A silver nanocluster and its application in methanol detection

Abstract

This invention discloses a silver nanocluster and its application in methanol detection, belonging to the field of nanomaterials technology. The molecular formula of the silver nanocluster of this invention is Ag. 30 (SR) 14 (L3)3(NO3)(CF3COO)4Cl2, abbreviated as Ag 30 Wherein, SR represents adamantane thiol, and L3 represents 1,3-bis(diphenylphosphino)propane. The silver nanoclusters Ag of this invention... 30 It can undergo a rapid structural transformation in methanol, converting into thermodynamically stable Ag. 23 It exhibits a high-contrast light-on response and can serve as a novel "on" type photoluminescent sensor for highly selective and ultrasensitive detection of methanol.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials, specifically relating to a silver nanocluster and its application in methanol detection. Background Technology

[0002] Atomic-precise metallic nanoclusters have attracted researchers' interest due to their structural diversity and wide range of applications in luminescence, sensors, and antibacterial applications. Silver nanoclusters, with their low cost and excellent optical properties, are considered a potential alternative to luminescent gold nanoclusters. Externally induced transformation of silver nanoclusters is a common phenomenon in nanomaterials technology and has been widely used to modulate their morphology and size, thereby significantly altering their optical properties. The emergence of organically ligand-stabilized silver nanoclusters has brought this research topic to the atomic level. However, the mechanism of externally induced structural transformation of silver nanoclusters remains a perplexing problem, such as the effects of changes in peripheral ligands, metal atoms, counterions, and solvent molecules on the cluster surface or core. In this context, a method capable of achieving efficient nanocluster transformation and a clearly defined transformation mechanism is essential. 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 novel 6-electron configuration of Ag. 30 (SR) 14 (L3)3(NO3)(CF3COO)4Cl2 nanoclusters, abbreviated as Ag 30 Ag 30 It can undergo a rapid structural transformation in methanol, converting into thermodynamically stable Ag. 23 Simultaneously, a strong red light emission is initiated. This transition process was tracked 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 "on" sensor for methanol detection. This work has significant application potential for understanding the transformation of metal clusters and selectively sensing methanol.

[0004] The silver nanoclusters of this invention have the molecular formula Ag. 30 (SR) 14 (L3)3(NO3)(CF3COO)4Cl2, abbreviated as Ag 30 SR represents adamantane thiol, and L3 represents 1,3-bis(diphenylphosphine)propane.

[0005] The silver nanoclusters of this invention consist of an Ag group protected by two Cl ions and one CF3COO ion. 13 An icosahedral core, and a large Ag on the outside.17 (SR) 14 The shell is composed of (L3)3(NO3)(CF3COO)3.

[0006] The method for preparing silver nanoclusters of the present invention includes the following steps:

[0007] Silver salt was dissolved in methanol and stirred at room temperature. 1,3-bis(diphenylphosphine)propane was added and allowed to dissolve completely. At the initial reaction, adamantane thiol was added and stirred until the solution turned milky white. Sodium borohydride was then added and reacted at room temperature to obtain an organic phase containing silver nanoclusters.

[0008] The silver salt is silver nitrate and silver trifluoroacetate.

[0009] During the preparation process, the ratio of silver nitrate, silver trifluoroacetate, adamantane thiol, 1,3-bis(diphenylphosphine)propane to sodium borohydride was 34 mg: 44 mg: 34 mg: 41 mg: 100 mg.

[0010] In a preferred embodiment, the initial reaction time is 10 min, and the reaction time at room temperature after adding sodium borohydride is 5 h.

[0011] In a preferred embodiment, the organic phase is washed with n-hexane and extracted with dichloromethane. Toluene and n-hexane (V... 甲苯 V 正己烷 The organic phase was crystallized using a ratio of 1:4.

[0012] The present invention relates to the application of silver nanoclusters in methanol detection.

[0013] In the silver nanoclusters of this invention, CF3COO with weak coordination ability - With NO3 - Ions connect silver atoms on the surface of silver nanoclusters, thereby releasing multiple unstable Ag sites on the surface. This invention utilizes this Ag... 30 The "unstable Ag sites" of nanoclusters can be used as recognition sites to intentionally induce structural transitions. Here, we utilize Ag... 30 As a nanocluster model, this study systematically investigated the progressive evolution of its structure and photoluminescence properties. Therefore, this invention provides an application of silver nanoclusters in methanol detection.

