Size-tunable silver nanoparticle synthesis in glycerol driven by a low-pressure nonthermal plasma

Abstract

Silver nanoparticles are extensively used in electronic components, chemical sensors, and disinfection applications, in which many of their properties depend on particle size. However, control over silver nanoparticle size and morphology still remains a challenge for many synthesis techniques. In this work, we demonstrate the surfactant-free synthesis of silver nanoparticles using a low-pressure inductively coupled nonthermal argon plasma. Continuously forming droplets of silver nitrate (AgNO3) precursor dissolved in glycerol are exposed to the plasma, with the droplet residence time being determined by the precursor flow rate. Glycerol has rarely been studied in plasma-liquid interactions but shows favourable properties for controlled nanoparticle synthesis at low pressure. We show that the droplet residence time and plasma power have strong influence on nanoparticle properties, and that improved size control and particle monodispersity can be achieved by pulsed power operation. Silver nanoparticles had mean diameters of 20 nm with geometric standard deviations of 1.6 under continuous wave operation, which decreased to 6 nm mean and 1.3 geometric standard deviation for pulsed power operation at 100 Hz and 20% duty cycle. We propose that solvated electrons from the plasma and VUV radiation induced electrons produced in glycerol are the main reducing agents of Ag+, the precursor for nanoparticles, while no significant change of chemical composition of the glycerol solvent was detected.

Silver Nanoparticle Synthesis in Glycerol by Low-Pressure Plasma-Driven Electrolysis: The Roles of Free Electrons and Photons

“…For photon energies of <4.5 eV, an NP density too small to determine the size distribution was obtained. The decrease in NP size is consistent with our previous observation that reducing the flux of plasma species to the droplet leads to smaller NPs, 16 as the rate of production of Ag neutrals driving NP growth is reduced.…”

“…We recently presented a new PDSE synthesis method of silver NPs using a low-pressure inductively coupled plasma (ICP) . Glycerol enabled stable low-pressure plasma treatment due to its low vapor pressure, and silver nitrate (AgNO 3 ) was selected as the precursor on the basis of its high solubility .…”

“…14,15 We recently presented a new PDSE synthesis method of silver NPs using a low-pressure inductively coupled plasma (ICP). 16 Glycerol enabled stable low-pressure plasma treatment due to its low vapor pressure, 17 and silver nitrate (AgNO 3 ) was selected as the precursor on the basis of its high solubility. 18 Glycerol is a major co-product of biodiesel production and has attracted considerable attention as the smallest polyol and a scavenger of OH•, a radical that yields low Faradaic efficiencies.…”

A Single-Step Bottom-up Approach for Synthesis of Highly Uniform Mie-Resonant Crystalline Semiconductor Particles at Visible Wavelengths

“…Over the past two decades, nonthermal plasma synthesis has emerged as a competitive technology for the formation of nanocrystals that are difficult or impossible to synthesize with other fabrication techniques. Nanocrystals of covalently bonded group IV elements, − noble and transition metals, − and compound semiconducting materials − are among the vast library of materials successfully synthesized by this all-gas-phase method. Nonthermal plasmas have excellent control over particle size and size distribution owing to the negative charge of the NPs immersed in the plasma, preventing particle agglomeration .…”

Capacitively coupled nonthermal plasma synthesis of aluminum nanocrystals for enhanced yield and size control

“…The I-V characteristics were measured by a source meter (Tektronix 2450, Tektronix, USA) connected to the double probe. More details can be found in [32].…”