Silver nanocluster and application thereof in methanol detection

Abstract

The invention discloses a silver nanocluster and application thereof in methanol detection, and belongs to the technical field of nano materials. The molecular formula of the silver nanocluster disclosed by the invention is Ag30 (SR) 14 (L3) 3 (NO3) (CF3COO) 4Cl2, and is abbreviated as Ag30; wherein SR represents adamantanethiol, and L3 represents 1, 3-bis (diphenylphosphino) propane. The structure of the silver nanocluster Ag30 can be quickly converted into Ag23 with thermodynamic stability in methanol, and the silver nanocluster Ag30 can be used as a novel'open 'type photoluminescence sensor for high-selectivity and ultra-sensitive detection of methanol along with high-contrast luminescence open response.

Description

Technical Field

[0001] The invention belongs to the field of nano materials, and in particular relates to a silver nanocluster and an application thereof in methanol detection. Background Art

[0002] Atomically precise metal nanoclusters have attracted the interest of researchers due to their structural diversity and wide applications in luminescence, sensors and bio-antibacterial. Silver nanoclusters are considered as potential alternatives to luminescent gold nanoclusters due to their low price and excellent optical properties. External environment-induced transformation of silver nanoclusters is a common phenomenon in nanomaterial technology and has been widely used to regulate their morphology and size, thereby providing significant changes in optical properties. The emergence of silver nanoclusters stabilized by organic ligands has brought this research topic to the atomic level. However, the mechanism of external environment-induced structural transformation of silver nanoclusters has always been a puzzling issue, such as changes in peripheral ligands, metal atoms, counterions and solvent molecules to the surface or core of the cluster. In this context, a method that can achieve efficient nanocluster transformation and a clear transformation mechanism is very necessary. Summary of the invention

[0003] Based on this, the present invention provides a silver nanocluster and its application in methanol detection. The present invention synthesizes a new 6-electron configuration of Ag 30 (SR) 14 (L3)3(NO3)(CF3COO)4Cl2 nanoclusters, referred to as Ag 30 . Ag 30 It can rapidly undergo structural transformation in methanol and transform into thermodynamically stable Ag. 23 , and simultaneously turned on strong red light emission. We tracked this transition using time-dependent ultraviolet-visible absorption (UV-Vis) spectroscopy, electrospray ionization mass spectrometry (ESI-MS), and photoluminescence (PL) spectroscopy. Based on this rapid transformation, we further developed an ultrasensitive "turn-on" sensor for methanol detection. This work has important application potential in understanding the transformation of metal clusters and selectively sensing methanol.

[0004] The silver nanoclusters of the present invention have a molecular formula of Ag 30 (SR) 14 (L3)3(NO3)(CF3COO)4Cl2, abbreviated as Ag 30 Wherein, SR represents adamantanethiol, and L3 represents 1,3-bis(diphenylphosphino)propane.

[0005] The silver nanocluster of the present invention is composed of an Ag protected by two Cl ions and one CF3COO ion. 13 Icosahedral core, and a large Ag outer17 (SR) 14 (L3)3(NO3)(CF3COO)3 shell composition.

[0006] The method for preparing silver nanoclusters of the present invention comprises the following steps: The silver salt is dissolved in methanol, stirred at room temperature, and 1,3-bis(diphenylphosphino)propane is added until it is completely dissolved; during the initial reaction, adamantane thiol is added and stirred until the color of the solution changes to milky white; sodium borohydride is then added and reacted at room temperature to obtain an organic phase containing silver nanoclusters.

[0007] The silver salts are silver nitrate and silver trifluoroacetate.

[0008] During the preparation process, the usage ratio of silver nitrate, silver trifluoroacetate, adamantane thiol, 1,3-bis(diphenylphosphino)propane and sodium borohydride is 34 mg:44 mg:34 mg:41 mg:100 mg.

[0009] As a preferred embodiment, the initial reaction time is 10 min, and the reaction time at room temperature after adding sodium borohydride is 5 h.

[0010] As a preferred embodiment, the organic phase is washed with n-hexane and extracted with dichloromethane. 甲苯 :V 正己烷 =1:4) and the organic phase is crystallized.

