Long afterglow nanoparticles, nanoprobe, double-probe system and detection method

Abstract

The invention belongs to the technical field of luminescent materials, and discloses long afterglow nanoparticles, a nanoprobe, a double-probe system and a detection method. The general chemical formula of the long afterglow nanoparticles is Li < x > Zn < 1-x > Ga < 2 > O < 4 >: Cr, and the value range of x is 0.1-0.5. According to the long-afterglow nanoparticles provided by the invention, the industrial problem that the luminescent property of ZnGa2O4: Cr < 3 + > PLNPs synthesized by a hydrothermal method is poor is successfully solved through an innovative doping strategy that Zn < 2 + > is partially replaced by Li < + >. The doping of Li < + > effectively optimizes the lattice structure and the concentration and depth of electron traps, so that the afterglow intensity and average life of the material in a near-infrared window are enhanced in a breakthrough manner. A hydroxyethyl chitosan layer is modified on the surface of a long afterglow nano particle to obtain a nano probe, and the probe has unique pH response charge conversion capability. The probe is used for polystyrene nano-plastic detection, the detection limit is low, and the linear range is wide.

Description

Technical Field

[0001] This invention relates to the field of luminescent materials technology, specifically to long-afterglow nanoparticles, nanoprobes, dual-probe systems, and detection methods. Background Technology

[0002] Persistent luminescence nanoparticles (PLNPs) are functional materials that continue to emit light after excitation has ceased. Their luminescence originates from the storage and slow release of excitation energy at defect energy levels within the material. With their unique advantages, such as no in-situ excitation and no background fluorescence interference, PLNPs show great application potential in fields such as bioimaging, disease diagnosis, environmental monitoring, and anti-counterfeiting encryption. Among them, zinc gallate-based doped trivalent chromium ions (ZnGa2O4:Cr) are particularly promising. 3+ PLNPs, due to their excellent near-infrared long afterglow performance and good biocompatibility, have become one of the current research hotspots.

[0003] Currently, the synthesis of ZnGa2O4:Cr 3+ The main methods for synthesizing PLNPs include high-temperature solid-state methods and hydrothermal methods. While high-temperature solid-state methods can produce materials with high luminescence, they typically require high energy consumption and harsh reaction conditions, easily leading to particle agglomeration, size inhomogeneity, and uncontrollable morphology, thus limiting their subsequent biological applications. In contrast, hydrothermal methods offer milder reaction conditions, controllable morphology, and good crystallinity, making them more suitable for synthesizing uniformly dispersed nanoscale PLNPs. However, the hydrothermal synthesis of ZnGa2O4:Cr... 3+ PLNPs generally suffer from weak luminescence intensity and short afterglow lifetime, and their performance is usually inferior to samples prepared by high-temperature solid-state methods, which greatly limits their application in high-sensitivity detection fields. The root cause lies in the failure to optimize and control the concentration and depth of crystal defect structures and electron traps in hydrothermal synthesis. Therefore, it is necessary to develop a novel ZnGa2O4:Cr luminescence material with high intensity and long lifetime luminescence that can be prepared by a mild hydrothermal method. 3+ Developing PLNPs-based materials and expanding their application in high-sensitivity detection is a pressing technical challenge in this field.

[0004] On the other hand, pollution from nanoplastics (NPs) in the environment is becoming increasingly serious, especially polystyrene nanoplastics (PS NPs), which pose a potential threat to ecosystems and human health. However, rapid, highly sensitive, and highly specific detection of trace PSNPs in the environment remains a significant challenge. Traditional methods such as chromatography and mass spectrometry suffer from problems such as complex sample preparation, expensive equipment, and difficulty in on-site detection. While antibody-based immunoassays are specific, antibodies are costly, have poor stability, and are easily affected by complex environmental matrices.

[0005] In recent years, although some studies have attempted to use functional nanomaterials for pollutant detection, their application in PS NPs detection still generally faces the following problems: (1) Insufficient detection sensitivity, making it difficult to achieve pg / mL detection. -1 (1) The detection of trace amounts of PS is not effective; (2) It has poor specificity and cannot effectively distinguish PS from other types of nanoplastics (such as PP, PE, PVC, etc.); (3) The detection process is complicated and easily affected by the environmental matrix, resulting in poor recovery rate and stability in actual samples.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] The present invention aims to solve at least one of the above technical problems, and provides long-afterglow nanoparticles, nanoprobes, dual-probe systems and detection methods.

[0008] To achieve the above objectives, the first technical solution adopted by the present invention is as follows: Long afterglow nanoparticles, with the general chemical formula Li x Zn 1-x Ga2O4:Cr³⁺, where x ranges from 0.1 to 0.5.

[0009] Preferably, the value of x is 0.3 or 0.5.

[0010] Preferably, the preparation method is as follows: dissolve zinc source, gallium source, lithium source and chromium source in water, adjust the pH of the solution to alkaline, and separate the long afterglow nanoparticles after hydrothermal reaction.

[0011] Preferably, the hydrothermal reaction temperature is 200 ℃-220 ℃, and the reaction time is 18-24 hours.

[0012] The second technical solution adopted in this invention is: The nanoprobe comprises long-afterglow nanoparticles as described in the first technical solution and a hydroxyethyl deacetylated chitosan layer modified on its surface, namely PLNPs@GCS probe.

[0013] Preferably, the mass ratio of long afterglow nanoparticles to hydroxyethyl deacetylated chitosan raw material is 1:(1-10).

[0014] The third technical solution adopted in this invention is: A dual-probe system for detecting polystyrene nanoplastics includes a second technical approach nanoprobe and a Fe3O4@Au-PSBP probe, which consists of gold-coated magnetite spheres coupled with a polypeptide that specifically binds to polystyrene.

[0015] Preferably, the PLNPs@GCS probe and the Fe3O4@Au-PSBP probe form a composite through electrostatic interaction and bridging by polystyrene nanoplastics.

[0016] The fourth technical solution adopted in this invention is: A method for detecting polystyrene nanoplastics, characterized by using a dual-probe system based on a third technical solution, comprising the following steps: The sample to be tested is brought into contact with PLNPs@GCS probe and Fe3O4@Au-PSBP probe to form a composite bridged by polystyrene nanoplastics, and unreacted free probes are removed. The composite was treated under conditions suitable for the dissociation of the PLNPs@GCS probe, and the Fe3O4@Au-PSBP probe was removed by magnetic separation. The afterglow emission signal of the separated PLNPs@GCS probe was detected, and the content of polystyrene nanoplastics in the sample was determined based on the signal intensity.

