Synthesis and formation mechanistic investigation of nitrogen-doped carbon dots with high quantum yields and yellowish-green fluorescence

Abstract

Heteroatom doped carbon dots (CDs) have received increasing attention due to their unique properties and related applications. However, previously reported CDs generally show strong emission only in the blue-light region, thus restricting their further applications. And the fundamental investigation on the preparation process is always neglected. Herein, we have developed a simple and solvent-free synthetic strategy to fabricate nitrogen-doped CDs (N-CDs) from citric acid and dicyandiamide. The as-prepared N-CDs exhibited a uniform size distribution, strong yellowish-green fluorescence emission and a high quantum yield of 73.2%. The products obtained at different formation stages were detailedly characterized by transmission electron microscopy, X-ray diffraction spectrometer, X-ray photoelectron spectroscopy and UV absorbance spectroscopy. A possible formation mechanism has thus been proposed including dehydration, polymerization and carbonization. Furthermore, the N-CDs could serve as a facile and label-free probe for the detection of iron and fluorine ions with detection limits of 50 nmol L(-1) and 75 nmol L(-1), respectively.

Excitons in Carbonic Nanostructures

“…The similarity among the different types of nanocarbons extends to fluorescence lifetimes that are always in the nanosecond time range, usually longer than that of typical monomeric dyes [69]. The fluorescence quantum yields were already reported to be relatively high, 30%-40% [45,49], and some recent data report a much higher level [196,197]. On the other hand, random formation of particle surface groups, their modification and heteroatom doping, and the interaction of these heterogeneously formed surfaces with solvent must result in microscopic heterogeneity, the issue raised by many researchers.…”

Boron and nitrogen co‐doped carbon dots as a sensitive fluorescent probe for the detection of curcumin

“…Recently, the doping of heteroatoms such as nitrogen (N) and sulfur (S) into CDs has been considered as the most useful method to improve the QY. [25] For example, Hou et al [26] have synthesized nitrogen doped CDs with a high QY of 73.2%. Dong et al [27] used citric acid and L-cysteine as the precursor to successfully synthesized N and S co-doped CDs with a high QY of 73.0%.…”

Confined Synthesis of Carbon Nitride in a Layered Host Matrix with Unprecedented Solid‐State Quantum Yield and Stability

“…Especially in recent years, carbon dots (CDs) and graphene quantum dots (GQDs) have drawn tremendous attention for their high aqueous solubility, facile preparation, and low toxicity; and prospective applications have been explored in bioimaging, photocatalysis, photovoltaic, and optoelectronic devices . Great efforts have been made to promote the photoluminescence quantum yield (PLQY) of CDs and GQDs, which is a crucial factor in practical applications . However, previous studies on nanocarbon fluorescent materials are mainly focused on aqueous or colloid systems; solid‐state quantum yield (SSQY) decreases sharply as a result of aggregation‐induced PL quenching, which restricts their employment in solid state devices (e.g., light‐emitting diodes (LEDs), optoelectronic devices) .…”