US 7052587 B2
In one aspect, the invention provides a photoelectrochemical (PEC) electrode or photoelectrode for use in splitting water by electrolysis. The photoelectrode has an electrically conductive surface in contact with an electrolyte solution. This surface is a doped tin oxide layer, which is in electrical contact with the semiconductor solar cell material of the PEC photoelectrode. In a variation of the present invention, another layer of metal oxide having transparent, anti-reflective, and conductive properties is disposed between the doped tin oxide layer and the semiconductor material.
1. A photoelectrode comprising a semiconductor layer having a first major surface in contact with an electrically conductive substrate, a second major surface in contact with a transparent, electrically conductive metal oxide (TCO) layer, a transparent, electrically conductive doped tin oxide (SnO2) layer adjacent said second major surface, said doped SnO layer arranged in electrically conductive contact with said TCO layer.
2. The photoelectrode of
3. The photoelectrode of
4. The photoelectrode of
5. The photoelectrode of
6. The photoelectrode of
7. The photoelectrode of
8. The photoelectrode of
9. The photoelectrode of
10. The photoelectrode of
11. The photoelectrode of
12. The photoelectrode of
13. The photoelectrode of
14. The photoelectrode of
15. The photoelectrode of
16. The photoelectrode of
17. The photoelectrode of
18. A photoelectrode comprising a semiconductor layer having a first major surface in contact with an electrically conductive substrate and a second major surface in contact with a transparent, electrically conductive doped tin oxide (SnO2) layer; wherein said semiconductor layer comprises photovoltaic, amorphous, silicon n-i-p material having said doped SnO2 layer in contact with p of said n-i-p.
19. The photoelectrode of
20. The photoelectrode of
21. The photoelectrode of
22. A photoelectrochemical device for electrolysis of water to produce hydrogen comprising:
a container housing a photoelectrode, a counter electrode and an electrolyte solution, said photoelectrode and said counter electrode spaced apart from one another in said container and each being in contact with said electrolyte solution;
a photoelectrode comprising: a semiconductor layer having a first major surface in contact with an electrically conductive substrate and a second major surface coated with a first conductive layer; said first conductive layer comprising a first metal oxide which is transparent, anti-reflective and electrically conductive; a second conductive layer comprising a second metal oxide which is transparent and electrically conductive; said second conductive layer adjacent to said second major surface and arranged in electrically conductive contact with said first conductive layer; and said second conductive layer being more stable in basic solutions than said first conductive layer;
said counter electrode comprising a metal;
said solution comprising a solvent which comprises water and a solute which comprises a base; and
an electrically conductive path between said photoelectrode and said counter electrode.
23. The photoelectrochemical device of
24. A photoelectrode comprising: a semiconductor layer having a first major surface in contact with an electrically conductive substrate and a second major surface coated with a first conductive layer; said first conductive layer comprising a first metal oxide which is transparent, anti-reflective and electrically conductive; a second conductive layer comprising a second metal oxide which is transparent and electrically conductive; said second conductive layer adjacent to said second major surface and arranged in electrically conductive contact with said first conductive layer; and said second conductive layer being more stable in basic solutions than said first conductive layer.
25. The photoelectrode of
26. The photoelectrode of
27. A photoelectrode comprising a semiconductor layer having a first major surface in contact with an electrically conductive substrate, a second major surface in contact with a transparent, electrically conductive metal oxide (TCO) layer, and a peripheral, surface defined by a thickness between said major surfaces of said semiconductor layer;
an electrically conductive material in contact with at least a portion of said peripheral surface of said semiconductor layer and in contact with said TCO layer; and
a transparent insulative layer adjacent said TCO layer.
28. The photoelectrode of
29. The photoelectrode of
30. The photoelectrode of
This invention relates to photoelectrochemical (PEC) devices for the solar photoelectrolysis of water to produce hydrogen.
Currently the major process by which hydrogen is produced is by the steam reforming of methane. Another means of making hydrogen is by the electrolysis of water. The electricity required for electrolysis is mainly derived from the electric power grid, and the predominant source of grid electricity, combustion of fossil fuels, generates emissions, such as nitrogen oxides and particulate matter, as well as carbon dioxide. One way to eliminate such emissions is to use solar generated electricity to electrolyze water to make hydrogen. Presently, efforts are directed toward improving the efficiency, durability, and cost of the hydrogen production processes.
However, systems consisting of solar cells to make electricity together with electrolyzers to dissociate water into hydrogen and oxygen are costly compared to producing hydrogen by the steam reforming of methane.
In one aspect, the invention provides a photoelectrochemical (PEC) electrode or photoelectrode for use in splitting water by electrolysis. The photoelectrode has an electrically conductive surface in contact with an electrolyte solution. This surface is a doped tin oxide layer, which is in electrical contact with the semiconductor solar cell material of the PEC photoelectrode. Such semiconductor solar cell is preferably a triple-junction amorphous silicon (a-Si) solar cell. Electrolyte solutions aggressively attack many kinds of surfaces including some metals and metal oxides by corrosion and dissolution. The doped tin oxide layer is robust with respect to aggressive attack by the electrolyte solution. The doped tin oxide material is a transparent conductive oxide (TCO), thus, it is electrically conductive and transparent. Such doped tin oxide is preferably fluorine doped tin oxide (SnO2:F).
In a variation of the present invention, another layer of metal oxide having transparent, anti-reflective, and conductive properties is disposed between the doped tin oxide layer and the amorphous semiconductor material. This inner metal oxide layer may be less robust with respect to aggressive attack by the electrolytic solution than the doped tin oxide layer. This inner metal oxide layer is deposited on the solar cell before the doped tin oxide layer. Such inner layer is preferably indium-tin oxide (ITO), which is typically used as an antireflection coating. ITO is also a TCO material. Thus, in this embodiment, there are two TCO layers.
In another embodiment, the semiconductor material of the photoelectrode is overlaid with a transparent, anti-reflective, electrically conductive metal oxide layer and such layer is protected by being overlaid with a non-conductive, transparent material, preferably glass, polymer, or plastic which is impervious to the electrolyte solution. The amorphous semiconductor layer has a peripheral surface and an electrically conductive material that in one embodiment is in contact with at least a portion of the peripheral surface of the semiconductor layer and is in contact with the TCO layer. The electrically conductive material preferably consists of a metal, metal polymer composite, or conductive sealant. By this arrangement, an electrically conductive path is provided from the semiconductor layer to the TCO layer and then to the electrically conductive material that is exposed to the electrolyte solution. The transparent insulative layer protects the TCO layer from contact with the aggressive electrolyte solution.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.
In one aspect of the present invention, there is provided a photoelectrochemical (PEC) device for electrolysis of water to produce hydrogen. The PEC device comprises a container housing a photoelectrochemical (PEC) electrode (photoelectrode), a counter electrode and an electrolyte solution. In a preferred aspect of the PEC device the TCO-coated photoelectrode is the anode and produces oxygen, while the counter electrode is the cathode and produces hydrogen. The photoelectrode and the counter electrode are spaced apart from one another in the container, and each electrode is in contact with the electrolyte solution. Preferably, the counter electrode comprises a metal such as Pt or Ni that is stable under the reducing conditions at the cathode and has a low overvoltage for hydrogen production. The electrolyte solution comprises a solvent which preferably comprises water, and a solute which preferably comprises a base. In a preferred embodiment the electrolyte is a basic (alkaline) aqueous solution. Use of an acid instead of a base is also possible. An acid is not recommended due to corrosion problems, but use of an acid or neutral salt in the electrolyte solution instead of a base is within the scope of the invention. An external (not in the solution) electrically conductive path is provided between the photoelectrode and the counter electrode.
The photoelectrode comprises a semiconductor layer, typically and preferably triple-junction a-Si, having first and second major surfaces. The first major surface is an electrically conducting substrate. In a preferred arrangement the first major surface is stainless steel (ss) on top of which is deposited a layer of silver, a layer of ZnO2, and then three layers of n-type, i-type, and p-type semiconductor materials (see Deng and Schiff, 2003, “Amorphous Silicon Based Solar Cells,” Chapter 12, pages 505–565 in Handbook of Photovoltaic Engineering, ed. A. Luque & S. Hegedus, by John Wiley & Sons, Ltd., such chapter separately published on Xunming Deng's website: http://www.physics.utoledo.edu/˜dengx/papers/deng03a.pdf in 2002 by Deng and Schiff). The second major surface is a robust transparent conducting and transparent metal oxide layer that is in contact with a first metal oxide layer which comprises a first transparent, anti-reflective, and electrically conductive metal oxide material. A second or outer metal oxide layer comprises a second transparent and electrically conductive material. This second layer is adjacent the second major surface of the semiconductor. The second metal oxide layer is arranged in electrically conductive contact with the first metal oxide layer; and the second metal oxide layer is more stable in basic solution than the first metal oxide layer. Preferably, the second layer forms the electrode surface where evolution of gaseous electrolysis product, typically oxygen, occurs.
In a preferred aspect, the first metal oxide material (first TCO) comprises indium tin oxide, In2O3:SnO2, referred to as ITO. The second metal oxide material (second TCO) is fluorine-doped tin oxide (SnO2:F). The SnO2:F is arranged in electrically conductive contact with the first TCO layer and is between the first TCO layer and the electrolyte solution.
In another related aspect, the invention provides a photoelectrode comprising a semiconductor layer having a first major surface in contact with an electrically conductive substrate and a second major surface in contact with a transparent, electrically conductive doped tin oxide (SnO2) layer; wherein the semiconductor comprises a photovoltaic, a-Si triple junction material.
