CN105929005A - Hybrid potential low-ppm acetone sensor based on YSZ and MNb2O6 sensitive electrodes, preparation method and application - Google Patents

Abstract

The invention provides a mixed-potential low-ppm acetone sensor based on YSZ and a MNb2O6 (wherein M is one selected from a group consisting of Cd, Co, Zn, Mn and Ni) sensitive electrode and a preparation method. The mixed-potential low-ppm acetone sensor is mainly used for detection of diabetes. The sensor is successively composed of an Al2O3 ceramic plate with a Pt heating electrode, an YSZ substrate, a Pt reference electrode and the MNb2O6 sensitive electrode, wherein the reference electrode and the sensitive electrode are discrete and are symmetrically arranged on two ends of the upper surface of the YSZ substrate, the lower surface of the YSZ substrate is bonded with the Al2O3 ceramic plate equipped with the Pt heating electrode. According to the invention, the YSZ is used as an ionic conducting layer, and the MNb2O6 composite oxide material with high electrochemical catalytic activity is used as the sensitive electrode for construction of five sensing devices separately; and a device with higher sensitivity is obtained through comparison of acetone response values.

Description

Hybrid potential type low ppm grade acetone sensor based on YSZ and MNb2O6 sensitive electrodes, Preparation method and its application

technical field

The invention belongs to the technical field of gas sensors, in particular to a hybrid potential type low-ppm grade acetone sensor based on YSZ and MNb ₂ O ₆ (M: Cd, Co, Zn, Mn or Ni) sensitive electrodes, a preparation method and its application in diabetes application in detection.

Background technique

Diabetes is a common endocrine and metabolic disease. With the improvement of national living standards, the number of diabetic patients in my country is increasing year by year, becoming the country with the largest number of diabetic patients in the world. Clinical medicine shows that acetone can be produced in diabetics, and the concentration of acetone in the breath of patients is significantly higher than that of normal people. The concentration of acetone in the breath of normal people is 0.3-0.9ppm, while that of diabetic patients exceeds 1.8ppm, which is 2-6 ppm higher. times. Therefore, acetone has been used as a breath marker for non-invasive early diagnosis of specific diabetes. Through accurate detection of acetone concentration in exhaled breath, non-invasive diagnosis can be carried out. If the miniaturization and low price of the detection instrument can be realized, it can be used for home diagnosis and condition monitoring of diabetic patients. Gas sensors have the characteristics of small size, low price, portability, high sensitivity and fast response, and can realize rapid real-time monitoring of acetone, so they have received more and more attention.

Currently, hybrid solid-state electrochemical gas sensors based on stabilized zirconia (YSZ) and metal oxide sensitive electrodes have been extensively developed and designed for in situ monitoring of gases. According to the mixed-type sensitive mechanism, the sensitive signal of the sensor is generated at the three-phase interface of the sensitive electrode/test gas/solid electrolyte through electrochemical reaction, and the sensitivity performance of the sensor is mainly determined by the electrochemical catalytic activity of the sensitive electrode material to the test gas. Therefore, it is very important to develop and find a suitable sensitive electrode material. In order to improve the sensitive characteristics of such sensors, a lot of research has been done on the sensitive electrode materials of sensors at home and abroad. For example, the YSZ-based mixed potential type acetone sensor made by our research group with Zn ₃ V ₂ O ₈ as the sensitive electrode material can achieve the lower detection limit of 1ppm acetone, and its mixed potential value is -2.5mV (Fangmeng Liu, YehuiGuan, Ruize Sun ,Xishuang Liang,Peng Sun,Fengmin Liu,and Geyu Lu,Mixed potential type acetone sensor using stabilized zirconia and M ₃ V ₂ O ₈ (M:Zn,Co and Ni)sensing electrode,Sensors and Actuators B:Chemical 221(2015 )673-680). Although this acetone sensor has good sensitive performance, it cannot detect low ppm acetone, so it is still urgent to continue to develop an acetone sensor for diabetes detection.

