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Menlo Park, Calif. The images, made at the Stanford-SLAC Cryo-EM Facilities, show two configurations of the CO2 molecule in its cage, in what scientists call a guest-host relationship; reveal that the cage expands slightly as the CO2 enters; and zoom in on jagged edges where MOF particles may grow by adding more cages. MOFs have the largest surface areas of any known material.
A single gram, or three hundredths of an ounce, can have a surface area nearly the size of two football fields, offering plenty of space for guest molecules to enter millions of host cages. Despite their enormous commercial potential and two decades of intense, accelerating research, MOFs are just now starting to reach the market. Scientists across the globe engineer more than 6, new types of MOF particles per year, looking for the right combinations of structure and chemistry for particular tasks, such as increasing the storage capacity of gas tanks or capturing and burying CO2 from smokestacks to combat climate change.
One of the most powerful methods for observing materials is transmission electron microscopy, or TEM, which can make images in atom-by-atom detail. But many MOFs, and the bonds that hold guest molecules inside them, melt into blobs when exposed to the intense electron beams needed for this type of imaging. The preparation of the hydrogel containing growth-factor-loaded GO is simple and straightforward. Meanwhile, the large surface area of GO means that only small quantities are needed to equal a similar amount of growth factor supplied externally.
The ability of GO to retain TGF-beta 3 means that a slow release rate can be maintained over an extended time period. Zhou et al. Tuberculosis represents a growing challenge for public health organizations around the world and can only be reliably diagnosed via identification of the bacteria Mycobacterium tuberculosis MTB.
But MTB is slow growing and existing diagnostic methods can be expensive and unreliable, so a new identification tool is desirable that can offer a swift diagnosis with low levels of false-positive responses. Immunological biomarkers of TB offer a promising target, particularly the antigen MPT64, a surface protein secreted by MTB, which is detectable in the immune system of most patients with TB.
Tetrahedron | Structure Bonding Material Type | Chemogenesis
Long-chain oligonucleotide or peptide molecules called aptamers are a practical means of detecting antigens because of their high affinity and specificity combined with stability and ease of preparation. The combination allows the composite to act as a nanocarrier and redox nanoprobe at the same time. The AuNP-decorated nanocomposite is then combined with a sensing platform consisting of a Fe-based metal-organic-framework functionalized with conductive polyethyleneimine PEI or P-MOF, which helps to amplify the detected signal. The sandwich-type layered sensor provides a two-pronged strategy to amplify the signal from low levels of MTB antigens in blood samples.
Some basic chemistry
The new sensor significantly improves the response performance for MPT64 antigen detection, say the researchers. As a demonstration of the nanocomposite aptasensor, the researchers tested serum samples from eight patients with TB and the same number of healthy volunteers. The samples from patients with TB showed significantly higher signal responses to MPT64 than the healthy controls. The researchers believe the results indicate that the proposed novel carbon nanocomposite aptasensor could offer an innovative platform for quick and simple TB detection in clinical applications.
Chen et al. If you want to make a super-strong material from nano-scale building blocks, then you should start with the highest quality building blocks, right? This finding will aid the production of higher-quality GO materials and also sheds light on a general problem in materials engineering: how to build a nano-scale material into a macroscopic material without losing its desirable properties. Here, we add some seemingly weaker players and they strengthen the whole team.
The research was a four-way collaboration; in addition to Huang's group, three other groups participated. These were led by: Horacio Espinosa, professor of mechanical engineering at the McCormick School of Engineering at Northwestern; SonBinh Nguyen, professor of chemistry at Northwestern; and Tae Hee Han, a former postdoc researcher at Northwestern who's now a professor of organic and nano engineering at Hanyang University in South Korea. The researchers report their findings in a paper in Nature Communications. GO is a derivative of graphite that can be used to make the two-dimensional 2D super material graphene.
Since GO is easier to make than pristine graphene, scientists study it as a model material. It generally comes as a dispersion of tiny flakes in water; from one end to the other, each flake is only 1nm thick. Intermolecular forces hold the flakes together, nothing more. Scientists can make strong GO in single layers, but layering the flakes into a paper form doesn't work too well. While testing the effect of holes on the strength of GO flakes, Huang and his collaborators discovered a possible solution to this problem.
