Method and system for detecting extinction, scattering and absorption properties of noble metal nanoparticles

Abstract

The application provides a noble metal nanoparticle extinction, scattering and absorption characteristic detection method and system, relates to the technical field of nano-optical detection, and comprises the following steps: preparing a single-particle distributed sample, collecting a dark field scattering spectrum of a single particle under dark field illumination, determining a characteristic resonance wavelength through pretreatment and resonance peak identification; switching to bright field illumination, collecting a transmission spectrum at the same position, calculating an extinction spectrum and combining the scattering intensity to determine an initial value of absorption intensity at the characteristic resonance wavelength; collecting a photothermal signal of the particle again, taking the amplitude as a correction factor, correcting the initial value of absorption intensity to obtain a corrected absorption intensity value; calculating scattering efficiency and absorption efficiency at the characteristic resonance wavelength according to the scattering intensity and the corrected absorption intensity value, and then determining a scattering-absorption adaptation coefficient; comparing the adaptation coefficient with a dominant type threshold value to judge whether the nanoparticle is suitable for scattering dominant type, absorption dominant type or scattering-absorption synergistic type application.

Description

Technical Field

[0001] This invention relates to the field of nano-optical detection technology, specifically to a method and system for detecting the extinction, scattering, and absorption characteristics of noble metal nanoparticles. Background Technology

[0002] Noble metal nanoparticles (such as gold nanospheres, gold nanorods, and silver nanotriangles) have shown great application potential in photocatalysis, nanointegrated photonics, medical imaging, and surface-enhanced Raman spectroscopy due to their unique localized surface plasmon resonance properties. The core of these applications lies in the precise characterization of the extinction, scattering, and absorption properties of nanoparticles to determine their suitability for scattering-dominated applications (such as dark-field imaging and optical labeling) or absorption-dominated applications (such as photothermal therapy and photoacoustic imaging). Currently, the main methods for detecting the optical properties of noble metal nanoparticles include ultraviolet-visible spectrophotometry, dark-field scattering spectroscopy, and photothermal spectroscopy. However, most of these methods measure at the population level, which can only obtain the average optical properties of the sample and cannot accurately resolve the scattering and absorption contributions of individual nanoparticles. Even in single-particle measurements, it is difficult to simultaneously and in situ distinguish the contributions of scattering and absorption in extinction, resulting in the inability to accurately assess the intrinsic relationship between the photothermal conversion efficiency and scattering imaging capability of individual nanoparticles.

[0003] In the prior art, the method and system for detecting the extinction, scattering and absorption characteristics of spherical metal nanoparticles disclosed in CN109781594A obtains the extinction efficiency, scattering efficiency and absorption efficiency of spherical metal nanoparticles through numerical calculation based on Mie theory and plots theoretical spectral images. This method belongs to the category of theoretical simulation calculation, and its calculation results depend on preset ideal parameters such as nanoparticle size and complex refractive index. It cannot perform in-situ measurements on actual synthesized single noble metal nanoparticles. At the same time, this method is only applicable to spherical nanoparticles and cannot be applied to noble metal nanoparticles with non-spherical shapes (such as nanorods and nanotriangular plates). In addition, this method can only obtain theoretical efficiency values ​​and lacks a correction mechanism for actual measurement data. It is difficult to eliminate errors introduced by scattering interference, environmental noise and other factors in actual measurement. It cannot achieve synchronous and accurate detection of extinction, scattering and absorption characteristics at the single particle level, nor can it provide a quantitative screening basis based on measured data for different application scenarios.

[0004] The information disclosed in the background section is only intended to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide a method and system for detecting the extinction, scattering and absorption characteristics of noble metal nanoparticles, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for detecting the extinction, scattering, and absorption properties of noble metal nanoparticles, comprising the following specific steps:

[0008] Step 1: Prepare a sample of noble metal nanoparticles with single-particle distribution. Under dark field illumination, collect raw dark field scattering spectrum data of a single nanoparticle and preprocess it to obtain the distribution data of scattering intensity with wavelength. Identify resonance peaks in the distribution data of scattering intensity with wavelength to determine the characteristic resonance wavelength of the nanoparticle.

