh/SiO(2)) was shown to be independent of the sol-gel process. However, acidic conditions afforded higher contents of encapsulated ionic liquid and xerogels with larger pore diameters, which in turn might be responsible for the higher catalyst activity in hydrogenation of the alkenes.
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Papers by Marcos Gelesky