REACTOR AND OPERATING METHOD

Abstract

In an embodiment a reactor includes an electron source having a first gate-insulator-substrate electron-emission structure (GIS-EE) and configured to inject electrons into a fluid and a transportation system for the fluid configured to adjust a velocity of the fluid when passing the electron source, wherein the electron source is configured to provide the electrons to be injected into the fluid in an interior of the electron source and distant from the fluid, wherein the injected electrons are to initiate at least one chemical reaction in the fluid, wherein, when reaching the fluid, at least part of the injected electrons has a kinetic energy of at most 50 eV, wherein the electrons are propagatable only in solid matter from the interior until emission into the fluid, and wherein the GIS-EE includes an electrically conductive substrate, a transfer layer of a material with a band gap of at least 4 eV on the substrate, a gate electrode of a further electrically conductive material directly on the transfer layer, a first electrical connection structure on the substrate, and a second electrical connection structure on the gate electrode.

Claims

1. A reactor comprising: an electron source comprising a first gate-insulator-substrate electron-emission structure (GIS-EE) and configured to inject electrons into a fluid, the fluid containing at least one gas and/or at least one liquid; and a transportation system for the fluid configured to adjust a velocity of the fluid when passing the electron source, wherein the electron source is configured to provide the electrons to be injected into the fluid in an interior of the electron source and distant from the fluid, wherein the injected electrons are to initiate at least one chemical reaction in the fluid, wherein, when reaching the fluid, at least part of the injected electrons has a kinetic energy of at most 50 eV, wherein the electrons are propagatable only in solid matter from the interior until emission into the fluid, and wherein the GIS-EE comprises: an electrically conductive substrate, a transfer layer of a material with a band gap of at least 4 eV on the substrate (21), a gate electrode of a further electrically conductive material directly on the transfer layer, a first electrical connection structure on the substrate, and a second electrical connection structure on the gate electrode.

2. The reactor according to claim 1, wherein the electron source comprises or is a one-dimensional or two-dimensional grid, wherein the transportation system is configured to transport the fluid through the grid, wherein the electron source further comprises control electronics configured to provide a voltage between the electrically conductive substrate and the gate electrode.

3. The reactor according to claim 1, wherein a distance between the fluid and the interior configured to provide the electrons to be injected into the fluid is between 1 monolayer and 100 nm.

4. The reactor according to claim 1, wherein the reactor is an electro-chemical cell, and wherein the electron source is a first electrode of the electrochemical cell.

5. The reactor according to claim 1, wherein the transportation system is configured so that a maximum distance of any portion of the fluid to the electron source is at most 30 m when passing the electron source and/or the transportation system is configured to stir the fluid when passing the electron source.

6. The reactor according to claim 1, wherein the transportation system comprises at least one of a pump configured to pump at least one liquid past the electron source, a temperature control unit, a single or a plurality of the electron sources, a detector arranged past the electron source along the transportation system, or an analytical instrument before or after the electron source to separate substances.

7. The reactor according to claim 1, further comprising a second gate-insulator stack on top of the GIS-EE, wherein an electric potential of the GIS-EE is configured to control an emitted current and the second gate-insulator stack, which is in contact with the fluid, is configured to either control a carrier energy or a surface potential to influence the at least one chemical reaction at an interface between the gate-insulator stack and the fluid.

8. The reactor according to claim 1, wherein either the gate electrode comprises of glassy carbon or the GIS-EE is based on a non-porous hot electron emitter comprising silicon.

9. A method for operating the reactor according to claim 1, the method comprising: transporting, by the transportation system, the fluid which contains the at least one gas and/or the at least one liquid past the electron source; and injecting, by the electron source, the electrons into the fluid, wherein the electrons to be injected into the fluid are provided in the interior of the electron source and distant from the fluid, wherein the injected electrons initiate the at least one chemical reaction in the fluid, and wherein, when reaching the fluid, at least part of the injected electrons has a kinetic energy of at most 50 eV.

10. The method according to claim 9, wherein the fluid is a liquid into which the injected electrons are solvated after emission into the fluid.

11. The method according to claim 9, wherein the at least one chemical reaction is or comprises at least one of a Birch reduction or a Bouvealt-Blanc reduction, and wherein solvated electrons are generated by direct electron injection without using alkali metals and/or solvents.

