近红外长余辉材料Zn1+xGa2-2xMxO4超薄纳米片状结构调控与其发光性能研究

The shortwave near-infrared (NIR) persistent luminescent nanomaterials have shown great potential on the application, but compared with bulk materials the nano size of materials will make their intensity of persistent luminescence weaker and lifetime shorter. Zn1+xGa2-2xMxO4 nanosheets materials were selected as the host in this project, because its thickness-surface distortion can be adjusted by the thickness of materials, and its wide emission band and bigger stokes shift can prove the effective energy transition between the host and luminescence centers. The Cr3+ ion was introduced in host as an effective luminescence center for shortwave NIR persistent luminescent, which is sensitive to the crystal field. Taking the adjustment of the thickness of the ultrathin nano-materials as a starting point, change the thickness-surface distortion of materials, and further control the numbers and distribution of the effective traps, that will benefit capture, release and delivery of the carrier. Then different M4+ codopants were used in this project to adjust bandgaps of host materials and different Ln3+ions codopants were also used to adjust the depth of effective traps, that ultimately improve NIR persistent luminescent properties of Zn1+xGa2-2xMxO4:Ln3+ in nano sizes. The luminescent mechanism of this kind of nanomaterials will be revealed by the studies about the intrinsic properties of the material defect states. This project will provide new ideas and theoretical basis for both the design and development of shortwave NIR persistent luminescent materials and its applications in biomedical field.

短波近红外长余辉纳米材料应用潜力巨大，但是相比块体材料其在较小纳米尺寸余辉发光强度较弱且余辉时间较短。基于超薄纳米片状结构表面扭曲度随厚度可调优势，本项目拟选择Zn1+xGa2-2xMxO4纳米片为基质，其具有的宽发射带和较大的stokes位移能保证其与近红外发光中心之间的能量传递。通过引入对晶体场敏感的Cr3+离子作为有效发光中心，可获得短波近红外长余辉发光。以调控其厚度为切入点，改变表面扭曲度，进而可控调节有效陷阱数量和分布，促进载流子的俘获、释放及传递。同时通过改变M4+（Si4+, Ge4+或Sn4+）离子的组成调节基质带隙，共掺不同Ln3+离子优化有效陷阱深度，实现其在较小纳米尺度近红外长余辉发光性能的提高。通过缺陷态本征属性的确认，揭示其纳米尺寸的发光机理。本项目的预期成果将为短波近红外长余辉纳米材料的设计及其在生物医学领域中的应用提供新思路和理论依据。

我们合成了系列Zn2-xGa2xGe1-xO4纳米发光材料，通过对其发光性质的研究，筛选出了长余辉发光性质最优的Zn1.9Ga0.2Ge0.9O4长余辉纳米片材料。在280 nm激发下，样品Zn1.9Ga0.2Ge0.9O4呈现出蓝白光的发射，其发射强度为Zn2GeO4的1.5倍，甚至是ZnGa2O4的4.5倍，其发射峰范围位于350~630 nm，主峰位置位于445 nm。通过比较其余辉性质，我们发现样品Zn1.9Ga0.2Ge0.9O4被紫外灯辐射10分钟后，在黑暗条件下仍然能够持续释放15s的宽谱白光余辉，而Zn2GeO4和ZnGa2O4的余辉发光已经降低的非常严重，此时Zn1.9Ga0.2Ge0.9O4的余辉发光强度为Zn2GeO4的20倍，甚至是ZnGa2O4的60倍。因此我们得出结论，少量的Ge4+被Ga3+取代，能够引入少量的陷阱深度较浅的Ga'Ge+Ga∙Zn+V'Zn+V∙O缺陷簇，其能够捕获一定的载流子并且在黑暗中释放出来，因此其能有效地帮助优化样品的发光性质以及余辉特性。我们对白光长余辉纳米材料Zn1.9Ga0.2Ge0.9O4发光性质以及发光机理的研究对设计和开发新型可见光长余辉纳米材料有重要的理论指导意义。