The aim of this article was an explanation of the gold nanoparticle (AuNP) formation mechanisms which take place in a redesigned Ultrasonic Spray Pyrolysis (USP). The effects of two influential synthesis parameters were evaluated on controlling the formation mechanisms: Gold concentration (2.5 and 0.5 g/l Au) in the precursor solution of HAuCl4 dissolved in water and gas flows of (i) aerosol carrier gas N2 (1.5, 3.0 and 4.5 l/min) and (ii) reduction gas H2 (1.0, 1.5 and 2.0 l/min). Depending on the parameter conditions, the AuNPs are formed from a combination of the liquid/solid phase (Droplet-to-Particle mechanism, DTP) and the gas phase (Gas-to-Particle mechanism, GTP). Increasing the gas flow affected the evaporation of the solvent (water) and diffusion of the solute ([AuCl4]-) in the aerosol droplets, which resulted in the GTP mechanism being the dominant formation mechanism for AuNPs in the system. Favorable parameter conditions for diminishing the influence of the DTP mechanism provides narrower sizes of more uniformly spherical AuNPs and achieves increased control over nanoparticle synthesis with USP.
COBISS.SI-ID: 20098582
The present investigation reports the first-time successful synthesis of AuNPs using a new precursor salt of Au (III) acetate through USP. An aqueous solution of this salt was prepared with very limited solubility with H2O. HCl and HNO3 were then added separately to increase the solubility, resulting in a clear, yellowish solution. This enabled the successful formation of AuNPs with USP. In order to improve AuNPs synthesis, NaOH and Na2CO3 were added into the precursor to increase its pH (6-7). With such approach, it was possible to perform USP syntheses using varying concentrations of [Au] in the precursor. Evaporation and reaction temperatures (100°C and 300°C) of USP were chosen based on detected decomposition temperatures of Au (III) acetate with TGA-DT. TEM confirmed the presence of circular shaped, unagglomerated AuNPs having an Fm-3m space group with diameter range of 15-30 nm and circularity value range of 0.89 - 0.92. The UV-vis spectroscopy showed absorbance peaks at 528 nm and 532 nm. ICP-MS indicated the highest concentration of AuNPs, 79 ppm, by the precursor with the lower initial concentration of [Au]. This could be due to the smallest sedimentation and turbulent losses of larger AuNPs in transport tubes and reaction USP zones.
COBISS.SI-ID: 20240150
Ultrasonic Spray Pyrolysis (USP) possesses a great potential for production of higher quantities of goldnanoparticles (AuNPs), thus overcoming the problem of batch to batch variations in their properties.Recently, we demonstrated that USP with an additional evaporation chamber (modular USP) led to a better size control of AuNPs. However, their morphology, stability, toxicity and immunomodulatory properties have not been investigated completely. Here, two types of spherical AUNPs were produced by using different USP parameters, followed by their stabilization in Na-citrate solution. No significant changes in their size, agglomeration and z-potential occurred 3 months after their initial production in citrate solution. However, the conditioning of AuNPs in serum containing cell-culture media for 24h induced an increase in the AuNPs`hydrodynamic size and a red-shift in their Surface Pasmon Resonance, pointing to their instability in biological media. Cytocompatibility tests showed that the produced AuNPs were internalized by L929 cells and primary human monocytes and were not cytotoxic at the concentrations lower than 200 µg/ml, but they exhibited anti-proliferative and anti-inflammatory effects, respectively. AuNPs reduced the percentage of CD14+CD16+, but not CD14 low CD16+, monocytes in vitro, and reduced the expression of CD86, HLA-DR, TNF- a and IL-12/IL 23 by these cells. These results indicate that the anti-inflammatory effects of citrate-capped AuNPs produced by modular USP could be beneficial for their application in the treatment of inflammatory conditions.
COBISS.SI-ID: 20098326
This article explains the mechanism of the metal/oxide core-shell Ag/TiO2 and Au/TiO2 nanoparticles formation via one-step Ultrasonic Spray Pyrolysis (USP) by setting up a new model. The general knowledge on 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) and gold (Au) TiO2 binary complex nanoparticles’ experimental findings revealed by Scanning Electron Microscopy (SEM), Focused Ion Beam (FIB) and High Resolution TEM 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 TiO2 core particle and these variations could be explained by the inherent physical and chemical property differences of Ag and Au.
COBISS.SI-ID: 20805142
Precipitation mechanisms and kinetics within an Al-Mn-Be-Cu quasicrystal strengthened alloy at 300°C were studied using in-situ transmission electron microscopy. Quasicrystalline precipitates formed throughout the Al-rich solid solution, whilst heterogeneous formations of Al2Cu and T-phase occurred on icosahedral quasicrystalline particles formed during solidification.
COBISS.SI-ID: 20321046