Self-assembled thin films, preparation and applications for improving sensitivity of surface-enhanced infrared spectroscopy

Abstract

The present application relates to a kind of self-assembled film, preparation and the application of improving surface-enhanced infrared spectroscopy sensitivity, belong to electrochemical catalytic characterization and analysis field.Process for preparing is as follows: preparation monocrystal nanometer cube: by two-step seed growth method, synthesis nanometer cube;Nanometer cube is mixed with certain concentration surfactant dispersion, on substrate through gas phase evaporation, self-assembled synthesis superlattice metal nanometer cube film.The superlattice nanometer cube film preparation method disclosed in the present application is simple, can be repeated in the process of electrochemical reaction, and has good stability, high sensitivity.In attenuated total reflection surface-enhanced infrared spectroscopy technology, detection sensitivity is improved by more than one order of magnitude.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical catalysis characterization and analysis, and more specifically, relates to a self-assembled thin film, its preparation and application in improving surface-enhanced infrared spectroscopy sensitivity. Background Technology

[0002] With the development of industrial technology, carbon dioxide emissions have increased, global temperatures have risen, and environmental pollution has become severe, posing a serious threat to human survival. The goal of "carbon peaking and carbon neutrality" has placed higher demands on pollutant emissions and environmental optimization. Electrocatalysis technology can use electrical energy to convert substances into clean and environmentally friendly energy, providing an important approach to solving environmental pollution. However, electrocatalytic reactions, such as carbon dioxide / carbon monoxide reduction, water oxidation / reduction, and methanol oxidation, are complex processes with numerous reaction pathways. In-situ characterization methods are often used to explore the mechanisms of electrocatalytic reactions, such as in-situ scanning electron microscopy (SEM), in-situ transmission electron microscopy (TEM), in-situ synchrotron radiation, in-situ Raman spectroscopy, and in-situ infrared spectroscopy. However, in-situ SEM and synchrotron radiation are costly and time-limited, lacking universal application. In-situ infrared spectroscopy, on the other hand, is less expensive, simpler to operate, and can monitor intermediate products generated during the reaction process in real time using molecular vibrations, determining the reaction pathways involved. By utilizing in-situ infrared characterization techniques and observing changes in catalytic reaction intermediates, high-performance, highly selective, and highly stable catalysts can be rationally designed. Over the past decade, in-situ attenuated total reflectance surface-enhanced infrared spectroscopy (SIR) has been employed to detect intermediates and reaction pathways in electrocatalytic reactions by simulating electrochemical experimental conditions and methods. Typically, the enhancing substrate for SIR is a metal island film with a certain degree of roughness. When a local electromagnetic field is enhanced, local surface plasmons oscillate, resonating with molecules adsorbed on the catalyst surface to enhance the infrared vibrational signal of the adsorbed molecules. Electrochemical reactions often involve strong acids and bases and rapid catalytic processes, such as hydrogen evolution, oxygen reduction, and methane oxidation. The formation and transformation of intermediates are very rapid, resulting in low yields of intermediate substances. The detection of these substances places higher demands on the stability, reproducibility, and sensitivity of the infrared substrate. Currently, most metal island films used in SIR are prepared via wet chemical deposition. While these methods can enhance the infrared signal, the preparation process cannot control the morphology and size of individual metal nanoparticles, leading to poor sensitivity and reproducibility of the enhanced infrared signal. This makes it difficult to accurately capture changes in catalytic reaction intermediates, resulting in insufficient evidence or bias in determining the catalytic reaction mechanism. Summary of the Invention

[0003] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention provides a technique for improving the sensitivity of surface-enhanced infrared spectroscopy by self-assembling thin films. Superlattice metal nanocubes self-assemble to form neatly arranged and uniformly morphological thin films, which exhibit excellent stability and repeatability in electrochemical catalytic reactions and improve the detection sensitivity of intermediate adsorbed species. The method is simple and easy to implement, and can meet the large-scale application of surface-enhanced in-situ infrared substrates for catalyst mechanism research.

