WO2023066775A1 - Supraparticle and additive for optically indicating hydrogen gas, method for producing the supraparticle(s) or the additive, and use of the supraparticle(s) or the additive - Google Patents

Abstract

The present invention relates to a supraparticle for optically indicating hydrogen gas or elemental hydrogen. The supraparticle comprises: - a particle superstructure consisting of nanoparticles; and - substances embedded into the particle superstructure. The nanoparticles are selected from the group consisting of SiO2 nanoparticles, metal oxide nanoparticles, polymer nanoparticles, and mixtures thereof. Furthermore, the substances embedded into the particle superstructure comprise: - at least one catalytically active substance for catalyzing a dissociation of hydrogen; and - at least one redox dye. The present invention additionally relates to an additive for optically indicating hydrogen gas, the additive containing or consisting of a plurality of the supraparticles. The present invention further relates to a method for producing the supraparticle(s) or the additive and to the use of the supraparticle(s) or the additive.

Description

The present invention relates to a supraparticle for the optical indication of hydrogen gas or elemental hydrogen Hydrogen. The supraparticle comprises a particle superstructure consisting of nanoparticles as well as substances embedded in the particle superstructure. The nanoparticles are selected from the group consisting of SiCh nanoparticles, metal oxide nanoparticles, polymer nanoparticles and mixtures thereof. In addition, the substances embedded in the particle superstructure contain at least one catalytically active substance for catalyzing a dissociation of hydrogen and at least one redox dye. The present invention also relates to an additive for the optical indication of hydrogen gas, which contains or consists of several of the supraparticles. Furthermore, the present invention also relates to a method for producing the supraparticle(s) or the additive and the use of the supraparticle(s) or the additive. Hydrogen is a colourless, tasteless and odorless gas that is imperceptible to the human senses. However, due to its special chemical and physical properties, hydrogen poses a high risk potential, as it is a strong reducing agent, highly flammable and explosive in air over a wide concentration range (4-75% by volume). Nevertheless, hydrogen is traded as a promising energy carrier and fuel of the future due to its high mass-related energy density and the potentially CCh-emission-free production and combustion.

So far, the detection of hydrogen has been of great importance mainly for special fields of application such as in the chemical industry, metallurgy, the semiconductor industry, medical technology and nuclear safety. As part of the "green hydrogen economy", however, an infrastructure is to be created in which large parts of the population come into direct contact with hydrogen. In order to guarantee high safety standards in the production, transport, extraction and consumption of hydrogen, a unintentional escape of hydrogen must be prevented and any leaks that have occurred must be identified and localized as quickly as possible. Therefore, sensors and indicators that, on the one hand, use simple means to indicate the presence of hydrogen in the atmosphere and, on the other hand, can precisely localize leaks are of great importance for the realization of a safe " Green Hydrogen Economy". Such indicators should be able to detect hydrogen quickly, with adjustable sensitivity and selectively, they should also be cheap and can be produced on a large scale, as well as being easy and flexible to apply and long-term stable.

There are many technical possibilities to detect hydrogen in a gas atmosphere. In addition to gas chromatographs and mass spectrometers, numerous hydrogen sensors based on microelectromechanical systems (MEMS) have been established in recent years (see eg Berndt et al., Sensors and Actuators A: Physical, 2020, 305, 111670). Other sensors use the high thermal conductivity of hydrogen to indicate the presence of the gas (see eg Simon et al., Sensors and Actuators A: Physical, 2002, 97-98, 104). Other sensor types are based on the specific interaction of hydrogen with special materials (metals, metal oxides, semi- conductors), which lead to a change in local temperature or acoustic, electrical or mechanical material properties. With the help of suitable detectors, these changes can be converted into an electrical signal that is proportional to the existing hydrogen concentration. Such sensors are suitable for determining the presence and concentration of hydrogen in gas atmospheres. The sensor systems mentioned each have different strengths in terms of costs, areas of application and work as well as sensitivities. However, they also have individual disadvantages such as cross-sensitivities to temperature and humidity fluctuations or other gases.

However, the sensor types mentioned so far combine a relatively complex structure of sensor and detector units, additional switching elements and the need for a constant power supply, which represents a potential ignition source. For this reason, electrical sensors can only be used to a limited extent and with special safety precautions in potentially explosive atmospheres.

For this reason, optical hydrogen sensors have also been developed that function independently of electrical signal transmission. These are based on a change in the optical properties of sensor materials such as their reflection or their color through interaction with hydrogen (see e.g. Liu et al., Nature Materials, 2011, 10, 631). With optical hydrogen sensors, the risk of the sensor itself representing an ignition source can be ruled out, since the measurement signal is not transmitted electrically but optically. Therefore, these sensors can also be used in potentially explosive atmospheres. However, the use of electrical control units is not ruled out. With the help of fiber optic cables, the optical signal can be transported quickly and safely to a locally separate electrical control unit.

In addition, optical hydrogen sensors offer the possibility not only to indicate the presence of the target gas, but also to visualize the distribution of the gas in a spatially resolved manner. In a specific application, not only would a leak be identifiable with optical sensors, but also localized in order to initiate adequate action. Another advantage of see compared to electrical sensors is a low susceptibility to electromagnetic interference signals.

Established optical hydrogen sensors are based, for example, on changing the reflection of palladium layers through interaction with hydrogen (see, for example, She et al., Light, Science & Applications, 2019, 8, 4). Other optical sensors use differences in the refractive index of special materials in the presence of hydrogen, which can be read interferometrically, or changes in the wavelength of the plasmon resonance of nanostructured metals such as palladium. Examples of plasmonic hydrogen sensors whose reversible interaction with hydrogen usually results in a shift in the extinction maximum or a change in transmission and which is detected by means of reflection measurements include AuPd or YH2 nanorods, Pd-Ti-Mg or Pd-Mg, Pd-Au , Pt-Pd or Pt-Pd9 ₈ Ni ₂ -, Pd or Pt nanodisks (also called nanoantennas). Other plasmonic hydrogen sensors include Pd nanoparticles or Pd-Au nanocomposite particles in a defined, thin polymer coating (see eg Darmadi et al., ACS Appl. Nano Mater., 2020, 3, 8438).

