Shape-selective isolation of Au nanoplates from complex colloidal media by depletion flocculation

Abstract

Au nanoplates represent an emerging class of plasmonic nanostructures of anisotropy that are promising great performance as a probe in biosensing and a building block for nanodevices. In spite of the rapid development of solution-phase synthesis, it has remained an open challenge for colloidal chemists to prepare Au nanoplates in high yield established for their Ag counterparts. This limitation largely compromises the practical use of Au nanoplates in plasmonic applications. Here we report a simple yet versatile approach for efficient purification of Au nanoplates in diverse colloidal mixtures based upon micelle-induced depletion flocculation. By means of calculation on free energy change upon depletion flocculation, we are able to pre-determine the flocculation conditions of different nanoparticles, allowing for predictable nanoparticle precipitation that depends on size and shape. We further demonstrate that the present approach is capable of isolating Au nanoplates of varied sizes in low yield (<10%) in various complex media, including a polyvinylpyrrolidone (PVP)-based colloid solution and a quadruple nanoparticle mixture. This post-synthesis purification method that doesn’t rely on professional background suggests wide applicability in extraction of frontier nanostructures at low abundance yet in high demand.