CN115414930B - Ru(bpy)32+ anode or cathode coreactant and preparation method thereof - Google Patents

Abstract

The invention discloses Ru (bpy) ₃ ²⁺ The anode or cathode coreactant and the preparation method thereof are both Au-rGO complexes, and the particle size of Au nano particles in the anode coreactant is 10-15nm; the particle size of Au nano-particles in the cathode coreactant is 2-4nm. The prepared anode coreactant has better OER reaction catalyzing performance and can promote the anode luminescence of terpyridyl ruthenium; the cathode coreactant has better ORR reaction catalyzing performance and can promote the cathode luminescence of terpyridyl ruthenium.

Description

Ru(bpy)32+ anode or cathode coreactant and preparation method thereof

Technical field

The invention belongs to the technical field of Ru(bpy) ₃ ²⁺ anode or cathode co-reactant, and specifically relates to Ru(bpy) ₃ ²⁺ anode or cathode co-reactant and its preparation method.

Background technique

The statements herein merely provide background information related to the present invention and do not necessarily constitute prior art.

In recent years, the development of sensitive and specific tumor marker detection methods has become a research hotspot. Among them, electrochemiluminescence has received widespread attention due to its advantages such as high sensitivity and good stability. Electrochemiluminescence means that when a certain voltage or current is applied, the luminophore in the system generates excited state substances through potential excitation and a series of redox reactions, which emit light and release energy when they transition back to the ground state. Among them, the noble metal complex terpyridine ruthenium(II) (Ru(bpy) ₃ ²⁺ ) and its derivatives are luminophores with high luminous efficiency, good stability and can be recycled. Because it can display potential-resolved luminescence properties when promoted by different corresponding co-reactants - that is, it produces electrochemical luminescence under different potentials, it can be used as the luminophore of single-emitter multi-co-reactant systems.

However, most ECL analysis systems are usually based on a single signal ("signal on" or "signal off" mode), which has disadvantages in detection: it is not conducive to the stability, accuracy and efficiency of signal output, as well as the integration and small size of biosensors. change.

The multi-signal output ECL detection system can avoid most of the defects of the single-signal ECL system and is more flexible, convenient and accurate in detection. Multi-signal ECL output often relies on introducing distinguishable signal output probes or constructing multi-channel detection. Among the resolution ECL strategies, although potential-resolved ECL has the advantages of low instrument requirements, shortened detection time, and increased sample throughput, a large number of potential-resolved multi-signal ECL systems mostly use dual illuminators, or two complex illuminants with resolvable potentials. and coreactant combinations are hampered by limited potential-resolved luminescent pairs, cumbersome assembly steps, complex labeling processes, and inevitable crosstalk between coreactants and luminophores, between coreactants, and between luminophores. trouble, which greatly limits the development of ratiometric ECL detection systems.

In related research on the dual-signal ratio ECL strategy of a single luminophore, the selection of co-reactants is very critical. Currently, there are relatively few studies on co-reactants under different potentials of luminophores, and most of them are complex to synthesize and difficult to prepare. Some researchers have tried to use The cathode and anode co-reactants are synthesized together or an electrolysis reaction is introduced to generate co-reactants in situ to simplify the preparation, addition and other processes of co-reactants. However, none of these studies has essentially solved the problem of the relative lack of coreactant research, and the synthesis of cathode-anode coreactant complexes is equally complex, and systems that generate coreactants in situ are extremely susceptible to environmental interference.

Contents of the invention

In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a Ru(bpy) ₃ ²⁺ anode or cathode co-reactant and a preparation method thereof. The prepared anode co-reactant has better performance in catalyzing OER reactions. , can promote the anodic luminescence of ruthenium terpyridine; the cathode co-reactant has good catalytic performance in the ORR reaction and can promote the cathodoluminescence of ruthenium terpyridine.

In order to achieve the above objects, the present invention is achieved through the following technical solutions:

In the first aspect, the present invention provides Ru(bpy) ₃ ²⁺ anode or cathode co-reactant, both of which are Au-rGO composites. The particle size of the Au nanoparticles in the anode co-reactant is 10-15nm; the cathode co-reactant The particle size of Au nanoparticles in is 2-4nm.

In a second aspect, the present invention provides a method for preparing the Ru(bpy) ₃ ²⁺ anode or cathode co-reactant, which includes the following steps:

After mixing the HAuCl ₄ aqueous solution and the r-GO suspension in proportion, they are dispersed ultrasonically to obtain mixture one;

Add NaBH ₄ to mixture one and mix well, then add sodium citrate and mix well;

After the reaction is completed, separate and wash the solid product, and then redisperse it to obtain a resuspended solution;

Centrifuge the resuspended solution at 11000-12500 rpm for 10-30 min, and collect the unsolved and unprecipitated components to obtain the solution.

The beneficial effects achieved by one or more embodiments of the present invention are as follows:

By adjusting the size of gold nanoparticles supported on reduced graphene oxide, ruthenium terpyridine cathode and anode coreactant transformation was achieved. In a single-emitter multi-signal output system, the crosstalk between cathode and anode co-reactants is greatly reduced;

By designing ORR and OER catalysts with appropriate catalytic capabilities as ruthenium anode and cathode co-reactants, the precise design of the cathode and anode co-reactants of ruthenium terpyridine was achieved.

The key point of the technical solution of the present invention is to adjust the catalytic ability of ORR and OER by changing the particle size of Au-γGO to achieve the transformation of ruthenium cathode and anode co-reactants.

Description of the drawings

The description and drawings that constitute a part of the present invention are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

In Figure 1, (a) is the large-scale transmission electron microscope (TEM) of Au-rGO, (b) is the annular dark field SEM of Au-rGO, and (c) is the scanning electron microscope SEM image of Au-rGO;

Figure 2 is a graph of Au/rGO of different sizes grown on rGO substrate in the embodiment of the present invention, where A is a transmission electron microscope image, B is the corresponding size histogram of Au/rGO-1; C is Au/rGO- The corresponding size histogram of 2, D is the corresponding size histogram of Au/rGO-3, and E is the corresponding size histogram of Au/rGO-4.

