Synthesis and Characterization of Ferrofluid-Chitosan-Au Nanoparticles as Brachytherapy Agent Candidate

Brachytherapy is expected to be a solution to the side effect of other cancer therapy methods. This study aims to synthesize ferrofluids (FF)-Chitosan-Au (so-called cold synthesis) as the initial step before using 198Au that is expected to be a targeted and controllable brachytherapy agent. In this research, the preparation of FF-Chitosan was done by the co-precipitation method. Furthermore, FF-Chitosan-Au was produced via self-assembly by the adsorption method. The adsorption followed the Langmuir model with a maximum capacity of 30.24 mg Au/g FF-Chitosan. The X-Ray Diffractometion (XRD) of FF-Chitosan-Au confirms the existence of Au. Particle Size Analyzer (PSA) indicates FF-Chitosan-Au has an average size of 82.93 nm with a polydispersity index of 0.175. Morphological and distribution analysis of nanoparticles using Scanning Electron Microscope (SEM) shows that nanoparticles have a homogenous spherical shape. Vibrating Sample Magnetometer (VSM) measurement confirms the superparamagnetic properties of FF-Chitosan and FF-Chitosan-Au with a saturated magnetization of 80.48 and 74.52 emu/g, respectively. The overall results are associated with biomedical requirements, such as high saturation magnetization and good polydispersity. The synthesis can also be applied to produce FF-Chitosan-198Au that has great potential as a brachytherapy agent, which will reduce the nuclear waste and potential danger of radiation received by workers during synthesis.

Influence of Co-Precipitation Agent on the Structure, Texture and Catalytic Activity of Au-CeO2 Catalysts in Low-Temperature Oxidation of Benzyl Alcohol

The aim of the study was to establish the influence of a co-precipitation agent (i.e., NaOH–immediate precipitation; hexamethylenetetramine/urea–gradual precipitation and growth of nanostructures) on the properties and catalytic activity of as-synthesized Au-CeO2 nanocomposites. All catalysts were fully characterized with the use of XRD, nitrogen physisorption, ICP-OES, SEM, HR-TEM, UV-vis, XPS, and tested in low-temperature oxidation of benzyl alcohol as a model oxidation reaction. The results obtained in this study indicated that the type of co-precipitation agent has a significant impact on the growth of gold species. Immediate co-precipitation of Au-CeO2 nanostructures with the use of NaOH allowed obtainment of considerably smaller and more homogeneous in size gold nanoparticles than those formed by gradual co-precipitation and growth of Au-CeO2 nanostructures in the presence of hexamethylenetetramine or urea. In the catalytic tests, it was established that the key factor promoting high activity in low-temperature oxidation of benzyl alcohol was size of gold nanoparticles. The highest conversion of the alcohol was observed for the catalyst containing the smallest Au particle size (i.e., Au-CeO2 nanocomposite prepared with the use of NaOH as a co-precipitation agent).

Glycerol Oxidation over Supported Gold Catalysts: The Combined Effect of Au Particle Size and Basicity of Support

Gold nanoparticles supported on various oxides (CeO2, CeO2/TiO2, MgO, MgO/TiO2, La2O3, La2O3/TiO2) (with 4 wt.% Au loading) were investigated in the liquid (aqueous) phase oxidation of glycerol by molecular oxygen under mild conditions, in the presence of alkaline earth (CaO, SrO and MgO) or alkaline (NaOH) bases. Full conversion and selectivity between 38 and 68% to sodium glycerate were observed on different Au supported catalysts (Au/MgO/TiO2, Au/La2O3/TiO2, Au/CeO2 and Au/CeO2/TiO2). The combined effect of Au particle size and basicity of the support was suggested as the determining factor of the activity. Agglomeration of gold nanoparticles, found after the reaction, led to the deactivation of the catalysts, which prevents the further oxidation of sodium glycerate into sodium tartronate. Promising results were obtained with the use of alkaline earth bases (CaO, SrO, MgO), leading to the formation of free carboxylic acids instead of salts, which are formed in the presence of the more usual base, NaOH.

Thermal Atomic Layer Deposition of Gold Nanoparticles: Controlled Growth and Size Selection for Photocatalysis

Gold nanoparticles have been extensively studied for their applications in catalysis. For Au nanoparticles to be catalytically active, controlling the particle size is crucial. Here we present a low temperature (105 °C) thermal atomic layer deposition approach for depositing gold nanoparticles on TiO₂ with controlled size and loading using trimethylphosphino-trimethylgold (III) and two co-reactants (ozone and water) in a fluidized bed reactor. We show that the exposure time of the precursors is a variable that can be used to decouple the Au particle size from the Au loading. Longer exposures of ozone narrow the particle size distribution while longer exposures of water broaden it. By studying the photocatalytic activity of Au/TiO₂ nanocomposites we show how the ability to control particle size and loading independently can be used not only to enhance performance but also to investigate structure-property relationships. This study provides insights into the mechanism underlying formation and evolution of Au nanoparticles via a vapor phase technique which eliminates the shortcomings of conventional liquid-base processes.

Thermal Atomic Layer Deposition of Gold Nanoparticles: Controlled Growth and Size Selection for Photocatalysis

Gold nanoparticles have been extensively studied for their applications in catalysis. For Au nanoparticles to be catalytically active, controlling the particle size is crucial. Here we present a low temperature (105 °C) thermal atomic layer deposition approach for depositing gold nanoparticles on TiO₂ with controlled size and loading using trimethylphosphino-trimethylgold (III) and two co-reactants (ozone and water) in a fluidized bed reactor. We show that the exposure time of the precursors is a variable that can be used to decouple the Au particle size from the Au loading. Longer exposures of ozone narrow the particle size distribution while longer exposures of water broaden it. By studying the photocatalytic activity of Au/TiO₂ nanocomposites we show how the ability to control particle size and loading independently can be used not only to enhance performance but also to investigate structure-property relationships. This study provides insights into the mechanism underlying formation and evolution of Au nanoparticles via a vapor phase technique which eliminates the shortcomings of conventional liquid-base processes.