Bhattacharya Arpan, Chatterjee Surajit, Prajapati Roopali, Mukherjee Tushar Kanti
Discipline of Chemistry, Indian Institute of Technology Indore, M-Block, IET-DAVV Campus, Khandwa Road, Indore-452017, M.P., India.
Phys Chem Chem Phys. 2015 May 21;17(19):12833-40. doi: 10.1039/c5cp00543d.
The origin of the excitation wavelength (λex)-dependent photoluminescence (PL) of carbon dots (CDs) is poorly understood and still remains obscured. This phenomenon is often explained on the basis of surface trap/defect states, while the effect of quantum confinement is highly neglected in the literature. Here, we have shown that the λex-dependent PL of CDs is mainly due to the inhomogeneous size distribution. We have demonstrated the λex-dependent PL quenching of CDs inside the ferritin nanocages through selective optical excitation of differently sized CDs. It has been observed that Fe(3+) ions of ferritin effectively quench the PL of CDs due to static electron transfer, which is driven by favorable electrostatic interactions. However, control experiment with aqueous Fe(3+) ions in bulk medium revealed λex-independent PL quenching of CDs. The λex-dependent PL quenching of CDs by Fe(3+) ions of ferritin has been rationalized on the basis of a different extent of accessibility of Fe(3+) ions by differently sized CDs through the funnel-shaped ferritin channels. PL microscopy of individual CDs has been performed to get further information about their inherent PL properties at single dot resolution. Our results have shown that these hydrophilic CDs can be used as potential iron sensors in biological macromolecules.
碳点（CDs）激发波长（λex）依赖性光致发光（PL）的起源尚不清楚，仍然模糊不清。这种现象通常基于表面陷阱/缺陷态来解释，而量子限制效应在文献中却被高度忽视。在此，我们表明CDs的λex依赖性PL主要归因于尺寸分布不均匀。我们通过对不同尺寸的CDs进行选择性光激发，证明了铁蛋白纳米笼内CDs的λex依赖性PL猝灭。据观察，铁蛋白的Fe(3+)离子由于静态电子转移而有效地猝灭了CDs的PL，这是由有利的静电相互作用驱动的。然而，在本体介质中用水性Fe(3+)离子进行的对照实验显示，CDs的PL猝灭与λex无关。基于不同尺寸的CDs通过漏斗状铁蛋白通道对Fe(3+)离子的可及程度不同，解释了铁蛋白的Fe(3+)离子对CDs的λex依赖性PL猝灭。已对单个CDs进行PL显微镜检查，以在单点分辨率下获取有关其固有PL特性的更多信息。我们的结果表明，这些亲水性CDs可作为生物大分子中潜在的铁传感器。
