TW558630B - Ammonia sensor and method for producing the same - Google Patents

Abstract

The present invention provides an ammonia sensor and a method for producing the same. The ammonia sensor comprises a piezoelectric substrate; a surface acoustic wave sensing component; and a coating layer of L-glutamic acid hydrochloride. The surface acoustic wave sensing component and the coating layer of L-glutamic acid hydrochloride are located on the piezoelectric substrate.

Description

558630

Field of the Invention In particular, the invention relates to: an ammonia gas sensing device and a method for manufacturing the same; m pieces of ^ 70 pieces of sonic ammonia gas sacrifice with zuoweiqian hydrochloride as a coating and a method for manufacturing the same. BACKGROUND OF THE INVENTION-= ϊ Optical sensing for magnetic sensing using a streamlined guide from ancient China, during which a long period of time has passed; the most important is the application of sensors to biochemical sensing Development

; Mainly because of the environment around which we live, the P factor, examples & dangerous gases in the air, as well as miscellaneous materials and jeopardy treasures are difficult to treat the human body ^ ^ + medically harmful to the human body Healthy virus or other ^ 2. In the fields of medicine, environmental science, and biochemistry, there are still great potentials for development of precise and accurate biochemical sensors.

A sensing interface is often coated on the sensing element to react with the sensing object. Commonly used coating interfaces include metal oxide coatings, metal coatings, and polymer coatings. These coatings have good sensitivity and selectivity for gas, but because metal coatings have a relatively small dynamic range for gas measurement, their use is limited. For metal oxide coatings and polymer coatings, polymer coatings have advantages such as higher sensitivity, lower sensing limits, and ability to operate at room temperature relative to metal oxides. It is widely used in sensing elements. Ammonia is a toxic gas. It ’s used in industrial or biochemical medicine.

0777-8647TWF (N); chiumeow.ptd

558630

Hazardous. Ammonia gas is irritating to residues, which will corrode the pipelines in the factory, which will affect work safety and product quality. In addition, ammonia gas has a very high solubility, so it is often adsorbed on the skin, mucous membranes, and eye conjunctiva. Stimulation and inflammation; ammonia can damage the cilia of the respiratory tract and the epithelial tissues of the mucosa, making it easier for pathogens to invade, resulting in decreased resistance. In addition, ammonia can be detected to detect the presence of certain diseases, for example, some patients with liver or kidney disease contain a trace amount of ammonia in the exhaled gas. For the detection of ammonia gas, it is known that the L-glutamic acid hydrochloride is used as a coating, and a bulk acoustic wave sensing element (BAW) made of 9 MHz AT quartz ° BAW The sensitivity of the ammonia gas sensing element is 74 Hz / ppm, at least 10 ppm ammonia can be detected. However, its perturbation mechanism only considers the mass load, and does not include other effects such as elastic effects and acoustic and electrical effects. Therefore, the sensing characteristics of levonate amine hydrochloride-ammonia are not completely analyzed. In addition, this b A W element is only measured statically and does not control environmental effects. And another known person who uses a surface acoustic wave sensing element to detect ammonia is a surface acoustic wave sensing element made by penza et al. Using Langmuir-Blodgett (LB) poly D Billo (Polypyrrole) as a coating (SAW), which can only detect 20 ppm (M. Penza, E. Milella, VI Anisimkin. IEEE Trans · Ultrason ·, Ferroelect ·, Freq · Contr ·, 45, pp. 1125-1131, 1 998), its LB polypyrrole response degradation rate is about 0.025 ppm per day (M. Penza, E. Milella, VI Anisimkin. Sensors and Actuators B, 47, pp. 218-224, 1998) o Therefore, sonic ammonia There is still much room for development of sensing elements.

0777-8647TWF (N); ch i umeow.ptd Page 5 558630 5. Description of the invention (3) Summary of the invention ^ ^ The purpose of the invention is to provide an ammonia gas sensing device with L-glutamate as a coating The device improves the shortcomings of the known BAW ammonia gas sensing element, and has high sensitivity, good resilience, good stability, small size, low cost, and a wide dynamic range that can be measured, and can be used in a variety of different environments. Advantages of operation. The ammonia gas sensing device of the present invention includes a piezoelectric substrate, a surface acoustic wave sensing element, and a L-glutamic acid hydrochloride coating. The surface acoustic wave sensing element and L-glutamine The hydrochloride coating is located on the piezoelectric substrate. The above surface acoustic wave sensing element includes a surface acoustic wave device and a shear-horizontal surf ace acoustic wave device (SH-SAW); when a surface acoustic wave sensing element is used, it may include A delay line system, a port resonator system, a dual port resonator system, and a reflective delay line system; the above systems include interdigital transducers (IDTs) and reflective thumbs (gratings). Another object of the present invention is to provide a method for manufacturing an ammonia gas sensing device. The manufacturing method is to provide a substrate, a surface acoustic wave sensing element is formed on the substrate, and a L-glutamate solution is deposited on the substrate. To form a L-glutamate coating, thereby obtaining an ammonia gas sensing device. The ammonia gas sensing device of the present invention uses an acoustic wave sensing element, so the volume is small, and it has the advantages of high sensitivity and good stability. And because the manufacturing method of the present invention uses the photolithography technology and the 1 ift-off technology to form the surface acoustic wave sensing element, the cost can be reduced.

