Abstract The interplay between physics and chemistry of nanoparticles dictate many useful properties for their practical applications. In this context, we synthesized well controlled CeO2/CePO4 nanocomposites using Artocarpus heterophyllus aqueous leaf extract as reducing agent. The as-synthesized nanocomposites were annealed at elevated temperatures (500–900 °C) for 3 h under air atmosphere and their characterizations were performed using X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Differential Scanning Calorimetry (DSC) –Thermo Gravimetric (TG) analysis, Raman, Fourier Transform Infrared (FTIR) and UV–Visible spectroscopy analysis. The formation of the CeO2/CePO4 nanocomposites could be realized by the presence of phosphate ions in aqueous leaf extract which has been confirmed by Gas Chromatography – Mass Spectrometry (GC-MS) analysis. Such stabilization of Ce3+ ions as CePO4 phase on the surface of nanoceria induced the reduction of grain growth and lowering of the bandgap of the nanocomposites. The antibacterial efficacy against both gram positive (S. aureus and B. cereus) and gram negative (S. typhimurium and E. coli) bacteria is attributed to the redox cycling between Ce3+ and Ce4+ ions at the oxide-phosphate interface of CeO2/CePO4 nanocomposites. The cytotoxicity analysis observed on two mammalian cell lines (HeLa and Vero) shows that the functional nanocomposites were non–toxic up to higher concentration (3 g/L). Our findings have implication that the phyto-synthesized CeO2/CePO4 nanocomposites could provide novel insights for mimicking multienzymes’ activities and safe for antibacterial applications in terms of in vitro cytotoxicity.

中文翻译：

---

植物合成的CeO2/CePO4纳米复合材料中Ce3+↔Ce4+电子跃迁的物理特性及其抗菌活性

摘要 纳米粒子的物理和化学之间的相互作用决定了其实际应用的许多有用特性。在这种情况下，我们使用异叶果果水叶提取物作为还原剂合成了控制良好的 CeO2/CePO4 纳米复合材料。合成的纳米复合材料在空气气氛下在高温（500-900°C）下退火 3 小时，并使用 X 射线衍射（XRD）、场发射扫描电子显微镜（FESEM）、差示扫描量热法（ DSC) – 热重 (TG) 分析、拉曼、傅里叶变换红外 (FTIR) 和紫外-可见光谱分析。CeO2/CePO4 纳米复合材料的形成可以通过叶提取物中磷酸盐离子的存在来实现，这已通过气相色谱 - 质谱 (GC-MS) 分析证实。Ce3+ 离子作为纳米氧化铈表面上的 CePO4 相的这种稳定诱导了纳米复合材料晶粒生长的减少和带隙的降低。对革兰氏阳性菌（金黄色葡萄球菌和蜡状芽孢杆菌）和革兰氏阴性菌（鼠伤寒沙门氏菌和大肠杆菌）的抗菌功效归因于 CeO2/CePO4 的氧化物-磷酸盐界面处 Ce3+ 和 Ce4+ 离子之间的氧化还原循环纳米复合材料。在两种哺乳动物细胞系（HeLa 和 Vero）上观察到的细胞毒性分析表明，功能性纳米复合材料在高达更高浓度（3 g/L）时是无毒的。