A Ni9S8@Au core-shell nanocrystal and its preparation method

Abstract

The present invention provides a Ni9S8@Au core-shell nanocrystal and a preparation method thereof. The Ni9S8@Au core-shell nanocrystal includes a core and a shell wrapped around the core, wherein the core is Ni9S8 and the shell is Au. The preparation method comprises the following steps: mixing nickel diethyldithiocarbamate with oleylamine, 1-octadecene, and 1-dodecylmercaptan to form a uniform solution; heating the uniform solution to a reaction temperature under a protective atmosphere, reacting to obtain a reaction solution; adding a tri-n-octylphosphine solution of chloroauric acid to the reaction solution, and reacting at the reaction temperature; cooling the obtained reaction solution to room temperature, adding a mixture of a polar solvent and a non-polar solvent, separating a solid product, and drying to obtain the Ni9S8@Au core-shell nanocrystal. Due to the unique structure and potential properties of the Ni9S8@Au core-shell nanocrystal, it has a wide range of application potentials in the fields of catalysis, energy storage, and sensing.

Description

Technical Field

[0001] The present invention belongs to the technical field of nano-synthesis preparation, and in particular relates to a Ni9S8@Au core-shell nanocrystal and a preparation method thereof. Background Art

[0002] As the global demand for sustainable energy solutions continues to grow, nickel sulfide has attracted widespread attention due to its potential applications in electrochemical energy storage and conversion. Nickel sulfide has a unique electronic structure and chemical stability, making it a candidate for electrode materials, electrocatalysts, electromagnetic materials, and semiconductor materials.

[0003] In order to improve the various properties of nickel sulfide, researchers began to explore nano-type nickel sulfide materials with novel structures and compositions. The development of nanocrystal technology provides new possibilities for the design and synthesis of nickel sulfide with specific morphologies and sizes, and it is possible to compound it with other active elements to produce multi-component composite nanomaterials with better performance. By precisely controlling the synthesis process of nanocrystals, nanomaterials with controllable specific surface area, pore structure, core-shell structure and special chemical binding ability can be prepared, which is crucial for improving various electrochemical properties. Nickel sulfide can be synthesized into different crystal structures by adjusting the ratio of nickel and sulfur. Common ones include NiS, NiS2 and Ni3S4. Different crystal structures have different physical and chemical properties. This diversity in composition allows for differences in the properties of the materials.

[0004] Nanocrystals of different morphologies exhibit distinct physical and chemical properties, requiring researchers to develop synthetic methods that can precisely control the morphology and phase of nanocrystals. However, precise control of these parameters during the synthesis process remains challenging. The methods for synthesizing nanocrystals are often complex and difficult to scale up, limiting their application in energy storage.

[0005] Chinese invention patent CN105060353B discloses a method for preparing orthorhombic nickel sulfide nanocrystals. The electrochemical activity of the obtained orthorhombic nickel sulfide nanocrystals needs to be improved, which limits their practical application in catalysis, energy storage, sensing and other fields. Summary of the Invention

[0006] In order to overcome the above-mentioned defects of the prior art, the object of the present invention is to provide a Ni9S8@Au core-shell nanocrystal and a preparation method thereof, thereby improving the electrochemical activity of nickelous sulfide nanocrystals.

[0007] The present invention is achieved through the following technical solutions:

[0008] A Ni9S8@Au core-shell nanocrystal comprises a core and a shell wrapped around the core, wherein the core is Ni9S8 and the shell is Au.

[0009] Preferably, in the Ni9S8@Au core-shell nanocrystals, the molar ratio of Ni9S8 to Au is 1:(1-5).

[0010] Preferably, the size of the Ni9S8@Au core-shell nanocrystals is 50-100 nm.

[0011] The method for preparing Ni9S8@Au core-shell nanocrystals of the present invention comprises the following steps:

[0012] (1) nickel diethyldithiocarbamate is mixed with oleylamine, 1-octadecene and 1-dodecylmercaptan to form a homogeneous solution;

[0013] (2) Under a protective atmosphere, heating the homogeneous solution to a reaction temperature, reacting to obtain a reaction solution;

[0014] (3) adding a tri-n-octylphosphine solution of chloroauric acid to the reaction solution, and reacting at the reaction temperature;

[0015] (4) After the reaction solution obtained in step (3) is cooled to room temperature, a mixture of a polar solvent and a non-polar solvent is added, the solid product is separated and dried to obtain Ni9S8@Au core-shell nanocrystals.

