System and method for detecting relative fluorescence lifetime of material

Abstract

The invention belongs to the field of optical detection, and particularly relates to a system and method for detecting the relative fluorescence lifetime of a material. The system comprises a light source used for exciting a sample to be detected; the pulse generator is electrically connected with the light source and used for generating pulse signals to drive the light source to excite the to-be-tested sample; the collector is arranged on a fluorescence emission path of the to-be-detected sample and is used for collecting a fluorescence intensity signal generated by the to-be-detected sample; and the processing unit is used for controlling the pulse generator to sequentially output multiple groups of pulse sequences with different duty ratios or frequencies. The processing unit is also used for detecting the relative fluorescence lifetime of different to-be-detected samples according to the change relation of the fluorescence intensity signal along with the duty ratio or the frequency. According to the system, high-precision time sequence equipment is not needed, the optical path and hardware requirements are simplified, and the cost is lower. The system provided by the invention can realize rapid detection of the relative fluorescence lifetime of the material, and is suitable for various scenes such as material screening, biosensing and anti-counterfeiting detection.

Description

Technical Field

[0001] This invention relates to the field of optical detection technology, and specifically to a system and method for detecting the relative fluorescence lifetime of a material. Background Technology

[0002] Fluorescence lifetime, a key parameter reflecting the electronic energy level relaxation characteristics of luminescent materials, has been widely used in biosensing, environmental monitoring, anti-counterfeiting identification, and material quality control. Fluorescence lifetime is generally defined as the time required for the emitted light intensity to decay to 1 / e of its initial value after excitation stops, and its value depends on the physicochemical properties of the material itself and its microenvironment.

[0003] Traditional fluorescence lifetime measurement techniques primarily focus on obtaining precise physical values ​​of lifetime, such as those at the microsecond or nanosecond level. Currently, mature fluorescence lifetime measurement techniques include time-correlated single-photon counting, phase-shifting methods, and gated detection methods, aiming to quantify the absolute value of fluorescence lifetime with high precision. For example, the phase-shifting method typically uses a periodic excitation source with a fixed frequency and acquires fluorescence signal intensities at different time points by changing the phase delay (Δt) of the detector's acquisition window relative to the excitation pulse, thereby constructing a complete fluorescence decay curve. These methods usually require complex and expensive equipment, such as high-precision cameras, high-speed detectors, precision choppers, or radio frequency phase detection systems. Furthermore, achieving high-precision time resolution at the nanosecond or even picosecond level requires complex optical path setup and signal processing.

[0004] However, in practical industrial and scientific research scenarios, the application requirements for fluorescence lifetime are gradually changing. In many fields such as material screening, biosensing, and authenticity verification, users' core demand is often not to obtain precise lifetime values, but rather to quickly and effectively identify the relative lengths or trends in fluorescence lifetimes between different samples. For example, in anti-counterfeiting applications based on upconversion luminescent materials, genuine and counterfeit materials may have similar emission colors, but their microstructural differences will lead to significant differences in fluorescence lifetimes. In this case, the key to detection is to quickly determine whether the sample exhibits the same lifetime characteristics as the standard, without needing to solve for its specific lifetime value. Similarly, in time-resolved fluorescence immunoassay, when a labeled probe binds to a target biomolecule, its fluorescence lifetime usually increases due to changes in the microenvironment. The core task of detection here is to sensitively identify this lifetime extension phenomenon to confirm the occurrence of the binding event, rather than precisely measuring the specific value of the lifetime extension.

[0005] When high-precision technologies designed for absolute numerical measurements are directly applied to scenarios requiring only comparisons of relative fluorescence lifetimes, their inherent complexity, high cost, and cumbersome data processing create a contradiction with the need for rapid and low-cost detection. Existing technological approaches often become cumbersome and uneconomical due to over-configuration in such applications, failing to meet the efficiency and cost requirements of practical applications.

[0006] Therefore, there is a need for low-cost and high-efficiency detection of the relative length of fluorescence lifetime to meet the needs of various application scenarios such as rapid screening and on-site detection. Summary of the Invention

[0007] (a) Technical problems to be solved

[0008] To address the problems of existing fluorescence lifetime detection systems being complex, costly, and unsuitable for detection scenarios requiring only the relative fluorescence lifetime of materials, this invention provides a system and method for detecting the relative fluorescence lifetime of materials.

[0009] (II) Technical Solution

[0010] To achieve the above objectives, the main technical solutions adopted by the present invention include:

[0011] A system for detecting the relative fluorescence lifetime of a material, comprising:

[0012] A light source is used to excite the sample to be tested, causing it to fluoresce.

[0013] A pulse generator, electrically connected to a light source, is used to generate pulse signals to drive the light source to excite the sample under test;

[0014] The collector is positioned in the fluorescence emission path of the sample to be tested and is used to collect the fluorescence intensity signal generated by the sample.

