Temperature as a key parameter for graphene sono-exfoliation in water

• Published in: Ultrasonics sonochemistry Vol. 90; p. 106187
• Main Authors: Kaur, Amanpreet, Morton, Justin A., Tyurnina, Anastasia V., Priyadarshi, Abhinav, Holland, Adam, Mi, Jiawei, Porfyrakis, Kyriakos, Eskin, Dmitry G., Tzanakis, Iakovos
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.11.2022; Elsevier
• Subjects: Cavitation bubbles; Eco-friendly; Exfoliation; Graphene; Shock waves; Short Communication; Ultrasonic processing; Water; Cavitation bubbles; Water; Shock waves; Graphene; Eco-friendly; Ultrasonic processing; Exfoliation
• ISSN: 1350-4177; 1873-2828
• DOI: 10.1016/j.ultsonch.2022.106187

•Control of temperature is the key for successful graphene exfoliation in water.•Increase in solution temperature reduces the intensity of the shockwave (SW) peak.•SWs wavelength was kept at 430–460 µm not being affected by the temperature.•Optimum balance of SWs and bubble clouds at 40 °C produced the efficient exfoliation.•High quality few-layer graphene with an area of ∼0.6 μm2 produced in 2 h. Graphene dispersions in water are highly desirable for a range of applications such as biomedicines, separation membranes, coatings, inkjet printing and more. Recent novel research has been focussed on developing a green approach for scalable production of graphene. However, one important parameter, which is often neglected is the bulk temperature of the processing liquid. This paper follows our earlier work where optimal sono-exfoliation parameters of graphite in aqueous solutions were determined based on the measured acoustic pressure fields at various temperatures and input powers. Here, we take the next step forward and demonstrate using systematic characterisation techniques and acoustic pressure measurements that sonication-assisted liquid phase exfoliation (LPE) of graphite powder can indeed produce high quality few layer graphene flakes in pure water at a specific temperature, i.e. 40 °C, and at an optimised input generator power of 50%, within 2-h of processing. UV–vis analysis also revealed that the exfoliation, stability and uniformity of dispersions were improved with increasing temperature. We further confirmed the successful exfoliation of graphene sheets with minimal level of defects in the optimized sample with the help of Raman microscopy and transmission electron microscopy. This study demonstrated that understanding and controlling processing temperature is one of the key parameters for graphene exfoliation in water which offers a potential pathway for its large-scale production.