Related Experiment Video
Updated: Oct 5, 2025
12:57
Resonance Fluorescence of an InGaAs Quantum Dot in a Planar Cavity Using Orthogonal Excitation and Detection
Published on: October 13, 2017
9.3K
Angle-resolved one and Two-Photon absorption spectrum in twisted bilayer graphene quantum dots
Xiangtao Chen1, Chen Lu1, Li Wang1
1College of Science, Liaoning Petrochemical University, Fushun 113001, China.
Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
|February 1, 2022
Summary
Twisted bilayer graphene quantum dots exhibit tunable optical properties. Changing the twist angle significantly impacts one-photon and two-photon absorption spectra, offering control over electronic transitions and charge transfer for advanced materials.
Area of Science:
- Materials Science
- Quantum Chemistry
- Condensed Matter Physics
Background:
- Graphene quantum dots (GQDs) possess unique electronic and optical properties.
- Bilayer graphene structures, particularly twisted ones, offer enhanced tunability.
- Understanding the interplay of Moiré patterns and twist angles is crucial for novel optoelectronic applications.
Purpose of the Study:
- To investigate the influence of twist angles and Moiré superlattices on the optical properties of zigzag edge twisted bilayer graphene quantum dots (Z-TwBLG-QDs).
- To analyze the electronic excitation, charge transfer, and magnetic induction current density in these structures.
- To reveal the physical mechanisms governing electron transition behavior regulated by twist angles.
Main Methods:
- Density Functional Theory (DFT) calculations.
- Analysis of one-photon absorption (OPA) and two-photon absorption (TPA) spectra.
- Utilizing excited state wave function, single electron approximation, and gauge-invariant atomic orbital (GIAO) methods.
- Partial Density of States (PDOS) and magnetic induction current density analysis.
Main Results:
- Twist angle critically determines the absorption spectrum, with larger angles causing a red shift.
- The twist angle regulates TPA cross-section and boundary effects in Z-TwBLG-QDs.
- Moiré superlattices with specific twist angles enhance edge effects in two-step transitions.
- Inter-layer excitation and intra-layer charge transfer are influenced by Moiré patterns and electron-hole pair density.
Conclusions:
- The twist angle is a key parameter for tuning the optical absorption and electronic properties of Z-TwBLG-QDs.
- DFT and advanced computational methods provide insights into the complex electronic behavior.
- These findings pave the way for designing novel graphene-based optoelectronic devices with tailored functionalities.
Related Concept Videos
01:12Two-Dimensional (2D) NMR: Overview
938
The 1D NMR spectrum of large and complex molecules like natural products has complicated splitting patterns and overlapping signals, which can be easily interpreted using 2-dimensional (2D) NMR. Unlike 1D NMR, 2D NMR has two frequency axes that provide the coupling information between the nucleus A and nucleus B in a molecule. The process from which 2D spectra are obtained has four steps.
The first step is the preparation period, during which nucleus A is excited with a radiofrequency pulse....
The first step is the preparation period, during which nucleus A is excited with a radiofrequency pulse....
938
01:14Molecular Spectroscopy: Absorption and Emission
3.6K
Molecules possess discrete energy levels called quantum states. Unlike atoms, which have simpler energy levels, molecules possess additional rotational and vibrational energy levels. Each energy level is separated by an energy gap, with the gaps between adjacent electronic, vibrational, and rotational levels varying significantly. The three types of energy levels in a diatomic molecule are shown in Figure 1.
3.6K
01:08IR Spectrum Peak Splitting: Symmetric vs Asymmetric Vibrations
1.3K
Identical bonds within a polyatomic group can stretch symmetrically (in-phase) or asymmetrically (out-of-phase). Similar to hydrogen bonding, these vibrations also influence the shape of the IR peak. Generally, asymmetric stretching frequencies are higher than symmetric stretching frequencies. For example, primary amines exhibit two distinct IR peaks between 3300–3500 cm−1 corresponding to the symmetric and asymmetric N-H stretching, while secondary amines exhibit a single...
1.3K
01:02¹H NMR: Interpreting Distorted and Overlapping Signals
1.1K
Spin systems where the difference in chemical shifts of the coupled nuclei is greater than ten times J are called first-order spin systems. These nuclei are weakly coupled, and their chemical shifts and coupling constant can generally be estimated from the well-separated signals in the spectrum.
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are...
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are...
1.1K
01:32UV–Vis Spectroscopy of Conjugated Systems
7.5K
Organic compounds with conjugated double bonds show strong absorption features in the UV–visible region of the electromagnetic spectrum attributed to π → π* electronic excitations. Generally, a UV–vis absorption spectrum is recorded as a plot of absorbance vs wavelength. The wavelength of maximum absorbance, which manifests as a peak in the absorption spectrum, is denoted as λmax.
One of the factors influencing λmax is the extent...
One of the factors influencing λmax is the extent...
7.5K
01:12Double Resonance Techniques: Overview
335
Double resonance techniques in Nuclear Magnetic Resonance (NMR) spectroscopy involve the simultaneous application of two different frequencies or radiofrequency pulses to manipulate and observe two distinct nuclear spins. One important application of double resonance is spin decoupling, which selectively suppresses coupling with one type of nucleus while observing the NMR signal from another nucleus, simplifying the spectrum and enhancing resolution.
Spin decoupling is usually achieved by...
Spin decoupling is usually achieved by...
335