阅读说明：本技术 金纳米团簇/碳布及基于电腐蚀的氨传感器及其应用 (Gold nanocluster/carbon cloth, electro-corrosion-based ammonia sensor and application thereof ) 是由 臧广超 张玉婵 舒丹婷 于 2021-07-13 设计创作，主要内容包括：本发明属于氨检测技术领域,具体涉及一种金纳米团簇/碳布及基于电腐蚀的氨传感器及其应用。所述金纳米团簇/碳布的制备方法包括先将所述碳布浸入HNO-(3)溶液中,然后去离子水洗涤；将碳布浸入Au离子沉积液中沉积,通过恒电电位法在-(0.2-0.4)v沉积300s-1500s。制备成的氨传感器的氨检测范围为1.5ppm-4775ppm。该金纳米团簇/碳布及氨传感器通过“电腐蚀”进行“传感”的方法避免了催化反应中高势垒和有毒产物(N-ads)的限制,并且在连续运行7周后表现出良好的稳定性,而且检测氨的灵敏度高,检测范围广。(The invention belongs to the technical field of ammonia detection, and particularly relates to gold nanocluster/carbon cloth, an ammonia sensor based on electro-corrosion and application of the ammonia sensor. The preparation method of the gold nanocluster/carbon cloth comprises the step of immersing the carbon cloth into HNO 3 In the solution, washing with deionized water; immersing the carbon cloth into Au ion deposition solution for deposition, and depositing for 300s-1500s at- (0.2-0.4) v by a constant potential method. The prepared ammonia sensor has the ammonia detection range of 1.5ppm-4775 ppm. The gold nanocluster/carbon cloth and the ammonia sensor perform sensing through electro-corrosion, so that the limitation of high potential barrier and toxic products (N-ads) in catalytic reaction is avoided, good stability is shown after continuous operation for 7 weeks, the ammonia detection sensitivity is high, and the detection range is wide.)

1. The gold nanocluster/carbon cloth is characterized in that the preparation method comprises the following steps: and (3) immersing the carbon cloth into the Au ion deposition solution, and depositing by a constant-potential method.

2. The gold nanocluster/carbon cloth according to claim 1, wherein the Au ion deposition solution is comprised of HAuCl₄The solution of (1).

3. The gold nanocluster/carbon cloth of claim 2, wherein the Au ion deposition solution is 0.5-1.5% by mass of HAuCl₄The solution is diluted 1-10 times by using 0.5-1.5M KCL solution₄And (4) diluting the solution.

4. The gold nanocluster/carbon cloth according to claim 1, wherein the voltage of the potentiostatic method is- (0.2-0.4) v.

5. The gold nanocluster/carbon cloth according to any one of claims 1 to 4, wherein the deposition time is 300s to 1500 s.

6. A method for detecting ammonia, the method comprising: applying a voltage to the gold nanocluster/carbon cloth according to any one of claims 1 to 5, and then contacting the gold nanocluster/carbon cloth with ammonia to perform quantitative and/or qualitative analysis on the ammonia by using the generated current response.

7. The method of claim 6, wherein the current response increases with an increase in the concentration of ammonia.

8. The method according to claim 6 or 7, wherein the ammonia concentration is 1.5ppm to 4775 ppm.

9. The method of claim 6, wherein the current response is related to the concentration of ammonia at a concentration of 25ppm to 325ppm, y-0.0601 x +0.977, R2-0.9953; when the concentration of ammonia is 325ppm-4775ppm, the relationship between the current response and the concentration of ammonia is 0.0408x +6.6327, and 0.9961 for R2; in the relation, y is the current response and x is the concentration of ammonia.

10. An electrode or ammonia sensor comprising gold nanoclusters/carbon cloth according to any one of claims 1 to 5.

Technical Field

The invention belongs to the technical field of ammonia detection, and particularly relates to gold nanocluster/carbon cloth, an ammonia sensor based on electro-corrosion and application of the ammonia sensor.

