Questions related to Mesoporous Materials
In the case of water splitting the water oxidation (OER) is the bottleneck for the process and because of the harsh conditions of the WO reaction, molecular catalysts with high TOFs are not stable in the matrix and quickly decompose. On the other hand heterogeneous catalysts are more stable but they often do not have high TOF quantities. Now what is your opinion about the future catalyst type? Will the ideal catalysts fabricated by turning the molecular catalysts to heterogeneous catalysts ( by loading the molecular catalysts on the solid surfaces ) or it will be from the single atom heterogeneous catalyst type?
I want to modify SiO2 surface with thin porous layer in order to adsorb humidity. So, please suggest about the type of mesoporous silica and also about the modification procedure.
When studying the adsorption of chlorate on activated carbon, it was noticed that adsorption is better at certain pH. Also noticed that the addition of activated carbon in the solution, resulted in a change in the pH of the solution being treated.
I am currently carrying out some BET analysis on several fly-ash geopolymer samples. They are powdered (>500um diameter), and are dried overnight (16-18 hours) at 105C in a vacuum oven to remove any pore water. Once they are put in to the glass tubes they are degassed for a further hour in a vacuum at 105C. I have attached a sample isotherm.
Why is the desorption isotherm crossing the adsorption curve?
Psoriasis has different types like plaque, flexural, guttate, pustular and nail psoriasis etc. having different signs like silvery scales, patches, red spots or pus filled etc, so why they are different? mean there are different triggers for each types which causes it and shows different signs? and if like this, so what are the difference in triggers that cause each types of psoriasis?
My oleate-capped NaCeF4:Gd,Tb NPs have been synthesized via the thermal decomposition method. 1mmol of NPs has been dispersed in 20 ml of cyclohexane.
I have tried dissolving 1 ml of NP in cyclohexane in 10 ml of 33 mg CTAB dissolved in DI water. I have washed my NPs with acetone 6 times, but I am unable to obtain a transparent and clear phase transferred solution. It is still a little cloudy after 24 hours at room temperature at 750 rmp with the first 3 hrs at 70 degrees at 1400 rpm.
However, I have carried on with the reaction and add in 150 microlitre of TEOS dropwise after adding in another 20 ml of DI water, 150 microlitre of 2M NaOH, and 3 ml of ethanol at 70 degrees 1000 rpm. The CTAB was removed via a ligand exchange method with 0.3g of NH4NO3 in ethanol on the next day.
May I seek advise on what went wrong and how I can improve?
The pictures contain before and after coating of the mesoporous shell.
Based on the data reported in many publications mentioning the drug loading of mesoporous silica nanoparticles (MSNs) since the drug precipitate as a crystalline form and requires separation. That was so confusing, and I want to discuss if this test is an actual test or a myth.
We have here a three mentioned scenarios
1- Measuring drug loading without washing MSNs after solvent evaporation or deposition or incipient witness method. So, why we measure drug loading, actually the drug loading efficiency should be 100%, and if there is a decrease in the drug content, that means only one thing "the preparation method was messy or inadequate preparation."
2- Measuring drug loading after washing with ethanol is inaccurate because ethanol will dissolve depending on drug solubility. Also, ethanol can dissolve amorphous and crystalline drugs, so there is no preferential separation.
3- Measuring drug loading after washing with water or water containing a minimum amount of ethanol. In this method, the drug is dissolved to the limit of drug solubility in water or the water-ethanol mixture.
-What is useful to do with crystalline form is to measure the degree of crystallinity in loaded mesoporous silica.
-If there is a washing method you can suggest to separate crystalline form efficiently out of the loaded carrier, please discuss it.
I have experimental data for the effect of time at different feed concentration on the permeate flux of the hybrid adsorption membrane process for the removal of dye from wastewater. I would like to get a mathematical model.
I have a question please how to calculate the concentration at the adsorbent surface?
Would please help me to understand the calculation of concentration at the adsorbent surface?
I would appreciate your reply.
I have just started to gain basic information about gas sensing materials. So here, I want to know what materials are in touch nowadays for efficient gas sensing, and what are the corresponding advantage and disadvantages?