[0004] To achieve the above objectives, according to one aspect of the present invention, a method for preparing a superlattice metal nanocube self-assembled thin film is provided, comprising the following steps:

[0005] (1) After mixing the solution containing metal ions with the capping agent, a reducing agent is added to obtain a metal cluster seed solution; the metal cluster is further grown to obtain a superlattice metal nanocube.

[0006] (2) The superlattice metal nanocubes obtained in step (1) are dispersed in a surfactant, then an acid is added, and then the mixed solution is dropped onto the substrate. After the superlattice metal nanocubes are naturally settled and dried, the superlattice metal nanocubes self-assembled film is obtained.

[0007] Preferably, in step (2), after the superlattice metal nanocubes are dispersed in the surfactant, the concentration of the superlattice metal nanocubes is 10-30 mmol / L.

[0008] Preferably, in step (2), the concentration of the surfactant is 1 mmol / L. -1 -10mmol L -1 .

[0009] Preferably, in step (1), the solution containing metal ions is a chloroauric acid solution, a chloropalladium acid solution, a chloroplatinic acid solution, or a copper chloride solution.

[0010] Preferably, the capping agent is polyvinylpyrrolidone, hexadecylamine, hexadecyltrimethylammonium bromide, or hexadecyltrimethylammonium chloride.

[0011] Preferably, in step (1), the reducing agent is ascorbic acid, diethylene glycol, ethylene glycol, or pentanediol;

[0012] In step (2), the acid is hydrochloric acid, sulfuric acid, perchloric acid, nitric acid, potassium permanganate, hydrofluoric acid, hydroiodic acid, hydrobromic acid, carbonic acid, acetic acid, silicic acid, phosphoric acid, or hypochlorous acid.

[0013] Preferably, the number of carbon atoms in the carbon chain of the surfactant is greater than or equal to 10;

[0014] Preferably, the surfactant is hexadecylpyridine bromide, hexadecylpyridine chloride, or dodecylpyridine bromide.

[0015] According to another aspect of the present invention, a self-assembled superlattice metal nanocube thin film prepared by any one of the methods is provided.

[0016] According to another aspect of the present invention, the superlattice metal nanocube self-assembled thin film is provided for use in enhancing infrared signal substrates.

[0017] According to another aspect of the present invention, the aforementioned superlattice metal nanocube self-assembled thin film is provided for use as a catalyst.

[0018] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve at least the following beneficial effects:

[0019] (1) The superlattice nanocube self-assembled film of the present invention has high sensitivity and can significantly improve the sensitivity of the attenuated total reflection surface enhanced infrared spectrum. Compared with the traditional infrared enhancement substrate, the superlattice metal nanocube self-assembled film enhances the signal by more than an order of magnitude.

[0020] (2) The present invention uses metal superlattice nanocubes as precursors for self-assembly. The preparation method is simple and easy to implement and can be effectively scaled up. Compared with traditional surface-enhanced infrared substrates, the self-assembled films obtained are neatly arranged and have uniform morphology, exhibiting higher stability in the electrocatalytic reaction process.

[0021] (3) The superlattice nanocube film of the present invention is used on an infrared substrate. When performing electrochemical catalytic reactions, the molecular vibration signal adsorbed on the catalyst surface is enhanced by more than an order of magnitude, exhibiting superior sensitivity.

[0022] (4) When superlattice nanocube films are used as infrared substrates, the molecular vibration signals adsorbed on the catalyst surface are enhanced and stabilized during electrochemical catalytic reactions, exhibiting better repeatability.

[0023] (5) The superlattice metal nanocube film of the present invention can exist stably in strong acids and bases. The superlattice metal nanocube film can stably carry out electrochemical reactions in perchloric acid, potassium bicarbonate and potassium hydroxide as substrates.

[0024] (6) The superlattice metal nanocube self-assembled thin film of the present invention has a localized plasmon resonance effect.

[0025] (7) The superlattice metal nanocube self-assembled film of the present invention has good repeatability and the infrared enhancement signal of the superlattice metal nanocube film for adsorbed molecules is stable. Attached Figure Description

[0026] Figure 1 This is a flowchart of the preparation process of superlattice nanocube thin films.

