中文摘要：

利用水热法制备了Cr3＋-Yb3＋-Er3＋共掺杂的NaYF4微管。在980nm的红外激光激发下，微管产生了强的可见上转换荧光。相比于Yb3＋-Er3＋共掺NaYF4微棒，微管的绿光和红光强度分别提高30倍及20倍。上转换荧光增强的原因被归结为Cr3＋掺入引起稀土离子周围晶体场对称性的减弱。对微管的生长过程及上转换发光机制进行了分析。

英文摘要：

Cr3＋-Yb3＋-Er3＋ co-doped NaYF4 microtubes were fabricated by hydrothermal method. Under the excitation of 980 nm infrared laser, strong visible upconversion luminescence were observed in microtubes. Compared to Yb3＋-Er3＋ codoped NaYF4 micrirods, the green and red emission intensity of the microtubes respectively enhanced by 30 times and 20 times, which is attributed to the destruction of the crystal-field symmetry around rare-earth ions due to Cr3＋ ions doping. The growth process and upconversion luminescence mechanism of the microtubes were dis- cussed.