The advantage of these sensors lies in their potentially high spatial resolution down to the nanometer range and the high selectivity for hydrogen. However, the optical signal changes are usually only changes in contrast, sometimes outside the visible spectral range, which are not accessible to humans without special aids such as physical measuring devices. In addition, layered materials such as palladium are prone to cracking and delamination due to volume expansions when interacting with hydrogen, and to the poisoning of the active material by other atmospheric gases such as carbon monoxide (CO) or nitrogen dioxide (NO ₂ ), which limits their long-term stability. Another disadvantage is that the active materials (nanoantennas) of the plasmonic hydrogen sensors have to be applied to special substrates in a defined nanostructure and in connection with special matrix materials.

In addition, chemochromic hydrogen sensors have also been established, which change their color (absorption in the visible spectral range) through interaction with hydrogen and thus offer people the opportunity to The presence of hydrogen can be detected with the naked eye without any additional tools. Examples of chromogenic thin films for hydrogen detection include Pd-Y or Pd-CuS composites, composites of MoOä and Pd nanoparticles, or assembled WCh-Pd nanofibers. Another example is a multi-component layer made of a special polymer matrix, an indicator dye and a catalyst material, which causes a change in the spectroscopic properties of the dye molecule when exposed to hydrogen (see, for example, US 2019/0094147 A1).

However, the functionality of such thin layers depends on their special nanostructuring or on the interaction of different components in the respective coating. Therefore, chromogenic thin layers are only suitable to a limited extent for area-wide use or for flexible components with complex geometries. A flexible additive that enables the optical indication of hydrogen with an easily detectable color change could significantly expand the range of applications for optical hydrogen indicators.

Proceeding from this, it was the object of the present invention to specify a product for the indication of hydrogen gas, which enables an optical indication of hydrogen gas in a simple manner.

This object is achieved with the features of claim 1 with regard to a supraparticle, with the features of claim 6 with regard to an additive and with the features of claim 9 with regard to a method. Patent claim 12 specifies possible uses of the supraparticle(s) or the additive. The respective dependent patent claims represent advantageous developments.

According to the invention, a supraparticle for the optical indication of hydrogen gas (H2 gas) is thus specified, comprising a particle superstructure consisting of nanoparticles and substances embedded in the particle superstructure, the nanoparticles being selected from the group consisting of SiCh nanoparticles, metal oxide nanoparticles, polymer Nanoparticles, and mixtures thereof, and wherein the substances embedded in the particle superstructure have at least one catalytically active substance for catalyzing a dissociation contain hydrogen (H2) and at least one redox dye.

The supraparticle according to the invention can indicate the presence of hydrogen gas at the application site with a reversible or irreversible color change in the visible spectral range, which can be detected with the naked eye, in a spatially resolved manner. The supraparticle can, for example, be used as a free-flowing powder or flexibly introduced into coatings or materials as an additive or pigment and requires no further physical aids for the indication of hydrogen gas.

The color change of the supraparticle according to the invention is based on a reversible or irreversible chemical redox reaction of an indicator dye or redox dye with dissociated hydrogen. In the presence of hydrogen gas, the dissociated hydrogen is produced by a dissociation of the hydrogen which is catalyzed by the catalytically active substance (for catalyzing a dissociation of hydrogen).

The supraparticle according to the invention is characterized both by its structure and by its components. The supraparticle thus comprises a plurality of nanoparticles which are arranged in the form of a complex particle superstructure. This particle superstructure can also be referred to as nanostructured particle superstructure or nanostructured particle architecture. Further substances are now embedded in the particle superstructure consisting of the nanoparticles. These substances embedded in the particle superstructure contain at least one catalytically active substance for catalyzing a dissociation of hydrogen and at least one redox dye. The structure of the supraparticle, ie the structure with the particle superstructure consisting of nanoparticles and the substances embedded therein, is of essential importance for the functioning of the supraparticle. Pure mixing of the individual components and drying does not lead to a powder in which there is no superstructure consisting of the nanoparticles in which the at least one catalytically active substance for catalyzing a dissociation of hydrogen and the at least one redox dye are embedded into a workable indicator of hydrogen gas. The special structure of the supraparticle can be achieved by a manufacturing process in which initially an aqueous Mixture containing the subsequent components of the supraparticle is prepared and the aqueous mixture produced is subjected to a spray drying process.

The nanoparticles (of the particle superstructure) are selected from the group consisting of SiCh nanoparticles, metal oxide nanoparticles, polymer nanoparticles, and mixtures thereof, with SiCh nanoparticles being particularly preferred. These nanoparticles enable the formation of the particle superstructure in which the other substances are embedded. In addition, a pore structure with a high specific surface area can be created by mutual attachment of the nanoparticles. This enables the adsorption of water from the ambient air and thus the transport of reactive hydrogen species or redox dye molecules. Furthermore, the nanoparticles mentioned can be used as a commercial, inexpensive filling material in order to reduce the price of the final supraparticles.

Hydrogen molecules can be dissociated on the surface of the at least one catalytically active substance for catalyzing a dissociation of hydrogen, as a result of which dissociated hydrogen or reactive hydrogen species are formed.

The redox dye used can change its color (reversibly or irreversibly) by reacting with reactive hydrogen species or dissociated hydrogen. For example, the redox dye can change color (reversibly or irreversibly) or at least partially decolorize (reversibly or irreversibly) upon reaction with dissociated hydrogen. The redox dye thus acts as a signaling element. The color change (or discoloration or discoloration) can already be recognized qualitatively with the naked eye and can be detected quantitatively using spectroscopic methods such as UV-Vis or fluorescence spectroscopy.

