JPH01110224A - Photoelectric transducer - Google Patents

Abstract

PURPOSE:To eliminate the complication in adjustment of an photoelectric transducer, by interposing a photosynthetic granule between electrodes. CONSTITUTION:An electrode 2 is provided on a substrate 1 and a dry immobilized film 3 of a photosynthetic granule and an electrode 4 as opposed pole are arranged sequentially thereon 2. A lead 5 is led out of electrodes 2 and 4. A photosynthetic granule employs chlorophyll or chromatophore. A supply source of a photosynthetic granule is most preferably from photosynthetic bacteria. The general photosynthetic bacteria is exemplified by Rhodopseudomonas bilidis (ATCC19567), Rhodospirillum rubrum (ATCC11170) and Rhodobacteriaceae ferroidis (ATCC17023). Other than the photosynthetic bacteria, the photosynthetic granule can be obtained from cyanophycean chlorella, aquatic plants, terrestrial plants and the like.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a photoelectric conversion element using biomaterials.

(Problems with the Prior Art) Photosynthetic granules, which are vesicles made of biological membranes containing components involved in photosynthetic reactions, can be obtained from cells of photosynthetic organisms such as plants and photosynthetic bacteria. These photosynthetic granules are closed vesicles composed of membranes made of proteins, lipids, etc. It is widely known that this type of membrane has a photosynthetic reaction center protein complex that performs photoelectric conversion reactions, and that a potential difference is generated across the membrane upon light stimulation. Construction of a photoelectric conversion device using a film of these photosynthetic granules (hereinafter referred to as a photosynthetic film) is being considered.

As a method of constructing the device, electrodes are inserted into photosynthetic granules,
It is possible to directly measure the membrane potential or collected current or to use the output, but since the chromatobore of photosynthetic bacteria, which is a photosynthetic granule, is a closed bag with a diameter of about 1000 angstroms, it is difficult to insert an electrode into it. was too small and difficult, and it was impossible to construct a photoelectric conversion element by such a method.

In addition, we created a dried solidified Chromatobore membrane across two graphite electrodes spaced apart on a flat plate, applied a high voltage between the electrodes, and found no phenomenon in which the conductivity of the Chromatobore membrane changed due to optical stimulation. [Proc, Na
tl, Acad, Sci.

46, pp. 769-776 (1960)], it has not been reported so far to obtain a photoinduced potential directly from a chromatobore.

On the other hand, if a photosynthetic membrane such as Chromatoboa is developed and immobilized on the electrode with the front and back sides of the membrane aligned, it will respond to optical stimulation.
It is easy to infer that the potential can be observed. However, in order to do this, it is necessary to deploy a photosynthetic membrane such as a microscopic bag-shaped chromatoboa with the front and back sides of the membrane aligned with the electrode, or to orient the constituent components of the photosynthetic membrane with respect to the electrode. However, it is difficult to achieve this with current technology, and research to date has only made it possible for materials with special properties. For example, fragments of the purple membrane of the halophilic photosynthetic bacterium Helobacterium halobium, which is the membrane of the photosynthetic membrane I There is a technique [Japanese Patent Application Laid-Open No. 62-63823] that utilizes the technique to orient and adhere on electrodes by electrophoresis, making it possible to observe potential generation by optical stimulation. It is known that the photosynthetic reaction center, which is a component of the chromatobore, is isolated and spread on the water surface using the Langmuir-Prodgett method to create a monomolecular film or a laminated film on the electrode. It has not yet been possible to achieve arbitrary orientation [Biochim, Biophys, Act
a, 681 volumes.

pp. 191-201 (1982), Chem, Phys.
, Lett, vol. 116, pp. 405-410 (1985
), Biochim, Biophys.

Acta, Vol. 851, pp. 3B-48 (1986).

These methods require complicated work steps such as decomposition of photosynthetic membranes, purification of components, and preparation of thin films, and the reality is that these methods have not yet been used industrially.

