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Glowing tags make nano-submarines easier to track

15 June 2016

The next generation of nanosubmarines have tags that fluoresce longer allowing them to be tracked for greater periods while being driven through solutions.

Rice alumnus Víctor García-Lopéz holds a vial of the original nanosubmersibles developed at Rice University. (Credit: Jeff Fitlow/Rice University)

The single-molecule vehicles may someday be used to deliver drugs or other cargo, says James Tour, chair in chemistry and professor of computer science and of materials science and nanoengineering at Rice University who introduced the technology last year.

The first nanosub, USN-1, could be monitored but not imaged by a technique that would irradiate it with light for very short times. But that didn’t provide any information about the submersible’s trajectory, says Víctor García-Lopéz, a former Rice graduate student and lead author of a new paper published in the journal Organic Letters. He is now a postdoctoral researcher at ETH Zurich.

The latest model, the 334-atom USN-2, can be viewed by single-molecule microscopy for at least 1.5 seconds, long enough for 30 frames of video.

“This makes it possible for us to track the trajectory of a single nanosubmersible,” Tour says. “It should lead to a better understanding of how our vehicles move.”

The lab attached cyclooctatetraene (COT) to the molecule’s body and motor to keep them from bleaching, which quenches fluorescence. The light-driven motor is a tail-like ligand that spins about a million times per second. The new subs, like the originals, are capable of moving 15m per second over nanoscale distances, based on the thrust provided by each turn of the rotating motor.

Between the frequent collisions that stop their forward motion, Tour says, they are “the fastest-moving molecules ever seen in solution.”

The nanosubmarines still can’t be steered in the traditional sense, but researchers are satisfied for the moment with achieving “enhanced diffusion” that lets them figure out how to move a one-molecule vehicle in a solution of similarly sized molecules.

“The next step is to track these nanosubmarines in solution and see if we can use them to deliver cargo or interact with cells,” Tour says.

Other researchers from Rice and from Toho University in Japan, and Tel Aviv University are coauthors of the study that was funded by the National Science Foundation, the Ministry of Education, Culture, Sports, Science and Technology of Japan, the Yamada Science Foundation, the Israel Science Foundation, and the European Research Councils.

The original article can be found on the Futurity website.

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