A platinum cluster-loaded vacancy carbon nitride material, its preparation method and application

Abstract

The present invention provides a platinum cluster-loaded vacancy carbon nitride material, its preparation method and application. The preparation method includes: (1) preparing carbon nitride g-C<subgt;3< / subgt;N<subgt;4< / subgt>; (2) preparing a cobalt single-atom doped vacancy carbon nitride material Co SACs / V<subgt;N< / subgt>-C<subgt;3< / subgt>N<subgt;4; (3) preparing platinum clusters Pt NCs; (4) preparing a platinum cluster-loaded vacancy carbon nitride material. The catalyst of Pt NCs / V<subgt;N-C<subgt;3N<subgt;4 prepared in this application has excellent detection effect on lead ions under neutral conditions. For the detection of 0.1-0.8 μM Pb(II) in neutral buffer solution, the detection sensitivity is as high as 102.16 μA / μM and the detection limit is 0.018 μM; for the detection of Pb(II) in neutral actual water samples, the detection sensitivity is as high as 93.8 μA / μM and the detection limit is 0.036 μM. Both are far lower than the tolerance values in drinking water set by the World Health Organization.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental detection, and specifically relates to a stable Pt NCs / V N -C3N4 nanomaterial, its preparation method and application in heavy metal ion detection. Technical Background

[0002] In recent years, metal cluster catalysts have become a research hotspot due to their high activity, high selectivity, extremely high atomic utilization rate, and advantages such as quantum size effect, and have been widely used in fields such as CO oxidation, CO2 reduction, hydrogen production and oxygen production, fuel cells, and selective hydrogenation. Different from single atoms (SACs) and large metal nanoparticles (NPs), metal cluster catalysts have unique geometric and electronic structures, so they show enhanced activity and specified selectivity during the catalytic process. Compared with single-atom catalysts, cluster-based catalysts can accommodate more metal atoms, thereby further increasing the metal loading. Moreover, the coordination environment of the metal centers in the cluster is different from that of the metal centers in the single atom, which often produces unique synergistic effects and optimized oxidation states, making them more conducive to energy conversion reactions. In addition, due to the very small size of the atomic clusters, they can not only maintain the maximum atomic utilization rate, but also provide multiple active sites, improving the economic efficiency and catalytic performance of the catalyst.

[0003] However, metal cluster catalysts also have some undeniable disadvantages. They have intrinsic instability. When working under harsh reaction conditions such as high temperature and high pressure, the phenomenon of partial atom migration and aggregation into nanoparticles in the cluster still exists, which to a certain extent affects the activity of the cluster catalyst. The strong interaction between the cluster and the support and the fixation effect of the ligand are the key factors hindering the aggregation of the cluster. Therefore, it is urgent to improve the interaction between metal atoms and the substrate or enhance the ligand effect between metal atoms and ligands to improve the stability of the catalyst.

[0004] In recent years, with the development of industrialization, the pollution of divalent lead ions in the water environment has become increasingly serious, posing a major threat to human health. Even if the content of Pb(II) in the water environment exceeds the standard, it is relatively low, and the water environment contains many other metal elements and minerals, etc., which have certain interference on the detection of Pb(II). Therefore, it is very necessary to achieve highly sensitive and stable detection of Pb(II).

[0005] Currently, the commonly used methods for detecting heavy metal ions include chromatography and spectroscopy, such as ultraviolet-visible spectrophotometry (UV), inductively coupled plasma method (ICP), etc. These methods are limited in their application due to disadvantages such as complex operation, a series of pretreatment required before use, large instruments, and the need for professional operators to conduct tests.

[0006] Electrochemical detection methods have attracted extensive attention due to their high sensitivity, fast analysis speed, ability for on-line continuous monitoring, low instrument cost, and especially the ability for direct detection on-site. The working principle of the electrochemical method is to enrich the target analyte on the surface of the working electrode, where an electrochemical reaction occurs on the electrode surface, generating an electrochemical signal to achieve the detection of the content of the target analyte in the sample. The working electrode is the core component of electrochemical detection. Modifying the surface of the working electrode with Pt clusters, Pt has strong adsorption, can effectively enrich Pb(II), and Pt clusters have high atomic utilization rate, many and uniform active sites, which can accelerate the electron transfer between it and the working electrode, promote the process of oxidation or reduction reaction on the electrode surface, and achieve highly sensitive quantitative detection of Pb(II). However, electrochemical detection is usually carried out in the solution phase, and the liquid environment will make the Pt clusters unstable and easily aggregate into fewer and larger nanoparticles, thus limiting their loading capacity on the electrode and affecting the catalytic performance of the material. Therefore, in order to meet the requirements of heavy metal ion electrochemical detection, it is crucial to effectively control the stability of clusters at the carrier interface when designing and preparing cluster catalysts.

