Effects of heating time on the growth and behavior of amorphous carbon nanostructures from ferrocene

Heating time is one of the crucial factors in various methods employed for the synthesis of carbon nanostructures (CNSs) from ferrocene. However, the effects of heating time on the growth and morphology of the nanostructured materials has not been well explored yet, particularly for amorphous carbon. Herein, we investigate how the variation of heating time impacts the growth of CNSs by carrying out the reaction between ferrocene and ammonium chloride in a solvent free condition at 250 °C. Several different forms of carbon nanostructures yielded from this reaction at 25 min (CNS-25), 30 min (CNS-30), 35 min (CNS-35) and 40 min (CNS-40) were analyzed by means of field emission scanning electron microscopy (FESEM) coupled with energy-dispersive x-ray (EDX), Fourier transform infrared (FTIR) and ultraviolet–visible (UV–Vis) spectroscopy. The final product CNS-40 was washed several times with concentrated hydrochloric acid solution to remove the impurities and then characterized by the means of similar techniques. FTIR spectra of all the nanostructures confirmed the presence of several functional groups such as C  =  C, C–O and –OH etc, which are common in carbonaceous nanostructures. However, the FESEM images obtained are significantly different and suggest a gradual growth of the carbon nanostructures ending up with long carbon nanotubes after 40 min. No absorption peak in the visible region of the UV–Vis spectra of the final product confirms the amorphous nature, which is also supported by XRD of the synthesized nanotube. Moreover, a noteworthy redshift in the UV–Vis peaks reflecting a huge increase in length and diameter of the nanostructures indicates the maximum longitudinal growth of the carbon nanotubes occurs during 35 min to 40 min. (paper)