Coordination nanosheets—two-dimensional materials made by linking metal ions with organic ligands—have captured attention in recent years due to their remarkable conductivity, redox activity, and catalytic performance. They are especially useful in areas such as energy storage, sensors, and electronics. However, producing these nanosheets, particularly heterometallic ones (which contain two or more metal ions), has traditionally relied on a complex two-phase interfacial reaction and lacked precise structural control.

Addressing this challenge, a team led by Professor Hiroshi Nishihara from the Research Institute for Science and Technology (RIST) at Tokyo University of Science (TUS) has demonstrated a single-phase synthetic method for creating colloidal coordination nanosheets—materials that are not only conductive and structurally well-defined, but also applicable as inks for coating or functionalizing surfaces. The study, published in Small on May 5, 2025, was featured on the journal’s front cover.

“When Ni ions are used in the two-phase interfacial reaction, porous nickelladithiolene (NiDT) and non-porous NiBHT structures are obtained. However, a rational method for selectively synthesizing them has not been fully established until now,” says Prof. Nishihara, explaining the motivation behind the present study.

A Simpler, Scalable Route to Nanosheet Inks

In the new method, researchers combined Ni²⁺ ions and benzenehexathiol (BHT) in a single-phase reaction to form a colloidal solution of nanosheets. By simply adjusting the molar ratios, they could selectively synthesize NiDT or NiBHT nanosheets—each with distinct structural and electrochemical properties. These colloidal nanosheets were then used to coat glassy carbon (GC) electrodes for testing.

Electrochemical analysis revealed clear differences: NiDT-coated electrodes showed a broad redox wave, confirming its porous nature, while the non-porous NiBHT did not exhibit similar redox behavior. Moreover, NiDT-coated GC electrodes displayed high activity in the hydrogen evolution reaction, making them promising electrocatalysts.

The researchers also succeeded in synthesizing Cu–BHT and Zn–BHT colloidal nanosheets. Notably, by introducing Cu²⁺ or Zn²⁺ ions into existing NiDT solutions, they could produce heterometallic nanosheets like NiCu₂BHT and NiZn₂BHT, where secondary metal ions occupied the porous structure’s interior.

Additionally, the team demonstrated a transmetallation reaction in which Cu²⁺ ions replaced some Ni ions in NiBHT, leading to the formation of NiCu₂BHT nanosheets.

“NiCu2BHT has high crystallinity and electrical conductivity and can be utilized in diverse electronic applications. This shows the superiority of the structure and physical properties of heterometallic coordination nanosheets with a defined structure,” states Prof. Nishihara.

Toward Real-World Applications: Printable and Functional

This research unlocks two versatile and scalable synthetic pathways to create coordination nanosheets that are printable, functional, and adaptable for multiple end uses. Whether as inks for flexible electronics or as components in next-generation hydrogen production systems, these colloidal materials offer significant practical potential.

“The first ink made from coordination nanosheets has made it possible to mass-produce them using printing technology and to apply them directly to devices, marking a major step forward in their practical use as next-generation flexible electronic devices, hydrogen production catalysts, and sensor materials,” Prof. Nishihara concludes.

With this achievement, the team from Tokyo University of Science has paved the way for low-cost, high-performance nanomaterials that can accelerate progress toward a more sustainable, energy-efficient future.

About Tokyo University of Science
Founded in 1881, TUS is Japan’s largest science-specialized private research university, with campuses across Tokyo and Hokkaido. Known for excellence in basic and applied research, TUS is the only private university in Asia to have produced Nobel Prize winners in natural sciences. 

About Professor Hiroshi Nishihara
Professor Nishihara is the Specially Appointed Vice President of TUS. With over 475 publications and six patents, his expertise spans coordination chemistry, nanoscience, and electrochemistry. He is a decorated researcher and an honorary member of several international scientific societies.

Original Publication
Authors: Miyu Ito, Naoya Fukui, Kenji Takada, Ziheng Yu, Hiroaki Maeda, Katsuya Mizuno and Hiroshi Nishihara.
Journal: Small
DOI: 10.1002/smll.202503227
Method of Research: Experimental study
Subject of Research: Not applicable
Article Title: Rationally Engineered Heterometallic Metalladithiolene Coordination Nanosheets with Defined Atomic Arrangements
Article Publication Date: 5-May-2025
COI Statement: The authors declare no conflict of interest.