Method for producing a hydrogen-detection sensor and resulting sensor

Abstract

A method is provided for producing a visual hydrogen sensor and to a sensor produced in this manner, the sensor allowing the presence of hydrogen gas in a medium to be detected by the naked eye as a result of a change of color in the sensor. The method involves the deposition of thin porous layers of oxides that do not absorb visible light in their completely oxidized state which become colored when they are partially reduced. This deposition is carried out using vapor phase deposition (PVD) in a glancing angle configuration (GLAD). The method also involves the preparation of a solution of an active metal precursor capable of dissociating the hydrogen molecule and a carrier vector and the deposition of this solution on the oxide layer in order to incorporate a minimum quantity of active metal within the pores of the oxide layer in the form of nanoparticles.

Claims

1. A method for producing a hydrogen-detection sensor, the method comprising: depositing a layer of WO.sub.3 on a quartz substrate by sputtering with a magnetron with a deposition angle of 80 as measured from a direction perpendicular to the quartz substrate to a direction perpendicular to a target of the magnetron; preparing a solution of 10.sup.3M of porphyrin with a platinum core and a poly(methyl methacrylate) (PMMA) of 1% concentration in dichloromethane; depositing the prepared solution onto a surface of the deposited layer of WO.sub.3 on the substrate by spin coating; and including platinum in pores of the deposited layer of WO.sub.3 on the quartz substrate by heat treatment at 350 C. of the prepared solution.

2. The method of claim 1, the sputtering by the magnetron being carried out at a residual pressure of 10.sup.3 mbar, at a working pressure of 5.Math.10.sup.3 mbar, a mixture of 20 sccm of argon and 5 sccm of oxygen at a source power of 125 watts, and having either a tungsten target or a cathode.

3. A method for producing a hydrogen-detection sensor, the method comprising: depositing an active mixed oxide of WO.sub.3 and SiO.sub.2 using sputtering by a magnetron with a deposition angle of 80 as measured from a direction of perpendicular to a substrate to a direction perpendicular to a target of the magnetron; preparing a solution of 10.sup.3M of porphyrin with a platinum core and a poly(methyl methacrylate) (PMMA) of 1% concentration in dichloromethane; depositing the prepared solution onto a surface of the deposited active mixture of WO.sub.3 and SiO.sub.2 by spin coating; and including platinum in pores of the deposited active mixed oxide of WO.sub.3 and SiO.sub.2 by heat treatment at 350 C. of the prepared solution.

4. The method of claim 3, the sputtering being carried out at a residual pressure of 10.sup.6 mbar, at a working pressure of 5.Math.10.sup.3 mbar, with a mixture of 40 sccm of argon and 5 sccm of oxygen, with a source power of 100 watts, a target or a cathode in which the target is a mixture of tungsten or silicon or two separate targets in which one target is tungsten and the other target is silicon.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) To complement the description being made and with the object of aiding toward a better understanding of the invention, a set of drawings is attached where the following has been represented with an illustrative and non-limiting character:

(2) FIG. 1.Diagram of a physical vapour deposition (PVD) process, glancing angle evaporation where the substrate is represented by reference (1) and the cathode by reference (2).

(3) FIG. 2.Diagram of a column layer of an oxide prepared using glancing angle evaporation, which includes metal nanoparticles in the layer pores.

(4) FIG. 3.View of a cross-section of a WO.sub.3 film prepared using glancing angle magnetron sputtering.

(5) FIG. 4.Optical response (transmittance spectrums) of a Pt/WO.sub.3 sensor before (solid line) and after (broken line) being exposed to hydrogen.

DETAILED DESCRIPTION OF THE INVENTION

(6) To achieve a better understanding of the invention, a preferred embodiment of the method described for preparing a gasochromic H.sub.2 sensor is described below.

(7) Stage 1: In first place, the deposition is carried out of a layer of WO.sub.3 on a quartz substrate (1). This deposition is carried out using the magnetron sputtering technique for a deposition angle ( of 80, with this measured from the perpendicular to the substrate to the direction perpendicular to the magnetron target (see FIG. 1). The magnetron sputtering process conditions used are: Residual pressure of 10.sup.6 mbar Working pressure of 5.10.sup.3 mbar A mixture of gases of 20 sccm of Ar (inert gas)+5 sccm of O.sub.2 (reactive gas) Source power: 125 w Tungsten target or cathode (2).

(8) A mixed oxide could alternatively be deposited: SixWyOx, consisting of a mixture of the oxides WO.sub.3 and SiO.sub.2. The magnetron sputtering technique would also be performed for a deposition angle of 80, with the following conditions: Residual pressure of 10.sup.6 mbar Working pressure of 5.Math.10.sup.3 mbar A mixture of gases of 40 sccm of Ar (inert gas)+5 sccm of O.sub.2 (reactive gas) Source power: 100 w Tungsten and silicon mixed target or cathode (2), or two separate targets one of tungsten and another of silicon.

(9) In a preferred embodiment of the invention, the thickness of the oxide layer deposited is of 400 nm.

(10) An image of the cross section of a WO.sub.3 film showing its column microstructure may be observed in FIG. 3

(11) Stage 2: Preparation of a 10.sup.3 M solution of porphyrin with platinum core (Pt) and PMMA (1% by weight) in dichloromethane (CH.sub.2Cl.sub.2).

(12) Stage 3: Deposition of the solution prepared in stage 2 on the surface of the porous layer of oxide prepared in stage 1 using a spin coating method. This achieves the evaporation of the solvent and the deposition of a layer of PMMA on the active layer of the porous oxide with a controlled concentration, typically of around 10.sup.16-10.sup.17 atoms per cm.sup.2 of metal atoms.

(13) Stage 4: Inclusion or incorporation in the pores of the active metal precursor, in addition to decomposition of the porphyrins with Pt core and the PMMA polymer using heat treatment at around 350 C. This also achieves elimination of the PMMA and the formation of metal nanoparticles of the active metal.

(14) The distribution of Pt resulting throughout the thickness of the oxide layer is homogenous according to RBS (Rutherford Back Scattering) measurements.

(15) After applying the previous drying and decomposition processes of the Pt precursor, the sensor is ready for use, giving rise to pores in the nanoparticle layer of 10 nm or less in size (see FIG. 2), according to measurements using TEM (Transmission electron Microscopy).

(16) When the sensor comes into contact with a gas containing hydrogen, said sensor begins to take on an increasingly blue colour as the exposure dose increases (exposure time and hydrogen concentration in the gas phase). FIG. 4 shows the change undergone in its transmittance before and after exposure to hydrogen.

(17) In these working conditions, a sensor is directly obtained which does not have colouring once prepared, meaning that it may be used directly for the visual or optical detection of hydrogen.