Contents of the invention

The object of the present invention is to provide a hybrid potential type low ppm level acetone sensor based on YSZ and MNb ₂ O ₆ (M: Cd, Co, Zn, Mn or Ni) sensitive electrodes, its preparation method and its application in diabetes detection . In order to improve the performance of sensor sensitivity, minimum detection limit, etc., the practical application of this sensor in diabetes detection will be promoted. In addition to high sensitivity, the sensor obtained by the invention also has lower detection limit, good selectivity, moisture resistance and stability.

The acetone sensor involved in the present invention is a new type of acetone sensor based on solid electrolyte YSZ and high electrochemical catalytic performance MNb ₂ O ₆ (M: Cd, Co, Zn, Mn or Ni) composite oxide materials as sensitive electrodes. YSZ (ZrO ₂ (8% Y ₂ O ₃ )) as the ion-conducting layer.

The YSZ-based hybrid potential type acetone sensor of the present invention, as shown in Figure ₁ , consists of an _Al2O3 ceramic plate with a Pt heating electrode, a YSZ substrate, a Pt reference electrode and a sensitive electrode; the reference electrode and the sensitive electrode Both ends of the upper surface of the YSZ substrate are separately and symmetrically prepared, and the lower surface of the YSZ substrate is bonded with an Al ₂ O ₃ ceramic plate with a Pt heating electrode; the sensitive electrode material is MNb ₂ O ₆ (M:Cd, Co, Zn, Mn or Ni), prepared by the following method:

Weigh Nb ₂ O ₅ , dissolve in 15-20mL of hydrofluoric acid, stir at 60-90°C for 2-4 hours; add ammonia water dropwise to the above solution, adjust the pH of the reaction system to 8- 10. Aging for 12 to 14 hours, filtered and washed to neutrality to obtain a white precipitate; dissolve the above white precipitate in citric acid solution, continue to stir at 60-80°C for 1-2 hours, then add NH ₄ NO ₃ and M(NO) ₃ ·nH ₂ O (M: Cd, Co, Zn, Mn or Ni, n=4~6) continue to stir until it becomes gel; Drying for 12 to 24 hours to obtain dry gel, and finally sintering at 800 to 1200°C for 2 to 4 hours to obtain MNb ₂ O ₆ sensitive electrode materials; where M(NO) ₃ ·nH ₂ O, Nb ₂ O ₅ and The molar ratio of NH ₄ NO ₃ is 1:1:12-14, the molar ratio of citric acid to Nb ₂ O ₅ is 2-5:1, and the mass concentration of ammonia water is 25-28%.

The preparation steps of the acetone sensor of the present invention are as follows:

(1) Making a Pt reference electrode: Use Pt paste on one end of the upper surface of the YSZ substrate to make a 15-20 μm thick Pt reference electrode, and at the same time fold a Pt wire in half and stick it to the middle of the reference electrode as an electrode lead, and then connect the YSZ The substrate is baked at 90-120°C for 1-2 hours, and then the YSZ substrate is sintered at 1000-1200°C for 1-2 hours to remove terpineol in the platinum paste, and finally lower to room temperature;

(2) Make MNb ₂ O ₆ (M: Cd, Co, Zn, Mn or Ni) sensitive electrode: adjust MNb ₂ O ₆ (M: Cd, Co, Zn, Mn or Ni) sensitive electrode material with deionized water form a slurry with a mass concentration of 2-20%; use this slurry to prepare a 20-30 μm thick sensitive electrode on the other end of the upper surface of the YSZ substrate that is symmetrical to the Pt reference electrode, and also fold a platinum wire in half and stick it on the sensitive electrode. The electrode is used as the electrode lead;

(3) Sinter the YSZ substrate prepared in the previous step with the reference electrode and the sensitive electrode at 800-1000°C for 1-3 hours; the preferred heating rate during high-temperature sintering is 1-2°C/min;

(4) Preparation of inorganic binder: Measure 2-4 mL of water glass (Na ₂ SiO ₃ ·9H ₂ O), weigh 0.7-1.0 g of Al ₂ O ₃ powder, mix water glass and Al ₂ O ₃ powder Mix and stir evenly to obtain the desired inorganic binder;

(5) Use an inorganic adhesive to bond the lower surface of the YSZ substrate and the _Al2O3 ceramic plate with a Pt heating electrode _;

Among them, the Al ₂ O ₃ ceramic plate with Pt heating electrode is obtained by screen printing Pt on the Al ₂ O ₃ ceramic plate, and the Al ₂ O ₃ ceramic plate with Pt heating electrode is used together as the heating plate of the device;

(6) Welding and packaging the bonded devices, so as to prepare the YSZ-based hybrid potentiometric sensor with MNb ₂ O ₆ as the sensitive electrode of the present invention.