[0027] Figure 2 Image (a) is a photograph of a superlattice nanocube thin film. Figure 2 Scanning electron microscope image of the superlattice nanocube thin film (b).

[0028] Figure 3 (a) is the intermediate product spectrum obtained by in-situ attenuated total reflection surface-enhanced in-situ infrared spectroscopy technique, based on the present invention, by depositing a superlattice nanocube thin film on single-crystal silicon and carrying out an electrocatalytic reaction. Figure 3 (b) is a spectral collection image obtained under the same conditions using a conventional infrared-enhanced substrate.

[0029] Figure 4 (a) shows the intermediate product spectrum obtained by in-situ attenuated total reflectance surface-enhanced infrared spectroscopy (SIR) using a commercial cuprous oxide catalyst applied to a superlattice nanocube film for electrocatalytic reaction. Figure 4 (b) is a spectral collection image obtained under the same conditions using a conventional infrared-enhanced substrate. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0031] The present invention discloses a method for preparing a self-assembled superlattice metal nanocube thin film, comprising the following steps:

[0032] (1) Mix the solution containing metal particles with the capping agent, and reduce it with a reducing agent to obtain a metal cluster seed solution. The metal clusters grow further, and after centrifugation, washing and concentration, superlattice metal nanocubes are obtained.

[0033] (2) Disperse the nanocubes in a surfactant, mix them with an acid, drop them onto a substrate (such as single-crystal silicon), and allow them to settle and evaporate naturally to obtain a superlattice metal nanocube film.

[0034] Preferably, the capping agent in step (1) is polyvinylpyrrolidone, hexadecylamine, hexadecyltrimethylammonium bromide, or hexadecyltrimethylammonium chloride.

[0035] Preferably, the metal nanocubes in step (1) have a localized surface plasmon effect.

[0036] Preferably, the metal nanocubes in step (1) include one of Au, Cu, Pt, Pd, Ag, Fe, and Ni.

[0037] Preferably, the centrifugation and washing in step (1) can be repeated 1 to 8 times.

[0038] Preferably, the concentration of the concentrated metal nanocubes in step (1) is 10–30 mmol / L.

[0039] Preferably, the size of the metal nanocubes in step (1) is 10 to 100 nm.

[0040] Preferably, in step (2), the number of carbon atoms in the carbon chain of the surfactant is greater than or equal to 10;

[0041] More preferably, the surfactant is hexadecylpyridine bromide, hexadecylpyridine chloride, or dodecylpyridine bromide.

[0042] Preferably, the acid in step (2) is hydrochloric acid, perchloric acid, nitric acid, hydrofluoric acid, hydroiodic acid, hydrobromic acid, or hypochlorous acid. The acid is mixed with nanocubes dispersed in a surfactant and then dropped onto the surface of a single-crystal silicon. The purpose of this is that the acid can etch the surface of the single-crystal silicon, so that the single-crystal silicon and the metal nanoparticles can interact, ensuring a stable interface in subsequent applications and meeting the application testing conditions.

[0043] According to another aspect of the present invention, the application of metal self-assembled thin films as both a substrate and a catalyst in surface-enhanced infrared spectroscopy is provided.

[0044] This invention discloses a method for using superlattice metal nanocube self-assembled thin films as substrates for surface-enhanced infrared spectroscopy. The use of superlattice metal nanocube self-assembled thin films can improve infrared molecular vibration signals by more than an order of magnitude.

[0045] The following are specific embodiments.

[0046] Example 1

[0047] A method for preparing a self-assembled superlattice metal nanocube thin film includes the following steps:

[0048] (1) Synthesis of gold nanocubes: 0.013 wt.% HAuCl4 solution was added to 3.75 mL of cetyltrimethylammonium bromide (100 mmol / L). -1 After mixing thoroughly, add 0.3 mL of sodium borohydride (10 mmol / L). -1Reduce for 3-5 minutes, then transfer to a 32°C water bath and react for 2 hours to obtain the seed solution. Add 16 mL of hexadecyltrimethylammonium bromide (200 mmol / L) to the solution. -1 Add the solution to 100 mL of H₂O and 0.8 wt.% HAuCl₄, stir well, and then add 9.5 mL of ascorbic acid (100 mmol L⁻¹) sequentially in a 32°C water bath. -1 The reducing agent was added to a 10 μL (240 times diluted) seed solution. After reacting for 2 h, gold nanocubes were obtained by centrifugation and washing.