[0007] In addition, when detecting Pb(II) by the electrochemical method, the detection effect is usually better under acidic conditions such as pH = 5 or 6, and the detection effect of Pb(II) decreases significantly under neutral conditions. However, the pH of the actual water environment is generally around 7, and current research has proven through simulation calculations that: when the pH value is between 5 and 4.65, the detection error of lead is about 20 - 30% compared with pH = 7. Therefore, it is necessary to seek a catalyst with high activity under neutral conditions to achieve efficient detection of Pb(II) under conditions closer to the actual water environment. Summary of the Invention

[0008] The object of the present invention is to provide a material of Pt cluster stably loaded on vacancy carbon nitride, its preparation method, and its application in the detection of heavy metal ions.

[0009] The technical solution of the present invention is as follows:

[0010] A preparation method of a platinum cluster loaded vacancy carbon nitride material, which comprises the following steps:

[0011] (1) Preparation of carbon nitride g-C3N4

[0012] Placing urea in a muffle furnace for calcination to obtain carbon nitride g-C3N4 powder;

[0013] (2) Preparation of cobalt single-atom doped vacancy carbon nitride material Co SACs / V N -C3N4

[0014] Disperse g-C3N4 powder in deionized water and stir evenly under oil bath conditions; then add an aqueous solution of Co salt and stir until the mixture evaporates to dryness; calcine the obtained sample to obtain a cobalt single-atom doped vacancy carbon nitride material;

[0015] (3) Prepare platinum clusters Pt NCs

[0016] Under continuous magnetic stirring, add the triphenylphosphine solution and the chloroplatinic acid hexahydrate solution to ethanol in sequence, and then add the tetrabutylammonium bromide solution, and stir to obtain a platinum cluster Pt NCs solution;

[0017] (4) Prepare a platinum cluster-loaded vacancy carbon nitride material

[0018] Add the platinum cluster Pt NCs solution and the cobalt single-atom doped vacancy carbon nitride material to ethanol in sequence and stir to react, wash and dry to obtain a platinum cluster-loaded vacancy carbon nitride material.

[0019] In a further embodiment, the calcination temperature of urea in step (1) is 600-700 °C, the time is 2-4 hours, and the heating rate is 5 °C / min.

[0020] In a further embodiment, the oil bath temperature in step (2) is 60-80 °C, and the sample is calcined in an inert atmosphere at 400-500 °C for 2-4 h with a heating rate of 5 °C / min;

[0021] The mass ratio of the g-C3N4 to the Co salt is 150-180:3;

[0022] The Co salt is Co(NO3)2·6H2O, CoCl2·6H2O or (CH3COO)2Co.

[0023] In a further embodiment, the triphenylphosphine solution in step (3) is a toluene solution with a concentration of 40-50 mM, the chloroplatinic acid hexahydrate solution is an aqueous solution with a concentration of 40-50 mM, and the tetrabutylammonium bromide solution is an ethanol solution with a concentration of 40-50 mM;

[0024] The volume ratio of the triphenylphosphine solution, the chloroplatinic acid hexahydrate solution and the tetrabutylammonium bromide solution is 200-300:150-200:300.

[0025] In a further embodiment, the volume-to-mass ratio of the platinum cluster Pt NCs solution and the cobalt single-atom doped vacancy carbon nitride material in step (4) is (5-8) mL:(20-30) mg.

[0026] The second object of the present invention is to provide a platinum cluster-loaded vacancy carbon nitride material prepared by the above preparation method.

[0027] The second object of the present invention is to provide an application of the above-mentioned platinum cluster-loaded vacancy carbon nitride material for the detection of Pb(II) in a neutral water environment.

[0028] In a further aspect, the detection of Pb(II) in a neutral water environment is carried out using an electrochemical workstation, which includes a working electrode, and the working electrode is a glassy carbon electrode modified with a platinum cluster-loaded vacancy carbon nitride material.

