Environment-friendly self-reference low-temperature temperature sensor based on AgInS2 / ZnS quantum dots

Abstract

The invention discloses a preparation method of an environment-friendly AgInS2 / ZnS quantum dot for self-reference fluorescence temperature sensing in a low-temperature range of 80K to 300K. The used AgInS2 / ZnS quantum dots are simple in preparation process and low in energy consumption, and do not contain heavy metal elements which have potential hazards to human bodies or the environment. The photoluminescence emission spectrum of the quantum dot has a remarkable temperature dependence characteristic, the luminous intensity is sequentially reduced along with the temperature rise, the red shift of an emission peak is weak along with the temperature rise, and the half-peak width change is not obvious. Two equal-width narrow spectrum windows are selected on the left side and the right side of an emission peak, and curve areas S1 and S2 in the left narrow window and the right narrow window selected at different temperatures are calculated through integration. R = (S1-S2) / (S1 + S2) is defined. Through fitting, R and the temperature are in a linear relation. The linear relation is a low-temperature self-reference fluorescence temperature sensing principle. Based on the characteristics, the environment-friendly quantum dot can be used as a core material of a self-reference temperature sensor, and an environment-friendly and efficient feasible scheme is provided for low-temperature detection.

Description

Technical Field

[0001] This invention relates to a fluorescent temperature sensor, and more particularly to an environmentally friendly quantum dot self-reference intensity type low-temperature temperature sensor, belonging to the field of optoelectronic sensing applications. Background Technology

[0002] In recent years, the modernization of my country's industry and the continuous high-speed growth of the electronic information industry have driven the rapid rise of the sensor market. Temperature sensors are used in consumer electronics, smart homes, industrial and agricultural commerce, military industry, aerospace and other fields to measure, detect, and provide auxiliary compensation for temperature in normal or extreme environments.

[0003] In recent years, semiconductor quantum dots, as a novel luminescent material, have been widely used in fields such as optical amplifiers, optical switches, cell biology, genomics, and proteomics. Optical sensors and temperature sensors developed using the photoluminescence properties of quantum dots have also exhibited a range of excellent performance characteristics. Furthermore, quantum dots offer high fluorescence yield, tunable emission wavelengths, and simple synthesis methods. Among them, group I-III-VI quantum dots have attracted significant attention due to their absence of harmful heavy metals, making them environmentally friendly materials.

[0004] The self-reference intensity-type temperature sensor proposed in this paper is insensitive to light source fluctuations, transmission losses, detector aging, etc., and provides stable and reliable measurements. It avoids many error sources in absolute intensity measurements and has high temperature measurement accuracy. Description

[0005] The purpose of this invention is to propose an environmentally friendly method for preparing quantum dots for use in low-temperature fluorescence self-reference intensity temperature sensors. This environmentally friendly quantum dot preparation process is simple and energy-efficient. The prepared quantum dots exhibit the following characteristics: the emission peak width, emission peak position, and spontaneous emission fluorescence intensity are temperature-dependent.

[0006] The present invention adopts the following technical solution.

[0007] An environmentally friendly, self-referenced intensity quantum dot for low-temperature fluorescence temperature sensing, characterized in that its preparation method includes the following steps: (1) Preparation of AgInS2 quantum dots: Silver nitrate (AgNO3), indium acetylacetone (In(acac)3), oleic acid (OA) and octadecene (ODE) were placed in a three-necked flask. The mixture was purged with nitrogen at room temperature for 30 min. The solution was then heated to 90°C within 5 min. Dodecanethiol (DDT) was injected into the reaction flask. Next, the mixture was heated to 130°C. A sulfur (S) source was injected into the three-necked flask. The reaction was continued for 12 min to obtain AgInS2 quantum dot stock solution. (2) Preparation of AgInS2 / ZnS quantum dots: Zn2+ The precursor solution was injected into the AgInS2 quantum dot stock solution at 130℃ and kept at that temperature for 90 min. After the reaction was completed, the AgInS2 / ZnS quantum dot stock solution was obtained. (3) The AgInS2 / ZnS quantum dot stock solution was purified to obtain AgInS2 / ZnS quantum dots.