12. The method according to claim 9, wherein the electron source serves as a cathode, and the at least one chemical reaction is or comprises an electrochemical reaction.

13. The method according to claim 9, wherein the at least one chemical reaction comprises a reduction reaction initiated by the injected electrons which are thermalized when initiating the at least one chemical reaction.

14. The method according to claim 10, wherein the solvated electrons trigger a dissociation of a target molecule.

15. The method according to claim 14, wherein the fluid contains CO.sub.2, and wherein, by the injected electrons, the CO.sub.2 is dissociated and/or converted to another chemical.

16. The method according to claim 9, wherein the fluid is air or seawater.

17. A detector system comprising: the reactor according to claim 1; and a detector unit configured to detect the fluid provided with the electrons.

18. The detector system of claim 17, wherein the reactor is part of a micro fluidic synthesis or analysis system.

19. The detector system of claim 17, wherein the detector unit comprises a spectrometer based on ion mobility.

20. The detector system of claim 17, further comprising a molecular separation device, wherein the molecular separation device is located before the electron source, seen along a direction of movement of the fluid.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0114] A reactor and an operating method described herein are explained in greater detail below by way of exemplary embodiments with reference to the drawings. Elements which are the same in the individual figures are indicated with the same reference numerals. The relationships between the elements are not shown to scale, however, but rather individual elements may be shown exaggeratedly large to assist in understanding.

[0115] FIG. 1 is a schematic sectional view of an exemplary embodiment of a reactor described herein;

[0116] FIG. 2 is a schematic block diagram of an exemplary embodiment of a method for operating a reactor described herein;

[0117] FIG. 3 is a schematic sectional view of an exemplary embodiment of a reactor described herein;

[0118] FIG. 4 is a schematic sectional view of an electrons source for an exemplary embodiment of a reactor described herein;

[0119] FIGS. 5 to 7 are schematic sectional views of exemplary embodiments of reactors described herein;

[0120] FIG. 8 is a schematic block diagram of an exemplary embodiment of a detector system described herein;

[0121] FIG. 9 is a schematic top view of an exemplary embodiment of a reactor described herein with a GIS-EE as an electron source;

[0122] FIG. 10 are schematic top views of a photo resist and a corresponding electron source before and after exposure with electrons emitted by a GIS-EE; and

[0123] FIG. 11 is a schematic representation of optical data and of a chemical reaction scheme of MB to LMB when using an exemplary embodiment of a reactor described herein.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0124] In FIG. 1, an embodiment of a reactor 1 for performing chemical reactions is illustrated. The reactor 1 comprises at least one electron source 2. In operation, the electron source injects electrons E into a fluid 4. The fluid 4 contains at least one gas and/or at least one liquid. The electrons are provided, for example, accelerated, in an interior 2X of the electron source 2. Hence, a location where the electrons E are emitted into a vacuum level or conduction band and the subsequent acceleration region is distant from the fluid 4.

[0125] The fluid 4 is transported past the electron source 2 by means of a transportation system 3. For example, by means of the transportation system 3 a velocity of the fluid 4 when passing the electron source 2 can be adjusted.

[0126] The injected electrons E are to initiate at least one chemical reaction in the fluid 4. For example, when reaching the fluid 4, all or at least part of the injected electrons E have a kinetic energy of at most 5 keV or of at most 1 keV or of at most 50 eV.

[0127] As in all other embodiments, the reactor 1 can optionally comprise at least one analytical instrument 61 before or after the electron source 2 to separate substances, for example.

[0128] FIG. 2 schematically shows a block diagram of an operating method of the reactor 1. In a first method step S1, the fluid 4 which contains the at least one gas and/or the at least one liquid is transported to the electron source 2. There, in method step S2, the electrons E are provided by the electron source 2 and injected into the fluid 4. Hence, the injected electrons E can initiate or increase the reaction rate of at least one chemical reaction in the fluid 4.

[0129] For example, the chemical reaction uses solvated electrons provided by the electron source 2. The chemical reaction may be a Birch reduction wherein because of the electron source 2 no alkali metals are required in the fluid 4 which is, for example, a mixture of liquids. Thus, for example, arenes can selectively be reduced to the corresponding 1,4-cyclohexadiene compounds. Another example to take place is the Bouveault-Blanc reduction. Hence, esters, aldehydes and ketones can be reduced to the corresponding alcohols. Again, the usage of alkali metals may be omitted.

