WO2019002352A1

WO2019002352A1 - Procedure for the manufacturing of nanostructured platinum

Info

Publication number: WO2019002352A1
Application number: PCT/EP2018/067222
Authority: WO
Inventors: Christian BÖHLER; Maria Asplund
Original assignee: Albert-Ludwigs-Universität Freiburg
Priority date: 2017-06-27
Filing date: 2018-06-27
Publication date: 2019-01-03
Also published as: US20200131655A1

Abstract

In order to provide for a procedure for the manufacturing of platinum nanostructures show- ing improved properties, that may also be usable in biomedical appliances, such a procedure is defined comprising in a first step provision of a solution containing hexachloroplatinate, the remainder water; and in a second step electrochemical deposition of platinum on a substrate, whereby platinum is deposited in a nanostructured form.

Description

Procedure for the manufacturing of nanostructured platinum

The present invention refers to a procedure for the manufacturing of nanostructured platinum as well as the use of a substrate with deposited nanostructured platinum manufac- tured in accordance with the procedure according to the invention.

Procedures for the deposition of platinum on substrates are well-known in the art. In a first alternative procedure, a platinum containing substance, for example hexachloroplatinate, is dissolved together with a reducing agent such as formic acid. Due to the reduction potential of the formic acid, the platinum compound is reduced and platinum is deposited on a substrate. Said first embodiment is known as the passive procedure for the depositing of platinum. It is for example used in connection with the manufacturing of platinum catalysts. Since the reduction of the platinum compound starts immediately after mixing the same with the reducing agent, the reaction can only be further influenced by a change of temperature or by the time the substrate on which the platinum deposits remains in the solution. The solution prepared can only be used once. The result is an uncontrolled deposition of platinum on surfaces of a substrate and also on surfaces of the reaction vessel.

There is also known another procedure for the deposition of platinum from platinum con- taining compounds in a solution. It is similar to the first passive process described above, however, in addition to a reducingagent, an electrolyte or a nucleating agent, also an electrochemical process is used. By this, the deposition is enhanced in time by the use of an electrical signal. However, the deposition starts already after mixing the platinum containing compound with the reducing agent, so that at least in part an uncontrolled deposition of the platinum takes place. However, due to the use of an additional electrochemical driven step, the platinum is advantageously deposited on the electrical connected substrate instead of other surfaces in the reaction vessel, and, in addition, the deposition time is reduced. Such a procedure is for example disclosed in WO 2007/050212 A2, where a new kind of a platinum deposition, called platinum grey, is described to be manufacturable under certain conditions. In the electrochemical driven process described therein, a constant voltage is used, and as a platinum containing compound platinumtetrachloride (PtCI₄) is used. In addition, sodiumdihydrogenphosphate and disodiumhydrogenphosphate as a buffer are used in the platinum containing solution. The platinum salt concentrations used are from 3 to 30 mM. Similarly, DE 10 2014 006 739 B3 discloses a process for the deposition of various metals, including platinum, in a solution containing I eadacetate-tri hydrate. Leadacetate is used in order to first deposit lead on a substrate, and, afterwards, the lead is substituted by platinum in the further deposition process.

All of the known procedures for the deposition of platinum suffer in that a reducing agent or an additional electrolyte such as disodium hydrogen phosphate or a kind of a nucleating agent such as lead acetate are used. In the deposition layer thus created on a substrate, at least minor amounts of said compounds are incorporated, limiting the use of such substrates especially for biomedical applications, but also other uses. Further, as far as reducing agents are used in the production of a deposition layer of platinum on a substrate, the procedure is at least in part not controllable in detail. Further, in most known procedures the passive reduction of the platin containing compound could not be stopped, so that the platin containing solution can not be used any further, enhancing the costs of said procedures.

Therefore, there exists a need for an alternative method for the deposition of platinum, especially in a nanostructured form.

It is, thus, the object of the present invention to provide for an advanced procedure for the manufacturing of nanostructured platinum which is costly attractive, controllable and yields in highly purified platinum deposition layers.