(Problems to be Solved by the Invention) Therefore, the present inventors repeatedly investigated a simpler method for preparing a photoelectric conversion element, and found that a photosynthetic granule solution was applied to the surface of a conductive material forming an electrode, dried, and It has been found that even when a conductive substance made of a material different from the above-mentioned conductive substance is brought into contact with the surface, a photoelectric response to optical stimulation is observed between the electrodes.

This phenomenon places emphasis on molecular orientation (a finding that can be said to be completely unexpected from a conventional perspective). Up until now, it has been considered to utilize the potential and current generated between the front and back sides of the photosynthetic membrane due to optical stimulation, but in order to align molecules on the electrode, it is necessary to decompose the photosynthetic membrane, purify its components, prepare thin films, etc. Complicated work has been required.

The present invention has been made based on such knowledge, and provides a novel photoelectric conversion element that solves the complexity of preparing conventional photoelectric conversion elements at once.

(Means for solving the problem) Chloroplasts or chromatobore are used as photosynthetic granules, but the most suitable source of photosynthetic granules is photosynthetic bacteria. Examples include S. viridis (ATCC 19567), Rhodospirillum rubrum (ATCC 11170), and S-Rhodobacter sphaeroides (ATCC 17023). It can also be obtained from other sources than photosynthetic bacteria, such as blue-green algae, chlorella, aquatic plants, and terrestrial plants. Indium Tin Oxide (ITO) is used for the electrode.
), tin oxide (NESA), metal vapor deposited film, semiconductor, etc. can be used. The electrodes applied to the present invention need to be made of different materials. The reason for this is that in order for a potential difference to occur between the two electrodes as a result of electrons separated at the photosynthetic reaction center of the chromatobore moving to the electrodes due to light stimulation, the work functions related to the ease of movement are different between the two electrodes. depending on what is considered necessary. Examples of such electrodes include NESA and mercury, ITO and gold, and gold and mercury.

Devices are generally prepared by means such as vacuum evaporation.
This is done by forming a conductive film on a substrate. Next, to prepare photosynthetic granules, photosynthetic bacteria etc. cultured under light irradiation are destroyed by a method such as ultrasonication, photosynthetic granules such as chromatoboa are collected, and the photosynthetic granules are coated on the electrode, dipping, spin cording, screen printing, etc. After coating using a technique such as offset printing, it is dried.

In this case, drying may be carried out by natural drying, vacuum drying, heating drying, etc., and vacuum drying is preferable. After drying, the opposite electrode is placed on top of the other, and the process is completed.

From the end of the picture electrode of the photoelectric conversion element prepared in this way,
By pulling out with electric wire etc., strobe, LED,
Potential and current changes in response to light irradiation from lasers, arc lights, etc. can be extracted.

(Example) The present invention will be explained in further detail by giving examples below.

1) [Culture of photosynthetic bacteria and preparation of chromatobore] Photosynthetic granules consisting of an endomembrane system obtained by crushing photosynthetic bacteria are called chromatobore. Rhodopseudomonas bilisis (ATCC 19567) was used as a photosynthetic bacterium and cultured at 30° C. under anaerobic light irradiation. The facepieces were collected by centrifugation and destroyed using ultrasound. After removing bacterial body debris and the like by low-speed centrifugation, chromatobore were collected by ultracentrifugation at 100,000×g or more, suspended in a buffer solution using a homogenizer, and then collected by ultracentrifugation again. This operation was repeated three times for purification.

2) [Preparation of spheroplast membrane vesicles generally
A cell such as a bacterium with its cell wall removed is called a spheroplast, and photosynthetic granules, which are membrane vesicles similar to chromatobore, can be obtained by preparing spheroplasts from photosynthetic bacteria using the method shown below. . Preparation of spheroplast membrane vesicles [Arch, Bioche
m, Bj.

phys, vol. 1985, p. 526-534 (1979
year)]. That is, Rhodobacter sphaeroides (
ATCC 17023) cells were treated with lysozyme to form spheroplasts, which were then lysed and membrane vesicles were prepared by centrifugal fractionation such as sucrose density gradient centrifugation.

