Preparation Of Functional Materials Based On Graphene Quantum Dots For White Light Emission Diode And The Generation Of Reactive Oxygen Species

Graphene quantum dots (GQDs) are a special class of carbon quantum dots. The size of GQDs is generally below 10 nm. The height of GQDs is around 2-3 nm (a thickness of single or a few layers graphene). Synthesis methods of GQDs consist of electrochemical exfoliation, acid oxidation, hydrothermal method, microwave method and so on. GQDs have stable and controllable fluorescence properties, and their fluorescence properties are better than that of organic fluorescent dyes. Compared with II-VI quantum dots, GQDs are more biocompatible and easier for surface modification. GQDs are widely considered as a novel nanomaterial in the future. Since the emergence of GQDs, great attentions have been paid by researchers for their light charge transfer characteristics, upconversion fluorescence characteristics. Due to the unique physical and chemical properties of GQDs, GQDs have potential applications in optical catalysis, optoelectronic devices, biological molecular probes and so on.In this paper, white-light-emission GQDs (WGQDs) and GQDs/Au nanoclusters composite were prepared. The application of WGQDs for white-light-emitting LEDs (WLEDs) were studied. The property of yielding reactive oxygen species (ROS) from GQDs/Au nanoclusters were explored. The main content of this paper could be summed as the following three aspects:1. There are relatively few reports about white-light-emission GQDs in comparison with blue or green fluorescent GQDs. The GQDs with white fluorescence emission are prepared by the two-step microwave hydrothermal synthesis method. The characterization of as-prepared GQDs and WGQDs are also carried out.2. The as-prepared WGQDs were used as light-emission phosphor for light-emission diodes (LEDs). A solution process was developed for constructed LEDs with WGQDs as an emissive layer. White-light emission could be obtained from the LEDs based on WGQDs (WLEDs), which showed a luminance of 200 cd m"2 at the applied voltage of 11-14 V. Furthermore, an external quantum efficiency of 0.2% can be reached, which is higher than the previous reports on the WLEDs based on graphene quantum dots or carbon dots. WGQDs as light-emission phosphor develops a new avenue for improving performance of WLEDs based on graphene quantum dots.3. Since GQDs have oxygen-contained functional groups on their surface and unique photoelectronic characteristics, the GQDs as stabilizer and reducer was used to prepare GQDs/Au nanoclusters composite through the UV irradiation method by controlling the amount of gold(III) chloride trihydrate (HAuCl4). The property of yielding reactive oxygen species (ROS) from GQDs and GQDs/Au nanoclusters composite was explored.