小尺寸NaLuF4:Yb3+/Tm3+纳米晶的生长及上转换发光

为了详细地探究NaLuF₄纳米晶的生长过程，利用自主研发的可以精确控制实验参数的自动纳米合成仪制备了不同系列的NaLuF₄：Yb³⁺/Tm³⁺纳米材料。对不同反应温度下（285，295，305℃）制备的样品进行物相分析，发现随着反应时间的增加，NaLuF₄纳米晶均遵循相似的生长规律，即α-相→α-相+β-相→均匀的β-相→聚集的β-相。在不同温度下，均有一个时间段可以获得小尺寸（小于50 nm）、单分散、粒径分布窄的纯β-NaLuF₄纳米晶。另外，测试了不同温度下制备的β-NaLuF₄：Yb³⁺/Tm³⁺纳米材料的上转换发射光谱，结果表明随着反应温度的升高，样品的发光先增强后减弱。出现这种光谱规律可能是受晶体尺寸和结晶性两方面因素的影响。此外，样品在紫外区的高阶多光子发光很强。例如，361 nm发射峰强度大约是800 nm发射峰强度的2倍。

Growth Process and Upconversion Luminescence of NaLuF4:Yb3+/Tm3+ Nanocrystals

In order to explore the growth process of NaLuF₄ nanocrystals in detail, we prepared a series of NaLuF₄:Yb³⁺/Tm³⁺ nanomaterials by using a self-developed automatic nanomaterial synthesizer which can precisely control the experimental parameters. The phase analysis of samples prepared at different reaction temperatures(285, 295, 305℃) shows that the NaLuF₄ nanocrystals follow the similar growth law with the increase of reaction time. We can obtain pure β-NaLuF₄ nanocrystals with small size(less than 50 nm), monodispersity, and narrow size distribution at different temperatures. On the other hand, we measured the upconversion spectra of β-NaLuF₄:Yb³⁺/Tm³⁺ nano-materials which prepared under 285, 295, and 305℃. These results indicate that the luminescence intensity of samples increase first and then decrease with the increase of reaction temperature. In addition, the luminescence of sample in ultraviolet region is stronger than that of the near-infrared region. For example, the intensity of 361 nm emission peak is twice large compared to that of 800 nm emission peak, which makes the nano-material suitable for near-infrared excited ultraviolet sensitive materials.