DABT nanofilm emitting strong two-photon fluorescence and preparation method and application thereof

Abstract

This invention discloses a DABT nanofilm emitting strong two-photon fluorescence, its preparation method, and its applications, belonging to the field of photoluminescence technology. The DABT nanofilm comprises a DABT nanofilm layer and a substrate layer. Specifically, this invention prepares a high-quality DABT nanofilm with molecularly oriented alignment by spraying and polarizing the substrate layer surface. The prepared DABT nanofilm emits high-intensity two-photon fluorescence with polarization characteristics under near-infrared light excitation, with a two-photon fluorescence signal peak center wavelength of 640 nm and a full width at half maximum (FWHM) of 36 nm. Furthermore, it possesses advantages such as low cost and ease of large-scale mass production, thus showing promising application prospects in optoelectronic displays, bioimaging, and other fields.

Description

Technical Field

[0001] This invention relates to the field of photoluminescence technology, and in particular to a DABT nanofilm that emits strong two-photon fluorescence, its preparation method, and its application. Background Technology

[0002] Since the 20th century, nonlinear optical materials emitting strong two-photon fluorescence have been widely used in optoelectronic displays, bioimaging, and other fields. However, many two-photon fluorescent materials suffer from high preparation costs, difficulties in mass production, poor modifiability, and high biotoxicity, which limit their practical applications. Therefore, developing and preparing a nonlinear optical thin film emitting strong two-photon fluorescence that combines advantages such as low cost, suitability for mass production, easy molecular modification, and low toxicity is of great significance for the rapid development of optoelectronic devices and medical diagnostics.

[0003] On the one hand, two-photon fluorescence is a fluorescence generation phenomenon based on nonlinear optical effects. Its core characteristic is that under specific conditions, molecules simultaneously absorb two low-energy photons, transition to an excited state, and then release a high-energy fluorescent photon through an excited-state relaxation process, thereby generating a fluorescence signal. This process strictly follows the laws of conservation of energy and angular momentum, which is an important nonlinear optical phenomenon that distinguishes it from traditional single-photon fluorescence. In bioimaging, long-wavelength excitation of two-photon fluorescent materials can reduce interference from autofluorescence in biological tissues, enabling high-resolution imaging of deep tissues. In optoelectronic devices, two-photon fluorescent materials can be used to fabricate high-efficiency light-emitting diodes, improving the performance of optoelectronic devices. However, two-photon fluorescent materials still face many challenges. From a cost perspective, complex synthesis processes and expensive raw materials limit large-scale production and increase application costs. From the material's inherent properties, many materials suffer from difficulties in molecular modification, contain heavy metals, and exhibit poor fluorescence stability, which also hinders practical applications (see TRKuo, CFLee, SJLin, CYDong, CCChen, HYTan, Chemical Research in Toxicology, 2011, 24, 253-261). Therefore, there is an urgent need to find an optical material with a simple preparation process, low cost, high molecular design potential, and environmentally friendly and stable properties to overcome existing limitations and promote greater progress in related technologies.

[0004] On the other hand, 4-4-dimethylaminostyrylmethylbenzothiazole p-toluenesulfonate (DABT), a newly emerging ionic small organic molecule in recent years, is composed of a benzothiazole salt cation with a special electron donor-conjugated π-bridge-electron acceptor structure and a sulfonate anion with a fixed cation arrangement. Due to its high chromophore density, highly delocalized conjugated structure, diverse molecular modification possibilities, stable physicochemical properties, low toxicity, and low cost, it has shown great research value in fields such as nonlinear optics and piezoelectric catalysis (M. Huang, W. Li, Y. Li, J. Tang, X. Xu, Chemical Engineering Journal, 2025, 524, 169378). Unfortunately, the development of most ionic small organic molecules, including DABT, has reached a bottleneck in recent years. This is because current research on them mainly focuses on terahertz wave radiation and frequency conversion, but the centrosymmetric stacking of 70% of ionic small organic molecules cannot meet the conditions for strong terahertz wave generation and frequency conversion. Although researchers have studied the nonlinear light absorption behavior and single-photon fluorescence emission effect of DABT (see AKMora, S. Murudkar, A. Alamelu, S. Chattopadhyay, S. Nath, Journal of Photochemistry & Photobiology A: Chemistry, 2019, 373, 20-27; Study on nonlinear absorption and fluorescence effects of DAST and its derivatives, Chengdu: University of Electronic Science and Technology of China, 2023, 70-91), they still cannot break the predicament that DABT and most other ionic organic small molecules currently face, namely, limited practical application areas and insufficient motivation for design and development.

