Carbon dots as photosensitisers for solar-driven catalysis

Artificial photosynthesis is the mimicry of the natural process of solar energy conversion into chemical energy carriers. Photocatalytic systems that combine light-harvesting materials and catalysts in solution or suspension provide a promising route towards this goal. A key requirement for a sustainable solar fuel production system is a low-cost, stable and non-toxic light harvester. Photoluminescent carbon nanoparticles, carbon dots (CDs), are promising emerging light-harvesters for photocatalytic fuel production systems. CDs possess many desirable properties for this purpose, such as inexpensive, scalable synthetic routes, low-toxicity and tuneable surface chemistry. In this tutorial review, the integration of CDs in photocatalytic fuel generation systems with metallic, molecular and enzymatic catalysts is discussed. An overview of CD types, synthesis and properties is given along with a discussion of tuneable CD properties that can be optimised for applications in photocatalysis. Current understanding of the photophysical electron transfer processes present in CD photocatalytic systems is outlined and various avenues for their further development are highlighted.