Rare earth doped lead-free double perovskite material and application thereof in temperature sensing and photochromism

Abstract

The invention discloses a rare earth doped lead-free double perovskite material and a preparation method and application thereof. According to the invention, a simple hydrothermal method is adopted to synthesize the Mn < 2 + > / Nd < 3 + > co-doped Cs2AgInCl6 double perovskite material. The preparation method disclosed by the invention is simple and convenient and low in cost, and the prepared double-perovskite material has a luminous characteristic from visible light to near infrared, a temperature sensing characteristic and reversible photochromic performance, and has wide application prospects and important social and economic values in the fields of high-precision temperature sensing detection, multiple fluorescent falsification prevention and the like.

Description

Technical Field

[0001] The present invention belongs to the field of rare earth doped fluorescent materials, and in particular relates to a lead-free double perovskite material based on rare earth doping, and a preparation method and application thereof. Background Art

[0002] Lead halide perovskites have been widely used in photodetectors, light-emitting diodes, and medical imaging in recent years due to their high fluorescence quantum efficiency, high carrier mobility, and bandgap flexibility. However, their poor structural stability and strong lead toxicity have greatly limited the further development of lead halide perovskites in the commercial field.

[0003] In recent years, lead-free double perovskites have attracted the attention of scientists due to their stable structure and weak toxicity. Rare earth-doped lead-free double perovskites have the advantages of multi-wavelength luminescence, photochromism, thermochromism and high stability, and show great potential in temperature sensing and fluorescent anti-counterfeiting applications. Therefore, the development of lead-free halide double perovskite materials with visible and near-infrared emission, temperature-dependent luminescence and reversible photochromism can not only make up for the defects of lead halide perovskites but also take into account their advantages, which is of great significance for the application expansion of optical materials.

[0004] The invention discloses a rare earth doped lead-free double perovskite material, which is synthesized by a simple hydrothermal method. 2+ / Nd 3+ Co-doped Cs 2 AgInCl 6 Double perovskite material, which has the characteristics of luminescence from visible light to near infrared; at the same time, using transition metal ions Mn 2+ With rare earth ion Nd 3+ The difference in temperature dependence enables accurate temperature sensing via the fluorescence intensity ratio (FIR) method; in addition, by 2 AgInCl 6 Mn doped 2+ The material can have reversible photochromic properties, which can produce a color change from light yellow to dark purple under ultraviolet irradiation, and can achieve reversible color recovery from dark purple to light yellow through heating or laser irradiation. Therefore, the temperature sensing, multi-wavelength luminescence and reversible photochromic properties of this material can be used in high-precision optical temperature sensing detection and multiple fluorescent anti-counterfeiting, which has broad application prospects and important social and economic value. Summary of the invention

[0005] The object of the present invention is to provide a rare earth-doped lead-free double perovskite material and a preparation method thereof, wherein the material has the characteristics of temperature sensing, multi-wavelength luminescence and photochromism, and can realize high-precision temperature sensing detection and multiple fluorescence anti-counterfeiting applications.

[0006] To achieve the above object, the present invention adopts the following technical solution: A rare earth-doped lead-free double perovskite material, specifically Mn 2+ / Nd 3+ Co-doped Cs 2 AgInCl 6 The material has multi-wavelength luminescence characteristics from visible light (640nm) to near infrared (890nm); at the same time, the transition metal ion Mn 2+ With rare earth ion Nd 3+ The difference in temperature dependence enables accurate temperature sensing detection by the fluorescence intensity ratio (FIR) method; in addition, by 2 AgInCl 6 (referred to as CAIC) doped with Mn 2+ The material can have reversible photochromic properties, which can produce a color change from light yellow to dark purple under ultraviolet light, and can achieve reversible color recovery from dark purple to light yellow through heating or laser irradiation.

[0007] The rare earth-doped lead-free double perovskite material is prepared by a hydrothermal method, which specifically includes the following steps: 1) Mix cesium chloride, silver chloride, indium chloride, manganese chloride and neodymium chloride in proportion, add hydrochloric acid and stir; 2) After stirring, the mixture is placed in a high pressure reactor for heating reaction; 3) After the reaction is completed, the mixture is cooled to room temperature, ultrasonically cleaned with isopropanol, and then dried to obtain the rare earth-doped lead-free double perovskite material.