Figure 3 is a DPV test chart of Au/rGO-2 in the embodiment of the present invention. The electrolyte is ruthenium terpyridine with pH value = 6;

Figure 4 is the EDS mapping image of Au-rGO in the embodiment of the present invention, where A is the SEM image of Au-rGO at 100nm scale; B is the EDS mapping image of the carbon element of Au-rGO at 100nm scale; C is 100nm The EDS mapping image of the nitrogen element of Au-rGO at the scale; D is the EDS mapping image of the oxygen element of Au-rGO at the 100nm scale; E is the EDS mapping image of the gold element of Au-rGO at the 100nm scale; F is the EDS mapping image of the gold element in Au-rGO at the 100nm scale. EDS mapping images of carbon, nitrogen, oxygen, and gold elements of Au-rGO; G is the element content analysis chart obtained by EDS mapping of Au-rGO at the 100nm scale;

Figure 5 is the XRD image of Au/rGO in the embodiment of the present invention;

Figure 6 is the UV-visible absorption spectrum image of Au/rGO in the embodiment of the present invention, where A is the UV-visible absorption spectrum of GO film and AuNPs/rGO nanocomposite film; B is the UV-visible absorption spectrum of Au/rGO with different reduction times of rGO. UV-visible absorption spectrum. Among them, Au/rGO-A, B, and C represent the reduction events of rGO at 3h, 6h, and 12h respectively;

Figure 7 is the Zeta potential image of Au/rGO in the embodiment of the present invention;

In Figure 8, A) XPS survey spectra of original graphene oxide film and AuNPsrGO nanocomposite film after being treated with Ar plasma for 15 minutes; B) high-resolution c1 deconvolution spectrum of graphene oxide film and C) AuNPsrGO film; D )Au4f XPS spectrum of AuNPsrGO;

Figure 9 is the Raman spectrum of Au/rGO in the embodiment of the present invention;

Figure 10 is the ECL and CV performance of AuNPs-rGO under different AuNPs particle sizes in the embodiment of the present invention, where A is the ECL performance of Au/rGO with different AuNPs particle sizes on Ru(bpy) ₃ ²⁺ ; B is the CV performance of Au/rGO with different particle sizes of AuNPs; C is the CV performance of the cathode co-reactant Au/rGO-2 and the bare electrode in Ru(bpy) ₃ ²⁺ and PBS respectively; D is the anode co-reaction CV performance of Au/rGO-3 and bare electrode in Ru(bpy) ₃ ²⁺ and PBS respectively;

Figure 11 shows the CV performance of Au-rGO with different particle sizes in A) _N2 atmosphere, B) in air atmosphere, C) in oxygen atmosphere in the embodiment of the present invention; D) Au-rGO-2 in different LSV image at rotating speed; ECL performance of E) cathode coreactant and F) anode coreactant under argon atmosphere.

Figure 12 is an ECL phenomenon diagram of different metal/reduced graphene oxide hybrids in an embodiment of the present invention, where A is an ECL image of the effect of different metal/reduced graphene oxide hybrids on Ru(bpy) ₃ ²⁺ ; B LSV images of different metal/reduced graphene oxide hybrids;

Figure 13 shows the ECL effect of Au-rGO-2 and Au-rGO-3 on ruthenium terpyridine in different atmospheres in the embodiment of the present invention, where A is the cathode co-reactant Au-rGO-2 in nitrogen, air, ECL performance of the action on Ru(bpy)32+ under oxygen atmosphere; B is the ECL performance of the anode co-reactant Au-rGO-3 on Ru(bpy)32+ under nitrogen, air and oxygen atmospheres;

In Figure 14, A) After adding the superoxide anion inhibitor, the ECL performance of the cathode co-reactant Au/rGO-2 on Ru(bpy) ₃ ²⁺ ; B) After adding the hydroxyl radical inhibitor, the anode co-reaction ECL performance of the effect of Au/rGO-3 on Ru(bpy) ₃ ²⁺ ;

In Figure 15, when Ru(bpy) ₃ ²⁺ eliminates all ORR and OER processes involving O ₂ , dissolved oxygen and oxygen atoms in an acetonitrile solution Ar atmosphere, A) the promotion effect of Au-rGO-2 on cathode luminescence and B ) Comparison of the promotion effect of Au-rGO-3 on cathodoluminescence;

Figure 16 is an ECL characterization diagram of Au-rGO in the embodiment of the present invention;

Figure 17 is a graph showing the change of Ic/Ia with reduction time in the embodiment of the present invention.

Detailed ways

It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings commonly understood by one of ordinary skill in the art to which this invention belongs.

The inventor tried to innovatively use ruthenium terpyridine (Ru(bpy) ₃ ²⁺ ) as a single luminophore without introducing excess reactants, and use it to act as both an anode and cathode under the action of the corresponding co-reactants. The nature of the emission, finding similar co-reactants to achieve opposite potential separation signal changes.

The inventor found through relevant research that the cathodic process of Ru(bpy) ₃ ²⁺ is related to the oxygen reduction reaction (ORR), and the generation of reactive oxygen species (ROS), the intermediate product of the ORR reaction, can significantly improve luminescence. The anodic process of ruthenium terpyridine can be quenched by _O2 and enhanced by OH·, which are the final product and intermediate product of the OER process (reverse reaction of ORR) respectively. Since Au and its related alloy clusters have the catalytic ability of ORR and OER, and the tunable catalytic properties by changing the particle size of AuNPs, it becomes an ideal reagent to achieve anodic and cathodoluminescent conversion of Ru(bpy) ₃ ²⁺ .

In the first aspect, the present invention provides Ru(bpy) ₃ ²⁺ anode or cathode co-reactant, both of which are Au-rGO composites. The particle size of the Au nanoparticles in the anode co-reactant is 10-15nm; the cathode co-reactant The particle size of Au nanoparticles in is 2-4nm.

Experiments have found that AuNPs and rGO alone cannot significantly catalyze the anodic or cathodic emission of Ru(bpy) ₃ ²⁺ ; AuNPs with smaller particle sizes have better cathode promotion effects. This is because smaller-sized Au particles have greater electrocatalytic activity for oxygen reduction reaction (ORR) than larger-sized AuNPs, and a considerable portion of surface atoms may absorb and activate oxygen molecules.

In some embodiments, the degree of reduction of rGO in the anode co-reactant is reduction in hydrazine hydrate steam for 5.5-6.5 hours.

Graphene oxide has certain anode stimulating properties, and the reduction of graphene oxide by hydrazine hydrate will change the anode stimulating properties, making its cathode luminescence promotion ability greater than that of graphene oxide.

The incomplete reduction reaction formed by the defective graphene substrate can accelerate the charge transfer from AuNPs to O ₂ , lowering the energy barrier of the rate-limiting step by destabilizing the ORR intermediate species and lowering the activation energy of the dissociation of O ₂ leading to more Reactive oxygen species production.

In some embodiments, the degree of reduction of rGO in the cathode co-reactant is reduction in hydrazine hydrate steam for 5.5-6.5 hours.

In a second aspect, the present invention provides a method for preparing the Ru(bpy) ₃ ²⁺ anode or cathode co-reactant, which includes the following steps:

After mixing the HAuCl ₄ aqueous solution and the r-GO suspension in proportion, they are dispersed ultrasonically to obtain mixture one;

Add NaBH ₄ to mixture one and mix well, then add sodium citrate and mix well;

After the reaction is completed, separate and wash the solid product, and then redisperse it to obtain a resuspended solution;

Centrifuge the resuspended solution at 11000-12500 rpm for 10-30 min, and collect the unsolved and unprecipitated components to obtain the solution.

The function of NaBH ₄ is to reduce HAuCl ₄ to gold element, thereby forming gold nanoparticles.