Said object is solved by the procedure as described in claims 1 to 6, as well by the use of a substrate with deposited nanostructured platinum manufactured by said procedure in accordance with claim 7. The procedure in accordance with the present invention for the manufacturing of nanostructured platinum comprises in a first step the provision of a solu- tion containing hexachloroplatinate, the remainder water; and, in a second step, the electrochemical deposition of platinum on a substrate, whereby platinum is deposited in a nanostructured form. The solution, thus, contains only water and hexachloroplatinate, and no further active agents such as a reducing agent, a nucleating agent or a buffer solution. The term "hexachloroplatinate" is to be understood in the sense of the present invention as to refer to the free acid with the chemical formula H₂PtCI₆, also called hydrogen hexachloroplatinate. Only very small amounts of impurities may be present in the solution, containing hexachloroplatinate acid and water. The concentration of such impurities shall be less than l OmM, preferable less than 3mM, more preferable less than 1 mM, and most preferable less that 0,1 mM. As the case may be, an electrolyte as a non active substance may be present in the solution, such as sodium or potassium chloride, especially in small amounts of not more than approximately 10 nM. Most preferred, however, is a solution only containing hexachloroplatinate and water. The main advantage by using a solution in accordance with the invention is that highly purified platinum deposition layers are obtainable by the procedure in accordance with the present invention, that may especially also be used in biomedical applications such as the measurement of brain currents and other applications. Further, due to the electrochemical deposition in the second step, a completely controlled process is provided for avoiding pas- sive platinum deposition. Thus, the deposition is truly restricted to the electrical connected substrate and can be performed for long times without having an overall passive coating of platinum structures on the substrate as well as the reaction vessel. Further, in the absence of any other agent, the pH-value of the solution used is in a range where it is possible to coat otherwise critical substrate materials, such as polymers or non-noble metals such as steel without side effects or the destruction of the substrate itself. Preferably, the pH-value of this solution provided for in the first step is in a range between approximately 1 ,5 and approximately 4, further preferred in a range between approximately 1 ,8 and approximately 3,9, and further preferred in a range between approximately 2 and approximately 3. Various materials may be used to form the substrate. As may be described below in connection with the examples in accordance with the present invention, for example a polyimide substrate may be used. Polyimide substrates are preferable because they may be provided for in a flexible form. In the polyimide itself, electrical conductive tracks, preferably made of platinum , can be embedded within the polyimide material. Such embedded tracks have on their first end region an active side with a surface being in contact with the deposition solution, being thus not embedded, whereas on the second end region an interconnection is provided for by the embedded track, being not in contact with the depositing solution. Such polyimide substrates may have, for example, as active sides a circular shape with a diameter between 5 μηι, preferably 100 μηι, and 2000 μηι, and even more. However, also other polymers may be used as substrate materials, such as silicone rubber (e.g. PDMS)

parylene (e.g. Parylene-C), or epoxy resins such as SU-8, as well as none-noble metals such as stainless steel (e.g. 31 6L), nickel-cobalt-base alloys such as MP35N, or indium tin oxide (ITO). In addition, also none-noble metals may be used embedded in polymers such as polyimide, as described before. Other substrate materials useable in accordance with the present invention are glass or PEM (Polymer Electrolyte Membrane). One PEM usable is Nafion (registered trademark), obtainable from the company DuPont. The glass or the PEM are coated with an electrical conductive material, preferably with platinum. However, instead of platinum, also other noble metals such as rhenium, ruthenium, rhodium, palladi- um, silver, osmium iridium or gold are usable.

As far as the terms "approximately" or "essentially" are used in the present invention with respect to values, value ranges or terms referring to values, they are to be understood herein to mean what the person skilled in the art would regard as typical in the given context, and from the perspective of a person skilled in the art. In particular, deviations of the given values, value ranges or terms referring to values comprised by the aforesaid terms amount to +/- 10 %, preferably +/-5 % and more preferably +/- 2%.

