Solid-Phase Synthesis of Highly Fluorescent Nitrogen-Doped Carbon Dots for Sensitive and Selective Probing Ferric Ions in Living Cells

Abstract

Carbon quantum dots (C-Dots) have drawn extensive attention in recent years due to their stable physicochemical and photochemical properties. However, the development of nitrogen-doped carbon quantum dots (N-doped C-Dots) is still on its early stage. In this paper, a facile and high-output solid-phase synthesis approach was proposed for the fabrication of N-doped, highly fluorescent carbon quantum dots. The obtained N-doped C-Dots exhibited a strong blue emission with an absolute quantum yield (QY) of up to 31%, owing to fluorescence enhancement effect of introduced N atoms into carbon dots. The strong coordination of oxygen-rich groups on N-doped C-Dots to Fe(3+) caused fluorescence quenching via nonradiative electron-transfer, leading to the quantitative detection of Fe(3+). The probe exhibited a wide linear response concentration range (0.01-500 μM) to Fe(3+) with a detection limit of 2.5 nM. Significantly, the N-doped C-Dots possess negligible cytotoxicity, excellent biocompatibility, and high photostability. All these features are favorable for label-free monitoring of Fe(3+) in complex biological samples. It was then successfully applied for the fluorescence imaging of intracellular Fe(3+). As an efficient chemosensor, the N-doped C-Dots hold great promise to broaden applications in biological systems.

Characterization and Analytical Separation of Fluorescent Carbon Nanodots

“…In the case of IR analysis of C-dots samples, apart from the evaluation of hydroxyl (-OH) and carbonyl (C=O) functional groups on the C-dots surface [41,49,69,127], IR is also able to examine the doping of heteroatoms into the C-dots framework. Important examples include the identification of the presence of amide/amine (-CN/NH 2 ) [15,20,21,[37][38][39][40][41][42][43][44][45][46], alkyl sulfide (C-S) [33,[46][47][48][49], organosiloxane (Si-OSi/Si-O-C) [89,127,140,141], phosphates (P=O and P-O-R) [38,49,93], and boronic acid (B-O and B-N) [114,142,143] moieties attached on the surface of C-dots, providing evidence for introduction of nitrogen (N), sulfur (S), silicon (Si), phosphorus (P), and boron (B) heteroatoms into Cdots. The merits of this technique for the characterization of surface functionalization of C-dots are being low cost, simple, rapid, and easy for sample preparation.…”

“…Recently, there is a considerable interest in developing labor, material, and energy efficient synthetic methods for C-dots such as carbonization of naturally available bioresources [15,19,24,26,27,[30][31][32][33][34][35][36][37], preparation with low heating temperature [38], and synthesis without external heating [39,40]. In addition, the flexibility in modification and functionalization of the C-dots surface has opened many possibilities in the incorporation of heteroatoms such as nitrogen [15,20,21,[37][38][39][40][41][42][43][44][45][46], sulfur [33,[46][47][48][49], phosphorous [39,49], and silane [50] into C-dots framework to enhance the PL properties of C-dots.…”

Carbon Based Dots and Their Luminescent Properties and Analytical Applications

“…After that, many similar works have been carried out to prepare hydrophilic CDs (Fig. 10a), using the complex of CA and some organic ammonium molecules such as cysteine, glycine [87], ethylenediamine [88], ethanolamine [89], urea and thiourea [90], and polyethylene glycol (PEG) diamine [91]. More works have carried out to find other organics as the precursor to synthesize CDs (see Table 1).…”

Progress of Luminescent Carbon Dots in Biomedicine Engineering

“…All in all, the preparation methods can be classified into two main groups: top-down and bottom-up methods (Scheme 1). Top-down methods consist of arc discharge [1,5], laser ablation [6][7][8][9], and electrochemical oxidation [10][11][12][13], where the C-dots are formed or "broken off" from a larger carbon structure (such as graphite, carbon rods, graphene Oxides and carbon nanotubes). Bottom-up strategies consist, for example, of combustion/hydrothermal/ acidic oxidation/ultrasonic [14][15][16], supported synthetic [17,18], or microwave methods [19][20][21][22] during which the C-dots are formed from molecular precursors.…”

“…Toxicity studies have been conducted by various research groups. While the reports are few at the moment, C-dots appear to have low toxicity [2,5,[20][21][22][23][24][25]. Ray, et al performed cell viability tests on HepG2 cells, a human hepatocellular liver carcinomaline, using MTT and Trypan blue assays [47].…”