0777-8647TWF (N); ch i umeow.p t d page 6 558630 5. Description of the invention (4) It is good for mass production. In addition, the L-glutamate coating used in the present invention greatly reduces the sensitivity of gas sensing. Detailed description of the invention 1 · Evolution of the acoustic wave sensing element The ammonia gas sensing device of the present invention uses a surface acoustic wave sensing element. In 1965, two scholars, White and Voltmer, produced interdigital transducers (IDTs) on piezoelectric substrates to generate surface acoustic waves. This wave is also called Rayleigh wave [R · M · White and F. W.

Voltmer, Appl. Phys. Lett., 17, 314, 1965.]. In 1979, Wohlt jen and Dessy published the first surface acoustic wave sensor. This surface acoustic wave element can operate at higher frequencies than BAW elements, so it has higher sensitivity [H. Wohlt jen and R.

Dessy, Anal · Chem ·, 51, 1458, 1979; Η · Wohltjen and R. Dessy, Anal. Chem ·, 51, 1465, 1979] ° In 1995, Nakahat a and Higaki proposed a diamond multilayer structure (Zn0 / diamond / Si02 ) Phase speed can be increased to 〇〇５０m / s [h. Nakahata, K. Higaki, S. Fujii, and A. Hachigo, IEEE Ultrasonics. Symp. Proc., 36 1, 1 995], this structure Reducing the difficulty of manufacturing surface acoustic wave devices at high frequencies [by Guo Peijing, Production and measurement of piezoelectric thin-film systems and surface acoustic wave devices, 1989 of the Republic of China]. 2. Basic principles of sound wave sensing elements 2. 1 Basic theory of sound waves

0777-8647TWF (N); ch i umeow.ptd Page 7 558630 V. Description of the invention (5) 2 · 1.1 Types of acoustic waves The formation of surface acoustic waves is mainly due to a semi-infinite isotropic (isotropic ) On an elastic substrate, which is excited by an interdigital transducer, the so-called Ray 1 ei gh wave; most of this elastic wave is concentrated on the surface of the substrate, and the energy is concentrated relative to the substrate The depth of the surface is greater than one wavelength (λ) of the sound wave and is almost non-existent. These wave particles move along an elliptical trajectory on the surface. When the phase velocity of this acoustic wave is less than the phase velocity of the bulk acoustic wave, since there is no phase matching between the surface acoustic wave and the bulk acoustic wave, there is no problem of scattering loss on the upper surface of the substrate in [B · A. Auld, Acoustic Fields and Waves in Solids, vol. 2, Wiley, New York, 1973.]. In addition, when the substrate is made of anisotropic material, more complicated wave patterns are generated, for example, shear-horizontal (SH). Each kind of wave has its own advantages and disadvantages. According to the different characteristics considered (for example: polarization, attenuation, scattering, coupling with other waves, etc.), usually only one wave is suitable for certain conditions. [Ulrich Wolff, Franz Ludwing Dickert, Gerhard K. Fischerauer, Wolfgang Greibl, and Clemes CW Ruppel, IEEE Sensors Journal, 1, 1, 2001] 〇 2 · 1 · 2 The excitation of surface acoustic waves is the technology of studying surface acoustic waves, The most important thing is the piezoelectric effect of the piezoelectric substrate. Piezoelectricity is a kind of mechanical energy and electricity

I1H 0777-8647TWF (N); chiumeow.ptd page 8 558630 5. Description of the invention (6) Features that can be converted to each other. In 1880, the brothers Jaucques and Pierre Curie discovered that if a mechanical press was applied to tourmaline, the material would deform and a charge would be generated on the surface. This phenomenon of electrical polarization caused by mechanical deformation is called the piezoelectric effect. In addition to tourmaline, piezoelectricity can be found in crystals such as quartz (91181 ^ 2) and Rhodes salt (1 ^ 0 (:} 16116 3311 :). [Ikeda Takuro, Chen Shichun Translator 'Basic Piezoelectric Materials Science : Fundamentals of

Piezoelectric Materials Science, printed by Fuhan Press. ]. In addition, the main structure of a piezoelectric material is a crystalline structure with a noncentrosymmetry, that is, its positive charge center and negative charge center are not in the same position, so that the positive and negative charges cannot show neutralization characteristics, so Generate an electric dipole.

An important key to exciting surface acoustic waves is the design of transducers (IDTs). The main role of IDTs is to use tigers to excite and receive surface acoustic waves [R · M · White and F · W · Voltmer, Appl · Phys · Let ·, 17,314, 1 65]. In general, the most basic IDT design is to periodically arrange a pair of metal electrodes in parallel on a piezoelectric substrate, and then apply an RF voltage to the crossed electrodes to generate an electric field. This electric field will cause mechanical deformation due to piezoelectricity and generate a surface elastic wave that will be emitted from both ends of the IDT. Due to the relationship between positive and inverse piezoelectric effects, this surface acoustic wave will be on the other finger electrode Converted to output voltage. Because of the mechanical properties between each electrode on the surface substrate,