[0015] The processing unit is communicatively connected to the pulse generator and the acquisition unit, and is used to control the pulse generator to output multiple sets of pulse sequences in sequence. The pulse frequencies of the multiple sets of pulse sequences are the same but the duty cycles are different, or the duty cycles are the same but the pulse frequencies are different.

[0016] The processing unit is also used to receive and process fluorescence intensity signals from the collector, and then detect the relative fluorescence lifetime of different test samples based on the relationship between fluorescence intensity signals and duty cycle or frequency.

[0017] In the system described above, preferably, the light source is a laser, and the pulse generator is a PWM generator or a device with pulse modulation function.

[0018] In the system described above, preferably, the data acquisition device is a camera, a spectrometer, or a photomultiplier tube.

[0019] In the system described above, preferably, when the duty cycles of multiple pulse sequences are different, the duty cycles of the pulse sequences increase or decrease in a set order; when the pulse frequencies of multiple pulse sequences are different, the pulse frequencies of the pulse sequences increase or decrease in a set order.

[0020] In the system described above, preferably, the sample to be tested is a rare-earth-doped upconversion luminescent material.

[0021] The present invention also provides a method for detecting the relative fluorescence lifetime of a material using the above-described system, comprising the following steps:

[0022] S1: Multiple pulse sequences are set by the processing unit, wherein the pulse frequencies of the multiple pulse sequences are the same but the duty cycles are different, or the duty cycles are the same but the pulse frequencies are different.

[0023] S2: The processing unit controls the pulse generator to output multiple pulse sequences in sequence, which drive the light source to excite the sample to be tested respectively. The processing unit synchronously controls the collector to collect the fluorescence intensity signal generated by the sample to be tested under different pulse sequences.

[0024] S3: The processing unit receives and processes fluorescence intensity signals from the collector;

[0025] S4: The processing unit detects the relative fluorescence lifetime of different test samples based on the relationship between fluorescence intensity signal and duty cycle or frequency.

[0026] In the method described above, preferably, in step S1, when multiple pulse sequences have the same pulse frequency but different duty cycles, in step S4, for each pulse sequence with a specific duty cycle, a curve of fluorescence intensity changing with time is obtained by processing the acquired fluorescence intensity signal, and then the integral area of ​​each curve is calculated. Then, a response curve of integral area changing with duty cycle is constructed with duty cycle as the abscissa and integral area of ​​the corresponding curve as the ordinate. By comparing the slope of the response curves of different test samples, the relative fluorescence lifetime of different test samples is detected.

[0027] In the method described above, preferably, in step S1, when multiple pulse sequences have the same duty cycle but different pulse frequencies, in step S4, for each pulse sequence at a specific frequency, a curve of fluorescence intensity changing with time is obtained by processing the acquired fluorescence intensity signal, and then the integral area of ​​each curve is calculated. Then, a response curve of integral area changing with frequency is constructed with frequency as the abscissa and the integral area of ​​the corresponding curve as the ordinate. By comparing the slope of the response curves of different test samples, the relative fluorescence lifetime of different test samples is detected.

[0028] In the method described above, preferably, in step S4, fluorescence intensity signals are acquired and their integrated area is calculated within the same time period, or fluorescence intensity signals are acquired and their integrated area is calculated under the action of the same number of excitation pulses.

[0029] (III) Beneficial Effects

[0030] First, this invention integrates conventional light sources, pulse generators, acquisition units, and processing units to construct a system that does not rely on high-precision time-resolution hardware. The system of this invention fundamentally eliminates the complex and expensive timing control equipment required in traditional fluorescence lifetime measurements, such as high-speed detectors, precision choppers, RF phase detection modules, or time-correlated single-photon counting units. This avoids hardware dependence on nanosecond or picosecond-level time resolution and significantly reduces the design complexity of the system in terms of optical path alignment, signal synchronization, and circuit timing matching.

[0031] Secondly, the system of the present invention implements specific logic control on the pulse generator through the processing unit, so that it sequentially outputs multiple sets of excitation sequences with the same pulse frequency but different duty cycles, or with the same duty cycle but different pulse frequencies. Combined with the acquisition unit to obtain the fluorescence intensity signal under the corresponding conditions, it can transform the judgment of the relative length of fluorescence lifetime into the task of analyzing the macroscopic response trend of fluorescence signal, without the need for high-precision time control, thereby greatly reducing the hardware requirements for the time response performance and data acquisition rate of the acquisition unit.

