WO2007107152A2

WO2007107152A2 - Deposition of nanoscale metals, semimetals and compounds of said metals and/or semimetals on the boundary surface between a low temperature discharge and an ionic liquid

Info

Publication number: WO2007107152A2
Application number: PCT/DE2007/000524
Authority: WO
Inventors: Jürgen Janek; Frank Endres; Marcus Rohnke; Sebastian A. Meiss
Original assignee: Justus-Liebig-Universität Giessen
Priority date: 2006-03-23
Filing date: 2007-03-21
Publication date: 2007-09-27
Also published as: WO2007107152A3; DE102006013871A1

Abstract

The invention relates to methods for producing particles comprising metals, semiconductors, metallic compounds or semiconductor compounds with diameters in the nanometer range. According to said methods, an electrochemically reducible precursor substance is dissolved in an ionic liquid, and is either reduced by free electrons in a plasma phase or is reacted with particles from the plasma phase. The particles obtained by the inventive method can be used, for example, as additives for polymers for coating medical instruments or as electrochemical catalysts. The particles can optionally be bound to or onto a substrate.

Description

Patent application

Deposition of nanoscale metals, semimetals and compounds of these metals and / or semimetals at the interface between a

dertemperaturentladung and an ionic liquid

The present invention relates to a method for the production of particles with diameters in the nanometer range, which consist of metals, semi-metals, metal compounds or semi-metal compounds. The nanoscale particles are obtained in the case of metals and semimetals by the reduction of a suitable precursor substance with free electrons from a plasma phase (gas discharge), in the case of metal and semimetal compounds by reaction of a suitable precursor substance with particles from the plasma phase. The precursor substance is dissolved for this purpose in a stable ionic liquid (low-melting organic salt) and is reduced under electric current flow on the free surface of the liquid in contact with the plasma.

Description and introduction of the general field of the invention

The present invention relates to the fields of physical solid state chemistry, redox chemistry, plasma chemistry, interfacial chemistry, and material sciences.

State of the art

An important chemical task today is the targeted production of substances with a size in the nanometer range. The general interest in nanocrystalline materials is based on the fact that they have partly different physical and chemical properties in relation to the volume due to the high surface proportion than significantly larger particles of the same materials. Nanoparticles are used both as free particles which change their properties by admixture with another material, as well as bound to a substrate.

There are a number of applications in which the nanoparticles have to be fixed on a substrate by application. One example is the application of nanocrystalline substances to glass panes. As a result, the surface properties are changed in such a way that impinging drops of water roll off the pane, thereby detaching adhering impurity particles. One speaks in this case of a self-cleaning effect (lotus effect).

Particles with sizes in the nanometer range, which consist of metals, semi-metals, metal compounds or semi-metal compounds, are used, inter alia, for the manufacture of medical instruments, microelectronic and nanoelectronic components as well as catalysts. Free silver ions have an antimicrobial effect as they both block the transmembrane energy metabolism and deliver a stop code to the DNA that prevents the reproduction of the microbes. In medicine, therefore, instruments are partially coated with polymers to which silver nanoparticles have been added as additives.

Noble metal nanoparticles (e.g., platinum nanoparticles) are used as electrochemical catalysts in a variety of electrochemical reactions. Examples include hydrogen oxidation, methanol oxidation and oxygen reduction. In these methods, the particles are bound as electrode material on a substrate or electrolyte.

In the field of photovoltaics, there are different solar cell types. One type, the so-called heterojunction solar cell (HIT) ₁ is currently in use. great international attention. So far, this solar cell type is made with monocrystalline silicon. In WR Fahrner, Nanotechnology and Nanoprocesses, Springer Verlag, Berlin 2003, page 132 is described that the efficiency can be significantly increased by the use of nanocrystalline silicon.

Previous methods for producing nanoscale particles are based on special chemical reduction, precipitation or template methods or on the decomposition of gaseous or liquid starting materials in a gas or plasma phase. Alternatively, nanoparticles can also be prepared by ablation of material by a plasma and subsequent deposition on a substrate. The production of nanoparticles by deposition from the plasma phase is described, for example, in:

- G.H. Popov et al .: "Nanoparticle production line with in situ control of the chemical composition, size and morphology of nanoscale particles", Proceedings of SPIE - The International Society for Optical Engineering (2005), 5592, 406-412;

- Loan Bica: "Plasma installation for nanoparticle production", Analele Universiteitie de Vest din Timisoara, Seria Stiinte Fizice (2002), 43, 6-11; A Bapat et al., Plasma Physics and Controlled Fusion (2004), 46, B97-B109;

- G Vissokov et al .: "On the plasma-chemical synthesis of nanopowders", Plasma Science & Technology (Beijing, China) (2003), 5 (6), 2039-2050; X Li et al .: "Synthesis and characterization of nanoparticles of Alnico alloys", Acta Materialia (2003), 51 (18), 5593-5600

EP 1 514 845 A1 describes the plasma synthesis of metal oxide particles in the nanometer range. WO 2003/096774 A1 describes catalysts and WO 2003/096382 A2 methods and devices for plasma processes. A disadvantage of all mentioned processes is that they are discontinuous processes. In addition, nanoparticles which are produced with the aid of the abovementioned processes are deposited on a carrier material (substrate) and are usually firmly bonded to the carrier material.

