A near-infrared film and a method for preparing the same

Abstract

The application discloses a near-infrared film and a preparation method thereof. The near-infrared film is prepared by the following method: mixing cadmium bromide, antimony bromide and propyl triphenyl phosphonium bromide, wherein the ratio of the sum of the molar amounts of the cadmium bromide and the antimony bromide to the molar amount of the propyl triphenyl phosphonium bromide is 1:2.001; the molar amount of the antimony bromide is 0.1% to 50% of the molar amount of the cadmium bromide; then adding a polar solvent to dissolve and filter to obtain a precursor solution, and finally using the precursor solution to prepare the near-infrared film. The application introduces the antimony element into the organic-inorganic hybrid cadmium halide, combines ligand regulation engineering and halogen regulation engineering, and prepares a novel near-infrared film. The near-infrared film realizes near-infrared light emission with a peak position of 760 nm for the first time by using the antimony element, the light emission is not affected by a matrix, the light emission efficiency is high, the stability is high, the film forming performance of the film is good, the preparation method is simple and easy to implement, and the near-infrared film has low cost and large-scale production potential.

Description

Technical Field

[0001] This application relates to the field of infrared imaging, and more particularly to a near-infrared thin film and its preparation method. Background Technology

[0002] The near-infrared region (typically referring to the 700–1000 nm wavelength range) is a crucial spectral window for biomedical photonics applications. Near-infrared light in this band has good penetrating power into biological tissues (such as skin and muscle) while being absorbed relatively little by components in the blood such as hemoglobin and water. Therefore, it is often referred to as the "biological tissue optical window." This characteristic makes it play an important role in non-invasive biomedical imaging (such as brain functional imaging), pulse oximetry monitoring, and superficial vascular imaging, among other biomedical diagnostic and monitoring technologies.

[0003] Currently, the material systems capable of achieving efficient light emission in this wavelength band are still relatively limited. Materials such as GaAs and InGaAs, which emit light in the near-infrared region I, typically have emission wavelengths fixed at specific values ​​such as 850nm and 940nm. They are widely used in the manufacture of LEDs and VCSEL lasers, serving as core light sources for applications such as 3D sensing and remote control. In bioimaging applications, small organic molecule dyes, such as indocyanine green (ICG) and certain cyanine dyes, are mainly used. These dyes have absorption and emission peaks in the 800-850nm wavelength range and have been applied in angiography and lymphography. However, the variety of light-emitting materials in the near-infrared region I is relatively small, and further development is needed.

[0004] In the field of inorganic luminescent materials, antimony-based halides or antimony-doped materials, due to their unique electronic structure, tunable band structure, and wide emission band, serve as excellent platforms for high-efficiency visible light luminescent materials, capable of preparing high-efficiency blue-green, yellow, orange, red, and white light sources. However, research on near-infrared luminescence based on antimony-based materials is extremely lacking, and a systematic material system has not yet been formed. A 2011 patent (CN 102002384 A) discloses the synthesis of KZn4Sb3O by a high-temperature solid-state reaction method. 12 It has an emission peak at 769 nm, but there are few in-depth studies and performance optimization reports since then. Although a literature in 2023 reported that antimony-doped tin halides can emit green, red and near-infrared light at the same time, the main emission body is located below 700 nm, which fails to effectively cover the core band of the near-infrared region I, especially above 700 nm.

[0005] In summary, the current selection of luminescent materials for the near-infrared 1 region is limited, and research on antimony-based material systems, which have broad potential for luminescence modulation, in this band is still in its infancy or nascent stage. Therefore, there is an urgent need to develop a novel, efficient near-infrared 1 luminescent material based on antimony-based materials with emission wavelengths in the 700–1000 nm range (especially above 750 nm) to fill the technological gap in this field. Summary of the Invention

[0006] One objective of this application is to provide a near-infrared thin film and a method for preparing the same, with the aim of providing a novel near-infrared thin film material that can be used for imaging.

