Nanohybrid material shows potential for fabricating valleytronic materials

Researchers, Chakraborty, Akhuli, Preeyanka, and Sarkar have synthesized an inorganic-organic nanohybrid material and investigated the interaction between its components using various spectroscopic techniques. The study showed efficient coupling between inorganic and organic excitons, leading to valley splitting of the quantum dot (QD) emission band.

The team used CdTe@ZnS QDs as the inorganic exciton and J-aggregates as the organic exciton. They found that there was a high Förster-type resonance energy transfer (FRET) from the QDs to the J-aggregates. They also observed a splitting of the QD emission band during the FRET event, indicating efficient coupling between inorganic and organic excitons.

The researchers noted that the valley splitting of the QD emission could be controlled by regulating the FRET process, and a linear relationship was observed between the energy separation value of the valley splitting and the FRET efficiency between QDs and J-aggregates. Additionally, the presence of an organic moiety made it possible to control the valley splitting through chemical modification.

The study’s findings demonstrate the potential of the nanohybrid system for the fabrication of valleytronic materials. The results are particularly exciting as the observation of valley splitting of the QD emission in the presence of J-aggregates without an external field is a new development.

The researchers highlighted that the present nanohybrid system has the potential to be used as a suitable nanoscale system for the fabrication of valleytronic materials. The study opens up new possibilities for the development of advanced materials with exciting electronic and optical properties.

Energy-Transfer-Induced Enhanced Valley Splitting of Excitonic Emission of Inorganic CdTe@ZnS QDs in the Presence of Organic J-Aggregates: A Spectroscopic Insight into the Efficient Exciton (Inorganic)−Exciton (Organic) Coupling

Chakraborty; Akhuli; Preeyanka; Sarkar

Full-text link: https://doi.org/10.1021/acs.jpcc.3c00769

What this paper is about

• Interestingly, it has been demonstrated that strong coupling can also lead to an interesting process known as valley splitting, where the observed emission band gets split into two distinct emission bands due to the lifting of the degeneracy of the two existing excitonic states of the emitting species.
• ZnS QDs are chosen as the inorganic exciton 4346 and organic cyanine dye-based J-aggregates as the organic exciton due to their favorable optical properties.
• More interestingly, the splitting of emission spectra of the QDs with the gradual addition of J-aggregates, indicating the presence of an efficient excitonexciton interaction between the inorganic exciton and the organic exciton, has been observed.

What you can learn

• It is to be noted that we also observed an increase in FRET efficiency from QDs to J-aggregates as the concentration of J-aggregates was increased.
• ZnS QDs’ emission in the presence of J-aggregates, the two emission peaks can be ascribed to two bright exciton fine structure states in the 64manifold 1S h 1S e state of the QDs.
• The ET efficiencies at 560 and 605 nm were found to Although the ET efficiencies from steady-state and time-resolved fluorescence measurements were similar, when monitored at different wavelengths, there was a difference. This difference might be due to the heterogeneity of the system.
• It is to be noted that there is no evidence in the literature where J-aggregates are found to participate in valley splitting of the QD emission band.
• However, a more careful analysis of the data revealed that apart from the usual quenching of donor emission, prominent valley splitting of the QD emission was also seen. This observation indicates efficient electronic coupling between QDs and J-aggregates.
• The observation of valley splitting of the QD emission in the presence of J-aggregates without the application of an external field is new and exciting.

Core Q&A related to this research

1. What is the focus of the paper “Energy-Transfer-Induced Enhanced Valley Splitting of Excitonic Emission of Inorganic CdTe@ZnS QDs in the Presence of Organic J-Aggregates: A Spectroscopic Insight into the Efficient Exciton (Inorganic)−Exciton (Organic) Coupling”?

• The paper focuses on investigating the strong exciton-exciton interaction between inorganic CdTe@ZnS quantum dots (QDs) and organic cyanine dye-based J-aggregates in a nanohybrid material, specifically exploring the efficient coupling between the inorganic and organic excitons and the observation of valley splitting of the QD emission in the presence of J-aggregates without an external field.

2. What are the materials used in the study?

• The study uses inorganic CdTe@ZnS QDs as the inorganic exciton and organic cyanine dye-based J-aggregates as the organic exciton.

3. What is Förster-type resonance energy transfer (FRET), and how is it related to the study?

• Förster-type resonance energy transfer (FRET) is a non-radiative energy transfer process from a donor to an acceptor molecule. The study analyzes the FRET efficiency from the QDs (donor) to the J-aggregates (acceptor) and finds a very high efficiency.

4. What is valley splitting?

• Valley splitting is an interesting process where the observed emission band gets split into two distinct emission bands due to the lifting of the degeneracy of the two existing excitonic states of the emitting species.

5. What is the significance of the observation of valley splitting of the QD emission in the presence of J-aggregates?

• The observation of valley splitting of the QD emission in the presence of J-aggregates without an external field is new and exciting. It indicates efficient electronic coupling between the QDs and J-aggregates and suggests that the present nanohybrid system has the potential to be used as a suitable nanoscale system for the fabrication of valleytronic materials.

6. Can the extent of the valley splitting process be controlled, and if so, how?

• Yes, the study has demonstrated that the extent of the valley splitting process can be controlled by regulating the FRET process, and a linear relationship between the energy separation value of the valley splitting and the FRET efficiency between QDs and J-aggregates is obtained. Moreover, the presence of an organic moiety in the nanohybrid system makes it advantageous, as the valley splitting can also be controlled easily through chemical modification of the organic moiety.

Basic Q&A related to this research

What is CdTe@ZnS?

CdTe@ZnS refers to a type of inorganic nanohybrid material composed of a CdTe core and a ZnS shell, which exhibits favorable optical properties and is widely used in optoelectronics.

What are J-aggregates?

J-aggregates are organic excitons, which are formed by the self-assembly of organic dye molecules into elongated structures, exhibiting unique optical properties due to their strong intermolecular interactions.

What is an exciton?

An exciton is a bound state of an electron and a hole in a semiconductor, which can absorb or emit light and play a crucial role in various optoelectronic devices.

What is valley splitting?

Valley splitting is a process where the observed emission band gets split into two distinct emission bands due to the lifting of the degeneracy of the two existing excitonic states of the emitting species.

What is FRET?

FRET, or Förster-type resonance energy transfer, is a process where the excitation energy of a donor molecule is transferred to an acceptor molecule without emission of a photon, which plays an important role in various energy transfer and sensing applications.

What is a nanohybrid?

A nanohybrid is a type of material composed of different components, which exhibit unique properties due to their synergistic interactions.

What is electrostatic and thermodynamic?

Electrostatic and thermodynamic refer to two different types of interactions that can drive the formation of nanohybrids. Electrostatic interactions arise from the attraction or repulsion between charged species, while thermodynamic interactions arise from the minimization of free energy due to enthalpy and entropy changes.

What is the fabrication of valleytronic materials?

The fabrication of valleytronic materials refers to the process of designing and synthesizing materials that can control and exploit the valley degree of freedom in semiconductors, which has potential applications in information processing and storage.

What are valleytronic materials?

Valleytronic materials are materials that can control and exploit the valley degree of freedom in semiconductors, which has potential applications in information processing and storage.