Luminescent Y₂Zr₂O₇ for Ultrasensitive Detection of Volatile Organic Compounds Driven by Oxygen Vacancies

Defect engineering is considered as one of the most efficient strategies to introduce different functionalities in materials suitable to achieve desired properties such as magnetism, catalysis, sensing, and optoelectronic applications. In this study, we have synthesized Y2Zr2O7 (YZO) by the gel combustion method, and subsequent annealing was carried out at different temperatures from 900 to 1300 degrees C for the engineering of defects. Electron spin resonance spectroscopy suggested the presence of singly ionized oxygen vacancies (F+-center) which resulted in a dual-band bluish-green emission. The color can be tuned from blue to green in moving from the nano to bulk sample in the domain of 900-1300 degrees C. Photoluminescence quantum yield increases substantially in the bulk samples owing to the lesser density of defect clusters and higher F+ centers. The particle size increases from nano (similar to 50 nm) to bulk (similar to 0.4 mu m) domain, and surface defects reduce on annealing from 900 to 1300 degrees C. The pore size is in the mesoporous range, making them suitable for gas sensing purposes. The sensing abilities of nano YZO-900 and bulk YZO-1300 pyrochlore were assessed in terms of detecting volatile organic compounds (VOCs) such as ethanol, acetone, and benzene. The study revealed that the defects in the materials play a significant role in sensing capabilities compared to morphology. On comparisons with other VOC sensors, bulk YZO-1300 not only demonstrated excellent sensitivity and superior response and recovery time toward benzene, but they are equally capable of sensing other polar VOCs such as acetone and ethanol with great ease and lower limit of detection. Moreover, our materials have demonstrated the capability to work as rare-earth-free luminescent materials as well driven by oxygen vacancies.