Showing papers by "Wang Zhang Yuan published in 2020"

Color‐Tunable, Excitation‐Dependent, and Time‐Dependent Afterglows from Pure Organic Amorphous Polymers

Abstract: Achieving persistent room-temperature phosphorescence (p-RTP), particularly those of tunable full-colors, from pure organic amorphous polymers is attractive but challenging. Particularly, those with tunable multicolor p-RTP in response to excitation wavelength and time are highly important but both fundamentally and technically underexplored. Here, a facile and general strategy toward color-tunable p-RTP from blue to orange-red based on amidation grafting of luminophores onto sodium alginate (SA) chains, resulting in amorphous polymers with distinct p-RTP and even impressively excitation-dependent and time-dependent afterglows is reported. p-RTP is associated with the unique semi-rigidified SA chains, effective hydrogen bonding network, and oxygen barrier properties of SA, whereas excitation-dependent and time-dependent afterglows should stem from the formation of diversified p-RTP emissive species with comparable but different lifetimes. These results outline a rational strategy toward amorphous smart luminophores with colorful, excitation-dependent, and time-dependent p-RTP, excellent solution processability, and film-forming ability for versatile applications.

A clustering-triggered emission strategy for tunable multicolor persistent phosphorescence.

Abstract: A clustering-triggered emission (CTE) strategy, namely the formation of heterogeneous clustered chromophores and conformation rigidification, for achieving tunable multicolor phosphorescence in single-component compounds is proposed. Non-conventional luminophores comprising just oxygen functionalities and free of π-bonding, i.e., D-(+)-xylose (D-Xyl), pentaerythritol (PER), D-fructose (D-Fru) and D-galactose (D-Gal), were adopted as a simple model system with an explicit structure and molecular packing to address the hypothesis. Their concentrated solutions and crystals at 77 K or under ambient conditions demonstrate remarkable multicolor phosphorescence afterglows in response to varying excitation wavelengths, because of the formation of diverse oxygen clusters with sufficiently rigid conformations. The intra- and inter-molecular O⋯O interactions were definitely illustrated by both single crystal structure analysis and theoretical calculations. These findings shed new light on the origin and simple achievement of tunable multicolor phosphorescence in single-component pure organics, and in turn, have strong implications for the emission mechanism of non-conventional luminophores.

Accessing Tunable Afterglows from Highly Twisted Nonaromatic Organic AIEgens via Effective Through-Space Conjugation

Abstract: Nonaromatic, cross-conjugated, and highly twisted luminogens consisting of acylated succinimides demonstrate aggregation-induced emission characteristics along with tunable multicolor photoluminescence and afterglows in their single crystals. Effective through-space conjugation among different moieties bearing n/π electrons promote the spin-orbit coupling and intersystem crossing and lead to diverse emissive clusters with concurrently rigidified conformations, thus allowing readily tunable emissions. Derived from it, the proof-of-concept application for advanced anti-counterfeiting is illustrated. These results should spur the rational design of novel nonaromatic AIEgens, and moreover advance understandings of the non-traditional intrinsic luminescence and the origin of tunable multicolor afterglows.

Nonconventional luminophores with unprecedented efficiencies and color-tunable afterglows

Abstract: Nonconventional luminophores without significant conjugations generally possess excitation-dependent photoluminescence (PL) owing to the coexistence of diverse clustered chromophores, which strongly implies the possibility of achieving color-tunable PL and/or persistent room temperature phosphorescence (p-RTP) from their crystals assisted by effective intermolecular interactions. Compared with traditional luminogens, however, nonconventional luminophores generally suffer from poor PL efficiencies. Here, inspired by the highly stable double-helix structure and multiple hydrogen bonds in DNA, we report a series of planar or twisted nonconventional luminophores based on hydantoin (HA), demonstrating unprecedentedly high PL/p-RTP efficiencies and p-RTP lifetimes of up to 87.5%/21.8% and 1.74 s, respectively, accompanying color-tunable p-RTP from sky-blue to yellowish-green. These findings will advance the exploitation of efficient nonconventional luminophores and provide deeper mechanistic insights into the origin of color-tunable p-RTP.

Intrinsic Luminescence from Nonaromatic Biomolecules

Abstract: Novel emitters that do not contain traditional chromophores but only electron-rich moieties (e. g. amine, C=O, -OH, ether, and imide), which are classified as nonconventional luminophores, have been more frequently reported. Although more and more examples have been demonstrated, their emission mechanism remains unclear. The clustering-triggered emission (CTE) mechanism has previously been proposed to rationalize the luminescence of unconventional chromophores. Moreover, great attention has been paid to the distinctive inherent luminescence from nonaromatic biomolecules such as cellulose, starch, sugars, and nonaromatic amino acids and proteins. In this Review, we summarize these unconventional biomolecular luminophores and apply the CTE mechanism to rationalize such a phenomenon. This Review may shed new light on the understanding of intrinsic emission of nonaromatic biomolecules and decipher the intrinsic fluorescence from cells and tissues.