[0017] Preferably, the method for determining the content of polystyrene nanoplastics in a sample based on signal intensity is as follows: the measured afterglow emission signal intensity is compared with a pre-established standard curve of polystyrene nanoplastic concentration and afterglow emission signal intensity.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The long afterglow nanoparticles provided by this invention, through Li + Partial replacement of Zn 2+ An innovative doping strategy was developed, successfully solving the problem of hydrothermal synthesis of ZnGa2O4:Cr 3+ The industry challenge of poor luminescent performance of PLNPs. Li + The doping effectively optimizes the lattice structure and the concentration and depth of electron traps, resulting in a breakthrough enhancement in the afterglow intensity and average lifetime of the material in the near-infrared window (~700 nm). By precisely controlling the doping ratio x, the luminescence intensity or afterglow time of the material can be specifically optimized to meet the needs of different application scenarios. At the same time, the material has excellent rechargeability and can be repeatedly activated by ultraviolet light or LED red light to achieve repeatable decay cycles, making it highly practical. This material can be synthesized in one step by hydrothermal method, avoiding the high energy consumption and particle agglomeration problems of high-temperature solid-state methods, and realizing the low-temperature, green, and controllable synthesis of small-sized, highly crystalline, and high-performance PLNPs.

[0019] The PLNPs@GCS probe provided by this invention modifies the surface of long-afterglow nanoparticles with a hydroxyethyl deacetylated chitosan (GCS) layer. This probe possesses a unique pH-responsive charge-switching capability. Under acidic conditions, the surface is positively charged, allowing it to efficiently bind to negatively charged PS NPs. Under alkaline conditions, the surface is negatively charged, enabling it to effectively dissociate from the always negatively charged Fe3O4@Au-PSBP-PS complex. This characteristic is the core for achieving high-sensitivity, low-background detection. The GCS shell not only provides PLNPs with good water solubility and dispersion stability but also lays the foundation for potential in vivo applications due to its natural biocompatibility. The surface modification process does not impair the excellent long-afterglow performance of the PLNP core, making it a stable, reliable, and autofluorescent signal reporter unit.

[0020] The "magnetic separation probe (Fe3O4@Au-PSBP) + signal probe (PLNPs@GCS)" dual probe system provided by this invention is used to detect PS NPs. Based on the highly specific targeting recognition ability of PSBP peptides for PS NPs, it can effectively distinguish PS from other common nanoplastics (such as PP, PE, PET, PVC, etc.), ensuring the specificity of detection from the source. The Fe3O4 magnetic core makes the separation operation in the entire detection process fast, simple and efficient, easy to automate, and can effectively enrich the target analyte and reduce matrix interference. PS NPs act as a "bridge" to convert their concentration information into the number of magnetically separable complexes, which are then amplified and output through the afterglow signal of the dissociated PLNPs@GCS, realizing a sensitive conversion from the recognition event to the optical signal.

[0021] The method for detecting polystyrene nanoplastics provided by this invention fully utilizes the advantages of long-afterglow luminescence without background interference and the dual-probe signal amplification mechanism, achieving a detection limit for PS NPs as low as 0.033 pg mL. -1 Wide linear range (0.01 pg mL) -1 - 800 pg mL -1 This method surpasses existing detection technologies in many aspects. It can also effectively eliminate interference from complex environmental matrices, and in actual sample testing, the spiked recovery rate is excellent (92.59% - 104.70%), with a small relative standard deviation (RSD) and good repeatability. This method does not require large and expensive instruments, the detection process can be completed in a short time, and the probe can be recharged and used, which significantly reduces the cost of a single detection. It provides a powerful and practical tool for large-scale environmental screening and daily monitoring of PSNPs. Attached Figure Description

[0022] Figure 1 In Example 1, Li (a) and (b) are respectively... x Zn1-x Ga2O4:Cr 3+ TEM images and particle size distribution maps (n=200) for x=0-0.5. Figure 2 In Example 1, Li (a) and (b) are respectively... x Zn 1-x Ga2O4:Cr 3+ XRD patterns (x=0-0.5), relative intensity of crystallinity of 311 crystal plane (x=0=100%). Figure 3 In Example 1, Li (a) and (b) are respectively... x Zn 1-x Ga2O4:Cr 3+ (x=0-0.5) Afterglow emission spectrum (ex. 254 nm), excitation spectrum (em. 700 nm); (c) Li x Zn 1-x Ga2O4:Cr 3+ (d) is the afterglow attenuation image of Li (x=0.3); x Zn 1-x Ga2O4:Cr 3+ Afterglow decay curve (x=0-0.5); Figure 4 In Example 1, (a), (b), (c), (d), (e), and (f) represent the values ​​of Li when x=0, x=0.1, x=0.2, x=0.3, x=0.4, and x=0.5, respectively. x Zn 1-x Ga2O4:Cr 3+ The afterglow decay curve of re-excitation; Figure 5 (a) is the afterglow emission spectrum of Li2Ga2O4:Cr; (b) is the transmission electron microscope image of Li2Ga2O4:Cr. Figure 6 In example (a), Li is shown in Example 1. x Zn 1-x Ga2O4:Cr 3+ The diffuse reflectance spectra of Li (x=0-0.5) are shown in (b), (c), (d), (e), (f), and (g), which represent the Li values ​​at x=0, x=0.1, x=0.2, x=0.3, x=0.4, and x=0.5, respectively. x Zn 1-x Ga2O4:Cr 3+ Kubelka-Munk diagram; Figure 7 In Example 1, Li (a) and (b) are respectively... + Doped ZnGa2O4:Cr3+ Thermoluminescence spectrum and luminescence mechanism diagram of PLNPs; Figure 8 In the middle, (a), (b), and (c) are respectively the transmission electron microscope image, particle size distribution map, and energy dispersive spectroscopy elemental distribution map of PLNPs@GCS in Example 2; Figure 9 (a) and (b) are the potential characterization diagrams and infrared characterization diagrams of PLNPs, PLNPs-OH, PLNPs-NH2 and PLNPs@GCS in Example 2, respectively; (c) is the potential change diagram of PLNP@GCS under different pH conditions; (d) is the thermogravimetric analysis diagram of PLNPs and PLNPs@GCS. Figure 10 (a) shows the photoluminescence spectra of Fe3O4@Au-PSBP, PLNPs@GCS and Fe3O4@Au-PSBP-PLNPs@GCS composites in Example 4; (b), (c) and (d) are the effects of PLNPs@GCS dosage, detection time and composite probe separation time on the detection signal, respectively. Figure 11 (a) shows the change of afterglow emission signal in the solution after magnetic separation with PS NPs in Example 4; (b) shows the relationship between the change in afterglow emission intensity in the solution after magnetic separation and the concentration of PS NPs; (c) shows the selectivity of PS NP detection. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0024] The first embodiment of the present invention provides long afterglow nanoparticles with the general chemical formula Li. x Zn 1-x Ga2O4:Cr³⁺, where x ranges from 0.1 to 0.5.

