Disclosure of Invention
In view of the above, the present invention aims to provide a nano heterojunction ethylene sensitive film, and a preparation method and an application thereof. The nano heterojunction ethylene sensitive film provided by the invention can realize the detection of low-concentration ethylene.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a nano heterojunction ethylene sensitive film which comprises a substrate and a sensitive layer, wherein the sensitive layer comprises reduced graphene oxide and a tungsten chalcogenide, and the mass ratio of the reduced graphene oxide to the tungsten chalcogenide is 1: 0.2 to 1, wherein the tungsten chalcogenide is tungsten disulfide or tungsten diselenide.
Preferably, the thickness of the nano heterojunction ethylene sensitive film is 60-150 nm.
Preferably, the substrate is a silicon wafer, a metal interdigital electrode on a flexible substrate or a metal annular electrode on the flexible substrate.
The invention also provides a preparation method of the nano heterojunction ethylene sensitive film, which comprises the following steps:
mixing a graphene oxide aqueous solution with a tungsten chalcogenide aqueous solution to obtain a mixed solution;
preheating a substrate to obtain a preheated substrate;
spraying the mixed solution on the surface of the preheated substrate to obtain a deposition substrate;
and annealing the deposition substrate to obtain the nano heterojunction ethylene sensitive film.
Preferably, the concentration of the graphene oxide aqueous solution and the concentration of the tungsten chalcogenide aqueous solution are both 0.5 mg/mL.
Preferably, the spraying takes nitrogen as carrier gas, the flow rate of the nitrogen is 8-10 mu L/s, and the air pressure is 18-20 psi.
The invention also provides a preparation method of the nano heterojunction ethylene sensitive film, which comprises the following steps:
providing a polydiallyl ammonium chloride aqueous solution, a graphene oxide aqueous solution and a tungsten chalcogenide aqueous solution;
sequentially dipping a substrate in the polydiallylammonium chloride aqueous solution, water, the graphene oxide aqueous solution, water, the polydiallylammonium chloride aqueous solution, water, the tungsten chalcogenide aqueous solution and water to obtain a dipped substrate;
and annealing the impregnated substrate to obtain the nano heterojunction ethylene sensitive film.
Preferably, the mass content of the poly-diallyl ammonium chloride in the poly-diallyl ammonium chloride aqueous solution is 10-30%; the graphene oxide aqueous solution and the tungsten chalcogenide aqueous solution have concentrations of 0.2 to 0.8mg/mL independently.
Preferably, the annealing temperature is 150-300 ℃ independently, and the time is 30-60 min independently.
The invention also provides the application of the nano heterojunction ethylene sensitive film in the technical scheme in the field of ethylene detection.
The invention provides a nano heterojunction ethylene sensitive film which comprises a substrate and a sensitive layer, wherein the sensitive layer comprises reduced graphene oxide and a tungsten chalcogenide, and the mass ratio of the reduced graphene oxide to the tungsten chalcogenide is 1: 0.2 to 1, wherein the tungsten chalcogenide is tungsten disulfide or tungsten diselenide. After the nano heterojunction ethylene sensitive film provided by the invention is contacted with ethylene, the resistance of the nano heterojunction ethylene sensitive film is changed, and the concentration of the ethylene can be detected by detecting the resistance of the nano heterojunction ethylene sensitive film.
Compared with the prior art, the invention has the following beneficial effects:
the invention adopts two-dimensional materials to reduce graphene oxide and tungsten chalcogenide as an ethylene sensitive material system, the reduced graphene oxide has the performance of a p-type semiconductor material, the tungsten chalcogenide has the performance of an n-type semiconductor material, the reduced graphene oxide and the tungsten chalcogenide are loaded on a substrate, and the interface of the reduced graphene oxide and the tungsten chalcogenide forms a heterojunction structure, also called a van der Waals force heterojunction. The nano heterojunction structure has unique properties and effects in the field of gas-sensitive detection: the lamination of the two-dimensional material prevents the stacking of the sheets, thereby increasing the contact area with gas molecules and being beneficial to the free diffusion of gas among the sheets; different sheet layers are closely connected through Van der Waals force, and the original properties of the two-dimensional material are kept; after the recombination, an n-p/n-n/p-p heterojunction is formed on the interface, and an interface potential barrier can block the electron transmission generated by the contact of gas with low electron affinity, so that the selectivity is improved; the heterojunction facilitates charge separation, avoiding charge accumulation during gas adsorption/desorption, thereby improving sensitivity and response speed. In addition, the tungsten chalcogenide has excellent catalytic capability, and can reduce the activation energy required by the gas adsorption/desorption process after being compounded with the reduced graphene oxide, effectively shorten the response/recovery time and improve the selectivity. By utilizing the characteristics of the nano heterojunction and the catalytic capacity of the tungsten chalcogenide to ethylene, the reduced graphene oxide/tungsten chalcogenide heterojunction film has a strong adsorption effect on ethylene at room temperature, after the reduced graphene oxide/tungsten chalcogenide heterojunction film is contacted with ethylene, the concentration of holes or electrons in a sensitive material layer in the heterojunction film is changed by the ethylene in a mode of donating or capturing electrons, so that the resistance of the graphene/tungsten chalcogenide heterojunction film is changed, and the concentration of the ethylene can be obtained through analysis by detecting the resistance change of the sensitive material film, namely, the response to low-concentration ethylene is realized at room temperature.
