• Xiang Li Xiang Li

As a novel fluorescent material, carbon dots (CDs) demonstrate many excellent properties such as low toxicity, high stability and high resistance to photo bleaching. They are very likely to be applied in sensing, bio-imaging, photo catalysis and lighting devices, which require that the CDs can be tuneable in emission colours. Research to date have pointed to that the functional groups of CDs are very important to the emission of CDs, this MPhil work attempts to make some contributions to the understanding of how the functional groups affect the emission colour and the sensing selectivity. By reviewing many research papers, it is concluded that instead of size effect, the surface status related to the functional groups, specifically the O, N and S contents of the CDs, becomes the major factor of adjusting the emission colour of CDs. When the O, N or S contents are increased, red-shift of the fluorescence was observed in many studies. Apart from the colour tuning, the role of functional groups in the sensing applications of CDs is even more important. They act as the receptors which could recognise and capture the specific type of analyte, before the subsequent fluorescence quenching caused by aggregation or electron transfer (ET) process.