Electrode for electrochemical biosensor for selectively detecting dopamine, electrochemical biosensor comprising same, and manufacturing method therefor

Abstract

The present invention relates to an electrode for an electrochemical biosensor for selectively detecting dopamine, an electrochemical biosensor comprising same, and a manufacturing method therefor and, specifically, to an electrode for an electrochemical biosensor for selectively detecting dopamine, an electrochemical biosensor comprising same, and a manufacturing method therefor, wherein the electrode has a lower trace detection limit compared with an existing dopamine detection sensor and exhibits superb stability, reproducibility, and selectivity.

Description

Electrode for an electrochemical biosensor for selectively detecting dopamine, an electrochemical biosensor including the same, and a method for manufacturing the same

[0001] The present invention relates to an electrode for an electrochemical biosensor for selectively detecting dopamine, an electrochemical biosensor including the same, and a method for manufacturing the same. The present invention relates to an electrode for an electrochemical biosensor for selectively detecting dopamine having a detection limit of a small amount and excellent stability, reproducibility, and selectivity compared to existing dopamine detection sensors, an electrochemical biosensor including the same, and a method for manufacturing the same.

[0002]

[0003] Dopamine, a substance belonging to the catecholamine and phenylethylamine family, plays a crucial role in the central nervous system, cardiovascular system, renal system, and hormonal system, and is an indicator of human metabolism. Abnormal dopamine levels in the human brain (either too low or too high) can lead to neurodegenerative diseases such as Alzheimer's and Parkinson's.

[0004] Therefore, there is a need to develop a simple, selective, and sensitive method to determine dopamine levels in the human body.

[0005] Pain is a common symptom in Parkinson's disease, and paracetamol has been frequently used to relieve this pain. Both paracetamol and dopamine are electrochemically active substances and are often found together in the extracellular fluid of the central nervous system, making them essential for human metabolism. Furthermore, tyrosine, a nonessential amino acid, has been reported to be a precursor to many neurotransmitters, such as dopamine, thyroxine, and epinephrine. Tyrosine plays a key role in the development of Alzheimer's and Parkinson's diseases, and studies have shown that tyrosine supplementation can increase norepinephrine and minimize orthostatic hypotension in Parkinson's patients. Because pharmacological treatment of Parkinson's disease often requires biomolecules such as dopamine, paracetamol, and tyrosine, it is crucial to establish simple and sensitive electrochemical methods that can simultaneously measure these substances.

[0006] Meanwhile, electrochemical sensors are widely used for the detection and analysis of chemical substances, playing a crucial role in biomedical and medical applications due to their high sensitivity and selectivity. The demand for electrochemical sensors continues to grow in diverse fields, including environmental monitoring, food safety assessment, pharmaceutical development, and biosensing.

[0007] As is well known, the electrochemical properties of an electrode are influenced by its electronic conductivity and large active surface area. Therefore, designing a composite material by combining an electrocatalytic material with a highly conductive material that modifies the electrode surface is emerging as an effective strategy for improving the electrochemical properties of a sensor.

[0008] Due to the rapid advancement of nanotechnology, a variety of nanomaterials are being used to fabricate electrodes for electrochemical sensing applications. Among these nanomaterials, transition metal nanoparticles, such as platinum (Pt), gold (Au), and palladium (Pd), are attracting particular attention due to their superior electrocatalytic activity and surface area. Currently, platinum-based nanoparticles are the most widely used, but their scarcity and high cost are disadvantages.

[0009] In this regard, recent studies have shown that palladium-based nanoparticles could be a viable alternative for developing electrochemical applications compared to platinum and gold due to their highly heterogeneous catalytic activity, low cost, and non-toxic properties. To enhance the performance of palladium-based nanoparticles and reduce palladium usage, selecting an appropriate support matrix that is stable, inexpensive, and capable of synergistic effects is essential. The most effective approach is to incorporate metal oxides into the catalyst to enhance electrocatalytic activity through a dual-functional mechanism.

[0010]

[0011] The present invention has been devised to solve the above problems, and has a high performance in detecting biochemical substances such as dopamine, and can be applied to medical diagnosis such as measuring the concentration of a specific drug in blood, and the purpose of the present invention is to provide an electrode for an electrochemical biosensor for selectively detecting dopamine, which can play an important role in disease diagnosis and treatment through rapid and sensitive detection, an electrochemical biosensor including the same, and a method for manufacturing the same.

[0012]

[0013] In order to solve the above-described problem, the electrode for an electrochemical biosensor for selectively detecting dopamine of the present invention may include an electrode and reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on a surface formed on one side of the electrode.

[0014] In a preferred embodiment of the present invention, the palladium-cerium oxide nanocomposite may have an average particle size of 7 to 10 nm.

[0015] In a preferred embodiment of the present invention, the palladium-cerium oxide nanocomposite may have an average crystalline size of 6.6 to 10.6 nm.

[0016] In a preferred embodiment of the present invention, the electrode for the electrochemical biosensor of the present invention has a thickness of 0.15 to 0.25 cm 2 It can have an electrochemically active surface area (EASA).

[0017] Meanwhile, the electrochemical biosensor for selectively detecting dopamine of the present invention may include an electrode for the electrochemical biosensor for selectively detecting dopamine of the present invention.

[0018] Furthermore, the method for manufacturing an electrode for an electrochemical biosensor for selectively detecting dopamine of the present invention may include a first step of preparing an electrode and a reduced graphene oxide aqueous solution having a palladium-cerium oxide nanocomposite formed on the surface thereof, respectively, and a second step of applying the reduced graphene oxide aqueous solution having a palladium-cerium oxide nanocomposite formed on the surface thereof to one surface of the electrode and then drying the solution to form reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface thereof on one surface of the electrode.

[0019] In a preferred embodiment of the present invention, a reduced graphene oxide aqueous solution having a palladium-cerium oxide nanocomposite formed on the surface is prepared by: Step 1-1 of preparing a graphene oxide dispersion, a solution containing a cerium oxide (CeO2) precursor, and a solution containing a palladium (Pd) precursor, respectively; Step 1-2 of mixing the graphene oxide dispersion, the solution containing a cerium oxide (CeO2) precursor, and the solution containing a palladium (Pd) precursor to prepare a mixture, and adding ascorbic acid and a pH adjuster to the mixture to prepare a reaction mixture having a pH of 10 to 14; Step 1-3 of stirring and reacting the reaction mixture at a temperature of 120 to 160°C for 3 to 7 hours to prepare a reaction product; Step 1-4 of drying the reaction product to prepare reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface; and Step 1-5 of adding the reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface to methanol. It can be manufactured by including steps 1-5 of manufacturing a reduced graphene oxide aqueous solution in which a palladium-cerium oxide nanocomposite is formed on the surface by dissolving graphene oxide and then ultrasonicating it.

[0020] In a preferred embodiment of the present invention, in step 1-1, graphene oxide, cerium oxide (CeO2) precursor, and palladium (Pd) precursor may have a weight ratio of 1:0.47 to 0.72:0.58 to 0.88.

[0021] In a preferred embodiment of the present invention, a graphene oxide dispersion can be prepared by adding graphene powder, sodium nitrate (NaNO3), and potassium permanganate (KMnO4) to sulfuric acid (H2SO4), stirring, and reacting to prepare a reactant, adding hydrogen peroxide (H2O2) to the reactant, filtering, and then washing the supernatant of the filtrate with ultrapure water to obtain a supernatant having a pH of 5 to 9, centrifuging a precipitate contained in the supernatant, and then drying to prepare graphene oxide, and adding the graphene oxide to ethylene glycol, and ultrasonicating to prepare a graphene oxide dispersion.

[0022]

[0023] The electrode for an electrochemical biosensor for selectively detecting dopamine of the present invention, the electrochemical biosensor including the same, and the method for manufacturing the same provide high detection sensitivity and selectivity, and the high detection ability of the sensor can be usefully utilized in various fields such as detection of hazardous substances in the environment, measurement of the concentration of specific drugs in blood, and detection of toxic substances in the food industry.

[0024] In addition, the electrode for an electrochemical biosensor for selectively detecting dopamine of the present invention, the electrochemical biosensor including the same, and the manufacturing method thereof suggest the possibility of a new sensor technology, which can play a technological leading role in the relevant field and greatly contribute to the technological advancement of the related industry.

[0025] In addition, the electrode for an electrochemical biosensor for selectively detecting dopamine of the present invention, the electrochemical biosensor including the same, and the method for manufacturing the same can equally apply high detection ability and selectivity to biological samples, and therefore can be used for detection of specific substances and detection of biological activities in biological materials.

