Patent Application
20220220027
The invention relates to the field of depositing metal particles on a substrate by photocatalysis. More precisely, the invention relates to a method for depositing metallic particles on a textile support by photocatalysis, as well as the textile support thus coated.
Photo-deposition of metal particles, such as silver, gold, nickel or platinum particles, on a titanium dioxide (TiO2) based substrate consists of immersing the substrate in an aqueous or alcoholic solution containing an ionic precursor of the metal to be deposited, then irradiating the assembly with a light source for a predefined time. The light source is usually placed at a distance from the substrate so as to ensure illumination of the area to be coated. However, when the surface of the area to be coated is very large, it is necessary to move the source away from the substrate and to adjust the intensity of the radiation in order to ensure uniform illumination of the different portions of the surface to be coated with metal particles. The resulting system is relatively cumbersome. Multiplication of light sources would make it possible to reduce the distances but would also require a complex adjustment of the position of these light sources to ensure a homogeneous illumination of the whole surface to be covered.
This invention therefore offers an alternative solution for photo-deposition of metal particles that is easier to implement, that saves space, and does not require complex setup steps.
In particular, the solution of this invention not only enables a complete or localized deposition of metallic particles on the surface of a support, regardless of the size of the support, but also the deposition of different types of metallic particles on the same support.
The invention thus provides a method for depositing metal particles on a textile substrate, comprising:
Thus, unlike the solutions of the prior art in which the light radiation is directed towards the substrate to be coated, in this invention the light radiation is emitted by the substrate itself. The textile sheet constitutes both the support to be covered with metal particles and a light guide bringing the light radiation as close as possible to the areas to be covered with metal particles. Irradiation of the semi-conductive particles is therefore optimal.
In practice, the textile sheet may be in fabric, knitted fabric or braided fabric form. The textile sheet is preferably in the form of a fabric composed of warp and weft threads arranged in predetermined patterns according to its application.
Advantageously, the method may include:
According to one variant, the free ends of all the optical fibers of the textile sheet simultaneously receive said light radiation inducing deposition of metallic particles on all the surfaces of the textile sheet in contact with the solution. In other words, the photocatalytic layer covers the entire textile sheet and the metal particles are evenly distributed over this layer.
According to another variant, the light radiation may be injected simultaneously at the ends of a group of optical fibers of the textile sheet, inducing the localized deposition of metal particles on the textile sheet. In other words, the metal particles are deposited only on the areas of the photocatalytic layer that are illuminated by the optical fibers. The result is a textile sheet with areas covered with metal particles and areas that are not covered.
It is thus understood that by making the choice to illuminate certain optical fibers or not, it is possible to carry out successive deposits of metallic particles of different types on separate zones of the textile sheet. For example, the textile sheet may have a first area covered with metallic particles of a first type, and a second area covered with metallic particles of a second type.
Thus, according to another variant, the method may comprise a first localized deposition of a first type of metallic particles, this first deposition consisting of carrying out the steps of the method described above by illuminating a first group of optical fibers, followed by a second localized deposition of a second type of metallic particles. This second deposit includes, in particular, after the deposit of the first type of metal particles:
In other words, the second localized deposit does not require a complete cleaning of the reactor chamber. In particular, it is sufficient to stop the illumination of the first group of optical fibers, to inject the precursor of the second type of metal into the solvent, to carry out the homogenization of the solution, and then to inject light radiation, also adapted to activate the photocatalysis of the semiconductor, into a second group of optical fibers separate from the first group in order to induce the deposition of the second type of metal particles on the irradiated areas of the textile sheet.
Furthermore, depending on the weaving technique used to weave the optical fibers with the binding threads, it is possible to make the optical fibers visible on only one side or on both sides of the textile sheet and thus obtain a complete or partial deposition of metallic particles on both sides of the sheet or on only one side of the textile sheet.
In practice, the photocatalytic layer is made of a material selected from the group comprising titanium dioxide, zinc oxide, zirconium dioxide, and cadmium sulfide. Preferably, the photocatalytic layer is titanium dioxide (TiO2) based.
