Oxygen-driven, high-efficiency production of nitrogen-doped carbon dots from alkanolamines and their application for two-photon cellular imaging

Abstract

A novel oxygen-driven method has been developed for low-cost, large-scale, and high-efficiency production of nitrogen-doped carbon dots (N-C-dots) by bubbling pure oxygen into monoethanolamine (MEA) under heating conditions. We find that the addition of pure oxygen significantly increases the reaction rate, and makes feasible one-pot gram scale fabrication (3.36 g) of highly photoluminescent N-C-dots in a couple of hours (2.0 h). With an instantaneous nucleation and gradual growth mechanism, precise control over the particle size of the N-C-dots from 2.0 to 16.1 nm is achieved by simply prolonging the heating time from 0.5 to 4.0 h. The as-prepared N-C-dots contain aromatic CN heterocycles in the core and have plentiful hydrophilic groups on the surface. Practically, the oxygendriven method can be used to synthesize fluorescent N-C-dots from other alkanolamines such as diethanolamine (DEA) and triethanolamine (TEA), which shows general universality. Due to the strong up-conversion photoluminescence, good aqueous dispersibility, high photostability, excellent biocompatibility, and low cytotoxicity, the N-C-dots are demonstrated to be promising two-photon probes for high contrast bioimaging applications.

β-C3N4 Nanocrystals: Carbon Dots with Extraordinary Morphological, Structural, and Optical Homogeneity

“…Although CDs can be obtained by many different routes, some of which are very simple and starting from common, raw materials, there is a certain lack of reliable methods to control their size distributions, crystalline structures, and surface functionalization, which are key elements that determine their optical features . This absence led to study highly inhomogeneous samples, characterized by a broad size distribution , and by an unstructured absorption spectrum without any definite features, increasing the complexity on understanding the emission processes, hindering further improvements of their optical properties, and paralyzing the possibility to tailor them for specific applications. The very fluorescence tunability of CDs, beneficial in some contexts, is indeed the sign of a dramatic dot-to-dot variability undesired for many applications, as recognized by very recent work .…”

How do nitrogen-doped carbon dots generate from molecular precursors? An investigation of the formation mechanism and a solution-based large-scale synthesis

“…Recently, bottom-up routes have been extensively developed, during which C-dots are formed from organic molecules by microwave pyrolysis, 17,18 hydrothermal treatment, [19][20][21][22] or thermal oxidation. [23][24][25][26] Among them, the microwave approach is unfeasible for bulk production of C-dots despite it is fast enough, while the hydrothermal technique and thermal oxidation method can be scaled up, but they are usually time-consuming (several hours or even a few days are typically needed for the reactions). It would be more favorable for industrial-scale synthesis if a large amount of carbon precursors can convert into C-dots in a short time.…”

Ethanol in aqueous hydrogen peroxide solution: Hydrothermal synthesis of highly photoluminescent carbon dots as multifunctional nanosensors

“…Owning to the significant progress in synthetic strategies, numerous routes including arc discharge [15], laser ablation [16], plasma treatment [17], electrochemical synthesis [18,19], ultrasonic/microwave approach [20,21], acidic/thermal oxidation [22][23][24], and hydrothermal technique [25][26][27][28][29], have been explored to fabricate C-dots from a variety of carbon precursors. However, most of these routes suffer from expensive equipments, harsh synthetic conditions, and tedious processes, leading to manufacturing difficulties and high costs for large scale production.…”