[0029] In a further aspect, the preparation method of the working electrode includes: dropping a dispersion of the platinum cluster-loaded vacancy carbon nitride material onto the surface of a treated bare glassy carbon electrode.

[0030] The electrochemical workstation further includes a silver / silver chloride electrode as a reference electrode and a platinum wire electrode as a counter electrode.

[0031] In a further aspect, the detection of Pb(II) in a neutral water environment is carried out by square wave anodic stripping voltammetry in an NH4Cl-NH4OH buffer solution with pH = 7 and an actual water sample respectively. For the detection of 0.1 - 0.8 μM of Pb(II) in the neutral buffer solution, the detection sensitivity is not higher than 102.16 μA / μM and the detection limit is 0.018 μM; for the detection of Pb(II) in the neutral actual water sample, the detection sensitivity is not higher than 93.8 μA / μM and the detection limit is 0.036 μM.

[0032] The present invention proposes a stable new material Pt NCs / V based on Pt cluster loading N -C3N4, using triphenylphosphine (PPh3) as a ligand and Co SACs / V N -C3N4 as a substrate to anchor Pt clusters, so that the Pt clusters maintain good stability and do not aggregate into larger Pt nanoparticles, and can still maintain good stability after multiple electrochemical detections. Using this stable Pt cluster-loaded nanocomposite for electrochemical analysis realizes highly sensitive detection of divalent lead ions. And this material has high catalytic activity under the condition of pH = 7, realizing highly sensitive detection of Pb(II) in a neutral water environment.

[0033] Therefore, the beneficial effects of the present invention are:

[0034] (1) In the present application, PPh3 is used as a ligand for Pt NCs. A Pt-P bond with moderate affinity is formed between the PPh3 ligand and Pt NCs, protecting Pt NCs while avoiding aggregation of Pt NCs.

[0035] In addition, Co SACs / V N-C3N4 serves as a substrate to anchor Pt NCs. A Pt-N / C bond is formed between Pt NCs and the N atoms on the substrate, further preventing the aggregation of Pt NCs into larger particles. Under the dual effects of the ligand effect and substrate fixation, PtNCs / V N -C3N4 material has good stability, and no obvious aggregation of Pt NCs occurs after multiple electrochemical tests.

[0036] (2) In this application, Co SACs / V N -C3N4 is used as a substrate material to stabilize Pt NCs. Compared with directly loading on the vacancy carbon nitride (V N -C3N4) material, theoretical calculations show that the formation energies of Co SACs / V N -C3N4 and V N -C3N4 are 0.35 eV and 0.33 eV respectively, indicating that the doping of Co SACs effectively improves the activity of the substrate material, making it easier for Pt NCs to anchor on the CoSACs / V N -C3N4 substrate. And when Pt NCs are loaded, they occupy the sites of Co SACs, resulting in the final product being PtNCs / V N -C3N4.

[0037] (3) Currently, most noble metal nanoparticles can only exhibit special catalytic abilities in acidic electrolytes such as 0.1 M sulfuric acid and hydrochloric acid, but this may damage the active structure of the catalyst and further affect the detection accuracy and sensitivity. When detecting Pb(II) by electrochemical methods, the detection effect is often better under acidic conditions with a pH of 5 or 6, and the detection effect of Pb(II) significantly decreases under neutral conditions.

[0038] The platinum cluster-loaded vacancy carbon nitride material (Pt NCs / V N -C3N4) prepared in this application is a new type of catalyst that can stably exhibit its high activity under neutral conditions. The Pt NCs / V N -C3N4 catalyst prepared in this application has excellent detection effects on lead ions under neutral conditions. For the detection of 0.1 - 0.8 μM Pb(II) in neutral buffer solutions, the detection sensitivity is as high as 102.16 μA / μM and the detection limit is 0.018 μM; for the detection of Pb(II) in neutral actual water samples, the detection sensitivity is as high as 93.8 μA / μM and the detection limit is 0.036 μM. Both are far lower than the tolerance value (0.048 μM) set by the World Health Organization for drinking water. Description of the Drawings

[0039] Figure 1 For the Pt NCs / V prepared in the present inventionN Schematic diagram of the structure of the -C3N4 material;

[0040] Figure 2 Pt NCs / V prepared according to the present invention N Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images of the -C3N4 material, where the inset is the size distribution diagram of Pt NCs loaded on the substrate;

