Strategic harmonization of silica shell stabilization with Pt embedding on AuNPs for efficient artificial photosynthesis

2020 ◽  
Vol 8 (11) ◽  
pp. 5734-5743 ◽  
Author(s):  
Dinesh Kumar ◽  
Chan Hee Park ◽  
Cheol Sang Kim
Keyword(s):  
Amorphous Silica ◽  
Artificial Photosynthesis ◽  
Pt Nanoparticles ◽  
Silica Shell ◽  
Silica Layer ◽  
Plasmonic Nanostructure

The Pt nanoparticles embedding on AuNPs through amorphous silica layer stabilizing plasmonic nanostructure for efficient CO2 photoreduction.

Synthesis of Core@Shell Composites with Gold Nanoparticles Trapped inside Ceramic Silica Shells by the Sol-Gel Method

2008 ◽  
Vol 368-372 ◽  
pp. 797-799 ◽  
Author(s):  
Chien Jung Huang ◽  
Pin Hsiang Chiu ◽  
Yeong Her Wang
Keyword(s):  
Gold Nanoparticles ◽  
Surface Plasmon Resonance ◽  
Surface Plasmon ◽  
Amorphous Silica ◽  
Plasmon Resonance ◽  
Sol Gel ◽  
Silica Shell ◽  
Core Shell ◽  
Gold Core ◽  
Spherical Gold Nanoparticles

This paper describes a sol-gel (SG) method for the coating of gold nanoparticles with uniform shells of amorphous silica. The thickness of silica could be conveniently controlled in the range of 10 to 120 nm by increasing the amount of water. Although spherical gold nanoparticles generally have a surface plasmon resonance (SPR) at a wavelength of about 520 nm, a spherical gold core with a silica shell offers a very highly tunable SPR wavelength depending on the thickness of the silica shell.

scholarly journals Effect of Different Silica Coatings on the Toxicity of upconversion nanoparticles on RAW 264.7 macrophage cells

2020 ◽  
Author(s):  
Cynthia E Kembuan ◽  
Helena Oliveira ◽  
Christina Graf
Keyword(s):  
Inductively Coupled Plasma ◽  
Charged Particles ◽  
Silica Shell ◽  
Lanthanide Ions ◽  
Raw 264.7 Cells ◽  
Emission Spectrometry ◽  
Upconversion Nanoparticles ◽  
Raw 264.7 ◽  
Silica Layer ◽  
Functionalized Particles

Upconversion nanoparticles (UCNP) consisting of NaYF₄ doped with 18% Yb and 2% Er were coated with microporous silica shells of 7±2 nm and 21±3 nm thickness. Subsequently, the initially negatively charged particles were optionally functionalized with N-(6-aminohexyl)-aminopropyltrimethoxysilane (AHAPS), providing a positive charge onto the nanoparticle surface. Inductively coupled plasma optical emission spectrometry (ICP-OES) measurements revealed that the particles with the thicker shells release fewer lanthanide ions in 24 h than particles with a thinner shell but that even a 21±3 nm thick silica layer does not entirely block the disintegration process of the UCNP. MTT tests and cell cytometry measurements with macrophages (RAW 264.7 cells) indicate that the cells treated with amino-functionalized particles with a thicker silica shell have higher viability than those incubated with UCNP with a thinner silica shell even if more particles with a thicker shell are taken up. This effect is less significant for negatively charged particles. A cell cycle analysis with amino-functionalized particles also confirms that a thicker silica shell reduces the cytotoxicity. Thus, growing silica shells of sufficient thickness is a simple approach to minimize the cytotoxicity of UCNP.

Oxidation of SiC powder by high-temperature, high-pressure H2O

1986 ◽  
Vol 1 (1) ◽  
pp. 100-103 ◽  
Author(s):  
Masahiro Yoshimura ◽  
Jun-ichiro Kase ◽  
Shigeyuki Sōmiya
Keyword(s):  
Amorphous Silica ◽  
Reaction Rate ◽  
Type Model ◽  
Silica Layer ◽  
Complete Oxidation ◽  
Silica Layers ◽  
Oxidative Atmosphere ◽  
Temperature And Pressure ◽  
Apparent Activation Energies ◽  
High Temperature High Pressure

The reaction between SiC powder and H2O has been studied at 400°–800 °C under 10 and 100 MPa. Silicon carbide reacted with H2O to yield amorphous SiO2 and CH4 by the reaction SiC + 2H2O→SiO2 + CH4 above 500 °C. Cristobalite and tridymite crystallized from amorphous silica after the almost complete oxidation of SiC above 700 °C. The oxidation rate, as calculated from the weight gain, increased with temperature and pressure. The Arrhenius plotting of the reaction rate based on a Jander-type model gave apparent activation energies of 167–194 kJ/mol. Contrasted with oxidation in oxidative atmosphere, oxidation in H2O is characterized by the diffusion of H2O and CH4 in an amorphous silica layer where the diffusion seemed to be rate determining. Present results suggest that the oxidation of SiC includes the diffusion process of H2O in silica layers when atmospheres contain water vapor.

