Nanomaterials

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13 pages, 3998 KiB

Open AccessArticle

Synthesis and Characterization of Erbium-Doped Silica Films Obtained by an Acid–Base-Catalyzed Sol–Gel Process

by Ali Abdullah, El Mostafa Benchafia, Daniel Choi and Sufian Abedrabbo

Nanomaterials 2023, 13(9), 1508; https://doi.org/10.3390/nano13091508 - 28 Apr 2023

Cited by 3 | Viewed by 1398

Erbium-doped silica films were synthesized using a two-step sol–gel methodology that involved acid and base catalysts, with erbium concentration ranging from 0.2% to 6% and annealing temperatures varying from 500 °C to 900 °C. The photoluminescence spectra showed that the samples exhibiting efficient [...] Read more.

Erbium-doped silica films were synthesized using a two-step sol–gel methodology that involved acid and base catalysts, with erbium concentration ranging from 0.2% to 6% and annealing temperatures varying from 500 °C to 900 °C. The photoluminescence spectra showed that the samples exhibiting efficient emission were annealed at 800 °C and 900 °C and doped with 3% and 6% erbium. The X-ray diffraction analysis revealed that the internal structure of the films was influenced by the different annealing temperatures and the doping concentrations. Samples with dominant 4f transitions were modelled. The results suggest that the proposed method is a promising approach for the synthesis of erbium-doped silica films with potential applications in optical devices. Full article

(This article belongs to the Special Issue Synthesis and Application of Silicon Dioxide Nanoparticles)

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19 pages, 4356 KiB

Open AccessArticle

Comparative Study of Commercial Silica and Sol-Gel-Derived Porous Silica from Cornhusk for Low-Temperature Catalytic Methane Combustion

by Clement Owusu Prempeh, Ingo Hartmann, Steffi Formann, Manfred Eiden, Katja Neubauer, Hanan Atia, Alexander Wotzka, Sebastian Wohlrab and Michael Nelles

Nanomaterials 2023, 13(9), 1450; https://doi.org/10.3390/nano13091450 - 24 Apr 2023

Cited by 2 | Viewed by 1618

Abstract

The synthesis and characterization of sol-gel-derived cornhusk support for low-temperature catalytic methane combustion (LTCMC) were investigated in this study. The prepared cornhusk support was impregnated with palladium and cerium oxide (Pd/CeO₂) via the classical incipient wetness method. The resulting catalyst was [...] Read more.

The synthesis and characterization of sol-gel-derived cornhusk support for low-temperature catalytic methane combustion (LTCMC) were investigated in this study. The prepared cornhusk support was impregnated with palladium and cerium oxide (Pd/CeO₂) via the classical incipient wetness method. The resulting catalyst was characterized using various techniques, including X-ray diffraction (XRD), N₂ physisorption (BET), transmission electron microscopy (TEM), and hydrogen temperature-programmed reduction (H₂-TPR). The catalytic performance of the Pd/CeO₂/CHSiO₂ catalyst was evaluated for methane combustion in the temperature range of 150–600 °C using a temperature-controlled catalytic flow reactor, and its performance was compared with a commercial catalyst. The results showed that the Pd/CeO₂ dispersed on SiO₂ from the cornhusk ash support (Pd/CeO₂/CHSiO₂) catalyst exhibited excellent catalytic activity for methane combustion, with a conversion of 50% at 394 °C compared with 593 °C for the commercial silica catalyst (Pd/CeO₂/commercial). Moreover, the Pd/CeO₂/CHSiO₂ catalyst displayed better catalytic stability after 10 h on stream, with a 7% marginal loss in catalytic activity compared with 11% recorded for the Pd/CeO₂/commercial catalyst. The N₂ physisorption and H₂-TPR results indicated that the cornhusk SiO₂ support possessed a higher surface area and strong reducibility than the synthesized commercial catalyst, contributing to the enhanced catalytic activity of the Pd/CeO₂/SiO₂ catalyst. Overall, the SiO₂ generated from cornhusk ash exhibited promising potential as a low-cost and environmentally friendly support for LTCMC catalysts. Full article