[0041] Figure 3 For Pt NCs / V N Schematic diagram for optimizing the electrochemical experimental conditions of the -C3N4 / GCE;

[0042] Figure 4 For Pt NCs / V N Square wave anodic stripping voltammetry (SWASV) curves of the -C3N4 material for 0.1 - 0.8 μM Pb(II) and the corresponding linear curve between the peak current and the Pb(II) concentration;

[0043] Figure 5 For Pt NCs / V N Stability and reproducibility tests of the -C3N4 material for 0.4 μM Pb(II);

[0044] Figure 6 For the transmission electron microscopy (TEM) image of Pt NCs / V N -C3N4 after multiple cyclic voltammetry (CV) tests, where the inset is the size distribution diagram of Pt NCs loaded on the substrate. Detailed implementation mode

[0045] Combined with the attached drawings and specific embodiments, the technical solutions of the present invention are further described. Example 1:

[0046] (1) Preparation of graphitic carbon nitride g-C3N4

[0047] Place urea in a covered alumina crucible and put it in a muffle furnace. Calcinate at 600 °C (heating rate of 5 °C / min) for 4 hours to obtain a light yellow powder.

[0048] (2) Synthesis of cobalt single-atom doped vacancy carbon nitride material (Co SACs / V N -C3N4) Take 150 mg of g-C3N4 and dissolve it in 30 mL of deionized water. Stir in an oil bath at 70 °C for 10 min. Immediately add 3 mL of Co(NO3)2·6H2O aqueous solution (1 mg / mL) to the above g-C3N4 aqueous solution and continuously stir for 16 h until the mixture is evaporated to dryness. Finally, put the obtained sample into a tubular furnace and heat it at 600 °C for 2 h (heating rate of 5 °C / min) in an Ar atmosphere.

[0049] (3) Synthesis of Pt NCs

[0050] Into a beaker containing 4.5 mL of ethanol solution, 200 μL of triphenylphosphine (PPh3) toluene solution (50 mM), 150 μL of chloroplatinic acid hexahydrate (H2PtCl6·6H2O) aqueous solution (50 mM), and 300 μL of tetrabutylammonium bromide (TBAB) ethanol solution (50 mM) were successively added under continuous magnetic stirring. After stirring for 3 h, a brownish-red platinum cluster (Pt NCs) solution was obtained.

[0051] (4) Pt NCs / V N -C3N4 Synthesis

[0052] 5 mL of the reddish-brown platinum cluster solution was added dropwise to 45 mL of ethanol solution. Subsequently, 20 mg of Co SACs / V N -C3N4 was added to the above solution. After continuous stirring for 6 h, it was washed several times with deionized water and ethanol, and finally freeze-dried for 12 h to obtain a platinum cluster-loaded vacancy carbon nitride material (Pt NCs / V N -C3N4).

[0053] Figure 1 is the atomic structure diagram of the Pt NCs / V N -C3N4 material. The figure shows that a Pt atom forms Pt-C and Pt-N bonds with a C atom and an N atom near the N vacancy in the substrate V N -C3N4 respectively, making the Pt cluster stably loaded on the substrate surface.

[0054] Figure 2 is the TEM image of different sizes of the Pt NCs / V N -C3N4 material prepared in Example 1. The figure shows that the material is in the form of irregular thin flakes. The Pt NCs are uniformly loaded on the V N -C3N4 substrate without agglomerating into Pt nanoparticles. From the inserted particle size distribution diagram, it can be seen that the size of the Pt NCs is about 1.85 nm.

[0055] Example 2:

[0056] (1) Preparation of graphitic carbon nitride g-C3N4

[0057] Urea was placed in a covered alumina crucible and placed in a muffle furnace. It was calcined at 700 °C (5 °C / min) for 2 h to obtain a light yellow powder.

[0058] (2) Synthesis of Co SACs / V N -C3N4

[0059] 160 mg of g-C3N4 was dissolved in 30 mL of deionized water and stirred in an oil bath at 70 °C for 10 min. Immediately, 3 mL of an aqueous Co(NO3)2·6H2O solution (1 mg / mL) was added to the above g-C3N4 aqueous solution, and the mixture was stirred in an oil bath for 17 h until the mixture was evaporated to dryness. Finally, the obtained sample was placed in a tubular furnace and heated at 400 °C for 2 h in an Ar atmosphere (heating rate: 5 °C / min).

