Obstruction of Photoinduced Electron Transfer from Excited Porphyrin to Graphene Oxide: A Fluorescence Turn-On Sensing Platform for Iron (III) Ions

A comparative reaserch of the assembly of different porphyrin molecules on graphene oxide (GO) and reduced graphene oxide (RGO) was carried out, respectively. Despite the cationic porphyrin molecules can be assembled onto the surfaces of graphene sheets, including GO and RGO, to form complexes through electrostatic and π-π stacking interactions, the more obvious fluorescence quenching and the larger red-shift of the Soret band of porphyrin molecule in RGO-bound states were observed than those in GO-bound states, due to the differenc of molecular flattening in degree. Further, more interesting finding was that the complexes formed between cationic porphyrin and GO, rather than RGO sheets, can facilitate the incorporation of iron (III) ions into the porphyrin moieties, due to the presence of the oxygen-contained groups at the basal plane of GO sheets served as auxiliary coordination units, which can high-efficiently obstruct the electron transfer from excited porphyrin to GO sheets and result in the occurrence of fluorescence restoration. Thus, a fluorescence sensing platform has been developed for iron (III) ions detection in this contribution by using the porphyrin/GO nanohybrids as an optical probe, and our present one exhibited rapid and sensitive responses and high selectivity toward iron (III) ions.本研究分别针对氧化石墨烯（Graphene Oxide, GO）与还原氧化石墨烯（Reduced Graphene Oxide, RGO）表面不同卟啉分子的组装行为开展了对比研究。尽管阳离子卟啉分子可通过静电作用与π-π堆叠相互作用，组装于包括GO与RGO在内的石墨烯片层表面以形成复合物，但相较于GO结合态，RGO结合态下卟啉分子的Soret带发生了更显著的荧光猝灭与更大程度的红移，这源于二者分子平面化程度的差异。进一步的有趣发现为：阳离子卟啉与GO片层（而非RGO片层）形成的复合物可促进铁(III)离子掺入卟啉位点，这是由于GO片层基面存在含氧官能团作为辅助配位单元，能够高效阻断激发态卟啉向GO片层的电子转移，进而实现荧光恢复。基于此，本研究以卟啉/GO纳米杂化物作为光学探针，开发了一种用于铁(III)离子检测的荧光传感平台，该平台对铁(III)离子展现出快速灵敏的响应与优异的选择性。