[0008] Furthermore, the molar ratio of cesium chloride, silver chloride, indium chloride, manganese chloride and neodymium chloride used in step 1) is 2:1:(1- xy ): x : y , where 0< x <1,0< y <1. Preferably, x=0.1, y=0.3.

[0009] Furthermore, the mass ratio of hydrochloric acid to cesium chloride used in step 1) is about 13:1.

[0010] Furthermore, the stirring speed in step 1) is 450-500 r / min, and the stirring time is 3-5 h.

[0011] Furthermore, the heating reaction in step 2) is carried out at a temperature of 180-200° C. and for a time of 12-24 hours.

[0012] Furthermore, the drying temperature in step 3) is 60-100° C. and the drying time is 2-3 hours.

[0013] The rare earth doped lead-free double perovskite material has Mn 2+ Red light at 640nm and Nd 3+ Near-infrared light at 890nm, 1072nm, and 1357nm, thus having multi-wavelength luminescence performance from visible light to near-infrared light.

[0014] At the same time, Nd 3+ Ion 890nm luminescence and Mn 2+ There is a temperature-dependent relationship between the fluorescence intensity ratio of the ion 640nm light emission and different temperatures (273K~378K). This characteristic enables the rare earth-doped lead-free double perovskite material to have temperature sensing performance and can be used to achieve high-sensitivity temperature sensing detection.

[0015] In addition, the rare earth-doped lead-free double perovskite material appears light yellow under natural light and has a 2 When exposed to 365nm ultraviolet light for 5-60s, the color of the film can change from light yellow to dark purple, while when heated at 180℃ for 5min or at 100mW / cm 2 When irradiated with a 520nm laser for 5 minutes, its color can be restored from dark purple to light yellow. Therefore, it has photochromic properties and can be used as a photochromic material.

[0016] Furthermore, based on the multi-wavelength luminescence and reversible photochromic properties of the rare earth-doped lead-free double perovskite material, it can also be used for multiple fluorescent anti-counterfeiting.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention proposes a new rare earth doped lead-free halide double perovskite material (CAIC-Mn-Nd), which is doped with Mn 2+ and Nd 3+ The luminescence from visible light to near-infrared, temperature sensing and reversible photochromic properties are achieved in this way.

[0018] (2) The material obtained by the present invention exhibits color change under ultraviolet irradiation and reversible color recovery achieved by heat treatment or laser irradiation. This photochromic property provides a new security feature in the field of anti-counterfeiting and provides higher security and reliability for anti-counterfeiting technology.

[0019] (3) The present invention utilizes transition metal ions Mn 2+ With rare earth ion Nd 3+ The difference in temperature dependence enables the resulting material to perform accurate temperature sensing through the fluorescence intensity ratio (FIR) method, with a maximum relative sensitivity of up to 1.99%, which has potential application value in the field of high-precision non-contact optical temperature sensing.

[0020] (4) Compared with traditional lead-containing perovskite materials, the lead-free halide double perovskite material of the present invention is more environmentally friendly and meets the current demand for environmentally friendly materials. At the same time, the preparation process of the present invention is simple, easy to operate, and low in cost, and is suitable for promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the application principle of the rare earth-doped lead-free double perovskite material prepared by the present invention.

[0022] Figure 2 The luminescence principle diagram (a) and the photochromic principle diagram (b) of the rare earth-doped lead-free double perovskite material prepared by the present invention under 350 nm ultraviolet light excitation.

[0023] Figure 3 Near-infrared fluorescence spectra of single Nd-doped CAIC-30Nd and CAIC-10Mn-30Nd prepared in Example 1 (a) and their photochromic mechanism diagram (b).

[0024] Figure 4 This is the XRD pattern of CAIC-10Mn-30Nd prepared in Example 1.

[0025] Figure 5 This is the SEM image of CAIC-10Mn-30Nd prepared in Example 1.

[0026] Figure 6 Visible fluorescence spectrum (a) and near-infrared fluorescence spectrum (b) of CAIC-10Mn-30Nd prepared in Example 1.

[0027] Figure 7 The temperature-dependent luminescence spectrum (a) and the corresponding temperature sensing sensitivity (b) of CAIC-10Mn-30Nd in Example 2.

