超细超长半导体纳米线及其核壳结构的可控制备与关键问题研究

Ultrathin & ultralong semiconductor nanowires (USNWs) and their core-shell heterostructures are ideal building blocks for the next generation of optical and electronic devices due to their fascinating properties and functions. Unfortunately, this kind of material is hard to obtain by normal synthetic methods. This project is aimed to not only solve such challenge but also fully figure out the technical and theoretical issues existing in the preparation and coating of USNWs. To reach such goals, we plan to realize controlled synthesis and coating of USNWs by employing a novel oriented attachment-based synthesis method and successive ion absorption/exchange-based coating method,respectively. We also plan to elucidate the formation mechanism and growth characteristics of USNWs through answering the key questions associated with nanocrystal oriented assembly(such as interaction force between nanoparticles) and epitaxial growth(such as stress accumulation). Moreover, we still plan to find out new approach for modulating the optoelectronic properties of USNWs via exploring the correlation between their structures and their properties.This project is therefore of particular importance in better understanding of the anisotropic growth, controlled assembly and epitaxial coating of nanocrystals as well as in developing novel methods for synthesis and functionalization of nanomaterials. In our opinion, the main novelty of this project lies in it is able to afford a simple, controlled and high-yield method for synthesizing high-quality USNWS.

超细超长半导体纳米线及其核壳结构，具备许多新奇的性质和功能，是新一代光电子器件的理想构筑单元；然而该类材料很难通过常规方法获得。本项目以超细超长半导体纳米线为研究对象，着眼于解决其液相制备与核壳修饰方面的技术与理论难题，获得满足结构和性能要求的超细超长纳米线。为此，我们通过创建"取向定位组装"制备技术和"交替离子吸附/交换"包覆技术，来实现超细超长纳米线与其核壳结构的可控制备；通过解答"组装过程粒子间作用力"和"包覆过程界面应力"等核心问题，来揭示纳米线定位生长与外延包覆的内在规律与机制；通过探究纳米线性质与结构间的关联，来建立其光电性质的调控新方法。因此，本项目无论对完善晶体微观生长、组装以及包覆理论，还是对发展纳米材料制备与功能化新技术都具有重要意义。本项目最显著的创新在于开发了一种简便、可控、高产率制备超细超长半导体纳米线及其核壳结构的新方法与新工艺。

超细超长半导体纳米线及其核壳与掺杂结构，受益于超细的线径（小于5.0nm）和高度的结构各向异性（长径比通常大于100），具备许多新奇的物理化学性质和功能，是新一代光电器件的理想构筑单元；然而该类材料很难通过常规方法制备。本项目以超细超长半导体纳米线为研究对象，着眼于解决其液相制备、外延包覆、掺杂修饰中存在的技术与理论难题，获得满足结构和性能要求的高质量纳米线产品。为此，我们通过创建“配体辅助高温快速组装"和“压力诱导配体辅助低温慢速组装”两种合成策略，实现了多种超细超长金属硫属化合物半导体纳米线（线径可细至1.0nm,长径比可大于500）的液相可控制备；通过开发低温包覆与掺杂新工艺，在不改变纳米线模板尺寸特征条件下，实现了对多种超细纳米线的可控外延包覆与掺杂修饰。通过对纳晶定位组装过程和外延包覆过程进行连续监测并结合计算模拟，来解答“组装过程粒子间作用力”和“包覆过程界面应力”等核心问题，进而初步揭示了纳米线定位生长与外延包覆的内在规律与机制。系统考察了超长超细纳米线的光电性质与其物性特征参数（如直径、长度、包覆层组成与厚度、掺杂离子种类与数量等）之间的关联，建立了调控其光电性质的有效方法。所制备的超细纳米线被证实具备显著的线径和长度依赖的光学吸收、荧光发射、Raman散射以及光催化等特性，显示出在光探测、紫外光过滤、偏振发光、生物检测以及有机染料光解等方面的应用前景。因此，本项目无论对完善超微晶体生长、定位组装以及包覆理论，还是对发展一维超细纳米材料制备与功能修饰新技术，乃至对开拓纳米线材料功能应用都具有重要意义。本项目最大创新在于发现压力效应可作为一种通用驱动力推动纳晶自组装形成纳米线，据此所开发的制备方法具有较好的普适性，解决了超细纳米线合成难题。另一个创新点是，我们以超细纳米线为光活性材料，首次制备出具有多个光响应单元的“光致变色”薄膜，实现了对不同波段紫外光（UVA/UVB/ UVC）的可视化检测。