Progress toward Light-Harvesting Self-Electrophoretic Motors: Highly Efficient Bimetallic Nanomotors and Micropumps in Halogen Media

Significance Statement

Many new technologies have been developed by fabricating and manipulating materials at the micro- and nano- scale level. But still, no technology has been developed to fully control the motion of these materials at micro and nanoscale level. For this, it is necessary to understand motion on a nanoscale.

Self-electrophoretic motors have the ability to undergo directed motion by generating an electric field. A bimetallic nanorod, composed of platinum (Pt) and gold (Au) in hydrogen peroxide (H2O2) was the first synthesized electrophoretic motor. This motor exhibits directed motion with a speed of about 5−20 μm/s. Self-electrophoresis happens due to the generation of an ion gradient across the motor surface due to asymmetric bipolar decomposition of H2O2.

Professor Ayusman Sen and Dr. Flory Wong from the Pennsylvania State University came up with a self-electrophoretic bimetallic motor, composed of silver (Ag) and platinum. The research work is now published in peer-reviewed journal, ACS Nano. This motor is efficient and bubble-free. In dilute aqueous solutions of iodine (I2), the nanometer acts as a nanobattery with the reduction of the iodine at the platinum end and oxidation of silver to silver iodide, resulting in the formation of an gradient of iodide (I) ions. This motor exhibits directed motion, moving at 10−20 μm/s. The speed of the motor depends on the current density, which in turn depends on the iodine concentration. Motion ceases when iodine is fully consumed.

In the presence of light, the redox reaction is reversed and the battery is “recharged.” In effect, the redox reaction acts as conduit for light energy conversion (light energy to mechanical motion). The designed silver-platinum motors are the most efficient of the currently known self-electrophoretic bimetallic motors, consuming less fuel because of the absence of side reactions.

The same chemistry can also be used to fabricate micropumps that cause directional fluid flow. The pumps involve the deposition of a silver patch on a platinum surface and fluid flow is initiated upon the addition of an aqueous solution of iodine. Although there are no moving parts, the pump allows the directed transport of fluid and suspended particles, and can be used to separate particles based on their surface charge.

The reported study is first step towards the design of light-harvesting autonomous moving systems. “Robotic motors and pumps that derive their propulsive energy directly from ambient light and uses little or no chemical fuel, and do not require an external power source to function, are likely to find applications that require minimal human intervention” according to Prof. Sen.  

About the author

Ayusman Sen is a Distinguished Professor of Chemistry at the Pennsylvania State University. He is Fellow of both the American Association for the Advancement of Science and the Royal Society of Chemistry.

His research interests encompass catalysis, polymer science, and nanotechnology. He is the author of approximately 360 scientific publications with an H-index of 75, and holds 25 patents. Sen’s pastime centers on enological and gastronomical explorations.  

Journal Reference

Flory Wong, Ayusman Sen, Progress toward Light-Harvesting Self-Electrophoretic Motors: Highly Efficient Bimetallic Nanomoters and Micropumps in Halogen Media, ACS Nano, 2016, 10 (7), pp 7172–7179

Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.

 

 

Go To ACS Nano

 

Check Also

Applying electric field to assemble nanostructured filaments for sustainable electronics - Advances in Engineering

Applying electric field to assemble nanostructured filaments for sustainable electronics