KR101797874B1 - Poisonous gas sensor capable of electrical sensing and optical sensing simultaneously, and method of fabricating thereof - Google Patents

Abstract

The present invention relates to a harmful gas sensor capable of simultaneously performing electrical sensing and optical sensing, and a method for manufacturing the same. The present invention relates to the gas sensor of high performance, capable of simultaneously performing electrical detection and optical detection of harmful gas by using reduced graphene oxide (R-GO) and bromophenol blue (BPB).

Description

TECHNICAL FIELD [0001] The present invention relates to a noxious gas detection sensor capable of simultaneously detecting an electrical signal and an optical signal, and a method of manufacturing the same,

The present invention relates to a noxious gas detection sensor capable of simultaneous electrical sensing and optical sensing, and a method of manufacturing the same.

TECHNICAL FIELD The present invention relates to a high-performance gas sensor capable of simultaneously performing electrical detection and optical detection of noxious gas using a laminated structure of reduced graphene oxide (R-GO) and bromophenol blue (BPB).

Recent rapid development of physics, chemistry and biosensors has led to a rapid increase in the speed and popularity of smart devices such as watches, glasses, bands, and patches with smart functions. In the case of a gas sensor, the technology of a gas sensor that can detect and monitor harmful gases or vapors as well as environmental conditions and provide a warning to humans when a dangerous level is reached has received much attention. Recently, many efforts have been made to mount such a gas sensor on a smart wearable platform, but there are still many problems to be solved.

To be applied as a wearable sensor, it must be lightweight, low power consumption, flexible enough to be attached to skin or clothes, transparency to avoid aesthetics, possibility of operation in various environments such as home or workplace . In addition, the technology for detecting and correcting the detection result of the sensor by detecting the harmful gas in various ways is one of the essential factors for enhancing the reliability of the result. In order to improve the detection performance, development of a better sensing material or detection method It is an urgent situation.

It is an object of the present invention to provide a sensor manufacturing technology and an approach method differentiated from the existing technology and to solve the problems of the related art and to maximize the performance improvement of the sensor, Of the present invention.

However, the present invention has been made in view of the fact that the present invention can be applied to the case of using reduced oxidized graphene (R-GO) and bromophenol blue (BPB) A sensor that can simultaneously detect the change in electrical resistance of oxidized graphene due to electrochemical changes due to interaction with the optical detection using the color conversion that occurs when the target sensing gas interacts with the bromophenol blue. It is possible to detect harmful gas even in case of imposition of strain without power restriction or power impermissible. It is possible to detect the sensitivity of sensor by using Interdigitated Electrode Array (IEA) electrode pattern structure. And the response can be greatly improved.

According to an embodiment of the present invention, a hazardous gas detection sensor capable of simultaneously performing electrical sensing and optical sensing includes a substrate; An electrode layer formed on the substrate; An R-GO (Reduced Graphene Oxide) layer formed on the electrode layer; And a BPB (bromophenol blue) layer formed on the R-GO layer. The color change of the BPB layer and the electrical change of the R-GO layer due to the electrochemical interaction between the BPB layer and the target gas occur simultaneously, Optical and electrical sensing is possible by detecting this.

The substrate is preferably a flexible substrate.

The electrode layer is composed of two electrode patterns, i.e., a first electrode pattern and a second electrode pattern. The first electrode pattern and the second electrode pattern are electrically insulated from each other to form an interdigitated electrode pattern .

The R-GO layer is preferably formed by self-assembly.

The BPB layer may be used as a passivation layer of the R-GO layer.

According to an embodiment of the present invention, there is provided a method of manufacturing a noxious gas sensing sensor capable of simultaneously performing electrical sensing and optical sensing, comprising: preparing a substrate; Forming an electrode layer on the prepared substrate; Forming an R-GO layer on the substrate on which the electrode layer is formed; And forming a BPB layer on the R-GO layer, wherein a color change of the BPB layer and an electrical change of the R-GO layer occur simultaneously due to the electrochemical interaction between the BPB layer and the target gas, Optical and electrical sensing is possible by detecting this.

