single-molecule devices
Credit: Venkatraman lab.

Researchers Create First-Ever Single-Molecule Devices That Can Be Turned ‘On’ and ‘Off’ Using Only Light

A team of researchers based at the Columbia University School of Engineering and Applied Science says they have successfully constructed single-molecule devices that can effectively be switched on or off using nothing but light.

According to a press release from the team, this first-ever successful creation of “highly conductive, tunable single-molecule” devices could lead to nano-scale electronic machines or sensors that are activated by a single wavelength of light. Such devices could offer numerous applications ranging from biology and agriculture to security or even espionage.

Single-Molecule Devices May Be Natural Endpoint of Continually Shrinking Electronics

Electronic devices are continually shrinking, opening up an increasing number of possibilities that had previously seemed like science fiction. Some include things like nano-scale robots that can be injected into the human body to conduct repairs at the cellular level. In contrast, others include things like miniature spy cameras that can conduct clandestine observations in plain sight.

Unfortunately, traditional semiconductors face challenges at the smallest scales. Some researchers have proposed bridging the gap with single-molecule devices that use organic molecules to conduct electrons. Still, they have also faced challenges, particularly when it comes to operating them externally.

Now, the Columbia researchers say they have found a process to create such single-molecule organic devices that can be controlled with light.

“With this work, we’ve unlocked a new dimension in molecular electronics, where light can be used to control how a molecule binds within the gap between two metal electrodes,” said Latha Venkataraman, a pioneer in molecular electronics and Lawrence Gussman Professor of Applied Physics and professor of chemistry at Columbia Engineering. “It’s like flipping a switch at the nanoscale, opening up all kinds of possibilities for designing smarter and more efficient electronic components.”

Using Light to Build an Organometallic Molecular Circuit

The study, published in the journal Nature Communications, was conducted by researchers from the Department of Chemistry, Columbia University, the Institute of Theoretical Physics, University of Regensburg, Germany, the Department of Chemistry, University of Southern California, Los Angeles, and the Department of Applied Physics and Applied Mathematics, Columbia Engineering.

In that publication, the researchers outline the painstaking work the team took to make their single-molecule dreams into a functional reality. Fortunately, Professor Venkataraman had over two decades of experience studying the properties underlying the idea of building single-molecule circuits with atomic precision that employ an organic molecule attached to each side by metal electrodes.

Still, connecting metal electrodes to organic, carbon-based molecules had proven difficult. This led the researchers to consider interfacing the metal electrical leads with metallic atoms already present within organometallic atoms.

The team ultimately selected a particular organometallic iron-containing ferrocene molecule that had just the right mix of organic properties to function at the nanometer scale and the presence of iron atoms within the cell itself. Notably, the researchers point out that these types of molecules are often considered to be tiny building blocks in the world of nanotechnology.

“Just like LEGO pieces can be stacked together to create complex structures, ferrocene molecules can be used as building blocks to construct ultra-small electronic devices,” the study’s announcement explains.

Next, the team exposed their selected cell to laser light, resulting in an electrochemically induced “direct bond” between the organic cell’s ferrocene iron center and the gold (Au) electrodes. This meant the team had successfully constructed a single-molecule electronic device that was essentially “turned on” using only the power of light.

“Our work thus supports an Fe-Au bond can be formed by manipulating the oxidation state of ferrocene using light, creating single-molecule devices linked through a metal-metal interface at room temperature,” the researchers explain.

“By harnessing the light-induced oxidation, we found a way to manipulate these tiny building blocks at room temperature, opening doors to a future where light can be used to control the behavior of electronic devices at the molecular level,” added the study’s lead author, Woojung Lee, a Ph.D. student in Venkararaman’s lab.

Unlimited Applications for Single-Molecule Devices Controlled by Light

Moving forward, the researchers say they plan to explore even more diverse chemistries that can be used to create different types of single-molecule devices. They also note great potential in their process due to a demonstrated ability to create light-switchable, ferrocene-based single-molecule devices, which they are also hoping to explore.

“The light-controlled devices could pave the way for the development of sensors and switches that respond to specific light wavelengths, offering more versatile and efficient components for a wide range of technologies,” the researchers explain.

Christopher Plain is a Science Fiction and Fantasy novelist and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at, or email him directly at