A metal-ligand protected silver nanocluster and its preparation and application in remote laser ignition

Abstract

The present invention provides a metal-ligand protected silver nanocluster and its preparation and application in remote laser ignition. The metal-ligand protected silver nanocluster of the present invention is composed of RS ‑ and [(TC4A)6(V9O 16 )] 11‑ binary mixed ligand protected Ag 14 nanoclusters, with the molecular formula {Ag 14 [(TC4A)6(V9O 16 )](RS)3}. The structure and composition of the silver nanoclusters synthesized by the present invention are clear and novel; the preparation steps are simple, the preparation conditions are mild, and the raw materials are easily available, having the potential for industrial production; the obtained silver nanoclusters have excellent photothermal conversion performance, have good photothermal conversion effect and rapid heating rate under the irradiation of 660 nm laser, and have potential application value in the field of laser remote ignition materials.

Description

Technical Field

[0001] The invention belongs to the cross field of nano clusters and coordination chemistry, and specifically relates to a silver nano cluster protected by a metal ligand, and a preparation method and a remote laser ignition application thereof. Background Art

[0002] Silver nanoclusters have attracted increasing attention due to their wide applications in photoluminescence, catalysis, optical imaging, and biology. In recent years, the synthetic chemistry of silver nanoclusters has developed towards highly controllable and precise synthesis through ligand engineering and template strategies. Organic ligands such as thiol, alkyne, and phosphine ligands have been commonly used, but recent research has been extended to nitrogen ligands, metal ligands, and macrocyclic ligands; among them, metal ligands have brought new opportunities for shaping ordered structures and improving the stability of silver nanoclusters.

[0003] However, the synthesis of metal ligands and their subsequent application in the synthesis of metal nanoclusters remains a major challenge. In addition, the difficult-to-determine structure and poor stability of most silver nanoclusters have greatly limited their application.

[0004] Therefore, developing metal ligands and utilizing them in the synthesis of silver nanoclusters and exploring the practical application value of silver nanoclusters have become issues that need to be urgently addressed by those skilled in the art. Summary of the invention

[0005] In view of the deficiencies of the prior art, the present invention provides a metal ligand-protected silver nanocluster and its preparation and remote laser ignition application. The structure and composition of the synthesized silver nanocluster of the present invention are clear and novel; the preparation steps are simple, the preparation conditions are mild, the raw materials are easily available, and it has the potential for industrial production; the obtained silver nanocluster has excellent photothermal conversion performance, has a good photothermal conversion effect and a fast heating rate under the irradiation of 660nm laser, and has potential application value in the field of laser remote ignition materials.

[0006] The technical solution of the present invention is as follows:

[0007] The first object of the present invention is to provide a silver nanocluster protected by a metal ligand, wherein the silver nanocluster protected by the metal ligand is composed of RS - and [(TC4A)6(V9O 16 )] 11- Binary mixed ligand protected Ag 14 Nanoclusters, molecular formula {Ag 14 [(TC4A)6(V9O 16 )](RS)3}.

[0008] According to the preferred embodiment of the present invention, the ligand RS -Among them, the substituent R is one of cyclohexyl, cyclopentyl, tert-butyl, phenyl or substituted phenyl; preferably, the substituent in the substituted phenyl is -OCH3, -CH3, -F, -Cl, -Br or -NO2.

[0009] According to the present invention, the ligand RS - is obtained by losing hydrogen from the substituted thiol RSH; the TC4A in the ligand [(TC4A)6(V9O 16 )] 11- is obtained by losing hydrogen from H4TC4A (p-tert-butylthiacalix[4]arene).

[0010] According to a preferred embodiment of the present invention, [(TC4A)6(V9O 16 )] 11- The metal ligand has a three-dimensional scaffold-like structure that penetrates the entire nanocluster. It should be noted that this type of ligand has never been reported in the prior art. In this structure, the calixarene ligand and the polyoxovanadate are integrated into a metal ligand, and this combination can play the dual roles of the multidentate coordination of the calixarene ligand and the anion template of the polyoxovanadate.

[0011] According to a preferred embodiment of the present invention, the microscopic morphology of the silver nanocluster protected by the metal ligand is a black cluster-like crystal.

[0012] The second object of the present invention is to provide a method for preparing the silver nanocluster protected by the above metal ligand, comprising the steps of:

[0013] (1) Dissolve the silver salt in an organic solvent, dropwise add the substituted thiol RSH under stirring conditions, then add triethylamine, stir and react, filter, wash and dry to obtain a silver sulfide precursor, abbreviated as (RSAg) n ;

[0014] (2) Disperse the silver sulfide precursor, vanadate, H4TC4A (p-tert-butylthiacalix[4]arene) ligand and silver salt in a polar solvent, stir and react, and then carry out a solvothermal reaction or volatilize under dark conditions to obtain a silver nanocluster protected by a metal ligand.

[0015] According to a preferred embodiment of the present invention, in step (1), the silver salt is AgNO3, AgBF4, CF3COOAg or CF3SO3Ag; the organic solvent is one or a combination of two or more of acetonitrile, methanol and ethanol.

[0016] According to a preferred embodiment of the present invention, in step (1), the molar amount of the silver salt and the volume ratio of the organic solvent is 0.1 - 0.8 mol / L.