[0014] The present invention monitors the structural transformation process of silver nanoclusters: specifically, the silver nanoclusters are dissolved in methanol or dichloromethane solution and time-dependent ultraviolet-visible absorption (UV-Vis) spectroscopy, electrospray ionization mass spectrometry (ESI-MS), and photoluminescence (PL) spectroscopy are used to track the process.

[0015] The silver nanoclusters were dissolved in thirteen common laboratory soluble solvents for qualitative detection of photoluminescence. The silver nanoclusters were dissolved in methanol solvents of different concentrations (with dichloromethane as an auxiliary solvent) for quantitative detection of photoluminescence.

[0016] Furthermore, the thirteen soluble solvents for qualitative detection are: toluene (Tol), dichloromethane (DCM), n-butanol (n-BuOH), n-propanol (n-PrOH), tetrahydrofuran (THF), ethyl acetate (EA), ethanol (EtOH), chloroform (TCM), acetone (ACE), acetonitrile (ACN), N,N-dimethylformamide (DMF), methanol (MeOH), and dimethyl sulfoxide (DMSO). Ag... 30 The nanoclusters dissolve in the above thirteen solvents.

[0017] Further, the quantitative detection process is as follows: Using dichloromethane as an auxiliary solvent, methanol solutions with a concentration gradient of 0-5 mM are prepared. The dichloromethane:methanol ratios are: 200 µL: 0 µL (0 mM), 180 µL: 20 µL (0.5 mM), 160 µL: 40 µL (1 mM), 140 µL: 60 µL (1.5 mM), 120 µL: 80 µL (2 mM), 100 µL: 100 µL (2.5 mM), 80 µL: 120 µL (3 mM), 60 µL: 140 µL (3.5 mM), 40 µL: 160 µL (4 mM), 20 µL: 180 µL (4.5 mM), and 0 µL: 200 µL (5 mM). Then, methanol solutions of different concentrations are added dropwise to Ag... 30 In nanoclusters.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] The silver nanoclusters of this invention, namely Ag 30 (SR) 14 (L3)3(NO3)(CF3COO)4Cl2(Ag 30 ), consisting of an Ag group protected by two Cl ions and one CF3COO ion. 13 An icosahedral core, and a large Ag on the outside. 17 (SR) 14 The shell is composed of (L3)3(NO3)(CF3COO)3. Ag 30 It can undergo a rapid structural transformation in methanol, converting into thermodynamically stable Ag. 23Simultaneously, a strong red light emission is initiated. This transition process was tracked 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 "on" sensor for methanol detection. This work has significant application potential for understanding the transformation of metal clusters and selectively sensing methanol. Attached Figure Description

[0020] Figure 1 Ag of the present invention 30 Structural analysis. Among them: (A) 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 The overall structure of (L3)3(NO3)(CF3COO)4Cl2.

[0021] Figure 2 For Ag 30 Bond lengths. Color labels: Sky blue, Ag; Red, S; Magenta, P; Green, Cl; Bright green, F; Blue, N; Orange, O.

[0022] Figure 3 For Ag 30 Digital images of crystals.

[0023] Figure 4 For Ag 30 Experimental (black) and simulated (red) X-ray powder diffraction (PXRD) patterns.

[0024] Figure 5 For Ag 30 Thermogravimetric analysis (TGA) curves in N2.

[0025] Figure 6 For Ag 30 The X-ray photoelectron spectroscopy (XPS) image.

[0026] Figure 7 For Ag 30 High-resolution XPS spectra of Ag3d.

[0027] Figure 8 For Ag 30 The Fourier transform infrared (FT-IR) characterization results.

[0028] Figure 9 For (A) Ag 30 and Ag 23 The structure of Ag. Color codes: sky blue, Ag; red, S; magenta, P; green, Cl; bright green, F; blue, N; orange, O; gray, C. For clarity, all H atoms are omitted. Inserted digital photograph: Ag illuminated by a 365nm UV lamp. 30 (Left, dark) Dichloromethane solution and Ag 30 (Right, bright red) methanol solution. (B) Ag 30 UV-Vis absorption spectrum showing the time-dependent dissolution of crystals in dichloromethane. (C) Ag 30 UV-Vis absorption spectrum of crystals dissolved in methanol over time.

[0029] Figure 10 For Ag 30 Photoluminescence kinetics of crystals dissolved in methanol (0.1 mg / mL).

