Pawar Shweta, Togiti Uday Kumar, Bhattacharya Anupam, Nag Amit
Department of Chemistry, Birla Institute of Technology and Science, Pilani, Hyderabad Campus, Hyderabad 500078, India.
ACS Omega. 2019 Jun 28;4(6):11301-11311. doi: 10.1021/acsomega.9b01208. eCollection 2019 Jun 30.
A novel nanoprobe was designed and synthesized by functionalizing chitosan-carbon dots (CDs) with a modified bipyridine-based heterocyclic molecule, 4-(pyridine-2-yl)-3-pyrrolo[2,3-]quinoline (PPQ), to detect trace amount of water via fluorescence methods. The functionalized CDs (PPQ-CDs) were thoroughly characterized using dynamic light scattering, UV-vis, X-ray diffraction, Fourier transform infrared, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and NMR techniques. The modified fluorescence intensity of PPQ-CDs was found to be an excellent indicator for water in organic solvents. The PPQ-CDs showed very weak fluorescence intensity in organic solvents due to a possible photoinduced electron transfer (PET) process between PPQ pyrrole nitrogen and acceptor groups of CDs. However, sequential addition of trace amount of water led to continuous enhancement in the fluorescence intensity for the PPQ-CD nanocomposites. The mechanism was proposed to follow suppression of the PET process due to the formation of "free-ions" by the proton transfer from the CD carboxyl group to pyrrole nitrogen through water bridging. The limit of water detection was determined to be 0.023% (v/v) in DMSO.
通过用修饰的基于联吡啶的杂环分子4-(吡啶-2-基)-3-吡咯并[2,3-]喹啉(PPQ)对壳聚糖-碳点(CDs)进行功能化,设计并合成了一种新型纳米探针,用于通过荧光方法检测痕量水。使用动态光散射、紫外可见光谱、X射线衍射、傅里叶变换红外光谱、X射线光电子能谱、高分辨率透射电子显微镜和核磁共振技术对功能化的CDs(PPQ-CDs)进行了全面表征。发现PPQ-CDs修饰后的荧光强度是有机溶剂中水的优良指示剂。由于PPQ吡咯氮与CDs的受体基团之间可能存在光致电子转移(PET)过程,PPQ-CDs在有机溶剂中显示出非常弱的荧光强度。然而,逐次添加痕量水会导致PPQ-CD纳米复合材料的荧光强度持续增强。提出的机制是,由于通过水桥从CD羧基向吡咯氮的质子转移形成了“自由离子”,从而抑制了PET过程。在二甲基亚砜中测定的水检测限为0.023%(v/v)。
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