Mar. 17, 2025
Agriculture
Are your silica nanosphere amorphous or crystalline?
Amorphous. Colloidal silica particles are non-crystalline, meaning that the atoms do not have long-range order, resembling the structure of bulk glass.
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How can I concentrate a sample of small silica nanoparticles?
Unfortunately, small silica (' 50 nm) can be difficult to collect via centrifugation. This process typically requires very high spin speeds for small particles, and often results in irreversible particle aggregation.
For larger silica particles, we are able to remove solvent through evaporation with mild heating, but for small particles, applying heat can induce particle growth or aggregation. You may try removing solvent by rotary evaporation, but it is essential to keep an eye on the particles and look for any signs of instability throughout the process. Under no circumstances should the particles be dried completely, as it is highly unlikely that they be colloidally stable thereafter without some degree of irreversible aggregation.
How can I calculate the concentration of my silica nanoparticles after solvent transfer or particle concentration?
Begin by measuring the mass concentration gravimetrically, by drying down a known volume of the dispersion into a tared container and recording the mass per unit volume after drying. Then use the following equation: nnp = ρnp / mnp where nnp is the particle number concentration, ρnp is the material density, and mnp is the average nanoparticle mass to calculate the particle concentration. We use 2.2 g/cm3 for the density of silica (ρnp). For more information on using this equation, please click here.
How should I store my silica nanoparticles?
Due to considerations around the solubility of silica, we recommend that non-functionalized silica stored in water should be kept at a concentration about ~10 mg/mL, at a neutral pH (7-8), and at room temperature for long term storage. The solubility of silica in aqueous solution is relatively low and the particles are typically stable in water for days. When you are ready to use the silica in water-based experiments, simply centrifuge the particles into water before use.
For aminated silica nanoparticles, we recommend long term storage in alcohol such as ethanol or isopropanol. Since the silica has low solubility and high stability in alcohols, this helps preserve the amine groups on the surface. If the aminated silica is not being used for subsequent surface chemistry via the amine, the storage conditions are not as critical and the particles can be stored in a low pH aqueous solution. Generally, we recommend a buffer such as acetate (pH=5). At this pH, the aminated silica is far enough away from the isoelectronic point that the positively charged particles remain stable.
For more information about particle stability, visit our page about Zeta Potential Measurements.
Do you offer fluorescently labelled silica?
We have considerable experience fabricating fluorescently labelled silica nanoparticles. Though we do not offer them as a standard product, we are happy to make them on a custom basis to suit your individual requirements. For more information about this, please visit our Custom Synthesis page.
Want more information on silica dispersant? Feel free to contact us.
Related links:What are silica nanoparticles used for?
Due to the versatility of silica in terms of porosity, surface chemistry, and nanoparticle size, silica has a wide range of applications, ranging from drug delivery and catalysis to its use as an ingredient in paint and cement. Visit our page about Silica Nanoparticle Applications to learn more.
How can I exchange the solvent of amine-terminated silica?
Silica particles > 50 nm can typically be centrifuged down for redispersion in the compatible solvent of your choice. For sizes ' 50 nm, we recommend performing dialysis overnight (or for several hours) to diffuse out the original solvent and enable suspension in the compatible solvent of your choosing.
This is a high-purity, natural crystalline silica that comes from quartz quarries in Oklahoma. It is a fine ground silica sand that is inherently inert, white, bright, and at least 99.2% silicon dioxide. Special processing assures a controlled particle size distribution, eliminating excessively coarse and fine particles. These properties, combined with its inertness and low cost, make silica an excellent filler and extender for paint.
The hardness and inertness of silica improve resistance to wear, burnish, abrasion and stains. The narrow size distribution and bright white color minimize binder demand and yield an excellent color. It is also often used to replace as much as 50% of titanium dioxide in paint formulations.
Silica (SiO2) is a compound formed from silicon and oxygen. Because oxygen is an abundant element and silicon is the second most abundant element in the Earth's crust, the formation of silica is quite common in nature. Silica sand, the substance used to derive pure silicon, is made of quartz, which is the most common form of silica found in nature. Crystalline silica exists in seven different forms. The three major forms, quartz, cristobalite, and tridymite, are stable at different temperatures. Within the three major forms are subdivisions. Crystalline silica is ubiquitous, being in rocks from every geologic era and from every location around the world.
Add silica to paint and mediums to create textural and bodying qualities in oil paint without affecting the color. Silica has a little color in drying oil, so it can be added to oil paint without affecting the tint of the color. Due to its hardness, it tends to add a discernible texture to paint. Add to chalk or gesso to add texture or 'tooth' in chalk or gesso grounds.
Properties Description Fine dry-ground silica with a closely-controlled particle size distribution. Source Mill Creek, Oklahoma Chemical Analysis Silicon Dioxide (SiO2) 99.4% Typical Physical Properties Median Particle Size 1.6 microns Particles Finer than 5 Microns 96.3% Hegman 8 Retained on 325 Mesh Screen 0.003% Hardness (Mohs) 7 Yellowness Index (ASTM E313)* 1.6 Reflectance 94.5% pH 6.7 Oil Absorption 42 g oil / 100 g pigment Specific Gravity 2.65 Bulk Density, Compacted 41.0 lbs./ft3 (656 kg/m3) Bulk Density, Loose 36 lbs./ft3 (576 kg/m3)* The Yellowness Index is a number calculated from spectrophotometric data that describes the change in color of a test sample from clear or white to yellow. This test is most commonly used to evaluate color changes in a material caused by outdoor exposure.
WARNING: This product contains crystalline silica, which can cause silicosis (an occupational lung disease) and lung cancer. For detailed information on the potential health effects of crystalline silica, see the Material Safety Data Sheet.
For more hydrophilic pyrogenic silicainformation, please contact us. We will provide professional answers.
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