An improved convective self-assembly method for the fabrication of binary colloidal crystals and inverse structures

We report an improved convective self-assembly method for the fabrication of highly ordered, crack-free binary colloidal crystals (BCCs) and the associated inverse structures in large domains at length scales of several centimeters. With this method, BCCs can be fabricated in a non-close packed pattern and binary inverse opal films can be obtained over a centimeter scale. The presence of tetraethyl orthosilicate (TEOS) sol in the self-assembly system was found to play a significant role in the resultant structures. The pseudostop band positions are adjustable via varying the number ratio of small to large polystyrene (PS) spheres. At a given TEOS-to-PS ratio, the binary inverse opal film thickness was controllable by varying the colloidal volume fraction with an upper thickness threshold (>16 layers).

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (206 K)Download as PowerPoint slideHighlights► Non-close packed binary colloidal crystals (BCCs) and binary inverse opals (BIOs). ► Crack-free BCCs and BIOs can be fabricated at length scales of several centimeters. ► The pseudostop band positions of BCCs and BIOs are adjustable. ► The film thickness was controllable by varying the colloidal volume fraction.