The role of adding sodium citrate is to further reduce the gold nanoparticles.

Since the particle sizes of the gold nanoparticles in the solution are not uniform and vary greatly before this step, the resuspended solution is centrifuged at 11000-12500 rpm for 10-30 minutes. During this process, the gold nanoparticles with larger particle sizes are removed. Unqualified products such as its complex with reduced graphene oxide and other products that do not meet the requirements are removed by centrifugation. Centrifuge at an appropriate speed and time and then take the supernatant to remove larger-sized gold nanoparticles in the precipitate.

In some embodiments, a step of reducing graphene oxide using hydrazine hydrate steam to prepare reduced graphene oxide is also included. Specifically, the water suspension of graphene oxide and hydrazine hydrate are placed in two containers respectively, and Place the two containers in the same closed space and stir for reaction.

In some embodiments, during the preparation process of the anode co-reactant, in the mixed reaction system of HAuCl ₄ , r-GO, NaBH ₄ and sodium citrate, the concentration of HAuCl ₄ is 18-22 mg/ml;

The concentration of r-GO is 1.8-2.2mg/ml;

The concentration of NaBH ₄ is 0.005-0.015M;

The concentration of sodium citrate is 0.005-0.015M.

In some embodiments, during the preparation process of the cathode coreactant, in the mixed reaction system of HAuCl ₄ , r-GO, NaBH ₄ and sodium citrate, the concentration of HAuCl ₄ is 18-22 mg/ml;

The concentration of r-GO is 1.8-2.2mg/ml;

The concentration of NaBH ₄ is 0.005-0.015M;

The concentration of sodium citrate is 0.005-0.015M.

In some embodiments, after the reaction is completed, in the step of separating and washing the solid product, the separation is centrifugal separation, the centrifugal speed is 14500-15500 rpm, and the centrifugation time is 30-60 min.

The rotation speed of this centrifugal separation is larger and the centrifugation time is longer, in order to completely separate the residual reducing agent (NaBH ₄ , sodium citrate) from AuNPs/rGO and avoid the influence of the residual reducing agent on AuNPs/rGO.

In some embodiments, after mixing the HAuCl ₄ aqueous solution and the r-GO suspension in proportion, the steps of ultrasonic treatment and stirring are included. The ultrasonic treatment time is 5-15 min, and the stirring time is 1.5-2.5 h. Ultrasonic stirring makes HAuCl ₄ and r-GO fully and evenly mixed. The ultrasonic power is 200w.

Preferably, the process of sonication and stirring of the mixed solution of HAuCl ₄ aqueous solution and r-GO suspension is repeated 2-4 times. Repeated ultrasonic stirring allowed HAuCl ₄ and r-GO to be fully mixed and evenly dispersed.

In some embodiments, after adding NaBH ₄ to the mixture of HAuCl ₄ aqueous solution and r-GO suspension, initial stirring is followed by ultrasonic treatment; the initial stirring time is 10-20 min, and the ultrasonic treatment time is 5-15 min. Stir to mix evenly and ultrasonic to disperse the particle size. The ultrasonic power is 200w.

In some embodiments, after adding sodium citrate to the mixed solution, preliminary stirring is followed by ultrasonic treatment; the preliminary stirring time is 20-40 min, and the ultrasonic treatment time is 5-15 min. Stir to mix evenly and ultrasonic to disperse the particle size. The ultrasonic power is 200w.

The present invention will be further described below in conjunction with examples.

Experimental Materials

Tetrachloroauric acid (HAuCl ₄ ), silver nitrate (AgNO ₃ ) and sodium citrate were purchased from Sangon Bioengineering (Shanghai) Co., Ltd.;

Terpyridyl(2,2'-bipyridyl)ruthenium(II)(Ru(bpy) ₃ ²⁺ ) was purchased from Suzhou Nakai Technology Co., Ltd.;

Natural graphite powder (325 mesh) was purchased from Nanjing Xianfeng Nano Materials Technology Co., Ltd.;

Sodium borohydride (NaBH ₄ ), ethyl mercaptan, ascorbic acid (AA) and isopropyl alcohol were purchased from Sinopharm Chemical Reagent Co., Ltd.

Add 0.1M KCl to a mixture of KH ₂ PO ₄ and Na ₂ HPO ₄ in an appropriate proportion to obtain a phosphate buffer solution (PBS, 0.1M pH 7.4) for ECL detection. All other chemicals were of analytical grade and used without further purification. All aqueous solutions were prepared freshly and diluted with ultrapure water (≥18MΩ, Milli-Q, Millipore).

equipment

ECL measurements were performed on an MPI-E multifunctional electrochemiluminescence analyzer (Xi'an Remai Analytical Instrument Co., Ltd.). Three-electrode ECL battery consists of modified glassy carbon working electrode An Ag/AgCl (saturated KCl) electrode was used as the reference electrode, and a platinum wire was used as the counter electrode. The photomultiplier tube (PMT) is biased at 600V. The scanning voltage is 1.5~-2V, and the scanning rate is 100mV/s.

Ultraviolet-visible (UV-vis) absorption spectra and fluorescence spectra were obtained using a spectrophotometer (Model UV2450, Shimadzu, Japan) and a spectrophotometer (Model F-7000, Hitachi, Japan) respectively.

X-ray photoelectron spectroscopy (XPS) characterization was measured by a VG Multilab 2000X X-ray photoelectron spectrometer (Thermoelectric Corporation, USA).

Fourier transform infrared spectroscopy (FT-IR) was observed on an infrared spectrometer (ALPHA, Bruker, Germany).

Transmission electron microscopy (TEM) images were obtained using a JEM-2010 transmission electron microscope (JEOL, Japan).

Cyclic voltammograms (CVs) and electrochemical impedance spectroscopy (EIS) were obtained using an electrochemical workstation (Ivium, Netherlands).

CVs were recorded in a 5mM K ₃ (CN) ₆ ]/K ₄ (CN) ₆ ] solution containing 0.1M KCL between -0.2V and +0.6V at a scan rate of 100mV/s.

EIS measurement is performed by applying a voltage of 5mV amplitude in the frequency range of 0.01Hz to 106Hz.

Inductively coupled plasma mass spectrometry (ICP-MS, iCAP Q, Thermo Fisher, America) was used to analyze real samples.

The preparation method is:

1)GO synthesis:

Graphene oxide is synthesized from oxidized natural graphite powder through Hummer's method. Graphite powder (3.0 g) was added to concentrated sulfuric acid (70 mL) while stirring vigorously in an ice bath. Then, potassium permanganate (9.0 g) was added gently to maintain the suspension temperature below 20°C. Transfer the reaction system to a 40°C oil bath in turn and stir vigorously for about 30 minutes. Then, 150 mL of water was added and the solution was stirred at 95°C for 15 minutes. Then add 500 mL of water, and then add 15 mL of hydrogen peroxide (30%) steadily to change the color of the solution from dark brown to yellow.