(This article belongs to the Special Issue Synthesis and Application of Silicon Dioxide Nanoparticles)

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13 pages, 2745 KiB

Open AccessArticle

Fumed Silica-Based Ultra-High-Purity Synthetic Quartz Powder via Sol–Gel Process for Advanced Semiconductor Process beyond Design Rule of 3 nm

by Ji-Ho Choi, Woo-Guk Lee, Tae-Hun Shim and Jea-Gun Park

Nanomaterials 2023, 13(3), 390; https://doi.org/10.3390/nano13030390 - 18 Jan 2023

Viewed by 2888

Abstract

Fumed silica-based ultra-high-purity synthetic quartz powder was developed via the sol–gel process to apply to quartz wares and quartz crucibles for use in advanced semiconductor processes. The process conditions of preparing potassium silicate solution, gelation, and cleaning were optimized, i.e., the relative ratio [...] Read more.

Fumed silica-based ultra-high-purity synthetic quartz powder was developed via the sol–gel process to apply to quartz wares and quartz crucibles for use in advanced semiconductor processes. The process conditions of preparing potassium silicate solution, gelation, and cleaning were optimized, i.e., the relative ratio of fumed silica (10 wt%) to KOH (4 wt%) for potassium silicate solution, gelation time 3 h, and cleaning for 1 h with 5 wt% HCl solution. It was observed that the gelation time strongly affected the size distribution of the quartz powder; i.e., a longer gelation time led to a larger size (d50) of the synthesized quartz powder: 157 μm for 2 h and 331 μm for 5 h. In particular, it was found that the morphology of the as-synthesized quartz powder greatly depended on the pulverizing process; i.e., the shape of quartz powder was shown to be rod-shaped for the without-gel-pulverizing process and granular-shaped with the process. We expect that the fumed silica-based ultra-high-purity quartz powder with an impurity level of 74.1 ppb synthesized via the sol–gel process is applicable as a raw material for quartz wares and crucibles for advanced semiconductor processes beyond the design rule of 3 nm. Full article

(This article belongs to the Special Issue Synthesis and Application of Silicon Dioxide Nanoparticles)

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21 pages, 8672 KiB

Open AccessArticle

Hydrothermal Synthesis and Properties of Nanostructured Silica Containing Lanthanide Type Ln–SiO₂ (Ln = La, Ce, Pr, Nd, Eu, Gd, Dy, Yb, Lu)

by Joana M. F. Barros, Glauber J. T. Fernandes, Marcio D. S. Araujo, Dulce M. A. Melo, Amanda D. Gondim, Valter J. Fernandes, Jr. and Antonio S. Araujo

Nanomaterials 2023, 13(3), 382; https://doi.org/10.3390/nano13030382 - 18 Jan 2023

Cited by 4 | Viewed by 1521

Abstract

The nanostructured lanthanide-silica materials of the Ln–SiO₂ type (Ln = La, Ce, Pr, Nd, Eu, Gd, Dy, Yb, Lu) were synthesized by the hydrothermal method at 100 °C, using cetyltrimethylammonium as a structural template, silica gel and sodium silicate as a source [...] Read more.

The nanostructured lanthanide-silica materials of the Ln–SiO₂ type (Ln = La, Ce, Pr, Nd, Eu, Gd, Dy, Yb, Lu) were synthesized by the hydrothermal method at 100 °C, using cetyltrimethylammonium as a structural template, silica gel and sodium silicate as a source of silicon, and lanthanide oxides, with Si/Ln molar ratio = 50. The resulting materials were calcined at 500 °C using nitrogen and air, and characterized by X-ray diffraction (XRD), Fourier-Transform infrared absorption spectroscopy, scanning electron microscopy, thermogravimetry (TG), surface area by the BET method and acidity measurements by n-butylamine adsorption. The XRD and chemical analysis indicated that the SiO₂ presented a hexagonal structure and the incorporation of lanthanides in the structure changes the properties of the Ln–SiO₂ materials. The heavier the lanthanide element, the higher the Si/Ln ratio. The TG curves showed that the decomposition of the structural template occurs in the materials at temperatures below 500 °C. The samples showed variations in specific surface area, mean pore diameter and silica wall thickness, depending on the nature of the lanthanide. The incorporation of different lanthanides in the silica generated acid sites of varied strength. The hydrothermal stability of the Ln–SiO₂ materials evaluated at high temperatures, evidenced that the properties can be controlled for application in adsorption and catalysis processes. Full article