558630 V. Description of the invention (7) The discontinuity of structure and electric field causes I DT to reflect a small amount of energy, so IDT can also be used as a sound wave reflector. Nowadays, due to the development of light engraving technology and lift-off technology, the IDT process can be accurately fabricated on piezoelectric substrates. So far, the length between electrodes is limited to 0.8 // m, the speed of sound waves is between 300,000 and 4000 m / s, and the maximum achievable operating frequency is about 2.5 GHz [Ulrich Wolff, Franz Ludwing Dickert, Gerhard K. Fischerauer, Wolfgang Greibl, and Clemes C, W. Ruppel, IEEE Sensors Journal, 1, 1, 2 00 1]. 2 · 2 Surface Acoustic Wave Sensing Element Surface Acoustic Wave Element can operate at higher frequencies than BAW sensing element, so it can produce greater frequency changes, that is, have higher sensitivity [D · S · Ballantine, R · M White, S.J. Martin, A.J. Ricco, E.T.Zellers, G.C. Frye, and W. Wohltjen, Acoustic Wave Sensors, Academic Press, London, 1 99 7]. This acoustic wave element often uses a dual device architecture, that is, a surface acoustic wave element without a sensing coating is used as a reference element to compare with a surface acoustic wave element with a sensing coating to reduce temperature or other factors. Environmental interference effects. The manufacture of surface acoustic wave sensing components can cause problems that do not occur with conventional hermetically sealed signal transmission components. For example, the welding work is very important because the surface acoustic wave element must not have other irrelevant pressure on it; or during the sensing process, the viscosity of the welding material will cause the gas to be removed, which is a factor

558630 V. Description of the invention (8) --- It will cause distortion of accuracy during sensing. In addition, in a corrosive environment, the addition of a passivation layer can prevent aluminum electrodes from being corroded, or a metal substance that does not cause chemical reactions can be used as the electrode, such as gold or platinum. In addition, in order to reduce the occurrence of water cross-sensitivity, it is necessary to hydrophobize the surface of the hydrophilic acoustic substrate. In the field of surface acoustic wave sensing elements, the more commonly used and widely used systems are generally divided into delay line systems and resonator systems. The delay line system is mainly determined by the distance from the center point of the IDTs on both sides of the substrate to the center point, as shown in the figure. The architecture of the resonator is composed of one or more IDTs and is surrounded by a reflecting grid (gratingS), so the energy of the sound wave can be limited to the resonance cavity ', which can have less loss, as shown in Figures 1 and 1C. As for Figure 1D, it is a reflective delay line. 2 · 3 Acoustic Wave Sensing Mechanism The first consideration of the sensing mechanism is the physical reaction phenomenon that occurs between the acoustic wave and the object to be measured. Although different acoustic wave elements will be different However, there are several main physical reactions that are the same. There are three main reaction mechanisms between the acoustic wave element and the gas: '(1) Mass loading (ML) effect · If there is a mass load On the surface of the acoustic wave sensing element, the oscillation frequency of the acoustic wave element will be caused to drift. Increasing or decreasing the mass load will usually cause a disturbance of the wave velocity, but it will not cause the attenuation effect of the acoustic energy.

0777-8647TWF (N); chiumeow.ptd page 11 558630 5. Description of the invention (9) The mass load mechanism can be found in all acoustic wave modes. Make J effect? The reason for the change 'is mainly the mass change caused by the reaction between the analyte and the coating film during the process of adsorbing (or absorbing) the analyte. (2) Acoustoelectric effect (AE) · Acoustoelectric effect is mainly when the acoustic wave propagates along the surface of the piezoelectric substrate, if it passes a conductive thin film coating, due to the piezoelectric conversion characteristics of the piezoelectric substrate 'Phenomena caused by the movement of charge carriers in their electric fields [Α · J. Ricco, SJ Martin, and T. Ε. Zipperian, Sen. Actuators Β, 319, 1 985 ·]. This effect will cause the attenuation of the sound wave energy or reduce the speed of the sound wave. (3) Elastic effects: When the thickness of the film is compared with the wavelength, the energy loss caused by the film can no longer be ignored, or when the characteristics of the film are viscoelastic, complex elastic effects will occur. This effect changes the energy and speed of sound waves. In addition, due to changes in the characteristics of the film, for example, when the volume of the film changes due to the adsorption of gas, this effect becomes more significant and important [S. J · Martin, GC Frye, and SD Senturia, Anal · Chem ·, 66, 2 20 1, 1, 994 ·]. For example, a humidity-sensing element using a polymer as a sensing coating has different effects on the mass loading effect and the elastic effect under different relative humidity [N · M · Tashtoush, J. D · N. Cheeke, and N. Eddy, Sen. Actuators B, 49, 218, 1998.]. In high humidity

0777-8647TWF (N); chiumeow.ptd Page 12 558630 5. In the context of the invention (ίο), the elastic effect is much larger than the mass load effect. Synthesizing the above three acoustic wave sensing mechanisms: the mass loading effect, the electro-acoustic effect, and the perturbation mechanism caused by the elastic effect, will cause the phase velocity change of the acoustic wave [A. J. Ricco and S. J. Martin, Thin Solid Films, 206, 94 , 1991 ·], as shown below: Αυ / υ0 = -cmfQAps + cef0hA [{^ M / 〇〇 \ λ + μ) ί (λ + 2μ)]-(^ 1/2 > [^ 51 / (σ51 + ^ 51)] (1) where C m and ~ are the mass sensitivity coefficient and elasticity sensitivity coefficient, respectively, i 0s is the sensing coating density, and # is the shear coefficient and volume coefficient of the sensing coating , K1 is the piezoelectric coupling coefficient of the substrate, is the sheet conductivity of the sensing coating, and G is the static capacitance value per unit length of the substrate. The first term to the right of the equal sign is the mass load and the second term This is the elastic effect, and the third term is the acousto-electric effect. From equation (1), it can be seen that if the mass load, elastic parameters and conductivity are changed, the phase velocity of the surface acoustic wave will be affected.