Detailed Description
The invention provides a nano heterojunction ethylene sensitive film which comprises a substrate and a sensitive layer, wherein the sensitive layer comprises reduced graphene oxide and a tungsten chalcogenide, and the mass ratio of the reduced graphene oxide to the tungsten chalcogenide is 1: 0.2 to 1, wherein the tungsten chalcogenide is tungsten disulfide or tungsten diselenide.
In the present invention, the mass ratio of the reduced graphene oxide to the tungsten-based chalcogenide is preferably 1: 0.2.
in the invention, the thickness of the nano heterojunction ethylene sensitive film is preferably 60-150 nm.
In the present invention, the reduced graphene oxide and the tungsten-based chalcogenide are preferably supported on the substrate in the form of a mixture.
In the present invention, the reduced graphene oxide and the tungsten-based chalcogenide are preferably supported on a substrate in a layered form, and more preferably, the nano heterojunction ethylene sensitive film sequentially includes a stacked substrate, a reduced graphene oxide layer, and a tungsten-based chalcogenide layer, and the substrate is in contact with the reduced graphene oxide layer because the area of the reduced graphene oxide layer is larger than that of the tungsten-based chalcogenide layer.
In the invention, the substrate is preferably a silicon wafer, a metal interdigital electrode on a flexible substrate or a metal annular electrode on the flexible substrate. The source of the substrate is not particularly limited in the present invention, and commercially available products known to those skilled in the art may be used.
The invention also provides a preparation method (spraying method) of the nano heterojunction ethylene sensitive film, which comprises the following steps:
mixing a graphene oxide aqueous solution with a tungsten chalcogenide aqueous solution to obtain a mixed solution;
preheating a substrate to obtain a preheated substrate;
spraying the mixed solution on the surface of the preheated substrate to obtain a deposition substrate;
and annealing the deposition substrate to obtain the nano heterojunction ethylene sensitive film.
The method comprises the step of mixing a graphene oxide aqueous solution with a tungsten chalcogenide aqueous solution to obtain a mixed solution.
In the present invention, the concentrations of the graphene oxide aqueous solution and the tungsten chalcogenide aqueous solution are both preferably 0.5mg/mL, and the amount of the graphene oxide aqueous solution and the tungsten chalcogenide aqueous solution used is not particularly limited, and the mass ratio of the reduced graphene oxide to the tungsten chalcogenide can be ensured to be 1: 0.2 to 1.
The invention preheats the substrate to obtain the preheated substrate.
In the invention, the preheating temperature is preferably 50-80 ℃, and the preheating can accelerate the volatilization of water in the mixed liquid.
In the invention, before use, the substrate is preferably subjected to ultrasonic cleaning in deionized water, ethanol and acetone in sequence, and then is dried by nitrogen. The specific manner of the ultrasonic cleaning and the nitrogen blow-drying is not particularly limited, and can be a manner known to those skilled in the art.
After the preheating substrate and the mixed solution are obtained, the mixed solution is sprayed on the surface of the preheating substrate to obtain the deposition substrate.
In the invention, the spraying is preferably carried out by taking nitrogen as a carrier gas, the flow rate of the nitrogen is preferably 8-10 mu L/s, and the air pressure is preferably 18-20 psi. In an embodiment of the invention, preferably, nitrogen is used as a carrier gas, a spray pen is fixed 5-10 cm above the preheating substrate, the mixed solution is dripped into a flowing cup of the spray pen, a switch of the spray pen is pressed, and the mixed solution is deposited on the preheating substrate in a form of a mist mixed solution.
After the deposition substrate is obtained, annealing the deposition substrate to obtain the nano heterojunction ethylene sensitive film.
In the invention, the annealing temperature is preferably 150-300 ℃, more preferably 200-250 ℃, and the time is preferably 30-60 min, more preferably 40-50 min. During the annealing, the graphene oxide is reduced.
