CN105092655A - Novel palladium porous silicon sensor for rapid detection of formaldehyde and preparation method thereof - Google Patents
Novel palladium porous silicon sensor for rapid detection of formaldehyde and preparation method thereof Download PDFInfo
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- CN105092655A CN105092655A CN201510180741.7A CN201510180741A CN105092655A CN 105092655 A CN105092655 A CN 105092655A CN 201510180741 A CN201510180741 A CN 201510180741A CN 105092655 A CN105092655 A CN 105092655A
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Abstract
The present invention discloses a novel palladium porous silicon sensor for rapid detection of formaldehyde, a preparation method and a gas sensitivity detection system thereof. The sensor comprises a p-type monocrystalline silicon base substrate, a polished surface of the silicon base substrate is provided with a porous silicon layer, the surface of the porous silicon layer is doped with nano Pd, and the porous silicon surface is provided with positive and negative aluminum electrodes. The present invention overcomes the unfavorable influences of uneven surface and uneven distribution of holes of porous silicon caused by uneven surface current distribution in traditional porous silicon preparation, and uses an iron-passivation hydrothermal corrosion method to prepare a nano-palladium doped porous silicon composite element with a flat surface and columnar arrangement of silicon as a gas-sensitive material. The sensor can operate at room temperature, has high selectivity, fast response and recovery characteristics to formaldehyde, and can realize immediate on-site detection. The sensor has the advantages of compact volume, simple structure, easy operation and low price, and is expected to be further promoted and applied in the field of formaldehyde sensor in the future.
Description
Technical field
The present invention relates to the preparation of porous silicon, porous silicon surface Technique of Nano Pd adulterates, and it can be used as the detection of sensor PARA FORMALDEHYDE PRILLS(91,95) gas.
Background technology
In recent years, along with the raising day by day of people's living standard, the requirement of people to IAQ (indoor air quality) is also more and more higher.The formaldehyde contained in indoor hardware fitting is one of indoor important pollutant, and its toxicity is comparatively large, and having potential carcinogenicity, is a kind of protoplasm poisonous substance.Formaldehyde (HCHO) is classified as potential danger carcinogen and important environmental contaminants by the World Health Organization (WHO).But at present about the main method of formaldehyde examination is as spectrophotometric method and chromatography, there is required instrument volume comparatively large, costly, detection time is long, cannot realize the shortcomings such as real-time online detection.Thus, develop cheap, easy to operate, the on-the-spot instant methylene oxide detecting instrument detected can be realized and have important practical significance.
Porous silicon has larger specific surface area and higher chemical mobility of the surface, is easy to adsorb various gas molecule, effectively can realize the detection to certain gas.The Cleaning Principle of porous silicon gas sensor changes into basis mainly with its physical characteristics in gas with various, as the change of electric property, gas molecule enters in the microcellular structure of porous silicon, the gas molecule of adsorption changes free carrier concentration in porous layer, or causes porous silicon electric conductivity and specific inductive capacity to change due to concentrated gas in hole; The change of optical property, as photoluminescence (PL), the fluorescence that chemisorption causes is broken to go out or interference.But the electrochemical method that the conventional many employings of porous silicon gas sensor are traditional is prepared from, there is the shortcoming such as porous silicon surface out-of-flatness, empty skewness because distribution of current inequality causes in the porous silicon prepared by this method; In addition, simple porous silicon gas sensor is also unstable, and is subject to the interference of other gas, and selectivity is poor.
Adopt porous silicon prepared by iron passivation hydrothermal etching, its surface topography is more smooth, pore size consistent, be evenly distributed, avoid the shortcomings such as the porous silicon surface out-of-flatness caused because distribution of current is uneven in electrochemical method.In addition, by method of chemical immersion after porous silicon surface doping metals palladium, susceptibility and the selectivity of its PARA FORMALDEHYDE PRILLS(91,95) gas can be significantly improved.This Novel Palladium-porous silicon formaldehyde compound sensor have easy to detect, cheap, sensitivity is higher, and can realize the advantages such as real-time online detection.
Summary of the invention
The object that the present invention is novel, be to overcome the adverse effect that porous silicon surface out-of-flatness that the preparation of conventional porous silicon causes because of Surface current distribution inequality, hole distribution are uneven, the surfacing adopting iron passivation hydrothermal etching to prepare, tool silicon columnar arrangement and the porous silicon composite component of dopen Nano palladium are as gas sensitive, can at room temperature work, PARA FORMALDEHYDE PRILLS(91,95) has high selectivity, quick response, recovery characteristics, can realize on-the-spot instant detection; This sensor bulk is small and exquisite, structure simple, easy to operate, cheap, is expected to get further promotion and application in formaldehyde sensor field future.