[0026]

[0027] Figure 1(A) is a graph showing a PXRD spectrum of reduced graphene oxide, b is a PXRD spectrum of reduced graphene oxide having palladium nanoparticles formed on the surface manufactured in Comparative Preparation Example 1, c is a PXRD spectrum of reduced graphene oxide having cerium oxide nanoparticles formed on the surface manufactured in Comparative Preparation Example 2, and d is a graph showing a PXRD spectrum of reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface manufactured in Preparation Example 2.

[0028] FIG. 1(B) shows the XPS full survey spectrum of the reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface prepared in Preparation Example 2, FIG. 1(C) shows the high-resolution XPS spectrum of C 1s in the reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface prepared in Preparation Example 2, FIG. 1(D) shows the high-resolution XPS spectrum of O 1s in the reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface prepared in Preparation Example 2, FIG. 1(E) shows the high-resolution XPS spectrum of Pd 3d in the reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface prepared in Preparation Example 2, and FIG. 1(F) shows the high-resolution XPS spectrum of Ce 3d in the reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface prepared in Preparation Example 2. It shows the spectrum (high-resolution XPS spectrum).

[0029] FIG. 2(A) and FIG. 2(B) are FESEM images of reduced graphene oxide having palladium nanoparticles formed on the surface manufactured in Comparative Preparation Example 1, FIG. 2(C) is an EDX spectrum of reduced graphene oxide having palladium nanoparticles formed on the surface manufactured in Comparative Preparation Example 1, and FIG. 2(D) is a mapping image, a C atom mapping image, a Pd atom mapping image, and an O atom mapping image of mixed C atoms, Pd atoms, and O atoms of reduced graphene oxide having palladium nanoparticles formed on the surface manufactured in Comparative Preparation Example 1.

[0030] FIG. 2(E) and FIG. 2(F) are FESEM images of reduced graphene oxide having cerium oxide nanoparticles formed on the surface manufactured in Comparative Preparation Example 2, FIG. 2(G) is an EDX spectrum of reduced graphene oxide having cerium oxide nanoparticles formed on the surface manufactured in Comparative Preparation Example 2, and FIG. 2(H) is a mapping image, a C atom mapping image, a Ce atom mapping image, and an O atom mapping image of mixed C atoms, Ce atoms, and O atoms of reduced graphene oxide having cerium oxide nanoparticles formed on the surface manufactured in Comparative Preparation Example 2.

[0031] FIG. 2(I) and FIG. 2(J) are FESEM images of reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface manufactured in Preparation Example 2, FIG. 2(K) is an EDX spectrum of reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface manufactured in Preparation Example 2, and FIG. 2(L) is a mapping image of mixed C atoms, O atoms, Pd atoms, and Ce atoms of reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface manufactured in Preparation Example 2, a C atom mapping image, a Ce atom mapping image, an O atom mapping image, and a Pd atom mapping image.

[0032] FIG. 3(A) to FIG. 3(B) are TEM images of reduced graphene oxide having palladium nanoparticles formed on the surface manufactured in Comparative Preparation Example 1, FIG. 3(C) is a TEM and HRTEM image of reduced graphene oxide having palladium nanoparticles formed on the surface manufactured in Comparative Preparation Example 1, and FIG. 3(D) is a particle histogram of reduced graphene oxide having palladium nanoparticles formed on the surface manufactured in Comparative Preparation Example 1.

[0033] FIG. 3(E) to FIG. 3(F) are TEM images of reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface manufactured in Preparation Example 2, FIG. 3(G) is a TEM and HRTEM image of reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface manufactured in Preparation Example 2, and FIG. 3(H) is a particle histogram of reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface manufactured in Preparation Example 2.

[0034] Figure 4(A) shows 1.0 mM [Fe(CN)6] in 0.1 M KCl solution. 3- / 4- This is a graph showing the CV curves measured at a scanning rate of 100 mV for each of the dopamine detection electrode (=Pd-CeO2 / rGO / GCE) manufactured in Example 1, the dopamine detection electrode (=Pd / rGO / GCE) manufactured in Comparative Example 1, the dopamine detection electrode (=CeO2 / rGO / GCE) manufactured in Comparative Example 2, and the glassy carbon electrode (=bare GCE).

[0035] Figure 4(B) shows 1.0 mM [Fe(CN)6] in 0.1 M KCl solution. 3- / 4- In this case, the graph shows the CV curve measured over a scanning rate range of 10 to 100 mV of the dopamine detection electrode (=Pd-CeO2 / rGO / GCE) manufactured in Example 1.

[0036] FIG. 4(C) is a graph showing a Tafel plot drawn between the peak potential and the current's logarithm of each of the dopamine detection electrode (=Pd-CeO2 / rGO / GCE) manufactured in Example 1, the dopamine detection electrode (=Pd / rGO / GCE) manufactured in Comparative Example 1, the dopamine detection electrode (=CeO2 / rGO / GCE) manufactured in Comparative Example 2, and the glassy carbon electrode (=bare GCE), based on the CV investigation results.

[0037] Figure 4(D) shows the electrochemical impedance spectroscopy (EIS) of 1.0 mM [Fe(CN)6] in 0.1 M KCl solution. 3- / 4- This is a graph showing the Nyquist plots of the dopamine detection electrode (=Pd-CeO2 / rGO / GCE) manufactured in Example 1, the dopamine detection electrode (=Pd / rGO / GCE) manufactured in Comparative Example 1, the dopamine detection electrode (=CeO2 / rGO / GCE) manufactured in Comparative Example 2, and the glassy carbon electrode (=bare GCE).

[0038] FIG. 5(A) and FIG. 5(B) are graphs showing the results of cyclic voltammetry (CV) performed at 100 mV / s in 0.1 M PBS (pH 7) containing 1 mM dopamine to evaluate the electro-oxidation of dopamine in each of the dopamine detection electrode (= Pd-CeO2 / rGO / GCE) manufactured in Example 1, the dopamine detection electrode (= Pd / rGO / GCE) manufactured in Comparative Example 1, the dopamine detection electrode (= CeO2 / rGO / GCE) manufactured in Comparative Example 2, and the glassy carbon electrode (= bare GCE).

[0039] Figure 5(C) is a graph showing the effect of pH on the electrochemical behavior of 1 mM dopamine in the dopamine detection electrode manufactured in Example 1 through CV using 0.1 M PBS (pH 5 to 9) of various pHs at 100 mV / s.

[0040] Figure 5(D) is a plot showing the peak current and potential of the dopamine detection electrode prepared in Example 1 for dopamine oxidation in relation to various pH levels.

[0041] Figure 6(A) is a graph showing CV curves for various scan rates of 10 to 200 mV / s in 1 mM dopamine dissolved in 0.1 M sterile phosphate buffer solution (PBS) (pH 7) for the dopamine detection electrode manufactured in Example 1.

[0042] Figure 6(B) is a graph showing a plot between the anodic and cathodic peak currents of dopamine and various sweep rates for the dopamine detection electrode manufactured in Example 1.

[0043] FIG. 6(C) is a graph showing a plot between the log of peak current versus the log of scan rate for the dopamine detection electrode manufactured in Example 1, and FIG. 6(D) is a graph showing a plot between the log of scan rate versus the log of peak transition for the dopamine detection electrode manufactured in Example 1.

[0044] Figure 7(A) is a DPV curve showing the degree of dopamine detection in the dopamine detection electrode manufactured in Example 1 at various concentrations of dopamine dissolved in 0.1 M sterile phosphate buffer solution (PBS) (pH 7).

[0045] Figure 7(B) is a DPV curve showing the degree of dopamine detection at the dopamine detection electrode manufactured in Example 1 in various concentrations of dopamine, 5 μM paracetamol (PC), and 10 μM tyrosine (TY) dissolved in 0.1 M sterile phosphate buffer solution (PBS) (pH 7).

[0046] Figure 7(C) is a DPV curve showing the degree of dopamine detection in the dopamine detection electrode manufactured in Example 1 at various concentrations of paracetamol (PC), 5 μM dopamine (DA), and 10 μM tyrosine (TY) dissolved in 0.1 M sterile phosphate buffer solution (PBS) (pH 7).

[0047] Figure 7(D) is a DPV curve showing the degree of dopamine detection in the dopamine detection electrode manufactured in Example 1 at various concentrations of tyrosine (TY), 5 μM dopamine (DA), and 5 μM paracetamol (PC) dissolved in 0.1 M sterile phosphate buffer solution (PBS) (pH 7).