In order to remove metal ions, the reaction mixture was first filtered and washed with 250 mL of a 1:10 hydrochloric acid and water mixed solution, and then the synthesized solid was dried in the air and diluted to 600 mL with water to form a graphite oxide aqueous dispersion. Then, a dialysis membrane (from Beijing Chemical Reagent Co., China) with a molecular weight of 8000 to 14,000 g mol ^-1 was used for dialysis purification for one week to eliminate residual metals.

The graphite oxide aqueous solution dispersion with metal ions removed was diluted to 1.2L, stirred overnight, and ultrasonicated for 30 minutes to peel it into graphene oxide. Finally, the graphene oxide dispersion was centrifuged at 3000 rpm for 40 min to remove the graphite that did not fall off.

2) Synthesis of reduced graphene oxide r-GO

Dissolve 2 mg graphene oxide in 2 ml ultrapure water; place the obtained 2 mg/ml graphene oxide and 2 ml hydrazine hydrate in two clean small beakers, and cover the two beakers with a large beaker. After 6 hours of stirring, the color of the graphene oxide fabric changed from light brown to black, indicating the generation of reduced graphene oxide.

3) Synthesis of cathode coreactant Au-rGO-2 and anode coreactant Au-rGO-3 of ruthenium terpyridine

HAuCl ₄ (for Au-rGO-2, 2.5 μl of 2% HAuCl ₄ , diluted to 10 μl with ultrapure water; for Au-rGO-3, 10 μl of 2% HAuCl ₄ used undiluted) Add 2 ml of r-GO and The solution was stirred, followed by sonication for 10 min and then stirred at room temperature for 2 h. This process was repeated three times.

After ultrasonic inspection for 10 minutes, quickly add 25 μl of 0.01M freshly prepared NaBH ₄ , stir for 15 minutes, and then sonicate for 10 minutes;

Then 10 μl of 0.01 M sodium citrate was added to the solution, stirred for 25 minutes, and then sonicated for 10 minutes.

Afterwards, centrifuge at 15,000 rpm for 45 min to remove _excess NaBH and sodium citrate, wash thoroughly with water, and finally redisperse in 2 mL of ultrapure water. The resuspended solution was then centrifuged at 12,000 rpm for 20 minutes to collect the unprecipitated components of the solution for further use and characterization.

Synthetic characterization

Electron microscopy and particle size analysis

The nanostructure of the composite material can be verified through morphological analysis. Large-scale transmission electron microscopy (TEM) and scanning electron microscopy (SEM) images show the typical wrinkled texture of Au-rGO films, indicating the existence of flexible ultrathin rGO flakes (as shown in Figure 1). In addition, clearly visible spherical AuNPs particles appeared on the background reduced graphene oxide flakes, namely black spots in the TEM image and bright spots in the SEM image, verifying the in-situ growth of AuNPs on the reduced graphene oxide flakes. The TEM image (Figure 1b) shows that the AuNPs are evenly distributed on the surface of the rGO sheet without forming loose clusters outside. The inset of Figure 1b shows that the diameter of AuNPs on Au/rGO is about 3.8 nm, which is smaller than the size of single AuNPs, indicating that the electrostatic or π-π stacking interaction between AuNPs and rGO surface is relatively strong.

According to Plieth's equation:

Among them, Ebulk is the oxidation potential of the bulk metal (taken as 1.15V), γ is the surface tension (1880erg cm ^-2 ), V _m is the molar volume (10.21cm ³ mol ^-1 ), Z is the number of electrons (1), F is Faraday's constant and d is the NP diameter (3.4nm).

Therefore, the peak oxidation potential of AuNPs (E AuNPs) (Au(0) to Au(I)) in Au/rGO-2 was calculated to be 0.92V (compared to SHE). E AuNPs and Ag/AgCl electrodes are converted according to the Nernst equation:

E° vs Ag/AgCl=E° vs SHE-E° _Ag/AgCl -(RT/(zF·lge))pH;

Among them, the E° vs SHE of AuNPs is 0.92V, and the E° _Ag/AgCl is 0.22V vs SHE. The pH of the system is 6.

Therefore, the E° AuNPs versus Ag/AgCl is calculated to be 0.35 eV, which is consistent with the CV of AuNPs (Au(0) to Au(I)) at 0.37V when 2 mol/L Au/rGO-2 is loaded on the electrode. The peaks are consistent (Figure 3).

EDS

Analysis of chemical composition was performed by EDS mapping. The presence of AuNPs on rGO was further confirmed by EDS mapping of the Au-rGO composite, which exhibited characteristic peaks of C, N, O, and Au, consistent with the chemical composition of graphene and AuNPs. The presence of oxygen characteristic peaks in the EDS spectrum indicates that the oxygen-containing groups on graphene oxide are not completely reduced (as shown in Figure 3).

XRD

The crystal phase composition of Au/rGO was analyzed using XRD (Figure 5). As GO decreases, the diffraction peak of GO at 10.2 (0 0 2) disappears (Figure 5, dark blue curve) and appears as a new peak at 29.0 (0 0 2) (Figure 5, light blue curve) ) for the generation of rGO. The characteristic diffraction peaks of rGO also appear in the diffraction spectrum Au/rGO, with a significant characteristic diffraction peak at 38.3° and two peaks with poor intensity at 44.5° and 82.4°, respectively. For Au(1 1 1), Au(2 0 0) and Au (2 2 2 2), this is attributed to the composite of the face-centered cubic (fcc) structure of AuNPs on rGO.

UV-visible absorption spectrum

In order to further confirm the double reduction effect, the UV-visible absorption spectrum of the Au-rGO composite film was also recorded, as shown in A in Figure 6. The rGO spectrum showed a characteristic absorption peak at 227 nm and a shoulder peak at 315 nm, respectively. Corresponds to the π-π* transition of the aromatic Csingle bond C bond and the n-π* transition of the Csingle bond O bond. In the spectrum of Au-rGO, the peak at 227nm is red-shifted to 258nm, and the peak at 315nm disappears, proving the existence of rGO. Furthermore, a new absorption peak at 535 nm appeared in the Au-rGO spectrum, which was attributed to the surface plasmon resonance in Au and confirmed the formation of Au.

In Figure 6, B, Au/rGO-A, Au/rGO-B and Au/rGO-C respectively refer to the reduction degree of rGO in Au/rGO: reduction in hydrazine hydrate steam for 3h, 6h and 12h. The red shift of the characteristic peaks of rGO indicates that the reduction time of rGO increases.

zeta potential

Zeta potential measurements were performed on GO, rGO and Au/rGO to detect surface charge characteristics. The average zeta potential of GO is about -44mV, which comes from the negatively charged oxygen-containing functional groups on the surface of GO, such as carboxyl and epoxy groups. After the reduction process, the 23.5 mV value of RGO became more negative, probably because the functionalization of RGO during partial reduction resulted in a higher surface negative charge density compared to GO. This results in stable dispersion of RGOs in aqueous solutions through electrostatic repulsion with water molecules. The estimated zeta potential of Au/rGONCs was found to be 7.95mV. Compared with rGO, the reduced negative charge of Au/rGO NCs indicates that Au NPs were successfully synthesized on rGO, as shown in Figure 7.