I I

0777-8647TWF (N); ch i umeow.ptd page 13 1 4 Performance guidelines In the application of sensors, many factors affecting performance must be considered, such as: sensitivity, selectivity, resilience, response time, dynamic range , Stability, reliability, and environmental (such as temperature) effects. Depending on some reaction factors, a more appropriate substrate or sonic mode can be selected. In addition, in choosing the coating 558630, the invention description (11) consideration of the layer or how to operate the sensor under ideal conditions, also # 二: in each ; Among the factors, selectivity and resilience are the most common: detailed, ,, and field time, mainly because they are unique to biochemical sensing elements [DS Ballantine, Jr., RM White, SJ Martin ET Zellers, and H. Wohltjen, ISBN 〇-l2 ^ 〇7746 (alk. Paper)] ° 2.4.1 Selectivity (seiectivity) Selectivity refers to the ability of a sensing element to distinguish between analytes and interferents. Ability: The ability to select is mainly related to coating Layer matter has a lot to do with it. : If you only use simple polymers, organic and inorganic thin films, and so on, you will not be able to achieve this. Selective determination: 疋 Sensing coatings will produce high sensitivity to the analytes to be detected and low sensitivity to other interferences. For example, a swollen film coated with butanone has a large frequency response and a small frequency response to isooctane. That is to say, the selectivity of FpoL membrane to methyl ethyl ketone is better; the other film coating piB has the opposite situation, and the selectivity of PIB to isooctane is better. Sensitivity and selectivity of the sensing coating are inherent to its chemical properties, so it can be: a thin film that matches the chemical properties of the precipitates to improve the choice of acoustic components. ^ When selecting analytes, it is necessary to avoid the development of several situations. Alas, the influence of humidity will cause great interference during sensing, because the water field exists in the environment [Ε · τ · Zellers and M. Xin, Er Sui 0777-8647TWF (N); ch i umeow.ptd No. 14 Page 558630 V. Description of the Invention (12)

Chem ·, 68, 240 9, 1 9 96 ·]; In addition, to avoid the simultaneous detection of analytes and interferences by the sensing element, the individual reactions should be measured and compared. 'Otherwise between the analyte and the interferences Internal molecules may react and cause changes in chemical properties, resulting in inaccurate reactions [E · T ·

Zellers, S. A. Batterman, M. Han,, and S. J.

Patrash, Anal Chem., 67, 1092, 1995]. 2 · 4.2 Reversibility Resilience refers to the ability of a sensing element to restore its original characteristics or to return to its original baseline after the analyte is removed. It should be noted that the reaction between the coating and the analyte must also take into account the reversion; the resilience of this reaction is mainly related to the strength of the two actions during the reaction, and the kinetic energy and thermal energy of the reaction. Sometimes the recovery is not too fast at room temperature, or even does not return. There are three main reasons: (1) If the energy to remove the analyte is very large, increase the temperature to help recovery, but there are Sometimes the sensing element or coating will be damaged by high temperature; (2) — new substances will be formed during some reactions, which will completely change the chemical properties of the coating; (3) the reactivity between the analyte and the coating material is too high High, causing permanent changes in the physical structure of the coating. For example, breaking a carbon-carbon bond in a polymeric coating can cause the polymer to form a powerful oxidant. 2 · 4 · 3 sensitivity

558630 V. Description of the invention (13) The ratio of the signal change to the analyte concentration change. Sensitivity is composed of many sensing factors. For an acoustic wave element, the sensitivity to the analyte is mainly determined by the amount of adsorption (thickness and surface area) of the coating and the strength of the reaction between the analyte and the coating. . 2 · 4 · 4 Dynamic range Dynamic range refers to the concentration interval of the continuous signal change response provided by the sensing element. Linear dynamic range (1 inear dynamic range, LDR) is the interval where the signal change is linearly proportional to the concentration, that is, the range covered from the lowest limit of detection (LOD) to the threshold of the saturation effect. Saturation is related to the chemical limitation of the system or the saturation of electronic circuits. If the concentration of the analyte is lower than Lod, it will be impossible to detect it, that is, it will not be able to distinguish between noise and signal, and when it is higher than the saturation concentration, the signal change will not increase and will maintain a certain value. LOD is the same as the response mechanism of sensitivity, which is related to the kinetic energy of the coating-analyte reaction and the thermal energy. However, Lod is a little different, that is, LOD is related to the noise level of the entire system (noiSeievel). lOd can be defined by the signal / noise ratio (S / N ratio). The signal / noise ratio is the ratio between the signal change in the presence of the analyte and the noise in the absence of the analyte. Usually the relative signal / noise ratio of L0D is 2 or 3. 2 · 4 · 5 Stability, repeatability, reliability, and reproducibility (staM Η〇, repeatability, reliability, an (j reproducibility) The stability of the system is very important, mainly to discuss the short-term stability, long-term

