A photonic crystal-based oxygen sensing film and a preparation method thereof
By introducing a photonic crystal substrate and a phosphorescent metalporphyrin compound into the oxygen sensing film, the Purcell effect and slow light effect of the photonic crystal are utilized to solve the problems of insufficient sensitivity and response speed of traditional thin films, and achieve oxygen sensing effect with high sensitivity and fast response.
Patent Information
- Application Number
- CN202610494819.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-04-15
- Publication Date
- 2026-08-25
AI Technical Summary
Existing oxygen sensing films have limited sensitivity and slow response speed, making it difficult to achieve efficient detection and rapid response for low concentrations of oxygen.
An oxygen-sensing thin film based on a photonic crystal was prepared by using a photonic crystal substrate and an oxygen-sensitive probe layer of a phosphorescent metal porphyrin compound. The Purcell effect and slow light effect of the photonic crystal were used to enhance the fluorescence signal, and the porous structure was combined to improve the gas diffusion efficiency.
It achieves ultra-high sensitivity and fast response in oxygen sensing, with a detection limit down to the ppb level and a response time shortened to 0.2 s, and the preparation process is simple and controllable.
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Figure CN122631600A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of sensors, and specifically relates to an oxygen sensing thin film based on photonic crystals and its preparation method. Background Technology
[0002] Oxygen (O2) is a core participant in life activities and industrial processes, and its real-time concentration monitoring plays an irreplaceable role in multiple fields such as biology, environment, and industry. The demand for oxygen sensing in emerging interdisciplinary fields (such as synthetic biology regulation and life support systems for deep space exploration) continues to grow, making accurate measurement of oxygen concentration crucial. Optical oxygen sensors based on the fluorescence / phosphorescence quenching principle have attracted much attention due to their non-invasiveness and lack of electromagnetic interference. However, traditional sensing films typically physically embed luminescent probes in a dense polymer matrix (such as polystyrene PS or polydimethylsiloxane PDMS), a method that faces two major bottlenecks:
[0003] Limited sensitivity: The spontaneous emission rate of the probe is limited by the optical environment of the matrix, and the fluorescence quantum efficiency is difficult to further improve, which limits the detection capability of low concentration (ppb level) oxygen.
[0004] Slow response speed: The diffusion of oxygen molecules in the dense matrix is hindered, resulting in a longer response time and recovery time for the sensor.
[0005] To overcome these limitations, researchers have begun exploring novel matrix materials with porous structures, such as metal-organic frameworks (MOFs) and mesoporous silica, to improve oxygen mass transfer efficiency and probe exposure. While porous materials can improve gas diffusion, they often lack active mechanisms for enhancing optical signals. Photonic crystals (PCs), as microstructured materials with a periodic dielectric constant distribution, possess unique photonic bandgap (PBG) edges exhibiting slow light and Purcell effects. Based on the structural characteristics of PCs, techniques for amplifying or converting detection signals into photoelectric readable signals can be used for quantitative and semi-quantitative analysis via instruments or the naked eye. Applying the excellent properties of PCs to sensor technology offers the possibility of developing novel sensor devices that are highly sensitive, small in size, intuitive, portable, and easy to integrate. Therefore, research on novel PC-based sensors has attracted widespread attention in recent years. The Purcell effect of photonic crystals can significantly enhance the radiative decay rate of probes, greatly improving fluorescence intensity and signal-to-noise ratio. The slow-light effect can greatly prolong the interaction time between light and matter, increasing the collisional quenching efficiency of gas molecules on excited-state probes. Theoretically, the combined effect of these two factors can significantly enhance the sensitivity, detection limit, and response speed of oxygen sensing. Therefore, applying the excellent properties of photonic crystals (PCs) to oxygen sensing technology and developing a novel oxygen sensing film that simultaneously enhances both light-matter and gas-molecule interactions is of great significance. Summary of the Invention
[0006] The technical problem to be solved by the present invention is to provide an oxygen sensing thin film based on photonic crystal and its preparation method, so as to improve the oxygen sensing sensitivity and response speed.
