Based on ZnO microballon and CsPbBr3Room temperature NO of quantum dot composite material2Sensor and preparation method thereof
阅读说明：本技术 一种基于ZnO微球与CsPbBr3量子点复合材料的室温NO2传感器及其制备方法 (Based on ZnO microballon and CsPbBr3Room temperature NO of quantum dot composite material2Sensor and preparation method thereof ) 是由 刘凤敏 李月月 卢革宇 孙思琦 于 2020-12-23 设计创作，主要内容包括：一种基于ZnO微球与CsPbBr-3量子点异质结构复合材料的室温NO-2传感器及其制备方法,属于半导体氧化物气体传感器技术领域。由带有金属叉指电极的陶瓷片衬底和涂覆在金属叉指电极上的ZnO微球与CsPbBr-3量子点异质结构复合材料敏感层组成。氧化锌形貌为球体结构,具有较大的比表面积,能提供较多的附着位点,从而与尺寸较小的钙钛矿CsPbBr-3量子点充分接触,从而获得具有较好气敏响应、较快响应恢复速度的气敏元件。此外,CsPbBr-3量子点作为极佳的光电材料,能吸收可见光,从而提供更多的光生载流子。本发明所述传感器采用平面式结构,工艺简单,制作周期短,适于大批量生产。(Based on ZnO microballon and CsPbBr 3 Room temperature NO of quantum dot heterostructure composites 2 A sensor and a preparation method thereof belong to the technical field of semiconductor oxide gas sensors. The method comprises a ceramic chip substrate with a metal interdigital electrode, ZnO microspheres coated on the metal interdigital electrode and CsPbBr 3 The quantum dot heterostructure composite material sensitive layer. The zinc oxide is in a spherical structure, has larger specific surface area and can provide more attachment sites, thereby being matched with perovskite CsPbBr with smaller size 3 The quantum dots are fully contacted, so that the gas sensitive element with better gas sensitive response and faster response recovery speed is obtained. Furthermore, CsPbBr 3 The quantum dots are used as an excellent photoelectric material and can absorb visible light, so that more photon-generated carriers are provided. The sensor of the invention adopts a plane structure, has simple process and short manufacturing period and is suitable for mass production.)
1. Based on ZnO microballon and CsPbBr3Room temperature NO of quantum dot heterostructure composites2The sensor consists of a ceramic wafer substrate with a metal interdigital electrode and a sensitive material coated on the metal interdigital electrode, and is characterized in that: the sensitive material is ZnO microsphere and CsPbBr3A quantum dot heterostructure composite material is prepared by the following steps,
(1) adding Zn (NO)3)2·6H2O, hexamethylenetetramine, C6H5NaO7·2H2O is prepared by mixing the following components in a molar ratio of 4: 4: 1, adding the mixture into deionized water, and stirring the mixture at room temperature until the mixture is dissolved; then carrying out oil bath reaction on the obtained mixture solution for 20-40 minutes under the conditions of sealing and 85-95 ℃, centrifugally washing the precipitate for several times by using deionized water and ethanol, collecting the precipitate, carrying out vacuum drying for 3-5 hours at the temperature of 110-130 ℃, and annealing for 1.5-3 hours at the temperature of 350-450 ℃ to obtain ZnO microspheres;
(2) 0.814g Cs2CO32.50mL oleic acid and 30.0mL octadecene were mixed and degassed under vacuum at 120 ℃ for 1 hour, then the resulting mixture was heated to 150 ℃ under nitrogen and reacted for 3 hours until a clear cesium and oleic acid precursor solution was formed;
(3) 0.376mmol of PbBr2Mixing with 10mL octadecene, vacuum drying at 120 deg.C for 1 hr, and further drying at 120 deg.C under N21.0mL of oleylamine and 1.0mL of oleic acid were injected thereto under an atmosphere; to PbBr2After complete dissolution, the temperature of the reaction system was raised to 180 ℃ and 0.8mL of the precursor solution of cesium and oleic acid obtained in step (2) was rapidly addedInjecting into the reaction solution, cooling the reaction solution to room temperature after 5 seconds of reaction, centrifuging, removing supernatant, dispersing the precipitate in n-hexane to obtain long-term stable colloidal CsPbBr3Quantum dot solution, wherein CsPbBr3The concentration of the quantum dots is 10mmol/L, and the quantum dots are marked as A solution;
(4) adding 48-52 mg of ZnO microspheres obtained in the step (1) into 2.8-3.2 mL of n-hexane, and marking as a solution B; adding different volumes of solution A to solution B, CsPbBr3The mass of the quantum dots is 0.5-1.5% of that of the ZnO microspheres; stirring for 20-40 minutes respectively at room temperature and under the sealing condition of 70-90 ℃; finally, vacuum drying is carried out at 70-90 ℃, so as to obtain ZnO microspheres and CsPbBr3A quantum dot heterostructure composite material.
