Hybrid Materials for Next-Generation Devices

Devices like smartphones and solar cells rely on the efficient movement of electrons. To enhance their performance, precisely controlling electron transfer is crucial. A promising approach involves “organic-inorganic hybrid materials,” which combine 2D semiconductors (materials only a few atoms thick, such as molybdenum disulfide, MoS2) with organic molecules. These materials hold immense potential for converting light into electricity (solar cells), accelerating chemical reactions (photocatalysis), and developing new electronic components (optoelectronic devices). However, a significant challenge lies in precisely dictating how electrons move at the “interface” where these different materials meet.

Molecular Connectivity: A New Design Parameter

This study focuses on covalently attaching anthracene (An), an organic molecule with a six-carbon ring structure, to thin sheets of the 2D semiconductor MoS2. The key innovation was to explore the impact of the specific “attachment position” of anthracene on the MoS2 surface. By connecting anthracene at two different positions (the 2- or 9-position), two distinct constitutional isomers, MoS2-2-An and MoS2-9-An, were synthesized. The goal was to investigate how this subtle difference in “molecular connectivity” influences the dynamics of electron movement at the interface.

Dramatic Differences in Charge-Transfer Dynamics

Using ultrafast transient absorption spectroscopy, a technique that tracks electron movement after light absorption, the researchers observed strikingly different electron dynamics depending on the anthracene’s attachment position. For MoS2-2-An, photoexcitation led to a relatively long-lived “interfacial charge-transfer (CT) excited state,” where electrons oscillated between MoS2 and anthracene. In contrast, MoS2-9-An exhibited rapid formation of a “full charge-separated state” immediately after light absorption, meaning electrons quickly and completely moved from MoS2 to anthracene. This contrasting behavior is attributed to differences in the “orientation” or tilt angle of the anthracene molecule relative to the MoS2 surface. Theoretical calculations supported this, showing that 2-An adopted a more coplanar geometry (tilt angle θ = 29.5°) while 9-An had a more upright orientation (θ = 42.1°). These orientation differences modulate the orbital overlap (how electron pathways connect) and the strength of “electronic coupling” (the electronic connection), thereby dictating the excited-state evolution.

Towards Advanced Optoelectronics and Energy Conversion

These findings demonstrate that “constitutional connectivity” – the specific way molecules are connected – serves as a powerful molecular-level design parameter for controlling electron dynamics at 2D hybrid interfaces. The ability to precisely tune the fate of photoexcited electrons simply by adjusting the molecular attachment position opens new avenues for developing high-performance optoelectronic devices, efficient photocatalysts, and next-generation solar cells. This research exemplifies how molecular design can lead to the creation of materials with tailored functionalities, showcasing a core strength of chemistry.

Reference Paper

• William Ryan Osterloh, Daizu Mizutani, Motohisa Kubota, Midori Akiyama, Akira Yamakata, Masahiro Higashi, Hiroshi Imahori (2026) “Molecular Connectivity Controls Electronic Coupling and Charge-Transfer Dynamics at Anthracene–MoS2 Interfaces” Journal of the American Chemical Society. DOI: 10.1021/jacs.6c09922

Learn more about Prof. Yamakata → Surface Physical Chemistry