(This article belongs to the Special Issue Synthesis and Application of Silicon Dioxide Nanoparticles)

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22 pages, 6406 KiB

Open AccessArticle

Particles’ Organization in Direct Oil-in-Water and Reverse Water-in-Oil Pickering Emulsions

by Diego M. Ramos, Véronique Sadtler, Philippe Marchal, Cécile Lemaitre, Frédérick Niepceron, Lazhar Benyahia and Thibault Roques-Carmes

Nanomaterials 2023, 13(3), 371; https://doi.org/10.3390/nano13030371 - 17 Jan 2023

Cited by 5 | Viewed by 1781

Abstract

This paper addresses the impact of the particle initial wetting and the viscosity of the oil phase on the structure and rheological properties of direct (Oil/Water) and reverse (Water/Oil) Pickering emulsions. The emulsion structure was investigated via confocal microscopy and static light scattering. [...] Read more.

This paper addresses the impact of the particle initial wetting and the viscosity of the oil phase on the structure and rheological properties of direct (Oil/Water) and reverse (Water/Oil) Pickering emulsions. The emulsion structure was investigated via confocal microscopy and static light scattering. The flow and viscoelastic properties were probed by a stress-controlled rheometer. Partially hydrophobic silica particles have been employed at 1 and 4 wt.% to stabilize dodecane or paraffin-based emulsions at 20 vol.% of the dispersed phase. W/O emulsions were obtained when the particles were dispersed in the oily phase while O/W emulsions were prepared when the silica was introduced in the aqueous phase. We demonstrated that, although the particles adsorbed at the droplets interfaces for all the emulsions, their organization, the emulsion structure and their rheological properties depend in which phase they were previously dispersed in. We discuss these features as a function of the particle concentration and the oil viscosity. Full article

(This article belongs to the Special Issue Synthesis and Application of Silicon Dioxide Nanoparticles)

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19 pages, 4893 KiB

Open AccessArticle

Synthesis, Characterization and Photocatalytic Activity of CoFe₂O₄/Fe₂O₃ Dispersed in Mesoporous KIT-6

by Johnatan de Oliveira Soares, Wesley Eulálio Cabral Cavalcanti, Marco Antonio Morales Torres, Sibele Berenice Castella Pergher, Fernando José Volpi Eusébio De Oliveira and Tiago Pinheiro Braga

Nanomaterials 2022, 12(20), 3566; https://doi.org/10.3390/nano12203566 - 12 Oct 2022

Cited by 3 | Viewed by 1583

Abstract

The present work aimed to synthesize and characterize a solid based on CoFe₂O₄/Fe₂O₃-KIT-6 and evaluate its performance in the photocatalytic degradation of the remazol red ultra RGB dye. By analyzing XRD, N₂ physisorption, and [...] Read more.

The present work aimed to synthesize and characterize a solid based on CoFe₂O₄/Fe₂O₃-KIT-6 and evaluate its performance in the photocatalytic degradation of the remazol red ultra RGB dye. By analyzing XRD, N₂ physisorption, and Mössbauer results, it was possible to identify that the desired CoFe₂O₄/Fe₂O₃ phase was achieved, which maintained its structural properties. The FTIR-pyridine indicated the presence of Lewis acid sites, while TPD-CO₂ showed a large amount of weak basic sites. The band-gap energy indicated that the compound can be applied in photocatalytic degradation under UV/visible light, with the possibility of magnetic separation at the end of the reaction. The photocatalysis results indicated that there was complete degradation of the remazol red ultra RGB dye within 1 h of reaction. Despite the absence of H₂O₂, the combination of the proposed photocatalyst with the anatase phase (TiO₂) showed significant improvements in the degradation process. The proposed mechanism for complete dye degradation indicated that a sequence of radical reactions is necessary, generating oxidant species such as •OH and the final products were CO₂ and H₂O. Full article