[0048] Figures 7(E) and 7(F) are DPV curves showing the degree of dopamine detection at the dopamine detection electrode manufactured in Example 1 in various concentrations of dopamine (DA), various concentrations of tyrosine (TY), and various concentrations of paracetamol (PC) dissolved in 0.1 M sterile phosphate buffer solution (PBS) (pH 7).

[0049] Figures 8(A) and 8(B) show the results of evaluating the selectivity of the dopamine detection electrode manufactured in Example 1, in which 30 μM dopamine (DA) was added to 0.1 M sterile phosphate buffer solution (PBS) (pH 7) as well as Na as an interferent. + , Al 3+ , AA (ascorbic acid), glucose, Zn 2+ and NO 3- This graph shows the results of performing DPV on this dissolved solution.

[0050] Figure 8(C) is a graph showing that, in order to evaluate the reproducibility of the dopamine detection electrode, six dopamine detection electrodes were manufactured and prepared as in Example 1, and DPV was performed on each of the six dopamine detection electrodes.

[0051] Figure 8(D) is a graph showing DPV of the dopamine detection electrode manufactured in Example 1 before and after storage to evaluate the storage stability of the dopamine detection electrode.

[0052] Figure 9(A) is a graph showing the results of DPV performed on a pharmaceutical injection sample and when dopamine (DA) was added at different concentrations, and Figure 9(C) is a graph showing the results of DPV performed on a human serum sample and when dopamine (DA) was added at different concentrations.

[0053] Figure 9(B) shows the peak current (I) according to the amount of pharmaceutical injection sample added. pa ) is a graph showing a linear plot of dopamine (DA), and Fig. 9(D) is a graph showing a linear plot of peak current versus dopamine (DA) according to the amount of human serum sample added.

[0054]

[0055] Hereinafter, with reference to the attached drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. The present invention may be implemented in various different forms and is not limited to the embodiments described herein. In the drawings, parts irrelevant to the description have been omitted for clarity of description, and the same reference numerals are assigned to identical or similar components throughout the specification.

[0056]

[0057] The electrode for an electrochemical biosensor for selectively detecting dopamine of the present invention may include an electrode and reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on a surface formed on one side of the electrode.

[0058] At this time, the electrode may include various electrodes used in the art as a working electrode, and preferably may be a glassy carbon electrode, a rotating disk electrode (RDE), a rotating ring-disk electrode (RRDE), a screen-printed carbon electrode, a carbon nanotube film, or an ITO electrode, and more preferably may be a glassy carbon electrode.

[0059] Meanwhile, the palladium-cerium oxide nanocomposite of the present invention may have an average particle size of 7 to 10 nm, preferably an average particle size of 8 to 9 nm.

[0060] Additionally, the palladium-cerium oxide nanocomposite may have an average crystalline size of 6.6 to 10.6 nm, preferably an average crystalline size of 7.6 to 9.6 nm, and more preferably an average crystalline size of 8.1 to 9.1 nm.

[0061] Meanwhile, the electrode for the electrochemical biosensor for selectively detecting dopamine of the present invention is 0.15 to 0.25 cm 2 Electrochemically active surface area (EASA), preferably 0.18 to 0.21 cm 2 It can have an electrochemically active surface area (EASA).

[0062]

[0063] Furthermore, the electrochemical biosensor for selectively detecting dopamine of the present invention may include the electrode for the electrochemical biosensor for selectively detecting dopamine described above.

[0064]

[0065] Meanwhile, the method for manufacturing an electrode for an electrochemical biosensor for selectively detecting dopamine of the present invention includes the first and second steps.

[0066] The first step of the method for manufacturing an electrode for an electrochemical biosensor for selectively detecting dopamine according to the present invention may comprise preparing an electrode and a reduced graphene oxide aqueous solution having a palladium-cerium oxide nanocomposite formed on the surface thereof. In this case, the electrode is as described above.

[0067] In addition, a reduced graphene oxide aqueous solution having a palladium-cerium oxide nanocomposite formed on the surface can be manufactured by including steps 1-1 to 1-5.

[0068] Step 1-1 of a method for producing a reduced graphene oxide aqueous solution having a palladium-cerium oxide nanocomposite formed on the surface may include preparing a graphene oxide dispersion, a solution containing a cerium oxide (CeO2) precursor, and a solution containing a palladium (Pd) precursor, respectively. At this time, the graphene oxide, the cerium oxide (CeO2) precursor, and the palladium (Pd) precursor may have a weight ratio of 1:0.47 to 0.72:0.58 to 0.88, preferably 1:0.53 to 0.66:0.65 to 0.81. If the weight ratio of the graphene oxide and the cerium oxide (CeO2) precursor is less than 1:0.47, it may be difficult to produce the desired palladium-cerium oxide nanocomposite, and if it exceeds 1:0.72, it may be difficult to produce the desired palladium-cerium oxide nanocomposite. In addition, if the weight ratio of graphene oxide and palladium (Pd) precursor is less than 1:0.58, there may be a problem of reduced yield of the manufactured palladium-cerium oxide nanocomposite, and if it exceeds 1:0.88, there may be a problem of economic feasibility.

[0069] Additionally, the cerium oxide (CeO2) precursor may include at least one selected from ceric ammonium nitrate, cerium(III) carbonate, and cerium(III) nitrate hexahydrate, and preferably ceric ammonium nitrate.

[0070] Additionally, the palladium (Pd) precursor may include at least one selected from palladium(II) acetate, tris(dibenzylideneacetone)dipalladium(0), palladium dipropionate, and palladium(II) acetylacetonate, and preferably, palladium acetate (Pd(CH3COO)2).

[0071] Meanwhile, a graphene oxide dispersion can be prepared by a step of adding graphene powder, sodium nitrate (NaNO3), and potassium permanganate (KMnO4) to sulfuric acid (H2SO4), stirring, and reacting to prepare a reactant, adding hydrogen peroxide (H2O2) to the reactant, filtering, and washing the supernatant of the filtrate with ultrapure water to obtain a supernatant having a pH of 5 to 9, preferably 6 to 7, centrifuging the precipitate contained in the supernatant, and then drying to prepare graphene oxide, and adding the graphene oxide to ethylene glycol and performing ultrasonic treatment to prepare a graphene oxide dispersion. At this time, if the pH of the supernatant is less than 5, there may be a problem that the reduction of graphene oxide does not proceed, and if it exceeds 9, there may be a problem that it is difficult to utilize it as an electrochemical biosensor.

[0072] In addition, specifically, the reactants can be manufactured by first reacting by stirring at a temperature of 0 to 5℃ for 4 to 6 hours, and second reacting by stirring at a temperature of 50 to 70℃, preferably 55 to 65℃, for 3 to 5 hours. If the temperature of the first reaction is lower than 0℃, there may be a problem of non-reaction, and if it exceeds 5℃, there may be a problem of significantly increasing the manufacturing time. In addition, by setting the temperature of the second reaction higher than that of the first reaction, the problem of non-reaction can be solved.

[0073] In addition, when adding hydrogen peroxide (H2O2) to the reactant, the temperature of the reactant may be lowered to 18 to 26°C, preferably 20 to 24°C, before adding it. If the temperature is not lowered in this manner, there may be a problem of non-reaction.

[0074] Additionally, drying can be performed at a temperature of 60 to 80°C.

[0075] Furthermore, a solution containing a cerium oxide (CeO2) precursor can be prepared by adding a cerium oxide precursor to ethylene glycol, and a solution containing a palladium (Pd) precursor can be prepared by adding a palladium precursor to ethylene glycol.

[0076]

[0077] Steps 1 and 2 of a method for producing a reduced graphene oxide aqueous solution having a palladium-cerium oxide nanocomposite formed on the surface include mixing the graphene oxide dispersion prepared in Step 1-1, a solution containing a cerium oxide (CeO2) precursor, and a solution containing a palladium (Pd) precursor, respectively, to produce a mixture, and adding ascorbic acid and a pH adjuster to the produced mixture to produce a reaction mixture having a pH of 10 to 14, preferably 11 to 13. At this time, if the pH of the reaction mixture is less than 10, there may be a problem that the speed of the reduction reaction is slowed down. In addition, the pH adjuster may include at least one selected from sodium hydroxide, potassium hydroxide, and calcium hydroxide.