[0060] (3) Synthesis of Pt NCs

[0061] To a beaker containing 5 mL of an ethanol solution, 250 μL of a toluene solution of PPh3 (50 mM), 180 μL of an aqueous H2PtCl6·6H2O solution (50 mM), and 300 μL of a TBAB ethanol solution (50 mM) were successively added under continuous magnetic stirring, and the mixture was vigorously stirred for 3 h to obtain a reddish-brown Pt NCs solution.

[0062] (4) Synthesis of Pt NCs / V N -C3N4

[0063] 5 mL of the reddish-brown Pt cluster suspension was added dropwise to 50 mL of an ethanol solution, and then 30 mg of Co SACs / V N -C3N4 was added to the above solution. The mixture was continuously stirred for 6 h, washed several times with deionized water and ethanol, and finally freeze-dried for 12 h to obtain a platinum cluster-loaded vacancy carbon nitride material (Pt NCs / V N -C3N4).

[0064] Example 3:

[0065] (1) Preparation of carbon nitride g-C3N4

[0066] Urea was placed in a covered alumina crucible and placed in a muffle furnace, calcined at 650 °C (5 °C / min) for 3 h to obtain a light yellow powder.

[0067] (2) Synthesis of Co SACs / V N -C3N4

[0068] 180 mg of g-C3N4 was dissolved in 30 mL of deionized water and stirred in an oil bath at 70 °C for 10 min. Immediately, 3 mL of an aqueous (CH3COO)2Co solution (1 mg / mL) was added to the above g-C3N4 aqueous solution, and the mixture was stirred in an oil bath for 18 h until the mixture was evaporated to dryness. Finally, the obtained sample was placed in a tubular furnace and heated at 400 °C for 2 h in an Ar atmosphere (heating rate: 5 °C / min).

[0069] (3) Synthesis of Pt NCs

[0070] Into a beaker containing 5 mL of ethanol solution, 300 μL of PPh3 toluene solution (40 mM), 200 μL of H2PtCl6·6H2O aqueous solution (40 mM), and 300 μL of TBAB ethanol solution (40 mM) were successively added under continuous magnetic stirring. The mixture was vigorously stirred for 3 h to obtain a brownish-red Pt NCs solution.

[0071] (4) Pt NCs / V N Synthesis of -C3N4

[0072] 5 mL of the reddish-brown Pt NCs suspension was added dropwise to 50 mL of ethanol solution. Subsequently, 30 mg of Co SACs / V N -C3N4 was added to the above solution. The mixture was continuously stirred for 6 h, washed several times with deionized water and ethanol, and finally freeze-dried for 12 h to obtain a vacancy carbon nitride material loaded with platinum clusters (Pt NCs / V N -C3N4).

[0073] Verification Example 1:

[0074] Using the Pt NCs / V N -C3N4 material prepared in Example 1 to modify the glassy carbon electrode as the working electrode, a platinum wire electrode as the counter electrode, and an Ag / AgCl (saturated KCl) electrode as the reference electrode to form an electrochemical working system for the electrochemical detection of 0.1 - 0.8 μM of Pb(II) in a neutral aqueous environment.

[0075] The preparation method of the working electrode is as follows:

[0076] 5 mg of Pt NCs / V N -C3N4 nanomaterials were uniformly dispersed in 5 mL of ultrapure water, ultrasonically dispersed evenly, and configured into a uniformly mixed dispersion with a concentration of 1 mg / mL.

[0077] The bare glassy carbon electrode was treated by first polishing with alumina (Al2O3) powder, and then ultrasonically treated in a 1:1 nitric acid solution, absolute ethanol, and ultrapure water for 30 s in sequence. After cleaning, it was dried with nitrogen (N2).

[0078] 8 μL of the prepared 1 mg / mL Pt NCs / V N -C3N4 aqueous solution was vertically dropped onto the surface of the treated bare glassy carbon electrode and left at room temperature for 24 h to obtain a glassy carbon electrode modified with Pt NCs / V N -C3N4 nanomaterials.

[0079] The specific detection process is as follows:

[0080] (1) 0.1 M ammonium chloride (NH4Cl) aqueous solution and 0.1 M ammonium hydroxide (NH4OH) were mixed in different proportions to prepare 0.1 M NH4Cl-NH4OH buffer solutions with different pH values;

[0081] By controlling variables, the type of buffer solution, pH value, enrichment voltage and enrichment time were optimized to obtain the optimal experimental conditions.