[0032] Third, the system of this invention is small in size, low in manufacturing cost, and low in maintenance threshold. It requires no complex operation or precise calibration, making it particularly suitable for applications requiring rapid screening, online monitoring, and on-site testing, such as preliminary material classification, industrial quality control, biosensing, and anti-counterfeiting authentication. Therefore, the system of this invention provides an efficient and economical solution for numerous applications that only need to detect the relative fluorescence lifetime of materials, without requiring precise lifetime values. This significantly improves engineering feasibility in environments such as industrial sites, portable devices, and large-scale screening, promoting the widespread adoption and application of fluorescence lifetime analysis technology in a wider range of fields. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the fluorescence intensity decay curve over time and the window acquisition timing in this invention;

[0034] Figure 2 This is a timing diagram showing the synchronous operation of the laser and the acquisition device (camera) in this invention;

[0035] Figure 3 This is a schematic diagram of the detection principle of the system for detecting the relative fluorescence lifetime of materials in this invention;

[0036] Figure 4This is a schematic diagram of the optical path of a system for detecting the relative fluorescence lifetime of a liquid sample.

[0037] Figure 5 This is a schematic diagram of the optical path of a system for detecting the relative fluorescence lifetime of a solid sample.

[0038] Figure 6 This is a time-fluorescence intensity curve of sample A at different frequencies with a fixed duty cycle in Example 1;

[0039] Figure 7 This is a time-fluorescence intensity curve of sample B at different frequencies with a fixed duty cycle in Example 1;

[0040] Figure 8 for Figure 6 Only the time-fluorescence intensity curves of sample A at 500 Hz and 1000 Hz are used;

[0041] Figure 9 for Figure 7 Time-fluorescence intensity curves for sample B at 500 Hz and 1000 Hz are used only;

[0042] Figure 10 Frequency-fluorescence intensity maps of samples A and B under a fixed-time mode;

[0043] Figure 11 The frequency-fluorescence intensity diagrams for samples A and B are shown in constant pulse number mode. Detailed Implementation

[0044] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] This invention provides a system for detecting the relative fluorescence lifetime of a material, comprising:

[0046] A light source is used to excite the sample to produce fluorescence.

[0047] A pulse generator, electrically connected to a light source, is used to generate pulse signals to drive the light source to excite the sample under test.

[0048] The collector is positioned in the fluorescence emission path of the sample to be tested and is used to collect the fluorescence intensity signal generated by the sample.

[0049] The processing unit is communicatively connected to both the pulse generator and the acquisition unit. It controls the pulse generator to sequentially output multiple pulse sequences, which may have the same pulse frequency but different duty cycles, or the same duty cycle but different pulse frequencies. The processing unit also receives and processes fluorescence intensity signals from the acquisition unit, and then fits the relative fluorescence lifetime of different test samples based on the relationship between the fluorescence intensity signal and the duty cycle or frequency.

[0050] It should be noted that the fluorescence intensity signal collected by the above-mentioned collector can be transmitted to the processing unit via an electrical signal.

[0051] This invention integrates a light source, pulse generator, collector, and processing unit to construct a system specifically designed for detecting the relative fluorescence lifetime of materials, fundamentally eliminating the dependence of traditional fluorescence lifetime measurement techniques on high temporal resolution hardware. Traditional methods, such as time-correlated single-photon counting or phase-shifting methods, must rely on nanosecond or even picosecond-level time gating, high-speed detectors, precision choppers, or radio frequency modulation systems, resulting in high equipment costs, complex optical paths, and difficult maintenance. Figure 1 This diagram illustrates the fluorescence intensity decay curve over time and the window acquisition sequence in this invention. It shows a typical fluorescence decay curve obtained from a single measurement and exemplarily explains the principle of obtaining lifetime-related data by adjusting the acquisition window, such as decreasing the window sequence, which forms the basis for constructing the response curve. The system of this invention controls the pulse generator through a processing unit to output multiple sets of pulse sequences with differentiated parameters—that is, the same frequency but different duty cycles, or the same duty cycle but different frequencies—to achieve gradient excitation of the sample, allowing the change trend of the fluorescence signal to directly reflect the lifetime characteristics of the material. Figure 2 This diagram illustrates the timing of the synchronous operation of the laser and camera in this invention, showing how the pulse generator coordinates and controls the laser excitation and camera exposure / readout to ensure synchronized and accurate signal acquisition. After acquiring fluorescence intensity signals under different excitation conditions, the processing unit analyzes their relationship with duty cycle or frequency to determine the relative fluorescence lifetime. This invention transforms the complex problem of absolute lifetime measurement into a comparison of macroscopic signal response trends, eliminating the need for exponential decay fitting or high-precision time-resolved acquisition, significantly reducing the hardware requirements for detector response speed, signal synchronization accuracy, and data acquisition rate. Therefore, the system of this invention achieves a technological breakthrough in simplified structure, reduced cost, and compact size, making it particularly suitable for industrial screening, on-site detection, and rapid discrimination scenarios where only lifetime differences need to be detected without obtaining precise values, demonstrating good engineering feasibility and promising application prospects.

