Patel Jyoti, Singh Ajaya K, Carabineiro Sónia A C
Department of Chemistry, Govt. V. Y. T. Post Graduate Autonomous College, Durg, Chhattisgarh 491001, India.
LAQV-REQUIMTE, Department of Chemistry, NOVA School of Science and Technology, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal.
Nanomaterials (Basel). 2020 May 18;10(5):964. doi: 10.3390/nano10050964.
Norfloxacin (NOFX), a broadly used fluoroquinolone antibiotic, has been a subject of great concern in the past few years due to its undesirable effect on human beings and aquatic ecosystems. In this study, novel Mn doped ZnS (Mn:ZnS) quantum dots (QDs) were prepared through a facile chemical precipitation method and used as photocatalysts for NOFX degradation. Prior to photodegradation experiments, morphological and optical parameters of the QDs were examined through transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray analysis, Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, fluorescence spectroscopy, Brunauer-Emmett-Teller analysis, and differential thermal and thermogravimetric analyses. Mn:ZnS QDs exhibited excellent properties of photodegradation, not only under UV irradiation but also in sunlight, which induced NOFX to photodegrade. The utmost photodegradation efficiency was obtained under optimal conditions (25 mL of NOFX, 15 mg/L, pH 10, 60 min UV irradiation, 60 mgs QDs), adopting first order kinetics. In addition, hydroxyl radicals produced by the conduction band electrons were found to be the primary reason dominating the transformation of NOFX in basic conditions, while holes, oxygen atoms, as well as the doped metal (Mn) enhanced the degradation. The QDs showed excellent reusability and stability in four repeated cycles. Finally, four different pathways were predicted, derived from the identified intermediates, with piperazinyl ring transformation being the primary one. It is expected that the synthesized Mn:ZnS QDs could be utilized as efficient photocatalytic materials for energy conversion and ecological remediation.
诺氟沙星（NOFX）是一种广泛使用的氟喹诺酮类抗生素，由于其对人类和水生生态系统产生不良影响，在过去几年中一直备受关注。在本研究中，通过简便的化学沉淀法制备了新型锰掺杂硫化锌（Mn:ZnS）量子点（QDs），并将其用作光催化剂来降解NOFX。在光降解实验之前，通过透射电子显微镜、扫描电子显微镜、能量色散X射线分析、傅里叶变换红外光谱、紫外可见光谱、荧光光谱、布鲁诺尔-埃米特-泰勒分析以及差示热分析和热重分析对量子点的形态和光学参数进行了检测。Mn:ZnS量子点不仅在紫外光照射下，而且在阳光照射下均表现出优异的光降解性能，能促使NOFX发生光降解。在最佳条件（25 mL的NOFX、15 mg/L、pH值为10、紫外光照射60分钟、60 mg量子点）下采用一级动力学可获得最高光降解效率。此外，发现导带电子产生的羟基自由基是碱性条件下主导NOFX转化的主要原因，而空穴、氧原子以及掺杂金属（Mn）则增强了降解效果。量子点在四个重复循环中表现出优异的可重复使用性和稳定性。最后，根据鉴定出的中间体预测了四条不同的途径，其中哌嗪环转化是主要途径。预计合成的Mn:ZnS量子点可作为高效光催化材料用于能量转换和生态修复。
