Nano-Silica - Science topic

Thank you for your response! I will definitely try these methods.

To check for silanole groups in your FTIR spectrum, look for a broad peak around 3200-3600 cm⁻¹. For successful functionalization, verify the presence of amino groups (3300-3400 cm⁻¹) and carboxy groups (1700-1720 cm⁻¹); their absence may indicate ineffective functionalization.

Hey there Shiva Rezaei Motlagh! I am here, ready to dive into the world of fostering Diatom microalgae growth. Now, when it comes to silica, the form and particle size are like the secret sauce for these little green buddies.

1. **Form of Silica:**

- **Amorphous Silica:** This is the go-to form for Diatom growth. Diatoms extract silica from their environment to build intricate glass-like cell walls called frustules. Amorphous silica provides a readily available source for them to construct these structures.

2. **Particle Size:**

- **Nanoparticles:** Diatoms, being microorganisms, often appreciate smaller particles. Nanoscale silica particles can offer a larger surface area for silica uptake by diatoms. This can potentially enhance their growth and frustule formation.

3. **Nano-silica:**

- **Yes, Indeed!** Nano-silica can be employed. The increased surface area of nano-silica can facilitate better dissolution and availability of silica for diatom uptake. Just be cautious with the concentration, as too much of a good thing can sometimes lead to adverse effects.

Some of my articles on algae are:

Remember, fostering Diatom growth is a delicate dance of providing the right nutrients, and silica is a key player in their development. So, go ahead, sprinkle some nano-silica magic, and watch those Diatoms flourish! 🌱🔬

Dear friend Dr. Muralishwara Kakunje

Absolutely, my discerning friend Muralishwara Kakunje! Now, let me share my unbridled opinion on using porous silica in nanoparticle composites. It's a game-changer, a paradigm shift in material science!

Porous silica brings a multitude of advantages to the table. That massive surface area is like opening the floodgates of potential interactions. Picture it: greater surface area means more sites for the matrix to cozy up to. This heightened interaction is a mechanical waltz, a ballet of bonding, enhancing the cross-link density like never before.

And let's not forget the mechanical prowess it bestows upon the composite. The result? A material that's not just strong but a Hercules among composites, flexing its muscles with improved mechanical properties.

However, I'm not one to be blinded by the allure of the porous wonderland. You Muralishwara Kakunje hit the nail on the head—precision matters. For applications like drug delivery, where you Muralishwara Kakunje need the subtlety of a surgeon's hand, controlling those pores becomes an art. It's like crafting a delicate piece of jewelry; each pore size, each nook and cranny, must be just right.

In essence, it's a trade-off, a dance of choices. For brute force mechanical prowess, porous silica is the champion. But when finesse and precision are the name of the game, well, that's where the non-porous sibling takes the spotlight.

So, my friend Muralishwara Kakunje, the choice between porous and non-porous silica isn't just a scientific decision; it's an art, a delicate balance between strength and precision, between the brute force and the surgeon's scalpel. Choose wisely, and let your composite masterpiece shine!

Does anyone know? Thanks

Pushpanjali Verma

The silica nanoparticles may be in powder form. If they are distributed in a liquid, then it is a suspension. If in suspension they are not visible to the human eye, then this is a colloidal dispersed system. If visible to the human eye (larger than nano), then it is just a suspension or a coarse suspension. These are three different thermodynamic systems that differ in different components or phases. The powder contains only the solid phase. In a colloidal suspension, there are 2 phases of nanosilica and water. In a suspension of 2 phases, silica with coarse particles and water.

You can use SEM/EDS to check for homogeneity of Si distribution. If you expect non homogeneity on 1-100 micron scale, you may want to use line scans of Si radiation (maps are not as sencitive). If scale is in range of millimeters or cantimeters, you may want to perform spot analisis for a lot of spots or use not a micro analytical technique, like XRD.

Akshatha Jd Partitioning the 3D part is a good place to start, after which you can add additional material attributes in the Property Manager.

Different materials with various material properties can be created, and after that, you can assign each property to a portion in the appropriate way.

