In the exciting intersection between biology and nano-scale engineering, comes the development of bionic particles that are capable of mimicking photosynthesis. These are the first bionic particles to be created by combining plant proteins and semiconductors. Furthermore, these particles are capable of fully assembling themselves. Applications of this technology might one day provide us with clean energy alternatives and better ways to clean up pollution.
Bionics can be described as electronic and mechanical systems that function like or as part of a living organism. Bionic technology is perhaps best known for its use in regenerative medicine—specifically its applications towards replacing or restoring the function of human body parts. Bionic technology, though still quite limited in its capacities when compared to a fully functional human body, has already restored functionality in the limbs of in quadriplegics, integrated into prosthetic limbs, and has helped the blind to see and the deaf to hear.
However, researchers from the University of Michigan and the University of Pittsburgh have taken the field of bionic technology to a whole different scale—the scale of molecules. In the coming online edition of Nature Communications, the members of this collaborative team will report having created the first bionic particles. The purpose of these particles? To generate chemical energy from sunlight in the same way that plants photosynthesize.
The technology is aimed at perhaps being an alternative method of creating solar energy. Currently generating solar energy remains inefficient—even at their best, single-junction solar cells are only 33 percent efficient at converting the sun’s light energy into electricity.
Another possibility is to use bionic particles to aid in the clean break down of pollutants. Researchers investigated this possibility by exposing their photosynthesizing nanoparticles to nitrate pollutants. They subsequently observed the conversion of nitrate into oxygen and nitrite.
These first bionic particles are a combination of semiconductors and proteins that play a critical role in the photosynthetic process. Telluride—the semiconductor—is a key component of most modern solar panels. When light strikes it, the material generates electrons in a high-energy state. These excited electrons can then be pulled into a pathway that generates chemical energy with the help cytochrome C—a protein that is essential to the photosynthetic process in plants (shown above).
Combining the electron-exciting powers of telluride with the chemical-energy-generating powers of cytochrome C is best accomplished by having the two components in very close proximity to each other. The research team addressed this issue by designing a self-assembling process by which the super-particles containing both telluride, cytochrome C, and several key enzymes spontaneously form. The resulting super-particles measure about 100 nanometers in diameter.
Self-assembly also carries the additional advantage of particles being able to re-generate themselves even after they have broken down. This is a very important feature because of the natural wear-and-tear that occurs to molecules that absorb light. Even in nature, the molecules used in the photosynthetic pathway also break down. However in the case of living organisms, these particles can naturally be replenished.
Now that the process of self-assembly in bionic particles is better understood, the research team is aiming to expand its inquiries to other nanoparticle-protein systems. The holy grail of their research would be to design photosynthetic bionic particles that could convert water and carbon dioxide into natural gas—thereby creating a sustainable energy source that would allow current USA energy infrastructure to remain in place.
By Sarah Takushi