One-pot synthesis of N-doped carbon dots by pyrolyzing the gel composed of ethanolamine and 1-carboxyethyl-3-methylimidazolium chloride and their selective fluorescence sensing for Cr(vi) ions

Abstract

N-Doped carbon dots (CDs) were directly synthesized with a high yield of 21.85% by one-pot pyrolysis of a gel composed of ethanolamine and 1-carboxyethyl-3-methylimidazolium chloride at 220 °C for 2 h. The as-synthesized CDs with a mean particle size of 7.8 nm were uniform, amorphous, and abundant in nitrogen content (23.15 wt%) and surface groups such as amide and hydroxyl. Thus, the CDs exhibited good water-solubility, bright blue excitation- and pH-dependent fluorescence with a quantum yield of 17.93%, and high ionic strength tolerance. In addition, a CD-based fluorescent sensor towards Cr(vi) ions with favorable sensitivity and selectivity was constructed based on the inner filter effect. Two good linear relationships between the concentration of Cr(vi) ions and the PL quenching efficiency were obtained in the ranges from 0.2 to 2 (R2 = 0.9965) and 2-40 μM (R2 = 0.9918), and the limits of detection (LOD = 3σ/S) were calculated as 0.018 and 0.25 μM, respectively. Importantly, this sensor was solid and capable of rapidly detecting Cr(vi) ions in tap water with detection ranges of 0.2-2 (R2 = 0.9817) and 2-60 μM (R2 = 0.9902), LODs of 0.048 and 0.40 μM, and recoveries of 102.1-106%.

Ultrafast and Energy-saving Synthesis of Nitrogen and Chlorine Co-doped Carbon Nanodots via Neutralization Heat for Selective Detection of Cr(VI) in Aqueous Phase

“…The fluorescence method proposed here possesses comparable linear range and relatively low LOD. Even though in some cases, some of the previously reported methods [ 28 , 29 , 30 , 31 ] have better sensitivity than our proposed fluorescence method, the reported fabrication methods for CDs usually require an external heat source and time-consuming heating process to assist the carbonization of the carbon source [ 29 , 30 , 31 ], and some of the methods were only performed in the preliminary test stage while their capability for real sample analyses were unknown [ 28 , 29 ]. In comparison with the other reported methods, our proposed N , Cl -CDs-based fluorescence method stands out in the use of a simple, ultrafast, and energy-saving synthetic route to fabricate CDs possessing the capability for Cr (VI) detection in real samples.…”

“…Recently, CD-based sensors [ 22 , 27 ] have attracted much attention in Cr(VI) detection due to their advantages in low cost, favorable selectivity, and ease of miniaturization. So far, a bunch of CDs have been developed for Cr(VI) recognition with high selectivity and sensitivity; however, most of the preparation procedures for CDs require external heat and long heating time to achieve the carbonization of carbon source [ 28 , 29 , 30 , 31 ], and some of the reported methods were only performed in the preliminary test stage with no real sample application employed [ 28 , 29 ]. As such, the development of a simple, fast, and energy-efficient synthetic route to produce highly selective and sensitive CDs with the capability for Cr(VI) detection in real samples is highly desirable.…”

Ionic Liquid‐Functionalized CQDs as Effective “Signal‐Off” Fluorescence Nanoprobes for Selective and Sensitive Detection of Iron (III) and Chromium (VI)

“…Recently, Lu et al prepared fluorescent CQDs by one-step sonochemistry for detecting Fe 2 + in both water and interior of cancer cells with a limit of detection (LOD) down to 38 nM. [38] Besides, detection of other metal ions with CQDs have also been presented, involving Hg 2 + , [39] Cu 2 + , [40] Cr 6 + , [41] Ag + , [42] Pb 2 + , [43] Zn 2 + , [44] and Co 2 + . [45] Despite of these pioneering works, currently the ultra-sensitive detection of heavy metal ions using CQDs is still a huge challenge.…”

“…[42] Precursors for synthesis of CQDs are generally divided into organic molecules and biomass carbon sources. [41] Citric acid is a standout carbon source to prepare CQDs, because it can compensate organic ammonium to provide the covalently linked surface modifier. [46] However, citric acid is relatively volatile.…”

“…The introduction of nitrogen source could also improve the performance of ILCQDs. [41] In addition, the IL is also promising to regulate the grain growth by electrostatic repulsion and tune the performance of ILCQDs through ion exchange. [39,47] In this contribution, we synthesized blue-emitting ILCQDs by one-pot pyrolysis using citric acid and [APMIm][Br].…”