[0009] Step 2: Switch to bright field illumination conditions, collect the raw bright field transmission spectrum data of the nanoparticle under the same spatial location, obtain the transmission intensity distribution data with wavelength after preprocessing, calculate the extinction spectrum based on this, and combine the scattering intensity distribution data with wavelength to perform differential calculation at the characteristic resonance wavelength to obtain the initial value of the absorption intensity of the nanoparticle.

[0010] Step 3: Collect the photothermal signal of the nanoparticle and extract the amplitude as a correction factor. Combine the initial value of the absorption intensity at the characteristic resonance wavelength to calculate the corrected absorption intensity value of the nanoparticle at the characteristic resonance wavelength.

[0011] Step 4: Based on the distribution data of scattering intensity with wavelength and the corrected absorption intensity value at the characteristic resonance wavelength, calculate the scattering efficiency and absorption efficiency of the nanoparticle at the characteristic resonance wavelength, and define the ratio of the two as the scattering-absorption fit coefficient.

[0012] Step 5: Compare the scattering-absorption adaptation coefficient with the preset dominant threshold, and determine the nanoparticle's suitability for scattering-dominant, absorption-dominant, or scattering-absorption synergistic applications based on the comparison results.

[0013] Furthermore, the specific logic for preparing a single-particle-distributed noble metal nanoparticle sample is as follows: dilute the noble metal nanoparticle solution with pure water to a predetermined multiple and sonicate for a predetermined time; use a syringe to draw the diluted solution and drop it onto a clean coverslip; quickly cover it with another coverslip to spread the solution; after standing for a predetermined time, remove the upper coverslip to allow the water in the solution to evaporate naturally, thereby forming a single-particle-distributed nanoparticle sample on the surface of the coverslip.

[0014] Under dark field illumination conditions, the scattered light of a single nanoparticle is collected through an objective lens, and after being dispersed by a spectrometer, its raw dark field scattering spectrum data is acquired by a detector.

[0015] The preprocessing includes using wavelet transform to remove high-frequency noise from the original dark-field scattering spectrum data, and using a baseline correction algorithm to subtract the background baseline drift in the dark-field scattering spectrum to obtain the distribution data of scattering intensity with wavelength; calculating the second derivative of the distribution data of scattering intensity with wavelength, identifying the extreme point of the curvature change in the spectral curve as a candidate resonance peak, and determining the wavelength corresponding to the maximum scattering intensity in the candidate resonance peak as the characteristic resonance wavelength of the nanoparticle.

[0016] Further, switch to bright field illumination conditions, and at the same spatial location as in step 1, collect the transmitted light passing through the nanoparticles through the objective lens. After the light is dispersed by the spectrometer, the detector collects the raw data of the bright field transmission spectrum. The raw data of the bright field transmission spectrum is preprocessed to obtain the distribution data of transmission intensity with wavelength.

[0017] The extinction spectrum is calculated based on the transmission intensity distribution data as a function of wavelength, and the extinction value is calculated using the following formula:

[0018]

[0019] In the formula, Indicates at wavelength The extinction value at that point, Wavelength; Indicates nanoparticles at wavelength The transmitted intensity collected at the location; Indicates the wavelength when there is no sample. The reference transmission intensity was collected at the location.

[0020] Furthermore, the scattering intensity values ​​at the characteristic resonant wavelength are extracted from the scattering intensity distribution data as a function of wavelength. The extinction value at the characteristic resonance wavelength is extracted from the extinction spectrum. According to the law of conservation of energy, at the characteristic resonance wavelength At that point, the extinction value is equal to the sum of the initial values ​​of the scattering intensity and the absorption intensity;

[0021] The initial value of the absorption intensity is obtained through differential calculation, and the calculation formula is as follows:

[0022]

[0023] In the formula, This indicates that the nanoparticles resonate at the characteristic wavelength. The initial value of the absorption intensity at that location.

