Production and characterization of reduced graphene oxide and carbon quantum dots filled polycaprolactone nanofibers

In this thesis, a comparative study between the morphology, the thermal, the mechanical, the electrical conductivity, and the biological properties of poly(ɛ-caprolactone) (PCL)-based electrospun nanofibers filled with both reduced graphene oxide (RGO) and carbon quantum dots (CQDs) is carried out. The crystal size value of the (200) plane increased by 50.6% at 1.5 and 2.0 wt% RGO contents and by 57.9% at 1.5 wt% CQDs content. 1.5 wt% CQDs was the only filler amount that increased the interlayer distance. Crystal size values showed that 1.5 wt% CQDs content increased by 57.9% and 50.6% at 1.5 wt% and 2.0 wt% RGO content compared to neat PCL nanofiber. Thermal analysis results showed that both RGO and CQDs fillers created a nucleation effect and increased thermal stability. From the Electron microscope images, an increase in the average nanofiber diameter with the addition of RGO filler and a decrease in the average nanofiber diameter with the addition of CQDs was observed. Conductivity test results of the PCL/RGO and PCL/CQDs nanofibers displayed insulating properties. Mechanical test results of nanofibers have shown that the homogeneous distribution of RGO and CQDs fillers in the PCL matrix could provide load transfer and that the polymer-filler interaction caused an increase in hardness in the matrix without the formation of voids even as the temperature increased in the structure. PCL/1.5CQDs nanofiber exhibited a 73% increase in elastic modulus and a 160% increase in nanohardness, while PCL/2CQDs nanofiber showed a 210.79% increase in storage modulus and a 595.27% increase in loss modulus compared to pure PCL nanofiber. The hydrophilic structure of the nanofibers increased biodegradability. At the end of 56 days, the highest % weight loss values were observed in nanofibers containing 2.0 wt% RGO and CQDs, at 3.66% and 3.75%, respectively. The formation of hydroxyapatite was revealed by the 7-day bioactivity test, electron microscope images of apatite crystals, Ca/P ratios (1.48) in the EDS analysis, and sharp peaks belonging to the 32.8° (211)–44.7° (222) planes pattern results. The nanofibers did not show antibacterial properties due to the fact that RGO and CQDs fillers cannot create oxidative stress.