[0082] Select Pt NCs / V N -C3N4 sample modified glassy carbon electrode as working electrode to optimize experimental conditions. First, the test was carried out in three different buffer solutions (NH4Cl-NH4OH, PBS, HAc-NaAC). Equal amounts of Pb(II) were added to the three buffer solutions respectively, and the same enrichment voltage (-1V) and enrichment time (120s) were set. The dissolution potential was continuously changed from -0.8 to 0V to reduce the ion Pb(II) on the electrode surface. The detection data of each time was recorded, and the relationship curve between the peak current and the Pb(II) concentration was drawn. It was found that Pt NCs / V N -C3N4 exhibits the best square-wave voltammetric response to Pb(II) in an NH4Cl-NH4OH buffer solution, so NH4Cl-NH4OH was selected as the optimal buffer solution. The Pb(II) signal was then monitored by varying the pH of the NH4Cl-NH4OH solution while maintaining the same deposition voltage and time. The peak current reached its maximum at pH = 7. The electrochemical signal of Pb(II) was then measured in an NH4Cl-NH4OH solution at pH = 7 by varying the deposition voltage. The peak current decreased with further negative voltage changes, likely due to hydrogen evolution at negative voltages. Finally, the deposition time was increased while maintaining the deposition voltage at -1.2V in an NH4Cl-NH4OH solution at pH = 7. The Pb(II) dissolution signal was measured at varying deposition times. The peak current initially increased and then leveled off with increasing deposition time. For efficiency reasons, a deposition time of 180 s was selected.

[0083] like Figure 3 Shown is the optimization of electrochemical detection conditions: (a) buffer solution; (b) pH value; (c) enrichment voltage; (d) enrichment time.

[0084] Pt NCs / V N The optimal experimental conditions for -C3N4 / GCE are: NH4Cl-NH4OH buffer solution; pH = 7; enrichment voltage -1.2V; enrichment time 180s.

[0085] (2) The aforementioned electrochemical workstation was tested using a three - electrode system in a 10 mL NH4Cl - NH4OH buffer solution with a pH of 7.

[0086] (3) Square - wave anodic stripping voltammetry (SWASV) was adopted. The enrichment voltage was - 1.2 V and the enrichment time was 180 s to detect Pb(II) in the range of 0.1 - 0.8 μM under neutral conditions.

[0087] 10 mL of NH4Cl - NH4OH buffer solution with a pH of 7 was taken, and nitrogen gas was continuously introduced into the mixed solution 1 for 15 minutes to remove dissolved oxygen. Using the prepared Pt NCs / V N -C3N4 - modified glassy carbon electrode as the working electrode, platinum wire electrode as the counter electrode, and Ag / AgCl (saturated KCl) electrode as the reference electrode, immersed in 10 mL of NH4Cl - NH4OH buffer solution with a pH of 7. The enrichment potential of the working electrode was set at - 1.2 V (relative to the Ag / AgCl reference electrode). 0.1 μM of Pb(II) was successively added to the mixed solution, and each time the enrichment time was maintained at 180 s. The stripping potential was continuously changed from - 0.8 V to 0 V. The Pb(II) ions to be detected were deposited on the electrode surface and reduced. The detection data for each time were recorded, and a relationship curve of peak current versus Pb(II) concentration was plotted. Other parameter settings were as follows: frequency 25 Hz; amplitude 25 mV; incremental potential 4 mV. After each square - wave anodic stripping voltammetry measurement, a desorption experiment was carried out by stirring at a speed of 300 rpm for 90 s at a working voltage of 1 V to ensure complete removal of the deposits remaining on the surface of the glassy carbon electrode.

[0088] As Figure 4 shown, it is the current response signal of Pt NCs / V N -C3N4 for detecting 0.1 - 0.8 μM Pb(II) and the linear relationship diagram between the corresponding peak current and Pb(II) concentration detected by Pt NCs / V N -C3N4. Pt NCs / V N -C3N4 has a good electrochemical response to Pb(II), and the detection sensitivity is as high as 102.16 μA / μM.

[0089] (4) Square - wave anodic stripping voltammetry (SWASV) was adopted. The enrichment voltage was - 1.2 V and the enrichment time was 180 s to detect Pb(II) in the range of 0.1 - 0.8 μM in actual water environment.

