A green heterogeneous synthesis of N-doped carbon dots and their photoluminescence applications in solid and aqueous states

Abstract

Compared with traditional semiconductor quantum dots (QDs) and organic dyes, photoluminescent carbon dots (CDs) are superior because of their high aqueous solubility, robust chemical inertness, facile functionalization, high resistance to photobleaching, low toxicity and good biocompatibility. Herein, a green, large-scale and high-output heterogeneous synthesis of N-doped CDs was developed by reacting calcium citrate and urea under microwave irradiation without the use of any capping agents. The obtained N-doped CDs with a uniform size distribution exhibit good aqueous solubility and yellowish-green fluorescence in the solid and aqueous states. These unique luminescence properties of N-doped CDs inspire new thoughts for applications as fluorescent powders, fluorescent inks, the growth of fluorescent bean sprouts, and fingerprint detection tools.

Synthesis of cellulose-derived carbon dots using acidic ionic liquid as a catalyst and its application for detection of Hg2+

“…Since then, this new class of carbon nanomaterials has garnered much focus of researchers, and various synthesis methods have been demonstrated for the preparation of CDs. Up to now, the main synthesis methods for the preparation of CDs consist of hydrothermal or solvothermal treatment [13], chemical ablation [3,14], microware irradiation [15], ultrasonic treatment [16], laser ablation [17], and electrochemical carbonization [18]. However, all the approaches above-mentioned suffer from several drawbacks such as drastic processes, time consuming, and expensive precursors [2], which limit the large-scale preparation and wide application of CDs.…”

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.…”

Fluorescently tuned nitrogen-doped carbon dots from carbon source with different content of carboxyl groups

“…22,24 The origin of NCDs' tunable fluorescence has been investigated by adjusting surface states, [25][26][27] and diverse fluorescence phenomena have been observed for NCDs prepared by various reactant precursors. For instance, Xu et al 28 developed a green heterogeneous synthetic method for NCDs with yellowish-green fluorescence. Qu et al 29 synthesized highly fluorescent blue-emission NCDs with citric acid (CA) and ethylene diamine.…”