The substrate is preferably a flexible substrate.

The electrode layer is composed of two electrode patterns, i.e., a first electrode pattern and a second electrode pattern. The first electrode pattern and the second electrode pattern are electrically insulated from each other to form an interdigitated electrode pattern .

Forming the first electrode pattern and the second electrode pattern includes: coating an electrode layer on the substrate; Forming a photoresist mask pattern on the substrate coated with the electrode layer; Removing an electrode layer of the portion excluding the photoresist mask pattern using an acid; And removing the photoresist mask pattern.

The step of forming the R-GO layer is preferably performed by self-assembly. The self-assembly includes: forming an adhesive layer on the electrode using a transparent adhesive; Forming a water soluble graphene oxide layer on the adhesive layer; And reducing the graphene oxide.

The step of reducing the graphene oxide is performed by exposing to hydrazine vapor, followed by thermal reduction in a nitrogen atmosphere.

The step of forming the BPB layer on the R-GO layer is carried out by immersing the BPB solution in a dip coating method.

The flexible and transparent noxious gas detection sensor manufactured using the present invention has excellent performance and is applicable to various working environments (temperature, humidity, strain, etc.) , And a sensor that can be used in a workplace with a large change in humidity. It is possible to use the sensor in a form that can be directly attached to the body or being worn by ensuring both flexibility and transparency.

In the present invention, a sensor in which reduced graphene (R-GO) and bromophenol blue (BPB) are combined on an Interdigitated Electrode Array (IEA) is manufactured on one substrate and two kinds of electric and optical methods , Which is a sensor that can detect simultaneously. It has a structure and an approach different from conventional sensors. It is a sensor element that maximizes improvement of sensitivity, responsiveness and reliability, It is a new concept of flexibility, transparency and harmful gas sensor applicable to sensor platform.

1 is a structural view of a noxious gas detection sensor capable of simultaneously performing electrical sensing and optical sensing according to an embodiment of the present invention.
2 is a flowchart illustrating a method of manufacturing a noxious gas detection sensor capable of simultaneously performing electrical sensing and optical sensing according to an embodiment of the present invention.
FIG. 3 illustrates a noxious gas sensing sensor of a thin film transistor structure fabricated to understand and analyze the principle of operation of the sensor according to the present invention.
4 is a photograph (left side) of an electrical / optical sensor having transparency flexibility according to an embodiment of the present invention and an image (left side) showing an optical microscope of a sensor having an IEA structure.
Figure 5 is an atomic force microscope image of R-GO (left) and BPB / R-GO (right).
FIG. 6 shows the results of Raman spectroscopy for successfully forming oxide graphene, R-GO, and BPB / R-GO on ITO.
FIG. 7 is a result of measuring transmittance using an ultraviolet-visible light spectrophotometer according to each manufacturing step and condition of the IEA device.
Fig. 8 shows the results of the detection of the ammonia gas detection characteristic by manufacturing a gas sensor having a BPB / R-GO IEA structure.
9 shows the results of the flexibility evaluation of the gas sensor of the BPB / R-GO IEA structure.
10 is an optical image of a color change of BPB according to ammonia gas concentration, taken by a camera.
FIG. 11 is a result of exposing the gas sensor to ammonia in part to check the change of color in various background colors and brightness.
Various embodiments are now described with reference to the drawings, wherein like reference numerals are used throughout the drawings to refer to like elements. For purposes of explanation, various descriptions are set forth herein to provide an understanding of the present invention. It is evident, however, that such embodiments may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to facilitate describing the embodiments.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is capable of various modifications and various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. It is to be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but on the contrary, is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the term "comprises" or "having ", etc. is intended to specify that there is a feature, step, operation, element, part or combination thereof described in the specification, , &Quot; an ", " an ", " an "

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

TECHNICAL FIELD The present invention relates to a high-performance gas sensor capable of simultaneously performing electrical detection and optical detection of noxious gas using a laminated structure of reduced graphene oxide (R-GO) and bromophenol blue (BPB). It is a sensor that can simultaneously detect noxious gas optically and electrically by sensing the change of dye color according to the oxidation and reduction reaction of BPB by the target gas and the change signal of the electrical resistance of R-GO layer according to pH change. It is very useful because it can utilize two sensors depending on the environment.

