CN111014716A

CN111014716A - Method for macroscopic preparation of AIE copper nanoclusters by cysteamine

Info

Publication number: CN111014716A
Application number: CN201911258061.7A
Authority: CN
Inventors: 韩冰雁; 辛泽; 燕琪芳; 姜静美; 闫琴
Original assignee: Dalian University of Technology
Current assignee: Dalian University of Technology
Priority date: 2019-12-10
Filing date: 2019-12-10
Publication date: 2020-04-17
Anticipated expiration: 2039-12-10
Also published as: CN111014716B

Abstract

The invention belongs to the technical field of preparation of fluorescent nano materials, and provides a method for macro-preparation of AIE copper nanoclusters by using cysteamine. The invention has the beneficial effects that: the invention synthesizes yellow fluorescent and precipitated copper nanoclusters by taking cysteamine as a ligand for the first time, and has the characteristics of high fluorescence intensity and strong stability of the AIE copper nanoclusters; meanwhile, high-yield and macro-preparation can be realized according to the structural characteristics of the cysteamine ligand. Compared with the prior art, the method has the characteristics of simple steps, strong stability, high fluorescence intensity and capability of realizing macro-preparation.

Description

Method for macroscopic preparation of AIE copper nanoclusters by cysteamine

Technical Field

The invention relates to a method for macroscopic preparation of AIE copper nanoclusters by cysteamine, and belongs to the technical field of preparation of fluorescent nano materials.

Background

The fluorescent metal nanocluster is composed of a central metal core and surface ligands, generally consists of several to dozens of atoms, has the size of less than 2nm, is between a nanoparticle and a single atom, and has unique physical, chemical and optical properties. The excellent properties of the fluorescent metal nanocluster enable the fluorescent metal nanocluster to be widely applied to the fields of sensing detection, cell imaging, catalysis, photoelectric devices and the like. Among them, copper element has been widely studied and developed because of its low price and abundant reserves. During the last decades, a wide variety of synthetic methods have been developed, such as etching, template-assisted, ligand-assisted, etc. In the method, a ligand-assisted method is adopted, and cysteamine which is simple in structure and easy to further study is selected as a ligand to synthesize the fluorescent copper nanocluster.

Photoluminescence is one of the important properties of fluorescent metal nanoclusters. At present, the stability of the synthesized fluorescent copper nanocluster is poor, on one hand, energy is mostly lost in a non-radiative transition form due to the fact that vibration or rotation of ligand molecules is intensified, and on the other hand, the fluorescent characteristic of the synthesized fluorescent copper nanocluster is lost due to the fact that a central copper core is easy to oxidize or agglomerate to form nano particles. Aggregation is generated by utilizing the interaction (such as hydrogen bond interaction) between ligand molecules, the vibration or rotation of the ligand molecules is effectively inhibited, the radiation transition capability of the copper nanocluster is greatly improved, and meanwhile, a stable assembly is formed to prevent the occurrence of the phenomenon of oxidation or further aggregation. Such fluorescence phenomenon due to aggregation is defined as Aggregation Induced Emission (AIE). The AIE nano-cluster is easy to generate precipitation phenomenon due to easy cross-linking of intermolecular force, thereby providing possibility for realizing macro-output of the metal nano-cluster and simultaneously ensuring that the nano-cluster material has high fluorescence performance and high stability. The method provides reference significance for industrialization and industrial development of the fluorescent nano-cluster material.

Disclosure of Invention

According to the invention, the AIE type fluorescent copper nano-cluster is synthesized by taking cysteamine (2-mercaptoethylamine) as a ligand, so that the defects of poor stability, low fluorescence yield, toxic reagent use and the like of the metal nano-cluster are overcome, and the macro-preparation can be realized.

The technical scheme of the invention is as follows:

a method for macro-preparation of AIE copper nanoclusters by cysteamine comprises the following steps:

mixing cysteamine and copper nitrate pentahydrate at room temperature, adding a reducing agent, adjusting the pH of the mixed solution to 10-14, then transferring the mixed solution to the temperature of 35-40 ℃, and reacting for 120min at the rotating speed of 120rpm to prepare the yellow aggregation state fluorescent copper nano-cluster.

The molar ratio of the cysteamine to the copper nitrate pentahydrate is 1: 1.

The reducing agent is hydroxylamine hydrochloride, and the concentration of the reducing agent in the reaction system is 6M.

The pH was 12 and the temperature was 37 ℃.

The invention has the beneficial effects that: the invention synthesizes yellow fluorescent and precipitated copper nanoclusters by taking cysteamine as a ligand for the first time, and has the characteristics of high fluorescence intensity and strong stability of the AIE copper nanoclusters; meanwhile, high-yield and macro-preparation can be realized according to the structural characteristics of the cysteamine ligand. Compared with the prior art, the method has the characteristics of simple steps, strong stability, high fluorescence intensity and capability of realizing macro-preparation.

Drawings

FIG. 1 is a graph showing the effect of different molar ratios of cysteamine to copper nitrate on fluorescence intensity of fluorescent copper nanoclusters.

FIG. 2 is a graph showing the effect of different amounts of reducing agent on the fluorescence intensity of fluorescent copper nanoclusters.

FIG. 3 is a graph of the effect of different reaction times on the fluorescence intensity of fluorescent copper nanoclusters.

FIG. 4 is a transmission electron micrograph (200nm) of fluorescent copper nanoclusters.

