Transfer of ordered nanoparticle array and its application in high-modulus membrane fabrication

This work has developed a method to transfer a nanoparticle array from the parent substrate to the target surface. A close-packed and ordered Au nanoparticle (Au NP) array has been successfully transferred using poly(lactic acid) (PLA) as the mediator. For the transfer, the last step, i.e. removing the PLA mediator, plays a crucial role. The commonly-used dissolution of PLA in organic solvents cannot maintain array integrity. In this study, we have introduced wedging to peel off the PLA mediator. Relative to dissolution, wedging is a mild procedure and able to meet the requirement of transferring the vulnerable nanoparticle array. The Au NP arrays before and after transfer were thoroughly characterized by optical microscopy, TEM and SAXS. All the experimental results proved that the structure of the array was well preserved after transfer, at both the macroscopic and microscopic scales. Further, the transfer method was combined with layer-by-layer (LbL) self-assembly to fabricate a freestanding nanoparticle-array-sandwiched membrane. In the polymer/nanoparticle nanocomposite membrane, the nanoparticles were arranged in a close, ordered and single-layer way, which is hardly achieved by in situ LbL self-assembly. The distinct architecture endows the membrane with excellent mechanical properties. Buckling instability testing exhibited that the modulus of the transfer membrane is four times higher than that of the LbL analogues. This exploration indicates an efficient way to manipulate two-dimensional nanoparticle structures, enabling them to fulfill their true potential.