In another embodiment, the invention provides a photoelectrode comprising a semiconductor layer having a first major surface in contact with an electrically conductive substrate, a second major surface in contact with a transparent electrically conductive metal oxide (TCO) layer. A transparent insulative layer is adjacent the TCO layer, and is disposed between the TCO layer and the electrolyte solution of the PEC device. The semiconductor has a peripheral surface defined by a thickness and an electrically conductive material is in contact with at least a portion of the peripheral surface of the semiconductor layer and is in contact with the TCO layer. The peripheral surface is also referred to as the outer surface or edges. Preferably, the electrically conductive material forms the electrode surface where evolution of gaseous electrolysis product occurs.
Before further describing the invention it is useful to understand the limitations of conventional designs. The production of hydrogen and oxygen via photoelectrolysis occurs in a cell wherein the electrolyte may be acidic, alkaline, or neutral. The arrangement of the cell and design of the electrode will be determined, at least in part, by the nature of the electrolyte. Typically, the generation of hydrogen using a photoelectrochemical cell requires a photoelectrode, and at least one counter electrode to the photoelectrode. Both the photoelectrode and its counter electrode are disposed in a suitable container having an electrolyte, which provides the source of hydrogen, and suitable ionic species for facilitating the electrolysis. The electrochemical cell typically utilizes a metal electrode such as Pt or Ni as the counter electrode.
In one arrangement, when the electrolyte is alkaline and the counter electrode is a metallic cathode, the reaction at the counter electrode is: 2H2O+2e−→H2+2OH−.
The reaction in the alkaline electrolyte at the photoelectrode which is a photoanode is: 4OH−→O2+2H2O+4e−.
When the electrolyte is acidic the reactions at the photoanode and at the counter electrode differ from the alkaline case. For example the cathodic reaction is: 2H+2e−→H2. The anodic reaction is: 2H2O→O2+4H++4e−. Notice that the H2 is produced at the cathode (the electrode where reduction occurs) and O2 at the anode (the electrode where oxidation occurs) in either acidic or basic conditions.
In a preferred system with a basic (alkaline) electrolyte, when the semiconductor photoanode is exposed to light, electrons are excited thereby creating holes in the valence band and free electrons in a conduction band. The electrons produced at the photoanode are conducted through an external conductive path to the counter electrode where the electrons combine with the water molecules in the electrolyte to produce hydrogen gas and hydroxide ions. At the photoanode, the electrons are provided from hydroxyl ions in the solution to fill holes created by the departure of excited electrons from the photoanode, and oxygen is evolved. For optimum performance, the semiconductor utilized in the system has a voltage in the necessary range to split water (1.6 to 2.2 volts) and in the preferred embodiment herein, such a semiconductor comprises a triple-junction photovoltaic type cell formed of amorphous silicon material.
Accordingly, the incident sunlight or simulated sunlight (electromagnetic radiation) absorbed in the semiconductor creates electron/hole pairs. The photo-excited electrons are accelerated toward the n-layer of the semiconductor due to the internal electric field at the p-n junction. The holes at the p-n junction are accelerated toward the p-layer of the semiconductor. When electrons and holes are accelerated with sufficient energy (voltage), they can react at the cathode and anode respectively, with ions present in the aqueous solution. Oxygen is evolved at the photoanode and hydrogen is evolved at the counter electrode (cathode) according to the reactions previously described hereinabove with respect to the alkaline or acidic solutions.
Conventional photovoltaic cells for the conversion of light into electricity are coated with indium-tin oxide (ITO). Such coating on the face of such cells is typically used as an anti-reflective coating and to collect the electric current from all parts of the cell surface, so that individual solar cells can be interconnected to form solar modules and panels. Due to their corrosion, such coatings have not heretofore been found suitable for use in the aggressive environment of an electrolysis cell.
Accordingly, one of the problems faced in optimizing conventional devices is the corrosion of the ITO and subsequent destruction of the semiconductor by the electrolyte. Indium-tin oxide coatings have not yet been developed to withstand the environment at such an interface. We found that when an n-type layer is adjacent to the electrolyte (a so-called pin device), and it is attempted to make hydrogen on the irradiated electrode (cathode), in a reducing type process, degradation of the ITO coating immediately occurs in the electrolyte.
Accordingly, the design of the present invention is based upon having the p-type layer adjacent to the ITO and on having the fluorine-doped tin oxide layer exposed to the electrolyte. This so-called n-i-p device provides a photoanode that can withstand the corrosive anodic production of oxygen. External connection of the anode to a metal counter electrode where hydrogen evolves completes the photoelectrolysis cell. In this preferred cell arrangement, the hydrogen and oxygen production reactions can be physically separated so the gases do not mix.
Because the very aggressive or corrosive reaction of oxygen production is occurring at the n-i-p type electrode (anode) of the present invention, there is a strong tendency for degradation of the ITO coating on the electrode at the electrolyte interface. The present invention addresses this difficulty by a novel design for such electrodes. By the present invention it is possible to use such coated cells in an electrolysis environment because the design of the present invention provides the necessary protection for such exposed ITO-coated electrode surfaces.
The metal epoxy sealant 13 was applied beneath the protective glass shield window 11 and contacted the conductive ITO layer 14 of photoelectrode 12. Note that the ITO was applied to the photovoltaic cell as an anti-reflection coating 14 and is also used to conduct electric current from the outer (p-layer) of the triple-junction a-Si solar cell 15. Thus, when the PEC device 10 was exposed to simulated solar radiation, the metallic composite sealant 13 very effectively conducted electric current from the solar cell photoelectrode 12 to the electrolyte (for example, aqueous KOH) 16 to split water and evolve hydrogen at the counter electrode 20 and oxygen at the photoelectrode 12. An area of the conductive sealant 13 approximately equal to the area of the a-Si solar cell photoelectrode 12 was left exposed to the electrolyte 16 to act as the anode while a nickel or platinum cathode 20 of approximately equal area was connected to the metal substrate or stainless steel backing 25 which forms the opposite pole (cathode) of the photoelectrode 12. The glass shield window 11 effectively kept the basic electrolyte 16 from contacting and attacking the ITO coating 14 and a-Si materials 15 of the PEC photoelectrode 12. This protective window design extended the lifetime of a PEC electrode immersed in 1 molar aqueous KOH. A PEC electrode with only a standard ITO coating (90% In2O3, 10% SnO2) lasted about 2 to 3 hours for water splitting in the KOH solution. An indefinitely long lifetime, greater than four days when irradiated with simulated sun light with an estimated irradiance of 120 to 140 mW/cm2 (at which time the test was ended) , was observed for the present design of PEC electrode 12 having both glass 11 and the ITO coating 14. Other transparent materials including transparent polymeric coatings and sealants, which can be applied to the front of the PEC electrode 12 more easily and cheaply than glass, can also be used for this shield 11 part of the PEC electrode 12 design. Oxygen bubbles are evolved at the metal composite sealant 13 (anode) of photoelectrode 12 and hydrogen is evolved at the metal cathode 20.
The silver composite 13 was an effective catalytic surface for electrolysis lasting an indefinite time, greater than several days. Severe gray discoloration (silver tarnish) formed on the surface of the silver composite. This suggests other alternative metals may be preferred in the composite 13. Nickel/resin composites, including nickel powder in epoxy and other metal powders in resin binders, are appropriate lower-cost sealants to replace silver epoxy for the purpose of this invention. A mixture of several conductive and catalytic metals in a binder could also be used.
In electrolysis experiments using PEC devices 10, nickel electrodes proved to be very corrosion resistant in KOH solutions and had good catalytic properties for hydrogen evolution from water splitting. Nickel oxides, iron oxides, molybdenum oxides, ruthenium oxides, and other transition metal oxides, and the corresponding metallic transition elements may also be added to the composite sealant (anode) or applied to the metal cathode 20 used as the hydrogen electrode to better catalyze the electrolysis reactions.
In testing both PEC 10,
The inexpensive materials used in constructing the PECs 10 and 50,
The technique used to obtain a SnO2:F coating on glass, as in
Spray pyrolysis techniques for preparing SnO2:F coatings are known and one example is described in a paper by Arcosta et al., 1996, “About the structural, optical and electrical properties of SnO 2 films produced by spray pyrolysis from solutions with low and high contents of fluorine,” Thin Solid Films, 288, 1–7. Several methods for producing SnO2:F films as known in the art are described, with spray pyrolysis being the least expensive. In the standard spray pyrolysis method, a spray solution of SnCl4 was dissolved in ethanol together with NH4F, and such solution was sprayed on substrates maintained at about 300° C. This temperature is considered a relative upper limit for a-Si-based PEC electrode. Thus, the spray pyrolysis technique may be useful in producing SnO2:F coatings directly on top of the ITO.
In another variation, a PEC photoelectrode 92 of
In still another variation a PEC electrode 102 of
Thus, the doped tin oxide 87 may be applied directly onto the ITO 84 (
The doped tin oxide coated transparent glass used in the example of
There are both electrically conductive and non-conductive epoxy systems that can be used for applications such as the aggressive basic environment of the photoelectrochemical device of the present invention. One such chemically resistant epoxy system which is non-conductive is available from Epoxies, Etc., of Cranston, R.I. and under the description of 20-3004 HV (high viscosity), which is a two component chemically resistant epoxy system with capability of good bonding to a variety of substrates.
The electrically conductive epoxy adhesive coating was also obtained from Epoxies, Etc. and the specific type was 40-3905 which is an electrically conductive system designed for applications requiring good adhesions to a variety of substrates such as metal, ceramic, glass, phenolics, and included a solvent free epoxy system filled with pure silver as the conductive agent.
