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Multivalency-induced structural variations of 2D selenium nanosheets: facile solution-phase synthesis and optical
Swathi V M1, Arjun K2, Anju Rajan1
1Department of Physics, National Institute of Technology Calicut (NITC), Kozhikode, Kerala 673601, India. aji@nitc.ac.in.
Physical Chemistry Chemical Physics : PCCP
|August 9, 2024
Summary
Researchers synthesized free-standing few-layer selenium nanosheets (SeNS) using liquid-phase exfoliation. These 2D selenium materials exhibit unique optical properties, including tunable luminescence and strong optical limiting effects.
Area of Science:
- Materials Science
- Nanotechnology
- Condensed Matter Physics
Background:
- Two-dimensional (2D) materials offer unique properties due to quantum confinement and high surface area.
- Selenium's multivalent nature suggests potential for diverse structural phases and applications.
- Theoretical predictions have indicated the existence of quasi-stable 2D selenium structures.
Purpose of the Study:
- To achieve facile synthesis of free-standing few-layer selenium nanosheets (SeNS).
- To characterize the structural, optical, and non-linear optical properties of synthesized SeNS.
- To explore the influence of surface functionalization and size quantization on SeNS properties.
Main Methods:
- Liquid-phase exfoliation of bulk selenium in N-methyl pyrrolidone (NMP) via magnetic stirring.
- High-resolution transmission electron microscopy (HRTEM) for structural analysis.
- Fourier transform infrared (FTIR) spectroscopy for surface functionalization.
- UV-vis-NIR spectroscopy and photoluminescence spectroscopy for optical characterization.
- Z-scan experiments for non-linear optical (NLO) property evaluation.
Main Results:
- Successfully synthesized free-standing few-layer SeNS with lateral dimensions up to microns and thickness ~1 nm.
- Identified α- and β-selenene allotropes using HRTEM.
- Observed enhanced dispersion stability due to NMP surface/edge functionalization.
- Demonstrated size-quantized tunable photoluminescence from blue-green to green-orange.
- Exhibited strong optical limiting behavior with reverse saturable absorption (RSA) at 532 nm.
- Observed a transition from RSA to saturable absorption (SA) with extended stirring time.
Conclusions:
- This work presents the first experimental realization of free-standing multivalent 2D selenium in allotropic forms.
- Synthesized SeNS possess unique optical properties, including tunable luminescence and significant optical limiting.
- The findings open avenues for 2D selenium in optoelectronics and photonics applications.