The term "nanostructure(d)" as used in connection with the deposited platinum on a sub- strate produced in accordance with the procedure of the present invention refers to grain- like platinum structures having an irregular outer shell with edges and corners having a grain size in a range between approximately 1 nm to approximately 500 nm, preferably in a range between approximately 5 nm to approximately 400 nm, and more preferably in a range between approximately 10 nm to approximately 200 nm.

Preferably the deposition time for the electrochemical deposition in the second step of the procedure in accordance with the present invention is in a range between approximately 1 s and approximately 60 min, further preferred in a range between approximately 1 s and 1000 s, and more preferred in a range between approximately 10 s and approximately 360 s. In a further preferred embodiment of the present invention, the temperature at which the deposition takes place is in a range between approximately 10°C and approximately 75 °C, more preferably in a range between approximately 15°C and approximately 62°C. Preferably, the concentration of the hexacloroplatinate in the solution before electrochemical deposition takes place is in a range between approximately 0,2 mM and approximately 3,1 mM, further preferred in a range between approximately 0,25 mM and approximately 3 mM, and further preferred in a range between approximately 1 mM and approximately 2,9 mM. By using such low concentrations of hydrogen hexachloroplatinate in the preparation of the solution in the first step of the procedure in accordance with the present invention, a very controlled deposition of the platinum and the form of nanostructures on a substrate are available. If the concentration of hydrogen hexachloroplatinate would exceed 5 mM, and also 4 mM, no controlled depostion of platinum in the form of nanostructures would be possible. Preferably, higly purified water is used, especially a highly purified water with a resistance of at least approximately 15MOhm* cm, preferably at least approximately

18MOhm*cm, at 25°C, such as Milli-Q (registered trademark) water of Type 1 in accordance with ASTM D1 1 93-91 provided for by Millipore Corporation.

In a further preferred embodiment of the present invention, the electrochemical deposition in the second step is carried out in a voltage range between approximately -0,6 V, preferably approximately -0.4 V, and approximately +0.4 V vs. Ag/AgCI. As far as in the following volt- ages or voltage ranges in relation to the electrochemical deposition in the second step of the procedure in accordance with the present invention are referred to, they are defined vs. Ag/AgCI. Preferably, the deposition in the electrochemical step is carried out with a three (3) electrode set-up. In such a three electrode set-up, a stainless steel counter electrode is used as well as a Ag/AgCI reference electrode. As working electrode the electrically connected substrate used in the second step of the procedure in accordance with the present invention is used. However, also a two-electrode setup may be used for the electrochemical deposition. Although the electrochemical deposition in the second step in accordance with the present invention may be carried out at a constant potential, it is preferred that electrochemical deposition is carried out as a dynamic potential deposition. Such a dynamic poten- tial deposition leads preferably to the platinum nanostructures as defined before in form of grain-like structures with edges and corners. In contrast thereto, an electrochemical deposition at a constant potential usually leads to grass-like structures with grass needles with an extension in a range between approximately 10 nm and approximately 1000 nm, thus, a range similar to the grain-like nanostructures preferably obtained in accordance with the procedure of the present invention. As a dynamic potential deposition in accordance with the present invention it is understood that at least over a certain voltage range with a lower vertex potential and a higher vertex potential the electrochemical deposition is carried out. Preferably, the voltage range comprises at least a sweep over a range of approximately 0.2 V, further preferred a sweep of a range of at least approximately 0.5 V, and preferable a sweep in a rang between 0.2 V and 0.9 V, in one direction. The dynamic potential deposition in the sense of the present invention may, thus, be carried out e. g. as a linear sweep from a negative voltage to a higher voltage or a linear sweep from a higher voltage to a lower voltage, or as a cyclic sweep between a lower potential and a higher potential. Also, the inclination of the sweep may be amended within one sweep. Besides the aforesaid linear sweeps and cyclic sweeps, it is also possible to use more complex sweeps using geometries like exponential signals or sinusoidal signals, square wave functions and/or saw tooth functions, especially between two or more potentials. The latter signals or functions are applicable at frequencies between approximately 5 Hz and approximately 200 Hz. For example, a saw tooth function may be used starting from a voltage of -0.2 V with a step of +/- 0.2 V at a frequency of 20 Hz. The deposition times for the aforesaid signals and functions are comparable to the deposition times already mentioned above.