Background

In amperometric detection of ammonia, the construction of an electrocatalytic interface, which plays an important role in the electrochemical sensing current response of ammonia, faces great difficulties. For constructing an electrocatalytic sensing interface, natural enzymes with electrocatalytic activity, hybrid nanostructures and nanoenzymes are commonly used at present, however, due to the lack of related ammonia oxidase, the toxic effect of high-energy barrier products on metals, which needs to be overcome by ammonia oxidation on the metal surface, is very difficult to monitor through an electrocatalytic process. Specifically, the electro-oxidation process of ammonia follows the mechanism of Gerischer-Mauerer, i.e., NH3 molecules are first adsorbed on the metal surface to deprotonate to form NHX-NHy-ads (x or y is 0-2), and then overcome a rather high energy barrier to form N-N bonds, thereby generating nitrogen and water as shown in formulas (1) to (5), and the strong adsorption reaction between N-ads and the metal surface irreversibly deactivates the metal, limiting the possibility of catalytic amination of most metals.

NH^*+OH^-→N^*+H₂O+e^- (3)

Overcoming the electrocatalytic energy barrier mediated by the Gerischer-Mauerer mechanism has been a major difficulty in ammonia detection. Although some electrocatalytic interfaces have been developed, the sensitivity of such sensors is still limited by energy barriers and N-adsorbate toxicity. Therefore, detecting ammonia nitrogen in a non-catalytic mode has become a main electrochemical sensing method. Few sensors rely on the mechanism of electrocatalytic redox reaction (as shown in equation (6)), namely NH3 with O adsorbed on the surface of AgO and guar gum/Au electrodes^2-The reaction, through an irreversible redox reaction, forms the corresponding nitrogen oxide, providing electrons to the surface. Oxygen andthe ammonia generates dynamic oxidation-reduction reaction on the surface of ZnO, and the conductivity of ZnO is increased by the action of the potential barrier of the ammonia to oxygen mediation.

In contrast, the more common technique at present is to detect the change in resistance caused by the change in the concentration of holes in the semiconductor and the deprotonation of the conductive polymer by the adsorption/desorption of ammonia gas. NH of p-type sensor₃The sensing capability can be attributed to the interaction of ammonia lone pair electron charge doping with holes. The ammonia adsorbed on the sensor transfers electrons, canceling out holes in the p-type semiconductor, such as rGO and CuO, the concentration of which decreases, resulting in an increase in the resistance of the sensor. Another common method is to deprotonate the ammonia using conducting polymers, a commonly used deprotonating carrier is polyaniline. The conductive polymer provides protons after exposure of the conductive polymer sensor to ammonia gas, and the positively charged-NH-centers on the polyaniline chains provide protons to form NH⁴⁺The ions, as shown in equation (7), cause the resistance of the polymer to increase and thus be detected. However, the two methods still have the defect of irreversible adsorption, and in order to overcome the defect, the carrier is dynamically modified by interaction force to increase NH₃Resistance to the vector. For example, by hydrogen bonding and covalent bonding of ammonia, the structure of the designed polymer changes, thereby causing an increase in electrical resistance.

In conclusion, although the irreversible oxidation reaction and the traditional adsorption/desorption reaction overcome the energy obstacle of the catalytic reaction, irreversible intermediate products are inevitably generated, and the service life of the product is greatly shortened. Therefore, how to prolong the shelf life of the ammonia gas sensor on the premise of overcoming the energy barrier of the ammonia gas sensor is a big difficulty of research in the field. In recent years, researchers have devised dynamic ammonia molecule assembly/disassembly and sensing interfaces by intermolecular forces and chemical bonds to address the above problems. However, increasingly complex molecular formula conversions will present challenges to the production of the sensor industry including design and process cost control.

Disclosure of Invention

In view of the above, the present invention aims to provide a gold nanocluster/carbon cloth, which can be used for detecting ammonia gas, has a wide detection range and high sensitivity, and is suitable for continuous monitoring of environmental sewage in some factories and quantitative analysis of products in chemical enterprises.

