Manufacturing method of tungsten trioxide nitrogen dioxide sensor with sensitivity

Abstract

The present invention relates to a method for manufacturing a tungsten trioxide nitrogen dioxide sensor with improved sensitivity and reactivity and selectivity for nitrogen dioxide, characterized by comprising: a first step of manufacturing tungsten trioxide (WO3) nanopowder; a second step of producing a nitrogen dioxide (NO2) sensing material by doping lead sulfide quantum dots into the tungsten trioxide nanopowder; a third step of applying the nitrogen dioxide sensing material to a sensor substrate; and a fourth step of irradiating ultraviolet (UV) light onto a sensor composed of the nitrogen dioxide sensing material applied to the sensor substrate.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing a tungsten trioxide nitrogen dioxide sensor with improved sensitivity, and more specifically, to a method for manufacturing a tungsten trioxide nitrogen dioxide sensor with improved sensitivity applicable to hazardous gas monitoring or gas sensors. Background Technology

[0003] Nitrogen dioxide (NO2) is classified as a representative hazardous gas emitted from automobile exhaust, industrial sites, and other sources.

[0004] In particular, nitrogen dioxide (NO2) is reported to be a powerful greenhouse gas that causes a greenhouse effect approximately 300 times greater than that of carbon dioxide.

[0005] Therefore, since the inhalation of nitrogen dioxide (NO2) can cause serious side effects in the human body, such as severe lung-related diseases or Parkinson's disease, it is necessary to establish a high-performance nitrogen dioxide (NO2) monitoring system, and to this end, the development of high-performance nitrogen dioxide (NO2) sensors is very important.

[0006] Meanwhile, nitrogen dioxide (NO2) sensors include resistance change type (semiconductor type) sensors in which resistance changes according to the chemical adsorption / desorption of nitrogen dioxide (NO2), and non-dispersive infrared (NDIR) sensors that utilize the infrared absorption wavelength of nitrogen dioxide (NO2).

[0007] Here, in the case of non-dispersive infrared nitrogen dioxide (NO2) sensors, there are difficulties in development and commercialization due to interference with the absorption wavelengths of other gases (NH3, CO, CO2, etc.) or moisture (H2O).

[0008] On the other hand, resistance-changing (semiconductor-type) nitrogen dioxide (NO2) sensors can be developed using various metal oxides and are being utilized in various fields due to advantages such as relatively low cost and simple development methods.

[0009] However, resistance-changing (semiconductor) sensors utilizing various metal oxides have the disadvantage of reacting simultaneously to various gases such as hydrogen sulfide (H2S), ammonia (NH3), and hydrogen (H2) in addition to nitrogen dioxide (NO2) (i.e., low selectivity), which increases the likelihood of sensor malfunction (false detection).

[0010] Therefore, it is necessary to develop a metal oxide-based nitrogen dioxide (NO2) sensing material that has high reactivity to nitrogen dioxide (NO2) and can secure high selectivity for other gases. Prior art literature

[0012] Registered Patent No. 10-2138442 The problem to be solved

[0013] The present invention was developed to improve upon the aforementioned problems and aims to provide a method for manufacturing a tungsten trioxide nitrogen dioxide sensor with improved sensitivity, having improved reactivity and selectivity toward nitrogen dioxide. means of solving the problem

[0015] To achieve the above objectives, the present invention provides a method for manufacturing a tungsten trioxide nitrogen dioxide sensor with improved sensitivity, characterized by comprising: a first step of manufacturing tungsten trioxide (WO3) nanopowder; a second step of producing a nitrogen dioxide (NO2) sensing material by doping lead sulfide quantum dots into the tungsten trioxide nanopowder; a third step of applying the nitrogen dioxide sensing material to a sensor substrate; and a fourth step of irradiating ultraviolet (UV) light onto a sensor made of the nitrogen dioxide sensing material applied to the sensor substrate.

[0016] Here, the first step comprises a first process of preparing a first mixture by mixing sodium tungstate (Na2WO4) powder and oxalic acid (C2H2O4), and

[0017] The method is characterized by comprising: a 12th step of preparing a second mixture by adding hydrochloric acid to the first mixture to acidify it; a 13th step of mixing potassium sulfate into the second mixture; a 14th step of synthesizing tungsten trioxide powder by heating the second mixture in an autoclave; a 15th step of dissolving the tungsten trioxide powder in hydrochloric acid, ultrasonically treating it, and then neutralizing it with sodium hydroxide (NaOH); and a 16th step of heat-treating the neutralized tungsten trioxide powder in an autoclave to form tungsten trioxide nanopowder.

