Effect of switching ultrasonic amplitude in preparing a hybrid of fullerene (C60) and gallium oxide (Ga2O3)

Abstract

In this study, we proposed 'switching ultrasonic amplitude' as a new strategy of applying ultrasonic energy to prepare a hybrid of buckminsterfullerene (C60) and gallium oxide (Ga2O3), C60/Ga2O3. In the proposed method, we switched the ultrasonic amplitude from 25% to 50% (by 5% amplitude per 10min, within 1h of ultrasonic irradiation) for the sonochemical treatment of a heterogeneous aqueous mixture of C60 and Ga2O3 by a probe-type ultrasonic horn operating at 20kHz. We found that compared to the conventional techniques associated with high amplitude oriented ultrasonic preparation of functional materials, switching ultrasonic amplitude can better perform in preparing C60/Ga2O3 with respect to avoiding titanium (Ti) as an impurity generating from the tip erosion of a probe-type ultrasonic horn during high amplitude ultrasonic irradiation in an aqueous medium. Based on SEM/EDX analysis, the quantity of Ti (wt.%) in C60/Ga2O3 prepared by the proposed technique of switching ultrasonic amplitude was found to be 1.7% less than that prepared at 50% amplitude of ultrasonic irradiation. The particles of C60/Ga2O3 prepared by different modes of amplitude formed large (2-12μm) aggregates in their solid phase.Whereas, in the aqueous medium, they were found to disperse in their nano sizes. The minimum particle size of the as-synthesized C60/Ga2O3 in an aqueous medium prepared by the proposed method of switching ultrasonic amplitude reached to approximately 467nm. Comparatively, the minimum particle sizes were approximately 658nm and 144nm, using 25% and 50% amplitude, respectively. Additionally, Ga2O3 went under hydration during ultrasonic irradiation. Moreover, due to the electron cloud interference from C60 in the hybrid structure of C60/Ga2O3, the vibrational modes of Ga2O3 were Raman inactive in C60/Ga2O3.