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

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 9 l/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 6 l/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 6 l/min argon flow rate. AFM micrograph also reveals the smallest size of NDs ~27 nm for 6 l/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 6 l/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 6 l/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.