Diatoms Biosilica as Efficient Drug-Delivery System

MRS Advances ◽  
2015 ◽  
Vol 1 (57) ◽  
pp. 3825-3830 ◽  
Author(s):  
Danilo Vona ◽  
Gabriella Leone ◽  
Roberta Ragni ◽  
Fabio Palumbo ◽  
Antonio Evidente ◽  
...  
Keyword(s):  
Drug Delivery ◽  
Drug Delivery System ◽  
Delivery System ◽  
Amorphous Silica ◽  
Model System ◽  
Silica Shell ◽  
Diatom Species ◽  
Size And Morphology ◽  
Fossil Diatoms

ABSTRACTDiatoms are the most abundant resource of biosilica on Earth. These microalgae are encased in a 3-D amorphous silica “shell” called frustule whose size and morphology is strictly dependent on the diatom species. Naturally nanostructured biosilica from diatoms exhibit unique adsorption and confinement properties useful for delivery of molecules of pharmacological interest.In this work fossil biosilica was used as a carrier for Ophiobolin A (a fungal macrolide with anticancer and antiparasitic properties), with the aim to develop a model system of Ophiobolin A loading / delivery. Ophiobolin A delivery properties of fossil diatoms were investigated by spectophotometric analyses.

scholarly journals Quartz dissolution associated with magnesium silicate hydrate cement precipitation

2020 ◽  
Author(s):  
Lisa de Ruiter ◽  
Anette Eleonora Gunnæs ◽  
Dag Kristian Dysthe ◽  
Håkon Austrheim
Keyword(s):  
Amorphous Silica ◽  
Magnesium Silicate ◽  
Rate Equations ◽  
Silica Layer ◽  
Bulk Fluid ◽  
Complete Replacement ◽  
High Ph ◽  
Quartz Dissolution ◽  
Hydrate Cement ◽  
Quartz Grains

Abstract. Quartz has been replaced by magnesium silicate hydrate cement at the Feragen ultramafic body in south-east Norway. This occurs in deformed and recrystallized quartz grains deposited as glacial till covering part of the ultramafic body. Where the ultramafic body is exposed, weathering leads to high pH (~10), Mg-rich fluids. The dissolution rate of the quartz is about 3 orders of magnitude higher than experimentally derived rate equations suggest under the prevailing conditions. Quartz dissolution and cement precipitation starts at intergranular grain boundaries that act as fluid pathways through the recrystallized quartz. Etch pits are also extensively present at the quartz surfaces as result of preferential dissolution at dislocation sites. Transmission electron microscopy revealed an amorphous silica layer with a thickness of 100–200 nm around weathered quartz grains. We suggest that the amorphous silica is a product of interface-coupled dissolution-precipitation and that the amorphous silica subsequently reacts with the Mg-rich, high pH bulk fluid to precipitate magnesium silicate hydrate cement, allowing for further quartz dissolution and locally a complete replacement of quartz by cement. The cement is the natural equivalent of magnesium silicate hydrate cement (M-S-H), which is currently of interest for nuclear waste encapsulation or for environmentally friendly building cement, but not yet developed for commercial use. This study provides new insights that could potentially contribute in the further development of M-S-H cement.

scholarly journals Effect of different silica coatings on the toxicity of upconversion nanoparticles on RAW 264.7 macrophage cells

2021 ◽  
Vol 12 ◽  
pp. 35-48
Author(s):  
Cynthia Kembuan ◽  
Helena Oliveira ◽  
Christina Graf
Keyword(s):  
Inductively Coupled Plasma ◽  
Charged Particles ◽  
Silica Shell ◽  
Lanthanide Ions ◽  
Raw 264.7 Cells ◽  
Emission Spectrometry ◽  
Upconversion Nanoparticles ◽  
Raw 264.7 ◽  
Silica Layer ◽  
Functionalized Particles