[0017] Preferably according to the present invention, in step (1), the substituent R in the substituted thiol RSH is one of cyclohexyl, cyclopentyl, tert-butyl, phenyl or substituted phenyl; preferably, the substituent in the substituted phenyl is -OCH3, -CH3, -F, -Cl, -Br or -NO2.

[0018] Preferably according to the present invention, in step (1), the dropping rate of the substituted thiol RSH is 1 - 2 mL / min.

[0019] Preferably according to the present invention, in step (1), the molar ratio of the silver salt to the substituted thiol RSH is 1:1; the molar ratio of the substituted thiol RSH to triethylamine is 1:2.

[0020] Preferably according to the present invention, in step (1), the stirring reaction temperature is room temperature and the stirring reaction time is 3 - 10 h.

[0021] Preferably according to the present invention, in step (1), the washing is carried out successively with ethanol and ether.

[0022] Preferably according to the present invention, in step (2), the vanadate is VOSO4, V2O5, NaVO3 or Na3VO4.

[0023] Preferably according to the present invention, in step (2), the silver salt is an inorganic silver salt or an organic silver salt; preferably, the silver salt is AgNO3, PhCOOAg, Ag2O, (CF3SO2N)2Ag, AgBF4, MePhSO3Ag, CH3SO3Ag, CH3COOAg, CF3COOAg or CF3SO3Ag.

[0024] Preferably according to the present invention, in step (2), the molar ratio of the silver sulfide precursor to the silver salt is (1:5) - (5:1), the molar ratio of H4TC4A to the silver salt is 1:(1 - 10), and the molar ratio of the vanadate to the silver salt is 1:(1 - 10). Preferably, the molar ratio of the silver sulfide precursor to the silver salt is 1:(2 - 4), and the molar ratio of the vanadate to the silver salt is 1:(1 - 2).

[0025] Preferably according to the present invention, in step (2), the polar solvent is one or a combination of two or more of methanol, N,N-dimethylformamide, ethanol, acetonitrile or tetrahydrofuran; the volume ratio of the molar amount of the silver salt to the polar solvent is 10 - 80 mmol / L.

[0026] Preferably according to the present invention, in step (2), the stirring reaction temperature is room temperature and the stirring reaction time is 3 - 10 h to obtain a brown solution.

[0027] Preferably according to the present invention, in step (2), the volatilization is to volatilize and crystallize at room temperature to obtain metal ligand-protected silver nanoclusters.

[0028] Preferably according to the present invention, in step (2), the solvothermal reaction temperature is 80 - 120 °C, and the solvothermal reaction time is 10 - 30 h; after the solvothermal reaction, it is naturally cooled to room temperature, and silver nanoclusters protected by metal ligands are crystallized out.

[0029] The third object of the present invention is to provide the application of the above-mentioned silver nanoclusters protected by metal ligands in photothermal conversion and remote laser ignition.

[0030] The silver nanoclusters in the present invention have excellent photothermal conversion performance and a rapid heating rate under the irradiation of a 660 nm laser, which makes them have potential application value in the field of laser remote ignition materials. The present invention uses matches as a model to study the application of the silver nanoclusters of the present invention in the field of remote laser ignition, and it is found that coating the silver nanoclusters of the present invention on the surface of matches can significantly reduce the laser ignition time and the laser power threshold, indicating that the silver nanoclusters of the present invention have the potential to be used as a laser igniter to achieve remote laser ignition and controllable explosion.

[0031] The technical features and beneficial effects of the present invention are as follows:

[0032] 1. The silver nanoclusters of the present invention are binary mixed ligand-protected Ag nanoclusters of RS and [(TC4A)6(V9O - )] 16 )] 11- , with the molecular formula {Ag 14 [(TC4A)6(V9O 14 )](RS)3}. Not only is the structure and composition clear, but a three-dimensional scaffold-like metal ligand [(TC4A)6(V9O 16 )] 16 )] 11- with novel structure and powerful function is discovered. It plays a dual role as an internal anion template and an external macrocyclic ligand in the structure. The internal polyoxovanadate part acts as a growth template for silver nanoclusters, and the external calixarene macrocyclic ligand plays a protective role to prevent further aggregation of silver nanoclusters. The three-dimensional scaffold-like metal ligand [(TC4A)6(V9O 16 )] 11- has multiple ligand sites and strong coordination ability, which is beneficial to enhancing the stability of the structure and is a good ligand in the synthesis of silver nanoclusters. The present invention is the first to use an organic-inorganic hybrid polyoxovanadate metal ligand in the synthesis of silver nanoclusters, which promotes the development and use of new metal ligands. Moreover, [(TC4A)6(V9O 16 )] 11-The structure has never been reported in the field of vanadium polyoxometalates and calixarenes. This type of structure can effectively exert the diversity of the polymerization form of vanadium polyoxometalates and the ligand effect of calixarenes, and also greatly promotes the development of the assembly diversity of polyoxometalates and calixarenes. The silver nanoclusters in the present invention do not emit fluorescence under the irradiation of a 660 nm laser, indicating that their radiative migration is very weak, and photothermal conversion becomes the main energy release pathway, and the solid has a strong absorption at 660 nm. There are few studies on the photothermal conversion properties of silver nanoclusters reported in the existing literature.