The supraparticle according to the invention can be constructed according to a modular principle. This makes it possible to flexibly and precisely optimize the optical sensor properties for a specific application. The adjustable sensor properties include the signal color (monitoring wavelength), sensitivity, response time, working range, long-term stability and the price.

The supraparticle according to the invention enables the optical indication of hydrogen gas for the first time as a powder, as a pigment in substances or as an additive in various flexible coating materials and, when interacting with hydrogen gas, shows a reversible and/or irreversible visible color change that can be detected with the naked eye. Previously established nanostructured additives, on the other hand, are based on a different mode of operation and usually only show a contrast change in real time in the presence of hydrogen gas.

The supraparticle according to the invention for the optical indication of hydrogen gas is characterized by its flexible applicability, e.g. in additives that can contain a majority of the supraparticles and can be present as a free-flowing powder (pigment, powder), from hydrogen indicators that are limited to an area of application in liquid media are. Thanks to its optical detection principle, the supraparticle can also be used in potentially explosive gas atmospheres without any further safety precautions, does not require any further tools to read its information and is therefore different from all electrical and electrochemical hydrogen sensors.

Compared to already known (thin) layer systems used as optical hydrogen indicators, the supraparticle according to the invention has the advantage that no special matrix materials, such as gas-permeable but moisture-storing polymers, or a special layer structure are required for the optical hydrogen indication, but instead flexible - e.g. in shape an additive which contains or consists of a plurality of the supraparticles - can be applied. The optical indication of hydrogen with the supraparticle according to the invention also does not require a high concentration of expensive noble metals such as palladium. In addition, with the supraparticle according to the invention, the presence of hydrogen gas can be indicated by a color change that can be seen with the naked eye and not just by a slight change in contrast that has to be detected using physical aids, as is the case with the known indicators in the prior art . Furthermore, the inventive appropriate supraparticles also an irreversible optical signal response or indication of the presence of hydrogen gas. The optical signal response to the presence of hydrogen, which is given by indicator layers from the prior art, is only reversible, so that only real-time monitoring of the target gas is possible there, but not an indication of hydrogen gas exposure from the past . Instead, such an indication of a hydrogen gas exposure from the past can also be displayed with the supraparticle according to the invention.

Such an irreversible indication of hydrogen is of great advantage in particular for the search for leaks after the shutdown of a gas-carrying facility.

The supraparticle according to the invention (or an additive which contains or consists of a plurality of the supraparticles according to the invention) thus represents a product for the indication of hydrogen gas, which makes optical indication of hydrogen gas possible in a simple manner.

The supraparticle according to the invention preferably has a particle size in the range from 0.1 μm to 1000 μm, particularly preferably from 1 μm to 1000 μm. The particle size can be determined, for example, by means of scanning electron microscopy (e.g. according to DIN SPEC 52407, e.g. DIN SPEC 52407:2015-03) or laser diffraction (e.g. according to DIN ISO 8130-13, e.g. DIN ISO 8130-13:2019-08).

The nanoparticles (of the particle superstructure) preferably have an average particle size in the range from 0.1 nm to 1000 nm, particularly preferably from 0.5 nm to 100 nm, very particularly preferably 1 nm to 50 nm. The average particle size can be determined, for example, by means of transmission electron microscopy (e.g. according to DIN ISO 21363, e.g. DIN ISO 21363:2020-06) or dynamic light scattering (e.g. according to DIN ISO 22412, e.g. DIN ISO 22412:2018-09).

A preferred embodiment of the supraparticle according to the invention is characterized in that the at least one catalytically active substance (for catalyzing a dissociation of hydrogen) contains or consists of at least one transition metal, Che is preferably selected from the group consisting of iridium, ruthenium, rhodium, gold, palladium, platinum, and mixtures and alloys thereof, wherein the at least one transition metal is particularly preferably selected from the group consisting of gold, palladium, platinum, and mixtures and alloys hereof, and/or

Contains or consists of nanoparticles, which are preferably selected from the group consisting of iridium nanoparticles, ruthenium nanoparticles, rhodium nanoparticles, gold-platinum nanoparticles, gold-palladium nanoparticles, palladium nanoparticles, platinum nanoparticles, and mixtures thereof, wherein the nanoparticles are particularly preferably selected from the group consisting of gold-platinum nanoparticles, gold-palladium nanoparticles, palladium nanoparticles, platinum nanoparticles, and mixtures thereof, and / or a sulfonated Wilkinson catalyst contains or from this consists.

The catalytic activity of the catalytically active substance can be influenced by the catalyst material used and its size, geometry and concentration, and the sensitivity, the response time and the working range of the supraparticles used for the optical indication of hydrogen gas can be specifically adapted.

The catalytically active substance (for catalyzing a dissociation of hydrogen) may contain or consist of nanoparticles or may be in the form of nanoparticles. The nanoparticles of the catalytically active substance can also be referred to as catalyst nanoparticles. The nanoparticles of the catalytically active substance preferably have an average particle size in the range from 0.1 nm to 1000 nm, particularly preferably from 0.5 nm to 100 nm, very particularly preferably from 1 nm to 50 nm. The average particle size can be determined, for example, using transmission electron microscopy (for example according to DIN ISO 21363, eg DIN ISO 21363:2020-06) or dynamic light scattering (for example according to DIN ISO 22412, eg DIN ISO 22412:2018-09). The catalytic activity of the catalytically active substance can be influenced by the material used and by the size, geometry and concentration of the (catalyst) nanoparticles can be influenced and thus the sensitivity, the response time and the working range of the supraparticles used for the optical indication of hydrogen gas can be adjusted in a targeted manner.

The catalytically active substance (for catalyzing a dissociation of hydrogen) can be present, for example, in the form of nanoparticles and/or in the form of (individual) molecules.

