Stepwise assembly of a cross-linked free-standing nanoparticle sheet with controllable shape. 
In this paper, we report a free-standing thin lamella consisting of nanoparticles with controllable shape.  A self-assembly technique is utilized to obtain this sheet in a step by step fashion with nanoparticles and polymer single crystals as the basic building blocks.  Inside the thin lamella, nanoparticles are not only immobilized on the surface of a polymer single crystal, which functions as a template, but also interconnected by a bifunctional crosslinker, i.e. 1,6-hexane dithiol.  As a consequence, the nanoparticle lamella is crosslinked and cannot be destructed by solvent and heat treatment.  This fabrication strategy is generally applicable and can be applied to a variety of different nanoparticles with various properties, including catalytically active platinum nanoparticles, superparamagnetic iron oxide nanoparticles or luminescent quantum dots, and different types of polymer single crystals, such as hexagonal polycaprolactone and square-shaped polyethylene glycol ones.  Based on the abundant properties originating from both nanoparticles and polymer single crystals, we have demonstrated that the resulting ensemble can function as recyclable catalytically active materials or magnetically responsive luminescent materials.