Porphyrin derived dual-emissive carbon quantum dots: Customizable synthesis and application for intracellular Cu2+ quantification

Exploring sensory systems from metal ion receptors enables the continuous development of ion sensing technologies. Herein we report the synthesis of carbon quantum dots (CQDs) from 5,10,15,20-tetrakis(4-sulfophenyl)porphyrin (TSPP) and additional carbon source, and its application in Cu 2+ imaging and quantifying in living cells. The CQDs are synthesized via a hydrothermal method in a successive polymerization and carbonization process. Due to the surface traps introduced by TSPP residue, the CQDs are featured with dual-emissive property of green (505 nm) and red (682 nm) fluorescence. Moreover, the red-to-green fluorescence ratio is readily customizable by tuning the molar fraction of TSPP. Benefited from Cu 2+ complexation induced red fluorescence quenching, the CQDs can be served as the ratiometric fluorescent nanosensor for Cu 2+ detection with ultra-high sensitivity and excellent specificity. The nanosensor is demonstrated to linearly detect Cu 2+ in the range of 0−50 nM, with an extremely low limit of detection (LOD) of 37 pM. More importantly, interference from other biological compositions, especially Fe 3+ , is successfully excluded via the site-selective coordination and specific electron transfer path. Based on the excellent analytical performance of the nanosensor, quantifying Cu 2+ in living cells is realized according to the linear correlation between fluorescence ratio and intracellular Cu 2+ content, which is parallelly detected by inductively coupled plasma mass spectrometry (ICP-MS). To demonstrate its practicality, the nanosensor is challenged to measure Cu 2+ uptake kinetics for cell lines derived from different tissues.