Corrosion strategies employed in the metallurgical industry offer the potential for developing more efficient, inexpensive and reusable electrochemical ammonia transport technologies, particularly in terms of reducing the electrocatalytic barrier to ammonia. Inspired by gold ore metallurgical engineering, we further perfected with gold. Gold is substantially stable to electrochemical or chemical reactions. However, recent studies have shown that certain amino compounds, such as amino acids, are active for electrodissolving gold in high-voltage-corroding anodes, like cyanides, to form complexes with gold ions. Therefore, it is speculated that ammonia molecules may also promote anodic corrosion activity of gold electrodes, showing an increase in faradaic current, thereby providing an alternative technique for electrochemical sensing of ammonia. The ammonia sensor adopts a constant potential electrodeposition method to grow gold crystals on the surface of the carbon cloth to form gold nanoclusters/carbon cloth. The performance of the gold nanocluster/carbon cloth electrode is shown by a cyclic voltammetry method and a Tafel curve, the relation between the ammonia nitrogen concentration and the current is predicted by further analyzing the Faraday law and the Fick law, and the i-t curve is used for verification. It is known from a simple analysis of faraday's law that the increasing faraday current (essentially the rate of corrosion) has no direct relationship to the remaining mass of the electrode. Therefore, the simple design of single metal sensor electrodes has the opportunity and potential to achieve efficient ammonia monitoring that is repeated for a long time, while keeping costs down. In addition, the method of "sensing" by "galvanic corrosion" avoids the high potential barrier and limitation of toxic products (N-ads) in catalytic reactions.

The invention takes a carbon cloth electrode (Au nanocluster/CC) as a sensing interface to construct the Au nanocluster. The corners and edges of the branched nanomaterial have a large number of atoms and therefore have high active surface area and reactivity. In addition, the large specific surface area and the excellent mass transfer performance of the carbon cloth are beneficial to the three-dimensional growth of the gold nanoclusters and the diffusion process of ions on the surface of the electrode, so that the sensing efficiency is improved. The morphology of compact and sufficient dendrites is synthesized by a potentiostatic method, and the time-controlled growth of the gold nanoclusters under a scanning electron microscope is displayed. The element distribution and composition of the sensing interface are characterized by EDX, XRD, XPS and other testing means. The electrochemical behavior of the electrode is researched by cyclic voltammetry, and the current monitoring of ammonia nitrogen is realized by a time-lapse amperometry (i-t).

The preparation method of the gold nanocluster/carbon cloth comprises the following steps: and (3) immersing the carbon cloth into the Au ion deposition solution, and depositing by a constant-potential method.

Preferably, the carbon cloth is high-porosity carbon cloth, and branched nano materials with high specific surface area are synthesized.

Preferably, the carbon cloth is dipped in HNO before deposition₃In solution, then washed with deionized water.

Preferably, the HNO3 solution has a concentration of 0.05-0.15M, more preferably 0.1M.

Preferably, the Au ion deposition solution contains HAuCl₄More preferably 0.05-1.5% by weight of HAuCl₄And (3) solution.

More preferably, the HAuCl-containing material is₄The solution of (a) is diluted with a salt solution, more preferably, with KCL.

More preferably, HAuCl with the mass percent of 0.5-1.5 percent₄The solution is diluted 1-10 times by 0.5-1.5M KCL solution.

More preferably, the HAuCl accounts for 1 percent by mass₄The solution was diluted 5 times with 1M KCL solution.

The Au ion deposition solution contains HAuCl₄The solution of (2) in KCL, the HAuCl₄The mass percent of the KCL is 0.5-1.5%, and the concentration of the KCL solution is 0.5-1.5M; more preferablyDi, the HAuCl₄The mass percentage of the KCL solution is 1 percent, and the concentration of the KCL solution is 1M.

Preferably, the potentiostatic method has a voltage of- (0.2-0.4) v, more preferably-0.3 v.

Preferably, the deposition time of the deposition is 300s to 1500s, more preferably 1000 s.

The invention also aims to provide a method for detecting ammonia, which is based on the gold nanocluster/carbon cloth and can effectively quantitatively or qualitatively analyze ammonia and the content thereof in the environment.

The method comprises the following steps: the gold nanoclusters/carbon cloth are applied with voltage and then contacted with ammonia, and the generated current response is utilized to perform quantitative and/or qualitative analysis on the ammonia.

Further, the ammonia concentration is 1.5ppm to 4775ppm, namely, the ammonia concentration range detected by the ammonia detection method is 1.5ppm to 4775 ppm.

