Investigação das propriedades luminescentes de pontos quânticos de carbono derivados de dansilamida

Abstract

The development of multifunctional nanomaterials free of heavy metals is an ongoing topic in the scientific community, yielding relevent results in bioimaging, sensing, treatment of pathogenic microorganisms, anti-counterfeiting, and the creation of optoelectronic devices with reduced environmental impact. Properties such as excitation dependency and independency of a fluorophore are of interest due to the potential to produce specific biocompatible nanoparticles. Carbon dots are one such material, primarily known for their fluorescence emission properties. However, there are reports of carbon dots exhibiting afterglow, characterized by high-intensity and long-lasting luminescence. Thus, it becomes of interest to explore co-doped carbon dots with excellent luminescent properties synthesized through a simple synthesis route. In this study, carbon dots using dansyl amide as a precursor were synthesized, aiming to obtain highly fluorescent nanoparticles and investigate their potential optical applications. By employing the hydrothermal synthetic method, we obtained carbon dots co-doped with nitrogen, sulfur, and chlorine, which exhibit blue-green emission with a quantum yield of 27.46% upon photoexcitation at 375 nm. To characterize the obtained carbon dots (CD-DNSA), techniques such as high-resolution transmission electron microscopy (HRTEM), infrared spectroscopy, X-ray photoeletronic spectroscopy, and UV-Vis spectroscopy were utilized. Additionally, the sensitivity of the carbon dots’ fluorescence to ions and environmental conditions was investigated, focusing on the polarity, pH, and temperature of the carrier liquid. Consequently, we analyzed the feasibility of using CD-DNSA for temperature and pH detection by determining the absolute and relative sensitivities and stability of the nanoparticles within the temperature range of biological systems and across the pH scale. Therefore, in the present work, we obtained highly fluorescent carbon dots doped with heteroatoms, displaying sensitivity to hydrogen potential, a non-trivial response of its intensity to temperature variations, and low sensitivity to polarity. Furthermore, CD-DNSA in solid-state demonstrated room temperature phosphorescence when incorporated into polymeric matrices, such as PVA and cellulose, as well as in ink, indicating potential applications in anti-counterfeiting.