Homogeneously Oriented Organic Single-Crystalline Patterns Grown by Microspacing In-Air Sublimation.

Fabrication of single-crystalline organic semiconductor patterns is of key importance to enable practical applications. However due to the poor controllability on nucleation locations and the intrinsic anisotropic nature of single-crystals, growth of single-crystal patterns with homogeneous orientation is a big challenge especially by the vapor method. Herein a vapor growth protocol to achieve patterned organic semiconductor single-crystals with high crystallinity and uniform crystallographic orientation is presented. The protocol relies on the recently invented microspacing in-air sublimation assisted with surface wettability treatment to precisely pin the organic molecules at desired locations, and inter-connecting pattern motifs to induce homogeneous crystallographic orientation. Single-crystalline patterns with different shapes and sizes, and uniform orientation are demonstrated exemplarily by using 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT). Field-effect transistor arrays fabricate on the patterned C8-BTBT single-crystal patterns show uniform electrical performance: a 100% yield with an average mobility of 6.28 cm2  V-1  s-1 and in a 5 × 8 array. The developed protocols overcome the uncontrollability of the isolated crystal patterns in vapor growth on non-epitaxial substrates, making it possible to align the anisotropic electronic nature of single-crystal patterns in large-scale devices integration.

A processable, scalable, and stable full-color ultralong afterglow system based on heteroatom-free hydrocarbon doped polymers.

Although room-temperature phosphorescence (RTP) organic materials are a widely-studied topic especially popular in recent decades, long-lived RTP able to fulfil broad time-resolved application requirements reliably, are still rare. Polymeric materials doped with phosphorescent chromophores generally feature high productivity and diverse applications, compared with their crystalline counterparts. This study proves that pure polycyclic aromatic hydrocarbons (PAHs) may even outperform chromophores containing hetero- or heavy-atoms. Full-color (blue, green, orange and red) polymer-PAHs with lifetimes >5000 ms under ambient conditions are constructed, which provide impressive values compared to the widely reported polymer-based RTP materials in the respective color regions. The polymer-PAHs could be fabricated on a large-scale using various methods (solution, melt and in situ polymerization), be processed into diverse forms (writing ink, fibers, films, and complex 3D architectures), and be used in a range of applications (anti-counterfeiting, information storage, and oxygen sensors). Plus their environmental (aqueous) stability makes the polymer-PAHs a promising option to expand the portfolio of organic RTPs.

Anisotropic Performance of High-Quality MAPbBr3 Single-Crystal Wafers.

It has been proved that bulk single crystals of a halide perovskite behave much better than its polycrystalline counterparts in multiple application scenarios. Thus, the growth of large-sized and high-quality single crystals is significant to guarantee their ultimate device performances. Here, based on our recently invented settled temperature and controlled antisolvent diffusion system, improvements achieved in this work include the following: (1) We modified the growth system to optimize the control over both mass and heat transport to alleviate defect formation. State-of-the-art-quality MAPbBr3 crystals were grown, and from the bulk crystals, differently oriented crystalline wafers were fabricated with the full width at half-maximum of X-ray rocking curves of 40-86 arcsec. (2) The optical band gaps revealed no anisotropy on differently oriented wafers, whereas the refractive index and extinction coefficient exhibited obvious anisotropy. (3) Angle-resolved polarized Raman spectra demonstrate distinct in-plane anisotropy on (100) and (110) wafers but not on the (111) wafer. The equilibrium MA+ orientations are deduced to adopt the <111> direction with the antiparallel MA+ orientation between adjacent domains. (4) Radiation detectors fabricated on differently oriented wafers proved photoresponse anisotropy to both visible and X-ray radiation, following a general order of (100) > (110) > (111). Because anisotropy is an inevitable issue for various applications employing crystalline materials, this study, based on the clarification of the debatable intrinsic dipole configuration in the pseudocubic crystal lattice, will provide quantitative information on physicochemical property anisotropy and subsequently facilitate optimization of device performance referring to crystal orientations of halide perovskite crystals.