2. The ZnO microsphere and CsPbBr-based material according to claim 13Room temperature NO of quantum dot heterostructure composites2The preparation method of the sensor comprises the following steps:
sequentially placing a ceramic wafer substrate with a Pd metal interdigital electrode in acetone, ethanol and deionized water, respectively ultrasonically cleaning for 15-30 minutes, and then drying at 50-70 ℃;
② mixing 10-20 mg of ZnO microspheres with CsPbBr3Dissolving the quantum dot heterostructure composite material in 2-5 mL of normal hexane, uniformly mixing, and then dripping and coating the mixture on a ceramic chip substrate with an interdigital electrode by using a liquid transfer gun to ensure that the ZnO microspheres and CsPbBr3The quantum dot heterostructure composite material completely covers the interdigital electrode; finally, heat treatment is carried out for 10-20 minutes at 70-90 ℃ to ensure that normal hexane is completely volatilized, thereby obtaining the ZnO microsphere and CsPbBr3Room temperature NO of quantum dot heterostructure composites2A sensor.
Technical Field
The invention belongs to the technical field of semiconductor oxide gas sensors, and particularly relates to a gas sensor based on ZnO microspheres and CsPbBr3Room temperature NO of quantum dot heterostructure composites2A sensor and a method for manufacturing the same.
Background
NO2As a toxic gas, it is mainly derived from high-temperature combustion such as automobile exhaust, boiler exhaust, and industrial waste. It is a precursor of photochemical smog and one of the causes of acid rain, and poses a number of serious problems to water circulation in the atmosphere and the growth of natural plants. In addition, when NO2After the formed nitrite enters blood, the nitrite is combined with hemoglobin to generate methemoglobin, and hypoxia can be caused to tissues. Thus, NO2Present in severe threat to human daily activities and physical health, for highly sensitive, highly selective NO2The research of the gas sensor has very important significance.
In recent decades, the mos gas sensor based on room temperature operation has the advantages of low energy consumption, long-term stability, safety, reliability, etc., and thus has attracted great interest to researchers. Currently, the operating temperature can be reduced by three common methods of surface morphology modification, addition of noble or transition metals, and photo-assist. In comparison, photo-assist is a promising approach to achieve gas sensors that operate at room temperature and achieve good performance. It can provide the energy needed by electrons to jump from the valence band to the conduction band of a semiconductor, and generate a large number of photon-generated carriers. At present, some materials with narrower band gaps, such as metal halide perovskites, are widely applied in the photoelectronic fields of solar cells, detectors, lasers and the like, but are less applied in the gas sensing field. Therefore, further exploration is needed for its suitable application in this field.
Metal halide perovskites have the advantages of high carrier mobility, long diffusion length, high light absorption coefficient and the like, and are rapidly emerging as photovoltaic materials in many fields in recent years. Although there are also a few experimental results that suggest that perovskite can also be used in gas sensing, it is noted that the use of pure perovskite as the gas sensing layer also exposes a number of drawbacks, such as low response, low repeatability, and lack of long-term stability. In view of this, perovskite can be simply used as a photosensitive material, and the surface of a conventional gas sensitive material such as a metal oxide semiconductor (e.g., ZnO) is modified, so that a sensor with excellent performance can be obtained under room temperature light-assisted conditions.