[0007] This invention provides an oxygen sensing thin film based on a photonic crystal, the core structure of which includes: a photonic crystal substrate formed by the self-assembly of periodically arranged microspheres, and an oxygen-sensitive probe layer containing a phosphorescent metalloporphyrin compound attached to the photonic crystal substrate; the photonic crystal substrate has a photonic bandgap that matches the emission peak wavelength of the oxygen-sensitive probe.
[0008] Preferably, the microspheres are polystyrene microspheres or silica microspheres, and the diameter of the microspheres is 200-300 nm.
[0009] Preferably, the phosphorescent metalloporphyrin compound is platinum tetra(pentafluorophenyl)porphyrin (PtTFPP).
[0010] This invention provides a method for preparing the above-mentioned oxygen sensing thin film based on photonic crystal, comprising the following steps:
[0011] S1. Self-assemble microspheres on a hydrophilic substrate to form a high-quality photonic crystal substrate;
[0012] S2. Disperse the phosphorescent metalloporphyrin compound in a solvent to form a uniform sensing solution;
[0013] S3. Spin-coat the sensing solution prepared in step S2 onto the surface of the photonic crystal substrate described in step S1 to form a composite functional layer, thereby obtaining an oxygen sensing film.
[0014] Preferably, the method for preparing the hydrophilic substrate in step S1 is as follows: selecting a quartz glass slide (1x2 cm) 2 Using acetone as a substrate, hydrophilic treatment was performed to ensure the uniformity of microsphere assembly: the substrate was ultrasonically cleaned sequentially with acetone, isopropanol, ethanol and deionized water, then immersed in piranha solution (98% H2SO4:30% H2O2 volume ratio = 3:1) for 24 h, and finally rinsed with a large amount of deionized water to obtain a hydrophilic substrate.
[0015] Preferably, the self-assembly method in step S1 is evaporation-induced self-assembly.
[0016] Furthermore, the evaporation-induced self-assembly specifically involves: pre-forming a water film of approximately 1 mm thickness on the surface of the hydrophilic substrate; mixing the microsphere suspension with anhydrous ethanol at a volume ratio of 1:1; and slowly injecting the mixture into the edge of the water film using a syringe; placing the hydrophilic substrate in a constant temperature and humidity chamber (25 °C, 60% relative humidity) and allowing it to dry; as the solvent evaporates, the microspheres self-assemble into a photonic crystal under the action of capillary force, thereby obtaining a photonic crystal substrate.
[0017] Preferably, the solvent in step S2 is at least one of ethanol, tetrahydrofuran, and toluene.
[0018] Preferably, the spin coating parameters in step S3 are set as follows: rotation speed 1400-1500 rpm, time 25-30 s.
[0019] The present invention also provides an optical oxygen sensor, comprising the above-mentioned oxygen sensing film based on photonic crystal, a pulsed light source for exciting the oxygen sensing film, a photodetector for detecting the emission signal, and a signal processor.
[0020] Beneficial effects
[0021] Compared with the prior art, the present invention has the following significant advantages:
[0022] (1) Ultra-high sensitivity: The strong Purcell effect at the edge of the photonic bandgap significantly enhances the radiative transition rate and luminescence intensity of platinum porphyrin, making the signal change caused by oxygen quenching more significant, and the theoretical detection limit can be reduced to the ppb level.
[0023] (2) Fast response: The porous structure of photonic crystals facilitates rapid gas diffusion, which greatly shortens the response time.
[0024] (3) Controllable preparation process: The spin coating process is simple, the conditions are mild, and it is easy to prepare large-area uniform films. Furthermore, the sensing performance can be flexibly controlled by adjusting the size of the microspheres and the probe. Attached Figure Description
[0025] Figure 1 This is a sample image of the photonic crystal substrate in Example 1.
[0026] Figure 2 This is a planar SEM image of the photonic crystal substrate prepared in Example 1.
[0027] Figure 3 This is a cross-sectional SEM image of the photonic crystal substrate prepared in Example 1.
[0028] Figure 4 This is a matching diagram of the reflection spectrum of the photonic crystal substrate and the emission spectrum of the PtTFPP probe in Example 1.
[0029] Figure 5 This is a comparison of the fluorescence brightness of the oxygen sensing film based on photonic crystal and a conventional film in a nitrogen atmosphere in Example 2.