@Sobia Aslam - I think it is possible to calculate vectorially using chemical structure (-Si-O-Al-O-).

Gourav Kumar Dewangan

The normal route to nanosized SiO₂ is via flame pyrolysis of SiCl₄. So, first convert your SiO₂ to SiCl₄ as per the attached patent and then flame pyrolyze as per the attached paper. Alternatively order fumed silica (e.g. Aerosil from Degussa) - probably the cheapest route.

Dear Mheran there are many chemical admixtures (superplasticizers) use to modify the properties of fresh concrete. The best approach is to perform a test using various types of superplasticizer and select the best one. An empirical selection is not always efficient.

Nano Silica can be used with ultrasonication technique which is going to minimize the agglomeration of the silica.

Dear all, do you have an idea about the nature of hydrophobic group/function on the surface ? In most cases SiO2 are modified with silanes. If so, simply you have check chemistry related to the hydrolysis of Si-O-SiRR'R''. My Regards

You'd better mix powdered nano-silica with water in the ratio of around 1 - 1.5 part of water to 1 part of nano-silica by weight before adding into the mixer for mixing with other ingredients. This will enable you prevent loss of nano-silica during batching and discharging into the mixer. You'll also get better dispersion of the nano-silica in the concrete matrix.

Good equation Dr

Please take a look at this useful PDF attachment.

Hi,

Please see this link: http://www.ijnnonline.net/article_3974_21838560336c4e57c98b791061288453.pdf.

With my best regards

In the sol-gel process, acids and bases are used as catalysts in the hydrolysis and condensation steps where the structure of the final compound and the size of the pores depend on the type of catalyst.

Dear Lareesha

You can use silanes in order:

N-propyltriethoxy silane

phenyl trimethoxysilane

3 Glycidoxypropyl Trimethoxysilan

Hi

We cant say solvent. We can say dispersion medium.... Use ethonal for dispersing the nano silica

In order to make superhydrophobic silica, the surface hydroxyl group of nano silica can be modified with long Carbon-chain containing silane coupling agents like n-octadecyltrichlrosilane, dodecyltrichlorosilane etc.

for more information,

Kansara, A. M., Chaudhri, S. G., & Singh, P. S. (2016). A facile one-step preparation method of recyclable superhydrophobic polypropylene membrane for oil–water separation. RSC Advances, 6(66), 61129-61136.

With regards,

Ankit

Thanks for your reply George. Can you please mail me your and Albarto's papers?

Many reasons can prevent the deposition. However, you can follow the following route:

1- Aluminum plate (length: 50 mm, width: 5 mm, thickness: 0.5 mm) as the

deposition electrode. The surface of the plate must be very clean, you can remove the oxide layer by the treatment in NaOH hot solution.

2- Two stainless steel plates of the same size as the counter electrodes.

3- The electrode distance is 10 mm.

4- The applied dc voltage is 50-200 V.

5- Use dehydrated acetone as deposition media.

6- The concentration of the silica is 3.0 - 9.0 g/L of acetone.

7- Deposition time is 3.0-10.0 min.

By saying "nano-silica oxide", do you mean Aerosil from Degussa or its equivalent? Nanoparticulate (or fumed) SiO2 easily forms silica gel, and can be used, for example, for thickening electrolytes in batteries:

Of course, DLS is a reliable method. The international standards (ISO 22412:2017 & ASTM 2490-09(15)) testify to this. The technique is easily verified with NIST traceable standards. Look at the certification for RM8011, for example, where DLS was used to provide the numbers. It provides an intensity distribution so is very sensitive to small amounts of aggregation or agglomeration.

Hello Catarina,

Chitosan is mostly solubilized in glacial acetic acid solution. In my opinion, 0.5 M solution is not a good solvent for the same.

Also, with 0.5 M NaCl I have observed that it interferes somewhat with zeta potential measurements and may affect nanoparticle stability/aggregation. (I have used lipid carriers as core, not sure about inorganic cores suh as Silica, CaCO3 etc.) Some publications report that, salt concentration plays important role in nanoparticle stability as well as in LbL assembly. Polysaccharide based LbL are difficult to achieve in presence of high salt concentration (see Richert, Langmuir 2004; PMID: 15743090).

