Luminescent carbon dots obtained from different precursors and methods and their applications as sensors for metal ions

Abstract

Carbon dots (CDs) represent a rising class of nanomaterials with numerous optical and physicochemical properties that make them useful for a variety of applications. In this work, three different methods, conventional hydrothermal carbonization (CHC), microwave-assisted irradiation and heating reflux reaction technique, were used as different bottom-up approaches to obtain different CDs. The carbon nanoparticles were prepared using three different carbon precursors (maleic, fumaric and adipic acids) and one nitrogen source (ethylenediamine). The CDs were characterized using different techniques including Fourier transform infrared spectroscopy, Transmission electron microscopy, Ultraviolet-visible, Fluorescence and Zeta potential measurements. Both, the experimental method used to obtain the CDs and the different precursors, presented a considerable influence on the quantum yield values (QY), and also on the fluorescence emission curves. The molar proportion between the carbon and nitrogen source was varied to improve the QY, and one of the samples prepared by CHC method reached QY = 25.4%. The carbon nanoparticles obtained by CHC were used as nanoprobes for metal ions and exhibited great selectivity and sensitivity for Fe³⁺ ions, reaching a limit of detection of 35 nM, which is lower than most reported values for CD-based PL method used as probes for Fe³⁺ ions.

Keywords:

• Carbon nanostructures
• carbon dots
• fluorescence
• sensor
• carbon nanoparticles

Acknowledgments

The author would like to acknowledge CNPq (EDT Universal N° 28/2018) and Fapemig (EDT Universal N° 1/2017) for financial support. The authors also acknowledge the Center of Microscopy at UFMG for providing the equipment and technical support for experiments involving electron microscopy.

Disclosure statement

The authors report there are no competing interests to declare.

Additional information

Funding

This work was supported by CNPq (427237/2018-1) and Fapemig (APQ-00979-17).