Nitrogen‐Doped Carbon Dots: A Facile and General Preparation Method, Photoluminescence Investigation, and Imaging Applications

Abstract

Carbon dots (Cdots) are an important probe for imaging and sensing applications because of their fluorescence property, good biocompatibility, and low toxicity. However, complex procedures and strong acid treatment are often required and Cdots suffer from low photoluminescence (PL) emission. Herein, a facile and general strategy using carbonization of precursors and then extraction with solvents is proposed for the preparation of nitrogen‐doped Cdots (N‐Cdots) with 3‐(3,4‐dihydroxyphenyl)‐L‐alanine (L‐DOPA), L‐histidine, and L‐arginine as precursor models. After they are heated, the precursors become carbonized. Nitrogen‐doped Cdots are subsequently extracted into N,N′‐dimethylformamide (DMF) from the carbogenic solid. A core–shell structure of Cdots with a carbon core and the oxygen‐containing shell was observed. Nitrogen has different forms in N‐Cdots and oxidized N‐Cdots. The doped nitrogen and low oxidation level in N‐Cdots improve their emission significantly. The N‐Cdots show an emission with a nitrogen‐content‐dependent intensity and Cdot‐size‐dependent emission‐peak wavelength. Imaging of HeLa cells, a human cervical cancer cell line, and HepG2 cells, a human hepatocellular liver carcinoma line, was observed with high resolution using N‐Cdots as a probe and validates their use in imaging applications and their multicolor property in the living cell system.

Enhanced photoluminescence and characterization of multicolor carbon dots using plant soot as a carbon source

“…The multicolor property of C-dots has made them promising "nano-lights" that can emit tuneable photoluminescence for various applications. Particularly, considerable research effort has been focused on their potential applications in biological field [12,[15][16][17].…”

One-Step Microwave-Assisted Green Synthesis of Luminescent N-Doped Carbon Dots from Sesame Seeds for Selective Sensing of Fe(III)

“…C.dots are spherical, oxygenous carbon nanoparticles with size below 10 nm. C.dots akin to Q.dots show several interesting properties such as excitation-dependent emission, chemical and photostability, enhanced fluorescence quantum yields and the possibility of fine-tuning the sensing properties by surface modification [5][6][7][8][9][10][11] In order to improve the photophysical and photochemical properties of C.dots, hetero-atom doped C.dots are synthesized by different ways. Among them, nitrogendoped C.dots received much attention because of their good biocompatibility and the related broad applications in the areas of bio-imaging, electrocatalysis and sensors 25,26 .…”

One step synthesis of Al/N co-doped carbon nanoparticles with enhanced photoluminescence

“…To further understand the cause for the higher photoluminescence, an Al-CNPs trial was conducted at the same time; however, no obvious luminescence enhancement was found. It was proposed that the high photoluminescence might be attributed to the nitrogen-containing functional groups formed during the hydrothermal treatment which serve as surface passivation [23][24][25][26]. The enhanced photoluminescence in CNPs is likely due to the passivated defects on the surface of carbon nanoparticles, which act as excitation energy traps.…”