Upconversion nanoparticles (UCNPs), consisting of NaYF4 doped with 18% Yb and 2% Er, were coated with microporous silica shells with thickness values of 7 ± 2 and 21 ± 3 nm. Subsequently, the negatively charged particles were functionalized with N-(6-aminohexyl)-3-aminopropyltrimethoxysilane (AHAPS), which provide a positive charge to the nanoparticle surface. Inductively coupled plasma optical emission spectrometry (ICP-OES) measurements revealed that, over the course of 24h, particles with thicker shells release fewer lanthanide ions than particles with thinner shells. However, even a 21 ± 3 nm thick silica layer does not entirely block the disintegration process of the UCNPs. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays and cell cytometry measurements performed on macrophages (RAW 264.7 cells) indicate that cells treated with amino-functionalized particles with a thicker silica shell have a higher viability than those incubated with UCNPs with a thinner silica shell, even if more particles with a thicker shell are taken up. This effect is less significant for negatively charged particles. Cell cycle analyses with amino-functionalized particles also confirm that thicker silica shells reduce cytotoxicity. Thus, growing silica shells to a sufficient thickness is a simple approach to minimize the cytotoxicity of UCNPs.

scholarly journals Synthesis of “Silica – Carbon Nanotubes” Composite and Investigation of its Properties

2015 ◽  
Vol 17 (2) ◽  
pp. 95
Author(s):  
V.V. Chesnokov ◽  
A.S. Chichkan ◽  
V.S. Luchihina ◽  
E.A. Paukshtis ◽  
V.N. Parmon ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Thermal Stability ◽  
Calcination Temperature ◽  
Amorphous Silica ◽  
Oxidation Rate ◽  
Silica Film ◽  
Silica Layer ◽  
Active Hydrogen ◽  
Order Of Magnitude ◽  
Thermal Stability Of

A new method for synthesis of CNT-SiO2 composite was developed. Oligomethylhydridesiloxane (OMHS) was used as the SiO2 precursor. The presence<br />of active hydrogen in the composition of OMHS made it possible to obtain chemical<br />interaction between the surface of carbon nanotubes and the deposited silica layer. The effect of the silica film on the CNT oxidizing ability was studied. It was found that the oxidation rate of the CNT-SiO2 composite decreases approximately by an order of magnitude in comparison with as-prepared CNT. The morphology and<br />structure of amorphous silica obtained after oxidation of the CNT-SiO2 composite<br />were studied. The thermal stability of the CNT-SiO2 composite was also studied. The CNT-SiO2 composite was found to be thermally stable up to temperatures of 1100-1200 ºC. An increase in the calcination temperature to 1300 ºC leads to segregation of the CNT-SiO2 composite into individual components: CNT and SiO2 particles.

Zirconia-mullite ceramics made from composite particles coated with amorphous phase: Part II. Effects of boria additions to the amorphous phase

1995 ◽  
Vol 10 (10) ◽  
pp. 2592-2598 ◽  
Author(s):  
Jiin-Jyh Shyu ◽  
Yuan-Chieh Chen
Keyword(s):  
Amorphous Phase ◽  
Amorphous Silica ◽  
Coating Layer ◽  
Silica Layer ◽  
Amorphous Coating ◽  
Composition Change ◽  
Kinetics Of ◽  
Zircon Phase ◽  
Mullite Ceramics ◽  
Viscous Sintering

Mullite and zirconia-mullite ceramics have been prepared by coating alumina/zirconia particles with an amorphous silica layer. The effect of composition change of the amorphous silica layer by adding B2O3 was investigated. For the zirconia-free compositions, the addition of B2O3 remarkably accelerates the kinetics of the crystallization of the amorphous coating layer, the viscous sintering, and the mullitization. For the zirconia-containing ceramics, the addition of B2O3 enhanced the viscous sintering kinetics and delayed the decomposition of the transient zircon phase and the subsequent t- to m ZrO2 transition, thus resulting in a higher ratio of t- to m-ZrO2. The B2O3-containing zirconia-mullite composites exhibit the same level of fracture toughness (Kic) as the B2O3-free zirconia-mullite composites.

Influence of amorphous silica layer formation on the dissolution rate of olivine at 90°C and elevated pCO2

2011 ◽  
Vol 284 (1-2) ◽  
pp. 193-209 ◽  
Author(s):  
Damien Daval ◽  
Olivier Sissmann ◽  
Nicolas Menguy ◽  
Giuseppe D. Saldi ◽  
François Guyot ◽  
...  
Keyword(s):  
Dissolution Rate ◽  
Amorphous Silica ◽  
Elevated Pco2 ◽  
Silica Layer ◽  
Layer Formation
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