In the present invention, YSZ is used as the ion-conducting layer, and MNb ₂ O ₆ (M: Cd, Co, Zn, Mn or Ni) composite oxide materials with high electrochemical catalytic activity are used as sensitive electrodes to construct sensor devices respectively. The size of the response value can obtain a device with higher sensitivity performance.

Advantages of the present invention:

(1) The sensor uses a typical solid electrolyte - stabilized zirconia (YSZ), which has good thermal and chemical stability and can detect acetone in harsh environments;

(2) The high-performance composite oxide MNb ₂ O ₆ is prepared by the sol-gel method as the sensitive electrode of the sensor. The preparation method is simple, and it is beneficial to mass industrial production.

(3) By comparing the performance of sensors constructed with five new sensitive electrode materials, it was found that the YSZ-based hybrid potential device with CdNb ₂ O ₆ as the sensitive electrode showed the highest response to acetone, and had a low detection limit of 0.2ppm, very With good sensitivity, selectivity, repeatability, moisture resistance and stability, it has potential application prospects in diabetes detection.

Description of drawings

Figure 1: Schematic diagram of the structure of the YSZ-based hybrid potentiometric acetone sensor of the present invention.

Names of each part: MNb ₂ O ₆ (M: Cd, Co, Zn, Mn or Ni) sensitive electrode 1, YSZ substrate 2, Pt reference electrode 3, Pt wire 4, Pt point 5, Al ₂ O ₃ ceramic plate 6, Pt heating electrode 7, inorganic binder 8.

Fig. 2: XRD patterns of five kinds of sensitive electrode materials prepared by the present invention (wherein, the abscissa is the angle, and the ordinate is the intensity).

As shown in Figure 2, it is the XRD patterns of CdNb ₂ O ₆ , CoNb ₂ O ₆ , ZnNb ₂ O ₆ , MnNb ₂ O ₆ and NiNb ₂ O ₆ sensitive electrode materials. The electrode materials are consistent with the standard card JCPDS (File Nos.38-1428, 32-304, 76-1827, 33-899 and 32-694), which are orthorhombic niobite composite materials. It shows that the sensitive electrode materials prepared by us are pure phase CdNb ₂ O ₆ , CoNb ₂ O ₆ , ZnNb ₂ O ₆ , MnNb ₂ O ₆ and NiNb ₂ O ₆ materials.

Figure 3: Response values of sensors constructed with CdNb ₂ O ₆ , CoNb ₂ O ₆ , ZnNb ₂ O ₆ , MnNb ₂ O ₆ and NiNb ₂ O ₆ as sensitive electrode materials to 5ppm acetone at a working temperature of 600°C Comparison chart.

The sensitive performance test of the device adopts a static test method (the specific process is shown in the embodiment), and the response value of the sensor is represented by ΔV=V _acetone -V _air . As shown in Figure 3, it is the response value contrast figure of the device made in embodiment 1～5 to 5ppm acetone, as can be seen from the figure, the device made in embodiment 1～5 is respectively to the response value of 5ppm acetone -25, -9, -14, -6.5, and -0.7mV. It can be seen that the YSZ-based hybrid potentiometric sensor with CdNb ₂ O ₆ as the sensitive electrode material has the highest response value to acetone.

Figure 4: Sensitivity curve of a sensor using CdNb ₂ O ₆ as a sensitive electrode material to acetone (wherein the abscissa is the concentration of acetone, and the ordinate is the potential difference; the working temperature is 600 degrees).

