CN114058362A

CN114058362A - Core-shell structure nanocrystalline material and its application in O2Application in gas detection

Info

Publication number: CN114058362A
Application number: CN202010789551.6A
Authority: CN
Inventors: 王从相; 王清清; 王双兰
Original assignee: Wenzhou Guangli Biomedical Technology Co ltd
Current assignee: Wenzhou Guangli Biomedical Technology Co ltd
Priority date: 2020-08-07
Filing date: 2020-08-07
Publication date: 2022-02-18

Abstract

The application relates to the field of novel nanocrystalline materials and gas detection thereof, in particular to a nanocrystalline material with a core-shell structure, a preparation method thereof and application thereof in gas molecule detection. A core-shell structure nanocrystalline material is provided, the molecular formula of the nanocrystalline is CaClF: Bi/Er @ CaClF. The surface of the nanocrystal is coated with a layer of inert shell layer CaClF, so that the defect of the surface is modified, the fluorescence efficiency of the nanocrystal is greatly improved, and the nanocrystal has the advantages of good fluorescence signal, high intensity and high detection limit.

Description

Core-shell structure nanocrystalline material and its application in O2Application in gas detection

Technical Field

The application relates to the field of novel nanocrystalline materials and gas detection thereof, in particular to a nanocrystalline material with a core-shell structure, a preparation method thereof and application thereof in O₂Application in the detection of gas molecules.

Background

The luminous efficiency of nanoparticles is generally less than that of the corresponding bulk materialThis is due to the large surface to volume ratio of the nanoparticles and the large amount of surface quenching present. In addition, ligands with high-energy vibration mode such as OH or NH are present on the surface of the nano-particles₂The group of radicals is also responsible for quenching the upconversion fluorescent nanomaterial. In rare earth doped up-conversion materials, if the concentration of the dopant in the host lattice is high, e.g. high Yb doping³⁺The energy of the central particle is transferred to the surface by the energy transfer of the adjacent dopant ions, further reducing the efficiency of upconversion. Therefore, it is now recognized that the energy loss of the nanomaterial can be greatly reduced by using a suitable shell material.

If the excitation energy is transferred to the shell material on the nanoparticle surface primarily through the adjacent dopant ions, the simplest strategy is to choose an inert shell coating. The structure between core-shell materials with a small lattice mismatch has been studied intensively, starting with semiconductor nanoparticles and nanomaterials with large band gaps. Recently, the synthesis process of core-shell structure nanocrystals of rare earth fluoride materials has also been developed. The growth of inert shell materials on the surface of rare earth doped fluoride nanoparticles has been reported by many researchers, for example: LaF₃、NaYF₄、KYF₄And NaGdF₄. In 2007, the NaYF hexagonal subject group reported₄:Yb³⁺/Er³⁺Hexagonal NaYF⁴The nanocrystals have excellent outer shells and greatly enhance the upconversion fluorescence efficiency.

The detection of gas molecules (oxygen, ammonia, carbon dioxide, etc.) is of great importance in analytical biomedical, clinical diagnostics and bioprocess testing. Liulina et al designed a unique multifunctional nano-compound detector with characteristics of up-conversion, oxygen detection, and bioaffinity. Professor Wolfbeis developed a method of using NaYF₄: a sensor for detecting PH by Yb/Er, and further extending the sensor to NH₄And CO₂And (6) detecting. Next, NH based on fluorescent chromogens₄And CO₂Probes have also been developed to accurately detect gases by means of PH changes in the solution.

At present, the problem of low luminescence efficiency of the up-conversion nanocrystals generally exists, so that when people detect gas in the field of medical application, sol nanocrystals with higher concentration are inevitably adopted, but the nanocrystals with high concentration have great toxicity to biological tissues. Therefore, in order to further increase the detection limit of gas detectors based on upconverting nanomaterials, the fluorescence efficiency of the upconverting nanomaterials must continue to increase.

Disclosure of Invention

In order to solve the technical problems, the application provides a core-shell structured nanocrystalline material, which is prepared from a CaClF: coating an inert shell layer outside the Bi/Er nano particles to obtain the following CaClF: Bi/Er @ CaClF nanocrystals; the application also provides a preparation method and application of the nanocrystalline material, and after the nanocrystalline material is wrapped by the inert shell layer CaClF, luminescent ions are protected, the quenching effect on the surface is inhibited, the fluorescence efficiency and the fluorescence intensity of the nanocrystalline material are greatly improved, and the nanocrystalline material can be well applied to detection of gas molecules.