[0011] Application of the silver nanoclusters of the present invention in methanol detection.

[0012] In the silver nanoclusters of the present invention, the weakly coordinated CF3COO - With NO3 - ions, connecting the silver atoms on the surface of the silver nanoclusters, thereby releasing multiple unstable Ag sites on the surface. 30 The “labile Ag sites” of nanoclusters serve as recognition sites, thereby deliberately inducing their structural transformation. 30 As a nanocluster model, this is systematically studied to achieve a gradual evolution of its structure and photoluminescence properties. To this end, the present invention provides an application of silver nanoclusters in methanol detection.

[0013] The monitoring of the structural transformation process of the silver nanoclusters of the present invention is specifically to dissolve the silver nanoclusters in methanol or dichloromethane solution and perform time-dependent ultraviolet-visible absorption (UV-Vis) spectroscopy, electrospray ionization mass spectrometry (ESI-MS) and photoluminescence (PL) spectroscopy tracking.

[0014] The silver nanoclusters were dissolved in thirteen common soluble solvents in the laboratory for qualitative detection of photoluminescence. The silver nanoclusters were dissolved in methanol solvents with different concentrations (with dichloromethane as auxiliary solvent) for quantitative detection of photoluminescence.

[0015] Furthermore, the thirteen soluble solvents for the qualitative detection are: toluene (Tol), dichloromethane (DCM), n-butanol (n-BuOH), n-propanol (n-PrOH), tetrahydrofuran (THF), ethyl acetate (EA), ethanol (EtOH), trichloromethane (TCM), acetone (ACE), acetonitrile (ACN), N,N-dimethylformamide (DMF), methanol (MeOH), dimethyl sulfoxide (DMSO). 30 The nanoclusters are dissolved in the thirteen solvents mentioned above.

[0016] Further, the quantitative detection process is as follows: using dichloromethane as an auxiliary solvent, a methanol solution with a concentration gradient of 0-5mM is prepared. Dichloromethane: methanol = 200µL: 0µL (0mM), 180µL: 20µL (0.5mM), 160µL: 40µL (1mM), 140µL: 60µL (1.5mM), 120µL: 80µL (2mM), 100µL: 100µL (2.5mM), 80µL: 120µL (3mM), 60µL: 140µL (3.5mM), 40µL: 160µL (4mM), 20µL: 180µL (4.5mM), 0µL: 200µL (5mM). And the methanol solutions of different concentrations are dropped into Ag 30 in nanoclusters.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The silver nanoclusters of the present invention, namely Ag 30 (SR) 14 (L3)3(NO3)(CF3COO)4Cl2(Ag 30 ), consisting of an Ag protected by two Cl ions and one CF3COO ion 13 Icosahedral core, and a large Ag outer 17 (SR) 14 (L3)3(NO3)(CF3COO)3 shell composition. Ag 30 It can rapidly undergo structural transformation in methanol and transform into thermodynamically stable Ag. 23, and simultaneously turned on strong red light emission. We tracked this transition using time-dependent ultraviolet-visible absorption (UV-Vis) spectroscopy, electrospray ionization mass spectrometry (ESI-MS), and photoluminescence (PL) spectroscopy. Based on this rapid transformation, we further developed an ultrasensitive "turn-on" sensor for methanol detection. This work has important application potential in understanding the transformation of metal clusters and selectively sensing methanol. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 For the present invention, Ag 30 Structural analysis of Ag. 13 Core; (B) Ag 13 (CF3COO)Cl2 structure; (C)Ag 17 (SR) 14 (L3)3 structure; (D) Ag 17 (SR) 14 (L3)3(NO3)(CF3COO)3 shell; (E) Ag 30 (SR) 14 Overall structure of (L3)3(NO3)(CF3COO)4Cl2.

[0019] Figure 2 Ag 30 The bond lengths of the atoms are shown in Figure 2. Color labels: sky blue, Ag; red, S; magenta, P; green, Cl; bright green, F; blue, N; orange, O.

[0020] Figure 3 Ag 30 Digital image of crystals.

