Related Experiment Video
Updated: Sep 24, 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
NIR-to-visible upconversion in quantum dots via a ligand induced charge transfer state
Noga Meir1, Iddo Pinkas2, Dan Oron1
1Department of Physics of Complex Systems, Weizmann Institute of Science Rehovot 7610001 Israel dan.oron@weizmann.ac.il.
RSC Advances
|May 6, 2022
Summary
Researchers developed a simplified method for photon upconversion (UC) using quantum dots (QDs) and organic ligands. This approach utilizes a charge-transfer state for efficient UC, applicable even in solid-state QD materials.
Area of Science:
- Materials Science
- Nanotechnology
- Photochemistry
Background:
- Photon upconversion (UC) enables converting low-energy photons to high-energy ones, with applications in various fields.
- Existing UC methods in quantum dot (QD) systems often involve complex heterostructures or organic molecule sensitization.
- Developing simplified and efficient UC strategies is crucial for broader technological adoption.
Purpose of the Study:
- To propose and demonstrate a simplified approach for achieving upconversion in semiconducting quantum dots (QDs).
- To investigate the mechanism of UC mediated by a charge-transfer state at the QD-ligand interface.
- To explore the applicability of this UC scheme in QD solid-state systems.
Main Methods:
- Synthesis of core/shell CdSe/CdS QDs with thiophenol ligand exchange.
- Utilizing pump-probe spectroscopy to confirm non-linear emission via sequential photon absorption.
- Employing transient absorption spectroscopy to characterize the QD-ligand energy landscape and charge-transfer dynamics.
Main Results:
- Demonstrated efficient upconversion in CdSe/CdS QDs functionalized with thiophenol ligands.
- Identified a charge-transfer state arising from the alignment of the molecular HOMO and QD conduction band as the UC pathway.
- Confirmed UC occurs through sequential photon absorption, not triplet-triplet annihilation.
- Showcased the feasibility of this UC mechanism in a QD solid.
Conclusions:
- A simplified and effective method for quantum dot upconversion has been established using organic thiol ligands.
- The charge-transfer state at the molecule-dot interface is a viable mechanism for promoting UC.
- This ligand-mediated UC strategy is adaptable for solid-state nanomaterials, broadening potential applications.
Related Concept Videos
01:23Photoluminescence: Fluorescence and Phosphorescence
2.4K
Photoluminescence is a process where a molecule absorbs light energy and re-emits it in the form of light. This phenomenon occurs when a substance absorbs photons, promoting its electrons to higher energy level excited states, followed by a relaxation process in which the electrons return to their original ground state energy levels and emit light. Photoluminescence is widely observed in various materials, including semiconductors, and organic and inorganic compounds.
A pair of electrons in a...
A pair of electrons in a...
2.4K
01:16UV–Vis Spectroscopy: Molecular Electronic Transitions
1.9K
In Ultraviolet–Visible (UV–Vis) spectroscopy, the absorption of electromagnetic radiation is used to probe the electronic structure of molecules. This technique provides insights into molecular electronic transitions, particularly the movement of electrons between different molecular orbitals. Radiation is absorbed if the energy of the electromagnetic radiation passing through the molecule is precisely equal to the energy difference between the excited and ground states. During this...
1.9K
01:25Deactivation Processes: Jablonski Diagram
953
Luminescence, the emission of light by a substance that has absorbed energy, is a process that involves the interaction of molecules with light. The energy-level diagram, or Jablonski diagram, is a graphical representation of these interactions, illustrating the various states and transitions a molecule can undergo. In a typical Jablonski diagram, the lowest horizontal line represents the ground-state energy of the molecule, which is usually a singlet state. This state represents the energies...
953
01:14Photoluminescence: Applications
511
Photoluminescence offers a wide range of applications due to its inherent sensitivity and selectivity. This technique allows for both direct and indirect analyses of the analyte. Direct quantitative analysis is possible when the analyte exhibits a favorable quantum yield for fluorescence or phosphorescence. However, an indirect analysis may be feasible if the analyte is not fluorescent or phosphorescent, or if the quantum yield is unfavorable. Indirect methods include reacting the analyte with...
511
03:02Colors and Magnetism
12.4K
Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human...
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human...
12.4K
01:14Molecular Spectroscopy: Absorption and Emission
3.5K
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.
3.5K