Al incorporation into the SBA-15 structure can be done with limitations.
Upto what extent we can load Al into the SBA-15 structure, without creating an extra framework of alumina in the synthesized material?
I have incorporated Fe in SBA-15. What could be possible reduction temperature when measured by Temperature program reduction (TPR).
I have obtained nitrogen adsorption desorption isotherms for a mesoporous sample. From these isotherms and BJH size distribution, I have calculated surface area, pore volume and average pore diameter. But, when I am asked "what is the pore volume fraction of meso and micropores?", what do I need to calculate and how?
I have mesoporous silica capsule which contains gold nanoparticles.
I have created that complex and nothing is known about it.
So I have a question about how to sterilize it.
I have tried autoclave, but the I think the complex was
aggregated and lost the original characteristics :(
Could you suggest any ideas?
or is there a special way for gold nanoparticle sterilization?
When I have screened a bit of literature trying to find an answer of following topic, there are some papers where the size of nanoparticles is increasing with the temperature of synthesis, because thermodynamics of liquid–crystal phases of surfactants and kinetics of the hydrolysis of TEOS strongly influence on it.
Microporous and Mesoporous Materials 128 (2010) 203–212,
However, we can find a lot of papers, where size is increasing with decreasing the temperature. The explanation that I found is: "The precipitation time at lower temperatures was much longer than that at higher temperatures. It is assumed that nucleation decreases when the synthesis temperature is lower, which presumably results in the generation of large particles."
J. Mater. Chem., 2003, 13, 2577–2581
Nanotechnology 24 (2013) 155601 (11pp)
Nanomaterials 2018, 8(4), 230;
On the other hand, I found also a paper when temperature of synthesis does not really affect on size.
J. Mater. Chem. , 2004, 1 4 , 1579–1584 (TABLE 2)
And here is the question: Can you explain, in what situations and why the size of the particles is increasing, decreasing or being constant with increasing the temperature ?
I am using the isotherm obtained by the BET technique to calculate the pore size of some materials; I obtained an average pore size of approximately 10 nm in all my samples (I think that means that I have mesopores in my material), but I am not sure if these results are correct since the standard pressure used in BET may won't be enough (mesopores require greater pressures (>0.3) to be calculated than micropores). Should I use a different technique?
Thanks for all your help!
I'm working with adsorption of organic compounds at materials that are functionalized with different concentration. It was expected that with high functionalization the higher is the adsorption capacity, however the opposite is happening. Any ideias why this happens? Note that there was insignificant surface area change.
I was thinking to use the BJH model to measure the pore size distribution of low porosity (mostly meso and macropores)-containing materials.
In this regard, I have got the following questions:
1) Which relative pressure range should I consider? P/P0 >0.35?
2) Which isotherm branch should I apply the BJH model to? Ads or Des? How does this choice relate to the Hysteresis type?
3) Would DFT model be more suitable?
If curve of adsorption branch overlap over desorption branch, what are the type of pores in these types of materials
Recently, I try to prepare mesoporous silica film on titanium substrate by evaporation-induced self-assembly process (EISA).
I have tried two ways to prepare precursor solutions:
1. P123 (0.5 g) was dissolved in the mixture of water (5.0 g) and hydrochloric acid (0.25 g, 2 M) at room temperature. Stirring it until a homogeneous solution was obtained. Then, 1.0 g of TEOS was added and the mixture was stirred for 10 min.
2. TEOS (1.50 g) , Ethanol (15.0 g), deionized water (0.78 g), and 0.1 M Hydrogen chloride (0.15 g) were stirred at room temperature for 1 h. P123 (0.30 g), Ethanol (14.25 g) were stirred at room temperature for another 1 h. After stirring, the two different solutions were mixed and then stirred at room temperature for 1 h.
After this process, EISA was carried out. (Ti substrates were immersed in precursor solutions and put in oven under 37 ℃ for about 6 h until the solvents completely evaporated. Finally, the thin, transparent mesoporous silica films were obtained)
Considering drug loading in the future, I use a more gently method for removing of P123 by reflux with ethanol overnight (90℃) instead of calcining.