The invention also provides another preparation method (layer-by-layer self-assembly method) of the nano heterojunction ethylene sensitive film, which comprises the following steps:
providing a polydiallyl ammonium chloride aqueous solution, a graphene oxide aqueous solution and a tungsten chalcogenide aqueous solution;
sequentially dipping a substrate in the polydiallylammonium chloride aqueous solution, water, the graphene oxide aqueous solution, water, the polydiallylammonium chloride aqueous solution, water, the tungsten chalcogenide aqueous solution and water to obtain a dipped substrate;
and annealing the impregnated substrate to obtain the nano heterojunction ethylene sensitive film.
The invention provides a polydiallylammonium chloride aqueous solution, a graphene oxide aqueous solution and a tungsten chalcogenide aqueous solution.
In the invention, the mass content of the poly-diallyl ammonium chloride in the poly-diallyl ammonium chloride aqueous solution is preferably 10-30%, and more preferably 15-25%; the concentrations of the graphene oxide aqueous solution and the tungsten chalcogenide aqueous solution are preferably 0.2 to 0.8mg/mL, and more preferably 0.4 to 0.6mg/mL, independently. According to the invention, the poly-diallyl ammonium chloride aqueous solution provides polycation, the layer-by-layer self-assembly method is electrostatic self-assembly, a film can be formed only by depending on the positive electricity or the negative electricity of a material band, the graphene oxide is negatively charged, and the tungsten disulfide and the tungsten diselenide are negatively charged.
The method comprises the step of sequentially dipping a substrate into the poly-diallyl ammonium chloride aqueous solution, water, the graphene oxide aqueous solution, water, the poly-diallyl ammonium chloride aqueous solution, water, the tungsten chalcogenide aqueous solution and water to obtain the dipped substrate.
In the invention, before use, the substrate is preferably subjected to ultrasonic cleaning in deionized water, ethanol and acetone in sequence, and then is dried by nitrogen. The specific manner of the ultrasonic cleaning and the nitrogen blow-drying is not particularly limited, and can be a manner known to those skilled in the art.
In the present invention, the water is preferably deionized water.
In the invention, the time for immersing in the polydiallylammonium chloride aqueous solution, the graphene oxide aqueous solution and the tungsten chalcogenide aqueous solution is preferably 10-20 min independently; the time for immersing in water is independently preferably 3 to 5 min.
In the invention, the substrate is firstly immersed in the polydiallyl ammonium chloride aqueous solution and then immersed in water, so that redundant polydiallyl ammonium chloride can be washed away.
In the present invention, the impregnation is preferably performed by fixing the object to be impregnated on a glass sheet, and vertically putting the object to be impregnated into an impregnation solution.
In the present invention, after each impregnation is completed, it is preferably taken out vertically and then blown dry with nitrogen.
After the impregnated substrate is obtained, annealing treatment is carried out on the impregnated substrate to obtain the nano heterojunction ethylene sensitive film. In the present invention, the annealing treatment is preferably the same as the annealing treatment described in the above scheme, and is not described herein again.
The invention also provides the application of the nano heterojunction ethylene sensitive film in the technical scheme in the field of ethylene detection.
In the invention, the concentration of the ethylene in the application is preferably 10-100 ppm, and more preferably 10-50 ppm.
The invention is not particularly limited to the specific manner of use described, as such may be readily adapted by those skilled in the art.
In order to further illustrate the present invention, the nano heterojunction ethylene sensitive film provided by the present invention, the preparation method and the application thereof are described in detail below with reference to examples, but they should not be construed as limiting the scope of the present invention.
Example 1
The nanometer heterojunction ethylene sensitive film comprises a silicon wafer substrate and a sensitive layer, wherein the sensitive layer comprises reduced graphene oxide and tungsten disulfide, and the mass ratio of the reduced graphene oxide to the tungsten disulfide is 1: 0.2, the film thickness is 150 nm.
The nano heterojunction ethylene sensitive film is prepared by adopting a spraying method, and comprises the following steps:
(1)0.5mg/mL of graphene oxide aqueous solution and 0.5mg/mL of tungsten disulfide aqueous solution according to the mass ratio of reduced graphene oxide to tungsten disulfide of 1: 0.2, uniformly mixing to obtain a mixed solution;
(2) ultrasonically cleaning the substrate in deionized water, ethanol and acetone solution respectively, drying the substrate with nitrogen, and fixing the substrate on a hot plate at the temperature of 50 ℃;
(3) nitrogen was used as a carrier gas at a flow rate of 8. mu.L/s and a pressure of 18psi, and the pen was fixed 15cm directly above the substrate. Respectively dripping 0.5mL of mixed solution and 1mL of mixed solution into a flowing cup of a spray pen, pressing a switch of the spray pen, and depositing the atomized mixed solution on a substrate;
(4) and (3) annealing the substrate at 150 ℃ for 60min to obtain the reduced graphene oxide/tungsten disulfide sensitive film device, namely a nano heterojunction ethylene sensitive film (reduced graphene oxide/tungsten disulfide nano heterojunction composite film).