[0018] At this time, the above 11th process is characterized by dissolving 1956 ml of sodium tungstate and 1512 ml of oxalic acid in 50 ml of ultrapure water (H2O).

[0019] And, the above 12th process is characterized by adding the above hydrochloric acid solution to adjust the pH of the above 2nd mixture, which is an aqueous solution, to 0.7 to 0.9.

[0020] And, the above 13th process is characterized by adding 3g of potassium sulfate (K2SO4) to the above 2nd mixture as a solution that has turned transparent.

[0021] And, the above 14th process is characterized by obtaining a green powder by placing the above second mixture, which is an aqueous solution, into the above autoclave, heating it at 100°C for 24 hours, and then cooling it to room temperature.

[0022] And, the above 15th process is characterized by dissolving the tungsten trioxide powder in 50 ml of hydrochloric acid, subjecting it to ultrasonic treatment, and then neutralizing it with 50 ml of sodium hydroxide.

[0023] And, the above 16th process is characterized by placing the neutralized aqueous solution of tungsten trioxide into the autoclave and heating it at 180°C for 4 hours, and then filtering the aqueous solution of tungsten trioxide to obtain the tungsten trioxide nano powder.

[0024] And, the second step is characterized by performing a doping process by mixing the tungsten trioxide nanopowder with lead sulfide quantum dots.

[0025] And, in the third step above, the sensor substrate is characterized by having a gold (Au) electrode deposited on a silicon wafer.

[0026] In addition, the third step is characterized by producing a sensor made of the nitrogen dioxide sensing material by depositing the nitrogen dioxide sensing material onto the sensor substrate using a droplet or spin-coating method and then drying it.

[0027] In addition, the fourth step is characterized by irradiating the ultraviolet light onto a sensor composed of the nitrogen dioxide sensing material to which the tungsten trioxide nanopowder doped with the lead sulfide quantum dots is applied. Effects of the invention

[0029] According to the present invention with the above-described configuration, the following effects can be achieved.

[0030] First of all, the present invention has the advantage of securing a technology that can be applied to tungsten trioxide nanopowder that reacts sensitively to nitrogen dioxide, and at the same time, by additionally introducing technologies such as quantum doping and ultraviolet irradiation, it can secure a manufacturing technology that can maximize sensitivity and selectivity to nitrogen dioxide.

[0031] In particular, the present invention has the distinctive advantage of being able to secure a method for manufacturing tungsten trioxide nanopowder having a high specific surface area in a nanostructure form.

[0032] Above all, the present invention has the advantage of maximizing sensitivity and selectivity to nitrogen dioxide (NO2) by applying quantum dots, which are one of the next-generation nanomaterials, to tungsten trioxide (WO3) nanopowder.

[0033] In addition, the present invention has the advantage of maximizing reactivity to nitrogen dioxide (NO2) through the generation of additional carriers via ultraviolet (UV) irradiation. Brief explanation of the drawing

[0035] FIG. 1 is a block diagram sequentially illustrating a method for manufacturing a tungsten trioxide nitrogen dioxide sensor with improved sensitivity according to an embodiment of the present invention. FIG. 2 is a block diagram sequentially illustrating the specific process of the first step of a method for manufacturing a tungsten trioxide nitrogen dioxide sensor with improved sensitivity according to an embodiment of the present invention. FIG. 3 is a perspective conceptual diagram for applying tungsten trioxide powder to a sensor substrate in the third step of a method for manufacturing a tungsten trioxide nitrogen dioxide sensor with improved sensitivity according to an embodiment of the present invention, and a drawing of the applied nitrogen dioxide sensor. FIG. 4 is a drawing showing an SEM image and an XRD graph of tungsten trioxide nanopowder prepared by a method for manufacturing a tungsten trioxide nitrogen dioxide sensor with improved sensitivity according to an embodiment of the present invention. Figure 5 is a graph showing the change in reactivity according to nitrogen dioxide concentration depending on the presence or absence of doping and UV irradiation of tungsten trioxide nanopowder prepared by the method for manufacturing a tungsten trioxide nitrogen dioxide sensor with improved sensitivity according to an embodiment of the present invention. FIG. 6 is a graph showing the change in reactivity according to nitrogen dioxide concentration depending on the presence or absence of doping and UV irradiation of tungsten trioxide nanopowder prepared by the method for manufacturing a tungsten trioxide nitrogen dioxide sensor with improved sensitivity according to an embodiment of the present invention. FIG. 7 is a graph comparing the reactivity and selectivity for each gas according to the presence or absence of doping and UV irradiation of tungsten trioxide nanopowder prepared by the method for manufacturing a tungsten trioxide nitrogen dioxide sensor with improved sensitivity according to an embodiment of the present invention. Specific details for implementing the invention

