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We report liquid-phase exfoliation (LPE) of bulk layered-structure semiconductor, MnIn 2 Se 4 , to nanoscale thick sheets by ultrasonication followed by sequential centrifugation at 2000, 5000, and 7500 rpm. The nanosheets exfoliated by LPE in isopropyl alcohol show an average thickness of 50, 40, and 14 nm, respectively. The smallest of these values corresponds approximately to ten 7-atom thick [Se–In–Se–Mn–Se–In–Se] layers that compose the bulk structure of MnIn 2 Se 4 . Both the bulk material and the exfoliated samples show photoluminescence, but the weak shoulder observed from the indirect band gap emission is obviously suppressed in the nanosheet samples as compared to the bulk sample. Similar to the bulk, the nanosheets isolated at 2000 and 5000 rpm exhibit spin-glass behavior with a freezing temperature of ∼3 K. In contrast, the nanosheets isolated at 7500 rpm do not exhibit any anomalies in their low-temperature magnetic behavior. These results demonstrate the possibility to extend the LPE technique to van-der-Waals materials with several-atom-thick layers.
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This content will become publicly available on September 18, 2025
Opening the Hysteresis Loop in Ferromagnetic Fe 3 GeTe 2 Nanosheets Through Functionalization with TCNQ Molecules
Abstract Ferromagnetic metal Fe3GeTe2(FGT), whose structure exhibits weak van‐der‐Waals interactions between 5‐atom thick layers, was subjected to liquid‐phase exfoliation (LPE) in N‐methyl pyrrolidone (NMP) to yield a suspension of nanosheets that were separated into several fractions by successive centrifugation at different speeds. Electron microscopy confirmed successful exfoliation of bulk FGT to nanosheets as thin as 6 nm. The ferromagnetic ordering temperature for the nanosheets gradually decreased with the increase in the centrifugation speed used to isolate the 2D material. These nanosheets were resuspended in NMP and treated with an organic acceptor, 7,7,8,8‐tetracyano‐quinodimethane (TCNQ), which led to precipitation of FGT‐TCNQ composite. The formation of the composite material is accompanied by charge transfer from the FGT nanosheets to TCNQ molecules, generating TCNQ⋅−radical anions, as revealed by experimental vibrational spectra and supported by first principles calculations. Remarkably, a substantial increase in magnetic anisotropy was observed, as manifested by the increase in the coercive field from nearly zero in bulk FGT to 1.0 kOe in the exfoliated nanosheets and then to 5.4 kOe in the FGT‐TCNQ composite. The dramatic increase in coercivity of the composite suggests that functionalization with redox‐active molecules provides an appealing pathway to enhancing magnetic properties of 2D materials.
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- Award ID(s):
- 2233902
- PAR ID:
- 10578676
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Angewandte Chemie International Edition
- Volume:
- 64
- Issue:
- 5
- ISSN:
- 1433-7851
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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