[0008] Specifically, in step (1) above, when preparing AgInS2 quantum dots, the amounts of In(acac)3, OA, ODE, DDT and S source added per 1 mmol of AgNO3 are 4 mmol, 0.47 mL, 8 mL, 1 mL and 1 part, respectively.

[0009] Specifically, the S source mentioned in step (1) above is prepared by dissolving 0.8 mmol of sulfur powder in 1.5 ml of oleylamine (OLA), heating to 90°C and maintaining for 20 min.

[0010] Specifically, the Zn mentioned in step (2) above 2+ The precursor solution is prepared as follows: for every 1 part of Zn 2+ The precursor solution was prepared by dissolving 0.4 mmol of zinc stearate (Zn(St)2) in 2 mmol of tri-n-octylphosphine (TOP) under a nitrogen atmosphere, heating to 100℃ and holding for 20 min, so that the solution changed from turbid to clear.

[0011] Specifically, the preparation of AgInS2 / ZnS quantum dots in step (2) above is characterized by injecting 1 part of ZnS based on the AgInS2 quantum dot stock solution prepared according to step (1) for every 1 mmol AgNO3. 2+ Precursor fluid.

[0012] Specifically, the purification of AgInS2 / ZnS quantum dot stock solution described in step (3) above is as follows: the obtained AgInS2 / ZnS quantum dot stock solution is centrifuged at 5000 rpm for 3 min, and the supernatant is collected; the supernatant, n-hexane, and ethanol are mixed in a ratio of 1:1:3, centrifuged at 7000 rpm for 5 min, and the precipitate is collected; the precipitate is dispersed in n-hexane solution for testing.

[0013] The AgInS2 / ZnS quantum dots prepared according to the above steps were subjected to thermochromic fluorescence testing: under 365 nm excitation light, fluorescence spectra were measured at several temperature points within the temperature range of 80 K to 300 K. The obtained thermochromic fluorescence spectra are shown below. Figure 1 As shown.

[0014] The AgInS2 / ZnS quantum dots prepared according to the steps described above have the following thermochromic fluorescence spectral characteristics: when excited by 365nm excitation light, they exhibit fluorescence emission with an emission peak of 581-587nm in the ambient temperature range of 80K-300K.

[0015] The AgInS2 / ZnS quantum dots prepared according to the steps described above are characterized in that, under 365nm excitation light, as the temperature increases from 80K to 300K, the emission fluorescence intensity decreases sequentially, the emission peak red-shifts by 6nm, and the full width at half maximum (FWHM) increases to 3nm.

[0016] Based on the temperature-dependent fluorescence spectra of AgInS2 / ZnS quantum dots, especially the characteristic that their fluorescence emission intensity decreases with temperature, we propose... A self-reference temperature sensing measurement method based on the thermochromic emission spectrum of this quantum dot is proposed.

[0017] Two narrow spectral windows with widths of 5–10 nm were symmetrically selected on both sides of the emission peak of the fluorescence spectrum of AgInS2 / ZnS quantum dots at various temperatures, and the surface areas S1 and S2 within the windows were calculated by integration. Figure 2 As shown.

[0018] Define R = (S1 - S2) / (S1 + S2). After fitting, R shows a linear relationship with temperature, as shown below. Figure 3 As shown in the figure, this linear relationship is based on the principle of low-temperature self-reference fluorescence temperature sensing. Attached Figure Description

[0019] The accompanying drawings are primarily intended to illustrate the following characteristics of the prepared quantum dots: temperature dependence of fluorescence intensity and low-temperature self-reference fluorescence temperature sensing principle, and do not constitute an undue limitation on this invention.

[0020] Figure 1 The images show the fluorescence emission spectra of AgInS2 / ZnS quantum dots from top to bottom at 10 temperature points (80K, 100K, 130K, 155K, 180K, 205K, 230K, 250K, 275K, and 300K) under 365nm excitation light.

[0021] Figure 2 To select a window of 550–555 nm to the left of the emission peak in the fluorescence spectrum of AgInS2 / ZnS quantum dots and a window of 645–650 nm to the right, the area integrals under the spectral curves within these two narrow windows at different temperatures were used to obtain a series of S1 and S2 at different temperatures.