0777-8647TWF (N); ch i umeow.p t d

Η Page 16 558630 V. Description of the invention (14) = Sex, noise and drift. The component responds quickly in a short button time: The main goal of sex is that the-numbering will be inaccurate. The short-term drift is often caused by the environment is too high, and the news such as' temporary changes in temperature, force, and relative humidity, caused by temporary changes. Long-term stability refers to the fact that both of them will form noise, such as coatings, components, and electronic circuits. The aging of the components will now drift and the frequency must be recalibrated. The test will cause the signal to repeat. It means that the same sensor can still get the same two in the phase analyte concentration: the operation ring is the same as the restorative, and must be coated: No. The most reproducible material is, the reaction between 卞 e h ::::: precipitates is highly recoverable or the reaction position is within the dynamic range, so the repeatability is high. Individual * Repetitiveness and repeatability are often confused by others. * Restrictiveness refers to the same-ασ uses the same manufacturing method, and products produced at different times or at different locations have the same performance. That is, a single sensing element can be accurately manufactured and produced in large quantities, and still have the same sensing characteristics. Reliability is the same as repeatability. 2. · 4 · 6 Response time The response time is related to the characteristics of the sensing system, such as the transport system of molecular volume and gas / liquid phase, coating characteristics (thickness), and the energy of the adsorption reaction. The rate of adsorption and desorption determines the response time of the sensing element. For a reactive coating, the reaction rate is related to the surface area of the reactants. Both small particles and porous structures increase the surface area to volume ratio, and can get a large response in a short time.

0777-8647TWF (N); ch i umeow.p t d p. 17 558630

2. · 4 · 7 environmental effect (environment effect) ^, the important environmental effect is the effect of temperature. Temperature has a wide range of sound wave components, for example, it will change the oscillation frequency of sound waves, and less sensitivity. In order to reduce the effect brought by temperature, a piezoelectric substrate with a small or no temperature and retardation coefficient can be selected, such as a quartz substrate. The other method is to use a variety of different metals or oxidation on a thin piezoelectric layer, so that the entire structure has a smaller temperature delay coefficient. In addition, a dual-element architecture can also be used to compensate for signal drift caused by temperature. However, because the effects of temperature on components do not exactly match, temperature drift cannot be fully compensated. Another important environmental effect is the effect of humidity. Humidity will change the characteristics of the coating, which softens the coating and causes the response frequency to drift. Therefore, in the selection of the layer material, try to choose a junction that will not react with water and gas. ‘So’ will not affect the accuracy of the measurement of the sensor. EXAMPLES However, the scope of the present invention is not limited to the scope of the examples. Embodiment 1 Manufacturing of an ammonia gas sensing device An embodiment of the invention provides an ammonia gas sensing device. As shown in FIG. 2, the device includes a piezoelectric substrate 1, a surface acoustic wave sensing element, and a delay line system 2. Contains two sets of finger resonators and one left

558630 V. Description of the invention (16) Rotary surface amine salt coating 3. The piezoelectric substrate is composed of quartz, Rhodes salt, tourmaline, lithium niobate (LiNb03), lithium tantalante (LiTa03), barium titanate (BaTi03), and titanate. It is made of leadzirconate (PZT), zinc oxide, aluminum nitride, aluminum tetraborate (Li2B4 07, LBO) or a combination of the above materials. In addition, the piezoelectric substrate may be a single layer or more than two layers. The ammonia gas sensing device of the present invention uses a surface acoustic wave device, which has the following advantages and is quite suitable for being applied to a sensor: (1) High sensitivity. The operating frequency varies from a few hundred Hz to a few hundred KHz, and the measuring instrument can be accurate to 1Hz. For example, 0%; [% deformation results in a 200MHz resonator frequency change of 200KΗζ; using an instrument with an accuracy of 1Hz, a theoretical 5 × 1 0-9 deformation can be measured. (2) Surface acoustic waves have a high signal / noise ratio (S / N ratio) and do not require expensive digital analog converters.

(3) It has a high-frequency resonance frequency (10 to 3000 MHz), which can be used in a wide range of sensing ranges and is more selective [多元 · Nakahata, K. Higaki, S. Fujii, and A. Hachigo, IEEE

Ultrasonics · Symp · Proc ·, 361, 1995 ·]. (4) The design of 'surface acoustic wave sensor is simpler than BAW sensor' can be manufactured in large quantities at one time using photolithography and left-off technology, so the production cost is less. In the present invention, a L-Glutamic Acid Hydrochloride coating 3 grown on a surface acoustic wave element is used. The infrared spectrum is used to know that this L-Glutamic Acid Hydrochloride is sensitive to ammonia gas. Have a brighter

