Structural analysis of carbon nanospheres synthesized by CVD: an investigation of surface charges and its effect on the stability of carbon nanostructures

A simple and effective method for mass production of highly homogeneous carbon nanospheres (CNSs) is reported here using xylene and benzene as carbon precursors. Effect of hydrocarbon precursors on the morphology of carbon nanostructures is investigated, keeping deposition temperature, deposition time, and gas flow rate constant. Morphological studies show that homogeneous CNSs are produced on large scale using xylene hydrocarbon as a carbon precursor. Role of ferrocene is also examined as a catalyst for different distinctive morphologies of carbon nanostructures. This study discloses that catalyst plays an important role for formation of carbon nanotubes during growth process. Excitation wavelength-dependent Raman studies reveal enhancement in the oscillator strength and phonon softening for Raman active modes when excitation wavelength is changed from 514 to 785 nm. Surface charges and colloidal stability of aqueous dispersion of CNSs and CNSs after surface modification with surfactants are also studied by zeta-potential measurement. It was found that CNSs modified with surfactants have higher zeta potential than that of as-synthesized CNSs. Roles of anionic and cationic surfactants are also studied here for determining the surface charges, stability, and agglomeration state in CNSs.