A further preferred embodiment of the supraparticle according to the invention is characterized in that the at least one redox dye is a polyaromatic compound which preferably contains a redox-sensitive chromophore and/or a redox-sensitive fluorophore and/or is selected from the group consisting of bromothymol blue, methyl red, Methyl blue, Evan's blue, methyl orange, Nile blue, dichloroindophenol, methylene blue, resazurin, resorufin and mixtures thereof, the at least one redox dye preferably being selected from the group consisting of dichloroindophenol, methylene blue, resazurin, resofurin and mixtures thereof, and/or or upon reaction with dissociated hydrogen

• reversibly discolored or reversibly at least partially discolored, or

• irreversibly discolored or irreversibly at least partially discolored.

The at least one redox dye can be present, for example, in the form of (individual) molecules.

Irreversible discoloration or discoloration of the redox dye is of great advantage, in particular when searching for leaks after a gas-carrying device has been switched off.

The nanoparticles (the particle superstructure) can be metal oxide nanoparticles. Preferably, the metal oxide nanoparticles are selected from the group consisting of CesC nanoparticles, TiCh nanoparticles, A^Ch nanoparticles, and mixtures thereof. through A particularly suitable particle superstructure can be obtained using these metal oxide particles.

The nanoparticles (of the particle superstructure) are preferably present in different particle sizes. In other words, the nanoparticles (the particle superstructure) contain nanoparticles of different sizes, for example nanoparticles with an average particle size of 16 nm to 24 nm, preferably 18 nm to 22 nm, and nanoparticles with an average particle size of 6 nm to 14 nm, preferably from 8nm to 12nm.

A further preferred embodiment of the supraparticle according to the invention is characterized in that the substances embedded in the particle superstructure additionally contain at least one organic or inorganic acid, which is preferably selected from the group consisting of hydrochloric acid, sulfurous acid, carbonic acid, acetic acid, phosphoric acid, sulfuric acid, and mixtures thereof, wherein the at least one organic or inorganic acid is particularly preferably sulfuric acid, and/or contain at least one substance for extinguishing electronic triplet states (triplet quencher), which is preferably selected from the group consisting of ascorbic acid, mercaptoethylamine, cysteamine, diphenylhexatriene, 2,2,6,6-tetramethylpiperidinyloxyl (TEMPO), urea, 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (TROLOX), and mixtures thereof.

The supraparticle preferably contains 0.01 to 40% by weight, preferably 0.1 to 20% by weight, of at least one organic or inorganic acid.

The supraparticle preferably contains 0.01 to 10% by weight, preferably 0.1 to 2% by weight, of the one substance for extinguishing electronic triplet states (triplet quencher).

The addition of an organic or inorganic acid reduces the pH of the supraparticle. This leads to a higher reactivity of the catalyst nanoparticles, improved ion conductivity in the particle superstructure, an accelerated redox reaction with the redox dye and reduces the fading of the dye molecules in the presence of light and oxygen. In addition, the ions of the acid introduce a hygroscopic component into the additive, which, under atmospheric conditions, binds moisture in the particle superstructure and thus makes the reactivity of the supraparticle with hydrogen stable over the long term. The at least one organic or inorganic acid can be present, for example, in the form of (individual) molecules.

In order to further reduce the fading behavior of the dye molecules in the presence of light and oxygen, a triplet quencher (or at least one substance for extinguishing electronic triplet states) can also be added to the supraparticle. The long-term stability of the hydrogen indicator additive can be significantly improved by the type and concentration of the triplet quencher. The at least one substance for erasing electronic triplet states can be present, for example, in the form of (individual) molecules.

A further preferred embodiment of the supraparticle according to the invention is characterized in that the supraparticle

60 to 99.99994% by weight, preferably 80 to 99.99994% by weight, particularly preferably 90 to 99.99% by weight, very particularly preferably 90 to

99.96% by weight, in particular 90 to 99.6% by weight, of the nanoparticles selected from the group consisting of SiO2 nanoparticles, metal oxide nanoparticles, polymer nanoparticles, and mixtures thereof, based on the total weight of the supraparticle, and or

0.00005 to 20% by weight, preferably 0.00005 to 1.0% by weight, particularly preferably 0.01 to 1.0% by weight, of the at least one catalytically active substance for catalyzing a dissociation of hydrogen, based on the total weight of the supraparticle, and/or

0.00001 to 5% by weight, preferably 0.00001 to 2% by weight, particularly preferably 0.01 to 2% by weight, of the at least one redox dye, based on the total weight of the supraparticle, wherein the supraparticle preferably additionally 0.01 to 40% by weight, preferably 0.1 to 20% by weight, of at least one organic or inorganic acid, based on the total weight of the supraparticle, and/or

0.01 to 10% by weight, preferably 0.1 to 2% by weight, of at least one substance for extinguishing electronic triplet states (triplet quencher), based on the total weight of the supraparticle.

The supraparticle preferably has the following composition:

60 to 99.99994% by weight, preferably 80 to 99.99994% by weight, particularly preferably 90 to 99.99% by weight, very particularly preferably 90 to

99.96% by weight, in particular 90 to 99.6% by weight, of the nanoparticles selected from the group consisting of SiCh nanoparticles, metal oxide nanoparticles, polymer nanoparticles, and mixtures thereof,

0.00005 to 20% by weight, preferably 0.00005 to 1.0% by weight, particularly preferably 0.01 to 1.0% by weight, of the at least one catalytically active substance for catalyzing a dissociation of hydrogen,

0.00001 to 5% by weight, preferably 0.00001 to 2% by weight, particularly preferably 0.01 to 2% by weight, of the at least one redox dye, optionally 0.01 to 40% by weight , preferably 0.1 to 20% by weight of at least one organic or inorganic acid, optionally 0.01 to 10% by weight, preferably 0.1 to 2% by weight, of at least one substance for erasing electronic triplet States (triplet quencher), the proportions of the components adding up to 100% by weight. The percentages by weight are in each case based on the total weight of the supraparticle.

