JP2868845B2 - Amine sensor - Google Patents

Description

The present 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 smell is known as putrid smell of fresh fish. It is common to use trimethylamine as a representative of the amine compound, and it has been proposed to measure the concentration of trimethylamine generated from fresh fish to determine the freshness of fish and shellfish.
However, the sensitivity of the semiconductor gas sensor to amine compounds is low, and it is difficult to apply the sensor to freshness determination of fish and shellfish. Note JP 60-202,345 discloses a gas sensor with the addition of RuO ₂ 2-10 wt% WO _3. This gas sensor is a gas sensor for carbon monoxide, and 2-10% by weight of RuO ₂
The addition corresponds to an addition of 3.5 to 17 atomic% in terms of the atomic ratio of Ru / W. The inventors performed an additional test of this gas sensor, but the sensor did not show amine sensitivity (see FIGS. 3 and 4).

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

[Configuration of the Invention] In the present invention, the WO ₃ in atomic ratio of Ru / W 0.01~0.6 (Ru / W
atm.%) of RuO ₂ is added. WO ₃ is a metal oxide semiconductor having a high amine sensitivity, and the addition of RuO ₂ in an atomic ratio of Ru / W of 0.01 atomic% or more significantly improves the amine sensitivity,
High amine sensitivity can be obtained up to about 0.6% atom. Ru /
The unit expressing the atomic ratio of W in units of% is simply referred to as% or atomic%. The formula weight of WO ₃ is 231.9, and the formula weight of RuO ₂ is 133.
1 and 1 atomic% of RuO ₂ in Ru / W is 0.57RuO ₂ / WO ₃ % by weight
Is equivalent to On the other hand, when RuO ₂ exceeds 1 atomic%, amine sensitivity is lost.

Even if Pt, Pd, Ir, or Au is used instead of RuO ₂ , no sensitizing effect on the amine is obtained.

[Example] Preparation of sensor Ammonium tungstate was pyrolyzed at 500 ° C, pulverized, and impregnated with an aqueous ruthenium chloride (tetravalent) solution.
The ruthenium chloride was pyrolyzed at ℃. WO ₃ impregnated with ruthenium chloride was applied to the surface of an alumina pipe and sintered at 700 ° C. for 5 minutes to obtain a sensor. Change to ruthenium chloride,
Aqueous solutions of chloroplatinic acid and Pd, aqueous solutions of iridium chloride and chloroauric acid were added to obtain sensors of comparative examples. A similar sensor was prepared using WO ₃ as a starting material instead of ammonium tungstate. Further change to WO ₃ ,
Using a stannic acid sol that was thermally decomposed at 500 ° C., it was similarly impregnated with an aqueous solution of ruthenium chloride and sintered after thermal decomposition to form a sensor.

Adjusting method and the method of adding the RuO ₂ of WO _3, or the structure of the sensor is optional. A binder such as alumina sol or silica gel may be added to the sensor during sintering. In addition, those using ammonium tungstate as a starting material,
Since the sensor using WO ₃ as a starting material showed the same result, a sensor using ammonium tungstate as a starting material will be described below.

FIG. 8 shows the structure of the sensor. 2 added RuO ₂
WO ₃ thick film, 4 is an alumina pipe, 6, 8 is a pair of electrodes, 10
Is a heater.

Characteristics FIG. 1 shows the results at 280 ° C. for a sensor obtained by adding 0.1 atomic% of RuO ₂ to WO ₃ . The result is 100 ppm ethanol
The resistance value _R0 is shown as a reference. Sensitivity to hydrogen is low, showing almost the same sensitivity to trimethylamine (TMA), NH ₃ and ethanol.

FIG. 2 shows the results at 350 ° C. for the same sensor. Even at this temperature, the sensitivity to TMA and NH ₃ is high.

FIG. 3 shows the effect of the RuO ₂ concentration on the RuO ₂ / WO ₃ sensor. The measurement temperature was 280 ° C., and the vertical axis represents the sensitivity to 100 ppm of each gas. Amine sensitivity increased markedly with the addition of 0.01 atomic% of Ru, with an optimum value near 0.1 atomic% and 0.5 atomic%.
However, high amine sensitivity can be obtained. However, the addition of 1 atomic% or more results in loss of amine sensitivity.

FIG. 4 shows Ru at 350 ° C. for the RuO ₂ / WO ₃ based sensor.
The effect of O ₂ concentration is shown. As in Fig. 3, 0.01 to 0.5 atomic%
And high amine sensitivity can be obtained.

FIG. 5 shows the effect of adding 0.1 atomic% of each to WO ₃ (measuring temperature 280 ° C.). Additives other than RuO ₂ are less sensitive to amines. FIG. 6 shows the result at the measurement temperature of 350 ° C. Except for RuO ₂ , amine sensitivity is low.

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

Table 1 shows a comparison result between the SnO ₂ / RuO ₂ sensor and the WO ₃ / RuO ₂ sensor. The measurement temperature is 280 ° C.

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

[Brief description of the drawings]

FIG. 1 is a characteristic diagram of the embodiment (Ru / W atomic ratio 0.1%, measurement temperature 280 ° C.). FIG. 2 is a characteristic diagram of the embodiment (Ru / W atomic ratio 0.1%, measurement temperature 350 ° C.). ), FIG. 3 is a characteristic diagram of the embodiment when the Ru / W ratio is changed (measuring temperature 280 ° C.), and FIG. 4 is a characteristic diagram of the embodiment when the Ru / W ratio is changed (measuring temperature). Fig. 5 is a characteristic diagram showing the effect of the type of additive (measurement temperature)
FIG. 6 is a characteristic diagram (measurement temperature) showing the effect of the type of additive.
FIG. 7 is a characteristic diagram showing the response waveform of the embodiment (measured at 43 ° C).
FIG. 8 is a sectional view of the sensor of the embodiment.

Claims (1)

(57) [Claims] 1. An amine sensor in which RuO ₂ is added to WO ₃ at an atomic ratio of Ru / W of 0.01 to 0.6 atomic%.