[0033] 2. The synthesis steps of the silver nanoclusters of the present invention are simple, the synthesis time is short, the synthesis conditions are mild, the raw materials are easily available, and the yield is relatively high, having the potential for industrial production.

[0034] 3. The preparation method of the silver nanoclusters of the present invention is simple and can be prepared by a one-pot solvothermal method or a volatilization method. The solvent used in the synthesis process is a polar solvent to promote the dissolution of the raw materials. Triethylamine added in step (1) of the present invention plays a role in removing the protons of the substituted thiol and promoting the formation of the silver sulfide precursor. Adding silver salt in step (2) of the present invention plays a role in promoting the depolymerization of the silver sulfide precursor. If the silver salt is not added, the silver sulfide precursor is not easily depolymerized and exists in the form of a polymer, which is not conducive to the formation of silver nanoclusters. In the preparation method of the present invention, the stirring time of steps (1) and (2) is more than 3 h, otherwise it will lead to a decrease in the yield of the target product of the present invention or the failure to obtain the target product of the present invention. As a whole, each step and each condition of the preparation method of the present invention work together to prepare the silver nanoclusters with the structure and performance of the present invention.

[0035] 4. The metal ligand-protected silver nanoclusters of the present invention have excellent photothermal conversion performance, have good photothermal conversion effect and fast heating rate under the irradiation of a 660 nm laser, and can be used for remote laser ignition, having practical application value. The present invention uses a match as a model to study the application of the silver nanoclusters of the present invention in the field of remote laser ignition, and finds that coating the silver nanoclusters of the present invention on the surface of the match can significantly reduce the laser ignition time and the laser power threshold, indicating that the silver nanoclusters of the present invention have the potential to be used as a laser igniter to achieve remote laser ignition and controllable explosion. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the overall structure of the metal ligand-protected silver nanocluster {Ag 14 [(TC4A)6(V9O 16 )](RS)3} prepared and synthesized in Example 1 of the present invention.

[0037] Figure 2 It is [(TC4A)6(V9O 16 )]11- Schematic diagram of the structure of the metal ligand.

[0038] Figure 3 Crystal photograph of the metal ligand-protected silver nanoclusters synthesized in Example 1 of the present invention.

[0039] Figure 4 Structure dissection diagram of the metal ligand-protected silver nanoclusters synthesized in Example 1 of the present invention.

[0040] Figure 5 Electrospray mass spectrum of the metal ligand-protected silver nanoclusters synthesized in Example 1 of the present invention.

[0041] Figure 6 Liquid ultraviolet spectrum of the metal ligand-protected silver nanoclusters synthesized in Example 1 of the present invention.

[0042] Figure 7 Solid ultraviolet spectrum of the metal ligand-protected silver nanoclusters synthesized in Example 1 of the present invention.

[0043] Figure 8 Research diagram of the photothermal conversion properties of the metal ligand-protected silver nanoclusters synthesized in Example 1 of the present invention.

[0044] Figure 9 Graph of the temperature change over time of the match coated with the metal ligand-protected silver nanoclusters synthesized in Example 1 of the present invention for remote laser ignition of the match.

[0045] Figure 10 Graph of the temperature change over time of the match coated with the metal ligand-protected silver nanoclusters synthesized in Example 1 of the present invention and the single match under irradiation with different laser powers.

[0046] Figure 11 Graph of the temperature change over time of the match coated with the metal ligand-protected silver nanoclusters synthesized in Example 1 of the present invention and the single match at different laser irradiation distances.

[0047] Figure 12 Comparison graph of the ignition time of the match coated with the metal ligand-protected silver nanoclusters synthesized in Example 1 of the present invention and the single match at different laser irradiation distances and different laser powers. Detailed implementation manners

[0048] The present invention will be further described below in conjunction with specific embodiments and the accompanying drawings, but is not limited thereto.

[0049] Unless otherwise specified, the raw materials used in the examples are all conventional products; unless otherwise specified, the methods used are all existing technologies.

[0050] Example 1:

[0051] The preparation method of the metal ligand-protected silver nanoclusters in the present invention is specifically as follows:

[0052] (1) The molar ratio of silver salt to substituted thiol RSH is 1:1. Acetonitrile is selected as the organic solvent. The molar amount of silver salt and the volume ratio of the organic solvent acetonitrile is 0.3 mol / L. The molar ratio of substituted thiol RSH to triethylamine is 1:2.

[0053] That is, 30 mmol of AgNO3 is dissolved in 100 mL of acetonitrile. Under stirring conditions, 30 mmol of CySH (cyclohexyl mercaptan, the dropping rate is 1.5 mL / min) is added dropwise, and then 60 mmol of triethylamine is added. Stir at room temperature for 6 h, filter, and wash and dry successively with ethanol and diethyl ether to obtain the silver sulfide precursor (CySAg). n , and the yield is 85%.

[0054] (2) The molar ratio of the silver sulfide precursor (CySAg) n to silver salt is 1:2, the molar ratio of vanadate to silver salt is 1:2, the molar ratio of H4TC4A to silver salt is 1:2, and methanol is selected as the polar solvent.

