Facile, green and energy-efficient preparation of fluorescent carbon dots from processed traditional Chinese medicine and their applications for on-site semi-quantitative visual detection of Cr(VI)

A Label-Free Fluorescent Sensor Based on Si,N-Codoped Carbon Quantum Dots with Enhanced Sensitivity for the Determination of Cr(VI)

“…The XRD patterns ( Figure 2 b) show the amorphous properties of Si,N-CQDs. The XRD pattern of Si,N-CQDs exhibited a broad peak at 2θ = 21.94°, which was attributed to the (002) plane of graphite [ 45 ].…”

“…The characteristic peak at 1148 cm −1 reflects the existence of C-O stretching vibration. The characteristic absorption bands of Si-O are shown at 1048 and 790 cm −1 [ 24 , 45 , 46 ].…”

Sustainable and Green Synthesis of Waste-Biomass-Derived Carbon Dots for Parallel and Semi-Quantitative Visual Detection of Cr(VI) and Fe3+

“…The deconvolution peaks of C 1s (Supplementary Figure S2b) could be attributed to the structure of the C-O/C-N (285.6 eV) [52,53], C-C/C=C (284.3 eV) [54] and C=O (287.4 eV) bonds [53], respectively. The high-resolution XPS spectrum of O 1s (Supplementary Figure S2c) exhibited three peaks at 530.3 eV, 513.6 eV and 534.8 eV, which were associated with the -OH [55], C=O [3] and C-OH bonds [56], indicating that plenty of hydrophilic groups, such as carboxyl and hydroxyl groups, were integrated into the FW-CDs. In addition, the three deconvolved peaks of N 1s (Supplementary Figure S2d) at 398.38 eV, 400.28 eV and 401.08 eV disclosed that the nitrogen atoms severally existed in the form of pyrrolic-like N, pyridinic-like N and graphitic-like N [57].…”

“…Because of the fact that the excitation wavelength of FW-CDs had a large overlap with the absorption spectrum of Cr(VI), the quenching mechanism of FW-CDs caused by Cr(VI) was considered to be an inner filter effect (IFE). To further confirm the deduction, the corrected fluorescence intensity (F cor ) of FW-CDs before considering IFE was calculated based on the Parker equation, the data processing of which was conducted following the same procedures and using the same parameters as our previous work [3]. As depicted in Figure 5c, when the content of Cr(VI) increased, both the correction factor (CF = F cor /F obsd ) values and the discrepancy between E obsd and E cor continuously increased, which indicated that IFE takes up a very large proportion of the observed total suppression efficiency in the fluorescence-quenching process.…”

“…Over the past 10 years, fluorescent carbon dots (CDs) have gained much attention in many areas such as photocatalysis [1,2], chemical sensing [3,4], biological imaging [5,6] and drug delivery [7], which have benefited from their unique advantages, including excellent fluorescence performance, good biocompatibility and easily modifiable functionalities [8,9]. A range of synthesis approaches such as electrochemistry and the chemical oxidation of bulk carbon precursors [10,11], and the hydrothermal [8,12,13], solvothermal [14], ultrasonication [3] and microwave [15] treatment of molecular precursors have been explored for the synthesis of CDs. Among them, hydrothermal synthesis has aroused wider attention due to its benefits of convenient operation, strong practicability and the "green" nature of water [16].…”