[0028] Figure 8 The CAIC-10Mn-30Nd in Example 3 at 3mW / cm 2 Power and photochromic process under 365nm UV light.

[0029] Fig. 9 This is a diagram of the multiple fluorescent anti-counterfeiting application of CAIC-10Mn-30Nd in Example 4. DETAILED DESCRIPTION

[0030] A rare earth-doped lead-free double perovskite material, the preparation of which comprises the following steps: 1) Cesium chloride, silver chloride, indium chloride, manganese chloride, and neodymium chloride are mixed in a molar ratio of 2:1:(1- xy ): x : y (0< x <1,0< y <1) Add to 50 mL polytetrafluoroethylene reaction liner for mixing, add hydrochloric acid (concentration 37%) about 13 times the mass of cesium chloride, add a magnet, and stir at a speed of 450-500 r / min for 3-5 hours; 2) After stirring, remove the magnet, place the liner containing the mixture into a high-pressure reactor, and place it in a high-temperature drying oven, heating at 180-200°C for 12-24 hours; 3) After the reaction is completed, cool to room temperature, use isopropanol ultrasonic cleaning to clean the residual hydrochloric acid 2-3 times (each ultrasonic cleaning for 10 min), and then dry in a vacuum drying oven at 60-100°C for 2-3 hours to obtain Mn 2+ / Nd 3+ Co-doped Cs 2 AgInCl 6 (Abbreviated as CAIC-Mn-Nd).

[0031] Figure 2 The luminescence principle diagram (a) and photochromic principle diagram (b) of CAIC-Mn-Nd prepared in the present invention under 350 nm ultraviolet light excitation. 2+ ions act as bridges to transfer the energy of CAIC excitons to Nd 3+ ions. Under 350 nm UV light excitation, electrons are excited from the CAIC valence band to the conduction band and then relax non-radiatively to the Mn 2+ of 4 T 1 state, emit Mn 2+ Ions at 640 nm 4 T 1 State to 6 A 1 At the same time, some of the Mn in the excited state 2+ The ions transfer energy to the Nd 3+ of 2 G 7 / 2 state, which then relaxes to 4 F 3 / 2 state and transition to 4 I 9 / 2 , 4 I 11 / 2 and4 I 13 / 2 state, emitting near-infrared light at 890 nm, 1072 nm, and 1357 nm (a). 2+ Doping for perovskite Cs 2 AgInCl 6 The photochromic phenomenon of the substrate plays an important role, because In 2+ Mn 2+ After replacement, it will be in Cs 2 AgInCl 6 In order to maintain the charge balance, a charge imbalance is generated in Cs 2 AgInCl 6 A small amount of Cl vacancies will be formed in the lattice. When CAIC-Mn-Nd is irradiated by ultraviolet light, the electrons in the valence band absorb the energy of photons and enter the conduction band. At the same time, Cs 2 AgInCl 6 Defect states in the lattice capture some electrons from the conduction band to form F - Color centers, resulting in color change (b).

[0032] In order to make the contents of the present invention easier to understand, the technical solution of the present invention is further described below in conjunction with specific implementation methods, but the present invention is not limited thereto.

[0033] Example 1: Hydrothermal synthesis of Mn 2+ / Nd 3+ Co-doped Cs 2 AgInCl 6 Double perovskite materials 2 mmol of cesium chloride, 1 mmol of silver chloride, 0.6 mmol of indium chloride, 0.1 mmol of manganese chloride, and 0.3 mmol of neodymium chloride were added to a 50 mL polytetrafluoroethylene reaction liner, and 10 mL of HCl (concentration 37wt%) was added. A magnetic bar was added and stirred on a magnetic stirrer at a speed of 450 r / min for 3 hours. After stirring, the magnetic bar was removed, and the polytetrafluoroethylene reaction liner was transferred to a 50 mL high-pressure reactor, which was placed in a high-temperature drying oven and heated at 180°C for 12 hours. After the reaction was completed, it was cooled to room temperature, and the sample was transferred to a 10 mL centrifuge tube. The residual hydrochloric acid was ultrasonically cleaned twice with 3 mL of isopropanol (each ultrasonic cleaning was 10 minutes), and the isopropanol after cleaning was removed. The product CAIC-10Mn-30Nd was obtained after drying at 80°C in a vacuum drying oven for 2 hours.