0777-8647TWF (N); ch i umeow.p t d p.19 558630 V. Description of the invention (17) '' It has obvious adsorption effect, and also has good selectivity for ammonia. • The manufacturing method of the ammonia gas sensing device of the present invention is to provide a substrate j on which a surface acoustic wave delay line system 2 is formed. The system includes a second group of interdigital transducers and a second group of finger transducers. Here, the surface acoustic wave delay line system 2 is formed by lift-off technology, and light engraving technology can also be used, and a left-side amine hydrochloride solution is deposited on the above substrate. The first set of interdigital transducers and the second Between the group of interdigitated transducers, a coating 3 ′ of a levonate amine hydrochloride is formed here. This method is spray coating, and a spin coating method may also be used. The above-mentioned substrate includes the material of the above-mentioned piezoelectric substrate. Here, a substrate of 28 ° YX-LiNb03 is used. The interdigital transducer is composed of aluminum metal, gold, or an alloy of gold. Here, an aluminum metal with a thickness of 1 500 A is used. As shown in Fig. 2, the center frequency of the surface acoustic wave delay line produced is 100 MHz, and the distance between each interdigital transducer is 40. There are 10 pairs of interdigital transducers, that is, 20 interdigitated metals, and the overlap width between the interdigitated metals and the metal is 1 60 0 / zm. The distance from the center point to the center point of the two sets of interdigital transducers is 8400 β m. A solution of L-glutamic acid hydrochloride (L-glutamic acid hydrochloride, Aldrich) in deionized water at 75 ° C was obtained at a concentration of 0.5 mg / m1. Before applying the coating, the surface of the surface acoustic wave delay line 2 was shaken with acetone, and then dried in a drying cabinet at 80 ° C. Thereafter, L-glutamate was deposited on the surface of the surface acoustic wave element by spray coating.

0777-8647TWF (N); ch i umeow.ptd Page 20 558630 V. Description of the invention (18) Ban Jiang The ammonia gas sensing device of the present invention uses a double delay line system to reduce the effect of clothes, as shown in Figure 3. As shown, the delay line system 4 of the test sample and the reference, the system 5 is connected to the electronic oscillation circuit 6 and the electronic oscillation circuit mixer 7 respectively. Connect the two systems and record the surface acoustic wave oscillation signal with a frequency counter 8. The frequency counter 8 is connected to the computer system through the GPIB interface panel, and the measured parameters are analyzed by a network analyzer (Hp8753C). . The two electronic oscillating circuits 6 used can generate RF surface acoustic wave signals. Example 2 Ammonia gas response is detected by an ammonia gas sensing device. The ammonia gas sensing device of the present invention is placed in a temperature-controllable closed container (about 132ml in volume), and a flow controller (mass fiow) is used. contro 1 ler) to control the flow of gas into and out of the container. The flow controller is set to 110 ml / min. The reference gas and carrier gas are dry air. Dry air is used to dilute the ammonia gas and observe the response changes of the ammonia gas sensing device under various ammonia gas concentrations. In addition, this embodiment also observes the effect caused by humidity, and changes the measured humidity from 0 to 90% RH. Different relative humidity is made by mixing different proportions of dry air and humid air in the bubble chamber. A frequency counter is used to record the change in frequency. The noise is calculated by inputting gas for 10 minutes and taking 20 points of frequency data per minute, which is then calculated by the standard deviation of the residuals of the linear least square fit method. Coming [C · Y · Shen, C · P · Huang, and HC Chuo, Sen. Actuators B, 84, 231, 2 002] 〇

0777-8647TWF (N); ch i umeow.ptd Page 21 558630 V. Description of the invention (19) Example 2.1 1 Response of ammonia sensing device at room temperature Figure 4 shows that ammonia sensing device can respond in time The reaction time of the coating 3 of the left-handed amine hydrochloride to ammonia is several seconds, and the figure shows that the cycle of the release and shutdown of the under-ammonia gas has a similar response, which represents this%. The ammonia gas sensing device has good sensitivity, reversibility and 4 i 彳 生 # sensing properties. Noise is 0.02 ppm in the response graph. Fig. 5 shows the relationship between the gas concentration and the response of the gas sensing device of the present invention. At low concentrations of gas, the frequency of the ammonia sensing device will decrease, and at high concentrations of ammonia, the frequency of the ammonia sensing device will increase. This is a & coating that absorbs high concentrations of ammonia, the mass load The effect is greater than the elastic effect, which reduces the frequency of the device, and because L-glutamate is a hard material (stiff mater i al), the elastic effect is more significant when the ammonia concentration is low, even larger than the mass load effect. The frequency increases. As for the acoustoelectric effect, it is not due to the fact that L-glutamate is a non-conductive material. It can be seen from this figure that the dynamic range of L-glutamate is very wide, and the lowest measurable ammonia concentration is 0 · 90ppm, but this result is a limitation of this system and is not a L-glutamate The lowest bottom line at which an acid salt coating can be measured. The slope of the response curve at a gas concentration above 2300 ρρπι is significantly smaller than that of an ammonia concentration below 2300 ppra. This is because the response tends to be saturated at high ammonia concentrations. The slope in the figure is defined as the response sensitivity & the sensitivity of the response is about 5 kHz / ppm at an ammonia concentration below 2300 ppm. It can be seen from this that the surface acoustic wave sensing element with a coating of L-glutamate has a relatively high sensitivity to ammonia gas.

