Playing Legos with Nanocubes
Nature is a master user of self-assembly. Sophisticated, three-dimensional structures exist in our environment, which are shaped from solution at or near room temperature (RT). Similarly, the fabrication of high-quality and complex architectures by simple wet-chemistry and bottom-up assembly is envisioned by the nanoscience community for decades. This dissertation proposes the idea of using nanocubes as the smallest building blocks for structures. It is a common thread that runs across all the chapters. These colloidal blocks can be synthesized from solution with high control over size and shape. A generalized imprinting technique to pattern nanocubes in arbitrary shapes is discussed in the beginning. The process can be implemented by using only 3 components, namely, an elastomeric stamp, substrate, and the desired nanocube ink. Since the nanocubes have 6 chemically equivalent (100) faces, they are an excellent candidate for epitaxial connections. As a result, it is shown that if the face-to-face and angular alignment is perfect between adjacent cubes after imprinting, it can also yield perfect single crystals (with no dislocations or strain at the interface). Following this, curved crystals are fabricated at RT by solution overgrowth of silver (Ag) on Ag with a variable radius of curvature and curved supercrystals by the overgrowth of gold on Ag. Optically transparent electrodes via nanocube assembly and overgrowth are also demonstrated. Often, working devices are made up of multilayers (patterned and/or continuous close-packed) of various materials. Thus, it is shown that highly uniform and compact monolayers can be made using perovskite nanocubes simply by dropcasting. In conclusion, this work describes an entirely new substrate-independent approach to build monocrystalline matetrials from single-crystalline nanocubes.
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