[0034] Figure 3The near-infrared fluorescence spectra of CAIC-30Nd doped with Nd and CAIC-10Mn-30Nd prepared in this example are shown in Figure 1. As can be seen from the figure, the luminescence effect of the sample can be significantly enhanced by the sensitization enhancement of Mn.

[0035] Figure 4 This is the XRD pattern of CAIC-10Mn-30Nd prepared in this example. As can be seen from the figure, all the diffraction peaks of the sample are consistent with Cs 2 AgInCl 6 The structure of the standard card (PDF#244519) is consistent with that of the standard card (PDF#244519), indicating that Mn is doped 2+ and Nd 3+ The ions are not introduced into the impurity phase.

[0036] Figure 5 This is a SEM image of CAIC-10Mn-30Nd prepared in this example. The image shows that the obtained CAIC-Mn-Nd has a regular octahedral structure, and its crystal size is about 100 μm.

[0037] Figure 6 The visible fluorescence spectrum (a) and near-infrared fluorescence spectrum (b) of CAIC-10Mn-30Nd prepared in this example. As shown in the figure, under 350nm ultraviolet light excitation, CAIC-10Mn-30Nd exhibits a broad red light emission band at 640nm, which can be attributed to the Mn 2+ Ionic 4 T 1 → 6 A 1 At the same time, CAIC-10Mn-30Nd generates near-infrared light at 890nm, 1072nm, and 1357nm in the near-infrared region, which come from Nd 3+ Ionic 4 F 3 / 2 → 4 I 9 / 2 , 4 I 11 / 2 , 4 I 13 / 2 The transition.

[0038] Example 2: High-precision temperature sensing through fluorescence intensity ratio (FIR) method The variable temperature luminescence spectrum of the CAIC-10Mn-30Nd sample prepared in Example 1 was tested in the temperature range of 273K~378K using a fluorescence spectrometer and a variable temperature accessory, and the Nd 3+ Ion 890nm luminescence and Mn 2+ Fluorescence intensity ratio of ions at 640 nm FIR, calculate the maximum absolute sensitivity of CAIC-10Mn-30Nd temperature sensor according to formula (2) and (3) respectively S a and maximum relative sensitivity S r , the results are shown in Figure 7 .

[0039] , in I Nd and I Mn Nd 3+ The emission intensity at 890 nm and Mn 2+ Emission intensity at 640 nm. k is the Boltzmann constant, A and B is the fitting constant, ΔE is the energy difference between the thermally coupled energy levels.

[0040] Figure 7 The temperature-dependent luminescence spectrum of the prepared CAIC-10Mn-30Nd (a), Nd 3+ Ion 890nm luminescence and Mn 2+ The fluorescence intensity ratio of ions at 640nm (b) and the corresponding temperature sensing sensitivity (c). As shown in the figure, in the temperature range of 273K~378K, the Mn in CAIC-10Mn-30Nd 2+ The 640nm emission intensity of Nd 3+ The 890nm luminescence intensity of the ions decreases slightly with increasing temperature, proving that CAIC-10Mn-30Nd has good temperature sensing properties (a). FIR Good fit with temperature (R 2 =0.999)(b), maximum absolute sensitivity S a and maximum relative sensitivity S r are 3.76% and 1.99% (c) respectively. 3+ Ion 890nm luminescence and Mn 2+ The temperature dependence between the fluorescence intensity ratio of ion 640nm emission and different temperatures (273K~378K) enables high-sensitivity temperature sensing detection.

[0041] Example 3: Reversible photochromic properties of CAIC-Mn-Nd The CAIC-10Mn-30Nd prepared in Example 1 was heated at 3 mW / cm2 The film was irradiated with 365nm ultraviolet light and its photochromic process was recorded.

[0042] Figure 8 The photochromic process of CAIC-10Mn-30Nd is shown in the figure. As the UV irradiation time increases from 5s to 60s, the color of the sample gradually changes from light yellow to dark purple; while by heating at 180℃ for 5min or at 100mW / cm 2 After irradiation with 520nm laser for 5min, the color of the sample can be restored from dark purple to light yellow.