Disclosure of Invention
The invention aims to provide a ZnO microsphere and CsPbBr-based composite material3Room temperature NO of quantum dot heterostructure composites2A sensor and a method for manufacturing the same.
The invention modifies the surface of the traditional gas sensing metal semiconductor oxide, and realizes the work under the excitation of visible light at room temperature. Namely, the perovskite with narrow band gap as a photosensitive material can absorb visible light and generate a large amount of photon-generated carriers, and the metal oxide as a gas-sensitive material completes the gas-sensitive process.
The invention relates to a ZnO microsphere and CsPbBr-based preparation method3Room temperature NO of quantum dot heterostructure composites2The sensor consists of a ceramic wafer substrate with a metal interdigital electrode and a sensitive material coated on the metal interdigital electrode, and is characterized in that: the sensitive material is ZnO microsphere and CsPbBr3A quantum dot heterostructure composite material is prepared by the following steps,
(1) adding Zn (NO)3)2·6H2O, hexamethylenetetramine, C6H5NaO7·2H2O is prepared by mixing the following components in a molar ratio of 4: 4: 1, adding the mixture into deionized water, and stirring the mixture at room temperature until the mixture is dissolved; then carrying out oil bath reaction on the obtained mixture solution for 20-40 minutes under the conditions of sealing and 85-95 ℃, centrifugally washing the precipitate for several times by using deionized water and ethanol, collecting the precipitate, carrying out vacuum drying for 3-5 hours at the temperature of 110-130 ℃, and annealing for 1.5-3 hours at the temperature of 350-450 ℃ to obtain ZnO microspheres;
(2) 0.814g Cs2CO32.50mL of oleic acid and 30.0mL of octadecene were mixed and degassed under vacuum at 120 ℃ for 1 hour, and the resulting mixture was heated to 150 ℃ under nitrogen and reacted for 3 hours until it was formedForming clear cesium and oleic acid precursor solution;
(3) 0.376mmol of PbBr2Mixing with 10mL octadecene, vacuum drying at 120 deg.C for 1 hr, and further drying at 120 deg.C under N21.0mL of oleylamine and 1.0mL of oleic acid were injected thereto under an atmosphere; to PbBr2After complete dissolution, raising the temperature of the reaction system to 180 ℃, quickly injecting 0.8mL of the precursor solution of cesium and oleic acid obtained in the step (2) into the reaction system, cooling the reaction solution to room temperature after 5 seconds of reaction, centrifuging, removing supernatant, dispersing the precipitate in n-hexane to obtain long-term stable colloidal CsPbBr3Quantum dot solution, wherein CsPbBr3The concentration of the quantum dots is 10mmol/L, and the quantum dots are marked as A solution;
(4) adding 48-52 mg of ZnO microspheres obtained in the step (1) into 2.8-3.2 mL of n-hexane, and marking as a solution B; adding different volumes of solution A to solution B, CsPbBr3The mass of the quantum dots is 0.5-1.5% of that of the ZnO microspheres; stirring for 20-40 minutes respectively at room temperature and under the sealing condition of 70-90 ℃; finally, vacuum drying is carried out at 70-90 ℃, so as to obtain ZnO microspheres and CsPbBr3A quantum dot heterostructure composite material.
The ZnO/CsPbBr-based material3Room temperature NO of hetero-composite structure2A sensor, characterized by: the morphology of the ZnO material is a micron sphere, and CsPbBr3The quantum dots are modified on the surface of the ZnO microsphere, and the diameter of the ZnO microsphere is about 1.5-3 mu m; CsPbBr3The size of the quantum dots is 5-7 nm; CsPbBr3Lead element in the quantum dot is positive valence and is similar to a positive charge potential field, and the surface of the zinc oxide is provided with an oxygen dangling bond, so that the zinc oxide and the zinc oxide are mutually attracted by virtue of electrostatic interaction. And the non-uniformity of the Fermi level between the two leads to the formation of a p-n heterojunction at the interface through charge transfer, thereby further enhancing the interface contact.