[0021] Figure 4 Ag 30 Experimental (black) and simulated (red) X-ray powder diffraction (PXRD) patterns.

[0022] Figure 5 Ag 30 Thermogravimetric analysis (TGA) curves in N2.

[0023] Figure 6 Ag 30 X-ray photoelectron spectroscopy (XPS) diagram.

[0024] Figure 7 Ag 30 High-resolution XPS spectrum of Ag3d.

[0025] Figure 8 Ag 30 Fourier transform infrared spectroscopy (FT-IR) characterization results.

[0026] Fig. 9 Ag 30 and Ag 23 Structure of. Color code: sky blue, Ag; red, S; magenta, P; green, Cl; bright green, F; blue, N; orange, O; gray, C. All H atoms are omitted for clarity. Insert digital photo: Ag illuminated by 365 nm UV light 30 (Left, dark) Dichloromethane solution and Ag 30 (Right, bright red) Methanol solution. (B) Ag 30 UV-visible absorption spectrum of the crystals dissolved in dichloromethane over time. (C) Ag 30 UV-Vis absorption spectrum of the crystals dissolved in methanol over time.

[0027] Fig.10 Ag 30 Photoluminescence kinetics of crystals dissolved in methanol (0.1 mg / mL).

[0028] Fig.11 (A) Intermediate detection: Ag 30 To Ag 23 Time-dependent ESI-MS spectra of the conversion process, (B) Ag 30 To Ag 23 Schematic diagram of the transformation structure.

[0029] Fig.12 Intermediate Ag 27 To Ag 23 ESI-MS spectrum of the dissociation fragment peaks.

[0030] Fig.13 The proposed mechanism: From Ag 30 To Ag 23 transformation process (ignoring all solvent molecules).

[0031] Fig.14 Ag 30 (A) PL spectra and (B) PL intensities of the crystals dissolved in different solvents (0.1 mg / mL). (C) Ag 30 PL spectra in different concentrations of methanol solvent (with DCM as auxiliary solvent). (D) The linear relationship of PL intensity with respect to methanol concentration.

[0032] Fig.15 Ag 30Digital photos of crystals in 13 solvents of different polarities (illuminated with 365 nm UV light). In 9 solvents, no luminescence was visible to the naked eye (top), and in 4 solvents, luminescence was visible to the naked eye (bottom).

[0033] Fig.16 Ag 30 Digital photos in different concentrations of methanol. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand the technical solution of the present invention and implement it, the present invention is further described below in conjunction with specific embodiments and drawings, but the embodiments are not intended to limit the present invention. The following test methods and detection methods, unless otherwise specified, are conventional methods; the reagents and raw materials, unless otherwise specified, are commercially available.

[0035] The transformation of nanoclusters induced by the external environment is a common phenomenon in nanotechnology and has been widely used to adjust their composition, morphology and size. In this case, inducing agents such as metal ions, organic ligands, counterions, solvents, and even light and pressure have been developed to modify the structure of metal nanoclusters, thereby adjusting their corresponding properties, such as catalysis, photoluminescence, etc. In view of the above problems, the present invention provides a silver nanocluster, which is initially reacted with silver salt and 1,3-bis(diphenylphosphino)propane as raw materials, and then adamantane thiol is added, stirred, sodium borohydride is added, and reacted at room temperature to obtain an organic phase solution containing silver nanoclusters. The organic phase is removed, the crude product is washed with n-hexane, extracted with dichloromethane, and crystallized at room temperature to obtain the silver nanocluster.

[0036] The present invention obtains Ag 30 The nanocluster is composed of a CF3COO - Auxiliary ligand-protected Ag 13 Icosahedral core, and a large Ag outer 17 (SR) 14 (L3)3(NO3)(CF3COO)3 shell composition. The present invention uses methanol as an inducing agent to explore the effect of nanocluster structure transformation on photoluminescence. Ag 30 It can rapidly undergo structural transformation in methanol and transform into thermodynamically stable Ag. 23 , and simultaneously turned on strong red light emission. We tracked this transition using time-dependent ultraviolet-visible absorption (UV-Vis) spectroscopy, electrospray ionization mass spectrometry (ESI-MS), and photoluminescence (PL) spectroscopy. Based on this rapid transformation, we further developed an ultrasensitive "turn-on" sensor for methanol detection. This work has important application potential in understanding the transformation of metal clusters and selectively sensing methanol.