[0055] That is, 0.05 mmol of (CySAg) n is mixed and dissolved in 3 mL of methanol with 0.1 mmol of AgNO3, and then 0.05 mmol of VOSO4 and 0.05 mmol of H4TC4A are added. Stir at room temperature for 6 h, and the solution slowly turns brown. The solution is slowly volatilized and crystallized at room temperature in a dark environment to obtain the silver nanoclusters with the molecular formula {Ag 14 [(TC4A)6(V9O 16 )](CyS)3}, and the yield is 12%.

[0056] Example 2:

[0057] The preparation method of the metal ligand-protected silver nanoclusters in the present invention is specifically as follows:

[0058] (1) The molar ratio of silver salt to substituted thiol RSH is 1:1. A mixed solvent of acetonitrile and methanol (the volume ratio of acetonitrile to methanol is 1:1) is selected as the organic solvent. The molar amount of silver salt and the volume ratio of the organic solvent is 0.15 mol / L. The molar ratio of substituted thiol RSH to triethylamine is 1:2.

[0059] That is, 30 mmol of AgNO3 was dissolved in 200 mL of a mixed solvent of acetonitrile and methanol with a volume ratio of 1:1. Under stirring conditions, 30 mmol of CySH (cyclohexanethiol, the dropping rate was 1.5 mL / min) was added dropwise, and then 60 mmol of triethylamine was added. Stir at room temperature for 6 h, filter, and wash and dry successively with ethanol and ether to obtain the silver sulfide precursor (CySAg). n , and the yield was 80%.

[0060] (2) The molar ratio of (CySAg) n to the silver salt was 1:4, the molar ratio of H4TC4A to the silver salt was 1:2, the molar ratio of the vanadate to the silver salt was 1:2, and the polar solvent was methanol.

[0061] That is, 0.025 mmol of (CySAg) n was mixed and dissolved in 3 mL of methanol with 0.1 mmol of AgNO3, and then 0.05 mmol of VOSO4 and 0.05 mmol of H4TC4A were added. Stir at room temperature for 10 h, and the solution slowly turned brown. After a solvothermal reaction at 100 °C for 30 h and cooling to room temperature for crystallization, silver nanoclusters with the molecular formula {Ag 14 [(TC4A)6(V9O 16 )](CyS)3} were obtained, and the yield was 25%.

[0062] Example 3:

[0063] The preparation method of the metal ligand-protected silver nanoclusters in the present invention is specifically as follows:

[0064] (1) The molar ratio of the silver salt to the substituted thiol RSH was 1:1, the organic solvent was a mixed solvent of acetonitrile and methanol (the volume ratio of acetonitrile and methanol was 1:1), the molar amount of the silver salt and the volume ratio of the organic solvent was 0.15 mol / L, and the molar ratio of the substituted thiol RSH to triethylamine was 1:2.

[0065] That is, 30 mmol of CF3SO3Ag was dissolved in 200 mL of a mixed solvent of acetonitrile and methanol with a volume ratio of 1:1. Under stirring conditions, 30 mmol of CySH (cyclohexanethiol, the dropping rate was 1.5 mL / min) was added dropwise, and then 60 mmol of triethylamine was added. Stir at room temperature for 5 h, filter, and wash and dry successively with ethanol and ether to obtain the silver sulfide precursor (CySAg). n , and the yield was 85%.

[0066] (2) The molar ratio of (CySAg) n to the silver salt was 1:2, the molar ratio of H4TC4A to the silver salt was 1:2, the molar ratio of the vanadate to the silver salt was 1:2, and the polar solvent was acetonitrile.

[0067] That is, 0.05 mmol (CySAg) n was mixed and dissolved with 0.1 mmol AgNO3 in 3 mL of acetonitrile. Then, 0.05 mmol VOSO4 and 0.05 mmol H4TC4A were added, and the mixture was stirred at room temperature for 8 h. The solution slowly turned brown. The solvent was slowly volatilized and crystallized at room temperature in a dark environment to obtain silver nanoclusters with the molecular formula {Ag 14 [(TC4A)6(V9O 16 )](CyS)3}, and the yield was 15%.

[0068] Example 4:

[0069] The preparation method of the metal ligand-protected silver nanoclusters in the present invention is specifically as follows:

[0070] (1) The molar ratio of the silver salt to the substituted thiol RSH is 1:1. Acetonitrile is selected as the organic solvent, the molar amount of the silver salt and the volume ratio of the organic solvent are 0.3 mol / L, and the molar ratio of the substituted thiol RSH to triethylamine is 1:2.

[0071] That is, 30 mmol CF3COOAg was dissolved in 100 mL of acetonitrile. Under stirring conditions, 30 mmol CySH (cyclohexyl mercaptan, the dropping rate was 1.5 mL / min) was added dropwise, and then 60 mmol triethylamine was added. The mixture was stirred at room temperature for 4 h, filtered, and washed and dried successively with ethanol and ether to obtain the thio-silver precursor (CySAg) n , and the yield was 80%.

[0072] (2) The molar ratio of (CySAg) n to the silver salt is 1:4, the molar ratio of H4TC4A to the silver salt is 1:1, the molar ratio of the vanadate to the silver salt is 1:2, and N,N-dimethylformamide is selected as the polar solvent.

