Das Ruma, Rajender Gone, Giri P K
Department of Physics, Indian Institute of Technology Guwahati, Guwahati - 781039, India.
Phys Chem Chem Phys. 2018 Feb 7;20(6):4527-4537. doi: 10.1039/c7cp06994d.
We explore the mechanism of the fluorescence enhancement and fluorescence quenching effect of single walled carbon nanotubes (SWCNTs) on highly fluorescent graphene quantum dots (GQDs) over a wide range of concentrations of SWCNTs. At very low concentrations of SWCNTs, the fluorescence intensity of the GQDs is enhanced, while at higher concentrations, systematic quenching of fluorescence is observed. The nature of the Stern-Volmer plot for the latter case was found to be non-linear indicating a combined effect of dynamic and static quenching. The contribution of the dynamic quenching component was assessed through the fluorescence lifetime measurements. The contribution of static quenching is confirmed from the red shift of the fluorescence spectra of the GQDs after addition of SWCNTs. The fluorescence intensity is first enhanced at very low concentration due to improved dispersion and higher absorption by GQDs, while at higher concentration, the fluorescence of GQDs is quenched due to the complex formation and associated reduction of the radiative sites of the GQDs, which is confirmed from time-resolved fluorescence measurements. Laser confocal microscopy imaging provides direct evidence of the enhancement and quenching of fluorescence at low and high concentrations of SWCNTs, respectively. This study provides an important insight into tuning the fluorescence of GQDs and understanding the interaction between GQDs and different CNTs, which is important for bio-imaging and drug delivery applications.
我们在很宽的单壁碳纳米管（SWCNTs）浓度范围内，探究了单壁碳纳米管对高荧光性的石墨烯量子点（GQDs）的荧光增强和荧光猝灭效应的机制。在SWCNTs浓度非常低时，GQDs的荧光强度增强，而在较高浓度时，则观察到荧光的系统性猝灭。发现后一种情况下的斯特恩-沃尔默图的性质是非线性的，表明存在动态猝灭和静态猝灭的综合效应。通过荧光寿命测量评估了动态猝灭成分的贡献。添加SWCNTs后GQDs荧光光谱的红移证实了静态猝灭的贡献。在非常低的浓度下，由于GQDs分散性改善和吸收增强，荧光强度首先增强，而在较高浓度时，由于复合物形成以及GQDs辐射位点相关减少，GQDs的荧光被猝灭，这通过时间分辨荧光测量得到证实。激光共聚焦显微镜成像分别提供了在低浓度和高浓度SWCNTs下荧光增强和猝灭的直接证据。本研究为调节GQDs的荧光以及理解GQDs与不同碳纳米管之间的相互作用提供了重要见解，这对于生物成像和药物递送应用具有重要意义。