[0052] Figure 3This is a schematic diagram illustrating the detection principle of the system used to detect the relative fluorescence lifetime of materials in this invention. It shows the core system architecture, consisting of a light source, pulse generator, acquisition unit, and processing unit (not shown in the diagram), as well as the signal flow and control relationship. The sample to be detected may be many different substances, and its emission wavelength can be... Figure 3 The 525nm, 498nm, and 469nm processes on display are among those shown.

[0053] Preferably, the light source used in the system of the present invention can be a laser, the output wavelength of which is within the excitation spectral response range of the material under test to ensure effective excitation of fluorescence. In addition, the laser can provide high-intensity, monochromatic excitation light. Monochromaticity ensures the concentration and specificity of excitation energy, avoiding multiphoton processes or background interference that may be caused by broadband light sources. High intensity ensures effective excitation, which is especially important for materials with nonlinear processes such as upconversion luminescence.

[0054] Preferably, the pulse generator in this invention is a PWM generator or a device with pulse modulation function, such as a data acquisition card with pulse modulation function. PWM generators are low in cost, fast in response, and high in control precision, making them very suitable for realizing excitation modes with duty cycle gradient changes. Pulse generators with data acquisition functions can further integrate signal acquisition tasks, reduce dependence on external devices, and simplify system connection and communication logic. The data acquisition device can be any of the following: a camera, a spectrometer, or a photomultiplier tube. The camera can be used for imaging detection, especially suitable for parallel acquisition of multi-point, array-type samples, such as rapid scanning of anti-counterfeiting labels, microplates, or microsphere arrays, which can simultaneously acquire spatial distribution and intensity information, improving detection efficiency. The spectrometer can acquire fluorescence emission spectra for analyzing the luminescence characteristics of materials, eliminating background interference or stray peaks, and improving discrimination accuracy, especially suitable for lifetime detection of mixed fluorescence systems or multi-color coded materials. The photomultiplier tube (PMT) has extremely high sensitivity and fast response capability, suitable for detecting weak fluorescence signals, and is often used for low-concentration samples or long-distance detection scenarios. Its output is an analog electrical signal, which is convenient for direct interface with the processing unit for integration and analysis. The three types of data acquisition devices can be flexibly selected according to the actual application scenario: if spatial resolution is required, choose a camera; if spectral resolution is required, choose a spectrometer; if high sensitivity is required, choose a PMT.

[0055] In addition, an objective lens / lens can be placed between the sample and the collector. The objective lens / lens is a key optical component connecting the sample and the collector, enabling efficient collection of fluorescence signals and spatially resolved imaging. Specifically, the objective lens can collect and converge the weak fluorescence signals scattered by the sample to the maximum extent and guide them to the collector, thereby significantly improving the detection sensitivity and signal-to-noise ratio of the system.

[0056] Preferably, when multiple pulse sequences have different duty cycles, the duty cycles of the pulse sequences increase or decrease in a set order. When multiple pulse sequences have different pulse frequencies, the pulse frequencies of the pulse sequences increase or decrease in a set order. To construct a response curve that clearly reflects the material's lifetime characteristics, regular and complete sampling is required in the excitation parameter space. Increasing or decreasing gradient changes are the optimal path to achieve this goal. Based on this logic, the processing unit can automatically, continuously, and without repetition complete the measurement of the entire parameter space, ensuring the uniformity and integrity of the data points. In the duty cycle gradient change mode, by gradually increasing or decreasing the pulse width, the average excitation energy per unit time is changed, thereby affecting the cumulative luminescence intensity of the material. Materials with longer lifetimes can continue to emit light after the excitation pulse is turned off, but due to their inherent slow decay characteristics, the signal growth tends to saturate at high duty cycles, and the integral area increases slowly with increasing duty cycle, resulting in a smaller slope of the response curve. Conversely, materials with shorter lifetimes exhibit stronger accumulation capabilities even at low duty cycles, and the signal increases sharply with increasing duty cycle, resulting in a more pronounced slope in the response curve. The incremental or decremental design ensures a smooth transition between measurement conditions, avoiding system disturbances caused by abrupt changes, while also facilitating automatic control and data alignment by the processing unit. This strategy not only improves experimental repeatability but also provides a high-quality data foundation for subsequent fitting analysis, representing a key control logic for achieving stable and reliable lifetime detection.

[0057] More preferably, the processing unit of the present invention can be a computer. The sample to be tested in the present invention can be a rare-earth-doped upconversion luminescent material, wherein the rare-earth ions are selected from Yb 3+ Er 3+ Tm 3+ Ho 3+ and Nd 3+ At least one of rare earth ions. Upconversion luminescent materials possess a unique energy level structure, capable of converting low-energy light, such as near-infrared, into high-energy light, such as visible light, through a multiphoton nonlinear process. They are widely used in fields such as bioimaging, anti-counterfeiting, and temperature sensing. Their fluorescence lifetime is significantly affected by factors such as the type and concentration of dopant ions, lattice environment, and surface modification; therefore, lifetime is a crucial parameter characterizing their performance and state. However, traditional lifetime measurement methods are difficult to implement in practical applications due to expensive equipment and complex operation. The systematic frequency / power response method of this invention allows for rapid detection of upconversion materials with different doping ratios, different synthesis processes, or different binding states without requiring precise lifetime measurements.