In particular, existing R-GO based gas detection sensors can detect various harmful gases (NO ₂ , NH ₃ , HCl, SO ₂ , HF, H _2, etc.) . In particular, the sensor device disclosed in the present invention has transparency and is transparent even when attached to the skin (face, neck, wrist, etc.) exposed to the outside, so that the sensor device can be applied to an attachable or wearable device.

The present invention of this toxic gas sensor is a smart sensor that must be developed for human health and safety from harmful gas, and shows an attractive sensing method different from conventional sensors.

In order to achieve the object of the present invention, a sensor element capable of electrical measurement based on reduced oxidized graphene (R-GO), which improves responsiveness and sensitivity using an interdigitated electrode array (IEA) electrode pattern structure, BPB) was fabricated on a single substrate to complement the limitations of each sensor to produce a noxious gas sensor capable of operating under unfavorable environmental conditions. Transparent and flexible substrates and materials were utilized to easily identify the versatility and color change.

1 is a structural view of a noxious gas detection sensor capable of simultaneously performing electrical sensing and optical sensing according to an embodiment of the present invention.

According to an embodiment of the present invention, a hazardous gas detection sensor capable of simultaneously performing electrical sensing and optical sensing includes a substrate 10; An electrode layer 30; An R-GO layer 40; And a BPB layer 50.

The substrate 10 is preferably a flexible substrate. Specifically, a flexible polymer substrate, a plastic substrate, or the like can be used. The noxious gas detection sensor of the present invention is not only mounted on a wearable smart device but also transparent to a skin (face, neck, wrist, etc.) exposed to the outside, It is preferable that the substrate to be used is also a flexible and transparent substrate.

The electrode layer 30 is composed of two electrode patterns, that is, a first electrode pattern 31 and a second electrode pattern 32. The first electrode pattern and the second electrode pattern are electrically insulated from each other, interdigitated electrode pattern. In FIG. 1, one of the electrode patterns of the electrode layer 30 becomes the first electrode pattern 31, and the other electrode pattern becomes the second electrode pattern 32.

The first and second electrode patterns are electrically insulated from each other and form an interdigitated electrode pattern (IEA pattern). 1, the first electrode pattern and the second electrode pattern are formed so as to be insulated from each other on the substrate. It is shaped like a comb. A portion corresponding to each flesh in the comb constitutes a plurality of electrodes.

In the present invention, the electrode of the electric sensor is manufactured by the Interdigitated Electrode Array (IEA) structure as described above, and the surface area enabling detection of the noxious gas is widely realized, so that the gas of very low concentration can be detected quickly. That is, using the electrode pattern of the IEA structure, the responsiveness and sensitivity can be improved, and also the flexibility can be ensured.

The R-GO layer 40 is formed on the electrode layer 30, and this R-GO layer is formed by self-assembly. I will explain this in more detail later. The R-GO layer can be electrically sensed by resistance change.

The BPB layer 50 is a part for detecting noxious gas by an optical method. The principle of this optical sensing sensor is to change the color by changing the pH when acidic or basic gas molecules are adsorbed on BPB. Also, the doping effect of the R-GO layer is caused by the pH change, thereby causing a resistance change. The BPB acts on the gas and electrochemically, which causes a color change and causes a change in the electrical resistance of the R-GO. H + or OH- generated by adsorption of gas molecules in the BPB moves to the R-GO layer and induces resistance change. If the thickness of the BPB thin film is large, the noise signal is strong and the thin film exhibits excellent characteristics.

In the case of BPB, it was previously used only as a sensor in UV environment. However, in the present invention, the usability of BPB is expanded to be applicable even in an ambient condition.