In order to achieve the above purpose, the present application adopts the following technical solutions:

a core-shell structure nanocrystalline material is provided, the molecular formula of the nanocrystalline is CaClF: Bi/Er @ CaClF.

Preferably, the molecular formula of the nanocrystal is CaClF: 10Bi/20Er @ CaClF.

Preferably, the nanocrystal is a water-soluble nanocrystal.

Further, the application provides a preparation method of the core-shell structure nanocrystalline material, which comprises the following steps:

1) adding bismuth acetate and erbium acetate with required doping amounts, 0.7 mmol of calcium acetate, 2 ml of trifluoroacetic acid, 2 ml of trichloroacetic acid, 10 ml of oleic acid and 25 ml of octadecene into a three-neck flask, stirring at 100 ℃ under the condition of nitrogen protection atmosphere, keeping the temperature for 90 minutes, then rapidly heating to 180 ℃, and keeping the temperature for 1 hour;

2) and after the solution is cooled to room temperature, washing for 3-5 times by using a mixed solution of ethanol and deionized water to obtain oily fluorochloride nanocrystalline CaClF: Bi/Er;

3) adding 2 ml of trichloroacetic acid into a mixed solvent of 10 ml of oleic acid and 25 ml of octadecene, heating to 110 ℃ to remove water, raising the temperature to 150 ℃ to react for 1 hour to form an oleic acid-rare earth complex, reacting 0.7 mmol of calcium acetate and 2 ml of trifluoroacetic acid into the mixed solution after cooling to room temperature, and adding an oily fluorochloride nanocrystal CaClF: adding Bi/Er into the reaction mixed solution, stirring for 2 hours, rapidly raising the temperature to 280 ℃ under the protection of nitrogen atmosphere, and reacting for 1 hour;

4) and after the solution is cooled to room temperature, washing for 3-5 times by using a mixed solution of ethanol and deionized water to obtain the core-shell structure nanocrystal CaClF: Bi/Er @ CaClF.

Preferably, the method further comprises a nanocrystalline surface treatment step: 10-100mg of prepared core-shell structure nanocrystalline CaClF: dispersing Bi/Er @ CaClF in a mixed solution of 1-3mL of ethanol and 0.2mol/L of HCl0.5-1mL, carrying out ultrasonic treatment on the mixed solution for 5-10min, and then adding ethanol for washing, centrifuging, drying and the like to obtain the water-based nanocrystal.

Further, the application provides an application of the nanocrystalline material in gas detection.

Further, the application provides an application of the nanocrystalline material in preparation of an oxygen sensor.

Further, the present application provides a gas sensor comprising the nanocrystalline material.

The present application prepares CaClF by a solvothermal process: and (3) treating the Bi/Er nanocrystalline by using an HCl solution to remove an oleic acid ligand on the surface of the nanocrystalline, wherein the nanocrystalline can be well dispersed in an aqueous solution. And then performing high-temperature coprecipitation on the mixture of CaClF: coating a layer of inert core shell on the surface of Bi/Er to obtain the following components: the core-shell structure of the Bi/Er @ CaClF nanocrystalline material modifies the surface defects, greatly improves the fluorescence efficiency of the nanocrystalline, and has the advantages of good fluorescence signal, high intensity and high detection limit.

Drawings

Fig. 1 (a) and (b) are CaClF: XRD pattern and transmission electron microscopy pattern of 10Bi/20Er, (c) is CaClF: transmission electron microscopy images of 10Bi/20Er @ CaClF.

FIG. 2 (a) CaClF: the up-conversion emission spectrum of 10Bi/20Er nanocrystalline under the excitation condition of 1530nm near-infrared laser, (b) the up-conversion emission intensity is along with Er³⁺The variation curve of ion doping concentration, (c) the physical schematic diagram of up-conversion luminescence machine, (d) the luminous intensity of the product along with the doping ion Bi³⁺The variation of (2).

FIG. 3 CaClF: 10Bi/20Er and CaClF: fluorescence emission spectrum of 10Bi/20Er @ CaClF nanocrystalline.

FIG. 4 shows a power density of 30W/cm²Sol (a) CaClF under excitation at 980 nm: 10Bi/20Er nanocrystalline and (b) core-shell structure CaClF: 10Bi/20Er @ CaClF nanocrystalline.

Fig. 5 CaClF: and (3) performing room-temperature fluorescence emission spectrum on the 10Bi/20Er @ CaClF nanocrystal under different concentrations of oxygen.

