Steric Stabilization of Nanocrystals in Supercritical CO<sub>2</sub> Using Fluorinated Ligands

Shah, Parag S.; Holmes, Justin D.; Doty, Chris; Johnston, and Keith P.; Korgel, Brian A.

doi:10.1021/ja9943748

Cited by 121 publications

(130 citation statements)

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“…To make full use of the advantages of supercritical CO 2 , a stable dispersion of fluorine-free nanoparticles in a single CO 2 phase would be ideal. While metallic nanoparticles have been stably dispersed in pure liquid and supercritical CO 2 [132,133], fluorinated ligands were required. The objective of this study is to illustrate the ability to stably disperse ligand coated metal nanoparticles in neat CO 2 without the need for fluorinated constituents.…”

Section: Non-fluorous Thiols Resultsmentioning

confidence: 99%

Synthesis and Evaluation of CO2 Thickeners Designed with Molecular Modeling

Enick¹,

Beckman²,

Johnson³

2009

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The objective of this research was to use molecular modeling techniques, coupled with our prior experimental results, to design, synthesize and evaluate inexpensive, non-fluorous carbon dioxide thickening agents.The first type of thickener that was considered was associating polymers. Typically, these thickeners are copolymers that contain a highly CO 2 -philic monomer, and a small concentration of a CO 2 -phobic associating monomer.Yale University was solely responsible for the synthesis of a second type of thickener; small, hydrogen bonding compounds. These molecules have a core that contains one or more hydrogen-bonding groups, such as urea or amide groups. Non-fluorous, CO 2 -philic functional groups were attached to the hydrogen bonding core of the compound to impart CO 2 stability and macromolecular stability to the linear "stack" of these compounds.The third type of compound initially considered for this investigation was CO 2 -soluble surfactants. These surfactants contain conventional ionic head groups and composed of CO 2 -philic oligomers (short polymers) or small compounds (sugar acetates) previously identified by our research team. Mobility reduction could occur as these surfactant solutions contacted reservoir brine and formed mobility control foams in-situ.The vast majority of the work conducted in this study was devoted to the copolymeric thickeners and the small hydrogen-bonding thickeners; these thickeners were intended to dissolve completely in CO 2 and increase the fluid viscosity. A small but important amount of work was done establishing the groundwork for CO 2 -soluble surfactants that reduced mobility by generating foams in-situ as the CO 2 +surfactant solution mixed with in-situ brine. PolymersIn this final report, we review our entire co-polymeric thickener effort and detail, for the first time, the phase behavior and viscosity results of the first non-fluorous, oxygenated hydrocarbon-based, associating polymer CO 2 thickener, poly(vinyl acetate -co -benzoyl 5% ). The CO 2 -philic monomer was vinyl acetate, and the associative thickener monomer was vinyl benzoate. Poly(vinyl acetate -co -benzoyl 5% ), Mw ~ 12000, is capable of increasing the viscosity of CO 2 by 70% at a concentration of 2wt%, a shear rate of ~5000s -1 , 298K and 9500 psia. Unfortunately, poly(vinyl acetate -co -benzoyl 5% ) is not capable of dissolving in CO 2 at pressures close to the MMP, roughly 1200 psia at 298 K. In fact, we are now convinced that a non-fluorous, hydrocarbon-based copolymeric thickener cannot be designed that will dissolve in CO 2 at typical reservoir conditions. Why? Every polymer that we designed using molecular modeling tools was indeed CO 2 soluble, a somewhat remarkable achievement given the small number of CO 2 soluble surfactants that have ever been identified, but each one was less soluble in CO 2 than poly(vinyl acetate). Therefore co-polymeric thickeners based on any CO 2 soluble polymer will undoubtedly be less soluble in CO 2 (i.e. require even greater pressures than 9500 psia)...

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Section: Non-fluorous Thiols Resultsmentioning

confidence: 99%

Synthesis and Evaluation of CO2 Thickeners Designed with Molecular Modeling

Enick¹,

Beckman²,

Johnson³

2009

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“…The poor solubility properties of perfluorinated nanoparticles are certainly a limit but represent also an opportunity of studying the chemistry of gold nanoparticles in fluorocarbons or supercritical CO 2 (Sc CO 2 ). Indeed silver nanoparticles protected by 1 were found to be soluble in Sc CO 2 [13] with solubility increasing with the increase of Sc CO 2 density.…”

Section: "Perfluorinated" Gold Nanoparticlesmentioning

confidence: 99%

“…Among these early attempts, the first preparation of perfluorinated silver nanoparticles was reported by Korgel [13] in 2000 by using 1 in a modified Brust-Schiffrin procedure. Later, the synthesis of gold (and silver) nanoparticles was reported by Yonezawa and Kimizuka [14,15] The characterization of the nanoparticles by TEM analyses revealed a narrow size distribution with a strong tendency of forming 2D superlattices onto the TEM support.…”