By contrast, the present invention provides methods that can be operated continuously. The reaction products are also not fixed on a carrier material. They are present as free particles in the solution and separate with time as sediment at the bottom of the reaction vessel. Those with this invention The nanoparticles produced can be bound, if necessary, by embedding in a matrix, by adhesion or sintering processes on or on a substrate.

task

The object of the present invention is to provide alternative processes for the production of particles comprising metals, semimetals, metal compounds or semi-metal compounds with diameters in the nanometer range, which can also be operated continuously.

Solution of the task

This object is achieved in accordance with the invention by dissolving at least one precursor substance in at least one ionic liquid and subsequently reducing it in a plasma phase either by free electrons or reacting with particles from the plasma phase, precursor substance meaning a salt of a metal or a metalloid and Plasma phase is generated by a homogeneous gas discharge of an inert or reactive process gas at a pressure of 1 Pa to 2000 Pa.

The precursor substances are salts of metals or semimetals on the one hand and inorganic or organic acids on the other hand, which have a sufficient solubility in the respective ionic liquid. The solubility is sufficient if solutions of the precursor substance can be prepared in the ionic liquid at concentrations of at least 0.0001 mol / l.

The salts to be used are, for example, but not exhaustive, oxides, hydroxides, fluorides, chlorides, bromides, iodides, hypochlorous te, chlorites, chlorates, perchlorates, hypobromites, bromites, bromates, perbromates, hypoiodites, iodates, iodates, periodates nitrites, nitrates, sulphides, sulphites, sulphates, phosphites, phosphates, formates, acetates, oxalates, maleates, fumarates, benzoates , Bis (trifluoromethylsulfonyl) imides, tris (trifluoromethylsulfonyl) methanes, bis (trifluoromethylsulfonyl) amides and trifluoromethanesulfonates of the following metals or semimetals, if these salts exist at room temperature.

Alkali metals: Li, Na, K, Rb,

- alkaline earth metals: Be, Mg, Ca, Sr, Ba,

- earth metals: Al, Ga, In, Tl, - metals of the 4th main group: Sn, Pb,

- Metals of the 5th main group: Bi,

- Metals of the 1st subgroup: Cu, Ag, Au,

- Metals of the 2nd subgroup: Zn, Cd

- metals of the 3rd subgroup: Sc, Y, - metals of the 4th subgroup: Ti, Zr, Hf,

Metals of the 5th subgroup: V, Nb, Ta,

- Metals of the 6th subgroup: Cr, Mo, W,

- Metals of the 7th subgroup: Mn, Re,

- Metals of the 8th subgroup: Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, - Lanthanides: La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, He, Tm, Yb, Lu

Semi-metals: B, Si, Ge, As, Sb, Se, Te

In order to produce particles of metals or semimetals with the aid of the method according to the invention, electrochemically reducible salts of the corresponding metals or semimetals are selected as precursor substances and reduced to metal or semimetal by free electrons from a plasma phase (gas discharge). In this case, a plasma must be ignited with a chemically inert gas. The precursor substance is dissolved for this purpose in an ionic liquid and reduced under current flow at the free surface of the liquid in contact with the plasma. The free surface of the liquid is understood to be that layer of a liquid in which the pressure which is applied to this layer is just as great as the ambient atmospheric pressure Pressure, provided that the ambient atmospheric pressure is substantially constant.

If metal compounds or semimetal compounds are produced by means of the process described, a plasma with a chemically reactive gas is produced. At the phase boundary between the liquid and the plasma, the metal or semimetallic cations of the at least one precursor substance react with particles from the plasma to form the desired metal or semimetal compound.

The gas used to generate the gas discharge is an inert gas if elemental metals or elemental semimetals are to be produced, and a reactive gas if a metal compound or metalloid compound is to be produced. Inert gases are selected according to the invention from the group of noble gases (helium, neon, argon, krypton, xenon) or mixtures thereof. According to the invention, reactive gases are selected from the group oxygen, nitrogen, nitrogen monoxide, nitrogen dioxide, nitrous oxide, carbon monoxide, carbon dioxide, hydrogen, methane, ethane, fluorine, chlorine, bromine, air or mixtures thereof.