[0030] Figure 11 For (A) intermediate detection: Ag 30 To Ag 23 Time-dependent ESI-MS spectra of the transformation process, (B) Ag 30 To Ag 23 A schematic diagram of the transformation.

[0031] Figure 12 intermediate Ag 27 To Ag 23 ESI-MS spectrum of dissociated fragment peaks.

[0032] Figure 13 The proposed mechanism: from Ag 30 To Ag 23 The conversion process (ignoring all solvent molecules).

[0033] Figure 14 For Ag 30 (A) PL spectra and (B) PL intensities (0.1 mg / mL) of crystals dissolved in different solvents. (C) Ag 30 PL spectra in methanol solvents of different concentrations (with DCM as an auxiliary solvent). (D) Linear relationship between PL intensity and methanol concentration.

[0034] Figure 15 For Ag 30Digital photographs of the crystal in 13 solvents of different polarities (illuminated with a 365 nm UV lamp). No visible luminescence was observed in 9 solvents (top), and visible luminescence was observed in 4 solvents (bottom).

[0035] Figure 16 For Ag 30 Digital photographs of methanol at different concentrations. Detailed Implementation

[0036] To enable those skilled in the art to better understand and implement the technical solutions of this invention, the invention will be further described below with reference to specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the invention. Unless otherwise specified, the following test methods and detection methods are conventional methods; unless otherwise specified, the reagents and raw materials are commercially available.

[0037] Externally induced transformation of nanoclusters is a common phenomenon in nanotechnology and has been widely used to regulate their composition, morphology, and size. In this context, 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 regulating their corresponding properties, such as catalysis and photoluminescence. This invention addresses the above-mentioned problems by providing a silver nanocluster. The initial reaction involves silver salt and 1,3-bis(diphenylphosphine)propane, followed by the addition of adamantane thiol, stirring, and the addition of sodium borohydride. The reaction is carried out 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 nanoclusters.

[0038] This invention yielded Ag 30 Nanoclusters, the above nanoclusters consist of a cluster of two Cl ions and one CF3COO ion. - Ag protected by auxiliary ligands 13 An icosahedral core, and a large Ag on the outside. 17 (SR) 14 The structure consists of a (L3)3(NO3)(CF3COO)3 shell. This invention uses methanol as an inducer to investigate the effect of nanocluster structure transformation on photoluminescence. Ag 30 It can undergo a rapid structural transformation in methanol, converting into thermodynamically stable Ag. 23 Simultaneously, a strong red light emission is initiated. This transition process was tracked 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 "on" sensor for methanol detection. This work has significant application potential for understanding the transformation of metal clusters and selectively sensing methanol.

[0039] The effects are explained below with reference to the specific experimental process and preparation method.

[0040] Test reagents: Silver nitrate (AgNO3, 99%), silver trifluoroacetate (CF3COOAg, 98%), adamantane mercaptan, 1,3-bis(diphenylphosphine)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.

[0041] Test methods:

[0042] 1. Single-crystal X-ray diffraction (SCXRD) testing involves testing intact single-crystal samples on a dual-micron focal spot X-ray single-crystal diffractometer. The test requires maintaining a low temperature of 120 K throughout and selecting Cu Kα (λ = 1.54186 Å) for operation. The test results need to be analyzed and refined using Olex 2 software and SHELXTL program.

[0043] 2. Powder X-ray Diffraction (PXRD): Using a polycrystalline X-ray diffractometer (Smart Lab 9KW, Bruker GmbH, Germany), the collected Ag... 30 Nanoclusters were poured into the sample cell of an X-ray polycrystalline diffractometer, compacted with a glass slide, and the scanning angle was 2-90° with a scanning rate of 16° / min.

[0044] 3. Thermogravimetric analysis (TGA) was performed using a thermogravimetric analyzer (HITACHI STA200, Hitachi Instruments). The test was conducted under nitrogen atmosphere. Approximately 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.

[0045] 4. X-ray photoelectron spectroscopy (XPS) is performed on a thermal scale ESCALAB 250 and requires 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 × 10⁻⁶. -9 mbar, with a data acquisition frequency of 20 eV.

