Exploring the Interior of Hollow Fluorescent Carbon Nanoparticles

We synthesized hollow fluorescent carbon nanoparticles (HFCNs) using the simple procedure reported by Fang et al. [ACS Nano 2012, 6, 400−409]. The size distribution was uniform, providing spherical carbon nanoparticles with a hollow. In the present work we have focused on exploration of the interior of the HFCNs as this was hardly clarified until now. Understanding the importance of HFCNs in biological aspects due to their potentially low cytotoxicity and inherent fluorescent property, we have defined that the polarity of the interior of the HFCNs resembles that of ethanol by using suitable hydrophobic and hydrophilic fluorescent probes. Moreover, we have shown that π-electron-rich hydrophobic molecules, such as pyrene, can form a π–π stack with the inner wall of the HFCNs. Our findings are expected to open avenues in the usage of HFCNs as drug carriers and markers in bioimaging.