[0078]

[0079] Steps 1-3 of the method for producing a reduced graphene oxide aqueous solution having a palladium-cerium oxide nanocomposite formed on the surface can produce a reaction product by stirring and reacting the reaction mixture produced in Steps 1-2 at a temperature of 120 to 160°C, preferably 130 to 140°C, for 3 to 7 hours, preferably 4 to 6 hours. If these production conditions are exceeded, there may be a problem in that the desired compound cannot be produced.

[0080]

[0081] Steps 1 to 4 of the method for producing a reduced graphene oxide aqueous solution having a palladium-cerium oxide nanocomposite formed on the surface can produce reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface by drying the reaction product produced in Steps 1 to 3. In this case, the drying can be performed at a temperature of 70 to 90°C, preferably 75 to 85°C, for 6 to 10 hours, preferably 7 to 9 hours.

[0082]

[0083] Steps 1 to 5 of the method for producing a reduced graphene oxide aqueous solution having a palladium-cerium oxide nanocomposite formed on the surface can be performed by dissolving the reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface prepared in Steps 1 to 4 in methanol and then ultrasonicating the same to produce a reduced graphene oxide aqueous solution having a palladium-cerium oxide nanocomposite formed on the surface.

[0084]

[0085] The second step of the method for manufacturing an electrode for an electrochemical biosensor for selectively detecting dopamine of the present invention comprises applying an aqueous solution of reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface of the electrode prepared in the first step, and then drying the solution to form reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface of the electrode. At this time, the drying can be performed in an oven at 40 to 60°C, preferably 45 to 55°C, for 2 to 20 minutes, preferably 7 to 13 minutes.

[0086]

[0087] Hereinafter, the present invention will be described in more detail through examples, but the following examples do not limit the scope of the present invention, and should be interpreted as helping to understand the present invention.

[0088]

[0089] Preparation Example 1: Preparation of graphene oxide

[0090] (1) 2 g of graphene powder was added to 100 ml of concentrated sulfuric acid (H2SO4), ultrasonicated for 1 hour, and then sodium nitrate (NaNO3) and potassium permanganate (KMnO4) were added, stirred for 5 hours at a temperature of 0 to 5°C for a first reaction, and stirred for 4 hours at a temperature of 60°C for a second reaction, thereby preparing a reactant.

[0091] (2) After lowering the temperature of the manufactured reactant to room temperature (22°C), 30% w / v hydrogen peroxide (H2O2) solution was added, filtered, and the supernatant of the filtrate was washed with ultrapure water to obtain a supernatant with a pH of 7.

[0092] (3) The precipitate contained in the obtained supernatant was centrifuged at 8,000 rpm and dried at a temperature of 70°C to produce graphene oxide.

[0093]

[0094] Preparation Example 2: Preparation of reduced graphene oxide with a palladium-cerium oxide nanocomposite formed on the surface

[0095] (1) 70 mg of graphene oxide prepared in Preparation Example 1 was added to 40 ml of ethylene glycol, and sonicated for 30 minutes to prepare a graphene oxide dispersion. In addition, 41.65 mg of ceric ammonium nitrate was added to 30 ml of ethylene glycol, and sonicated for 1 hour to prepare a solution containing 10 wt% of cerium oxide (CeO2) precursor. In addition, 51.25 mg of palladium acetate (Pd(CH3COO)2) was added to 30 ml of ethylene glycol, and sonicated for 1 hour to prepare a solution containing 20 wt% of palladium (Pd) precursor.

[0096] (2) A mixture was prepared by mixing a graphene oxide dispersion, a solution containing 10 wt% of a cerium oxide (CeO2) precursor, and a solution containing 20 wt% of a palladium (Pd) precursor, and 50 mg of ascorbic acid and a small amount of sodium hydroxide for pH maintenance were slowly added to the mixture to prepare a reaction mixture having a pH of 12.

[0097] (3) The reaction mixture was stirred at room temperature (22°C) for 24 hours, and then refluxed and reacted at 140°C for 5 hours to prepare a reaction product.

[0098] (4) The reaction product was washed three times with an ethanol-water mixture (50%:50%) and then dried at a temperature of 80°C for 8 hours to produce reduced graphene oxide with a palladium-cerium oxide nanocomposite formed on the surface.

[0099]

[0100] Comparative Preparation Example 1: Preparation of reduced graphene oxide with palladium nanoparticles formed on the surface

[0101] (1) 70 mg of graphene oxide prepared in Preparation Example 1 was added to 40 ml of ethylene glycol, and sonicated for 30 minutes to prepare a graphene oxide dispersion. In addition, 51.25 mg of palladium acetate (Pd(CH3COO)2) was added to 30 ml of ethylene glycol, and sonicated for 1 hour to prepare a solution containing 20 wt% of a palladium (Pd) precursor.

[0102] (2) A mixture was prepared by mixing a solution containing a graphene oxide dispersion and 20 wt% of a palladium (Pd) precursor, and 50 mg of ascorbic acid and a small amount of sodium hydroxide for pH maintenance were slowly added to the mixture to prepare a reaction mixture having a pH of 12.

[0103] (3) The reaction mixture was stirred at room temperature (22°C) for 24 hours, and then refluxed and reacted at 140°C for 5 hours to prepare a reaction product.

[0104] (4) The reaction product was washed three times with an ethanol-water mixture (50%:50%) and then dried at a temperature of 80°C for 8 hours to produce reduced graphene oxide with palladium nanoparticles formed on the surface.

[0105]

[0106] Comparative Preparation Example 2: Preparation of reduced graphene oxide with cerium oxide nanoparticles formed on the surface

[0107] (1) 70 mg of graphene oxide prepared in Preparation Example 1 was added to 40 ml of ethylene glycol, and the mixture was sonicated for 30 minutes to prepare a graphene oxide dispersion. In addition, 41.65 mg of ceric ammonium nitrate was added to 30 ml of ethylene glycol, and sonicated for 1 hour to prepare a solution containing 10 wt% of cerium oxide (CeO2) precursor.

[0108] (2) A mixture was prepared by mixing a solution containing a graphene oxide dispersion and 10 wt% of a cerium oxide (CeO2) precursor, and 50 mg of ascorbic acid and a small amount of sodium hydroxide for pH maintenance were slowly added to the mixture to prepare a reaction mixture having a pH of 12.

[0109] (3) The reaction mixture was stirred at room temperature (22°C) for 24 hours, and then refluxed and reacted at 140°C for 5 hours to prepare a reaction product.

[0110] (4) The reaction product was washed three times with an ethanol-water mixture (50%:50%) and then dried at a temperature of 80°C for 8 hours to produce reduced graphene oxide with cerium oxide nanoparticles formed on the surface.

[0111]

[0112] Experimental Example 1: Structural Analysis 1

[0113] In order to confirm the crystal phase and chemical phase composition of the reduced graphene obtained by reducing the graphene oxide prepared in Preparation Example 1, the reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface prepared in Preparation Example 2, the reduced graphene oxide having palladium nanoparticles formed on the surface prepared in Comparative Preparation Example 1, and the reduced graphene oxide having cerium oxide nanoparticles formed on the surface prepared in Comparative Preparation Example 2, PXRD (powder X-ray diffraction) analysis was performed. The PXRD analysis was performed using an X-ray diffractometer (3003 TT) with Cu Kα radiation (λ = 1.54106 Å), and the results are shown in Fig. 1(A) below.

[0114] Figure 1(A) a shows a PXRD spectrum of reduced graphene oxide, b shows a PXRD spectrum of reduced graphene oxide having palladium nanoparticles formed on the surface manufactured in Comparative Preparation Example 1, c shows a PXRD spectrum of reduced graphene oxide having cerium oxide nanoparticles formed on the surface manufactured in Comparative Preparation Example 2, and d shows a PXRD spectrum of reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface manufactured in Preparation Example 2.

[0115] As can be seen in a of Fig. 1(A), the PXRD plot shows a broad diffraction peak of 2θ with a value of approximately 24.6° for the (002) crystal plane, which is a peak indicating reduced graphene oxide.

[0116] As can be seen in b of Fig. 1(A), the PXRD pattern corresponds to the face-centered cubic phase of palladium (Pd), and the diffraction peaks at 2θ values ​​of 39.77°, 46.20°, and 67.56° can be indexed to the (111), (200), and (220) planes, respectively.

[0117] As can be seen in c of Fig. 1(A), the PXRD pattern corresponds to the cubic fluorite structure of cerium oxide (CeO2), and the diffraction peaks at 2θ values ​​of 28.69°, 33.45°, 47.64°, 59.09°, and 69.40° can be indexed to the (111), (200), (220), (222), and (400) planes, respectively.