[0049] (2) Preparation of superlattice gold nanocube thin films: 2 μmol of superlattice gold nanocubes were dispersed in 200 μL of 10 mmol L -1 The solution was prepared by adding 100 μL of 1% hydrobromic acid to a solution of hexadecylpyridine bromide, then dropping the mixture onto a single crystal silicon substrate. The substrate was allowed to settle and evaporate at room temperature, then washed with water and dried.

[0050] Example 2

[0051] (1) Synthesis of gold nanocubes: 0.013 wt.% HAuCl4 solution was added to 3.75 mL of cetyltrimethylammonium bromide (100 mmol / L). -1 After mixing thoroughly, add 0.3 mL of sodium borohydride (10 mmol / L). -1 Reduce for 3-5 minutes, then transfer to a 32°C water bath and react for 2 hours to obtain the seed solution. Add 16 mL of hexadecyltrimethylammonium bromide (200 mmol / L) to the solution. -1 Add the solution to 100 mL of H₂O and 0.8 wt.% HAuCl₄, stir well, and then add 9.5 mL of ascorbic acid (100 mmol L⁻¹) sequentially in a 32°C water bath. -1 The reducing agent was added to a 10 μL (240 times diluted) seed solution. After reacting for 2 h, gold nanocubes were obtained by centrifugation and washing.

[0052] (2) Preparation of superlattice gold nanocube thin films: 2 μmol of superlattice gold nanocubes were dispersed in 200 μL of 7 mmol L -1 The solution was prepared by adding 100 μL of 1% hydrobromic acid to a solution of hexadecylpyridine bromide, then dropping the mixture onto a single crystal silicon substrate. The substrate was allowed to settle and evaporate at room temperature, then washed with water and dried.

[0053] Example 3

[0054] (1) Synthesis of gold nanocubes: 0.013 wt.% HAuCl4 solution was added to 3.75 mL of cetyltrimethylammonium bromide (100 mmol / L). -1After mixing thoroughly, add 0.3 mL of sodium borohydride (10 mmol / L). -1 Reduce for 3-5 minutes, then transfer to a 32°C water bath and react for 2 hours to obtain the seed solution. Add 16 mL of hexadecyltrimethylammonium bromide (200 mmol / L) to the solution. -1 Add the solution to 100 mL of H₂O and 0.8 wt.% HAuCl₄, stir well, and then add 9.5 mL of ascorbic acid (100 mmol L⁻¹) sequentially in a 32°C water bath. -1 The reducing agent was added to a 10 μL (240 times diluted) seed solution. After reacting for 2 h, gold nanocubes were obtained by centrifugation and washing.

[0055] (2) Preparation of superlattice gold nanocube thin films: 3 μmol of superlattice gold nanocubes were dispersed in 200 μL of 4 mmol L -1 The solution was prepared by adding 100 μL of 1% hydrobromic acid to a solution of hexadecylpyridine bromide, then dropping the mixture onto a single crystal silicon substrate. The substrate was allowed to settle and evaporate at room temperature, then washed with water and dried.

[0056] Example 4

[0057] (1) Synthesis of gold nanocubes: 0.013 wt.% HAuCl4 solution was added to 3.75 mL of cetyltrimethylammonium bromide (100 mmol / L). -1 After mixing thoroughly, add 0.3 mL of sodium borohydride (10 mmol / L). -1 Reduce for 3-5 minutes, then transfer to a 32°C water bath and react for 2 hours to obtain the seed solution. Add 16 mL of hexadecyltrimethylammonium bromide (200 mmol / L) to the solution. -1 Add the solution to 100 mL of H₂O and 0.8 wt.% HAuCl₄, stir well, and then add 9.5 mL of ascorbic acid (100 mmol L⁻¹) sequentially in a 32°C water bath. -1 The reducing agent was added to a 10 μL (240 times diluted) seed solution. After reacting for 2 h, gold nanocubes were obtained by centrifugation and washing.