The present invention also relates to an additive for the optical indication of hydrogen gas (Fh gas), containing or consisting of supraparticles according to the invention. The additive according to the invention thus contains a plurality of the supraparticles according to the invention or consists of a plurality of the supraparticles according to the invention. In addition to the inventive According to supraparticles, the additive can also contain other components.

The additive according to the invention for the optical indication of hydrogen gas is clearly distinguished from hydrogen indicators, which are limited to an area of application in liquid media, by its flexible applicability, e.g. as a free-flowing powder (pigment, powder). Due to its optical detection principle, the additive can also be used in potentially explosive gas atmospheres without further safety precautions, does not require any further tools to read its information and is therefore different from all electrical and electrochemical hydrogen sensors.

The supraparticles of the additive according to the invention preferably have an average particle size in the range from 0.1 μm to 1000 μm, particularly preferably from 1 μm to 1000 μm. The particle size can be determined, for example, by means of scanning electron microscopy (e.g. according to DIN SPEC 52407, e.g. DIN SPEC 52407:2015-03) or laser diffraction (e.g. according to DIN ISO 8130-13, e.g. DIN ISO 8130-13:2019-08).

A preferred embodiment of the additive according to the invention is characterized in that the additive is present as a powder, preferably as a free-flowing powder.

A further preferred embodiment of the additive according to the invention is characterized in that the additive

60 to 99.99994% by weight, preferably 80 to 99.99994% by weight, particularly preferably 90 to 99.99% by weight, very particularly preferably 90 to

99.96% by weight, in particular 90 to 99.6% by weight, of the nanoparticles selected from the group consisting of SiO2 nanoparticles, metal oxide nanoparticles, polymer nanoparticles, and mixtures thereof, based on the total weight of the additive, and or

0.00005 to 20% by weight, preferably 0.00005 to 1.0% by weight, particularly preferably 0.01 to 1.0% by weight, of the at least one catalytically active substance for catalyzing a dissociation of hydrogen, based on the total weight of the additive, and/or

0.00001 to 5% by weight, preferably 0.00001 to 2% by weight, particularly preferably 0.01 to 2% by weight, of the at least one redox dye, based on the total weight of the additive, where the additive preferably additionally

0.01 to 40% by weight, preferably 0.1 to 20% by weight, of at least one organic or inorganic acid, based on the total weight of the additive, and/or

0.01 to 10% by weight, preferably 0.1 to 2% by weight, of at least one substance for extinguishing electronic triplet states (triplet quencher), based on the total weight of the additive.

The additive preferably has the following composition:

60 to 99.99994% by weight, preferably 80 to 99.99994% by weight, particularly preferably 90 to 99.99% by weight, very particularly preferably 90 to 99.96% by weight, in particular 90 to 99 .6% by weight of the nanoparticles selected from the group consisting of SiCh nanoparticles, metal oxide nanoparticles, polymer nanoparticles, and mixtures thereof,

0.00005 to 20% by weight, preferably 0.00005 to 1.0% by weight, particularly preferably 0.01 to 1.0% by weight, of the at least one catalytically active substance for catalyzing a dissociation of hydrogen,

0.00001 to 5% by weight, preferably 0.00001 to 2% by weight, particularly preferably 0.01 to 2% by weight, of the at least one redox dye, optionally 0.01 to 40% by weight , preferably 0.1 to 20% by weight of at least one organic or inorganic acid, optionally 0.01 to 10% by weight, preferably 0.1 to 2% by weight, of at least one substance for erasing electronic triplet States (triplet quencher), the proportions of the components adding up to 100% by weight. The percentages by weight are in each case based on the total weight of the additive. The additive preferably contains 0.01 to 40% by weight, preferably 0.1 to 20% by weight, of the at least one organic or inorganic acid.

The additive preferably contains 0.01 to 10% by weight, preferably 0.1 to 2% by weight, of the one substance for extinguishing electronic triplet states (triplet quencher).

The present invention also relates to a method for producing one or more of the supraparticles according to the invention or the additive according to the invention, in which a) an aqueous mixture is prepared which

Nanoparticles selected from the group consisting of SiCh

Nanoparticles, metal oxide nanoparticles, polymer nanoparticles, and mixtures thereof, at least one catalytically active substance for catalyzing a dissociation of hydrogen, at least one redox dye, and

Contains water, and b) the aqueous mixture produced is subjected to a spray drying process, preferably a scalable spray drying process.

The metal oxide nanoparticles are preferably selected from the group consisting of SiC nanoparticles, CesC nanoparticles, TiCh nanoparticles, AbCh nanoparticles, and mixtures thereof.

Furthermore, it is preferred that the at least one catalytically active substance (for catalyzing a dissociation of hydrogen) contains or consists of at least one transition metal, which is preferably selected from the group consisting of iridium, ruthenium, rhodium, gold, palladium, platinum, and Mixtures and alloys thereof, wherein the at least one transition metal is particularly preferably selected from the group consisting of gold, palladium, platinum, and mixtures and alloys thereof, and/or

Contains or consists of nanoparticles, which are preferably selected from the group consisting of iridium nanoparticles, ruthenium nanoparticles, rhodium nanoparticles, gold-platinum nanoparticles, gold-palladium nanoparticles, palladium nanoparticles, platinum nanoparticles, and mixtures thereof, wherein the nanoparticles are particularly preferably selected from the group consisting of gold-platinum nanoparticles, gold-palladium nanoparticles, palladium nanoparticles, platinum nanoparticles, and mixtures thereof, and / or a sulfonated Wilkinson catalyst contains or from this consists.

