Selective Detection of Fe3+ by Nitrogen–Sulfur-Doped Carbon Dots Using Thiourea and Citric Acid

Abstract

The quantum yield and fluorescence properties of carbon dots are key issues for environmental detection. In this study, nitrogen–sulfur-doped carbon dots (N,S-CDs) were prepared hydrothermally by adding thiourea to provide the N source. By adjusting the ratio of citric acid (CA) to thiourea (N,S) and adding anhydrous ethanol, blue fluorescent doped carbon dots with a quantum yield of up to 53.80% were obtained. The particle morphology and crystalline organization of the N,S-CDs were analyzed using transmission electron microscopy (TEM) and X-ray diffraction (XRD). Fourier transform infrared (FTIR) spectroscopy was used to illuminate distinct functional units through the recording of typical vibration bands. The luminescence properties of the N,S-CDs were investigated using ultraviolet–visible (UV-vis) absorption spectroscopy and steady-state fluorescence spectroscopy (PL). In addition, the fluorescence stability of the N,S-CDs was studied in detail. The results showed that the functional groups of the N,S-CDs chelate Fe3+ ions to quench the fluorescence of carbon dots. This shows that the N,S-CDs exhibit high selectivity for Fe3+ ions. With the addition of Fe3+ in the concentration of 0–100 µM, the fluorescence intensity of the N,S-CDs exhibited distinct and linear dependence upon the Fe3+ concentration (R2 = 0.9965), and the detection limit (D = 3ơ/m) was measured as 0.2 µM. The excellent optical properties and Fe3+ selectivity of the N,S-CDs provide a huge boost for application in the field of environmental monitoring.

Bottom‐Up Synthesis Optimization Through The Design Of Experiments Using Blue N,S‐Carbon Dots With Interesting Affinity For Potentially Toxic Elements

“…As we can see in Figure 3(b), some of the candidates have demonstrated moderate (Cd 2+ , Hg 2+ , and Sb 3+ ) and good (Bi 3+ , Hg 2 2+ , and Pb 2+ ) interactions with the proposed chemosensor. In that condition, at pH 7.0, it is noticeable that occurred coordination between the analyte and deprotonated carboxyl groups [71] . We hoped that −SH, and −NH 2 interactions were also made.…”

“…In that condition, at pH 7.0, it is noticeable that occurred coordination between the analyte and deprotonated carboxyl groups. [71] We hoped that À SH, and À NH 2 interactions were also made. The alkaline range was not employed in this study because most metals (especially heavy metals) begin to form insoluble species such as oxides/ hydroxides around neutral pH [83] and can continue to form [X(OH) y ] z complexes in further alkali range.…”

Green Synthesis of Carbon Dots for Rapid Selective Detection and Photoreduction of Cr(VI) under Sunlight

“…With increasing the concentration of dichromate, the blue emission of the solution phase was diminished, which is presented in Figure S11. The lower limit of detection (LOD) was computed to be 0.5 μM with an R 2 value of 0.98 (LOD = 3σ/ S , where σ represents the standard deviation and S is the slope of the calibration curve) . The FL quenching effect of different cations (Co 2+ , Pb 2+ , Hg 2+ , Zn 2+ , Fe 2+ , Cu 2+ , Ca 2+ , Cd 2+ , and Na 2+ ) and anions (Br – , Cl – , I – , SO 4 2– , NO 3 – , ClO 4 – , H 2 PO 4 – , CO 3 2– , AcO – , and Cr 2 O 7 2– ) on the ILCDs was examined (Figure c,d).…”

“…The lower limit of detection (LOD) was computed to be 0.5 μM with an R 2 value of 0.98 (LOD = 3σ/S, where σ represents the standard deviation and S is the slope of the calibration curve). 49 The FL quenching effect of different cations (Co 2+ , Pb 2+ , Hg 2+ , Zn 2+ , Fe 2+ , Cu 2+ , Ca 2+ , Cd 2+ , and Na . In contrast, no significant drop in FL intensity was observed when other ions are added to the ILCD solution.…”

Rose Bengal‐Derived Carbon Quantum Dots as a Fluorescence Probe for the Highly Sensitive Detection of Fe3+ Ions

“…High‐resolution TEM images (Figure 1c) exhibited RB‐CQDs with a graphitic structure of lattice fringes about 0.15 nm. The XRD patterns (Figure S2) displayed highly disordered carbon structure with a center of broad diffraction peak at 22.0° [37] . The functional group information was obtained through FTIR spectroscopy (Figure 1d).…”