Nanoporous Materials - Science topic

As for the most suitable porous material for trapping perovskite, MOFs are indeed a strong candidate due to their large surface area, tunable pore sizes, and ability to enhance charge transfer and reduce recombination. Other materials like mesoporous silica and carbon dots have also shown promise in enhancing the performance and stability of perovskites.

Dear Sarabjeet Kaur ，For more details please visit the conference website:

Thank you, Pavel, I will take a look on CN link and get back to you

Hello,

I believe that science is moving from continuum mechanics to particle mechanics. Here, depending on the size of the particles, I expect major breakthroughs across the whole range of particle sizes. Up to now, even particle mechanics in the micro to centimeter range is mostly modeled by continuum mechanics. Of course, with respect to the rapid development of DEM methods. This will allow the modelling of particles with respect to their sizes and the digitalization of the field. I wish you a lot of success in finding new properties of particles and their collectives.

Prof. Dr. Jiří Zegzulka, TU Ostrava

Zaid H. Mahmoud

The surface porosity of nanoparticles can be increased by grafting other desired molecules to the surface. They will increase porosity and modify the surface for new nanoparticle properties.

Shumao Wang Argon gas... In air or aqueous based systems Fe_⁰ is rapidly oxidized often in a pyrophoric manner if small. You need to keep oxygen out of the system to prevent this - this included water, alcohols, esters etc all of which contain O.

Prem Baboo thanks for sharing the details

PVA is more suited to solution electrospinning as it is a water-soluble polymer. However, for the case of melt electrospinning, it is best to consider high temp. durable grade material for components when setting up a melt electrospinner. Peripherals such as the container, pumps and tubes need to withstand high temperatures. In addition to this, you may need to think about setting up a heating compartment for the polymer-filled syringe or container to maintain the temperature when the polymeric melt (liquid polymer) is pumping all the way to anode, it should not cool down and solidify before reaching the HV anode.

Crystalline silica SiO2 may cause the gel to be blue when dry and pink when hydrated.

It is always good to return to the original definition and meaning of the terms.

Entropy is often correlated with the disorder but not always. Entropy is the measure of unknown information. How do we understand this? The trick is to understand what is macrostate and what microstate.

* Macrostate is observable value.

* Microstate usually not.

Unknown are microstates as we can not measure them.

Just an example with a dice, where we can observe microstates. Macrostate is the sum of all values of all thrown dice. The trick is that there are existing many microstates giving one macrostate. Not every macrostate has the same number of microstates.

Macro states with the highest number of associated microstates have logically the highest probability to be observed in the system as far as all microstates have the same probability It leads to the original Boltzmann definition of entropy.

When there are microstates with different probabilities, we just group them together and we get the well-known definition of Boltzmann entropy and similar Shannon entropy

H = - sum(p_i * ln(p_i))

They are the same except for the Boltzmann constant.

I am a bit confused about the answers, although they are correct.

For the question:

"How can I adjust the pore size without changing the metal and ligand?"

the answer must be simply: You basically CANNOT for a ridig linker (and most of the linkers so far used are rigid).

The size and shape of a rigid ligand together with the coordination are determining the maximum pore size, there are no synthesis parameters whatsoever than can change this.

E.g. if you use the rigid terephthalate as linker (ligand), the space between two metal atoms (ions) is rather fixed. For flexible linkers there is a lot of room for variation, see e.g.

But also for them, there is an upper limit given through the bonds and angles within the linker.

Is their any effect of tdamp on results we get ?

@Xiaowen Zhan, I have also used Keithley 2400 and it worked! Did you use GPIB connector ?

Thank you guys so much. I appreciate it.

Sattar

In my opinion, given your analogy is not entirely appropriate in this case. Do you have data on the distribution of pore sizes for your samples? Do pore distribution curve vary in size depending on the thickness of the sample? The pores are isolated or communicating? The pores are what form? Apparently it can be assumed that the layer thickness affects the diffusion coefficient of the material to a lesser extent in the case where there is evidence of its homogeneity

You can consider the 'phase separation process' induced by a non solvent.

The starting point is a solution of a polymer. Then if you cast a layer of this solution on an inert support (e.g., glass) and put this system in contact with a non solvent for the polymer (e.g., water) you will end up with a porous structure. In this method you don't need to increase the temperature.

The morphology can be tuned by properly choosing the polymer conc. and the solvent/non solvent system.

This is the method to prepare porous polymeric mmebranes. You probably need the pores as for microfiltration membranes.

Metal "complexe'ss" definition comes from A. Werner. Complexes are composed by metal to oxygen or nitrogen bonds (some times phosphorus), but never carbon. The metal complex is generally a separated molecule with one or more metals in it but without connection to neighbor molecules. On the other hand, Cotton I believe, defined organometallic (circa 1964) as molecules with metal-to-carbon bonds (vitamin B12 for example). Besides that, coordination compounds can be tailored to have intermolecular bridges so as to build cages, tunnels, spheres, wheel catenated and so on. These supramolecular arrays (or FRAMES, frameworks) are very stable (Keq) and exchange ligands very slowly (k). Therefore the difference,  is a matter of design and structure but nature had already made "Zeolites" long before we started designing frameworks.If you can't crystallize'em heat'em. 