[0030] Figure 6 This is a schematic diagram comparing the fluorescence brightness of the oxygen sensing film based on photonic crystal and a conventional film under different atmospheres in Example 2.
[0031] Figure 7 The fluorescence intensity of the oxygen sensing film based on photonic crystal in Example 2 is measured under nitrogen, air, and oxygen conditions.
[0032] Figure 8 The fluorescence intensity of the oxygen sensing film based on photonic crystal in Example 2 is measured by sequentially introducing nitrogen / oxygen mixtures of different concentrations.
[0033] Figure 9 The response time of the oxygen sensing film based on photonic crystal in Example 2 was tested.
[0034] Figure 10 This is a stability test of the oxygen sensing film based on photonic crystal in Example 2. Detailed Implementation
[0035] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.
[0036] Example 1
[0037] This embodiment prepares a photonic crystal substrate formed by the self-assembly of silica microspheres. The specific process is as follows:
[0038] a. Substrate pretreatment: Select a quartz glass slide (1x2 cm) 2 The substrate was used as a base. To ensure the uniformity of microsphere assembly, a hydrophilic treatment was performed: the substrate was ultrasonically cleaned sequentially with acetone, isopropanol, ethanol, and deionized water, followed by immersion in a piranha solution (98% H2SO4:30% H2O2 volume ratio = 3:1) for 24 h, and finally rinsed with plenty of deionized water. The treated substrate surface showed a significant reduction in contact angle, forming a superhydrophilic surface.
[0039] b. Microsphere self-assembly: Evaporation-induced self-assembly was employed. A water film approximately 1 mm thick was pre-placed on the surface of the hydrophilic substrate prepared in step a. A monodisperse silica (SiO2) microsphere suspension (particle size approximately 300 nm, solid content 5 wt%) was mixed with anhydrous ethanol at a volume ratio of 1:1. The mixture was slowly injected into the edge of the water film using a syringe. The hydrophilic substrate was placed in a constant temperature and humidity chamber (25 °C, relative humidity 60%) and allowed to dry. As the solvent evaporated, the microspheres self-assembled into an opal-type photonic crystal with a face-centered cubic (FCC) structure under capillary forces. The resulting photonic crystal substrate is shown below. Figure 1 As shown.
[0040] c. Structural characterization: SEM images show that the SiO2 microspheres are arranged in a highly ordered manner. Figure 2 , Figure 3 Reflectance spectroscopy test () Figure 4 This indicates that the photonic crystal has a distinct reflection peak near 650 nm, corresponding to the edge of the photonic bandgap. This peak overlaps with the emission peak of the oxygen-sensitive probe used subsequently, laying the physical basis for optical enhancement.
[0041] Example 2
[0042] This embodiment prepares an oxygen sensing thin film based on a photonic crystal. The specific process is as follows:
[0043] a. Preparation of sensing solution: Take 5 mg of platinum tetra(pentafluorophenyl)porphyrin (PtTFPP) powder, dissolve it in 5 mL of toluene, and ultrasonically disperse it for 15 min to form a homogeneous sensing solution;
[0044] b. Preparation of the sensing film: The sensing solution was coated onto the surface of the photonic crystal substrate prepared in Example 1 using a spin-coating method. The spin-coating parameters were set as follows: rotation speed 1500 rpm, time 30 s. The spin-coating process ensured that the probe molecules mainly adhered to the surface of the microspheres and the inner walls of the pores, thus preserving the gas diffusion channels rather than completely filling the pores. After the sample was dried at room temperature, the oxygen sensing film (PtTFPP PCs film) was obtained.
[0045] As a control, the same sensing solution from step a was spin-coated onto a regular quartz glass slide using the same process to prepare a regular thin film (PtTFPP film).
[0046] The performance of the oxygen sensing thin film based on photonic crystal and ordinary thin film was tested and analyzed.
[0047] a. Fluorescence enhancement effect (Purcell effect verification): The two prepared thin films were placed in a fluorescence spectrometer for spectral testing. Figure 5 The results showed that, in a pure nitrogen environment, the fluorescence peak intensity of the oxygen sensing film based on the photonic crystal was approximately 16 times that of the ordinary film. This is attributed to the high photonic density of states (DOS) at the edge of the photonic bandgap, which significantly enhances the radiative decay rate (Purcell effect) of the PtTFPP molecules, while the slow light effect enhances the interaction between the excitation light and the probe.