[0024] Furthermore, under the bright-field illumination condition, the photothermal signal generated by the nanoparticles under bright-field excitation is detected, and the amplitude of the photothermal signal is extracted. Based on the characteristic resonance wavelength of nanoparticles Initial value of absorption intensity at the location and the amplitude of photothermal signal The corrected absorption intensity value is calculated using the following formula:

[0025]

[0026] In the formula, This indicates that the nanoparticles resonate at a characteristic wavelength. The corrected absorption intensity value, The preset proportionality coefficient is obtained by calibration using standard samples.

[0027] Furthermore, based on the distribution data of scattering intensity with wavelength and the corrected absorption intensity value at the characteristic resonance wavelength, the scattering efficiency and absorption efficiency of the nanoparticle at the characteristic resonance wavelength are calculated using the following formula:

[0028]

[0029] In the formula, This indicates that the nanoparticle is at the characteristic resonance wavelength. Scattering efficiency at that location, This indicates that the nanoparticle is at the characteristic resonance wavelength. Absorption efficiency at the site;

[0030] The and The ratio is defined as the scattering-absorption fit coefficient, denoted as .

[0031] Furthermore, a predefined dominant threshold is established, including a scattering dominant threshold. and absorption-dominant threshold And satisfy 1 ;

[0032] The scattering-absorption fit coefficient is compared with the dominant threshold, specifically as follows:

[0033] when At that time, it was determined that the nanoparticles were suitable for scattering-dominant applications;

[0034] when At that time, it was determined that the nanoparticles were suitable for absorption-dominant applications;

[0035] when When the scattering and absorption characteristics of the nanoparticles are determined to be comparable, they are suitable for scattering-absorption synergistic applications.

[0036] The present invention also provides a system for detecting the extinction, scattering, and absorption characteristics of noble metal nanoparticles, for performing the above-described method for detecting the extinction, scattering, and absorption characteristics of noble metal nanoparticles, comprising:

[0037] The dark field scattering acquisition module is used to prepare noble metal nanoparticle samples with single-particle distribution. Under dark field illumination conditions, it acquires the raw dark field scattering spectrum data of a single nanoparticle and preprocesses it to obtain the distribution data of scattering intensity with wavelength. The resonance peak is identified from the distribution data of scattering intensity with wavelength to determine the characteristic resonance wavelength of the nanoparticle.

[0038] The extinction difference calculation module is used to switch to bright field illumination conditions, collect the original bright field transmission spectrum data of the nanoparticle under the same spatial position, obtain the transmission intensity distribution data with wavelength after preprocessing, calculate the extinction spectrum based on this, and combine the scattering intensity distribution data with wavelength to perform difference calculation at the characteristic resonance wavelength to obtain the initial value of the absorption intensity of the nanoparticle.

[0039] The photothermal correction absorption module is used to collect the photothermal signal of the nanoparticle and extract the amplitude as a correction factor. Combined with the initial value of the absorption intensity at the characteristic resonance wavelength, the corrected absorption intensity value of the nanoparticle at the characteristic resonance wavelength is calculated.

[0040] The adaptation coefficient construction module is used to calculate the scattering efficiency and absorption efficiency of the nanoparticle at the characteristic resonance wavelength based on the distribution data of scattering intensity with wavelength and the corrected absorption intensity value at the characteristic resonance wavelength, and the ratio of the two is defined as the scattering-absorption adaptation coefficient.

[0041] The application type determination module is used to compare the scattering-absorption adaptation coefficient with a preset dominant threshold, and determine the nanoparticle's suitability for scattering-dominant, absorption-dominant, or scattering-absorption synergistic applications based on the comparison result.

[0042] Compared with the prior art, the beneficial effects of the present invention are:

[0043] 1. This invention obtains the scattering intensity distribution of a single nanoparticle, calculates the extinction value by combining it with bright-field transmission spectroscopy, and performs differential calculations at the characteristic resonance wavelength. For the first time, it simultaneously obtains the initial data of scattering and absorption at the same particle and the same spatial position, solving the problem that the existing technology cannot distinguish the contributions of scattering and absorption at the single-particle level.

