Particle size of the as-deposited carbon spheres (CSs) from plant-derived oil precursor was modified through the addition of a corona discharge ionizer as an attachment to the conventional atmospheric chemical vapor deposition (CVD) setup. Influences of synthesis parameters such as temperature, solvent-oil concentration, and the presence of ionization on the particle size distribution, graphitization, and conductivity of the CSs were also investigated. The addition of pyridine as a solvent to the Calophyllum inophyllum (CI) oil improved precursor atomization, breaking down the viscous oil into finer vapor intermediates and consequently, the process of decomposition. Measured particle size distribution from scanning electron microscope (SEM) and atomic force microscope (AFM) images show a decrease in mean particle diameter, from > 180 nm without ionization to < 100 nm with ionization. This relates mostly to the decrease in Brownian motion of particles within the system during deposition due to the presence of opposing electrostatic forces brought about by particles having the same electric charge. TEM images confirm the presence of concentrically-wrapped layers of carbon at the surface. Raman spectra also show the presence of graphitic layering within the carbon spheres, with two primary peaks located at 1350 cm(-1) and 1580 cm(-1) pertaining to both the D and the G bands of all in-plane bonded carbon atoms, respectively. Ionized samples have higher I-D/I-G ratios, suggesting a short order graphitization compared to non-ionized samples. However, samples prepared at higher temperatures show a slight improvement in the level of graphitization with a decreased I-D/I-G ratio. Current-voltage measurements from conductive AFM have a general ohmic behavior for all non-powdered CSs. Ionized samples show lower sheet resistance (23.13-160.72 k Omega) possibly due to reduced particle size. The nanometer size may have resulted to lower void fraction, allowing efficient electron flow. This study emphasizes nanometer size control of conducting carbon spheres from sustainable resources.