In the preferred embodiment of the present invention, such PEC cell comprises a photovoltaic amorphous silicon triple junction cell. Such an amorphous silicon-based cell comprises amorphous silicon thin-film materials deposited by a preferred rf plasma enhanced chemical vapor deposition method (PECVD), as described in Deng and Schiff, 2003, “Amorphous Silicon Based Solar Cells,” Chapter 12, pages 505–565 in Handbook of Photovoltaic Engineering, ed. A. Luque & S. Hegedus, by John Wiley & Sons, Ltd., such chapter separately published on Xunming Deng's website: http://www.physics.utoledo.edu/˜dengx/papers/deng03a.pdf in 2002 by Deng and Schiff. Amorphous silicon and silicon germanium materials for high efficiency triple-junction solar cells are fabricated by United Solar, ECD, Fuji, University of Neuchatel, BP Solar, Canon, University of Toledo and Sharp. For the experiments described herein, the triple-junction amorphous silicon solar cells were purchased from the University of Toledo (Professor Xunming Deng). The process is conducted in an ultra-high vacuum multi-chamber arrangement, in a system isolated from the environment. Preferably two deposition chambers are used. One chamber is used for the growth of a-Si and a-SiGe materials. By alloying the Si with Ge the band gap of the resulting semiconductor, and thus the production of photoelectrons by light quanta, can be adjusted, so that the solar spectrum is more efficiently used. The other is used for the preparation of n-type, a-Si and p-type microcrystalline silicon (μc-Si) layer. In the method, Si2H6 GeH4 and hydrogen are used for the deposition of a-Si and a-SiGe materials, respectively. Deposition of p-layers is accomplished using BF3 doping, while deposition of n-layers is accomplished using PH3 doping. The combination of the n- and p-layers, along with an i-layer in between them to improve performance, ultimately forms the a-Si and a-SiGe n-i-p junctions. Even though the triple-junction cells contain Ge, and the amorphous silicon is hydrogenated amorphous silicon (a-Si:H), they are referred to as a-Si cells.
A preferred substrate is stainless steel foil, with or without a silver-zinc oxide back reflector coating, for supporting the silicon-based layers. The top of the silicon based electrode is covered with a layer of ITO deposited by use of an rf sputtering chamber, using various mixtures of In2O3 and SnO2 having predominately In2O3 and varying amounts of SnO2, for example 5%, 10% and 15% SnO2. The sputtering conditions for the ITO coating are these: sputtering target=90% In2O3/10% SnO2; deposition time=50 min; temperature=215° C.; pressure=8 mTorr; atmosphere=argon containing 0% oxygen; radio frequency (rf) power=50 Watts. The thickness of the ITO coating was approximately 4200 Angstroms. The ITO coatings were prepared by a sputtering process as described earlier hereinabove (Proceedings of 2nd World Conference and Exhibition on Photovoltaic Solar Energy Conversion, 1998) and conducted at the University of Toledo.
The aforesaid solar cells have three pin junctions to utilize a wide range of the solar spectrum using a technique called “spectrum splitting”. The upper cell (pin junction) utilizes the ultraviolet and some of the visible region of the solar spectrum to generate photoelectrons. The middle cell uses the visible and some portion of the infrared region, while the bottom cell uses some of the visible more of the infrared region to generate photoelectrons. The three cells are arranged in series so their respective voltages are added together. The bottom layer, meaning that layer adjacent the zinc oxide/silver/stainless steel substrate in the preferred semiconductor of the present invention, is the n-type semiconductor of the bottom cell. The top layer, meaning the layer adjacent to the ITO, is the p-layer of the top cell. There are intermediate i-layers between the n- and p-layers of each cell.
The series electrical arrangement of the aforesaid three cells makes it possible to achieve a potential of over 2 volts suitable for the electrolysis of water. Theoretically, it is possible to electrolyze water at 1.23 volts. With inherent losses, referred to as over voltages, a potential of at least 1.6 volts is needed for water electrolysis. Thus, the approximately 2-volt potential produced by the triple-junction a-Si arrangement is quite satisfactory.
Several types of multijunction solar cells are known for direct conversion of sunlight to electricity in a-Si photovoltaics. Dual-junction a-Si/a-SiGe cell and triple junction a Si/a-SiGe/a-SiGe cells enable a “spectrum splitting” to collect the sunlight, and this achieves higher conversion efficiencies. It is known that a-Si(1.8 eV)/a-SiGe(1.6 eV)/a-SiGe (1.4 eV) triple-junction solar cells are among the most efficient a-Si based cells.
Discussion of the design, construction, and advantages of amorphous silicon solar cells, including triple-junction amorphous silicon solar cells is contained in Deng and Schiff, 2003, “Amorphous Silicon Based Solar Cells,” Chapter 12, pages 505–565 in Handbook of Photovoltaic Engineering, ed. A. Luque & S. Hegedus, by John Wiley & Sons, Ltd., such chapter separately published on Xunming Deng's website: http://www.physics.utoledo.edu/˜dengx/papers/deng03a.pdf in 2002 by Deng and Schiff. A review of the basic photoelectrochemical properties of amorphous silicon based structures can be found in Proceedings of the 2002 U.S. DOE Hydrogen Program Review NREUCP-610-32405 entitled, “Photoelectrochemical Systems for Hydrogen Production”, authored by Varner et al., 2002; and “Proceedings of the 2000 Hydrogen Program Review” NREL/CP-570-28890 entitled, “Photoelectrochemical Hydrogen Production”, authored by Miller and Rocheleau, 2000.
The invention described here comprises a photoelectrochemical (PEC) device made from an inexpensive triple-junction amorphous silicon (a-Si) solar cell that is protected from corrosion by a durable transparent and electrically conductive material. This design results in a practical method for direct generation of hydrogen by in-situ electrolysis of water. Such a system can potentially produce large quantities of hydrogen much more cheaply by eliminating the elaborate electric collection grid and mounting needed by photovoltaic cells. In PEC devices, greater efficiency is achieved by supplying electrons from the active silicon directly through the shortest distance to catalyst layers deposited on the outside where hydrogen and oxygen are evolved. Each of the three stacked solar cells in the triple-junction device absorbs a portion of the solar spectrum and is used to boost the voltage output of the device to over two volts—more than enough to split water (it takes a minimum of 1.23 volts to split water, and for practical purposes more than 1.6 volts is needed to overcome “overvoltage” effects at the electrodes). Here, a-Si cells are inexpensive compared to crystalline or polycrystalline-silicon and especially compared to highly efficient but very expensive crystalline semiconductor wafers such as GaAs, GalnP2, and AlGaAs. In addition, a variety of bases may be used besides KOH, such as Na2CO3 or NaOH. Use of acids and neutral salts are within the scope of the invention to produce the aqueous electrolyte.
The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.


Anthracene can be used as a scaffold for intramolecular SN2 degenerate reactions of the “bell clapper” type, where a central boron atom or its isoelectronic carbocation bonds alternatively towards one or the other lateral Lewis bases at the first and eight anthracene positions. This ping-pong bond-switching reaction possesses a symmetrical double-well potential with low activation barrier and relatively narrow barrier width. Herein we show by computational means the active role played by heavy atom quantum tunneling in this degenerate rearrangement reaction at cryogenic temperatures. At these conditions the thermal “over the barrier” reaction is forbidden, whereas the tunneling effect enhances the rate of reaction up to an experimentally measurable half-life. Kinetic isotope effects and cryogenic NMR spectroscopy can, in principle, experimentally demonstrate the tunneling mechanism.
A good deal of attention has been paid to the established chemistry of hypercoordinated compounds , , , , ,  (also called, controversially, hypervalent systems) by both experimentalists and theoreticians, due to their unique reactivity and properties. These molecules are usually described by a three-center four-electron bond , , and are typical within main group elements in and below the third row of the periodic table. Pentacoordinated bond formation by second row elements such as carbon and boron are, due to their low polarizability and high relative electronegativity, very scarce (though the trigonal bipyramidal geometry is common in the transition state of SN2 reactions). Still, they are possible, as many computational and experimental studies have shown , , , , , , , , , , , . For example, Akiba et al. ,  used an anthracene scaffold to synthesize potentially pentacoordinated carbocation and boron containing compounds (see CR,Y and BR,Y in Fig. 1). Although some species have very loose bonding between the boron or the carbocation to the lateral Lewis bases, and therefore cannot be considered as hypercoordinative (for instance BOMe,OMe or COMe,OMe), other molecules have tight symmetrical binding, showing a clear symmetrical pentacoordinated geometry (such as BF,OMe) .
Yet, other species prefer an unsymmetrical geometry, with the central atom leaning to one or the other donor group (for example BMe,NMe2 or BCl,NMe2) . These almost symmetrical molecules are of particular interest for the present research, as they can undergo a very fast intramolecular degenerate bond-making and breaking between the sp3 central atom and the lateral substituents. This rearrangement occur through a symmetrical SN2 mechanism, as was shown by 1H NMR and DFT studies, in what was called a “bell-clapper” mechanism (Fig. 1) , , . The energy barrier for this rearrangement reaction was found to be too small to measure by the NMR coalescence method. Encouraged by the low barrier and small displacement of the central carbon or boron, we envisaged that these reactions may occur by heavy atom tunneling, analogous to a quantum ping-pong game .
