ABSTRACT

Photoluminescent carbon nanoparticles (CNPs), such as carbon dots (CDs), have attracted much attention owing to a unique set of properties, like high and tunable fluorescence. In this way, the use of carbon-rich lignin has been demonstrated to be a sustainable approach to producing a broad range of photoluminescent CNPs. However, the valorization of this complex polyphenol is limited when it comes to green and efficient ways of conversion. In addition, the existing solvothermal approaches using lignin often result in CDs with low photoluminescence, while flammable and/or toxic solvents are employed. Here, we depolymerized technical lignins, i.e. kraft and soda, through electroreductive cleavage in two different sustainable media: deep eutectic solvent and levulinic acid. After depolymerization, lignin-derived monomers were generated, with a predominance of aryl ether and phenolic groups, which were further combined with 1,2-Phenylenediamine to produce N-doped CNPs in a solvent-free approach. Photoluminescent CNPs with varied sizes were generated (5–50 nm), which presented a wide photoluminescence emission, from blue to red, depending on solvent polarity. These results demonstrate a feasible and sustainable route for the solvent-free synthesis of photoluminescent CNPs using lignin-derived monomers as carbon source, which may find applications in a wide range of fields.

摘要

碳点 (CD) 等光致发光碳纳米粒子 (CNP) 因其独特的一组特性（如高荧光和可调谐荧光）而备受关注。通过这种方式，已证明使用富含碳的木质素是生产范围广泛的光致发光 CNP 的可持续方法。然而，当涉及到绿色和高效的转化方式时，这种复杂多酚的价值化是有限的。此外，现有的使用木质素的溶剂热方法通常会导致 CD 具有低光致发光，同时使用易燃和/或有毒溶剂。在这里，我们通过在两种不同的可持续介质（低共熔溶剂和乙酰丙酸）中的电还原裂解，解聚了技术木质素，即硫酸盐和苏打。解聚后，产生了木质素衍生的单体，以芳基醚和酚基为主，它们进一步与 1,2-苯二胺结合，以无溶剂方法生产 N 掺杂的 CNP。产生了具有不同尺寸（5-50 nm）的光致发光 CNP，根据溶剂极性，它呈现出从蓝色到红色的宽光致发光发射。这些结果证明了使用木质素衍生单体作为碳源的无溶剂合成光致发光 CNP 的可行且可持续的途径，可能会在广泛的领域得到应用。