title: Presence of photoluminescent carbon dots in Nescafe® original instant coffee: applications to bioimaging.
abstract: The presence of the carbon dots (C-dots) in food is a hotly debated topic and our knowledge about the presence and the use of carbon dots (C-dots) in food is still in its infancy. We report the finding of the presence of photoluminescent (PL) C-dots in commercial Nescafe instant coffee. TEM analysis reveals that the extracted C-dots have an average size of 4.4 nm. They were well-dispersed in water and strongly photoluminescent under the excitation of ultra-violet light with a quantum yield (QY) about 5.5%, which were also found to possess clear upconversion PL properties. X-ray photoelectron spectroscopy characterization demonstrates that the C-dots contain C, O and N three elements with the relative contents ca. 30.1, 62.2 and 7.8%. The X-ray diffraction (XRD) analysis indicates that the C-dots are amorphous. Fourier-transform infrared (FTIR) spectra were employed to characterize the surface groups of the C-dots. The C-dots show a pH independent behavior by varying the pH value from 2 to 11. The cytotoxicity study revealed that the C-dots did not cause any toxicity to cells at a concentration as high as 20 mg/mL. The C-dots have been directly applied in cells and fish imaging, which suggested that the C-dots present in commercial coffee may have more potential biological applications.
authors.affiliation: School of Biological & Food Engineering, Dalian Polytechnic University, Dalian 116034, China; Division of Biotechnology, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China.
authors.forename: Chengkun
authors.initials: C
authors.lastname: Jiang
authors.affiliation: Division of Biotechnology, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China.
authors.forename: Hao
authors.initials: H
authors.lastname: Wu
authors.affiliation: Division of Biotechnology, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China.
authors.forename: Xiaojie
authors.initials: X
authors.lastname: Song
authors.affiliation: Division of Biotechnology, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China.
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Ma
authors.affiliation: School of Biological & Food Engineering, Dalian Polytechnic University, Dalian 116034, China. Electronic address: wangjh@dlpu.edu.cn.
authors.forename: Jihui
authors.initials: J
authors.lastname: Wang
authors.affiliation: Division of Biotechnology, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China. Electronic address: mqtan@dicp.ac.cn.
authors.forename: Mingqian
authors.initials: M
authors.lastname: Tan
mesh_terms: D000818:Animals; D016466:CHO Cells; D002244:Carbon / Q000008:administration & dosage / Q000032:analysis*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D003069:Coffee / Q000737:chemistry*; D006224:Cricetinae; D003412:Cricetulus; D006801:Humans; D049449:Luminescence; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles / Q000008:administration & dosage / Q000032:analysis* / Q000648:ultrastructure; D061848:Optical Imaging; D011036:Poecilia
chemical_list: D003069:Coffee; D002244:Carbon
keywords: Bioimaging; Carbon dots; Nescafe(®) original instant coffee; Photoluminescent