Detailed Description

1. Experimental part

1.1 Main instruments and reagents:

bismuth acetate (99.0%), trichloroacetic acid (99.0%), trifluoroacetic acid (99.0%), calcium acetate (99.0%), erbium acetate (99.9%), oleic acid (90.0%), and octadecene (90.0%) were purchased from Sigma-Aldrich, oxygen from kyotong gas limited, and anhydrous ethanol, concentrated hydrochloric acid, and ethyl cellulose from the national pharmaceutical group chemical agents limited.

1.2 CaClF: preparing Bi/Er @ CaClF nanocrystals:

the method comprises the following steps of mixing the components of CaClF: taking 10Bi/20Er @ CaClF nanocrystals as an example, 0.1 mmol of bismuth acetate, 0.7 mmol of calcium acetate, 0.2 mmol of erbium acetate, 2 ml of trifluoroacetic acid, 2 ml of trichloroacetic acid, 10 ml of oleic acid and 25 ml of octadecene are added into a three-neck flask, stirred and kept at 100 ℃ for 90 minutes under the condition of nitrogen protection atmosphere, and then rapidly heated to 180 DEG C

And incubated for 1 hour. After the solution is cooled to room temperature, washing the product for 3-5 times by using a mixed solution of ethanol and deionized water; adding 2 ml of trichloroacetic acid into a mixed solvent of 10 ml of oleic acid and 25 ml of octadecene, heating to 110 ℃ to remove water, raising the temperature to 150 DEG CReacting for 1 hour to form an oleic acid-rare earth complex, cooling to room temperature, reacting 0.7 mmol of calcium acetate and 2 ml of trifluoroacetic acid in the mixed solution, and adding an oily fluorochloride nanocrystal CaClF: adding Bi/Er into the reaction mixed solution, stirring for 2 hours, rapidly raising the temperature to 280 ℃ under the protection of nitrogen atmosphere, and reacting for 1 hour; and after the solution is cooled to room temperature, washing for 3-5 times by using a mixed solution of ethanol and deionized water to obtain the core-shell structure nanocrystal CaClF: Bi/Er @ CaClF.

And doping the sample with ions of different concentrations or species by changing the corresponding ion concentration or species in the precursor solution.

And (3) surface treatment of the nanocrystalline: dispersing 10-100mg of nanocrystal in a mixed solution of 1-3mL of ethanol and HCl (0.2 mol/L,0.5-1 mL), carrying out ultrasonic treatment on the mixed solution for 5-10min, and then adding ethanol for washing, centrifuging, drying and the like to obtain the water-based nanocrystal.

1.3 characterization Instrument

X-ray diffraction patterns (bruker d8Advance, Cu-K α (λ =1.5405 a)), transmission electron microscope (TEM, feitecnag 2F20), spectrometer (FLUROHUB-B, horiba jobinyvon), ultraviolet lamp power 50W, 1530nm near infrared laser (power range 0-1W).

Preparation of X-ray diffraction samples: paving the dried nanocrystalline in the groove of the sample support;

preparation of transmission electron microscope samples: dissolving all the nanocrystals synthesized in each time in 4 ml of ethanol solution, and dropping 3-6 drops of liquid on the ultrathin carbon film after ultrasonic treatment for 5 minutes.

1.4 core-shell structure nanocrystalline morphology, size contrast

CaClF: the X-ray diffraction pattern of the 10Bi/20Er nanocrystal is shown in figure 1a, all diffraction peaks correspond to JCPDS24-0185 number of standard PDF card one to one, and no redundant diffraction peaks exist, so that the product obtained by the method is a pure hexagonal phase. The transmission electron microscope analysis result is shown in figure 1b, which shows that the product is uniform block and has better dispersibility. It should be noted that the crystal structure of the nanocrystals was not changed after the hydrochloric acid treatment. As shown in fig. 1c, is a core shell CaClF: a transmission electron microscope photo of the 10Bi/20Er @ CaClF nanocrystal shows that the appearance size of the core-shell structure nanocrystal is more uniform and spherical, the average size of particles is increased to 29nm, and the fact that a shell layer with the thickness of 8nm is successfully and epitaxially grown on the surface of the nanocrystal core is also shown, and the core-shell structure has better crystallization degree after coating.

