The fabrication of molecular structures with a desired morphology, e.g., nanotubes, nanoribbons, nanosprings, and sponges, is essential for the advancement of nanotechnology. Unfortunately, realization of this objective is expensive and complicated. Here, we report that irradiating a film comprising azobenzene derivatives with UV light produces oriented arrays of helical nanofilaments via the photoisomerization-induced Weigert effect. As a result, structural colors are observed due to the extrinsic chiral reflection in the visible wavelength range, and the reflected color can be tuned by adjusting the molecular length of the azobenzene derivative. This simple fabrication method can be used for fabricating large, reversible, and patternable color reflectors, providing a new platform for interference-based structural coloration as it exists in nature, such as morpho butterflies, green-winged teal, and various beetles.

Electron donor (D)-acceptor (A)-type conjugated polymers (CPs) have emerged as promising semiconductor candidates for organic field-effect transistors. Despite their high charge carrier mobilities, optimization of electrical properties of D-A-type CPs generally suffers from complicated post-deposition treatments such as high-temperature thermal annealing or solvent-vapor annealing. In this work, we report a high-mobility diketopyrrolopyrrole-based D-A-type CP nanowires, self-assembled by a simple but very effective solvent engineering method that requires no additional processes after film deposition. In situ grown uniform nanowires at room temperature were shown to possess distinct edge-on chain orientation that is beneficial for lateral charge transport between source and drain electrodes in FETs. FETs based on the polymer nanowire networks exhibit impressive hole mobility of up to 4.0 cm V s. Moreover, nanowire FETs showed excellent operational stability in high temperature up to 200 °C because of the strong interchain interaction and alignment.

Detecting the chirality of material is very important in material science, chemistry, pharmacology, and biomaterial science because it is useful for identifying and discarding unintended side effects. Here, directly visualized is the optical activity of chiral samples using an orientation‐controlled helical nanofilament (HNF, B4) liquid crystal (LC) phase made of achiral bent‐shaped molecules. The vertical orientation of the HNFs is induced by shining unpolarized UV light. Right‐ or left‐handed domains of the HNFs are formed because of the lack of molecular chirality, each single‐handed domain is large enough to be seen with the naked eye, up to ≈several mm2. The periodic arrays of aligned HNFs reflect a specific color, here green, due to the Bragg reflection. Such a reflector enables an easy detection of optical activity of a sample placed on it. The device is tested with naturally chiral substances, like fructose and glucose, which exhibit opposite sense of optical activity, as well as with structurally chiral nematic LC phase and reveals high sensitivity of a detection.

The color change of photonic crystal (PC) has been widely studied due to its beauty and anti-counterfeiting purpose. Here we demonstrated security codes based on chiral PCs that are not...