Scientists in Peking University photographed the internal structure of water molecules for the first time in the world, revealing the spatial posture of a single water molecule and four water masses. This achievement was published in the latest issue of Nature-Materials. Water molecules are the most abundant molecules on the earth's surface, and their internal structure is very basic, but they also have many wonderful chemical properties. As a good solvent, water provides basic conditions for the existence of life, and its unique hydrogen bond structure has always been difficult for scientists to explain.

Peking University Quantum Materials Center and Jiang Ying Research Group of Quantum Materials Science Collaborative Innovation Center cooperated with Wang Enge Research Group to make a major breakthrough in the field of water science, realizing the sub-molecular resolution imaging of water molecules for the first time in the world, making it possible to directly analyze the hydrogen bond network configuration of water in real space. The related research results were published online in the form of articles on Nature-Materials [Nature Materials Dior: 10.1038/nmat3848] on10. Jiang Ying and Wang Enge are co-authors of this paper, and doctoral students Claire Kuo, Meng Xiangzhi and Chen Ji are co-authors of this paper. Li Xinzheng, a researcher at the School of Physics, and Professor of the History of the Center of Quantum Materials provided important support and help in theory. This work was funded by China National Foundation, Ministry of Science and Technology, Ministry of Education and Peking University.

The peculiar physical and chemical properties of water are closely related to the hydrogen bond interaction between water molecules. How to determine the hydrogen bond network configuration of water at the molecular level is one of the key scientific problems in the field of water science. Because the formation of hydrogen bonds mainly comes from the electrostatic force (O-H…O) between hydrogen atoms and oxygen atoms, it is necessary not only to determine the position of oxygen atoms, but also to identify the position of hydrogen atoms, that is, to detect the orientation of water molecules in space at the sub-molecular level. However, due to the very small mass and size of hydrogen atoms, it is very challenging to image water molecules at the sub-molecular level.

Jiang Ying, head of the Peking University Spectroscopy and High Resolution Detection Laboratory, said that the diameter of water molecules is only one millionth of that of a hair, so it is very mobile. The first problem of taking a photo is to choose a suitable background for it. And if you want to take pictures with an electron microscope, the background must be conductive. In the past, scientists used metal as the substrate, and once observed the vague shape of water molecules without any internal structure. This time, scientists in China chose sodium chloride (NaCl) film as the background, adsorbed water molecules on the salt surface for observation, and captured a clearer face of water molecules.