A Fluorescent Nanosensor for Silver (Ag+) and Mercury (Hg2+) Ions Using Eu (III)-Doped Carbon Dots

Abstract

Carbon dots doped with Eu3+ ions (Eu-Cdots) were prepared by a hydrothermal treatment, using citric acid and urea as precursors and Eu (NO3)3 as a europium source. The Eu3+ ions are strongly coordinated with the carboxylate groups at the surface of the Cdots and incorporated within the nanographene network in the carbon core. Vibrational spectroscopy provides evidence of such interaction with identification of bands assigned to the stretching of the Eu-O bond. Eu3+ doped Cdots have larger diameters then undoped Cdots, but they are divided into smaller domains of sp2 carbon. The UV-vis excitation spectrum provides evidence of energy transfer from the Cdots to the Eu3+. The luminescence spectrum shows the characteristic sharp peaks of Eu3+ in the red part of the visible spectrum and a broad emission of Cdots centered at 450 nm. The luminescence of the Cdots is strongly quenched by Hg2+ and Ag+, but not by other cations. The quenching mechanism differs significantly depending on the nature of the ion. Both the blue emission of Cdots and the red emission of Eu3+ are quenched in the presence of Hg2+ while only the emission of the Cdots is affected by the presence of Ag+. A ratiometric sensor can be built using the ratio of luminescence intensities of the Cdots to the Eu3+ peaks.

Therapeutic Potential of Chlorophyll Functionalized Carbon Quantum Dots against Cervical Cancer

“…Figure 2a–d illustrates the full‐scan and high‐resolution XPS (HR‐XPS) spectra of C1s, O1s, and N1s. Figure 2a illustrates the entire survey spectrum of Chl‐CQDs, with notable peaks at 285, 400, and 532 eV corresponding to C1s, N1s, and O1s, respectively [31] . The C1s peak may be deconvoluted into six peaks at 284.2, 284.8, 285.7, 286.5, 287.6, and 288.9 eV using Lorentzian Asymmetric peak shape fit, which corresponds to aromatic C=C, C−C, C−O/C−N, C−O‐C, C=O, and O‐C=O groups, respectively (Figure 2b) [32,33] .…”

“…Figure 2a illustrates the entire survey spectrum of Chl-CQDs, with notable peaks at 285, 400, and 532 eV corresponding to C1s, N1s, and O1s, respectively. [31] The C1s peak may be deconvoluted into six peaks at 284.2, 284.8, 285.7, 286.5, 287.6, and 288.9 eV using Lorentzian Asymmetric peak shape fit, which corresponds to aromatic C=C, CÀ C, CÀ O/CÀ N, CÀ O-C, C=O, and O-C=O groups, respectively (Figure 2b). [32,33] Due to the presence of the ester bond, the carboxylic acid peak occurred at 288.9 eV in Chl-CQDs.…”

Recent Advances in Synthesis, Modification, Characterization, and Applications of Carbon Dots

“…Furthermore, color recognition and processing software put on a smartphone may detect Hg 2+ in real time and at a high rate. The CDs doped with Eu 3+ ions (Eu-CDs) were produced hydrothermally, utilizing citric acid and urea as precursors and Eu(NO 3 ) 3 as a europium source by Correia et al [ 174 ]. The Eu 3+ ions are strongly linked to the carboxylate groups on the CDs’ surfaces and incorporated into the carbon core’s nanographene network.…”

Emerging and Versatile Platforms of Metal‐Ion‐Doped Carbon Dots for Biosensing, Bioimaging, and Disease Therapy

“…Due to the small size effect of CDs, M‐CDs can reveal better performance in contrast with that of free metal ions [36–38] . M‐CDs facilely integrate the advantages of CDs and metal ions, and have been taken as versatile nanoplatforms for numerous applications, such as, nanozymes‐based chemo/biosensing, magnetic resonance imaging, therapy, antibacterial test and so on [39–47] …”

“…[36][37][38] M-CDs facilely integrate the advantages of CDs and metal ions, and have been taken as versatile nanoplatforms for numerous applications, such as, nanozymes-based chemo/biosensing, magnetic resonance imaging, therapy, antibacterial test and so on. [39][40][41][42][43][44][45][46][47] Recently, some reviews have been published about the preparation and applications of M-CDs. For instance, Lin et al first summarized the fabrication methods, physicochemical properties, and typical applications of M-CDs in environmental, biological, and energy related fields.…”