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Diastereoisomer-Induced Morphology Tunable Self-Assembled Organic Microcrystals of Conjugated Molecules for Ultraviolet Laser
摘要： Precisely controlling self-assembly behavior and micro/nanostructure morphology of conjugated materials is significant for constructing optoelectronic devices. Inspired by natural functional materials, molecular stereoisomerism strategy (MSS) is an effective and convenient means to tune their molecular arrangement and macroscopic property of conjugated materials. Herein, a supramolecular chiral difluorenols, 9,9′-diphenyl-9H,9′H-[2,2′-bifluorene]-9,9′-diol (DPFOH), is set as a desirable model to reveal the diastereomeric effects of conjugated molecules toward controlling the micro/nanostructure morphology and optoelectronic behavior for deep-blue organic laser. Two diastereomers, raceme (rac)- and mesomer (meso)-DPFOH, are obtained and unambiguously elucidated by X-ray crystallography. It is common sense to observe the slight diastereomeric effects on photophysical properties and electrochemical characteristics in solution or pristine film state for the isotropic phase. Interestingly, as a consequent of the disparate multi-dimensional intermolecular interaction, rac-DPFOH molecule can self-assemble into 1D rod-shaped but rectangular plate-shaped microcrystals for meso-DPFOH. Impressively, rac-DPFOH microrod presents a well-defined emission with an excellent ultraviolet microlasing behavior at 398 nm, whereas the 2D microplate of meso-DPFOH show a broad emission centered at 420 nm without gain processing. Therefore, MSS provides a new approach to design conjugated molecules and tune superstructure morphology for optoelectronic applications.
关键词： optical properties,tunable morphology,organic ultraviolet microlasers,diastereoisomer effect,microcrystals
更新于2025-09-23 15:21:01
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Chiral Helical Polymer Nanomaterials with Tunable Morphology: Prepared with Chiral Solvent To Induce Helix-Sense-Selective Precipitation Polymerization
摘要： We report an unprecedented strategy for using achiral monomer to construct chiral helical polymer nanomaterials with tunable morphology—helix-sense-selective precipitation polymerization induced by a chiral solvent (HSSPP-CS). CHCl3, chiral α-pinene, and an alkanol were employed to constitute a solvent mixture for performing HSSPP-CS. (R)- or (S)-α-pinene worked as chiral source and transferred its chirality to the resulting helical polyacetylenes derived from achiral monomer in the course of polymerization, thereby forming chiral helical polymers and endowing the nanomaterials thereof with optical activity. Simply changing solvent composition provided chiral polymer products varying in morphology from fibrous to rod-like and finally to spherical morphology. This is the first report dealing with chirality transfer from chiral solvent to induce helix-sense-selective precipitation polymerizations. The study establishes a straightforward and effective alternative for making use of achiral monomers to construct chiral helical polymer nanomaterials with diverse morphology.
关键词： tunable morphology,chiral solvent,achiral monomer,chiral helical polymer nanomaterials,helix-sense-selective precipitation polymerization
更新于2025-09-23 15:21:01
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pH Variation as a Simple and Selective Pathway for Obtaining Nanoparticle or Nanocapsule Polysaccharides
摘要： The fabrication of polysaccharides to be nanoparticles or nanocapsules is quite specific due to various parameters and factors. The present work demonstrates a simple pathway to selectively prepare the ionic polysaccharide flakes to be nanoparticles or nanocapsules. The systematic studies on the model cases of cationic polysaccharide (i.e. chitosan) and anionic polysaccharide (i.e. alginate) confirm that pKa is the key point to tune the polysaccharides to be nanoparticles or nanocapsules. When the ionic polysaccharides were in an oil/water emulsion system, the pH close to pKa leads to the densely packed polysaccharide chains under the hydrogen bond networks, and as a result the crosslink occurs all through the chains to be nanoparticles. On the other hand, when pH was adjusted to the lower or higher than pKa depending on the types of ionic polysaccharide, the polysaccharide chains are under charge-charge repulsive force, resulting in the alignment of polysaccharide chains to be hollow nanospheres, and at that time the crosslink initiates the formation of nanocapsules. The present work, for the first time, clarifies that pH variation is the key to selectively prepare nanoparticles or nanocapsules, and this is important for delivery systems, coatings, sensors, etc.
关键词： pH-tunable morphology,chitosan,alginate,emulsion system,Polysaccharide
更新于2025-09-10 09:29:36