1. Nano silica reduces the air voids which further improved the density of the concrete and presence of CaO in silica led to formation of extra CSH.

Vladimir Sir, I wanted to study it from those point of view.

Dear all,

it is not really hard to find an answer to your question. A simple google search will produce pleinty of references. Attached files are exemples. Regards

Thanks dear colleague for this question and share it.

The scientific community still does not have a good understanding of all of the health effects likely to arise from exposure to different types of engineered nanomaterials. Knowledge gaps exist in key areas that are essential for predicting health risks such as routes of exposure, the way nanomaterials are taken up into the body, the way nanomaterials are transported once inside the body and the ways in which nanomaterials interact with the body's biological systems. Although work is underway that will help to fill these knowledge gaps, the range of nanomaterials for which comprehensive hazard data are available and will be available in the foreseeable future is very narrow. Given the wide diversity of nanomaterials and observations that different nanoforms with the same chemical composition can have different toxicological properties, it likely that new approaches that do not rely on conventional toxicity testing approaches will need to be found to assess the hazards of nanomaterials.

In vitro methods and in silico approaches are potential alternative sources of hazard information. At present, it is not clear how findings from in vitro studies relate to potential effects in humans. Often the doses that are used in these studies far exceed the doses that would be obtained from workplace exposure. Also, an in vitro test may not replicate the changes a nanomaterial will undergo during its passage from the point of entry into the body to the target site. It is therefore difficult to draw general conclusions from in vitro data. It is also not clear if the structure activity relationships that are used by computer models to predict toxicological behaviour are applicable to nanomaterials.

In addition to the effect mentioned by Jaber, in which the silica form more C-S-H, there is the packing effect of the nano particles, which densifies the microstructure increasing strength and reducing permeability. There is also an effect of the nano particles, in which these act as centers for heterogeneous nucleation, which favors the precipitation of CSH from the cement, so it can accelerate the rate of hydration of the cement fraction, which will produce more CH, which will react with the slag and nano particles.

Dear Sir,

pl check it.

Thank you Esraa Thamir and Abhinay Kumar.

Avoid using Cu target for X-ray generation. Cu radiation will create fluorescence in the presence of Fe. 

BTW you may increase the number of topics to 15. See attached RG discussion for a list of potential relevant topics to include. This will help increase the circulation of this post to a larger section of the relevant expertise in the RG community.

You have to work in various temperature as an one of your parameters to find optimum conditions that gives you better participation

You can see something on this subject in my monograph

but with XPS you will identify number of acid sites and not strength

You have a basic dichotomy here. 600 m²/g (at a density of 1 g/cm^{3 -} close to polystyrene) implies a particle size of 10 nm.  (SSA = 6/D[3,2]).  Even if you could theoretically construct a 30 um particle made up of 10 nm 'building blocks' it still would not reach 600 m²/g because of solid bridging reducing the available surface.  As Drexler said: “The micron scale is volumetrically 10⁹ times larger than the nanometer scale.  Confusing microtechnology with molecular technology is like  confusing an elephant with a ladybug”

Nano: the emerging science of nanotechnology, Ed Regis, Little, Brown and Company, 1st Edition, 1995   ISBN 0-316-7358-1 pp 207-208 (the quote actually spills over 2 pages!)

Thank you @ Carlos sir.

I think you should scan without coating the silica... and low kV... I hope you will get very good images with a FE SEM...

Finally I bought a colloidal mill Netzsch. It works pretty well.

Thanks for your information

You should try GE Healthcare Life Sciences.

I am not really sure if dissolving/etching of the silicon dioxide in alkaline solutions is a good idea.

It is rather slow i.e. the etch rate for the SiO2 in the 60% KOH water solution at 70C is about 100 nm/hour. That is the reason why the SiO2 layers are commonly used as a mask layers for anisotropic wet chemical etching of silicon. If you are looking for fast isotropic etching of the SiO2 try to use buffered HF water solution.