[0025] This invention creatively introduces Li + Doped ZnGa2O4:Cr 3+ PLNPs, Li + Doping replaces part of the zinc ion Zn 2+ And by precisely controlling the Zn / Li ratio x, the synthesized Li x Zn 1-xGa2O4:Cr³⁺ exhibits excellent long-term near-infrared (NIR) luminescence performance, maintaining the advantage of its original nanoscale size (<40 nm). It adds new traps and deepens the inherent trap depth, significantly optimizing the defect structure and luminescence properties of the material, thus enhancing the performance of ZnGa2O4:Cr. 3+ The afterglow emission (PL) intensity and lifetime of the long afterglow nanoparticles (PLNPs) were investigated. These PLNPs have a cubic spinel structure, and the crystallinity of the 311 crystal facet increases with increasing x, reaching a maximum at x=0.3. They exhibit a near-infrared afterglow emission peak at 700 nm and can be repeatedly activated by ultraviolet or red light.

[0026] In some preferred embodiments, the value of x is 0.3 or 0.5.

[0027] The long-afterglow nanoparticles used in this invention are prepared by a commonly used hydrothermal synthesis method. The preparation method involves dissolving zinc, gallium, lithium, and chromium sources in water, adjusting the pH of the solution to alkaline, and then separating the nanoparticles after a hydrothermal reaction. Specific parameters are not limited, and those skilled in the art can select appropriate parameters based on the suitability of the raw materials.

[0028] As an example, Zn is mixed under vigorous stirring. 2+ Ga 3+ Li + Cr 3+ The pH was adjusted to 8-9, and the resulting turbid solution was stirred vigorously at room temperature for 1-2 hours. The mixture was then subjected to hydrothermal reaction at 200-220 °C for 18-24 hours. The nanoparticles were collected by centrifugation and washed. The zinc, gallium, lithium, and chromium sources used could be zinc nitrate hexahydrate, gallium nitrate, lithium nitrate, and chromium nitrate, respectively.

[0029] The second embodiment of the present invention provides a nanoprobe comprising the long afterglow nanoparticles described in the first embodiment and a hydroxyethyl deacetylated chitosan layer modified on its surface, namely, a PLNPs@GCS probe.

[0030] After modification with GCS, PLNPs yielded PLNPs@GCS probes with a clear core-shell structure. The GCS shell thickness was approximately 2 nm, and the particle size was around 23 nm. GCS surface modification endowed the PLNPs@GCS probes with pH-responsive charge-switching capabilities. In acidic environments, the protonation of free amino groups in the GCS backbone was enhanced, resulting in a positively charged probe that could efficiently bind to negatively charged PS NPs. In alkaline environments, the probe surface became negatively charged.

[0031] There are no specific limitations on the preparation method of PLNPs@GCS probes, as long as GCS can be loaded onto the surface of PLNPs. Those skilled in the art can select appropriate preparation methods based on the modifying components and the target of modification. For example, the surface of PLNPs can be sequentially modified by hydroxylation, amylation, and amide reaction to modify GCS. The amount of GCS grafted is directly related to the pH-responsive charge conversion ability of the PLNPs@GCS probe. Therefore, the amount of GCS grafted can be adaptively adjusted by those skilled in the art according to the required response pH, using the amounts of PLNPs and GCS as raw materials. For example, if the mass ratio of PLNPs to GCS is 1:(1-10), the amount of hydroxyethyl deacetylated chitosan grafted onto the surface of the nanoprobe is approximately 0.047 mg GCS per 1 mg PLNPs.

[0032] As a specific example: 1) Hydroxylation modification: PLNPs were uniformly dispersed in NaOH solution and stirred vigorously for 10-16 h to obtain hydroxylated long afterglow nanomaterials (PLNPs-OH), which were then centrifuged, washed, and vacuum dried; 2) Aminoation modification: PLNPs-OH were uniformly dispersed in anhydrous ethanol solution, and 3-aminopropyltriethoxysilane was added dropwise under magnetic stirring. The mixture was stirred at 60℃ for 12-14 h, and the amino-functionalized long afterglow nanomaterials (PLNPs-NH2) were collected by centrifugation, washed, and dried; 3) Amide reaction modification of GCS: PLNPs in PBS solution, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDC), and N-hydroxysuccinimide (NHS) were mixed uniformly and pre-activated by electromagnetic stirring at room temperature for 2-4 h. Then GCS was added, and the pH of the reaction system was adjusted to 7.5-8.5. The reaction was stirred at 60℃ for 10-14 h. Centrifuge after h, wash and redisperse the precipitate in PBS solution (pH 5.5 and pH 7.4), and store at 4℃ for later use.

[0033] The third embodiment of the present invention provides a dual probe system for detecting polystyrene nanoplastics, comprising the nanoprobe of the second embodiment; and the Fe3O4@Au-PSBP probe, which is composed of a gold-shelled magnetite ball coupled with a polypeptide that specifically binds to polystyrene.

[0034] The amino acid sequence of the polypeptide PSBP that specifically binds to polystyrene is CHWGMWSY, cysteine-histidine-tryptophan-glycine-methionine-tryptophan-serine-tyrosine.