[0005] In summary, to overcome the problems existing in two-photon fluorescent materials, break through the current research bottleneck of DABT plasmonic organic small molecules, and promote the development of optoelectronic devices and bioimaging technologies, it is of significant scientific research and practical application value to prepare high-quality DABT nanofilms using a simple and low-cost method and explore their two-photon fluorescence properties. Therefore, this invention proposes a DABT nanofilm emitting strong two-photon fluorescence, its preparation method, and its application to solve the problems existing in the prior art. Summary of the Invention

[0006] To address the aforementioned problems, the present invention aims to propose a DABT nanofilm emitting strong two-photon fluorescence, its preparation method, and its applications. A novel ionic small molecule DABT is deposited on a substrate using a spray coating method followed by annealing and polarization, successfully obtaining a DABT nanofilm with molecularly oriented alignment. This nanofilm emits red two-photon fluorescence with polarization characteristics under near-infrared light excitation. In particular, the developed DABT nanofilm exhibits high two-photon fluorescence response, a simple preparation process, and low cost, facilitating large-scale mass production. This successfully overcomes the difficulties faced in the development of existing two-photon fluorescence materials and opens up new avenues for the diversified applications and development of DABT plasmonic organic small molecules.

[0007] To achieve the objective of this invention, the invention is implemented through the following technical solution: a DABT nanofilm emitting strong two-photon fluorescence, comprising a DABT nanofilm layer and a substrate layer, wherein the DABT nanofilm layer is deposited on the surface of the substrate layer by mixing DABT and a solvent, and the mixing ratio is 1 to 20 mg of DABT added per 1 mL of solvent.

[0008] A further improvement is that the solvent is selected from at least one of methanol, deionized water, ethanol, propanol, isobutanol, butanol, pentanol, dimethylformamide, and dimethyl sulfoxide; the thickness of the DABT nanofilm layer is 10–1000 nm; the center wavelength of its linear absorption peak is 300–600 nm; the center wavelength of its two-photon fluorescence emission peak is 600–700 nm; and its full width at half maximum (FWHM) is 20–100 nm.

[0009] A further improvement is that the substrate layer is selected from one of the following: fused silica sheet, glass slide, silicon nitride sheet, hydroxylated silicon sheet, silanized silicon sheet, indium tin oxide sheet, sapphire sheet, mica sheet, polymethyl methacrylate film, polydimethylsiloxane film, polydimethyl methacrylate film, polyethylene terephthalate film, polyethylene film, and polypropylene film.

[0010] A further improvement is that the microscopic molecules in the DABT nanofilm are arranged in an orderly manner, and can emit high-intensity two-photon fluorescence with polarization characteristics under near-infrared laser excitation. The polarization method for the orderly arrangement of microscopic molecules is one of the following: external electric field method, external magnetic field method, photo-induced method, and high-temperature annealing method.

[0011] A further improvement is that the DABT nanofilm emits high-intensity two-photon fluorescence when excited by a laser with a wavelength of 780–1100 nm.

[0012] A method for preparing a DABT nanofilm emitting strong two-photon fluorescence includes the following steps:

[0013] Step 1: Mix the ionic organic small molecule DABT with the solvent and sonicate for 1-5 hours to obtain a DABT solution with a concentration of 1-20 mg / mL;

[0014] Step 2: Under a pressure of 0.2–1 MPa, the DABT solution is sprayed onto a clean substrate surface using a carrier gas, and then polarized to arrange the DABT molecules in an orderly manner to obtain a DABT nanofilm.

[0015] A further improvement is made in the following: In step two, the specific parameters for spraying the DABT solution include: each spraying time is 5 to 50 seconds, the interval between each spraying is 10 to 60 seconds, and the spraying is repeated 3 to 10 times.

[0016] A further improvement is that, in step two, the carrier gas is selected from one of nitrogen, ammonia, hydrogen, oxygen, and argon.

[0017] An application of a DABT nanofilm emitting strong two-photon fluorescence, wherein the DABT nanofilm has application potential in the field of bioimaging, and the emission wavelength (emitting two-photon / single-photon) can be adjusted by changing the excitation wavelength to meet different requirements in the field of bioimaging.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] (1) This invention first prepared DABT nanofilm and disclosed its two-photon fluorescence properties. DABT nanofilm can exhibit high-intensity red two-photon fluorescence with polarization characteristics under near-infrared laser excitation of 800-1040nm, with a center wavelength of 640nm. This not only breaks through the current research scope of ionic nonlinear organic optical material DABT, but also provides excellent new photosensitive films and materials for the development of optoelectronic display devices, biological cell imaging and other fields.