The present invention is novel to be achieved by following technical solution.
For a preparation method for Novel Palladium-Porous Silicon Sensors that formaldehyde detects fast, there are following steps:
(1) silicon chip pre-service
By resistivity be 0.009 Ω cm p-type monocrystalline silicon first after through the mixed liquid dipping (until silicon chip surface no longer produces bubble) of 98% concentrated sulphuric acid and 30% hydrogen peroxide (volume ratio is 3: 1), deionized water rinsing, 20% hydrofluoric acid solution soak that about 20s, in a large number deionized water rinse repeatedly, absolute ethyl alcohol ultrasonic cleaning about 25min, to remove the oxide layer of silicon chip surface, organic impurities and greasy dirt;
(2) porous silicon preparation
Adopt iron passivation hydrothermal etching to prepare porous silicon, water heating kettle is 100mL, and activity coefficient is 0.7, and corrosive liquid is made up of the mixed liquor of 12mol/L hydrofluorite and 0.03mol/L ferric nitrate, and etching time is 55min, and corrosion temperature is 135 DEG C;
(3) modification of porous silicon surface Metal Palladium
By the porous silicon prepared by step (2), be fixed on negative electrode, be placed in the electrolytic cell of palladium bichloride and hydrofluorite mixed electrolytic solution, reaction 30s, take out with dry after a large amount of deionized water rinsing;
(4) assembling of palladium-porous silicon gas sensor
By the palladium-porous silicon prepared by step (3), by Vacuum Coating method at its surperficial two ends AM aluminum metallization film as electrode, then on electrode, be adhered metallic copper wire with conductive silver glue, wire two ends are connected with testing circuit, make palladium-porous silicon gas sensor.
The silicon chip substrate of described step (1) is of a size of 1.5cm × 1.5cm.
The average pore size of the porous silicon layer of described step (2) is 130nm, and thickness is 3 μm, and porosity is 78%.
Palladium bichloride in described step (3) and hydrofluoric acid concentration are respectively 5mmol/L and 0.5mol/L.
The present invention has following beneficial effect:
1. adopt iron passivation hydrothermal etching legal system for porous silicon herein, the porous silicon surface gone out than traditional electrochemical production is more smooth, and hole size is consistent, and be evenly distributed, surface holes becomes silicon columnar arrangement, is more conducive to gas absorption;
2. adopt immersion deposition method at porous silicon surface modified metal palladium, make palladium-porous silicon compound sensor, effectively improve porous silicon stability, and the sensitivity that detects of PARA FORMALDEHYDE PRILLS(91,95) and selectivity;
3. formaldehyde examination system adopts simple circuit, carries out electrical signal detection, make detection more convenient operation by digital multimeter, achieves the on-the-spot instant possibility detected of formaldehyde.
Accompanying drawing explanation
Fig. 1 is the structural representation of the novel a kind of Novel Palladium-Porous Silicon Sensors element detected fast for formaldehyde of the present invention;
Reference numeral in Fig. 1 is:
1---silicon chip substrate 2---porous silicon layer
3---aluminium Electrode Negative 4---aluminium electrode anode
Fig. 2 is the scanning electron microscope figure of the novel a kind of Novel Palladium Porous Silicon Sensors element detected fast for formaldehyde of the present invention;
Fig. 3 is the corresponding relation of the novel a kind of Novel Palladium Porous Silicon Sensors element affinity that detects fast for formaldehyde of the present invention and ammonia, ethanol, formaldehyde gas concentration;
Fig. 4 is the corresponding relation of the resistance of the novel a kind of Novel Palladium Porous Silicon Sensors element detected fast for formaldehyde of the present invention and ammonia, ethanol, formaldehyde gas concentration;
Fig. 5 is the present invention's novel a kind of response/release time of Novel Palladium Porous Silicon Sensors element of detecting fast for formaldehyde and the corresponding relation of formaldehyde gas concentration;
Fig. 6 is the novel a kind of Novel Palladium Porous Silicon Sensors element PARA FORMALDEHYDE PRILLS(91,95) gas stabilization test curve figure detected fast for formaldehyde of the present invention.
Fig. 7 is the typical curve of the novel a kind of Novel Palladium Porous Silicon Sensors element PARA FORMALDEHYDE PRILLS(91,95) gas detect detected fast for formaldehyde of the present invention.
Embodiment
Be described in further detail the present invention is novel below in conjunction with specific embodiment.Reagent involved in embodiment all adopts commercially available chemically pure reagent.
