Effect of Frequency and Number of Piezoelectric Probes in Sonication-assisted Exfoliation of Graphite Layers into Graphene Oxide

ABSTRACT

A self-custom-made ultrasound generator using piezoelectric probes has been constructed to reduce graphite layers via liquid-phase exfoliation into graphene oxide (GO) material. The ultrasound frequency and the number of piezoelectric probes are varied with values of 20 kHz, 30 kHz and 35 kHz, and 1 probe, 2 probes and 3 probes, respectively. The solutions obtained from the sonication process show a temperature increase of 1°C or 2°C compared to room temperature. Colour changes of the solution before sonication, after sonication, and after being left overnight are also exhibited; that is from dark, dark blue, to greyish blue, respectively. The solutions are then characterised using UV-Vis spectrophotometer and scanning electron microscope (SEM). The UV-Vis results show the presence of GO material at an absorbance peak of 270 nm. Increasing the frequency and number of the probes decreases the absorbance peaks of the solutions. The best GO sample solution is obtained for an ultrasound frequency of 35 kHz and using 3 piezoelectric probes. Images from SEM show rod-like carbon materials stacked on top of each other in the form of flower-like structures. The widths of these rod-like materials vary from 1 to 2 microns, whereas the thicknesses of these materials are around 300 nm to 1.5 microns.

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