Core@shell nanoparticles by inflight controlled coating

Abstract

Controlled synthesis of core@shell nanoparticles (NPs) for certain applications is a difficult challenge in many nanotechnology projects. In this report, a conventional arrangement composed of a gas aggregation source is employed to generate the core nanoparticles, which are subsequently coated by the shell materials in a secondary planar magnetron sputtering. The important difference to the usual system is the application of the two opposing planar magnetrons in a closed field configuration. The prepared core Ag NPs by a gas aggregation source are coated/treated by the two magnetrons with Ti targets. Our findings clearly show that the shell thickness can be controlled by tuning the power delivered to the secondary magnetron plasma. Characterizations of the prepared films, by X-ray diffraction technique, disclose multi-crystalline cores covered by amorphous shells. Based on XPS and EDX measurements, different chemistry on the NPs surfaces and volume of the NPs can be achieved by tuning the operation conditions. Furthermore, the thermal annealing process leads to the growth of the crystallite size which results in emerging some microparticles caused by accelerating Ag surface mobility. The employed technique promises a reliable route to synthesize different heterogeneous NPs with stoichiometry tunable in a wide range for multi-functional devices.

Silver nanoparticles with plasma-polymerized hexamethyldisiloxane coating on 3D printed substrates are non-cytotoxic and effective against respiratory pathogens

“…The layer of AgNPs (approx. size of 25 nm, Figure 1A ) visualized by SEM appeared very porous with partially sintered NPs, which is typical for these highly pure AgNP films, previously described by Ahadi et al (2022) . However, such coatings have poor mechanical stability, even worse than smooth Ag layers, since the NPs are held together only by Van der Waals forces and can be easily wiped off the substrates.…”

“…The NPs were produced in the so-called gas aggregation source (GAS) of nanoparticles. The method and experimental conditions were described in detail by Ahadi et al (2022) . Briefly, AgNPs were produced in a GAS equipped with a 76 mm in diameter planar magnetron with the silver target.…”

A novel method for the synthesis of core–shell nanoparticles for functional applications based on long-term confinement in a radio frequency plasma

“…This approach however is limited by the time of flight of the particles and the length of the aggregation zone and is mostly used for metal@metal nanoparticles. In a second approach by Ahadi et al 35 and Kylián et al , 36 the Haberland type GAS is combined with a secondary direct current (DC) magnetron discharge to synthesize pure NPs in the GAS and then coat them prior to deposition in the second discharge with a shell material. The achievable coating thickness is limited by the maximum power, which can be applied to the target and the residence times defined by the strength of the gas flow.…”