The invention relates to a ZnO microsphere and CsPbBr-based preparation method3Room temperature NO of quantum dot heterostructure composites2The preparation method of the sensor comprises the following steps:
placing a ceramic wafer substrate with interdigital electrodes in acetone, ethanol and deionized water in sequence, respectively ultrasonically cleaning for 15-30 minutes, and then drying at 50-70 ℃;
② mixing 10-20 mg of ZnO microspheres with CsPbBr3Dissolving the quantum dot heterostructure composite material in 2-5 mL of normal hexane, uniformly mixing, and then dripping and coating the mixture on a ceramic chip substrate with an interdigital electrode by using a liquid transfer gun to ensure that the ZnO microspheres and CsPbBr3The quantum dot heterostructure composite material completely covers the interdigital electrode; finally, heat treatment is carried out for 10-20 minutes at 70-90 ℃ to ensure that normal hexane is completely volatilized, thereby obtaining the ZnO microsphere and CsPbBr3Room temperature NO of quantum dot heterostructure composites2A sensor.
ZnO microsphere and CsPbBr-based prepared by the invention3Room temperature NO of quantum dot heterostructure composites2The sensor has the following advantages:
1. the ZnO microspheres and CsPbBr can be prepared by simple water bath method and thermal injection method3Two materials of quantum dots are mixed and stirred to obtain the material based on ZnO microspheres and CsPbBr3The quantum dot heterostructure composite material has the advantages of simple synthetic method and low cost;
2. the zinc oxide is in a spherical structure, has larger specific surface area and can provide more attachment sites, thereby being matched with perovskite CsPbBr with smaller size3The quantum dots are fully contacted, so that the gas sensitive element with better gas sensitive response and faster response recovery speed is obtained. Furthermore, CsPbBr3The quantum dots are used as an excellent photoelectric material and can absorb visible light, so that more photon-generated carriers are provided.
3. The sensor of the invention adopts a plane structure, has simple process and short manufacturing period and is suitable for mass production.
Drawings
Fig. 1 (a): is SEM picture under ZnO microsphere high power lens, (a) the inset is SEM picture under ZnO microsphere low power lens; (b) is ZnO-1% CsPbBr3SEM image under high power lens, and the inset in (b) is ZnO-1% CsPbBr3SEM image under low magnification; (c) is CsPbBr3TEM image under quantum dot low power mirror; (d) is CsPbBr3TEM image under quantum dot high magnification mirror;
as shown in figure 1, the diameter of the ZnO microsphere is 1.5-3 micronsRice, CsPbBr3The size of the quantum dots is 5-7 nm, and the magnified view shows that ZnO-1% CsPbBr3The surface appearance of the ZnO microspheres is not obviously changed relative to the ZnO microspheres.
FIG. 2(a) shows ZnO and CsPbBr3Quantum dot, ZnO-0.5% CsPbBr3、ZnO-1％CsPbBr3And ZnO-1.5% CsPbBr3XRD pattern of the composite material within 20-80 degrees and XRD standard card pattern of ZnO material; (b) is CsPbBr3Quantum dot, ZnO-0.5% CsPbBr3、ZnO-1％CsPbBr3And ZnO-1.5% CsPbBr3XRD pattern of the composite material in the range of 20-32 degrees.
As shown in FIG. 2(a), the ZnO microspheres are well matched with the standard card of hexagonal wurtzite ZnO (JCPDS File No 36-1451), and mainly have 11 peaks. Compared with ZnO standard card, ZnO-0.5 percent CsPbBr3、ZnO-1％CsPbBr3And ZnO-1.5% CsPbBr3The main peak position of the XRD diffraction spectrum of the composite material is not obviously changed, which shows that CsPbBr3The quantum dots are not incorporated into the ZnO lattice. CsPbBr was measured in FIG. 2(b)3Quantum dots and ZnO-0.5% CsPbBr3、ZnO-1％CsPbBr3、ZnO-1.5％CsPbBr3The XRD pattern of the composite material has a scanning speed of 5 degrees/minute and an angle range of 20-32 degrees; ZnO-0.5% CsPbBr3、ZnO-1％CsPbBr3、ZnO-1.5％CsPbBr3The composite materials all contain CsPbBr3The peak of the quantum dot corresponds to the (110) plane, and the peak tends to increase as the doping concentration of the quantum dot increases.