In addition, the BPB layer covers the R-GO layer 40 together with the optical sensing function, thereby simultaneously serving as a passivation layer for the R-GO layer. The gas sensor based on R-GO has a problem that it is affected by humidity and is not available in a high humidity region. In the present invention, by using the BPB layer, the sensor using the R-GO layer as a passivation layer can solve the problem of being inoperable in a high humidity environment.

The noxious gas detection sensor capable of simultaneously performing electrical sensing and optical sensing according to the present invention can be installed in a smart device such as a smart device and can be applied to a wearable device and thus can be used as a wearable sensor or a wearable smart device.

A noxious gas detection sensor capable of simultaneously performing electrical sensing and optical sensing according to an embodiment of the present invention has been described, and a method of manufacturing such a sensor will be described below. The description of the parts overlapping with those described above will be omitted, and the description will be focused on the method characteristic.

2 is a flowchart illustrating a method of manufacturing a noxious gas detection sensor capable of simultaneously performing electrical sensing and optical sensing according to an embodiment of the present invention.

A method of manufacturing a noxious gas sensing sensor capable of simultaneously performing electrical sensing and optical sensing according to an embodiment of the present invention includes: preparing a substrate (S 210); Forming an electrode layer on the prepared substrate (S 220); Forming an R-GO layer on the substrate on which the electrode layer is formed (S 230); And forming a BPB layer on the R-GO layer (S 240).

In step S 210, a substrate is prepared. The substrate is preferably a flexible and transparent substrate as described above.

In step S 220, an electrode layer is formed on the prepared substrate. The electrode layer is composed of two electrode patterns, that is, a first electrode pattern and a second electrode pattern. The first electrode pattern and the second electrode pattern are electrically insulated to form an interdigitated electrode pattern.

The formation of the first electrode pattern and the second electrode pattern includes: coating an electrode layer on a substrate; Forming a photoresist mask pattern on a substrate coated with an electrode layer; Removing an electrode layer of the portion excluding the photoresist mask pattern using an acid; And removing the photoresist mask pattern.

An electrode is coated on a substrate and then a photosensitive liquid is coated to form a pattern by a photolithography process to form a photoresist mask pattern and an electrode layer is partially removed using an acid solution to form an electrode pattern structure and finally a photoresist mask pattern is removed .

In step S 230, an R-GO layer is formed on the substrate on which the electrode layer is formed. The step of forming the R-GO layer is performed by self-assembly. Such self-assembly may include forming an adhesive layer on the electrode using a transparent adhesive; Forming a water soluble oxidized graphene on the adhesive layer; And reducing the oxidized graphene. The step of reducing the graphene oxide is exposed to hydrazine vapor and then thermally reduced in a nitrogen atmosphere. Specifically, for the reduction of the oxidized graphene, the hydrazine vapor is exposed to the hydrazine vapor at a temperature of 40 to 60 for 15 to 20 hours, followed by heating at a temperature of 110 to 130 for 4 to 6 hours in a nitrogen atmosphere for thermal reduction, The formation is completed.

In step S 240, a BPB layer is formed on the R-GO layer. The step of forming the BPB layer on the R-GO layer is performed by immersing the BPB solution in a dip coating method.

Hereinafter, the contents of the present invention will be described in detail with concrete examples.

1, a specific embodiment of the present invention will be described. A positive photoresist AZ-5214E was spin-coated on a PET substrate 10 coated with a transparent electrode ITO, and then a photoresist mask 20 pattern was formed by a photolithography process. Subsequently, the ITO was removed for a sufficient time of about 40 to 60 seconds using a 30% HCl solution. After the photoresist mask used as a photoresist mask was sufficiently removed using acetone, the remaining portion of the sensitizing solution Water was completely removed to form an ITO electrode 30 having an interdigitated electrode array (IEA) structure.

Then, the R-GO is formed in the following order by using the self-assembly process method as follows so that the R-GO having the electric conductivity can be formed. First, an electrodeposited monolayer was formed by drop coating of poly (diallyldimethylammonium chloride) (PDDA, 20% in water). Second, water soluble oxidized graphene was formed on the PDDA by drop coating. Third, the hydrazine vapor was exposed for 18 hours at a temperature of 50 to reduce oxidized graphene. Finally, the formation of the R-GO (40) layer was completed by additionally heating at 120 for 5 hours in a nitrogen atmosphere for thermal reduction.

