廉价荧光染料的完整调色板

诸平

Polymer fluorescent inks can now also be produced in red. (Photograph: ETH Zurich)

据瑞士苏黎世联邦理工学院(Swiss Federal Institute of Technology Zurich, ETHZ）2023年1月3日报道，廉价荧光染料的完整调色板(Entire colour palette of inexpensive fluorescent dyes)。ETHZ研究人员开发了一种模块化系统，用于简单且廉价地生产安全油墨。它基于聚合物，未来也可用于太阳能发电厂和屏幕。现在也可以生产红色聚合物荧光油墨(上述图示)。

ETHZ研究人员开发的新型荧光染料生产起来相对简单且成本低廉。染料是具有模块化结构的聚合物。它们由不同数量的亚基组成，具体取决于它们的颜色。使用的亚基是化学上简单的分子，这些分子可以从市场上买到，也可以由化学家在一个反应​​步骤中生产。

现在，由包银银（Yinyin Bao音译）领导的科学家们已经成功地使用这种新方法产生了多种颜色，包括以前难以产生的红色。包银银是ETHZ约翰·克里斯朵夫·勒鲁（Jean-Christophe Leroux）教授研究小组和施志仁（Shih, Chih-​Jen）教授研究小组的资深科学家。该团队与澳大利亚皇家墨尔本理工大学(Royal Melbourne Institute of Technology简称RMIT)的科学家一起开发了人工智能算法，帮助确定特定颜色需要多少分子亚基。相关研究结果于2023年1月2日已经《化学》（Chem）杂志网站发表——Suiying Ye, Nastaran Meftahi, Igor Lyskov, Tian Tian, Richard Whitfield, Sudhir Kumar, Andrew J. Christofferson, David A. Winkler, Chih-Jen Shih, Salvy Russo, Jean-Christophe Leroux, Yinyin Bao. Machine learning-assisted exploration of a versatile polymer platform with charge transfer-dependent full-color emission. Chem, Available online 2 January 2023. DOI: 10.1016/j.chempr.2022.12.003. https://doi.org/10.1016/j.chempr.2022.12.003

荧光油墨的潜在应用包括用于钞票、证书、护照或加密信息的紫外线激活安全油墨。该方法还可用于生产在长时间紫外线照射后变色的墨水。在科学家们发表在科学杂志《化学》（Chem）上的新作品中，他们以两种最初为红色的荧光墨水为例证明了这一点，其中一种在紫外线照射几分钟后变成蓝色，而另一种则保持红色。此属性也可用于安全功能。

新型荧光分子的其他应用是在太阳能发电厂，或者有朝一日它们可以与半导体分子结合生产用于显示器的低成本有机发光二极管 (OLED)。

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Highlights

• Machine learning directs the design of through-space charge transfer polymers

• Full-color emission of solid polymers is tuned by simple polymerization

• Donor-acceptor distance within ～7 Å is crucial for charge transfer emission

• Photoresponsive donor monomer allows high-contrast photochromic fluorescence

The bigger picture

Understanding the color tuning of solid-state emissive materials is essential from a fundamental mechanistic viewpoint, as well as for practical applications. Despite copious research into molecular design and engineering, a general and facile polymer platform that offers high flexibility and broad extensibility in emission color tuning is still lacking. Here, guided by a machine learning model, we developed a series of through-space charge transfer polymers with full-color-tunable emission. This is achieved by simple polymerization of aromatic monomers with varied electron-donating ability, using an electron-withdrawing fluorophore as the initiator. Theoretical calculations reveal that redshifted charge transfer emission can be generated at a donor-acceptor spatial proximity within ～7 Å, which could be influenced by the donor group concentration in polymers. This work opens new perspectives for the design of color-tunable solid polymers and stimuli-responsive fluorescent materials.

Summary

The development of color-tunable fluorescent materials with simple chemical compositions that are easy to synthesize is highly desirable but practically challenging. Here, we report a versatile yet simple platform based on through-space charge transfer (TSCT) polymers that has full-color-tunable emission and was developed with the aid of predictive machine learning models. Using a single-acceptor fluorophore as the initiator for atom transfer radical polymerization, a series of electron donor groups containing simple polycyclic aromatic moieties (e.g., pyrene) are introduced either by one-step copolymerization or by end-group functionalization of a pre-synthesized polymer. By manipulating donor-acceptor interactions via controlled polymer synthesis, continuous blue-to-red emission color tuning was easily achieved in solid polymers. Theoretical investigations confirm the structurally dependent TSCT-induced emission redshifts. We also exemplify how these TSCT polymers can be used as a general design platform for solid-state stimuli-responsive materials with high-contrast photochromic emission by applying them to proof-of-concept information encryption.

Graphical abstract