Fig. 1 is the structural representation of the novel a kind of Novel Palladium-Porous Silicon Sensors element detected fast for formaldehyde of the present invention, and in figure, silicon chip substrate (1) is p-type monocrystalline silicon piece, is of a size of 1.5cm × 1.5cm; Be provided with porous silicon layer (2) above silicon chip substrate, the average pore size of this porous silicon layer is 130nm, and thickness is 3 μm, and porosity is 78%; Aluminium Electrode Negative (3) and aluminium electrode anode (4) is provided with above porous silicon layer.
The concrete preparation method of the novel a kind of Novel Palladium-Porous Silicon Sensors element detected fast for formaldehyde of the present invention, step is as follows:
(1) silicon chip pre-service
By resistivity be 0.009 Ω cm p-type monocrystalline silicon first after through the mixed liquid dipping (until silicon chip surface no longer produces bubble) of 98% concentrated sulphuric acid and 30% hydrogen peroxide (volume ratio is 3: 1), deionized water rinsing, 20% hydrofluoric acid solution soak that about 20s, in a large number deionized water rinse repeatedly, absolute ethyl alcohol ultrasonic cleaning about 25min, to remove the oxide layer of silicon chip surface, organic impurities and greasy dirt;
(2) porous silicon preparation
Adopt iron passivation hydrothermal etching to prepare porous silicon, water heating kettle is 100mL, and activity coefficient is 0.7, and corrosive liquid is made up of the mixed liquor of 12mol/L hydrofluorite and 0.03mol/L ferric nitrate, and etching time is 55min, and corrosion temperature is 135 DEG C;
(3) modification of porous silicon surface Metal Palladium
By the porous silicon prepared by step (2), be fixed on negative electrode, be placed in the electrolytic cell of 5mmol/L palladium bichloride and 0.5mol/L hydrofluorite mixed electrolytic solution, reaction 30s, take out with dry after a large amount of deionized water rinsing;
(4) assembling of palladium-porous silicon gas sensor
By the palladium-porous silicon prepared by step (3), by Vacuum Coating method at its surperficial two ends AM aluminum metallization film as electrode, then on electrode, be adhered metallic copper wire with conductive silver glue, wire two ends are connected with testing circuit, make palladium-porous silicon gas sensor.
The concrete result of use of the novel a kind of Novel Palladium-Porous Silicon Sensors element detected fast for formaldehyde of the present invention is as follows:
Novel sensor element of the present invention at room temperature has the response of obvious gas to low concentration formaldehyde, to ammonia, ethanol, formaldehyde gas sensitivity response curve as shown in Figure 3.Increase with gas concentration, element sensitivity increases gradually, when gas concentration is 1mg/m
3time, the sensitivity of gas sensor to ethanol, ammonia, formaldehyde is respectively 1.05,1.03,1.17; When gas concentration is 5mg/m
3time, the sensitivity of gas sensor to ethanol, ammonia, formaldehyde is respectively 1.24,1.15,5.23.As seen from Figure 4, increase with gas concentration, gas sensor resistance reduces gradually, when gas concentration is 0.5mg/m
3time, the electrical response value of gas sensor to ethanol, ammonia, formaldehyde is respectively 6.5k Ω, 6.6k Ω, 5.8k Ω; When gas concentration is 5mg/m
3time, the electrical response value of element to ethanol, ammonia, formaldehyde is respectively 5.5k Ω, 5.9k Ω, 1.3k Ω.Significantly, gas sensor sensitivity and electrical resistance formaldehyde gas concentration increase, and variation range is comparatively large, responds sensitive, and with the increase of ammonia and ethanol gas concentration, component resistance and change of sensitivity faint, without obviously responding.
As seen from Figure 5, Novel air photosensitive elements PARA FORMALDEHYDE PRILLS(91,95) gas of the present invention has response/recovery characteristics fast, and response stabilization time is 150s, and release time is 270s.
Under the same conditions, standby to brand-new and after preserving January Novel Palladium of the present invention-porous silicon gas sensor carries out formaldehyde gas concentration determination, and result as shown in Figure 6.As seen from Figure 6, except component resistance increases slightly, the variation tendency of twice test result is identical, and the length of description time does not affect the response pattern of gas sensor, describes having good stability of Novel Palladium of the present invention-porous silicon formaldehyde compound sensor element thus.
For the accuracy of research novel sensor of the present invention PARA FORMALDEHYDE PRILLS(91,95) gas detect in atmospheric environment (actual environment), we have done the control experiment of formaldehyde sample.Concentration is set and is respectively 2mg/m
3, 4mg/m
3, 6mg/m
3three formaldehyde gas samples, calculate and configure the formaldehyde sample liquid of three groups of different volumes corresponding to three variable concentrations gas samples, then three groups of institutes are joined sample solution and add (control air chamber temperature constant) in three sealed gas chambers respectively, it is to be measured that built-in small-sized fans can accelerate its volatilization.According to Fig. 7 formaldehyde examination typical curve, record result as table 1.Result show, survey sample coefficient of variation < 5%, illustrate that Novel Palladium of the present invention-porous silicon formaldehyde compound sensor measured value accuracy is higher, can be used for the detection of formaldehyde in actual environment.
