Sonochemical Synthesis of Gold Nanoparticles by Using High Intensity Focused Ultrasound

Abstract

The sonochemical synthesis of gold nanoparticles (GNPs) with different shapes and size distributions by using high-intensity focused ultrasound (HIFU) operating at 463 kHz is reported. GNP formation proceeds through the reduction of Au(3+) to Au(0) by radicals generated by acoustic cavitation. TEM images reveal that GNPs show irregular shapes at 30 W, are primarily icosahedral at 50 W and form a significant amount of nanorods at 70 W. The size of GNPs decreases with increasing acoustic power with a narrower size distribution. Sonochemiluminescence images help in the understanding of the effect of HIFU in controlling the size and shapes of GNPs. The number of radicals that form and the mechanical forces that are generated control the shape and size of the GNPs. UV/Vis spectra and TEM images are used to propose a possible mechanism for the observed effects. The results presented demonstrate, for the first time, that the HIFU system can be used to synthesise size- and shape-controlled metal nanoparticles.

Reactional Ultrasonic Systems And Microwave Irradiation For Pretreatment Of Agro-Industrial Waste To Increase Enzymatic Activity

“…The ultrasonic probe increases reaction rates, especially hydrolysis processes (Zou et al 2016). Ultrasonic systems facilitate structural degradation via propagation of ultrasonic waves that cause bubble cavitation, causing temperature rise, favoring the formation of rapidly reacting radicals (Wang 1981;Manasseh et al 2010;Yusof and Ashokkumar 2015), improving the enzymatic attack on the substrate (Yang and Fang 2015). The cavitation process is the fundamental factor for the e ciency of ultrasound pretreatment, because the explosion of bubbles near the surface of the material causes abrasion and erosion, reducing the surface area of the structure and, consequently, improving the processes.…”

“…Because of the biotechnological importance of keratinases, several studies have been performed to improve the activity and to evaluate the conformational change of enzymes in general, when exposed to different reaction systems, including ultrasonic probe and bath and microwave (Ma et al 2011;Jin et al 2015;Mazinani, DeLong and Yan 2015). Simple and e cient heating technologies increase enzyme activity and conformational change (Ma et al 2011); residue pretreatment techniques using an ultrasonic probe (Azmi, Idris and Yusof 2018), makes the structures more accessible to microbial and enzymatic attack (Yusof and Ashokkumar 2015).…”

Reactional Ultrasonic Systems and Microwave Irradiation For Pretreatment Of Agro-Industrial Waste To Increase Enzymatic Activity

“…The ultrasonic probe increases reaction rates, especially hydrolysis processes (Zou et al 2016). Ultrasonic systems facilitate structural degradation via propagation of ultrasonic waves that cause bubble cavitation, causing temperature rise, favoring the formation of rapidly reacting radicals (Wang 1981;Manasseh et al 2010;Yusof and Ashokkumar 2015), improving the enzymatic attack on the substrate (Yang and Fang 2015). The cavitation process is the fundamental factor for the e ciency of ultrasound pretreatment, because the explosion of bubbles near the surface of the material causes abrasion and erosion, reducing the surface area of the structure and, consequently, improving the processes.…”

Merging Metallic Catalysts and Sonication: A Periodic Table Overview

“…It should be finally pointed out that Au-NPs can be efficiently generated by means of high-intensity focused ultrasound (HIFU), working at 463 kHz [109]. Formation of NPs proceeds through the reduction of Au(III) ions to Au(0) by radicals generated under ultrasonic cavitation.…”