[0016] Preferably, in step (1), the molar ratio of nickel diethyldithiocarbamate, oleylamine, 1-octadecene and 1-dodecylmercaptan is 0.035:2:1:1.

[0017] Preferably, step (1) is specifically as follows:

[0018] mixing nickel diethyldithiocarbamate with oleylamine, 1-octadecene, and 1-dodecylmercaptan;

[0019] The resulting mixture was heated to 40-60 °C under vacuum for 30-60 min to form a homogeneous solution.

[0020] Preferably, in step (2), the reaction temperature is 160-240°C, and the reaction time is 1-2 h.

[0021] Preferably, in step (3), the reaction time is 2-3 h.

[0022] Preferably, in step (4), the polar solvent is anhydrous ethanol, and the non-polar solvent is cyclohexane.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention provides a core-shell nanocrystal Ni9S8@Au, which has a core-shell structure as a whole. The core is a Ni9S8 nanoscale crystal, and the shell is coated with Au nanoparticles. The composition is uniform, and the shell Au nanoparticles have excellent electrochemical activity. Due to the unique structure and potential properties of Ni9S8@Au core-shell nanocrystals, it has broad application potential in catalysis, energy storage, sensing and other fields, and can be further explored by other researchers.

[0025] This invention successfully prepared nanoscale Ni9S8@Au materials with a core-shell structure using a synthesis method based on hot injection and high-temperature thermal decomposition. In this method, oleylamine, 1-octadecene, and 1-dodecylmercaptan serve as solvents, providing the high temperature required for the reaction; they also act as surfactants, uniformly coating the surface of the nanomaterial, ensuring uniform growth and preventing agglomeration. During the Au coating of the Ni9S8 surface, Au readily bonds with the sulfur atoms due to the exposed sulfur atoms on the Ni9S8 surface and the presence of 1-dodecylmercaptan. Consequently, Au can be uniformly coated on the Ni9S8 surface during the preparation process. This preparation method is simple and convenient, with a short overall synthesis time, high yield, and good reproducibility. High-quality core-shell nanocrystals of Ni9S8@Au can be obtained without the use of high-pressure reaction conditions. This synthesis method can also be applied to the synthesis of other novel core-shell nanomaterials, providing a novel approach for the more efficient, green, convenient, and low-cost preparation of novel multifunctional nanomaterials.

[0026] Furthermore, by precisely controlling the synthesis conditions such as reaction temperature, reaction time, and the amount of each organic reagent, the present invention can produce nanocrystals with a size in the range of 50-100 nm. Nanomaterials of this size generally have good physical and chemical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 This is a transmission electron microscope (TEM) image of the Ni9S8@Au core-shell nanocrystals prepared in Example 3 of the present invention.

[0029] Figure 2 The energy spectrum element mapping and mixed element mapping diagram corresponding to Ni, S, and Au of the Ni9S8@Au core-shell nanocrystals prepared in Example 3 of the present invention.

[0030] Figure 3 for Figure 2 Relative intensity plot of each element in the energy spectrum element map.

[0031] Figure 4 This is the X-ray powder diffraction pattern (XRD) of the Ni9S8@Au core-shell nanocrystals prepared in Example 3 of the present invention.

[0032] Figure 5 X-ray photoelectron spectroscopy (XPS) analysis of different elements in the Ni9S8@Au core-shell nanocrystals prepared in Example 3 of the present invention: (a) Ni 2p; (b) S 2p; (c) Au 4f. DETAILED DESCRIPTION

[0033] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0034] It should be noted that the process equipment or devices not specifically specified in the following embodiments are all conventional equipment or devices in the art.

[0035] It should be noted that the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products, or apparatuses. Furthermore, unless otherwise specified, the numbering of each method step is merely a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or to define the scope of the present invention. Changes or adjustments to their relative relationships, without substantially changing the technical content, should also be considered within the scope of the present invention.

