SU1741027A1 - Method of making indicator coating - Google Patents

Abstract

The essence of the method is that after the oxide film is preliminarily applied to the body surface and before the luminescent dye is applied, the film is kept in a solution of heavy metal salts with a concentration of 10-20 g / l at a temperature of 15-25 ° C for 1-2 h, after which the oxide layer is rinsed with distilled water, as the dye used complexes of platinum metals with organic ligands. 5 il.

Description

The invention relates to a technique for measuring gas pressure on a solid surface, and more specifically to a technique for contactless recording pressure and gas concentration for quenching luminescence of indicator coatings, and can be used to quickly measure air pressure on aircraft models tested in wind tunnels, propellers, gas turbine blades etc., to measure the oxygen concentration in the air of industrial and other premises, as well as to measure the concentration of other gases extinguishing luminescence o, in gas mixtures under various conditions.

The purpose of the invention is to increase the accuracy and range of measured air pressures and oxygen concentration in gas mixtures by increasing the degree of luminescence quenching by reducing the effect of temperature on the luminescence intensity and reducing the background luminescence.

The invention consists in the use as luminescent dyes of complexes of platinum metals with organic ligands and in the treatment of an oxide film on the surface of a solid used as an adsorbing base before applying the dye with a solution of amphoteric hydroxide of a heavy metal.

The use of complexes of platinum metals (Pt, Ru, Os, etc.) with organic ligands is due to the fact that the spectral-luminescent characteristics of many compounds of this group most fully satisfy the requirements imposed on dyes for the luminescent indicator coating (LIP). The long-wavelength absorption band of ruthenium complexes lies in the region of 400-500 nm, which makes it possible to use

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These include visible light sources, including as cheap as incandescent bulbs. At the same time, organic contaminants that fall from the air to the surface of the LIP, as a rule, weakly or completely do not absorb radiation in this area, which leads to a decrease in the background luminescence. The complexes luminesce in the region of 50-700 nm with a high quantum yield, which increases the signal-to-noise ratio and allows to increase the measurement accuracy. In general, this group of dyes provides a wide choice of compounds with different positions of the absorption and luminescence bands within the visible spectrum and different values of lifetimes and quantum yields of luminescence, which allows us to choose LIP (pressure range, temperature, recording parameters equipment) optimal connection, providing the best metrological characteristics.

It has been established experimentally that the complexes adsorbed on an oxide film on the surface of aluminum and its alloys, as well as on other solids, such as silicon oxide Si02, aluminum oxide, fine-pore glass, firmly hold on the surface of these bodies and at the same time maintain their spectral - luminescent characteristics and ability to quench luminescence under the influence of atmospheric oxygen. Dye adsorption on such surfaces occurs due to weak coupling, in which dispersion forces, hydrogen bonding with surface OH groups, or weak donor – acceptor interactions take part. Such a connection of dye molecules with the adsorption centers of the surface does not lead to significant distortions in the structure of the electronic states of the dye, but affects the kinetics of the processes of degradation of the excitation energy.

It was established experimentally that the treatment of an oxide film deposited on the surface of aluminum or its alloys by the method of oxidation in an aqueous solution of (NH4) 2W04 before applying the dye-ruthenium complex leads to a significant decrease in the temperature dependence of its luminescence intensity. During processing, the surface of the oxide film is modified, new adsorption centers are formed as a result of the interaction of dissociation fragments (and -W042) with surface OH groups, incompletely coordinated aluminum atoms and other

surface centers. The fixation of the complexes at the modified adsorption centers decreases the molecular mobility, which leads to a weakening of the dependence of the luminescence on temperature. The atoms of a heavy metal (W) located on the surface in the –W042 groups can also affect the electronic states of dye molecules by disturbing the spin-orbit interaction (the so-called external heavy atom effect), which leads to an increase in the quantum yield luminescence from triplet states.

5 It was determined that the optimal treatment mode is to hold the oxide film in (NH4) 2W04 solution with a concentration of 10-20 g / l at 15-25 ° C for 1-2 hours, followed by rinsing.