The gas discharge is generated according to the invention by radio waves, microwaves, direct current or alternating current.

Preferably, a highly concentrated solution of the at least one precursor substance in the at least one ionic liquid is used. For this purpose, the at least one precursor substance is selected such that the at least one anion of this substance is identical to at least one anion of the at least one ionic liquid. In cases where this is not possible because there is no precursor substance whose anion is identical to the anion of the ionic liquid, a precursor substance with a chemically similar selected anion. Those skilled in the art will know which anions are chemically similar and may select suitable anions without departing from the scope of the claims.

In a particularly preferred embodiment, saturated solutions are used to prepare nanoparticles in a particularly efficient and economical manner.

For the purposes of the present invention, ionic liquids are to be understood as meaning those ionic compounds whose melting point is less than or equal to 100 ^° C. These are exemplary, but not exhaustive:

monosubstituted imidazolium derivatives such as, for example, 1-methylimidazolium tosylate, 1-methylimidazolium tetrafluoroborate;

disubstituted imidazolium derivatives, such as, for example, 1,3-dimethylimidazolium methylsulfate, 1,3-dimethylimidazolium trifluoromethanesulfonate, i-ethyl-3-methylimidazolium hydrogensulfate, 1-ethyl-3-methylimidazolium octylsulfate, 1-ethyl-3- methylimidazolium thiocyanate, 1-ethyl-3-methylimidazolium p-toluenesulfonate, 1-ethyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium bromide, 1-ethyl-3-methylimidazolium methylsulfate, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, 1-ethyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium bis (pentafluoroethyl) phosphinate, 1-ethyl-3-methylimidazolium bis [oxalato (2) -] borate, 1-ethyl-3 -methylimidazolium bis [1,2-benzenediolato (2 -)] borate, 1-ethyl-3-methylimidazolium trifluoroacetate, 1-butyl-3-methylimidazolium dicyanamide, 1-butyl-3-methylimidazolium iodide, 1-butyl 3-methylimidazolium octylsulfate, 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium bromide, 1-propyl-3-methylimidazolium iodine d, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium tosylate, 1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-methylimidazolium methylsulfate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium trifluoroacetate, 1-butyl-3-ethylimidazolium trifluoromethanesulfonate, 1-hexyl-3-methylimidazolium tris (trifluoromethylsulfonyl) methide, 1-hexyl-S-methylimidazolium chloride, 1-hexyl-3-methylimidazolium-t-trifluoroborate, 1-hexyl-3-methylimidazolium hexafluorophosphate, 1-hexyl-3-methylimidazolium trifluoromethanesulfonate, 1-hexyl- 3-methylimidazolium bis (trifluoromethylsulfonyl) imide, 1-hexyl-3-methylimidazolium tris (pentafluoroethyl) trifluorophosphate, 3-methyl

1 octylimidazolium chloride, 3-methyl-1-octylimidazolium octylsulfate, 3-methyl-1-octylimidazolium trifluoromethylsulfonate, 3-methyl-1-octylimidazolium tetrafluoroborate, 3-methyl-1-octylimidazolium hexafluorophosphate, 3-methyl-1 - octylimidazolium bis (trifluoromethylsulfonyl) imide, 1-decyl-3-methylimidazolium chloride, 1-decyl-3-methylimidazolium bromide, 1-decyl-3-methylimidazolium tetrafluoroborate, 1-dodecyl-3-methylimidazolium tetrafluoroborate, 3 -Methyi-1 - tetradecylimidazolium chloride ^ -methyl-i-tetradecylimidazolium tetrafluoroborate, 1 -hexadecyl-S-methylimidazolium chloride, 1-octadecyl-3-methylimidazolium chloride, 1-octadecyl-3-methylimidazolium hexafluorophosphate, 1 - Octadecyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide, 1-octadecyl-3-methylimidazolium tris (pentafluoroethyl) trifluorophosphate, i -benzyl-3-methylimidazolium chloride, 1-benzyl-3-methylimidazolium trifluoromethylsulfonate, 1-benzyl- 3-methylimidazolium tetrafluoroborate, 1-benzyl-3-methylimidazole ium-hexafluorophosphate, 1-phenylpropyl-3-methylimidazolium bromide, 1-phenylpropyl-3-methylimidazolium hexafluorophosphate, 1-propyl-3-methylimidazolium iodide, 1-butyl-3-methylpyrrolidinium trifluoromethanesulfonate, trisubstituted imidazolium derivatives, such as 1, 2,3-trimethylimidazolium iodide, 1-ethyl-2,3-dimethylimidazolium trifluoromethylsulfonate, 1-ethyl-2,3-dimethylimidazolium chloride, 1-ethyl-2,3-dimethylimidazolium bromide, 1-ethyl 2,3-dimethylimidazolium methylsulfate, 1-ethyl-2,3-dimethylimidazolium p-toluenesulfonate, 1-ethyl-2,3-dimethylimidazolium hexafluorophosphate, 1-ethyl-2,3-dimethylimidazolium tetrafluoroborate, 1-ethyl 2,3-dimethylimidazolium trifluoromethanesulfonate, 1-butyl-2,3-dimethylimidazolium iodide, 1-butyl-2,3-dimethylimidazolium octylsulfate, 1-butyl-2,3-dimethyl-chloride, 1-butyl-2, 3-dimethylimidazolium tetrafluoroborate, 1-butyl-2,3-dimethylimidazolium hexafluorophosphate, 1-butyl-2,3-dimethylimidazolium trifluoromethanesulfonate, 1-Pr opyl-2,3-dimethylimidazolium chloride, 1-hexyl-2,3-dimethylimidazolium tetrafluoroborate, i-Hexyl ^ .S-dimethylimidazolium chloride, 1-hexadecyl-2,3-dimethylimidazolium chloride, 1-hexyl-2,3-dimethylimidazolium tris (pentafluoroethyl) trifluorophosphate