[0130] A further example is the decomposition of CO.sub.2 that could take place during the reaction. In this case, for example, the fluid 4 is a mixture of gases with one gas being CO.sub.2.

[0131] In FIG. 3, another example of the reactor 1 is shown. For example, the transportation system 3 comprises a pump 31 configured to transport the fluid 4 past the electron source 2. Other than shown in FIG. 3, the electron source 2 may completely or almost completely surround a channel in the transportation system so that the fluid 4 could run through an opening in the electron source 2. Thus, the electron source 2 may be arranged in a plane perpendicular to a flow direction of the fluid 4. Along the flow direction, according to FIG. 3 the pump 31 is arranged before the electron source 2. However, the pump 31 can alternatively be arranged after the electron source 2, or there is a pump 31 before and after the electron source 2.

[0132] As a further option, the transportation system 3 can contain a mixing unit 33 to provide the fluid 4 in a homogeneous way to the electron source 2.

[0133] Moreover, it is possible that the transportation system 3 includes at least one educt storage unit 34 and/or at least one product storage unit 35. Accordingly, the transportation system 3 may have the ability to mix the fluid 4 from the educt storage units 34 to have the desired constituents and/or to split the fluid 4 into products and to lead the respective products into the product storage units 35, if desired. For the latter purpose, there can be a molecular separation device 62, for example.

[0134] Additionally, it is possible that the transportation system 3 includes a temperature control unit 32. The temperature control unit 32 may be applied along the channel the fluid 4 travels along and/or at the storage units 34 and/or 35. It is possible that different temperatures may be kept at different locations along the way of the fluid 4 through the reactor.

[0135] Furthermore, there can be one or more detector units 6 along the transportation system 3. For example, there is one detector unit 6 before and one detector unit 6 after the electron source 2. By means of the at least one detector unit 6, for example, concentrations of the educts and products and/or lifetimes of the electrons E in the fluid 4 can be determined to optimize the reaction initiated by the electrons E, for example, by adjusting the kinetic energy of the injected electrons E and/or by adjusting their concentration.

[0136] All these options concerning the transportation system 3 and the at least one detector unit 6 can be realized in all the embodiments of the reactor 1, individually or in any combination.

[0137] Otherwise, the same as to FIGS. 1 and 5 may also apply to FIG. 3, and vice versa.

[0138] FIG. 4 shows an example of an electron source 2 designed as a gate-insulator-substrate-electron emission structure, abbreviated as GIS-EE. The GIS-EE 2 includes an electrically conductive substrate 21, which may be replaced by a combination of a carrier and an electrically conductive layer. Furthermore, the GIS-EE 2 comprises a transfer layer, such as an insulator layer 22, on the substrate 21. Atop the insulator layer 22, there is a gate electrode 23. Instead of the dielectric material, the transfer layer can also be made of a material with a large band gap, such as SiC, GaN, AlN, Ga.sub.2O.sub.3 or diamond, as is also possible in all other examples. The gate electrode 23 forms an emission side 20 for the electrons E. For electrical contacting, a first and a second electrical connection structure 25, 26 are optionally present.

[0139] It is possible for the second electrical connection structure 26 to be applied to the gate electrode 23 as a grid or in strips in order to ensure a uniform voltage across the gate electrode 23. Furthermore, it is possible that a protective layer 24 is present which covers the gate electrode 23. Optionally, portions of the second electrical connection structure 26 extending across the gate electrode 23 are located between the gate electrode 23 and the protective layer 24.

[0140] By means of field emission, the electrons E can thus tunnel into the conduction band of the insulator 22. If there is a sufficient voltage drop and low scattering probability, the energy gain of the potential drop in the insulator is sustained and hot electrons E can be transmitted through the gate electrode 23 and injected into the fluid 4 next to the emission side 20. The achievable energy is limited by the dielectric strength and/or by the service life of the insulator layer 22. With the voltage, the tunnel current increases with a given thickness of the insulator layer 22 and, thus, the load and the service life decreases. To a certain extent, the thickness of the insulator layer 22 can be increased in order to reduce the tunnel current at a given voltage, however, scattering effects increase, as a result of which the efficiency decreases. Likewise, a maximum charge transported by the tunnel process can decrease before a breakdown with increasing thickness.

