Nanopartículas semicondutoras: síntese e caracterização

Abstract

Semiconductor nanomaterials play a fundamental role in the manufacturing of modern electronic devices, including LEDs, displays, fiber-optic communication systems, and lasers. Technological development requires a constant search for new materials and synthesis methods. In this Undergraduate Thesis (TCC), nanoparticles based on Carbon Dots (CDs) and group II-VI semiconductors we synthesized and characterized, aiming to explore their optical and electronic properties. Optical characterization was performed using techniques such as photoluminescence (PL), photoluminescence excitation spectroscopy (PLE), and absorbance measurements, enabling a detailed investigation of light absorption and emission mechanisms, as well as the coupling between electronic states. The PL spectra were analyzed through deconvolution into Gaussian curves, which allowed the identification and separation of contributions from different emissive centers present in the Carbon Dots. To evaluate the stability of the samples' optical properties, we studied the fitting parameters of the luminescence spectrum immediately after synthesis and then six months later. We observed that some of these fitting parameters vary over time, while others tend to remain constant, which is of crucial importance for applications of these structures in optoelectronic devices. Finally, the dependence of PL spectra on the excitation wavelength was investigated, providing relevant conclusions about the nature of the emissive sites and their characteristic energies. This approach allowed us to distinguish between emissions related to surface states and transitions involving the core of the nanoparticles. We believe this work was beneficial for our academic development, providing practical and theoretical knowledge in the synthesis and characterization of new semiconductor materials, a field of critical importance for the advancement of nanotechnology.