FIG. 3: ZnO microsphere, CsPbBr3Quantum dots and ZnO-0.5% CsPbBr3、ZnO-1％CsPbBr3、ZnO-1.5％CsPbBr3Ultraviolet visible spectrum of the composite material, wherein the inset is CsPbBr3Ultraviolet-visible spectrum of quantum dots.
As shown in FIG. 3, the absorbance of ZnO before and after modification was examined. The uv-vis absorption spectrum shows the absorption band edges for the four materials. As can be seen, the ZnO microspheres have obvious absorption band edges at 380nm, the composite material has absorption at 400-530 nm, and the absorption intensity is along with CsPbBr3In mass content ofAnd increased by an increase. The absorption in the visible region is due to CsPbBr3Caused by the narrow band gap of quantum dots. Therefore, we have chosen three typical LEDs (365nm, 460nm and 520nm) as the light source for gas sensing measurements.
FIG. 4: ZnO microsphere, ZnO-0.5% CsPbBr3、ZnO-1％CsPbBr3、ZnO-1.5％CsPbBr3Composite materials provide 5fppm NO at 365nm, 460nm and 520nm illumination2The response curve of (c).
As shown in FIG. 4, CsPbBr can be seen3The optimal impurity content of the quantum dots is 1%. CsPbBr3The quantum dots are used as a photosensitive material and cover the surface of the ZnO microspheres. At high doping levels, the exposed surface of the gas sensitive material is reduced and the surface active chemical reaction sites are reduced. More importantly, even though CsPbBr is added at a low doping level3The number of carriers generated is sufficient, but their lifetime is also short due to the lack of sufficient heterojunctions to transport and separate electron holes
FIGS. 5(a) - (c) are graphs showing 3ppm, 5ppm, 7ppm and 10ppm NO at 520nm wavelength for light2ZnO-0.5% CsPbBr under the condition of concentration3、ZnO-1％CsPbBr3、ZnO-1.5％CsPbBr3Resistance change curve of the composite material; (d) the sensitivity-gas concentration curve after linear fitting is obtained for the three composite materials; (e) is ZnO-1% CsPbBr3Histograms of response and recovery times at 3ppm, 5ppm, 7ppm and 10 ppm; (f) is ZnO-1% CsPbBr3Repeatability curve at 3 ppm.
Wherein the sensitivity is defined as: sensitive electrode materials in NO2Resistance value in/resistance value in air;
as can be seen from FIG. 5, NO2As an oxidizing gas, electrons can be extracted from the n-type semiconductor, increasing the resistance of the sensor. This also indicates that the ZnO material is the primary gas sensing portion. From the point of view of the response recovery time, the reaction rate tends to decrease with increasing concentration, and the recovery rate is significantly lower than the reaction rate. There is no doubt that at high concentrations, the rates of diffusion, adsorption and desorption are much faster. In addition, light energy can also affect the rate of recovery, causing NO2Molecular and ZnO tableThe bonding of the facets is unstable. The device also has better repeatability.
FIG. 6: ZnO-1% CsPbBr3Bar graph for selectivity to oxidizing or reducing gases.
NO due to low activation energy required at room temperature2Molecules are easily adsorbed on the surface of ZnO, so that the sensor is used for detecting NO2Has good selection.
Detailed Description
Example 1:
1. 1.188g of Zn (NO)3)2·6H2O, 0.56g of hexamethylenetetramine, 0.296g C6H5NaO7·2H2O was added to 150mL of deionized water. The mixture was stirred constantly at room temperature and the sealed mixture was then placed in an oil bath at 90 ℃ for 30 minutes. The precipitate generated in the process is collected after being centrifugally washed for a plurality of times by deionized water and ethanol, and is placed in a vacuum oven at 120 ℃ for heating for 4 hours. Finally, the powder was annealed at 400 ℃ for 2 hours to obtain ZnO microspheres.