[0007] To achieve the above objectives, the technical solution adopted in this application is: a near-infrared thin film and its preparation method, wherein the infrared thin film is prepared by the following method: S1: Cadmium bromide, antimony bromide, and propyltriphenylphosphine bromide are mixed, wherein the ratio of the sum of the molar amounts of cadmium bromide and antimony bromide to the molar amount of propyltriphenylphosphine bromide is 1:2.001; the molar amount of antimony bromide is 0.1% to 50% of the molar amount of cadmium bromide. S2: Dissolve and filter the precursor solution using a polar solvent; S3: Use this solution to prepare near-infrared thin films.

[0008] As a preferred embodiment, the polar solvent includes N,N-dimethylformamide or acetonitrile.

[0009] As a preferred embodiment, the dissolution method includes heating dissolution, magnetic stirring dissolution, heating and magnetic stirring dissolution, or ultrasonic dissolution.

[0010] As a preferred embodiment, the heating and melting temperature is not higher than 100°C.

[0011] As a preferred embodiment, the thin film preparation method includes spin coating, blade coating, drop coating, dip coating, or inkjet printing.

[0012] Compared with the prior art, the beneficial effects of this application are mainly reflected in the following aspects: 1. Excellent material properties to meet the requirements of near-infrared imaging applications: This invention provides a near-infrared thin film. By introducing antimony into an organic-inorganic hybrid cadmium halide and combining ligand regulation engineering and halogen regulation engineering, a novel near-infrared thin film is prepared. The near-infrared thin film is the first to use antimony to achieve near-infrared emission with a peak position of ~760 nm. Moreover, the near-infrared emission of the near-infrared thin film is the only solution that is not affected by the cadmium halide matrix, reducing unnecessary emission loss and resulting in high luminous efficiency. 2. High stability: The near-infrared film is not sensitive to air and has high stability, so it can be placed in air for a long time; 3. Can be used in flexible devices: The near-infrared thin film has good film-forming properties and can be used to prepare flexible large-area and curved near-infrared imaging systems; 4. Simple preparation process: The formulation and preparation method of the near-infrared film are simple and easy to implement, and have the potential for low cost and large-scale production. Attached Figure Description

[0013] Figure 1 This is a flowchart of a near-infrared thin film and its preparation method according to the present invention; Figure 2 The emission spectra of the near-infrared thin films obtained under different antimony bromide doping concentrations according to the present invention are shown. Figure 3 This is a near-infrared image obtained using the obtained near-infrared thin film in Embodiment 2 of the present invention; Figure 4 The emission spectra of the near-infrared films obtained with different antimony chloride contents in Comparative Example 1 are shown. Figure 5 The emission spectra of the near-infrared films obtained with different antimony chloride contents in Comparative Example 2 are shown. Figure 6 The emission spectra of the near-infrared films obtained with different antimony chloride contents in Comparative Example 3 are shown. Figure 7 The emission spectra of the near-infrared films obtained with different antimony bromide contents in Comparative Example 4 are shown. Figure 8 The emission spectra of the near-infrared films obtained with different antimony bromide contents in Comparative Example 5 are shown. Figure 9 The emission spectra of the near-infrared films obtained under different antimony iodide contents in Comparative Example 6 are shown. Figure 10 The emission spectra of the near-infrared films obtained under different chlorine-bromine ratios in Comparative Example 7 are shown. Figure 11 The emission spectra of the near-infrared films obtained under different chlorine-iodine ratios in Comparative Example 8 are shown. Figure 12 The emission spectra of the near-infrared films obtained under different bromine-iodine ratios in Comparative Example 9 are shown. Detailed Implementation

[0014] The present application will be further described below with reference to specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0015] like Figure 1The diagram shows a flowchart of a near-infrared thin film and its preparation method according to the present invention, wherein the near-infrared thin film is prepared by the following method: S1. Mix cadmium bromide, antimony bromide, and propyltriphenylphosphine bromide; wherein the ratio of the sum of the molar amounts of cadmium bromide and antimony bromide to the molar amount of propyltriphenylphosphine bromide is 1:2.001; the molar amount of antimony bromide is 0.1% to 50% of the molar amount of cadmium bromide; S2. Add a polar solvent, dissolve and filter to obtain the precursor solution; S3. Near-infrared thin films are prepared using the precursor solution.

