Department of Chemistry , Korea University , 145 Anam-ro , Seoul 02841 , Republic of Korea.
Division of RI Convergence Research , Korea Institute of Radiological & Medical Sciences (KIRAMS) , 75, Nowon-ro , Nowon-gu, Seoul 01812 , Republic of Korea.
ACS Appl Mater Interfaces. 2018 Apr 18;10(15):12331-12340. doi: 10.1021/acsami.7b18078. Epub 2018 Apr 4.
In this study, intense single-band red-emitting upconversion nanophosphors (UCNPs) excited with 800 nm near-infrared (NIR) light are reported. When a NaYF:Nd,Yb active-shell is formed on the 12.7 nm sized NaGdF:Yb,Ho,Ce UCNP core, the core/shell (C/S) UCNPs show tunable emission from green to red, depending on the Ce concentration under excitation with 800 nm NIR light. Ce-doped C/S UCNPs (30 mol %) exhibit single-band red emission peaking at 644 nm via a F → I transition of Ho. A high Nd concentration in the shell results in strong absorption at around 800 nm NIR light, even though the shell thickness is not large, and small-sized C/S UCNPs (16.3 nm) emit bright red light under 800 nm excitation. The formation of a thin NaGdF shell on the C/S UCNPs further enhances the upconversion (UC) luminescence and sub-20 nm sized core/double-shell (C/D-S) UCNPs exhibit 2.8 times stronger UC luminescence compared with C/S UCNPs. Owing to the strong UC luminescence intensity and Gd ions on the surface of nanocrystals, they can be applied as a UC luminescence imaging agent and a T contrast agent for magnetic resonance (MR) imaging. In vivo UC luminescence and high-contrast MR images are successfully obtained by utilizing the red-emitting C/D-S UCNPs.
在这项研究中，报告了用 800nm 近红外（NIR）光激发的强单带红光上转换纳米荧光粉（UCNP）。当在 12.7nm 大小的 NaGdF:Yb，Ho，Ce UCNP 核上形成 NaYF：Nd，Yb 活性壳时，取决于 Ce 浓度，C/S UCNP 在激发 800nm NIR 光时显示从绿光到红光的可调发射。掺杂 Ce 的 C/S UCNP（30mol%）通过 Ho 的 F→I 跃迁显示出在 644nm 处的单带红光发射。壳中的高 Nd 浓度导致在 800nm NIR 光附近的强吸收，即使壳厚度不大，并且小尺寸的 C/S UCNP（16.3nm）在 800nm 激发下发射明亮的红光。在 C/S UCNP 上形成薄的 NaGdF 壳进一步增强了上转换（UC）发光，并且与 C/S UCNP 相比，核/双壳（C/D-S）UCNP 表现出 2.8 倍更强的 UC 发光。由于强的 UC 发光强度和纳米晶体表面上的 Gd 离子，它们可用作 UC 发光成像剂和磁共振（MR）成像的 T 对比剂。通过利用红色发射的 C/D-S UCNP，成功获得了 UC 发光和高对比 MR 图像。
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