Quantum mechanical tunneling (QMT) of hydrogen is a well-known effect that has been widely studied both experimentally and theoretically , . The extent to which tunneling occurs in a chemical reaction depends on the barrier width (w), barrier height (ΔE‡), and atomic masses (m) of the moving parts of the molecule, according to:
where P is the tunneling probability (“barrier permeability”), and x is a factor that depends on the shape of the potential energy curve . It can be seen from eq. 1 that the tunneling probability is particularly sensitive to the barrier width (a variable with no significance in semi-classical transition state theory), making the amplitude of the atomic movements the most critical factor for a swift tunneling. In this sense, it was recently shown that “heavy” atom tunneling (i.e. atoms from the second row of the periodic table) is indeed possible, as long as the barrier height is low and, more important, the barrier width is markedly narrow , . The first experimental evidence of such kind of tunneling was found in the automerization (aka π-bond shifting) of cyclobutadiene , , . From there, several other documented reactions emerged, such as the ring expansion of methyl-cyclobutyl-fluorocarbene , ring opening of cyclopropyl-carbinyl radical , , degenerate rearrangement of semibullvalene , , ketenimine ring expansion , and ring closure of cyclopentane-1,3-diyl ,  (see also Refs. , ,  and references within). All these examples share the already cited characteristics: a low and narrow activation barrier. To the best of our knowledge, the heaviest atom predicted to tunnel from the ground state in a realistic (albeit theoretical) reaction involves a fluorine, in another case of a quantum ping-pong mechanism . We can divide all these reactions in two groups, the exothermic ones (asymmetric reaction profiles such as the cited ring expansion, opening or closing), and the isothermic ones (degenerate rearrangements with symmetric reaction coordinates, such as the cyclobutadiene and semibullvalene cases). In the latter group, which includes our current bell-clapper reaction, we can also find many examples of H-transfer, such as proton sponges and formic acid dimer , , .
In this work, through computational tools we predict the boron and carbon atom tunneling by rapid bond switching on the bell clapper mechanism (Fig. 1). Additionally, we propose an experimental test to check the QMT effect by NMR spectroscopy.
To accurately account for the rates of reaction, especially including tunneling corrections, it is critical to properly describe the potential energy surface. Hence, in order to select a suitable functional and basis set in terms of accuracy and computational cost, we performed benchmark calculations on the barrier height (ΔE‡) of the title reaction using fourteen different DFT functionals (four GGAs –B97D3, PBE, BLYP and BP86–, three meta-GGAs –BB95, MN15L and TPSS–, three hybrid-GGAs –PBE0, TPPSh and B3LYP–, and four hybrid-meta-GGAs –B1B95, BMK, MN15 and M06-2X–) in combination with five basis sets (Def2-SVP, 6-31+G(d), 6-31+G(d,p), aug-cc-pVDZ and aug-cc-pVTZ, the latter taken only as a reference, as it is currently impossible to carry out SCT tunneling computations on medium sized molecules with this basis set). All these methods were benchmarked against DLPNO-CCSD(T)/aug-cc-pVQZ//MN15/aug-cc-pVTZ energies for the rearrangement of BH,NF2 and CH,NH2. The resulting best combination (ΔE‡ within 0.9 kJ·mol-1 for the former and 0.5 kJ·mol−1 for the latter), and the one we used for all the computations, was MN15/aug-cc-pVDZ , a method that stretched our computation capabilities to the limit. DFT geometry optimizations and frequency calculations were carried out with Gaussian16 , while the DLPNO-CCSD(T) ,  benchmark was computed with ORCA4.0 ,  with the “tightPNO” option .
For the tunneling corrections there are various approximate methods that can be used to study the reaction rate, such as the use of a parabolic potential, the Eckart barrier, or the renowned Wigner approximation . However, these approximations lack the thermal-activated tunneling correction from the vibrationally excited states level and the possibility to “cut-corners” to pass through the least-action pathway (were the barrier height may be higher than the TS, but the atom trajectory, the main factor for a fast QMT, is shorter) . A highly demanding but accurate method that include the above effects is the small-curvature tunneling (SCT) methodology , . This method has the extra capability of mapping the potential energy surface with multidimensional contributions by calculating energies, gradients and second derivatives not only at the reactant and transition state geometries, but also at many points along the reaction pathway. We carried out all the semi-classical dynamics with the canonical variational transition-state theory (CVT) , and the QMT corrections with SCT using the POLYRATE package , with GAUSSRATE  as the interface with Gaussian16. After some accuracy tests we decided to use a step size of 0.002 Bohr, with the quantized reactant state tunneling (QRST) method .
As a crude but fast method to pre-filter the systems with potential for reacting via QMT at cryogenic temperatures, we considered the tunneling limit (TL) approximation , . This expression, based on eq. 1, is written as:
where m is the mass of the tunneling determining atom (TDA) whenever there is a clear one (see below), ΔE‡ the activation energy, and w½ the barrier width taken at half the barrier height (in here we estimated it by the difference between the long and short X–Y distances divided by two). Previous tests indicate that TL linearly correlates with the logarithm of accurately computed rates , , where reactions with TL<10 could, in principle, react by QMT from the ground state in a sensible experimental time.
Results and discussion
Figure 1 shows the key intramolecular SN2 reaction (bell-clapper mechanism) for BR,Y and CR,Y. This reaction undergoes a bond switching between the central X and lateral Y groups via a C2v trigonal bipyramidal transition state structure which resembles a pentacoordinated bonding pattern, with a symmetrical double-well potential energy surface. Table 1 lists the activation energy, the bond length of the bonded (r1) and non-bonded (r2) X–Y bond, the effective barrier width (w½) and the tunneling limit (TL) for BR,Y and CR,Y studied systems.
In the original BCl,NMe2 system reported by Akiba et al. our computed activation energy is 39.7 kJ·mol−1, with bond distances of 1.675 and 3.137 Å for the shorter (r1) and longer (r2) B–N distances (see Table 1 and Fig. 1), in good agreement with the X-ray diffraction analysis (r1=1.664 and r2=3.129 Å) . The effective barrier width (w½=0.73 Å) is significantly narrower than the complete movement that the boron must travel, but it is a more accurate proxy to use for the TL; close to the minima the displacement of the atom requires a negligible energy, and therefore those sections of the reaction coordinate are kinetically irrelevant for tunneling. Still, the high TL value of 24.4 for BCl,NMe2 indicates that the reaction will not occur by QMT from the ground state. We therefore tuned the system by attempting various substitutions that would shrink both the barrier height and width, thus giving better candidates for tunneling. Due to clashing effects, this process is more trial an error than a systematic search. For instance, a weaker Y electron donor will make the short X–Y bond (r1) more labile and longer (with a lower ΔE‡), but it will make the long X–Y bond (r2) longer as well, compensating the effect; therefore, a weaker Y nucleophile may or may not lower w½ and TL. Similarly, a strong σ electron withdrawing atom in the R groups may also act as a π donor (as in the case of halogens), blurring the possibility of predictions. In addition, some steric hindrance pushes the Y groups inside (for instance when comparing Y=NH2 and NMe2), changing the potential energy surface exclusively by brute force. Still, a couple of rules of thumb can be grasped: the asymmetric potential with higher activation energy tends to be favored by stronger Y electron donors (compare BH,NH2 to BH,NCl2) or by weaker R π donors (BH,NF2 vs. BCl,NF2, the latter being a symmetrical pentacoordinated species, and therefore not included in Table 1). These effects strengthen the charge transfer interaction between X and Y.
Analyzing the trends between similar systems in Table 1 we can still find one clear, expected trend. Narrower w½ correlates with lower ∆E‡, hence both of them correlate with a smaller TL. This can be explained by considering the harmonic potentials of the reactant and product states being closer, which puts the crossing point in a lower position . Since our objective is to find systems with a fast QMT, low activation barriers should produce the desired outcome (as long as it is not so low that the system will prefer the C2v geometry!). Therefore, we carried out accurate QMT computations (SCT) on the most promising systems, BH,NCl2 and BH,NBr2 (TL=7.4 and 7.7, respectively). To our delight, we obtained quite fast tunneling rate constants of 590 and 61 s−1 (t½=1 and 11 ms), respectively, close to the absolute zero (that is, QMT from the ground state, where it is completely independent of the temperature). Considering that the computed semi-classical rates (CVT, without any tunneling correction) have the “impossible” values of k=5×10−45 and 5×10−54 s−1, we can ascertain that in cryogenic conditions the reaction occurs exclusively by a QMT mechanism. This might be, to the best of our knowledge, the first predicted case of a boron atom tunneling.
In parallel to the boron bell-clapper, also the isoelectronic carbocation-based reaction has been thoroughly studied in previous works , , , and therefore it is de rigueur to include it here. However, we must take into consideration that the necessary inclusion of a counterion in most experimental setup will change the reaction , and therefore our computational results will only match the experiment where the carbocation can be isolated at low temperature (for instance in a supersonic expansion equipment). Due to the much stronger interactions with Y, carbocations have much higher activation energies, with very stable Cs geometries. Hence, all the studied systems based on amine substituents were unsuitable for QMT (TL ≫10, see for example, CH,NH2 in Table 1). However, with much weaker Y groups there is a slim chance, as can be seen in Table 1 for halides, with TL=11.5 and 11.7 for CH,Cl and CH,Br, respectively (CH,F prefers the C2v geometry). The ensuing SCT computations yielded k=7×10−11 s−1 when approaching the zero Kelvin regime for CH,Br (with a semi-classical value of kCVT=3×10−139 s−1 at 6 K), which can hardly be considered a realistic tunneling (t½=300 years). But CH,Cl gave k=6×10−5 s−1 (t½=3 h, with kCVT=7×10−122 s−1 at 6 K), well within what can be considered “experimental time”. Therefore, this molecule can be included in the pantheon of systems that can react by carbon atom tunneling .
Figure 2a shows the Arrhenius plot of BH,NCl2 and CH,Cl. In the low temperature region, the SCT rate constants deviates from the classical CVT rates reaching a clear plateau where the rates become independent of temperature, a distinct signature of tunneling from the ground state. For BH,NCl2, at ~50 K the tunneling rate becomes dominant (kSCT=4×105 s−1, kCVT=9×104 s−1), while at ~30 K the semi-classical rate is negligible (kSCT=3×103 s−1, kCVT=3 s−1). Below ~10 K the rate is entirely dominated by heavy atom tunneling from the ground state (note that in the case of hydrogen tunneling the vibrational states are usually more separated, showing larger independence from the temperature compared to heavy atom QMT). For CH,Cl we start to see QMT dominance at ~75 K (kSCT=98 s−1, kCVT=38 s−1), negligible semi-classical reaction at ~40 K (kSCT=4×10−4 s−1, kCVT=10−8 s−1), and exclusive tunneling from the ground state again at ~10 K.
