Waterproof molecular monolayers stabilize 2D materials

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 116; no. 42; pp. 20844 - 20849
• Main Authors: Su, Cong, Yin, Zongyou, Yan, Qing-Bo, Wang, Zegao, Lin, Hongtao, Sun, Lei, Xu, Wenshuo, Yamada, Tetsuya, Ji, Xiang, Zettsu, Nobuyuki, Teshima, Katsuya, Warner, Jamie H., Dincă, Mircea, Hu, Juejun, Dong, Mingdong, Su, Gang, Kong, Jing, Li, Ju
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 15.10.2019; Proceedings of the National Academy of Sciences
• Subjects: Alkylamines; anticorrosion; Drying; MATERIALS SCIENCE; molecular monolayer stabilizer; Monolayers; multilayer 2D materials; Optoelectronics; Organic acids; Organic solvents; Phosphorus; Physical Sciences; Protective coatings; Theoretical analysis; Transition metal compounds; Two dimensional materials; Water chemistry; multilayer 2D materials; anticorrosion; molecular monolayer stabilizer
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.1909500116

Two-dimensional van der Waals materials have rich and unique functional properties, but many are susceptible to corrosion under ambient conditions. Here we show that linear alkylamines n-Cm H2m+1NH₂, with m = 4 through 11, are highly effective in protecting the optoelectronic properties of these materials, such as black phosphorus (BP) and transition-metal dichalcogenides (TMDs: WS₂, 1T′-MoTe₂, WTe₂, WSe₂, TaS₂, and NbSe₂). As a representative example, n-hexylamine (m = 6) can be applied in the form of thin molecular monolayers on BP flakes with less than 2-nm thickness and can prolong BP’s lifetime from a few hours to several weeks and even months in ambient environments. Characterizations combined with our theoretical analysis show that the thin monolayers selectively sift out water molecules, forming a drying layer to achieve the passivation of the protected 2D materials. The monolayer coating is also stable in air, H₂ annealing, and organic solvents, but can be removed by certain organic acids.