[0058] (2) Preparation of superlattice gold nanocube thin films: 3 μmol of superlattice gold nanocubes were dispersed in 200 μL of 1 mmol L -1 The solution was prepared by adding 100 μL of 1% hydrobromic acid to a solution of hexadecylpyridine bromide, then dropping the mixture onto a single crystal silicon substrate. The substrate was allowed to settle and evaporate at room temperature, then washed with water and dried.

[0059] Example 5

[0060] (1) Synthesis of gold nanocubes: 0.013 wt.% HAuCl4 solution was added to 3.75 mL of cetyltrimethylammonium bromide (100 mmol / L). -1 After mixing thoroughly, add 0.3 mL of sodium borohydride (10 mmol / L). -1 Reduce for 3-5 minutes, then transfer to a 32°C water bath and react for 2 hours to obtain the seed solution. Add 16 mL of hexadecyltrimethylammonium bromide (200 mmol / L) to the solution. -1 Add the solution to 100 ml of H2O and 0.8 wt.% HAuCl4, stir well, and then add 9.5 mL of ascorbic acid (100 mmol L) sequentially in a 32°C water bath. -1 The reducing agent was added to a 10 μL (240 times diluted) seed solution. After reacting for 2 h, gold nanocubes were obtained by centrifugation and washing.

[0061] (2) Preparation of superlattice gold nanocube thin films: 4 μmol of superlattice gold nanocubes were dispersed in 200 μL of 10 mmol L -1 The solution was added to a hexadecylpyridine chloride solution, and then 100 μL of 1% hydrobromic acid was added and mixed. The mixture was then dropped onto a single crystal silicon, and the solution was allowed to settle and evaporate at room temperature. The silicon was then washed with water and dried.

[0062] Example 6

[0063] (1) Synthesis of gold nanocubes: 0.013 wt.% HAuCl4 solution was added to 3.75 mL of cetyltrimethylammonium bromide (100 mmol / L). -1 After mixing thoroughly, add 0.3 mL of sodium borohydride (10 mmol / L). -1 Reduce for 3-5 minutes, then transfer to a 32°C water bath and react for 2 hours to obtain the seed solution. Add 16 mL of hexadecyltrimethylammonium bromide (200 mmol / L) to the solution. -1 Add the solution to 100 ml of H2O and 0.8 wt.% HAuCl4, stir well, and then add 9.5 mL of ascorbic acid (100 mmol L) sequentially in a 32°C water bath. -1 The reducing agent was added to a 10 μL (240 times diluted) seed solution. After reacting for 2 h, gold nanocubes were obtained by centrifugation and washing.

[0064] (2) Preparation of superlattice gold nanocube thin films: 4 μmol of superlattice gold nanocubes were dispersed in 200 μL of 7 mmol L -1 The solution was added to a hexadecylpyridine chloride solution, and then 100 μL of 1% hydrobromic acid was added and mixed. The mixture was then dropped onto a single crystal silicon, and the solution was allowed to settle and evaporate at room temperature. The silicon was then washed with water and dried.

[0065] Example 7

[0066] (1) Synthesis of gold nanocubes: 0.013 wt.% HAuCl4 solution was added to 3.75 mL of cetyltrimethylammonium bromide (100 mmol / L). -1 After mixing thoroughly, add 0.3 mL of sodium borohydride (10 mmol / L). -1 Reduce for 3-5 minutes, then transfer to a 32°C water bath and react for 2 hours to obtain the seed solution. Add 16 mL of hexadecyltrimethylammonium bromide (200 mmol / L) to the solution. -1 Add the solution to 100 ml of H2O and 0.8 wt.% HAuCl4, stir well, and then add 9.5 mL of ascorbic acid (100 mmol L) sequentially in a 32°C water bath. -1 The reducing agent was added to a 10 μL (240 times diluted) seed solution. After reacting for 2 h, gold nanocubes were obtained by centrifugation and washing.