3) [Structure of the device: A glass substrate with an area of about 6 square centimeters is coated with a tin oxide, ITOl, or gold vapor-deposited film as one electrode, and a chromatobore or spheroplast prepared with an absorbance of 100 at 1020 nanometers is placed on top of the glass substrate with an area of about 6 square centimeters. Membrane vesicle solution 20
After 0 microliter was evenly placed on it, it was evaporated and dried at room temperature. A counter electrode was created by depositing a metal on top of the dried assimilation film, placing a mercury ball on top, or press-bonding a film of metal foil such as tin (Figure 1).

4) [Measurement of photoelectric conversion] Optical stimulation was performed using a strobe lamp or LED.

A monitor was set up to measure the light intensity each time the light was emitted, and the light intensity was standardized. Electric wires were connected to each electrode of the device, and potential changes were observed using an oscilloscope.

Figure 2 shows the potential response to optical stimulation. In response to strobe light stimulation, they showed a rapid response time of less than a millisecond. Figure 3 shows the current response of the device to optical stimulation. The wavelength dependence of the potential response of the device prepared by this method is as shown in FIG. 4, and has a spectrum similar to the light absorption of the dried assimilated membrane of photosynthetic granules.

(Effects of the Invention) The photoelectric conversion element according to the present invention can use microorganisms that can be easily cultivated as a material source, and can also use photosynthetic granules as they are, which can be purified by an extremely simple method compared to semiconductor materials. Therefore, it is considered to be a useful technology for industrial use.

[Brief explanation of the drawing]

FIG. IA, FIG. IB, and FIG. IC show conceptual diagrams of the device configuration of the present invention. In the figure, 1 is a substrate, 2 is an electrode, 3 is a dry solidified film of photosynthetic granules, 4 is an electrode serving as a counter electrode, and 5 is an electric wire. As for the configuration of the device of the present invention, Figure IA shows the case where a gold vapor deposited film is used as 4, Figure IB shows the case where mercury is used as 4, and Figure IC shows 4.
The case is shown in which tin foil is crimped and used. FIG. 2 shows the photopotential response of the device of the invention. FIG. 28 shows NESA as 2 in FIG. 1, Chromatobore as 3,
An example of the response when mercury is used as 4 is shown below. Figure 2B is
An example of a photoelectric response is shown when 2 in FIG. 1 is NESA, 3 is a spheroplast membrane vesicle, and 4 is mercury. FIG. 2C shows a response example when ITo is used as 2 in FIG. 1, chromatobore is used as 3, and gold vapor-deposited film is used as 4. FIG. 2D shows a gold deposited film as 2 in FIG.
A response example is shown when chromatobore is used as 3 and mercury is used as 4. The vertical axis is voltage (millivolts), and the horizontal axis is time (
ms), arrows indicate stimulation by light pulses. FIG. 3 shows an example of the photocurrent response of the device of the present invention. As for the configuration of the element, 2 in FIG. IC was an ITO 13 chromatobore, and 4 was a tin foil crimp electrode. For optical stimulation, an LED (emission center wavelength: 850 nanometers) was used. The vertical axis is current (picoampere), the horizontal axis is time (milliseconds), and the broken line in the figure shows the light emission pulse of the LED. FIG. 4 shows the wavelength dependence of the photopotential response of the device of the present invention. In the figure, the black circles (.) indicate the maximum potential response corrected for the energy of irradiation light, and the solid line (-) indicates the absorbance of the chromatobore dry solidified membrane. The vertical axis shows electric potential for black circles and absorbance for solid lines. The horizontal axis indicates wavelength (nanometers). Patent applicant: Director of the Agency of Industrial Science and Technology Kozo Iizuka (Tsukuda/A) Figure 1 Figure 2 A ↓ ゛ B ↓ C↓ ro
↓Figure 3 Figure 4

Claims (1)

[Claims] A photoelectric conversion element with photosynthetic granules interposed between electrodes.