Flakes left soaking for one to three hours were drastically weaker than un-etched flakes. After five hours of soaking, the flakes became so weak they couldn't be measured. Then, the team found something surprising: paper made from the weakened flakes was stronger than expected. Things got even more interesting when the team mixed solid and porous flakes together, Huang said.
If GO sheets can be likened to aluminum foil, Huang explained, making GO paper is just like stacking the foil up to make a thick aluminum slab. If you start with large sheets of aluminum foil, chances are good that many will wrinkle, impeding tight packing between sheets. On the other hand, smaller sheets don't wrinkle as easily. They pack together well but create tight stacks that don't integrate well with other tight stacks, creating voids within the aluminium slab or GO paper where it can easily break.
This finding will be directly applicable to other 2D materials, like graphene, Huang said, and will also lead to the design of higher-quality GO products. He hopes to test it out on GO fibers next. This story is adapted from material from Northwestern University , with editorial changes made by Materials Today.
Hexagonal-boron nitride h-BN is tough, but scientists at Rice University are making it easier to get along with. But those qualities also make h-BN hard to modify. Its tight hexagonal lattice of alternating boron and nitrogen atoms is highly resistant to change, unlike graphene and other 2D materials that can be easily modified — or functionalized — with other elements. These turn the 2D tough guy into a material that retains its strength but is more amenable to bonding with polymers or other materials in composites. The protocol is described in a paper in the Journal of Physical Chemistry , which also suggests that h-BN can be made more dispersible in organic solvents.
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Birch reduction, which was discovered in the s and enhanced in by Rice chemistry professor Edward Billups to functionalize carbon nanotubes, frees electrons to bind with other atoms. Lithium is an alkali metal that sheds free electrons when combined with liquefied ammonia. Mixed with h-BN flakes and a carbon source — in this case, 1-Bromododecane — the reaction produces an alkyl radical, a chemical species that reacts with h-BN and makes a bond.
The material is good for certain applications, but to control its properties for manufacturing, you have to graft different groups onto the surface. He said that a to-1 molar ratio of lithium to h-BN optimized the process of grafting carbon chains to the surface and edges of h-BN. Furthermore, because the base h-BN remains stable under high temperatures, it can be returned to its pristine state by simply burning off the functional chains. While h-BN is naturally hydrophilic water-attracting , the functional carbons make them nearly superhydrophobic water-avoiding , a good property for making protective films.
But even when enhanced, the flakes remain amenable to dispersion in non-polar solvents. What about ethers? What about groups that will make it compatible with other materials? Ultimately, we'd like to graft different groups onto h-BN and build a library, kind of a toolbox, of functional groups that can be used with these materials. This story is adapted from material from Rice University , with editorial changes made by Materials Today.
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When two mesh screens are overlaid, beautiful patterns appear when one screen is offset from the other. These findings, reported in a paper in Nature , could help in the search for novel quantum materials, such as superconductors that work at room temperature. Such materials would dramatically reduce energy consumption by making power transmission and electronic devices more efficient. Graphene comprises a layer of carbon atoms arranged like a honeycomb; it's a great conductor of electricity and much stronger than steel. The Rutgers-led team studied twisted bilayer graphene, created by superimposing two layers of graphene and slightly misaligning them.
At a twist angle of about 1. The sluggish electrons start seeing each other and interacting with their neighbors to move in lockstep. As a result, the material acquires amazing properties such as superconductivity or magnetism. Using a technique invented by Andrei's group to study twisted bilayer graphene, the team discovered a state where the electrons organize themselves into stripes that are robust and difficult to break.
This story is adapted from material from Rutgers University , with editorial changes made by Materials Today. When is a circle less stable than a jagged loop? Apparently when you're talking about carbon nanotubes.
These terms refer to the shape of the nanotube's edge: a zigzag nanotube's end looks like a saw tooth, while an armchair is like a row of seats with armrests. They are the basic edge configurations of the two-dimensional honeycomb of carbon atoms known as graphene as well as other 2D materials and determine many of the materials' properties, especially electrical conductivity. This work is a continuation of the team's discovery last year that Janus interfaces are likely to form on a catalyst of tungsten and cobalt, leading to a single chirality, called 12,6 , that other labs had reported growing in The Rice team, made up of materials theorist Boris Yakobson, researcher and lead author Ksenia Bets and assistant research professor Evgeni Penev, now shows that such structures aren't unique to a specific catalyst, but are a general characteristic of a number of rigid catalysts.