2. 0.814g Cs2CO32.5mL oleic acid and 30mL octadecene were mixed and degassed under vacuum at 120 ℃ for 1 hour, then the resulting mixture was heated to 150 ℃ under nitrogen and reacted for 3 hours until a clear precursor solution of cesium and oleic acid was formed; secondly, 0.376mmol of PbBr was added2Mixing with 10mL octadecene, vacuum drying at 120 deg.C for 1 hr, and further drying at 120 deg.C under N21.0mL of oleylamine and 1.0mL of oleic acid were injected thereto under an atmosphere; to PbBr2After complete dissolution, the temperature of the reaction system is raised to 180 ℃, 0.8mL of cesium and oleic acid precursor solution is rapidly injected into the reaction system, the reactant solution is cooled to room temperature after 5 seconds of reaction, supernatant is discarded after centrifugation, and precipitate is dispersed in n-hexane to obtain long-term stable colloidal CsPbBr3Quantum dot solution, CsPbBr3The concentration of the quantum dots is 10 mmol/L.
3. Putting 50mg of zinc oxide material into 3mL of n-hexane to obtain a n-hexane solution of zinc oxide; taking CsPbBr with concentration of 10mmol/L30.086mL of quantum dot solution was mixed with 3mL of n-hexane solution containing 50mg of zinc oxide, resulting in CsPbBr3The mass of the quantum dots is 1 percent of that of the zinc oxide. Stirring in a glove box for 30 minutes respectively under the sealing conditions of room temperature and 80 ℃; finally vacuum drying at 80 ℃ to obtain ZnO microspheres and CsPbBr3Quantum dot heterostructure composite material (labeled as ZnO-1% CsPbBr)3)。
4. And sequentially placing the ceramic wafer substrate with the Pd metal interdigital electrode in acetone, ethanol and deionized water, sequentially ultrasonically cleaning for 20 minutes, and then placing the ceramic wafer substrate into a 60-DEG C drying oven for drying.
5. Mixing 10mg of ZnO microspheres with CsPbBr3The quantum dot heterostructure composite material and 3mL of normal hexane are uniformly mixed, and then the mixture is dripped and coated on the surface of the Pd metal interdigital electrode by a liquid transfer gun to serve as a sensitive material layer. The Pd metal interdigital electrode consists of twelve pairs of interdigital electrodes, the ceramic chip substrate has a length and a width of 10mm and a thickness of 0.38mm, and the ZnO microspheres and CsPbBr are arranged on the ceramic chip substrate3The interdigital electrode is completely covered by the quantum dot heterostructure composite material.
6. Mixing the microspheres with ZnO and CsPbBr3Baking the quantum dot heterostructure composite material and the ceramic chip substrate of the interdigital electrode for 10 minutes under an infrared lamp, connecting two ends of the Pd metal interdigital electrode with a test system after an organic solvent is volatilized, testing the sensor, and irradiating the sensor with an LED lamp bead with a single wavelength (365nm, 460nm or 520nm) at a position 1.5cm away from the sensor, thereby obtaining the composite material based on the ZnO microsphere and the CsPbBr3Gas sensor pair of quantum dot heterostructure composite material2Gas sensitive response characteristic data of (1).
Example 2:
ZnO microspheres and CsPbBr were prepared according to the method of example 13Quantum dots, the mixing ratio of the two is changed. 0.043mL of CsPbBr was taken3The solution was mixed with 3mL of an n-hexane solution containing 50mg of zinc oxide to prepare CsPbBr in the device3The mass of the ZnO is 0.5 percent of the mass of the ZnO, and the mark is CsPbBr of ZnO-0.5 percent3. The device fabrication method and test method were consistent with example 1.
Example 3:
ZnO microspheres and CsPbBr were prepared according to the method of example 13Quantum dots, the mixing ratio of the two is changed. Take 0.129mLCsPbBr3The solution was mixed with 3mL of an n-hexane solution containing 50mg of zinc oxide to prepare CsPbBr in the device3The mass of the ZnO is 1.5 percent of the mass of the ZnO, and the label is CsPbBr of ZnO-1.5 percent3. The device fabrication method and test method were consistent with example 1.
Comparative example 1:
the preparation process of the pure phase ZnO microsphere is the same as that of the embodiment 1, and only 365nm wavelength light is tested in the gas sensitive test process.
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