1.5 core-shell structure CaClF: 10Bi/20Er @ CaClF enhanced up-conversion fluorescence

Under the excitation condition of 1530nm near infrared light, the ratio of CaClF: the 10Bi/20Er nanocrystals showed strong up-conversion luminescence in the green and red regions (FIG. 2 a), with green light corresponding to Er³⁺Transition of ion 2H11/2/4S3/2 → 4I15/2, red light corresponding to Er³⁺Transition of ion 4F9/2 → 4I 15/2. With Er³⁺When the ion concentration is increased from 5 to 20mol%, the absorption capacity of the nanocrystalline on incident photons is increased, so that the luminous intensity is obviously enhanced, and when the Er is used³⁺Ion concentration of over 20mol%, Er³⁺The probability of radiationless cross relaxation between ions increases, leading to a decrease in the luminescence intensity (fig. 2 b). The above luminescence mechanism is explained as follows: under the condition of 1530nm near infrared light excitation, after an electron at a 4I15/2 ground state energy level absorbs an incident photon, the electron transits to a 4I13/2 energy level, because rare earth ions have longer fluorescence life at an excited state energy level, the energy level continues to absorb the next incident photon, the electron transits to a 4F9/2 energy level, when the electron returns to the ground state, a red photon is emitted, if the electron at the 4F9/2 energy level relaxes to the 4I9/2 energy level without radiation and absorbs the next incident photon, the electron transits to a 4F9/2 energy level, and after the electron relaxes to a 2H11/2/4S3/2 energy level without radiation, the electron returns to the ground state to emit green light (FIG. 2 c). By Bi³⁺Ion doping, Er³⁺The up-conversion luminous intensity of ions is obviously enhanced when Bi³⁺At an ion doping concentration of 10%, the total luminescence intensity increased by a factor of about 5 (fig. 2 d).

The CaClF can be seen in fig. 3: the core-shell structure nanocrystalline ratio of 10Bi/20Er @ CaClF is CaClF: the fluorescence intensity of the 10Bi/20Er nanocrystal is 10 times greater, which shows that the coating structure can greatly enhance the upconversion fluorescence intensity. In addition, the shapes of the fluorescence spectra of the two types of nanocrystals are approximately the same, but the fluorescence intensity is obviously changed, and the main reason of the enhancement is that after the shell layer is coated, luminescent ions on the surface are transferred to the inside to isolate rare earth ions on the surface from high-acoustic groups on the surface, and particularly, the surface defects are greatly reduced.

FIG. 4 shows sol (a) CaClF under excitation of 980 nm laser at a power density of 30W/cm 2: 10Bi/20Er nanocrystalline and (b) core-shell structure CaClF: digital photographs of up-converted fluorescence of 10Bi/20Er @ CaClF nanocrystals. The sharp increase in upconversion fluorescence can be clearly seen with the naked eye.

1.6 core-shell structure nanocrystalline oxygen detection experiment

In gas detection, oxygen detection is important, especially for the semiconductor industry, and in application, inert gas is generally used to protect the surface of a material, and even a small amount of oxygen introduced into a system can cause the surface of the material to be damaged by oxidation, so that it is important to be able to accurately detect the concentration of oxygen in situ.

And (3) carrying out core-shell structure CaClF: the 10Bi/20Er @ CaClF nanocrystals are fixed on the ethyl cellulose film, when the nanocrystals are in contact with oxygen molecules, the oxygen molecules are firstly physically adsorbed to the surfaces of the nanocrystals, and then the oxygen molecules capture electrons to form chemically adsorbed oxygen anions, so that the quenching effect of the surfaces of the nanocrystals is reduced, and the rapid response is probably caused by the small sizes of the nanocrystals. As shown in FIG. 4, the oxygen sensor prepared from the nanocrystal can accurately detect 0-100% of O₂。

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present disclosure, including any person skilled in the art, having the benefit of the present disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art. The general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A core-shell structure nanocrystalline material is characterized in that the molecular formula of the nanocrystalline is CaClF: Bi/Er @ CaClF.

2. The core-shell structure nanocrystal material of claim 1, wherein a molecular formula of the nanocrystal is CaClF: 10Bi/20Er @ CaClF.

3. The core-shell structure nanocrystal material of claim 1, wherein the nanocrystal is a water-soluble nanocrystal.

4. The preparation method of the core-shell structure nanocrystalline material according to claim 1 or 2, characterized in that the method comprises the following steps:

5. The method of claim 4, further comprising a step of surface treatment of the nanocrystals: 10-100mg of prepared core-shell structure nanocrystalline CaClF: dispersing Bi/Er @ CaClF in a mixed solution of 1-3mL of ethanol and 0.2mol/L of HCl0.5-1mL, carrying out ultrasonic treatment on the mixed solution for 5-10min, and then adding ethanol for washing, centrifuging, drying and the like to obtain the water-based nanocrystal.

6. Use of a nanocrystalline material according to any one of claims 1-3 for gas detection.

7. Use of a nanocrystalline material according to any one of claims 1-3 in the preparation of an oxygen sensor.

8. A gas sensor comprising the nanocrystalline material of any one of claims 1-3.