[0036] The advantages and features of the present invention and the methods for achieving them will become clear by referring to the embodiments described in detail below together with the accompanying drawings.

[0037] However, the present invention is not limited to the embodiments disclosed below but will be implemented in various different forms.

[0038] The embodiments described in this specification are provided to ensure that the disclosure of the invention is complete and to fully inform those skilled in the art of the scope of the invention.

[0039] And the present invention is defined only by the scope of the claims.

[0040] Accordingly, in some embodiments, well-known components, well-known operations, and well-known techniques are not specifically described to avoid the invention being interpreted ambiguously.

[0041] Additionally, throughout the specification, the same reference numerals refer to the same components, and the terms used (mentioned) in this specification are for describing embodiments and are not intended to limit the invention.

[0042] In this specification, the singular form includes the plural form unless specifically stated otherwise in the text, and components and operations referred to as 'comprising (or comprising)' do not exclude the presence or addition of one or more other components and operations.

[0043] Unless otherwise defined, all terms used in this specification (including technical and scientific terms) may be used in a meaning that is commonly understood by those skilled in the art to which the present invention belongs.

[0044] Also, terms defined in commonly used dictionaries are not interpreted ideally or excessively unless otherwise defined.

[0046] Hereinafter, preferred embodiments of the present invention will be described with reference to the attached drawings.

[0048] First, FIG. 1 is a block diagram sequentially illustrating a method for manufacturing a tungsten trioxide nitrogen dioxide sensor with improved sensitivity according to one embodiment of the present invention.

[0049] And, FIG. 2 is a block diagram sequentially illustrating the specific process of the first step of the method for manufacturing a tungsten trioxide nitrogen dioxide sensor with improved sensitivity according to one embodiment of the present invention.

[0050] And, FIG. 3 is a perspective conceptual diagram for applying tungsten trioxide powder to a sensor substrate in the third step of a method for manufacturing a tungsten trioxide nitrogen dioxide sensor with improved sensitivity according to one embodiment of the present invention, and a drawing of the applied nitrogen dioxide sensor.

[0051] And, FIG. 4 is a drawing showing SEM images and XRD graphs of tungsten trioxide nanopowder prepared by a method for manufacturing a tungsten trioxide nitrogen dioxide sensor with improved sensitivity according to one embodiment of the present invention.

[0052] And, FIG. 5 is a graph showing the change in reactivity according to nitrogen dioxide concentration depending on the presence or absence of doping and ultraviolet irradiation of tungsten trioxide nanopowder prepared by the method for manufacturing a tungsten trioxide nitrogen dioxide sensor with improved sensitivity according to one embodiment of the present invention.

[0053] In addition, Figure 6 is a graph showing the change in reactivity according to nitrogen dioxide concentration depending on the presence or absence of doping and ultraviolet irradiation of tungsten trioxide nanopowder prepared by the method for manufacturing a tungsten trioxide nitrogen dioxide sensor with improved sensitivity according to one embodiment of the present invention.

[0054] In addition, FIG. 7 is a graph comparing the reactivity and selectivity of tungsten trioxide nanopowder prepared by the method for manufacturing a tungsten trioxide nitrogen dioxide sensor with improved sensitivity according to one embodiment of the present invention, depending on the presence or absence of doping and ultraviolet irradiation.

[0056] The present invention can manufacture a tungsten trioxide nitrogen dioxide sensor by preparing tungsten trioxide (WO3) nanopowder as shown in FIG. 1 (Step 1), producing a nitrogen dioxide (NO2) sensing material by doping lead sulfide quantum dots into the tungsten trioxide nanopowder (Step 2), applying the nitrogen dioxide sensing material to a sensor substrate (Step 3), and then irradiating ultraviolet (UV) light onto the sensor made of the nitrogen dioxide sensing material applied to the sensor substrate (Step 4).

