手性光学活性可调的螺旋贵金属纳米晶的制备及圆偏振光催化研究

Chiral metamaterials have a special chiroptical response in the visible to near-infrared region, which has been widely applied in numerous fields, such as, negative refractive index media, chemical sensing, photocatalysis, cancer therapy. However, there are still many challenges in the synthetic technology of chiral plasmonic nanocrystals, which limit the application and development of chiral metamaterials. Herein, the challenging topic we have investigated is to prepare the helical noble plasmonic nanocrystals with a larger size, uniform morphology and structural parameters (screw diameter, pitch, ring number) through wet chemical method. It could overcome the challenges in practical application because of the dipole-dipole coupling between the super-electromagnetic field in the hot spot and the chiral molecule, and its inherent chiral structure effect. A theoretical model was established to study the effects of morphology, compositions and structural parameters on chiroptical activity. Meanwhile, we will also set up a theoretical model to demonstrate the mechanism of chirality origin from biomolecules to helical noble metal nanocrystals. Afterward, a novel helical chiral photocatalyst was prepared to overcome the instability issue of the nanostructure and chiroptical activity during the catalytic applications and the low circularly polarized photocatalytic efficiency issue. This project will provide experimental and theoretical models for new nanophotonics, molecular spectroscopy and photocatalysis.

手性超材料在可见到近红外区域具有特异的光学响应，在圆偏振器、负折射率材料、化学传感器、光催化、癌症治疗等领域具有广泛的应用前景。但是，手性等离激元纳米材料的制备技术还存在着许多挑战，限制着手性超材料的应用和发展。本项目着重研究的挑战性课题是用湿化学法大批量地制备出尺寸较大、形貌均一和结构参数（螺径、螺距、环数）可调的螺旋等离激元纳米晶。螺旋等离激元纳米晶具有超强、稳定和可调的光学活性，其光学起源机制包含手性结构和热点中超电磁场增强与手性分子的耦合强度。建立理论模型，研究形貌、组分和结构参数对光学活性的影响。揭示在分子与胶体晶面的界面处，生物分子的构象转移给仿生型螺旋等离激元纳米晶的机理。在此基础上制备出结构新颖的螺旋型手性光催化剂，克服手性光催化剂结构和光学活性在催化过程中的不稳定性以及圆偏振光催化产氢效率低的难题。本项目将为新型纳米光子学，分子光谱学及光催化提供实验和理论。

手性超材料在可见到近红外区域具有特异的光学响应，在圆偏振器、负折射率材料、化学传感器、光催化、癌症治疗等领域具有广泛的应用前景。本项目采用种子介导生长法，通过控制反应体系中热力学参数（前驱体的浓度、比例和反应温度）和动力学参数（滴加前驱体溶液的速度）制备出了不同长径比的手性金纳米棒，其形貌显示扭曲状态，并且等离激元圆二色光谱峰也具有可光学可调谐性。证明了手性金纳米棒的手性起源于热点增强和手形结构的协同效应，总结了手性分子-晶面处的相互作用机制。将手性金纳米棒上修饰上一层半导体（TiO2）和金属（Ag）层，发现构筑成的复合型等离激元纳米材料依然保持着其手性效应，并且能够将金纳米棒的手性传递给表面的金属Ag纳米层。通过表面增强拉曼技术监控了热电子增强光催化的动力学过程，深入分析了手性纳米材料手性传递和热电子增强光催化的机制。本项目将为新型纳米光子学，分子光谱学及光催化提供实验和理论。