Researchers at MIT have developed a new way of revealing the presence of specific chemicals — whether toxins, disease markers, pathogens or explosives. The system visually signals the presence of a target chemical by emitting a fluorescent glow.
The approach combines fluorescent molecules with an open scaffolding called a metal-organic framework (MOF). This structure provides lots of open space for target molecules to occupy, bringing them into close proximity with fluorescent molecules that react to their presence.
The findings were reported in the Journal of the American Chemical Society in a paper by assistant professor of chemistry Mircea Dincã, with postdoc Natalia Shustova and undergraduate student Brian McCarthy, published online in November and to appear in a forthcoming print issue.
The work could have significant applications in sensors attuned to specific compounds whose detection could be read at a glance simply by watching for the material to glow. “A lot of known sensors work in reverse,” Dincã says, meaning they “turn off” in the presence of the target compound. “Turn-on sensors are better,” he says, because “they’re easier to detect, the contrast is better.”
Mark Allendorf, a research scientist at Sandia National Laboratory, who was not involved in this work, agrees. “Present materials generally function via luminescence quenching,” and thus “suffer from reduced detection sensitivity and selectivity,” he says. “Turn-on detection would address these limitations and be a considerable advance.”
For example, if the material is tuned to detect carbon dioxide, “the more gas you have, the more intensity in the response,” making the device’s readout more obvious. And it’s not just the presence or absence of a specific type of molecule: The system can also respond to changes in the viscosity of a fluid, such as blood, which can be an important indicator in diseases such as diabetes. In such applications, the material could provide two different indications at once — for example, changing in color depending on the presence of a specific compound, such as glucose in the blood, while changing in intensity depending on the viscosity.
MOF materials were first produced about 15 years ago, but their amazing porosity has made them a very active area of research. Although they simply look like little rocks, the sponge-like structures have so much internal surface area that one gram of the material, if unfolded, would cover a football field, Dincã says.
The material’s inner pores are about one nanometer (one billionth of a meter) across, making them “about the size of a small molecule” and well suited as molecular detectors, he says.
The new material is based on the MIT team’s discovery of a way to bind a certain type of fluorescent molecules, also known as chromophores, onto the MOF’s metal atoms. While these particular chromophores cannot emit light by themselves, they become fluorescent when bunched together. When in bunches or clumps, however, target molecules cannot reach them and therefore cannot be detected. Attaching the chromophores to nodes of the MOF’s open framework keeps them from clumping, while also keeping them close to the empty pores so they can easily respond to the arrival of a target molecule.
Ben Zhong Tang, a professor of chemistry at the Hong Kong University of Science and Technology, who was not involved in this work, says the MIT researchers have taken “an elegant approach” to producing functional MOFs, and “have already demonstrated the utility of their MOFs for detection and differentiation of normally difficult-to-distinguish” molecules called volatile organic compounds.
Tang says the new system still needs further refinement to improve the efficiency of production, which he says should be easily accomplished. Once that is achieved, he says, it could find many uses. “Many more applications may be envisioned: For example, the MOFs may serve as smart vehicles and monitors for controlled drug deliveries,” with the additional benefit that “the fluorescence should be gradually weakened in intensity along with progressive release of the drugs, thus enabling in situ real-time monitoring of the drug release profiles.” But for now, he says, “the work is excellent in terms of proof of concept.”
The work was supported by MIT’s Center for Excitonics, an Energy Frontier Research Center funded by the U.S. Department of Energy, and by the National Science Foundation.
Caroline McCall | EurekAlert!
Cancer diagnosis: no more needles?
25.05.2018 | Christian-Albrechts-Universität zu Kiel
Less is more? Gene switch for healthy aging found
25.05.2018 | Leibniz-Institut für Alternsforschung - Fritz-Lipmann-Institut e.V. (FLI)
The more electronics steer, accelerate and brake cars, the more important it is to protect them against cyber-attacks. That is why 15 partners from industry and academia will work together over the next three years on new approaches to IT security in self-driving cars. The joint project goes by the name Security For Connected, Autonomous Cars (SecForCARs) and has funding of €7.2 million from the German Federal Ministry of Education and Research. Infineon is leading the project.
Vehicles already offer diverse communication interfaces and more and more automated functions, such as distance and lane-keeping assist systems. At the same...
A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.
The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...
At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.
At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...
There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?
At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...
So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics
Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...
25.05.2018 | Event News
02.05.2018 | Event News
13.04.2018 | Event News
25.05.2018 | Event News
25.05.2018 | Machine Engineering
25.05.2018 | Life Sciences