Fluolab【Angew.Chem.】衢州人民医院洪广亮、南京邮电大学黄维院士等|纳米限制效应：余辉寿命超2.5秒，机械强度达7.7兆帕，多功能水凝胶颠覆加密与抑菌
通讯作者： Ye Tao, Heng Dong, Wei Huang, Guangliang Hong
文章概要
在这篇发表于《Angewandte Chemie》的研究中，团队提出了一种纳米限制工程策略，成功研发出兼具高效率、长寿命及强韧机械性能的多色有机余辉水凝胶。通过将刚性的多色氢键超分子框架嵌入水凝胶网络，研究人员解决了有机余辉材料在水氧环境下极易猝灭的难题。该水凝胶不仅实现了从深蓝色到橙红色的全色域调节，其余辉寿命更是达到了惊人的2535毫秒，量子产率超过29.4%。这种材料在时空分辨率信息加密和病原体清除领域展现出巨大的应用潜力。
Schematic design of multicolor afterglow hydrogels. (a,b) Schematic comparison of photophysical processes between conventional (a) and nano-restriction engineered (b) afterglow hydrogel system. Compared to the conventional afterglow hydrogel, the proposed nano-restriction engineered hydrogel involves suppressed non-radiative decay for enhanced afterglow efficiency and lifetime. ISC represents intersystem crossing. (c) Demonstration of the construction of multicolor hydrogel through incorporating nano-restriction engineered supramolecular framework stabilized multicolor afterglow emitters (left) into hydrogel matrix (middle) and their corresponding tension (top right) and compression illustration (bottom right). (d) Molecular structures of melamine (MA), cyanuric acid (CA), trimesic acid (TMA), benzene-1,3,5-triyltriboronic acid (BTA), and pyrene 1,3,6,8-tetracarboxylic acid (PTCA). The blue and red rings represent a rigid and confined supramolecular framework. The dashed red line indicates a hydrogen bond existing among the afterglow emitters, melamine-cyanuric acid supramolecular framework, and polymer chain.
引言
多色荧光水凝胶在防伪、生物成像和信息加密中虽有应用，但严重的激子猝灭现象限制了其效率。特别是将三线态发射体置于富含水和氧的环境中，由于水分子的运动和氧气的碰撞，三线态激子会迅速发生非辐射衰减。目前的有机余辉水凝胶普遍存在寿命短、亮度低、颜色单一等瓶颈。为了打破这一僵局，受氢键超分子框架保护激子的启发，研究团队决定利用三聚氰胺与三聚氰酸构建稳定的二维超分子框架（MCA）。这种纳米限制微环境能有效锁定发光客体分子的排列，抑制振动耗散，从而在含水网络中实现高效的余辉发射。
Photophysical properties and mechanism investigations of multicolor afterglow hydrogels. (a–c) Normalized steady-state photoluminescence and delayed PL (10 ms delay) spectra (top panel) as well as excitation-delayed PL mappings (bottom panel) of HB (a), HG (b), and HO (c) (d,e) Photoluminescence quantum yield (PLQY, d) and lifetime decay profiles (e) of HB, HG, and HO. (f) Commission Internationale de L'Eclairage chromaticity diagram for delayed PL emission of HB, HG, and HO. (g) The comparison of lifetimes and PLQY of our work with the reported afterglow hydrogel. (h) Theoretical calculated energy level diagram and spin–orbital coupling values of MCATMA, MCABTA, and MCAPTCA. (i) Proposed luminescence mechanism.
主要实验及结论
实验过程选取了具有不同能级的芳香族生色团作为客体，将其掺入MCA超分子框架中。研究发现，通过精确调节掺杂分子的结构，水凝胶展现出深蓝色、青绿色和橙红色的可调余辉，且余辉现象在紫外光关闭后可肉眼观察超过10秒。通过理论计算和机理研究证实，MCA框架不仅能提供限制环境，其自身的三线态能级还能在部分系统中充当“桥梁”，促进系际窜跃过程，显著提升激子利用率。此外，该策略表现出极佳的稳定性，在经历50次循环光激发或冷藏存储一个月后，发光强度仍能保持在较高水平。
Structural characterization of multicolor hydrogels. (a,b) X-ray diffraction (a) and Fourier transform infrared (b) spectra of MCA powder, H, HB, HG, and HO. Inserts show the magnified views of the characteristic diffraction regions. (c) Scanning electron microscopy images (top) and the corresponding pore size distribution (bottom) of the H (left) and HG (right, scale bar = 100 µm). (d) Confocal laser scanning microscopy image of HO. (_λ_ex = 405 nm, scale bar = 200 µm). (e,f) Atomic force microscopy images of H (e) and HG (f).