[0058] To achieve effective detection of samples in different states, the system of this invention can employ a targeted optical path configuration. Specifically, Figure 4This is a schematic diagram of the optical path of a relative fluorescence lifetime system for detecting liquid samples. It illustrates a typical optical path layout for solution samples, the core feature of which is the use of a sample cell to hold the liquid being tested. Liquid samples are fluid and must be contained within a sample cell. Therefore, the optical path design must consider the interface effects such as refraction and reflection caused by the light-transmitting window of the sample cell (usually glass or quartz). Figure 4 The orthogonal angle optical path shown can effectively separate excitation light and emission light, and manage these interface reflections, ensuring that the excitation light efficiently penetrates the liquid and collects real in vivo fluorescence signals. Figure 5 This is a schematic diagram of a system for detecting the relative fluorescence lifetime of materials used in solid test samples. It shows a typical optical path layout for solid films, powders, or bulk samples, typically using a glass slide to support the sample. Solid samples, such as films, chips, and powder pellets, are morphologically stable and can usually be placed directly on the glass slide. Therefore, the optical path uses epi-illumination. This design is relatively compact and can maximize the collection of fluorescence emitted from the sample surface while preventing reflected light from the lower surface of the glass slide from entering the collector.

[0059] The present invention also provides a method for detecting the relative fluorescence lifetime of a material using the above-described system, comprising the following steps:

[0060] S1: Multiple pulse sequences are set by the processing unit, wherein the pulse frequencies of the multiple pulse sequences are the same but the duty cycles are different, or the duty cycles are the same but the pulse frequencies are different.

[0061] S2: The processing unit controls the pulse generator to output multiple sets of pulse sequences in sequence, which drive the light source to excite the sample to be tested respectively. The processing unit synchronously controls the collector to collect the fluorescence intensity signal generated by the sample to be tested under different pulse sequences.

[0062] S3: The processing unit receives and processes fluorescence intensity signals from the collector.

[0063] S4: The processing unit detects the relative fluorescence lifetime of different test samples based on the relationship between fluorescence intensity signal and duty cycle or frequency.

[0064] The detection method of this invention first involves a processing unit setting multiple pulse sequences and controlling their frequency or duty cycle variation patterns. Subsequently, a pulse generator sequentially outputs these sequences, driving a light source to perform gradient excitation on the sample. Simultaneously, the processing unit synchronously controls the acquisition unit to collect fluorescence intensity signals under corresponding conditions and converts them into electrical signals. The processing unit receives and processes these signals, extracting the effective fluorescence intensity values. Finally, based on the relationship between intensity and duty cycle or frequency, the relative fluorescence lifetime is detected. This method eliminates the need for complex exponential decay fitting or time-gating techniques, avoiding the reliance on high-precision timing equipment in traditional methods. It significantly reduces algorithm complexity and computational resource requirements. The entire process can be automated, with rapid response, making it suitable for online detection and batch screening. This invention transforms precise lifetime value discrimination into the analysis of macroscopic signal trends, achieving simplicity while maintaining accuracy and significantly improving detection efficiency. It is an ideal solution for low-cost, high-throughput fluorescence lifetime detection.

[0065] Preferably, in step S1 above, when multiple pulse sequences have the same pulse frequency but different duty cycles, in step S4, for each pulse sequence with a specific duty cycle, a curve showing the change of fluorescence intensity over time is obtained by processing the acquired fluorescence intensity signal. Then, the integral area of ​​each curve is calculated. Next, a response curve showing the change of integral area with duty cycle is constructed with the duty cycle as the abscissa and the integral area of ​​the corresponding curve as the ordinate. By comparing the slopes of the response curves of different test samples, the relative fluorescence lifetime of different test samples is detected.

[0066] For each pulse excitation with a specific duty cycle, the collector acquires a curve showing the fluorescence intensity changing over time. The processing unit integrates this curve to obtain the integrated area, which represents the total luminescence. The integrated area reflects the cumulative luminescence capability of the material at that duty cycle. Subsequently, a response curve is constructed with the duty cycle as the x-axis and the integrated area as the y-axis. Due to the slow decay characteristics of materials with longer lifetimes, the integrated area changes gradually at different duty cycles, resulting in a smaller slope in the response curve. Conversely, materials with shorter lifetimes are more sensitive to changes in duty cycle, and the integrated area increases sharply with increasing duty cycle, resulting in a larger slope in the response curve. Therefore, by comparing the slopes of the response curves of different test samples, their relative fluorescence lifetime can be intuitively determined: a larger slope indicates a shorter lifetime, and a smaller slope indicates a longer lifetime. The detection method of this invention does not require precise measurement of the decay time constant, avoiding complex fitting, and can collect more data points within the same time period, improving statistical accuracy. It is particularly suitable for the discrimination of materials with small lifetime differences but obvious trends, representing a high-sensitivity, low-complexity lifetime detection strategy.

