JPH0450756A - Amine sensor - Google Patents

Abstract

PURPOSE:To obtain the sensor which is highly sensitive with an amine compd., such as trimethyl amine, and to allow the utilization of the sensor to the decision of the freshness of fishes and shellfishes by adding RuO2 at 0.01 to 0.6atomic% by the atomic ratio of Ru/w to WO3. CONSTITUTION:The RuO2 is added at 0.01 to 0.6 (Ru/Watom.%) by the atomic ratio of Ru/W to the WO3 to form a thick film 2. The prepn. is executed by thermally decomposing ammonium tungstate at 500 deg.C and impregnating an aq. ruthenium chloride (quadrivalent) soln. therein after grinding and thermally decomposing ruthenium chloride at 500 deg.C. The WO3 impregnated with the rutheni um chloride is then applied on the surface of an aluminum pipe 4 and is sintered for 5 minutes at 700 deg.C to form the sensor. The method for preparing the WO3, the method for adding the RuO2 and the structure of the sensor are arbitrary in this case. The WO3 is a metal oxide semiconductor having a high amine sensitivity and if >=0.01atomic% RuO2 is added thereto, the amine sensitivity is greatly improved and the high amine sensitivity is obtd. up to about 0.6atomic % and, therefore, this sensor is utilized as the high-sensitivity sensor for deciding the freshness.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention 1] This invention relates to a sensor for amine compounds such as ammonia, trimethylamine, and aniline.

[Prior Art] Amine compounds such as ammonia, trimethylamine, and aniline are one of the typical malodorous substances, and the odor thereof is known as the odor of putrid fresh fish.

Trimethylamine is generally used as a representative amine compound, and it has been proposed to determine the freshness of seafood by measuring the concentration of trimethylamine generated from fresh fish. However, the sensitivity of semiconductor gas sensors to amine compounds is low, making it difficult to apply them to determining the freshness of seafood.
A gas sensor is disclosed in which 2 to 10% by weight of RuO2 is added to WO3. This gas sensor is a gas sensor for carbon monoxide, and contains 2 to 10% by weight of Rub.
When converted to an atomic ratio of u/W, this corresponds to addition of 3.5 to 17 atomic %. The inventors performed additional tests on this gas sensor, but the sensor did not show amine sensitivity (Figures 3 and 4).
(see figure).

[Problem of the Invention] An object of the present invention is to provide a semiconductor gas sensor that is highly sensitive to amine compounds.

[Structure of the Invention] In this invention, the WOl has an atomic ratio of Ru/W of 0°01 to
0.6 (Ru/W at m, %) of RuO'2 is added. WO8 is a metal oxide semiconductor with high amine sensitivity, and when RuO2 is added to it in an Ru/W atomic ratio of 0.01 atomic % or more, the amine sensitivity is significantly improved, and 0.
．． High amine sensitivity can be obtained up to about 6% atoms. Below R
The unit expressing the u/W atomic ratio in % is simply called % or atomic %. In addition, the fire cover of WO, is 231.9, Ru
A 5t fire lid is 133.1, and 1 atomic % RuO2 in Ru/W corresponds to 0.57 Ru02/WO, weight %. On the other hand, when RuO2 is added in excess of IW%, amine sensitivity is lost.

Even if Pt, Pcl, Ir, or Au is used instead of Rub, no sensitizing effect to amines can be obtained.

[Example] Preparation of sensor Ammonium tungstate was thermally decomposed at 500°C, crushed and then impregnated with a ruthenium chloride (tetravalent) aqueous solution.
Ruthenium chloride was thermally decomposed at 0°C. Apply WO impregnated with ruthenium chloride to the surface of the alumina pipe, and
The sensor was sintered at 00°C for 5 minutes. Instead of ruthenium chloride, aqueous solutions of chloroplatinic acid, Pct aqua regia, iridium chloride, and chloroauric acid were added to prepare a comparative sensor.

Also changed to ammonium tungstate and used WO.

