TY - JOUR
T1 - Aggregation Behavior of Inorganic 2D Nanomaterials beyond Graphene
T2 - Insights from Molecular Modeling and Modified DLVO Theory
AU - Mohona, Tashfia M.
AU - Gupta, Anusha
AU - Masud, Arvid
AU - Chien, Szu Chia
AU - Lin, Li Chiang
AU - Nalam, Prathima C.
AU - Aich, Nirupam
N1 - Publisher Copyright:
© 2019 American Chemical Society.
PY - 2019/4/16
Y1 - 2019/4/16
N2 - We report the comparative aggregation behavior of three emerging inorganic 2D nanomaterials (NMs): MoS2, WS2, and h-BN in aquatic media. Their aqueous dispersions were subjected to aggregation under varying concentrations of monovalent (NaCl) and divalent (CaCl2) electrolytes. Moreover, Suwanee River Natural Organic Matter (SRNOM) has been used to analyze the effect of natural macromolecules on 2D NM aggregation. An increase in electrolyte concentration resulted in electrical double-layer compression of the negatively charged 2D NMs, thus displaying classical Derjaguin-Landau-Verwey-Overbeek (DLVO)-type interaction. The critical coagulation concentrations (CCC) have been estimated as 37, 60, and 19 mM NaCl and 3, 7.2, and 1.3 mM CaCl2 for MoS2, WS2, and h-BN, respectively. Theoretical predictions of CCC by modified DLVO theory have been found comparable to the experimental values when dimensionality of the materials is taken into account and a molecular modeling approach was used for calculating molecular level interaction energies between individual 2D NM nanosheets. Electrostatic repulsion has been found to govern colloidal stability of MoS2 and WS2 while the van der Waals attraction has been found to govern that of h-BN. SRNOM stabilizes the 2D NMs significantly possibly by electrosteric repulsion. The presence of SRNOM completely stabilized MoS2 and WS2 at both low and high ionic strengths. While h-BN still showed appreciable aggregation in the presence of SRNOM, the aggregation rates were decreased by 2.6- and 3.7-fold at low and high ionic strengths, respectively. Overall, h-BN nanosheets will have higher aggregation potential and thus limited mobility in the natural aquatic environment when compared to MoS2 and WS2. These results can also be used to mechanistically explain fate, transport, transformation, organismal uptake, and toxicity of inorganic 2D NMs in the natural ecosystems.
AB - We report the comparative aggregation behavior of three emerging inorganic 2D nanomaterials (NMs): MoS2, WS2, and h-BN in aquatic media. Their aqueous dispersions were subjected to aggregation under varying concentrations of monovalent (NaCl) and divalent (CaCl2) electrolytes. Moreover, Suwanee River Natural Organic Matter (SRNOM) has been used to analyze the effect of natural macromolecules on 2D NM aggregation. An increase in electrolyte concentration resulted in electrical double-layer compression of the negatively charged 2D NMs, thus displaying classical Derjaguin-Landau-Verwey-Overbeek (DLVO)-type interaction. The critical coagulation concentrations (CCC) have been estimated as 37, 60, and 19 mM NaCl and 3, 7.2, and 1.3 mM CaCl2 for MoS2, WS2, and h-BN, respectively. Theoretical predictions of CCC by modified DLVO theory have been found comparable to the experimental values when dimensionality of the materials is taken into account and a molecular modeling approach was used for calculating molecular level interaction energies between individual 2D NM nanosheets. Electrostatic repulsion has been found to govern colloidal stability of MoS2 and WS2 while the van der Waals attraction has been found to govern that of h-BN. SRNOM stabilizes the 2D NMs significantly possibly by electrosteric repulsion. The presence of SRNOM completely stabilized MoS2 and WS2 at both low and high ionic strengths. While h-BN still showed appreciable aggregation in the presence of SRNOM, the aggregation rates were decreased by 2.6- and 3.7-fold at low and high ionic strengths, respectively. Overall, h-BN nanosheets will have higher aggregation potential and thus limited mobility in the natural aquatic environment when compared to MoS2 and WS2. These results can also be used to mechanistically explain fate, transport, transformation, organismal uptake, and toxicity of inorganic 2D NMs in the natural ecosystems.
UR - http://www.scopus.com/inward/record.url?scp=85064960228&partnerID=8YFLogxK
U2 - 10.1021/acs.est.8b05180
DO - 10.1021/acs.est.8b05180
M3 - 期刊論文
C2 - 30884220
AN - SCOPUS:85064960228
SN - 0013-936X
VL - 53
SP - 4161
EP - 4172
JO - Environmental Science and Technology
JF - Environmental Science and Technology
IS - 8
ER -