The sensitivity of the sensor is the slope of the linear relationship between the sensor's response value and the corresponding concentration logarithm within a certain measurement concentration range. As shown in Figure 4, it is the sensitivity curve of the sensor using CdNb ₂ O ₆ as the sensitive electrode material to acetone. It can be seen from the figure that the sensitivity of the device to 0.2-10ppm acetone is -19mV/decade, and the lowest can detect 200ppb acetone, the sensor showed good sensitivity and low detection limit.

Figure ₅ : Selectivity of sensors using _CdNb2O6 as a sensitive electrode material (wherein, the abscissa is the potential difference, and the ordinate is the test gas: from top to bottom are 5ppm ethylene, nitrogen dioxide, carbon monoxide, ammonia, Xylene, Acetone, Toluene, Isooctane, Benzene, Formaldehyde. The working temperature is 600 degrees).

As shown in Figure 5, it is the selectivity of the sensor with CdNb ₂ O ₆ as the sensitive electrode material. It can be seen from the figure that the device shows the maximum sensitivity to acetone, and the response of other interfering gases is low. It can be seen that , the device has good selectivity.

Figure 6: Humidity effect of a sensor using CdNb ₂ O ₆ as a sensitive electrode material (the abscissa is the relative humidity, the ordinate is the potential difference, the test gas concentration is 10ppm, and the working temperature is 600 degrees).

As shown in Figure 6, it is the response of the device with CdNb ₂ O ₆ as the sensitive electrode material to 10ppm acetone at different humidity. The change in response is less than 23%, indicating that the sensor has good moisture resistance.

Fig. 7: The stability of the sensor using CdNb ₂ O ₆ as the sensitive electrode material (wherein, the abscissa is time, and the ordinate is the potential difference and the change of the potential difference).

The stability test of the device is to keep the sensor at a working temperature of 600 degrees, and after 30 days of continuous high temperature testing, the response values to 2, 5 and 10ppm acetone are used as standards. During the test, a point is taken every two days to determine Changes are recorded for 30 days. As shown in Figure 7, it is the stability test of the device with CdNb ₂ O ₆ as the sensitive electrode material within 30 days. It can be seen from the figure that the device responds to 2, 5 and 10ppm acetone within 30 days. The amount fluctuation range is less than 9%, which shows that the device has good stability.

detailed description

Example 1:

The CdNb _{2 O 6 material was prepared by the sol-gel method, and the prepared CdNb 2 O 6 was} used as a sensitive electrode material to make a YSZ-based hybrid potentiometric sensor, and the gas sensitivity of the sensor to acetone was tested. The specific process is as follows:

1. Make a Pt reference electrode: use Pt slurry to make a Pt reference electrode with a size of 0.5mm×2mm and a thickness of 15μm on one end of the upper surface of the YSZ substrate with a length and width of 2×2mm and a thickness of 0.2mm, and fold it in half with a Pt wire Then stick the electrode lead wire on the middle position of the reference electrode; then bake the YSZ substrate at 100°C for 1.5 hours, and then sinter the YSZ substrate at 1000°C for 1 hour, so as to eliminate the terpineol in the platinum paste, and finally reduce the to room temperature.

2. Fabrication of CdNb ₂ O ₆ sensitive electrodes: First, CdNb ₂ O ₆ materials were prepared by sol-gel method. Weigh 3 mmol of Nb ₂ O ₅ , dissolve it in 15 mL of hydrofluoric acid, and stir at 80°C for 2 hours; add ammonia water with a mass concentration of 25% to the above solution drop by drop, and adjust the pH to 9, Aging for 14 hours, filtered and washed to neutrality to obtain a white precipitate; dissolve the above white precipitate in 1.891g citric acid solution, continue stirring at 80°C for 2 hours, add 2.880g NH ₄ NO ₃ and 0.9254g Cd (NO) ₃ ·4H ₂ O continued to stir until gelling. The obtained gel-like substance was dried in a vacuum oven at 80°C for 12 hours to obtain a dry gel, and finally sintered in a muffle furnace at 1000°C for 2 hours to obtain 1.135g of CdNb ₂ O ₆ sensitive electrode material.

Take 5mg of CdNb ₂ O ₆ powder and make a slurry with 100mg of deionized water, and coat the CdNb ₂ O ₆ slurry with a layer of 0.5mm×2mm and 20μm thick on the other end of the upper surface of the YSZ substrate symmetrical to the reference electrode. The sensitive electrode is also folded in half with a platinum wire and glued to the sensitive electrode to lead out the electrode lead.

