Inorganic Chemistry Communications 127 (2021) 108551 Available online 10 March 2021 1387-7003/© 2021 Elsevier B.V. All rights reserved. Short communication Sonochemical-assisted synthesis of highly stable gold nanoparticles catalyst for decoloration of methylene blue dye Mohammed Ali Dheyab a, b, * , Azlan Abdul Aziz a, b, * , Mahmood S. Jameel a, b , Pegah Moradi Khaniabadi c , Baharak Mehrdel d a Nano-Biotechnology Research and Innovation (NanoBRI), Institute for Research in Molecular Medicine (INFORMM), Universiti Sains Malaysia, 11800 Pulau Pinang, Malaysia b Nano-Optoelectronics Research and Technology Lab (NORLab), School of Physics, Universiti Sains Malaysia, 11800 Pulau Pinang, Malaysia c Department of Radiology and Molecular Imaging, College of Medicine and Health Science, Sultan Qaboos University. PO. Box: 35, 123, Al Khod, Muscat, Oman d New Technologies Research Centre, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran A R T I C L E INFO Keywords: AuNPs Sonochemistry method Colloidal stabilisation Ultrasound output power Catalysis ABSTRACT Gold nanoparticles (AuNPs) can be easily synthesised using several methods for various applications in the in- dustrial and medical sectors. However, their performance as a catalyst has not yet to be appropriately studied and optimised due to large size distribution and high agglomeration property. In this work, AuNP were synthesized by a sonochemical method using sodium citrate as a reducing agent and capping material. A Vibra-Cell ultrasonic solid horn with a half-inch tip size, frequency of 20 kHz and different ultrasound output powers (12, 20 and 36 W) was used in the synthesis. The as-synthesized AuNPs exhibited a spherical morphology with smooth geom- etry, excellent stability and high monodispersity after 10 min of sonication. AuNPs sizes decreased with increased sonication output power, which implies that the particle size, surface plasmon resonance, stability and mono- dispersity of the AuNPs depended on ultrasound output power and reaction time. Overall, this study showed that the sonochemical synthesis of AuNPs was an easy and controllable approach and can be potentially applied to fabricate other nanosized particles. AuNP’s catalytic effciency for the degradation of methylene blue has a fast decoloration rate of about 10 min. 1. Introduction Sonochemistry involves the application of potent ultrasound radia- tion to molecules to activate chemical reactions [1–3]. The passage of ultrasound through a solution generates high- and low-pressure regions consistent with periodic compression and expansion, respectively [4,5]. This variation in pressure denotes the sonochemical reaction initiation, which precedes the critical route of acoustic cavitation, specifcally the formation, expansion, and collapse of the acoustic bubble [6,7]. The collapse bubble’s potential energy is changed over to the microjet’s active energy with speeds of hundreds of meters per second. However, solid particles with sizes less than the collapsing bubble size (~150 µm) are incapable of producing microjets after irradiation with a 2 kHz ul- trasonic feld [8,9]; instead, cavitation and shock wave emissions arise [10,11]. The formation of the acoustic bubble entails the diffusion of dissolved air molecules at the low-pressure cycle. Subsequently, the acoustic bubble and its internal matter are violently compressed by the high external pressure. This expansion and compression of the acoustic bubble are maintained until the external pressure completely takes over and the bubble eventually collapse. The pressure and temperature within the bubble exceed 1000 atm and 5000 K, respectively, in the course of cavitation [12]. Several factors, including ultrasonic output power and frequency, solvent type and solution temperature, affect the effciency of cavitation and its derivative chemical and physical prop- erties [13]. These factors determine the properties of the synthesized AuNPs, such as size, structure, stability and surface plasmon resonance (SPR). AuNPs have been the subject of considerable research in science and technology for several years [14]. Au is generally a non-reactive or inert metal, but its properties are totally transformed at nanosized because of drastic alterations in its electron behaviour within this size [15]. AuNPs catalysts has also found many uses for organic and inorganic reactions. * Corresponding authors at: Nano-Biotechnology Research and Innovation (NanoBRI), Institute for Research in Molecular Medicine (INFORMM), Universiti Sains Malaysia, 11800 Pulau Pinang, Malaysia. E-mail addresses: mohammed@student.usm.my (M. Ali Dheyab), lan@usm.my (A. Abdul Aziz). Contents lists available at ScienceDirect Inorganic Chemistry Communications journal homepage: www.elsevier.com/locate/inoche https://doi.org/10.1016/j.inoche.2021.108551 Received 25 January 2021; Received in revised form 27 February 2021; Accepted 1 March 2021