Chair for Photonics and Optoelectronics, Department of Physics and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität München, Amalienstr. 54, 80799, Munich, Germany.
Nanosystems Initiative Munich (NIM), Schellingstr. 4, 80799, Munich, Germany.
Nat Commun. 2017 Nov 9;8(1):1401. doi: 10.1038/s41467-017-01463-x.
Carbon dots (CDs) are a versatile nanomaterial with attractive photoluminescent and photocatalytic properties. Here we show that these two functionalities can be easily tuned through a simple synthetic means, using a microwave irradiation, with citric acid and varying concentrations of nitrogen-containing branched polyethyleneimine (BPEI) as precursors. The amount of BPEI determines the degree of nitrogen incorporation and the different inclusion modes within the CDs. At intermediate levels of BPEI, domains grow containing mainly graphitic nitrogen, producing a high photoluminescence yield. For very high (and very low) BPEI content, the nitrogen atoms are located primarily at the edge sites of the aromatic domains. Accordingly, they attract photogenerated electrons, enabling efficient charge separation and enhanced photocatalytic hydrogen generation from water. The ensuing ability to switch between emissive and photocatalytic behavior of CDs is expected to bring substantial improvements on their efficiency for on-demand light emission or energy conversion applications.
碳点（CDs）是一种多功能纳米材料，具有吸引人的光致发光和光催化性能。在这里，我们展示了这两种功能可以通过一种简单的合成方法轻松调节，使用微波辐射，以柠檬酸和不同浓度的含氮支化聚乙烯亚胺（BPEI）为前体。BPEI 的量决定了氮的掺入程度和 CDs 内的不同包含模式。在 BPEI 的中等水平下，含有主要石墨氮的域生长，产生高的光致发光产率。对于非常高（和非常低）的 BPEI 含量，氮原子主要位于芳构域的边缘位点。因此，它们吸引光生电子，能够有效地进行电荷分离，并增强水的光催化制氢。预期能够在 CDs 的发光和光催化行为之间进行切换的能力将为按需发光或能量转换应用带来其效率的实质性提高。