[0057] The present invention is applicable to the above-described embodiments, and it goes without saying that it is also applicable to various embodiments as follows.

[0059] First, the first step involves a series of processes in which a first mixture is prepared by mixing sodium tungstate (Na2WO4) powder and oxalic acid (C2H2O4) as shown in FIG. 2 (Process 11), a second mixture is prepared by adding hydrochloric acid to the first mixture to acidify it (Process 12), potassium sulfate is mixed into the second mixture (Process 13), and then the second mixture is heated in an autoclave to synthesize tungsten trioxide powder (Process 14), the tungsten trioxide powder is dissolved in hydrochloric acid and subjected to ultrasonic treatment, then neutralized with sodium hydroxide (NaOH) (Process 15), and finally, the neutralized tungsten trioxide powder is heat-treated in an autoclave to form tungsten trioxide nanopowder (Process 16).

[0060] Here, in the 11th step, 1956 ml of sodium tungstate and 1512 ml of oxalic acid are dissolved in 50 ml of ultrapure water (H2O).

[0061] At this time, in the 12th step, a hydrochloric acid solution is added to the first mixture to adjust the pH of the second mixture, an aqueous solution, to 0.7 to 0.9.

[0062] And, in the 13th step, 3g of potassium sulfate (K2SO4) is added to the second mixture as a clear solution.

[0063] And, in the 14th process, a green powder is obtained by placing the second mixture, which is an aqueous solution, into an autoclave, heating it at 100°C for 24 hours, and then cooling it to room temperature.

[0064] In addition, in the 15th process, tungsten trioxide powder is dissolved in 50 ml of hydrochloric acid, subjected to ultrasonic treatment, and then neutralized with 50 ml of sodium hydroxide.

[0065] In addition, in the 16th process, an aqueous solution of neutralized tungsten trioxide is placed in an autoclave and heated at 180°C for 4 hours, and then the aqueous solution of tungsten trioxide is filtered to obtain tungsten trioxide nanopowder.

[0067] Meanwhile, in the second step, a doping process is performed by mixing tungsten trioxide nanopowder with lead sulfide quantum dots.

[0068] Here, since the doping process is substantially the same as the process described in the inventors' prior patent application, Published Patent No. 10-2024-0020515, a detailed description of the doping process is omitted for convenience in this invention.

[0070] Meanwhile, in the third step, it can be seen that the sensor substrate has a gold (Au) electrode deposited on a silicon wafer as shown in Fig. 3.

[0071] Here, in the third step, a sensor made of nitrogen dioxide sensing material is fabricated by depositing the nitrogen dioxide sensing material onto a sensor substrate using a droplet or spin-coating method and then drying it.

[0073] Meanwhile, in the fourth step, ultraviolet light can be irradiated onto a sensor composed of a nitrogen dioxide sensing material to which tungsten trioxide nanopowder doped with lead sulfide quantum dots is applied.

[0074] In particular, it can be seen through Figures 5 to 7 that the reactivity and tolerance to nitrogen dioxide of the sensor applied with lead sulfide quantum doped tungsten trioxide nanopowder is improved compared to the sensor applied with tungsten trioxide nanopowder.

[0075] In particular, it can be confirmed through Figures 5 to 7 that the reactivity and selectivity of the nitrogen dioxide sensor, which is equipped with tungsten trioxide nanopowder doped with lead sulfide quantum dots, are significantly improved when the sensor is irradiated with ultraviolet light.

[0077] In other words, when tungsten trioxide (WO3) with n-type characteristics is exposed to air, oxygen is adsorbed on its surface, and a depletion layer is formed due to the adsorbed oxygen species (O2-).

[0078] Here, when tungsten trioxide (WO3) is exposed to nitrogen dioxide (NO2), nitrogen dioxide (NO2) is adsorbed onto the surface, and the depletion layer expands due to the strong oxidizing power of nitrogen dioxide (NO2).

[0079] At this time, when lead sulfide quantum dots (PbS Quantum Dot) having p-type characteristics are doped into tungsten trioxide (WO3) having n-type characteristics, a heterojunction is formed, and a depletion layer is formed as electrons move from tungsten trioxide to the lead sulfide quantum dots.

