Carbon quantum dots directly generated from electrochemical oxidation of graphite electrodes in alkaline alcohols and the applications for specific ferric ion detection and cell imaging

Abstract

Carbon quantum dots (CQDs) are attracting tremendous interest owing to their low toxicity, water dispersibility, biocompatibility, optical properties and wide applicability. Herein, CQDs with an average diameter of (4.0 ± 0.2) nm and high crystallinity were produced simply from the electrochemical oxidation of a graphite electrode in alkaline alcohols. The as-formed CQDs dispersion was colourless but the dispersion gradually changed to bright yellow when stored in ambient conditions. Based on UV-Vis absorption, fluorescence spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and high-resolution transmission electron microscopy (HRTEM), this colour change appeared to be due to oxygenation of surface species over time. Furthermore, the CQDs were used in specific and sensitive detection of ferric ion (Fe(3+)) with broad linear ranges of 10-200 μM with a low limit of detection of 1.8 μM (S/N = 3). The application of the CQDs for Fe(3+) detection in tap water was demonstrated and the possible mechanism was also discussed. Finally, based on their good characteristics of low cytotoxicity and excellent biocompatibility, the CQDs were successfully applied to cell imaging.

Facile synthesis of N-rich carbon quantum dots from porphyrins as efficient probes for bioimaging and biosensing in living cells

“…The results demonstrate that the CQDs have good biocompatibility and low toxicity toward HeLa cells. 48 The low cytotoxicity confirms the suitability of the fluorescent CQDs for bioimaging applications.…”

“…The high selectivity could be ascribed to the strong coordination between Fe 3+ and the phenolic hydroxyl groups on the surface of CQDs. 48 The electrons in the excited state of CQDs are then transferred to the half-filled 3d orbitals of Fe 3+ , facilitating the nonradiative electron/hole recombination and resulting in significant fluorescence quenching. To prove our speculation, time-correlated single photon counting method was used to analyze the charge transfer in the exciton recombination process of CQDs with and without Fe 3+ .…”

A facile synthesis of nontoxic luminescent carbon dots for detection of chromium and iron in real water sample and bio‐imaging

“…There are different methods to synthesize CDs, such as the electrochemical method, hydrothermal method, microwave synthesis technique, simple heating technique, etc. The hydrothermal method, or simple heating technique, is advantageous and is better than other techniques due to its simple preparation process and low energy consumption, and it enables easy control over reactions.…”

One‐pot synthesis of fluorescent nitrogen‐doped carbon dots with good biocompatibility for cell labeling

“…In addition, the chemical composition of the as‐synthesized N‐CDs was provided by XPS analysis. Three predominant peaks at 284.08, 399.08 and 530.08 eV of the XPS survey spectrum corresponded to C1s, N1 s and O1s (Figure a), respectively, suggesting that the nitrogen is successfully doped into the CDs . Specifically, the deconvolution of the C1s spectrum (Figure b) could be fitted into four component peaks at 284.6, 285.9, 286.7, and 288.4 eV, which are attributed to C–C, C–N, C–O, and C = O, respectively.…”

“…Fluorescent carbon dots (CDs) are novel and fascinating carbon nanomaterials with ecofriendly original materials, superior optical properties and good biocompatibility, which have been utilized as fluorescent probes for high‐sensitive detection and high‐contrast bioimaging . To date, various synthesis approaches containing arc discharge, laser ablation, electrochemical oxidation, chemical oxidation, thermal carbonization, combustion, acid dehydration and ultrasonic treatment have been presented to synthesize CDs using various precursors. Considering the above methods with expensive raw materials and intricate synthesis conditions, it is still urgent to develop a low‐cost and environmental strategy for the synthesis of CDs with strong fluorescence and good biosafety.…”