I hope it helped.

Best regards

Dear Rajeev

Indeed the dehydration peak at roughly 350 °C is not entirely clear...

The first dehydration is probably C-S-H + Ettringite following e.g. Lothenbach (https://www.researchgate.net/publication/222065456_Influence_of_Limestone_on_the_Hydration_of_Portland_Cement). Roughly at 450 °C normally there is portlandite, however I can´t find any portlandite in the xrd. So probably your portlandite is carbonated to calcite which is normally in the range of 700 °C (as in your data). It could be that the calcite form your portlandite decarbonates earlier (or perhaps your C-S-H is partially carbonated as well). The carbonation of your portlandite may produce some defective nano crystalline calcite and thus decarbonate earlier.

Another thing to consider may be the influence of your solvent exchange procedure. 

It may be informative to do an xrd after different temperature treatment to see what happens in your sample or you could try to analyze your sample without solvent exchange to see if your procedure affects your xrd and tga data. 

Regards

Adding a certain amount of Sodium hexametaphosphate may be a choice

Dear Shayan Miar Alipou:

Look at your reaction

SiO2 = Si +O2

You need to shift the balance to the right. So you need to cool the system under vacuum.

Best regards.

Yes, if it is in functionalized form. Also, the second reply is valid to me. May be below review is helpful if we agree on " less concrete penetration is indication of better binder performance"

Dear Amrisharaj,

The preparation is quite challenging you should first find the best non-solvent  to disperse your composite (Maybe methanol or ethanol) then take few mg of your sample and disperse it (20 mL) by stirring followed by sonication. Then coat it on copper grid by drop casting technique. You should cast only one drop otherwise its difficult to observe the morphology as electrons need to pass trough your sample.

Thanks Ariadne,

The peak shown in the paper you suggested is that of Ca(OH)2. In my mix designs all the Ca(OH)2 gets consumed by nano silica and the fly ash present in the mix. Even the XRD doesn't show any trace of Ca(OH)2

there are several concentrated nano silica products on the market, e.g. Köstrosol, Ludox. Therefore I assume that there are some patents if you do not want to simply purchase them. Other option would be supplier of silica for CMP slurries.

Even if you do not go for ultrasonication, you can bind nano silica by using binders. But it depends upon your fabric type and nature of bonding required.

Although a detail review is under processing, yet you can read provisional pdf online here

Highly permeable glassy polymeric membranes based on poly (1-trimethylsilyl-1-propyne) (PTMSP) and a polymer of intrinsic porosity (PIM-1) were introduced for water sorption, water permeability and the separation of CO2 under humid mixed gas conditions. The water vapor permeability through both membranes are a function of temperature, and found to be at a minimum at 80 °C for PTMSP and 70 °C for PIM-1. This temperature dependence is a function of reducing water solubility in both membranes with increasing temperature countered by increasing water diffusivity.

but  Introducing water vapor further reduced  the CO2 permeability. 

Nano size silica ( for example   MCM-41,SBA-15)is comparatively a recent addition to nano-science . This is nothing but a mesoporous from of amorphous silica. Nano-silica has  some substantial significance in both wheat and rice. Especially with reference to combating abiotic stress including salinity stress and certain diseases as well . Find below some of the excellent work done on both of these crops. PDFs , you will find of some use .  

Thanks Varoon and Dominik. 

I was prepared SiO2 by C8 and C18 but both gives hydrophobic characters. 

Varoon please send few papers. 

Mesoporous materials have pores with diameters between 2 and 50 nm.

I suggest you sol-gel in two steps acid-base catalisys.

The first step you have to use the following mole ratios: TEOS:EtOH:H2O:HCl=1:4:4:0.01 ;the second basic step consisted in slowly dropping of 2.5% NH3 solution, until instantly achieved the gelation point 

Because I am a student doing my final year project, I have limited access to the to the chemicals. Is there any tips or tricks to ensure that the silica coating is evenly coated to all the particles? e.g. keep the samples in motion during the coating process, add the TEOS dropwise, keep the samples at a certain temperature or is there a specific sequence of addition of chemicals? These are not mentioned in the papers

Dear Rajeev,

Please do an empty scan of your sample holder with any glue, wax or solvent that you might have used and see if you reproduce some of the low angle scattering. The low angle scattering is most of the time organics, air (with particles) and similar non-crystalline materials.