0 in distilled water.

It was also established that such treatment promotes the acceleration of the adsorption of complexes from solutions, so that their optimum concentration on the surface (0.1-0.5 mono-5 layers) is achieved in a shorter period of time compared with adsorption on the untreated film surface.

On .1 is a diagram of the device in which LIPs are tested;

0 in FIG. 2-5 are curves explaining the method.

The device (Fig. 1) consists of an excitation light source 1 (DKSSh-500 lamp), lenses 2 and 3, a luminescence excitation monochromator 4 (MDR-2) focusing

5 mirrors 5 of a Dewar vacuum quartz cell 6, sample 7 emitting luminescence from a monochromator 8 recording the luminescence intensity of a photomultiplier 9, block

0 10 high-voltage supply of a FZU, amplifier 11, a tablet two-coordinate electronic potentiometer 12, valves 13-16 of a vacuum unit, a pressure gauge sensor 17 of pressure, absorption

5 of pump 18, source 19 of a stream of cooled nitrogen vapors (Dewar flask with boiling liquid nitrogen), tube furnace 20 for heating the gas stream to the required temperature, adjustable source 21

0 power tube furnace, temperature sensor 22, switching unit 23,

The test procedure is as follows.

Test sample 7 with applied

5 LIPs are placed in a cuvette 6, in which a vacuum is created with the help of pump 18 with a residual Torr pressure. The sample is illuminated with monochromatic radiation, selected using a monochromator 4 in the radiation of source 1 and a focused mirror 5 on the sample. The luminescence produced by this light with the help of a lens 3, a monochromator 8 and a photomultiplier 9 is converted into an electrical signal, amplified by an amplifier 11 and recorded by an electronic potentiometer 12 at input Y. At the input X of the potentiometer a switching signal is applied to the input X of the potentiometer one of the following sources: a wavelength sweep sensor for the monochromator 4, similar to the monochromator sensor 8, a pressure sensor 17, a temperature sensor 22. Monochromator sweep sensors are used to record the luminescence spectra and luminescence excitation of LIP. When studying the dependence of the luminescence intensity LIP on the air pressure in the cuvette 6 with sample 7 metered portions the inlet valve 15 with the valves 13 and 14 open, air is injected, the pressure of which is measured by sensor 17, the signal from which is fed to input X of potentiometer 12. With increasing the air pressure in the cuvette luminescence intensity decreases, which is recorded by potentiometer 12, as described above. In the third test, the cuvette is filled with air to achieve a predetermined pressure, a stream of cold nitrogen vapor from source 19 is heated in a furnace 20, blown into the cuvette finger, on the inner surface of which sample 7 is fixed, as a result of which the sample acquires a predetermined temperature measured by a sensor 22, the signal from which is fed to the input X of the potentiometer 12. The sample temperature is varied by varying the temperature of the nitrogen vapor with the help of the furnace 20, while simultaneously the input s sample luminescence.

Figure 2 shows, as an example, the luminescence excitation spectra (curve 24) and the luminescence spectrum (curve 25) of the LIP formed by the porous oxide film on aluminum and the dye Ru (bpy) sCl2 adsorbed on it. Curves 26 and 27 show the absorption and luminescence spectra of the same dye in an alcohol solution. Curve 28 is the luminescence spectrum of Pu (La) adsorbed on microporous glass. From these curves, it can be seen that the spectral characteristics of the dye (ruthenium complex) adsorbed on the surface of solids of different nature vary slightly compared with its characteristics in solution,

Example 1. Two samples of LIP are an oxide film deposited on aluminum by oxidation in a sulfuric acid electrolyte, with an adsorbed dye - Pu complex (Lex) CS12. Sample 1 oxide film before applying the dye was treated in a solution of salt (NH4) aW04 with a concentration of 10-20 g / l at 15-25 ° C for 1-2

h, rinsed with distilled water, after which a dye was applied to it with a surface concentration of 0.1-0.5 monolayer. Sample 2 was prepared in the same way, but without treatment in a salt solution.