In addition, when the textile sheet coated with metal particles is to be used in an oxygenated, humid or gaseous environment, it is preferable to place a silica-based protective layer under the photocatalytic coating layer, so as to limit the aging of the optical fibers. Thus, the textile sheet may further comprise a silica-based protective layer under the photocatalytic layer.
Furthermore, depending on the intended application of the textile sheet, the metal particles to be deposited may be selected from the group comprising platinum (Pt), nickel (Ni), silver (Ag), gold (Au), copper (Cu), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), or even iridium (Ir).
The method of the invention thus offers a multitude of possibilities for the creation of metallized textile sheets. The subject-matter of this invention is a textile sheet coated with metallic particles which may be obtained by the above method.
In particular, the textile sheet shown above comprises metal particles, uniformly distributed on the surface of the photo catalytic layer. For example, the distribution of metal particles on the surface of the photocatalytic layer is selectively made on the actually illuminated photocatalyst grains. The deposited metal particles are advantageously of nanometric size, for example between 1-3 nm or 5-50 nm.
The metallized textile sheet is suitable for a wide range of applications, such as disinfection of a humid or gaseous environment, but also for the production of hydrogen.
Further characteristics and advantages of the invention will become clear from the following description, which is indicative and not limiting, with reference to the attached drawings, in which:
In these figures, the same references designate identical or similar elements and the different structures are not to scale. Furthermore, only those elements that are essential for understanding the invention are shown in these Figures for the sake of clarity.
The method of the invention for depositing metal particles consists of depositing by photocatalysis metal particles on a woven fiber optic-based textile sheet covered with a semiconducting layer having photocatalytic properties, such as TiO2. In particular, under ultraviolet (UV) radiation, a reduction reaction of the metal ions on the photocatalyst occurs, metal particles are formed, and these metal particles attach to the TiO2 layer.
Such a textile sheet according to one embodiment is illustrated in
The optical fibers may be based on a polymer and the binding threads may be made of polyester. The optical fibers are uniformly distributed in one plane, parallel to each other. These optical fibers also have invasive alterations on their outer surface, so that light that propagates in the fiber may escape from the fiber through these alterations. These alterations may be created in several ways, including, for example, surface treatments adapted to produce surface modifications of the optical fibers, namely modifications of the geometry and/or physico-chemical properties of the optical fiber surface. These alterations, which allow the light propagating in the fiber to leave the fiber at the level of these alterations, may for example be obtained by sandblasting, chemical etching, or laser treatment methods. In addition, these alterations may be distributed progressively over the surface of the optical fibers in order to ensure homogeneous illumination. The surface density or the size of the alterations may thus vary from one zone to another of the water table. For example, in the vicinity of the light source, the surface density of the alterations may be low, while further away from the source, they become larger. In practice, the distribution of the alterations along the optical fibers is adapted to ensure a homogeneous lateral emission along the entire length of the optical fibers.
In addition, different weaving techniques may be used. For example, it is possible to weave the optical fibers on only one side of the textile sheet, i.e., the textile sheet has only one illuminated side. It is also possible to weave the optical fibers on both sides of the textile sheet, i.e., the textile sheet has two illuminated sides.
The textile sheet is further coated with a semi-conductive particle-based layer with photocatalytic properties, such as for example, titanium dioxide (TiO2) particles. The photocatalytic particles may be applied to the textile sheet in different ways and may form a layer covering the entire textile sheet or only specific areas, for example, on only one side of the textile sheet. The photocatalytic coating layer may be applied, before weaving, to one or more components of the textile sheet, such as to the binding threads and/or the optical fibers. The photocatalytic layer may also be deposited after weaving on both components of the fabric, and in particular either on the entire fabric formed by the optical fibers associated with the binding threads, or on specific areas of the fabric. In addition, the photocatalytic layer may be deposited in different ways, e.g., by bathing, smearing, emulsion, spraying, printing, encapsulation, electroplating, etc.
As shown in
In addition, to avoid premature aging of the optical fibers caused by titanium dioxide, it is possible to provide for the deposition of a silica-based protective layer prior to the deposition of the photocatalytic layer. Such a protective layer is advantageous if the textile sheet is to be used in an oxygen-containing environment. However, when the textile sheet is to be integrated in an oxygen-free environment, it is preferable to omit such a protective layer. Indeed, the absence of the silica layer (SiO2) allows deposition of metallic particles of a smaller nanometric size.
