Visible-light driven sonophotocatalytic removal of tetracycline using Ca-doped ZnO nanoparticles

Highly efficient, long-term, eco-friendly catalysts for water decontamination technology are urgently needed to meet the prioritized objectives of green development and societies worldwide. Ca-doped ZnO were investigated as environmentally friendly sono-photocatalytic system under LED visible light irradiation to efficiently mineralize tetracycline-based antibiotics. The effects of pH, Ca doping, light, ultrasound, and pH on the mineralization of tetracycline by Ca-doped ZnO nanopowders and on the chemical, sono-, photo- and sono-photostability of Ca-doped ZnO nanopowders were systematically investigated. The ZnO-based catalyst with 2 at. % of Ca dopant exhibited the best sono-photocatalytic performance in mineralizing tetracyclines under visible LED light and ultrasound irradiation (i.e., 99% mineralization in 90 min), with excellent reusability and minimal sono-photocorrosion (i.e., 1% of catalyst dissolution in 180 min), which were even greater in the absence of organic pollutants and in the pH range of most natural waters. For Ca-doped ZnO nanopowders, the role of the generated reactive oxygen species under light and ultrasound stimulation and the mechanism of the mineralization of tetracycline were analyzed. In conclusion, the sono-photocatalytic mineralization of antibiotics synergizing visible LED light and weak ultrasound irradiation in the presence of Ca-doped ZnO nanopowders presents an outstanding start to developing highly efficient, long-term, eco-friendly catalysts for efficiently treating emerging organic pollutants

Selective and rapid detection of acetone using aluminum-doped zno-based sensors

We report the preparation and characterization of pure and doped ZnO nanoparticles with 1%, 3%, and 5% aluminum (AZO) using a sol-gel method followed by annealing at 400 °C for 2 h. The structural and morphological properties of the AZO nanoparticles were analyzed using X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) techniques, and Scanning Electron Microscopy (SEM) equipped with Energy Dispersive Spectrometry (EDS). Optical and specific area properties were investigated by photoluminescence (PL) and N2 physisorption measurements. The results showed that pure and doped AZO nanoparticles crystallize under a hexagonal wurtzite structure and exhibit spherical shapes with nanometric dimensions. TEM and SEM images revealed that the pure and Al-doped ZnO were round nanoparticles with a size smaller that 100 nm. FTIR measurements were conducted to investigate the presence of Al-O stretching vibrations, which served as an indication of aluminum incorporation into the ZnO lattice. The results confirmed the successful integration of aluminum into the ZnO structure. Additionally, XPS measurements were performed to examine the elemental composition of the AZO samples. The presence of Zn 2p peaks in all AZO samples, along with the presence of Al 2p peaks in the Al-doped ZnO structures, provided further evidence for the successful incorporation of Al ions into the ZnO lattice. The PL spectra revealed the presence of various defects (oxygen vacancies, interstitials) in the structure of pure and doped ZnO. Moreover, we fabricated gas sensors by spray-coating the AZO nanoparticles on alumina substrates equipped with interdigitated gold electrodes. The sensors demonstrated linear responses to gas concentration in the range of 5 to 50 ppm, with high sensitivity and good reproducibility, particularly for A1ZO (1% Al-doped ZnO), which exhibited the highest response (~12) at 300 °C under 10 ppm of acetone. Furthermore, A1ZO demonstrated excellent selectivity to acetone compared to other volatile organic compounds (VOCThis work is financially supported by the Tunisian Ministry of Higher Education and Scientific Research (PRF 2019-D4P2), the European Regional Development Fund (ERDF), and the Walloon Region of Belgium through the Interreg V France-Wallonie-Vlaanderen program, under PATHACOV project, and the Micro + project co-funded by the European Regional Development Fund (ERDF) and Wallonia, Belgium (No. 675781-642409). In addition, this work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding Contract UIDB/04650/2020. J.P.B.S. also expresses gratitude to FCT for the contract under the Institutional Call to Scientific Employment Stimulus – 2021 Call (CEECINST/00018/2021)