[0067] (2) Preparation of superlattice gold nanocube thin films: 5 μmol of superlattice gold nanocubes were dispersed in 200 μL of 4 mmol L -1 The solution was added to a hexadecylpyridine chloride solution, and then 100 μL of 1% hydrobromic acid was added and mixed. The mixture was then dropped onto a single crystal silicon, and the solution was allowed to settle and evaporate at room temperature. The silicon was then washed with water and dried.

[0068] Example 8

[0069] (1) Synthesis of gold nanocubes: 0.013 wt.% HAuCl4 solution was added to 3.75 mL of cetyltrimethylammonium bromide (100 mmol / L). -1 After mixing thoroughly, add 0.3 mL of sodium borohydride (10 mmol / L). -1 Reduce for 3-5 minutes, then transfer to a 32°C water bath and react for 2 hours to obtain the seed solution. Add 16 mL of hexadecyltrimethylammonium bromide (200 mmol / L) to the solution. -1 Add the solution to 100 ml of H2O and 0.8 wt.% HAuCl4, stir well, and then add 9.5 mL of ascorbic acid (100 mmol L) sequentially in a 32°C water bath. -1 The reducing agent was added to a 10 μL (240 times diluted) seed solution. After reacting for 2 h, gold nanocubes were obtained by centrifugation and washing.

[0070] (2) Preparation of superlattice gold nanocube thin films: 6 μmol of superlattice gold nanocubes were dispersed in 200 μL of 1 mmol L -1The solution was added to a solution of hexadecylpyridine chloride, and then 100 μL of 1% hydrofluoric acid was added and mixed. The mixture was then dropped onto a single crystal silicon and allowed to settle and evaporate at room temperature. The solution was then washed with water and dried.

[0071] Example 9

[0072] (1) Synthesis of copper nanocubes: 1.56 × 10⁻⁶ copper nanocubes were added sequentially to a 25 mL glass bottle. -2 mol / L CuCl2·2H2O, 7.45×10 -2 mol L -1 Hexadecylamine and 2.78 × 10 -2 mol L -1 A glucose solution, with a total volume of 10 mL, was added and stirred overnight to dissolve. The glass bottle was then transferred to an oil bath and reacted at 100°C for 6 hours. After the reaction, the solution was centrifuged and washed twice with water at 70°C to obtain copper nanocubes.

[0073] (2) Preparation of superlattice copper nanocube thin films: 5 μmol of superlattice copper nanocubes were dispersed in 200 μL of 10 mmol L -1 The solution was prepared by adding 100 μL of 1% hydrofluoric acid to a hexadecylpyridine chloride solution, then dropping the mixture onto a single-crystal silicon substrate. The substrate was allowed to settle and evaporate at room temperature, then washed with water and dried. The concentration of hexadecylpyridine chloride can range from 1 to 10 mmol / L. -1 Adjust between them.

[0074] Example 10

[0075] (1) Synthesis of palladium nanocubes: 105 mg PVP, 60 mg AA, 1200 mg KBr and 185 mg KBr were added to 8 mL of deionized water and stirred in a water bath at 80 °C for 10 min. Then 57 mg Na2PdCl4 was added and the reaction was carried out at the same temperature for 3 h. After the reaction was completed, Pd nanocubes were obtained by centrifugation and washing.

[0076] (2) Preparation of superlattice palladium nanocube thin films: 4 μmol of superlattice palladium nanocubes were dispersed in 200 μL of 10 mmol L -1 The solution was prepared by adding 100 μL of 1% hydrofluoric acid to a hexadecylpyridine chloride solution, then dropping the mixture onto a single-crystal silicon substrate. The substrate was allowed to settle and evaporate at room temperature, then washed with water and dried. The concentration of hexadecylpyridine chloride can range from 1 to 10 mmol / L. -1 Adjust between them.