[0022] Figure 3 According to R = (S 1-The series of R values ​​are obtained by S2) / (S1+S2), and the results of fitting R with temperature are shown in the figure; and the fitting results are shown in the figure when the window is selected at (left: 550~560nm, right: 610~620nm) and (left: 570~580nm, right: 605~615nm). Detailed Implementation

[0023] Preparation of S source: Dissolve 0.8 mmol sulfur powder in 1.5 mmol oleylamine and heat to 90 °C for 20 min.

[0024] Preparation of Zn 2+ Precursor solution: Dissolve 0.4 mmol of zinc stearate in 2 mmol of tri-n-octylphosphine under vacuum conditions, and heat to 100°C. Keep it for 20 minutes, and the solution will change from cloudy to clear.

[0025] Preparation of AgInS2 quantum dots: 0.1 mmol silver nitrate, 0.4 mmol indium acetylacetonate, 0.47 mL oleic acid, and 8 mL octadecene were placed in a three-necked flask. The mixture was purged with nitrogen at room temperature for 30 min. The solution was then heated to 90 °C over 5 min. 1 mL of n-dodecyl mercaptan was injected into the reaction flask. The mixture was then heated to 130 °C. An S source was then rapidly injected into the reaction solution, and the reaction was allowed to proceed for 12 min.

[0026] Preparation of AgInS2 / ZnS quantum dots: After the synthesis of AgInS2 quantum dots, ZnS was added at 130℃. 2+ The precursor solution was injected into the AgInS2 core solution and kept at this temperature for 1.5 h to grow AgInS2 / ZnS quantum dots.

[0027] Purification: The synthesized AgInS2 / ZnS quantum dots were centrifuged at 5000 rpm for 3 min to remove impurities. The supernatant was then transferred to a centrifuge tube, and hexane and ethanol were added. The volume ratio of supernatant, hexane, and ethanol was 1:1:3. The mixture was centrifuged at 7000 rpm for 5 min to obtain the precipitate, which is the AgInS2 / ZnS quantum dots. The purified AgInS2 / ZnS quantum dots were dispersed in hexane for testing.

[0028] Test samples: hexane solutions of AgInS2 / ZnS quantum dots were excited using 365nm excitation light, and fluorescence spectra were measured at 10 temperature points: 80K, 100K, 130K, 155K, 180K, 205K, 230K, 250K, 275K, and 300K.

[0029] Two narrow windows of equal width (5–10 nm) are selected on either side of the emission peak in the thermochromic fluorescence spectrum. The area enclosed by the curves of the selected narrow windows at different temperatures is calculated, resulting in a series of values ​​S1 and S2. R is defined as (S1-S2) / (S1+S2). After fitting, R shows a linear relationship with temperature. This linear relationship is based on the principle of low-temperature self-reference fluorescence temperature sensing.

[0030] A window of 550–555 nm was selected to the left of the emission peak in the fluorescence spectrum of AgInS2 / ZnS quantum dots, and a window of 645–650 nm was selected to the right. The calculated fit yielded R = -8.33 × 10⁻⁶. -4 T+0.25, this linear expression of R value and temperature T can be used for self-reference fluorescence temperature sensing and measurement needs in the temperature range of 80 to 300K.

[0031] A window of 550–560 nm was selected to the left of the emission peak in the fluorescence spectrum of AgInS2 / ZnS quantum dots, and a window of 610–620 nm was selected to the right. The calculated fit yielded R = -5.10 × 10⁻⁶. -4 T-0.13, this linear expression of R value and temperature T can be used for self-reference fluorescence temperature sensing and measurement needs in the temperature range of 80 to 300K.

[0032] A window of 570–580 nm was selected to the left of the emission peak in the AgInS2 / ZnS quantum dot fluorescence spectrum, and a window of 605–615 nm was selected to the right. The calculated fit yielded R = -3.10 × 10⁻⁶. -4 T+0.14, this linear expression of R value and temperature T can be used for self-reference fluorescence temperature sensing and measurement needs in the temperature range of 80 to 300K.