[0141] An energy range for the emitted injected electrons E of, for example, up to 50 eV is possible. In this type of electron emitter, the actual tunnel barrier is the interface between insulator 22 and substrate 21, which is thus not exposed to the influence of the environment. Hence, the very sensitive tunneling process as well as the energy gain to overcome the work function is buried in the interior of the electron source 22 at the insulation layer 22 at a side facing the substrate or substrate electrode 21.

[0142] This principle works not only in vacuum, but also at atmospheric pressure and in liquids and renders an evacuated package superfluous. Since the electron energy can be adjusted in a certain range by means of the voltage and/or by means of the thickness of the insulator 22, it is thus possible to realize an electron source 2 with variable electron energy, if necessary also by a plurality of GIS-EEs with different thicknesses of the insulator layer 22, for example on a common substrate 21. Alternatively, a further gate-insulator stack can also be used in order to vary the energy.

[0143] In order to achieve as low a scattering as possible in the gate electrode 23 and at the interface with respect to the insulator 22, the gate electrode 23 is designed to be as thin as possible on the one hand. For example, a thickness of the gate electrode 23 is in the range of the wavelength of the electrons E, for example, at a maximum of 10 nm. The gate electrode 23 should also have a low energy difference of the conduction band edge to the conduction band edge of the insulator 22 in order to minimize quantum mechanical reflection.

[0144] Due to the requirement of the small layer thickness, the conductivity of a material of the gate electrode 23 should also be selected as high as possible in order to realize a low voltage drop at the gate electrode 23 and, thus, the possibility of as large an active area as possible. One possibility is to have carbon-based gate electrodes 23. Here, on the one hand, a diamond or diamond-like, that is sp3-hybridized, and a graphite-like, that is, sp2-hybridized, dominated body of the gate electrode 23 are suitable. In both forms, carbon materials exhibit very high, under certain circumstances direction-dependent electrical conductivities, and a very high electron transmission efficiency. This applies in particular to graphene.

[0145] A semiconductor-based gate electrode 23 can also enable a low energy jump to the insulator conduction band of the insulator layer 22. For example, silicon is suitable as a material for the gate electrode 23 in the case of a silicon oxide as the insulator layer 22.

[0146] Metals, in particularly thin metal layers, are also suitable for the gate electrode 23. Metal layers produced in particular by atomic layer deposition, ALD for short, can be homogeneous and very thin.

[0147] Some examples of sp2-hybridized dominated carbon-based materials for the gate electrode 23 are: graphene, multi-layer graphene, two-layer graphene, three-layer graphene, exfoliated graphene. Materials of the graphene family can be grown, in particular catalytically, for example, on copper, and then transferred. The growth can be carried out, for example, on SiO.sub.2, SiC, metals such as, for example, copper, or on hexagonal boron nitride or sapphire. Likewise, graphene can be grown directly on the insulator layer 22 without subsequent transfer, for example, on hexagonal boron nitride. Furthermore, a solid-phase graphenization, such as HOPG (Highly Oriented Pyrolytic Graphite), can be used with subsequent transfer. Furthermore, the use of nanocrystalline graphene, pyrolytic graphene, pyrolytic carbon, graphitic carbon or graphenic carbon is possible. Possible production processes are chemical vapor deposition, CVD for short, such as APCVD (Atmospheric Pressure CVD), LPCVD (Low Pressure CVD), PECVD (plasma enhanced CVD) or EVD (electro chemical vapor deposition); also physical vapor deposition, PVD for short, and transfer methods can be applied to produce the gate electrode 23. So-called glassy carbon or pyrolyzed polymer films can be produced by pyrolysis, for example.

[0148] Examples of sp3-hybridized dominated carbon-based materials for the gate electrode 23 are: diamond, diamond like carbon, DLC for short, ultra-nanocrystalline diamond, UNCD for short, which may be doped and can be prepared, for example, by CVD, such as PECVD.

