Strategies to improve the efficiency of piezoelectric catalysis have long focused on piezo-optical coupling and construction of heterojunctions. However, it is a challenge to reinforce the performance of piezoelectric catalysis in a single material. Herein the built-in nanopores in single-crystal ZnO rods are employed to form stress to intensify piezo-catalytic efficiency. The piezo-catalytic efficiency of the ZnO rods with built-in nanopores (holey ZnO NRs) for degrading dyes was about 1.7 times that of the ZnO rods without built-in nanopores (ZnO NRs). X-ray diffraction and Raman peaks of holey ZnO NRs appeared blue-shifted in comparison to ZnO NRs, uncovering the existence of tensile stress in holey ZnO NRs. The piezoelectric coefficient d₃₃ of holey ZnO NRs increased by 1.92 times, triggering the amplification of piezoelectric catalytic property. Additionally, the piezoelectric current, carrier lifetime, and diffusion length of holey ZnO NRs were larger than that of ZnO NRs, respectively. These factors all contribute to the enhanced piezoelectric catalytic efficiency of holey ZnO NRs. This work demonstrates that the method of induced stress with built-in nanopores is a promising strategy for improving the piezoelectric catalytic efficiency of single-crystal ZnO rods.

The resistive switching (RS) mechanism of hybrid organic-inorganic perovskites has not been clearly understood until now. A switchable diode-like RS behavior in MAPbBr₃ single crystals using Au (or Pt) symmetric electrodes is reported. Both the high resistance state (HRS) and low resistance state (LRS) are electrode-area dependent and light responsive. We propose an electric-field-driven inner p-n junction accompanied by a trap-controlled space-charge-limited conduction (SCLC) conduction mechanism to explain this switchable diode-like RS behavior in MAPbBr₃ single crystals.

Flexoelectricity refers to the mechanical-electro coupling between strain gradient and electric polarization, and conversely, the electro-mechanical coupling between electric field gradient and mechanical stress. This unique effect shows a promising size effect which is usually large as the material dimension is shrunk down. Moreover, it could break the limitation of centrosymmetry, and has been found in numerous kinds of materials which cover insulators, liquid crystals, biological materials, and semiconductors. In this review, we will give a brief report about the recent discoveries in flexoelectricity, focusing on the flexoelectric materials and their applications. The theoretical developments in this field are also addressed. In the end, the perspective of flexoelectricity and some open questions which still remain unsolved are commented upon.