[0033] It should be noted that those skilled in the art can make various improvements and modifications without departing from the concept of this invention, and these improvements and modifications are also considered to be within the scope of protection of this invention.

Claims

1. An environmentally friendly self-referenced quantum dot for low temperature fluorescence temperature sensing, characterized in that, The preparation method comprises the following steps: (1) preparing AgInS2 quantum dots: silver nitrate (AgNO3), indium acetylacetonate (In(acac)3), oleic acid (OA) and octadecene (ODE) are loaded into a three-necked flask, the mixture is purged with nitrogen for 30 minutes at room temperature, then the solution is heated to 90°C within 5 minutes, dodecanethiol (DDT) is injected into the reaction bottle, then the mixture is heated to 130°C, a sulfur (S) source is injected into the three-necked flask, and the reaction is continued for 12 minutes to prepare an AgInS2 quantum dot stock solution; (2) Preparation of AgInS2 / ZnS quantum dots: Zn 2+ The precursor solution was injected into AgInS2quantum dot stock solution at 130°C, and incubated for 90 min. After the reaction was completed, AgInS2 / ZnS quantum dot stock solution was obtained. (3) purifying the AgInS2 / ZnS quantum dot stock solution to obtain AgInS2 / ZnS quantum dots.

2. The AgInS2 quantum dots prepared according to claim 1 step (1), characterized in that, The amounts of In(acac)3, OA, ODE, DDT and the S source added per 1 mmol of AgNO3 are 4 mmol, 0.47 mL, 8 mL, 1 mL and 1 part, respectively.

3. According to the S source in step (1) of claim 1, the preparation method of 1 part of the S source is as follows: 0.8 mmol of sulfur powder is dissolved in 1.5 ml of oleylamine (OLA) and heated to 90°C and kept for 20 min.

4. Zn according to claim 1, step (2) 2+ Precursor solution, 1 part Zn 2+ The precursor solution was prepared by dissolving 0.4 mmol of zinc stearate (Zn(St)2) in 2 mmol of tri-n-octylphosphine (TOP) under nitrogen atmosphere, and heating to 100 °C for 20 min, until the solution changed from turbid to clear.

5. The AgInS2 / ZnS quantum dots prepared according to step (2) of claim 1, wherein, Based on per 1 mmol AgNO3, the amount of AgInS2 quantum dot stock solution prepared according to step (1) in claim 1, inject 1 part of Zn 2+ Precursor solution.

6. According to the purification of the AgInS2 / ZnS quantum dot stock solution in step (3) of claim 1, the specific process is as follows: the obtained AgInS2 / ZnS quantum dot stock solution is centrifuged at a speed of 5000 rpm for 3 min, and the supernatant is taken; the supernatant, n-hexane and ethanol are mixed in a ratio of 1:1:3, and centrifuged at a speed of 7000 rpm for 5 min, and the precipitate is taken to obtain AgInS2 / ZnS quantum dots; the AgInS2 / ZnS quantum dots are dispersed in n-hexane solution for testing.

7. The AgInS2 / ZnS quantum dots prepared by the preparation method according to claim 1, characterized in that, Under the excitation of 365 nm excitation light, there is a fluorescence emission peak at 581-587 nm in the temperature range of 80K-300K.

8. The AgInS2 / ZnS quantum dots prepared by the preparation method according to claim 1, characterized in that, Under the excitation of 365 nm excitation light, the emission fluorescence intensity decreases in turn as the temperature increases from 80K to 300K, and the emission peak only has a red shift of 6 nm; the half peak width only increases by 3 nm.

9. The AgInS2 / ZnS quantum dots prepared by the preparation method according to claim 1, characterized in that, Two equal-width narrow spectral windows are selected around the peak of the AgInS2 / ZnS quantum dots, a number of temperature points in the temperature range of 80K-300K are selected, the spectral line integral areas S1 and S2 in the selected equal-width narrow spectral windows are calculated, after fitting, R=(S1-S2) / (S1+S2) is linearly related to the temperature, and can be used for self-reference fluorescence temperature sensing and measurement requirements in the temperature range of 80-300K.

10. The narrow spectral window of claim 9, wherein, The window width is 5-10 nm.

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