Furthermore, it is preferred that the at least one redox dye is a polyaromatic compound, which preferably contains a redox-sensitive chromophore and/or a redox-sensitive fluorophore, and/or is selected from the group consisting of bromothymol blue, methyl red, methyl blue, Evan's blue, methyl orange , Nile blue, dichloroindophenol, methylene blue, resazurin, resorufin and mixtures thereof, the at least one redox dye being particularly preferably selected from the group consisting of dichloroindophenol, methylene blue, resazurin, resofurin and mixtures thereof, and/or on reaction with dissociated hydrogen

• reversibly discolored or reversibly at least partially discolored, or

• irreversibly discolored or irreversibly at least partially discolored.

A preferred variant of the process according to the invention is characterized in that the aqueous mixture prepared in step a) additionally contains at least one organic or inorganic acid and/or at least one substance for extinguishing electronic triplet states (triplet quencher).

Preferably, the at least one is organic or inorganic acid selected from the group consisting of hydrochloric acid, sulfurous acid, carbonic acid, acetic acid, phosphoric acid, sulfuric acid, and mixtures thereof, the at least one organic or inorganic acid being particularly preferably sulfuric acid.

The at least one substance for quenching electronic triplet states (triplet quencher) is preferably selected from the group consisting of ascorbic acid, mercaptoethylamine, cysteamine, diphenylhexatriene, 2,2,6,6-tetramethylpiperidinyloxyl (TEMPO), urea, 6-hydroxy - 2,5,7,8-tetramethylchroman-2-carboxylic acid (TROLOX), and mixtures thereof.

A further preferred variant of the method according to the invention is characterized in that the aqueous mixture produced in step a) is an aqueous dispersion, preferably a homogeneous aqueous dispersion, and/or the aqueous mixture in step a) is produced by homogeneously mixing the individual components.

Furthermore, the present invention also relates to the use of one or more of the supraparticles according to the invention or the additive according to the invention for the optical indication of hydrogen gas (H2 gas).

A preferred variant of the use according to the invention is characterized in that the supraparticle(s) or the additive is/are introduced into a carrier component or applied to a carrier component, the carrier component preferably being selected from the group consisting of textile fabrics, clothing, coatings , paints, moldings, components, technical devices, charging stations, pipelines, reactors, transformers, gas cylinders, test strips, adhesive strips, polymer films, safety cabinets, mobile phones, car bodies, body components, e.g. tank caps, and combinations thereof.

A further preferred variant of the use according to the invention is characterized in that the supraparticle or the additive is/are used as an indicator for leaks in safety-relevant components of the water Material management, with the components preferably being tanks, charging stations and/or electrolysis reactors, as an indicator for safety shutdowns in current transformers or other technical devices whose operation produces hydrogen, in permeation test strips for the search for leaks , e.g. in hydrogen gas cylinders, gas safety cabinets, pipelines, fuel cell test benches or ultra-high vacuum equipment, as a pigment for the fabric of safety clothing (e.g. a glove) for the detection of potentially explosive gas atmospheres, e.g. when working on hydrogen pipelines, hydrogen reactors, fuel cells or when refueling an automobile at a hydrogen filling station, in the medical field e.g integrated into a mobile end device, eg a mobile phone, a smartphone, a tablet or a laptop.

A further preferred variant of the use according to the invention is characterized in that the use takes place in a method for detecting hydrogen gas, in which the / the supraparticles or the additive or a carrier component, in which the / the supraparticles or the additive introduced or on which the supraparticle(s) or the additive is/are applied, comes into contact with hydrogen gas and thereby causes a change in at least one spectroscopic property of the supraparticle(s) or the additive, and the change in the at least one spectroscopic property is caused by optical observation or by detection with a detector, preferably using an optical waveguide for signal transmission, wherein the at least one spectroscopic property is preferably a color, an absorption and/or a luminescence.

The present invention thus also relates to a method for detecting Hydrogen gas, in which one or more of the supraparticles according to the invention or the additive according to the invention or a carrier component, in which the / the inventive (s) supraparticles or the additive according to the invention introduced or on which the / the inventive ß (s) supraparticles or the inventive Is applied additively / are with hydrogen gas in contact / come into contact and thereby a change in at least one spectroscopic property of / the Supraparti- kel (s) or the additive is caused, and the change in at least one spectroscopic property by optical observation or by Detection is established with a detector, preferably using an optical waveguide for signal transmission, wherein the at least one spectroscopic property is preferably a color, an absorption and/or a luminescence.

The present invention is to be explained in more detail on the basis of the following figures and examples, without restricting it to the specific embodiments and parameters shown here.

FIG. 1 shows a schematic representation of an exemplary embodiment of a supraparticle according to the invention. The supraparticle comprises a particle superstructure consisting of nanoparticles 1 and substances embedded in the particle superstructure. The nanoparticles 1 can be SiCh nanoparticles, for example. The substances embedded in the particle superstructure contain at least one redox dye 2, at least one catalytically active substance 3 for catalyzing a dissociation of hydrogen, at least one substance for extinguishing electronic triplet states 4 (triplet quencher) and at least one organic or inorganic acid 5.

Example 1

50 g of a SiCh nanoparticle dispersion with an average particle size of 20 nm and a concentration of 40% by weight were mixed with 20 ml of an AuPd nanoparticle dispersion with an average particle size of 20 nm and a concentration of 0.01% by weight. -% mixed with stirring. Afterward 5 ml of a resazurin solution with a concentration of 1 mg/ml and 35 g of deionized water were added. The pH of the dispersion was determined to be pH 11. The resulting dispersion was spray-dried to give a free-flowing powder.

The resulting powder was purple in color. In the presence of hydrogen, the color changed from violet to pink within a few seconds. Upon further exposure to hydrogen, a colorless state was then achieved before the powder turned pink again within one minute after the hydrogen exposure had ended. Upon further exposure to hydrogen, the color of the powder again changed from pink to colorless and back again.

The color change reaction of the additive present as a powder in the presence of hydrogen gas is also shown schematically in FIG. Here, the violet color is shown as horizontal hatching, the pink color is shown as diagonal hatching, and the colorless state is shown with dots.

