Bologna: The first artificial molecular pump powered by light

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Researchers at University of Bologna designed the first self-assembling molecular motor capable of converting light energy into work. The study was published in Nature Nanotechnology.

The new Leap (Light energy automatic pump) system developed at the University of Bologna can convert continuously and automatically the light energy of a constant source (such as the Sun) into mechanical work and it is the first example of an artificial molecular pump powered by light.

The other artificial molecular machines realized so far have highly sophisticated structures, cannot exploit their energy source in a continuous and autonomous manner, and cannot do work. Leap overcomes these limitations. Once the light is on, the device operates without the need of other external inputs, similarly to a combustion engine which runs autonomously as long as the fuel is supplied.

Unlike a combustion engine, Leap exploits a renewable energy (light) and does not generate waste products. The next goal of the research team is to incorporate the nanomotor in a membrane separating two compartments, and investigate its actual ability to “pump” molecules from a compartment to the other under the action of light.

The size of the motor is on the nanometre (millionth of millimetre) scale and it is extremely simple and adaptable to various purposes. It operates similarly to biological motors which regulate the transport of substances inside cells, or the contraction of muscles.

The motor is the only automatic and self-assembling molecular machine developed in the laboratory. It builds up by itself and, if exposed to sunlight, it functions in an autonomous fashion without the need of human intervention.

Nature Nanotechnology says the nanodevice has been designed and tested by a team of researchers at the “G. Ciamician” Department of Chemistry of the University of Bologna. The team was coordinated by Alberto Credi and composed of Giulio Ragazzon, Massimo Baroncini, Serena Silvi and Margherita Venturi.

The development of artificial nanomotors is of great significance both to increase our understanding of biological nanomotors and to construct a new generation of ultra-miniaturized devices capable, for example, to actively affect cell mechanisms, and treat diseases by preventing or repairing biological damages.

Moreover, building a nanodevice that can use light to transport molecules is the first step forward towards the development of new methodologies for the conversion of solar energy into chemical energy. It is well known that such a conversion is of crucial importance for the exploitation of solar energy in many fields of technology.
 
The project

Leap is the result of a project that started four years within a broader research track pursued by the Photochemical Nanoscience Laboratory, an internationally recognized leader in nanotech research. The laboratory already caught the attention of the general public by developing a prototype of a nanometre scale elevator (published in Science in 2004) and of a molecular electrical extension cable (published in Proceedings of the National Academy of Sciences in 2006).

The research is taking the concepts of “device” and “machine”, to the nanometre level. It is generally considered that nanotechnology will not only lead to lighter, tougher and smarter materials and to smaller and more powerful computers, but also revolutionise medicine and other areas of science and technology.

The motor


The molecular motor consists of two components in shape of a ring and a string respectively. Scientists ensured that each molecular ring and string yield rapidly and efficiently a threaded assembly. This is already an amazing result, since the diameter of the ring is only 0.7 nanometres.

The ring threads the string only by passing over the azobenzene unit (in green). An incoming photon of light causes a profound structural change in the azobenzene: the new species (in red) not only blocks the backward motion of the ring but also pushes it until dethreading occurs from the other side of the string. Another photon regenerates the original azobenzene form (in green), thus enabling the system to restart the cycle. Overall, by the action of light, the ring molecules are repeatedly transported along the molecular string in a specific direction for a distance of about 1.7 nanometers. Under the conditions used in the experiments, at room temperature in a volume of 1 milliliter, the system pumps about 20 billions of ring molecules per second.

 


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