The prepared YSZ substrate with the reference electrode and the sensitive electrode was heated to 800°C at a heating rate of 2°C/min and kept for 2h before cooling down to room temperature.

3. Bonding ceramic plates with heating electrodes. Using an inorganic binder (Al ₂ O ₃ and water glass Na ₂ SiO ₃ 9H ₂ O, prepared at a mass ratio of 5:1), bond the lower surface of the YSZ substrate (the side not coated with electrodes) with the same size The Al ₂ O ₃ ceramic plate (length and width 2×2mm, thickness 0.2mm) of the Pt heating electrode is bonded;

4. Device welding and packaging. Weld the device on the hexagonal socket, put on the protective cover, and complete the hybrid potential type acetone sensor.

Example 2:

NiNb ₂ O ₆ material is used as sensitive electrode material to make acetone sensor. The preparation process of the NiNb ₂ O ₆ sensitive electrode material and the device fabrication process are the same as those in Example 1.

Example 3:

ZnNb ₂ O ₆ material is used as sensitive electrode material to make acetone sensor. The preparation process of the ZnNb ₂ O ₆ sensitive electrode material and the device fabrication process are the same as those in Example 1.

Example 4:

Using MnNb ₂ O ₆ material as the sensitive electrode material, the acetone sensor was fabricated. The preparation process of the MnNb ₂ O ₆ sensitive electrode material and the device fabrication process are the same as in Example 1.

Example 5:

CoNb ₂ O ₆ material is used as sensitive electrode material to make acetone sensor. The preparation process of the CoNb ₂ O ₆ sensitive electrode material and the device fabrication process are the same as those in Example 1.

Connect the sensor to the Rigol signal tester, place the sensor in air, 200ppb, 500ppb, 1ppm, 2ppm, 5ppm, 8ppm, and 10ppm acetone atmospheres for voltage signal testing. The test method of the device adopts the traditional static test method, and the specific process is as follows:

1. Connect the sensor to the Rigol signal tester, and place the device in a test bottle filled with air with a volume of 1L to achieve stability, which is the electromotive force value (Vair) of the device in _air .

2. Quickly transfer the sensor to a test bottle containing acetone gas of the concentration to be measured until the response signal reaches a stability, which is the electromotive force value of the device in _acetone (Vacetone).

3. Transfer the device back to the air bottle until it reaches a stable state, and the device completes a response recovery process. The electromotive force difference (ΔV=V _acetone -V _air ) of the device in acetone and air is the response value of the device to the concentration of acetone. The slope of the linear relationship between the response value of the sensor in a certain measurement concentration range and the corresponding concentration logarithm is the sensitivity of the sensor.

Table 1 lists the response values of YSZ-based hybrid potentiometric sensors with CdNb ₂ O ₆ , CoNb ₂ O ₆ , ZnNb ₂ O ₆ , MnNb ₂ O ₆ and NiNb ₂ O ₆ as sensitive electrodes to 5 ppm acetone. It can be seen from the table that the device with CdNb ₂ O ₆ as the sensitive electrode shows the highest response value, which is -25mV.

Table 2 lists the difference between the electromotive force of the YSZ-based hybrid potentiometric sensor made of CdNb ₂ O ₆ in the atmosphere of different concentrations of acetone and the difference of the electromotive force in air with the acetone concentration. It can be seen from the table that the sensitivity (slope) and detection limit of the device are -19mV/decade and 0.2ppm respectively. It can be seen that the device composed of the new CdNb ₂ O ₆ sensitive electrode material developed by us showed good sensitivity to acetone, and a YSZ-based hybrid potential acetone sensor with high sensitivity and low detection limit was obtained.