Considering the fast tunneling rate of the BH,NCl2 at cryogenic conditions, we decided to check the possibilities of QMT by substituting the lower carbon at the central anthracene ring. We expected that by having there a bulkier hetero atom, it will push out the lateral rings, bringing closer the Y groups and producing a narrower and lower rearrangement barrier. For this purpose we introduced a Si atom forming a 10-silaanthracene scaffold for BH,NCl2 (Scheme 1). Preliminary results suggested a large influence of the Si atom on the w½ (0.41 Å) and ΔE‡ (8.2 kJ·mol−1), producing a TL of only 6.2. However, and to our surprise, the rate constant for this system was extremely slow (kSCT=5×10−07 s−1, with t½=15 days) at 6 K, which can barely be considered as a viable tunneling mechanism. This stark disparity between the accurate SCT rate constants and the TL can be explained based on the displacement vectors of the imaginary frequency at the TS. In contrast to BH,NCl2, where the movement is basically centralized at the boron, the 10-silaanthracene structure leads to a more collective motion in the molecular reorganization. As the TL approximation depends on only one TDA, a system with several atoms moving concertedly interfere in the correct TL interpretation. This acts as a warning in the use of the simple tunneling limit model.
KIE and NMR probes for tunneling
To answer the question of which atom is determining the QMT rate, we carried out several isotopic substitutions on BH,NCl2. In principle, at low temperatures where the reaction goes exclusively by tunneling, the atom with larger kinetic isotope effect (KIE) should be the “tunneling determining atom” (TDA), that is the one hindering the QMT process the most. However, in practice this is not so easy to define, as the mass ratio for different atomic substitutions is completely different (especially when comparing light and heavy QMT). Still, there should be a correlation between the KIEs and the atoms with the larger displacement in the imaginary normal mode of the TS (at least when comparing atoms of comparable masses). Therefore, we carried out a detailed investigation of the KIE on the atoms that showed maximum movement at the TS. A close inspection of the translation vector for BH,NCl2 system showed, as expected, a large displacement of the boron, along with a slight movement of the lateral nitrogens and the hydrogens attached to the boron.
On substitution of these atoms by their isotopic analogues, B leads to the highest KIE (10B/11B) of 2.83 at cryogenic conditions, followed by a KIE (H/D) of 2.30 for the hydrogens, while for the nitrogens is, surprisingly, negligible (1.01), as can be seen in Fig. 2b. As we said before, it is not convenient to draw a distinction between the KIEs of light and heavy atoms due to the differences in their effective masses and isotopic mass ratio. However, for our system it can be explicitly seen that among the three studied KIEs the boron atom is the TDA, reflected by its remarkably high KIE. The KIE for hydrogens is, actually, very low, considering that the D/H mass ratio (2) is enormous compared to the ratio between the boron isotopes (1.1). In addition, there are two hydrogens involved, which would make the individual KIE approximately equal to the square root of both atoms taken together (KIE~1.52, considering that the hydrogens have independent influence on the KIE). We also checked the KIE (12C/13C) for the carbocation in CH,Cl, again producing a high value of 2.5, undoubtfully indicating that the reaction is occurring exclusively via QMT from the ground vibrational state, and that the carbocation is the TDA.
To provide an experimental proof for the detection of heavy atom tunneling in the bell-clapper reaction we propose the use of cryogenic solid-state NMR spectroscopy (a complicated but possible experiment ). The NMR coalescence temperature (TC) is defined as the temperature at which two separate peaks of exchanging pairs of atoms merge into a single peak. At this temperature, the coalescence rate constant (kC) is proportional to the frequency of the NMR equipment (υinst) and the separation of the chemical shifts (Δδ, in ppm), according to:
If the merging of peaks occurs at significantly lower temperature than what would be expected in a thermal mechanism, there we will have a sign of QMT , , . Table 2 lists the computed differences in the NMR chemical shift of the exchanging pairs of atoms and the corresponding kC values for systems BH,NCl2, BH,NBr2 and CH,Cl. In all these systems the coalescence rate constants for the hydrogens and nitrogens are much smaller than Cl and Br due to its small differences in their chemical shifts.
If our predictions are correct, in BH,NCl2 the peaks of all the equivalent atoms except Cl should be merged at any temperature due to tunneling from the ground state; in the hypothetical absence of tunneling two peaks would be observed for hydrogens and nitrogen below ~35 K. The significant difference between TCCVT and TCSCT is a strong indication of tunneling for this system, a prediction that, although not straightforward, can be experimentally tested. For BH,NBr2 the largest difference appears at the β-hydrogen atoms, where TCSCT is 37 K lower than TCCVT; only below liquid He temperature we will see two peaks, while in the absence of tunneling we would see two peaks up to 41 K. A similar but significantly less marked scenario should be seen for carbocationic system CH,Cl, where such a small TC difference with and without tunneling correction can hardly be taken as a strong proof of QMT.
In this paper, we have investigated intramolecular degenerate SN2 rearrangement reactions of the “bell-clapper” type, where a central boron atom (or its isoelectronic carbocation) switches bond alternatively with its lateral Lewis bases placed at one and eight position of the anthracene molecule. This rapid ping-pong like reaction can be accompanied by low activation energy and relatively narrow barrier width. Tuning of the systems by introducing relatively weak bases (such as nitrogen dihalides for the boron and halogens in the carbocation systems) at the lateral “Y” positions can significantly reduce the effective barrier width along with lowering in the energy barrier, making them an ideal system for heavy atom tunneling. Calculation including the small curvature tunneling (SCT) approximation reveals that the reaction on BH,NCl2 occurs exclusively by boron atom tunneling close to absolute zero, while the classical thermal over the barrier reaction is virtually non-existence. The remarkably high KIE for the B atom is also a witness of the QMT effect. To the best of our knowledge, this is the first example of reaction involving boron atom tunneling. Other promising candidates that are found to be driven by heavy atom tunneling are BH,NBr2 and CH,Cl, where the latter involves carbon atom tunneling. Additionally, we postulate an experimental test to probe the QMT mechanism by cryogenic NMR spectroscopy.
A collection of invited papers based on presentations at the 24th IUPAC International Conference on Physical Organic Chemistry (ICPOC 24) held in Faro, Portugal, 1–6 July 2018.
Funding source: Israeli Science Foundation
Award Identifier / Grant number: 631/15
Funding statement: This research was supported by the Israeli Science Foundation, Funder Id: http://dx.doi.org/10.13039/501100003977 (grant no. 631/15). A.N. acknowledges the financial support of the Negev-Tsin Scholarships.
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Analysis of Contract Pharmaceutical Fermentation Services market covering 30 + countries including analysis of US, Canada, UK, Germany, France, Nordics, GCC countries, Japan, Korea and many more
The contract pharmaceutical services manufacturing market is fairly fragmented, with manifold contract manufacturing organizations (CMOs) showing high dependence on limited number of clients. To gain a competitive edge in this highly fragmented market, contract pharmaceutical fermentation services’ providers are creating unique strategies based on prevailing pharmaceutical industry landscape and trends.
To capitalize on the growing trend of pharmaceutical companies avoiding internal capacity investment to embrace outsourcing, contract pharmaceutical fermentation services’ providers continue to embed advancing technology in their processes. Further, several contract pharmaceutical fermentation services providers are indulging into collaborations with local integrators.
To move ahead of the competition in contract pharmaceutical fermentation services market, leading players are focusing on extending and diversifying their businesses, as pharmaceutical industries turn to outsourcing to CMOs to underpin gains.
Detailed profiles of other leading market players operating in contract pharmaceutical fermentation services market have also been included in contract pharmaceutical fermentation services market report.
Key players operating in contract pharmaceutical fermentation services market include AbbVie, Inc., Aumgene Biosciences, EKF Diagnostics-Stanbio, Boehringer Ingelheim International GmbH, Biocon, AMRI, Pfizer, Lonza, CordenPharma International, and Fujifilm Holdings Corporation.
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The overall pharmaceutical industry has been changing and developing at a rapid pace with several manufacturing firms struggling with massive challenges caused by high market growth, frequently changing regulations, novel therapy and medicine forms as well as progressing digitization.
To address such challenges, pharmaceutical medicines’ manufacturers are increasingly mimicking already existing manufacturing equipment to further transfer them to contract manufacturing service providers. Being the core for production of a wide range of pharmaceutical based products, microbial fermentation has frequently evolved in recent past.
As a result several pharmaceutical manufacturers are deriving medical products from fermented products encompassing active pharmaceutical ingredients (API), which is further creating demand for contract pharmaceutical fermentation services for bulk supply.
The growing adoption of microbial fermentation as a production method for therapeutic proteins, fragmented antibodies, intermediates, peptides, etc., has become an optimal economic route for pharmaceutical companies to meet production demand and market delivery time.
This burgeoning demand for fermentation processes in tandem with the rapidly expanding pharmaceutical industry are likely to fuel growth in contract pharmaceutical fermentation services market in forthcoming years.
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Though the pharmaceutical industry is rapidly changing and accelerating, the basic understanding of diverse diseases at a molecular level is improving constantly. This growing understanding of different diseases is further accelerating the demand for faster production.
Amid the burgeoning production demand, several pharmaceutical companies are increasingly collaborating with contract pharmaceutical fermentation services’ providers to introduce innovative molecules in the market. Further the growing prevalence of diverse diseases, such as cancer, anemia, diabetes, rheumatoid arthritis, etc., is likely to boost demand for diverse pharmaceutical products with applications in disease management.
