Spherical Gd₂O₃:Er³⁺ and Gd₂O₃:Er³⁺ @ silica nanoparticles have been successfully synthesized by a multistep procedure including precipitation and sol–gel processes from rare-earth nitrates, TEOS and urea as starting precursors. The structure, morphology and chemical composition of the products were characterized by X-ray diffraction, field emission scanning electron microscopy, and fourier transform infrared spectroscopy. The results indicated that the obtained phosphors consist of separated, non-agglomerated spheres in nanoscale with an uniform, ideal spherical shape. The suitable amount of TEOS was addressed to obtain the spherical Gd₂O₃:Er³⁺ @ silica nanocomposites with the luminescence intensity almost unchanged with respect to the uncoated Gd₂O₃:Er³⁺ sample. Besides, the upconversion emission spectra showed intense green and red emission bands under 980-nm laser diode excitation with remarkable increase in the red emissions. The upconversion luminescence followed the two-photon mechanism for green and red emissions. With obtained results, the prepared nanospheres are expected to be a potential material to create functional groups for subsequent bio-conjugation with various biomolecules in medical diagnostics.

中文翻译：

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球形Gd 2 O 3：Er和Gd 2 O 3：Er @二氧化硅的多步合成和上转换发光

球形的Gd ₂ O ₃：Er ³⁺和Gd ₂ O ₃：Er ³⁺ @二氧化硅纳米粒子已通过多步过程成功地合成，包括沉淀和溶胶-凝胶过程，是由稀土硝酸盐，TEOS和尿素作为起始前体。通过X射线衍射，场发射扫描电子显微镜和傅里叶变换红外光谱对产物的结构，形态和化学组成进行表征。结果表明，所获得的磷光体由纳米尺寸的分离的，非团聚的球组成，具有均匀，理想的球形。确定合适的TEOS量以获得球形的Gd ₂ O ₃：Er ³⁺ @二氧化硅纳米复合材料的发光强度相对于未涂覆的Gd ₂ O ₃：Er ³⁺样品几乎不变。此外，上转换发射光谱显示在980 nm激光二极管激发下强烈的绿色和红色发射带，红色发射显着增加。上转换发光遵循绿色和红色发射的双光子机制。根据获得的结果，制备的纳米球有望成为潜在的材料，以创建用于随后在医学诊断中与各种生物分子进行生物偶联的官能团。