Mechanical analyses and afterglow properties. (a) Photographs of HB, HG, and HO during stretching at various strains after the removal of the UV light. (b,c) Tensile (b) and compressive (c) stress-strain curves of the H-MCA with different MCA concentrations. The mass ratio (wt.%) is defined as the mass of MCA divided by the combined mass of AM and PVP. The inset (c) shows photographs of H-MCA during the compression loop at various compressive strains. (d,e) Loading-unloading tests of H-MCA with varying maximum tensile (d) and compressive (e) strains. The inset (e) shows an enlarged view of the 20%, 40%, and 60% compression range. (f) The calculated dissipated and total toughness of H-MCA during the loading-unloading cycles at varying tensile (top panel) and compressive (bottom panel) strains. (g,h) Fatigue resistance of the H-MCA under the repeated tensile (g) and compressive (h) loading-unloading cycles.
除了卓越的光学性能，这种水凝胶还具备令人惊叹的机械强韧性。得益于超分子框架作为应力耗散节点，水凝胶在含水量高达66%的情况下，仍能承受7.7兆帕的压缩强度，拉伸应变接近1400%。在多次拉伸和压缩循环实验中，材料表现出优秀的疲劳抗性，且变形过程不影响余辉发射的稳定性。利用这种独特的时空动力学特性，研究者展示了一个基于二阶魔方的多维加密系统，只有通过特定的时间节点捕获余辉信号并进行位运算合成，才能解码出真实信息。
Spatiotemporal encryption. (a) Schematic illustration of the reversible transformation of a second-order Rubik's cube enabled by the afterglow hydrogel units (left) and the photographs of the corresponding cube during rotation and recovery after removal of the xenon lamp (right). The inset shows the colors represent the hydrogels used for the fabrication of a second-order Rubik's cube (scale bar = 1 cm). (b) The unfolding cube serves as a spatiotemporal information encoding carrier, in which the six faces with four positions per face constitute 24 spatial units. Accurate decryption of the embedded information requires combinatorial analysis (X = _X_0 + _X_1 + _X_2) of the emission patterns captured at three distinct times of 0 s (_X_0), 2 s (_X_1), and 5 s (_X_2) after removal of the xenon lamp (scale bar = 2 cm). The areas with and without afterglow emission represent “1” and “0,” respectively. (c) Decryption processes of varied afterglow encrypted sequence of a second-order Rubik's cube.
在生物应用方面，该材料利用长寿命三线态激子与氧气的能量转移，高效产生单线态氧。实验结果显示，该水凝胶对金黄色葡萄球菌和大肠杆菌的杀菌率超过99.9%。在活体小鼠创面愈合模型中，研究团队将其制成微针贴片，通过光动力治疗显著加速了受感染伤口的愈合速度。与传统抗生素相比，这种基于物理机制的活性氧清除方式具有更持久的抑制效果，且表现出极高的生物安全性和细胞相容性。
In vivo antimicrobial activity. (a) Schematic illustration of the fabrication of the multicolor afterglow hydrogel microneedle patch and the photodynamic therapy process. The hydrogels were irradiated using a xenon lamp as the white light source with a power density of 0.2 W cm−2 for 5 min. (b) Photographs showing the progression of wound healing over 11 days for different treatment groups (scale bar = 5 mm). C(−): control without light irradiation; C(+): control with light irradiation; HO(−): HO without light irradiation; HO(+): HO with light irradiation. (c) Quantitative analysis of wound area over different treatment times. Data are presented as mean ± s.d. (n = 3 independent experiments). ***p < 0.001. (d) Bacterial viability across different treatment groups at day 11 post-treatment. Data are presented as mean ± s.d. (n = 3 independent experiments). ***p < 0.001. (e,f). Representative hematoxylin and eosin (H&E) (e) and Masson trichrome stained (f) images (scale bar = 1 mm) along with their corresponding localized enlarged images (scale bar = 200 µm) of wound tissues at day 11 post-treatment.
总结及展望
这项研究为开发下一代智能软物质光子材料提供了通用策略。通过纳米限制工程，研究团队在同一材料体系中完美融合了高激子利用率、超长余辉寿命与卓越的力学稳定性。这不仅为光学防伪和高安全性信息存储提供了新的维度，也为生物电子学、微创治疗和先进组织工程提供了理想的材料平台。未来，这种具备感知与治疗双重功能的智慧型水凝胶有望在临床医学和精密安全领域发挥关键作用。