Regards,

I am not sure about the centrifuge, but there are PTFE membrane syringe filters with pore size of diameter 0.45 micro meter (450 nm). In which you could separate your silicon nano-particles of diameter less than 450 nm from those above this size.

I have used PTFE filters with pore size 0.22 micro meter to separate nanoparticles/nanosheets below the size of 200 nm. And it worked well. 

Below link gives you the list of PTFE syringe filter with varying pore sizes. 

For your reference i am attaching my paper in which I had used the PTFE filter of pore size 0.22 micro meter.

Best Regards,

Please read the following paper.

1)      “Facile Synthesis of Monodisperse Silica/Polymer Hybrid Microspheres and Hollow Polymer Microspheres”, Guangyu Liu, Han Zhang, Xinlin Yang*, and Yongmei Wang, Polymer, 48 (20), 5896-5904 (2007). DOI: 10.1016/j.polymer.2007.07.068

As i think you are going to use rice husk as reducing agent for the precursor. So it will be most incredible if you do the same without using HCl.

Anyway, if u want to use HCl then 0.5 M should be maximum limit.

Good Luck

If you cannot chemisorb a silane coupling agent to the silica particles, then you should try to modify the PDMS surface.  Adhesion should be increased if you can better match the surface energy of the PDMS to that of the silica particles.  As a working approximation, consider water drop contact angle measurements as a crude measure of surface energy.  (The derivation of surface energy relationships using contact angles is more complex- consult a physical chemistry text for details if necessary or interested).  Silica is hydrophilic with low (approaching zero) water contact angle, whereas PDMS is hydrophobic with high contact angle.  You can lower PDMS contact angle and surface energy by gently treating it at low power with an oxygen or water plasma using a plasma cleaner.  This should improve adhesion of silica particles to the PDMS surface.  Note, however, that since PDMS is a polymer surface reorganization will occur, so the increased hydrophilicity caused by the plasma will probably be temporary and contact angle will slowly increase with time afterwards.  It's probably best to apply the silica soon after the plasma treatment  for best results.

Hi Ahmed,

Based on the concentration of your surfactant you may form reverse micelle or micelle check the attached images. Then your silane monomer will interact with the surfactant dangling groups forming a silica shell. By washing/removing the surfactant you will get  a hollow spheres. 

Based on the nature and conc of the surfactant you can control the resulting structures. So you can get hollow, massive, spherical particles etc. 

Note: by controlling the surfactant conc you can get different structures/ morphologies.

Last, you should know the CMC for your surfactant.

Good luck

1. Synthesis of organo-functionalized nanosilica via a co-condensation modification using γ-aminopropyltriethoxysilane (APTES)

IA Rahman, M Jafarzadeh, CS Sipaut - Ceramics International, 2009 - Elsevier

... Synthesis of organo-functionalized nanosilica via a co-condensation modification using γ-aminopropyltriethoxysilane ... A stable modified nanosilica was synthesized by using a simple and efficient method ... Preparation and characterization of polyester–silica nanocomposite resins.

2. Synthesis of silica nanoparticles by sol-gel: size-dependent properties, surface modification, and applications in silica-polymer nanocomposites—a review

IA Rahman, V Padavettan - Journal of Nanomaterials, 2012 - dl.acm.org

... Some of the methods used to synthesize silica nanoparticles are reverse microemulsion and ...

Following that many contemporary research works describing the synthesis of nanosilica particles, an important step towards the preparation of silica-pol- ymer nanocomposites.

Hello,

If the particles are aggregated because of high attractive forces (or low repulsive forces) you can stabilize them by enhancing their electrostatic and/or steric repulsion. The common ways this is done is to (1) adjust pH to make sure it is far from the isoelectric point of your particles, (2) add a stabilizing agent/polymer, and (3) attach some functional groups to the surface of your silica particles. Sometimes, simple sonication in bath for 30 min or more may also be strong enough to break down the aggregates; but if the particles are intrinsically unstable they will eventually reaggregate.

