Electrospun cyclodextrin nanofibers as precursor for carbon nanofibers
The carbon nanofibers (CNF) based on the electrospun polymer-free hydroxypropyl-β-cyclodextrin (HPβCD) nanofibers were obtained by the combination of chemical and thermal (pyrolysis) treatment. The thermal and chemical decomposition of HPβCD makes it challenging to obtain persistent CNF from HPβCD nanofibers. The chemical treatment of HPβCD nanofibers by using 0.6 mM H2SO4 partially dissolves nanofibers and resulted in fused CNF while direct pyrolysis of HPβCD nanofibers totally ruins the nanofiber structure and produces char. The partial chemical treatment of HPβCD nanofibers with 10 µM H2SO4 dehydrates the top layer of the nanofibers, and a shield-like structure is formed which helps to retain the fibrous morphology during the pyrolysis. The diameter of HPβCD nanofibers was reduced after carbonization process where CNF having average diameter of 380 ± 150 nm were obtained. The presence of typical D and G Raman bands and XRD peak at 2θ ~ 26° further validates CNF formation from HPβCD nanofibers. The oxygen content is decreased from 34.7 to 5.8%, and carbon content increased from 62.3% to 94.2% after transformation of HPβCD nanofibers into CNF. To the best of our knowledge, for the first time, this study reports the use of electrospun polymer-free HPβCD nanofibers as a precursor to produce CNF.