[0016] Antimony bromide and cadmium bromide can form solid solutions and smooth films with propyltriphenylphosphine bromide at a wide range of doping ratios. However, if the antimony bromide content is too high, phase separation will occur, causing the emission spectrum to shift to the short wavelength range, approaching the emission of the product formed solely by antimony bromide and propyltriphenylphosphine bromide. Figure 2 The emission spectra of the near-infrared films obtained under different antimony bromide doping concentrations according to the present invention are shown.

[0017] In some embodiments, the polar solvent includes N,N-dimethylformamide or acetonitrile.

[0018] In some embodiments, the dissolution method includes heating dissolution, magnetic stirring dissolution, heating and magnetic stirring dissolution, or ultrasonic dissolution.

[0019] In some embodiments, the heating and dissolution temperature does not exceed 100°C. When N,N-dimethylformamide is used as the solvent, the heating temperature can reach 100°C; when acetonitrile is used as the solvent, the heating temperature does not exceed 60°C.

[0020] In some embodiments, the thin film preparation method includes spin coating, blade coating, drop coating, dip coating, or inkjet printing. The precursor solution has good flowability and film-forming properties, making it suitable for various existing thin film preparation methods. The thickness of the thin film can be achieved by adjusting the concentration of the precursor solution or by adjusting the coating parameters. Since N,N-dimethylformamide volatilizes slowly, the obtained thin film can be annealed to accelerate film crystallization.

[0021] In some embodiments, the precursor solution is a filtered solution. Filtering the solution is beneficial for ensuring the uniformity of the membrane.

[0022] In some embodiments, the order in which the steps are performed may be reversed.

[0023] Example 1 2 mmol cadmium bromide, 0.002 mmol antimony bromide, and 4.006 mmol propyltriphenylphosphine bromide were mixed, and 6 mL N,N-dimethylformamide was added. The reaction system was magnetically stirred at 100 °C to ensure complete dissolution of the reactants. The reaction was stopped, and after the temperature of the reaction system dropped to room temperature, the precursor solution was obtained by filtration. An appropriate amount of the precursor solution was drop-coated onto a glass slide and spin-coated. The resulting film was annealed to obtain a semi-transparent near-infrared film with an emission wavelength of ~760 nm. It is insensitive to air, has high stability, and can be stored in air for a long time.

[0024] Example 2 1 mmol cadmium bromide, 0.05 mmol antimony bromide, and 2.101 mmol propyltriphenylphosphine bromide were mixed, and 2 mL acetonitrile was added. The reaction system was heated at 60 °C to fully dissolve the reactants. Heating was stopped, and after the reaction system cooled to room temperature, the precursor solution was obtained by filtration. An appropriate amount of the precursor solution was drop-coated onto a glass slide. After the acetonitrile evaporated naturally, a semi-transparent near-infrared film was obtained, with emission peaks as shown in the figure. Figure 2 The concentration of CdBr-0.05SbBr in the sample is shown at ~760 nm, without the addition of antimony bromide (e.g., ...). Figure 2 CdBr did not emit light; samples without cadmium bromide, i.e., samples prepared from pure antimony bromide (such as...) Figure 2 SbBr₂ emits light at ~596 nm. Figure 3 The image shown is an image of a rose obtained by imaging the obtained near-infrared film. The near-infrared film has good film-forming properties and can be used to prepare flexible large-area and curved near-infrared imaging systems.

[0025] Example 3 2 mmol cadmium bromide, 0.4 mmol antimony bromide, and 4.802 mmol propyltriphenylphosphine bromide were mixed, and 6 mL acetonitrile was added. The reaction system was magnetically stirred at 60 °C to ensure complete dissolution of the reactants. The reaction was stopped, and after the temperature of the reaction system cooled to room temperature, the precursor solution was obtained by filtration. An appropriate amount of the precursor solution was coated onto a transparent substrate using a blade coating method. After the acetonitrile completely evaporated, a translucent near-infrared film was obtained, with emission peaks as shown in the figure. Figure 2 The CdBr-0.20SbBr in the image is shown at ~760nm.

