Carbon Nanoparticles (C-Dots):Polyol Synthesis, Fluorescence, Screening of Material Properties

除了富勒烯、碳纳米管(CNT)和石墨烯之外，碳纳米颗粒(也称为：碳点或C点)代表着另一种形式的碳，由于其强烈的荧光，在过去的2-3年里受到了极大的关注。目前，碳点是通过高温处理常规碳源(如石墨、煤、煤烟)或分解有机碳物种(如糖、树叶、鸡蛋)而制备的。然而，到目前为止，对C-点的合成和性质在许多方面都缺乏基本的了解。本项目的目标是在可控的粒度和掺杂条件下合成C-点的多元醇。鉴于C-点的高度可重复性，Lewis-酸性金属盐被用来支持颗粒成核和颗粒生长。通过关联颗粒大小、结晶度、表面钝化和化学成分，可以从根本上了解材料的性质。特别是，稀土金属修饰(如Tb~(3+)，Eu~(3+)，Yb~(3+))C-点的荧光具有很高的相关性，这是因为C-点激发时的有效线型发射，因此在水存在下的能量转移和荧光稳定性的机制还没有被理解和解决。基于C点的受控液相合成，最后，打算筛选材料性能(例如，聚合物薄膜和电池中的荧光，C点薄膜作为透明导体，C点对气体的吸附/气体分离，(光)催化性能，向纳米钻石的相变)。

Carbon nanoparticles (also named: carbon dots or C-dots) - besides fullerenes, carbon nanotubes (CNTs) and graphene - represent an additional form of carbon that received significant attention during the last 2-3 years due to their intense fluorescence. Currently, C-dots are prepared via high-temperature treatment of conventional carbon sources (e.g. graphite, coal, soot) or decomposition of organic carbon species (e.g. sugar, leaves, eggs). A fundamental understanding of synthesis and properties of C-dots, however, to many regards is missing by now.This project aims at a controlled polyol synthesis of C-dots at adjustable particle size and doping. Lewis-acid metal salts are used to support particle nucleation and particle growth in view of a highly reproducible availability of C-dots. By correlating particle size, crystallinity, surface passivation, and chemical composition, a fundamental understanding of the material properties is intended. Especially, the fluorescence of rare-earth-metal-modified (e.g., Tb3+, Eu3+, Yb3+) C-dots is highly relevant due to the efficient line-type emission upon excitation of the C-dots, whereupon the mechanism of energy transfer and the stability of fluorescence in the presence of water are neither understood nor solved. Based on a controlled liquid-phase synthesis of C-dots, finally, a screening of materials properties is intended (e.g., fluorescence in polymer thin-films and cells, C-dot thin-films as transparent conductors, gas sorption/gas separation with C-dots, (photo)catalytic properties, phase transition to nanodiamonds).