[0080] In addition, the application of lead sulfide quantum dots increases the specific surface area, thereby increasing the number of sites that can react with the gas, and thus improving reactivity to the gas.

[0081] In addition, when lead sulfide quantum dot-doped tungsten trioxide (WO3) is exposed to air, oxygen is adsorbed on the surface of the lead sulfide quantum dot-doped tungsten trioxide (WO3), and the depletion layer expands due to the adsorbed oxygen species (O2-).

[0082] In addition, when lead sulfide quantum doped tungsten trioxide (WO3) is exposed to nitrogen dioxide (NO2), nitrogen dioxide (NO2) is adsorbed onto the surface of the lead sulfide quantum doped tungsten trioxide (WO3), and due to the strong oxidizing power of nitrogen dioxide (NO2), the depletion layer expands, i.e., the resistance increases.

[0083] However, due to existing adsorbed oxygen species (O2-), the number of electrons available to react with nitrogen dioxide (NO2) is insufficient, resulting in relatively low reactivity.

[0084] On the other hand, when ultraviolet (UV) light is irradiated when tungsten trioxide (WO3) doped with lead sulfide quantum dots is exposed to nitrogen dioxide (NO2), electron-hole pairs (EHPs) are generated.

[0085] As a result, the number of electrons capable of reacting with nitrogen dioxide (NO2) on the surface of tungsten trioxide (WO3) doped with lead sulfide quantum dots increases, thereby improving reactivity to nitrogen dioxide (NO2).

[0086] In addition, lead sulfide quantum dots are materials that have high selectivity for nitrogen dioxide (NO2) even at relatively low temperatures, and can significantly improve the selectivity for nitrogen dioxide (NO2) of existing tungsten trioxide (WO3) materials.

[0088] As described above, it can be seen that the basic technical concept of the present invention is to provide a method for manufacturing a tungsten trioxide nitrogen dioxide sensor with improved sensitivity and improved reactivity and selectivity toward nitrogen dioxide.

[0089] And, it goes without saying that many other variations and applications are also possible for those skilled in the art within the scope of the basic technical concept of the present invention.

Claims

Claim 1 A first step for manufacturing tungsten trioxide (WO3) nanopowder comprising: a first step of preparing a first mixture by dissolving sodium tungstate (Na2WO4) powder and oxalic acid (C2H2O4) in ultrapure water (H2O); a second step of preparing a second mixture by adding a hydrochloric acid solution to the first mixture to acidify the first mixture to a pH of 0.7 to 0.9; a third step of mixing potassium sulfate (K2SO4) into the second mixture; a fourth step of synthesizing tungsten trioxide powder by heating the second mixture in an autoclave; a fifth step of dissolving the tungsten trioxide powder in hydrochloric acid, ultrasonically treating it, and then neutralizing it with sodium hydroxide (NaOH); and a sixth step of forming tungsten trioxide nanopowder by placing the neutralized aqueous solution of tungsten trioxide into an autoclave and hydrothermally treating it. A method for manufacturing a tungsten trioxide nitrogen dioxide sensor with improved sensitivity, comprising: a second step of producing a nitrogen dioxide (NO2) sensing material in which a heterojunction is formed by doping lead sulfide quantum dots (PbS Quantum Dot) having p-type characteristics into the tungsten trioxide nanopowder having n-type characteristics; a third step of applying the nitrogen dioxide sensing material to a sensor substrate; and a fourth step of irradiating ultraviolet (UV) light onto a sensor made of the nitrogen dioxide sensing material applied to the sensor substrate. Claim 2 delete Claim 3 delete Claim 4 delete Claim 5 delete Claim 6 delete Claim 7 delete Claim 8 delete Claim 9 delete Claim 10 A method for manufacturing a tungsten trioxide nitrogen dioxide sensor with improved sensitivity according to claim 1, wherein, in the third step, the sensor substrate is characterized by having a gold (Au) electrode deposited on a silicon wafer. Claim 11 A method for manufacturing a tungsten trioxide nitrogen dioxide sensor with improved sensitivity according to claim 1, wherein the third step comprises depositing the nitrogen dioxide sensing material onto the sensor substrate by a droplet or spin-coating method and then drying to produce a sensor made of the nitrogen dioxide sensing material. Claim 12 delete

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