This widespread prevalence of diseased population that is constantly requiring therapies and treatment is triggering the demand for time-efficient drug production.
As contract pharmaceutical fermentation services’ providers offer reduced time-to-market for various key pharmaceutical products by collaborating with molecule owners and giving platforms for time-efficient drug development and other analytical services, their demand is set to grow. This growing trend is likely to trigger growth in contract pharmaceutical fermentation services market during the forecast period.
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Despite extensive utilization of fermentation processes, the technology is yet to gain maturity like chemical synthesis, in terms of adoption of mathematical models and optimization techniques.
The significant fermentation challenges, such as scale up and scale down fermentation, controlling insightful process parameters, mass transfer, and establishing novel sensors have been restraining market growth. Further the challenges associated with advanced therapy medicinal products that demand thoughtful and appropriate facility design and equipment continue to hinder contract pharmaceutical fermentation services market growth.
As contract pharmaceutical fermentation services need huge capital investment for set-ups and fulfilling technical staff requirements, several market players deal with large-scale fermentation challenges. Such challenges are likely to hamper growth in contract pharmaceutical fermentation services market in forthcoming years.
With manifold manufacturers, contract pharmaceutical fermentation services market remains highly fragmented, propelling service providers to seek novel and innovative ways of differentiating their services from counterparts.
Amid the rigorous competition in contract pharmaceutical fermentation services market, the service providers are increasingly focusing on value-added services which is likely to bring tremendous changes in the market, thereby paving way for growth opportunities.
Contract pharmaceutical fermentation services are mainly used by pharmaceutical industries when they need abundant fermentation of products required for the development of drug formulations.
Contract pharmaceutical fermentation services deploy different kinds of fermentation techniques with the help of skilled staff.
The report on contract pharmaceutical fermentation services market offers a comprehensive evaluation of the business opportunities in contract pharmaceutical fermentation services market.
It also offers insights on contract pharmaceutical fermentation services market outlook, and list of service providers in the contract pharmaceutical fermentation services market for the duration from 2018 to 2026.
Some of the additional questions addressed in report on the contract pharmaceutical fermentation services market are-
Key insights provided on contract pharmaceutical fermentation services market are fully based on dynamic research methodology deployed to create the contract pharmaceutical fermentation services market report.
The report on Contract pharmaceutical fermentation services is made of comprehensive primary and secondary researches to obtain significant information related to aspects of the Contract pharmaceutical fermentation services market.
Analysts have performed an in-depth research to attain the numbers mentioned in the report, such as, CAGR, y-o-y growth and revenue share of all the market segments.
The unique research followed by Fact.MR offers authenticity of every minute detail published in the report. The actionable insights related to Contract pharmaceutical fermentation services market are presented in easy to understand way to help clients in make well-informed decisions for future growth of their businesses in the contract pharmaceutical fermentation services market.
The Fact.MR report on contract pharmaceutical fermentation services offers a comprehensive taxonomy of the contract pharmaceutical fermentation services market on the basis of contract pharmaceutical fermentation service type, platform, product type, and end user of contract pharmaceutical fermentation services.
On the basis of service type, the global contract pharmaceutical fermentation services market has been segmented into development services and commercial services. On the basis of platform, the global contract pharmaceutical fermentation services market has been segmented into bacterial and fungal/yeast.
Based on product type, the global contract pharmaceutical fermentation services market has been segmented into bio-therapeutics, enzymes, peptides, plasmids, cytokines & growth factors, vaccines, others (fusion proteins, etc.).
By end user, the global contract pharmaceutical fermentation services market has been segmented into pharmaceutical companies, biotechnology companies, animal health companies, and academic & research institutes. Based on region, the contract pharmaceutical fermentation services market has been bifurcated into North America, Latin America, Europe, and Asia Pacific excluding Japan (APEJ), Japan, and the Middle East & Africa (MEA).
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Key players identified in the global market include AbbVie, Inc., Aumgene Biosciences and EKF Diagnostics-Stanbio
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Copper is one of the most widely used elements on earth. It is an essential element that can be found in everything from electrical wiring and plumbing to jewellery and coins. Copper has various physical properties that make it so useful and versatile. Let’s look at five properties that make copper an essential part of our modern world.
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Enriched with naturally hydrating honey and organic virgin olive oil, this translucent facial soap foams into a rich, creamy lather to gently and thoroughly cleanse skin while preserving its natural moisture balance.
This beauty bar is a great second step of the Japanese double cleanse regimen (after oil-based cleanser).
Ideal for all skin types.
sodium oleate, sodium palmitate, sucrose, sodium laurate, water/aqua/eau, glycerin, sodium myristate, sorbitol, sodium stearate, sodium behenate, tetrasodium etidronate, olea europaea (olive) fruit oil, alcohol denat., honey/mel/miel
Wet face with lukewarm water. Create lather in palms, then massage face and neck with foam to cleanse. Rinse thoroughly. To extend the life of the soap, do not allow to stand in water.


Information on Buying the Real Oregano Oil
Oregano oil is known to be an excellent medicinal herb that is useful in treating many conditions. It is simply an excellent antiviral, antibacterial, and antifungal that has the potential to protect against bacteria.
In addition, in the 15th century, Paracelsus used wild oregano to treat fungal diseases. Each of these details shows exactly how important oregano is to animal health. Until recently, natural oregano oil was used in animals to treat many ailments. In addition, its additional capabilities are now being identified by health researchers.
You can check out here https://www.feedworks.com.au/oregano-oil-for-animals/ to buy organic oregano oil for animals.
Image Source: Google
Oregano oil is an organic compound made from the oregano species. The oregano plant is found in remote mountainous areas that are free from air pollution. Essential oils are extracted only from the leaves of flowering plants. The leaves are chosen with care because the oregano plant contains the largest amount of essential oil.
This plant is hard to find and therefore not available almost everywhere. Oregano is commonly used in cooking and is often mixed with oregano oil. In common oregano oil is extracted from oregano vulgare.
Oregano essential oil consists of carvacrol, an organic phenol that can have a strong antimicrobial effect. On the other hand, the flavonoids in oregano provide organic antiseptic properties and the terpenes are organic anti-inflammatory components.
Wild Oregano Essential Oil is better known for masking the main antioxidant abilities and promoting bile circulation which greatly improves the process of digestive function.


Explore Essential Daily Vitamin + For Immunity
Estimated Delivery : Jun 09
You will not be charged until your order is shipped.
Return within 30 days if unopened and unused
Brimming with super antioxidant Vitamin C, BEAR Explore daily vitamins help promote improved immune function and support the production of energy. Vitamin E acts as a free radical scavenger and antioxidant to protect against cellular damage, while Rhodiola is used to enhance physical performance and improve the body's ability to adapt to stress.
- BEAR uses activated ingredients and potent botanical extracts of the highest quality and proven efficacy to deliver optimal bio-availability and ensure that nutrients are readily absorbed by the body
- Certified Organic
- Vegan, GMO-free, gluten-free, and non-toxic
- 60 tablets
- This item is not available for international export
- Revolve Style No. BAER-WU4
- Manufacturer Style No. EXPLORE
- Actual packaging and materials may vary. Please read labels, warnings, and directions before use.
How to Use
- Take one tablet in the morning or as professionally prescribed
- Vitamin supplements should not replace a balanced diet
- Store in a cool, dry place away from direct sunlight
Vitamin C (Ascorbic Acid) 150mg; Rhodiola rosea ext equiv to dry root 1.6g Standardized to rosavins 6mg; Natural Vitamin E (as d-alpha-Tocopherol) 10IU; Curcuma Longa (Turmeric) ext equiv to dry rhizome 50mg; Vitamin B1 (Thiamine Hydrochloride) 20mg; Vitamin B2 (Riboflavin Sodium Phosphate) 15.75mg; Vitamin B3 (Nicotinamide) 150mg; Vitamin B5 (Calcium Pantothenate) 46mg; Vitamin B6 Phosphate (Pyridoxal 5-Phosphate) 6.17mg; Vitamin B12 mecobalamin (co-methylcobalamin) 200ug;
Guided by respect for simplicity, design and function, BEAR brings together a portfolio of wellness essentials for the modern professional. With a clean, minimalist aesthetic, their products are designed to fit seamlessly into your morning routine. Made with the utmost care in Australia, BEAR carefully sources ingredients from small scale farms, cooperatives and leading laboratories from around the world and takes pride in designing and formulating each product with integrity and transparency.
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Placing a Special Order Inquiry is absolutely free and there is no obligation to follow through with a purchase.
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|Structural and thermodynamic signatures of marine microlayer surfactant films|In: Journal of Sea Research. Elsevier/Netherlands Institute for Sea Research: Amsterdam; Den Burg. ISSN 1385-1101, more
|Also published as |
- Pogorzelski, S.J.; Kogut, A.D. (2003). Structural and thermodynamic signatures of marine microlayer surfactant films, in: Ohlson, M. et al. (Ed.) Proceedings of the 22nd Conference of the Baltic Oceanographers (CBO), Stockholm, Sweden, 25-29 November 2001. Journal of Sea Research, 49(4): pp. 347-356, more
Enthalpy; Entropy; Structural dynamics; Surface films; Surfactants; Thermodynamic properties; ANE, Baltic, Gdansk Gulf [Marine Regions]; Marine
|Authors|| || Top |
- Pogorzelski, S.J.
- Kogut, A.D.