[0073] That is, 0.025 mmol (CySAg) n was mixed and dissolved with 0.1 mmol AgNO3 in 3 mL of N,N-dimethylformamide. Then, 0.05 mmol V2O5 and 0.1 mmol H4TC4A were added, and the mixture was stirred at room temperature for 8 h. The solution slowly turned brown. The solution was slowly volatilized and crystallized at room temperature in a dark environment to obtain silver nanoclusters with the molecular formula {Ag 14 [(TC4A)6(V9O 16 )](CyS)3}, and the yield was 15%.

[0074] Example 5:

[0075] The preparation method of the metal ligand-protected silver nanoclusters in the present invention is specifically as follows:

[0076] (1) The molar ratio of silver salt to substituted thiol RSH is 1:1. Acetonitrile is selected as the organic solvent. The molar amount of silver salt and the volume ratio of acetonitrile is 0.15 mol / L. The molar ratio of substituted thiol RSH to triethylamine is 1:2.

[0077] That is, 15 mmol of CF3COOAg is dissolved in 100 mL of acetonitrile. Under stirring conditions, 15 mmol of CySH (cyclohexyl mercaptan, the dropping rate is 1.5 mL / min) is added dropwise, and then 30 mmol of triethylamine is added. Stir at room temperature for 4 h, filter, and wash and dry successively with ethanol and ether to obtain the silver sulfide precursor (CySAg). n , and the yield is 90%.

[0078] (2) (CySAg) n The molar ratio to silver salt is 1:4. The molar ratio of H4TC4A to silver salt is 1:10. The molar ratio of vanadate to silver salt is 1:2. Tetrahydrofuran is selected as the polar solvent.

[0079] That is, 0.025 mmol of (CySAg) n is mixed and dissolved with 0.1 mmol of AgNO3 in 3 mL of tetrahydrofuran. Then 0.05 mmol of V2O5 and 0.01 mmol of H4TC4A are added. Stir at room temperature for 8 h, and the solution slowly turns brown. Crystals are obtained by slowly evaporating the solvent at room temperature in a dark environment, and the silver nanocluster with the molecular formula {Ag 14 [(TC4A)6(V9O 16 )](CyS)3} is obtained, and the yield is 12%.

[0080] Example 6:

[0081] The preparation method of the metal ligand-protected silver nanocluster in the present invention is specifically as follows:

[0082] (1) The molar ratio of silver salt to substituted thiol RSH is 1:1. A mixed solvent of acetonitrile and ethanol (the volume ratio of acetonitrile to ethanol is 1:1) is selected as the organic solvent. The molar amount of silver salt and the volume ratio of the organic solvent is 0.2 mol / L. The molar ratio of substituted thiol RSH to triethylamine is 1:2.

[0083] That is, 20 mmol of AgNO3 is dissolved in 100 mL of a mixed solvent with a volume ratio of acetonitrile to ethanol of 1:1. Under stirring conditions, 20 mmol of CySH (cyclohexyl mercaptan, the dropping rate is 1.5 mL / min) is added dropwise, and then 40 mmol of triethylamine is added. Stir at room temperature for 10 h, filter, and wash and dry successively with ethanol and ether to obtain the silver sulfide precursor (CySAg). n , and the yield is 85%.

[0084] (2) (CySAg) n The molar ratio of (CySAg) to silver salt is 1:4, the molar ratio of H4TC4A to silver salt is 1:1, the molar ratio of vanadate to silver salt is 1:1, and the polar solvent is acetonitrile.

[0085] That is, 0.025 mmol of (CySAg) n was mixed and dissolved with 0.1 mmol of AgNO3 in 3 mL of acetonitrile, then 0.1 mmol of V2O5 and 0.1 mmol of H4TC4A were added, and the mixture was stirred at room temperature for 6 h. The solution slowly turned brown. Slow evaporation of the solvent at room temperature in a dark environment gave crystals of the silver nanocluster with the molecular formula {Ag 14 [(TC4A)6(V9O 16 )](CyS)3}, with a yield of 23%.

[0086] Comparative Example 1:

[0087] The silver nanoclusters were prepared as described in Example 1, except that: the silver-sulfur precursor was not added during the reaction.

[0088] The molar ratio of H4TC4A to silver salt is 1:1, the molar ratio of vanadate to silver salt is 1:1, and the polar solvent is methanol.

[0089] That is, 0.1 mmol of AgNO3 was dissolved in 3 mL of methanol, then 0.05 mmol of VOSO4 and 0.05 mmol of H4TC4A were added, and the mixture was stirred at room temperature for 6 h. Slow evaporation of the solvent at room temperature in a dark environment did not yield crystals.

[0090] Comparative Example 2:

[0091] The silver nanoclusters were prepared as described in Example 1, except that: in step (2), the vanadate was replaced with molybdate, i.e., VOSO4 was replaced with Na2MoO4.

[0092] The specific steps are as follows:

[0093] Step (1) is the same as in Example 1;

[0094] Step (2): In this step, the vanadate was replaced with molybdate, and the silver-sulfur precursor (CySAg) n The molar ratio of (CySAg) to silver salt is 1:2, the molar ratio of molybdate to silver salt is 1:2, the molar ratio of H4TC4A to silver salt is 1:2, and the polar solvent is methanol.

