Krzyszkowska Ewelina, Walkowiak-Kulikowska Justyna, Stienen Sven, Wojcik Aleksandra
Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89 b, 61-614 Poznan, Poland.
Phys Chem Chem Phys. 2017 Jun 7;19(22):14412-14423. doi: 10.1039/c7cp01267e.
Graphene oxide sheets (GO) were covalently functionalized with thionine molecules. The obtained hybrid material, Th-GO, was characterized by means of scanning electron microscopy (SEM), Auger electron spectroscopy (AES), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. Subsequently, the interaction of light with the free dye molecules and with dye molecules bound to the graphene oxide sheets was probed via UV-Vis spectroscopy, fluorescence spectroscopy and femtosecond pump-probe spectroscopy. The experimental results proved that thionine was successfully grafted onto the GO sheets, however, only one of the two amino groups of thionine was always involved in the amide bond formation. The Th-GO hybrid suspended in N,N-dimethylformamide (DMF) exhibited suppressed fluorescence as compared to the free dye in the same solvent, pointing to an efficient interaction between the photoexcited dye and the graphene sheets. Yet, no electron transfer products were detected by transient absorption measurements, even though there was a shortening of the singlet excited state lifetime of thionine (from the 567 ps for the free dye to the 313 ps for the dye in Th-GO). These results can be rationalized in terms of a fast back electron transfer process or possibly an energy transfer process.
氧化石墨烯片（GO）与硫堇分子进行了共价功能化。通过扫描电子显微镜（SEM）、俄歇电子能谱（AES）、傅里叶变换红外光谱（FTIR）和拉曼光谱对所得的杂化材料Th-GO进行了表征。随后，通过紫外-可见光谱、荧光光谱和飞秒泵浦-探测光谱研究了光与游离染料分子以及与结合在氧化石墨烯片上的染料分子之间的相互作用。实验结果证明硫堇成功接枝到了GO片上，然而，硫堇的两个氨基中只有一个总是参与酰胺键的形成。与相同溶剂中的游离染料相比，悬浮在N，N-二甲基甲酰胺（DMF）中的Th-GO杂化物表现出荧光猝灭，这表明光激发染料与石墨烯片之间存在有效的相互作用。然而，即使硫堇的单重激发态寿命缩短了（从游离染料的567 ps缩短到Th-GO中染料的313 ps），瞬态吸收测量也未检测到电子转移产物。这些结果可以通过快速的反向电子转移过程或可能的能量转移过程来解释。