Pyridinium derivative θ, such as, for example, N-ethylpyridinium chloride, N-ethylpyridinium bromide, N-butylpyridinium chloride, N-butylpyridinium bromide,

N-butylpyridinium methylsulfate, N-butylpyridinium tetrafluoroborate, N-butylpyridinium hexafluorophosphate, N-butyl-3,4-dimethylpyridinium chloride, N-butyl-3,5-dimethylpyridinium chloride, N-butyl-3-methylpyridinium chloride hexafluorophosphate, N-butyl-3-methylpyridinium chloride, N-butyl-3-methylpyridinium bromide, N-butyl-3-methylpyridinium methylsulfate, N-butyl-3-methylpyridinium tetrafluoroborate, N-butyl-3-methylpyridinium trifluoromethanesulfonate, N-butyl-4-methylpyridinium chloride, N-butyl-4-methylpyridinium bromide, N-butyl-4-methylpyridinium tetrafluoroborate, N-butyl-4-methylpyridinium hexafluorophosphate, N-hexylpyridinium chloride, N- Hexylpyridinium bromide, N-hexylpyridinium tetrafluoroborate, N-

Hexylpyridinium hexafluorophosphate, N-hexylpyridinium trifluoromethanesulfonate, N-hexylpyridinium bis (trifluoromethylsulfonyl) imide, N-octylpyridinium chloride, N-octylpyridinium bis (trifluoromethylsulfonyl) imide, A-methyl-N-octylpyridinium chloride - pyrrolidinium derivatives, such as 1,1-dimethylpyrrolidinium iodide, 1,1-dimethylpyrrolidinium tris (pentafluoroethyl) trifluorophosphate, 1-ethyl-1-methylpyrrolidinium bromide, 1-ethyl-1-methylpyrrolidinium hexafluorophosphate, 1-ethyl-1 - methylpyrrolidinium tetrafluoroborate, 1-ethyl-1-methylpyrrolidinium methylsulfate, 1,1-dipropylpyrrolidinium bis (trifluoromethylsulfonyl) imide, 1,1-dibutylpyrrolidinium bis (trifluorosulfonyl) imide, 1-butyl-1-methylpyrrolidinium bis [oxalato ( 2 -)] borate, 1-butyl-1-methylpyrrolidinium dicyanamide, 1-butyl-1-methylpyrrolidinium chloride, 1-butyl-1-methylpyrrolidinium bromide, 1-butyl-1-methylpyrrolidinium methylsulfate, 1-butyl 1-methylpyrrolidinium trifluoromethanesulfonate, 1-butyl 1-methylpyrrolidinium tetrafluoroborate, 1-butyl-1-methylpyrrolidinium hexafluorophosphate, 1-butylmethylpyrrolidinium trifluoroacetate, 1-butyl-1-methylpyrrolidinium bis (pentafluoroethyl) trifluorophosphate, 1, 1-dihexylpyrrolidinium bis (trifluoromethylsulfonyl) imide, 1-hexyl-1-methylpyrrolidinium chloride, 1 -hexyl 1-methylpyrrolidinium bis-trifluoromethylsulfonydimide, 1-methyl-1-octylpyrrolidinium chloride, 1-octyl-1-methylpyrrolidinium bis (trifluoromethylsulfonyl) imide