Section: "Perfluorinated" Gold Nanoparticlesmentioning

confidence: 99%

Gold nanoparticles protected by fluorinated ligands: Syntheses, properties and applications

Pengo

Pasquato

2015

Journal of Fluorine Chemistry

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Abstract:The development of fluorinated gold nanoparticles is presently arising and increasing attention across several fields of nanotechnology. The synthetic approaches evolved over time from the use of almost perfluorinated alkanethiols and perfluorinated arylthiols to amphiphilic fluorinated thiols capable of ensuring solubility in conventional organic solvents and water. The interest in these systems stems from the unique properties of both nanosized and fluorous compounds. In perspective, the development of our understanding of the fluorophilic interactions at the nanoscale will allow to devise novel strategies for self-assembly, molecular recognition and new materials for biomedical applications. In this paper we present, through selected examples, the potential of fluorous ligands in the synthesis of gold nanoparticles and the relevance of mastering the properties of these systems in the development of new materials.

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“…Supercritical fluids (SCFs) have attracted considerable interest as a reaction medium to synthesize nanoparticles, [11][12][13][14] because the variations in SCF solvent properties, such as density, diffusivity, viscosity, and dielectric constant, can be easily manipulated by changing the system temperature and pressure., [15,16] In addition to these advantages, scCO 2 provides an attractive substitute for petroleum-based organic solvents for chemical synthesis since it is nontoxic, environmentally-benign, nonflammable, inexpensive, and readily available in large quantities. The unique property of supercritical fluids, including scCO 2 , is its tunable solvent strength through manipulation of its density (1), which can be easily controlled, as mentioned above, by varying temperature and pressure of the fluid phase.…”

Section: Introductionmentioning

confidence: 99%

Continuous Tuning of Cadmium Sulfide and Zinc Sulfide Nanoparticle Size in a Water‐in‐Supercritical Carbon Dioxide Microemulsion

Fernández

Wai

2007

Chemistry A European J

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The size and size dispersion of cadmium sulfide and zinc sulfide semiconductor nanoparticles can be continuously tuned over a wide range of values by adjusting the density of the fluid phase in water-in-supercritical CO2 microemulsions. The average size of the ZnS nanoparticles decreases linearly from approximately 9.1 to 1.9 nm with increasing fluid density from 0.86 to 0.99 g cm(-3) at a water-to-surfactant ratio (W value) of 10. At a W value of 6, the particle size can be tuned from 7.0 to 1.5 nm in the same density range. In the case of CdS nanocrystals, the size varied from 7.1 to 2.0 nm when the W value was 10 and from 4.0 to 1.3 nm when the W value employed was 6, in the same density range. Monodispersive CdS and ZnS nanoparticles were synthesized by chemical reaction of cadmium or zinc nitrate with sodium sulfide, using two water-in-supercritical CO2 microemulsions as nanoreactors followed by protection with a fluorinated-thiol stabilizer. The stabilizer is introduced at 6 and 16 minutes after the mixing of the two microemulsions where the intensity of the characteristic absorption peak due to the quantum confinement properties of the CdS and ZnS nanoparticles (280 and 360 nm) reaches a maximum, respectively. The supercritical CO2 microemulsion method represents a simple approach to use a density-tunable solvent for synthesizing size-controlled semiconductor nanoparticles over a broad range of values.

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Steric Stabilization of Nanocrystals in Supercritical CO₂ Using Fluorinated Ligands

Cited by 121 publications

References 19 publications

Synthesis and Evaluation of CO2 Thickeners Designed with Molecular Modeling

Synthesis and Evaluation of CO2 Thickeners Designed with Molecular Modeling

Gold nanoparticles protected by fluorinated ligands: Syntheses, properties and applications

Continuous Tuning of Cadmium Sulfide and Zinc Sulfide Nanoparticle Size in a Water‐in‐Supercritical Carbon Dioxide Microemulsion

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Steric Stabilization of Nanocrystals in Supercritical CO2 Using Fluorinated Ligands

Cited by 121 publications

References 19 publications

Synthesis and Evaluation of CO2 Thickeners Designed with Molecular Modeling

Synthesis and Evaluation of CO2 Thickeners Designed with Molecular Modeling

Gold nanoparticles protected by fluorinated ligands: Syntheses, properties and applications

Continuous Tuning of Cadmium Sulfide and Zinc Sulfide Nanoparticle Size in a Water‐in‐Supercritical Carbon Dioxide Microemulsion

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Steric Stabilization of Nanocrystals in Supercritical CO₂ Using Fluorinated Ligands