Example 2

25 g of a SiCh nanoparticle dispersion with an average particle size of 20 nm and a concentration of 40% by weight were mixed with 0.7 ml of a Pt nanoparticle dispersion with an average particle size of 5 nm and a concentration of 0.01 wt .-% mixed with stirring. Then 6 ml of a resazurin solution with a concentration of 1 mg/ml and 10.4 ml of sulfuric acid with a concentration of 2% by weight were added. The pH of the dispersion was determined to be pH1. The resulting dispersion was spray-dried to give a free-flowing powder.

The resulting powder was orange in color. In the presence of hydrogen, the color changed from orange to blue within a few seconds. Upon further exposure to hydrogen, a colorless state was subsequently achieved. After the end of the exposure, the particles first turned blue again before turning orange again. This color differed slightly from the orange color of the initial state. At Upon re-exposure of the particles to hydrogen gas, the particles exhibited a reversible color change from orange to blue and on to colorless and back after the end of exposure.

The color change reaction of the additive present as a powder in the presence of hydrogen gas is also shown schematically in FIG. Here, the orange initial color is shown as a vertical-horizontal hatching, the blue color as a vertical hatching and the colorless state with dots. In addition, the orange hue obtained after re-dyeing, which differs slightly from the orange starting color, is shown horizontally hatched.

Compared to the initial state, the powder showed a slight color difference after exposure to hydrogen, even when viewed with the naked eye. When the powder was observed under a UV lamp with a wavelength of 365 nm, it could be seen that the orange powder after reaction with hydrogen showed a significantly less intense reddish fluorescence compared to the powder before exposure to hydrogen. Upon further exposure to hydrogen, the color of the powder again changed from orange to blue and on to colorless and back again.

Example 3

1 g of a SiCh nanoparticle dispersion with an average particle size of 20 nm and a concentration of 40% by weight was mixed with 1 ml of a Pt nanoparticle dispersion with an average particle size of 5 nm and a concentration of 0.01% by weight. -% mixed with stirring. Then 0.25 ml of a methylene blue solution with a concentration of 1 mg/ml and 20 mg of urea were added. The pH of the dispersion was determined to be pH 11. The resulting dispersion was spray-dried to give a free-flowing powder.

The resulting powder was blue in color. In the presence of hydrogen, the color changed from blue to colorless within a few seconds. After the exposure to hydrogen ceased, the powder became colored blue again within a minute. Upon further exposure to hydrogen, the color of the powder again changed from blue to colorless and back again.

Example 4

1 g of a SiCh nanoparticle dispersion with an average particle size of 20 nm and a concentration of 40% by weight was mixed with 1 ml of a Pt nanoparticle dispersion with an average particle size of 5 nm and a concentration of 0.01% by weight. -% mixed with stirring. Then 0.25 ml of a dichloroindophenol solution with a concentration of 1 mg/ml and 20 mg of urea were added. The pH of the dispersion was determined to be pH 11. The resulting dispersion was spray-dried to give a free-flowing powder.

The resulting powder was blue in color. In the presence of hydrogen, the color changed from blue to colorless within a few seconds. After cessation of hydrogen exposure, the powder turned blue again within one minute. Upon further exposure to hydrogen, the color of the powder again changed from blue to colorless and back again.

Example 5

1 g of a SiCh nanoparticle dispersion with a particle size of 10 nm and a concentration of 30% by weight was mixed with 1 ml of a Pt nanoparticle dispersion with a mean particle size of 5 nm and a concentration of 0.01% by weight. % mixed with stirring. Then 2 ml of a resazurin solution with a concentration of 1 mg/ml and 10 mg Trolox were added, which had previously been dissolved in a few milliliters of isopropanol. The pH of the dispersion was determined to be pH 11. The resulting dispersion was spray-dried to give a free-flowing powder.

The resulting powder was purple in color. In the presence of Hydrogen changed color from violet to pink within a few seconds. Upon further exposure to hydrogen, a colorless state was then achieved before the powder turned pink again within one minute after the hydrogen exposure had ended. After further exposure to hydrogen, the color of the powder changed again from pink to colorless and back again.