[0090] Take the natural water sample to be tested and filter the natural water sample using a microporous filter membrane with a pore size of 220 nm. Take 1 mL of the filtered natural water sample and mix it with 9 mL of NH4Cl-NH4OH buffer solution. Add 0.1 μM of Pb(II) to the mixed water sample successively, and enrich it at -1.2 V for 180 s. The ions to be detected are reduced on the electrode surface, record the detection data each time, and plot the relationship curve between the peak current and the concentration of Pb(II). After each square wave anodic stripping voltammetry measurement, perform a desorption experiment by stirring at a speed of 300 rpm for 90 s at a working voltage of 1 V to ensure complete removal of the deposits remaining on the surface of the glassy carbon electrode.

[0091] Pt NCs / V N The sensitivity of the Pt NCs / V N -C3N4 material to Pb(II) in the actual water environment is 93.8 μA / μM, which is not much different from the detection results in the laboratory. Therefore, Pt NCs / V

[0092] As can be seen from the above, the present invention uses Pt NCs / V N -C3N4 material has a good electrochemical response to Pb(II), with a detection sensitivity as high as 102.16 μA / μM, a detection limit of 0.018 μM, and even the sensitivity to Pb(II) in the actual water sample can reach 93.8 μA / μM -1 , and the detection limit is 0.036 μM, which is much lower than the tolerance value (0.048 μM) of drinking water set by the World Health Organization. In addition, the stability and reproducibility of this material in the electrochemical process are also excellent, and the relative standard deviations (RSD) are only 1.87% and 1.93%.

[0093] That is, the present invention uses Co SACs / V N -C3N4 as a substrate to load Pt clusters, and uses this stable Pt cluster-loaded nanocomposite material for electrochemical analysis, realizing highly sensitive detection of divalent lead ions.

[0094] Figure 5 It is the test result of the stability and reproducibility of the Pt NCs / V N -C3N4 material during the electrochemical detection process.

[0095] Prepare eleven Pt NCs / V N -C3N4 / GCE, take one of the Pt NCs / V N-C3N4 / GCE, 0.4 μM of Pb(II) was added dropwise to 10 mL of NH4Cl-NH4OH buffer solution with a pH of 7. The enrichment potential of the working electrode was set at -1.2 V, and the enrichment time was 180 s. The stripping potential was continuously varied from -0.8 to 0 V, enabling the deposition and reduction of the ions to be measured on the electrode surface. The measurement was repeated 10 times to obtain the current curve of the repeated stripping of 0.4 μM of Pb(II) on the surface of the glassy carbon electrode modified with Pt NCs / V N -C3N4 material for 10 times. Take the remaining ten Pt NCs / V N -C3N4 / GCE was successively immersed in NH4Cl-NH4OH buffer solution (pH = 7) containing 0.4 μM of Pb(II), enriched at -1.2 V for 180 s, and the stripping potential was continuously varied from -0.8 to 0 V. The response curve of the stripping of 0.4 μM Pb(II) on the surface of the 10 Pt NCs / V N -C3N4 / GCE electrode surface was measured.

[0096] [[ID=P9]]Among them Figure 5 a is the response curve of the repeated stripping of 0.4 μM Pb(II) on the surface of the Pt NCs / V N -C3N4 / GCE electrode for 10 times, and the relative standard deviation (RSD) is only 1.87%, indicating that the Pt NCs / V N -C3N4 material electrode has good stability during the detection of Pb(II). Figure 5 b is the response curve of the stripping of 0.4 μM Pb(II) on the surface of the 10 Pt NCs / V N -C3N4 / GCE electrodes, and the relative standard deviation (RSD) is only 1.93%, indicating that the Pt NCs / V N -C3N4 material has good reproducibility during the detection of Pb(II).

[0097] Verification Example 2:

[0098] The material Pt NCs / V N -C3N4 on the surface of the glassy carbon electrode after multiple electrochemical tests was gently scraped off with a spatula, dissolved in an appropriate amount of deionized water, and ultrasonically homogenized, followed by scanning electron microscopy (SEM) testing.

[0099] Usually, small-sized Pt clusters are extremely unstable during the electrochemical reaction process due to their high surface energy. In the present invention, triphenylphosphine is used as a ligand and V N -C3N4 is used as a substrate to stabilize the Pt clusters. Experiments have shown that the dual action of the ligand and the substrate enables the material to have good stability after multiple electrochemical tests, and the Pt clusters do not aggregate into larger particles.

