title: High Performance Photoluminescent Carbon Dots for In Vitro and In Vivo Bioimaging: Effect of Nitrogen Doping Ratios.
abstract: Photoluminescent carbon dots (CDs) have received ever-increasing attention in the application of optical bioimaging because of their low toxicity, tunable fluorescent properties, and ultracompact size. We report for the first time on enhanced photoluminescence (PL) performance influenced by structure effects among the various types of nitrogen doped (N-doped) PL CDs. These CDs were facilely synthesized from condensation carbonization of linear polyethylenic amine (PEA) analogues and citric acid (CA) of different ratios. Detailed structural and property studies demonstrated that either the structures or the molar ratio of PEAs altered the PL properties of the CDs. The content of conjugated π-domains with C═N in the carbon backbone was correlated with their PL Quantum Yield (QY) (up to 69%). The hybridization between the surface/molecule state and the carbon backbone synergistically affected the chemical/physical properties. Also, long-chain polyethylenic amine (PEA) molecule-doped CDs exhibit increasing photostability, but at the expense of PL efficiency, proving that the PL emission of high QY CDs arise not only from the sp(2)/sp(3) carbon core and surface passivation of CDs, but also from the molecular fluorophores integrated in the CDs. In vitro and in vivo bioimaging of these N-doped CDs showed strong photoluminescence signals. Good biocompatibility demonstrates their potential feasibility for bioimaging applications. In addition, the overall size profile of the as-prepared CDs is comparable to the average size of capillary pores in normal living tissues (∼5 nm). Our study provides valuable insights into the effects of the PEA doping ratios on photoluminescence efficiency, biocompatibility, cellular uptake, and optical bioimaging of CDs.
authors.affiliation: †Department of Imaging and Interventional Radiology, Prince of Wales Hospital, The Chinese University of Hong Kong Shatin, New Territories Hong Kong SAR, P. R. China.
authors.forename: Junqing
authors.initials: J
authors.lastname: Wang
authors.forename: Pengfei
authors.initials: P
authors.lastname: Zhang
authors.forename: Chao
authors.initials: C
authors.lastname: Huang
authors.forename: Gang
authors.initials: G
authors.lastname: Liu
authors.affiliation: §Department of Chemistry and Partner State Key Laboratory of Environmental and Biological Analysis, The Hong Kong Baptist University, Kowloon Tong, Kowloon, Hong Kong SAR, P. R. China.
authors.forename: Ken Cham-Fai
authors.initials: KC
authors.lastname: Leung
authors.affiliation: †Department of Imaging and Interventional Radiology, Prince of Wales Hospital, The Chinese University of Hong Kong Shatin, New Territories Hong Kong SAR, P. R. China.
authors.forename: Yì Xiáng J
authors.initials: YX
authors.lastname: Wáng
mesh_terms: D002244:Carbon / Q000737:chemistry*; D009584:Nitrogen / Q000737:chemistry*; D011094:Polyethyleneimine / Q000737:chemistry
chemical_list: D002244:Carbon; D011094:Polyethyleneimine; D009584:Nitrogen