[0035] In this dual-probe system, the Fe3O4@Au-PSBP has a negative potential that does not change with pH, ​​while the PLNPs@GCS has a positive potential under acidic conditions and a negative potential under alkaline conditions. It can switch between electrostatic adsorption and electrostatic repulsion depending on pH changes. Based on this characteristic, Fe3O4@Au-PSBP serves as a magnetic separation probe, and PLNPs@GCS as a pH-responsive signal probe. The two can form a complex through electrostatic interactions and bridging with polystyrene nanoplastics. Furthermore, based on the highly specific targeting ability of PSBP peptides for PS NPs, it can effectively distinguish PS from other common nanoplastics, ensuring the specificity of the detection from the source. The Fe3O4 magnetic core makes the separation operation in the entire detection process fast, simple, and efficient, easily automatable, and effectively enriches the target analyte while reducing matrix interference. PS NPs act as a "bridge," converting their concentration information into the number of magnetically separable complexes, which are then amplified and output through the afterglow signal of the dissociated PLNPs@GCS, achieving a sensitive conversion from event recognition to optical signal.

[0036] The preparation method of the Fe3O4@Au-PSBP probe is a commonly used method in this field, which can achieve the modification of gold-encapsulated iron(III) oxide with PSBP. As a specific example, PSBP is dissolved in dimethyl sulfoxide (DMSO), mixed with Fe3O4@Au for 12-24 hours, magnetically separated, and unreacted peptides are discarded by magnetic separation. The Fe3O4@Au-PSBP probe is collected and washed.

[0037] The fourth embodiment of the present invention provides a method for detecting polystyrene nanoplastics, using the dual-probe system of the third embodiment, and includes the following steps: The sample to be tested is brought into contact with PLNPs@GCS probe and Fe3O4@Au-PSBP probe to form a composite bridged by polystyrene nanoplastics, and unreacted free probes are removed. The composite was treated under conditions suitable for the dissociation of the PLNPs@GCS probe, and the Fe3O4@Au-PSBP probe was removed by magnetic separation. The afterglow emission signal of the separated PLNPs@GCS probe was detected, and the content of polystyrene nanoplastics in the sample was determined based on the signal intensity.

[0038] This detection method utilizes the negative charge of PS NPs and the pH-responsive charge conversion characteristics of PLNPs@GCS probes as a switch to control the "on" and "off" of the signal. The main principle is "dual probe recombination-dissociation-detection". Initially, black Fe3O4@Au-PSBP binds to luminescent PLNPs@GCS, causing light shielding and signal shutdown. The number of captured PS NPs determines how much negative charge Fe3O4@Au-PSBP gains after capture, attracting more positively charged PLNPs@GCS for quenching via electrostatic adsorption. Magnetic separation removes any unquenched PLNPs@GCS probes. When the pH switches to alkaline, the PLNPs@GCS reverse from positive to negative charge, releasing the attracted PLNPs@GCS probes for detection via electrostatic repulsion. The higher the concentration of PS NPs in the sample, the more negative charge Fe3O4@Au-PSBP captures, attracting more positively charged PLNPs@GCS. This results in more PLNPs@GCS being released after pH switching, leading to a stronger detected afterglow signal. This method enables highly sensitive detection of polystyrene nanoplastics, with a detection range of 0.01 pg / mL. −1 -800 pg mL −1 The detection limit is as low as 0.033 pg mL. −1 .

[0039] As some preferred embodiments, during the detection process, the amount of PLNPs@GCS is 300 μL-700 μL, and the amount of Fe3O4@Au-PSBP is 150 μL-250 μL; the detection time, which is the time for the Fe3O4@Au-PSBP probe to capture PS and react with PLNPs@GCS, is generally controlled to be 20 min-90 min; the separation time, which is the time for PLNPs@GCS to dissociate from the combination of Fe3O4@Au-PSBP and PS, is generally controlled to be 30 min-70 min.

[0040] Due to Cr 3+ The "fingerprint" characteristic peak of the luminescent center is around 700 nm. In order to obtain the strongest luminescence signal while minimizing background interference, the intensity of the afterglow luminescence signal of the PLNPs@GCS at a wavelength of 700 nm was detected.

[0041] In some preferred embodiments, the measured afterglow emission signal intensity is compared with a pre-established standard curve of PS NPs concentration versus afterglow emission signal intensity to determine the content of polystyrene nanoplastics in the sample.

[0042] The following provides several specific embodiments to describe in detail the long-afterglow nanoparticles, nanoprobes, dual-probe systems, and detection methods, and characterize their respective properties.

[0043] The reagents used in the following examples are from the following sources: Zinc nitrate hexahydrate (Zn(NO3)2·6H2O, 99.99%), gallium nitrate (Ga(NO3)3, 99.99%), chromium nitrate (Cr(NO3)2·9H2O, 99.99%), lithium nitrate (LiNO3, 99.99%), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDC), N-hydroxysuccinimide (NHS), and hydroxyethyl deacetylated chitosan (GCS) were all purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. (Shanghai, China); 3-aminopropyltriethoxysilane (APTES) was purchased from Sangon Biotech (Shanghai) Co., Ltd. (Shanghai, China); ultrapure water was purchased from Wahaha Group Co., Ltd. (Hangzhou, China); Ga(NO3)3 solution (0.5 mol / L) −1 Zn(NO3)2 solution (0.5 mol L) −1 LiNO3 solution (1 mol L) −1 ) and Cr(NO3)2 solution (0.01 mol L −1 Both are used as precursor solutions.

[0044] Example 1: Preparation and Characterization of Long Afterglow Nanoparticles 1.1 Preparation of long afterglow nanoparticles: Based on the general chemical formula Li x Zn 1-x Ga2O4:Cr 3+ Determine the amount of each raw material, and mix Zn(NO3)2·6H2O, Ga(NO3)3, Cr(NO3)2·9H2O, and LiNO3 thoroughly under vigorous stirring. Adjust the pH to 8-9, and stir the resulting turbid solution vigorously at room temperature for 1-2 h, then react at 200°C-220°C for 18-24 h. Collect the prepared nanoparticles by centrifugation, wash twice with ultrapure water, and finally wash with anhydrous ethanol. Adjust the Zn content according to the above method. 2+ and Li + Similarly, by varying the ratio x of the precursor solution, PLNPs with different Li ion doping concentrations were synthesized.