[0048] b. Sensitivity and detection limit: Figure 6 A schematic diagram showing the fluorescence brightness comparison of two thin films under nitrogen, air, and oxygen conditions is presented. Figure 7 The fluorescence intensity of the photonic crystal-based oxygen sensing film under different atmospheres is shown. The sensitivity S = I0 / I (where I0 is the fluorescence intensity under nitrogen and I is the fluorescence intensity under oxygen) can reach 152.5. At room temperature and in an atmospheric environment, a series of analyte gases with different concentrations of oxygen were prepared by mixing high-purity nitrogen with standard oxygen. The volume fractions were 0 ppb, 50 ppb, 100 ppb, 250 ppb, 500 ppb, 1 ppm, 2 ppm, 3 ppm, 4 ppm, and 5 ppm. Different concentrations of nitrogen / oxygen mixtures were sequentially introduced, and the phosphorescence intensity was found to decrease with increasing oxygen concentration. Even at an extremely low oxygen concentration of 50 ppb, the fluorescence intensity still showed a recognizable decrease, demonstrating its ultra-high detection sensitivity (e.g., ). Figure 8 (As shown).
[0049] c. Response speed: Dynamic testing was conducted by rapidly switching between nitrogen and air streams. Figure 9 Define t. 95 This is the time required for the signal change to reach 95% of the total amplitude. Test results show that the t-value of the oxygen sensing thin film based on photonic crystals in this invention... 95 The time is only 0.2 s. This is thanks to the three-dimensional through-pore structure preserved by the photonic crystal, which allows gas molecules to contact the probe surface much faster compared to traditional dense films.
[0050] d. Stability: Fluorescence intensity changes were measured over 300 s under continuous UV excitation and nitrogen flow. Figure 10 In this invention, the fluorescence intensity of the oxygen sensing film based on photonic crystal decreased by only 0.3%, indicating that the photonic crystal structure has a certain protective effect on the probe and the device has good photostability.
Claims
1. An oxygen sensing thin film based on a photonic crystal, characterized in that, The oxygen sensing film comprises: a photonic crystal substrate formed by the self-assembly of periodically arranged microspheres, and an oxygen-sensitive probe layer containing a phosphorescent metalloporphyrin compound attached to the photonic crystal substrate; the photonic crystal substrate has a photonic bandgap that matches the emission peak wavelength of the oxygen-sensitive probe.
2. The oxygen sensing thin film based on photonic crystal according to claim 1, characterized in that, The microspheres are polystyrene microspheres or silica microspheres, and the diameter of the microspheres is 200-300 nm.
3. The oxygen sensing thin film based on photonic crystal according to claim 1, characterized in that, The phosphorescent metalloporphyrin compound is platinum tetra(pentafluorophenyl)porphyrin.
4. A method for preparing an oxygen sensing thin film based on a photonic crystal as described in claim 1, comprising the following steps: S1. Self-assemble microspheres on a hydrophilic substrate to form a photonic crystal substrate; S2. The phosphorescent metalloporphyrin compound is dispersed in a solvent to form a sensing solution; S3. Spin-coat the sensing solution prepared in step S2 onto the surface of the photonic crystal substrate described in step S1 to form a composite functional layer, thereby obtaining an oxygen sensing film.
5. The preparation method according to claim 4, characterized in that, The self-assembly method described in step S1 is evaporation-induced self-assembly.
6. The preparation method according to claim 4, characterized in that, The solvent in step S2 is at least one of ethanol, tetrahydrofuran, and toluene.
7. The preparation method according to claim 4, characterized in that, The spin coating parameters in step S3 are set as follows: rotation speed 1400-1500 rpm, time 25-30 s.
8. An optical oxygen sensor, characterized in that, The optical oxygen sensor includes a photonic crystal-based oxygen sensing film as described in claim 1, a pulsed light source for exciting the oxygen sensing film, a photodetector for detecting the emission signal, and a signal processor.