Carbon-polymer dot-based UV absorption and fluorescence performances for heavy metal ion detection

In previous reports, carbon dots (CDs) were customarily used as fluorescent probes to detect heavy metal ions. However, scientists neglected to take advantage of the excellent UV absorption properties of CDs to detect heavy metal ions. Herein, we synthesized nitrogen-containing carbon polymer dots (N-CPDs) for the determination of Co2+ ions in water samples by a one-step hydrothermal method using L-histidine and ethylene imine polymer as raw materials. The N-CPDs were characterized by ultraviolet-visible spectrum (UV-vis), infrared spectrum (FT-IR), X-ray photoelectron spectrum (XPS) and transmission electron microscopy (TEM) techniques. They possess superior full-band UV absorption performance and the surface is rich in multifunctional groups such as -COOH, -C--N-, -OH, etc. When Co2+ was added to N-CPDs solution, the color of the solution rapidly changed from colorless to yellow-brown, which was visible to the naked eye. The UV absorption intensity of N-CPDs changed, and the fluorescence was instantly quenched, due to the formation of chelate between Co2+ and N-CPDs, and the FRET process occurred. The detection of Co2+ showed good linearity for both fluorescence and UV absorption spectroscopy modes in the range of 0-200 mu M, and the limit of detection were 1.0023 mu M and 0.75 mu M, respectively. These two methods have the advantages of simple operation, remarkable selectivity and small sample size, which can be applied to the field detection of Co2+ in water samples. It is possible to develop the UV absorption properties of CDs to detect the ions.

Automated summary

In this study, nitrogen-containing carbon polymer dots (N-CPDs) were synthesized and used to detect Co2+ ions in water samples by taking advantage of their excellent UV absorption properties. The detection methods showed good linearity and had the advantages of simple operation, remarkable selectivity, and small sample size. The development of the UV absorption properties of carbon dots for ion detection was proven to be feasible.