New properties of carbon nanomaterials through zinc doping and application as a ratiometric fluorescence pH sensor

Abstract

Fluorescence intensity of carbon nanomaterials (CNMs) synthesized with ethanolamine hardly changed with pH value. Doping Zinc into CNMs improved optical properties of CNMs. On the one hand, the fluorescence quantum yield of CNMs increased, on the other hand, the fluorescence intensity of Zn-doped CNMs decreased with pH value. Coupling Zn-doped CNMs with ZnCdS quantum dots (QDs) as a dual emission system, the blue fluorescence intensity of CNMs (I450) decreased while the orange fluorescence intensity of QDs (I580) enhanced with pH value increasing. The ratio (I450/I580) varied linearly with pH value in the range of 1–9 and correlation coefficient (R2) was 0.991. Furthermore, using the system as a ratiometric fluorescence pH sensor to determine ascorbic acid, a good linear relationship (R2 = 0.998) was found when the concentration of ascorbic acid ranged from 0–1600 μM and limit of detection (LOD) was as low as 0.082 μM.