- Phosphonium derivatives such as tetrabutylphosphonium tris (pentafluoroethyl) trifluorophosphate, trihexyl (tetradecyl) phosphonium chloride, trihexyl (tetradecyl) phosphonium tetrafluoroborate, trihexyl (tetradecyl) phosphonium bis (trifluoromethylsulfonyl) imide, trihexyl (tetradecyl) phosphonium tris (pentafluoroethyl) trifluorophosphate, trihexyltetradecylphosphonium hexafluorophosphate, trihexyl (tetradecyl) phosphonium bis [oxalato (2 -)] borate, trihexyl (tetradecyl) phosphonium bis [1,2-ben2oldiolata (2 -) - O, O '] - borate

Ammonium derivatives, such as, for example, tetramethylammonium tris (pentafluoroethyl) trifluorophosphate, tetramethylammonium bis [oxaIato (2-)] borate, tetraethylammonium tris-c pentafluoroethyldifluorophosphate, tetraethylammonium bis [1,2-benzenediolato (2-) O , O '] borate, tetraethylammonium bis [salicylato (2 -)] borate, tetraethylammonium bis [2,2'-biphenyldiolato (2-) O, O'] borate, tetraethylammonium bis [malonato (2 )] borate, tetrabutylammonium bis (trifluoromethylsulfonyl) imide,

- Tetrabutylammonium tris (pentafluoroethyl) trifluorophosphate, methyltrioctyl ammonium bis (trifluoromethylsulfonyl) imide, methyltrioctylammonium trifluoroacetate, ethyl-dimethyl-propylammonium bis (trifluoromethylsulfonyl) imide, methyltrioctylammonium trifluoromethanesulfonat

Guanidinium derivatives such as, for example, guanidinium p-toluenesulfonate, guanidinium tris (pentafluoroethyl) trifluorophosphate, guanidinium trifluoromethanesulfonate, N, N, N ', N'-tetramethyl-N'-ethylguanidinium tris (pentafluoroethyl) trifluorophosphate, N, N, N ⁽ , N'-tetramethyl-N "-ethylguanidinium trifluoromethanesulfonate, N, N, N ', N'-pentamethyl-N'-propylguanidinium trifluoromethanesulfonate, N, N, N'-N, N'-pentamethyl-N'-isopropylguanidinium trifluoromethanesulfonate, hexamethylguanidinium tris (pentafluoroethyl) trifluorophosphate

Isouronium derivatives such as O-methyl-N, N, N ', N'-tetramethylisouronium trifluoromethanesulfonate, O-ethyl-N, N, N', N'-tetramethylisouronium tris (pentafluoroethyl) trifluorophosphate, O-ethyl - NNN'.N'-tetramethylisouronium trifluoromethanesulfonate, S-ethyl-N, N, N ', N'-tetramethylisouronium tris (pentafluoroethyl) trifluorophosphate, S-ethyl-NNN'.N'-tetramethylisothiouronium trifluoromethanesulfonate

A purity level "for synthesis" is essentially sufficient for both the precursor substance and the ionic liquid, and for the removal of pure substances it is necessary to avoid contamination of the ionic liquid or the precursor substance with other reducible substances, both the precursor substance and the ionic substance Liquid is preferably anhydrous.

The present invention provides methods for making particles comprising metals, semi-metals, metal compounds or nanometer-sized metalloid compounds.

The method according to the invention comprises the following steps:

Preparation of a solution comprising at least one precursor substance in at least one ionic liquid, precursor substance being understood as meaning an electrochemically reducible compound of a metal or a semimetal, and the solution being produced in an evacuable device containing two electrodes or the solution after its production into an evacuable device containing two electrodes, adjusting the pressure in the evacuatable device to a value between 1 Pa and 2000 Pa,

Introducing an inert or reactive gas, the pressure in the evacuable apparatus being kept between 1 Pa and 2000 Pa,

Removal of gas dissolved in the solvent and / or residual moisture, generation of a gas discharge,

- Separation of the particles formed.

The person skilled in the art knows, on the basis of his expertise, which precursor substances can be converted by reduction or reaction into the corresponding metals, semimetals, metal compounds or semimetal compounds. The person skilled in the art is also aware of how to generate a plasma with a chemically reactive gas which reacts with the metal or semimetal cations of the at least one precursor substance to give the desired metal or semimetal compounds. He can therefore select suitable precursors and process gases, without departing from the scope of the claims.

