Self-Powered 2D Material-Based pH Sensor and Photodetector Driven by Monolayer MoSe₂ Piezoelectric Nanogenerator

Abstract

The large piezoelectricity of monolayer MoSe 2 , which is predicted to be stronger than that of all of the other group VIB transition-metal dichalcogenides (including MoS 2 ), has only been theoretically investigated. Here, we report experimental evidence of in-plane piezoelectricity in MoSe 2 . Monolayer single-crystalline MoSe 2 flake derived from chemical vapor deposition demonstrates a peak output voltage of 60 mV at 0.6% strain, which is ∼50% larger than that of MoS 2 . Piezoelectric signal along the armchair orientation of MoSe 2 is ∼6 times larger than that along the zigzag orientation, indicative of strong anisotropic piezoelectricity. Piezoelectric nanogenerator based on a single MoSe 2 flake illustrates remarkable electromechanical conversion ability, and thus is able to noninvasively monitor vital health signs, such as respiratory rate and heart rate. Despite the extremely small size, MoSe 2 nanogenerator is able to drive pH sensor based on MoS 2 and photodetector based on MoS 2 /WSe 2 heterojunction due to the outstanding piezoelectricity of MoSe 2 and the ultralow power consumption of two-dimensional (2D) material sensors. The selfpowered, solely 2D-material-based sensor units demonstrate superb sensing performance. Therefore, the discovery of piezoelectricity in monolayer MoSe 2 provides a route for achieving self-powered atomic-scale electromechanical systems that could stimulate further fundamental research and potential applications.

Piezotronics in two‐dimensional materials

“…Since then, 2D nanogenerators based on various 2D materials have been researched passionately, such as MoSe 2 , 47 α‐In 2 Se 3 , 49 BP, 55 hollow 2D MoS 2 shells, 185 BN, 186 ZnO, 187,188 bilayer WSe 2 , 191 multi‐pores MoS 2 , 192 and so on. The bilayer WSe 2 nanogenerator indicates that stacking direction of TMDCs with even number of atomic layers determines symmetry and piezotronic performance (Figure 9D–F).…”

“…since the first discovery of single atomic thickness graphene. Thus, piezotronics based on 2D materials was presented and developed rapidly from microscopic mechanism, various materials to the practical applications on nanogenerators, sensors, catalysis, information storage, and other flexible devices 42–54 …”

Nano Sensor for Near Zero Emission Monitoring of Sulfur Hexafluoride

“…In order to verify the applicability and effectiveness of the proposed nano sensor for near zero emission monitoring of SF6, relevant experimental tests were designed.In the experiment, in order to highlight the advantages of the proposed method, the ultraviolet imaging remote sensing monitoring method and the acoustic method are comparatively analyzed, so as to ensure the reliability of the experimental results (Li and Zhang, 2020;Wen et al, 2019;Xiao et al, 2019).…”

Effect of cobalt phosphide (CoP) vacancies on its hydrogen evolution activity via water splitting: a theoretical study

“…Much attention has been spent in seeking alternative catalysts to replace noble catalysts. So far, various non-noble based electrocatalysts, including transition metal carbides, 7,8 nitrides, 9 sulfides, 10,11 oxides, 12 selenides, 13,14 and phosphides, 15,16 have been demonstrated as promising electrocatalysts for HER. Transition metal phosphides (TMPs), such as MoP 2 , 17,18 FeP, 19,20 Ni 2 P, 21 CoP, 22,23 and so on, have proved to be a group of excellent non-precious metal catalysts for HER due to their higher conductivity than metal oxide-based catalysts.…”