Carbon Dots with Tunable Photoluminescence Properties

A facile process for producing carbon dots with tunable luminescence properties has been developed by using microwaveassisted technique. Citric acid and L-histidine were used as carbohydrate precursors. By varying the precursors concentration in ethylene glycol, adjustable multicolor carbon dots of blue, green to yellow under UV excitation were easily obtained. We found that the photoluminescence of carbon dots (diameter < 40 nm) can be adjusted by simply varying precursor amount, which has not yet been reported before. Other methods for preparing different photoluminescent carbon dots often use oxidative/reductive chemicals, our method is facile and environmental friendly. The tuneable photoluminescence range can extend from 430 nm to 550 nm in this system.