"Networked molecular cages as crystalline sponges for fullerenes and other guests" "Yasuhide Inokuma, Tatsuhiko Arai, & Makoto Fujita" Nature Chemistry, 2, 780–783, (2010). doi:10.1038/nchem.742

If you want something porous I think you should try polysaccharide reticulation using the classical reaction with epichlorohydrin or softer ones with citric acid for example. Probably you can just try some Sephadex beads, they actually come with different porosities.

I am sorry to say this Dr. Hao Qi, but it is possible to dissolve the AAO layer in a H3PO4 solution without damaging the Al nanostructure.

While H3PO4 reacts with the Al foil (I never said it didn't), this does not mean that it cannot be used for removing the AAO layer without affecting the nanostructure left on the aluminium foil, specially if used with caution and in a well-controlled manner. It's just a matter of avoiding any overetching that could damage the Al nanostructure.

In fact, this process (i.e. H3PO4 dissolution) has already been used and published twice that I can recall with successful results:

Regards,

Gerard

Well, it depends on how porous and how robust your material is. The higher the temperature the better it is but the question is: will your material resist to the thermal treatment and conserve its porous structure? As I am not an expert on your specific material, I recommend you to check the literature. But to start, lets say 3h at 250 ^oC for the oxide and 18h at 75 ^oC for the hydroxide seems appropriate to me.  

Dear Gil,

I am waiting your paper.Please drop your paper in gowhar@du.edu.om

Dear Anderson thanks for your suggestion.

My question is regarding the effect of silica nanoparticles on the pore pore morphology.

From the last 5 years. i concluded that pore size decreases by encapsulation of silica nps into the porous materials.

Probably due to the presence of defect sites

Sputtering will be one of the methods in terms of controlled manner, e.g. uniformity, thickness, porosity, and physical (optical/electrical) property.

It is important to distinguish to what extent, on the surfaces at least, the metal has been transformed to metal oxide. Metal oxides are usually thought of as ionic solids, where the metal and oxygen are in particularly charged valence states. If water is accessible, the surface oxides will have a population of protonated hydroxyl groups. In any case, you will have interatomic electrostatic and dispersion forces operating, and in the surface layer polar and hydrogen bonding forces. The curvature of the nanopores, along with the basic metal oxide surface energy, will attract solvents such as water, and these structures introduce what are known as capillary forces, generally defined by the Laplace equation [at any point on the surface one has two radii of curvature, and a surface free energy]. If you examine different types of solvents of varying molecular size, you may run into phenomena connected with solvation forces that Israelachvili popularized in hte 80's and 90's. In a given space or thickness, you can fit a certain number of oriented and ordered solvent molecules. Energetic differences arising from being able to "just fill" such a space compared to being able to only partially fill a space give rise to so called solvation forces. If you apply electric fields, as is easy to do with a metal/metal oxide material, with ground in solution, you can induce polarization forces and elecgtrochemical forces.

The feature size of the Te is definitely at most 100 nm but do you know the ratio of pore to occupied space for this material? You could consider using BET and backing out a length scale from the surface area.

Sorry for the ambiguity. What I meant by solids was the nanorods. After you've removed the alumina, the nanorods may have some salt residue - even with good filtering, some of the dissolution liquid will remain on them. Washing the nanorod solids should help remove any residual salts or incompletely dissolved alumina.

Is there something about the calculations that you wish to ask more specifically?

nanoporous gold with pore/ligament size around 10 nm, and FDTD simulation.

Take a look at the paper - doi: 10.1038/nature12070.  Rob Rambo was considering using the AXS invariant Vc to characterize voids in materials.

Dear Jorge, in simulations using periodic boundary conditions all the properties  that be computed significantly are those possessing a characteristing size smaller or equal to the simulation box. A simulation yielding an amorphous system in the simulation box in fact generates a crystal with a unit cell corresponding to the simulation box and symmetry group  P1. Strictly speaking, an amorphous system does not show any translational symmetry, but the experimentalists seem to consider as amorphous a systems without symmetry in patches of about 100 nm in size, and in this sense the simulations are not fully adequate. However, if one wants to study the amorphyzation mechanism, the simulations of relatively small systems, in my opinion, can be useful, provided that the interatomic interactions are short-ranged and then the influence of the periodic images are negligible.

Dear Abdullah,

There may be also some positive rolling of particles in nano-grooves parallel to the sliding direction. The article below may be of interest to you:

International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 2, March - April (2013) ,

"MICROSTRUCTURE AND TRIBOLOGICAL PROPERTIES OFNANOPARTICULATE WC/AL METAL MATRIX COMPOSITES" by Amarnath.G and K.V. Sharma

Good luck!

Luiza

Thank you very much!

I will read your contributions and then ask you some questions.