[0037] The effects are described below in conjunction with the specific test process and preparation method.

[0038] Experimental chemicals: silver nitrate (AgNO3, 99%), silver trifluoroacetate (CF3COOAg, 98%), adamantanethiol, 1,3-bis(diphenylphosphino)propane (L3) and sodium borohydride (NaBH4) were purchased from Shanghai MacLean Biochemical Co., Ltd. Solvents including methanol (MeOH, HPLC grade), dichloromethane (DCM, HPLC grade), toluene (Tol, HPLC grade) and n-hexane (n-HeX, HPLC grade) were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0039] Test method: 1. The single crystal X-ray diffraction (SCXRD) test is carried out on a complete single crystal sample on a double-microfocus X-ray single crystal diffractometer. The test needs to maintain a low temperature of 120 K throughout the test and select Cu Kα (λ = 1.54186 Å) for operation. The test results need to be analyzed and refined using Olex 2 software and SHELXTL program.

[0040] 2. Powder X-ray Diffraction (PXRD) Using an X-ray polycrystalline diffractometer (Smart Lab 9KW, Bruker, Germany), the collected Ag 30 The nanoclusters were poured into the sample slot of the X-ray polycrystal diffractometer and compacted with a glass sheet. The scanning angle was 2-90° and the scanning rate was 16° / min.

[0041] 3. Thermogravimetric analysis (TGA) A thermogravimetric analyzer (HITACHI STA200, Hitachi Instruments) was used for the test under nitrogen conditions. About 15 mg of nanoclusters were placed in a silica crucible and heated at a rate of 10°C / min from 30°C to 1000°C.

[0042] 4. X-ray Photoelectron Spectroscopy (XPS) was measured on a thermal scale ESCALAB 250, which required the following configuration: a monochromatic aluminum Kα (1486.8 eV) 150 W X-ray source, a 0.5 mm circular spot size, an ejector to counteract charging effects, and a base pressure in the analysis chamber below 1×10 -9 mbar, and the data acquisition frequency was 20 eV.

[0043] 5. Fourier transform infrared spectroscopy (FT-IR) was performed using an infrared spectrometer (Vertex80, Bruker, Germany). Preparation of FT-IR samples: Ag 30 The nanoclusters and KBr powder were mixed and ground evenly in a mass ratio of 1:50, and thin sheets were made using a tablet press.

[0044] 6. Ultraviolet-visible absorption spectra (UV-Vis) were recorded using Agilent 8453. The samples were dissolved in methanol or other soluble solvents, and the background correction was performed using methanol or other soluble solvent blank samples.

[0045] 7. Photoluminescence (PL) spectra were measured using a HORIBA Fluorescence Max+ fluorescence spectrometer with the same optical density (OD) of ~ 0.05 and a sample concentration of 0.1 mg / mL.

[0046] 8. Electrospray ionization time-of-flight mass spectrometry (ESI-MS) measurements were performed using a Waters XEVO G2-XS Qtof mass spectrometer. The sample was directly injected into the chamber at a rate of 5 μL / min. 30 The nanoclusters were first dissolved in dichloromethane (0.2 mg / mL) and then diluted with methanol (V:V = 1:1).