Claims

26 FRAUNHOFER-GESELLSCHAFT...eV, Friedrich-Alexander-University Erlangen-Nuremberg 229PCT 1682 patent claims 1. Supraparticles for the optical indication of hydrogen gas, comprising a particle superstructure consisting of nanoparticles (1) and substances embedded in the particle superstructure, the nanoparticles (1) being selected from the group consisting of SiCh nanoparticles, metal oxide nanoparticles, polymer nanoparticles, and mixtures thereof, and wherein the substances embedded in the particle superstructure contain at least one catalytically active substance (3) for catalyzing a dissociation of hydrogen and at least one redox dye (2). 2. Supraparticles according to the preceding claim, characterized in that the at least one catalytically active substance (3) contains or consists of at least one transition metal, which is preferably selected from the group consisting of iridium, ruthenium, rhodium, gold, palladium, platinum, and mixtures and alloys thereof, wherein the at least one transition metal is particularly preferably selected from the group consisting of gold, palladium, platinum, and mixtures and alloys thereof, and/or Contains or consists of nanoparticles, which are preferably selected from the group consisting of iridium nanoparticles, ruthenium nanoparticles, rhodium nanoparticles, gold-platinum nanoparticles, gold-palladium nanoparticles, palladium nanoparticles, platinum nanoparticles, and mixtures thereof, wherein the nanoparticles are particularly preferably selected from the group consisting of gold-platinum nanoparticles, gold-palladium nanoparticles, palladium nanoparticles, platinum nanoparticles, and mixtures thereof, and / or contains or consists of a sulfonated Wilkinson catalyst. 3. supraparticles according to any one of the preceding claims, characterized in that the at least one redox dye (2) is a polyaromatic compound, which preferably contains a redox-sensitive chromophore and / or a redox-sensitive fluorophore, and / or is selected from the group consisting of Bromothymol blue, methyl red, methyl blue, Evan's blue, methyl orange, Nile blue, dichloroindophenol, methylene blue, resazurin, resorufin and mixtures thereof, wherein the at least one redox dye is preferably selected from the group consisting of dichloroindophenol, methylene blue, resazurin, resofurin and mixtures thereof, and/or upon reaction with dissociated hydrogen • reversibly discolored or reversibly at least partially discolored, or • irreversibly discolored or irreversibly at least partially discolored. 4. supraparticles according to any one of the preceding claims, characterized in that the metal oxide nanoparticles are selected from the group consisting of CesC nanoparticles, TiCh nanoparticles, AbCh nanoparticles, and mixtures thereof. 5. supraparticles according to any one of the preceding claims, characterized in that the substances embedded in the particle superstructure additionally contain at least one organic or inorganic acid (5), which is preferably selected from the group consisting of hydrochloric acid, sulfurous acid, carbonic acid, acetic acid, phosphoric acid , sulfuric acid, and mixtures thereof, the min- at least one organic or inorganic acid (5), particularly preferably sulfuric acid, and/or contain at least one substance for extinguishing electronic triplet states (4), which is preferably selected from the group consisting of ascorbic acid, mercaptoethylamine, cysteamine, diphenylhexatriene, 2 ,2,6,6-Tetramethylpiperidinyloxyl (TEMPO), Urea, 6-hydroxy-2,5, 7, 8-tetramethylchroman-2-carboxylic acid (TROLOX), and mixtures thereof. Additive for the optical indication of hydrogen gas, containing or consisting of supraparticles according to one of the preceding claims. Additive according to Claim 6, characterized in that the additive is present as a powder, preferably as a free-flowing powder. Additive according to claim 6 or 7, characterized in that the additive 60 to 99.99994% by weight, preferably 80 to 99.99994, particularly preferably 90 to 99.99% by weight, of the nanoparticles (1) selected from the group consisting of SiO2 nanoparticles, metal oxide nanoparticles, polymer nanoparticles, and mixtures thereof, based on the total weight of the additive, and / or 0.00005 to 20% by weight, preferably 0.00005 to 1.0% by weight, of the at least one catalytically active substance (3) for catalyzing a dissociation of hydrogen, based on the total weight of the additive, and/or 0.00001 to 5% by weight, preferably 0.00001 to 2% by weight, of the at least one redox dye (2), based on the total weight of the additive, the additive preferably additionally 0.01 to 40% by weight, preferably 0.1 to 20% by weight, of at least one organic or inorganic acid (5), based on the total weight of the additive, and/or 29 0.01 to 10% by weight, preferably 0.1 to 2% by weight, of at least one substance for extinguishing electronic triplet states (4), based on the total weight of the additive. 9. A method for producing one or more supraparticles according to any one of claims 1 to 5 or an additive according to any one of claims 6 to 8, in which a) an aqueous mixture is prepared which - Nanoparticles (1) selected from the group consisting of SiCh nanoparticles, metal oxide nanoparticles, polymer nanoparticles, and mixtures thereof, - at least one catalytically active substance (3) for catalyzing a dissociation of hydrogen, - at least one redox dye (2), and - Contains water, and b) the aqueous mixture produced is subjected to a spray drying process. 10. The method according to claim 9, characterized in that the aqueous mixture produced in step a) additionally contains at least one organic or inorganic acid (5) and/or at least one substance for extinguishing electronic triplet states (4). 11. The method according to claim 9 or 10, characterized in that the aqueous mixture produced in step a) is an aqueous dispersion, preferably a homogeneous aqueous dispersion, and/or the aqueous mixture in step a) is produced by homogeneously mixing the individual components . 30 Use of one or more supraparticles according to any one of claims 1 to 5 or an additive according to any one of claims 6 to 8 for the optical indication of hydrogen gas. Use according to Claim 12, characterized in that the supraparticle(s) or the additive is/are introduced into a carrier component or applied to a carrier component, the carrier component preferably being selected from the group consisting of textile fabrics, items of clothing, coatings, lacquers, moldings , components, technical devices, charging stations, pipelines, reactors, transformers, gas cylinders, test strips, adhesive strips, polymer films, safety cabinets, mobile phones, car bodies, body components, e.g. tank caps, and combinations thereof. Use according to Claim 12 or 13, characterized in that the supraparticle(s) or the additive is/are used as an indicator for leaks in safety-relevant components in the hydrogen economy, the components preferably being tanks, charging stations and/or electrolysis reactors , as an indicator for safety shutdowns in power transformers or other technical devices whose operation generates hydrogen, in permeation test strips for the search for leaks, e.g. in hydrogen gas cylinders, gas safety cabinets, pipelines, fuel cell test stands or ultra-high vacuum equipment, as Pigment for the fabric of safety clothing (e.g. a glove) for the detection of potentially explosive gas atmospheres, e.g. when working on hydrogen pipelines, hydrogen reactors, fuel cells or when refueling an automobile at a hydrogen tank station, in the medical field e.g. in test strips for Breath tests for early detection of gastrointestinal or other diseases or 31 as proof of the in-vivo resorption of Mg implant materials, or as a gasochromic element in a mobile gas sensor unit or integrated into a mobile end device, e.g. a mobile phone, a smartphone, a tablet or a laptop. Use according to any one of claims 12 to 14, characterized in that the use takes place in a method for detecting hydrogen gas, in which the / the supraparticles or the additive or a carrier component, in which the / the supraparticles or the additive introduced or on which the supraparticle(s) or the additive is/are applied, comes into contact with hydrogen gas and thereby causes a change in at least one spectroscopic property of the supraparticle(s) or the additive, and the change in the at least one spectroscopic property by optical observation or by detection with a detector, preferably using an optical waveguide for signal transmission, the at least one spectroscopic property preferably being a colour, an absorption and/or a luminescence.