Most preferred in accordance with the present invention is the use of single sweep or multi- pie sweeps in a given potential range in the second step of the electrochemical deposition. More preferably, multiple sweeps are used in a given potential range, and most preferably cyclic multiple sweeps. Such cyclic multiple sweeps are obtainable by using cyclic voltam- metry technics. Especially preferred is the use of cyclic voltammetry in a voltage range between approximately -0.3 V and 0.3 V. When using multiple cyclic sweeps, at least prefera- bly 5 sweeps back and forth, more preferably at least 10 sweeps back and forth, and most preferably more than approximately 20 sweeps back and forth are used, with an uppre max- imun of approximately 1000 sweeps, preferable up to approximately 600 sweeps.

Preferably, a scan rate used for single sweeps or multiple sweeps, especially multiple cyclic sweeps, in a given potential range are in a range between approximately 1 mV/s and approximately 200 mV/s, preferably in a range between approximately 2 mV/s and approximately 150 mV/s. In a further preferred embodiment of the present invention, the total charge transferred is in an amount between approximately 0,5 C/cm² and approximately 5 C/cm², more preferably in a range between approximately 0,8 C/cm² and approximately 4 C/cm². The charge transferred can be used to control the deposition process in the second step of the procedure in accordance with the present invention in detail. The charge transferred is measureable by cyclic voltammetry.

The substrate with deposited nanostructured platinum thereupon produced in accordance with the procedure of the present invention show very dense, grain-like platinum

nanostructures on the surface of the substrate. The complex impedance Z, that may be measured by electrochemical impedance spectroscopy, of such a coated substrate is below the complex impedance of an uncoated substrate, and is lowered by a factor in a range between approximately 10 to approximately 100 in the coated substrate compared to the un- coated substrate. The complex impedance of a coated substrate produced by multiple cyclic sweeps, especially produced by cyclic voltammetry, is lower than the complex impedance of a coating produced with a constant potential process, whereby all other parameters are hold equal. The lowering of the complex impedance when using a dynamic potential process, at especially multiple cyclic sweeps, especially produced by cyclic voltammetry, com- pared to a constant potential process, has a magnitude of a factor between approximately 0,3 and approximately 2,5.

The present invention also refers to use of a substrate with deposited nanostructured platinum thereupon manufactured in accordance with the procedure as discussed before as an adhesion promoter for coatings, as a corrosion protection and/or as a means for the enhancement of electrochemical properties, such as a voltage influencing means, an impedance reducing means, or an enhancement means for charge transfer. Especially, the platinum nanostructures on a substrate produced in accordance with the present invention may function as an adhesion promoter for a subsequent deposition of bio-functional coatings for neural probes. Such coatings may be made, for example, by conducting polymers, especially in the form of electrodeposited films. Due to the procedure used for the manufacturing of the platinum nanostructures on a substrate, a rough layer that provides a higher amount of nucleation sites as well as a higher degree of mechanical interaction to a subsequently electrodeposited conducting polymer layer is obtainable and useable, resulting in a significantly improved adhesion of the conducting polymer electrodeposited thereupon. Further, a substrate with an electrocoating of platinum nanostructures produced in accordance with the present invention is useable as an intermediate layer on none-noble metal surfaces, that may be used as working electrodes. When used as a voltage influencing means, one or more layers of electrodeposited platinum nanostructures produced in accordance with the pre- sent invention on a substrate influence the reducing or oxidizing potential of the original surface, so that the field of use of the original surface is amended and/or widened. The present invention also relates to a substrate with an electrocoating made of platinum

nanostructure, produced in accordance with the present invention, whereby a mechanical strengthing of the electrodeposited platinum nanostructure is achieved by filling the plati- num nanostructure with at least one conductive polymer, e.g. PEDOT. This is especially ad- vantageous in case the platinum nanostructures are long and/or the deposit will showa weblike structures with holes therebetween or openings. The substrate may exist of an insulation layer and a conducting electrode layer, arranged at least on a part of said insulation layer. The electrocoating of nanostructured platinum free of ions and salts is arranged at least in part on said conducting electrode layer.