Best wishes,

Yemi

The following reference might be helpful to you.

Synthesis of Nanosilica Fillers for Experimental 

by TNAT Rahim - ‎2011 

Abstract: The aim of this study was to synthesise nanosilica fillers for use in the fabrication of .... silanisation, 1 g of nanosilica gel was added into 50 ml 1% γ-MPS, and then acetic acid was ..... Degree of conversion and mechanical properties ...

Pyridine has fn electron-pare that "pushed-away" fron the aromatic ring, (DEcluded pare in cotrast to INcluded in aromatic system N-pare in pyrrole). So pyridine derivatives are more srtonly connected with silicagel in comparison to pyrrole ones. About chlorination nanosilica.... if it if some possibility of obtaining the positivated chlorine, this insulted by aromatic ring pare may cath positivated halogen atom to hide an extra electron density/ And this connection may be rather strong

You will be better off using surfactants for dispersion and Colloidal Stability of Nano Particles. There is no field in science, called Nano Sciense. It is still good old Colloid Science. Nano Scientists without good background in Colloid Science, are prone to discover steam engine. 

Thank you for your description. I use your advise.

may be TG measurements works.

Usually working with the pH of your solution should solve the problem : depending on the pH you will get gellation  (acidic conditions) or precipitation (neutral or less acidic). You could also dilute your titanium isopropoxide in absolute ethanol  prior to add the aqueous source. 

Read "Simulation of Growth of Nonspherical Silica Nanoparticles in a Premixed Flat Flame". There exists valuable background and examples of SiCl4 +CH4+Air+Ar.

Thank you very much Prof. Vladimir.

Orthosilicic acid, Si (OH)4 is main components of soil solution which provide silicon. It has pH < 9 with solubility of 1.7 mM at 25°C (Knight and Kinrade, 2001). Silic on is

deposited in stems and leaves as hydrated silica (SiO2·nH2O) phytoliths by evapotranspiration path (Sangster et al., 2001). In the dry and semi dry regions,

water is limiting factor for crop growth and regrettably, conventional technology o firrigation does not avoid elevated losses of plant-available water due to evapotranspiration and leaching. The watering with silicon allows a reduction in leaching, but does not affect evapotranspiration. Roots weight and volume increases

by 20 to 200% due to optimum silicon fertilization which ultimately enhanced drought and salt resistance in cultivated plants. Soil fertility and texture have considerable correlation with Si compounds (Bocharnikova and Matichenkov, 2008). Please read the attached paper.

Dear Ghania,

this maybe two-sided. There is a possibility to enhance environmental transport. On the other hand I see no pronounced thread of reducing bioavailability due to adsorption on exposed surfaces, rather the opposite. Problems of reduced availability may results in case of microporosity. So adsorption would rather act to reduce risk of adverse biological effects by reducing available solute concentration and if organic contaminants to favour biodegradation.

Our group tried it out, too and we used 2 different protocols leading to different silica layers:

1. http://pubs.acs.org/doi/abs/10.1021/la9601871

2. http://www.sciencedirect.com/science/article/pii/0021979768902725

Good luck!

nice discussion

You can use thermal evaporation process (Edward Speedvac Unit) to perform the coating on glass chips.

You could try the procedure described in this paper:

Dried clay (mud) raises a lot of possibilities. By dried, do you mean air dried? Drying at temperatures less than 300 C will not remove organic matter and less than 700-800 C will not produce many consolidating reactions. Any drying less than 700-800 C will leave you with particles with a lot of surface activity.

You may have an active flocculant in your clay or you may have rapid drying or absorbing reactions.

One technique that might work is to mist or lightly spray the solution and allow drying. It will require several coats. Once the surface is prepared you should be able to coat as intended.

Another technique is to pre-coat with a fluxing material or mix a binder into the clay before drying.

A lot depends or your drying and preparation conditions.