[0149] For example, the gate electrode 23 is made of glassy carbon, GC for short, which may also be referred to as glass-like carbon, GLC. Further synonyms are vitreous carbon and polymeric carbon. When GC is used for the gate electrode 23, a thickness of the respective carbon layer is at least one monolayer or is at least two monolayers or is at least 1 nm or is at least 2 nm, for example. Alternatively or additionally, this thickness is at most 20 nm or is at most 10 nm or is at most 6 nm. For example, the gate electrode 23 has a specific electric conductivity of at least 10 S/m or of at least 10.sup.3 S/m or of at least 10.sup.4 S/m or of at least 10.sup.5 S/m; alternatively or additionally, said value is at most 10.sup.7 S/m. The GLC may optionally comprise filaments with a length-to-width ratio of at least 10.

[0150] In case of GLC for the gate electrode 23, it is possible that the substrate electrode 21 is made of GLC as well, and that the insulating layer 22 is made of hexagonal boron nitride, for example.

[0151] The GLC may be manufactured, for example, as follows: [0152] applying an organic raw material onto a substrate, the raw material is applied as a liquid; [0153] solidifying the raw material so that a raw material layer is formed; and [0154] pyrolyzing the raw material layer at a temperature of at least 400 C. and of at most 2000 C. so the GLC layer as the gate electrode 23 is formed.

[0155] Concerning GLC and its use and manufacture, reference is made to US patent application document U.S. Ser. No. 18/484,797, the disclosure content of which is incorporated by reference.

[0156] The gate electrode 23 may be a continuous, uninterrupted and hole-free layer and may optionally be of constant thickness. Otherwise, it is possible that the gate electrode 23 comprises a plurality of pores or holes which may be distributed regularly or also randomly.

[0157] Further 2D materials are also possible for the gate electrode 23, such as borophene, phosphor-based materials or else transition metal dichalcogenides.

[0158] Examples of semiconductor materials for the gate electrode 23 are: crystalline Si, poly-Si, amorphous Si, Ge, which can be produced, for example, by means of CVD, such as LPCVD. Examples of metals for the gate electrode 23 are: Al, Au, Ag, Pt, Ni, Co, which can be produced, for example, by means of ALD.

[0159] For example, the gate electrode 23 has a specific conductance of 10.sup.1 S/m to 10.sup.9 S/m. A thickness of the gate electrode 23 is, for example, at least one monolayer and at most 20 nm.

[0160] The insulator layer 22 is to be selected in particular as robust as possible against the tunnel currents used in order to enable the highest possible current density and service life of the GIS-EE. A manufacturing process in which the thickness of the insulator layer 22 can be accurately controlled is preferable to achieve very thin homogeneous insulation layers 22 and a high homogeneity of emission.

[0161] For example, the insulator layer 22 is made of silicon dioxide, since the achievable high oxide quality and the relatively precisely adjustable thickness permit a high current density and, thus, service life. Established production methods are also available above all in conjunction with a silicon substrate 21. In addition, the insulator 22 may be made of hexagonal boron nitride, hBN for short, allowing, among other things, direct epitaxial growth of graphene on its surface. Since the thickness can also be controlled very well by various production methods, hBN is an interesting possibility for the insulator layer 22. Particularly in combination with hBN as insulator layer 22 and graphene as gate electrode 23, very low-scattering can be achieved and, thus, a sharp energy distribution of the emitted electrons E can be realized. High-k dielectrics used in CMOS technology are also suitable for the insulator layer 22. In particular, production methods such as ALD are capable of achieving very homogeneous layers with a relatively high quality.

[0162] Silicon dioxide for the insulator layer 22 can be produced, for example, thermally, in particular wet, dry, at room temperature or in an oxidation furnace, or by means of CVD or by means of vapor deposition. hBN or BN can be produced, for example, by means of PECVD and heating, LPCVD, catholyte growth and transfer. High-k dielectrics such as Al.sub.2O.sub.3 or HfO can be produced by vapor deposition, sputtering or ALD.

[0163] For example, the insulator layer 22 has a dielectric strength of 0.02 V/nm to 1 kV/nm or of 0.1 V/nm to 500 V/nm.

[0164] Using silicon as material for the substrate 21, also referred to as substrate electrode, common methods are available from the CMOS industry and a scalable, reproducible production can be achieved. By varying the doping, the electrical properties can be influenced and even a voltage drop across the gate electrode 23 can be compensated for by a suitable doping profile. Silicon also offers the possibility of integrating further functionalities on a chip.

