Synthesis and research of carbon nanodots and nanoparticles from activated carbon

Abstract

A brief literature review proves that nanosized fluorescent carbon materials are widely used. In particular, they are promising in biomedicine (due to biocompatibility – for example, for biovisualization); optoelectronics; as chemical fluorescent sensors for measuring the concentration of metals, pH, anions, organic substances and biomolecules; as markers for fingerprinting. This paper investigates carbon materials obtained by oxidation of activated carbon, which are similar in their optical characteristics to carbon nanotubes. The aim of this work was the synthesis of nanocarbon material from available chemical raw materials. As a prototype, the synthesis is based on the method of obtaining carbon weakly acid cation-exchange resin. The nanocarbon material is easily dispersed in water, forming stable colloidal solutions that exhibit luminescence in the blue-green region of the visible spectrum. According to the results of thermogravimetric analysis, the thermal destruction of surface functional groups was found. The nature of the functional groups on the surface of the carbon nanomaterial was based on the obtained data of infrared spectra. The purity of the samples was monitored by X-ray diffraction analysis of the powder. For the pure sample, only the amorphous carbon spectrum was observed, and for the crude, NaCl reflexes were observed. In the region of MALDI positive ions, clusters of molecular mass have been obtained, which may belong to fullerene-like carbon structures. We believe that the high signal intensity at m/z 44 indicates a significant number of carboxyl groups. For aqueous solutions, the luminescence spectrum was measured, on which blue-green fluorescence was observed. Excitation by radiation with a wavelength was chosen based on the results of preliminary measurements of the dependence of the emission intensity on the length of the excitatory radiation. The fluorescence spectrum shows a wide maximum at 450 nm, which is slightly shifted to the long-wavelength region after centrifugation of the sample and precipitation of large fractions. The method of dynamic light scattering shows that particles with a wide range of sizes are present in the solution, the maximum distribution occurs in relatively large units.