Natural surface film experiments in inland waters and shallow offshore regions of the Baltic and Mediterranean Seas were carried out in the time period 1990-1999 under calm sea conditions using a novel device for sampling and force-area studies. The sampler-Langmuir trough-Wilhelmy filter paper plate system `cuts out' an undisturbed film-covered sea area to perform pi-A studies without any initial physico-chemical sample processing. The limiting specific area Alim (2.68-31.57 nm2/molecule) and mean molecular mass Mw (0.65-9.7 kDa) of microlayer surfactants were determined from the 2D virial equation of state applied to the isotherms. Enthalpy deltaH and entropy deltaSt of the 2D first-order phase transitions were evaluated using the Clausius-Clapeyron equation applied to the isotherms. Miscibility of film components and film structure evolution is expressed by the scaling exponent y adopting the 2D polymer film scaling theory. The stress-relaxation measurements revealed a two-step relaxation process at the interface with characteristic times T1=1.1-2.8 and T2=5.6-25.6 seconds suggesting the presence of diffusion-controlled and structural organisation relaxation phenomena. The obtained results suggest that natural films are a complex mixture of biomolecules covering a wide range of solubilities, surface activity and molecular masses with an apparent structural organisation exhibiting a spatial and temporal variability.


This work was conducted to determine the effect of oxygen on hydrothermal liquefaction of softwood for the production of valuable chemicals. Softwood was subjected to liquefaction in the presence and absence of either 1.6 g/L sodium carbonate or 5 bar oxygen gas. The oxygen supplementation diverted sugars from dehydration toward oxidation resulting in 4-fold elevated yields of organic acids. Dissolved sugars and furans showed maxima in narrow temperature regions of 170-190 and 210-230 °C while the yields (weight percentage based on dry wood) of organic acids, phenolic substances, and bio-oil reached their respective maxima of 10.4%, 3.5%, and 7.4% at 230-270 °C. These results of oxidative hydrothermal liquefaction advance sustainable production of chemicals from renewable lignocellulose.
- organic acids


In the scientific community, the possibilities of using plastic in road construction have also been studied for some time. German road construction expert Prof. Johannes Beckedahl, who worked for a long time at the University of Wuppertal, thinks it's basically good to think about "upcycling" plastic waste, but is skeptical about prefabricated solutions like those used by VolkerWessels. He doubts that a durable road construction is possible with modules. The modules would have to be laid on the base in such a way that the same storage conditions exist everywhere. Otherwise, each module or precast element would settle unevenly under use. With the consequence of possible fractures or step formations. Beckedahl, on the other hand, takes a more positive view of processing plastic waste into granules. "A correctly produced asphalt modified with plastic granulate or rubber granulate, for example from used tires, and its high-quality paving can be an advantageous and service life-extending alternative to conventional asphalts," says the expert. However, he said, the prerequisite is always that the formulation for a modified asphalt mixture is determined and tested in the laboratory so that the mixture is optimized for the intended use. The environmental compatibility of roads with modified asphalt could be problematic, Beckedahl finds. Abrasion on roads with plastic content, for example, could release microplastics.
Roads made of or with recycled plastic waste nevertheless have the potential in principle to make a significant contribution to sustainability. They can help to conserve resources in terms of materials and land on a large scale - and that all over the world, because there are roads everywhere and plastic waste is a resource everywhere. However, it is not yet possible to predict the extent to which this type of construction will become established and which type will then prove to be the best.


Geckos, which are capable of walking on walls and hanging from ceilings with the help of micro-/nano-scale hierarchical fibrils (setae) on their toe pads, have become the main prototype in the design and fabrication of fibrillar dry adhesives. As the unique fibrillar feature of the toe pads of geckos allows them to develop an intimate contact with the substrate the animal is walking on or clinging to, it is expected that the toe setae exchange significant numbers of electric charges with the contacted substrate via the contact electrification (CE) phenomenon. Even so, the possibility of the occurrence of CE and the contribution of the resulting electrostatic interactions to the dry adhesion of geckos have been overlooked for several decades. In this study, by measuring the magnitude of the electric charges, together with the adhesion forces, that gecko foot pads develop in contact with different materials, we have clarified for the first time that CE does contribute effectively to gecko adhesion. More importantly, we have demonstrated that it is the CE-driven electrostatic interactions which dictate the strength of gecko adhesion, and not the van der Waals or capillary forces which are conventionally considered as the main source of gecko adhesion.
When any two materials, similar or dissimilar, touch each other, electric charges transfer from one to the other, leading to the formation of a net negative charge on one substrate and a net positive one on the other [1–3]. Development of an electrical double layer (EDL)  at the contact interface via this contact electrification (CE) phenomenon [1,2] essentially gives rise to the formation of electrostatic interactions between the charged objects [5,6]. Despite the familiarity and importance, the contribution of CE-driven electrostatic interactions in gecko adhesion—which arises from the intimate contact of the fibrillar feature of the gecko toe pads with the substrate the animal is walking on or clinging to [7,8]—has always been overlooked [7–10]. In this study, we have estimated—for the first time—the amount of electric charges and, therefore, the magnitude of electrostatic forces that gecko toe pads develop upon contact. Experiments were conducted on two distinct substrates: on one such substrate geckos adhere strongly, while on the other they do not. Interestingly, simultaneous measurement of electric charges and adhesion forces revealed that CE-driven electrostatic interactions have a decisive contribution to the dry adhesion of geckos over these materials. Better insight into the role of CE-driven electrostatic interactions in gecko adhesion is not only very important for understanding the principles of the supreme adhesion of geckos [8,11], but also is fundamentally very crucial in the design and fabrication of synthetic fibrillar dry adhesives [12–14], which have been recently hypothesized to be largely affected by CE-generated electrostatic interactions [15–17].
2. Results and discussion
In order to determine the occurrence of CE and the extent of the electrostatic interactions arising from it in gecko adhesion, the magnitude of electric charges—together with the adhesion forces—that build up upon contact of gecko foot pads with two substrates (Teflon AF and polydimethylsiloxane (PDMS)) were measured. Charge and force measurements were performed simultaneously by putting a single foot pad of five live Tokay geckos (Gekko gecko) against a vertically aligned thin film of the polymer, which was coated on a 5 × 5 cm2 ultra-polished (RMS roughness = 13.6 ± 1.6 nm, n = 3), mirror-finished copper sheet. The foot pad was subsequently pulled down the polymer thin film, dragging the toes across the substrate, until the developed shear force on the polymer was saturated. At the end of the course of dragging, the foot pad was pulled upward (perpendicular from the polymer surface), in order to detach the toes from the substrate. The five steps of the adhesion tests are shown in figure 1a, while the characteristic adhesion traces for Teflon AF and PDMS are plotted in figure 1b and c, respectively. The static adhesion strength (i.e. adhesion force per unit pad area) over Teflon AF—which was determined at the point where the toes started to slide—was 2.3 ± 0.3 N cm−2 (n = 10), on average more than twice as large as that of PDMS (1.1 ± 0.2 N cm−2, n = 10) (figure 1d). Following the onset of the sliding on both substrates, however, the shear strength increased. Enhancement of the shear strength during dragging is because of the directionality of the adhesion of gecko toe pads [7,18], considering that they develop a superior contact when the toes get aligned in the direction of dragging (compare figure 1a-2 with a-3). Owing to the familiar stick–slip phenomenon [19,20], on the other hand, the increase of the shear strength throughout the dragging step happened in a fluctuating manner.
In order to determine the contribution of CE-driven electrostatic interactions in the generated adhesion forces, during the adhesion tests, the magnitude of the electric charges—developed right after contact occurred—was estimated by image charge analysis [4–6]. When an electrically neutral gecko foot pad was brought into contact with the polymer thin film, the toes made contact with the substrate via the nano-scale spatulas (each 200–300 nm wide and 5–10 nm thick) [8,21] at the tip of the keratinous setae [22,23] of each toe on the foot pad (figure 2a). As illustrated in figure 2b and c, the exchange of electric charges between the fibrillar feature of the toe pads and the substrate gave rise to the formation of an EDL at the contact interface. Separation of electric charges at the contact zone induced an image charge, with the density of σimage, in the backing copper sheet. Knowing the magnitude of σimage from the readings of the electrometer connected to the back of the copper sheet, the surface charge density over the polymer (σs), which can practically be considered equal to that on the foot pad [5,6], was determined (see the electronic supplementary material for more details). Charge estimation results revealed that, during almost all contacts, the gecko foot pad became positively charged while the polymer was negatively charged. The absolute values of the surface charge densities immediately after intimate contact with Teflon AF and PDMS were 1.6 ± 0.2 mC m−2 (n = 10) and 1.3 ± 0.1 mC m−2 (n = 10), respectively (figure 2d). In principle, these charge densities (equivalent to approx. 1 elementary charge per 89–134 nm2) are relatively large [2,15], albeit typical for an intimate contact [5,6].
According to the charge estimation results and considering the toe pad–substrate interface as that between two parallel plates, the electrostatic adhesion strengths that gecko foot pads develop with Teflon AF and PDMS—in the normal direction before sliding—are 4.7 ± 1.2 N cm−2 and 2.4 ± 0.4 N cm−2, respectively (see the electronic supplementary material for more details). Interestingly, as illustrated in figure 3, the estimated adhesion strengths are of the same magnitude and also, more or less, of the same proportion (almost, on average, twice larger) as the static lateral shear strengths that were experimentally measured for these substrates.
