近红外染料化学键桥连的高效上转换纳米材料的设计合成及性能研究

Yb3+ is used as sensitizer to absorb light in all the upconversion nano crystals(UPNCs) up till now and the luminescent efficiency of UPNCs is very low due to the narrow absorption of Yb3+. The low luminescent efficiency greatly limited their applications. To solve this problem, the project will adopt near infrared dyes which can strongly absorb near infrared light in 800-1100nm to subsitute Yb3+ as sensitizer. The luminescent efficiency can be greatly enhanced by utilizing strong absorption of near infrared dyes in 800-1100nm. Firstly, near infrared dyes which can strongly absorb light in 800-1100nm will be designed and synthesized through group modification. The stucture characteristics of the near infrared dyes which can effcttively transfer energy to UPNCs will be obtained by investigting the effect of the maximun absorption wavelength of near infrared dyes on energy transfer efficency. Near infrared dyes bridged UPNCs through chemical bond can be formed by surface modification of UPNCs. The best type of chemical bond bridge for energy transfer from near infrared dyes to UPNCs will be found by studying the effect of different chemical bond bridges on energy transfer efficiency. Finally, the luminescent efficiency will be greatly enhanced by utilizing strong absorption and effectve nergy transfer of near infrared dyes .

目前研究的上转换纳米材料都采用Yb3+离子做为敏化剂吸收光，由于Yb3+离子的吸收光谱窄导致上转换纳米材料发光效率有限，使其在很多方面的应用受到限制。本项目针对这一问题采用对800-1100nm宽范围的近红外光有强吸收的染料替代Yb3+离子，设计近红外染料敏化的上转换纳米材料。利用近红外染料的强吸收大大增强对红外光的利用，提高上转换发光效率。首先通过官能团修饰设计合成在800-1100nm的近红外区有强吸收的近红外染料，研究近红外染料的最大吸收波长对两者能量传递效率的影响，得到具有最佳能量传递效果的近红外染料的结构特征；将纳米上转换材料通过表面修饰使其可以和近红外染料发生化学键结合，构筑近红外染料化学键桥连的上转换纳米材料；研究不同化学键结合对两者能量传递效率的影响，探索具有最高能量传递效率的桥连方式；最终通过近红外染料对红外光的强吸收和向上转换纳米材料的有效传递提高上转换材料的发光效率。

摘要：目前研究的上转换纳米材料的吸收光谱窄、发光效率低，导致上转换纳米材料很难被太阳光中的红外光激发，使其在光伏器件等很多方面的实际应用受到限制。本项目针对这一问题采用对800-1100 nm宽范围的近红外光有强吸收的染料或石墨烯与上转换材料通过化学键桥连，设计近红外材料敏化的上转换纳米材料。本项目首次通过调节配体的碳链长度，控制非辐射跃迁几率将NaYF4:Yb3+,Er3+的上转换发光提高25倍，为上转换发光材料效率的提高提供了新的思路；通过多功能配体的选择制备了表面含有羧基、氨基等官能团的上转换纳米颗粒；成功的合成了三种近红外吸收染料，在800-1000 nm的近红外区有强吸收，其中有两种的摩尔消光系数大于20000；另外通过原位法合成了石墨烯-上转换化学键桥连的复合材料，将其应用于光伏器件，由于还原的氧化石墨烯在近红外区有很强的吸收，通过两者之间有效的能量传递，首次实现可以在模拟太阳光下的红外光区照射下产生器件可电流；另外，本项目设计合成了NaYF4:Yb3+,Er3+/TiO2 纳米异质结构，首次利用上转换和电极材料间的电子传递实现太阳能电池效率提高15%，上述研究成果使上转换发光材料在光伏器件中的实际应用成为可能。