Unveiling the Scale-dependent anomalous behavior of water under nanoconfinement
New study reveals the critical threshold marking the transition between confined and bulk water behavior.
image: The anomalous properties of confined water are mainly attributed to surface interactions; however, their significant scale-dependence is shown to be predominantly governed by spatial confinement. A confinement range of 10 to 20 nm is identified as the critical threshold marking the transition between confined and bulk water behavior.
Credit: Nano Research, Tsinghua University Press
Water confined within nanoscale environments exhibits peculiar behavior distinct from that of its bulk counterpart — a phenomenon that could impact everything from catalysis to biological systems. In a new study published in Nano Research, a team of Chinese scientists has revealed how the behavior of water confined between layers of aluminum oxide (Al2O3) depends critically on the degree of spatial confinement.
Led by Prof. Xihui Zhang and Dr. Shengyin Tang at Tsinghua University, the researchers used molecular dynamics simulations to explore how confined water behaves across a wide confinement range (1 to 50 nm). They discovered that while surface interactions largely dictate the structure and orientation of interfacial water, it is the spatial confinement that propagates these effects into the entire confined region — especially at sub-20 nm scales.
The team published their research article in Nano Research on June 4, 2025.
“Understanding how water behaves under confinement is key to optimizing chemical transport and reactions in confined systems,” said Dr. Tang. “Our work reveals a clear scale-dependent behavior and defines a critical threshold between 10 and 20 nanometers where confined water starts to behave like bulk water.”
The team found that at strong confinement (1–5 nm), water exhibits highly ordered hydrogen bond networks, suppressed dielectric responses, and dramatically anisotropic diffusion, especially enhancing in-plane diffusion. Surprisingly, even at larger scales like 20 nm, remnants of these anomalous properties persist. Only beyond 50 nm do the characteristics of bulk water fully return.
The researchers also explored the effects of pH, ion concentrations, and surface functionalization on confined water behavior. These findings highlight the importance of surface chemistry, particularly the role of hydroxyl groups and surface polarity, in modifying interfacial water properties in metal oxide systems, which are commonly used in environmental and catalytic applications.
“This study offers foundational insights for the rational design of nanoconfined systems such as catalytic interfaces, energy devices, and water purification technologies,” said Prof. Zhang, “Our next step is to extend this theoretical understanding to more complex, realistic systems, combining experiments and simulations to study confined water in action.”
Other contributors include Tianhao Tang from Tsinghua University, Wenhui Ding from Chinese Academy of Sciences, and Wanyi Fu from Nanjing University.
This study was supported by the Shenzhen Science and Technology Program (Grant No. WDZC20231128115832002), National Natural Science Foundation of China (Grant No. 22306091, and No. 52460003), Natural Science Foundation of Jiangsu Province (Grant No. BK20230797), and the Key-Area Research and Development Program of Guangdong Province (2022B0111130001).
About Nano Research
Nano Research is a peer-reviewed, open access, international and interdisciplinary research journal, sponsored by Tsinghua University and the Chinese Chemical Society, published by Tsinghua University Press on the platform SciOpen. It publishes original high-quality research and significant review articles on all aspects of nanoscience and nanotechnology, ranging from basic aspects of the science of nanoscale materials to practical applications of such materials. After 18 years of development, it has become one of the most influential academic journals in the nano field. Nano Research has published more than 1,000 papers every year from 2022, with its cumulative count surpassing 7,000 articles. In 2024 InCites Journal Citation Reports, its 2024 IF is 9.0 (8.7, 5 years), and it continues to be the Q1 area among the four subject classifications. Nano Research Award, established by Nano Research together with TUP and Springer Nature in 2013, and Nano Research Young Innovators (NR45) Awards, established by Nano Research in 2018, have become international academic awards with global influence.