DE102014008290A1 - Composition and method for sample preparation - Google Patents

Abstract

The present invention relates to an agent and a method with which particles, in particular nanoparticles, can be prepared and separated for a measurement by means of microscopic methods. The agent contains at least paraformaldehyde and a solvent.

Description

The present invention relates to an agent and a method with which particles, in particular nanoparticles, can be prepared and separated in particular for a measurement by means of microscopic methods.

In the field of research, production and processing of particle-containing systems, apart from the elemental composition of the particles, the particle size, their number distribution and the particle shape have a strong effect on the system properties. For example, the coercive force of magnetic particles depends on both the shape and the size of the particles. In the case of pigments, the optical properties also depend on the aspect ratio and the size distribution. In particular for particles which are <100 nm in at least one dimension (nano-objects, in particular nanoparticles), these quantities are not only of technical but also legal significance, whereby the number distribution of the particle size will be decisive in the legal classification [ COMMISSION RECOMMENDATION of 18 October 2011 on the definition of nanomaterials; Official Journal of the European Union, L 275 / 38-40, 2011 ].

Accordingly important and required by law, are suitable methods for determining the particle size, their number distribution and the particle shape. Here are mainly microscopic methods into consideration, which can detect individual particles in shape and extent. For the characterization of nanoparticles, especially electron microscopic methods (SEM, TEM, STEM) as well as raster-force and scanning tunneling microscopy are relevant.

Typically, depending on their mutual interactions and their specific surface area, particles tend more or less to form aggregates or agglomerates (for a more detailed definition of the terms see ISO 14887 [ISO 14887, Sample preparation - Dispersing procedures for powders in liquids, 2000 ] from the primary particles. Precisely because of their high specific surface area, nanoparticles tend to form extremely aggregates, driven by the high surface energy of the system. This represents a major problem especially for the microscopic characterization, since a meaningful characterization of the primary particles is only possible if they are isolated.

Correspondingly important are suitable methods for sample preparation for the above-mentioned microscopic methods, which are able to break up the agglomerates and aggregates up to the primary particles and to apply the separated particles to a suitable sample carrier.

• – Die Probe muss gleichmäßig auf den Probenträger appliziert werden, wobei der Probenträger selbst nur minimale Oberflächenrauheit aufweisen darf.
• – Die Probe muss speziell für die Elektronenmikroskopie im Hochvakuum stabil sein.
• – Die Partikel dürfen zur besseren (evtl. automatischen) Auswertung der Mikroskopaufnahmen nur in einer Monolage auf den Probenträger aufgebracht werden.

In addition, the preparation method must meet the requirements for preparations for electron microscopy or AFM (atomic force microscopy):

• - The sample must be applied evenly to the sample carrier, whereby the sample carrier itself may only have minimal surface roughness.
• - The sample must be stable especially for electron microscopy in a high vacuum.
• - The particles may only be applied to the sample carrier in a monolayer for better (possibly automatic) evaluation of the microscope images.

Known is a method used to measure nanoparticles in which powdered samples are manually kneaded with a eutectic mixture of 60% camphor and 40% naphthalene for disaggregation. Subsequently, a piece of the mixture is placed on a slide, a coverslip placed over it and fixed by melting, cooling and removing the coverslip, a layer of the mixture on the slide. Subsequently, the camphor and naphthalene eutectic is sublimated in vacuo so that the particles remain on the slide and can be examined microscopically [ N. Thaulow and EW White; General method for dispersing and disaggregating particulate samples for quantitative SEM and opticla mircroscopic studies; Powder Technology, 6, 377-379 (19971172) ]

Furthermore, the preparation of the particle-containing solid samples directly as a solid (dry dispersion). By impact or shear forces is thereby trying to break up any aggregates or agglomerates present in the primary particles. The aerosol thus generated is z. B. using Scanning Mobility Particle Sizer (SMPZ), or an Optical Particle Counter (OPC) analyzed [ S. Füchsel, K. Husemann and U. Peuker; Dry deagglomeration of nanoparticle agglomerates in a classifier mill; Chemical Engineer Technology, 83, no. 8, 1262-1275, 2011 ].