[0044] 2. This invention synchronously acquires the photothermal signal of a single nanoparticle, extracts the amplitude of the photothermal signal as a correction factor, and proportionally corrects the initial value of absorption intensity obtained by differential calculation. This effectively eliminates measurement errors introduced by factors such as scattering interference and environmental noise, and improves the accuracy of absorption intensity measurement.

[0045] 3. Based on the scattering intensity and the corrected absorption intensity value, this invention calculates the scattering efficiency and absorption efficiency at the characteristic resonance wavelength, and defines the ratio of the two as the scattering-absorption fit coefficient. This dimensionless parameter intuitively reflects the optical property bias of nanoparticles. Combined with the preset dominant threshold, it can accurately determine whether a single nanoparticle is suitable for scattering-dominant or absorption-dominant applications, providing a quantitative basis for the application screening of nanoparticles.

[0046] 4. This invention is based on actual measurement data rather than theoretical models and does not rely on specific morphological assumptions of nanoparticles. It can be widely applied to noble metal nanoparticles with various morphologies such as gold nanospheres, gold nanorods, and silver nanotriangles, breaking through the limitation of existing theoretical simulation methods that are only applicable to spherical particles. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of the overall method flow of the present invention;

[0048] Figure 2 A comparison of the extinction spectra of gold ball 1, silver triangle plate, and gold rod 1;

[0049] Figure 3 A comparison of the superimposed extinction spectra of silver triangle 2-6;

[0050] Figure 4 This is a comparison of the superimposed extinction spectra of gold rods 2-6;

[0051] Figure 5 This is a schematic diagram of the overall system modules of the present invention. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0053] It should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0054] Example:

[0055] Please see Figure 1-4 The present invention provides a technical solution:

[0056] A method for detecting the extinction, scattering, and absorption properties of noble metal nanoparticles, comprising the following specific steps:

[0057] Step 1: Prepare a sample of noble metal nanoparticles with single-particle distribution. Under dark field illumination, collect raw dark field scattering spectrum data of a single nanoparticle and preprocess it to obtain the distribution data of scattering intensity with wavelength. Identify resonance peaks in the distribution data of scattering intensity with wavelength to determine the characteristic resonance wavelength of the nanoparticle.

[0058] In this embodiment, three typical morphologies of noble metal nanostructures are used as the detection objects: gold nanospheres (gold sphere 1), silver nanotriangles (silver triangles 1, 2, 3, 4, 5, 6), and gold nanorods (gold rods 1, 2, 3, 4, 5, 6).

[0059] The sample preparation method was as follows: The noble metal nanoparticle solution was diluted to a suitable concentration with deionized water, and ultrasonically treated for 5–10 minutes. The diluted solution was then dropped onto a clean coverslip surface, where it naturally evaporated to form a film, creating a sample with single particles dispersed on the coverslip surface. The sample was placed in the detection system, and the dark-field illumination mode was activated. The scattered light from individual nanoparticles was collected using a high numerical aperture objective lens. After spectrometry, the raw scattering spectrum data was acquired by a CCD detector. Wavelet transform denoising and asymmetric least squares baseline correction were performed on the scattering spectrum to obtain the distribution data of scattering intensity with wavelength. Second derivative peak finding was performed on the scattering spectrum, and the wavelength corresponding to the maximum scattering intensity was determined as the characteristic resonance wavelength. The test results showed that the characteristic resonance wavelength of gold sphere 1 was located in the range of 510–520 nm; the characteristic resonance wavelengths of silver triangles 1–6 were located in the range of 450–580 nm, exhibiting multi-peak resonance characteristics; gold rods 1–6 showed transverse resonance peaks in the range of 510–530 nm and longitudinal characteristic resonance peaks in the near-infrared band. These characteristic resonance wavelengths were consistent with the TEM morphology characterization results.