[0067] Preferably, in step S1, when multiple pulse sequences have the same duty cycle but different pulse frequencies, in step S4, for each pulse sequence at a specific frequency, a curve showing the change of fluorescence intensity over time is obtained by processing the acquired fluorescence intensity signal. Then, the integral area of ​​each curve is calculated. Next, a response curve showing the change of integral area over frequency is constructed with frequency as the abscissa and the integral area of ​​the corresponding curve as the ordinate. By comparing the slopes of the response curves of different test samples, the relative fluorescence lifetime of different test samples is detected.

[0068] For each specific frequency pulse excitation, the collector acquires a time-fluorescence intensity curve, and the processing unit calculates its integral area, representing the total fluorescence output at that frequency. A frequency response curve is constructed with frequency on the x-axis and integral area on the y-axis. Materials with longer lifetimes have sufficient time to fully decay at low frequencies, resulting in a high integral area. As the frequency increases, the excitation interval shortens, and the material is re-excited before complete decay, leading to signal saturation, slower growth of the integral area, and a smaller curve slope. Conversely, materials with shorter lifetimes complete the luminescence process rapidly, and their cumulative fluorescence intensity is approximately proportional to the excitation frequency, thus exhibiting a larger slope on the frequency-integral area response curve. Therefore, the response curves of materials with different lifetimes exhibit significantly different slope characteristics: the shorter the lifetime, the steeper the slope of the response curve; the longer the lifetime, the steeper the slope of the response curve. Thus, the response curves of materials with different lifetimes exhibit different slope characteristics. By comparing these slopes, the relative lifetimes of different materials can be effectively determined. This method is equivalent to power response analysis. Since frequency changes directly affect the average power, it is particularly suitable for nonlinear luminescent systems such as upconversion materials. It can reveal the excitation dynamics of materials and is a physically meaningful and easy-to-implement lifetime determination method.

[0069] More preferably, the processing unit of the present invention can also be used to control the light source, enabling the light source to output multiple sets of excitation light with different excitation powers. The processing unit can detect the relative fluorescence lifetime of different test samples based on the relationship between fluorescence intensity signal and excitation power. Specifically, in step S1, multiple sets of excitation powers can be set by the processing unit. Correspondingly, in step S4, for each specific excitation power, a fluorescence intensity-time curve is obtained by processing the acquired fluorescence intensity signal. Then, the integral area of ​​each curve is calculated. Next, a response curve of integral area changing with laser power is constructed with power as the abscissa and the integral area of ​​the corresponding curve as the ordinate. By comparing the slopes of the response curves of different test samples, the relative fluorescence lifetime of different test samples is detected.

[0070] More preferably, in step S4 above, fluorescence intensity signals are collected and their integrated area is calculated within the same time period, or fluorescence intensity signals are collected and their integrated area is calculated under the action of the same number of excitation pulses.

[0071] In a constant-duration mode, such as within 20 ms, fluorescence signals are acquired for a fixed duration under each frequency or duty cycle condition. The integral area reflects the cumulative luminescence per unit time. Long-lived fluorescent materials may have a larger integral area in this mode due to continuous luminescence, but their growth rate (slope) with parameter changes is smaller. In a constant-pulse-number mode, such as 10 pulses, fluorescence signals are acquired after a fixed number of pulses of excitation under each condition. The integral area reflects the average response of each excitation cycle. Long-lived materials emit more luminescence in each cycle, but are prone to saturation at high frequencies, resulting in a smaller slope in the response curve.

[0072] Traditional fluorescence lifetime measurement is a time-domain method, while this invention achieves an equivalent Fourier transform of the fluorescence decay response at the hardware level through systematic modulation of the pulse frequency or duty cycle.

[0073] To further clarify the present invention and its technological advancements, the following description is provided in conjunction with specific embodiments and technical effects.

[0074] Example 1

[0075] This embodiment aims to verify whether the present invention can effectively detect the relative fluorescence lifetimes of two upconversion luminescent nanomaterials with different rare-earth doping. Specifically, it is known that sample A has a longer fluorescence lifetime, while sample B has a shorter fluorescence lifetime.

[0076] A detection system for measuring the relative fluorescence lifetime of materials was employed, which included a 980nm semiconductor laser, a PWM pulse generator, a spectrometer set to acquire data at the 550nm emission peak, and a computer.