(NH4) 2W04.

Fig. 3 shows the characteristics of luminescence quenching of samples 1 (straight 29) and 2 (straight 30) in the form of Stern-Volmer dependencies (ratios I0 / lp as functions of p, where p is air pressure, I0, Ip is intensity luminescence at the corresponding value of p). It can be seen from the graph that as the air pressure changes, the luminescence intensity of the sample 1

varies much more than sample 2, i.e. treatment of the oxide film with (NH4) 2W04 salt significantly increases the efficiency of luminescence quenching of Pu complex (Lpu) with oxygen

of air. Obviously, the luminescence intensity of the adsorbed dye will vary in the same way as with a change in air pressure with a constant relative fraction of oxygen, and

when changing the relative proportion of oxygen in the air at a constant total pressure. This means that not only air pressure can be measured with LIP, but also oxygen content in the air.

or in a mixture with other non-extinguishing luminescence gases.

Figure 4 presents the dependence of the luminescence intensity of sample 1 at an air pressure of 760 Torr (curve 31) and 300

Torr (curve 32) and sample 2 at an air pressure of 760 Torr (curve 33) and 300 Torr (curve 34) versus temperature in the range of 0-50 ° C.

Comparison of curves 31 and 33, as well as curves 32 and 34 between them, shows that the treatment of the oxide film before applying the dye-ruthenium complex with the (NH4) 2W04 salt is much more dependent on the dependence of the luminescence intensity

on temperature.

Example 2. Two samples 3 and 4 are prepared by the same procedure as sample 1, but the complex is used as dye for sample 3

Ru (Ph2phen) 3CL.2, and for sample 4, the complex Ru (bpy) 3Cl2.

Figure 5 shows the Stern-Volmer dependences of luminescence quenching of samples 3 (curve 35) and 4 (curve 36) in the range of air pressure variation of 0.01-0.1 atm. As can be seen from the graph, the quenching efficiency of sample 3 is 2.5 times higher than that of sample 4.

Thus, when measuring low air pressures (or low oxygen concentrations), LIP with the Ru (Pb2phen) 3Cl2 complex provides greater accuracy of measurement than LIP with the Ru (bpy) aCl2 complex. At the same time, in the range of high pressures (high oxygen concentrations), it is advisable to use LIPs with the Ru (bpy) sCl2 complex, since, due to the high extinguishing efficiency of the Ru (Ph2phen) 3Cl2 complex, the intensity of its luminescence at elevated pressure becomes low, which leads to a decrease in measurement accuracy.

By using complexes with different ligands, it is possible to optimize the characteristics of LIPs for operation in different pressure ranges in order to achieve maximum measurement accuracy.

Claims (1)

Invention Formula A method of manufacturing an indicator coating intended for measuring the pressure and concentration of a gas extinguishing luminescence, comprising applying on the surface of a solid body in contact with the analyzed gas an oxide film with a thickness of 10-20 µm by anodic oxidation in a sulfuric acid electrolyte with a concentration of 180-200 g / l with a current density of 0.8-2.0 A / dm2, an electrolyte temperature of 13-23 ° C and an oxidation time of 15-20 minutes and a luminescent dye with a surface concentration deposited on the resulting oxide layer 0.1-0.5 monolayer, characterized in that, in order to increase measurement accuracy and expand the measurement range by increasing the degree of luminescence quenching by reducing the effect of temperature on the luminescence intensity and reducing background luminescence, before applying the luminescent dye, the oxide film is treated with a solution of amphoteric hydroxide of a heavy metal with a concentration of 10–20 g / l at a temperature of 15–25 ° C for 1–2 h, after which the oxide layer is rinsed with distilled water, and is used as a dye zuyut platinum metal complexes with organic ligands. f 500 Io / Ip W ten 0 0.2 0.4 0.6 Fig.Z 21 600 700 L, IM FIG. 2 0, d 1.0 Р, atm 0.02 0, OS FIG. 5 0.10 P, atm