[0077] Example 11

[0078] (1) Synthesis of platinum nanocubes: 0.025 mmol Na2PtCl6·6H2O, 167 mmol glucose, 0.1 mmol hexadecyltrimethylammonium bromide and 5 mL oleylamine solution were mixed and stirred at 80 °C for 30 min, and then reacted at 160 °C for 2 h. After the reaction was completed, the mixture was cooled to room temperature, acetone solution was added and centrifuged, and the mixture was washed three times with hexane to obtain platinum nanocubes.

[0079] (2) Preparation of superlattice platinum nanocube thin films: 3 μmol of superlattice platinum nanocubes were dispersed in 200 μL of 10 mmol L -1 The solution was prepared by adding 100 μL of 1% hydrofluoric acid to a hexadecylpyridine chloride solution, then dropping the mixture onto a single-crystal silicon substrate. The substrate was allowed to settle and evaporate at room temperature, then washed with water and dried. The concentration of hexadecylpyridine chloride can range from 1 to 10 mmol / L. -1 Adjust between them.

[0080] Comparison Implementation 1

[0081] Preparation of traditional chemically deposited gold film: (1) Weigh 0.2g sodium chloroaurate and 0.07g sodium hydroxide and dissolve them in 1.5mL deionized water. Sonicate for 1h to disperse and dissolve until the color becomes colorless; (2) Weigh 0.075g ammonium chloride, 0.052g sodium sulfite and 0.035g sodium thiosulfate pentahydrate and dissolve them in 25mL deionized water. Sonicate for 1h; (3) Mix the solutions prepared in step (1) and step (2), sonicate for 2h, and store overnight to obtain a precursor solution; (4) Mix the solution obtained in step (3) with hydrofluoric acid in a ratio of 4:1 and place it in a water bath at 50-80℃. Then, place the single crystal silicon in the solution for wet chemical deposition for 4-8min to obtain a traditional chemically deposited gold film.

[0082] Figure 1 This is a flowchart of the preparation process of superlattice nanocube thin films.

[0083] Depend on Figure 1 It is known that the prepared superlattice nanocubes are centrifuged, washed, and dispersed in a surface active agent; then acid is added and mixed, and the mixture is directly drop-coated onto single-crystal silicon. Under room temperature conditions, the superlattice nanocube thin film material is obtained.

[0084] Figure 2 Image (a) is a photograph of a superlattice nanocube thin film. Figure 2 Scanning electron microscope image of the superlattice nanocube thin film (b).

[0085] Depend on Figure 2 (a) It can be seen that after natural sedimentation, superlattice nanocubes can macroscopically assemble into a 2 cm diameter metal thin film with good conductivity. Figure 2 (b) It is evident that the superlattice nanocubes can form a uniformly arranged thin film at the microscopic level using the aforementioned preparation method. The method successfully prepares a self-assembled thin film.

[0086] Figure 3 (a) is the intermediate product spectrum obtained by in-situ attenuated total reflection surface-enhanced in-situ infrared spectroscopy technique, based on the present invention, by depositing a superlattice nanocube thin film on single-crystal silicon and carrying out an electrocatalytic reaction. Figure 3 (b) is a spectral collection image obtained under the same conditions using a conventional infrared-enhanced substrate.

[0087] Depend on Figure 3 It is evident that, in the same electrochemical reaction, the superlattice nanocube film prepared in Example 7 exhibits stronger infrared vibrational signals from molecules adsorbed on the film at reversible hydrogen electrodes from 0.8 to -0.3 V compared to traditional chemically deposited films, resulting in a sensitivity increase of more than 10 times. This indicates that the self-assembled film method effectively improves the detection sensitivity of surface-enhanced infrared spectroscopy. Compared to traditional metal films, the superlattice nanocube film, due to its lower sensitivity, can detect other substances that are difficult to detect. Lower sensitivity means that smaller amounts of intermediate products are detected, which is beneficial for more accurate inference of the electrocatalytic reaction process, thereby enabling the design of highly active and selective catalysts.

[0088] Figure 4 (a) shows the intermediate product spectrum obtained by in-situ attenuated total reflectance surface-enhanced infrared spectroscopy (SIR) using a commercial cuprous oxide catalyst applied to a superlattice nanocube film for electrocatalytic reaction. Figure 4 (b) is a spectral collection image obtained under the same conditions using a conventional infrared-enhanced substrate.