[0165] Furthermore, highly conductive, flexible material is also possible for the substrate 21.

[0166] In addition, sapphire, hBN, silicon carbide or also a metal film is possible as the substrate 21. In the case of a non-conductive carrier layer, the conductivity can be realized by an additional layer. For example, graphene can be grown directly on a surface of such a non-conductive carrier layer.

[0167] The substrate electrode 21 can thus be made of silicon, with a possible doping either p or n and a doping level of to ++, with P, As, Sb, B, Al, Ga and/or In as possible dopants. For example, the doping concentration is between 10.sup.12/cm.sup.3 and 10.sup.21/cm.sup.3 or between 10.sup.11/cm.sup.3 and 10.sup.22/cm.sup.3. Furthermore, HOPG and graphite foils as well as sapphire wafers, possibly with a carbon layer, and SiC, possibly with a carbon layer, are usable, as well as metal films.

[0168] For example, a thickness of the substrate 21 is at least one monolayer and/or at most 5 mm. The substrate 21 can be mechanically rigid or also flexible. For example, a specific electrical conductivity of the substrate 21 is between 10.sup.1 S/m and 10.sup.9 S/m.

[0169] Since the electron source 2 is used in air with oxygen or under aggressive environment or in contact with a liquid, the protective layer 24 for the gate electrode 23 may also be necessary under certain circumstances. What is important here is, in particular, the chemical resistance of the protective layer 24 as well as the controlled, homogeneous deposition of very small thicknesses. Gate dielectrics production processes and ALD are of particular interest here.

[0170] The protective layer 24 is, for example, made of silicon dioxide, as is possible in the case of the insulator layer 22. In addition, the protective layer 24 can be made of hBN or BN, which enables very thin layers and is a suitable material above all in conjunction with graphite or graphene layers for the gate electrode 23. Here, above all, the same lattice structure as in graphitic carbon would also be advantageous. Furthermore, the protective layer 24 can be made of glassy carbon, and high-k dielectrics are also possible to be applied by ALD processes or pulsed laser deposition. Silicon oxide and silicon carbide or silicon nitride are also possible materials for the protective layer 24, as well as Al.sub.2O.sub.3, for example, produced by high-frequency sputtering processes or reactive sputtering processes or ALD or pulsed laser deposition, PLD for short.

[0171] The protective layer 24 is preferably chemically insensitive to, for example, oxygen ions and oxygen radicals. A thickness of the protective layer 24 is, for example, at least one monolayer and/or at most 10 nm.

[0172] A current density of the GIS-EE 2 is, for example, at most 100 A/cm.sup.2, an emission electrode voltage can be between 0.5 V and 50 V inclusive, an efficiency can be up to 95% or in particular also up to 90%.

[0173] A functional capability of the GIS-EE 2 for ionization can be independent of pressure and type of the fluid 4 into which the GIS-EE 2 emits the electrons E.

[0174] A channel of the transportation system 3 for the fluid 4 can be constructed like a plate capacitor or a cylinder condenser, wherein openings or grid arrangements of the electron source 2 are also possible and a fluid flow from all sides is conceivable.

[0175] Otherwise, the same as to FIGS. 1 to 3 may also apply to FIG. 4, and vice versa.

[0176] FIG. 5 shows that the electron source 2, which in turn can be designed as a GIS-EE, is divided into a plurality of lamellae 41. The lamellae 41 are arranged, for example, in a common plane. It is possible that main sides of the lamellae 41 are oriented perpendicular to this common plane. By the lamellae, a one-dimensional grid 5 is formed.

[0177] Especially if the electron source 2 is realized as a GIS-EE, the GIS-EEs 2 can each be applied to one or both sides of the lamellae 41. Thus, the fluid 4 passes the electron source 2 by running through the lamellae 41. Alternatively, one side of the lamellae 41 can also be embodied in an insulating manner. Then, ions can first accumulate there and build up an electric counter-field so that the ionized molecules are not discharged at a rear-side lamella wall. A conductive connection to a ground potential and to positive or negative voltages is then also possible. A distance between adjacent lamellae 41 is, for example, at least 0.1 m or at least 1 m and/or at most 1 cm or at most 0.1 mm or at most 10 m.