[0095] That is, 0.05 mmol of (CySAg) nIt was mixed with 0.1 mmol of AgNO3 and dissolved in 3 mL of methanol. Then, 0.05 mmol of Na2MoO4 and 0.05 mmol of H4TC4A were added, and the mixture was stirred at room temperature for 6 h. The solution slowly turned blue. No crystals were obtained when the solvent was slowly volatilized at room temperature in the dark environment.

[0096] Comparative Example 3:

[0097] The preparation of silver nanoclusters was as described in Example 1, except that: in step (2), no silver salt was added.

[0098] The specific steps were as follows:

[0099] Step (1) was the same as in Example 1;

[0100] Step (2): No silver salt was added in this step, and the molar ratio of (CySAg) n to H4TC4A was 1:1, the molar ratio of vanadate to H4TC4A was 1:1, and methanol was selected as the polar solvent.

[0101] That is, 0.05 mmol of (CySAg) n was dissolved in 3 mL of methanol, then 0.05 mmol of VOSO4 and 0.05 mmol of H4TC4A were added, and the mixture was stirred at room temperature for 6 h. The solution slowly turned blue. No crystals were obtained when the solvent was slowly volatilized at room temperature in the dark environment.

[0102] From the above comparative examples and examples, it shows that the silver-sulfur precursor and the metal ligand [(TC4A)6(V9O 16 )] 11- play a very crucial role in the protection of Ag 14 . If the silver-sulfur precursor is not added, it is very difficult to crystallize and precipitate silver nanoclusters. Secondly, polyoxovanadate is more likely to assemble with the H4TC4A ligand. When molybdate is used instead, no crystals are obtained, which reflects the superiority of polyoxovanadate in forming metal ligands and participating in the assembly of silver nanoclusters. Finally, the addition of silver salt plays an important role in this reaction. One is to depolymerize the silver-sulfur precursor, and the other is to provide silver atoms for the assembly of silver nanoclusters. If no silver salt is added, the silver-sulfur precursor is difficult to depolymerize and it is difficult to obtain crystals.

[0103] Test Example 1: Structure Characterization

[0104] The crystal structure of the silver nanoclusters synthesized in Example 1 was characterized, and the specific structure was referred to Figures 1-5 .

[0105] Based on the structural analysis, the silver nanoclusters have the following characteristics: (1) The crystal structure of the silver nanoclusters is simple, consisting of an Ag 14 shell and [(TC4A)6(V9O 16 )]11- Metal ligand, RS - consists of a binary ligand combination of; (2) a three-dimensional scaffold-like [(TC4A)6(V9O 16 )] 11- The metal ligand penetrates the silver nanocluster, balancing the local positive charge and increasing the structural stability ( Figure 1 ).

[0106] In addition, the most attractive part of the silver nanocluster is the three-dimensional scaffold-like [(TC4A)6(V9O 16 )] 11- metal ligand ( Figure 2 ), which plays a dual role in the assembly process of the silver nanocluster: (1) The internal POVs (POVs represent polyoxovanadates) part plays an anion template effect; (2) The surface TC4A 4- acts as a passivator to stabilize the entire silver nanocluster. In addition, all vanadium ions in the two clusters are in the highest oxidation state of +5, which has a smaller ionic radius and a higher charge density, as confirmed by bond valence sum (BVS) calculations. V 5+ ions and Ag + ions are speculated to follow the hard-soft acid-base (HSAB) theory in the coordination process with TC4A 4- , where V 5+ cations are oxygenophilic and easily coordinate with the deprotonated phenolic hydroxyl groups of TC4A 4- , while Ag + ions prefer to coordinate with the thioether groups. Compared with Nb, Ta, Mo, and W, etc., the radius of V 5+ ions is smaller, which makes it easier for them to coordinate into the bottom of TC4A 4- .

[0107] From Figure 3 it can be seen that the silver nanocluster synthesized and prepared by the present invention is a black cluster crystal.

[0108] Figure 4 Further analyzed the structure of the silver nanocluster and the metal ligand [(TC4A)6(V9O 16 )] 11- .

[0109] Ag 14 contains 14 silver atoms, a three-dimensional scaffold-like [(TC4A)6(V9O 16 )] 11- metal ligand and three RS - ligands. [(TC4A)6(V9O 16 )] 11- The metal ligand penetrates the entire Ag14 nanocluster ( Figure 4a, 4b), six V atoms are connected to TC4A through V-phenolic hydroxyl groups 4- at the lower edge of, and adopt an octahedral coordination mode with another two oxygen atoms, one from the {VO4} tetrahedron and the other from the terminal oxygen atom, forming six TC4A-VO2 units. These TC4A-VO2 units are connected to the vertices at both poles of the rod-shaped [V3O 10 5- anion. The rod-shaped [V3O 10 5- anion is composed of {VO4} tetrahedrons sharing three vertices. [V9O 16 11- has three {VO6} distributed in a triangular shape at each of the upper and lower poles, and is connected by sharing vertices with the rod-shaped [V3O 10 5- . There are three TC4A 4- located at the upper and lower poles of Ag 14 ([[]] Figure 4 c, 4d). Interestingly, the three-dimensional scaffold-like [(TC4A)6(V9O 16 )] 11- metal ligand penetrates through the silver shell and connects all silver atoms through Ag-S and Ag-O bonds. The waist of [(TC4A)6(V9O 16 )] 11- is surrounded by 12 silver atoms, which are similar to a silver crown and are connected by Ag-Ag interactions through three parallelograms. Two silver atoms suspended above and below the silver crown are fixed at the center of the three-dimensional scaffold through Ag-S bonds. In addition to [(TC4A)6(V9O 16 )] 11- metal ligand, 3 RS - cover the coronary Ag 12 in a μ4 coordination mode.