[0036] The Ni9S8@Au core-shell nanocrystals of the present invention have a core-shell structure as a whole, wherein the core is a Ni9S8 nanoscale crystal, and the core is coated with Au nanoparticles, which form an outer shell.

[0037] The size of the Ni9S8@Au core-shell nanocrystals is 50-100 nm, and the molar ratio of Ni9S8 to Au is 1:(1-5).

[0038] The method for preparing Ni9S8@Au core-shell nanocrystals of the present invention comprises the following steps:

[0039] (1) nickel diethyldithiocarbamate is mixed with oleylamine, 1-octadecene and 1-dodecylmercaptan to form a homogeneous solution;

[0040] (2) In order to prevent the reactants from being oxidized at high temperatures, the uniform solution needs to be heated to the reaction temperature under a protective atmosphere and reacted within a certain period of time to obtain a reaction solution;

[0041] (3) adding a tri-n-octylphosphine solution of chloroauric acid to the reaction solution, and reacting at the reaction temperature;

[0042] (4) After the reaction solution obtained in step (3) is cooled to room temperature, a mixture of a polar solvent and a non-polar solvent is added, the solid product is separated and dried to obtain Ni9S8@Au core-shell nanocrystals.

[0043] In step (1) of the present invention, the molar ratio of nickel diethyldithiocarbamate, oleylamine, 1-octadecene and 1-dodecylmercaptan is 0.035:2:1:1.

[0044] As a specific embodiment of the present invention, step (1) is specifically as follows:

[0045] Nickel diethyldithiocarbamate was mixed with oleylamine, 1-octadecene, and 1-dodecylmercaptan in a three-necked flask;

[0046] The resulting mixture was heated to 40-60 °C under vacuum for 30-60 min to form a homogeneous solution.

[0047] In step (2) of the present invention, the reaction temperature is 160-240°C and the reaction time is 1-2 h. In step (3), the reaction time is 2-3 h.

[0048] In step (4) of the present invention, the polar solvent is anhydrous ethanol, and the non-polar solvent is cyclohexane. Cyclohexane is used to remove excess non-polar surfactant oleylamine from the surface of the product. Based on the principle of like dissolves like, the polar solvent anhydrous ethanol can precipitate the product coated with the non-polar surfactant. Separation methods include centrifugation at 8000 rpm for 10 minutes. Drying can be performed in a vacuum drying oven at 65°C for 12 hours.

[0049] Example 1

[0050] This embodiment includes the following steps:

[0051] (1) 0.35 mmol (159.75 mg) of nickel diethyldithiocarbamate (Ni(S2CNEt2)2) precursor was mixed with 20.0 mmol of oleylamine (OM), 10.0 mmol of 1-octadecene (ODE), and 10 mmol of 1-dodecylmercaptan in a 50 mL three-necked flask;

[0052] (2) After magnetic stirring, the mixture of step (1) was heated to 40 °C for 30 min under vacuum conditions to remove the air in the reaction system and form a uniform solution;

[0053] (3) The homogeneous solution was then rapidly heated to 160°C under a pure nitrogen atmosphere, and Ni9S8 was grown at 160°C for 1 hour to obtain a reaction solution. Simultaneously, 13.22 mg of chloroauric acid (HAuCl4) was ultrasonically dispersed in 2.4 g of tri-n-octylphosphine (TOP) to form a colorless and transparent HAuCl4-TOP solution.

[0054] (4) Subsequently, the HAuCl4-TOP solution was injected into the reaction solution and reacted at 160 °C for 2 h;

[0055] (5) After the reaction solution was rapidly cooled to room temperature, a certain amount of anhydrous ethanol and cyclohexane were added to separate the core-shell nanocrystals Ni9S8@Au. The reaction solution was then centrifuged (8000 rpm, 10 min) and placed in a vacuum drying oven at 65 °C for 12 h to obtain core-shell nanocrystals Ni9S8@Au.