Due to their vanishingly small vapor pressure (<1 Pa) and their large electrochemical window, ionic liquids are suitable for the processes according to the invention. Conventional solvents, unlike ionic liquids at room temperature, usually already have a high vapor pressure, which can not produce a sufficiently good vacuum. The latter, however, is essential for the ignition of a homogeneous gas discharge. A homogeneous gas discharge is characterized by the fact that with the exception of the space charge zones, which form the walls adjacent to the plasma, on the one hand substantially equal particle concentrations prevail and on the other hand, the plasma temperatures (electron, ion and neutral particle temperature) substantially are the same size in the plasma phase. In the context of this invention, the gas discharge is considered to be homogeneous as soon as the luminous appearance of the plasma appears uniformly intense and evenly colored to the human eye. For carrying out the method according to the invention, it is sufficient if the plasma is homogeneous in the immediate vicinity of the ionic liquid.

By electrochemical window is meant that region of the applied electrical voltage in which anions and cations of the ionic liquid are inert to oxidation and reduction. Depending on the substances used, the electrochemical window is up to 7 V.

In the method according to the invention, the deposition of the nanoparticles takes place at the interface of liquid and plasma. This interface thus has the function of a gaseous electrode and is thus mechanically contact-free.

It will be readily apparent to those skilled in the art that in the production of metals and semi-metals, the amount of product formed, i. the amount of particles formed depends directly on the amount of electric charges that have flowed (product of current and time). The amount of product formed is so

M l 't.

with / 77 = mass of the particles formed in g

M = molar mass in g / mol

/ = Current in A t = time in s

F = Faraday constant = 96.485 C / mol z = charge number f _{MeV +} = transfer number of the cations of the precursor substance

In a particularly advantageous embodiment, the process according to the invention is operated continuously. Here, anode and cathode space are separated. The educts are fed continuously; at the same time, the liquid is removed together with the sedimented products.

The size of the resulting particles depends on various parameters that influence the growth process of the particles. Consequently, the particle size can be controlled both by process control and by substance selection. The skilled person can adjust the particle size by appropriate optimization experiments.

The greater the surface tension of the solution used, consisting of at least one precursor substance and at least one ionic liquid, the longer the product particles can grow before they finally submerge and sink by gravity into the ionic liquid. The reaction of the metal or semimetallic cations and thus the growth of the product particles takes place exclusively in the phase boundary region between ionic liquid and plasma.

The higher the viscosity of the solution used, the slower the product particles formed at the phase boundary to the plasma sink into the liquid. The slower the product particles sink in, the more time is available Grow available, so that form in larger viscous solutions larger particles than in lower viscous.

The higher the density of the product particles, the faster they move away from the phase boundary due to gravity. This leads to shorter growth times and consequently smaller particle diameters.

If the solution is not stirred, the downward movement of the product particles is determined only by the viscosity of the liquid, the density of the particles and the surface tension of the liquid. An additional stirring action leads to a higher convection in the solution, whereby the particles are transported away from the reactive phase boundary more quickly. The diameters of the product particles are correspondingly smaller.

The ionic liquid used as a solvent substantially does not participate in the reaction and is therefore usable for a long time, provided that no significant decomposition phenomena occur. With the method according to the invention particles with diameters of 1 nm to 1000 nm can be formed. The size of the particles depends as described on the process control and the selection of the substances used. The size distribution of the particles in each individual implementation of the method according to the invention is essentially monodisperse and reproducible.

The separation of the particles formed can optionally be carried out continuously or batchwise. The particles according to the invention can be used, for example, for applications in medicine, energy technology and the chemical industry. If necessary, the particles can be bound by embedding in a matrix, by adhesion or sintering processes on or on a substrate.

For example, because of their antimicrobial effect, silver nanoparticles can be added to polymers used to coat medical instruments. Noble metal nanoparticles are further useful as catalysts for electrochemical reactions, e.g. for the oxidation of hydrogen and methanol as well as the reduction of oxygen.

FIG. 1 shows the reduction of a metal or semimetal with the aid of an argon charge. A metal anode (6) is in contact with the ionic liquid. The anode material used is platinum. Alternatively, an anode made of the metal to be deposited can also be used. This then dissolves gradually during the experiment. The cathode (1) projecting into the plasma (2) consists of platinum. In the argon plasma argon cations are moved by the electric field to the cathode (1) and reduced there. In the ionic liquid (5), metal cations (3) migrate in the electric field to the phase boundary with the plasma, where they are reduced by electrons originating from the plasma to the elemental metal or semimetal.