• – Herstellung einer stabilen Dispersion von Primärpartikeln aus einer Probe aus aggregierten bzw. agglomerierten Partikeln
• – Fixierung der stabilen Dispersion von Primärpartikeln auf einen für REM, TEM, AFM geeigneten Probenträger
• – Entfernung des Dispergiermedium, ohne dass eine Reaggregation stattfindet und die vollständig genug ist, so dass eine Auswertung möglich ist

In microspheroscopic investigations of nanoparticles, the image analysis is usually computer-aided and results in a statistical interpretation (size distribution). In particular, three aspects are important in the sample preparation of nanoparticles for microscopy (with subsequent image analysis):

• Preparation of a stable dispersion of primary particles from a sample of aggregated or agglomerated particles
• Fixation of the stable dispersion of primary particles to a sample carrier suitable for SEM, TEM, AFM
• Removal of the dispersing medium, without any reaggregation taking place, which is complete enough so that an evaluation is possible

Except for the camphor naphthalene method and the direct dry dispersion, no sufficiently effective methods are known which are able to solve the above problem. However, existing methods have disadvantages and limitations.

a) camphor naphthalene method

The method is very sensitive as it only works exactly on the eutectic. Crystal formation next to the eutectic mixture causes the particles to collapse by forming large crystals. Only at the eutectic point are the crystals small enough.

In addition, the system is nonpolar. Particles with more polar surface tend to segregate / segregate from the camphor naphthalene system.

b) dry dispersion

Only substances which are present as pure solid as possible can be dispersed. Preparation by this method with prior drying of nanodispersions can lead to irreversible aggregation and thus falsification of the results.

The energy input for deaggregation of agglomerates and aggregates is limited. A stabilization of the primary particles (eg by auxiliaries) is not possible.

The object of the present invention was therefore to provide a means and a method by means of which particle-containing samples can be applied to a carrier in such a way that the particles present in the sample are isolated as much as possible, d. H. present as primary particles, and not contaminated by matrix residues and can be measured.

It has been found that a matrix of paraformaldehyde and a solvent is particularly well suited to disperse and apply samples containing nanoparticles to a support. The solvent can then be evaporated and the paraformaldehyde depolymerized and thus also evaporated. The remaining on the sample carrier and separated by dispersing particles can be examined microscopically.

• a) Mischen einer partikelhaltigen Probe zumindest mit Paraformaldehyd und einem Lösungsmittel
• b) Aufgabe der in Schritt a) erhaltenen Mischung auf einen Träger
• c) Entfernen des Lösungsmittels und des Paraformaldehyds

The subject matter of the present invention is therefore a method for applying particle-containing samples to carriers characterized by the following method steps:

• a) mixing a particle-containing sample at least with paraformaldehyde and a solvent
• b) applying the mixture obtained in step a) to a support
• c) removing the solvent and the paraformaldehyde

In a preferred embodiment, paraformaldehyde is first mixed with a solvent in step a) and then the particle-containing sample is added. The mixture of paraformaldehyde and a solvent is also called matrix.

In a preferred embodiment, in step a) as solvent 1-butanol, 2-pentanol, xylene, butyl acetate, anisole, DMF (dimethylformamide), NMP (N-methyl-2-pyrrolidone), 1,1,2,2-tetrachloroethane , Tripropylamine, n-octane, pyridinium acetate, pyridine, methylpyridine or mixtures thereof. A preferred mixture is a mixture containing pyridine and pyridinium acetate.

In a further preferred embodiment, the mixture prepared in step a) contains between 5 and 50% by weight, preferably between 5 and 25% by weight, of paraformaldehyde.

In a further embodiment, the particle-containing sample in step b) is suspended in a solvent prior to mixing with the matrix. Preferably, it is suspended in the solvent which is also contained in the matrix.

In a further preferred embodiment, the mixture obtained in step a) is treated with ultrasound waves before being applied to the carrier.

In a further preferred embodiment, the mixture from step a) is added to the carrier by immersing it therein. This kind of task is called dip-coating.

