Development of novel near-infrared persistent phosphors for bio-imaging

今年，本课题由两部分组成：(I)用于无激发脑成像的光学探针；(Ii)用于交流(AC)-wLED中有效抑制闪烁的陶瓷永久型荧光粉。对于(I)，基于近红外光的荧光光学成像是一种非侵入性成像技术，它具有高速获取实时数据的可能性，并允许以高空间和时间分辨率对体内动态过程进行时间分辨检测。SWIR中大于1.0um的波长区域；第二个(NIR-II，1.0-1.35um)和第三个(NIR-III，1.5-1.8um)窗口比较短的NIR-I窗口更具优势，因为较低的散射系数可以改善对比度质量，提高空间分辨率。受石榴石或钙钛矿等基质中稀土离子和过渡金属离子能级的启发，利用GaG石榴石结构中Cr3+到Er3+的持续能量传递，以及NIR-II窗口中Cr3+到Nd3+LaAlO3的持续能量传递，我们在NIR-III窗口实现了长时间的持续发光(停止外部激发后超过10小时)。对于(Ii)，在石榴石基长余辉发光材料的研究成果基础上，通过对Ce3+-Cr3+共掺的GaG石榴石中的Ga3+取代，制备了能够产生强烈的初始长余辉发光的黄色长余辉发光材料，从而抑制了交流驱动LED的闪烁效应。最好的样品对闪变有明显的抑制作用，正弦波形的闪变约为26.15%，指数约为0.07。

In this year, the subject is composed of two parts: (i) Optical probes for excitation-free brain imaging; (ii) Ceramic persistent phosphors toward efficient flicker suppression in alternating current (AC)-wLEDs. For (i), Fluorescence based optical imaging using NIR light is a noninvasive imaging technique, which possesses the possibility to acquire real-time data at a high speed, and allows for the time-resolved detection of in vivo dynamic processes with high spatial and temporal resolution. The wavelength region longer than 1.0um in SWIR; the 2nd (NIR-II, 1.0-1.35um) and 3rd (NIR-III, 1.5-1.8um) windows, is highly advantageous over the shorter NIR-I one because of lower scattering coefficient result in improved contrast quality, higher spatial resolution. Inspired by the energy levels of lanthanoid and transition metal ions in host matrix like garnets or perovskites, we realized long persistent luminescence (over 10 hours after ceasing external excitation) in the NIR-III window utilizing the persistent energy transfer from Cr3+ to Er3+ in GAGG garnet structure, and Cr3+ to Nd3+ LaAlO3 perovskite structure in the NIR-II window. For (ii), based on the research result in garnet-based persistent phosphors, by modifying the Ga3+ substitution in Ce3+-Cr3+ co-doped GAGG garnets, yellow persistent phosphors have been fabricated able to generate intense initial persistent luminescence to suppress the flicker effect of AC-driven LEDs. The best sample exhibits obvious flicker suppression, with flicker ~26.15% and index ~0.07 for the sinusoidal waveform.