Fig. 1 and 2 are responses of the reduced graphene oxide/tungsten disulfide nano-heterojunction composite thin film device with spraying amount of 0.5mL and 1mL to 50ppm ethylene, and the response rates (change resistance/initial resistance) are 0.95% and 1.2%, respectively. And as can be seen from fig. 1-2, with the increase of the thickness of the film, the resistance of the sensor device is reduced, the surface of the film is more compact, and better adsorption conditions are provided for ethylene molecules.
Example 2
The nanometer heterojunction ethylene sensitive film comprises a silicon wafer substrate and a sensitive layer, wherein the sensitive layer comprises reduced graphene oxide and tungsten diselenide, and the mass ratio of the reduced graphene oxide to the tungsten diselenide is 1: 1, the thickness of the film is 60 nm.
The nanometer heterojunction ethylene sensitive film is prepared by adopting a layer-by-layer self-assembly method, and comprises the following steps:
(1) polydiallyl ammonium chloride is dispersed in deionized water, and the mass concentration is 10%; the concentration of the graphene oxide aqueous solution is 0.2mg/mL, and the concentration of the tungsten diselenide aqueous solution is 0.8 mg/mL; putting the three solutions into 20mL beakers respectively;
(2) ultrasonically cleaning the substrate in deionized water, ethanol and acetone solution, drying the substrate with nitrogen, and fixing the substrate on a glass slide;
(3) vertically and slowly placing the substrate fixed on the glass slide into a polydiallyl ammonium chloride aqueous solution for 10min, vertically and slowly taking out, and drying by nitrogen;
(4) the substrate fixed on the glass slide is vertically and slowly put into deionized water for 5min, vertically and slowly taken out, and is dried by nitrogen;
(5) vertically and slowly placing a substrate fixed on a glass slide into a graphene oxide aqueous solution for 20min, vertically and slowly taking out, and drying by nitrogen;
(6) vertically and slowly putting deionized water into the substrate fixed on the glass slide for 3min, vertically and slowly taking out, and drying by using nitrogen;
(7) vertically and slowly placing the substrate fixed on the glass slide into a polydiallyl ammonium chloride aqueous solution for 20min, vertically and slowly taking out, and drying by nitrogen;
(8) the substrate fixed on the glass slide is vertically and slowly put into deionized water for 4min, vertically and slowly taken out, and is dried by nitrogen;
(9) vertically and slowly placing a substrate fixed on a glass slide, vertically and slowly taking out a tungsten diselenide aqueous solution for 15min, and drying by nitrogen;
(10) vertically and slowly putting deionized water into the substrate fixed on the glass slide for 3min, vertically and slowly taking out, and drying by using nitrogen;
(11) and taking down the substrate, and carrying out annealing treatment on the substrate at 300 ℃ for 30min to obtain the reduced graphene oxide/tungsten diselenide sensitive thin film device, namely the nano heterojunction ethylene sensitive thin film device.
Fig. 3 and 4 are real-time response/recovery curves of the resistance of the reduced graphene oxide and reduced graphene oxide/tungsten diselenide thin film sensor device to 10-50ppm ethylene at room temperature, respectively. It can be seen from the figure that after the ethylene gas is contacted, the resistance of the prepared thin film sensing device all shows a downward trend, which indicates that the sensitive material is in the characteristic of p-type material, the resistance of the thin film sensing device quickly reaches saturation and keeps a basically stable state, and after the ethylene gas is turned off, the resistance of the thin film sensing device gradually returns to an initial value. As the concentration of the contact ethylene gas increases, the resistance change of the thin film sensor device increases.
Fig. 5 is a real-time response rate curve of the reduced graphene oxide and reduced graphene oxide/tungsten diselenide composite thin film sensor device to 10-50ppm of ethylene at room temperature, where the response rate is defined as a resistance change value after contacting ethylene gas divided by an initial resistance value before contacting ethylene, and the response rate is adopted to better compare response capacities of the two thin film sensor devices to ethylene. As can be seen from fig. 5, the reduced graphene oxide/tungsten diselenide composite thin film sensing device shows a greater response to ethylene than the reduced graphene oxide thin film sensing device, mainly due to the electron transfer promotion and synergistic enhancement effect of the composite material exerted by the nano heterojunction formed by the reduced graphene oxide and the tungsten diselenide.
The foregoing is merely a preferred embodiment of the invention and is not intended to limit the invention in any manner. It should be noted that, for those skilled in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be construed as the protection scope of the present invention.