Tuning the fluorescence performance of carbon dots with a reduction pathwayElectronic supplementary information (ESI) available: Supplementary figures and table. See DOI: 10.1039/c8nr09587f

A reduction pathway was developed to tune the fluorescence quantum yield (QY) and emission wavelength of carbon dots (CDs). Reducing the original CDs (QY ca. 1.55%, maximum emission ca. 520 nm) with NaBH 4 increased QY to 7.25% and blue-shifted the maximum emission to 450 nm. Treating the original CDs with LiAlH 4 increased QY to ca. 7.44% and blue-shifted the maximum emission to 345 nm. The distinct fluorescence characteristics of the original CDs, NaBH 4 -treated CDs, and LiAlH 4 -treated CDs were conferred by their differing surface groups. Moreover, the original CDs, NaBH 4 -treated CDs, and LiAlH 4 -treated CDs responded differently to a specific oxidizer of hydroxyl groups. The increase in the fluorescence QY and blue-shift of the emission wavelength were explained. This study provides a foundation for the preparation and tuning of CDs with excellent fluorescence performance, as well as for the development CD-based fluorescent probes. The fluorescence emission and quantum yield can be tuned by reduction.