[0047] Example 1: Ag 30 Preparation of nanoclusters In a 100 mL round-bottom flask, AgNO3 (34 mg, 0.2 mmol) and CF3COOAg (44 mg, 0.2 mmol) were dissolved in 20 mL methanol, and then L3 (41 mg, 0.1 mmol) was added to the above AgNO3 and CF3COOAg methanol solution and stirred for about 10 min to fully dissolve. At this time, the solution was colorless and transparent. Adamantanethiol (Adm-SH, 34 mg, 0.2 mmol) was added, and the colorless and transparent solution turned milky white. After 30 min, 100 mg NaBH4 (2.64 mmol) was weighed and dissolved in 5 mL methanol, and then slowly added to the above mixture. The color of the solution gradually changed from milky white to brown-black. The reaction was continued at room temperature for 5 h. After 5 h, the crude product was centrifuged at 10,000 rpm for 3 min to remove large particles that were insoluble in methanol during the reaction. The supernatant was dried using a rotary evaporator, and the crude product was repeatedly washed with a large amount of n-hexane, and then extracted with dichloromethane solvent for two to three times. The purified product was dissolved in toluene for the last time, and diffused with toluene / n-hexane solvent at room temperature, with a small amount of ethanol as a buffer layer. After about a week, black block crystals grew at the bottom of the single crystal bottle to obtain Ag. 30 Nanoclusters, namely Ag30 (SR) 14 (L3)3(NO3)(CF3COO)4Cl2.

[0048] Example 2: Ag 30 Characterization of nanoclusters Ag 30 A one-pot synthesis method was used, as described in the preparation method of Example 1. Single crystal X-ray diffraction (SC-XRD) analysis showed that Ag 30 It crystallizes in the triclinic P-1 space group (Table 1) and has the structural formula Ag 30 (SR) 14 (L3)3(NO3)(CF3COO)4Cl2. Figure 1 As shown, Ag 30 The structure can be divided into two parts: the internal Ag 13 Icosahedral core (surrounded by 2 Cl ions and 1 CF3COO - auxiliary ligands), and a large external Ag 17 (SR) 14 (L3)3(NO3)(CF3COO)3 shell. 13 Ag atoms form icosahedral Ag through Ag-Ag interaction 13 nuclear( Figure 1 A), the Ag-Ag bond length ranges from 2.744 to 3.284 Å, with an average of 2.892 Å. 13 The Ag atoms at the upper and lower vertices of the nucleus combine, a CF3COO - Auxiliary ligand and Ag 13 The two Ag atoms at the waist of the nucleus combine ( Figure 1 B), Ag core The average bond length of -Cl is 2.488Å. 17 (SR) 14 The (L3)3(NO3)(CF3COO)3 shell can be regarded as an Ag 10 (SR) 10 The (L3)3 structure is formed by three CF3COO - Auxiliary ligand and 1 NO3 - Protected by auxiliary ligand ( Figure 1 C and Figure 1 D). These three CF3COO - The auxiliary ligands all adopt the monodentate μ1 mode and bind to Ag through the Ag-O bond. 17 (SR) 14 (L3)3 structure with exposed Ag atoms. Ag-O (CF3COO) The bond length range is 2.216 - 2.381 Å, with an average of 2.323 Å.- In the μ6-k1:k2:k3 mode, the Ag-O bond 13 Core and Ag 17 (SR) 14 (L3)3 structure of Ag atoms combined, Ag-O (NO3) The bond length ranges from 2.213 to 2.711 Å, with an average value of 2.423 Å. Both Cl ions adopt μ3 coordination mode, except for the bond to Ag. 13 In addition to an Ag atom in the nucleus, 17 (S-Adm) 14 The two Ag atoms in the (DPPP)3(NO3)(CF3COO)3 shell are connected, Ag shell The average bond length of -Cl is 2.800Å, which is longer than that of Ag. core -Cl bond of 2.488Å. The Cl ion comes from dichloromethane. Although the chlorine content in the system is very small, it is crucial for the formation and stability of Ag nanoclusters as protective ligands or innermost templates. Finally, Ag 17 (SR) 14 The (L3)3(NO3)(CF3COO)3 shell binds to Ag via Ag-Ag and Ag-S bonds. 13 The Ag atoms on the (CF3COO)Cl2 structure combine to form Ag 30 (SR) 14 The overall structure of (L3)3(NO3)(CF3COO)4Cl2 ( Figure 1 E). Ag 30 All bond length data of nanoclusters are as follows Figure 2 shown.