Further, when the concentration of ammonia is 25ppm-325ppm, the relationship between the current response and the concentration of ammonia is 0.0601x +0.977, and R2 is 0.9953; when the concentration of ammonia is 325ppm-4775ppm, the relationship between the current response and the concentration of ammonia is 0.0408x +6.6327, and 0.9961 for R2; in the relation, y is the current response and x is the concentration of ammonia. That is, between 25 and 4755ppm of ammonia content, the current after voltage application increases in a linear relationship with the increase of ammonia content, and quantitative analysis of ammonia in ammonia environment can be performed.

In certain embodiments, the current response showing the oxidation peak in ammonia detection using the gold nanoclusters/carbon cloth is linearly related to the square root of the scan rate of 50mV/s to 200mV/s, indicating that the electrode process is diffusion controlled. The rate limiting reaction is a diffusion process, the reaction is negligible after ammonia enters the helmholtz layer, so the reaction rate is only related to the ammonia concentration, as Fick's law (equation (8)):

J＝-D×dC/dx (8)，

wherein D is a diffusion coefficient (square meter/s), C is the volume concentration (kg/m3) of the diffusion liquid, and dC/dX is a concentration gradient; i. the diffusion is from high to low concentration.

In amperometric detection, it is assumed that the current response will increase linearly with the ammonia concentration in the corrosion reaction. This is because the increase in current density is determined by the rate of the corrosion reaction, which can be explained by Faraday's law (equation (9)):

where m is the total mass of the electrolytic metal, m is the molar mass of the electrolytic metal, n is the stoichiometric number, and F is the Faraday constant.

The invention also aims to provide an ammonia sensor comprising the gold nanocluster/carbon cloth. The ammonia sensor comprises but is not limited to ammonia detection equipment, an ammonia alarm and an ammonia content analysis instrument.

Further, the ammonia sensor has an ammonia detection range of 1.5ppm to 4775 ppm.

Further, when the ammonia sensor is used for quantitative analysis, a plurality of calculating plug-ins or calculating tools or manual calculation can be introduced, and the ammonia concentration is calculated according to the current through the linear relation between the current response and the ammonia concentration, so that the ammonia content is determined. The linear relationship between the current response and the ammonia concentration is: when the concentration of ammonia is 25ppm-325ppm, the current response and the concentration of ammonia are in a relation of y being 0.0601x +0.977 and R2 being 0.9953, wherein y is current and x is the concentration of ammonia; when the concentration of ammonia is 325ppm-4775ppm, the current response is related to the concentration of ammonia by y 0.0408x +6.6327 and R2 0.9961, wherein y is the current and x is the concentration of ammonia.

Specifically, in some embodiments, the ammonia sensor was placed under room conditions and subjected to a long-term stability test at 50ppm ammonia concentration for 7 weeks, with little change in response over time (response remained around 95% over a month), with small fluctuations within acceptable error limits, and the current response reached 89.9% by week 7 despite the downward trend in overall current response, indicating good stability of the sensor. The faraday law (equation 10) can be used to explain:

M＝KQ＝Kit (10)，

wherein i is the corrosion rate of gold, the metal quality of the surface of the current electrode does not determine the electrochemical corrosion condition of the metal, and although the surface topography of the electrode has little influence on the corrosion rate, the surface topography is not a main factor causing the galvanic corrosion. It can therefore also be explained that the reproducibility of the same concentration response in high intensity continuous sample loading operation of gold nanocluster/CC ammonia sensors is rather excellent, and that the stability of gold nanocluster/CC ammonia sensors is also an important parameter for long term re-use of the sensors.

Further, the application of the gold nanocluster/carbon cloth in ammonia environment detection is provided, for example, the gold nanocluster/carbon cloth is used for continuous monitoring of certain factory environment sewage and qualitative and quantitative analysis of chemical industry enterprise products.

In the present invention, the data such as "weight", "time" and "current" do not include numerical changes due to operation errors and instrument errors, that is, numerical changes due to operation errors and instrument errors are also included in the technical means of the present invention.

The invention has the beneficial effects that

The gold nanocluster/carbon cloth provided by the invention has an ammonia sensitive response characteristic, expands an ammonia electrochemical detection method, and provides a brand new thought for the construction of an electrochemical sensor.