[0026] Example 4 1 mmol cadmium bromide, 0.5 mmol antimony bromide, and 3.0015 mmol propyltriphenylphosphine bromide were mixed, and 3 mL N,N-dimethylformamide was added. The reaction system was magnetically stirred at 100 °C to ensure complete dissolution of the reactants. The reaction was stopped, and after the temperature of the reaction system dropped to room temperature, the precursor solution was obtained by filtration. A clean transparent substrate was placed into the precursor solution and coated using the dip-coating method. The resulting film was annealed to obtain a translucent near-infrared film.

[0027] In addition to the schemes proposed in the above claims and embodiments, the applicant also conducted multiple series of experiments with different types of cadmium halides, different types of antimony halides, different types of organic ligands, and different concentrations of antimony halides, some of which are shown in Comparative Examples 1 to 9. The comparison shows that only the formulation of cadmium bromide, antimony bromide, and propyltriphenylphosphine bromide can achieve near-infrared emission at ~760 nm and good infrared imaging. Furthermore, cadmium bromide and propyltriphenylphosphine bromide do not emit light as a matrix, unlike some matrices in other formulations that produce blue-green emission.

[0028] Comparative Example 1 Cadmium chloride, antimony chloride of different concentrations, and methyltriphenylphosphine chloride were mixed, and an appropriate amount of acetonitrile was added. The reaction system was heated at 60 °C to fully dissolve the reactants. Heating was stopped, and after the reaction system temperature dropped to room temperature, the mixture was filtered to obtain a precursor solution. A suitable amount of the precursor solution was used to prepare a translucent near-infrared thin film on a glass slide. Figure 4 The emission spectra of near-infrared films with different antimony chloride contents are shown. The emission peaks of the film with 5% antimony chloride are 527 nm and 712 nm, while the emission peak of the film with 20% antimony chloride is at 631 nm, which is close to the emission peak of the film obtained by the reaction of pure antimony chloride with methyltriphenylphosphine chloride.

[0029] Comparative Example 2 Cadmium chloride, antimony chloride of different concentrations, and ethyltriphenylphosphine chloride were mixed, and an appropriate amount of acetonitrile was added. The reaction system was heated at 60 °C to fully dissolve the reactants. Heating was stopped, and after the reaction system temperature dropped to room temperature, the mixture was filtered to obtain a precursor solution. A suitable amount of the precursor solution was used to prepare a translucent near-infrared thin film on a glass slide. Figure 5 The emission spectra of the near-infrared films with different antimony chloride contents are shown. The emission peaks basically include double peaks at ~526 nm and ~720 nm.

[0030] Comparative Example 3 Cadmium chloride, antimony chloride of different concentrations, and butyltriphenylphosphine chloride were mixed, and an appropriate amount of acetonitrile was added. The reaction system was heated at 60 °C to fully dissolve the reactants. Heating was stopped, and after the reaction system temperature dropped to room temperature, the mixture was filtered to obtain a precursor solution. A suitable amount of the precursor solution was used to prepare a semi-transparent near-infrared thin film on a glass slide. Figure 6 The emission spectra of near-infrared films with different antimony chloride contents are shown. The emission peaks of the films with 5% and 20% antimony chloride are located at ~515 nm and ~675 nm, respectively. The long-wavelength emission peaks are close to the emission peaks of the films obtained by the reaction of pure antimony chloride with butyltriphenylphosphine chloride.

[0031] Comparative Example 4 Cadmium bromide, antimony bromide of different concentrations, and ethyltriphenylphosphine bromide were mixed, and an appropriate amount of acetonitrile was added. The reaction system was heated at 60 °C to fully dissolve the reactants. Heating was stopped, and after the reaction system temperature dropped to room temperature, the mixture was filtered to obtain a precursor solution. A suitable amount of the precursor solution was used to prepare a translucent near-infrared thin film on a glass slide. Figure 7 The emission spectra of the near-infrared films with different antimony bromide contents are shown. The emission peaks basically include double peaks at ~512 nm and ~714 nm.

[0032] Comparative Example 5 Cadmium bromide, antimony bromide of different concentrations, and butyltriphenylphosphine bromide were mixed, and an appropriate amount of acetonitrile was added. The reaction system was heated at 60 °C to fully dissolve the reactants. Heating was stopped, and after the reaction system temperature dropped to room temperature, the mixture was filtered to obtain a precursor solution. A suitable amount of the precursor solution was used to prepare a translucent near-infrared thin film on a glass slide. Figure 8 The emission spectra of the near-infrared films with different antimony bromide contents are shown, with the emission peaks mostly around 696 nm.