The working electrodes used as substrates or the substrate itself may have each kind of geometry, depending also on the further use of the substrate with an electrodeposited platinum nanostructure thereupon produced in accordance with the procedure of the present invention. For example, the electrode may have a needle-like or tip-like structure, a flat structure, as already disclosed above in connection with polyimide substrates, or may have any other geometry.

An especially preferred embodiment of the procedure in accordance with the present invention is the use of cyclic voltammetry in a voltage range between approximately -0.3 V and 0.3 V, whereby more than 20 sweeps, and not more than approximately 1000 sweeps, preferably not more than approximately 500 sweeps back and forth are used with a scan rate in a range between 1 mV/s and approximately 120 mV/s. Preferably, such an electrochemical deposition by way of cyclic voltammetry is carried out with a concentration of the hydrogen hexachloroplatinate in a range between approximately 1 .5 mM and approximately 2.8 mM. Thereby, improved mechanical properties especially when using the platinum nanostructures on the substrate as an intermediate or enabling layer for bio-functional coatings, for non-noble metal surfaces and as a voltage-influencing means are obtainable. The advantageous effects of the present invention are explained in more detail in connection with the following figures:

Fig. 1 : A time-potential-diagram showing possible linear sweeps A and B as well as a multiple sweeps C useable in the electrochemical deposition step of the pre- sent invention; Fig. 2: Cyclic voltammetry diagrams of an uncoated substrate, a substrate produced in a constant potential process as well as a substrate coated in a dynamic potential process by using cyclic voltammetry;

Fig.3: Complex impedance of the three substrates shown in Fig. 2;

Fig. 4: Photographs of a polyimide substrate with a platinum nanostructure deposition carried out by a dynamic potential process on the left side and by a con- stant potential process of the right side, showing overgrowing of the deposited nanostructures;

Fig. 5A-5D: Electron microscopy pictures of platinum nanostructures deposited on a substrate by different dynamic potential process (Fig. 5A to 5C) and a constant potential process (Fig. 5D);

Fig. 6A-6B: Electron microscopy pictures of platinum nanostructures deposited on a polyimide substrate by way of a constant potential process; and Fig. 7A-7B: Electron microscopy pictures of platinum nanostructures deposited on a polyimide substrate by way of a dynamic potential process.

Fig. 1 shows three alternatives for carrying out a dynamic potential deposition of platinum nanostructures on a substrate. A linear sweep A starting from a low potential of -0.3 V and ending at a higher potential of 0.3 V is characterized in a general way, whereas a linear sweep B is shown starting at a higher potential of 0.3 V and ending at a lower potential of - 0.3 V is also shown. Further, a multiple sweeps C are shown in Fig. 1 with three peaks within the time frame shown, the multiple sweeps starting at a lower potential of -0.3 V and running to a higher potential of 0.3 V back and forth. Such multiple sweeps C may be obtained by using cyclic voltammetry, and is also similar to a multiple sweep using a saw tooth function.

Fig. 2 now shows the cyclic voltammetry properties of an uncoated substrate, a substrate coated by way of a dynamic potential process as well as a substrate obtained by constant potential process. For the constant potential process, a potential of -0.3 V is used, whereas for the dynamic potential process, cyclic voltammetry with a voltage range between -0.3 V to 0.3 V back and forth is used. For the dynamic potential process, 300 multiple cyclic sweeps back and forth between -0.3 V and 0.3 V are used with a scan rate of 12 mV/s. The total charge transferred was about 2 C/cm². An identical charge is transferred with respect to the constant potential process to the substrate. The potential was held constant for 2310 s at -0.3 V. The hydrogen hexachloroplatinate aqueous solution used with respect to the constant potential process as well as the dynamic potential process was identical and contained 2.5 mM hydrogen hexachloroplatinate. One may clearly obtain form Fig. 2 that the electrochemical active area of the substrate produced with the dynamic potential process is greater than the electrochemical active are of the substrate produced with a constant potential process. For the cyclic voltammetry measurements done with respect to Fig. 2, an aqueous solution of highly purified water with a phosphate bufered saline (PBS) at a concentration of 0.01 M without hydrogen hexachloroplatinate (as well as any other kind of agents) is used. The cyclic voltammetry is carried out at room temperature (25°C).

