Nitrogen‐doped carbon dots from Kraft lignin waste with inorganic acid catalyst and their brain cell imaging applications

Abstract

Carbon quantum dots (C‐QDs) show potential to replace traditional semiconductive quantum dots as the next generation of fluorescent probes. We demonstrate here a new C‐QD production process using lignin, a high‐volume but low market‐value industrial waste and/or environmental hazards, as the starting carbon source. By adding a small amount of inorganic acid, the rich phenolic components in lignin were successfully converted to C‐QDs through a coking formation mechanism similar to what happens on solid acid catalysts in traditional fossil fuel cracking process. Their aqueous solution presence of the received lignin C‐QDs is beneficial for brain cell imaging applications, attributing to their fast internalization, low toxicity, tunable photoluminescence by appropriate acidity and reaction temperature during hydrothermal synthesis. This method not only provides a low‐cost C‐QDs production route, but also helps gain extra profit and/or improve environment for many small agricultural business and paper and pulp industry located in rural area.

Green and continuous microflow synthesis of fluorescent carbon quantum dots for bio‐imaging application

“…High‐resolution TEM image indicates their crystalline structure, in which parallel lattice fringes spreading over the whole particle are clearly observed (Figure 2C). Such lattice fringes suggest that these clusters are assembled individual M‐CQDs 5 . By measuring the distance across 10 atomic planes, the lattice spacing is determined to be 2.09 Å, corresponding to the (100) facet of graphite (insert).…”

Recent Advances in Carbon Dots for In Vitro/Vivo Fluorescent Bioimaging: A Mini-Review

“…A large accumulation of CDs was observed in the cytoplasm and nucleus, which indicated that CDs have good permeability of cell membrane and other intracellular organelle membranes. It could be applied to biological imaging of brain cells in the future ( Pei et al, 2021 ). Besides.…”

In situ coupling of lignin‐derived carbon‐encapsulated CoFe‐CoxN heterojunction for oxygen evolution reaction

“…40,41 Furthermore, lignin-derived carbon has recently been reported as the catalyst support in the applications of electrocatalysis, 42,43 photocatalysis degradation, 44,45 Fischer-Tropsch synthesis, 46 and other fields. 47,48 However, most lignin-derived carbon catalysts are prepared using the direct carbonization of lignin followed by the impregnation of metal active ingredients, which are easily dissoluble and difficult to effectively inhibit their agglomeration, resulting in the inferior activity, and durability. 49 In this study, the inherent properties and abundant carboxyl/ hydroxyl functional groups of lignin biomacromolecule were used to precisely coordinate with transition metal ions Co 2+ and Fe 3+ using an aqueous self-assembly process to form lignin-metals complex, which were then co-doped with nitrogen precursor urea in situ…”

“…Additionally, with a three‐dimensional network structure formed by phenylpropane units, lignin is rich in phenolic hydroxyl groups, alcoholic hydroxyl groups and part of carboxyl groups, and its carbon content is as high as 60% 40,41 . Furthermore, lignin‐derived carbon has recently been reported as the catalyst support in the applications of electrocatalysis, 42,43 photocatalysis degradation, 44,45 Fischer‐Tropsch synthesis, 46 and other fields 47,48 . However, most lignin‐derived carbon catalysts are prepared using the direct carbonization of lignin followed by the impregnation of metal active ingredients, which are easily dissoluble and difficult to effectively inhibit their agglomeration, resulting in the inferior activity, and durability 49…”