Table 1 Comparison of the response values of sensors with CdNb ₂ O ₆ , CoNb ₂ O ₆ , ZnNb ₂ O ₆ , MnNb ₂ O ₆ and NiNb ₂ O ₆ as sensitive electrode materials to 5ppm acetone

Table 2 Variation of ΔV with acetone concentration for devices using CdNb ₂ O ₆ as sensitive electrodes

Claims (5)

1. one kind based on YSZ and MNb₂O₆Sensitive electrode blend together electric potential type low ppm grade acetone sensor, depend on Secondary by the Al adding thermode with Pt₂O₃Ceramic wafer, YSZ substrate, Pt reference electrode and sensitive electrode composition； Reference electrode and sensitive electrode is separate and prepares at the two ends of YSZ upper surface of base plate symmetrically, YSZ base Plate lower surface and the Al adding thermode with Pt₂O₃Ceramic wafer is bonded together, M is Cd, Co, Zn, Mn or Ni；It is characterized in that: sensitive electrode material is MNb₂O₆, and prepare by the following method:

Weigh Nb₂O₅, it is dissolved in the hydrofluoric acid of 15～20mL, at 60～90 DEG C, stirs 2～4 little Time；Dropwise being added drop-wise to by ammoniacal liquor in above solution, the pH value of regulation reaction system is 8～10, is aged 12～14 Hour, through filtering, washing neutrality, obtain white precipitate；Above white precipitate is dissolved in citric acid solution In, at 60～80 DEG C, continue stirring 1～2 hour, add NH₄NO₃With M (NO)₃·nH₂O continues stirring To gel；The gel obtained is dried 12～24 hours under 80～90 DEG C of vacuum conditions and obtains xerogel, After under the conditions of 800～1200 DEG C sinter 2～4 hours, obtain MNb₂O₆Sensitive electrode material；Wherein M(NO)₃·nH₂O、Nb₂O₅And NH₄NO₃Mol ratio be 1:1:12～14, citric acid and Nb₂O₅ Mol ratio be 2～5:1, ammonia concn scope is 25～28%.

2. the one described in claim 1 is based on YSZ and MNb₂O₆Sensitive electrode blend together the low ppm of electric potential type The preparation method of grade acetone sensor, its step is as follows:

(1) Pt reference electrode is made: use Pt slurry to make 15～20 μm in one end of YSZ upper surface of base plate Thick Pt reference electrode, draws being bonded on reference electrode centre position after a Pt silk doubling as electrode simultaneously Line, then toasts YSZ substrate 1～2 hour under the conditions of 90～120 DEG C, then is existed by YSZ substrate Sinter 1～2 hour at 1000～1200 DEG C, get rid of the terpinol in platinum slurry, be finally down to room temperature；

(2) MNb is made₂O₆Sensitive electrode: the MNb that will obtain₂O₆Sensitive electrode material deionized water Furnishing slurry, mass concentration is 2～20%；Another of the YSZ upper surface of base plate that slurry and reference electrode are symmetrical The sensitive electrode of end preparation 20～30 μ m-thick, will be bonded on sensitive electrode after a platinum filament doubling as electricity equally Pole goes between；

(3) the YSZ substrate that above-mentioned preparation has reference electrode and sensitive electrode sinters at 800～1000 DEG C 1～3 hour；

(4) use inorganic bond by YSZ base lower surface and the Al that adds thermode with Pt₂O₃Ceramic wafer It is bonded together；

(5) carry out welding, encapsulating by the device bonded, thus make and obtain based on YSZ and MNb₂O₆ Sensitive electrode blend together electric potential type low ppm grade acetone sensor.

3. as claimed in claim 2 a kind of based on YSZ and MNb₂O₆Sensitive electrode blend together the low ppm of electric potential type The preparation method of grade acetone sensor, it is characterised in that: heating rate during high temperature sintering is 1～2 DEG C/min.

4. as claimed in claim 2 a kind of based on YSZ and MNb₂O₆Sensitive electrode blend together the low ppm of electric potential type The preparation method of grade acetone sensor, it is characterised in that: it is to measure 2～4mL waterglass Na₂SiO₃·9H₂O, And weigh 0.7～1.0g Al₂O₃Powder, by waterglass and Al₂O₃Powder is mixed and stirred for uniformly, prepares institute Need inorganic bond.

5. the one described in claim 1 is based on YSZ and MNb₂O₆Sensitive electrode blend together the low ppm of electric potential type The application in diabetes detect of the grade acetone sensor.