A new kind of chemical 'glue'

May 30, 2013 by David L. Chandler
Illustration depicts a gold surface (in yellow) with a polymer material (depicted as complex shapes of green, black and pink) attached to the gold surface by carbenes (depicted as blue spheres). MIT research has shown that certain carbenes can be used to attach many different kinds of material to gold or other kinds of surfaces. Credit: CHRISTINE DANILOFF/MIT

Over the past three decades, researchers have found various applications of a method for attaching molecules to gold; the approach uses chemicals called thiols to bind the materials together. But while this technique has led to useful devices for electronics, sensing and nanotechnology, it has limitations. Now, an MIT team has found a new material that could overcome many of these limitations.

The new approach uses a family of chemicals called carbenes to attach other substances to gold—and potentially to other material surfaces as well. The work, led by assistant professor of chemistry Jeremiah Johnson, has been published in the Journal of the American Chemical Society by a team that also included professor of chemistry Troy Van Voorhis and graduate students Aleksandr Zhukhovitskiy and Michael Mavros.

Thiols have two main limitations in binding other materials to gold, Johnson explains: The binding is relatively weak, so the attached molecules can come loose with heating, and the connection does not typically conduct electricity well, limiting use in .

The MIT team envisioned that certain carbenes can overcome both hurdles. In so doing, they would enable a wide variety of applications, Johnson says, such as in the development of .

"You could scale down to the molecular level by wiring a molecule between two ," he says. "It would be the smallest possible component."

Others have tried to do this with thiol-based connections, but these have a rather large resistance. By comparison, preliminary indications suggest that carbenes could provide highly conductive linkages: " could flow through it like a wire," Johnson says.

These carbenes could function as "surface anchors" to link many compounds to many different surface materials—a process known to as "functionalizing" the surface. Johnson says, "I can count on one hand the number of methods you can use to functionalize surfaces, and they are different for different surfaces. If we could find a general one, that could make a big difference."

Carbenes—specifically, a type the MIT team calls addressable N-heterocyclic carbenes (ANHCs)—may provide such a generalized solution. While further experiments will be needed to confirm the material's performance, the technology holds much promise.

It was already known, Johnson says, that some carbenes can bond securely to a variety of metal surfaces, as well as many other materials. But there had been no investigation of their possible use as anchors, stably binding dissimilar materials.

Such combinations could be used as biosensors, for example: A molecule designed to bond with a specific biological marker could be attached to a gold wire, activating a circuit when that marker bonds with it. It could also be used to create protective surface coatings: antifouling surfaces to prevent buildup of biological deposits, or antibiotic coatings to prevent the spread of infections.

Another possible application might be to coat gold nanoparticles with a biomolecule that binds to tumors. The particles could then be heated using infrared light, killing the tumors with heat. ANHC coated surfaces could be beneficial in this regard, as they should be stable at higher temperatures, which would prevent particle degradation.

Once specific applications are found, the material has great potential because "it's cheap to make, and you can make it at large scale," Johnson says.

Brent Segal, chief scientist for nanotechnology at Lockheed Martin's Advanced Technology Center in Billerica, Mass., says this work "represents a shift in the paradigm for attachment chemistry to metal atoms." He adds that, "When I first learned of the approach, I said, 'Finally!' It seems as if someone might have come across something like this previously, but in terms of novelty, Johnson and his team have really executed beautifully to work out details for a viable system approach."

Segal cautions, however, "As is often the case, this is still quite early-stage work and will have various hurdles yet to overcome. Scaling up the material and understanding the limitations of performance in various solutions … will be paramount."

Explore further: Recycling industrial waste water: Scientists discover a new method of producing hydrogen

More information: The paper is titled "Addressable Carbene Anchors for Gold Surfaces." pubs.acs.org/doi/abs/10.1021/ja401965d

Related Stories

Gold squeezed into micro-Velcro

Feb 08, 2013

Researchers at Ruhr University have used self-assembling techniques to produce gold microwires that have suitable properties for micro-Velcro. The research is published today in Science and Technology of ...

Recommended for you

A greener source of polyester—cork trees

Apr 16, 2014

On the scale of earth-friendly materials, you'd be hard pressed to find two that are farther apart than polyester (not at all) and cork (very). In an unexpected twist, however, scientists are figuring out ...

A beautiful, peculiar molecule

Apr 16, 2014

"Carbon is peculiar," said Nobel laureate Sir Harold Kroto. "More peculiar than you think." He was speaking to a standing-room-only audience that filled the Raytheon Amphitheater on Monday afternoon for the ...

Metals go from strength to strength

Apr 15, 2014

To the human hand, metal feels hard, but at the nanoscale it is surprisingly malleable. Push a lump of metal with brute force through a right-angle mould or die, and while it might look much the same to the ...

User comments : 0

More news stories

Hackathon team's GoogolPlex gives Siri extra powers

(Phys.org) —Four freshmen at the University of Pennsylvania have taken Apple's personal assistant Siri to behave as a graduate-level executive assistant which, when asked, is capable of adjusting the temperature ...

Deadly human pathogen Cryptococcus fully sequenced

Within each strand of DNA lies the blueprint for building an organism, along with the keys to its evolution and survival. These genetic instructions can give valuable insight into why pathogens like Cryptococcus ne ...

Researchers discover target for treating dengue fever

Two recent papers by a University of Colorado School of Medicine researcher and colleagues may help scientists develop treatments or vaccines for Dengue fever, West Nile virus, Yellow fever, Japanese encephalitis and other ...