XPS

The chemical structures of rGO and Au/rGO were further confirmed by X-ray photoelectron spectroscopy (XPS). It can be clearly seen from A in Figure 8 that carbon (C) and oxygen (O) are the main components of RGO, while Au-RGO is composed of C, O and gold (Au). The proportion of nitrogen (N) in rGO and Au-RGO is very small. B in Figure 8 shows the high-resolution C1s deconvolution spectrum of Au-rGO, which can be divided into four peaks, centered at 284.6 eV (C-C/C=C in the aromatic ring), 286.3eV (C-O), 287.2eV (C=O) and 288.4eV (O-C=O), the relatively higher C=O peak indicates that rGO is not completely reduced. The high-resolution N 1s spectrum of C in Figure 8 can be deconvoluted into three Gaussian-Lorenzi peaks with binding energies of 398.6 eV (sp2-bonded nitrogen in the N-containing aromatic ring (C-N=C)), 399.7 eV (tertiary nitrogen N-(C)3 group) and 400.7eV (amino (C-N-H)), which confirms the presence of amino groups on Au/rGO.

The high-resolution Au 4f spectrum obtained from the Au-RGO sample, as shown in Figure 8 D, shows that in the binding energy scale of Au(I), the more prominent Au 4f7/2 is found at 88.3eV and 84.5eV and Au 4f5/2 spin-orbit twins, as well as weaker Au 4f5/2 and Au 4f7/2 at 87.2V and 83.4eV due to Au(0). Therefore, the chemical properties of gold in Au-rGO have been determined as the combination of metal-Au(0) and Au(I) present in the Au-N bond. The slight negative shift (0.4 eV) shown by the Au 4f spin-orbit doublet region relative to the traditional reference position of metal-Au implies a strong interaction between Au and the RGO framework.

Raman spectroscopy

Raman spectroscopy tests were performed on Au/rGO and rGO. Given that the Raman spectra between Au/rGO and rGO are almost identical (Fig. 9), it is reasonable to assume that the formation of AuNPs has little effect on the in-plane sp2 domain size of graphene, probably because of the low loading volume of AuNPs ( 0.01 atomic %) does not appear to be sufficient to structurally damage rGO.

ECL characterization

In order to explore and prove, a series of Au-rGO with particle sizes (Au-rGO-1, Au-rGO-2, Au-rGO-3, Au-rGO-4) were synthesized, with particle sizes corresponding to 3.1 and 3.4 respectively. , 13.5, 30.6nm).

A in Figure 10 shows the corresponding ECL performance of Ru(bpy) ₃ ²⁺ and the prepared Au/rGO. When Au/rGO-1 was used as a coreactant, strong cathodoluminescence (red line) of Ru(bpy) ₃ ²⁺ was observed at -1.7V (5123A.U). In Au/rGO-2, under the condition of -1.7V (blue line), Ru(bpy) ₃ ²⁺ has super strong cathodoluminescence (14488a.u), which is stronger than the corresponding peak of Au/rGO-1. Both Au/rGO-3 and Au/rGO-4 show poor cathode catalytic performance, and their lowest cathode peaks are lower than bare GCE. Therefore, the ECL results verify that Au/rGO can exhibit the strong cathodic co-reaction characteristics of Ru(bpy) ₃ ²⁺ at medium to small AuNPs particle sizes.

mechanism

Ruthenium cathode coreactants and ORR reactions

The cathode co-reactant of ruthenium terpyridine is an ORR catalyst that is strong enough to generate sufficient ROS but also avoids the complete reaction to produce excess water. Au/rGO has tunable catalytic performance, which can be enhanced by shrinking AuNPs and vice versa. In addition, according to the d-band theory, as the core size of Au nanoclusters decreases, the d-band becomes narrower and moves toward the Fermi level, indicating that smaller Au clusters are energetically more conducive to the adsorption of _O2 . Therefore, based on the above theory, medium-sized Au/reduced graphene oxide has the greatest promotion effect on Ru(bpy) ₃ ²⁺ cathodoluminescence.

A series of Au-rGO with particle sizes (Au-rGO-1, Au-rGO-2, Au-rGO-3, Au-rGO-4, corresponding to particle sizes of 3.1, 3.4, 13.5, and 30.6nm respectively) were synthesized. . The ECL results verify that Au/rGO can exhibit strong cathode coreaction characteristics of Ru(bpy) ₃ ²⁺ at medium to small AuNPs particle sizes (shown as A in Figure 10).

The cyclic voltammograms (CVs) show that in addition to the reversible peaks of the Ru(bpy) ₃ ²⁺ redox reaction (at 1.13V and +1.05V, respectively) and the reduction and oxidation reaction of Ru(bpy) ₃ ²⁺ (respectively at - 1.65V and -1.60V) (Figure 10B), the small peak at -0.65V observed on the GCE of PBS and Ru(bpy) ₃ ²⁺ /PBS belongs to the oxygen reduction reaction (ORR). After Au/rGO-2 was modified on GCE, the peak at -0.65V greatly increased, indicating its catalytic performance in the ORR process (Figure 10C).

The catalytic performance of a series of Au/rGO was compared by performing cyclic voltammetry in _O2 or _N2 saturated aqueous 0.1 M KOH solution at room temperature. As shown in Figure 11B, the ORR onset potential is approximately -0.08V (vs Ag/AgCl), and the reduction peak is approximately -0.22V (vs Ag/AgCl). The suppression and enhancement of the reduction peak in nitrogen and oxygen atmospheres indicate that oxygen is involved in the reaction, which proves the ORR process (Figure 11A-C). Under the same atmosphere, the tunable catalytic performance of Au/RGO was demonstrated by changing the particle size of Au/RGO. Among them, the Au/rGO-1 catalyst with the smallest particle size has the best ORR catalytic performance. As the particle size increases, the catalytic performance decreases. These findings indicate that Au/rGO-2 with moderate ORR catalytic ability will have superior cathode coreactant performance.

In O2 _- saturated 0.1M KOH solution, the electron transfer number during the catalytic process was calculated using linear scan voltammetry (LSV) at different rotation speeds (ω) of the rotating disk electrode (RDE) from 225 rpm to 3600 rpm. (Fig. 11D). The ORR onset potential of the Au/rGO-2 modified electrode is about -0.20V (vs Ag/AgCl) at 1600 rpm, and the ORR current density at 0.8V (vs Ag/AgCl) is about 0.28mA/cm ² . The inset of Figure 1 ID depicts the Koutecky–Levich equation (J-1 vs ω-1/2) at different electrode potentials (from 0.5 V to 0.7 vs Ag/AgCl). According to the KL equation, in the potential range of -0.5~-0.7V (vs Ag/AgCl), the number of transferred electrons (N) per oxygen molecule catalyzed by Au/rGO-2 is 1.2-1.7.