In a preferred embodiment, the solvent is removed by treating the carrier with a stream of nitrogen.

In a preferred embodiment, the paraformaldehyde is removed by heating the support in a stream of nitrogen up to 400 ° C.

The present invention also provides an agent comprising at least from 5 to 50% by weight of paraformaldehyde and one or more solvents selected from the group of 1-butanol, 2-pentanol, xylene, butyl acetate, anisole, DMF, NMP, 1,1,2 , 2-tetrachloroethane, tripropylamine, n-octane, pyridinium acetate, pyridine and methylpyridine.

The present invention also provides the use of the method according to the invention for providing sample carriers for microscopic examinations.

1 shows a high resolution SEM image of magnetite nanoparticles at 5000x magnification. The application on the carrier was carried out according to Example 1.

2 shows a possible device for removing the matrix.

According to the invention, nanoparticles are particles which have an extent of less than 100 nm in each dimension. Microscopic examinations or microscopic procedures are known to the person skilled in the art. In particular, these are electron microscopic methods such as SEM, TEM and STEM and atomic force and scanning tunneling microscopy methods. FIB microscopy and light microscopy are also microscopic methods according to the invention.

A carrier according to the invention is any agent that can be used as a sample substrate in microscopic examinations. Typically, carriers are flat slices or pieces. Particularly suitable for microscopic investigations are substrates which have a very low surface roughness and whose surface is so flat that the particles to be examined lie in a focal plane. The person skilled in the art is aware of carriers for the respective microscopic methods. Examples are silicon wafers, silicon nitride or mica TEM substrates. A sample carrier is a carrier on which a sample is applied.

A particle-containing sample is a sample containing at least particles. Particulate-containing samples preferably contain at least particles in the micrometer or sub-micron range. Typically, these are particles whose largest dimension is less than 1 μm. However, the method according to the invention is also applicable to particles whose largest dimension is greater than 1 .mu.m, for example during sample preparation for light microscopy. The sample particularly preferably contains nanoparticles. Paraformaldehyde is the short-chain polymer of formaldehyde, the degree of polymerization is typically between 8 and 100. It is a white powder, which is split back into formaldehyde in water under heating or by dry heating. The formula of paraformaldehyde with a degree of polymerization of 8 to 100 is shown in formula I.

To carry out the method according to the invention, a particle-containing sample is mixed with paraformaldehyde and a solvent. Suitable solvents are hereinafter referred to as "preparation of the paraformaldehyde matrix". All components can be mixed. Since paraformaldehyde is poorly soluble in most solvents, a mixture of paraformaldehyde and the solvent can first be produced. This mixture is also called matrix. The sample is then mixed with the matrix. In order to produce as homogeneous a mixture as possible, the sample is preferably dispersed in the matrix and homogenized. For this purpose, methods are suitable which expose the sample to shear forces. These are z. As ultrasonic, rotor-stator homogenizers (Ultra Thurrax) and flow homogenizers (dispersers). Preferably, the prepared mixture of sample, solvent and paraformaldehyde contains between 5 and 50% by weight, preferably between 5 and 25% by weight, of paraformaldehyde. The proportion of the sample in the mixture is typically very low. Suitable values are for example between 20 and 500 ppm (g / g). however, this may vary depending on the density of the sample material. It should be added so much sample material that as many particles as possible can be represented as isolated as possible on a particular carrier surface.

The most homogeneous mixture thus produced is then placed on the carrier. In this case, application methods which produce as homogeneous and thin a distribution of the mixture as possible on the carrier are preferred. The support (eg a silicon wafer) is preferably wetted by immersion in the mixture with the sample (dipcoating). Alternatively, the mixture may for example also be applied to the carrier, for. B. dripped and distributed there. This is particularly preferred in transmission recordings, since this would disturb particles on the underside of the carrier, as they occur in dip coating. Subsequently, the matrix consisting of solvent and paraformaldehyde is removed. The more complete the matrix is removed, the more accurate the results of the microscopic examination can be. This can be done for example by heating, applying a vacuum or in a gas stream. Also, several of these possibilities can be combined. Typically, the solvent is first removed. The removal of the solvent preferably takes place in the gas stream. The gas stream may consist of any inert gas or air or oxygen. It is preferably a nitrogen stream. This is passed over the carrier so that the solvent is removed. The choice of gas for the gas flow depends on the nature of the sample. For oxidation-sensitive samples, the use of oxygen or air should be avoided.

