Recently, Professor Dai Ying's team at the Institute of Physics found that biaxial stretching can be realized in two-dimensional materials, which is of great significance to the development of materials with negative Poisson's ratio. The relevant research results are titled "single-layerag2s: atwo-dimensionalbi-directional auxetic semiconductor" and published online in the international journal Nano Letters (the impact factor is 12.08). The first author of the paper is Peng Rui, a 2017 master's degree student, and professors ma yandong and Dai ying are co-authors of the communication. Shandong university is the first author unit. Two-dimensional negative Poisson's ratio materials will expand laterally when subjected to uniaxial tension. This abnormal "expansion" behavior enhances the mechanical properties of such materials, including shear modulus, fracture toughness, thermal impact strength, indentation resistance, etc. It has important application value in the field of materials. At present, two-dimensional materials showing tensile expansion are relatively rare, while two-dimensional materials showing tensile expansion in both directions are even more rare. Professor Dai Ying's team found that two-dimensional Ag2S can show tensile swelling. More importantly, the negative Poisson's ratio of the material not only exists in the in-plane direction, but also exists in the out-of-plane direction, which means that the material has a rare phenomenon of biaxial tensile expansion. This is relatively rare in previous reports on stretch-out materials. The team also revealed that the two-dimensional negative Poisson's ratio of Ag2S originates from its unique zigzag structure and explained its physical mechanism.
In recent years, professor Dai ying's team has carried out a series of theoretical researches on the novel properties and applications of two-dimensional materials. the relevant research results have been published in such internationally renowned academic journals as nanoenergy, ACS nano, nanoletter, adv. mate, angew. chem. in. ed., j. am. chem. SOC, phys. rev. b, etc. The research work is supported by the State Key Laboratory of Crystal Materials, the National Natural Science Foundation Youth Project, the Mount Tai Scholar Program of Shandong Province, the Qilu Scholar Program of Shandong University and the 111 Program. Article link: https://pubs.acs.org/doi/10.1021/acs.nanolett.8b04761