By recording the RDE curve (1600 rpm) corresponding to ORR, the catalytic activity of Au/rGO and different metal/reduced graphene oxide hybrids under different AuNPs particle sizes was characterized. As shown in Figure 11, the ORR onset potential of Au/rGO-2 (-0.20V) is more positive than that of Au/rGO-3 (-0.25V), but more positive than that of Au/rGO-1 (-0.18V). ) has a more negative ORR onset potential. Furthermore, the ORR current density (e.g., at -0.8V vsAg/AgCl.) of Au/RGO-2 (0.28 mA/cm ² ) is significantly larger than that of Au/RGO-3 (0.18 MA/cm ² ), but lower than that of Au/ rGO-1(0.38MA/cm2).

As shown in Figure 12B, the ORR onset potential of Au/rGO-2 (-0.20V) is more negative than that of Ag/rGO (-0.15V), Cu/rGO and Pt/rGO (-0.10V). The electrochemiluminescence properties of these metal nanoparticles/graphene as coreactants of Ru(bpy) ₃ ²⁺ were compared (Figure 12A). Therefore, the superior cathode coreactant performance of Au/rGO-2 can also be explained by its moderate ORR catalytic activity.

Anodic co-reactant of ruthenium terpyridine and OER reaction

OH· plays an important role in promoting the anodic oxidation of Ru(bpy) ₃ ²⁺ , and oxygen is toxic to anode luminescence. Therefore, the advantage of Au/rGOs as a controlled Ru(bpy) ₃ ²⁺ cathode or anode promoter is that it exhibits an increase in OER catalytic performance with decreasing particle size. Therefore, a suitable anode promoter should not only catalyze H ₂ O to lose one electron to produce a large amount of OH·, but also avoid the production of excessive O ₂ . Therefore, a weaker OER reaction catalyst is needed to make the reaction shift to reaction (Equation 2-1) instead of reaction (Equation 2-2). At the same time, the d-band theory is also considered, so the larger particle size of Au-rGO has better Anodic coreactant properties of ruthenium.

H ₂ Oe→HO ^˙ +H ⁺ (2-1)

O2 ^˙ --e→O ₂ (2-2)

As shown in Figure 10A, when Au/RGO-3 and Au/RGO-4 with medium, large size (13Nm) and maximum size (30Nm) of AuNPs are loaded on the electrode, Ru(bpy) ₃ ²⁺ at 1.1V The anodic luminescence is significantly amplified. However, Au/rGO-1 and Au/rGO-2 with the small particle size of AuNPs only produce weak fluorescence with Ru(bpy) ₃ ²⁺ , which is weaker than bare GCE. This may be due to the quenching of O ₂ generated by OER. annihilation effect. The electroluminescence of Ru(bpy) ₃ ²⁺ on Au/rGO-3 catalyst is better than that of Au/RGO-4. This is because the Au/RGO-4 catalyst with too large AuNPs particle size is too weak to catalyze OER. , is not enough to produce enough OH·, which can be proved by the cyclic voltammogram.

Under anodic scanning of exposed GCE in Ru(bpy) ₃ ²⁺ solution, the current rises at the background current at +1.0V due to the oxidation of Ru(bpy) ₃ ²⁺ and then increases faster due to the oxidation of water, and peaks at +1.3V. The peak current at +1.3V can be used as an indicator of the degree of OER. Cyclic voltammetry was used to evaluate the OER catalytic performance of a series of synthesized Au/rGO. Figure 10B shows the OER catalytic ability of Au/rGO-1 to Au/rGO-4. decreasing gradually. The results also confirmed that the anode promoter Au/rGO-3 with medium and weak OER catalytic performance can slow down the OER reaction, thereby prolonging the residence time of the product OH· on the catalyst surface. In addition, the larger particle size of AuNPs can make OH· more inclined to desorb from Au/rGO-3, resulting in a large amount of OH· gathering near the electrode, which is conducive to strong ECL luminescence.

The enhancement effect of cathode and anode Au/rGOs on ECL luminescence under nitrogen and oxygen atmospheres was characterized.

In a nitrogen environment, the promotion effect of cathode accelerator Au/rGO-2 (dark blue line) on Ru(bpy) ₃ ²⁺ cathodoluminescence is weakened. This is because the nitrogen in this system removes dissolved oxygen, thereby inhibiting The occurrence of ORR reaction. The enhancement of anodic luminescence is due to the disappearance of the quenching effect of dissolved oxygen on Ru(bpy) ₃ ^2+* . In contrast, the ORR process is stimulated in an _O2 environment (light blue line) ^{, resulting in enhanced Ru(bpy)32+} _{cathodoluminescence} .

Figure 13B shows the effect of the anode promoter Au/rGO-3 on the luminescence of Ru(bpy) ₃ ²⁺ under different atmospheres. Under nitrogen atmosphere (dark blue line), the anodic luminescence of Ru(bpy) ₃ ²⁺ is significantly enhanced. This may be due to the fact that the OER reaction catalyzed by Au/rGO-3 produces intermediate products OH· and other active oxygen components that promote anodic luminescence, while the by-product O ₂ and dissolved oxygen are removed by the nitrogen gas flow. After the introduction of O ₂ , the anodic luminescence of Ru(bpy) ₃ ²⁺ was significantly weakened, while the cathodoluminescent luminescence was not significantly enhanced. This is because Au/rGO-3 lacks strong ORR catalytic ability, and the increase in dissolved oxygen in the electrolyte has a strong quenching effect on the anodic luminescence.

The above results show that the ORR catalytic ability of Au/rGO-2 can promote the cathodoluminescence of Ru(bpy) ₃ ²⁺ , while the O ₂ produced by the dissolved oxygen in the solution and the OER reaction on the electrode surface can inhibit the Ru(bpy) ₃ ^{2 +} anode luminescence.

Therefore, the inhibitors of OH·-superoxide dismutase SOD and isopropyl alcohol, and the inhibitor-agent benzoquinone (BQ) of O2-· were introduced to independently reflect the effects of various catalytic active oxygen components on Ru(bpy) ₃ Specific effects of ²⁺ cathodoluminescence.

The results are shown in Figure 14. SOD, isopropanol, and benzoquinone (BQ) all significantly reduced the cathode luminescence promoted by Au/rGO-2, indicating that Au/rGO-2 mainly promotes the cathode by catalyzing the reduction of oxygen to O2-· luminescence (Fig. 14A).

For the anode promoter Au/rGO-3, when benzoquinone (BQ), SOD and isopropyl alcohol were added respectively, the anodic luminescence of Ru(bpy) ₃ ²⁺ was significantly reduced, which confirmed that Au/rGO-3 was successfully prepared. into a weak OER catalyst, thus proving that OH· is generated on the electrode surface as the main OER product to promote anodic luminescence (Figure 14B).

