Novel Nanosheet allows for efficient ‘Molecular Sieving’ – Zeolite Membranes have enormous potential in Energy and Chemical industries


Zeolites have played an important role in the chemical industry in past decades. These microporous, aluminosilicate materials are well-known catalysts and adsorbents for catalytic reforming and separation of petrochemicals. More recently, zeolites have also been used to remove radioactive cesium from seawater following the Fukushima Daiichi nuclear disaster. Now, recent work from the University of Cincinnati, has opened even more doors for the material by tweaking its geometry and surface chemistry.

Zishu Cao and her colleagues fabricated membranes by tiling with 6-nanometre-thick zeolite flat sheets, they synthesized by a modified hydrothermal crystallization procedure. The resultant membrane was much thinner than a conventional zeolite membrane, with a thickness of less than 500 nanometres versus a traditional membrane’s thickness of several micrometres.

Tiling enhancements

Cao’s adviser, Junhang Dong of the Department of Chemical and Environmental Engineering, says Cao’s two-dimensional zeolite sheets overcome the major transport issues the conventional thicker zeolite membranes typically experience when they are several microns thick.

Fukushima 1 Infographic jpg

“The potential for zeolite membranes in the energy and chemical industries is enormous,” says Dong, “but the practical realization of their use is hindered by two serious issues caused by intercrystalline spaces in the films and their randomly oriented polycrystalline structure.”

These intercrystalline spaces, or gaps between the randomly oriented crystals that comprise the films, undermine the separation selectivity by causing nonselective permeation of molecules and ions. In addition, the random orientation of the crystals in the films results in longer and un-preferred diffusion paths making the membrane permeation inefficient.

The two-dimensional, zeolite nanosheet tiled membranes synthesized by Cao, however, provide an oriented straight channel structure that provides both reduced intercrystalline spaces and shortened diffusion lengths for enhanced selectivity and membrane flux.

“Imagine you are using blocks to waterproof a roof. Now we are using tiles or shingles to construct the roof,” says Dong.

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Petrochemical inspiration

Their readily scalable membrane fabrication by zeolite nanosheet lamination was inspired by recent work from the University of Minnesota, where researchers synthesized organophilic pure-silica zeolite nanosheets suitable for petrochemical separations. In Cao’s work, they incorporated aluminium ions into the silica-based zeolite framework to make the surface ionic and strongly hydrophilic – both favorable properties for water and ion separations. To the group’s knowledge, the ionic zeolite nanosheet laminated membrane is the first of its kind.

In their recently published paper, Cao displayed its potential for water desalination. The group chose to study this application because of its relevance to a wide range of needs in treating high salinity wastewaters, from industrial activities such as oil and gas drilling and power plant desulphurization and cooling. They reported high water flux with high salt rejection rates for brines containing up to 24% dissolved sodium chloride by weight.

The group says many routes are possible – desalination was just an example of the membrane’s capabilities. From here, they are exploring high-performance battery ion separators, catalysts, adsorbents, and thin-film sensors.

More details can be found in Science Advances.

New unique nanostructure to target drug-delivery treatment of cancer cells


Human BodyA unique nanostructure developed by a team of international researchers, including those at the University of Cincinnati, promises improved all-in-one detection, diagnoses and drug-delivery treatment of cancer cells.

 

The first-of-its-kind nanostructure is unusual because it can carry a variety of cancer-fighting materials on its double-sided (Janus) surface and within its porous interior. Because of its unique structure, the nano carrier can do all of the following:

  • Transport cancer-specific detection nanoparticles and biomarkers to a site within the body, e.g., the breast or the prostate. This promises earlier diagnosis than is possible with today’s tools.
  • Attach fluorescent marker materials to illuminate specific cancer cells, so that they are easier to locate and find for treatment, whether drug delivery or surgery.
  • Deliver anti-cancer drugs for pinpoint targeted treatment of cancer cells, which should result in few drug side effects. Currently, a cancer treatment like chemotherapy affects not only cancer cells but healthy cells as well, leading to serious and often debilitating side effects.

This research, titled “Dual Surface Functionalized Janus Nanocomposites of Polystyrene//Fe304@Si02 for Simultaneous Tumor Cell Targeting and pH-Triggered Drug Release,” will be presented as an invited talk on Oct. 30, 2013, at the annual Materials Science & Technology Conference in Montreal, Canada. Researchers are Feng Wang, a former UC doctoral student and now a postdoc at the University of Houston; Donglu Shi, professor of materials science and engineering at UC’s College of Engineering and Applied Science (CEAS); Yilong Wang of Tongji University, Shanghai, China; Giovanni Pauletti, UC associate professor of pharmacy; Juntao Wang of Tongji University, China; Jiaming Zhang of Stanford University; and Rodney Ewing of Stanford University.

This recently developed Janus nanostructure is unusual in that, normally, these super-small structures (that are much smaller than a single cell) have limited surface. This makes is difficult to carry multiple components, e.g., both cancer detection and drug-delivery materials. The Janus nanocomponent, on the other hand, has functionally and chemically distinct surfaces to allow it to carry multiple components in a single assembly and function in an intelligent manner.

“In this effort, we’re using existing basic nano systems, such as carbon nanotubes, graphene, iron oxides, silica, quantum dots and polymeric nano materials in order to create an all-in-one, multidimensional and stable nano carrier that will provide imaging, cell targeting, drug storage and intelligent, controlled drug release,” said UC’s Shi, adding that the nano carrier’s promise is currently greatest for cancers that are close to the body’s surface, such as breast and prostate cancer.

If such nano technology can someday become the norm for cancer detection, it promises earlier, faster and more accurate diagnosis at lower cost than today’s technology. (Currently, the most common methods used in cancer diagnosis are magnetic resonance imaging or MRI; Positron Emission Tomography or PET; and Computed Tomography or CT imaging, however, they are costly and time consuming to use.)

In addition, when it comes to drug delivery, nano technology like this Janus structure, would better control the drug dose, since that dose would be targeted to cancer cells. In this way, anticancer drugs could be used much more efficiently, which would, in turn, lower the total amount of drug administered.

Source: University of Cincinnati