Synthesis of novel carbon dots from taurine for Cu2+ sensing and nanohybrid with ceria for visible light photocatalysis

Abstract

Here, we have prepared a new water-soluble carbon dots (CDs) from a conditionally essential amino acid, “taurine” via thermal decomposition method. The as-synthesized CDs displayed oval/spherical shape with size less than 10 nm. The existence of nitrogen, sulphur and oxygen in the CD was confirmed by x-ray photoelectron spectroscopy. The CDs exhibited a quantum yield value of 7.2% and excitation dependent fluorescence (FL) emission spectra, and they were used for sensitive and selective detection of Cu2+ ions with a limit of detection of 0.62 μM. Furthermore, the aqueous solution of the CDs showed significant stability up to 90 days with very negligible effect on their fluorescence intensity under high salt concentration. After that we have prepared the nanohybrid (CDs-CeO2) consisting of CDs (0.025–0.3 wt %) and CeO2 as a visible light photocatalyst for the removal of methyl orange (MO) dye from water. The nanohybrid consisting of 0.1 wt % CDs displayed highest (66%) degradation towards MO at pH ∼ 6 under visible light irradiation for 5 h. However, 85% and 100% MO degradation were observed in strongly basic (pH ∼ 11) and acidic (pH ∼ 3) medium respectively. The enhanced photodegradation ability of the 0.1 wt % CDs-CeO2 is attributed to the highest visible light absorbing capacity and lowest band gap energy. Superoxide radicals (O2−.) were found to play the primary role in the photocatalysis process within the pH range of 3–6. Besides, good stability and reusability of the nanocatalysts were also confirmed. Taken together our synthesized CDs and its nanohybrid with CeO2 can be considered as a promising candidate for sensing and photocatalytic activities.