Applications of functionalized carbon nanotubes in energy and biotechnology areas

In this study, the functionalized multi-walled carbon nanotubes were produced from multi-walled carbon nanotube (MWCNT) by different chemical reactions and, Li-doped MWCNT and Li-doped functionalized MWCNTs by solvent and hydrothermal methods. Samples were characterized using Brunner–Emmett–Teller (BET), Fourier transform infrared spectroscopy (FTIR), differential thermal analysis/thermogravimetry (DTA/TG) and scanning electron microscopy (SEM). The hydrogen storage capacities of all samples were measured using IMI PSI gas storage instrument. The usability of the MWCNT-O-L-Tyrosine-PABA structure as a filling matrix in the affinity column for the purification of PPO from Salvia aethiopis L. was investigated. New bands belonging to functional groups were observed in the FTIR spectrum of MWCNT. Functionalized MWCNTs degraded at different temperatures and steps. SEM images showed that the changes in the morphology of MWCNT with functionalization and Li-doping occured. While the BET surface area of MWCNT decreased with functionalization, an increase in its hydrogen storage capacity was observed in general. The hydrothermal method is more effective than the solvent method and functionalization in increasing the hydrogen storage capacity of MWCNT. All samples had higher hydrogen storage capacity at lower temperatures. The sample with the highest hydrogen storage capacity was Li-doped MWCNT. While the isotherm curves obeyed Henry's law at room temperature, they exhibited multilayer adsorption behavior at cryogenic temperatures. The adsorption process was physical and isotherm type was Type IV. PPO extracted from the leaves and flowers of Salvia aethiopis L. was purified 8.4-fold and 3-fold by ammonium sulfate, dialysis and affinity chromatography, respectively. For each purification step, optimum pH and temperature values were determined using catechol, 4-methyl catechol and pirogallol substrates. The Vmax/Km value increased with the purification process and the enzyme showed the highest specificity for pyrogallol, followed by 4-methylcatechol and catechol.