The free ends 6 of the optical fibers 2 are connected to one or more light sources 7 each configured to generate light radiation suitable for causing photocatalysis of the TiO2 layer. These free ends 6 may or may not be bundled together via ferrules. For example, as shown in
Preferably, the light sources 7 are configured to generate light radiation of a wavelength suitable for photocatalysis of the semiconductor particles. For example, for TiO2 particles, ultraviolet radiation with a wavelength in the range 300 nm to 400 nm is preferred. Preferably, the applied light intensity is at least 0.1 mW/cm2.
The various steps of the above method for metallizing the textile sheet, according to a particular embodiment, will be detailed below with reference to
Preparation 100 of a solvent 90: first of all, a water and/or alcohol-based solution is prepared to act as a solvent in which the precursor of the metal to be deposited will be injected. In practice, as alcohol has the power to accelerate the photo-deposition reaction, this solution may be for example glycerol, or a hydroalcoholic solution.
Filling 101 of the chamber of the reactor 9: this solution 90 is then placed in the reactor chamber 9, for example a two-phase cylindrical reactor (liquid/gas) integrating a bubbling system 91 of inert gas in vertical direction or a bubbling system via a tube inserted in the reactor. The bubbling system will remove the oxygen (O2) contained in the volume before the injection of the precursors. Of course, any other volume suitable for the implementation of the method may be used. For example, a single-phase (liquid) reactor may be used. In this case, to eliminate the O2, a photocatalytic reaction may be carried out to consume the O2; then the heat may be increased to degas. The reactor 9 may also incorporate a mechanical system, such as a stirrer 92, which will homogenize the precursor injected into the solvent.
Introduction 102 of the textile sheet 1 to be coated with metal particles: the textile sheet 1 coated with a layer of TiO2 particles is immersed in the water/alcohol solution. In the example shown in
Deoxygenation 103 of the chamber of the reactor: to eliminate the oxygen (O2) present in the chamber of the reactor, bubbling of inert gas such as argon or nitrogen is performed, via the bubbling system 91 for example. This step must be performed before the injection of the metal precursor.
Injection 104 of metal precursors: in the absence of light and oxygen, and at room temperature (between 20° C. and 35° C., for example), a predefined volume of a metal precursor solution 94 is injected into the reactor. For example, when platinum is to be deposited on the textile sheet, the precursor solution may be based on chloroplatinic acid (H2PtCl6), at the concentration necessary to photo-deposit a determined amount of metal on the titanium dioxide. For example, when silver is to be deposited, the precursor solution may be based on silver nitrate (AgNO3), and for gold deposition, the precursor solution may be based on chloroauric acid (HAuCl4). Of course, other precursors may be used. In practice, the amount of precursor is defined as a function of the percentage of metal particles to be deposited on the surface of the substrate.
Homogenization 105 of the precursor in the solvent: after injection, the solution contained in the chamber of the reactor is homogenized. Homogenization may be carried out using the inert gas bubbling system 91. In practice, one waits for at least thirty minutes under inert gas bubbling to ensure that the liquid medium is well mixed, in order to avoid a deposit by conglomerates and on only one part of the textile sheet. Stirring may also be performed using a stirrer 92 to reduce the homogenization time.
Photo-deposition reaction 106: after homogenization, the textile sheet is illuminated by injecting UV radiation into the optical fibers 2 via the light source 70. Metal particles are thus deposited by photo-deposition on the TiO2 layer illuminated by the optical fibers. Pour le TiO2, un rayonnement UV de longueur d'onde comprise entre 300 nm et 400 nm peut être approprié.
In practice, a darkening of the surface of the textile sheet is observed due to the presence of the metal. Furthermore, it is observed that all the precursors present in the solution is deposited on the textile sheet in the form of metallic particles. The metal particles deposited on the textile are of nanometric size, generally between 1 nm and 50 nm. The duration of the illumination depends on the type of metal particles to be deposited. Some metals are more easily deposited than others: for example, platinum (Pt) particles are deposited in four (4) hours while nickel (Ni) particles take twelve (12) hours to deposit. On average, the amount of metal particles deposited on the TiO2 layer relative to the amount of TiO2 particles present on the textile sheet may advantageously be in the range of 0.1% to 10%.
