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 NASA study improves search for habitable worlds
20.10.2017 | NASA/Goddard Space Flight Center

nachricht Physics boosts artificial intelligence methods
19.10.2017 | California Institute of Technology

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: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>