The gold nanocluster/carbon cloth provided by the invention has a simple and controllable structure of single metal and has the performance of repeated long-term use, so that the cost is greatly reduced, and the gold nanocluster/carbon cloth can be used for actual industrial production.

The preparation method of the gold nanocluster/carbon cloth and the ammonia sensor thereof avoids the limitation of high potential barrier and toxic products (N-ads) in catalytic reaction by using a method of performing sensing through electro-corrosion.

The gold nanocluster/carbon cloth and the ammonia sensor thereof have good reproducibility in high-strength work, and show good stability after continuous operation for 7 weeks.

The method for detecting ammonia provided by the invention has the advantages that the detected ammonia concentration is 1.5-4775 ppm, the range is wide, the ammonia concentration can be quantitatively analyzed according to the linear relation between the current response and the ammonia concentration, and the method is very favorable for continuous monitoring of environmental sewage of certain factories and quantitative analysis of products of chemical enterprises.

Drawings

FIG. 1 is a graph of CVs of a bare gold electrode in the absence and presence of 1500ppm ammonia.

FIG. 2 is a Tafel polarization curve for a bare gold electrode in the absence and presence of 1500ppm ammonia.

FIG. 3 is a graph of the amperometric response (i-t) of bare gold electrode to continuous ammonia addition in 50mM CBS (pH 10).

Fig. 4 is an SEM image of Au nanoclusters on CC at different deposition times.

Fig. 5 is an SEM image of gold nanoclusters on CC with electrodeposition time 1000s at different magnifications.

Figure 6 EDS mapping plot of Au nanoclusters on CC.

Figure 7 EDS spot scan of Au nanoclusters on CC.

Fig. 8 is an XRD pattern of gold nanoclusters on CC.

Fig. 9 is an XPS spectrum of Au nanoclusters on CC.

Fig. 10 is a high resolution XPS spectrum of Au nanocluster Au4f on CC.

Fig. 11 is a high resolution XPS spectrum of Au nanocluster c1s on CC.

FIG. 12 is the CVs of Au nanoclusters on CC in the absence and presence of 100ppm ammonia.

Fig. 13 is a Tafel polarization curve of Au nanoclusters on CC in the absence and presence of 100ppm ammonia.

FIG. 14 shows the CVs of gold nanoclusters on CC in the presence of varying concentrations of ammonia.

FIG. 15 shows CVs of gold nanoclusters on CC at different scan rates.

FIG. 16 is an i-t plot of Au nanoclusters on CC with continuous addition of 25ppm to 1000ppm ammonia (three injections per concentration) to CBS (pH 10).

Fig. 17 is a calibration curve of i-t of Au nanoclusters on CC when 25 to 1000ppm ammonia (three injections per concentration) was continuously added in CBS (pH 10).

FIG. 18 is the stability of gold nanoclusters/CC after 0-7 weeks of detection with 100ppm ammonia.

Wherein, in fig. 4, a-C are SEM images of Au nanoclusters on CC recording 300s electrodeposition time at different magnifications; D-E is SEM image of Au nanoclusters on CC for 500s electrodeposition time; f is SEM image of Au nanoclusters on CC at 1500s electrodeposition time.

Detailed Description

The examples are given for the purpose of better illustration of the invention, but the invention is not limited to the examples. Therefore, those skilled in the art should make insubstantial modifications and adaptations to the embodiments of the present invention in light of the above teachings and remain within the scope of the invention.

In the examples of the present invention, commercial carbon cloth CC (Ce-Tech Co., Ltd.) was produced by Hubei Rocktex Instrument Co., Ltd (Shanghai, China). Tetrachlorogold (III) trihydrate, dibutylamine and L-glutamine were purchased from Admas Beta (Shanghai, China). Sodium bicarbonate and ammonia were obtained from Chongqing Chundong chemical group, Inc. (Chongqing, China). Glycine and lysine were purchased from Sangong bioscience (Shanghai, China). Deionized water and ultrapure water (18.2 μ cm) were from HHiTech (shanghai, china).