[0045] 1.2 Detection of the effect of Li ion doping on morphology and crystal structure: In order to systematically study the effect of Li ion doping on morphology and crystal structure... + The effect of doping on nanoparticles was investigated using transmission electron microscopy (TEM) and X-ray powder diffraction (XRD) to study the size and crystal structure of the nanoparticles. The results are as follows: Figure 1-2 It should be noted that in the general formula, x represents Li. + Replace Zn 2+ The degree of, that is, Li + Amount in the precursor solution.

[0046] from Figure 1 It can be seen that in the absence of Li + In the case of (x=0), the obtained ZnGa2O4:Cr 3+ PLNPs are spherical, and with Li + The addition of , yields Li x Zn 1-x Ga2O4:Cr 3+ Gradually shifting towards a square or round shape, doping has no significant effect on the size of PLNPs. From Figure 2 (a) It can be seen that the prepared Li x Zn 1-x Ga2O4:Cr 3+ (x=0-0.5) The nanocrystals possess a highly crystalline, typical cubic spinel structure (JCPDS 86-0413), i.e. Figure 2 (a) Sample PDF#86-0413, regardless of Li + Regardless of the ion doping concentration, PLNPs consistently match the cubic spinel structure. From Figure 2 (b) It can be seen that, with Li + With increasing ion doping concentration, the crystallinity of the 311 crystal plane gradually increases, reaching a maximum at x=0.3. The synthesized Li... x Zn 1-x Ga2O4:Cr 3+ The elemental composition was characterized, and the results are shown in Table 1. As can be seen from Table 1, the Li element content increases with the increase of the added amount, while the Zn element content gradually decreases, which confirms the successful doping of Li.

[0047] Table 1: Elemental quantification by ICP-MS (x=0-0.5) .

[0048] 1.3 Detection of the effect of Li ion doping on optical properties: Excitation spectrum, emission spectrum, and afterglow decay spectrum of Li were measured by fluorescence spectrophotometer to investigate the effect of Li ion doping on optical properties. +The effect of doping on sustained luminescence is investigated using the following methods: (1) Li x Zn 1- x Ga2O4:Cr 3+ Afterglow emission spectroscopy of nanoparticles: Li measurement using 254 nm UV excitation in phosphorescence mode. x Zn 1-x Ga2O4:Cr 3+ The afterglow of the solid powder was used to obtain the emission spectrum. (2) Excitation spectrum: Using a fluorescence spectrophotometer, the characteristic emission peak of 700 nm was fixed, and the emission spectrum of Li was measured. x Zn 1-x Ga2O4:Cr 3+ The solid powder was excited to a spectrum. (3) Afterglow attenuation image: In the imaging experiment, a UV lamp (254 nm) was used as the light source, and 50 mg of Li was used to excite the powder. x Zn 1-x Ga2O4:Cr 3+ (x=0.3) Nanoparticles were placed in a 96-well plate and irradiated with PLNPs for a fixed time. After irradiation, the 96-well plate was placed in an IVIS imaging system to acquire attenuation images. The continuous luminescence of each sample was then analyzed by radiation intensity. (4) Afterglow attenuation curve: Before measurement, the sample was excited with a 254 nm UV lamp for 5 min. After the excitation stopped for 15 s, the attenuation curve was recorded. The curve was normalized with the strongest PL intensity as 1. The lifetime of PLNPs was fitted using the multi-exponential attenuation fitting method and the triple-exponential attenuation fitting method (ExpDec3): I( T = I0 + A1exp(−t / τ1) + A2exp(−t / τ2) + A3exp(−t / τ3). Where I0 is the initial afterglow intensity, I( T ) is the afterglow intensity at time t; A1, A2 and A3 are constants; τ1, τ2 and τ3 are the lifetimes of three different decay processes. (5) Re-excitation afterglow decay curve: Before measurement, the sample was first excited with a 254 nm ultraviolet lamp for 5 min (i.e., the first decay curve), and then activated with a red LED lamp for 2 min every 1000 s before measurement. The re-excitation afterglow decay curve was recorded 15 s after the excitation was stopped. The results are as follows Figures 3-4 As shown in Tables 2 and 3.

[0049] from Figure 3 (a) It can be seen that the luminescence intensity of PL in Li-doped PLNPs is enhanced, with the maximum luminescence intensity from x=0 to x=0.5 being 1650, 2299, 2627, 2906, 1951, and 2790, respectively, reaching a maximum at x=0.3; from Figure 3 (b) A slight redshift is observed in the excitation peak; from Figure 3(c) It can be seen that the PL can continue for 6 hours after the excitation light stops, and can be repeatedly excited by a red LED lamp; from Figure 3 (d) It can be seen that Li-doped PLNPs exhibit slower decay in the PL decay curve, with a maximum luminescence lifetime of x=0.5, while x=0.3 is second only to x=0.5. Tables 2 and 3 show that the optimal average lifetime of Li-doped PLNPs is 30% longer than that of undoped PLNPs (τ). av (x=0.5)=36.07 s, τ av (x=0)=8.84 s).

[0050] from Figure 4 It can be seen that Li x Zn 1-x Ga2O4:Cr 3+ (x=0-0.5) exhibits excellent rechargeability under both UV (254nm) and visible light (650nm red LED light) re-excitation conditions, with repeatable decay cycles. Figure 5 It can be seen that the applicant attempted to adjust the Li ion doping ratio to 100%, i.e., completely replacing Zn ions, but the resulting Li₂Ga₂O₄:Cr particle size reached approximately 1.8 μm, and it lacked photoluminescence properties. In conclusion, appropriate Li ion doping can effectively improve the particle size of ZnGa₂O₄:Cr. 3+ The PL strength and lifetime of the synthesized Li. x Zn 1-x Ga2O4:Cr 3+ It exhibits excellent long-term NIR luminescence performance.

[0051] Table 2: Attenuation parameters for afterglow decay curve fitting

[0052] Table 3: Li x Zn 1-x Ga2O4:Cr 3+ Average afterglow lifetime .

