稀土掺杂CaSc2O4纳米晶上转换荧光调制及其发光物理

Upconversion luminescence (UCL) in rare earth ions doped crystals has played an important role on sensitive biological fluorescent labeling and medical imaging. Although the host material for achieving the most efficient UCL is fluoride，highly efficient UCL is still strongly expected in oxide materials for their stable chemical and thermal properties. The promising oxide host CaSc2O4 which attracts the attention owns a low cutoff phonon frequency of about 540 cm-1, exhibiting highly efficient upconversion luminescence. Compared with that in dopant concentration optimized Y2O3: Tm3+/Yb3+, the UCL around 800 nm of CaSc2O4: Tm3+/Yb3+ is enhanced by a factor of 3.5. The present UCL intensity at 800 nm matching the bio-optical window in CaSc2O4: Tm3+/Yb3+ is in principle comparable to that in NaYF4: Tm3+/Yb3+. The upconversion luminescence can be improved and spectral distribution can be modulated further via changing concentrations and species of doped lanthanide ions, surface modification of nanoparticles, core-shell structure etc.As far as we know,the UCL properties of CaSc2O4 nano-crystals for biological applications have not been demonstrated yet. Thus, this project is looking for novel chemistry method to achieve controlled synthesis and optimized luminescence of calcium scandate nano-crystals. Upconversion luminescence and energy transfer mechanism along with the dynamic processes of calcium scandate nano-crystals are investigated by means of electronic spectroscopy techniques including the emission and absorption spectroscopy, surface-enhanced Raman spectroscopy (SERS), etc. Clear and potent mechanisms and scenarios should be put forward to elucidate the upconversion modulated/enhanced luminescence. Much more importantly and valuably to be addressed, our proposal is aiming at establishing the physical and experimental basis of biological applications of calcium scandate nano-crystals which owns highly efficient and modulated UCL.

荧光上转换纳米晶可望在示踪、成像等生物医用领域有重要应用。与效率最高的氟化物相比，氧化物具有更稳定的理化性质。新型氧化物钪酸钙声子能量仅540 cm-1, 显示出高效上转换荧光潜力。相对于典型高效上转换材料氧化钇，Tm/Yb掺杂钪酸钙体材料中Tm离子 800 nm发射增强3.5倍,与氟钇钠基质中强度相当。通过激活剂/敏化剂浓度、种类优化，表面修饰及核壳包覆等手段可对上转换荧光在可见光范围内进行调制并进一步提高荧光效率。然而目前尚未见有关适于生物应用钪酸钙纳米晶物理特性的报道。本项目针对钪酸钙纳米晶进行研究，拟采用湿化学法实现材料的可控合成及上转换性能优化。利用发光学原理及光谱技术手段,重点研究钪酸钙纳米晶发光性质、能量传递及动力学过程,揭示稀土离子在钪酸钙纳米晶中上转换荧光调制/增强的规律及物理机制。为研制出高效可控且颜色可调钪酸钙纳米晶,实现其在生物医学领域的广泛应用奠定材料与物理基础。

荧光上转换纳米晶在示踪、成像等生物医用领域有重要应用。本项目主要围绕含Sc元素的氧化物（氟化物）纳米晶材料进行研究，讨论材料结构、形态、粒径与发光特性诸要素之间的相关性，研究稀土离子种类/浓度，表面修饰以及表面等离子激元对材料发光特性的影响并讨论各类相互作用的内部物理机制。取得了一系列成果具体包括：(1) 采用两相溶剂热法合成Sc2O3: Yb3+/Er3+纳米晶。研究材料的上转换发光性质，明确了离子掺杂浓度对光谱的调节能力及离子间的能量传递等发光物理问题。(2) 首次采用绿色水热法合成Sc2O3: Yb3+/Er3+纳米晶。纳米晶尺寸更小，分布更均匀，发光更强。Sc2O3: Yb3+/Er3+作为典型半氧化物展示出最高的红光比例，并且红光发射波长红移8 nm。(3) 采用绿色水热法合成棒状CaSc2O4上转换纳米晶材料。通过调节表面螯合剂和活性剂种类（Cit-3Na、EDTA、CTAB、PVP和PEG），调控纳米晶的尺寸形貌和发光性能。(4) 研究了钪基氧化物Sc2(MoO4)3: Eu3+荧光材料的结构、下转换发光性质与光谱分布。该材料是适合紫外激发的红光发光材料。(5) 控制合成Sc元素掺杂NaErF4: Yb3+上转换纳米晶。研究了Sc离子掺杂对光谱的调节能力及离子间的能量传递等发光物理问题。(6) 设计并合成了多种上转换纳米晶发光材料,如Y2O3: Yb3+/Er3+、NaErF4: Yb3+/Gd3+, NaYF4: Yb3+/Er3+/Mn2+/Fe3+等发光材料。项目执行期间共计在Dalton Transactions, Nanoscale Research Letters，Materials Research Bulletin等国际二区 SCI 杂志上发表论文5 篇以及中文核心论文3篇, 申请中国发明专利 2 项，培养硕士毕业生5名，在读硕士生3名。