Carbon dots originated from carnation for fluorescent and colorimetric pH sensing

Herein, fluorescent carbon dots (CDs) originated from carnation were creatively synthesized with well-distributed size. By detailed characterization, the prepared CDs were mainly composed of C and O as well as limited amount of N, and there existing O–H, N–H, C–H, C=N, C=O, C=C and C–O groups on their surfaces. Significantly, these CDs showed a distinct pH-sensitive feature. To be specific, the fluorescence intensity of CDs exhibited a linear fashion over the pH range from 11.7 to 3.2. Simultaneously, the color of the CDs solution varied from yellow to yellow–orange, and the corresponding hue parameter decreased linearly with the pH value range from 10.6 to 5. All these evidence illustrated that this CDs have potential as colorimetric and fluorescent sensors for pH sensing. Additionally, The CDs were applied for cellular imaging and painting.