Mesoporous Au–TiO2 Nanoparticle Assemblies as Efficient Catalysts for the Chemoselective Reduction of Nitro Compounds

2014 ◽  
Vol 1641 ◽  
Author(s):  
Ioannis Tamiolakis ◽  
Ioannis N. Lykakis ◽  
Gerasimos S. Armatas
Keyword(s):  
Particle Size ◽  
Gold Particle ◽  
Nitro Compounds ◽  
Nitroaromatic Compounds ◽  
Pore Surface ◽  
Nanoparticle Assemblies ◽  
Gold Particle Size ◽  
Pore Surface Area ◽  
Hydrogenation Reactions ◽  
Amine Groups

ABSTRACTHere, we propose novel mesoporous Au-loaded TiO2 nanoparticle assemblies (Au-MTA) as highly effective catalysts for the reduction of nitroaromatic compounds into the corresponding aryl amine products. The obtained materials possess a continuous network of interconnected gold and anatase TiO2 (ca. 9 nm in size) nanoparticles with controllable gold particle size (i.e. ranging from ∼3.2 to ∼9.4 nm) and exhibit large and accessible pore surface area (ca. 100–160 m2/g), as evidenced by SAXS, XRD, TEM and N2 physisorption measurements. Interestingly, the Au-MTA mesophases have exhibited remarkable activity and selectivity for the reduction of nitro into amine groups using NaBH4 as reducing agent. Indeed, the Au loading and particle size have a key effect on hydrogenation reactions, affecting significantly the yield and product composition.

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

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 971
Author(s):  
Oktawian Bialas ◽  
Mateusz Lis ◽  
Anna Woźniak ◽  
Marcin Adamiak
Keyword(s):  
Particle Size ◽  
Laser Beam ◽  
Gold Particle ◽  
Laser Power ◽  
Biomedical Application ◽  
Parameters Optimization ◽  
Size Reduction ◽  
Particle Size Reduction ◽  
Nano Gold ◽  
Gold Particle Size

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.

Supported Au catalysts for propene total oxidation: Study of support morphology and gold particle size effects

2011 ◽  
Vol 176 (1) ◽  
pp. 7-13 ◽  
Author(s):  
M. Ousmane ◽  
L.F. Liotta ◽  
G. Pantaleo ◽  
A.M. Venezia ◽  
G. Di Carlo ◽  
...  
Keyword(s):  
Particle Size ◽  
Gold Particle ◽  
Size Effects ◽  
Total Oxidation ◽  
Particle Size Effects ◽  
Oxidation Study ◽  
Gold Particle Size

scholarly journals Gold Particle Size Determination on Au/TiO2-CeO2 Catalysts by Means of Carbon Monoxide, Hydrogen Chemisorption and Transmission Electron Microscopy

2009 ◽  
Vol 5 ◽  
pp. 13-23 ◽  
Author(s):  
C. Guzmán ◽  
Gloria Del Angel ◽  
Ricardo Gómez ◽  
F. Galindo ◽  
R. Zanella ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Carbon Monoxide ◽  
Particle Size ◽  
Gold Particle ◽  
Precipitation Method ◽  
Hydrogen Chemisorption ◽  
Gold Particles ◽  
Transmission Electron ◽  
Gold Particle Size

Au/TiO2 and Au/TiO2-CeO2 catalysts were prepared by the sol-gel method and carbon monoxide, hydrogen chemisorption and TEM spectroscopy have been exploited to determine the size of gold particles. The gold nanoparticles (8.1 to 2.1 nm) were deposited by using the deposition-precipitation method. The XRD characterization shows the presence of anatase as the TiO2 crystalline phase; while by XPS spectroscopy, the presence of Au°, Au2O3, Ce3+ and Ce4+ species co-existing in the Au/TiO2-CeO2 catalysts is shown. The characterizations by TPD-CO as well as by TPD-H2 (temperature programmed desorption) showed that on catalysts containing cerium, the gold particle size can be determined with great accuracy by using these chemisorption methods. The gold particle size calculated from either the CO or H2 thermodesorption values is in good agreement with that obtained by High Resolution Transmission Electron Microscopy (HRTEM) and Scanning Transmission Electron Microscopy (STEM) analyses. It was proposed that the TPD-CO and/or TPD-H2 techniques could be helpful for the characterization of the gold particles by TEM; especially when the high contrast in the pictures of the supports containing CeO2 prevents the particle size from being determined.

scholarly journals Effective diameters of protein A-gold and goat anti-rabbit-gold conjugates visualized by field emission scanning electron microscopy.

