[论文解读] Controlling morphology-structure of particles at different pulse rate, polarity and effect of photons on structure

Mubarak Ali, I‐Nan Lin|arXiv (Cornell University)|May 14, 2016

Gold and Silver Nanoparticles Synthesis and Applications参考文献 43被引用 29

一句话总结

本研究证明，在电子-光子-溶液界面过程中，脉冲频率、极性和光子照射量可精确调控胶体金纳米颗粒的形貌与结构。通过调节脉冲关断与开启时间的比例及极性，形成了包括三角形、伸长形和各向异性在内的多种形状；在最佳条件下，获得光滑、低长径比的结构，且光子照射增强了表面平整度。

ABSTRACT

Controlling the shape and structure of metallic colloids is an important topic. Here, different morphologies-structures of colloidal gold particles are investigated for different process parameters in a pulse-based electron-photon-solution interface process. Different tiny-shaped particles of gold are developed for different types of nano-energy. Depending on the set ratios of pulse OFF to ON times and pulse polarity, packets of nano-energy assemble largely transitional-state atoms of gold monolayer assembly in their own shapes. Tiny particles in joined triangular-shape are developed under appropriate set ratio of bipolar pulse OFF to ON time. At unipolar pulse, tiny particles of a triangular-shape are developed directly. When the ratio of bipolar pulse OFF to ON time was at large difference, distorted shapes of the particles developed. Geometric anisotropic shapes of particles developed under appropriate ratios of pulse OFF to ON times. When the ratio of bipolar pulse OFF to ON time was 3, particles get developed in low aspect ratio. But under the fraction of this ratio, particles get developed in high aspect ratio. For longer pulse ON time, structures of smooth elements get developed in width less than inter-spacing distance and travelling photons along interface flat them further. When elongated atoms of tiny particles deformed largely, they did not form structures of smooth elements even for the case of travelling photons along their interface. Morphology and structure of tiny particles, nanoparticles and particles are discussed for different process parameters opening multiple routes of materials research and their counterparts. This is the overall attained orientation of electrons for their elongated atoms forming colloidal particles of different size and shape, which maintains the certain color of solution under sunlight.

研究动机与目标

• 研究脉冲频率、极性和光子照射量如何影响胶体金颗粒的形貌与结构。
• 识别能生成特定纳米颗粒形状（如三角形或伸长形）的最优脉冲比（关断/开启）。
• 考察沿粒子-溶液界面传播的光子在平坦化粒子界面及促进光滑、低长径比结构形成中的作用。
• 理解原子级组装动力学与宏观光学性质（如溶液颜色）之间的关系。

提出的方法

• 采用基于脉冲的电子-光子-溶液界面过程，生成纳米能量包。
• 通过调节脉冲关断与开启时间的比例，控制过渡态金原子聚合成特定形状。
• 应用单极脉冲与双极脉冲模式，比较直接与振荡式原子组装机制。
• 监测沿粒子-溶液界面传播的光子对表面平坦化与结构平滑的影响。
• 基于脉冲参数设置，分析粒子结构的几何各向异性和长径比变化。
• 在阳光下观察所得胶体溶液的颜色，作为颗粒尺寸与形状分布的指示。

实验结果

研究问题

• RQ1 脉冲关断与开启时间比如何影响三角形与伸长形金纳米颗粒结构的形成？
• RQ2 脉冲极性（单极与双极）在引导金原子自组装成特定形貌中起什么作用？
• RQ3 沿粒子-溶液界面传播的光子如何影响表面光滑度与结构均匀性？
• RQ4 在双极脉冲配置中，粒子长径比与关断/开启脉冲比之间存在何种关系？
• RQ5 原子形变与能量包输送的变化如何影响胶体金最终的形貌与光学性质？

主要发现

• 在双极脉冲关断/开启比为3时，金纳米颗粒呈现出低长径比，表明其为致密、稳定的结构。
• 当关断/开启比降低至3以下时，纳米颗粒表现出高长径比，表明其为伸长、各向异性的形态。
• 当关断/开启比差异较大时，由于原子组装动力学不规则，出现扭曲的颗粒形状。
• 单极脉冲直接生成了三角形单元，表明其为形成对称纳米结构的直接路径。
• 沿界面传播的光子可使颗粒表面平坦化，当颗粒宽度小于间距时，促进形成光滑、低长径比的结构。
• 即使在光子照射下，严重形变的伸长原子仍无法形成光滑结构，表明结构弛豫存在极限。