School of Physics and Astronomy, Queen Mary, University of London, 327 Mile End Road, London, E1 4NS, UK.
Materials Research Institute, Queen Mary University of London, Mile End Road, E14NS, London, UK.
Sci Rep. 2018 Apr 26;8(1):6559. doi: 10.1038/s41598-018-25012-8.
Carbon nanodots are a new and intriguing class of fluorescent carbon nanomaterials and are considered a promising low cost, nontoxic alternative to traditional inorganic quantum dots in applications such as bioimaging, solar cells, photocatalysis, sensors and others. Despite the abundant available literature, a clear formation mechanism for carbon nanodots prepared hydrothermally from biomass precursors along with the origins of the light emission are still under debate. In this paper, we investigate the relationships between the chemical structure and optical properties of carbon nanodots prepared by the hydrothermal treatment of glucose. Our major finding is that the widely reported excitation-dependent emission originates from solvents used to suspend the as-prepared carbon nanodots, while emission from dry samples shows no excitation-dependence. Another important highlight is that the hydrothermal conversion of biomass-derivatives under subcritical conditions leads to a heterogeneous mixture of amorphous-like nanoparticles, carbon onion-type and crystalline carbons composed of at least three different phases. The potential chemical reaction pathways involved in the formation of these hydrothermal carbon products along with a comprehensive structural and optical characterization of these systems is also provided.
碳点是一类新型的荧光碳纳米材料，被认为是在生物成像、太阳能电池、光催化、传感器等应用中替代传统无机量子点的一种有前途的低成本、无毒替代品。尽管有大量的相关文献，但对于通过水热法从生物质前体制备的碳点的明确形成机制以及发光的起源仍存在争议。在本文中，我们研究了通过水热法处理葡萄糖制备的碳点的化学结构与光学性质之间的关系。我们的主要发现是，广泛报道的激发依赖性发射源于用于悬浮所制备的碳点的溶剂，而干燥样品的发射则没有激发依赖性。另一个重要的发现是，在亚临界条件下生物质衍生物的水热转化会导致无定形样纳米颗粒、洋葱型碳和由至少三种不同相组成的结晶碳的不均匀混合物。还提供了这些水热碳产物形成过程中涉及的潜在化学反应途径，以及对这些体系的全面结构和光学特性的描述。