Although direct charge measurements clearly demonstrate that the contribution of CE-driven electrostatic interactions in gecko adhesion is dominant, it should be noted that, along with electrostatic forces, van der Waals (vdW) and capillary forces could also contribute to the measured adhesion forces [7,9,24]; vdW interactions naturally exist between two materials in contact , whereas capillary interactions become effectual in humid conditions [24,25]. Concerning the latter, however, as all the experiments were carried out at the constant relative humidity of 50 ± 4% (temperature, T = 24 ± 1°C), and as both substrates share an almost similar hydrophobicity (Teflon AF, θ = 108.4 ± 0.6°, n = 6; PDMS, θ = 106.0 ± 0.7°, n = 6), the contribution of capillary interactions in the overall interfacial interactions for both polymers should be essentially identical—while capillary interactions for PDMS could be even slightly more effective [24,26]. With respect to vdW forces, on the other hand, Teflon AF is also expected to generate somewhat smaller vdW forces in comparison with PDMS. In particular, both polymers share a comparable sub-nanometric roughness (Teflon AF, RMS roughness = 0.2 ± 0.2 nm, n = 3; PDMS, RMS roughness = 0.6 ± 0.2 nm, n = 3), and therefore have similar geometry of contact with the gecko foot pad [9,27,28]. Hence, Teflon AF (with a Hamaker constant of 5.1 × 10−20 J) should develop almost 0.8 times smaller vdW forces than PDMS, which has a Hamaker constant of 6.5 × 10−20 J (see the electronic supplementary material for more details). With Teflon AF having a weaker ability than PDMS to generate both vdW and capillary forces, development of the observed enhanced adhesion forces by Teflon AF (figures 1d and 3) again confirms the decisive contribution of CE-driven electrostatic interactions in gecko adhesion.
As illustrated, what makes the difference between geckos sticking strongly to one substrate and not to the other is the extent of the contribution of CE-driven electrostatic interactions for each substrate. Even so, during the last 80 years of research on gecko adhesion, the role of electrostatic interactions in gecko adhesion was always passed over [7–10] by referring to the experiments conducted by Dellit , in which adhesion of a gecko (12 g Tarentola mauritanica) was tested against a vertically aligned chromed metal surface. After bombardment with ionized air, supposedly eliminating electrostatic interactions, and observing that the adhesion between the gecko and the metal surface did not change, Dellit concluded that the electrostatic interactions did not contribute to the adhesion of geckos . The control sample used by Dellit was small pieces of paper that were brought to adhere to a glass rod, which was charged by rubbing in advance . In regard to Dellit's experiments, it should be noted that air ionization can only be employed to eliminate electrostatic interactions from non-tight contacts but not those from intimate contacts—like the CE-driven electrostatic interactions of gecko foot pads. Put otherwise, during ionization of air by radioactive materials or X-ray radiation, as employed by Dellit , elementary air ions (typically approx. 0.4 nm in size), within a fraction of a second after their creation, attract 8–15 (mostly water) molecules to themselves and form positive and negative molecular clusters, known as ‘air ions’ . As a matter of fact, owing to their relatively massive size, air ions can only be employed to eliminate electric charges from an electrostatic contact—like that of the paper–glass with typical micro-scale roughness—where air ions can reach the contact interface to dissipate surface charges. In the intimate contact of seta-substrate, with an atomic separation distance of approximately 0.3 nm [7,21], however, eliminating CE-generated electrostatic forces by air ionization is not physically practical, simply because air ions cannot penetrate between the contact interface in order to dissipate surface charges.
- Received April 8, 2014.
- Accepted June 19, 2014.
- © 2014 The Author(s) Published by the Royal Society. All rights reserved.


Type: Injectable Pack: 10 amp (1000 mcg/amp) Substance: Vitamin B12 Manufacturer: March Pharmaceutical, Thailand
Pack: 10amp (1000mcg/amp)
Substance: Vitamin B12
Manufacturer: Market Pharmaceutical, Thailand
VITAMIN B12 is involved in the metabolism and in the synthesis of fatty acids and the production of energy.
VITAMIN B12, also called Cobalamin, or Cyanocobalamin is a water-soluble (water-soluble) vitamin and has a key role in the normal functioning of the brain, nervous system and in blood formation.
VITAMIN B12 is one of the 8 B vitamins.
VITAMIN B12 is used to boost mood, energy, concentration, immune system and slow down cellular aging.
B12 or cyanocobalamin is considered the most powerful vitamin.
VITAMIN B12 also works closely with vitamin B9 (folic acid) to regulate the formation of red blood cells and allow better functioning of iron in the body.
VITAMIN B12 is important for the activity of certain enzymes in cells that control fat, amino acid and carbohydrate metabolism (enzymes are special substances that speed up reactions in the body).


Galvanic corrosion protection system for severe exposure concrete elements in tidal marine environments.
Galvashield LJ is a galvanic protection system based upon the installation of prefabricated GRP jackets lined with expanded zinc mesh conforming to ASTM B69-92 for A190 alloy. The mesh is connected to the steel reinforcement to provide the required protective current to the steel.
Technical Data Sheet
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Levels of rare earth elements in hair from a group of young Spanish adults (aged 20-24 years).
The rapid agricultural, medical and industrial development is occurring on a global scale and bringing with emerging environmental threats for humans. Contamination by rare earth elements (REE) has emerged as a public health concern due to their numerous applications in the current industry. However, little is known about their toxicological effects despite they can accumulate in different organs including brain and bone. To determine the exposure to these contaminants in a young Spanish population, scalp hair samples were collected in 37 young adults (20 to 24 years-old; 28 female and 9 male) from different towns in the Community of Madrid (Spain). Despite being controversial, human hair could be an appropriate tool to determine environmental exposure to inorganic metal contaminants and to estimate the chemical burden in the individual. Lanthanum (La), cerium (Ce), praseodymium (Pr), erbium (Er) and gadolinium (Gd) were analysed in these samples by ICP-MS following appropriate methodologies. The limits of detection were (in ng/g): La (1.87), Ce (4.29), Pr (0.47), Er (0.06) and Gd (0.24 ng/g). Gd was detected only in one of the monitored samples (2.66 ng/g). The concentrations were as follow (median and percentiles are provided in ng/g): La 5.30 (4.22, 7.13), Ce 11.18 (8.97, 15.45), Pr 1.28 (1.04, 1.72) and Er 0.19 (0.14, 0.28). In general, the presence of these metals in the Spanish group’s hair monitored were lower than those reported in environmentally exposed groups, which may indicate that the studied group would have a low exposure to REE. None of these elements showed influence due to sex, although slightly higher levels were observed for La (5.57 vs. 5.17 ng/g), Pr (1.40 vs. 1.27 ng/g), Nd (2.48 vs. 2.29 ng/g) and Er (0.21 vs. 0.19 ng/g) in men’s hair and in women’s hair for Ce (11.58 vs 10.30 ng/g). Despite is unclear, our results would be in agreement with those studies that have suggested that men may be more sensitive to REE than women.
The Publisher's final version can be found by following the DOI link.
Citation : Peña-Fernández A., Angulo S., Lobo-Bedmar MC. Levels of rare earth elements in hair from a group of young Spanish adults (aged 20-24 years). Abstracts of the 54th Congress of the European Societies of Toxicology (EUROTOX 2018), 2-5 September 2018, Brussels. Toxicology Letters, 295(1). pp.S161.
Research Group : Biomedical and Environmental Health
Research Institute : Leicester Institute for Pharmaceutical Innovation - From Molecules to Practice (LIPI)
Peer Reviewed : Yes


Print Email Facebook Twitter Increasing oxime efficacy by blood-brain barrier modulation Title Increasing oxime efficacy by blood-brain barrier modulation Author Joosen, M.J.A. van der Schans, M.J. van Dijk, C.G.M. Kuijpers, W.C. Wortelboer, H.M. van Helden, H.P.M. Publication year 2011 Abstract One of the shortcomings of current treatment of nerve agent poisoning is that oximes hardly penetrate the blood-brain barrier (BBB), whereas nerve agents easily do. Increasing the concentration of oximes in the brain, would therefore provide an attractive approach to improve medical countermeasures. An explanation for limited penetration might be that oximes are substrates for the active P-glycoprotein (Pgp) efflux transporter located in the BBB.Using quantitative brain microdialysis in rats, the effect of i.v. injected tariquidar, a non-competitive, specific Pgp-inhibitor, on HI-6 levels in blood and brain was investigated. It appeared that tariquidar enhanced HI-6 levels in the brain approximately 2-fold during the first hour after HI-6 administration, whereas plasma levels did not differ between the treatment groups. A subsequent proof-of-concept study in rats showed that soman-induced seizures and convulsions were prevented almost completely when they were, in addition to HI-6 and atropine, pretreated with tariquidar. Moreover, twice as much AChE activity was present in their brains as compared to control rats.These results in rats indicate that modulation of the BBB by a drug like tariquidar, which is non-toxic by itself, is of great value in enhancing the efficacy of oximes. © 2011 Elsevier Ireland Ltd. Subject LifeCBRN - CBRN Protection PHS - Pharmacokinetics & Human StudiesEELS - Earth, Environmental and Life SciencesHI6Nerve agentP-glycoproteinSeizuresTariquidar1 (4 carbamoylpyridinio) 1' (2 hydroxyiminomethylpyridinio)dimethyl etherAcetylcholinesteraseAtropineTariquidarAnimal experimentAnimal modelArticleBlood brain barrierBlood levelBrain blood volumeControlled studyConvulsionDrug effectDrug efficacyDrug intoxicationDrug penetrationMaleMicrodialysisModulationNerve agent poisoningNonhumanPriority journalQuantitative analysisRatSeizureRattus1 (4 carbamoylpyridinio) 1' (2 hydroxyiminomethylpyridinio)dimethyl ether, 34433-31-3Acetylcholinesterase, 9000-81-1Atropine, 51-55-8, 55-48-1Tariquidar, 206873-63-4Tradenames: hi 6, TNO; xr 9576, avaantManufacturers: TNO; avaant To reference this document use: http://resolver.tudelft.nl/uuid:13c5876c-1cda-4bf6-9d49-2a09a93cf9c9 DOI https://doi.org/10.1016/j.toxlet.2011.05.231 TNO identifier 435959 ISSN 0378-4274 Source Toxicology Letters, 206 (1), 67-71 Document type article Files To receive the publication files, please send an e-mail request to TNO Library.