Nanda Gyana Prakash, Suraksha Rajan, Rajamalli Pachaiyappan
Materials Research Centre, Indian Institute of Science, Bangalore 560012, India.
ACS Mater Au. 2024 Sep 4;4(6):604-611. doi: 10.1021/acsmaterialsau.4c00036. eCollection 2024 Nov 13.
Moisture-sensitive fluorescent emitters are a class of smart materials that can change their emission behavior upon exposure to water. In this study, we have synthesized two highly fluorescent organic emitters, 4BPy-PTA and 2BPy-PTA, and showed how moisture sensitivity can be enhanced by molecular design modification. Owing to the different nitrogen atom positions in the acceptor units, the emitters show different degrees of moisture sensitivity. Upon moisture exposure, both emitters change their emission color from greenish-yellow to blue, but a larger shift was witnessed in 4BPy-PTA (81 nm) than in 2BPy-PTA (68 nm). Moisture exposure enhances the photoluminescence quantum yield (PLQY) of 4BPy-PTA from 37 to 48%, whereas it suppresses the PLQY of 2BPy-PTA from 59 to 15%. A shorter moisture sensing time, large emission color shift, and enhanced PLQY make 4BPy-PTA a better moisture-sensitive material than 2BPy-PTA. Interestingly, the emission colors of the emitters can be completely regained by heating and partially by applying mechanical force to the moisture-exposed solids. In addition, these emitters also show mechanochromic luminescence behavior with a completely reversible emission color switch between blue and green.
对湿度敏感的荧光发射体是一类智能材料，在接触水时会改变其发射行为。在本研究中，我们合成了两种高荧光有机发射体4BPy-PTA和2BPy-PTA，并展示了如何通过分子设计修饰来增强湿度敏感性。由于受体单元中氮原子位置不同，这些发射体表现出不同程度的湿度敏感性。在接触湿气时，两种发射体的发射颜色均从绿黄色变为蓝色，但4BPy-PTA（81 nm）的变化比2BPy-PTA（68 nm）更大。接触湿气使4BPy-PTA的光致发光量子产率（PLQY）从37%提高到48%，而使2BPy-PTA的PLQY从59%降低到15%。更短的湿度传感时间、较大的发射颜色变化以及增强的PLQY使4BPy-PTA成为比2BPy-PTA更好的湿度敏感材料。有趣的是，通过加热可使发射体的发射颜色完全恢复，对接触湿气的固体施加机械力也可使其部分恢复。此外，这些发射体还表现出机械变色发光行为，在蓝色和绿色之间有完全可逆的发射颜色切换。
