Santhanam Venugopal, Liu Jia, Agarwal Rajan, Andres Ronald P
School of Chemical Engineering, Purdue University, West Lafayette, Indiana 47907.
Langmuir. 2003 Sep 16;19(19):7881-7887. doi: 10.1021/la0341761.
Five nanometer diameter gold particles encapsulated by alkanethiol molecules have been self-assembled into well-ordered monolayers on a water surface, and these nanoparticle films have been transferred intact onto various solid substrates. The method involves spreading a thin layer of an organic solvent containing the gold nanoparticles on a water subphase that has a controlled surface curvature. As the solvent evaporates, a nanoparticle monolayer free of microscopic cracks and voids nucleates at the center of the apparatus and grows radially outward until it covers practically the entire water surface. This monolayer is transferred from the water surface to a polydimethylsiloxane (PDMS) stamp pad by the Langmuir-Schaefer (LS) technique and is applied to the solid substrate by microcontact printing (μCP). Uniform centimeter-scale films have been produced with this method. The quality of the transferred films has been verified by transmission electron microscopy (TEM). The nanoparticle monolayer is a hexagonal close-packed array with a center-to-center spacing that is approximately equal to the sum of the diameter of the gold particles and twice the height of a self-assembled monolayer (SAM) of the alkanethiol molecules on Au(111). The transferred films are free of multilayer regions and of microscopic voids and grain boundaries over their entire area and exhibit crystalline order across the openings in the TEM grid (∼4000 μm).
由链烷硫醇分子包裹的直径为5纳米的金颗粒已在水表面自组装成有序的单分子层，并且这些纳米颗粒薄膜已完整地转移到各种固体基质上。该方法包括在具有可控表面曲率的水亚相上铺展一层含有金纳米颗粒的有机溶剂薄层。随着溶剂蒸发，在装置中心形成一个没有微观裂纹和空隙的纳米颗粒单分子层，并径向向外生长，直到几乎覆盖整个水表面。通过朗缪尔-谢弗（LS）技术将该单分子层从水表面转移到聚二甲基硅氧烷（PDMS）印章垫上，并通过微接触印刷（μCP）施加到固体基质上。用这种方法制备了均匀的厘米级薄膜。通过透射电子显微镜（TEM）验证了转移薄膜的质量。纳米颗粒单分子层是一种六方密堆积阵列，其中心间距大约等于金颗粒的直径与在Au(111)上链烷硫醇分子自组装单分子层（SAM）高度的两倍之和。转移后的薄膜在其整个区域内没有多层区域、微观空隙和晶界，并且在TEM网格的开口（约4000μm）上呈现出晶体有序性。
