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A diarylethene-based zwitterionic molecule (DZM) is newly synthesized for the development of smart films exhibiting reversible color change and switchable ionic conductivity in response to external light stimuli. This dual molecular building block is constructed through zwitterionic interlocking and strong phase separation between the dendron-shaped aliphatic tails and the diarylethene head. Uniaxial shear coating and molecular self-assembly result in anisotropically oriented nanostructures, which are further solidified through photopolymerization. In the absence of zwitterionic interlocking, DZM fails to form ordered structures and remains disordered. The anisotropically oriented nanostructures of DZM exhibit polarization-dependent photochromic properties despite the inherent low anisotropy of a single diarylethene chromophore. Structural analysis reveals that the zwitterion-interlocked molecular building block self-assemble into nanocolumns that align uniaxially during the shear coating process. Alternating ultraviolet and visible light reversibly switches the ionic conductivity of the DZM thin film and a change in color is observed due to the photoisomerization of the diarylethene chromophore. Utilizing the polarization-dependent photochromic properties, light-sensitive smart thin films are demonstrated with potential applications in anti-counterfeiting labels and sensors., (© 2024 Wiley‐VCH GmbH.)

Nanoparticle clusters provide new degrees of freedom for light control due to their mutual interaction compared with an individual one. Here, the authors demonstrate theoretically and experimentally a type of optical anapole (a nonradiating state) termed as extrinsic anapole, with mode field spreading across Si nanodisk dimers unlike the intrinsic one that is confined within individual nanodisks. The extrinsic anapole is sensitive to the polarized excitation. When the electric vector E of excitation is perpendicular to the dimer axis, the coupled toroidal dipole (TD) mode is largely enhanced and broadened to be spectrally overlapped with the electric dipole (ED) mode. The destructive interference of these two modes results in the generation of the extrinsic anapole. However, it vanishes when E is parallel to the dimer axis. Such polarization dependence can be relieved with the participation of the third nanodisk. Scattering spectra of Si nanodisk trimers stay almost unchanged under different polarized excitations, although the near-field distributions are quite different. Finally, enhanced white-light emission is observed in Si nanodisk clusters, which can be attributed to the near-infrared absorption enhancement induced by extrinsic anapole states. The findings manifest that high-index all-dielectric nanodisk clusters are promising for light manipulation based on mode interference., (© 2022 Wiley-VCH GmbH.)

The development of smart inks that change color and transparency in response to external stimuli is very important for various fields, from modern art to safety and anticounterfeiting technology. A uniaxially oriented diacetylene thin film on a macroscopic area is obtained by coating, self-assembling and topochemical photopolymerizing of imidazolium-functionalized diacetylenes (M-DA and T-DA) and 4,6-decadiyne ink (70 wt%:20 wt%:10 wt%) exhibiting a lyotropic smectic A liquid-crystalline phase at room temperature. The color and transparency of letters and symbols written with the DA-based secret inks change reversibly from blue to red as well as from colorless transparent to black opaque depending on the temperature and polarization axis. A secret code written with thermoresponsive and polarization-dependent secret inks consisting of imidazolium-functionalized diacetylenes is successfully deciphered by wearing polaroid glasses and holding a burning torch., (© 2020 Wiley-VCH GmbH.)

A micro-spectroscopic method has been developed to probe the accessibility of zeolite crystals using a series of fluorescent 4-(4-diethylaminostyryl)-1-methylpyridinium iodide (DAMPI) probes of increasing molecular size. Staining large zeolite crystals with MFI (ZSM-5) topology and subsequent mapping of the resulting fluorescence using confocal fluorescence microscopy reveal differences in structural integrity: the 90° intergrowth sections of MFI crystals are prone to develop structural imperfections, which act as entrance routes for the probes into the zeolite crystal. Polarization-dependent measurements provide evidence for the probe molecule's alignment within the MFI zeolite pore system. The developed method was extended to BEA (Beta) crystals, showing that the previously observed hourglass pattern is a general feature of BEA crystals with this morphology. Furthermore, the probes can accurately identify at which crystal faces of BEA straight or sinusoidal pores open to the surface. The results show this method can spatially resolve the architecture-dependent internal pore structure of microporous materials, which is difficult to assess using other characterization techniques such as X-ray diffraction., (© 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

The atomic-scale origin of the unusually high performance and long-term stability of wurtzite p-GaN oriented nanowire arrays is revealed. Nitrogen termination of both the polar (0001¯) top face and the nonpolar (101¯0) side faces of the nanowires is essential for long-term stability and high efficiency. Such a distinct atomic configuration ensures not only stability against (photo) oxidation in air and in water/electrolyte but, as importantly, also provides the necessary overall reverse crystal polarization needed for efficient hole extraction in p-GaN., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)