[0118] As can be seen in d of Fig. 1(A), the PXRD pattern shows diffraction peaks (indexed to the (111), (200), and (220) planes, respectively) at 2θ values ​​of 39.37°, 46.20°, and 67.12° due to palladium (Pd), and diffraction peaks (indexed to the (111), (200), and (222) planes, respectively) at 2θ values ​​of 28.96°, 33.42°, and 59.10° due to cerium oxide (CeO2).

[0119] Meanwhile, the average crystalline size was calculated as 8.6 nm for the palladium-cerium oxide nanocomposite, 11.2 nm for the palladium nanoparticles, and 11.9 nm for the cerium oxide nanoparticles on the surface.

[0120]

[0121] Experimental Example 2: Structural Analysis 2

[0122] To confirm the chemical properties and chemical characteristics of the reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface manufactured in Preparation Example 2, XPS analysis was performed. XPS analysis was performed using an X-ray photoelectron microscope (XPS; Kratos, AXIS Supra, Manchester, UK) using a monochromatic Al-Kα X-ray source (15 Kv, 375 W), and the results are shown in Figs. 1(B) to 1(F).

[0123] FIG. 1(B) shows the XPS full survey spectrum of the reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface prepared in Preparation Example 2, FIG. 1(C) shows the high-resolution XPS spectrum of C 1s in the reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface prepared in Preparation Example 2, FIG. 1(D) shows the high-resolution XPS spectrum of O 1s in the reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface prepared in Preparation Example 2, FIG. 1(E) shows the high-resolution XPS spectrum of Pd 3d in the reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface prepared in Preparation Example 2, and FIG. 1(F) shows the high-resolution XPS spectrum of Ce 3d in the reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface prepared in Preparation Example 2. It shows the spectrum (high-resolution XPS spectrum).

[0124] As can be seen in Fig. 1(B), the peaks at binding energies of 283 eV, 530 eV, 330 eV, 560 eV, 900 eV, and 115.1 eV represent C 1s, O 1s, Pd 3d, Pd 3p, Ce 3d, and Ce 4d, respectively.

[0125] As can be seen in Fig. 1(C), the binding energy of C 1s was confirmed to have a strong peak at 284.8 eV. This indicates that the CC / C=C of non-oxygenated carbon is the dominant sp in the reduced graphene oxide support. 2It exhibits a hybrid graphene structure, with a significant decrease in the oxygen-rich functional group. Furthermore, peaks appear at 286.2 eV and 288.8 eV, which are attributed to the epoxy and carbonyl groups, respectively.

[0126] As can be seen in Figure 1(D), the binding energy of O 1s shows a peak at 532.1 eV, which represents a CO group. In addition, the peak at 529.3 eV represents a Ce-O bond, confirming that an interaction is occurring between graphene oxide and cerium oxide.

[0127] As can be seen in Figure 1(E), Pd 3d in the Pd 3d spectrum 5 / 2 and Pd 3d 3 / 2 Subpeaks of 338.1 eV and 343.2 eV were observed, and the peaks at 338.1 eV and 343.2 eV can be attributed to Pd (II), and the peaks at 335.8 eV and 341.2 eV indicate the presence of Pd (0).

[0128] As can be seen in Figure 1(F), Ce 3d in the Ce 3d spectrum 5 / 2 and Ce 3d 3 / 2 A group of peaks appeared, and the binding energy peaks of 883.8 eV, 886.4 eV, and 905.4 eV were assigned to Ce, respectively. 3+ 3d 5 / 2 and Ce 3+ 3d 3 / 2 It is due to. Also, Ce 4+ 3d 3 / 2 corresponds to a binding energy peak of 902.2 eV. Therefore, Ce 4+ In Ce 3+The change in the valence state of the graphene layer is due to the oxygen vacancy in the cerium oxide structure, and this is a result showing that the charge transfer from the mobile hole in the graphene layer to the localized electron in the cerium oxide structure acts favorably on the electrocatalytic properties of the reduced graphene oxide on which the palladium-cerium oxide nanocomposite was formed in Preparation Example 2.

[0129]

[0130] Experimental Example 3: Structural Analysis 3

[0131] Field emission scanning electron microscopy (FESEM, S-4800) and mapping using energy dispersive X-ray (EDX) were performed on each of the reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface manufactured in Preparation Example 2, the reduced graphene oxide having palladium nanoparticles formed on the surface manufactured in Comparative Preparation Example 1, and the reduced graphene oxide having cerium oxide nanoparticles formed on the surface manufactured in Comparative Preparation Example 2, and the results are shown in Fig. 2.

[0132] FIG. 2(A) and FIG. 2(B) are FESEM images of reduced graphene oxide having palladium nanoparticles formed on the surface manufactured in Comparative Preparation Example 1, FIG. 2(C) is an EDX spectrum of reduced graphene oxide having palladium nanoparticles formed on the surface manufactured in Comparative Preparation Example 1, and FIG. 2(D) is a mapping image, a C atom mapping image, a Pd atom mapping image, and an O atom mapping image of mixed C atoms, Pd atoms, and O atoms of reduced graphene oxide having palladium nanoparticles formed on the surface manufactured in Comparative Preparation Example 1.

[0133] FIG. 2(E) and FIG. 2(F) are FESEM images of reduced graphene oxide having cerium oxide nanoparticles formed on the surface manufactured in Comparative Preparation Example 2, FIG. 2(G) is an EDX spectrum of reduced graphene oxide having cerium oxide nanoparticles formed on the surface manufactured in Comparative Preparation Example 2, and FIG. 2(H) is a mapping image, a C atom mapping image, a Ce atom mapping image, and an O atom mapping image of mixed C atoms, Ce atoms, and O atoms of reduced graphene oxide having cerium oxide nanoparticles formed on the surface manufactured in Comparative Preparation Example 2.

[0134] FIG. 2(I) and FIG. 2(J) are FESEM images of reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface manufactured in Preparation Example 2, FIG. 2(K) is an EDX spectrum of reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface manufactured in Preparation Example 2, and FIG. 2(L) is a mapping image of mixed C atoms, O atoms, Pd atoms, and Ce atoms of reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface manufactured in Preparation Example 2, a C atom mapping image, a Ce atom mapping image, an O atom mapping image, and a Pd atom mapping image.

[0135] As can be seen in Fig. 2(A) and Fig. 2(B), some spherical particles, which are palladium nanoparticles, were confirmed to be brightly colored and visible on the surface of the three-dimensional interconnected wrinkled reduced graphene oxide flakes. In addition, as can be seen in Fig. 2(C), the reduced graphene oxide on the surface of which palladium nanoparticles were formed in Comparative Preparation Example 1 was primarily confirmed. In addition, as can be seen in Fig. 2(C) and Fig. 2(D), the observed elements were carbon (C), oxygen (O), and palladium (Pd), and no other impurities were observed.

[0136] As can be seen in Figs. 2(E) and 2(F), it was confirmed that cerium oxide nanoparticles were attached to the surface of the reduced graphene oxide flakes. In addition, as can be seen in Fig. 2(G), it was confirmed that reduced graphene oxide with cerium oxide nanoparticles formed on the surface was successfully manufactured. In addition, as can be seen in Figs. 2(G) and 2(H), the observed elements were carbon (C), oxygen (O), and cerium (Ce), and no other impurities were observed.

[0137] As can be seen in Figs. 2(I) and 2(J), palladium-cerium oxide nanocomposites were observed on the surface of the reduced graphene oxide. In addition, as can be seen in Figs. 2(K) and 2(L), the reduced graphene oxide on the surface of which palladium-cerium oxide nanocomposites were formed, manufactured in Preparation Example 2, was found to contain carbon (C), oxygen (O), palladium (Pd), and cerium (Ce) without any other impurities.

[0138]

[0139] Experimental Example 4: Structural Analysis 4

[0140] Transmission electron microscopy (TEM, JEM-F200) images of the reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface manufactured in Preparation Example 2 and the reduced graphene oxide having a palladium nanoparticle formed on the surface manufactured in Comparative Preparation Example 1 were performed, respectively, and are shown in Fig. 3.

[0141] FIG. 3(A) to FIG. 3(B) are TEM images of reduced graphene oxide having palladium nanoparticles formed on the surface manufactured in Comparative Preparation Example 1, FIG. 3(C) is a TEM and HRTEM image of reduced graphene oxide having palladium nanoparticles formed on the surface manufactured in Comparative Preparation Example 1, and FIG. 3(D) is a particle histogram of reduced graphene oxide having palladium nanoparticles formed on the surface manufactured in Comparative Preparation Example 1.