558630 5. Description of the invention (20) Figure 6 shows the reaction situation under very low concentration of ammonia. It is known from the figure that when the ammonia gas concentration is less than 1 ppm, the ammonia gas sensing device of the present invention can easily detect ammonia gas. The measurable range of the ammonia sensor means that the response signal will not be less than twice the noise, which means that the signal / noise ratio will not be less than two. The signal / noise ratio of the ammonia gas sensing device of the present invention when the ammonia gas concentration is 〇09〇1) 1) 111 is 1 2 · 29, which is much greater than 2. Therefore, it can be known that the ammonia gas sensing device of the present invention has no effect on ammonia. The lowest sense measurement of gas should be less than 0.90 ppm. Fig. 7 shows the transient response of the ammonia gas sensing device of the present invention to ammonia gas. The response of the ammonia gas sensing device will decrease as the ammonia gas concentration decreases, so the change in ammonia gas concentration can be monitored online in real time. Fig. 8 shows the reaction of the ammonia gas sensing device of the present invention to carbon monoxide (c0). It is known from the figure that L-glutamate has almost no response to the interference gas such as ⑶, and has the same results for other interference gases, and no response is generated. Therefore, the levulinic acid salt has good selectivity for ammonia. Fig. 9 ^ Figure I shows the long-term stability test of the atmosphere sensing device of the present invention. Results: ′ The ammonia concentration is 3.04%, and the measurement is 34 days. The figure shows that the response has shifted, ‘this can be attributed to the aging of L-glutamate itself’ and its response degradation rate is about 0.01 ppm per day. This degradation rate is extremely high, so the ammonia sensing device of the present invention exhibits fairly good stability. Example 2 · Frequency response of humidity to helmet ef ^ T wind milk sensing device in different phase inversions, θ &. ^ ^, Under humidity environment, detecting the frequency response of surface acoustic wave element to ammonia 0 Gradually describe π ^ ^ ^ How to increase the operating humidity, the component response will increase slightly

0777-8647TWF (N); ch i umeow.p t d p. 23 558630 5. Description of the invention (21) Add. Therefore, the ammonia gas sensing device of the present invention also responds to water molecules. In this way, the effect of relative humidity on the sensitivity of ammonia must also be calculated. Equation (2) represents the relationship between the ammonia gas sensing device's response to different humidity and ammonia: 5 (nh3, h2o) ^ 3) + ^ 2〇) + DS, (NH3) ° (h2〇) (2) Among them, gas book 332〇) In the dry ammonia frequency environment of ammonia, it is produced less, with a humidity of 35 and much lower. 0 Contrast ratio in air The response amount intersects with moisture, the entire phylogenetic effect of the present invention is ~ 50% ring. Therefore, it is the total frequency response of the system. Qiyang 3) is the frequency response of the element gas, and s (H2O) is the element's sensitivity to moisture ′ D. The third term on the right side of the equation shows the interaction relationship, that is, the combined reaction of ammonia and moisture will be additionally affected by the interaction of these two factors. In addition, D will reduce the sense of gas as the relative humidity increases. The test results of the testing device show that in general relative conditions, its D value is 〇11. Compared with known sensing elements, the ammonia gas sensing device of the present invention has better moisture resistance. Conclusion The ammonia gas sensing of the present invention The measurement device uses a coating of L-glutamate, and the results show that the device has good gas sensing characteristics such as reliability, sensitivity, recovery, reproducibility and selectivity for ammonia gas. At room temperature

P.24 558630 Description of the invention (22) Levoglutamate on the layer has a low minimum detection limit for ammonia gas and p-slave master " 1, which is better than known surface acoustic wave sensors (about 10 ~ 20ppm) low, = surface acoustic wave sensors usually require a sensing environment higher than room temperature, and are installed with the following operations: the response; the rate of the stomach 'and the ammonia sensing of the present invention' Stability is still very 'this is also a breakthrough. In addition, the hydrochloride salt has a transient response to the ammonia content measured in the air, and will not have any effect on other interference gases. Finally, humidity also affects the adsorption characteristics of ammonia gas. Operation will be better in the absence of %%. However, the sonic sensor of the present invention is much less fishy. No matter what, the present invention has been disclosed in the preferred embodiment as above, but it does not limit the present invention. Anyone who is familiar with this skill can use it in the scope and range. It can be used as a variety of two = the spirit of the invention. , When the scope of the attached patent application is deemed to be guaranteed

558630 Brief description of the drawings In order to make the present invention more obvious and easy to understand, the above-mentioned and other objects, features, and advantages of the following two can be explained in detail as follows: ... Figures 1A to 1D are Λ diagrams of the delay line system and the surface surface wave components. Figure 1. Port resonator system. Figure 1C is the port resonator system. Figure 1C is. Figure 2. The diagram of the present invention is a reflective delay line system. Fig. 3 is a schematic diagram of the "sensing device" of the present invention. Schematic diagram of detection. The lice gas sensing device performs a double delay line system. Fig. 4 shows the frequency response of the present invention at 0.09%. Fig. 5 The frequency change of the present invention is shown. Fig. 6 shows the frequency response of the present invention at 0 · 90ppm. Fig. 7 shows the state response curve of the present invention. Fig. 8 shows the frequency response of the present invention. Fig. 9 The results of the present invention are shown.

