This article explains the mechanism of the metal/oxide core-shell Ag/TiO 2 and Au/TiO 2 nanoparticle formation via one-step ultrasonic spray pyrolysis (USP) by establishing a new model. The general knowledge on the standard "droplet-to-particle" (DTP) mechanism, nucleation, and growth processes of noble metals, as well as physical and chemical properties of core and shell materials and experimental knowledge, were utilized with the purpose of the construction of this new model. This hypothesis was assessed on silver (Ag)/titanium oxide (TiO 2 ) and gold (Au) TiO 2 binary complex nanoparticles' experimental findings revealed by scanning electron microscopy (SEM), focused ion beam (FIB), high-resolution transmission electron microscopy (HRTEM), and simulation of crystal lattices. It was seen that two mechanisms run as proposed in the new model. However, there were some variations in size, morphology, and distribution of Ag and Au through the TiO 2 core particle and these variations could be explained by the inherent physical and chemical property differences of Ag and Au.Keywords: ultrasonic spray pyrolysis; core shell nanostructure; formation mechanism; TiO 2 ; Ag; Au Motivation and BackgroundCore shell complex nanostructures comprised of binary systems have been the focus of great interest due to their high functionality [1,2]. Preserving the core material's properties and modifying the surface with another material multiplies properties and, owing to the core/shell interface, superior performance has been introduced to a system that cannot be achieved by a single constituent. In recent studies, it was seen that thin surface layers on fine particles affect various properties substantially, such as chemical and thermal stability [3], catalytic activity [4], optical, magnetic, and electrical properties [5][6][7][8].Among various combinations of materials that have been utilized as core-shell systems this study targets on inorganic-inorganic group of Ag/TiO 2 and Au/TiO 2 . TiO 2 is proposed as a core material due to its inertness, chemical stability, and non-toxic nature [9]. It is a crystalline material with three polymorphic phases; anatase (tetragonal), rutile (tetragonal), brookite (orthorhombic), with an order of enthalpy of formation as; ∆H f (rutile) < ∆H f (brookite) < ∆H f (anatase) [10,11]. Regarding the energetics of three polymorphs, rutile is the most stable phase, thermodynamically. However, these three compounds have a surface energy order as; Abstract: This article explains the mechanism of the metal/oxide core-shell Ag/TiO2 and Au/TiO2 nanoparticle formation via one-step ultrasonic spray pyrolysis (USP) by establishing a new model. The general knowledge on the standard "droplet-to-particle" (DTP) mechanism, nucleation, and growth processes of noble metals, as well as physical and chemical properties of core and shell materials and experimental knowledge, were utilized with the purpose of the construction of this new model. This hypothesis was assessed on silver (Ag)/titanium oxide (TiO2)...

This article reports the synthesis of Ag/TiO 2 and Au/TiO 2 nanoparticles by single-step ultrasonic spray pyrolysis (USP) conducted by an investigation of the process parameters and the morphological characteristics of the obtained nanostructures. The influence of the ratio in the precursor solution, physical characteristics of used components, and temperature had a large influence on the formation of different nanoparticle morphologies. The experimental investigations were performed using classic USP equipment, with variations of the process parameters. Scanning electron microscopy, transmission electron microscopy, and focused ion beam analyses were used to characterize the complex nanostructures. Based on the obtained results, the optimal process window for the formation of the different morphologies for the Ag/TiO 2 and Au/TiO 2 nanoparticles is determined and the possibility of synthesis of the core-shell structures in one step by USP is confirmed.

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Using precious metals as plating materials is an effective measure to avoid failures of electrical contacts caused by fretting. When using precious metals, such as gold, one of the limitations to their lifetime is the wear resistance. In order to improve the wear resistance of gold plates, gold alloy is usually used. Instead of alloying elements, nanoscale particles of metal oxides were used for the modification of plates in our investigation. Some of the nanoscale particles show considerable impact on the performance of plates for electrical contacts. This paper shows the first results and new challenges when using nanoscale particles for electroplating.