[0142] FIG. 3(E) to FIG. 3(F) are TEM images of reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface manufactured in Preparation Example 2, FIG. 3(G) is a TEM and HRTEM image of reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface manufactured in Preparation Example 2, and FIG. 3(H) is a particle histogram of reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface manufactured in Preparation Example 2.

[0143] As can be seen in Figures 3(A) to 3(C), palladium nanoparticles were confirmed to be well fixed on the reduced graphene oxide support. In addition, as can be seen in Figure 3(D), the palladium nanoparticles were confirmed to have an average particle size of 10 to 12 nm.

[0144] As can be seen in FIGS. 3(E) to 3(G), it was confirmed that the spherical palladium-cerium oxide nanocomposite was well fixed on the reduced graphene oxide support. In addition, as can be seen in the HRTEM image of FIG. 3(G), the reduced graphene oxide on the surface of which the palladium-cerium oxide nanocomposite was formed manufactured in Preparation Example 2 exhibited lattice fringes of 0.28 nm and 0.34 nm, which were attributed to the palladium and cesium oxide nanocomposites, respectively. In addition, as can be seen in FIG. 3(H), it was confirmed that the palladium-cerium oxide nanocomposite had an average particle size of 8 to 9 nm.

[0145]

[0146] Example 1: Preparation of a dopamine detection electrode

[0147] (1) A glassy carbon electrode was prepared as a working electrode. In addition, 1 mg of reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface prepared in Preparation Example 2 was dissolved in 1.0 ml of methanol, and ultrasonicated for 20 minutes to prepare an aqueous solution of reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface.

[0148] (2) 5.0 ㎕ of a reduced graphene oxide aqueous solution having a palladium-cerium oxide nanocomposite formed on the surface was dropped onto one side of the working electrode, and then dried in an oven at 50°C for 10 minutes to form reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface of the working electrode, thereby manufacturing a dopamine detection electrode.

[0149]

[0150] Comparative Example 1: Manufacturing of a dopamine detection electrode

[0151] (1) A glassy carbon electrode was prepared as a working electrode. In addition, 1 mg of reduced graphene oxide having palladium nanoparticles formed on the surface prepared in Comparative Preparation Example 1 was dissolved in 1.0 ml of methanol, and ultrasonicated for 20 minutes to prepare an aqueous solution of reduced graphene oxide having palladium nanoparticles formed on the surface.

[0152] (2) 5.0 ㎕ of a reduced graphene oxide solution having palladium nanoparticles formed on the surface was dropped onto one side of the working electrode, and then dried in an oven at 50°C for 10 minutes to form reduced graphene oxide having palladium nanoparticles formed on the surface of one side of the working electrode, thereby manufacturing a dopamine detection electrode.

[0153]

[0154] Comparative Example 2: Manufacturing of a dopamine detection electrode

[0155] (1) A glassy carbon electrode was prepared as a working electrode. In addition, 1 mg of reduced graphene oxide having cerium oxide nanoparticles formed on the surface prepared in Comparative Preparation Example 2 was dissolved in 1.0 ml of methanol, and ultrasonicated for 20 minutes to prepare an aqueous solution of reduced graphene oxide having cerium oxide nanoparticles formed on the surface.

[0156] (2) 5.0 ㎕ of a reduced graphene oxide aqueous solution having cerium oxide nanoparticles formed on the surface was dropped onto one side of the working electrode, and then dried in an oven at 50°C for 10 minutes to form reduced graphene oxide having cerium oxide nanoparticles formed on the surface of the working electrode, thereby manufacturing a dopamine detection electrode.

[0157]

[0158] Experimental Example 5: Electrochemical Analysis

[0159] In order to perform electrochemical analysis on the dopamine detection electrodes manufactured in Example 1 and Comparative Examples 1 and 2, a three-electrode system was manufactured. Specifically, the dopamine detection electrode manufactured in Example 1, the dopamine detection electrode manufactured in Comparative Example 1, the dopamine detection electrode manufactured in Comparative Example 2, and a glassy carbon electrode (GCE) were each used as working electrodes, a platinum wire (Pt wire) was used as a counter electrode, and a saturated Ag / AgCl electrode was used as a reference electrode.

[0160]

[0161] (1) CV curve

[0162] Figure 4(A) shows 1.0 mM [Fe(CN)6] in 0.1 M KCl solution. 3- / 4-This is a graph showing the CV curves measured at a scanning rate of 100 mV for each of the dopamine detection electrode (=Pd-CeO2 / rGO / GCE) manufactured in Example 1, the dopamine detection electrode (=Pd / rGO / GCE) manufactured in Comparative Example 1, the dopamine detection electrode (=CeO2 / rGO / GCE) manufactured in Comparative Example 2, and the glassy carbon electrode (=bare GCE).

[0163] As can be seen in Fig. 4(A), the glassy carbon electrode (=bare GCE) shows the minimum response of peak current and peak potential (ΔE p ; peak potential) was about 115 mV, which did not meet the requirements of a high-performance electrochemical sensor. In addition, the dopamine detection electrode (=CeO2 / rGO / GCE) manufactured in Comparative Example 2 had a peak potential (ΔE p ) was measured to have a maximum separation of approximately 105 mV, and it was confirmed that it exhibited superior electron transferability than the glassy carbon electrode (=bare GCE). In addition, the dopamine detection electrode (=Pd / rGO / GCE) manufactured in Comparative Example 1 had a peak potential (ΔE p ) was measured to have a maximum separation of approximately 96 mV, which was judged to be due to excellent electronic conductivity. Finally, the dopamine detection electrode (=Pd-CeO2 / rGO / GCE) manufactured in Example 1 had a peak potential (ΔE p ) was measured to have the highest separation of approximately 88 mV, confirming that it had the best electron transferability. That is, it was confirmed that the dopamine detection electrode (=Pd-CeO2 / rGO / GCE) manufactured in Example 1 showed the maximum augmentation of the redox peak current response.

[0164] Meanwhile, the electrochemically active surface area (EASA) was calculated and the dopamine detection electrode manufactured in Example 1 had an electrochemically active surface area of ​​0.194 cm 2 , the dopamine detection electrode manufactured in Comparative Example 1 was 0.097 cm 2 , the dopamine detection electrode manufactured in Comparative Example 2 was 0.074 cm 2 , the glassy carbon electrode is 0.068 cm 2 In conclusion, it was confirmed that the dopamine detection electrode manufactured in Example 1 has a large electrochemically active surface area and excellent conductivity compared to other detection electrodes, thereby promoting electrochemical detection performance for dopamine.

[0165]

[0166] Figure 4(B) shows 1.0 mM [Fe(CN)6] in 0.1 M KCl solution. 3- / 4- In this graph, the CV curve of the dopamine detection electrode (=Pd-CeO2 / rGO / GCE) manufactured in Example 1 is measured over a scanning rate range of 10 to 100 mV. As can be seen in Fig. 4(B), as the scanning rate increases from 10 mV to 100 mV, the redox peak currents (I pa / I pc ) was confirmed to increase linearly.

[0167]

[0168] FIG. 4(C) is a graph showing a Tafel plot drawn between the peak potential and the current's logarithm of each of the dopamine detection electrode (=Pd-CeO2 / rGO / GCE) manufactured in Example 1, the dopamine detection electrode (=Pd / rGO / GCE) manufactured in Comparative Example 1, the dopamine detection electrode (=CeO2 / rGO / GCE) manufactured in Comparative Example 2, and the glassy carbon electrode (=bare GCE), based on the CV investigation results. As can be seen in Fig. 4(C), the glassy carbon electrode (=bare GCE) shows very small peak separation, and the dopamine detection electrode (=Pd-CeO2 / rGO / GCE) manufactured in Example 1 shows large peak separation, which indicates that the absorption properties and electrocatalytic activity of the dopamine detection electrode (=Pd-CeO2 / rGO / GCE) manufactured in Example 1 are superior to those of other dopamine detection electrodes. In addition, the high potential shift of the dopamine detection electrode (=Pd-CeO2 / rGO / GCE) manufactured in Example 1 indicates excellent electrical conductivity.