(This article belongs to the Special Issue Synthesis and Application of Silicon Dioxide Nanoparticles)

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13 pages, 1581 KiB

Open AccessArticle

Synthesis and Characterization of Reproducible Linseed Oil-Loaded Silica Nanoparticles with Potential Use as Oxygen Scavengers in Active Packaging

by Juan Felipe Alvarado, Daniel Fernando Rozo, Luis Miguel Chaparro, Jorge Alberto Medina and Felipe Salcedo-Galán

Nanomaterials 2022, 12(18), 3257; https://doi.org/10.3390/nano12183257 - 19 Sep 2022

Cited by 4 | Viewed by 1940

Abstract

Commercially available oxygen scavengers used to prevent lipid autoxidation, microbial growth and enzymatic browning in food products present several issues, which include the usage of metals and their moisture dependence to work properly. We present the synthesis and characterization of a moisture-independent oil-based [...] Read more.

Commercially available oxygen scavengers used to prevent lipid autoxidation, microbial growth and enzymatic browning in food products present several issues, which include the usage of metals and their moisture dependence to work properly. We present the synthesis and characterization of a moisture-independent oil-based oxygen scavenging system comprised of linseed oil and silica nanoparticles. The system was synthesized via sol-gel chemistry and was characterized using morphological analysis (SEM, AFM, TEM, and N₂ adsorption/desorption), oil-loading analysis (TGA), and surface analysis (ζ-potential and ATR-FTIR). Performance of the system was evaluated through headspace measurements and reproducibility of synthetic procedure was verified using six replicates. Nanoparticles showed the desired spherical shape with a diameter of (122.7 ± 42.7 nm) and mesoporosity (pore diameter = 3.66 ± 0.08 nm), with an encapsulation efficiency of 33.9 ± 1.5% and a highly negative ζ-potential (−56.1 ± 1.2 mV) in basic solution. Performance of the system showed a promising high value for oxygen absorption of 25.8 ± 4.5 mL O₂/g of encapsulated oil (8.3 ± 1.5 mL O₂/g of nanocapsules) through a moisture independent mechanism, which suggests that the synthesized system can be used as an oxygen scavenger in dry atmosphere conditions. Full article

(This article belongs to the Special Issue Synthesis and Application of Silicon Dioxide Nanoparticles)

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16 pages, 5286 KiB

Open AccessArticle

Organic-Free Synthesis of Finned Mordenite Zeolite

by Rafael C. Lima, Christian W. Lopes, Jhonny Villarroel-Rocha, Lindiane Bieseki, Karim Sapag and Sibele B. C. Pergher

Nanomaterials 2022, 12(15), 2623; https://doi.org/10.3390/nano12152623 - 29 Jul 2022

Cited by 3 | Viewed by 1636

Abstract

Mordenite is a well-known zeolite widely used for industrial processes. However, its pore architecture can be inconvenient due to diffusional issues. A study of the synthesis parameters from an organic-free dense gel was carried out to control the crystal morphology, which resulted in [...] Read more.

Mordenite is a well-known zeolite widely used for industrial processes. However, its pore architecture can be inconvenient due to diffusional issues. A study of the synthesis parameters from an organic-free dense gel was carried out to control the crystal morphology, which resulted in finned mordenite zeolite particles. The obtained materials were characterized by XRD, FTIR, ²⁹Si and ²⁷Al MAS-NMR, elemental analysis, nitrogen physisorption, SEM, and TEM. We found that careful manipulation of the hydrothermal parameters directly affected the sizes and morphologies of the crystallites and particles, as well as the textural properties of the final products. Additionally, it was found that mordenite could exhibit a fin morphology with additional mesoporosity, which is a promising means to reduce the diffusional problems of one-dimensional-channel zeolites. Full article

(This article belongs to the Special Issue Synthesis and Application of Silicon Dioxide Nanoparticles)

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