Full-colour carbon dots: from energy-efficient synthesis to concentration-dependent photoluminescence properties.

We present a facile approach, without the need for external heating and any additional energy input, to produce fluorescent carbon dots (CDs) inexpensively and on a large scale. Fluorescence emission wavelengths from the obtained CDs shift gradually from 630 to 400 nm with reduction in their concentration in solution. This work offers a novel avenue for tuning band gaps in CDs and endowing them with potential for various applications.