Gold and Ceria as Catalysts for VOC Abatement: A Review

Due to its excellent oxygen storage capacity, ceria is a well-known oxidation catalyst. However, its performance in the oxidation of volatile organic compounds can be improved by the introduction of gold. Depending on the type of VOC to be oxidized, the surface of gold nanoparticles and the gold/ceria interface may contribute to enhanced activity and/or selectivity. Choosing a proper preparation method is crucial to obtain optimal gold particle size. Deposition–precipitation was found to be more suitable than coprecipitation or impregnation. For industrial applications, monolithic catalysts are needed to minimize the pressure drop in the reactor and reduce mass and heat transfer limitations. In addition to the approach used with powder catalysts, the method employed to introduce gold in/on the washcoat has to be considered.

Gold Particles Recovery using Novel Reducing Agent with Regard to Continuous Approach

Background: Over 300 tonnes of gold utilised in electronics devices every year, end-of-life electronic equipment offers an crucial recycling potential for secondary gold supply. Electronic boards are among common and exploitable sources of gold that are widely used in various industry. The aims of this paper is to use gold element of electronic boards by adjusting its surface functionality and particle size to make this metal to be used in various applications Methods: to gain this purpose by using acidic solutions and up to bottom chemical synthesis method among physical, chemical, and biological methods and by transferring gold particle size from micrometer to nanometer, surface-area-to-volume ratio will be increase such that new structural properties emerge, change, or improve. Results: Tests such as Fourier-Transform Infrared spectroscopy, X-Ray Diffraction, and Field Emission Scanning Electron Microscopy have confirmed high-quality production and proper extraction of gold particles on a nanometer scale from electronic plates and confirmed crystalline structure of extracted gold in range of 70-110 nm. Conclusion: The main objective of this research is to derive and fabricate gold nanoparticles using chemical oxidative route using HCl and Aqua regia to produce gold nanoparticles in Nano dimension scale. Results has shown that gold nanoparticles are synthesized successfully via chemical process. Moreover, Acid concentration and reaction time has enormous effect on production procedure.

Laser Superficial Fusion of Gold Nanoparticles with PEEK Polymer for Cardiovascular Application

This paper analyses the possibility of obtaining surface-infused nano gold particles with the polyether ether ketone (PEEK) using picosecond laser treatment. To fuse particles into polymer, the raw surface of PEEK was sputtered with 99.99% Au and micromachined by an A-355 laser device for gold particle size reduction. Biomimetic pattern and parameters optimization were key properties of the design for biomedical application. The structures were investigated by employing surface topography in the presence of micron and sub-micron features. The energy of the laser beam stating the presence of polymer bond thermalisation with remelting due to high temperature was also taken into the account. The process was suited to avoid intensive surface modification that could compromise the mechanical properties of fragile cardiovascular devices. The initial material analysis was conducted by power–depth dependence using confocal microscopy. The evaluation of gold particle size reduction was performed with scanning electron microscopy (SEM), secondary electron (SE) and quadrant backscatter electron detector (QBSD) and energy dispersive spectroscopy (EDS) analysis. The visibility of the constituted coating was checked by a commercial grade X-ray that is commonly used in hospitals. Attempts to reduce deposited gold coating to the size of Au nanoparticles (Au NPs) and to fuse them into the groove using a laser beam have been successfully completed. The relationship between the laser power and the characteristics of the particles remaining in the laser irradiation area has been established. A significant increase in quantity was achieved using laser power with a minimum power of 15 mW. The obtained results allowed for the continuation of the pilot study for augmented research and material properties analysis.

Lights and Shadows of Gold Introduction into Beta Zeolite

Four different methods for gold deposition on Beta zeolite, namely impregnation, ion-exchange, deposition-reduction, and grafting on (3-aminopropyl)trimethoxysilane functionalized support, were applied to investigate their influence on textural/structural changes in the zeolite support and its surface acidity. The as-prepared materials were fully characterized by XRD, N2 physisorption, ICP-OES, XPS, TEM, and pyridine adsorption. The obtained results indicated that bifunctional redox–acidic materials prepared within this work were characterized not only by different gold loading and gold particle size, but also different textural parameters and acidity. All these features were strongly affected by the procedure applied for gold deposition. The introduction of Au into Beta zeolite by ion exchange caused a significant decrease in the Si/Al ratio in the zeolite framework. The size of Au particles determined the textural parameters of the zeolite and the number of Lewis acid sites (LAS). The Brønsted acid sites (BAS) number was decreased if (3-aminopropyl)trimethoxysilane or NaBH4 were used in the procedure of gold deposition. The highest BAS/LAS ratio was achieved for the sample prepared by ion exchange in the ammonium form of Beta zeolite. The presented results permit making a proper choice of the gold modification procedure for the preparation of bifunctional (redox–acidic) materials, addressed to a desired application.

Immobilization of Stabilized Gold Nanoparticles on Various Ceria-Based Oxides: Influence of the Protecting Agent on the Glucose Oxidation Reaction

The influence of the protecting agent’s nature on gold particle size and dispersion was studied in this work over a series of gold-based catalysts. CO and glucose oxidation were chosen as catalytic reactions to determine the catalyst’s structure–activity relationship. The nature of the support appeared to be the predominant factor for the increase in activity, as the oxygen mobility was decisive for the CO oxidation in the same way that the Lewis acidity was decisive for the glucose oxidation. For the same catalyst composition, the use of montmorillonite as the stabilizing agent resulted in better catalytic performance.

Oxygen vacancies dependent Au nanoparticle deposition and CO oxidation

Au deposition on CeO2 support is oxygen vacancies dependent. Optimized VOs result in small gold particle size and positively charged Auδ+ to promote CO oxidation; excess VOs lead to agglomerated Au NPs and the reduction of Au3+ reactive species, with catalysis deactivation.