In conjunction with the photo-deposition, a method may be used to monitor the reaction and verify that all metal particles present in the solution have been deposited on the textile. For example, one might consider monitoring by chemical dosage or by measuring the pH of the solution.
The use of a luminous textile as a support for the photocatalytic semi-conductor optimizes irradiation of the photocatalytic particles. Thus, it has been found that the entirety of the metal precursor present in the solution is deposited as metal particles on the textile sheet. The solution of the invention is therefore a deposition method that does not induce metal particle waste, which therefore does not require effluent reprocessing to recover the metal particles, and which therefore reduces manufacturing costs.
Visualization by microscopy of the textile sheet's state of coloration thus obtained makes it possible to confirm the homogeneous deposit of the metal particles. The textile sheet is generally free of aggregates and the deposited metal particles can therefore all be active.
Thus, on the same principle and using a textile sheet woven according to a weaving technique which makes it possible to make the optical fibers visible on one side or both sides of the textile sheet and by choosing to illuminate certain optical fibers or group of optical fibers or not, it is possible to create textile sheets upon which metallic particles are completely or partially deposited using one or more types of metals. In other words, the use of a luminous textile support based on side-emitting optical fibers makes it possible to create localized photo-deposits as well as successive photo-deposits. Examples of metal deposition configurations are described below.
Photo-deposit on the entire textile sheet: the textile sheet is woven in such a way as to allow the illumination by optical fibers of both sides of the sheet. All optical fibers are connected to a light source and receive UV radiation simultaneously. During photocatalysis, the metal particles are deposited on both surfaces of the sheet.
Photo-deposition on one side of the textile sheet: the textile sheet is woven in such a way as to allow the illumination by optical fibers of only one of the two sides of the sheet. All optical fibers are connected to a light source and receive UV radiation simultaneously. During the photocatalysis reaction, the metal particles are only deposited on the surface illuminated by the optical fibers. For example, as shown in
Localized/selective photo-deposition on an area of the textile sheet: the textile sheet is woven in such a way as to allow the illumination by optical fibers of one or two sides of the sheet. However, we choose to illuminate only one part of the optical fibers, for example, every other optical fiber or group of optical fibers bundled together. As shown in
Multi-photo-deposits located on specific areas of the textile sheet: the textile sheet is woven in such a way as to allow the illumination by optical fibers of one or two sides of the sheet. A succession of deposits is carried out by photocatalysis so as to deposit several types of metal particles on separate zones of the textile sheet. As shown in
Of course, following the same principle, one may choose to weave the optical fibers so that one group of optical fibers diffuses only on one side of the textile sheet and a second group of optical fibers diffuses only on the opposite side of the textile sheet. In this way, it is possible to deposit a first type of metal particles on one side that may have, for example, antibacterial properties, and to deposit on the other side a second type of metal particles, that may be suitable for the treatment of pollutants.
It is also possible to simultaneously immerse several textile sheets in the solution containing the precursor and to modulate the connection of the optical fibers of each sheet so as to carry out a simultaneous photo-deposition on the sheets in identical or different configurations. This solution is a time-saver.
Such metallized textile sheets may be used in various applications, such as in hydrogen (H2) production. In particular, the textile sheets may be placed in a reactor chamber under pressure. As schematically illustrated in
According to one embodiment, the hydrogen production process may be carried out in the same reactor, just after the photo-deposition of the metal particles. It is then sufficient to adapt the environment of the reactor chamber for the production of hydrogen.
The textile sheets may also be used for the disinfection of an oxygenated environment, for example, the inactivation of bacteria, viruses, molds, or other organic molecules present in the air and in the water. For example, the textile sheet makes it possible to prevent the formation of biofilms and may also be used for the treatment of aqueous or gaseous effluents.
| Number | Date | Country | Kind |
|---|---|---|---|
| FR1905457 | May 2019 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/FR2020/050750 | 5/5/2020 | WO | 00 |