[0100] Figure 6 Pt NCs / V after multiple electrochemical tests N -C3N4 material SEM image, where the inset is the particle size distribution map of the corresponding Pt NCs. After multiple electrochemical tests, Pt NCs N show no obvious agglomeration on the surface of the V N -C3N4 substrate, with a size of about 1.87 nm, indicating that Pt NCs can effectively remain stable on the V

[0101] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a platinum cluster-loaded vacancy carbon nitride material, characterized in that: It includes the following steps: (1) Prepare graphitic carbon nitride g-C3N4 Place urea in a muffle furnace for calcination to obtain graphitic carbon nitride g-C3N4 powder; (2) Prepare cobalt single-atom doped vacancy graphitic carbon nitride material Disperse the graphitic carbon nitride g-C3N4 powder in deionized water and stir evenly under oil bath conditions; then add an aqueous Co salt solution and stir until the mixture evaporates to dryness; calcine the obtained sample to obtain a cobalt single-atom doped vacancy graphitic carbon nitride material; the mass ratio of the g-C3N4 to the Co salt is 150-180:3; the sample calcination is carried out in an inert atmosphere at 400-500 °C for 2-4 h with a heating rate of 5 °C / min; (3) Prepare platinum clusters Pt NCs Under continuous magnetic stirring, add a triphenylphosphine solution and a chloroplatinic acid hexahydrate solution to ethanol in sequence, and then add a tetrabutylammonium bromide solution and stir to obtain a platinum cluster Pt NCs solution; (4) Prepare a platinum cluster-loaded vacancy graphitic carbon nitride material Add the platinum cluster Pt NCs solution and the cobalt single-atom doped vacancy graphitic carbon nitride material to ethanol in a volume-to-mass ratio of (5-8) mL:(20-30) mg in sequence, stir and react, wash and dry to obtain a platinum cluster-loaded vacancy graphitic carbon nitride material.

2. The preparation method according to claim 1, characterized in that: In step (1), the calcination temperature of urea is 600-700 °C, the time is 2-4 h, and the heating rate is 5 °C / min.

3. The preparation method according to claim 1, wherein: In step (2), the oil bath temperature is 60-80 °C, and the Co salt is Co(NO3)2·6H2O, CoCl2·6H2O or (CH3COO)2Co.

4. The preparation method according to claim 1, characterized in that: In step (3), the triphenylphosphine solution is a toluene solution with a concentration of 40-50 mM, the chloroplatinic acid hexahydrate solution is an aqueous solution with a concentration of 40-50 mM, and the tetrabutylammonium bromide solution is an ethanol solution with a concentration of 40-50 mM; The volume ratio of the triphenylphosphine solution, the chloroplatinic acid hexahydrate solution and the tetrabutylammonium bromide solution is 200-300:150-200:

300.

5. A platinum cluster-loaded vacancy graphitic carbon nitride material prepared by the preparation method according to any one of claims 1-4.

6. Use of the platinum cluster-loaded vacancy carbon nitride material according to claim 5, characterized in that: It is used for the detection of Pb(II) in a neutral water environment.

7. The application according to claim 6, wherein: The detection of Pb(II) in the neutral water environment is carried out using an electrochemical workstation, and the electrochemical workstation includes a working electrode, and the working electrode is a glassy carbon electrode modified with a platinum cluster-loaded vacancy graphitic carbon nitride material.

8. The application according to claim 7, wherein: The preparation method of the working electrode includes: dropping a dispersion of the platinum cluster-loaded vacancy graphitic carbon nitride material onto the surface of a treated bare glassy carbon electrode; The electrochemical workstation further includes a silver / silver chloride electrode as a reference electrode and a platinum wire electrode as a counter electrode.

9. The application according to claim 7, wherein: The detection of Pb(II) in a neutral aqueous environment was carried out by square wave anodic stripping voltammetry in an NH4Cl-NH4OH buffer solution with pH = 7 and in actual water samples. For the detection of 0.1 - 0.8 μM Pb(II) in the neutral buffer solution, the detection sensitivity was not higher than 102.16 μA / μM and the detection limit was 0.018 μM; for the detection of Pb(II) in the neutral actual water samples, the detection sensitivity was not higher than 93.8 μA / μM and the detection limit was 0.036 μM.

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