In the examples of the present invention, the microstructure and the composition distribution characteristics thereof were characterized by using a scanning electron microscope (SEM, SU8010, Hitachi, Tokyo, Japan) and an X-ray energy spectrometer (EDX, X-MaxN, Oxford Instruments, UK). The nanomaterials were analyzed using X-ray diffraction (XRD) (PANalytical b.v., netherlands). The elemental state and surface properties of Au/CC were measured using X-ray photoelectron spectroscopy (XPS, K-Alpha, Sammer Feishol science, USA).

In the embodiment of the invention, the electrochemical experiment is carried out on a chi660e electrochemical workstation (Shanghai Chen Hua apparatus Co., Ltd., China).

Example 1 construction of gold nanoclusters/CCs

Immersing CC in 0.1M HNO₃The solution was left overnight and then washed in deionized water. Using 1M KCl solution to prepare a solution of HAuCl with the mass percent of 1%Diluting by 5 times to obtain HAuCl diluted solution; the treated CC was immersed in HAuCl diluted solution and run and deposited by potentiostatic method at-0.3 v.

Example 2 validation of ammonia on gold electrode corrosion

In order to verify the feasibility of improving the current response of the ammonia water by the electrochemical corrosion, a bare gold electrode is taken as a model, and the research on the electrochemical behavior of the bare gold electrode is simplified.

Cyclic Voltammograms (CVs) as shown in fig. 1, a typical 0.15v anodic peak is due to the formation of the mos, while a 0.8v anodic peak is an indication of the continued oxidation of the mos. After the ammonia injection, galvanic corrosion occurs and the current increases.

The most common electroerosion method was studied using the Tafel polarization curve and the effect of ammonia on the gold electrode erosion rate was tested, as shown in fig. 2, with an increase in the erosion current indicating that ammonia promotes anodic erosion of gold and shows an enhanced faraday current.

By the chronoamperometry (i-t), as shown in fig. 3, it was found that the increase in the faraday current is related to the ammonia concentration, and gold has a potentially sensitive effect on ammonia, but the bare gold electrode has a disadvantage of low sensitivity.

Therefore, the embodiment of the invention selects the carbon cloth electrode with high porosity as the substrate material to further synthesize the branched nano material with high specific surface area.

Example 3 morphological evolution of electrodeposited gold nanoclusters on CC

In the deposition process of example 1, the time-controlled morphology of the gold nanostructure was observed by a scanning electron microscope, and the morphology evolution with time is shown in fig. 4, at 300s, the Au nanocluster seeds of about 150nm begin to assemble, wherein several small nanoparticles form flower-like nanostructures (as in a in fig. 4), and the coverage rate of the carbon fiber surface is low (as in B, C in fig. 4). At 500, 1000 seconds of electrodeposition, the gold seed crystal covers the surface of the carbon fiber and dendrite is formed in situ (D, E, F in FIG. 4). These results indicate that the morphology of the electrodeposited gold nanoclusters evolves; a seed crystal is first deposited on the carbon fiber and then a lattice structure is formed after diffusion limited aggregation.

When the deposition time was extended to 500 seconds, the nanoclusters began to randomly aggregate, forming leaf-like branched structures while overlapping the CC surface (D, E in fig. 4). After 1500s of electrodeposition, the gold nanoclusters continue to grow unevenly into a three-dimensional structure, forming a continuous growth process of core-adsorption-growth-branching-growth (e.g., F in fig. 4).

Example 4 characterization of gold nanocluster/CC electrode

Characterization of gold nanoclusters/CC deposited for 1000s in example 1, with nanoclusters uniformly distributed over CC (as shown in fig. 5 a, B) and branch size between 0.5-1 μm (as shown in fig. 5C), corresponding to 500s (as shown in fig. 3E) at 1000s deposition time as shown in fig. 5. Under a 500nm high power mirror, small assembled nanoclusters of the CC surface and formation of leaf morphology (see D in fig. 5) can be observed. This indicates that the distribution is substantially uniform, and that the three-dimensional structure and the rough surface impart a high aspect ratio and excellent sensing conductivity.

