One-pot synthesis of multicolor carbon quantum dots: One as pH sensor, one with ultra-narrow emission as fluorescent sensor for uric acid

In this work, tricolor carbon quantum dots (CQDs) including blue-, green-, and orange-CQDs were prepared in one-pot. Impressively, the full width at half maximum of blue-CQDs narrowed greatly to 8 nm, serving as the narrowest bandwidth emissive CQDs so far, to our knowledge, which even compared to colloidal semiconductor quantum dots. Based on the blue-CQDs exhibited highly selective and sensitive ‘on-off’ response towards Fe3+ and the outstanding antioxidant properties of uric acid, we constructed ‘on-off-on’ switching sensor to achieve quantitative measurement of uric acid. The green-CQDs served as simple pH sensor qualitatively judging acid rain based on ultrasensitive spectral redshift property at pH < 5.6. The sensors based on CQDs withstood actual sample matrix effects, pH and temperature change, and long-term storage. The ultra-narrow bandwidth emissive CQDs and fluorescent sensors based on distinctive optical properties of CQDs are meaningful and attractive research directions.