[0056] Example 2

[0057] This embodiment includes the following steps:

[0058] (1) 0.35 mmol (159.75 mg) of nickel diethyldithiocarbamate (Ni(S2CNEt2)2) precursor was mixed with 20.0 mmol of oleylamine (OM), 10.0 mmol of 1-octadecene (ODE), and 10 mmol of 1-dodecylmercaptan in a 50 mL three-necked flask;

[0059] (2) After magnetic stirring, the mixture of step (1) was heated to 40 °C for 30 min under vacuum conditions to remove the air in the reaction system and form a uniform solution;

[0060] (3) The homogeneous solution was then rapidly heated to 240 °C under a pure nitrogen atmosphere, and Ni9S8 was grown at 240 °C for 1 h to obtain a reaction solution. Simultaneously, 66.1 mg of chloroauric acid (HAuCl4) was ultrasonically dispersed in 2.4 g of tri-n-octylphosphine (TOP) to form a colorless and transparent HAuCl4-TOP solution.

[0061] (4) Subsequently, the HAuCl4-TOP solution was injected into the reaction solution and reacted at 240 °C for 2 h;

[0062] (5) After the reaction solution was rapidly cooled to room temperature, a certain amount of anhydrous ethanol and cyclohexane were added to separate the core-shell nanocrystals Ni9S8@Au. The reaction solution was then centrifuged (8000 rpm, 10 min) and placed in a vacuum drying oven at 65 °C for 12 h to obtain core-shell nanocrystals Ni9S8@Au.

[0063] Example 3

[0064] (1) 0.35 mmol (159.75 mg) of nickel diethyldithiocarbamate (Ni(S2CNEt2)2) precursor was mixed with 20.0 mmol of oleylamine (OM), 10.0 mmol of 1-octadecene (ODE), and 10 mmol of 1-dodecylmercaptan in a 50 mL three-necked flask;

[0065] (2) After magnetic stirring, the mixture of step (1) was heated to 40 °C for 30 min under vacuum conditions to remove the air in the reaction system and form a uniform solution;

[0066] (3) The homogeneous solution was then rapidly heated to 240 °C under a pure nitrogen atmosphere, and Ni9S8 was grown at 240 °C for 1 h to obtain a reaction solution. Simultaneously, 33.05 mg of chloroauric acid (HAuCl4) was ultrasonically dispersed in 2.4 g of tri-n-octylphosphine (TOP) to form a colorless and transparent HAuCl4-TOP solution.

[0067] (4) Subsequently, the HAuCl4-TOP solution was injected into the reaction solution and reacted at 240 °C for 2 h;

[0068] (5) After the reaction solution was rapidly cooled to room temperature, a certain amount of anhydrous ethanol and cyclohexane were added to separate the core-shell nanocrystals Ni9S8@Au. The reaction solution was then centrifuged (8000 rpm, 10 min) and placed in a vacuum drying oven at 65 °C for 12 h to obtain core-shell nanocrystals Ni9S8@Au.

[0069] The Ni9S8@Au core-shell nanocrystals prepared in Example 3 were characterized by transmission electron microscopy. Figure 1 As shown in Figure 2, it can be seen that the obtained sample has good crystallinity. The energy spectrum element mapping and mixed element mapping of Ni, S, and Au under transmission electron microscopy are shown in Figure 2. Figure 2 As shown in the figure, the relative intensity of each element is as follows Figure 3 As shown. Figure 2 and Figure 3, it can be seen that Ni and S elements are evenly distributed in the core, and Au is evenly distributed in the shell.

[0070] The core-shell nanocrystals Ni9S8@Au obtained in Example 3 were subjected to XRD phase analysis and XPS element valence analysis.

[0071] (1) X-ray powder diffraction analysis (XRD). The synthesized sample was ground into powder using a mortar and pestle and spread flat on a dedicated XRD sample stage for testing. A high-energy electron beam of Cu (Cu Kα, λ = 1.5418 Å) was used as the target. The scan rate was 5° / min and the scan range was 10°-70°.

