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Fractionation of surface - modified gold nanorods using gas - expanded liquids / Gregory White in Industrial & engineering chemistry research, Vol. 51 N° 14 (Avril 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 14 (Avril 2012) . - pp. 5181–5189 Titre : Fractionation of surface - modified gold nanorods using gas - expanded liquids Type de document : texte imprimé Auteurs : Gregory White, Auteur ; Matthew Grant Provost, Auteur ; Christopher Lawrence Kitchens, Auteur Année de publication : 2012 Article en page(s) : pp. 5181–5189 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Gold  nanorods  Nanocomposites Résumé : Gold nanorods (GNRs) have found widespread applications in nanocomposites and thin films, because of their unique optical, chemical, and photothermal properties, which are dictated by the rod size and aspect ratio. In this study, gold nanorods (GNRs, aspect ratio of 3–4) were synthesized using a high-yield, aqueous, solution-based method, followed by a surface modification reaction to facilitate their dispersion in organic media. A gas-expanded liquid (GXL) precipitation technique was used to effectively size-fractionate the GNRs with CO2 as a green antisolvent for hydrophobic nanorods dispersed in toluene, hexane, and cyclohexane. The advantages of using GXL media lie in the tunable solvent properties that enable size-selective nanoparticle precipitation that is easily controlled by the CO2 antisolvent partial pressure. This work demonstrated effective GNR size fractionation and a 73% reduction in the number of residual 4-nm-diameter spherical seed nanoparticles remaining after synthesis with a single precipitation and redispersion. The GNR dispersibility and precipitation was monitored by ultraviolet-visible (UV–vis) absorbance spectroscopy and found to be dependent on the solvent choice and GNR ligand. CO2-expanded cyclohexane provided the greatest dispersibility of GNRs stabilized by 18-carbon-chain-length ligands, which were dispersible at pressures up to roughly 30 bar (0.44 mol fraction CO2), compared to a lower pressure, on the order of 24 bar for CO2-expanded toluene (0.21 mol fraction CO2) and n-hexane (0.31 mol fraction CO2). Varying the hydrophobic stabilizing ligand chain length also impacted nanorod dispersibility in CO2-expanded toluene, where 12-carbon-chain-length dodecanethiol ligands yielded nanorod dispersion/precipitation at CO2 pressures much greater than those for the 18-carbon octadecanethiol ligands. This work is the first application of a GXL solvent medium for the processing, purification, and size fractionation of nonspherical particles, which has led to a greater understanding of gold nanorod dispersibility and demonstrated the feasibility of GXLs as a green solvent medium for post-synthesis nanorod processing. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie201975p [article] Fractionation of surface - modified gold nanorods using gas - expanded liquids [texte imprimé] / Gregory White, Auteur ; Matthew Grant Provost, Auteur ; Christopher Lawrence Kitchens, Auteur . - 2012 . - pp. 5181–5189. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 14 (Avril 2012) . - pp. 5181–5189 Mots-clés : Gold  nanorods  Nanocomposites Résumé : Gold nanorods (GNRs) have found widespread applications in nanocomposites and thin films, because of their unique optical, chemical, and photothermal properties, which are dictated by the rod size and aspect ratio. In this study, gold nanorods (GNRs, aspect ratio of 3–4) were synthesized using a high-yield, aqueous, solution-based method, followed by a surface modification reaction to facilitate their dispersion in organic media. A gas-expanded liquid (GXL) precipitation technique was used to effectively size-fractionate the GNRs with CO2 as a green antisolvent for hydrophobic nanorods dispersed in toluene, hexane, and cyclohexane. The advantages of using GXL media lie in the tunable solvent properties that enable size-selective nanoparticle precipitation that is easily controlled by the CO2 antisolvent partial pressure. This work demonstrated effective GNR size fractionation and a 73% reduction in the number of residual 4-nm-diameter spherical seed nanoparticles remaining after synthesis with a single precipitation and redispersion. The GNR dispersibility and precipitation was monitored by ultraviolet-visible (UV–vis) absorbance spectroscopy and found to be dependent on the solvent choice and GNR ligand. CO2-expanded cyclohexane provided the greatest dispersibility of GNRs stabilized by 18-carbon-chain-length ligands, which were dispersible at pressures up to roughly 30 bar (0.44 mol fraction CO2), compared to a lower pressure, on the order of 24 bar for CO2-expanded toluene (0.21 mol fraction CO2) and n-hexane (0.31 mol fraction CO2). Varying the hydrophobic stabilizing ligand chain length also impacted nanorod dispersibility in CO2-expanded toluene, where 12-carbon-chain-length dodecanethiol ligands yielded nanorod dispersion/precipitation at CO2 pressures much greater than those for the 18-carbon octadecanethiol ligands. This work is the first application of a GXL solvent medium for the processing, purification, and size fractionation of nonspherical particles, which has led to a greater understanding of gold nanorod dispersibility and demonstrated the feasibility of GXLs as a green solvent medium for post-synthesis nanorod processing. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie201975p