Table 1 formaldehyde pattern detection
Claims (6)
1. the Novel Palladium Porous Silicon Sensors detected fast for formaldehyde and preparation method, it is characterized in that, comprising: p-type monocrystalline silicon substrate substrate, silicon chip substrate polished surface is provided with porous silicon layer, porous silicon layer surface doping Metal Palladium nano particle, porous silicon layer surface is provided with positive and negative aluminium electrode.
2. a kind of Novel Palladium Porous Silicon Sensors of detecting fast for formaldehyde according to claim 1 and preparation method, it is characterized in that, described porous silicon adopts iron passivation hydrothermal etching to be prepared from, water heating kettle is 100mL, activity coefficient is 0.7, corrosive liquid is made up of the mixed liquor of 12mol/L hydrofluorite and 0.03mol/L ferric nitrate, and etching time is 55min, and corrosion temperature is 135 DEG C;
3. a kind of Novel Palladium Porous Silicon Sensors of detecting fast for formaldehyde according to claim 1 and preparation method, it is characterized in that, described silicon chip substrate is of a size of 1.5cm × 1.5cm, and the average pore size of described porous silicon layer is 130nm, thickness is 3 μm, and porosity is 78%.
4. a kind of Novel Palladium Porous Silicon Sensors of detecting fast for formaldehyde according to claim 1 and preparation method, it is characterized in that, the modification of described porous silicon surface Metal Palladium nano particle, adopt method of chemical immersion, porous silicon is fixed on negative electrode, be placed in the electrolytic cell of 5mmol/L palladium bichloride and 0.5mol/L hydrofluorite mixed electrolytic solution, reaction 30s, dry after using a large amount of deionized water rinsing afterwards.
5. a kind of Novel Palladium Porous Silicon Sensors of detecting fast for formaldehyde according to claim 1 and preparation method, it is characterized in that, described Metal Palladium nano particle PARA FORMALDEHYDE PRILLS(91,95) gas molecule has stronger suction-operated, the combination of iron passivation hydro-thermal corrosion technology and the nano-particle doped technology of Metal Palladium, when described sensor is placed in the mixed gas containing formaldehyde, it can high selectivity in conjunction with formaldehyde gas molecule, and produce electric signal, its intensity is relevant to concentration of formaldehyde, detect its electric signal by multimeter, and then analyze its air-sensitive performance.This Novel Palladium-Porous Silicon Sensors PARA FORMALDEHYDE PRILLS(91,95) gas response is sensitive, and has good selectivity.
6. a kind of Novel Palladium Porous Silicon Sensors of detecting fast for formaldehyde according to claim 1 and preparation method, it is characterized in that, the sensing range of described a kind of Novel Palladium-Porous Silicon Sensors PARA FORMALDEHYDE PRILLS(91,95) concentration detected fast for formaldehyde is at 0.1-6.0mg/m
3between, detect and be limited to 0.1mg/m
3, detection time is 3min.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101144789A (en) * | 2007-09-24 | 2008-03-19 | 武汉工程大学 | Formaldehyde air-sensitive material and its preparation method and preparation method for formaldehyde air-sensitive device |
| US20140264642A1 (en) * | 2012-09-27 | 2014-09-18 | Sensirion Ag | Gas sensor |
| CN104502422A (en) * | 2014-12-19 | 2015-04-08 | 清华大学 | Method for preparing porous silicon nanowire NO2 gas sensor |
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2015
- 2015-04-15 CN CN201510180741.7A patent/CN105092655A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101144789A (en) * | 2007-09-24 | 2008-03-19 | 武汉工程大学 | Formaldehyde air-sensitive material and its preparation method and preparation method for formaldehyde air-sensitive device |
| US20140264642A1 (en) * | 2012-09-27 | 2014-09-18 | Sensirion Ag | Gas sensor |
| CN104502422A (en) * | 2014-12-19 | 2015-04-08 | 清华大学 | Method for preparing porous silicon nanowire NO2 gas sensor |
Non-Patent Citations (5)
| Title |
|---|
| V. POLISHCHUK 等: "A Study of hydrogen detection with palladium modified porous silicon", 《ANALYTICA CHIMICA ACTA》 * |
| 李新建等: "铁钝化多孔硅形成过程中的形貌演化和腐蚀机理", 《科学技术与工程》 * |
| 杨亚娣: "金属颗粒膜/多孔硅气体传感器的研究", 《中国优秀硕士学位论文全文数据库 信息科技辑》 * |
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