Carbon quantum dots (C-Dots) have drawn extensive attention in recent years due to their stable physicochemical and photochemical properties. However, the development of nitrogen-doped carbon quantum dots (N-doped C-Dots) is still on its early stage. In this paper, a facile and high-output solid-phase synthesis approach was proposed for the fabrication of N-doped, highly fluorescent carbon quantum dots. The obtained N-doped C-Dots exhibited a strong blue emission with an absolute quantum yield (QY) of up to 31%, owing to fluorescence enhancement effect of introduced N atoms into carbon dots. The strong coordination of oxygen-rich groups on N-doped C-Dots to Fe(3+) caused fluorescence quenching via nonradiative electron-transfer, leading to the quantitative detection of Fe(3+). The probe exhibited a wide linear response concentration range (0.01-500 μM) to Fe(3+) with a detection limit of 2.5 nM. Significantly, the N-doped C-Dots possess negligible cytotoxicity, excellent biocompatibility, and high photostability. All these features are favorable for label-free monitoring of Fe(3+) in complex biological samples. It was then successfully applied for the fluorescence imaging of intracellular Fe(3+). As an efficient chemosensor, the N-doped C-Dots hold great promise to broaden applications in biological systems.

Fluorescence sensing of specific biological molecules by artificial chemosensors is a versatile technique. In the present work, a switch-on fluorescence sensor for rapid, sensitive, and selective sensing of glutathione (GSH) in food samples was developed. This method was based on the g-CNQDs-Hg(2+) system, in which the initial fluorescence from g-CNQDs was quenched by Hg(2+) with an electron transfer process. In the presence of GSH, the fluorescence sensor was switched to the "on" state, which was attributed to a competitive affinity of Hg(2+) to GSH and the functional groups on the surface of g-CNQDs. Under the optimal conditions, the limit of detection (LOD) of 37 nM for GSH was achieved with a wide range of 0.16-16 μM. The repeatability was better than 5.3% for GSH in both standard and food samples (n = 3). Finally, this fluorescence sensor was successfully employed for the determination of GSH in various kinds of food samples with excellent recoveries. Furthermore, this application may pave a new way for fluorescence sensing of other substances in food samples.

Because of the unusual properties of the structure, the metal organic frameworks (MOFs) have received great interest in separation science. However, the most existing methods for the applications of MOFs in separation science require an off-line procedure to prepare the materials. Here, we report an in situ, layer-by-layer self-assembly approach to fabricate MIL-100(Fe) coated open tubular (OT) capillary columns for capillary electrochromatography. By a controllable manner, the OT capillary columns with a tailored MIL-100(Fe) coating have been successfully synthesized. The results of SEM, XRD, FT-IR, and ICP-AES indicated that MIL-100(Fe) was successfully grafted on the inner wall of the capillary. Some neutral, acidic and basic analytes were used to evaluate the performance of the MIL-100(Fe) coating OT capillary column. Because of the size selectivity of lattice aperture and hydrophobicity of the organic ligands, three types of analytes were well separated with this novel MIL-100(Fe) coating OT capillary column. For three consecutive runs, the intraday relative standard deviations (RSDs) of migration time and peak areas were 0.4-4.6% and 1.2-6.6%, respectively. The interday RSDs of migration time and peak areas were 0.6-8.0% and 2.2-9.5%, respectively. The column-to-column reproducibility of retention time was in range of 0.6-9.2%. Additionally, the 10 cycles OT capillary column (10-LC) could be used for more than 150 runs with no observable changes on the separation efficiency.

No abstract

A novel and effective ratiometric fluorescence strategy was developed for rapidly, sensitively and selectively probing sulfide anions (S(2-)). A dual-emission nanosensor was prepared by covalently attaching fluorescent carbon nanoparticles (CNPs) to gold nanoclusters (Au NCs), triggering the sensing mechanism of fluorescence resonance energy transfer (FRET) from CNPs (donor) to Au NCs (acceptor). Once S(2-) was added, considerable fluorescence recovery of CNPs and quenching of Au NCs were observed due to the inhibition of FRET progress via the formation of Au2S. The ratiometric probe showed good, specific S(2-) sensing behavior and high sensitivity with a detection limit of 18 nM. Significantly, the assay was successfully employed to determine the S(2-) content in biological and water samples, presenting immense promise in the biological and environmental fields.