FIG. 2 shows the sketch of an apparatus for the discontinuous production of nanoparticles. It consists in the core of a glass vessel (16) with two

Metal electrodes (13, 14). Through a pump connected to the apparatus

(11) a vacuum is generated in the apparatus. With the help of an automatically gere¬

apply gas supply can be introduced through the valves (7, 8, 9) individual gases or gas mixtures in the experimental setup controlled. The pressure- Messers (10) is also linked to the gas control unit, which allows the setting of predetermined pressures in the apparatus. The precursor substance (12) dissolved in the ionic liquid is located in the lower part of the glass apparatus, the lower electrode (13) being covered by the liquid (12). The high voltage source (17) serves to supply power to the electrodes. The lower one

Electrode (13) is anodic and the upper electrode (14) connected cathodically. The reaction product is separated from the liquid after completion of the experiment outside the apparatus.

Figure 3 shows a structure for a continuous reaction by continuous addition of starting material and sedimentation of the product with simultaneous separation of anode and cathode space. The apparatus also has an automatically controlled gas supply (18, 19, 20, 21) and a

Pump for vacuum generation (22). However, the reaction vessel has a separate anode (30) and cathode (25) each. In order to bring the liquid level in anode and cathode space to the desired level, located in the gas phase region of the apparatus, the valve (26). If required, this valve can be used to establish a connection between the gas phases of the anode and cathode compartments. Via the valve (32) are continuously the educts

supplied and discharged via the valve (29), the liquid together with the products. The pressure conditions must be selected so that the liquid levels do not change during operation. This includes the inlet and outlet pressure at the valves (29) and (31) with a. FIG. 4 shows an apparatus for depositing nanoscale particles in a radio-frequency discharge. In contrast to the sketch shown in Figure 2, the high voltage source is replaced by a commercially available DC voltage source (40), and around the glass body there is a copper coil (38) to which a radio frequency is applied. This structure has the advantage that the introduced electrodes (37) and (43) are used exclusively for the deposition of the nanoparticles and not for the generation of the gas discharge.

Embodiment 1

Deposition of silver from a silver-containing 1-butyl-3-methylimidazolium trifluoromethanesulfonate solution

In a vacuum apparatus made of commercially available borosilicate glass (see FIG. 2), there are two platinum electrodes at a distance of approximately 10 cm. The lower electrode consists of a platinum sheet of 1 cm ² , the upper electrode consists of a one-sided closed platinum hollow cathode (height 1, 5 cm, diameter 0.75 cm), with the open side facing the counter electrode in the ionic liquid see , Both electrodes are connected to a high voltage source from Heinzinger (model HNC10.000-10). The lower electrode is anodically connected in the experiment, the upper electrode is cathodically connected. About 10 ml of a solution of silver trifluoromethanesulfonate in 1-butyl-3-methylimidazolium trifluoromethanesulfonate (c = 0, M7 mol / l) are added to the cleaned glass vessel. The lower electrode is located after filling about 2 cm below the phase boundary between the ionic liquid and the gas phase. By means of a rotary vane pump, the apparatus is evacuated and exposed to the solution for at least 15 minutes the final vacuum of the pump. Residual moisture in the solution as well as any gases dissolved in the ionic liquid are thereby expelled. If the bubbling does not stop after 15 minutes, you must continue pumping until no more bubbles are released from the solution.

Following evacuation, argon (purity 99.996%) is introduced into the apparatus via an automated gas supply and continuously pumped out. The control is adjusted so that the apparatus has a constant pressure of 100 Pa (+/- 1%). After reaching a stable pressure, a DC discharge between the ionic liquid and the cathode is ignited by applying a voltage between the electrodes. At currents of 10 mA, a voltage of approx. 0.5 kV is applied between the electrodes. The current density at the phase boundary between plasma and ionic liquid is of the order of 1 mA / cm ² . At the phase boundary between the ionic liquid and the plasma, optically visible silver precipitates in the form of a black product. After 10 minutes, the gas phase discharge is switched off and the resulting silver is separated in a centrifuge. Examination of the particles in the transmission electron microscope shows that they are pure silver particles, with more than 95% having a diameter in the range of 5-50 nm.