Then, to form a color conversion sensor for optical sensing, it was immersed in a BPB (50) solution for about 5 minutes by a dip coating method, and then coated at 450 rpm for 2 minutes to further improve the surface roughness. And the production of the noxious gas detection sensor is completed.

Then, in order to form the BPB layer on the R-GO layer, the sensor element is immersed in the BPB (50) solution for about 5 minutes by a dip coating method to help the R-GO and BPB bond. Then, in order to obtain a thin 100 nm thin film having excellent surface roughness, the coating was performed at 450 rpm for 2 minutes by spin coating and then heated at 95 ° C. for 5 minutes to complete the manufacture of the noxious gas sensing sensor.

4 is a photograph (left side) of an electrical / optical sensor having transparency flexibility according to an embodiment of the present invention and an image (left side) showing an optical microscope of a sensor having an IEA structure. All materials, including PET, have transparency and flexibility and thus have excellent permeability and flexibility.

FIG. 5 is an atomic force microscope image of R-GO (left side) and BPB / R-GO (right side). It can be confirmed that even when BPB is additionally formed, the surface roughness of nm is excellent.

FIG. 6 shows that R-GO and BPB / R-GO were successfully formed on ITO by using Raman spectroscopy. As a result, the Raman spectra of D, G, 2D, .

FIG. 7 shows the results of measurement of transmittance using an ultraviolet-visible light spectrophotometer according to the respective manufacturing steps and conditions of the IEA device, in which (1) to (4) Shows the permeability after exposure to ammonia gas. It was confirmed that all of the samples had good transmittance in the wavelength range of visible light of 550 nm, and it was confirmed that the operation was successful when noxious gas was detected.

Fig. 8 shows the results of the detection of the ammonia gas detection characteristic by manufacturing a gas sensor having a BPB / R-GO IEA structure. (a) The results showed that 25ppm ammonia was detected in a 25% humidity environment and the response and recovery characteristics were confirmed. (b) The results showed that the ammonia concentration was 5ppm, 10ppm, 20ppm, 40ppm concentration. The results of (c), (d), (e) and (f) show the results of the detection of ammonia concentration at 25%, 50%, 80% It is confirmed that the detection performance of ammonia gas is lowered at a humidity higher than 80%.

FIG. 9 shows the result of the flexibility evaluation of the gas sensor of the BPB / R-GO IEA structure. As a result, (a) shows a result of measuring the change in resistance of the R-GO with repeated mechanical deformation 50 times at each radius of curvature. (b) The result shows 5,000 repetitive mechanical deformations with a radius of curvature of 0.95cm and a frequency of 1.9Hz. As a result of measuring the resistance in real time, it can be confirmed that there is no large resistance change before and after the deformation. The results of (c) and (d) show the characteristics of sensing the ammonia gas at 20ppm while applying mechanical strain to the sensor. (c) is the result of evaluation under mechanical strain, and (d) As a result of comparing the characteristics of detecting ammonia gas before and after applying the mechanical deformation, it can be confirmed that it works well without mechanical deformation. All evaluations were performed in air at 25 ° C and 30% humidity.

FIG. 10 is an optical image of a color change of BPB according to ammonia gas concentration taken by a camera. FIG. 10 (a) is a result of comparing the color change of BPB and BPB / R-GO. It is yellow at the time of production and turns green when reacted with ammonia gas at low concentration, and changes color to blue when reacted with ammonia gas at high concentration. Even when the BPB is formed on the R-GO, it can be confirmed that there is no problem in the color change when compared with the BPB. (b), (c), (d), (e), (f) and (g) show the color change of gas sensor of BPB / R-GO IEA structure according to various ammonia gas concentration at different humidity As a result, the blue gas sensor was marked with a red dotted line.

FIG. 11 is a graph showing that the detection results can easily be visually confirmed in various environments as a result of exposing the gas sensor to ammonia in part to check the change of color in various background colors and brightness.