The ammonia gas sensing device detects different ammonia gas concentrations when the ammonia gas concentration is

The ammonia gas sensing device is in the ammonia concentration. The ammonia gas sensing device has a temporary ammonia concentration. The ammonia gas sensing device is set to 1% —the stability test of the carbon monoxide-based ammonia gas sensing device.

558630 Brief description of symbols: 1 ~ Piezo substrate; 2 ~ Surface sensing element; 3 ~ L-glutamate coating; 4 ~ Delay line system for testing samples; 5 ~ Reference delay line system; 6 ~ electronic oscillation circuit; 7 ~ oscillation signal mixer; 8 ~ frequency analyzer.

0777-8647TWF (N); ch i umeow.p t d p.27

Claims (1)

558630 6. Scope of patent application 1. An ammonia gas sensing device, comprising: a piezoelectric substrate; a surface acoustic wave sensing element; and a coating of a left-handed surface amine hydrochloride; wherein the surface acoustic wave sensing element A coating with a left-handed amine salt is located on the piezoelectric substrate. 2. The ammonia gas sensing device according to item 1 of the scope of the patent application, wherein the piezoelectric substrate is a single layer. 3. The ammonia gas sensing device according to item 1 of the scope of patent application, wherein the piezoelectric substrate is a double layer. 4. The ammonia gas sensing device according to item 2 or 3 of the scope of the patent application, wherein the piezoelectric substrate is made of quartz, lithium niobate (LiNb03), lithium tantalante (LiTa03), four It is composed of boric acid (Li2B4 07, LBO), barium titanate (BaTi03), lead zirconate titanate (leadzirconate (PZT)), oxide, aluminum nitride or a combination of the above materials. 5. The ammonia gas sensing device according to item 1 of the scope of the patent application, wherein the surface acoustic wave sensing element includes a delay line system, a port resonator system, a dual-band resonator system, or a reflective delay line system. 6. The ammonia gas sensing device according to item 5 of the scope of patent application, wherein the delay line system is a double delay line system. 7. The ammonia gas sensing device according to item 6 of the patent application scope, wherein the system includes two sets of interdigital transducers. 8. The ammonia gas sensing device as described in item 7 of the scope of the patent application, wherein the interdigitated pedigree is composed of Ming, gold or other gold alloy. 0777-8647TWF (N); chiumeow.ptd Page 28 558630 6. Application for patent scope 9 · The ammonia gas sensing device as described in item 7 of the patent application scope, which further includes an electronic oscillator circuit connected to the finger fork Transducer. I 0 · The ammonia gas sensing device according to item 1 of the scope of patent application, wherein the coating of the L-glutamate is deposited on the piezoelectric substrate from a / L-glutamate solution. II. The ammonia gas sensing device as described in the item No. 0 of the scope of the patent application, wherein the L-tyrosine hydrochloride solution is deposited by spray coating or spin coating. 1 2 · The ammonia gas sensing device described in item 9 of the scope of patent application, further comprising a frequency counter connected to the electronic shock circuit to receive a signal, wherein the signal is received by the electronic shock circuit produce. 1 3. A method for manufacturing an ammonia gas sensing device, comprising the following steps: providing a substrate; forming a surface acoustic wave sensing element on the substrate; and depositing a coating of levonamic acid on the substrate Floor. 1 4. The method for manufacturing an ammonia gas sensing device according to item 13 of the scope of patent application, wherein the substrate is a single layer. 15 · The method for manufacturing an ammonia gas sensing device as described in item 13 of the scope of patent application, wherein the substrate is a double layer. 16 · The method for manufacturing an ammonia gas sensing device according to item 14 or 15 of the scope of the patent application, wherein the substrate is made of quartz, lithium niobate (L i Nb03), or lithium group (lithium tantal ante (LiTa03), lithium tetraborate (Li2B4 07, LBO), barium titanate (BaTi03), leadzirconate (PZT), 0777-8647TWF (N); ch i umeow.p t d page 29 558630 _____ _______ VI. Patent application S-* ---- Composed of zinc oxide, aluminum nitride or a combination of the above materials. ^ 17 The method of manufacturing the ammonia gas sensing device as described in Item 13 of the scope of the patent application, wherein the surface acoustic wave sensing element is formed by light carving technology and separation technology. — ^ 18 · Method for manufacturing an ammonia gas sensing device as described in Item 13 of the scope of patent application ', wherein the surface acoustic wave sensing element includes a delay line system, a port resonator system, a dual port resonator system or a reflection Sexual delay line system. [19] The method for manufacturing an ammonia gas sensing device as described in item 18 of the scope of patent application ', wherein the delay line system is a double delay line system. 20. The method for manufacturing an ammonia gas sensing device according to item 19 of the scope of the patent application, wherein the system includes two sets of interdigital transducers. 2 1 · The method for manufacturing an ammonia gas sensing device as described in item 20 of the scope of the patent application, wherein the interdigital transducer is composed of aluminum, gold or other gold alloy. 22. The method for manufacturing ammonia sensing sensor according to item 3 of the patent application, wherein the coating on which the L-glutamate is deposited is sprayed from a solution of L-glutamate Formed by coating or spin coating.