After evaporation of the solvent, a thin layer of paraformaldehyde with particles dispersed therein remains on the sample carrier.

To remove the paraformaldehyde, a gas stream is typically insufficient. For this purpose must be heated in addition. It has been found that paraformaldehyde in the gas stream at a temperature between 200 and 500 ° C, preferably between 300 and 400 ° C can be removed. Alternatively, it can also be removed in vacuo at temperatures between 20 and 200 ° C, preferably between 50 and 200 ° C or in aqueous, preferably acidic solutions, or in acidic vapors. The paraformaldehyde depolymerizes and the monomers can be vaporized. The isolated particles remain on the carrier.

In a preferred embodiment, the removal of the matrix takes place in a gas stream by passing a gas stream over the carrier, while over a period of between 10 and 30 minutes, the temperature is steadily increased to the maximum desired temperature.

In one embodiment, after evaporation of the solvent and paraformaldehyde by means of a gas stream of an inert gas and optionally elevated temperature to completion at the maximum temperature instead of the inert gas may be gasified for a short time with oxygen or air. The oxygen can be used to remove any remaining residues of the matrix by oxidation. Typically, 5 to 10 minutes are sufficient for this.

Alternatively, the matrix can also be removed by heating in the presence of water. This is particularly applicable to solvents which are miscible with water, e.g. As for pyridinium acetate or pyridine. By the addition of water, the paraformaldehyde decomposes and can then be evaporated or stripped off together with the solvent. Preferably, after the addition of the water to temperatures between 60 and 90 ° C is heated.

2 shows a possible device for removing the matrix. The carrier with the matrix located thereon is introduced with particles into a flow chamber. The carrier can now optionally be heated simultaneously or at different times, gas can be supplied and / or vacuum can be applied.

In addition, the process according to the invention offers the possibility of adding auxiliaries (for example surface-active substances) to the matrix in order to prevent reaggregation of the particles by steric and / or electrostatic repulsion ISO 14887 section 8.5.3 and Annex B , In this way, the method according to the invention makes it possible to produce stable dispersions of isolated particles in auxiliaries which are particularly suitable for the preparation of conventional sample carriers for transmission electron microscopy (TEM). In the case of direct use of the auxiliaries without prior separation of the particles, this leads in most cases only to a more or less stable dispersion of aggregates.

Preparation of paraformaldehyde matrix

To prepare the mixture, which consists at least of paraformaldehyde and a solvent, the ingredients are mixed.

Since paraformaldehyde is practically insoluble in most solvents, it is preferred to first heat the paraformaldehyde together with the solvent to near the melting point, which is 120 ° C. As a rule, no clear solutions arise, but rather a swelling takes place. Suitable solvents are all solvents containing not more than 0.2% (weight%) of water. Since the matrix should be removed after applying the sample, the solvents should also be easy to remove again. The solvents therefore preferably have a vapor pressure of at least 20 mbar at 20 ° C.

Preference is also given to solvents having a boiling point above 110 ° C., since the swelling of the paraformaldehyde is preferably heated to about 110 ° C. Suitable solvents are, for example, alcohols such as 2-pentanol or 1-butanol, aromatics such as o-xylene, ethers such as diethylene glycol dimethyl ether, anisole or ethylene glycol monomethyl ether, esters such as butyl acetate, amides such as N, N-dimethylformamide, alkanes such as octane, amines such as pyridine or tripropylamine, ketones such as isobutyl methyl ketone or N-methyl-2-pyrolidone, haloalkanes such as 1,1,2,2-tetrachloroethane, organic acids such as acetic acid, organic salts such as pyridinium acetate. Mixtures of two or more solvents can be used according to the invention as a solvent. Suitable solvents are also ionic liquids, in which case ionic liquids are preferred, the z. B. can be removed by targeted decomposition again. Preferred solvents are 1-butanol, 2-pentanol, xylene, butyl acetate, anisole, DMF (dimethylformamide), NMP (N-methyl-2-pyrrolidone), 1,1,2,2-tetrachloroethane, tripropylamine, n-octane, pyridinium acetate , Pyridine, methylpyridine (all isomers are suitable) or mixtures thereof. Also, mixtures of pyridinium acetate and acetic acid are suitable. Preferred are DMF, NMP and 1,1,2,2-tetrachloroethane.