FIG. 5 is a transmission electron micrograph (20nm) of fluorescent copper nanoclusters.

Fig. 6 is an infrared spectrum of a fluorescent copper nanocluster.

FIG. 7 is an X-ray photoelectron spectrum of copper element in fluorescent copper nanoclusters.

FIG. 8 shows fluorescence spectra at different excitation wavelengths.

Detailed Description

The following further describes a specific embodiment of the present invention with reference to the drawings and technical solutions.

Examples 1 to 4

A method for macro-preparation of AIE copper nanoclusters from cysteamine, the method comprising the steps of:

cysteamine solution (10mM, 5mL) and copper nitrate solution were mixed at room temperature. Adding hydroxylamine hydrochloride reducing agent 6M, adjusting the pH value to 12, and reacting in a water bath at 37 ℃ for 120 min.

The molar ratio of cysteamine to copper nitrate of examples 1-4 is shown in Table 1.

The copper nanoclusters in a precipitation state are external appearance with AIE characteristics, and provide a foundation for macroscopic preparation of the fluorescent copper nanoclusters. It was shown by transmission electron microscopy (fig. 4 and 5) that the copper nanoclusters exhibited a network aggregation state, which was composed of individual copper nanoclusters having an average particle size of 1.96nm, crosslinked due to the presence of intermolecular hydrogen bonding force. An infrared spectrum (figure 6) shows that the copper nanoclusters are 3200-3500 cm^-1The compound has an obvious-NH-stretching vibration peak, and a wider peak shape indicates the existence of hydrogen bonding; while being positioned at 2550cm^-1the-SH of (a) disappears, and the cysteamine is preliminarily shown to be connected with the fluorescent copper nanocluster through Cu-S as a protective agent. Peaks appearing at 932eV and 952eV in the X-ray photoelectron spectrum (FIG. 7) of the Cu element are assigned to Cu 2p_3/2And Cu 2p_1/2This indicates that the copper nitrate was successfully reduced to zero-valent copper nanoclusters. The force of hydrogen bonding due to the amino group is susceptible to pH. Under acidic conditions, the yellow precipitate disappeared with a decrease in fluorescence, indicating that the copper nanoclusters have AIE properties. In addition, the copper nanoclusters under different excitation lights in fig. 8 have excitation independence and show good size uniformity.

As the copper nanocluster has AIE characteristics, the stability of the copper nanocluster is greatly improved, and the fluorescence intensity of the copper nanocluster is kept unchanged in an aqueous solution for at least 3 months. The fluorescence quantum yield is kept between 5 and 6 percent. The macroscopic visible fluorescent metal nanoparticles can be prepared after centrifugal purification and freeze drying due to the existence of the precipitated nanoclusters, and the yield is over 60 percent. When the mixed solvent of ethanol/water (1:1) is added in the preparation process, the yield can reach more than 80 percent. The cysteamine is poorly dissolved in ethanol, so that the cysteamine reaches a microphase separation state in an ethanol/water mixed solvent, and the yield of the cysteamine is greatly enhanced; meanwhile, the preparation of the gram-scale fluorescent nano-cluster material can be easily realized by increasing the reactants in proportion. The fluorescent nano-cluster material is prepared in a large scale and high yield according to the characteristics of the cysteamine ligand by a simple solvent mixing mode. The practical application value of the metal nano-cluster is enhanced, and the application prospect of the metal nano-cluster material is further expanded and developed.

TABLE 1 molar ratio of cysteamine to copper nitrate of examples 1-4

	Example 1	Example 2	Example 3	Example 4
					Molar ratio of	1:1	1:2	1:4	1:6

Examples 5 to 10

cysteamine solution (10mM, 5mL) and copper nitrate solution (10mM, 5mL) were mixed at room temperature. Adding hydroxylamine hydrochloride reducing agent, adjusting the pH value to 12, and reacting in a water bath at 37 ℃ for 120 min.

The hydroxylamine hydrochloride concentrations of examples 5-10 are shown in Table 2.

TABLE 2 hydroxylamine hydrochloride concentrations of examples 5-10

	Example 5	Example 6	Example 7	Example 8	Example 9	Example 10
							Concentration (M)	1	2	4	6	8	20

Examples 11 to 14

cysteamine solution (10mM, 5mL) and copper nitrate solution (10mM, 5mL) were mixed at room temperature. Hydroxylamine hydrochloride reducing agent 6M is added, the pH value is adjusted to 12, and the reaction is carried out in a water bath at 37 ℃.

The reaction times for the examples 11 to 14 are shown in Table 3.

TABLE 3 different reaction times for examples 11 to 14

Claims

1. A method for macro-preparation of AIE copper nanoclusters by cysteamine is characterized by comprising the following steps:

2. The method for macro-preparation of AIE copper nanoclusters by cysteamine according to claim 1, wherein the molar ratio of cysteamine to copper nitrate pentahydrate is 1: 1.

3. The method for macro-preparation of AIE copper nanoclusters by using cysteamine according to claim 1 or 2, wherein the reducing agent is hydroxylamine hydrochloride, and the concentration in the reaction system is 6M.

4. The method for macro-preparation of AIE copper nanoclusters by cysteamine according to claim 1 or 2, wherein the pH is 12 and the temperature is 37 ℃.

5. The method for macro-preparation of AIE copper nanoclusters by cysteamine according to claim 3, wherein the pH is 12 and the temperature is 37 ℃.