[0089] Depend on Figure 4 It is evident that the superlattice nanocube film prepared in Example 7, used as a substrate for in-situ surface-enhanced infrared spectroscopy, with commercial cuprous oxide as a catalyst, exhibits an infrared vibration signal at the reversible hydrogen electrode adsorbed on cuprous oxide that is more than 10 times stronger than that of traditional substrates from 0 to -1.0 V. This demonstrates that self-assembled nanocube films, as infrared substrates, have significant application value for intermediate products with low content and rapid generation and conversion. In in-situ electrochemical catalytic reactions, more observation of intermediate species adsorbed on the catalyst surface allows for more accurate deduction of the electrocatalytic reaction process, leading to the design of highly active and selective catalysts. This provides valuable insights for addressing energy consumption and environmental pollution issues.

[0090] The investigation of self-assembled superlattice metal nanocube films as catalysts and substrates confirmed their role in improving sensitivity and lowering the detection limit in attenuated total reflectance surface-enhanced in-situ infrared spectroscopy (SIR). Therefore, besides the commercial cuprous oxide catalyst mentioned in this invention, any other catalyst used in electrocatalytic reactions can be drop-coated onto self-assembled superlattice metal nanocube films, and the intermediate adsorbed species during the electrocatalytic reaction process can be observed using SIR to infer the catalytic reaction mechanism. Examples include inorganic metal compound catalysts such as zinc, palladium, lead, titanium, and iron, as well as organic compound catalysts such as carbon nitride, metal-organic frameworks, and graphene.

[0091] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a self-assembled superlattice metal nanocube thin film, characterized in that, Includes the following steps: (1) After mixing the solution containing metal ions with the capping agent, a reducing agent is added to obtain a metal cluster seed solution; the metal cluster is further grown to obtain a superlattice metal nanocube. The solution containing metal ions is a chloroauric acid solution, a chloropalladium acid solution, a chloroplatinic acid solution, or a copper chloride solution; the end-capping agent is a polyvinylpyrrolidone, hexadecylamine, hexadecyltrimethylammonium bromide, or hexadecyltrimethylammonium chloride; the reducing agent is ascorbic acid, diethylene glycol, ethylene glycol, or pentanediol. (2) The superlattice metal nanocubes obtained in step (1) are dispersed in a surfactant, wherein the number of carbon atoms in the carbon chain of the surfactant is greater than or equal to 10, and then an acid is added. The mixed solution is then dropped onto the substrate. After the superlattice metal nanocubes are naturally settled and dried, the superlattice metal nanocubes self-assembled film is obtained.

2. The method for preparing a superlattice metal nanocube self-assembled thin film as described in claim 1, characterized in that, In step (2), after the superlattice metal nanocubes are dispersed in the surfactant, the concentration of the superlattice metal nanocubes is 10~30 mmol / L.

3. The method for preparing a superlattice metal nanocube self-assembled thin film as described in claim 1 or 2, characterized in that, In step (2), the concentration of the surfactant is 1 mmol L. -1 - 10 mmol L -1 .

4. The method for preparing a superlattice metal nanocube self-assembled thin film as described in claim 1, characterized in that, In step (2), the acid is hydrochloric acid, sulfuric acid, perchloric acid, nitric acid, potassium permanganate, hydrofluoric acid, hydroiodic acid, hydrobromic acid, carbonic acid, acetic acid, silicic acid, phosphoric acid, or hypochlorous acid.

5. The method for preparing a superlattice metal nanocube self-assembled thin film as described in claim 1, characterized in that, The surfactant is hexadecyl pyridine bromide, hexadecyl pyridine chloride, or dodecyl pyridine bromide.

6. The superlattice metal nanocube self-assembled thin film prepared by any one of claims 1-5.

7. The application of the superlattice metal nanocube self-assembled thin film as described in claim 6 for enhancing infrared signal substrates.

8. The superlattice metal nanocube self-assembled thin film as described in claim 6 is used in catalyst applications.

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