1992 ◽  
Vol 40 (6) ◽  
pp. 751-758 ◽  
Author(s):  
P Lea ◽  
D K Gross
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Particle Size ◽  
Field Emission ◽  
Gold Particle ◽  
Protein A ◽  
Gold Complexes ◽  
Gold Particles ◽  
Gold Particle Size ◽  
Scanning Electron

High-voltage (15-30 kV) field emission scanning electron microscopy (FESEM) was used to evaluate the effects of gold particle size and protein concentration on the formation of protein-gold complexes. Six colloidal gold sols were prepared, ranging in diameter from 7.6 to 39.8 nm. The minimal protecting amounts (m.p.a.) of protein A and goat anti-rabbit antibody (GAR) were experimentally determined. Gold particles were conjugated at the m.p.a., one half the m.p.a., and ten times the m.p.a. for both proteins, and protein-gold complexes prepared for FESEM. The smallest colloidal gold particles required the most protein per milliliter of gold suspension for stabilization. Transmission electron microscopy was found to be the preferred method for accurate sizing of gold particles, whereas FESEM of protein-gold complexes permitted visualization of a protein halo around a spherical gold core. Protein halo width varied significantly with changes in gold particle size. Measurements of protein halos indicated that conjugation with the m.p.a. of protein A resulted in the thickest protein layers for all gold sizes. GAR conjugation with the m.p.a. again produced the thickest protein layers. However, GAR halos were significantly smaller than those obtained with protein A conjugation. The proteins used showed similar adsorption patterns for the larger gold particles. For smaller gold particles, proteins may act differently, and these complexes should be further characterized by low-voltage FESEM.

Effect of Gold Particle Size and Deposition Method on the Photodegradation of 4-Chlorophenol by Au/TiO2

2011 ◽  
Vol 54 (8-9) ◽  
pp. 519-526 ◽  
Author(s):  
S. Oros-Ruiz ◽  
J. A. Pedraza-Avella ◽  
C. Guzmán ◽  
M. Quintana ◽  
E. Moctezuma ◽  
...  
Keyword(s):  
Particle Size ◽  
Gold Particle ◽  
Deposition Method ◽  
Gold Particle Size

scholarly journals Methane Adsorption Interpreting with Adsorption Potential and Its Controlling Factors in Various Rank Coals

Processes ◽  
2020 ◽  
Vol 8 (4) ◽  
pp. 390 ◽  
Author(s):  
Feng Qiu ◽  
Dameng Liu ◽  
Yidong Cai ◽  
Ning Liu ◽  
Yongkai Qiu
Keyword(s):  
Particle Size ◽  
Controlling Factors ◽  
Methane Adsorption ◽  
Coal Rank ◽  
Pore Surface ◽  
Adsorption Potential ◽  
N2 Adsorption ◽  
Isothermal Adsorption ◽  
Coal Matrix ◽  
Pore Surface Area

Water content, metamorphism (coal rank) particle size, and especially pore structure, strongly influence the adsorption capacity of coal to methane. To understand the mechanism of methane adsorption in different rank coals, and its controlling factors, isothermal adsorption experiments with different coal ranks, moisture contents and particle sizes at the temperature of 303.15 K were conducted. In addition, the pore structures of coals were investigated through N2 adsorption/desorption experiments at the low-temperature of 77 K for selected coals from the Junggar Basin of NW China, Qinshui Basin and Ordos Basin of north China. Moreover, the adsorption potential of methane on the surface of the coal matrix was calculated, the controlling factors of which were discussed. The obtained methane isothermal adsorption result shows that the Langmuir volume (VL) of coal is independent of the particle size, and decreases with the increase of moisture content, which decreases first and then increases when the coal rank increases. Combined with the pore structure by the N2 adsorption at 77 K, VL increases with the increase of pore surface area and pore volume of coal pores. Besides, the adsorption potential of all selected coals decreased with the increase of the methane adsorption volume, showing a negative relationship. The interesting phenomena was found that the surface adsorption potential of the coal matrix decreases with the increase of moisture content, and increases with the decrease of particle size at the same pressure. With the same adsorption amount, the adsorption potential on the surface of coal matrix decreases first, and then increases with the increase of coal rank, reaching a minimum at Ro,m of 1.38%, and enlarging with the increase of pore surface area and the pore volume of coal pores. These findings may have significant implications for discovering CBM accumulation areas and enhancing CBM recovery.

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