[0077] The pulse duty cycle was set to 50%, and the pulse frequency was increased in 10 gradients from 50 Hz to 1000 Hz. At each frequency, the spectrometer acquired fluorescence signals over a fixed time period (40 ms). Figure 6 as well as Figure 7 , Figure 6 as well as Figure 7 The image only shows the time-fluorescence intensity curves for 50Hz, 500Hz, and 1000Hz. The curve at 50Hz does not exhibit a periodic pattern and should be discarded. The time-fluorescence intensity curve at 50Hz is then discarded, and a fixed time period (20ms) is selected to obtain... Figure 8 as well as Figure 9 Processing unit calculation Figure 8 as well as Figure 9 The integral area of ​​each time-fluorescence intensity curve is calculated, and then the slope of each response curve is calculated to obtain... Figure 10 .

[0078] pass Figure 10It can be seen that the slope of the response curve corresponding to sample A is smaller than that of sample B. Therefore, the fluorescence lifetime of sample A is longer and the fluorescence lifetime of sample B is shorter, which is completely consistent with the actual relative fluorescence lifetimes of samples A and B.

[0079] Example 2

[0080] This embodiment also aims to verify whether the present invention can effectively detect the relative fluorescence lifetimes of two upconversion luminescent nanomaterials with different rare earth doping. Specifically, it is known that sample A has a longer fluorescence lifetime, while sample B has a shorter fluorescence lifetime.

[0081] The difference between this embodiment and Embodiment 1 is that, after discarding the time-fluorescence intensity curve at 50Hz, a quantitative pulse method is used. The current data is still used, but 10 pulses are employed. The processing unit calculates the integral area of ​​each selected time-fluorescence intensity curve, and then calculates the slope of each response curve to obtain... Figure 11 .

[0082] pass Figure 11 It can be seen that the slope of the response curve corresponding to sample A is smaller than that of sample B. Therefore, the fluorescence lifetime of sample A is longer and the fluorescence lifetime of sample B is shorter, which is completely consistent with the actual relative fluorescence lifetimes of samples A and B.

[0083] Example 3

[0084] This embodiment aims to verify whether the present invention can effectively detect the relative fluorescence lifetimes of two upconversion luminescent nanomaterials with different rare-earth doping. Specifically, it is known that sample C has a longer fluorescence lifetime, while sample D has a shorter fluorescence lifetime.

[0085] A detection system for measuring the relative fluorescence lifetime of materials was employed, which included a 980nm semiconductor laser, a PWM pulse generator, a spectrometer set to acquire data at the 525nm emission peak, and a computer.

[0086] The pulse frequency was set to 500 Hz, and the pulse duty cycle was decreased in five gradients from 50% to 10%. At each pulse duty cycle, the spectrometer acquired fluorescence signals within 40 ms. The area under the integral of each time-fluorescence intensity curve was selected within a fixed time period (20 ms), and the slope of each response curve was calculated. Sample C had a smaller slope, while sample D had a larger slope; therefore, sample C had a longer fluorescence lifetime, and sample D had a shorter fluorescence lifetime. This is completely consistent with the actual relative fluorescence lifetimes of samples C and D.

[0087] Example 4

[0088] This embodiment aims to verify whether the present invention can effectively detect the relative fluorescence lifetimes of two upconversion luminescent nanomaterials with different rare-earth doping. Specifically, it is known that sample C has a longer fluorescence lifetime, while sample D has a shorter fluorescence lifetime.

[0089] The difference between this embodiment and embodiment 3 is that it switches to a fixed pulse quantity mode, using 10 pulses in both. The processing unit calculates the integral area of ​​each selected time-fluorescence intensity curve, and then calculates the slope of each response curve. It still concludes that the slope of sample C is less than that of sample D. Therefore, the fluorescence lifetime of sample C is longer and the fluorescence lifetime of sample D is shorter.

[0090] Example 5

[0091] This embodiment aims to verify how the present invention detects the relative fluorescence lifetimes of two upconversion luminescent nanomaterials with different rare-earth doping by changing the excitation power. Specifically, it is known that sample E has a longer fluorescence lifetime, while sample F has a shorter fluorescence lifetime.

[0092] A detection system for measuring the relative fluorescence lifetime of materials is employed, which includes a 980nm semiconductor laser, a laser driver with power control, a spectrometer set to acquire data at the 469nm emission peak, and a computer.

[0093] The laser's drive current is controlled by the processing unit, causing the laser's output power to increase in gradients from 50mW to 300mW, for a total of eight gradients. At each power point, the laser operates in pulse mode with a fixed frequency of 500Hz and a duty cycle of 50%. The spectrometer collects fluorescence signals over a fixed time period (30ms), obtaining the time-fluorescence intensity curve for each power point. The processing unit calculates the integral area of ​​each time-fluorescence intensity curve, then constructs a response curve of the integral area as a function of laser power, with laser power as the abscissa and the integral area as the ordinate, and calculates the slope of this response curve.