[0053] 1.4 Mechanism study of the effect of Li ion doping on optical properties The Li was estimated by combining diffuse reflectance spectroscopy with Tauc plotting and Kubelka-Munk function transformation. x Zn 1-x Ga2O4:Cr 3+ The optical band gap (Eg) of (x=0–0.5) is shown in the following results. Figure 6As shown, the calculated values ​​of Eg are 4.12 eV (x=0), 4.42 eV (x=0.1), 4.12 eV (x=0.2), 3.96 eV (x=0.3), 3.91 eV (x=0.4), and 4.27 eV (x=0.5). Li + After ion doping, Li x Zn 1-x Ga2O4:Cr 3+ The band gaps (x=0.3 and x=0.4) are slightly narrower than the band gap (x=0), which means that under UV excitation, electrons are more likely to be excited from the valence band to the conduction band, thus enhancing the electron transition efficiency to some extent.

[0054] Thermoluminescence (TL) spectroscopy was further investigated to understand its mechanism. TL measurement is a common tool for studying the properties and distribution of electron traps in fluorescent materials. The results are as follows: Figure 7 As shown in (a), for undoped Li + ZnGa2O4:Cr 3+ PLNPs exhibit a pristine TL peak at approximately 338.2 K. However, in Li... + In doped PLNPs, the intensity of the original TL peak increases, indicating an increase in the concentration of intrinsic electron traps. Furthermore, the TL peak associated with intrinsic electron traps undergoes a slight shift upon mg doping (when x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, Li...). x Zn 1-x Ga2O4:Cr 3+ The TL peaks are at 338.2, 345.2, 339.2, 345.6, 345.2, and 351.4 K, respectively. Interestingly, Li... + When the doping concentrations are x=0.2 and x=0.3, new peaks appear at approximately 420 K and 410 K, respectively, with the peaks reaching their maximum at x=0.3. In the above PL decay curves, when x=0.5, Li... x Zn 1-x Ga2O4:Cr 3+ PL is the largest. (Reference) Figure 7 (b) shows the luminescence mechanism diagram, which is mainly because excessively low concentration and depth of electron traps can affect afterglow performance. Considering the key role of electron trap concentration and depth in the afterglow mechanism, the integral area under the TL intensity (299K to 450K) curves was further compared, and the results are shown in Table 4. This reflects the concentration in the shallow layer, where the concentration in the shallow layer is the highest at x=0.5, which corresponds to the longest afterglow decay time at x=0.5.

[0055] Table 4: Area of ​​integration under the TL intensity (299 K to 450 K) curve .

[0056] As can be seen from the above, the PL intensity reaches its highest level when the Li content (x=0.3) is moderate; while further increasing the Li content (x=0.5) significantly prolongs the afterglow duration. This indicates that Li + Doping effectively enhances the luminescence properties of ZnGa2O4:Cr by controlling the concentration and depth of electron traps. However, excessive Li... + Doping (x>0.5) actually reduces luminescence efficiency, highlighting the importance of precisely controlling the doping ratio. Furthermore, Li... + Doping has no significant effect on the size of PLNPs, and the doped material exhibits excellent rechargeability, enabling repeatable decay cycles and providing stability for practical applications. Thermoluminescence spectroscopy further reveals the properties of Li... + Mechanism of doping: The intensity of the original TL peak increases with the increase of Li⁺ doping amount, indicating that the concentration of inherent electron traps in the material increases, thereby delaying the carrier release process and prolonging the afterglow time.

[0057] Example 2: Preparation and characterization of PLNPs@GCS probes 2.1 Preparation of PLNPs@GCS probes: 1) Hydroxylation modification: 80 mg-120 mg of PLNPs were ultrasonically dispersed in 80 mL-120 mL of NaOH (5 mmol / L). −1 The solution was stirred vigorously for 10-16 hours to obtain hydroxylated long afterglow nanomaterials (PLNPs-OH). The materials were then centrifuged, washed three times with ultrapure water, and vacuum dried. 2) Aminoation modification: 80 mg-120 mg of PLNPs-OH were ultrasonically dispersed in anhydrous ethanol solution (80 mL-120 mL). Under magnetic stirring, 3-aminopropyltriethoxysilane (300 μL-500 μL) was added dropwise. The mixture was stirred at 60 °C for 12-14 h. The amino-functionalized long afterglow nanomaterials (PLNPs-NH2) were collected by centrifugation, washed with anhydrous ethanol, and dried under vacuum for later use. 3) Amide reaction modification of GCS: at 4 mg / mL −1 -6 mg mL −1 PLNPs were pre-activated in PBS solutions (pH 5.5-6.5) by adding 13-18 mg EDC and 40-50 mg NHS, respectively, with electromagnetic stirring at room temperature for 2-4 hours. Then, 80-120 mg GCS was added, and NaOH solution (concentration 1 mol / L) was used for further activation. −1Adjust the pH of the reaction system to 7.5-8.5; after stirring the reaction solution at 60 ℃ for 10 h-14 h, centrifuge and separate the precipitate by washing with ultrapure water and centrifuging again. Then, redisperse the precipitate in PBS solution (pH 5.5 and pH 7.4) and store at 4 ℃ for later use.

[0058] 2.2 Functional characterization of PLNPs@GCS probes Following the preparation methods in 1.1 and 2.1, the prepared PLNPs@GCS probes (x=0.3, GCS grafting amount of 0.047 mg GCS per 1 mg PLNPs) were functionalized and characterized. Figure 8 Transmission electron microscopy (a) shows that the GCS-modified PLNPs@GCS probe exhibits a clear core-shell structure with a GCS shell thickness of approximately 2 nm. Figure 8 The particle size distribution diagram in (b) shows that the particle size increases from about 14 nm to about 23 nm. Figure 8 (c) shows the elemental distribution diagram of the energy dispersive spectroscopy analysis as a high-angle annular dark field image. The results show that Zn, Ga and O elements are mainly enriched in the core region of PLNPs, while N and C elements are uniformly distributed throughout the nanostructure.

