以Langmuir-Blodgett 及自組裝技術製備奈米粒子單分子層薄膜及其在超疏水表面之應用

Nanoparticulate monolayers were prepared by using Langmuir-Blodgett and self-assembly techniques and used for superhydrophobic surface application. Langmuir monolayers of octadecylamine (ODA), octadecylthiol (ODT), and mixed ODA/ODT at air/liquid interface were used as template layers to adsorb gold nanoparticles (AuNPs) dispersed in the subphase. Furthermore, the adsorption of AuNPs was also enhanced by the destabilization effect of ethanol introduced into the colloidal solution. The monolayer not only acts as a template layer to incorporate AuNPs but also as a capping agent to in-situ modify the adsorbed NPs, providing van der Waals interaction among NPs for self-organization into ordered domains. The behaviors of the monolayers were studied using the pressure-area (π-A) isotherms, hysteresis and relaxation curves, and the observations of transmission electron microscopy (TEM) and Brewster angle microscope (BAM). For the ODA/AuNPs and ODT/AuNPs systems, the results indicated that ODA monolayer has a much higher ability, than the ODT monolayer, in incorporation AuNPs, attributed to the electrostatic interaction between ODA and AuNPs. By using ODA monolayer with appropriate molecular density, as well as the adjusting of the ethanol concentration, a close-packed particulate film of AuNPs can be prepared through the monolayer compression. The results also show that over loading of the ODA molecules increases the fractional ratio of free ODA molecules at the interface which obstructs the coalescence of particulate domains and, therefore, a close-packed particulate monolayer cannot be approached. The presence of ethanol in the subphase not only enhances the particle adsorption to the interface but also triggers a more expanded ODA monolayer, which plays a key role in preparing a close-packed particulate monolayer. For the mixed ODA/ODT systems, the incorporation of AuNPs was mainly performed by ODA molecules through the electrostatic interaction, while the specific affinity of ODT molecules to the AuNPs plays a role to increase the density of capping agents on an AuNPs, leading to a higher van der Waal interaction among NPs for self-organization into ordered domains. The experimental results showed that the utilization of the mixed ODA/ODT monolayer can improve the stability of AuNPs incorporated at the air/liquid interface and is helpful to the formation of an AuNPs particulate film with close-packed and ordered structure. For the application of particulate thin films on surperhydrophobic surface, a micro/nano dual-scale particulate film with raspberry-like morphology was prepared by using LB deposition and electrostatic layer-by-layer (ELBL) technique. Micro-size silica particles were used to prepare a surface with microscale roughness. Nano-size silica particles were then assembled on the particulate film to construct a finer structure on top of the coarse one. The as-deposited particulate films were surface-modified with alkylsilane to render a surface with surperhydropboic property. The advancing and receding contact angles of water on the dual-size structured surface were 169o and 165o, respectively. The scale ratio of the micro/nano surface structure and the regularity of the particulate films on the superhydrophobic surface performance are discussed.