Fig. 3 shows the complex impedance measured by electrochemical impedance spectroscopy of the substrates as defined in connection with Fig. 2 above. One may clearly take from Fig. 3 that the complex impedance of the coated substrates are lowered by a factor of 35 to 50 compared to the uncoated substrate. Further, one may clearly see that the complex impedance of the substrate having platinum nanostructures electrodeposited thereupon by way of a dynamic potential process show a lowered impedance by a factor of around 1 .5 compared to the substrate obtained by a constant potential process, as defined before in connection with Fig. 2. Thus, one may obtain from Fig. 2 and 3 that the electrodeposition of platinum nanostructures by way of a dynamic potential process, especially by multiple sweeps, more preferably multiple cyclic sweeps, obtainable by cyclic voltammetry, leads to a substrate with at least one layer of platinum nanostructures with preferable properties. Indeed, as may be taken from Fig. 5 (see discussion below), by way of a dynamic potential process a more homogeneous and also thinner electrodeposition of platinum nanostructures on sub- strates is obtainable. Due to the increased homogeneity, such layers of platinum nanostructures on substrates show improved properties especially when used as intermediate layers or adhesion promotion layers as discussed before.

Fig. 4 now shows the coated substrates produced in accordance with the solutions and the electrochemical deposition as defined with respect to Fig. 2 above, whereby on the left- handed side of Fig. 4 the substrate with platinum nanostructures produced by way of a dynamic potential process as described above is shown, and on the right-handed side platinum nanostructures deposited on the substrate produced by the constant potential process as defined above is shown. One may clearly obtain from the right-handed side of Fig. 4 an overgrow of the platinum nanostructures over the rim of the active area of a substrate, whereas no such overgrow takes place by the dynamic potential process as evidenced by the left-handed platinum nanostructures deposited on the active area of the polyimide substrate. Fig. 5A to 5C show electronic microscopy pictures of substrates with electrocoated platinum nanostructures obtained by various dynamic potential processes, whereas Fig. 5D shows the result of a constant potential process. In Fig. 5A, the electrodeposition of platinum nanostructures was carried out using a dynamic potential process, namely a linear voltage ramp starting from a negative potential of -0.3 V and ending at a positive potential of 0.3 V. The scan rate was 2 mV/s and the total deposition time was 300 s. In contrast thereto, Fig. 5B, again, shows a linear voltage ramp, however starting from a higher potential of 0.3 V and ending at a lower potential at -0.3 V. The other conditions are identical to the linear voltage ramp as used for the deposition of platinum nanostructures shown in Fig. 5A. Fig. 5C shows platinum nanostructures deposited by a dynamic potential process using cyclic voltammetry in a potential range between -0.3 V and 0.3 V at a scan rate of 120 mV/s. 58 sweeps back and forth were carried out. Fig. 5D shows the electrodeposited platinum nanostructures produced by using a constant potential of -0.3 V. The charge transferred in view of Fig. 5A, 5B, and 5D was 1 .1 C/cm², whereas the charge transferred regarding Fig. 5C was doubled to 2.2 C/cm². It may be clearly taken from Fig. 5A to 5C referring to a dynamic potential process that a more homogeneous and also denser surface structure of the electrodeposited layer of platinum nanostructures is obtained compared to the electrodeposited layer produced by a constant potential process in accordance with Fig. 5D. Fig. 5D shows more or less very coarse and grass-like platinum nanostructures with extensions between approximately 20 nm to approximately 700 nm, whereas the platinum nanostructures ob- tained by the dynamic potential process in accordance with Fig. 5A to 5C show more or less a grain-like structure with corners and edges, with dimensions for the grain size between approximately 25 nm to approximately 150 nm (Fig. 5A), between approximately 10 nm to approximately 10 nm (Fig. 5B), and between approximately 20 nm to approximately 200 nm (Fig. 5C). The finest nanostructures were obtained by the linear voltage ramp starting from the higher potential in accordance with Fig. 5B, whereas the most homogeneous surface structure was obtainable by using a linear voltage ramp starting from the lower potential in accordance with Fig. 5A. The structure of the platinum nanostructures produced in accordance with cyclic voltammetry as shown in Fig. 5C is in the middle between the structures of the platinum nanostructures shown in Fig. 5A and 5B.

