Red-Emissive Carbon Dots for “Switch-On” Dual Function Sensing Platform Rapid Detection of Ferric Ions and l-Cysteine in Living Cells

Abstract

Ferric ions (Fe 3+ ions) and l -cysteine ( ( l -Cys) in the human body have always played an irreplaceable role in biological processes, and overload or deficiency of Fe 3+ ions and l -Cys in the biological system leads to various diseases. In this work, N,S-co-doped red-emitting carbon dots (R-CDs) were synthesized by a facile hydrothermal method. Because the doping of N and S gives a unique functional group distribution on the surface of R-CDs, it can be complexed with Fe 3+ ions to construct an energy transfer quenching system. However, the presence of l -Cys competitively binds to Fe 3+ ions, thus resulting in the photoluminescence recovery of R-CDs. Therefore, a “switch-on” dual function sensing platform has successfully been developed based on R-CDs for rapid identification and quantification of Fe 3+ ions and l -Cys. The linear detection range of Fe 3+ ions is 0–30 μM (limit of detection (LOD): 0.27 μM) and that of l -Cys is 0–24 μM (LOD: 0.14 μM). The sensor platform was used to detect Fe 3+ ions and l -Cys in human serum samples with satisfactory results. Compared with traditional detection methods, this method is more time-saving and efficient and can be completed in 3 min. It is worth mentioning that the R-CDs not only has high optical stability but also has negligible cytotoxicity and has been successfully applied to in vitro/vivo imaging, indicating that R-CDs have excellent tissue penetration and biomarker potential. More interestingly, the switch-on fluorescence behavior for stepwise detection of Fe 3+ ions and l -Cys can also be observed in cell imaging, which provides the possibility of visual detection of the probe to be applied in vivo.

Nitrogen-doped carbon dots for sensitive detection of ferric ions and monohydrogen phosphate by the naked eye and imaging in living cells

“…S4d, ESI †). 19 The XPS analyses of the N-CDs are in good agreement with FT-IR assignments (Fig.S5a, ESI †). The FTIR spectrum of the N-CDs displays the sharp peaks at 3388 cm -1 and 1584 cm -1 , corresponding the stretching vibration and bending vibration of N-H group, respectively.…”

“…Today some carbon dots based on Fe 3+ sensing have been reported. [19][20][21][22][23][24][25][26][27][28][29][30] Unfortunately, due to the intrinsic drawbacks of carbon dots, these carbon dots need UV excitation and their Stokes shifts are small, [28][29][30] which seriously restrict their application in living system. As for HPO 4 2-, there is little report based on carbon dots for phosphate anions (H 2 PO 4 -/HPO 4 2-) detection so far.…”

Polyol-Mediated Synthesis of Nitrogen-Containing Carbon-Dots from Tetracyanobenzene with Intense Red Fluorescence

“…The observed lattice distance of 1.91 Å relates to graphite ( d 101 with 2.03 Å, [32,33]) but definitely shows a certain reduction. Such reduced lattice fringe distance was already observed for nitrogen-containing C-dots and is ascribed to the higher polarity of heteroatom-containing graphite layers in comparison to pure graphite layers [6,20,21,22,23,24,25]. In contrast, C-dots prepared via the polyol synthesis with similar conditions but in absence of TCB exhibited a larger lattice fringe distance of 2.05 Å [16,18].…”

“…Although reliable liquid-phase syntheses of C-dots have been established, the realization of C-dots showing intense red emission is still a challenge. Most often red emission was reported for nitrogen- or sulfur-doped C-dots, Eu 3+ -containing C-dots, or C-dots that were modified with plasmonic metal nanoparticles [6,19,20,21,22,23,24,25]. The quantum yield for red emission with 30%–35% is nevertheless comparably low in comparison to the blue and green emission of C-dots (up to 80%) [1,3,4,5,6,7,8].…”

Recent advances in fluorescence probes based on carbon dots for sensing and speciation of heavy metals

“…In vivo fluorescence images after tail vein injection exhibited bright emissions along with the distribution of La-CQDs in mice, which demonstrated that La-CQDs could serve as a new platform of fluorescent bioimaging and showed promise for drugs delivery. Sun et al [140] also reported similar work that N, S-codoped redemitting CDs (R-CDs) could be used as a Fe(III) sensor through an ET quenching process by cell imaging, and showed the possibility as imaging reagent in vivo by subcutaneous injection of CDs into nude mice.…”