[0110] Figure 5 is the mass spectrum of the silver nanocluster protected by the metal ligand. Among them,

[0111] a-c species are respectively: {Ag 14 [(TC4A)6(V9O 16 )](RS)(DMF)(CH3OH)2} 2+ 、{Ag 14 [(TC4A)6(V9O 16 )](RS)(CH2Cl2)2} 2+ 、{Ag 14 [(TC4A)6(V9O 16 )](RS)(CH2Cl2)2(H2O)} 2+ ​​​​The d and e species are respectively: {Ag 15 [(TC4A)6(V9O 16 )](RS)2(CH3OH)2} 2+ 、{Ag 15 [((TC4A)6(V9O 16 )](RS)2(CH3OH)3} 2+

[0112] It can be seen from this that the metal-ligand-protected silver nanoclusters are stable under mass spectrometry conditions. Two RS 14 ligands are stripped from Ag - to form the a-c species, but the silver skeleton and [(TC4A)6(V9O 16 )] 11- metal ligand integrity are still maintained. The d and e species involve the coordination dissociation of surface silver atoms and thiol ligands.

[0113] Experimental Example 2: Performance determination

[0114] (1) The solution and solid UV spectra of the metal-ligand-protected silver nanoclusters synthesized in Example 1 were tested, as Figure 6 , shown in Figure 7.

[0115] It can be seen through Figure 6 that the silver nanoclusters dissolved in dichloromethane (concentration 25 μM) have two absorption bands at 300 nm and 340 nm. It can be seen through Figure 7 that the crystals of the silver nanoclusters show a broad absorption spanning the UV and visible regions, centered around 338 nm. The low-energy broad absorption band can be considered as the charge transfer from the ligand to the metal, and the high-energy absorption peak is considered as the absorption of the ligand.

[0116] (2) Study on the photothermal conversion properties of the metal-ligand-protected silver nanoclusters synthesized in Example 1, as Figure 8 .

[0117] No fluorescence was observed for the silver nanoclusters synthesized in Example 1 of the present invention under 660 nm laser irradiation, indicating that the radiative transition is very weak and photothermal conversion becomes the main energy release pathway. Therefore, the photothermal conversion performance of it was studied by the present invention. As Figure 8 shown, under 660 nm laser irradiation with a distance of 20 cm and 0.9 W cm -2 , the temperature of the silver nanoclusters reached 194 °C within 1.5 seconds. Surprisingly, the heating rate of the silver nanoclusters reached 115 °C s -1 , and the heating rate is much higher than that of other reported silver nanoclusters SD / Ag18a (8.2 °C s -1 , 660 nm, 0.9 W cm-2 )(Angew. Chem. Int. Ed. 2022, 61, e202200823) and most reported photothermal materials, such as sSMONRs-PDMS (18.8 °C s -1 , 808 nm, 1 W cm -2 )(Nat. Commun. 2017, 8, 1559) and MoO 3-x SNW-PVA-4 (4 °C s -1 , 808 nm, 1 W cm -2 )(J. Am. Chem. Soc. 2021, 143, 9858 - 9865).

[0118] (3) Research on the remote laser ignition application of the metal-ligand-protected silver nanoclusters synthesized and prepared in Example 1, as Figures 9-12 shown.

[0119] We used a match as a simple research model. The preparation method is as follows: Disperse the metal-ligand-protected silver nanoclusters (2 mg) synthesized and prepared in Example 1 in 0.1 mL of ethanol, sonicate for about 10 minutes, and then evenly apply it to the match head part and dry at room temperature.

[0120] The measurement range of the thermal imager is 0 - 650 °C. When the temperature is higher than 650 °C, it can only display 650 °C. As Figure 9 shown, at a distance of 50 cm, the match coated with 2 mg of silver nanoclusters (hereinafter referred to as Ag 14 / match) can be ignited within 1 second under 660 nm laser irradiation at 0.9 W cm -2 , while the single match cannot be ignited under the same conditions after 3 minutes of laser lamp irradiation.

[0121] Next, by changing the laser power and irradiation distance, the ignition time was studied in depth. In the laser power range of 0.2 to 0.6 W cm -2 , the Ag 14 / match can be successfully ignited within a distance of 20 cm ( Figure 10 a). However, under the same conditions, the time to ignite the match is much longer than that of the Ag 14 / match. When the laser power is lower than 0.4 W cm -2 , the match cannot be ignited ( Figure 10 b).