Effective Internal and External Modulation of Nontraditional Intrinsic Luminescence.

Abstract: The rational modulation of the nontraditional intrinsic luminescence (NTIL) of nonconventional luminophores remains difficult, on account of the limited understanding on the structure-property relationships and emission mechanisms. Herein, the effective modulation of NTIL is demonstrated based on a group of nonaromatic anhydrides and imides. Mutual bridging of isolated subgroups effectively promotes intramolecular through-space conjugation (TSC), leading to red-shifted emission, enhanced efficiency, and prolonged persistent room-temperature phosphorescence (p-RTP). The substitution of heteroatoms from oxygen to nitrogen drastically changes the TSC and enhances intermolecular interactions, resulting in enhanced emission efficiency. In addition, upon freezing, compression, or embedding into polymer matrices, the emission intensity and color remain well regulated. These results shed new light on the rational modulation of the NTIL and p-RTP of nonconventional luminophores.

Clustering-Triggered Efficient Room-Temperature Phosphorescence from Nonconventional Luminophores.

Abstract: Pure organic room-temperature phosphorescence (RTP) and luminescence from nonconventional luminophores have gained increasing attention. However, it remains challenging to achieve efficient RTP from unorthodox luminophores, on account of the unsophisticated understanding of the emission mechanism. Herein, we propose a strategy to realize efficient RTP in nonconventional luminophores through incorporation of lone pairs together with clustering and effective electronic interactions. The former promotes spin-orbit coupling and boosts the consequent intersystem crossing, whereas the latter narrows energy gaps and stabilizes the triplets, thus synergistically affording remarkable RTP. Experimental and theoretical results of urea and its derivatives verify the design rationale. Remarkably, RTP from thiourea solids with unprecedentedly high efficiency of up to 24.5 % is obtained. Further control experiments testify the crucial role of through-space delocalization on the emission. These results will spur the future fabrication of nonconventional phosphors and advance the understanding of the underlying emission mechanism.

Clustering-Triggered Emission and Luminescence Regulation by Molecular Arrangement of Nonaromatic Polyamide-6

Abstract: Photoluminescent polymers with merely nonaromatic chromophores have attracted rapidly growing attention owing to their importance in the significant fundamental, encryption, and anticounterfeiting fields. Based on the clustering-triggered emission mechanism, through-space conjugation and conformational rigidification of nonaromatic chromophores are crucial to photoluminescence, which are also dependent on molecular arrangement. Herein, polyamide-6 (PA-6) with well-defined molecular arrangements was thus studied. The luminescence from the PA-6 solution is enhanced upon aggregation from solution to amorphous solid and further boosted with the formation of highly regular molecular arrangement. More importantly, both blue and green fluorescence from PA-6/formic acid (FA) solutions were observed because of the variable clusters formed among PA-6 and FA. To make clear of this, PA-6 cast film (PCF) and PA-6 electrospun film (PEF) were prepared and belonged to α- (antiparallel molecular arrangement) and γ (parallel molecular arrangement)-form crystals, as confirmed by Fourier transform infrared, X-ray diffraction, and Raman measurements. The relationship between molecular arrangement and luminescence of PA-6 molecules was clarified by their photophysical properties in solids and solutions. Notably, color-tunable cryogenic phosphorescence of PA-6 solids was also detected. Such aggregation-enhanced emission and tunable phosphorescence of PA-6 solids are ascribed to the formation of diversified amide clusters together with remarkably rigidified molecular conformations owing to the highly regular molecular arrangement in the aggregated states.

DNA Inspirited Rational Construction of Nonconventional Luminophores with Efficient and Color-Tunable Afterglow

Abstract: Persistent room-temperature phosphorescence (p-RTP) from pure organics is attractive due to its fundamental importance and potential applications in molecular imaging, sensing, encryption, anticounterfeiting, etc.1-4 Recently, efforts have been also made in obtaining color-tunable p-RTP in aromatic phosphors5 and nonconjugated polymers6,7. The origin of color-tunable p-RTP and the rational design of such luminogens, particularly those with explicit structure and molecular packing, remain challenging. Noteworthily, nonconventional luminophores without significant conjugations generally possess excitation-dependent photoluminescence (PL) because of the coexistence of diverse clustered chromophores6,8, which strongly implicates the possibility to achieve color-tunable p-RTP from their molecular crystals assisted by effective intermolecular interactions. Here, inspirited by the highly stable double-helix structure and multiple hydrogen bonds in DNA, we reported a series of nonconventional luminophores based on hydantoin (HA), which demonstrate excitation-dependent PL and color-tunable p-RTP from sky-blue to yellowish-green, accompanying unprecedentedly high PL and p-RTP efficiencies of up to 87.5% and 21.8%, respectively. Meanwhile, the p-RTP emissions are resistant to vigorous mechanical grinding, with lifetimes of up to 1.74 s. Such robust, color-tunable and highly efficient p-RTP render the luminophores promising for varying applications. These findings provide mechanism insights into the origin of color-tunable p-RTP, and surely advance the exploitation of efficient nonconventional luminophores.