Florea Mihaela, Avram Daniel, Cojocaru Bogdan, Tiseanu Ion, Parvulescu Vasile, Tiseanu Carmen
Faculty of Chemistry, Department of Organic Chemistry, Biochemistry and Catalysis, University of Bucharest, 4-12 Regina Elisabeta Bvd., Bucharest, Romania.
Phys Chem Chem Phys. 2016 Jul 21;18(27):18268-77. doi: 10.1039/c6cp02754g. Epub 2016 Jun 22.
We investigate the effects of heterovalent co-dopants on the structural and emission properties of 1% Er-CeO2 nanoparticles. The CeO2 oxide host was selected on the basis of its fairly well-understood defect chemistry in either a pure or doped state. As a luminescent activator, Er is acknowledged as an interesting element due to its rich luminescence and excitation properties spanning the visible to near-infrared range. The optically inactive trivalent La and monovalent Li metal ions with a concentration of up to 20% were chosen to presumably generate a variable amount of defects in the Er-CeO2 lattice. It was found that La and Li co-dopants induced distinct changes related to the size, lattice constant, bandgap energy, lattice and surface defects of Er-CeO2. As a result of these changes, a strong modulation of the luminescence intensity and shape was measured using a suite of excitation conditions (charge-transfer absorption band of CeO2, direct/up-conversion into Er absorptions and X-ray excitation modes). The use of Eu as a luminescent probe offered additional information concerning the effects of La/Li co-doping on the local structure surrounding the luminescent activator. Remarkably high percentages of 90 and 98% of the total emission of Er measured between 500 and 1100 nm are measured in the near-infrared region at 980 nm under X-ray and up-conversion excitation at ∼1500 nm, respectively. The optical properties suggest that Li, Er co-doped CeO2 has good potential for therapy and biological imaging.
我们研究了异价共掺杂剂对1% Er-CeO₂纳米颗粒的结构和发光特性的影响。选择CeO₂氧化物基质是基于其在纯态或掺杂态下相当清楚的缺陷化学。作为发光激活剂，Er因其丰富的发光和跨越可见光到近红外范围的激发特性而被认为是一种有趣的元素。选择浓度高达20%的光学惰性三价La和一价Li金属离子，推测它们会在Er-CeO₂晶格中产生不同数量的缺陷。研究发现，La和Li共掺杂剂导致了与Er-CeO₂的尺寸、晶格常数、带隙能量、晶格和表面缺陷相关的明显变化。由于这些变化，在一系列激发条件下（CeO₂的电荷转移吸收带、直接/上转换到Er吸收以及X射线激发模式）测量到了发光强度和形状的强烈调制。使用Eu作为发光探针提供了关于La/Li共掺杂对发光激活剂周围局部结构影响的额外信息。在X射线激发和~1500 nm的上转换激发下，分别在980 nm的近红外区域测量到在500至1100 nm之间测量的Er总发射的90%和98%的极高百分比。光学性质表明，Li、Er共掺杂的CeO₂在治疗和生物成像方面具有良好的潜力。