Alternatively, paraformaldehyde may be reacted with a suitable solvent by sonication to thereby swell the polymer to a viscous gel.

The particle-containing sample is dispersed in this gel of paraformaldehyde and solvent.

Anhydrous solvents are preferably used to prepare the matrix.

However, small amounts (<0.2% by weight) of water do not disturb the process. With larger amounts of water it can lead to the decomposition of the paraformaldehyde, since this completely decomposes in water when heated and forms a formaldehyde solution. However, it has been found that a suitably concentrated (1-4% solids content) aqueous dispersion of the sample can be diluted with a suitable anhydrous solvent and can also be used as a sample.

Preparation of sample carriers

The process according to the invention is outstandingly suitable for coating carriers. It is known to the person skilled in the art that specific requirements are made of the carrier for certain microscopic examinations. Typically, the support should have a smooth surface, with the surface roughness preferably being at least an order of magnitude smaller than the smallest particle of the sample. In addition, for use in electron microscopy, the carrier should preferably be electrically conductive in order to prevent adulteration due to charging effects. By vapor deposition (sputtering) with suitable materials (eg C, Pd, Pt, Au) it is also possible to use non-conductive or insufficiently conductive supports. Depending on the sample, sputtering can be done both before and after preparation. Sputtering can negatively influence the measurement result (eg covering of the particles by the sputtering layer).

The following table gives examples of suitable carriers for various microscopic examinations. REM TEM AFM light microscopy aluminum silicon nitride mica Glass carbon silica Glass quartz gold carbon silicon silicon silicon nitride silica

For the application of the mixture of the matrix with the sample any type of application is suitable, which produces a uniformly thin layer of the mixture on the support. For example, the mixture of the matrix with the sample can be placed on the support and spread there evenly. The order is preferably carried out by dipcoating. Simply by briefly immersing the sample carrier in the particle-containing paraformaldehyde matrix (dipcoating), a very homogenous film remains adhering to the carrier, which does not contract, peel off or burst during the thermal decomposition of the polymer.

The sample carrier thus produced can now be examined by means of microscopic methods after the above-described removal of the matrix.

• – Es ist geeignet für Feststoffe und Dispersionen
• – Es ist geeignet für polare und unpolare Stoffe, da durch Wahl des Lösungsmittels und der Hilfsstoffe eine entsprechende Anpassung erfolgen kann
• – Auch stark wechselwirkende Partikel (auch magnetische Partikel) werden deagglomeriert.
• – Das erfindungsgemäße Verfahren ermöglicht die Herstellung stabiler Dispersionen durch Zersetzen des Paraformaldehyd-Polymers in Lösung nach Aufbrechen der Agglomerate.
• – Das Aufbringen auf den Träger kann durch einfaches Dipcoating erfolgen.
• – Das Verfahren ist reproduzierbar in hoher Qualität.
• – Das Verfahren kann sehr variabel z. B. in Bezug auf Lösungsmittel, Hilfsstoffe, Polymerkonzentration, Polymereigenschaften, Temperatur, Ultraschallbehandlung etc. durchgeführt werden und ist damit optimierbar auf das jeweilige Stoffsystem
• – durch das erfindungsgemäße Verfahren ist es möglich, den gesamten Träger gleichmäßig mit der Probe zu beschichten, so dass nicht nur bestimmte Teile des Trägers sondern der gesamte Träger für mikroskopische Untersuchungen herangezogen werden kann.
• – Das erfindungsgemäße Verfahren ist zur Probenvorbereitung für viele verschiedene mikroskopische Verfahren, beispielsweise auch für TEM (STEM) und AFM einsetzbar.