[0049] Ag 30 The single crystal of the nanocluster is a black block crystal ( Figure 3 ). In the powder x-ray diffraction (PXRD) spectrum, the experimental spectrum is in good agreement with the simulated spectrum, proving that the synthesized product Ag 30 The phase purity ( Figure 4 ), which will be used directly in the next step of characterization and application. Thermogravimetric (TGA) measurement results show that Ag 30 The mass reduction is 55.63%, which is comparable to Ag 30 The theoretical ligand content is 56.29% consistent ( Figure 5 ). X-ray photoelectron spectroscopy (XPS) showed that Ag 30 All expected elements in ( Figure 6 ), Ag 3d 5 / 2 The peak indicates that the valence state of Ag is close to that of Ag (I) ( Figure 7). In addition, Fourier transform infrared spectroscopy (FT-IR) analysis further verified the Ag 30 Cluster structure. For the FT-IR results in the figure ( Figure 8 ). At 2900 and 1293 cm -1 The characteristic peaks at 828 cm-1 were mainly identified as the stretching and bending vibrations of the CH bonds of the adamantanethiol ligand. -1 The characteristic absorption peak at 1659 cm -1 The characteristic peak at is attributed to Ag 30 In addition, 1198 cm -1 The characteristic peak at belongs to the CF vibration of the CF3COO ligand.

[0050]

[0051] Example 3: Ag 30 Nanocluster structure transformation When Ag 30 When the crystals are dissolved in dichloromethane, Ag 30 The UV-Vis absorption (UV-Vis) spectrum has three obvious characteristic absorption peaks at 413, 450, and 525 nm, and its absorbance remains basically unchanged within 1 hour ( Fig. 9 B), with Ag 30 Crystalline similar, Ag 30 The methylene chloride solution of the nanoclusters showed no photoluminescence. Surprisingly, when Ag 30 When the crystals are dissolved in methanol, Ag 30 The structural transformation can occur rapidly, and the solution can produce a strong red light emission under 365 nm ultraviolet light ( Fig. 9 A). The transformation process was monitored by UV-Vis spectroscopy over time. 30 Compared with the dichloromethane solution, Ag 30 The UV-Vis spectrum of the methanol solution of Fig. 9 C), as time goes by, the characteristic peak at 525nm gradually disappears, the absorbance of the peak at 450nm gradually decreases and red-shifts, transforming into a new absorption peak at 480nm, while the absorption peak at 420nm remains unchanged, and the absorption peak at 322nm is enhanced. The similar absorption peaks at 322 and 420nm and the changes in the absorption peaks at 450, 480 and 525nm indicate that Ag 30 It may undergo a surface structure reconstruction process. At the same time, the photoluminescence (PL) kinetics spectrum studied the Ag 30In methanol, the PL intensity of the solution at 670 nm increased with time and reached a saturation intensity within 60 s ( Fig.10 By comparing the UV-Vis and PL spectra after conversion, we found that it was similar to the previously reported pure adamantanethiol-protected Ag 23 The converted solution was added to NaSbF6 and the resulting red block single crystals were identified by SCXRD to have the molecular formula Ag. 23 (SR) 12 , which is consistent with the previously reported Ag 23 Have the same structure.

[0052] In order to further understand the conversion mechanism, we used in situ ESI-MS to monitor the reaction. Fig.11 In A, we observed four obvious signal peaks in the ESI-MS spectrum from 5 s to 60 s during the reaction. 30 3+ Quickly to Ag 23 3+ conversion, and two key intermediates Ag were observed 28 3+ and Ag 27 3+ , which should be due to Ag 30 The nanoclusters gradually dissociated under methanol conditions, and the relevant peak matching data and molecular formula are shown in Table 2. According to in situ ESI-MS, Ag 30 3+ and intermediate Ag 28 3+ and Ag 27 3+ Gradually disappears with the reaction ( Fig.11 A). At the same time, Ag 23 3+ The signal gradually increases as the reaction progresses ( Fig.11 A). These results show that Ag 30 3+ The nanoclusters gradually transform into the intermediate Ag under methanol conditions. 28 3+ and Ag 27 3+ dissociate, eventually forming thermodynamically stable Ag 23 3+ Nanoclusters ( Fig.11 B). Due to this rapid structural transformation, we do not get Ag 28 3+ and Ag 27 3+The crystal structure of Fig.12 and Table 3), we proposed a methanol-induced Ag 30 Nanoclusters towards thermodynamically stable Ag 23 The mechanism of nanocluster structure dissociation ( Fig.13 ).