[0178] Control electronics 9 are shown only schematically in a greatly simplified manner. For example, the control electronics 9 include one or a plurality of voltage sources for applying a voltage between the substrate 21 and the gate electrode 23. The control electronics 9 can comprise means to keep, for example, the gate electrode 23 at a desired electric potential, like ground potential. It is possible that the control electronics 9 comprise a comparator and/or amplifiers. Further, by means of the control electronics 9 a current through the gate electrode 23 may be measured and adjusted, if required.

[0179] Otherwise, the same as to FIGS. 1 to 4 may also apply to FIG. 5, and vice versa.

[0180] FIG. 6 shows that the electron source 2, which is, for example, again a GIS-EE, is shaped as a two-dimensional grid 5, so that a plurality of holes 42 extend through the substrate 21, the insulator layer 22 and the gate electrode 23, wherein optionally the protective layer 24 may also be present. In this case, the insulator layer 22 and the gate electrode 23 as well as the optional protective layer 24 can either be located only on side surfaces of the holes 42 or only on the sides of the substrate 2 facing the second electrode 72 or on all of these three sides, as shown in FIG. 6. The holes 42 can be placed in a regular rectangular grid. Alternatively, other types of grating are also possible, for example hexagonal lattice arrangements of the holes 42.

[0181] For example, like in all other embodiments, the electron source 2 can replace a cathode in an electrochemical cell. In this case, the electron source 2 can be a first electrode 71 of the electrochemical cell opposite a second electrode 72 which is an anode. Other than shown in FIG. 6, both electrodes 71, 72 can be of the same shape, that is, can be continuous, hole-free plates or can be grids. However, as in FIG. 6, for example, a grid-shaped electron source 2 can be combined with a plate-shaped second electrode 72, for example, to better define a flow of the fluid 4.

[0182] It is further possible that an optional acceleration electrode is present, not shown, to accelerate the electrons E into a specific direction after being provided by the electron source 2.

[0183] Otherwise, the statements relating to FIGS. 1 to 5 may apply in the same way to FIG. 6, and vice versa.

[0184] In the example of FIG. 7, the electron source 2 is of a housed design and could comprise, for example, a housing 29, like a TO housing. In the electron source 2, the electrons E can be released, for example, on a heating wire 27 or also by a single field emitter or a field emitter array and subsequently accelerated within the interior 2X of the electron source 2. Alternatively, photo emission is also possible, for example, in in pulsed manner by means of, for example, a femtosecond laser or a picosecond laser that illuminates a photo cathode with a high repletion rate, for example, in the range above 1 MHz or in the range above 10 kHz.

[0185] The emission side 20 is formed by a transmission window 28 of the electron source 2. The transmission window 28 allows transmission of the electrons E and can be formed, for example, by a carbon layer or by one of the materials mentioned above with respect to the gate electrode 23.

[0186] Furthermore, an inner space of such an electron source 2 is preferably evacuated, for example, supported by a getter in the housing 29, in order to achieve a sufficient service life of the heating wire 27 or of the field emitter array or of a photo cathode. The fluid 4 is guided past the transmission window 28 so that the transmission window 28 may directly adjoins the fluid 4. However, the electrons E are provided distant from the fluid 4 in the interior 2X of the electron source 2.

[0187] Otherwise, the same as to FIGS. 1 to 6 may also apply to FIG. 7, and vice versa.

[0188] In FIG. 8, a detection system 8 is schematically illustrated. The detection system 8 comprises the at least one reactor 1 as well as the at least one detector unit 6. For example, by means of the reactor 1 the fluid, not shown in FIG. 8, is moved and the electrons are provided, and by means of the detector unit 8 products of the reaction taking place in the reactor 1 can be detected and analyzed and optionally also sorted and/or separated from each other. Thus, by combining the reactor 1 and the detector unit 6, a detector system which is a filter system can be created as well. For example, if the detector unit 1 is an ion mobility spectrometer or a mass spectrometer or the like, different kinds of ions created by means of the electrons can be efficiently be separated from each other. This separation of products of the reaction can be used to provide a further reaction with ions or products from the preceding reaction, as well as optimization of process parameters in the reactor 1 is enabled.

[0189] Otherwise, the same as to FIGS. 1 to 7 may also apply to FIG. 8, and vice versa.

