TY - JOUR
T1 - Poly(sodium 4-styrenesulfonate) Stabilized Janus Nanosheets in Brine with Retained Amphiphilicity
AU - Luo, Dan
AU - Wang, Feng
AU - Chen, Jianfa
AU - Zhang, Fanghao
AU - Yu, Luo
AU - Wang, Dezhi
AU - Willson, Richard C.
AU - Yang, Zhaozhong
AU - Ren, Zhifeng
N1 - Funding Information:
The work performed at the University of Houston is supported in part by the US Department of Energy under Contract DE-SC0010831. We thank the support from the Center of Advanced Computing and Data Systems at the University of Houston.
Funding Information:
The work performed at the University of Houston is supported in part by the US Department of Energy under Contract DESC0010831. We thank the support from the Center of Advanced Computing and Data Systems at the University of Houston.
Publisher Copyright:
© 2018 American Chemical Society.
Copyright:
Copyright 2018 Elsevier B.V., All rights reserved.
PY - 2018/3/27
Y1 - 2018/3/27
N2 - Maintaining colloidal stability in unfriendly environments while retaining surface chemical properties is challenging for fundamental science and crucial for many applications. Here, we report for the first time that by using a low concentration of poly(sodium 4-styrenesulfonate) (PSS), graphene-based amphiphilic Janus nanosheets (AJNs) can be stabilized in high salt brine (3 wt % NaCl and 0.5 wt % CaCl2), whereas the interfacial behavior of the nanosheets is not affected. The adsorption of PSS on the hydrophilic and hydrophobic surfaces of AJNs in brine was investigated experimentally and by molecular dynamics simulations. Simulations further showed that the spatial configuration of absorbed PSS molecules with sulfonate functional groups facing outward favored the generation of electrosteric repulsive interactions. Calculations of the interaction energy between PSS molecules and the nanosheet revealed surface charge as a key parameter to stabilize AJNs in the salt environment, as demonstrated by the case of graphene oxide with higher surface charge. Simulations were also used to examine the interfacial behavior of graphene-based AJNs in biphasic systems. The AJNs, which exhibited asymmetry in surface wettability, remained at the oil/brine interface because of PSS detachment from the hydrophobic surface. The results were subsequently experimentally confirmed, consistent with our previously reported graphene-based AJN fluid prepared in fresh water. The process was thermodynamically supported by the demonstrated negative change of Gibbs free energy. We believe that such a strategy could benefit for the stabilization of other AJNs with surface chemical accessibility under harsh conditions.
AB - Maintaining colloidal stability in unfriendly environments while retaining surface chemical properties is challenging for fundamental science and crucial for many applications. Here, we report for the first time that by using a low concentration of poly(sodium 4-styrenesulfonate) (PSS), graphene-based amphiphilic Janus nanosheets (AJNs) can be stabilized in high salt brine (3 wt % NaCl and 0.5 wt % CaCl2), whereas the interfacial behavior of the nanosheets is not affected. The adsorption of PSS on the hydrophilic and hydrophobic surfaces of AJNs in brine was investigated experimentally and by molecular dynamics simulations. Simulations further showed that the spatial configuration of absorbed PSS molecules with sulfonate functional groups facing outward favored the generation of electrosteric repulsive interactions. Calculations of the interaction energy between PSS molecules and the nanosheet revealed surface charge as a key parameter to stabilize AJNs in the salt environment, as demonstrated by the case of graphene oxide with higher surface charge. Simulations were also used to examine the interfacial behavior of graphene-based AJNs in biphasic systems. The AJNs, which exhibited asymmetry in surface wettability, remained at the oil/brine interface because of PSS detachment from the hydrophobic surface. The results were subsequently experimentally confirmed, consistent with our previously reported graphene-based AJN fluid prepared in fresh water. The process was thermodynamically supported by the demonstrated negative change of Gibbs free energy. We believe that such a strategy could benefit for the stabilization of other AJNs with surface chemical accessibility under harsh conditions.
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U2 - 10.1021/acs.langmuir.8b00397
DO - 10.1021/acs.langmuir.8b00397
M3 - Article
C2 - 29509429
AN - SCOPUS:85044660970
SN - 0743-7463
VL - 34
SP - 3694
EP - 3700
JO - Langmuir
JF - Langmuir
IS - 12
ER -