Desenvolvimento de filamentos de nanotubos de carbono preenchidos com pontos quânticos para aplicação em mechanical energy harvesters

Abstract

The growing demand for sustainable technologies is driving the development of devices capable of converting mechanical energy into electrical energy, known as mechanical energy harvesters. Among the promising materials for this application, carbon nanotube filaments (f-CNTs) stand out due to their high electrical conductivity, mechanical strength, chemical stability, and large surface area. To enhance their performance, the incorporation of graphene quantum dots (GQDs) emerges as a viable alternative, as these nanoparticles offer favorable electronic and structural properties for electric double layer formation and increased specific capacitance. This work aimed to produce f-CNTs with different proportions of GQDs and evaluate their electrochemical, mechanical, and electrical properties. GQDs were synthesized via a hydrothermal method using citric acid and urea (ratios 1:2 and 1:3) and applied to the filaments in volumes of 0.5, 1.0, and 1.5 mL. A custom lab setup was developed to fabricate pure and GQD-modified f-CNTs, using carbon nanotube forest, airbrush deposition, and controlled filament twisting. Morphological analyses revealed uniform, helically structured filaments. Cyclic voltammetry indicated typical electric double-layer behavior, with symmetric curves and no redox peaks. Specific capacitance increased with the presence of GQDs, reaching 9.58 F/g for 1.5 mL of GQD 1:2, compared to 1.03 F/g for the pure f-CNT, due to increased active surface area and the presence of oxygen-containing functional groups. Mechanically, the filaments maintained their strength, with some formulations showing slight improvement. Electrical tests showed that low GQD concentrations enhanced conductivity, while higher concentrations led to aggregation and reduced performance. The incorporation of GQDs into f-CNTs shows great potential for improving the performance of materials used in MEH, maintaining mechanical integrity while enabling flexible and sustainable applications.