[0190] The following proof of concept measurements demonstrate the usage of the GIS-EE as a switchable supply of solvated electrons for chemical reactions, for example.

[0191] By emitting electrons into water as the liquid 4, reduction reactions occur, resulting in the formation of hydrogen and hydroxide. While hydrogen is in a gaseous phase and escapes the water via visible bubbles 43, the hydroxide accumulates over time, resulting in the formation of hydrogen peroxide. The bubbles 43 in the water were observed during operation of the electron emitter 2, indicating the hydrogen formation. The bubbles 43 were generated next to the gate electrodes 23 near the emission side 20 wherein a 33-array of the gate electrodes 23 are kept at a same electric potential by means of a common electrode 51, and not further electrode is required in the liquid 4, see FIG. 9. The gate electrodes 23 may be of GLC and may thus have a black appearance. An edge length of the individual gate electrodes 23 is around 0.7 mm, for example, and the gate electrodes 23 may be of square shape, seen in top view.

[0192] The hydrogen peroxide concentration was measured at approximately 3 mg/L after the operation. This confirms the water splitting reaction and chemical reduction of water by the emitted electrons:

##STR00001##

[0193] Furthermore, see FIG. 10, electrons emitted into an electron beam resist 44 trigger chemical reactions for crosslinking the polymers. After an additional post-exposure bake and subsequent development of the resist, only the resist 45 exposed by the electrons will remain. An electron-sensitive resist was coated on the GIS-EE to confirm the chemical effectiveness of the GIS-EE. Operated devices coated with the resist showed resist on the active area and in close proximity to the active area, indicating sufficient electron concentration for crosslinking as well as diffusion of the electrons away from the active area.

[0194] Another test for the chemical reactivity of the switchable microreactor 1 equipped with a GIS-EE 2 is the reduction of methylene blue 46, MB, to leucomethylene blue 47, LMB, compare FIG. 11. Free electrons can be considered very strong reduction agents. By introducing electrons into a methylene blue solution 46, it is reduced and forms the colourless form of leucomethylene blue 47. Therefore, a droplet of methylene blue solvated in dimethylsulfoxide, DMSO, was dropped onto an emission side 20 of the GIS-EE 2. During operation of the GIS-EE 3, bubbles were observed, resulting from the reduction reaction of the DMSO with the solvated electrons. After a short period of time, the blue colour faded and a clear solution remained consisting of leucomethylene blue 47. A quantitative measurement of the solution before and after operation can be seen in the UV-VIS spectrograph showing a clear reduction of the red absorbance after operation, see FIG. 11, top part. The corresponding reaction scheme is illustrated in FIG. 12, bottom part.

[0195] In particular, with the GIS-EE as the electron source 2, especially the following aspects can be achieved: [0196] electron energies of less than 10 eV upon entry into the fluid can efficiently be achieved; [0197] no influence on the fluid due to operation of the electron source apart from the insertion of the electrons, that is, no external electric field is required, and operation at room temperature is possible; [0198] longer lifetime compared to emitters with an electron-generating structure directly in a liquid; [0199] comparably low manufacturing costs can be achieved, for example, due to using glassy carbon in the GIS-EE.

[0200] Hence, especially the following applications can be served efficiently: [0201] Birch reduction and similar processes based on solvated electrons can be performed, without using alkali metals and/or solvents, or simpler solvents and process conditions can be applied; [0202] CO.sub.2 capturing from liquids inclusive further processing can be done by emitters operated directly in the liquids; [0203] the GIS-EE can directly serve as an electrode for an electrochemical cell.

[0204] The components shown in the figures follow, unless indicated otherwise, exemplarily in the specified sequence directly one on top of the other. Components which are not in contact in the figures are exemplarily spaced apart from one another. If lines are drawn parallel to one another, the corresponding surfaces may be oriented in parallel with one another. Likewise, unless indicated otherwise, the positions of the drawn components relative to one another are correctly reproduced in the figures.

[0205] The invention described here is not restricted by the description on the basis of the exemplary embodiments. Rather, the invention encompasses any new feature and also any combination of features, which includes in particular any combination of features in the patent claims, even if this feature or this combination itself is not explicitly specified in the patent claims or exemplary embodiments.