Ru(bpy) ₃ ²⁺ was used to emit light in the Ar atmosphere of acetonitrile solution to eliminate the influence of all ORR and OER processes involving O ₂ , dissolved oxygen and oxygen atoms to test the direct interaction between Au/rGO and Ru(bpy) ₃ ²⁺ effect.

The results are shown in Figure 15A. Compared with bare GCE, the Au/rGO-2 modified electrode has a weak promotion effect on Ru(bpy) ₃ ²⁺ cathodoluminescence, while Au/rGO-3 can significantly promote Ru(bpy) ₃ ²⁺ anode emission (Figure 15B), indicating that Au/rGO can not only indirectly promote Ru(bpy) ₃ ²⁺ emission by catalyzing OER or ORR reactions, but also directly perform reduction reduction oxidation reactions with Ru(bpy) ₃ ²⁺ And redox reaction, directly enhance the luminescence.

The co-reaction characteristics of AuNPs, graphene oxide, reduced graphene oxide and various combinations isolated in Ru(bpy) ₃ ²⁺ solution were detected. As shown in Figure 16, it can be found that AuNPs and rGO alone cannot significantly catalyze the anodic or cathodic emission of Ru(bpy)32+. This may be because, in previous studies, both experimental results and density function theory (DFT) calculations showed that none of them showed obvious ORR or OER catalytic performance. In addition, we also changed the particle size of AuNPs. As shown in Figure 16A, AuNPs with smaller particle size have better cathode promotion effect. This is because smaller-sized Au particles have greater electrocatalytic activity for oxygen reduction reaction (ORR) than larger-sized AuNPs, and a considerable portion of surface atoms may absorb and activate oxygen molecules. In addition, the degree of reduction of reduced graphene oxide also has a certain impact on the properties of its co-reactants. It can be seen from Figure 16C that graphene oxide has certain anode stimulation characteristics, and the reduction of graphene oxide by hydrazine hydrate will change the anode stimulation characteristics, and its cathode luminescence promotion ability is greater than that of graphene oxide. Based on the elemental ratio of XPS and the lower amino ratio (5% of N) than the oxygen-containing functional groups shown by the infrared spectrum, it is speculated that the relatively weak anodic co-reaction property of reduced graphene oxide is due to the The anodic promotion function of amino groups cannot offset the weakening of anodic luminescence caused by the reduction of oxygen-containing functional groups.

The degree of reduction of reduced graphene oxide also has a certain impact on the properties of its co-reactants. The cathode and anode luminescence of the co-reaction of Au/rGO reduced with different reduction times of reduced graphene oxide and Ru(bpy) ₃ ²⁺ were measured. (Ic/Ia) ratio, further measured the effect of the reduction degree of reduced graphene oxide on the co-reaction performance of Au/rGO. The red shift of the uv-vis spectrum shows that when the reduction degree of graphene oxide increases, Ic/Ia reaches the maximum value when the reduction time is 6h, and then decreases as the reduction time increases (see Figure 17). The optimal Ic/Ia for the Au/rGO catalytic reduction of Ru(bpy) ₃ ²⁺ by partially reduced graphene can be attributed to the fact that the incomplete reduction reaction formed by the defective graphene substrate can accelerate the charge transfer from AuNPs to O ₂ , lowering the energy barrier of the rate-limiting step by destabilizing the ORR intermediate species and lowering the activation energy of dissociation of O ₂ leads to more reactive oxygen species production.

It is speculated that the relatively weak anodic co-reaction property of reduced graphene oxide may be due to the anodic promotion function of amino groups on reduced graphene oxide being unable to offset the weakening of anodic luminescence caused by the reduction of oxygen-containing functional groups. It can be seen from Figure 16C that graphene oxide has certain anode stimulation properties, and the reduction of graphene oxide by hydrazine hydrate will change the anode stimulation properties, and its cathode luminescence promotion ability is greater than that of graphene oxide. This is due to the fact that the incomplete reduction reaction due to the formation of defective graphene substrate can accelerate the charge transfer from AuNPs to O ₂ , lowering the energy barrier of the rate-limiting step by destabilizing the ORR intermediate species and lowering the activation energy of the dissociation of O ₂ Resulting in greater production of reactive oxygen species.

reaction equation

The principle of cathodoluminescence is shown in Figure 16. First, Ru(bpy) ₃ ²⁺ and water are simultaneously reduced at negative potential and converted into Ru(bpy) ₃ ⁺ and ·O ₂ H. Then, the highly oxidized ·O ₂ H can directly oxidize Ru(bpy) ₃ ⁺ to Ru(bpy) ₃ ^2+* , or oxidize Au/rGO to generate [Au/rGO] _ox , and then indirectly oxidize Ru(bpy) ₃ ⁺ . During this process, ·O ₂ H can be reduced to hydrogen peroxide, and then further reduced to OH, and hydrogen peroxide has strong oxidizing properties. Similarly, OH can also oxidize Ru(bpy) ₃ ²⁺ to form high-energy state Ru(bpy) ₃ ^2+* , thereby triggering cathode luminescence. In addition, since ROS has a high oxidation potential, O ₂ H and OH can directly oxidize Ru(bpy) ₃ ²⁺ to generate Ru(bpy) ₃ ³⁺ , which then reacts with Ru(bpy) ₃ ⁺ and is released through an annihilation reaction. Light.

The reaction equation for Au-rGO-2 to promote terpyridine ruthenium cathode emission is as follows:

Ru(bpy) ₃ ²⁺ +e ^- →Ru(bpy) ₃ ⁺ (1)

Primary Pathway:

Pathway 1:

O ₂ +e ^- +H ⁺ →·O ₂ H (2)

Ru(bpy) ₃ ⁺ +·O ₂ H+H ⁺ →Ru(bpy) ₃ ^2+* +H ₂ O ₂ (3)

Pathway 2:

Au/rGO+·O ₂ H→[Au/rGO] _ox ^· +H ₂ O ₂ (4)

Ru(bpy) ₃ ⁺ +[Au/rGO] _ox ^· →Ru(bpy) ₃ ^2+* +[Au/rGO] _ox ^· +Au/rGO (5)

Secondary Pathway:

Pathway 3:

H ₂ O ₂ +H ⁺ +e ^- →H ₂ O+·OH (6)

Ru(bpy) ₃ ⁺ +·OH+H ⁺ →Ru(bpy) ₃ ^2+* +H ₂ O (7)

Pathway 4:

Au/rGO+·OH→[Au/rGO] _ox ^· +H ₂ O (8)

Ru(bpy) ₃ ⁺ +[Au/rGO] _ox ^· →Ru(bpy) ₃ ^2+* +[Au/rGO] _ox ·+Au/rGO (5)

Pathway 5:

Ru(bpy) ₃ ²⁺ +·O ₂ H+H ⁺ →Ru(bpy) ₃ ³⁺ +H ₂ O ₂ (9)

Ru(bpy) ₃ ²⁺ +·OH+H ⁺ →Ru(bpy) ₃ ³⁺ +H ₂ O ₂ (10)

