Nitrogen and sulfur co‐doped carbon nanodots toward bovine hemoglobin: A fluorescence quenching mechanism investigation

Abstract

A deep understanding of the molecular interactions of carbon nanodots with biomacromolecules is essential for wider applications of carbon nanodots both in vitro and in vivo. Herein, nitrogen and sulfur co-doped carbon dots (N,S-CDs) with a quantum yield of 16% were synthesized by a 1-step hydrothermal method. The N,S-CDs exhibited a good dispersion, with a graphite-like structure, along with the fluorescence lifetime of approximately 7.50 ns. Findings showed that the fluorescence of the N,S-CDs was effectively quenched by bovine hemoglobin as a result of the static fluorescence quenching. The mentioned quenching mechanism was investigated by the Stern-Volmer equation, temperature-dependent quenching, and fluorescence lifetime measurements. The binding constants, number of binding sites, and the binding average distance between the energy donor N,S-CDs and acceptor bovine hemoglobin were calculated as well. These findings will provide for valuable insights on the future bioapplications of N,S-CDs.

Finding Value in Wastewaters from the Cork Industry: Carbon Dots Synthesis and Fluorescence for Hemeprotein Detection

“…The amounts of α-helices, β-sheets and random coil structures in C-dots-metHgb ([metHgb] = 1.0 µM) were 39%, 8% and 53%, respectively, almost identical to those of native metHgb (41%, 6% and 53%), meaning that the initial protein conformation was conserved. This contrasts with reported works wherein the content of the α-helix dropped by 6% [38] or nearly 10% [31,37] upon interaction with C-dots. A different situation arises from the interaction of C-dots with metMyo ([metMyo] = 3 µM).…”

“…The limit of detection (LOD) was estimated as 7.8 nM and the limit of quantification (LOQ) as 26.0 nM. The sensorial efficiency toward haemoglobin, as measured by the Stern-Volmer constant, is higher or similar to other reported results [15,[31][32][33][34]37].…”

“…277-330), which is not the case here. Although the possibility of RET occurrence has been indicated in a series of studies [15,30,36,37], no flawless demonstration of such a non-radiative reduction of emission was revealed. Static quenching either involve the formation of a ground-state non-fluorescent complex or the development of less-specific interactions between the C-dots and the protein through a sphere of effective quenching [58].…”

“…Previous accounts have traced IFEs as responsible for the observed quenching of C-dots' fluorescence [15,32,35,40]. In some others works, although not recognised, strong IFEs should exist as indicated by the heavily distorted emission spectra in the region of spectral overlap [31,36,37].…”

Recent Advancements in Doped/Co-Doped Carbon Quantum Dots for Multi-Potential Applications

“…Moreover, Simoes et al synthesized N and S co-doped CQDs via microwave (700 W for 5 min) reaction of citric acid, urea and sodium thiosulfate (in the proportion of 1:1:3)-utilized as C, N and S sources, respectively[134]. Furthermore, Wang et al have synthesized N and S co-doped CQDs with blue emission and QY of 16% through hydrothermal reaction (6 h at 200 • C) of thiourea, urea, and sodium citrate[135].C 2019, 5, 24 11 of 40 2.3.5. N, S Co-Doped CQDs…”