In addition, I also found a more gentle way, which was performed in an ethanol solution containing 0.1M HCl under stirring conditions for 15 min.
Unfortunately, no matter which precursor solution or which extraction method was used, the film was destroyed into small pieces and detached from the substrate.
Did I forget any details, or make something wrong?
Whats your protocol?
As all we know, there are two conventional ways to tune MOF structures and specially pore size by altering the metal clusters or the ligands.
But the question arises when we want to have a specified pore size in an exact copled metal and ligand.
How can I adjust the pore size without changing the metal and ligand?
Which variants are involve in MOF synthesis that influence pore size?
TiO2 nanoparticles are white itself, but what is the cause of transparency after sintering?
I am using Surfactants i.e CTAB, P-123 and F-127 in meso-structured materials synthesis. After synthesis i want to remove these surfacrtants by washing the materials with boiling EtOH for 6h. Is such kind of washing will be enough to remove surfactants because in my case calcination is not suitable for the as synthesized materials. So only washing will be enough to remove CTAB, P-123, F-127? kindly share your kind suggestions.
I have a really big problem to get really good data plots for pore size distribution when doing the BET/BJH measurement. The Isotherm curve of my sample looks pertty nice. However, When I plot the pore size distribution data, I find most of the data plots are concentrated <5nm, beyond that range the data plots are so few for me to get a nice shape of peak.the pore size of my sample Is any way solve this problem? such as changing the test setup. current I am using 80 plot method.
Hi dear Scientists! :)
I was impregnating Fe or Cu over different mesoporous materials, and after TPDA analysis I concluding that when I decrease the percentage of metal over surface of material, acidity increase (more specifically, strong acidity)...
So, I thought that with increasing of percentage of metal will increase the percentage of acidity, but, this was not like I thought..
I just looking for explanation of this fact, but..... I can't found a very well explanation...
Some one could help me?
Here I have attached the isotherm of two samples? I have used BET multipoint for surface area (SA) calculation. For First sample SA is ~4.55 and for 2nd sample ~53.95 m2/g. Which isotherm shall I use for calculating pore size distribution? How I understand which type of pore it is?
When preparing mesoporous materials with aluminum and comparing them with siliceous ones, the degree of organization generally decreases when increasing aluminum content. What is the explanation for this behavior?
Some cases like; CTAB, CTAOH, TPABr, TPAOH, SDS, etc. are commonly used in laboratory scale uses, but not yet have been industrialized due to high costs. Based on the chemical structures of the long-chain alcohols (such as; pentanol, hexanol and so on) since they are amphiphilic compounds, I presumed that they can be potential cases in forming micelles to form a template structure in nano-meso-structured materials synthesis, but they often are used as co-template or intermicellar agent. Can they be used solely? or any general recommendation?
for example Vm= 71 cm3.g-1. That's a very high number
This question continues the previous question, which so far I do not know the answer
While the BJH method is used only for mesopores.
TPV (BET): 0.474 cm3.g-1
Vp (BJH): 0.616 cm3.g-1
Naturally, the total pore volume (micropores+mesopores+macropores) should not be less than the mesopores volume.
I synthesized mesoporous carbon nitride. TEM and BET approve that it is mesoporous.
also, i test low angle XRD and there is one peak at 0.85 degree.
i found that we can show that our material is mesoporous with low angle XRD, but i could not find any connection between them.
i appreciate, if you could help me about this issue
I looking for nanoporous thin filim of mesoporous silica on SiO2 surface which can adsorb humidity. There should be uniform hexagonal pores in the thin film.
So, please suggest about the type of mesoporous silica and also about the modification procedure.
In activated carbon samples synthesized by KOH and NaOH as activation agents, KOH activated samples have higher rate of micropore area than NaOH activated samples.
Although NaOH provides higher surface area than KOH, but the pore size distribution is wider.
My question is why KOH can produce smaller pores rather than NaOH?
Usually, the pore diameter increases with increase in surface area and pore volume. However, in my case, pore diameter is decreasing with increasing surface area and pore volume. What could be the possible case?