The description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features presented herein.

Claims (14)

Board;
An electrode layer formed on the substrate;
A reduced graphene oxide (R-GO) layer formed on the electrode layer; And
And a bromophenol blue (BPB) layer formed on the reduced oxidized graphene layer,
The color change of the bromophenol blue layer due to the electrochemical interaction between the bromophenol blue layer and the target gas and the electrical change of the reduced oxidized graphene layer occur at the same time and can be detected optically and electrically,
Hazardous gas sensor capable of simultaneous electrical and optical sensing.
The method according to claim 1,
Wherein the substrate is a flexible substrate,
Hazardous gas sensor capable of simultaneous electrical and optical sensing.
The method according to claim 1,
The electrode layer is composed of two electrode patterns, i.e., a first electrode pattern and a second electrode pattern,
Wherein the first electrode pattern and the second electrode pattern are electrically insulated and form an interdigitated electrode pattern,
Hazardous gas sensor capable of simultaneous electrical and optical sensing.
The method according to claim 1,
The reduced oxidized graphene layer is formed by self-assembly,
Hazardous gas sensor capable of simultaneous electrical and optical sensing.
The method according to claim 1,
Wherein the bromophenol blue layer is used as a passivation layer of the reduced oxidized graphene layer.
Hazardous gas sensor capable of simultaneous electrical and optical sensing.
A wearable smart device, equipped with a harmful gas sensing sensor capable of simultaneous electrical sensing and optical sensing according to any one of claims 1 to 5.
Preparing a substrate;
Forming an electrode layer on the prepared substrate;
Forming a reduced oxidized graphene layer on the substrate on which the electrode layer is formed; And
And forming a bromophenol blue layer on the reduced oxidized graphene layer,
The color change of the bromophenol blue layer due to the electrochemical interaction between the bromophenol blue layer and the target gas and the electrical change of the reduced oxidized graphene layer occur at the same time and can be detected optically and electrically,
A method of manufacturing a noxious gas detection sensor capable of simultaneous electrical sensing and optical sensing.
8. The method of claim 7,
Wherein the substrate is a flexible substrate,
A method of manufacturing a noxious gas detection sensor capable of simultaneous electrical sensing and optical sensing.
8. The method of claim 7,
The electrode layer is composed of two electrode patterns, i.e., a first electrode pattern and a second electrode pattern,
Wherein the first electrode pattern and the second electrode pattern are electrically insulated and form an interdigitated electrode pattern,
A method of manufacturing a noxious gas detection sensor capable of simultaneous electrical sensing and optical sensing.
10. The method of claim 9,
The formation of the first electrode pattern and the second electrode pattern may be performed,
Coating an electrode layer on the substrate;
Forming a photoresist mask pattern on the substrate coated with the electrode layer;
Removing an electrode layer of the portion excluding the photoresist mask pattern using an acid; And
And removing the photoresist mask pattern.
A method of manufacturing a noxious gas detection sensor capable of simultaneous electrical sensing and optical sensing.
8. The method of claim 7,
The step of forming the reduced oxidized graphene layer may be performed by self-
A method of manufacturing a noxious gas detection sensor capable of simultaneous electrical sensing and optical sensing.
12. The method of claim 11,
The self-
Forming an adhesive layer on the electrode using a transparent adhesive;
Forming a water-soluble oxide graphene layer on the adhesive layer; And
And reducing the graphene oxide.
A method of manufacturing a noxious gas detection sensor capable of simultaneous electrical sensing and optical sensing.
13. The method of claim 12,
The step of reducing the graphene oxide comprises:
Hydrazine vapor, followed by thermal reduction in a nitrogen atmosphere,
A method of manufacturing a noxious gas detection sensor capable of simultaneous electrical sensing and optical sensing.
8. The method of claim 7,
The step of forming a bromophenol blue layer on the reduced oxidized graphene layer comprises:
A dip coating method is used to dip into a BPB solution.
A method of manufacturing a noxious gas detection sensor capable of simultaneous electrical sensing and optical sensing.

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