Weili Zang

High Piezo-photocatalytic Efficiency of CuS/ZnO Nanowires Using Both Solar and Mechanical Energy for Degrading Organic Dye

High piezo-photocatalytic efficiency of degrading organic pollutants has been realized from CuS/ZnO nanowires using both solar and mechanical energy. CuS/ZnO heterostructured nanowire arrays are compactly/vertically aligned on stainless steel mesh by a simple two-step wet-chemical method. The mesh-supported nanocomposites can facilitate an efficient light harvesting due to the large surface area and can also be easily removed from the treated solution. Under both solar and ultrasonic irradiation, CuS/ZnO nanowires can rapidly degrade methylene blue (MB) in aqueous solution, and the recyclability is investigated. In this process, the ultrasonic assistance can greatly enhance the photocatalytic activity. Such a performance can be attributed to the coupling of the built-in electric field of heterostructures and the piezoelectric field of ZnO nanowires. The built-in electric field of the heterostructure can effectively separate the photogenerated electrons/holes and facilitate the carrier transportation. The CuS component can improve the visible light utilization. The piezoelectric field created by ZnO nanowires can further separate the photogenerated electrons/holes through driving them to migrate along opposite directions. The present results demonstrate a new water-pollution solution in green technologies for the environmental remediation at the industrial level.

Hydrothermal synthesis of Co–ZnO nanowire array and its application as piezo-driven self-powered humidity sensor with high sensitivity and repeatability

A high sensitive and repeatable self-powered humidity sensor has been realized from Co-doped ZnO nanowires (NWs). The piezoelectric output of the device acts not only as a power source, but also as a response signal to the relative humidity (RH) in the environment. When the relative humidity is 70% RH at room temperature, the piezoelectric output voltage of the humidity sensor under compressive force decreases from 1.004 (at 20% RH) to 0.181 V. The sensitivity of self-powered humidity sensing based on Co-doped ZnO nanoarrays is much higher than that of undoped ZnO nanoarrays. The device exhibits good repeatability for humidity detection, and the response maintains ∼90% after one month. Such a high performance can be attributed to the piezo-surface coupling effect of the nanocomposites and more active sites introduced by the Co dopants. Our study can stimulate a research trend on exploring composite materials for piezo-gas sensing.

Humidity-dependent piezoelectric output of Al–ZnO nanowire nanogenerator and its applications as a self-powered active humidity sensor

Al-doped ZnO nanowire arrays are used to fabricate a piezoelectric nanogenerator, and its output is significantly dependent on the humidity in the environment, showing its applications as a self-powered active humidity sensor. The piezoelectric output of the device acts as both the power source and response signal to the humidity.