[0046] 5. Fourier Transform Infrared Spectroscopy (FT-IR) was performed using an infrared spectrometer (Vertex 80, Bruker GmbH, Germany). FT-IR sample preparation: Ag... 30 Nanoclusters and KBr powder were mixed and ground evenly at a mass ratio of 1:50, and then pressed into thin sheets using a tablet press.

[0047] 6. Ultraviolet-visible absorption spectra (UV-Vis) were all recorded using an Agilent 8453. The samples were dissolved in methanol or other soluble solvents, and background correction was performed using blank samples in methanol or other soluble solvents.

[0048] 7. Photoluminescence (PL) spectra were measured using a HORIBA Max+ fluorescence spectrometer with the same optical density (OD) of ~0.05 and sample concentration of 0.1 mg / mL.

[0049] 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 injected directly into the chamber at a rate of 5 μL / min. For ESI sample preparation, Ag... 30 The nanoclusters were first dissolved in dichloromethane (0.2 mg / mL) and then diluted with methanol (V:V = 1:1).

[0050] Example 1: Ag 30 Preparation of nanoclusters

[0051] 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 of methanol. Then, L3 (41 mg, 0.1 mmol) was added to the AgNO3 and CF3COOAg methanol solution and stirred for about 10 min until fully dissolved; the solution was colorless and transparent at this point. Then, adamantane thiol (Adm-SH, 34 mg, 0.2 mmol) was added, and the colorless transparent solution turned milky white. After 30 min, 100 mg of NaBH4 (2.64 mmol) was weighed and dissolved in 5 mL of methanol, then slowly added dropwise to the above mixture; the solution gradually changed from milky white to brownish-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 insoluble in methanol that had formed during the reaction. The supernatant was evaporated to dryness using a rotary evaporator. The crude product was repeatedly washed with a large amount of n-hexane, followed by extraction with dichloromethane solvent two to three times. The final purification product was dissolved in toluene and diffused at room temperature with toluene / n-hexane solvent, using a small amount of ethanol as a buffer layer. After about a week, black blocky crystals grew at the bottom of the single crystal flask, yielding Ag.30 Nanoclusters, namely Ag 30 (SR) 14 (L3)3(NO3)(CF3COO)4Cl2.

[0052] Example 2: Ag 30 Characterization of nanoclusters

[0053] Ag 30 A one-pot synthesis method was employed, as described in Example 1. Single-crystal X-ray diffraction (SC-XRD) analysis indicated that Ag... 30 It crystallizes in the triclinic P-1 space group (Table 1) with the structural formula Ag. 30 (SR) 14 (L3)3(NO3)(CF3COO)4Cl2. For example... Figure 1 As shown, Ag 30 The structure can be divided into two parts: the internal Ag 13 An icosahedral core (containing 2 Cl ions and 1 CF3COO ion) - (protected by auxiliary ligands), and a large external Ag 17 (SR) 14 (L3)3(NO3)(CF3COO)3 shell. Thirteen Ag atoms form an icosahedral Ag structure through Ag-Ag interactions. 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. Two Cl ions react with Ag... 13 Ag atoms at the two vertices of the nucleus bond together, forming a CF3COO - Support ligands and Ag 13 The two Ag atoms at the waist of the nucleus are bonded together ( Figure 1 B), Ag core The average -Cl bond length is 2.488 Å. There is a large Ag bond on the outside. 17 (SR) 14 The shell of (L3)3(NO3)(CF3COO)3 can be viewed as an Ag 10 (SR) 10 The (L3)3 structure is composed of three CF3COO groups. - Support ligand and 1 NO3 - Auxiliary ligand protection ( Figure 1 C and Figure 1 D). These 3 CF3COO - All auxiliary ligands adopt a monodentate μ1 mode, binding to Ag via Ag-O bonds. 17 (SR) 14 (L3)3 structure with exposed Ag atoms bonded together. Ag-O (CF3COO)The bond lengths range from 2.216 to 2.381 Å, with an average of 2.323 Å. One NO3 molecule... - In the μ6-k1:k2:k3 mode, Ag is linked to Ag via the Ag-O bond. 13 nuclei and Ag 17 (SR) 14 Ag atoms in the (L3)3 structure are bonded together, Ag-O (NO3) The bond lengths range from 2.213 to 2.711 Å, with an average of 2.423 Å. Both Cl ions employ a μ3 coordination mode, except for the Ag bond. 13 Besides one Ag atom in the nucleus, it also interacts with Ag. 17 (S-Adm) 14 In the shell of (DPPP)3(NO3)(CF3COO)3, two Ag atoms are connected, Ag shell The average bond length of the -Cl bond is 2.800 Å, which is longer than that of the Ag bond. core The -Cl bond is at 2.488 Å. The Cl ions originate 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 is bonded to Ag via Ag-Ag and Ag-S bonds. 13 Ag atoms in the (CF3COO)Cl2 structure combine to ultimately 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, such as Figure 2 As shown.

[0054] Ag 30 The single crystals of nanoclusters are black, bulky crystals. Figure 3 In powder X-ray diffraction (PXRD) spectroscopy, the experimental and simulated spectra showed good agreement, confirming the synthesis of the Ag product. 30 Phase purity ( Figure 4 This will be used directly in the next step of characterization and application. Thermogravimetric (TGA) measurements show that Ag... 30 The quality decreased to 55.63%, compared to Ag. 30 The theoretical ligand content of 56.29% is consistent ( Figure 5 X-ray photoelectron spectroscopy (XPS) showed Ag 30 All expected elements ( Figure 6 ), Ag 3d 5 / 2 The peak indicates that the valence state of Ag is similar to that of Ag(I). Figure 7 Furthermore, Fourier transform infrared spectroscopy (FT-IR) analysis further verified the presence of Ag. 30 The structure of the cluster. Regarding the FT-IR results in the figure ( Figure 8 ). At 2900 and 1293 cm -1 The characteristic peak at 828 cm⁻¹ was mainly identified as the stretching and bending vibrations of the CH bond in the adamantanethiol ligand. -1 The characteristic absorption peak at 1659 cm⁻¹ corresponds to the =CH stretching vibration of the benzene ring on L3. -1 The characteristic peak at that location belongs to Ag. 30 The carbon-based structure, in addition, 1198 cm -1 The characteristic peak at this location belongs to the CF vibration of the CF3COO ligand.

[0055]

[0056] Example 3: Ag 30 Nanocluster structure transformation

[0057] When Ag 30 When crystals dissolve in dichloromethane, Ag 30 The ultraviolet-visible absorption (UV-Vis) spectrum shows three distinct characteristic absorption peaks at 413, 450, and 525 nm, and its absorbance remains essentially unchanged within 1 hour. Figure 9 B), with Ag 30 Similar to crystals, Ag 30 The dichloromethane solution containing nanoclusters did not exhibit photoluminescence. Surprisingly, when Ag... 30 When the crystals dissolve in methanol, Ag 30 It can undergo a rapid structural transformation, and the solution can produce a strong red light emission under 365 nm ultraviolet light irradiation. Figure 9 A). This conversion process was monitored using time-varying UV-Vis spectroscopy, and compared with Ag. 30 Compared to dichloromethane solutions, Ag 30 The UV-Vis spectrum of the methanol solution changed rapidly within 60 s. Figure 9 (C) As time increases, the characteristic peak at 525 nm gradually disappears, the absorbance of the peak at 450 nm gradually decreases and redshifts, transforming into a new absorption peak at 480 nm. Meanwhile, the absorption peak at 420 nm remains unchanged, while the absorption peak at 322 nm strengthens. The similar absorption peaks at 322 and 420 nm, and the changes in absorption peaks at 450, 480, and 525 nm, indicate that Ag... 30 It may undergo a surface structure reconstruction process. Simultaneously, photoluminescence (PL) kinetics were investigated in Ag. 30In methanol, the response time at 670 nm shows that the PL intensity of the solution increases with time and reaches saturation intensity within 60 s. Figure 10 By comparing the UV-Vis and PL spectra of the transformed Ag, we found that it was similar to that of Ag protected by pure adamantane thiol, as previously reported. 23 It exhibits almost identical UV-Vis spectral peaks and PL emission peaks. A red, bulky single crystal obtained by adding the converted solution to NaSbF6 and crystallizing was identified by SCXRD as having the molecular formula Ag. 23 (SR) 12 Similar to the previously reported Ag 23 They have the same structure.

[0058] To further understand the transformation mechanism, we monitored the reaction using in-situ ESI-MS. Figure 11 In A, we observed four distinct signal peaks in the ESI-MS spectrum from 5 s to 60 s during the reaction. At the beginning of the reaction, Ag... 30 3+ Quickly towards Ag 23 3+ The transformation was observed, and two key intermediates, Ag, were identified. 28 3+ and Ag 27 3+ This should stem from Ag 30 The stepwise dissociation of nanoclusters under methanol conditions, along with relevant peak matching data and molecular formulas, are shown in Table 2. Based on in-situ ESI-MS, Ag... 30 3+ and intermediate Ag 28 3+ and Ag 27 3+ It gradually disappears as the reaction progresses. Figure 11 A). At the same time, Ag 23 3+ The signal gradually increases as the reaction process progresses. Figure 11 A). These results indicate that Ag 30 3+ Nanoclusters gradually transform into intermediate Ag under methanol conditions. 28 3+ and Ag 27 3+ Dissociation eventually forms thermodynamically stable Ag. 23 3+ Nanoclusters ( Figure 11 B). Due to this rapid structural transformation, we did not obtain Ag. 28 3+ and Ag 27 3+The crystal structure. Based on the key intermediates and corresponding dissociation fragment peaks observed by ESI-MS ( Figure 12 (and Table 3), we propose a methanol-induced Ag 30 Nanoclusters towards thermodynamically stable Ag 23 Mechanism of dissociation of nanocluster structures Figure 13 ).

[0059]

[0060]

[0061] Example 4: Ag 30 Selective detection of methanol using nanoclusters

[0062] To evaluate Ag 30 To investigate the selectivity of the nanoclusters, we studied the photoluminescence (PL) response of their crystals to different solvents, most of which are volatile substances harmful to humans, including toluene (Tol), dichloromethane (DCM), chloroform (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 initiate high-contrast red light emission within 60 seconds. Figure 14 A) indicates a selective response to methanol. Figure 14 B). This selectivity is attributed to Ag. 30 Nanoclusters rapidly transform into Ag with red fluorescence emission in methanol. 23 Nanoclusters. The perception of methanol can be observed with the naked eye. Figure 15 Furthermore, due to Ag 30 Its high sensitivity to methanol can also be used for the quantitative detection and analysis of methanol. Specifically, methanol solutions with concentration gradients of 0-200 μL are prepared using dichloromethane as an auxiliary solvent. As the methanol content increases, Ag... 30 The red light emission of the solution gradually increases ( Figure 16 At 670 nm, the corresponding PL intensity gradually increases ( Figure 14 C), Ag 30 There is a strong linear correlation between the PL strength of the solution and the methanol content. Figure 14 D). These results indicate that Ag 30 It can be used as an "on" type photoluminescent probe for the selective detection of methanol.

[0063] In summary, this invention synthesizes a novel 6-electron Ag by a one-pot method controlled by a dual silver source.30 (SR) 14 (L3)3(NO3)(CF3COO)4Cl2 nanoclusters. Ag 30 It can undergo a rapid structural transformation in methanol, converting into thermodynamically stable Ag. 23 Simultaneously, a strong red light emission is initiated. We tracked this transition process using time-dependent UV-Vis spectroscopy, ESI-MS, and PL spectroscopy. Based on this rapid transformation, we further developed an ultrasensitive "on" sensor for methanol detection. This work has significant application potential for understanding the transformation of metal clusters and selectively sensing methanol.

[0064] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A silver nanocluster, characterized in that: The molecular formula of the silver nanoclusters is Ag. 30 (SR) 14 (L3)3(NO3)(CF3COO)4Cl2, abbreviated as Ag 30 ; In this context, SR represents adamantane thiol, and L3 represents 1,3-bis(diphenylphosphine)propane.

2. The method for preparing the silver nanoclusters according to claim 1, characterized in that... Includes the following steps: Silver salt was dissolved in methanol and stirred at room temperature. 1,3-bis(diphenylphosphine)propane was added and allowed to dissolve completely. Adamantane thiol was added for the initial reaction, and the mixture was stirred until the solution turned milky white. Sodium borohydride was 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 salt is silver nitrate and silver trifluoroacetate.

4. The preparation method according to claim 3, characterized in that: During the preparation process, the ratio of silver nitrate, silver trifluoroacetate, adamantane thiol, 1,3-bis(diphenylphosphine)propane to sodium borohydride was 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 the addition of sodium borohydride was 5 h.

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

7. The application of the silver nanoclusters of claim 1 in methanol detection.

8. The application according to claim 7, characterized in that: A detection reagent was prepared using the silver nanoclusters, and the detection reagent is capable of qualitative or quantitative detection of methanol.

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