[0169]

[0170] (2) Electrochemical impedance spectroscopy (EIS)

[0171] Figure 4(D) shows the electrochemical impedance spectroscopy (EIS) of 1.0 mM [Fe(CN)6] in 0.1 M KCl solution. 3- / 4-This is a graph showing the Nyquist plots of the dopamine detection electrode (=Pd-CeO2 / rGO / GCE) manufactured in Example 1, the dopamine detection electrode (=Pd / rGO / GCE) manufactured in Comparative Example 1, the dopamine detection electrode (=CeO2 / rGO / GCE) manufactured in Comparative Example 2, and the glassy carbon electrode (=bare GCE). The Nyquist plots are the charge transfer resistance (R ct ; charge transfer resistance), double layer capacitance (C dI ; double layer capacitance), Warburg resistance (Z W ; Warburg resistance), solution resistance (R s ; solution resistance) was used. As can be seen in Fig. 4(D), the glassy carbon electrode (=bare GCE) has a charge transfer resistance (R ct ) was measured to have a larger semicircular diameter than other detection electrodes, with a value of 235 Ω. This result shows that the glassy carbon electrode (=bare GCE) has the lowest active site and thus poor electron mobility. Meanwhile, the charge transfer resistance (R of the dopamine detection electrode (=Pd-CeO2 / rGO / GCE) manufactured in Example 1 ct ) value is 88 Ω, the charge transfer resistance (R) of the dopamine detection electrode (=Pd / rGO / GCE) manufactured in Comparative Example 1 ct ) value is 191 Ω, the charge transfer resistance (R) of the dopamine detection electrode (=CeO2 / rGO / GCE) manufactured in Comparative Example 2 ct ) values ​​were measured as 205 Ω, respectively. Therefore, the lowest charge transfer resistance (R ct ) It was confirmed that the dopamine detection electrode manufactured in Example 1 with the value had the best electron transfer kinetics.

[0172] In conclusion, since the dopamine detection electrode manufactured in Example 1 has low impedance, high electrochemically active surface area (EASA), and excellent conductivity, it was confirmed that a biosensor including the dopamine detection electrode manufactured in Example 1 is highly suitable for electrochemical applications.

[0173]

[0174] (3) Electrochemical behavior of dopamine

[0175] In order to evaluate the electro-oxidation of dopamine in each of the dopamine detection electrode (=Pd-CeO2 / rGO / GCE) manufactured in Example 1, the dopamine detection electrode (=Pd / rGO / GCE) manufactured in Comparative Example 1, the dopamine detection electrode (=CeO2 / rGO / GCE) manufactured in Comparative Example 2, and the glassy carbon electrode (=bare GCE), cyclic voltammetry (CV) was performed at 100 mV / s in 0.1 M PBS (pH 7) containing 1 mM dopamine, and the results are shown in Fig. 5(A) and Fig. 5(B). As can be seen in Fig. 5(A), no peak current response is observed in the glassy carbon electrode without dopamine (=GCE without DA), indicating that no Faraday reaction occurs on the surface of the glassy carbon electrode. A reversible redox peak current response was observed in the glassy carbon electrode (=bare GCE). However, compared to other detection electrodes, the glassy carbon electrode (=bare GCE) showed the lowest peak current response, indicating that the conductivity was reduced due to the lowest active site. The reason why the dopamine detection electrode (=CeO2 / rGO / GCE) manufactured in Comparative Example 2 showed a higher peak current response than the glassy carbon electrode (=bare GCE) is because oxygen vacancies exist in the cerium oxide nanoparticles and reduced graphene oxide was introduced. On the other hand, the reason why the dopamine detection electrode (=Pd / rGO / GCE) manufactured in Comparative Example 1 showed a higher peak current response than the glassy carbon electrode (=bare GCE) is because of the synergistic effect of palladium nanoparticles and reduced graphene oxide. Meanwhile, the dopamine detection electrode (=Pd-CeO2 / rGO / GCE) manufactured in Example 1 was able to confirm a peak current response superior to other detection electrodes.Specifically, as can be seen in Fig. 5(B), it was confirmed that the dopamine detection electrode (=Pd-CeO2 / rGO / GCE) manufactured in Example 1 showed a peak current response that was 2.5 times higher than the dopamine detection electrode (=Pd / rGO / GCE) manufactured in Comparative Example 1, 3.6 times higher than the dopamine detection electrode (=CeO2 / rGO / GCE) manufactured in Comparative Example 2, and 7 times higher than the glassy carbon electrode (=bare GCE).

[0176] Meanwhile, the effect of pH on the electrochemical behavior of 1 mM dopamine in the dopamine detection electrode manufactured in Example 1 was measured through CV using 0.1 M PBS (pH 5 to 9) at 100 mV / s, and the results are shown in Fig. 5(C). As can be seen in Fig. 5(C), as the pH gradually increased, the oxidation peak potential shifted to a less positive potential. When the pH decreased below 7, both the anodic and cathodic peak potentials shifted toward the anode due to the strong electrostatic repulsion between the anode surface and positively charged dopamine. In addition, when the pH increased from 7 to above, both the anodic and cathodic peak potentials shifted toward the cathode due to the strong electrostatic repulsion between the cathode surface and positively charged dopamine. In conclusion, it was confirmed that the dopamine detection electrode manufactured in Example 1 was affected by the pH of the electrolyte during the oxidation of dopamine.

[0177] Figure 5(D) is a plot showing the peak current and potential of the dopamine detection electrode manufactured in Example 1 for dopamine oxidation in relation to various pH levels. As can be seen in Figure 5(D), the oxidation peak (I pa ) In the plot of pH vs. pH, the maximum peak current of dopamine was observed at pH 7.0, confirming that pH 7.0 was the optimal pH.

[0178] Meanwhile, the CV curves for various scan rates of 10 to 200 mV / s in 1 mM dopamine dissolved in 0.1 M sterile phosphate buffer solution (PBS) (pH 7) for the dopamine detection electrode manufactured in Example 1 are shown in Fig. 6(A). As can be seen in Fig. 6(A), it was confirmed that the peak current response of dopamine gradually increased as the scan rate increased. In addition, Fig. 6(B) is a graph showing a plot between the anodic and cathodic peak currents of dopamine and various sweep rates for the dopamine detection electrode manufactured in Example 1. As can be seen in Fig. 6(B), it was confirmed that the electrooxidation of dopamine using the dopamine detection electrode manufactured in Example 1 was controlled by the adsorption process. In addition, Fig. 6(C) is a graph showing a plot between the log of the peak current versus the log of the scan rate for the dopamine detection electrode manufactured in Example 1, and Fig. 6(D) is a graph showing a plot between the log of the scan rate versus the log of the peak transition for the dopamine detection electrode manufactured in Example 1. As can be seen in Fig. 6(C) and Fig. 6(D), it was confirmed that dopamine had fast electron transfer dynamics at the electrode interface by the dopamine detection electrode manufactured in Example 1. In addition, the amount of dopamine adsorbed on the surface of the dopamine detection electrode manufactured in Example 1 was 1.34 mol / cm 2 It was calculated as , and it was confirmed that the dopamine detection electrode manufactured in Example 1 had excellent absorbency.

[0179]

[0180] (4) Electrochemical measurement of dopamine

[0181] The electrochemical properties of dopamine in the dopamine detection electrode manufactured in Example 1 were measured using the DPV method (differential pulse voltammetry method) and are shown in Fig. 7.

[0182] Figure 7(A) is a DPV curve showing the degree of dopamine detection in the dopamine detection electrode manufactured in Example 1 at various concentrations of dopamine dissolved in 0.1 M sterile phosphate buffer solution (PBS) (pH 7). As can be seen in Figure 7(A), it was confirmed that the dopamine peak current gradually increased as the concentration of dopamine (DA) increased. Meanwhile, through these results, the limit of detection (LOD; limit of detection) of the dopamine detection electrode manufactured in Example 1 was 0.69 μM, the limit of quantification (LOQ; limit of quantification) was 2.31 μM, and the sensitivity was 0.894 μA / μM. -1 cm -2 It was calculated as follows. Compared to the previously used dopamine detection biosensor, it was confirmed to have a low detection limit and excellent sensitivity.

[0183] Figure 7(B) is a DPV curve showing the degree of dopamine detection at the dopamine detection electrode manufactured in Example 1 at various concentrations of dopamine, 5 μM paracetamol (PC), and 10 μM tyrosine (TY) dissolved in 0.1 M sterile phosphate buffer solution (PBS) (pH 7). As can be seen in Figure 7(B), the oxidation peak currents of paracetamol (PC) and tyrosine (TY) remained almost constant, confirming that paracetamol (PC) and tyrosine (TY) did not interfere with the detection of dopamine (DA).

