Filtration-assembling colloidal crystal templates for ordered macroporous nanoparticle films

Ordered macroporous nanoparticle thin films are achieved on porous substrates by combining ultrathin metal hydroxide nanostrands, colloidal crystal templates and the advantage of filtration technique. The preformed nanostrands layer plays two key roles for both uniform formation of hexagonal close-packed latex colloidal crystals on macroporous substrate and efficiently filling the interstitial voids of the colloidal crystal templates with nanoparticles. The stacking number of the colloids is simply controlled by the filtration volume. The uniformity of the film was guaranteed by the filtration process. After removing the latex templates and copper hydroxide nanostrand layer, free-standing ordered macroporous nanoparticle films were obtained. The robust free-standing gold nanoparticle films could be easily transferred onto various solid substrates and has potential application for electrodes, surface enhanced Raman detectors and catalyst. This method could be extended for the other ordered macroporous functional nanoparticle thin films.