Then, element mapping analysis was performed on the gold nanoclusters/CCs, and as shown in fig. 6, the EDS mapping pattern of the Au nanoclusters on the CCs confirmed the distribution of the metal Au (E1) on the CCs (E2). As shown in fig. 7, the EDX spectrum of Au nanoclusters/CCs showed peaks associated with Au and C, which determined the key elemental composition of the electrode material and the presence of gold on the carbon cloth. The XRD pattern of the gold nanoclusters on CC as shown in fig. 8 shows that the diffraction peaks are centered at θ values of 26.28 °, + 38.38 °, + 44.2 °,54.42 °, + 4.66 °, + 77.78 °, and + 81.82 ° at 2, corresponding to (002), (111), (200), (004), (220), (311), and (222) planes, respectively. The peaks marked with asterisks are identical to the plane of the gold face centered cubic crystal structure (JCPDS 00-065-8601), while the other peaks correspond to the peaks of the CC surface (JCPDS 00-041-1487). As shown in FIG. 9, XPS measurement spectrum confirmed the presence of many gold nanoclusters on the carbon cloth, with peaks of Au4f5/2 and Au4f7/2 centered at 87.88 and 84.18eV, respectively, in relation to Au0, where the spin separation energy of 3.7eV is consistent with those of Au4f5/2 and Au4f 7/2. As shown in FIG. 10, the peak corresponding to C1s at 284.6eV is likely to be due to the formation of a C-C covalent bond, while the shoulder at 288eV can be attributed to-COOH.

Example 5 electrochemical behavior of gold nanoclusters/CC

As can be seen from example 1, ammonia injection significantly increased the current response, and CVs of Au nanoclusters on CC in the absence and presence of 100ppm ammonia are shown in fig. 11. Furthermore, the Tafel polarization curve is shown in FIG. 12, showing that the current response of the oxidation peak is linearly related to the square root of the scan rate from 50mV/s to 200mV/s, with R2 ═ 0.999, indicating that the electrode process is diffusion controlled. I.e., ammonia increases the rate of gold dissolution by forming a complex in a concentration-dependent manner, which results in an increase in current in amperometric detection, and in fact, corrosion current density is a measure of the reaction rate.

It is proved by using a tafel polarization curve that as shown in fig. 13, the corrosion current Icorr of the ammonia water is obviously higher than the corrosion current Icorr without the ammonia water, which indicates that the corrosion rate (Icorr) of the Au by the ammonia water is increased, and the corrosion potential is also shifted negatively with the addition of the ammonia water, which indicates that the ammonia water is favorable for promoting the corrosion of the gold. To further investigate the application of Au nanoclusters/CCs in ammonia sensing, simplified CV analysis was used to evaluate the current response of different concentrations of ammonia, including the amperometric detection potential of ammonia, over a shortened range of oxidation potentials (from 0.4V to 1.6V), with results as shown in fig. 14 and fig. 15, since NHads or Nads cannot form on gold surfaces, there is no electro-oxidation of ammonia (geriscer-Mauerer mechanism) activity, this increase is very similar to previous reports (unchanged peak I, significant increase in peak II) due to anodic dissolution of gold and enhancement of the corrosive agent.

Example 6 amperometric analysis

Gold nanocluster/CC sensing of ammonia was performed by i-t analysis, in which ammonia was applied with voltage at 1V, 50mM CBS (25ppm to 1000ppm) was injected continuously at 10pH, and as a result, as shown in fig. 16, the current response increased with increasing ammonia concentration, gradually saturating after 4775 ppm. The corresponding calibration curve as shown in fig. 17 shows two linear regions: from 25ppm to 325ppm (y 0.0601x +0.977, R2 0.9953) and from 325ppm to 4775ppm (y 0.0408x +6.6327, R2 0.9961), with a limit of detection (LOD) of 1.5ppm (3N/S), with LODs and linear ranges similar to some ammonia electrochemical sensors reported previously.

The sensor was placed under room conditions and subjected to a long-term stability test at 50ppm ammonia concentration for 7 weeks, and the results are shown in fig. 18, where the current response hardly changed with time (the response remained around 95% in one month), there was small fluctuation within an acceptable error range, and although the overall current response tended to decrease, the current response reached 89.9% by 7 weeks, indicating that the sensor had good stability.

Finally, the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all of them should be covered in the claims of the present invention.