Effect of Surface Tension from MD Simulations on Size-Dependent Deliquescence of NaCl Nanoparticles

Bahadur, Ranjit Prasad; Russell, Lynn M.

doi:10.1080/02786820802104965

Cited by 38 publications

(41 citation statements)

References 54 publications

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“…13 Smaller particles also tend to interact with gases differently than do bulk solids; for example, at 298 K bulk NaCl deliquesces at 75% relative humidity (RH), but for particles smaller than B40 nm, the deliquescence RH increases, as does the efflorescence RH. [33][34][35][36][37][38][39][40][41][42][43] Second, the chemical composition of individual particles can vary significantly, even within one air mass. Before the advent of techniques for single particle analysis, it was uncertain if airborne particles were ''externally'' or ''internally'' mixed, i.e., whether an ensemble of particles in air consisted of individual particles with single components or whether each particle contained a mixture.…”

Section: Introductionmentioning

confidence: 99%

Reactions at surfaces in the atmosphere: integration of experiments and theory as necessary (but not necessarily sufficient) for predicting the physical chemistry of aerosols

Finlayson-Pitts

2009

Phys. Chem. Chem. Phys.

229

272

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Section: Introductionmentioning

confidence: 99%

Reactions at surfaces in the atmosphere: integration of experiments and theory as necessary (but not necessarily sufficient) for predicting the physical chemistry of aerosols

Finlayson-Pitts

2009

Phys. Chem. Chem. Phys.

229

272

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“…68 However, for particles larger than 20 nm, this effect is relatively small and quantitatively predictable from bulk thermodynamics properties. 86,87 The Kelvin correction factor for the IL nanoparticles was estimated using surface tension versus water content measurements from Rilo et al 85 For the ∼27 nm nanoparticles, the anticipated reduction in χ w compared to bulk is less than 5% for [ From the ATR-FTIR measurements, χ w in the IL film exposed to water vapor can be estimated by comparing the relative areas of the C−H and O−H stretching vibrations. We calibrated this method by recording the ATR-FTIR spectra of premixed aqueous solutions of ILs of known composition.…”

Section: ■ Introductionmentioning

confidence: 99%

Interaction of Water Vapor with the Surfaces of Imidazolium-Based Ionic Liquid Nanoparticles and Thin Films

et al. 2012

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Understanding the interactions of humid air with ionic liquids (ILs) is critical for predicting how their physicochemical properties are affected by water. Using experimental and theoretical techniques, water vapor's interaction with aerosolized nanoparticles and thin films of [C 2 MIM][Cl] and [C 2 MIM][BF 4 ] was studied. Solutions were electrosprayed to produce dry particles. Particles' hygroscopic growth was quantified using tandem nanodifferential mobility analysis as a function of relative humidity (RH). This is the first report of the interaction of water with aerosolized IL nanoparticles. The particles' small size allows true IL−water vapor equilibrium achieved quickly. Growth curves for both ILs show steady water uptake with increasing RH. Water vapor uptake by IL thin films was also examined using ATR-FTIR spectroscopy. . They represent a large class of molecules that have unique and widely tunable physical and chemical properties. 1−3 For example, there is a significant interest in the use of ILs in green chemistry, 2,4,5 due to their negligible vapor pressure at room temperature, 6 and for many other applications including solvents in synthesis and catalysis, 1,6 chemical extraction, 1,2,5 and fuel cells. 7 Physical properties such as conductivity, viscosity, density, and surface tension of ILs are known to depend on the presence of water, both adsorbed and absorbed. 3,8 Water is ubiquitous in the environment, and hygroscopic ILs such as those with imidazolium-based cations can uptake significant amounts of water vapor from ambient air, which alters their physical and chemical properties. 1,3 Thus, quantification of water uptake by hygroscopic ILs and understanding how the presence of water affects the nature of the ion−ion and ion−water interactions are critical for use of ILs in future applications. 8−14 Numerous experimental and theoretical studies have investigated the interaction of imidazolium-based ILs with water. 3,8−35 It is understood that both the cation and the anion have an effect on how ILs interact with water, with the anion having a stronger effect. 3,17,19 Early experimental work by Seddon et al. investigated the miscibility of water with ILs containing 1-nalkyl-3-methylimidazolium ([C n MIM + ], n = number of carbons on the linear alkyl chain) cations and various anions at room temperature. 3 It was determined that, regardless of the alkyl chain length, all halide anions were fully soluble in water and all hexafluorophosphate ([PF 6 − ]) anions were insoluble. 3 However, alkyl chain length did have an effect on water miscibility of [C n MIM + ]-based ILs with tetrafluoroborate ([BF 4 − ]) anions; for chain lengths of n = 2 or 4, the ILs were fully miscible, but for n > 4, the ILs formed biphasic systems. 3 Cammarata et al. performed early attenuated total reflection (ATR) infrared (IR) studies on the molecular states of water