Fig. 6A and 6B show an electron microscopy picture of an active area of a polyimide substrate coated with platinum nanostructures in accordance with the present invention by way of a constant potential process. The potential was held constant at -0.3 V over 220 s. The concentration of the hexachloroplatinate was 2.5 mM. From the enlargement shown in Fig. 6A one clearly sees the needle-like or grass-like structure of the platinum nanostructures produced by the constant potential process. The constant potential process further shows undefined and substantially larger structures at the edge of the substrate as a consequence of an inhomogenous growth. Fig. 7, in contrast, shows an active area coated with platinum nanostructures produced by the process in accordance with the present invention using a dynamic potential process, namely cyclic voltammetry in a range between -0.3 V and 0.3 V at a scan rate of 1 20 mV/s. 300 sweeps back and forth were carried out. The total charge transfer was 2.1 C/cm², iden- tical to the total charge transferred in the example shown in Fig. 6A/B. One clearly sees the homogeneous and dense grain-like structure of the platinum nanostructures deposited on the polyimide substrate material in Fig. 7 A being an enlargement of Fig. 7B. Further, the deposition area as shown in Fig. 7A/B is more homogeneous and shows well defined nanostructures also at the rim of the substrate in contrast to the undefined large structures resulting from the constant potential process as illustrated in Fig. 6AB.

By way of the present invention, it is provided a new procedure for the manufacturing of platinum nanostructures from a solution containing only water and hexachloroplatinate yielding to substrates coated with platinum nanostructures that are also usable in biomedi- cal applications. The solution may preferably be used various times, as no active agents such as reducing agents are present. The electrodeposited platinum nanostructures, especially when using the preferred dynamic potential process, have a dense and homogeneous appearance with a grain-like structure with edges and corners on the grains. The deposition process is definable in detail, so that depositions of platinum nanostructures in one or more layers are obtainable with predefined properties.

Claims

1 . Procedure for the manufacturing of nanostructured platinum comprising in a first step provision of a solution containing hexachloroplatinate, the remainder water; and in a second step electrochemical deposition of platinum on a substrate, whereby platinum is deposited in a nanostructured form.

2. Procedure according to claim 1 , characterized in that the solution of the first step is provided with a pH-value between approximately 1 ,5 and approximately 4,4.

3. Procedure in accordance with anyone of the proceeding claims, characterized in that the hexachloroplatinate is provided for in a concentration between approximately 0,2 mM and approximately 3,1 mM.

4. Procedure in accordance with anyone of the proceeding claims, characterized in that in the second step the electrochemical deposition is carried out in a voltage range between approximately -0,4 V and approximately +0,4 V vs. Ag/AgCI.

5. Procedure in accordance with anyone of the proceeding claims, characterized in that the electrochemical deposition in the second step is carried out as a dynamic potential deposition.

6. Procedure in accordance with anyone of the proceeding claims, characterized in that the electrochemical deposition in the second step is carried out by means of a single sweep or by means of multiple sweeps in a given potential range.

7. Use of a substrate with deposited nanostructured platinum manufactured in accordance with anyone of the proceeding claims as an adhesion promotor for coatings, as a corrosion protection and/or as a means for enhancement of electrochemical properties.