Identification and biological evaluation of natural product Biochanin A.

Natural products have shown promise for epigenetic modulations and thus are therapeutically potential for cancer prevention and treatment. In this work, we report the identification of natural product Biochanin A as a new LSD1 inhibitor and further biological evaluation in gastric MGC-803 cells. Biochanin A effectively and reversibly inhibited LSD1 (IC50 = 2.95 µM) and showed selective inhibition to LSD1 over MAO-A/B. In gastric MGC-803 cells, Biochanin A induced accumulation of H3K4me1/2, inhibited cell growth moderately (IC50 = 6.77 µM), but was less toxic to normal GES-1 (IC50 > 32 µM). Mechanistic studies showed that Biochanin A suppressed colony formation, cell apoptosis, and migration of MGC-803 cells. This study may help to elucidate the anticancer mechanisms of Biochanin A.

1D versus 2D cocrystals growth via microspacing in-air sublimation.

Organic cocrystals possess valuable properties owing to the synergistic effect of the individual components. However, the growth of molecular cocrystals is still in its primary stage. Here we develop a microspacing in-air sublimation method to grow organic cocrystals, and furthermore to realize morphology control on them, which is essential for structure-property relations. A series of polycyclic aromatic hydrocarbon (PAH)‒1,2,4,5-tetracyanobenzene (TCNB) complexes cocrystals are grown directly on the substrate, with the morphology tunable from 1D needle-like to 2D plate-like on demand. Spatially resolved photoluminescence spectra analyses on different cocrystals display morphology dependent and anisotropic optical waveguiding properties. In situ observation and energy calculations of the crystallization processes reveal the formation mechanism being from a competition between growth kinetics-defined crystal habit and the thermodynamics driving force. This growth technique may serve the future demand for tunable morphology organic cocrystals in different functional applications.

The Role of Weak Interactions in the Mechano-induced Single-Crystal-to-Single-Crystal Phase Transition of 8-Hydroxyquinoline-Based Co-crystals.

Mechano-induced single-crystal-to-single-crystal (SCSC) phase transitions in crystalline materials that change their properties have received more and more attention. However, there are still too few examples to study molecular-level mechanisms in the mechano-induced SCSC phase transitions, making the systematic and in-depth understanding very difficult. We report that bis-(8-hydroxyquinolinato) palladium(II)-tetracyanoquinodimethane (PdQ2 -TCNQ) and bis-(8-hydroxyquinolinato) copper(II)-tetracyanoquinodimethane (CuQ2 -TCNQ) show very different mechano-response behaviors during the SCSC phase transition. Phase transition in CuQ2 -TCNQ can be triggered by pricking on the crystal surface, while in PdQ2 -TCNQ it can only be induced by applying pressure uniformly over the whole crystal face. The crystallography data and Hirshfeld surface analysis indicate that the weak intra-layer C-H⋅⋅⋅O, C-H⋅⋅⋅N hydrogen bonds and inter-layer stacking interactions determine the feasibility of the SCSC phase transition by mechanical stimuli. Weaker intra-layer interactions and looser inter-layer stacking make the SCSC phase transition occur much more easily in the CuQ2 -TCNQ.

In Situ Microscopic Observation of the Crystallization Process of Molecular Microparticles by Fluorescence Switching.

To clearly understand the solid-state amorphous-to-crystalline transformation is a long-standing challenge because such crystallization occuring in confined environments is difficult to observe directly. We developed an in situ and real-time imaging procedure to record the interface evolution in a solid-state crystallization of molecular amorphous particles. The method, by employing a tetra-substituted ethene with novel morphology-dependent fluorescence, which can distinguish the interfaces between the crystalline and amorphous phase by fluorescence color, is a simple and practical method to probe the inner process of a molecular microparticle. The crystallization of amorphous microparticles in different cases was clearly recorded, where the perfect microparticles and those with defects demonstrate diverse destinies. The details disclosed in this observation will deepen the understanding for a series of solid-state crystallization that we know little about before.