Colloidal Self‐Assembly Meets Nanofabrication: From Two‐Dimensional Colloidal Crystals to Nanostructure Arrays

Self‐assembly of colloidal microspheres or nanospheres is an effective strategy for fabrication of ordered nanostructures. By combination of colloidal self‐assembly with nanofabrication techniques, two‐dimensional (2D) colloidal crystals have been employed as masks or templates for evaporation, deposition, etching, and imprinting, etc. These methods are defined as “colloidal lithography”, which is now recognized as a facile, inexpensive, and repeatable nanofabrication technique. This paper presents an overview of 2D colloidal crystals and nanostructure arrays fabricated by colloidal lithography. First, different methods for fabricating self‐assembled 2D colloidal crystals and complex 2D colloidal crystal structures are summarized. After that, according to the nanofabrication strategy employed in colloidal lithography, related works are reviewed as colloidal‐crystal‐assisted evaporation, deposition, etching, imprinting, and dewetting, respectively.     

Self‐Assembly Approaches to Three‐Dimensional Photonic Crystals

A brief review of the historical development of photonic bandgap (PBG) materials is provided and the fabrication methods employed are discussed with emphasis on self‐assembly processes. The factors influencing the generation of a complete bandgap, from both an experimental and a calculational standpoint are then presented and discussed. The Figure shows a diamond‐like 3D periodic structure.     

Inside Front Cover: Line Defects Embedded in Three‐Dimensional Photonic Crystals (Adv. Mater. 15/2005)

The inside cover illustrates an approach to creating line defects embedded in the interior of a self‐assembled photonic crystal, as reported by Zhao and co‐workers on p. 1917. Photoresist patterns are first constructed on the surface of a silica opal film by conventional optical photolithography. After regrowth of the silica colloidal crystal, photoresist line defects are successfully introduced into the self‐assembled silica colloidal crystal. Further processing results in an inverse opal with air‐core line defects embedded in its interior, which provides a prototype for future optical waveguide devices based on self‐assembled three‐dimensional photonic crystals.     

Perfecting Imperfection—Designer Defects in Colloidal Photonic Crystals

Current progress in the exciting and burgeoning field of functional defects in colloidal photonic crystals (CPCs) is reported. After a brief introduction into the importance and nature of defects in CPCs the state‐of‐the‐art in fabricating point, line, and planar defects is described. Measurement and characterization techniques as well as the corresponding theory are discussed. Besides normal, passive defects, the recent development of reversibly tunable defects adds important functionality. In particular, the addition of chemical functionality is demonstrated to open a path to a wide range of color readout devices for ultrasensitive optical detection of biomolecules and pharmaceuticals.