Gram-Scale Green-Emission Carbon Quantum Dots Produced from Wood via the Hydrothermal Synthesis Method for the Detection of Fe (III)

Carbon quantum dots (CQDs), a distinctive class of fluorescent carbon nanomaterials, exhibit considerable potential for widespread application across several industries due to their safety, environmental sustainability, excellent water solubility, and tunable yet stable fluorescence properties. Nevertheless, the mass field is limited, and the cost of production is higher for the majority of methods. This study examines a cost-effective approach for the hydrothermal synthesis of nitrogen-doped carbon quantum dots (N-CQDs) from wood using NH3·H2O as the nitrogen precursor, facilitated by H2O2 and ultraviolet light. The produced N-CQDs demonstrate superior crystallinity and solubility in water, with the average particle size of 5.02 nm. After 10 experiments under the same conditions, a significant and stable yield of 5.04 g (42 wt%) was finally obtained by hydrothermal synthesis. The N-CQDs solution exhibits green fluorescence when exposed to ultraviolet light, and its fluorescence performance is influenced by concentration and excitation wavelength. Furthermore, it explores their application in identifying Fe (III) in water. The surface of N-CQDs is abundant in hydrophilic hydroxyl groups, distinctive nitrogen-containing groups, and various oxygen-containing functional groups. Fe (III) can extinguish fluorescence in water. The ratio of fluorescence intensity before and after to the addition of Fe (III) solution to the N-CQDs solution (F0/F) exhibits the effective linear correlation within the concentration range of 0.1 to 100 μmol/L. Within the concentration range of 100 to 1000 μmol/L, the increase in Fe (III) concentration results in substantial aggregation of Fe (III) and N-CQDs, along with a blue shift in the fluorescence wavelength. This discovery possesses significant potential for the synthesis and application of environmentally friendly, high-yield N-CQDs.