Hierarchical Nanostructures Constructed by Soft Epitaxial Self-Assembly of Organic-Inorganic Hybrid Giant Amphiphiles.

2D nanomaterials with ångström-scale thicknesses offer a unique platform for confining molecules at an unprecedentedly small scale, presenting novel opportunities for modulating material properties and probing microscopic phenomena. In this study, mesogen-tethered polyhedral oligomeric silsesquioxane (POSS) amphiphiles with varying numbers of mesogenic tails to systematically influence molecular self-assembly and the architecture of the ensuing supramolecular structures, are synthesized. These organic-inorganic hybrid amphiphiles facilitate precise spatial arrangement and directional alignment of the primary molecular units within highly ordered supramolecular structures. The correlation between molecular design and the formation of superlattices through comprehensive structural analyses, incorporating molecular thermodynamics and kinetics, is explored. The distinct intermolecular interactions of the POSS core and the mesogenic tails drive the preferential formation of a 2D inorganic sublattice while simultaneously guiding the hierarchical assembly of organic lamellae via soft epitaxy. The findings reveal the intricate balance between shape, size, and interaction strengths of the inorganic and organic components, and how these factors collectively influence the structural hierarchy of the superstructures, which consist of multiple sublattices. By controlling this unique molecular behavior, it is possible to modulate or maximize the anisotropy of optical, mechanical, and electrical properties at the sub-nanometer scale for nanotechnology applications.

Liquid Metal Grid Patterned Thin Film Devices Toward Absorption-Dominant and Strain-Tunable Electromagnetic Interference Shielding.

The demand of high-performance thin-film-shaped deformable electromagnetic interference (EMI) shielding devices is increasing for the next generation of wearable and miniaturized soft electronics. Although highly reflective conductive materials can effectively shield EMI, they prevent deformation of the devices owing to rigidity and generate secondary electromagnetic pollution simultaneously. Herein, soft and stretchable EMI shielding thin film devices with absorption-dominant EMI shielding behavior is presented. The devices consist of liquid metal (LM) layer and LM grid-patterned layer separated by a thin elastomeric film, fabricated by leveraging superior adhesion of aerosol-deposited LM on elastomer. The devices demonstrate high electromagnetic shielding effectiveness (SE) (SET of up to 75 dB) with low reflectance (SER of 1.5 dB at the resonant frequency) owing to EMI absorption induced by multiple internal reflection generated in the LM grid architectures. Remarkably, the excellent stretchability of the LM-based devices facilitates tunable EMI shielding abilities through grid space adjustment upon strain (resonant frequency shift from 81.3 to 71.3 GHz @ 33% strain) and is also capable of retaining shielding effectiveness even after multiple strain cycles. This newly explored device presents an advanced paradigm for powerful EMI shielding performance for next-generation smart electronics.

Polarization-Dependent Thin Films with Biaxial Anisotropic Absorption Constructed by a Single Coating and Subsequent Topochemical Polymerization of Chromophores.

For the construction of hierarchical superstructures with biaxial anisotropic absorption, a newly synthesized diacetylene-functionalized bipyridinium is self-assembled to use an electron-accepting host for capturing and arranging guests. The formation of the donor-acceptor complex triggers an intermolecular charge transfer, leading to chromophore activation. Polarization-dependent multichroic thin films are prepared through a sequential process of single-coating, self-assembly, and topochemical polymerization of host-guest chromophores. Molecular packing structures constructed in the single-layer optical thin film possess orthogonal absorption axes for two different wavelengths. By tuning the linear polarization angle, the color of the optical thin film can be intentionally controlled. This single-layered multichroic film provides a new pathway for the development of anticounterfeiting and multiplexing encryptions.

Photochemically and Thermally Programmed Optical Multi-States from a Single Diacetylene-Functionalized Cyanostilbene Luminogen.

To develop advanced optical systems, many scientists have endeavored to create smart optical materials which can tune their photophysical properties by changing molecular states. However, optical multi-states are obtained usually by mixing many dyes or stacking multi-layered structures. Here, multiple molecular states are tried to be generated with a single dye. In order to achieve the goal, a diacetylene-functionalized cyanostilbene luminogen (DACSM) is newly synthesized by covalently connecting diacetylene and cyanostilbene molecular functions. Photochemical reaction of cyanostilbene and topochemical polymerization of diacetylene can change the molecular state of DACSM. By thermal stimulations and the photochemical reaction, the conformation of polymerized DACSM is further tuned. The synergetic molecular cooperation of cyanostilbene and diacetylene generates multiple molecular states of DACSM. Utilizing the optical multi-states achieved from the newly developed DACSM, switchable optical patterns and smart secret codes are successfully demonstrated.

Suppressing Redox Reactions at the Perovskite-Nickel Oxide Interface with Zinc Nitride to Improve the Performance of Perovskite Solar Cells.

For p-i-n perovskite solar cells (PSCs), nickel oxide (NiOx) hole transport layers (HTLs) are the preferred interfacial layer due to their low cost, high mobility, high transmittance, and stability. However, the redox reaction between the Ni≥3+ and hydroxyl groups in the NiOx and perovskite layer leads to oxidized CH3NH3 + and reacts with PbI in the perovskite, resulting in a large number of non-radiative recombination sites. Among various transition metals, an ultra-thin zinc nitride (Zn3N2) layer on the NiOx surface is chosen to prevent these redox reactions and interfacial issues using a simple solution process at low temperatures. The redox reaction and non-radiative recombination at the interface of the perovskite and NiOx reduce chemically by using interface modifier Zn3N2 to reduce hydroxyl group and defects on the surface of NiOx. A thin layer of Zn3N2 at the NiOx/perovskite interface results in a high Ni3+/Ni2+ ratio and a significant work function (WF), which inhibits the redox reaction and provides a highly aligned energy level with perovskite crystal and rigorous trap-passivation ability. Consequently, Zn3N2-modified NiOx-based PSCs achieve a champion PCE of 21.61%, over the NiOx-based PSCs. After Zn3N2 modification, the PSC can improve stability under several conditions.

Self-Assembled and Polymerized Hierarchical Nanostructure Films of Cyanostilbene-Based Reactive AIEgens for Smart Chemosensors.

For the development of acid-responsive advanced fluorescent films with a 2D nanostructure, a pyridyl cyanostilbene-based AIEgen (PCRM) is newly synthesized. The synthesized PCRM exhibits aggregation-induced emission (AIE) and responds reversibly to acid and base stimuli. To fabricate the nanoporous polymer-stabilized film, PCRM and 4-(octyloxy)benzoic acid (8OB) are complexed in a 1:1 ratio through hydrogen bonding. The PCRM-8OB complex with a smectic mesophase is uniaxially oriented at first and photopolymerized with a crosslinker. By subsequently removing 8OB in an alkaline solution, nanopores are generated in the self-assembled and polymerized hierarchical 2D nanostructure film. The prepared nanoporous fluorescent films exhibit not only the reversible response to acid and base stimuli but also mechanical and chemical robustness. Since the nanoporous fluorescent films have different sensitivities to trifluoroacetic acid (TFA) depending on the molecular orientation in the film, advanced acid vapor sensors that can display the risk level according to the concentration of TFA are demonstrated. Reactive AIEgens-based hierarchical nanostructure films with nanopores fabricated by a subsequent process of self-assembly, polymerization, and etching can open a new door for the development of advanced chemosensors.