Size-dependent hydrophobic to hydrophilic transition for nanoparticles

A molecular dynamics study

Chi-cheng Chiu, Preston B. Moore, Wataru Shinoda, Steven O. Nielsen

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

The physical properties of nanoscale materials often vary with their size, unlike the corresponding bulk material properties, which can only be changed by modifying the material composition. In particular, it is believed that hydration phenomena are length scale dependent. The manifestation of hydrophobicity over multiple length scales plays a crucial role in self-assembly processes such as protein folding and colloidal stability. In the case of particles composed of a bulk hydrophobic material, it is well known that the free energy of hydration monotonically increases with particle size. However, the size-dependent free energy of hydration for particles composed of a bulk hydrophilic material has not been studied. Here we show that the free energy of hydration is not a monotonic function of particle size, but rather, changes sign from positive to negative as the particle size increases. In other words, the particle is hydrophobic at small size and hydrophilic at large size. This behavior arises from a purely geometrical effect caused by the curvature of the particle-water interface. We explore the consequences of this phenomenon on colloidal stability and find that it dictates the shape of colloidal aggregates.

Original languageEnglish
Article number244706
JournalJournal of Chemical Physics
Volume131
Issue number24
DOIs
Publication statusPublished - 2009 Dec 1

Fingerprint

Hydration
Molecular dynamics
molecular dynamics
Free energy
Nanoparticles
nanoparticles
Particle size
hydration
Protein folding
free energy
Hydrophobicity
Self assembly
Materials properties
Physical properties
hydrophobicity
Water
folding
Chemical analysis
self assembly
physical properties

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

Cite this

Chiu, Chi-cheng ; Moore, Preston B. ; Shinoda, Wataru ; Nielsen, Steven O. / Size-dependent hydrophobic to hydrophilic transition for nanoparticles : A molecular dynamics study. In: Journal of Chemical Physics. 2009 ; Vol. 131, No. 24.
@article{2d5560d15af94cf7af85418314e0bc06,
title = "Size-dependent hydrophobic to hydrophilic transition for nanoparticles: A molecular dynamics study",
abstract = "The physical properties of nanoscale materials often vary with their size, unlike the corresponding bulk material properties, which can only be changed by modifying the material composition. In particular, it is believed that hydration phenomena are length scale dependent. The manifestation of hydrophobicity over multiple length scales plays a crucial role in self-assembly processes such as protein folding and colloidal stability. In the case of particles composed of a bulk hydrophobic material, it is well known that the free energy of hydration monotonically increases with particle size. However, the size-dependent free energy of hydration for particles composed of a bulk hydrophilic material has not been studied. Here we show that the free energy of hydration is not a monotonic function of particle size, but rather, changes sign from positive to negative as the particle size increases. In other words, the particle is hydrophobic at small size and hydrophilic at large size. This behavior arises from a purely geometrical effect caused by the curvature of the particle-water interface. We explore the consequences of this phenomenon on colloidal stability and find that it dictates the shape of colloidal aggregates.",
author = "Chi-cheng Chiu and Moore, {Preston B.} and Wataru Shinoda and Nielsen, {Steven O.}",
year = "2009",
month = "12",
day = "1",
doi = "10.1063/1.3276915",
language = "English",
volume = "131",
journal = "Journal of Chemical Physics",
issn = "0021-9606",
publisher = "American Institute of Physics Publising LLC",
number = "24",

}

Size-dependent hydrophobic to hydrophilic transition for nanoparticles : A molecular dynamics study. / Chiu, Chi-cheng; Moore, Preston B.; Shinoda, Wataru; Nielsen, Steven O.

In: Journal of Chemical Physics, Vol. 131, No. 24, 244706, 01.12.2009.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Size-dependent hydrophobic to hydrophilic transition for nanoparticles

T2 - A molecular dynamics study

AU - Chiu, Chi-cheng

AU - Moore, Preston B.

AU - Shinoda, Wataru

AU - Nielsen, Steven O.

PY - 2009/12/1

Y1 - 2009/12/1

N2 - The physical properties of nanoscale materials often vary with their size, unlike the corresponding bulk material properties, which can only be changed by modifying the material composition. In particular, it is believed that hydration phenomena are length scale dependent. The manifestation of hydrophobicity over multiple length scales plays a crucial role in self-assembly processes such as protein folding and colloidal stability. In the case of particles composed of a bulk hydrophobic material, it is well known that the free energy of hydration monotonically increases with particle size. However, the size-dependent free energy of hydration for particles composed of a bulk hydrophilic material has not been studied. Here we show that the free energy of hydration is not a monotonic function of particle size, but rather, changes sign from positive to negative as the particle size increases. In other words, the particle is hydrophobic at small size and hydrophilic at large size. This behavior arises from a purely geometrical effect caused by the curvature of the particle-water interface. We explore the consequences of this phenomenon on colloidal stability and find that it dictates the shape of colloidal aggregates.

AB - The physical properties of nanoscale materials often vary with their size, unlike the corresponding bulk material properties, which can only be changed by modifying the material composition. In particular, it is believed that hydration phenomena are length scale dependent. The manifestation of hydrophobicity over multiple length scales plays a crucial role in self-assembly processes such as protein folding and colloidal stability. In the case of particles composed of a bulk hydrophobic material, it is well known that the free energy of hydration monotonically increases with particle size. However, the size-dependent free energy of hydration for particles composed of a bulk hydrophilic material has not been studied. Here we show that the free energy of hydration is not a monotonic function of particle size, but rather, changes sign from positive to negative as the particle size increases. In other words, the particle is hydrophobic at small size and hydrophilic at large size. This behavior arises from a purely geometrical effect caused by the curvature of the particle-water interface. We explore the consequences of this phenomenon on colloidal stability and find that it dictates the shape of colloidal aggregates.

UR - http://www.scopus.com/inward/record.url?scp=73649109910&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=73649109910&partnerID=8YFLogxK

U2 - 10.1063/1.3276915

DO - 10.1063/1.3276915

M3 - Article

VL - 131

JO - Journal of Chemical Physics

JF - Journal of Chemical Physics

SN - 0021-9606

IS - 24

M1 - 244706

ER -