[0033] Comparative Example 6 Cadmium iodide, antimony iodide of different concentrations, and ethyltriphenylphosphine iodide were mixed, and an appropriate amount of acetonitrile was added. The reaction system was heated at 60 °C to fully dissolve the reactants. Heating was stopped, and after the reaction system cooled to room temperature, the precursor solution was obtained by filtration. A suitable amount of the precursor solution was used to prepare thin films on a glass slide. No near-infrared luminescence was observed, only light luminescence was observed. Figure 9 The green light emitted is shown at different excitation wavelengths.

[0034] Comparative Example 7 Cadmium chloride, 20% antimony chloride, appropriate amounts of ethyltriphenylphosphine chloride and ethyltriphenylphosphine bromide were mixed, and an appropriate amount of acetonitrile was added. The reaction system was heated at 60 °C to fully dissolve the reactants. Heating was stopped, and after the reaction system temperature dropped to room temperature, the precursor solution was obtained by filtration. An appropriate amount of the precursor solution was used to prepare a semi-transparent near-infrared thin film on a glass slide. Figure 10The emission spectra of near-infrared films with different chlorine-bromine ratios are shown. When the total chlorine content in the feed is 3 times the total bromine content, the emission peak of the film is at ~716 nm; when the molar ratio of chlorine to bromine in the feed is 1:1, the emission peak of the film is at ~626 nm.

[0035] Comparative Example 8 Cadmium chloride, 20% antimony chloride, appropriate amounts of ethyltriphenylphosphine chloride and ethyltriphenylphosphine iodide were mixed, and an appropriate amount of acetonitrile was added. The reaction system was heated at 60 °C to fully dissolve the reactants. Heating was stopped, and after the reaction system temperature dropped to room temperature, the precursor solution was obtained by filtration. An appropriate amount of the precursor solution was used to prepare a semi-transparent near-infrared thin film on a glass slide. Figure 11 The emission spectra of the near-infrared films with different chlorine-iodine ratios are shown. The emission peaks of the films are mainly at ~520 nm and ~715 nm.

[0036] Comparative Example 9 Cadmium bromide, 5% antimony bromide, appropriate amounts of ethyltriphenylphosphine bromide and ethyltriphenylphosphine iodide were mixed, and an appropriate amount of acetonitrile was added. The reaction system was heated at 60 °C to fully dissolve the reactants. Heating was stopped, and after the reaction system temperature dropped to room temperature, the precursor solution was obtained by filtration. An appropriate amount of the precursor solution was used to prepare a semi-transparent near-infrared thin film on a glass slide. Figure 12 The emission spectra of the films with different bromine-iodine ratios are shown. There is no obvious near-infrared emission, only green light emission.

[0037] The basic principles, main features, and advantages of this application have been described above. Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely the principles of this application. Various changes and modifications can be made to this application without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection claimed by this application is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a near-infrared thin film, characterized in that, It is prepared by the following method: S1: Mix cadmium bromide, antimony bromide, and propyltriphenylphosphine bromide; wherein the ratio of the sum of the molar amounts of cadmium bromide and antimony bromide to the molar amount of propyltriphenylphosphine bromide is 1:2.001; the molar amount of antimony bromide is 0.1% to 50% of the molar amount of cadmium bromide; S2: Dissolve and filter the precursor solution by adding a polar solvent; S3: Prepare near-infrared thin films using the precursor solution.

2. The preparation method according to claim 1, characterized in that, The polar solvent in step S2 includes N,N-dimethylformamide or acetonitrile.

3. The preparation method according to claim 1, characterized in that, The dissolution method in step S2 includes heating dissolution, magnetic stirring dissolution, heating and magnetic stirring dissolution, or ultrasonic dissolution.

4. The preparation method according to claim 3, characterized in that, The heating temperature shall not exceed 100°C.

5. The preparation method according to claim 1, characterized in that, The method for preparing the near-infrared thin film in step S3 includes spin coating, blade coating, drop coating, dip coating, or inkjet printing.

6. A near-infrared thin film prepared by any one of claims 1 to 5.

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