A similar sensor was prepared using the starting base material. Further, instead of using WO3, a sol of stannic acid was thermally decomposed at 500° C., impregnated with an aqueous solution of ruthenium chloride in the same manner, and sintered after thermal decomposition to form a sensor.

The method of adjusting WO3, the method of adding RuO2, and the structure of the sensor are arbitrary. Further, a binder such as alumina sol or silica sol may be added to the sensor during sintering.

Note that both the sensor using ammonium tungstate as a starting material and the sensor using WO as a starting material showed equivalent results, so the sensor using ammonium tungstate as a starting material will be described below.

FIG. 8 shows the structure of the sensor. 2 is a thick film of WOs doped with RuO2, 4 is an alumina pipe, 6°8 is a pair of electrodes, and 10 is a heater.

Figure 1 shows the results at 280°C for a sensor in which WO and 0.1% Rub were added. The results are shown based on the resistance value R0 in ethanol 10Opprn.

Sensitivity to hydrogen is low, and trimethylamine (TMA
), NHs, and ethanol.

Figure 2 shows the results for the same sensor at 350°C. Even at this temperature, the sensitivity to TMA and NH is high.

FIG. 3 shows the influence of the RuOz concentration on the RuOx/WOs-based sensor. The measurement temperature was 280° C., and the vertical axis indicates the sensitivity to each 1100 pp gas. The amine sensitivity increases significantly with the addition of Ru of 0 and O1 urine atoms, with an optimum value around 0.1 atomic %, and high amine sensitivity can be obtained even at 0.5 * atomic %. However, if 1 atomic % or more is added, amine sensitivity is lost.

FIG. 4 shows the influence of Rub and concentration at 350° C. for the RuOt/WOs system sensor. As in FIG. 3, high amine sensitivity can be obtained at o, oi to 0.5 atom %.

FIG. 5 shows the effect of each addition of 0.1 atomic % to WO3 (measurement temperature: 280° C.). Additives other than RuOs have low sensitivity to amines. FIG. 6 shows the results at a measurement temperature of 350°C. Amine sensitivity is low except for RuOx.

FIG. 7 shows the response characteristics to TMA at 430°C. The vertical axis indicates the sensor resistance Rs.

Table 1 shows the comparison results between the SnO,/RuO2 sensor and the WO3/Ru0z sensor. The measurement temperature is 280°C.

Table 1 SnO□ series 0.1 atomic% Rub.

1.0 atomic% Ru O2 WO3 system 0.1 atomic% Ru01 35 90 401.
0*child%Ru5t 1.5 2 3*
Sensitivity was measured using 1100pp of each gas.

[Effects of the Invention] According to the present invention, a gas sensor that is highly sensitive to amine compounds such as trimethylamine can be obtained, and the sensor can be used for determining the freshness of seafood, etc.

1.4

[Brief explanation of drawings]

The m1 diagram is a characteristic diagram of the example (Ru/W atomic ratio 0.1%).
, measurement temperature 280°C), Figure 2 is a characteristic diagram of the example (Ru/W atomic ratio 0.1%).
, measurement temperature: 350℃), Figure 3 is a characteristic diagram of the example when the Ru/W ratio is changed (measurement temperature: 280℃), $4r! lJ is the characteristic diagram of the example when changing the Ru/W ratio (measurement temperature 350 ° C), Figure 5 is the characteristic diagram showing the effect of the type of additive (measurement temperature 280 ° C), Figure 6 is , a characteristic diagram showing the effect of the type of additive (w constant temperature 350°C), and Figure 7 a characteristic diagram showing the response waveform of the example (measured temperature 4
30° C.), FIG. 8 is a cross-sectional view of the sensor of the example. Fig. Gas Cone, (pprn) 100 1α Gas Conc, (pl:XTI) Fig. Ru/W (atm, '10) Fig. on u t d r u Additive (0,1 atm, '10) Figure Ru/W (atmolo) Figure Additive (1Ωatm, '10)

Claims (1)

[Claims] (1) RuO_2 in WO_3 at the atomic ratio of Ru/W,
An amine sensor containing 0.01 to 0.6 at%.