[0059] Depend on Figure 9 (a) Potential characterization shows that the potential of unmodified PLNPs is −8.31 mV, while the potentials after hydroxyl and amino modification are −23.21 mV and 3.99 mV, respectively. Modification of the GCS shell via an amide reaction resulted in a positive potential at pH 5.5 and a negative potential at pH 7.4; this potential shift is due to the successful modification of the GCS with charge-transfer capabilities. Furthermore, the surface modification of PLNPs was further confirmed by Fourier transform infrared spectroscopy (FT-IR). Figure 9 (b) The FT-IR spectrum shows that PLNPs-NH2 at 1001 cm⁻¹ −1 A new absorption peak, Si−O−Si, appeared at 1636 cm⁻¹, proving the successful modification of APTES. After GCS functionalization, a peak at 1636 cm⁻¹ could be observed. −1 An absorption peak appears at -CO−NH−, and also at 2929 cm⁻¹. −1 and 2858cm −1 Symmetric and asymmetric stretching vibrations of C−H and GCS at 1091 cm −1 The stretching and contraction vibrations at the site confirm the successful modification of GCS. Further investigation was conducted into the pH-dependent effect of GCS surface modification on the surface charge of PLNPs@GCS, and the results are as follows: Figure 9As shown in (c), it is confirmed that it endows the material with pH-responsive charge conversion ability. In acidic environment, the free amino groups of GCS backbone are protonated and the charge conversion of PLNPs@GCS changes with pH. Figure 9 Thermogravimetric analysis (TGA) curves in (d) show that the weight loss below 200℃ is mainly due to the desorption of adsorbed water in the material, while the weight loss in the range of 200℃ to 800℃ is mainly caused by the thermal decomposition of the GCS shell in PLNPs@GCS, with a weight loss rate of 4.5%. Based on this, the amount of GCS grafted onto the surface of PLNPs is calculated to be 0.047 mg / mg PLNPs (i.e., 0.047 mg GCS loaded per mg PLNPs).

[0060] Example 3: Preparation of Fe3O4@Au-PSBP probe PSBP at 2 mg mL −1 The concentration was dissolved in dimethyl sulfoxide (DMSO) and stored as a stock solution at 4°C, diluted with water to 0.4 mg / mL. −1 Then, add 2 mL of PSBP (0.4 mg / mL). −1 ) and 2 mL Fe3O4@Au (1 mg mL) −1 Mix for 12–24 h, then magnetically separate and discard unreacted peptides. Collect the Fe3O4@Au-PSBP probe and wash it.

[0061] Example 4: Method for detecting and optimizing polystyrene nanoplastics 4.1 The PS NPs were detected using a dual-probe system composed of Fe3O4@Au-PSBP and PLNPs@GCS synthesized in Example 3. The specific method is as follows: Standard curve construction: Different concentrations of 2 mL PS solutions (0.01, 50, 300, 400, 800 pg / mL) were prepared using PBS at pH 5.5. −1 Add 20 μL of Fe3O4@Au-PSBP probe and 400 μL of PLNPs@GCS probe to a shaker, and incubate for 20-120 min. Then, magnetically separate the PLNPs@GCS probe that has not electrostatically bound to the Fe3O4@Au-PSBP probe, and redissolve it in PBS (pH 7.4) to a final volume of 3 mL. Incubate on a shaker for 20-80 min. After incubation, separate the Fe3O4@Au-PSBP probe and measure the persistent luminescence (PL) intensity at 700 nm of the remaining PLNPs@GCS probe. Construct a standard curve based on the changes in PL intensity. Quantify the PS concentration in the actual sample based on the standard curve.

[0062] The sample preparation method is as follows: Dissolve 0.35 g of edible salt in ultrapure water and bring the volume to 10 mL; take 10 mL of bottled drinking water for later use; after sample preparation, take 1 mL each of bottled drinking water and edible salt solution and add 1 mL of PS at different concentrations (0, 200, 400, 800 pg / mL). −1 The solution was prepared by mixing thoroughly, then adding 200 μL of Fe3O4@Au-PSBP probe and 400 μL of PLNPs@GCS probe. The mixture was incubated on a shaker for 60 min. PLNPs@GCS probe that had not electrostatically bound to the Fe3O4@Au-PSB probe were then removed by magnetic separation. The remaining PLNPs@GCS probe was redissolved in PBS (pH 7.4) to a final volume of 3 mL and incubated on a shaker for 40 min. After incubation, the Fe3O4@Au-PSBP probe was separated, and the PL intensity at 700 nm of the remaining PLNPs@GCS probe was measured. The PS concentration in the sample was quantified according to the standard curve, and the spiked recovery rate was calculated.

[0063] The following three solutions were prepared and their afterglow emission spectra were measured in phosphorescence mode on a fluorescence spectrophotometer: 1) 200 μL Fe3O4@Au-PSBP probe was added to PBS (pH 7.4) to a final volume of 3 mL; 2) 400 μL PLNPs@GCS probe was added to PBS (pH 7.4) to a final volume of 3 mL; 3) A mixture of 200 μL Fe3O4@Au-PSBP probe and 400 μL PLNPs@GCS probe was added to PBS (pH 7.4) to a final volume of 3 mL. Results are as follows: Figure 10 As shown in (a). The results show that when the Fe3O4@Au-PSBP probe and the PLNPs@GCS probe are combined through electrostatic interaction to form a composite probe, the black Fe3O4@Au-PSBP probe will have an optical shielding effect on the PLNPs@GCS probe, resulting in a significant reduction in its PL signal. Figure 10 a). Therefore, after detecting PS·NPs, a two-step separation operation is required: the first step is to remove the unbound excess PLNPs@GCS probe; the second step is to dissociate the Fe3O4@Au-PSBP-PLNPs@GCS complex and separate the PLNPs@GCS probe for signal detection.

[0064] 4.2 Optimization of Detection Method: To improve detection efficiency, it is necessary to systematically optimize experimental conditions and fix the Fe3O4@Au-PSBP probe (1 mg / mL). −1 The dosage was 200 μL, and the PS NPs concentration was 400 pg / mL. −1 The effects of PLNPs@GCS probe concentration, detection time, and separation time on the detection of PS NPs using the Fe3O4@Au-PSBP and PLNPs@GCS dual-probe system were investigated. Figure 10 (b) It can be seen that the afterglow intensity (700 nm) of the system gradually increases with the increase of PLNPs@GCS probe dosage in the range of 100 μL-400 μL, and the intensity tends to reach equilibrium at 400 μL. Further increasing the dosage results in almost no change in the final afterglow signal intensity. This is presumably because the electrostatically bound Fe3O4@Au-PSBP-PLNPs@GCS complex reaches saturation at 400 μL, and excess PLNPs@GCS probe can no longer effectively bind with the Fe3O4@Au-PSBP probe. Next, the effect of detection time on the final afterglow signal detection of the system was investigated, and the results are as follows: Figure 10 As shown in (c), the effect of detection time on the afterglow intensity of the system exhibits a trend of first increasing and then decreasing. When the detection time is less than 60 min, the afterglow intensity shows an increasing trend, reaching its maximum value at 60 min. When the detection time exceeds 60 min, the afterglow intensity begins to gradually decrease. This may be because excessively long detection times lead to probe wear, reducing the final detection signal intensity. After determining the probe dosage and detection time, to ensure that the PLNPs@GCS probe in the Fe3O4@Au-PSBP-PLNPs@GCS composite can be fully dissociated, the separation time of the PLNPs@GCS probe was also investigated. The results are as follows: Figure 10 As shown in (d), the 40 min with the highest afterglow intensity was selected.

