Electrospun zinc oxide nanofibers for UV sensing with quartz crystal microbalance technique

Abstract

An ultraviolet (UV) sensor consisting of a zinc oxide (ZnO) nanofiber sensing membrane and a quartz crystal microbalance (QCM) was fabricated. ZnO nanofibers were prepared by electrospinning and calcination. The morphology and structure of the nanofiber sensing membrane were characterized by scanning electron microscopy and X-ray diffraction. The QCM sensor based on ZnO nanofibers was found to be sensitive to 254-nm UV light in nitrogen, oxygen and air atmospheres. When the QCM sensor was placed under UV irradiation, the resonant frequency difference rapidly decreased. When the light was removed, the frequency difference recovered until reaching 0 Hz. The stability and repeatability of the proposed ZnO nanofiber-based QCM sensor were demonstrated, and the sensing mechanism was briefly discussed.

A Porous Nanostructured ZnO Layer for Ultraviolet Sensing with Quartz Crystal Microbalance Technique

“…Thus, the sensing principle of the ZnO-QCM-based UV sensor is mainly explained by some change in the capacitance of the porous ZnO layer due to the generation of electron-hole pairs in it [ 30 , 40 , 42 ], and not by the principle of direct detection of a mass change by the QCM due to desorption from the ZnO surface of previously adsorbed spices (O 2 , OH, organic molecules, etc.) [ 31 ].…”

“…So, we believe that the composition of spices adsorbed on the surface of porous zinc oxide before the first cycle could differ from the composition of spices newly adsorbed on zinc oxide during the first UV-off cycle (from 60 to 120 s). The difference in composition of adsorbed spices can affect the kinetics of the release of trapped spices from the ZnO surface due to the neutralization of their negative charge by photogenerated holes [ 31 , 42 ].…”

“…Thus, we herein report the use of a modified two-step approach for forming porous ZnO layers, wherein a process of co-sputtering Zn and Ga-doped ZnO targets is employed to fabricate the porous Zn–ZnO layer at the first stage, with its subsequent oxidation to ZnO at the second thermal annealing stage. Finally, the porous ZnO layer was fabricated on the surface of the 5 MHz AT-cut α-quartz crystal in order to test the possibility of creating a resonant type ultraviolet (UV) radiation sensor, in which the operation principle is based on detecting a change in the frequency of the oscillator due to the desorption of oxygen from the surface of the layered ZnO upon UV irradiation [ 29 , 30 , 31 ].…”