Navigation Links
Successful Test Of Single Molecule Switch Opens The Door To Biomolecular Electronics

A team of scientists led by biophysicist Stuart Lindsay from the Biodesign Institute at Arizona State University has created the first reproducible single molecule negative differential resistor ?and in the process has developed a groundbreaking experimental technique that provides a “roadmap?for designing single-molecule devices based on biochemistry.

The findings were presented Feb. 18 by Lindsay at the American Association for the Advancement of Science annual meeting in Washington , D.C. , in a session titled “Frontiers in Bioinspired Materials and Nanosystems.?The findings also will be reported in a forthcoming edition of the American Chemical Society’s journal Nano Letters.

Lindsay’s team reports achieving an experimental result that physicists have been trying to detect for a long time: negative differential resistance in a single molecule attached to electrodes.

The specifically designed molecule, a hepta-aniline oglimer, belongs to a group of molecules that biochemists believe to be capable of being molecular switches but that have failed to exhibit those properties in conductance experiments. The team solved the problem by developing a technique where the molecule could be tested in an electrolyte solution, a condition that past experiments didn’t attempt because of the problem of interaction between the solution and the electrodes.

“Almost everything we know about charge transfer in molecules is based on measurements made with the molecules suspended in solution,?Lindsay says. “Chemists have understood for a while that the solvent itself plays a major part in charge transfer processes ?the ions in the solution are necessary to make the process happen. Yet almost every ‘molecular electronic?measurement made to date has been made in a vacuum or other conditions that suppress solvent-mediated events. It’s no wonder that we could not get reliable results.?/p>

Though numerous molecules have been identified as targets for use as nano-scale electronic components such as switches, photoelectric devices and hydrogen generators, some major technical problems have stymied further research. The first of these has been the difficulty in making reliable connections with single molecules to test their electronic behavior. Recently, this problem may have been solved by using the scanning probe microscope to make and measure single-molecule contacts, with molecules designed to bond at their ends with a surface and the probe tip.

The second problem has been that these connected molecules have failed to exhibit the predicted electrical properties when tested without a conducting solution. Physicists attempting these measurements avoided using electrolyte solutions because the applied current would leak into the surrounding solution. Lindsay and his team solved this problem by applying an insulating coating to the entire probe, except its very tip, so there was minimal electrical contact with the solution.

According to Lindsay, the solution is required to make the process work because, without it, the initial insulating property of the molecule prevents the first electron from ever jumping on to the molecule, a kind of “Catch-22.?Ions in the solution “jiggle?the molecule enough to bring about an unusual configuration of the molecule that does allow the electrons from the electrodes to jump on to the molecule, a process first pointed out by Rudy Marcus of Cal Tech (for which he was awarded the 1992 Nobel prize in chemistry).

The oligoaniline molecule the team tested has three electrical states: a neutral state where it is an insulator, a second state where electrons are removed to oxidize the molecule and make it a conductor, and a third state where more electrons are removed and turn it back into an insulator. By measuring the connected molecule in a sulfuric acid solution, the team was able to make reproducible measurements showing all three states by measuring the current thr ough it as electrons were removed by another electrode, turning it from an insulator to a strong conductor and then back into an insulator again.

Given the measured electrical properties of the oligoaniline, Lindsay notes that if the molecule is maintained at its highly conductive state (at low voltage) and then the voltage applied to the molecule is increased, the connections to the molecule will rip electrons out of the molecule, pushing it back into its insulating state. This decrease of current with increasing voltage is called “negative differential resistance?(NDR) and it allows a useful device to be made with just two electrodes, not the three originally used.

“NDR is the basis for memories, switches and logic elements,?Lindsay says. “It has been observed in molecules before but never in controlled conditions, never at low voltages, and not in a predictable way.?/p>

Lindsay stresses that the main value of the finding is not in having found a molecule that could be developed into a working electrical switch, but in discovering some critical design parameters that should make possible successful research in designing molecular devices.

“We have a working rational roadmap now for how to do this, and we’re already hard at work applying it to a wide variety of potentially exciting applications,?he says.

Authors on the Nano Letters paper are Lindsay, who also is the Nadine and Edward Carson Professor of Physics and Chemistry and Biochemistry at ASU; ASU physicists Fan Chen, and Jin He; and Columbia University chemists Colin Nuckolls, Tucker Roberts and Jennifer E. Klare.


'"/>

Source:Arizona State University


Related biology news :

1. Visceral Leishmaniasis: Successful Vaccine Trial In Dogs
2. Penn Surgeons Use Completely Robotic Surgery to Successfully Treat Prostate Cancer
3. Successful cell engineering may lead to mad cow prevention, say researchers
4. Successful transplantation from pig embryos to mice
5. Successful lung cancer surgery not enough to break nicotine dependence in many smokers
6. Novel Asthma Study Shows Multiple Genetic Input Required; Single-gene Solution Shot Down
7. Single stem cells from bone heal a broken heart
8. Single-donor Islet Transplantation Procedure Shows Promise For Patients With Type 1 Diabetes
9. Single gene is genetic switch for fly sexual behavior
10. Single microRNA causes cancer in transgenic mouse
11. Single cell amoeba increases MRSA numbers 1000- fold
Post Your Comments:
*Name:
*Comment:
*Email:


(Date:6/22/2016)... 22, 2016   Acuant , the ... solutions, has partnered with RightCrowd ® ... Visitor Management, Self-Service Kiosks and Continuous Workforce ... add functional enhancements to existing physical access ... venues with an automated ID verification and ...
(Date:6/20/2016)... -- Securus Technologies, a leading provider of civil ... investigation, corrections and monitoring announced that after exhaustive ... the final acceptance by all three (3) Department ... (MAS) installed. Furthermore, Securus will have contracts for ... October, 2016. MAS distinguishes between legitimate wireless device ...
(Date:6/9/2016)...  Perkotek an innovation leader in attendance control systems is proud to announce the ... employers to make sure the right employees are actually signing in, and to even ... ... ... ...
Breaking Biology News(10 mins):
(Date:6/27/2016)... PHILADELPHIA , June 27, 2016  Alex,s Lemonade ... announced that that it will open a state-of-the-art bioinformatics ... childhood cancer research. This announcement comes as Liz ... attends the National Cancer Moonshot Summit in ... Dr. Biden as a participant and advocate of pediatric ...
(Date:6/27/2016)... -- Global demand for enzymes is forecast to grow ... billion.  This market includes enzymes used in industrial ... animal feed, and other markets) and specialty applications ... beverages will remain the largest market for enzymes, ... containing enzymes in developing regions.  These and other ...
(Date:6/27/2016)... GUELPH, ON , June 27, 2016 /PRNewswire/ - BIOREM ... it has been advised by its major shareholders, Clean ... LP, United States based venture ... common shares of Biorem (on a fully diluted, as ... for the disposition of their entire equity holdings in ...
(Date:6/27/2016)... , June 27, 2016  Sequenom, Inc. (NASDAQ: ... enabling healthier lives through the development of innovative products ... the United States denied its ... the claims of Sequenom,s U.S. Patent No. 6,258,540 (",540 ... criteria established by the Supreme Court,s Mayo Collaborative Services ...
Breaking Biology Technology: