A method for preparing high quantum yield copper nanoclusters for alcohol detection by constructing hydrogen bond network with water molecules

Abstract

A method for preparing high quantum yield copper nanoclusters for alcohol detection by constructing hydrogen bond network with water molecules, 4,6-dihydroxy-2-mercaptopyrimidine is used as ligand, and copper sulfate is used as copper source to synthesize red light emitting R-CuNCs@TBA, and water molecules are introduced to prepare yellow light emitting Y-CuNCs@TBA with significantly enhanced fluorescence intensity. The application utilizes 4,6-dihydroxy-2-mercaptopyrimidine as ligand to synthesize CuNCs with multiple hydrogen bond sites on the surface, and after introducing water molecules, the intermolecular aggregation of CuNCs is more compact, the fluorescence intensity is enhanced by more than 15 times, the quantum yield is increased from 15.3% of R-CuNCs@TBA to 50.1% of Y-CuNCs@TBA, and the fluorescence wavelength is blue shifted from 638 nm to 573 nm. The significant "turn-on" fluorescence display effect of R-CuNCs@TBA on water molecules is used to detect whether different alcohols are adulterated with water.

Description

Technical Field

[0001] This invention relates to a method for synthesizing copper nanoclusters (CuNCs) with multiple hydrogen bond sites on their surface using 4,6-dihydroxy-2-mercaptopyrimidine as a ligand, and for enhancing the fluorescence color change of the copper nanoclusters by constructing a hydrogen bond network with water molecules. This method is applied to alcohol detection and belongs to the field of fluorescent nanomaterials technology. Background Technology

[0002] Metal nanoclusters (MNCs) are nanomaterials with sizes between single atoms and nanoparticles. Their ultra-small size induces quantum size effects, causing energy level splitting and resulting in photoluminescence properties. Compared to traditional organic light-emitting molecules and quantum dots, metal nanoclusters offer advantages such as simple synthesis, precise and solvable structures, large Stokes shifts, and good biocompatibility. Copper is also less expensive to synthesize than noble metals like platinum, gold, and silver. However, low fluorescence intensity and a predominantly red-light wavelength are major drawbacks of copper nanoclusters.

[0003] Based on the fluorescence mechanism, after CuNCs absorb a certain amount of light energy, the electrons in the ground state are excited by the light energy and transition to the excited state. According to the principle of minimum energy for material stability, the excited electrons radiate part of their energy in the form of fluorescence, which forms the photoluminescence phenomenon. The other part of the energy is dissipated through heat or other forms of energy. To increase the fluorescence intensity, the energy consumed by non-fluorescent radiation methods must be reduced. The aggregation-induced emission (AIE) theory proposed by Academician Tang Benzhong suggests that by using molecular aggregation to limit the energy loss caused by molecular vibration and rotation, the energy radiation in the form of fluorescence is increased, thereby increasing the fluorescence intensity and improving the quantum yield.

[0004] To induce CuNCs aggregation, enhance their fluorescence intensity, and achieve high quantum yields, current methods include: intertwining and interlacing of chain-like ligands ("Nucleic acid-driven aggregation-induced emission of Au nanoclusters for visualizing telomerase activity in living cells and invivo"), hydrophobic interactions induced by the environment on CuNCs ("Fabrication of Stable and Luminescent Copper Nanocluster-Based AIE Particles and Their Application in β-Galactosidase Activity Assay"), and electrostatic interactions between CuNCs and the target region ("Probing Cancer Cells through Intracellular Aggregation-Induced Emission Kinetic Rate of Copper Nanoclusters"). These methods effectively induce CuNCs aggregation, thereby enhancing fluorescence. However, these methods often rely on environmental involvement or have poor aggregation effects, thus failing to further improve quantum yields. Further research is needed to effectively design the ordered aggregation of molecules to achieve the synthesis of CuNCs with higher quantum yields.

[0005] Therefore, by designing and using 4,6-dihydroxy-2-mercaptopyrimidine as a protective and reducing ligand, R-CuNCs@TBA with multiple hydrogen bond sites on the surface was synthesized, and water molecules with multidirectional hydrogen bond binding sites were used as initiators for a dense hydrogen bond network, resulting in Y-CuNCs@TBA with high fluorescence intensity and quantum yield. Summary of the Invention

[0006] This invention synthesizes R-CuNCs@TBA with multiple hydrogen bond sites on its surface by designing and using 4,6-dihydroxy-2-mercaptopyrimidine as a protecting and reducing ligand, and uses water molecules with multidirectional hydrogen bond binding sites as an initiator for a dense hydrogen bond network, resulting in Y-CuNCs@TBA with a quantum yield of 50.1%. The "turn-on" fluorescence effect of R-CuNCs@TBA before water initiation on water molecules is utilized for detecting the alcohol content of different types of alcoholic beverages.

[0007] The technical solution of the present invention:

[0008] A method for preparing high-quantum-yield copper nanoclusters for alcohol detection using water molecules to construct hydrogen-bonded networks involves synthesizing red-emitting R-CuNCs@TBA using 4,6-dihydroxy-2-mercaptopyrimidine (TBA) as a ligand and copper sulfate as a copper source. Water is then added to prepare yellow-emitting Y-CuNCs@TBA with significantly enhanced fluorescence intensity. The steps are as follows:

[0009] (1) Synthesis of R-CuNCs@TBA: At room temperature, CuSO4 solution and TBA solution were mixed evenly, and the molar ratio of CuSO4 to TBA was controlled at 1:3. The mixture was stirred at 25℃ for 10 h, centrifuged, washed and dried to obtain yellow R-CuNCs@TBA solid. The yellow R-CuNCs@TBA solid showed a significant fluorescence enhancement behavior for water molecules, which can be used for reverse detection of alcohol content in different wines.

[0010] (2) Synthesis of Y-CuNCs@TBA: Add ultrapure water to the obtained yellow R-CuNCs@TBA solid and stir until the solid is evenly dispersed. The solid color changes from yellow to white. After centrifugation and drying, white Y-CuNCs@TBA solid is obtained, and the fluorescence intensity increases by more than 15 times.

[0011] The concentrations of both the CuSO4 solution and the TBA solution were 0.1 mol·L⁻¹. -1 .

[0012] The solvent for the CuSO4 solution is water, the solvent for the TBA solution is dimethyl sulfoxide (DMSO), and the reaction system is a mixed solution of DMSO / H2O = 3:1 (v / v).

[0013] The R-CuNCs@TBA solid was washed and dried with a mixed solution of DMSO / H2O = 3:1 (v / v).

[0014] The beneficial results of this invention are as follows: This invention utilizes 4,6-dihydroxy-2-mercaptopyrimidine as a ligand to synthesize R-CuNCs@TBA with multiple surface hydrogen bond sites. After introducing water molecules, the CuNCs molecules achieve more compact aggregation, resulting in a fluorescence intensity increase of more than 15 times, a quantum yield increase from 15.3% before water addition to 50.1% after water addition, and a blue shift in fluorescence wavelength from 638 nm to 573 nm. The significant "turn-on" fluorescence display effect of R-CuNCs@TBA on water molecules before water addition can be used to detect whether different types of alcoholic beverages have been adulterated with water. Attached Figure Description

[0015] Figure 1 It is a different Cu 2+ Fluorescence comparison of the synthesized product at a molar ratio of / TBA.

[0016] Figure 2 These are fluorescence comparison images of the products synthesized using CuSO4, Cu(NO3)2, and CuCl2 as copper sources, respectively.

[0017] Figure 3 It is the quantum yield of R- / Y-CuNCs@TBA under 365nm irradiation.

[0018] Figure 4 This is the UV-Vis absorption spectrum of R- / Y-CuNCs@TBA.

[0019] Figure 5 These are X-ray photoelectron spectra of copper; where a is the X-ray photoelectron spectrum of copper in R-CuNCs@TBA; and b is the X-ray photoelectron spectrum of copper in Y-CuNCs@TBA.

[0020] Figure 6 This is a comparison graph of the fluorescence intensity of R- / Y-CuNCs@TBA.

[0021] Figure 7 These are scanning electron microscope (SEM) images; where a is an SEM image of R-CuNCs@TBA; and b is an SEM image of Y-CuNCs@TBA.

[0022] Figure 8 These are the optimal excitation and emission spectra. a is the optimal excitation and emission spectrum of R-CuNCs@TBA; b is the optimal excitation and emission spectrum of Y-CuNCs@TBA.

[0023] Figure 9 This is the infrared spectrum of R- / Y-CuNCs@TBA.

[0024] Figure 10 This is a differential scanning calorimeter analysis graph of R- / Y-CuNCs@TBA.

[0025] Figure 11 This is a schematic diagram of the color-changing fluorescence effect of R-CuNCs@TBA in different ethanol / water (v / v) mixed solvents.

[0026] Figure 12 The graph shows the analysis results for different types of alcoholic beverages; where a is a schematic diagram of five different types of alcoholic beverages and their ethanol concentrations; and b is a schematic diagram of the color-changing fluorescence effect of five different types of alcoholic beverages and their diluted solutions. Detailed Implementation

[0027] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0028] Example 1

[0029] 4.5 mL of 0.03 mol / L, 0.10 mol / L, and 0.17 mol / L solutions of 4,6-dihydroxy-2-mercaptopyrimidine in dimethyl sulfoxide were added, respectively, to 1.5 mL of 0.1 mol / L CuSO4 aqueous solution (i.e., Cu) under stirring. 2+ The molar ratios of TBA were 1:1, 1:3, and 1:5, respectively. The mixture was stirred at 25°C for 10 h to prepare a yellow CuNCs turbid liquid. After centrifugation, the product was washed twice with a mixed solvent of DMSO / H2O = 3:1 (v / v), centrifuged again, and dried in a vacuum oven at 80°C for 4 h to obtain a solid product.

[0030] Figure 1 To different Cu 2+ The fluorescence comparison diagram of the synthesized product under the TBA molar ratio shows that the optimal synthesis molar ratio is 1:3, that is, the strongest fluorescence is obtained when CuNCs are synthesized under the reaction conditions of 1.5 mL of 0.1 mol / L CuSO4 aqueous solution and 4.5 mL of 0.10 mol / L TBA dimethyl sulfoxide solution.

[0031] Example 2

[0032] 4.5 mL of a 0.10 mol / L solution of 4,6-dihydroxy-2-mercaptopyrimidine in dimethyl sulfoxide was added to 1.5 mL of a 0.1 mol / L CuSO4 aqueous solution, 1.5 mL of a 0.1 mol / L Cu(NO3)2 aqueous solution, and 1.5 mL of a 0.1 mol / L CuCl2 aqueous solution under stirring. The mixture was stirred at 25 °C for 10 h to prepare a yellow CuNCs turbid liquid. After centrifugation, the product was washed twice with a DMSO / H2O mixture of 3:1 (v / v), centrifuged again, and dried in a vacuum oven at 80 °C for 4 h to obtain a solid product.

[0033] Figure 2 The fluorescence comparison diagrams show the products synthesized using CuSO4, Cu(NO3)2, and CuCl2 as copper sources, respectively. By comparing the fluorescence intensity, CuSO4 was found to be the optimal copper source.

[0034] Example 3

[0035] 4.5 mL of a 0.1 mol / L solution of 4,6-dihydroxy-2-mercaptopyrimidine in dimethyl sulfoxide was added to 1.5 mL of a 0.1 mol / L CuSO4 aqueous solution under stirring. The mixture was stirred and reacted at 25 °C for 10 h. After centrifugation, a yellow solid precipitate was obtained. The precipitate was washed twice with a DMSO / H2O mixture of 3:1 (v / v), centrifuged, and dried in a vacuum oven at 80 °C for 4 h to obtain a yellow solid product emitting red light for later use.

[0036] Figure 3 The quantum yield of R-CuNCs@TBA solution under 365 nm irradiation was shown, and its QYs was determined to be 15.3%. Figure 4 The broad absorption peak at 325 nm in the UV-Vis absorption spectrum of R-CuNCs@TBA indicates that the reaction product generated a new electron transfer pathway, namely electron transfer from ligand to metal. Figure 5 The characteristic peaks of 953.03 eV and 933.25 eV in the X-ray photoelectron spectrum of copper in R-CuNCs@TBA indicate that copper mainly exists in the form of Cu(0) / Cu(I), which proves the successful preparation of CuNCs. Figure 7 As can be seen, R-CuNCs@TBA is a layered stack with a rough surface. Figure 8 a shows that the optimal excitation wavelength and optimal emission wavelength of R-CuNCs@TBA are 380 nm and 638 nm, respectively. Figure 11 The color-changing effect of R-CuNCs@TBA in different ethanol / water (v / v) mixed solvents was demonstrated. A clear boundary was observed between 20% and 30% ethanol volume concentrations. Above 30% ethanol, R-CuNCs@TBA still exhibited its original red fluorescence, while below 30% ethanol concentration, it exhibited bright yellow fluorescence. This can be used to detect adulteration in different types of alcoholic beverages. Figure 12 Image a shows images of five different ethanol concentrations of alcoholic beverages (I-V) available on the market, along with their respective ethanol concentrations: 4.5%, 8%, 23%, 40%, and 52%. Figure 12 b shows the results of R-CuNCs@TBA testing on five different types of alcoholic beverages (I-V) and nine different types of alcoholic beverages with different ethanol contents (25%, 30%, and 35% obtained by diluting alcoholic beverages III and IV with water). The results show that different types of alcoholic beverages with alcohol contents above 30% and below 30% can be clearly distinguished.

