Rapid and facile ultrasonic synthesis of nanodiamonds

Abstract

Nanodiamonds (NDs), a new type of carbon nanomaterials, have drawn attention because of their distinctive qualities, such as low toxicity, easy functionalization, and intrinsic biocompatibility. NDs are usually synthesized using techniques, such as high temperature and high pressure (HTHP), chemical vapor deposition (CVD) and detonation, etc., which require hazardous chemicals, high energy and long reaction time.

In this study, we have investigated the synthesis of NDs by using probe ultrasonication method at ambient temperature and pressure using organic salts as precursors in an aqueous medium. The obtained carbon particles were characterized using FESEM, HRTEM, FTIR, Raman and XRD analyses. It was observed that ultrasonication time had a profound effect on the morphology of the formed NDs. At low reaction times of 30 min, the NDs were nucleated having metastable morphologies, which readily transformed into cubic nanodiamonds of high quality after just 1 h of ultrasonication. After acid purification, the particles were found to show a sharp diamond Raman peak at 1332 cm⁻¹ in Raman spectroscopy and predominantly a cubic crystal structure by HRTEM-SAED pattern, confirming the formation of NDs. The study presents a simple green approach for synthesizing NDs in ecologically safe manner.