Optoelectronic devices like solar cells, photodetectors, and photocatalysts are typically constructed from materials with tunable and stable properties. Because of this, they are able to precisely control the optical properties of the materials and guarantee that their properties will remain unchanged over time despite changing environmental conditions.
Organic ligands attached via coordinate bonds to the surface of colloidal inorganic nanocrystals make organic-inorganic nanohybrids, which are promising in this regard. They are known to show upgraded soundness, inferable from the development of a defensive layer by natural ligands around the receptive inorganic nanocrystal. However, inorganic nanocrystal conductivity and photon absorption efficiency have been found to decrease when organic ligands are added.
The displacement of organic ligands on the surface of nanocrystals is now demonstrated to be quasi-reversible in a groundbreaking study on ligand-nanocrystal interactions by Japanese researchers. The common belief that the organic ligands are anchored to the surface of the nanocrystals is challenged by their findings, which were published in the journal ACS Nano.
“A precise understanding of ligand-nanocrystal interaction is critical not only for fundamental nanoscience but also for developing advanced photo functional materials based on nanomaterials.” Photocatalysts for the degradation of persistent compounds using visible light, as well as photoconductive microcircuit patterning for wearable electronics, are examples of these.”
Professor Yoichi Kobayashi from Ritsumeikan University, Japan.
The team of researchers, led by Professor Yoichi Kobayashi of Ritsumeikan University in Japan, discovered that the coordination bond between inorganic zinc sulfide (ZnS) nanocrystals and perylene bisimide with a carboxyl group (PBI) can be reversibly displaced by exposing the substance to visible light.
Revealing insight into this clever way of behaving in natural inorganic nanohybrids, Prof. According to Kobayashi, “We investigated the ligand properties of natural inorganic nanohybrid frameworks by utilizing perylene bisimide with a carboxyl gathering (PBI)-facilitated zinc sulfide (ZnS) NCs (PBI-ZnS) as a model framework. Our findings provide the first instance of photoinduced displacement of aromatic ligands by semiconductor nanocrystals.
In order to comprehend the material’s distinctive photoinducible properties, the researchers conducted both theoretical and experimental research in their study. In order to investigate the structure and orbitals of PBI-ZnS ([PBI-Zn25S31]) in both its ground and first excited states, they first carried out calculations using density functional theory.
Then, they performed time-settled, invigorated Raman spectroscopy to energize the example with an ultrafast laser. This assisted them with breaking down the Raman range that uncovered the idea of the energized territory of PBI-ZnS.
The exploratory perceptions, and that’s what computations showed, showed that upon photoexcitation, an electron is energized from the PBI atom, and the relating “hole” (the opening shaped because of the shortfall of the electron) quickly moves from the fragrant ligand (PBI) to ZnS. This results in a seemingly perpetual, adversely charged PBI particle that is dislodged from the outer layer of the ZnS nanocrystal.
However, over time, the surface defects of the ZnS nanocrystal recombine the displaced ligands, resulting in a quasi-reversible photoinduced displacement of coordinated PBI. Outstandingly, the unique way of behaving of composed ligand atoms seen in this study is not the same as that noticed for regular photoinduced charge move processes in which the opening commonly stays on the benefactor particle, empowering it to rapidly recombine with the electron.
“The precise understanding of ligand-nanocrystal interaction is important not only for fundamental nanoscience but also for developing advanced photofunctional materials using nanomaterials,” Prof. Kobayashi explains the significance of these findings. Photoconductive microcircuit patterning for wearable devices and photocatalysts for the decomposition of persistent chemicals using visible light are two examples of these.
In fact, the study’s findings indicate a promising path for using aromatic molecules to improve the tunability and functionality of inorganic materials. In turn, this could have a significant impact on the fundamental nanoscience and photochemistry fields in the future.
More information: Daisuke Yoshioka et al, Quasi-Reversible Photoinduced Displacement of Aromatic Ligands from Semiconductor Nanocrystals, ACS Nano (2023). DOI: 10.1021/acsnano.2c12578