[0122] When the laser power is fixed at 0.4 W cm -2 , the ignition time of the Ag 14 / match increases as the distance increases from 10 cm to 40 cm ( Figure 11a), while under the same conditions, when the distance exceeds 20 cm, the match cannot be ignited Figure 11 b). Based on the above experiments, it is summarized and obtained that Figure 12 , and it can be concluded that coating Ag 14 onto the match can greatly reduce the ignition time and the threshold of laser power, which indicates that Ag 14 has the potential to be used as a laser ignition material to achieve remote ignition and control explosion.

[0123] In summary, the metal ligand-protected silver nanoclusters synthesized and disclosed by the present invention not only have an atomically precise structure, but also contain calixarene-modified polyoxovanadate metal ligands, and also have good photothermal conversion effects and the potential to be used as remote laser ignition materials; and the synthesis method disclosed and protected by the present invention has the advantages of short synthesis time, simple operation, mild conditions, easy availability of raw materials and convenience for industrial production.

[0124] The above-described embodiments are only the preferred embodiments of the present invention and not all embodiments. All other embodiments obtained by any equivalent replacement, improvement, recombination, etc. without creative efforts based on the embodiments of the present invention fall within the scope of protection of the present invention.

Claims

1. A metal ligand-protected silver nanocluster, characterized in that, The metal-ligand protected silver nanoclusters are composed of RS - and [(TC4A)6(V9O 16 )] 11- binary mixed ligand protected Ag 14 nanoclusters with the molecular formula {Ag 14 [(TC4A)6(V9O 16 )](RS)3}; in the ligand RS - , the substituent R is a cyclohexyl group; in the ligand [(TC4A)6(V9O 16 )] 11- TC4A is obtained by dehydrogenation of p-tert-butylthiacalix[4]arene.

2. The silver nanocluster protected by the metal ligand according to claim 1, characterized in that, [(TC4A)6(V9O 16 )] 11- The metal ligand is a three-dimensional scaffold-like structure that penetrates the entire nanocluster.

3. The silver nanocluster protected by a metal ligand according to claim 1, wherein The microscopic morphology of the metal-ligand-protected silver nanoclusters is black cluster-shaped crystals.

4. The preparation method of the metal-ligand-protected silver nanoclusters according to any one of claims 1-3, comprising the steps: (1) Dissolve the silver salt in an organic solvent, dropwise add the substituted mercaptan RSH under stirring conditions, then add triethylamine, stir and react, filter, wash, and dry to obtain a silver sulfide precursor, abbreviated as (RSAg). n ; The substituent R in the substituted mercaptan RSH is a cyclohexyl group; (2) Fully disperse the silver sulfide precursor, vanadium source, p-tert-butylthiacalix[4]arene ligand and silver source in a polar solvent, stir and react, and then carry out a solvothermal reaction or volatilize under dark conditions to obtain the metal-ligand-protected silver nanoclusters.

5. The preparation method of the metal ligand-protected silver nanoclusters according to claim 4, wherein In step (1), one or more of the following conditions are included: i. The silver salt is AgNO3, AgBF4, CF3COOAg or CF3SO3Ag; the organic solvent is one or a combination of two or more of acetonitrile, methanol, and ethanol; ii. The molar amount of the silver salt and the volume ratio of the organic solvent are 0.1-0.8 mol / L; iii. The dropping rate of the substituted thiol RSH is 1-2 mL / min; iv. The molar ratio of the silver salt to the substituted thiol RSH is 1:1; the molar ratio of the substituted thiol RSH to triethylamine is 1:

2.

6. The preparation method of the metal ligand-protected silver nanoclusters according to claim 4, characterized in that, In step (1), the stirring reaction temperature is room temperature, and the stirring reaction time is 3-10 h.

7. The preparation method of the metal ligand-protected silver nanoclusters according to claim 4, characterized in that, In step (2), one or more of the following conditions are included: i. The vanadium source is VOSO4, V2O5, NaVO3 or Na3VO4; ii. The silver source is AgNO3, PhCOOAg, Ag2O, (CF3SO2N)2Ag, AgBF4, MePhSO3Ag, CH3SO3Ag, CH3COOAg, CF3COOAg or CF3SO3Ag; iii. The molar ratio of the silver sulfide precursor to the silver salt is (1:5)-(5:1), the molar ratio of H4TC4A to the silver salt is 1:(1-10), and the molar ratio of the vanadate to the silver salt is 1:(1-10); iv. The polar solvent is one or a combination of two or more of methanol, N,N-dimethylformamide, ethanol, acetonitrile or tetrahydrofuran; the molar amount of the silver salt and the volume ratio of the polar solvent are 10-80 mmol / L.

8. The preparation method of the metal ligand-protected silver nanoclusters according to claim 4, wherein, In step (2), one or more of the following conditions are included: i. The stirring reaction temperature is room temperature, the stirring reaction time is 3-10 h, and a brown solution is obtained; ii. The volatilization is room temperature volatilization crystallization to obtain the metal-ligand-protected silver nanoclusters; iii. The solvothermal reaction temperature is 80-120 °C, the solvothermal reaction time is 10-30 h; after the solvothermal reaction, it is naturally cooled to room temperature, and the metal-ligand-protected silver nanoclusters are crystallized and precipitated.

9. The application of the metal-ligand-protected silver nanoclusters according to any one of claims 1-3 in photothermal conversion and remote laser ignition.

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