RESUMO
Colloidal self-assembly allows rational design of structures on the micrometer and submicrometer scale. One architecture that can generate complete three-dimensional photonic bandgaps is the diamond cubic lattice, which has remained difficult to realize at length scales comparable with the wavelength of visible or ultraviolet light. In this work, we demonstrate three-dimensional photonic crystals self-assembled from DNA origami that act as precisely programmable patchy colloids. Our DNA-based nanoscale tetrapods crystallize into a rod-connected diamond cubic lattice with a periodicity of 170 nanometers. This structure serves as a scaffold for atomic-layer deposition of high-refractive index materials such as titanium dioxide, yielding a tunable photonic bandgap in the near-ultraviolet.
RESUMO
Liquid phase assembly is among the most industrially attractive routes for scalable carbon nanotube (CNT) processing. Chlorosulfonic acid (CSA) is known to be an ideal solvent for CNTs, spontaneously dissolving them without compromising their properties. At typical processing concentrations, CNTs form liquid crystals in CSA; however, the morphology of these phases and their concentration dependence are only qualitatively understood. Here, we use small-angle neutron scattering (SANS), combined with polarized light microscopy and cryogenic transmission electron microscopy to study solution morphology over a range of concentrations and two different CNT lengths. Our results show that at the highest concentration studied the long CNTs form a highly ordered fully nematic phase, while short CNTs remain in a biphasic regime. Upon dilution, long CNTs undergo a 2D lattice expansion, whereas short CNTs seem to have an intermediate expansion between 2D and 3D probably due to the biphasic nature of the system. The average spacing between the CNTs scaled by the CNT diameter is the same in both systems, as expected for infinitely long aligned rods.