基于时空整形超快激光液相剥离的单层量子点快速绿色可控制备

Novel monolayer quantum dots (QDs) exfoliated from layered materials (such as transition metal dichalcogenides, graphite, black phosphorus and so on) have become frontier and hotspot in nanomanufacturing and nanomaterials, indicating important potential applications in electrocatalytic hydrogen evolution, bio-imaging, energy storage, gas sensing, optoelectronic devices, etc. However, the present preparation methods may suffer from long time consuming, introduction of metal ion impurities or contaminations from chemical reagent, etc. In this project, we propose novel methods and mechanisms to prepare monolayer quantum dots by using temporally and spatially shaped ultrafast laser ablation of layered materials in liquids, including the following aspects: (1) To unravel the effect and mechanism of the ultrafast laser induced interlayer Coulomb repulsion on the exfoliation of monolayer materials. The controlling mechanism of temporally and spatially shaped ultrafast laser on the localized transient electron dynamics, phase transformation process and formation of quantum dots will be revealed. (2) We propose the combination of both techniques of ultrafast pulse train and circular flat-topped pulse, in order to adjust localized transient electron density slightly higher than the critical density, and induce nonthermal phase transformation to control the preparation of monolayer quantum dots. Furthermore, we propose to combine temporally and spatially shaped ultrafast laser and sonication liquid exfoliation or electrochemical methods. The above novel methods are expected to prepare quantum dots based on electron dynamics control, with much reduced preparation duration, green process without contamination, for a wide range of layered materials. (3) To apply the proposed novel methods and mechanisms in the fabrication of nanostructures and performance optimization in both electrocatalytic hydrogen evolution and bio-imaging, which will provide basic manufacturing techniques for the above areas.

层状材料（包括过渡金属硫化物、石墨、黒磷等）剥离而成的新型单层量子点，是纳米制造和纳米材料的前沿热点，在催化产氢、生物成像、能源存储、气体传感、光电器件等领域具有重要应用前景。然而现有制备方法受限于所需时间较长、引入金属离子杂质、化学试剂污染等。本项目提出基于时空整形超快激光液相剥离的单层量子点制备新方法及理论，包括：（1）探索超快激光诱导层间库仑排斥对层状材料单层剥离的影响机制，揭示时空整形超快激光对局部瞬时电子动态、材料相变以及量子点形成的控制规律；（2）提出结合超快脉冲序列和圆形平顶脉冲等，调控局部瞬时电子密度略高于临界密度，产生非热相变以控制量子点制备，并复合整形激光与超声液相剥离、电化学方法，有望从电子层面可控制备单层量子点、显著缩短制备时长、绿色/无污染、材料适用范围广；（3）将所提新方法与理论应用于电催化产氢和生物成像中典型纳米结构加工及性能优化，为上述领域提供关键制造支撑。

一、主要进展.单层量子点的形成机理和可控制备不仅具有深远的理论意义，而且因其在催化产氢、能源存储等应用前景而具有重要的实际意义。本项目围绕时空整形超快激光液相剥离的单层量子点快速绿色可控制备开展研究，取得如下成果：.1）在制造机理方面.基于含时密度泛函理论，揭示了飞秒激光烧蚀层状材料制备单层量子点的光剥离机理；揭示了飞秒激光诱导溶剂化电子产生及其对后续子脉冲能量的增强吸收机制。.2）在制造方法方面.提出了基于时空整形超快激光液相剥离的单层量子点快速绿色可控制备方法，量子点纯度高、粒径和结构可控，包括：i）时域整形飞秒激光液相烧蚀制备MoS2/WS2/VS2/石墨烯量子点，实现了平均粒径2.6nm、厚度小于1nm的MoS2单层量子点等制备；ii）通过设计飞秒激光空间光场分布将高斯脉冲点聚焦拓展为线聚焦可控制备了平均粒径3.2nm、厚度约1.2nm的强耦合MoS2/N-rGO量子点异质结构；iii）电场辅助时域整形飞秒激光可控制备了平均粒径2-3nm孪晶石墨烯量子点，电场诱导纳米颗粒定向运动并控制其碰撞结晶，是形成孪晶量子点的关键；iv）飞秒脉冲序列结合贝塞尔激光液相烧蚀制备MXene量子点，产率达65.89wt%。.3）在应用方面.制备了多种纳米粒子/量子点及其异质结构，调控了材料活性边缘和荧光特性，实现了电催化产氢和低浓度检测等应用。包括：i）电催化产氢：MoS2量子点，Tafel斜率66mV/dec（添加碳黑后47mV/dec）,开启电势0.14V；a-MoSx纳米粒子，Tafel斜率40mV/dec,开启电势0.105V；MoS2/N-rGO量子点异质结构，Tafel斜率39mV/dec,开启电势0.097V；ii）低浓度检测：(Ag,Pt)-MoS2复合结构，浓度检测极限低至10^-11M。.二、研究成果.（1）在Advanced Materials、Advanced Functional Materials、Nature Communications等主流期刊发表/接收SCI论文12篇（1篇接收且First published），《中国激光》特邀综述论文1篇，国际会议keynote报告2次；.（2）申请发明专利4项；.（3）项目负责人获批国家自然科学基金优秀青年科学基金资助；.（4）培养“博新计划”博士后1名、博士生7名（含北理优博1名）。