Embodiment 2

Deposition of copper from a copper-containing 1-butyl-3-methylimidazolium trifluoromethanesulfonate solution

In the same way as silver was deposited in embodiment 1, copper can be deposited from a solution of copper (II) trifluoromethanesulfonic dissolved in 1-butyl-3-methylimidazolium trifluoromethanesulfonate. The experimental conditions are the same as those of Embodiment 1. LIST OF REFERENCE NUMBERS

1st cathode

2. Gas discharge 3. Metal or semi-metal cations

4. Anions of ionic liquidity

5. Ionic liquid with dissolved precursor substance

6. anode

7. Adjustable valve 8. Adjustable valve

9. Adjustable valve

10. Pressure gauge

11. Rotary vane pump

12. Ionic liquid with dissolved precursor substance 13. Anode

14th cathode

15. Gas discharge

16. Glass vessel

17. High voltage source 18. Adjustable valve

19. Adjustable valve

20. Adjustable valve

21. Pressure gauge

22. Rotary vane pump 23. High voltage source

24. Cathode 25. Gas phase discharge in the cathode compartment

26th valve

27. Ionic liquid with dissolved precursor substance

28. Glass apparatus 29. Ionic liquid outlet valve and product 30. Anode compartment 3 I.Anode

32. inlet valve for ionic liquid with precursor substance

33. Adjustable valve 34. Adjustable valve

35. Adjustable valve

36. Pressure gauge

37. cathode

38. Copper coil for coupling in the radio frequency 39. Gas phase discharge

40. DC voltage source

41. Rotary vane pump

42. Ionic liquid with dissolved precursor substance 43. Anode

Claims

claims

1. A process for the preparation of particles comprising metals, semimetals, metal compounds or metalloid compounds with diameters in the nanometer range, characterized in that at least one precursor substance is dissolved in at least one ionic liquid and then reduced in a plasma phase either by free electrons or with particles reacts from the plasma phase, wherein precursor substance is understood to mean a salt of a metal or a metalloid and the plasma phase is generated by a homogeneous gas discharge of an inert or reactive process gas at a pressure of 1 Pa to 2000 Pa.

2. A process for the preparation of particles according to claim 1, characterized by the steps: a) preparing a solution comprising at least one precursor substance in at least one ionic liquid, wherein the precursor substance is an electrochemically reducible compound of a metal or a semimetal understood, and wherein the solution in an evacuatable device containing two electrodes, or the solution is transferred after its preparation into an evacuable device containing two electrodes, b) adjusting the pressure in the evacuatable device to a value between 1 Pa and 2000 Pa, c) introducing an inert or reactive gas, the pressure in the evacuable apparatus being kept between 1 Pa and 2000 Pa, d) removing gas dissolved in the solvent and / or residual moisture, e) generating a gas discharge, f) separating off the particles formed ,

3. A process for the preparation of particles according to claim 2, characterized in that the ionic liquid is selected from the group monosubstituted imidazolium derivatives, disubstituted imidazolium derivatives, trisubstituted imidazolium derivatives, pyridinium derivatives, pyrrolidinium derivatives, Phosphonium derivatives, ammonium derivatives, guanidinium derivatives, isouronium derivatives.

4. A process for the preparation of particles according to any one of claims 1 to 3, characterized in that the precursor substance is a metal compound.

5. A process for the preparation of particles according to any one of claims 1 to 3, characterized in that the precursor substance is a compound of a semi-metal selected from the group boron, silicon, germanium, arsenic, antimony, selenium and tellurium.

6. A process for the preparation of particles according to any one of claims 1 to 5, characterized in that the homogeneous gas discharge is carried out at a pressure of 100 Pa ± 1 Pa.

7. A process for the preparation of particles according to any one of claims 2 to 6, characterized in that an inert gas selected from the group helium, neon, argon, krypton, xenon or mixtures thereof is used.

8. A process for the preparation of particles according to any one of claims 2 to 6, characterized in that a reactive gas selected from the group

Oxygen, nitrogen, nitrogen monoxide, nitrogen dioxide, nitrous oxide, carbon monoxide, carbon dioxide, hydrogen, methane, ethane, fluorine, chlorine, bromine,

Air or mixtures thereof is used.

9. A process for the preparation of particles according to any one of claims 1 to 8, characterized in that the homogeneous gas discharge by radio waves, microwaves, direct current or alternating current is generated. 100. Method for producing particles according to one of claims 1 to 9, characterized in that the method is operated continuously.

11. Particles comprising metals, semiconductors, metal compounds or semiconductor compounds with diameters of 1 nm to 1000 nm, by methods according to claims 1 to 10.

12. Particles according to claim 11, characterized in that a proportion of greater than or equal to 95% of the particles has diameters of 5 nm to 50 nm, preferably from 15 nm to 30 nm.

13.Vorrichtung comprising particles according to claim 11 or 12 and a substrate, characterized in that the particles are bound by embedding in a matrix, by adhesion or sintering processes on or on the substrate.

14.Use of noble metal nanoparticles prepared according to one of claims 1 to 10 as electrochemical catalysts.

15.Use of silver nanoparticles prepared according to one of claims 1 to 10 as antimicrobial additives for polymers for coating medical instruments.