Atomically thin, large area aluminosilicate nanosheets fabricated from layered clay minerals
Introduction
Two-dimensional (2-D) layers with atomic or molecular thickness have led to a surge of interest in a wide range of applications from electronics to electrochemistry [1,2]. The 2-D nanosheets could normally be obtained by either top-down or bottom-up approaches which are exfoliation of the layered crystals and monolayer growth utilizing precise deposition methods (CVD, ALD, etc), respectively. The top-down approach was quite successful when the layered crystals were formed by weak interlayer bonding while strong covalent bonding is associated between the atoms in each layer [[3], [4], [5], [6], [7], [8], [9]]. However, it has been challenging to mechanically exfoliate monolayer oxide sheets from the layered clay minerals due to the relatively strong electrostatic bonding force which is originated from the nature of layer charge [10,11].
Muscovite; KAl3Si3O10(OH)2 is a representative form of mica, a layered clay mineral comprised with negatively charged aluminosilicate layers and potassium interlayer cations. As a consequence of isomorphic substitutions of Si4+ ions by Al3+ ions in the muscovite, each aluminosilicate layer has negative layer charge of 2e− in the half unit cell. For that reason, the potassium cations are tightly locked in the muscovite interlayers by the strong electrostatic forces between them [12,13]. Several works have been reported concerning the cation exchange to remove the potassium cations. White reported that potassium cations could be partially removed by molten salt reaction with lithium nitrate [14]. Zhao et al. found that the interlayer spacing of the muscovite could be expanded by the cation exchange process [12]. Ion exchange with large-chain cations also showed possibility to pillar the interlayer and significantly increase the spacing [15]. Yu et al. reported that the alkylammonium cations were uniformly anchored on the surface of aluminosilicate layers thereby further increase in the interlayer spacing was achieved [[16], [17], [18]]. Jia et al. also found that octadecyl trimethyl ammonium chloride (OTAC) also could be intercalated into the interlayer of muscovite and thereby yielded muscovite monolayers [19,20]. But the resulting exfoliated nanosheets were still in the level of tiny fragments. Lateral sizes of them were mostly smaller than 100 nm. Recently, Harvey et al. have reported that surfactants could successfully promote the exfoliation of layered silicates without chemical pretreatment through a liquid phase exfoliation (LPE) process (sonication in a surfactant solution followed by centrifugation). The average thickness of the nanosheets was 2.37 nm, which corresponds to the thickness of a few layers of the layered silicate. However, the size of the exfoliated nanosheets were still quite small with lateral sizes in sub micrometers [21]. For the practical applications of ceramic nanosheets, it is anticipated to develop more effective way to exfoliate large area 2-D nanosheets from layered oxides.
Here, we attempted to investigate the possibility to exfoliate muscovite by using amphiphilic polymer (Poly (vinylpyrrolidone); PVP), not using ionic polymers. The PVP molecules contain strong hydrophilic components (the pyrrolidone moiety) and a considerably hydrophobic group (the alkyl group). Generally, PVP has been commonly used as a dispersant for colloidal solutions that could prevent the aggregation of colloidal nanoparticles through steric hindrance effect [22]. For the muscovite exfoliation, this amphipathic PVP polymer was introduced for two roles. One is the exfoliation through bonding between carbonyl groups on the pyrrolidone moiety in PVP molecules and hydroxyl groups on the surface of the muscovite. The other is to prevent self-aggregation of exfoliated nanosheets through the repulsive forces stemming from hydrophobic polyvinyl chains that stretch towards solvents. In this work, we demonstrate that muscovite can be exfoliated in aqueous solutions through the presence of amphiphilic polymer without repetitive ion exchange. Also, aluminosilicate nanosheets with relatively large-scale can be obtained from this amphiphilic polymer without agglomeration.
Section snippets
Materials and methods
The muscovite powder (IMERYS, USA, average particle size: 30 μm) was heat-treated at 750 °C for 5 h in a muffle furnace (C-14, Hantech Co., Ltd.). The heat-treated muscovite powder was subjected to molten salt reaction with LiNO3 (Sigma-Aldrich Prod. No. 227986) at 300 °C for 48 h. The resulting products were washed with deionized water and isolated by centrifugation in a Labogene 1248 centrifuge with a fixed-angle rotor (GRF-G-85-6) for 15 min at 7870.72 × g. The washing and centrifugation
Results and discussion
The overall exfoliation procedure of the 2-D aluminosilicate nanosheets is schematically illustrated in Fig. 1. Pristine muscovite was heat-treated to remove inherent hydroxyl crosslinking between aluminosilicate layers and potassium cations in the layered muscovite structure. The heat-treated muscovite was subjected to a molten salt reaction with LiNO3. It is known that small Li cations are able to occupy octahedral sites in the muscovite layers by this molten salt reaction [14]. The Li
Conclusions
An effective route to exfoliate ceramic nanosheets from layered clay minerals was developed. Atomically thin aluminosilicate layers in muscovites were facilely exfoliated by sequential wet chemical techniques of cation exchange and amphiphilic polymer intercalation processes in the aqueous media. The amphiphilic nature of the PVP molecules took critical role in successful exfoliation of the large-area monolayer nanosheets and stable dispersion of the exfoliated nanosheets in the aqueous
Acknowledgments
This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (Grant #: NRF- 2017R1D1A1B03036309).
References (33)
- et al.
The intercalation of cetyltrimethylammonium cations into muscovite by a two-step process: I. The ion exchange of the interlayer cations in muscovite with Li+
J. Solid State Chem.
(2006) - et al.
The intercalation of cetyltrimethylammonium cations into muscovite by a two-step process: II. The intercalation of cetyltrimethylammonium cations into Li-muscovite
J. Solid State Chem.
(2006) The preparation and characterization of cetyltrimethylammonium intercalated muscovite
Microporous Mesoporous Mater.
(2007)- et al.
Can natural muscovite be expanded?
Colloid. Surface. Physicochem. Eng. Aspect.
(2015) - et al.
Electric field effect in atomically thin carbon films
Science
(2004) - et al.
Two dimensional atomic crystals
Proc. Natl. Acad. Sci. U.S.A.
(2005) - et al.
Macromolecule-like aspects for a colloidal suspension of an exfoliated titanate: pairwise association of nanosheets and dynamic reassembling process initiated from it
J. Am. Chem. Soc.
(1996) Introduction to Clay Minerals: Chemistry, Origins, Uses, and Environmental Significance
(1992)- et al.
Two-dimensional molybdenum trioxide and dichalcogenides
Adv. Funct. Mater.
(2013) - et al.
Detection of individual gas molecules adsorbed on graphene
Nat. Mater.
(2007)
High yield exfoliation of two-dimensional chalcogenides using sodium naphthalenide
Nat. Commun.
Electrospun metal oxide composite nanofibers gas sensors: a review
J. Korean Ceram. Soc.
Water oxidation mechanism for 3d transition metal oxide catalysts under neutral condition
J. Korean Ceram. Soc.
Single-layer semiconducting nanosheets: high-yield preparation and device fabrication
Angew. Chem. Int. Ed.
An effective method for the fabrication of few-layer-thick inorganic nanosheets
Angew. Chem. Int. Ed.
Cleaving of muscovite powder by molten lithium nitrate
Colloid Polym. Sci.
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