研究目的
Investigating the size-dependent optical absorption and emission properties of two-dimensional phosphorene, arsenene, antimonene single-element quantum dots.
研究成果
The study reveals that the absorption gap of two-dimensional quantum dots decreases with increasing size due to the quantum confinement effect, while the emission gap presents an anomalous increase with size within ~3 nm diameter range. This anomaly is attributed to the competition between the quantum confinement effect and structural rearrangement during excited state relaxation. The insights deepen the understanding of size effects in quantum dots and guide their optical applications.
研究不足
The study is limited to theoretical calculations and does not include experimental validation. The band gap of quantum dots is generally underestimated by the PBE exchange-correlation functional, although the trend was verified using the B3LYP hybrid exchange-correlation functional.
1：Experimental Design and Method Selection:
The study employs time-dependent density functional theory (TDDFT) calculations to investigate the optical properties of quantum dots. The Amsterdam Density Functional program package (ADF) with the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional and the triple-zeta plus polarization (TZP) basis set was used for DFT and TDDFT computations.
2：Sample Selection and Data Sources:
The study focuses on two-dimensional phosphorene, arsenene, and antimonene quantum dots with varying sizes. The edge dangling bonds are passivated by hydrogen atoms.
3：List of Experimental Equipment and Materials:
The computational resources provided by Southeast University were utilized.
4：Experimental Procedures and Operational Workflow:
The optimal ground structure was first obtained based on the ground state minimum energy at DFT level. Then, the first forty singlet excited states were calculated using TDDFT. The absorption spectrum was determined by the first forty singlet excited states. The emission spectrum was determined by optimizing the first singlet excited state and evaluating the optical emission gap via the ultimately vertical electronic transition between excited state minimum and corresponding ground state energy.
5：Data Analysis Methods:
The size-dependent optical absorption and emission gaps were analyzed and fitted using specific formulas to quantify the size effect.
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