Fan Shiwen, Bi Sheng, Li Qikun, Guo Qinglei, Liu Junshan, Ouyang Zhongliang, Jiang Chengming, Song Jinhui
Institute of Photoelectric Nanoscience and Nanotechnology, School of Mechanical Engineering, Dalian University of Technology, Dalian 116024, People's Republic of China. Key Laboratory for Precision and Non-traditional Machining Technology of the Ministry of Education, Dalian University of Technology, Dalian 116024, People's Republic of China.
Nanotechnology. 2018 Mar 23;29(12):125702. doi: 10.1088/1361-6528/aaa929.
The mechanical properties of size-dependent nanowires are important in nano-electro-mechanical systems (NEMSs), and have attracted much research interest. Characterization of the size effect of nanowires in atmosphere directly to broaden their practical application instead of just in high vacuum situations, as reported previously, is desperately needed. In this study, we systematically studied the Young's modulus of vertical ZnO nanowires in atmosphere. The diameters ranged from 48 nm to 239 nm with a resonance method using non-contact atomic force microscopy. The values of Young's modulus in atmosphere present extremely strong increasing tendency with decreasing diameter of nanowire due to stronger surface atomic bonds compared with that in vacuum. A core-shell model for nanowires is proposed to explore the Young's modulus enhancement in atmosphere, which is correlated with atoms of oxygen occurring near the nanowire surface. The modified model is more accurate for analyzing the mechanical behavior of nanowires in atmosphere compared with the model in vacuum. Furthermore, it is possible to use this characterization method to measure the size-related elastic properties of similar wire-sharp nanomaterials in atmosphere and estimate the corresponding mechanical behavior. The study of the size-dependent Young's modulus in ZnO nanowires in atmosphere will improve the understanding of the mechanical properties of nanomaterials as well as providing guidance for applications in NEMSs, nanogenerators, biosensors and other related areas.
尺寸依赖型纳米线的力学性能在纳米机电系统（NEMS）中很重要，并且已经引起了很多研究兴趣。迫切需要直接在大气环境中表征纳米线的尺寸效应，以拓宽其实际应用范围，而不仅仅局限于如先前报道的高真空环境。在本研究中，我们系统地研究了大气环境中垂直排列的ZnO纳米线的杨氏模量。使用非接触原子力显微镜的共振方法，纳米线直径范围为48纳米至239纳米。与在真空中相比，由于更强的表面原子键，大气环境中纳米线的杨氏模量值随着纳米线直径的减小呈现出极强的增加趋势。提出了一种纳米线的核壳模型来探究大气环境中杨氏模量的增强，这与纳米线表面附近出现的氧原子有关。与真空中的模型相比，改进后的模型在分析大气环境中纳米线的力学行为时更准确。此外，有可能使用这种表征方法来测量大气环境中类似线状尖锐纳米材料的尺寸相关弹性性能，并估计相应的力学行为。对大气环境中ZnO纳米线尺寸依赖型杨氏模量的研究将增进对纳米材料力学性能的理解，并为NEMS、纳米发电机、生物传感器及其他相关领域的应用提供指导。