[0020] (2) The DABT nanofilm preparation method used in this invention is simple, low-cost, and easy to industrialize. The DABT nanofilm with molecular orientation was successfully prepared by spraying and annealing at 150°C. Compared with the preparation process of many two-photon fluorescent materials, the preparation method used in this invention does not involve expensive film deposition and polarization equipment, and does not rely on the synthesis of special elements or functional groups. It has the advantages of being simple, low-cost, and suitable for mass production. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the DABT nanofilm emitting strong two-photon fluorescence of the present invention;

[0022] Figure 2 This is a schematic diagram of the linear absorption spectrum of the DABT nanofilm of the present invention;

[0023] Figure 3 This is a schematic diagram of the fluorescence spectrum of the DABT nanofilm of the present invention under laser excitation with a wavelength of 800-1040 nm and a power of 60 mW;

[0024] Figure 4 This is a schematic diagram of the fluorescence spectrum of the DABT nanofilm of the present invention under laser excitation at a wavelength of 800 nm and different power.

[0025] Figure 5 This is a schematic diagram of the logarithmic relationship between excitation power and fluorescence intensity of the DABT nanofilm of the present invention at a wavelength of 800 nm;

[0026] Figure 6 This is a two-photon fluorescence polarization polarization diagram of the DABT nanofilm of the present invention under laser excitation with a wavelength of 800-1040 nm and a power of 60 mW.

[0027] in, Figure 1 The numbers are ①DABT nanofilm layer; ②substrate layer; ω1 and ω2 represent the frequencies of incident and emitted photons, respectively. Figure 3-5 TPEF on the medium coordinate axis represents two-photon fluorescence. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. It should be noted that technical means not described in detail in the embodiments of the present invention can be implemented by conventional means and are not the key points of the invention, and will not be elaborated upon.

[0029] Figure 1 This is a schematic diagram of the structure of a DABT nanofilm emitting strong two-photon fluorescence proposed in this invention. Figure 1 It can be seen that the DABT nanofilm ① proposed in this invention is deposited on the surface of the substrate layer ②, and the thickness c of the former is significantly smaller than that of the latter. It should be noted that the DABT nanofilm layer is deposited on the surface of the substrate layer by a spray coating method, wherein the DABT solution mixing ratio is 10 mg of DABT per 1 mL of solvent, the solvent is methanol, the thickness of the DABT nanofilm layer is 100-900 nm, the center wavelength of its linear absorption peak is 300-600 nm, and the substrate layer is a fused silica sheet with a thickness of 0.5-3 mm.

[0030] In this embodiment, the DABT nanofilm has an ordered arrangement of micro-molecules, which can emit high-intensity two-photon fluorescence under near-infrared laser excitation. The polarization method that enables the ordered arrangement of micro-molecules is high-temperature annealing.

[0031] The DABT nanofilm in this embodiment emits high-intensity two-photon fluorescence when excited by a laser with a wavelength of 780–1100 nm.

[0032] This embodiment also provides a method for preparing DABT nanofilms that emit strong two-photon fluorescence, including the following steps:

[0033] Step 1: Prepare DABT solution

[0034] DABT was mixed with methanol and sonicated for 2 hours to obtain a homogeneous DABT solution with a concentration of 10.0 mg / mL.

[0035] Step 2: Deposition of DABT nanofilm

[0036] Under a pressure of 0.3 MPa, high-purity nitrogen was used as the carrier gas to spray the DABT solution prepared in step one onto the surface of a clean quartz sheet, and then the sheet was annealed and polarized at 150 °C for 2 h. The final DABT nanofilm prepared had a thickness of 415 nm.

[0037] The specific parameters for spraying the DABT solution include: each spraying time is 10 seconds, the interval between each spraying is 20 seconds, and the spraying is repeated 5 times.

[0038] The DABT nanofilm prepared in this embodiment can be applied to the field of bioimaging. By changing the excitation wavelength, the emission wavelength can be adjusted to meet different requirements in the field of bioimaging.

[0039] Figure 2 This is the linear absorption spectrum of the DABT nanofilm fabricated in this embodiment. As shown in the figure, the center wavelength of the linear absorption peak of the DABT nanofilm is 508 nm, suggesting that the photoluminescence signal emitted after the DABT nanofilm is excited by an 800-1040 nm laser in this embodiment may be two-photon fluorescence.

[0040] Figure 3 This is the fluorescence spectrum of the DABT nanofilm fabricated in this embodiment under laser irradiation with an excitation wavelength of 800-1040 nm and a power of 60 mW. Figure 3 It is noted that when the excitation wavelength is 800, 900, 1000, and 1040 nm, the fluorescence signal intensities emitted by the DABT nanofilm are 711, 1200, 1636, and 2246, respectively, and the center wavelength of the emission peak is 640 nm.

[0041] Figure 4The figure shows the fluorescence spectra of the DABT nanofilm fabricated in this embodiment under different excitation powers at an excitation wavelength of 800 nm. As can be seen from the figure, when the excitation power is 60, 90, 120, 150, 180, and 210 mW, the fluorescence signal emitted by the DABT nanofilm is significantly enhanced, with intensities of 711, 1365, 2180, 3022, 4100, and 5240, respectively.