Ru(bpy) ₃ ⁺ +Ru(bpy) ₃ ³⁺ →Ru(bpy) ₃ ^2+* +Ru(bpy) ₃ ²⁺ (11)

For the anodic reaction, Au/rGO-3 can be used as a co-reactant and OER catalyst to promote the luminescence of Ru(bpy) ₃ ²⁺ . The reaction between Au/rGO-3 and Ru(bpy) ₃ ²⁺ mainly converts Ru(bpy) ₃ ²⁺ into an excited state through its surface oxygen-containing groups (carboxyl group, hydroxyl group) and amino group. In addition, Au/rGO-3 serves as a weak catalyst in the OER process and can catalyze the oxidation of water to form ·OH. Then, ·OH can enhance the decarboxylation process of Au/rGO-COO to generate Au/rGO, which can transfer electrons to Ru(bpy) ₃ ³⁺ to generate Ru(bpy) ₃ ^2+* . In addition, a small amount of ·OH may interact with Au/rGO-COO ^- to produce reducing CO ₂ ^-· , thereby reducing Ru(bpy) ₃ ²⁺ to Ru(bpy) ₃ ⁺ and then interacting with Ru(bpy) ₃ ³⁺ interactions. The specific equation is as follows:

Ru(bpy) ₃ ²⁺ -e ^- →Ru(bpy) ₃ ³⁺ (1)

Pathway 1:

Au/rGO(ArCHOHR)-e ^- →[Au/rGO(ArCHOHR)] ^+· →[Au/rGO(ArCOHR)] ^· (2)

[Au/rGO(ArCOHR)] ^· +Ru(bpy) ₃ ³⁺ →Ru(bpy) ₃ ^2+* +Au/rGO(ArCOR) (3)

Pathway 2:

Au/rGO(ArNCH ₂ R)-e ^- →[Au/rGO(ArNCH ₂ R)] ^+· (4)

[Au/rGO(ArNCH ₂ R)] ^+· -H ⁺ →[Au/rGO(ArNCH ₂ R)] ^· +H ₂ O (5)

[Au/rGO(ArNCH ₂ R)] ^· +Ru(bpy) ₃ ³⁺ →Ru(bpy) ₃ ²⁺ +[Au/rGO(ArN＝CHR)] ⁺ (6)

[Au/rGO(ArN＝CHR)] ⁺ +H ₂ O→Au/rGO-NH ₂ +Au/rGO-CHO (7)

Pathway 3:

H ₂ Oe ^- →H ⁺ +·OH (8)

Au/rGO-COO ^- +·OH+H ⁺ →Au/rGO-COO·+H ₂ O→Au/rGO ^· +CO ₂ +H ₂ O (9)

Ru(bpy) ₃ ²⁺ -e ^- →Ru(bpy) ₃ ³⁺ (10)

Au/rGO ^· +Ru(bpy) ₃ ³⁺ →Au/rGO ⁺ +Ru(bpy) ₃ ^2+* →Ru(bpy) ₃ ²⁺ +hv (11)

The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims (10)

1. The application of an Au-rGO composite as a Ru(bpy) ₃ ²⁺ anode and cathode co-reactant, characterized in that: the Ru(bpy) ₃ ²⁺ anode and cathode co-reactants are both Au-rGO In the composite, the particle size of the Au nanoparticles in the anode co-reactant is 10-15 nm; the particle size of the Au nanoparticles in the cathode co-reactant is 2-4 nm; Ru(bpy) ₃ ²⁺ , anode co-reactant and cathode co-reactant form a single emitter multi-signal output system. Ru(bpy) ₃ ²⁺ serves as a single emitter. Under the action of the anode and cathode co-reactant, It has the properties of both anode and cathode to enhance ECL luminescence. 2. The application according to claim 1, characterized in that: in the anode coreactant, the reduction degree of rGO is 5.5-6.5h in hydrazine hydrate steam; Among the cathode co-reactants, the degree of reduction of rGO is 5.5-6.5 hours in hydrazine hydrate steam. 3. The application according to claim 1, characterized in that: the preparation method of the Ru(bpy) ₃ ²⁺ anode and cathode coreactants includes the following steps: After mixing the HAuCl ₄ aqueous solution and the rGO suspension in proportion, they are dispersed ultrasonically to obtain mixture one; Add NaBH ₄ to mixture one and mix well, then add sodium citrate and mix well; After the reaction is completed, separate and wash the solid product, and then redisperse it to obtain a resuspended solution; Centrifuge the resuspended solution at 11000-12500 rpm for 10-30 min, and collect the unprecipitated components of the solution to obtain the solution. 4. Application according to claim 3, characterized in that: it also includes the step of using hydrazine hydrate steam to reduce graphene oxide to prepare reduced graphene oxide, specifically: mixing the water suspension of graphene oxide and hydrazine hydrate respectively. Place it in two containers, place the two containers in the same closed space, and stir the reaction. The stirring reaction time is 5.5-6.5 hours. 5. The application according to claim 3, characterized in that: in the preparation process of the anode co-reactant, in the mixed reaction system of HAuCl ₄ , rGO, NaBH ₄ and sodium citrate, the concentration of HAuCl ₄ is 18-22 mg/ mL; The concentration of rGO is 1.8-2.2mg/mL; The concentration of NaBH ₄ is 0.005-0.015M; The concentration of sodium citrate is 0.005-0.015M; During the preparation process of the cathode co-reactant, the concentration of HAuCl ₄ in the mixed reaction system of HAuCl ₄ , rGO, NaBH ₄ and sodium citrate is 18-22 mg/mL; The concentration of rGO is 1.8-2.2mg/mL; The concentration of NaBH ₄ is 0.005-0.015M; The concentration of sodium citrate is 0.005-0.015M. 6. The application according to claim 3, characterized in that: after the reaction is completed, in the step of separating and washing the solid product, the separation is centrifugal separation, the centrifugal speed is 14500-15500 rpm, and the centrifugation time is 30-60 min. 7. The application according to claim 3, characterized in that: after mixing the HAuCl ₄ aqueous solution and the rGO suspension in proportion, the steps of ultrasonic treatment and stirring are included, the ultrasonic treatment time is 5-15min, and the stirring time is 1.5- 2.5h. 8. The application according to claim 3, characterized in that: the process of ultrasonic treatment and stirring of the mixed solution of HAuCl ₄ aqueous solution and rGO suspension is repeated 2-4 times. 9. Application according to claim 3, characterized in that: after adding NaBH ₄ to the mixture of HAuCl ₄ aqueous solution and rGO suspension, after preliminary stirring, ultrasonic treatment; the time of preliminary stirring is 10-20min, ultrasonic treatment The time is 5-15min. 10. The application according to claim 3, characterized in that: after adding sodium citrate to the mixed solution, after preliminary stirring, ultrasonic treatment is carried out; the time of preliminary stirring is 20-40min, and the time of ultrasonic treatment is 5-15min.