[0043] Example 4: Multiple fluorescence anti-counterfeiting applications of CAIC-Mn-Nd The CAIC-Mn-Nd sample appears light yellow under natural light, and can emit Mn 2+ Ion red light, and the color changes from light yellow to dark purple; after heating at 180℃ or irradiation with 520nm laser, its color can be restored from dark purple to the original light yellow. 3+ The ions emit near-infrared light and are captured by a near-infrared camera. Therefore, CAIC-Mn-Nd has good photochromic properties as well as red and near-infrared properties, and has potential applications in the field of multiple fluorescent anti-counterfeiting.

[0044] The digital pattern "8" (where "4" is composed of CAIC-Mn-Nd) was formed using CAIC-Mn and CAIC-10Mn-30Nd prepared in Example 1 to investigate the application of CAIC-Mn-Nd in multiple fluorescent anti-counterfeiting applications. The results are shown in FIG. Fig. 9 .like Fig. 9 As shown, the digital pattern "8" appears light yellow under natural light and emits Mn under ultraviolet light. 2+ Ion red light produces photochromism from light yellow to dark purple. At the same time, the dark purple can be restored to the original light yellow by heating at 180℃ or irradiating with 520nm laser. 3+ The near-infrared luminescence of the ions can capture the encrypted information "4" under a near-infrared camera (CAIC-Mn does not have near-infrared luminescence and is invisible to near-infrared cameras), which confirms the great potential of CAIC-Mn-Nd in multiple fluorescent anti-counterfeiting applications, which can effectively expand the scope of anti-counterfeiting technology and provide higher security.

[0045] In summary, the CAIC-Mn-Nd double perovskite material synthesized by a simple hydrothermal method in the present invention has luminescence characteristics from visible to near-infrared; at the same time, the transition metal ion Mn 2+ With rare earth ion Nd 3+The difference in temperature dependence enables accurate temperature sensing via the fluorescence intensity ratio method; in addition, by doping CAIC with Mn 2+ It can achieve reversible photochromic properties, which can produce a color change from light yellow to dark purple under ultraviolet irradiation, and can achieve reversible color recovery from dark purple to light yellow by heating or laser irradiation. Therefore, the temperature sensing, multi-wavelength luminescence and reversible photochromic properties of this material make it have broad application prospects and important social and economic value in the fields of high-precision optical temperature sensing detection and multiple fluorescent anti-counterfeiting.

[0046] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A rare earth-doped lead-free double perovskite material, characterized in that: The material is specifically Mn 2+ / Nd 3+ Co-doped Cs2AgInCl6, this material has multi-wavelength luminescence properties from visible light to near-infrared light, temperature sensing properties and reversible photochromic properties.

2. A method for preparing the rare earth-doped lead-free double perovskite material according to claim 1, characterized in that: The rare earth-doped lead-free double perovskite material is prepared by a hydrothermal method.

3. The method for preparing the rare earth-doped lead-free double perovskite material according to claim 2, characterized in that: The following steps are involved: 1) Mix cesium chloride, silver chloride, indium chloride, manganese chloride and neodymium chloride in proportion, add hydrochloric acid and stir; 2) After stirring, the mixture is placed in a high pressure reactor for heating reaction; 3) After the reaction is completed, the mixture is cooled to room temperature, ultrasonically cleaned with isopropanol, and then dried to obtain the rare earth-doped lead-free double perovskite material.

4. The method for preparing the rare earth doped lead-free double perovskite material according to claim 3, characterized in that: The molar ratio of cesium chloride, silver chloride, indium chloride, manganese chloride and neodymium chloride used in step 1) is 2:1:(1- xy ): x : y , where 0< x <1,0< y <1.

5. The method for preparing the rare earth doped lead-free double perovskite material according to claim 3, characterized in that: The mass ratio of hydrochloric acid to cesium chloride used in step 1) is 13:

1.

6. The method for preparing the rare earth doped lead-free double perovskite material according to claim 3, characterized in that: The stirring speed in step 1) is 450-500 r / min, and the stirring time is 3-5 h.

7. The method for preparing the rare earth doped lead-free double perovskite material according to claim 3, characterized in that: The temperature of the heating reaction in step 2) is 180-200°C and the time is 12-24 hours.

8. Use of the rare earth doped lead-free double perovskite material as claimed in claim 1 in temperature sensing.

9. Use of the rare earth doped lead-free double perovskite material as claimed in claim 1 in multiple fluorescent anti-counterfeiting.

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