The inventive method is very simple in its implementation and also offers the following advantages:

• - It is suitable for solids and dispersions
• - It is suitable for polar and nonpolar substances, since by choosing the solvent and the auxiliaries can be made a corresponding adjustment
• - Even strongly interacting particles (also magnetic particles) are deagglomerated.
• The process according to the invention makes it possible to prepare stable dispersions by decomposing the paraformaldehyde polymer in solution after breaking up the agglomerates.
• - The application to the carrier can be done by simple dipcoating.
• - The process is reproducible in high quality.
• - The process can be very variable z. B. in relation to solvents, auxiliaries, polymer concentration, polymer properties, temperature, ultrasound treatment, etc., and is thus optimized for the respective material system
• - By the inventive method, it is possible to uniformly coat the entire carrier with the sample, so that not only certain parts of the carrier but the entire carrier can be used for microscopic examinations.
• The method according to the invention can be used for sample preparation for many different microscopic methods, for example also for TEM (STEM) and AFM.

Even without further statements, it is assumed that a person skilled in the art can use the above description to the greatest extent. The preferred embodiments and examples are therefore to be considered as merely illustrative, in no way limiting as in any way limiting disclosure.

The complete disclosure of all applications, patents and publications listed above and below, in particular the corresponding application EP 13003493.7 , filed on Jul. 10, 2013, is incorporated by reference into this application.

Examples

• 1. Preparation of an aqueous dispersion of magnetite nanoparticles for SEM images: Into a 1.5 mL Eppendorf tube, 14.3 mg of aqueous magnetite dispersion are obtained from a coprecipitation (3.51% wt., BET 23.434 m ² / g) and 0.8415 g of a pyridine / acetic acid mixture (molar ratio pyridine: acetic acid 1.993: 1) and homogenized for 2-3 seconds by means of a sonotrode at 3-5 W power input homogenized. 44.6 mg of this dispersion are added with 0.1952 g of paraformaldehyde and 2.3806 g of the above-mentioned pyridine / acetic acid mixture in a 4 mL sample vial and homogenized for 65 minutes by means of a sonotrode, the mixture is heated. Immediately after completion of the ultrasound treatment is a Wrapped about 1 × 1 cm large silicon wafer fragment by briefly immersing in the gel-like solution and placed in a horizontally mounted glass tube with one-sided gas connection and an inner diameter of about 1.5-2 cm. In the nitrogen stream (400 mL / min), the solvent is first evaporated at room temperature. The temperature in the glass tube is increased over several stages up to approx. 400 ° C and at the end is converted from nitrogen to air at 400 ml / min. After cooling, the wafer fragment is fixed on a SEM carrier and examined by SEM. shows a high-resolution SEM image of magnetite nanoparticles deposited on a support in this manner at 5000X.
• 2. Preparation of an Aqueous Dispersion of Magnetite Nanoparticles for AFM Images: 14.5 mg of aqueous magnetite dispersion from a coprecipitation (4.59% by wt., BET 21.7474 m ² / g) are introduced into a 1.5 mL Eppendorf vessel ) and 0.9827 g of a pyridine / acetic acid mixture (molar ratio pyridine: acetic acid 1.985: 1) and homogenized for 2-3 seconds by means of a sonotrode at 3-5 W power input. 80.8 mg of this dispersion are added with 0.1976 g of paraformaldehyde and 2.4121 g of the above-mentioned pyridine / acetic acid mixture in a 4 mL sample vial and homogenized for 60 minutes by means of a sonotrode, the mixture is heated. Immediately after completion of the ultrasound treatment, an approximately 1 × 1 cm large silicon wafer fragment is wetted by brief immersion in the gel-like solution and placed in a horizontally mounted glass tube with one-sided gas connection and an inner diameter of about 1.5-2 cm. In the nitrogen stream (400 mL / min), the solvent is first evaporated at room temperature. The temperature in the glass tube is increased over several stages up to approx. 400 ° C and at the end is converted from nitrogen to air at 400 ml / min. After cooling, the wafer fragment is fixed on an AFM support sputtered with 15 nm platinum and then examined.
• 3. Preparation of an aqueous dispersion of TiO ₂ nanoparticles for SEM images: In a 1.5 mL Eppendorf tube are added 3.6 mg of TiO ₂ powder (TTO-N5E8 Lot No. SH88 LA 47-10 / 1) and 1.075 g of a Weighed pyridine / acetic acid mixture (molar ratio of pyridine: acetic acid 1,993: 1) and homogenized for 2-3 seconds by means of a sonotrode. 7.5 mg of this dispersion are added with 0.1756 g of paraformaldehyde and 2.1666 g of the above pyridine / acetic acid mixture in a 4 mL sample glass and homogenized for 65 minutes by means of a sonotrode at 3-5 W power input, the mixture is heated. Immediately after completion of the ultrasound treatment, an approximately 1 × 1 cm large silicon wafer fragment is wetted by brief immersion in the gel-like solution and placed in a horizontally mounted glass tube with one-sided gas connection and an inner diameter of about 1.5-2 cm. In the nitrogen stream (400 mL / min), the solvent is first evaporated at room temperature. The temperature in the glass tube is increased over several stages up to approx. 400 ° C and at the end is converted from nitrogen to air at 400 ml / min. After cooling, the wafer fragment is fixed on a SEM carrier and examined.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 13003493 [0055]

