An amino acid-conjugated naphthalene diimide (NDI)-based highly red fluorescent radical anion has been found in a water medium under the photoradiated condition. This molecule has failed to form the radical anion in the monomeric state; however, the J aggregation in the aqueous medium has ensured the formation of radical anion in the ambient condition after the irradiation of both sunlight and UV light exposure. Electron paramagnetic resonance (EPR) studies clearly suggest the formation of radical anions. Herein, the stability of the radical anion in the aqueous medium is only a few minutes as a small amount of shaking is enough to quench the radical anion in the solution state. Furthermore, the incorporation of this molecule into a peptide-based hydrogel matrix and the consequent photoirradiation have not only helped to develop radical anion in the gel matrix but also increased the enormous stability of the radical anion inside the hydrogel matrix even for 30 days. It is envisaged that the formation of the radical anion within the gel matrix prevents the free movement of the NDI molecules and restricts the diffusion of molecular oxygen in the system, which leads to the stability of the radical anions in the gel. Moreover, the stability of the radical anion within the gel has helped to enhance the conductivity of the hybrid gel to a great extent. Interestingly, the radical anion-containing hybrid hydrogel has shown a potential photoswitching property.

中文翻译：

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肽基凝胶基质内光辐射萘二酰亚胺基有机自由基阴离子的稳定化以及光电性能的改进

在光辐射条件下，在水介质中发现了基于氨基酸共轭萘二酰亚胺（NDI）的高红色荧光自由基阴离子。该分子在单体状态下无法形成自由基阴离子；然而，水介质中的J聚集确保了在阳光和紫外光照射后在环境条件下自由基阴离子的形成。电子顺磁共振（EPR）研究清楚地表明自由基阴离子的形成。这里，自由基阴离子在水性介质中的稳定性仅为几分钟，因为少量的摇动就足以猝灭溶液状态的自由基阴离子。此外，将该分子掺入基于肽的水凝胶基质中以及随后的光照射不仅有助于在凝胶基质中产生自由基阴离子，而且还提高了水凝胶基质内自由基阴离子的巨大稳定性，甚至可以持续30天。据设想，凝胶基质内自由基阴离子的形成阻止了NDI分子的自由运动并限制了分子氧在系统中的扩散，这导致凝胶中自由基阴离子的稳定性。此外，凝胶内自由基阴离子的稳定性有助于在很大程度上增强杂化凝胶的电导率。有趣的是，含有自由基阴离子的杂化水凝胶显示出潜在的光开关特性。