Obtenção, caracterização e funcionalização de pontos de carbono a partir de diferentes precursores e suas aplicações como sensores

Abstract

Carbon dots (PCs) represent a relatively new class of carbon nanomaterials and have attracted great interest due to their interesting properties such as high water solubility, possibility of functionalization, resistance to photodegradation, low toxicity, and excellent optical properties with a relatively high fluorescence. The PCs properties enable their applications in several areas ranging from photocatalysis and optoelectronics, to bioimaging, in addition to acting as sensors for different substances, due to the sensitivity of photoluminescence in the presence of certain analytes. In this work, PCs were prepared by two routes, acid dehydration and hydrothermal carbonization, using chitosan and cellulose as precursors. Hydrothermal carbonization proved to be a more suitable route to obtain higher quantum yield (QY) values. In addition, the functionalization of the carbon dots was performed using ammonia, boric acid and PEG1500N. The materials were characterized by different characterization techniques to investigate the optical and morphological properties of the PCs. The PC sample obtained from cellulose when modified with ammonia, showed an increase in the QY value from ~1.0% (PCCEL sample) to 6.1% (PCCEL-N). Also, the chemical modification with the PEG1500N reagent significantly increased the QY of the PCCEL sample to 5.5%. With the PC sample obtained from chitosan, a QY value of 9.3% was obtained for the unmodified sample whereas 15.3% of QY was obtained after a simple modification with ammonia. The PCs which presented higher QY values were studied as sensors for a series of metallic ions. Both PCs obtained from chitosan and from cellulose showed selectivity for the Fe3+ ion and the samples PCCEL-N and PCCEL-PEGN presented the lowest detection limits, 0.22 and 0.13μM, respectively.