[0065] 4.3 Evaluation of Detection Performance: Under the optimal detection conditions described in 4.2, a standard curve for PS NPs was constructed according to the method in 4.1, and the analytical performance of the method was evaluated. From Figure 11 (a) It can be seen that after magnetic separation, the intensity of afterglow luminescence increases with the increase of PS NP concentration; this indicates that the higher the concentration of PS NPs, the more negatively charged PS NPs are captured by the Fe3O4@Au-PSBP probe, thus increasing the negative charge density on its surface, and consequently loading more PLNPs@GCS probe through electrostatic interaction, resulting in a higher intensity of afterglow luminescence. Figure 11 (b) It can be seen that at a PS NPs concentration of 0.01 pg / mL −1 -800 pg mL −1 Within the specified range, the concentration of PS NPs shows a linear relationship with ΔPL (the change in afterglow luminescence intensity at 700 nm), and the linear relationship is Y = 35.465 + 1.214X (X: PS NPs concentration, Y: ΔPL), R 2 The limit of detection (3s) was 0.9896. −1 .

[0066] As can be seen, this invention can achieve highly sensitive detection of polystyrene nanoplastics, with a detection range of 0.01 pg / mL. −1 –800 pg mL −1 The detection limit is as low as 0.033 pg mL. −1 .

[0067] 4.4 Specificity test for PS NPs detection: The test method is as follows: prepare 400 pg mL of PBS with pH 5.5. −1 200 μL of Fe3O4@Au-PSBP probe and 400 μL of PLNPs@GCS probe were added to 2 mL of PS, polypropylene (PP), polyethylene (PE), polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), and polyvinyl chloride (PVC) solutions. The mixture was incubated on a shaker for 60 min. Then, unbound PLNPs@GCS probes were magnetically separated, and the remaining PLNPs@GCS probes were redissolved in PBS (pH 7.4) to a final volume of 3 mL. The mixture was incubated on a shaker for 40 min. After incubation, the Fe3O4@Au-PSBP probe was separated, and the PLNPs@GCS probes at 700 nm were measured.

[0068] The results are as follows Figure 11 As shown in (c), the results indicate that the detection system exhibits a specific response to PS NPs in PBS buffer, while showing no significant response to other nanoplastics (PP, PE, PMMA, PET, PVC), confirming its high specificity for PS NPs. Subsequently, the spiked recovery rate was tested in bottled drinking water and saline solution, and the results are shown in Table 5. The recovery rate in bottled drinking water was 96.16%–104.70%, and the recovery rate in saline solution was 92.59%–103.46%. This method can effectively overcome the interference of food matrices and demonstrates good practical application value.

[0069] Table 5: Spike Recovery Rate .

[0070] The embodiments described above illustrate only a portion of the implementation methods of the present invention, and not all of them. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. For those skilled in the art, various modifications and improvements can be made without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. Long afterglow nanoparticles, characterized in that, Its general chemical formula is Li x Zn 1-x Ga2O4:Cr³⁺, where x ranges from 0.1 to 0.

5.

2. The long afterglow nanoparticles as described in claim 1, characterized in that, The value of x is 0.3 or 0.

5.

3. The long afterglow nanoparticles as described in claim 1 or 2, characterized in that, The preparation method is as follows: zinc source, gallium source, lithium source and chromium source are dissolved in water, the pH of the solution is adjusted to alkaline, and the long afterglow nanoparticles are obtained after hydrothermal reaction.

4. The long afterglow nanoparticles as described in claim 3, characterized in that, The hydrothermal reaction is carried out at a temperature of 200 ℃-220 ℃ for 18-24 hours.

5. A nanoprobe, characterized in that, The probe comprises the long afterglow nanoparticles as described in any one of claims 1-4 and a hydroxyethyl deacetylated chitosan layer modified on its surface, namely PLNPs@GCS probe.

6. The nanoprobe as described in claim 5, characterized in that, The mass ratio of long afterglow nanoparticles to hydroxyethyl deacetylated chitosan raw material is 1:(1-10).

7. A dual-probe system, characterized in that, For detecting polystyrene nanoplastics, the device comprises the nanoprobe as described in claim 5 or 6; and the Fe3O4@Au-PSBP probe, which is composed of a gold-shelled magnetite sphere coupled with a polypeptide that specifically binds to polystyrene.

8. The dual-probe system as described in claim 7, characterized in that, PLNPs@GCS probes and Fe3O4@Au-PSBP probes form a composite through electrostatic interaction and bridging by polystyrene nanoplastics.

9. A method for detecting polystyrene nanoplastics, characterized in that, Detection using the dual-probe system as described in claim 7 or 8 includes the following steps: The sample to be tested is brought into contact with PLNPs@GCS probe and Fe3O4@Au-PSBP probe to form a composite bridged by polystyrene nanoplastics, and unreacted free probes are removed. The composite was treated under conditions suitable for the dissociation of the PLNPs@GCS probe, and the Fe3O4@Au-PSBP probe was removed by magnetic separation. The afterglow emission signal of the separated PLNPs@GCS probe was detected, and the content of polystyrene nanoplastics in the sample was determined based on the signal intensity.

10. The method for detecting polystyrene nanoplastics as described in claim 9, characterized in that, The method for determining the content of polystyrene nanoplastics in a sample based on signal intensity is as follows: the measured afterglow emission signal intensity is compared with a pre-established standard curve of polystyrene nanoplastic concentration and afterglow emission signal intensity.

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