[0042] Figure 5 This is the logarithmic curve of excitation power versus fluorescence intensity for the DABT nanofilm fabricated in this embodiment at an excitation wavelength of 800 nm. Figure 5 It is noted that the slope of the fitted curve is 1.60, which is close to 2, revealing that the photoluminescence signal detected in this embodiment is indeed two-photon fluorescence.

[0043] Figure 6 The polarization polarization diagram of the two-photon fluorescence signal of the DABT nanofilm fabricated in this embodiment under laser radiation with an excitation wavelength of 800-1040 nm and a power of 60 mW shows that the two-photon fluorescence polarization polarization diagram of the DABT nanofilm exhibits dual rotational symmetry. The two-photon fluorescence signals are strongest at ~150° and ~330°, revealing that the DABT molecules in the DABT nanofilm prepared in this embodiment have an orientational arrangement.

[0044] In summary, this embodiment successfully prepared molecularly aligned DABT nanofilms using a simple and low-cost spraying and annealing process. Furthermore, this high-quality DABT nanofilm emitted high-intensity, red two-photon fluorescence under near-infrared light excitation, with a center wavelength of 640 nm. Thus, the novel DABT nanofilm developed in this invention solves the current challenges in the development of two-photon fluorescent materials and ionic small organic molecules, and makes a positive contribution to promoting the rapid development of DABT and other ionic small organic molecules, as well as to the development of two-photon fluorescent optoelectronic devices, biological cell imaging, and other fields.

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A DABT nanofilm emitting strong two-photon fluorescence, comprising a DABT nanofilm layer and a substrate layer, characterized in that: The DABT nanofilm layer is deposited on the surface of the substrate layer after mixing DABT and solvent, with a mixing ratio of 1 to 20 mg of DABT added per 1 mL of solvent.

2. The DABT nanofilm emitting strong two-photon fluorescence according to claim 1, characterized in that: The solvent is selected from at least one of methanol, deionized water, ethanol, propanol, isobutanol, butanol, pentanol, dimethylformamide, and dimethyl sulfoxide. The thickness c of the DABT nanofilm layer is 10-1000 nm, the center wavelength of its linear absorption peak is 300-600 nm, the center wavelength of its two-photon fluorescence emission peak is 600-700 nm, and the full width at half maximum (FWHM) is 20-100 nm.

3. The DABT nanofilm emitting strong two-photon fluorescence according to claim 1, characterized in that: The substrate layer is selected from one of the following: fused silica sheet, glass slide, silicon nitride sheet, hydroxylated silicon sheet, silanized silicon sheet, indium tin oxide sheet, sapphire sheet, mica sheet, polymethyl methacrylate film, polydimethylsiloxane film, polymethyl methacrylate film, polyethylene terephthalate film, polyethylene film, and polypropylene film.

4. The DABT nanofilm emitting strong two-photon fluorescence according to claim 1, characterized in that: The DABT nanofilm has an ordered arrangement of micro-molecules, which can emit high-intensity two-photon fluorescence with polarization characteristics under near-infrared laser excitation. The polarization method that enables the ordered arrangement of micro-molecules is one of the following: external electric field method, external magnetic field method, photo-induced method, and high-temperature annealing method.

5. The DABT nanofilm emitting strong two-photon fluorescence according to claim 1, characterized in that: The DABT nanofilm emits high-intensity two-photon fluorescence when excited by lasers with wavelengths of 780–1100 nm.

6. A method for preparing a DABT nanofilm emitting strong two-photon fluorescence as described in any one of claims 1-5, characterized in that, Includes the following steps: Step 1: Mix the ionic organic small molecule DABT with the solvent and sonicate for 1-5 hours to obtain a DABT solution with a concentration of 1-20 mg / mL; Step 2: Under a pressure of 0.2–1 MPa, the DABT solution is sprayed onto a clean substrate surface using a carrier gas, and then polarized to arrange the DABT molecules in an orderly manner to obtain a DABT nanofilm.

7. The method for preparing a DABT nanofilm emitting strong two-photon fluorescence according to claim 6, characterized in that: In step two, the specific parameters for spraying the DABT solution include: each spraying time is 5 to 50 seconds, the interval between each spraying is 10 to 60 seconds, and the spraying is repeated 3 to 10 times.

8. The method for preparing a DABT nanofilm emitting strong two-photon fluorescence according to claim 6, characterized in that: In step two, the carrier gas is selected from nitrogen, ammonia, hydrogen, oxygen, and argon.

9. An application of a DABT nanofilm emitting strong two-photon fluorescence, characterized in that: The DABT nanofilm has potential applications in the field of bioimaging. By changing the excitation wavelength, the emission wavelength can be adjusted (emitting two photons / single photons), thus meeting different requirements in the field of bioimaging.

Images