title: Carbon dots as fluorescent probes for "off-on" detection of Cu2+ and L-cysteine in aqueous solution.
abstract: Copper ion (Cu(2+)) and L-cysteine (L-Cys) detection is critically important since an abnormal level of Cu(2+) or L-Cys is an indicator for many diseases. In this paper, we demonstrate an "off-on" approach for highly sensitive and selective detection of Cu(2+) and L-Cys using carbon dots (CDs) as fluorescent probes. CDs were prepared by using mesoporous silica (MS) spheres as nanoreactors. The binding ability of CDs towards metal ions was examined by comparing the fluorescence intensities of CDs before and after the addition of the metal ions. The addition of Cu(2+) cations leads to their absorption on the surface of CDs and the significant fluorescence quench of CDs (turn-off). The resulting in CDs-Cu(2+) system was found to be sensitive to L-Cys. The addition of L-Cys not only serves to shelter the CDs effectively from being quenched, but also to reverse the quenching and restore the fluorescence (turn-on) due to its ability to remove Cu(2+) from the surface of CDs. This method is facile, rapid, low cost, and environment-friendly. A detection limit as low as 2.3×10(-8) M for Cu(2+) and 3.4×10(-10) M for L-Cys is obtained, which is promising for biological applications.
authors.affiliation: Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237, PR China; CSIRO Materials Science and Engineering (CMSE), Clayton, VIC 3168, Australia; CSIRO Materials Science and Engineering (CMSE), Lindfield, NSW 2070, Australia.
authors.forename: Jie
authors.initials: J
authors.lastname: Zong
authors.forename: Xiaoling
authors.initials: X
authors.lastname: Yang
authors.forename: Adrian
authors.initials: A
authors.lastname: Trinchi
authors.forename: Simon
authors.initials: S
authors.lastname: Hardin
authors.forename: Ivan
authors.initials: I
authors.lastname: Cole
authors.forename: Yihua
authors.initials: Y
authors.lastname: Zhu
authors.forename: Chunzhong
authors.initials: C
authors.lastname: Li
authors.forename: Tim
authors.initials: T
authors.lastname: Muster
authors.forename: Gang
authors.initials: G
authors.lastname: Wei
mesh_terms: D015374:Biosensing Techniques / Q000379:methods*; D002244:Carbon / Q000737:chemistry*; D003300:Copper / Q000032:analysis*; D003545:Cysteine / Q000032:analysis*; D005456:Fluorescent Dyes / Q000737:chemistry*; D057230:Limit of Detection; D045663:Quantum Dots; D012822:Silicon Dioxide / Q000737:chemistry; D013050:Spectrometry, Fluorescence / Q000379:methods
chemical_list: D005456:Fluorescent Dyes; D002244:Carbon; D012822:Silicon Dioxide; D003300:Copper; D003545:Cysteine
keywords: Carbon dots; Copper ions; Fluorescent probe; Mesoporous silica; l-cysteine; “off–on” detection.