[0094] By comparing the slopes of the response curves of samples E and F, it was found that in the low-power region (50-150mW), the slope of the response curve of sample E was significantly smaller than that of sample F. Therefore, it was determined that sample E, with its smaller slope in the low-power region, has a longer fluorescence lifetime. This is completely consistent with the actual relative fluorescence lifetimes of samples E and F.

[0095] Example 6

[0096] The difference between this embodiment and Embodiment 5 is that a fixed pulse number mode is used for data acquisition. At each power point, a fixed number (8) of fluorescence signals generated by pulse excitation are acquired, their integral area is calculated, and a power-integral area response curve is constructed.

[0097] The results showed that, under constant pulse number mode, the slope of the response curve of sample E was still smaller than that of sample F, further verifying that sample E has a longer fluorescence lifetime.

[0098] Additionally, it should be noted that the above embodiments are only applicable to rare-earth upconversion nanomaterials. For other types of fluorescent materials, the relationship between the slope of the response curve and the relative fluorescence lifetime needs to be determined based on the corresponding luminescence characteristics. The result may be that a larger slope corresponds to a shorter relative lifetime, or vice versa. However, there is no doubt that the system and method of the present invention can distinguish the relative lifetimes of different fluorescent / luminescent materials based on the differences in the slopes of the response curves.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A system for detecting the relative fluorescence lifetime of a material, characterized in that, include: A light source is used to excite the sample to be tested, causing it to fluoresce. A pulse generator, electrically connected to a light source, is used to generate pulse signals to drive the light source to excite the sample under test; The collector is positioned in the fluorescence emission path of the sample to be tested and is used to collect the fluorescence intensity signal generated by the sample. The processing unit is communicatively connected to the pulse generator and the acquisition unit, and is used to control the pulse generator to output multiple sets of pulse sequences in sequence. The pulse frequencies of the multiple sets of pulse sequences are the same but the duty cycles are different, or the duty cycles are the same but the pulse frequencies are different. The processing unit is also used to receive and process fluorescence intensity signals from the collector, and then detect the relative fluorescence lifetime of different test samples based on the relationship between fluorescence intensity signals and duty cycle or frequency.

2. The system according to claim 1, characterized in that, The light source is a laser, and the pulse generator is a PWM generator or a device with pulse modulation function.

3. The system according to claim 1, characterized in that, The data acquisition device is a camera, spectrometer, or photomultiplier tube.

4. The system according to claim 1, characterized in that, When multiple pulse sequences have different duty cycles, the duty cycles of the pulse sequences increase or decrease in a set order; when multiple pulse sequences have different pulse frequencies, the pulse frequencies of the pulse sequences increase or decrease in a set order.

5. The system according to claim 1, characterized in that, The sample to be tested is a rare-earth-doped upconversion luminescent material.

6. A method for detecting the relative fluorescence lifetime of a material using the system according to any one of claims 1-5, characterized in that, Includes the following steps: S1: Multiple pulse sequences are set by the processing unit, wherein the pulse frequencies of the multiple pulse sequences are the same but the duty cycles are different, or the duty cycles are the same but the pulse frequencies are different. S2: The processing unit controls the pulse generator to output multiple pulse sequences in sequence, which drive the light source to excite the sample to be tested respectively. The processing unit synchronously controls the collector to collect the fluorescence intensity signal generated by the sample to be tested under different pulse sequences. S3: The processing unit receives and processes fluorescence intensity signals from the collector; S4: The processing unit detects the relative fluorescence lifetime of different test samples based on the relationship between fluorescence intensity signal and duty cycle or frequency.

7. The method according to claim 6, characterized in that, In step S1, when multiple pulse sequences have the same pulse frequency but different duty cycles, in step S4, for each pulse sequence with a specific duty cycle, a curve showing the change of fluorescence intensity over time is obtained by processing the acquired fluorescence intensity signal. Then, the integral area of ​​each curve is calculated. Next, a response curve showing the change of integral area with duty cycle is constructed with the duty cycle as the abscissa and the integral area of ​​the corresponding curve as the ordinate. By comparing the slopes of the response curves of different test samples, the relative fluorescence lifetime of different test samples is detected.

8. The method according to claim 6, characterized in that, In step S1, when multiple pulse sequences have the same duty cycle but different pulse frequencies, in step S4, for each pulse sequence at a specific frequency, a curve showing the change of fluorescence intensity over time is obtained by processing the acquired fluorescence intensity signal. Then, the integral area of ​​each curve is calculated. Next, a response curve showing the change of integral area over frequency is constructed with frequency as the abscissa and the integral area of ​​the corresponding curve as the ordinate. By comparing the slopes of the response curves of different test samples, the relative fluorescence lifetime of different test samples is detected.

9. The method according to any one of claims 7-8, characterized in that, In step S4, fluorescence intensity signals are collected and their integrated area is calculated within the same time period, or fluorescence intensity signals are collected and their integrated area is calculated under the same number of excitation pulses.

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