[0053]

[0054]

[0055] Example 4: Ag 30 Nanoclusters selectively detect methanol In order to evaluate the Ag 30 To investigate the selectivity of nanoclusters, we studied the PL response of its crystals to different solvents, most of which are volatile substances that are harmful to the human body, including toluene (Tol), dichloromethane (DCM), trichloromethane (TCM), tetrahydrofuran (THF), ethyl acetate (EA), acetone (ACE), acetonitrile (ACN), N, N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), n-butanol (n-BuOH), n-propanol (n-PrOH), ethanol (EtOH) and methanol (MeOH). We found that only methanol solvent could turn on high-contrast red light emission within 60 seconds ( Fig.14 A), showing a selective response to methanol ( Fig.14 B). This selectivity is attributed to Ag 30 The nanoclusters quickly transformed into Ag with red fluorescence emission in methanol. 23 Nanoclusters. The perception of methanol can be observed by the naked eye ( Fig.15 ). In addition, due to Ag 30 The high sensitivity to methanol can also be used for the quantitative detection and analysis of methanol. Specifically, dichloromethane was used as the auxiliary solvent to prepare a methanol solution with a concentration gradient of 0-200 μL. As the methanol content increased, Ag 30 The red emission of the solution gradually increases ( Fig.16 ), at 670 nm, the corresponding PL intensity gradually increases ( Fig.14 C), Ag 30 There is a strong linear correlation between the PL intensity of the solution and the methanol content ( Fig.14 D). These results show that Ag 30 It can be used as a “turn-on” photoluminescent probe for the selective detection of methanol.

[0056] In summary, the present invention adopts a dual silver source regulation one-pot method to synthesize a new 6-electron configuration of Ag 30(SR) 14 (L3)3(NO3)(CF3COO)4Cl2 nanoclusters. Ag 30 It can rapidly undergo structural transformation in methanol and transform into thermodynamically stable Ag. 23 , and simultaneously turned on strong red light emission. We tracked this transition using time-dependent UV-Vis spectroscopy, ESI-MS, and PL spectroscopy. Based on this rapid transformation, we further developed an ultrasensitive "turn-on" sensor for methanol detection. This work has important application potential in understanding the transformation of metal clusters and selectively sensing methanol.

[0057] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A silver nanocluster, characterized in that: The molecular formula of the silver nanocluster is Ag 30 (SR) 14 (L3)3(NO3)(CF3COO)4Cl2, abbreviated as Ag 30 ; Here, SR represents adamantanethiol, and L3 represents 1,3-bis(diphenylphosphino)propane.

2. The method for preparing the silver nanoclusters according to claim 1, characterized in that The steps include: The silver salt is dissolved in methanol, stirred at room temperature, and 1,3-bis(diphenylphosphino)propane is added until it is completely dissolved; adamantane thiol is added for initial reaction, stirred, and the color of the solution turns milky white; sodium borohydride is then added and reacted at room temperature to obtain an organic phase containing silver nanoclusters.

3. The preparation method according to claim 2, characterized in that: The silver salts are silver nitrate and silver trifluoroacetate.

4. The preparation method according to claim 3, characterized in that: During the preparation process, the usage ratio of silver nitrate, silver trifluoroacetate, adamantane thiol, 1,3-bis(diphenylphosphino)propane and sodium borohydride is 34 mg:44 mg:34 mg:41 mg:100 mg.

5. The preparation method according to claim 2, characterized in that: The initial reaction time was 10 min, and the reaction time at room temperature after adding sodium borohydride was 5 h.

6. The preparation method according to claim 2, characterized in that: The organic phase is washed with n-hexane and extracted with dichloromethane, and the organic phase is crystallized with a mixed solvent of toluene and n-hexane.

7. Use of the silver nanoclusters according to claim 1 in methanol detection.

8. The use according to claim 7, characterized in that: The silver nanoclusters are used to prepare a detection reagent, and the detection reagent can detect methanol qualitatively or quantitatively.

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