Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

From Bacterium to Semiconductor

01.02.2008
Proteins of photosynthetic bacteria can be used to generate photocurrent. How to do that – this can be learnt from the article by Russian researchers.

Researchers from different countries are accommodating to their purposes proteins of photosynthesis system bacteria. They are used as an active component of the photocurrent generation chain in the sensory and energy-storing systems.

In Russia, the problem is being addressed by specialists of the Lomonosov Moscow State University, Institute of Problems of Chemical Physics (Russian Academy of Sciences), Moscow Institute of Applied-Physics and the Institute of Chemical Physics (Russian Academy of Sciences). The researchers built proteins of reactionary center for purple bacteria photosynthesis into porous nano-crystalline films of titanium oxide.

Proteins of the photosynthesis system (bacteriochlorophyll, bacteriopheophytin and ubiquinones) – are natural solar energy bioaccumulators. Excited bacteriochlorophyll molecule transmits electron along the chain to other proteins of photosystem. These proteins attract attention of biophysicists due to high quantum yield of reaction of primary charge division and relative stability of these charges. As of today, there exist two different approaches to creation of hybrid light-storing and sensitive devices based on bacterial proteins. For elements of the first type, a layer of photosensitive molecules are applied on a metal (golden or platinum) or graphite plate. At that, the proteins should be orientated on the plate surface in a certain way. Depending on the protein disposition on the electrode, there occurs either a cathodic charge (in this case, the electron is carried from the electrode to proteins), or an anodic charge, if there occurs reverse direction current.

In the devices of the second type, the proteins are applied on meso-porous semicoductors made of metal oxide. In such systems, excited protein molecules transmit very quickly, within fractions of a picosecond, an electron into the semiconductor’s conduction band. Besides, the pores are so tightly stuffed with proteins, that the special procedure of their orientation may be omitted. Proteins will get orientated spontaneously on the electrode hydrophobic surface, the donor section being turned to the semiconductor.

The photocurrent density is directly dependent on both the porous film structure and on the quantity of protein molecules on the electrode. Therefore, the Russian researchers tried to obtain thick film (4 micrometers thick) made of titanium o?ide. The researchers selected a structure which is optimal to maximum protein sorbtion.

The TiO2 meso-porous films are obtained from nano-crystalline powders, which are added into special paste. They were applied on glass with a conducting covering of titanium- indium oxide. The film was dried up and calcined for 30-60 minutes at 550 degrees. Calcination adds mechanical strength to films. Then the plate was soaked in the photosynthetic proteins solution, and the main electrode was ready. The researchers managed to get a film with small pores and large specific surface area (300 m2/g). Thanks to the film depth and porosity, a lot of proteins get stuck to it, their concentration in the sample being 160 times higher than that in the solution. Proteins on the main electrode preserve activity even after the two week keeping in a refrigerator. Illuminating the electrode by red light, which only proteins react to, generates the anodic photocurrent of almost 2 microamperes. Titanium o?ide also reacts to white light, but presence of the photosynthesis system proteins in the electrode increases the photocurrent by more than twice.

The researchers note that nano-porous semiconductors possess not only a very high sorbing ability, but also tremendous energy diversity of surface states, which significantly impacts the electron transmission process.

Nadezda Markina | alfa
Further information:
http://www.informnauka.ru

More articles from Physics and Astronomy:

nachricht New manifestation of magnetic monopoles discovered
08.12.2017 | Institute of Science and Technology Austria

nachricht NASA's SuperTIGER balloon flies again to study heavy cosmic particles
07.12.2017 | NASA/Goddard Space Flight Center

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

Im Focus: Successful Mechanical Testing of Nanowires

With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong

Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...

Im Focus: Virtual Reality for Bacteria

An interdisciplinary group of researchers interfaced individual bacteria with a computer to build a hybrid bio-digital circuit - Study published in Nature Communications

Scientists at the Institute of Science and Technology Austria (IST Austria) have managed to control the behavior of individual bacteria by connecting them to a...

Im Focus: A space-time sensor for light-matter interactions

Physicists in the Laboratory for Attosecond Physics (run jointly by LMU Munich and the Max Planck Institute for Quantum Optics) have developed an attosecond electron microscope that allows them to visualize the dispersion of light in time and space, and observe the motions of electrons in atoms.

The most basic of all physical interactions in nature is that between light and matter. This interaction takes place in attosecond times (i.e. billionths of a...

Im Focus: A transistor of graphene nanoribbons

Transistors based on carbon nanostructures: what sounds like a futuristic dream could be reality in just a few years' time. An international research team working with Empa has now succeeded in producing nanotransistors from graphene ribbons that are only a few atoms wide, as reported in the current issue of the trade journal "Nature Communications."

Graphene ribbons that are only a few atoms wide, so-called graphene nanoribbons, have special electrical properties that make them promising candidates for the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

Blockchain is becoming more important in the energy market

05.12.2017 | Event News

 
Latest News

Making fuel out of thick air

08.12.2017 | Life Sciences

Rules for superconductivity mirrored in 'excitonic insulator'

08.12.2017 | Information Technology

Smartphone case offers blood glucose monitoring on the go

08.12.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>