Cited non-patent literature

• COMMISSION RECOMMENDATION of 18 October 2011 on the definition of nanomaterials; Official Journal of the European Union, L 275 / 38-40, 2011 [0002]
• ISO 14887 [ISO 14887, Sample preparation - Dispersing procedures for powders in liquids, 2000 [0004]
• N. Thaulow and EW White; General method for dispersing and disaggregating particulate samples for quantitative SEM and opticla mircroscopic studies; Powder Technology, 6, 377-379 (19971172) [0007]
• S. Füchsel, K. Husemann and U. Peuker; Dry deagglomeration of nanoparticle agglomerates in a classifier mill; Chemical Engineer Technology, 83, no. 8, 1262-1275, 2011 [0008]
• ISO 14887 Section 8.5.3 and Annex B [0041]

Claims (10)

Method for applying particle-containing samples to carriers characterized by the following method steps: a) mixing a particle-containing sample with at least paraformaldehyde and a solvent b) applying the mixture obtained in step a) to a support c) removing the solvent and the paraformaldehyde A method according to claim 1, characterized in that in step a) as solvent 1-butanol, 2-pentanol, xylene, butyl acetate, anisole, DMF (dimethylformamide), NMP (N-methyl-2-pyrrolidone), 1,1,2 , 2-tetrachloroethane, tripropylamine, n-octane, pyridinium acetate, pyridine, methylpyridine or mixtures thereof. Process according to Claim 1 or 2, characterized in that the mixture prepared in step a) contains between 5 and 50% by weight, preferably between 5 and 25% by weight, of paraformaldehyde. Method according to one or more of claims 1 to 3, characterized in that in step a) first the particle-containing sample and the paraformaldehyde are suspended separately in a solvent and the two suspensions are then mixed. Method according to one or more of claims 1 to 4, characterized in that the mixture obtained in step a) is treated before the task on the carrier with ultrasonic waves. Method according to one or more of claims 1 to 5, characterized in that the mixture from step a) is added to the carrier by immersing it in the mixture. Method according to one or more of claims 1 to 6, characterized in that the solvent is removed by treating the carrier with a stream of nitrogen. Method according to one or more of claims 1 to 7, characterized in that the paraformaldehyde is removed by the carrier is heated in a stream of nitrogen up to 400 ° C. Means consisting of at least from 5 to 50% by weight of paraformaldehyde and one or more solvents selected from the group consisting of 1-butanol, 2-pentanol, xylene, butyl acetate, anisole, DMF (dimethylformamide), NMP (N-methyl-2-pyrrolidone), 1,1,2,2-tetrachloroethane, tripropylamine, n-octane, pyridinium acetate, pyridine and methylpyridine Use of the method according to one or more of claims 1 to 8 for the provision of sample carriers for microscopic examinations.

Images