[0184] Figure 7(C) is a DPV curve showing the degree of dopamine detection at the dopamine detection electrode manufactured in Example 1 in the presence of various concentrations of paracetamol (PC), 5 μM dopamine (DA), and 10 μM tyrosine (TY) dissolved in 0.1 M sterile phosphate buffer solution (PBS) (pH 7). As can be seen in Figure 7(C), the peak current response of paracetamol (PC) linearly increases with increasing concentration, and the oxidation peak currents of dopamine (DA) and tyrosine (TY) remain almost constant, confirming that the presence of dopamine (DA) and tyrosine (TY) does not interfere with the oxidation of paracetamol (PC).

[0185] Figure 7(D) is a DPV curve showing the degree of dopamine detection at the dopamine detection electrode manufactured in Example 1 in the presence of various concentrations of tyrosine (TY), 5 μM dopamine (DA), and 5 μM paracetamol (PC) dissolved in 0.1 M sterile phosphate buffer solution (PBS) (pH 7). As can be seen in Figure 7(D), the peak current response of tyrosine (TY) linearly increases with increasing concentration, and the oxidation peak currents of dopamine (DA) and paracetamol (PC) remain almost constant, confirming that the presence of dopamine (DA) and paracetamol (PC) does not interfere with the oxidation of tyrosine (TY).

[0186] From these results, it was confirmed that dopamine (DA), paracetamol (PC), and tyrosine (TY) could be individually detected using the dopamine detection electrode manufactured in Example 1.

[0187] Figures 7(E) and 7(F) are DPV curves showing the degree of dopamine detection at the dopamine detection electrode manufactured in Example 1 in various concentrations of dopamine (DA), various concentrations of tyrosine (TY), and various concentrations of paracetamol (PC) dissolved in 0.1 M sterile phosphate buffer solution (PBS) (pH 7). As can be seen in Figures 7(E) and 7(F), when the concentrations of all three substances increased simultaneously, it was confirmed that the DPV oxidation peak currents were each divided and increased linearly.

[0188] Figures 8(A) and 8(B) show the results of evaluating the selectivity of the dopamine detection electrode manufactured in Example 1, in which 30 μM dopamine (DA) was added to 0.1 M sterile phosphate buffer solution (PBS) (pH 7) as well as Na as an interferent. + , Al 3+ , AA (ascorbic acid), glucose, Zn 2+ and NO 3- This graph shows the results of performing DPV on this dissolved solution. As can be seen in Fig. 8(A) and Fig. 8(B), even if 100 times the amount of interfering substances is included, it was confirmed that there was no significant effect on the detection of dopamine (DA). In other words, the relative error of the signal was less than 6%, confirming that the dopamine detection electrode manufactured in Example 1 had excellent selectivity for dopamine detection.

[0189] Furthermore, in order to evaluate the reproducibility of the dopamine detection electrode, six dopamine detection electrodes were manufactured and prepared as in Example 1, and DPV of each of the six dopamine detection electrodes was performed, as shown in Fig. 8(C). As can be seen in Fig. 8(C), it was confirmed that the relative standard deviation was 6.2%, indicating excellent reproducibility.

[0190] In addition, in order to evaluate the storage stability of the dopamine detection electrode, DPV of the dopamine detection electrode manufactured in Example 1 before and after storage was performed and shown in Fig. 8(D). As can be seen in Fig. 8(D), it was confirmed that it had high storage stability by maintaining 94.6% of the initial value even after 10 days.

[0191]

[0192] (5) Detection of dopamine in biological samples

[0193] Fig. 9 is a graph showing the results of DPV performed on pharmaceutical injection samples and human serum samples to evaluate the applicability of the dopamine detection electrode manufactured in Example 1 to a biological environment. A commercial dopamine (DA) injection sample was diluted with an appropriate amount of 0.1 M PBS (pH 7.0), and a standard solution was also prepared as a dopamine injection solution with the same concentration. To secure a concentration range suitable for dopamine detection before analysis, a human serum sample was diluted 100-fold with 0.1 M PBS (pH 7.0). Fig. 9(A) is a graph showing the results of DPV performed on pharmaceutical injection samples and when dopamine (DA) was added at various concentrations, and Fig. 9(C) is a graph showing the results of DPV performed on human serum samples and when dopamine (DA) was added at various concentrations. As can be seen in Figures 9(A) and 9(C), the recovery rates in pharmaceutical injection samples and human serum samples were measured to be 98.3 to 100.15%. Figure 9(B) shows the peak current (I) according to the amount of pharmaceutical injection sample added. pa) is a graph showing a linear plot of dopamine (DA) versus peak current, and Fig. 9(D) is a graph showing a linear plot of dopamine (DA) versus peak current according to the amount of human serum sample added. As can be seen in Fig. 9(B) and Fig. 9(D), the dopamine detection electrode manufactured in Example 1 was confirmed to be more sensitive and reliable in clinical and diagnostic applications.

[0194]

[0195] Simple modifications or changes of the present invention can be easily implemented by a person having ordinary skill in the art, and all such modifications or changes can be considered to be included in the scope of the present invention.

Claims

1. Electrode; and Reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on one surface of the electrode; An electrode for an electrochemical biosensor for selectively detecting dopamine, characterized by comprising:

2. In paragraph 1, An electrode for an electrochemical biosensor for selectively detecting dopamine, characterized in that the above palladium-cerium oxide nanocomposite has an average particle size of 7 to 10 nm.

3. In paragraph 1, An electrode for an electrochemical biosensor for selectively detecting dopamine, characterized in that the palladium-cerium oxide nanocomposite has an average crystalline size of 6.6 to 10.6 nm.

4. In paragraph 1, The electrode for the above electrochemical biosensor is 0.15 to 0.25 cm 2 An electrode for an electrochemical biosensor for selectively detecting dopamine, characterized by having an electrochemically active surface area (EASA) of .

5. An electrochemical biosensor for selectively detecting dopamine, comprising an electrode for the electrochemical biosensor of claim 1.

6. A first step of preparing a reduced graphene oxide aqueous solution in which a palladium-cerium oxide nanocomposite is formed on the electrode and the surface; and A second step of forming reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface by applying an aqueous reduced graphene oxide solution having a palladium-cerium oxide nanocomposite formed on the surface to one side of the electrode and then drying the solution; A method for manufacturing an electrode for an electrochemical biosensor for selectively detecting dopamine, characterized by including a.

7. In the 6th paragraph, the reduced graphene oxide aqueous solution having a palladium-cerium oxide nanocomposite formed on the surface Graphene oxide dispersion, cerium oxide (CeO 2 ) Step 1-1 of preparing a solution containing a precursor and a solution containing a palladium (Pd) precursor, respectively; Graphene oxide dispersion, cerium oxide (CeO 2 ) Step 1-2: mixing a solution containing a precursor and a solution containing a palladium (Pd) precursor to prepare a mixture, and adding ascorbic acid and a pH regulator to the mixture to prepare a reaction mixture having a pH of 10 to 14; Step 1-3 of producing a reaction product by stirring and reacting the above reaction mixture at a temperature of 120 to 160°C for 3 to 7 hours; Step 1-4 of drying the above reaction product to produce reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface; and Step 1-5 of dissolving reduced graphene oxide having a palladium-cerium oxide nanocomposite formed on the surface in methanol and then ultrasonicating to prepare a reduced graphene oxide aqueous solution having a palladium-cerium oxide nanocomposite formed on the surface; A method for manufacturing an electrode for an electrochemical biosensor for selectively detecting dopamine, characterized in that the electrode is manufactured including:

8. In paragraph 7, In the above step 1-1, graphene oxide and cerium oxide (CeO 2 ) A method for manufacturing an electrode for an electrochemical biosensor for selectively detecting dopamine, characterized in that the precursor and the palladium (Pd) precursor have a weight ratio of 1:0.47 to 0.72:0.58 to 0.

88.

9. In paragraph 7, the graphene oxide dispersion is Sulfuric acid (H 2 SO 4 ) in graphene powder, sodium nitrate (NaNO 3 ) and potassium permanganate (KMnO 4 ) and then stirring and reacting to prepare a reactant; Hydrogen peroxide (H) was added to the above reaction product. 2 0 2 ) and filtering, and then washing the supernatant of the filtrate with ultrapure water to obtain a supernatant having a pH of 5 to 9; A step of centrifuging and drying the precipitate contained in the above supernatant to produce graphene oxide; and A step of preparing a graphene oxide dispersion by adding the above graphene oxide to ethylene glycol and performing ultrasonic treatment; A method for manufacturing an electrode for an electrochemical biosensor for selectively detecting dopamine, characterized in that the electrode is manufactured including:

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