1. BET =11.51 m2/g, BJH pore volume = 0.013 cm3/g and BJH pore diameter =4.6 nm.
2. BET= 456 m2/g, BJH pore volume= 0.302 cm3/g and BJH pore diameter= 2.5nm.
I synthesized mesoprous carbon nitride. After getting XRD test, I found that there are some impurity in my sample. After checking with different software, I found that these impurity is related to ammonium hexafluorosilicate.
I used silica nanoparticles (Ludox HS40, Aldrich) as a template and Ammonium bifluoride for removal of silica.
At the end of procedure, my sample centrifuged and washed with distilled water.
how can i remove these impurities from my sample?
I have mesoporous carbon nitride and I want to support cobalt on it.
The structure of final product is very important and it should be mesoporous material.
what is your idea about the precursor of cobalt?
I would like to fit my adsorption isotherm data with a Redlich-Peterson model, but I am confused as to how to determine the alpha values, Could someone suggested me how to prove this?
Sometimes analyzing mesoporous materials I observe appereance of phantom peak of 3.7 nm on BJH pore size distribution curves. I would like to know what is a reason for its apperance?
I am looking for polyurethane foam/sponge material with pore sizes up to 1000 ppi. In other words the pore size should be in the range of 20 micrometer to 100 micrometer. Thank you in advance.
I have a platinum black of specific surface area of 31 m2/g. What will be the estimated real surface area (CO stripping)? Greatly appreciated if there is any publications on this.
Hello , I would like to ask for your help please. I do my research on the synthesis of mesoporous materials and their application with the adsorption of pollutants (pesticides) but after several experiments carried out in the laboratory on this subject, I found that mesoporous materials do not adsorb pesticides The more polar ones such as methomyl and cymoxanil for example while all my work is based on this, someone can propose me a grouping or a precursor which can be useful for the functionalization of the mesoporous materials of the MSU family with to these Chemical ances, please it is urgent, thank you in advance. my greetings
Increase in salt concentration (NaCl) in presence of block copolymer can generally increase the mesopore diameter and decrease the no of micropore. Is there any way that it can increase the surface area and no of mesopore somehow? Please reply.
Such as title
How to calculate the specific surface area of the inverse opal structure?
Is there any formula to calculate the specific surface area of inverse opal?
I would like to synthesis the rod-shape mesoporous silica nanoparticles of sizes smaller than 100nm. Does anyone has some experiences? Also, any tips and tricks that goes along with will be extremely useful.
Thank you much in advance.
While measuring the BET area of various sorbents, I noticed that in some samples desorption curve goes slightly lower than adsorption curve. I wonder whether this is just an artifact or has some physical explanation?
Example: adsorption/desorption curves for N2 on sepiolite (degassed in vacuum at 100 °C for 24 h). BET surface area is 312.9±4.3 m2/g.
I prepare porous silicon with conditions used before with the same properties of silicon substrate, but usually i get pore diameter lower than the one previously obtained. Could anyone tell me what is the problem?
Thanks for attention.
Two micropore each having radius r will have a surface area of 2pi*r2h (if h is the depth of the pore).Instead of that one mesopore have a radius of 2r. Then its surface area will be pi(2r2)h = 4pir2h. So mesopore should have more surface area and pore volume than micropore.
Graphene was used at the initial stage, after hydrogenation we found some additional peaks at 15.5, 18.8 and 20.4, 2-theta positions in the XRD patterns. Before hydrogenation the system contains Mg, Graphene and MgO, after complete hydrogenation under hydrogen pressure of 3.5 MPa, we found MgH2, MgO and unreacted Mg, and these additional peaks. Obviously there is no graphene peak after hydrogenation.
I have prepared ZnO and Zn0.98Pd0.02O by sol-gel method. Increase in BET surface area was observed on substitution.
What could be the probable reason for increase in SA? Can someone help me out to get some good references on same.
hello, I have synthesized gold nanorod and follow standard procedure to core with mesoporous silica shell, however I can not clearly see the porous on the TEM picture, can you teach me how to use another simple way to know my sample is mesoporous or not?
From the characterization analyses, it was found that the addition of the new functional group to the adsorbent decreased the rigidity of the material itself. However, the modified adsorbent are still giving the best performance during the regeneration and reusability study? Could anyone elaborate the findings, giving some theoretical evidence?
