模板转印法制备磁等离子体纳米材料及界面磁电耦合对其磁光特性互动的作用机制

Hybrid nanostructures not only endow individual nanoparticles (NPs) multi-functions often greater than the simple sum of each part but also produce novel physicochemical properties and phenomena through the inner-coupling and the interfacial proximity quantum effects from their constructing parts. The most amazing benefit for nanotechnology from these hybrid structures may be the possible methodology development used to overcome some conflicts with the size decrease. These effects are expressed as the inner interfacial magnetoelectric exchange coupling (IFMEC) in magnetoplasmonic nanostructures including magnetic components and noble metals. IFMEC not only tunes the magnetic phase transfer and the localized surface plasmon resonance (LSPR),but also enhance their megneto-optic effecs （MOE）and the exchange abilities among magnetic，optical，electronic, accoustic and biological signals. IFMEC is indoubt determinded by the structure and composition of each component (particular of the interface). However, the precise investigation on their relationship is still in challenge since the current method cannot precisely obtain the exact structure and composition of the specific nanoparticles and localize them. This challenge limits the application progress of these nanocomposites in the interdisciplinary field of information technology, new energy and biomedical engineering. In this project, a combined technique involving template transfer nanoimprinting process and multi-hierarchy arrayed-microwindows identification will be developed to fabricate recoganizable uniform hybrid nanostructures constructed by ferromagnetic layers (e.g., CoFeB), noble metal layers (e.g., Ag) and controlled interfacial layers (e.g., ITO, SiO2). Relationship between microstructures of each layer and their magnetic properties, localized surface plasmon resonance (LSPR) and magneto-optical effects, together with the effect of the interfacial structure/composition on these properties would be investigated for specific individual nanoparticles (NPs) arrays. The inner IFMEC in the specific NPs would be analyzed by the first-principles calculation, leading to address the inner IFMEC in NPs. The physical mechanism of inner IFMEC to control the interaction among magnetic,LSPR and magneto-optical properties in the magnetoplasmonic nanostructures would be elucidated by comparing the experimental results and the theoretical analyses of the magnetic and electric features by first-principles, the LSPR coupling and MOE by the numerical solution of Maxwell equations(e.g., DDA, SMM, FDTD). These studies would be critical to reveal the fundamental physical mechanism of IFMEC effects in hybrid nanostructures for the design and fabrication of active magnetoplasmonics for specific magnetic and optical properties. In addition, this project itself will develop a new efficient process to fabricate uniform hybrid nanomaterials at large scale.

混合纳米材料独特的物化性能主要由各层近邻耦合宏观量子效应制约。在由磁性层和贵金属层构建的纳米磁等离子体中表现为受各层特别是界面层制约的界面磁电耦合(IFMEC)效应，控制着其磁性、局域表面等离子共振(LSPR)和磁光效应间的耦合互动。目前大面积制备各层结构可控、规整可识的该类材料仍极具挑战，不易精确调控IFMEC效应，解析其调控磁性能、LSPR和磁光效应互动的机制，制约着其与信息、能源和生物医学等领域的交叉和应用。本课题开发模板转印和多级微窗口技术制备磁性层、贵金属层和界面层可调、规整可识的混合纳米材料。结合第一性原理和Maxwell方程组数值求解理论分析，重点研究结构参数对IFMEC的调控机理及其对磁性能、LSPR和磁光效应的影响，解析IFMEC调控磁性、LSPR和磁光效应耦合互动的物理机制，揭示磁等离子体在低光损耗下增强磁光效应的机理, 并为大面积可控制备规整混合纳米材料提供新方法。

本项目发展以多孔氧化铝（AAO）和纳米球为模板的模板辅助纳米转印新方法，发明纳米结构拓印复合新方法，大面积制备出异质结构纳米阵列（点、柱、线、孔、锥、漏斗）薄膜和嵌入到聚合物基板内的异质结构纳米阵列复合膜。实验和理论模拟（COMSOL、SMM、DDA、FDTD）相结合，对纳米结构异质薄膜的磁性、表面等离子体共振（SPR）、法布里-珀罗相干（FP-If）、磁光效应与特征尺寸（10-800nm）和形貌、各层组成和性质（如介电特性、导电率）等的相关性进行研究，揭示内在的自旋轨道耦合和界面磁电耦合效应。实验上率先发现了（1）SPR可大幅度提高纳米孔薄膜透光率、磁光克尔效应和铁磁性，多级结构（孔、球、帽）复合可大幅度提高薄膜光吸收率、拓宽吸收波段；（2）SPR层、磁性层及介电缓冲层灵活调节异质结构孔阵列薄膜的FP-If效应，缓冲层导电性对FP-If的强度、振幅和频段有独特影响；（3）纳米漏斗阵列磁性薄膜的逆磁光克尔旋转新现象，并具有孔径、各层组成、厚度依赖性，可通过结构参数对光极化方向灵活调控；（4）利用AAO模板特有的FP-If实现对磁光信号调控；(5)和纳米结构异质薄膜相比，核壳结构纳米颗粒磁性层和贵金属层间的超薄异质结的界面磁电耦合可产生新的SPR。分析发现：纳米孔可以增强磁畴旋转的钉扎效果和局域磁各向异性；贵金属的高导电性及其巡游电子和磁性层d电子在界面处具有强磁电耦合协同效应，大幅度提高薄膜垂直磁各向异性。理论上，首次根据自旋-轨道耦合理论和FP-If理论对具有垂直孔结构薄膜的磁光效应进行多重分析和计算，逆向磁光克尔旋转的理论计算和实验高度吻合。结果表明（1）多重反射和光学腔体效应对磁光信号具有调节作用，菲涅尔反射系数的相位跃变与克尔角的翻转是对应的；（2）磁光克尔角的翻转来源于多层薄膜多重光反射和光的干涉。本研究发表19篇SCI/EI论文，在写4篇；申请发明专利7个，获批6个；编著一部专著、受邀编辑另一部专著；获得一项省部级科技一等奖；培养毕业博士1名（联合）、硕士7名，在培3名博士和4名硕士。