[0072] The results are as follows Figure 4 As shown in Figure 2, several main diffraction peaks in the XRD diffraction pattern of the sample are consistent with the peak positions on the PDF standard cards of Ni9S8 and Au (Ni9S8: PDF#22-1193 and Au: PDF#04-0784). According to the information on the PDF card, Ni9S8 belongs to the orthorhombic system and the crystal space group is C222 , the lattice constant is: a = 9.18 Å, b =11.263 Å, c = 9.457 Å; Au belongs to the cubic system and the crystal space group is Fm-3m , the lattice constant is: a = b = c = 4.0786 Å.

[0073] (2) X-ray photoelectron spectroscopy (XPS). XPS was used to analyze the Ni, S, and Au elements in Ni9S8@Au core-shell nanocrystals. Correlated peaks appeared for the three elements, proving that all three elements were present.

[0074] like Figure 5 (a) shows the deconvoluted XPS spectrum of Ni 2p, which is well fitted with the spin-orbit doublet and vibration satellite peaks; the two peaks with binding energy values ​​of 853.07 and 870.72 eV represent the Ni 2+ 2p 3 / 2 and 2p 1 / 2 The two peaks with binding energy values ​​of 855.92 and 874.46 eV represent Ni 3+ The existence of 2p 3 / 2 and 2p 1 / 2 state; in addition, the vibrational satellite peaks are at 861.17 and 880.55 eV, respectively. Figure 5(b) is the XPS data curve of S in Ni9S8@Au core-shell nanocrystals. The peaks with binding energies of 161.87 and 163.01 eV correspond to 2p 3 / 2 and 2p 1 / 2 state; the peak at a binding energy of 166.43 eV is likely attributed to the Au-S bond. The vibrational satellite peaks are at 163.98 and 168.58 eV, respectively. Figure 5 (c) is the XPS spectrum of Au 4f, and the peaks with binding energies of 84.06 and 87.74 eV correspond to 4f 7 / 2 and 4f 5 / 2 state; the binding energy peak at 86.86 eV is attributed to the vibrational satellite peak.

Claims

1. A Ni9S8@Au core-shell nanocrystal, characterized in that: It comprises an inner core and an outer shell wrapped around the inner core, wherein the inner core is made of Ni9S8 and the outer shell is made of Au.

2. The Ni9S8@Au core-shell nanocrystal according to claim 1, characterized in that The molar ratio of Ni9S8 and Au is 1:(1-5).

3. The Ni9S8@Au core-shell nanocrystal according to claim 1, characterized in that The size of the Ni9S8@Au core-shell nanocrystals is 50-100 nm.

4. The method for preparing Ni9S8@Au core-shell nanocrystals according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) nickel diethyldithiocarbamate is mixed with oleylamine, 1-octadecene and 1-dodecylmercaptan to form a homogeneous solution; (2) Under a protective atmosphere, heating the homogeneous solution to a reaction temperature, reacting to obtain a reaction solution; (3) adding a tri-n-octylphosphine solution of chloroauric acid to the reaction solution, and reacting at the reaction temperature; (4) After the reaction solution obtained in step (3) is cooled to room temperature, a mixture of a polar solvent and a non-polar solvent is added, the solid product is separated and dried to obtain Ni9S8@Au core-shell nanocrystals.

5. The method for preparing Ni9S8@Au core-shell nanocrystals according to claim 4, characterized in that: In step (1), the molar ratio of nickel diethyldithiocarbamate, oleylamine, 1-octadecene and 1-dodecylmercaptan is 0.035:2:1:

1.

6. The method for preparing Ni9S8@Au core-shell nanocrystals according to claim 4, characterized in that: Step (1) is as follows: mixing nickel diethyldithiocarbamate with oleylamine, 1-octadecene, and 1-dodecylmercaptan; The resulting mixture was heated to 40-60 °C under vacuum for 30-60 min to form a homogeneous solution.

7. The method for preparing Ni9S8@Au core-shell nanocrystals according to claim 4, characterized in that: In step (2), the reaction temperature is 160-240 °C, and the reaction time is 1-2 h.

8. The method for preparing Ni9S8@Au core-shell nanocrystals according to claim 4, wherein: In step (3), the reaction time is 2-3 h.

9. The method for preparing Ni9S8@Au core-shell nanocrystals according to claim 4, wherein: In step (4), the polar solvent is anhydrous ethanol, and the non-polar solvent is cyclohexane.

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