[0037] 4.5 mL of a 0.1 mol / L solution of 4,6-dihydroxy-2-mercaptopyrimidine in dimethyl sulfoxide was added to 1.5 mL of a 0.1 mol / L CuSO4 aqueous solution under stirring. The mixture was stirred at 25 °C for 10 h. After centrifugation, a yellow solid precipitate was obtained. Ultrapure water was added and stirred until the solid was uniformly dispersed. The yellow solid precipitate turned into a white solid precipitate. The white solid precipitate was dried in a vacuum oven at 40 °C for 4 h to obtain a white solid product that emits yellow light for later use.

[0038] Figure 3 The fluorescence spectrum of Y-CuNCs@TBA solution under 365 nm irradiation was measured to be QYs = 50.1%. Figure 4 and Figure 5 The results of Y-CuNCs@TBA are similar to those of R-CuNCs@TBA, indicating the successful preparation of Y-CuNCs@TBA. Figure 6 A comparison of the fluorescence intensity of R-CuNCs@TBA and Y-CuNCs@TBA before and after water introduction shows that the fluorescence intensity increased by more than 15 times after the introduction of water molecules. Figure 7 As shown in b, the Y-CuNCs@TBA structure formed after the introduction of water molecules is more compact and smooth, indicating that water molecules induce a more ordered and compact aggregation of CuNCs. Figure 9 In the infrared spectrum of R- / Y-CuNCs@TBA, the 3303 cm⁻¹ in Y-CuNCs@TBA is observed. -1 The -OH stretching vibration peak at this point indicates the presence of hydrogen bonding forces, and at the same time Figure 10 The differential scanning calorimetry (DSC) analysis results for Y-CuNCs@TBA show an endothermic peak around 98℃, indicating the presence of intramolecular water molecules. These results demonstrate that water molecules form numerous hydrogen bonds within Y-CuNCs@TBA, resulting in a more compact structure that further restricts molecular motion and enhances fluorescence.

Claims

1. A method for preparing high quantum yield copper nanoclusters for alcohol detection using a hydrogen-bonded network constructed from water molecules, characterized in that, Using 4,6-dihydroxy-2-mercaptopyrimidine (TBA) as a ligand and copper sulfate as a copper source, red-emitting R-CuNCs@TBA were synthesized. Based on this, hydrate was added to prepare yellow-emitting Y-CuNCs@TBA with significantly enhanced fluorescence intensity. The steps are as follows: (1) Synthesis of R-CuNCs@TBA: At room temperature, CuSO4 solution and TBA solution were mixed evenly, and the molar ratio of CuSO4 to TBA was controlled at 1:

3. The mixed solution was stirred at 25℃ for 10h, and then centrifuged, washed and dried to obtain yellow R-CuNCs@TBA solid. (2) Synthesis of Y-CuNCs@TBA: Add ultrapure water to the obtained yellow R-CuNCs@TBA solid and stir until the solid is evenly dispersed. The solid color changes from yellow to white. After centrifugation and drying, white Y-CuNCs@TBA solid is obtained, and the fluorescence intensity increases by more than 15 times.

2. The method according to claim 1, characterized in that, The concentrations of both the CuSO4 solution and the TBA solution were 0.1 mol·L⁻¹. -1 .

3. The method according to claim 1, characterized in that, The CuSO4 solution is in water, the TBA solution is in dimethyl sulfoxide, and the reaction system is a mixed solution of DMSO and H2O in a volume ratio of 3:

1.

4. The method according to claim 1, characterized in that, The R-CuNCs@TBA solid was washed and dried with a mixed solution of DMSO and H2O in a volume ratio of 3:1.

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