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“…19 In this size range, there is a nontrivial contribution of the surface energy to the free energy of the particle: G particle ) µ bulk n bulk + µ surface n surface ≈ µ bulk n bulk + σ surface A particle (2) In other words, the surface energy term in the free energy expression, which can be safely neglected for particles larger than 100 nm, starts to be comparable in magnitude to the bulk free energy contribution. [20][21][22][23][24] As a result of the large surfaceto-volume ratios of nanoparticles, their GF, ERH, and DRH values can be size-dependent. Only a few experimental and theoretical studies of hygroscopic growth of nanoparticles are currently available.…”

Section: Introductionmentioning

confidence: 99%

“…22 It was possible to use a macroscopic description for the theoretical prediction of phase transitions in even smaller particles (down to 2 nm in size) by allowing for phenomenological size dependence of the surface tension. 23,31 Atmospheric particles generally represent complicated mixtures of organic and inorganic species with very different levels of water solubility. To better understand the consequences of having poorly miscible species in the same particle, hygroscopic properties of particles with inorganic core-organic shell morphologies were investigated by several groups.…”

Section: Introductionmentioning

confidence: 99%

Hygroscopic Growth and Deliquescence of NaCl Nanoparticles Coated with Surfactant AOT

et al. 2009

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Aerosolized nanoparticles of NaCl coated with variable amounts of surfactant AOT were generated by electrospraying AOT/NaCl aqueous solutions, followed by neutralizing and drying the resulting particles. A tandem differential mobility analyzer was used to select a narrow size distribution of particles with mobility equivalent diameters below 20 nm and monitor their hygroscopic growth as a function of relative humidity. Effects of the particle size and relative amount of surfactant on the hygroscopic growth of NaCl were studied. For pure NaCl nanoparticles, the deliquescence relative humidity (DRH) increased as the particle size was decreased, in full agreement with previous measurements. Below the DRH the NaCl nanoparticles had an equivalent of one-four monolayers of water adsorbed on the surface. The addition of a sub-monolayer AOT coating reduced the DRH and suppressed the hygroscopic growth of the NaCl core. At AOT coverage levels exceeding one monolayer, a clear deliquescence transition was no longer discernible. The Zdanovskii-StokesRobinson (ZSR) model failed to predict the observed growth factors of mixed AOT/NaCl nanoparticles reflecting a large contribution of the interfacial interactions between NaCl and AOT to the total free energy of the particles. There were indications that AOT/NaCl nanoparticles prepared by the electrospray aerosol source were enhanced in the relative mass fraction of AOT in comparison with the solution from which they were electrosprayed.

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Effect of Surface Tension from MD Simulations on Size-Dependent Deliquescence of NaCl Nanoparticles

Cited by 38 publications

References 54 publications

Reactions at surfaces in the atmosphere: integration of experiments and theory as necessary (but not necessarily sufficient) for predicting the physical chemistry of aerosols

Reactions at surfaces in the atmosphere: integration of experiments and theory as necessary (but not necessarily sufficient) for predicting the physical chemistry of aerosols

Interaction of Water Vapor with the Surfaces of Imidazolium-Based Ionic Liquid Nanoparticles and Thin Films

Hygroscopic Growth and Deliquescence of NaCl Nanoparticles Coated with Surfactant AOT

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