光磁双功能纳米晶的可控合成及磁控制发光

Recently, optical-magnetic (OM) bifunctional materials have received increasing attention. However, the ever reported OM bifunctional materials are composed of optical materials and magnetic ones, in which the OM interaction can not be achieved due to the high density of interfacial dislocations and resulting in the limitation of their application developments. In this applied program, we intend to synthesize single-phase OM bifunctional nanocrystals and study their magnetic tuning of luminescent intensity. First, calculating the paramagnetism and crystal field parameters of OM bifunctional nanocrystals according to the giant spin model; controlly synthesizing the OM bifunctional nanocrystals based on the calculated composition; then, addressing the best combination of optical and magnetic properties so that the OM bifunctional materials with high luminescent efficiency and excellent magnetic tuning efficiency of luminescent intensity; finally, building the qualitative and quantitative relationship between the tuning efficiency of luminescent intensity and paramagnetism/luminescent efficiency. For resolving the conflict between luminescence and magnetism, the doping of sensitizing ions is combined with theoretical calculation to optimize the parameters of crystal field. The successful achievement of this program is useful for developing the application of OM bifunctional nanomaterials and their magnetically controlled luminescence in the fields of high accuracy communication, guidance of aircraft, and optical and magnetic field detection, and supply the further improvement of OM bifunctional nanomaterials and their magnetically controlled luminescence with theoretical basis.

近几年，光磁双功能材料成为了国际研究热点。但已经报道的光磁双功能材料主要是光学材料和磁性材料复合的多相材料，高密度界面位错导致不能实现光磁相互作用，极大的限制了其应用发展。在此申请项目中， 我们拟合成单相光磁双功能纳米晶并研究其"发光强度的磁调制效应"。首先，基于自旋相干模型计算光磁双功能纳米晶的顺磁性和晶体场参数；基于理论估算参数的指导，可控合成相应光磁双功能纳米晶；然后，确定发光和磁性的最佳结合点，制备出同时具有高发光效率和优异光磁调制效率的双功能纳米晶；最后，构建发光强度的磁调制效率与样品的顺磁性和发光效率之间的定性定量关系。为了解决发光和磁性之间的竞争矛盾，拟采取敏化离子掺杂和理论计算相结合的方案优化晶体场参数。此项目的成功实施将加快光磁双功能纳米材料及其磁控制发光在高精度通讯、制导及光场和磁场检测等领域的应用步伐，并为进一步改进光磁双功能材料的磁控制发光特性提供理论依据。

稀土光磁双功能纳米晶既具有优异的光致发光特性，又具有优异的顺磁性或超顺磁性，最近在磁控制发光、光磁多模成像、显示、生物分子检测等领域受到了广泛关注。（1）本项目首先深入探究了稀土光磁双功能纳米晶的光学特性。首次合成了核/多孔壳结构上转换纳米晶，并且观察到了介于块体材料和纳米尺度之间的荧光衰减现象。通过拟合衰减谱，我们证实核/多孔壳结构上转换纳米晶同一能级存在两种长短不一的寿命。机理分析表明，这主要是由于该能级处在裸露的纳米晶表面时，由于高密度缺陷而展现出较短的荧光寿命；但处在核/壳界面上时，由于不存在缺陷而展现出较长的荧光寿命。（2）本项目同步调控了稀土光磁双功能纳米晶的光磁特性。通过在NaGdF4基质中引入La3+ 和Lu3+两种既不发光也没有顺磁性的基质离子，改变基质材料的声子振动模式和发光中心的能级寿命，以及材料的顺磁性，实现了上转换发光强度和顺磁性的同时提高。并确定了9mol% La3+ 和9mol% Lu3+的引入可以实现最佳发光强度，同时导致顺磁性的显著提高。同时优化和调控了NaLuF4: Yb3+/Tm3+/Gd3+/Sm3+样品的上转换发光和磁性。通过掺杂Sm3+离子，实现了Tm3+离子的800nm红外发射的红移调控，并分析了Tm3+和Sm3+离子之间的能量交换产生800nm红移的机制。磁性分析表明，Sm3+离子掺杂同时可以调控样品的磁性，并可实现铁磁到顺磁性的转变。（3）本项目探索了稀土光磁双功能纳米晶在生物分子检测和无噪音信号检测中的应用。合成了Yb3+, Er3+, Tm3+掺杂NaLuF4纳米晶，通过表面控制，实现了对荧光素钠注射液中的荧光分子的快速荧光成像及定量检测。在本项目实施过程中，共发表SCI论文13篇，申请发明专利1项，培养研究生5名。