Concerning the surface of the zeolit, it should be composed by silanol groups and some bronsted sites - as Si-OH-Al... But I would like to know if we can find groups as Al-OH on the surface...Any reference proving that?
How to characterize?
I would like to know the reason as to why most papers report that coating of unordered silica before adding a shell of mesoporous silica over it.
Does anybody have a complete calculation example (like a xlsx file) showing how to go from an adsorption/desorption isotherm to BJH pore volume distribution? I am trying to implement the calculations from the original 1951 BJH paper into Python coding. I am not confident that I am using the "A*c" correction term correctly, so I would be nice to see it being used in like Excel. Thanks.
Siliceous zeolites or with low Si/Al are synthesized with easily, however, high Al-containing zeolite synthesis end up with mixed phases of amorphous silica-alumina with desired zeolite. Please suggest me some literature.
Hi, I am trying to analyze HZSM-5 external acid sites change before and after modification. I know there are papers employing 2, 6 di-tert-butylpyridine as a probe, which is assumed to absorb exclusively on acid sites outside of the micropore due to its large molecule size, and using FTIR to detect the molecule-relevant peak change to characterize HZSM-5 external surface acid sites change. Theoretically, there is no problem with this method. However, technically, when prepare a HZSM-5 sample for FTIR test, the pelletizing process (to make a HZSM-5 wafer) could easily crack HZSM-5 crystals into fragments (discovered by SEM, also Journal of Catalysis 1983, 80, 221-227) and expose much interal aicd sites to the 2, 6 di-tert-butylpyridine atmosphere. Thus I don't think it is a reliable way to characterize the external acid sites.
For XPS, provided the Al is tetrahydrally cordinately in HZSM-5 framework, the total acid sites numbers (by NH3-TPD) has a good linear relationship with the Al content in zeolite (Meshram, Zeolite 1986, 6, 434-438), and the fact XPS singnal only comes from surface layer less than 3nm, I feel it is reasonalble to estimate HZSM-5 external surface acid change with HZSM-5 surface Si/Al ratio change.
What's your ideas? Comments welcome!
what is the significance of the position of H1 type hysteresis loop?
What conclusion can be drawn if the H1 hysteresis loop closes at the relative pressure of close to 1 (0.98) for mesoporous polymer nanofibers?
Please find the attached figure and paper
Why when we doped Yb broad peak is coming not intense peaks are coming which sites Yb is going to occupied it size is too bigger as compare to tiania Yb3+ is 86 pm and Ti4+ is 74 pm. What kind of geometry be possible for Yb3+ ion if it is in lattice postion.
For gas phase reactions, such as cracking or methanol-to-olefins, the introduction of mesopores (2 - 50 nm) and/or macropore (>50 nm) into zeolite structure leads to the occurence of Knudsen diffusion mechanism since diffusion relies on wall collisions to direct molecular flow.
Does this diffusion also occur when hierarchical zeolite used as catalyst in liquid phase reaction, i.e. self condensation of cylohexanone??
Please refer me to articles or books regarding the diffusion of organic liquid phase reaction in hierarchical zeolites.
I am working on mesoporous silica nanoparticles for the treatment of pancreatic cancer. I am planning to put PEG over the surface of the mesoporous silica nanoparticles. I want good suggestions from researchers.
I read some papers about chemical dissolution of the matrix, burn it off in an inert atmosphere and TGA.
Do you have any advices or references about it?
I'm working on mesoporous catalyst experimentally and now I'm going to investigate these catalysts with computational methods so I want to know how can I do this work with MS. Indeed I want to know how can I build a mesoporous structure via the materials studio.
I have molecularly imprinted polymer samples for the BET analysis.
Why small angle XRD pattern shows peaks for hexagonal and cubic symmetric structure like SBA-15, MCM-41.
Reflection at 100, 110 and 200
1.Can I caculate the microporous surface by BET surface -mesoporous surface?
2.Can I compare the micropous surface and volume by the adsorption quantity in the relative pressure range below 0.1?
Pressure-area isotherms obtained for lipid monolayers are constantly shifted after repeating the experiment with the same type of lipid.