Impact of carrier gas flow rate on the synthesis of nanodiamonds via microplasma technique

Abstract

Nanodiamonds (NDs) have been fabricated utilizing micro plasma facility. The mixture of argon as carrier gas and ethanol as precursor has been dissociated in micro plasma. The argon flow rate was varied from 4 to 9l/min. The influence of argon gas flow rates on structural, surface and optical properties of NDs was compared. An increased amount of diamond has been reported with the increase in flow rate, obtaining the maximum value at 6l/min. Further increase in flow rate starts decreasing the quality of NDs. Raman and XRD confirm that the smallest size and stress free NDs are obtained at 6l/min argon flow rate. AFM micrograph also reveals the smallest size of NDs ~27nm for 6l/min argon flow rate. The hydrophobicity of NDs increases with increasing argon flow rate as confirmed by FTIR. Photoluminescence indicates the presence of nitrogen vacancy defect centers such as N3, H3 and NV for all the flow rates. The smallest PL peak intensity at 6l/min argon flow rate indicates the lowest density of vacancy defects in the diamond. UV–Visible spectroscopy indicates the presence of nitrogen-hydrogen defect and nitrogen vacancy defect centers (N4 and N5). The largest band gap at 6l/min argon flow rate also confirms the highest quality of NDs. The centers offer promising applications as, active laser material, fluorescent markers, quantum information, nanoscale magnetic and electric filed sensors.