[0060] In this process, wavelet transform was used to denoise the raw dark-field scattering spectrum data. The db4 wavelet basis function was selected, and the decomposition level was set to 5 levels. The raw spectral signal was decomposed into approximation coefficients and detail coefficients. The detail coefficients of levels 1 to 5 were processed using a soft thresholding method. The calculation formula is ,in The standard deviation of noise. For the signal length, detail coefficients with amplitudes below a threshold are set to zero, while those above the threshold are retained. Wavelet reconstruction is then performed using the processed approximation coefficients and detail coefficients to obtain the denoised spectral data. After denoising, an asymmetric least squares baseline correction algorithm is used to subtract background baseline drift, and smoothing parameters are set. asymmetric parameters By estimating the background baseline curve in the spectrum through iterative weighted least squares fitting, the distribution data of scattering intensity with wavelength is obtained by subtracting the fitted baseline curve from the denoised spectral data.

[0061] The second derivative of the scattering intensity distribution data with wavelength is calculated, and the extreme point with the largest curvature change in the spectral curve is identified as the candidate resonance peak. The wavelength corresponding to the maximum scattering intensity in the candidate resonance peak is determined as the characteristic resonance wavelength of the nanoparticle.

[0062] Step 1 achieved single-particle-level sample preparation by diluting, sonicating, and naturally dispersing the noble metal nanoparticle solution onto the cover glass surface, providing a reliable foundation for subsequent optical property detection of individual nanoparticles. Based on this, the scattering spectra of individual particles were acquired using dark-field illumination, and the original spectral data were preprocessed using wavelet transform and asymmetric least-squares baseline correction, effectively eliminating high-frequency noise and background baseline drift, significantly improving the signal-to-noise ratio and data quality of the scattering spectra. Furthermore, the extreme point of maximum curvature change was identified by second-order derivative calculation as a candidate resonance peak, and the wavelength corresponding to the maximum scattering intensity was determined as the characteristic resonance wavelength. This achieved accurate and automatic identification of the characteristic resonance wavelength of individual noble metal nanoparticles, avoiding errors introduced by manual selection, and laying an accurate data foundation for subsequent extinction difference calculation, photothermal correction, and adaptation coefficient construction.

[0063] Step 2: Switch to bright field illumination conditions, collect the raw bright field transmission spectrum data of the nanoparticle under the same spatial location, obtain the transmission intensity distribution data with wavelength after preprocessing, calculate the extinction spectrum based on this, and combine the scattering intensity distribution data with wavelength to perform differential calculation at the characteristic resonance wavelength to obtain the initial value of the absorption intensity of the nanoparticle.

[0064] In this embodiment, the illumination is switched to bright field conditions. At the same spatial location as in step 1, the transmitted light passing through the nanoparticles is collected by the objective lens. After the light is dispersed by the spectrometer, the detector collects the original bright field transmission spectrum data. The original bright field transmission spectrum data is preprocessed in the same way as in step 1 to obtain the transmission intensity distribution data with wavelength.

[0065] The extinction spectrum is calculated based on the transmission intensity distribution data as a function of wavelength, and the extinction value is calculated using the following formula:

[0066]

[0067] In the formula, Indicates at wavelength The extinction value at that point, Wavelength; Indicates nanoparticles at wavelength The transmitted intensity collected at the location; Indicates the wavelength when there is no sample. The reference transmission intensity was collected at the location.

[0068] Extract the scattering intensity value at the characteristic resonant wavelength from the scattering intensity distribution data as a function of wavelength. The extinction value at the characteristic resonance wavelength is extracted from the extinction spectrum. According to the law of conservation of energy, at the characteristic resonance wavelength At that point, the extinction value is equal to the sum of the initial values ​​of the scattering intensity and the absorption intensity;

[0069] The initial value of the absorption intensity is obtained through differential calculation, and the calculation formula is as follows:

[0070]

[0071] In the formula, This indicates that the nanoparticles resonate at the characteristic wavelength. The initial value of the absorption intensity at that location.

[0072] Actual measurement data shows that: the gold sphere 1 has an extinction value of 0.92 to 0.97 at 510 to 520 nm and an initial absorption intensity of 0.15 to 0.25; the silver triangle has an extinction value of 0.3 to 0.6 at the characteristic resonance wavelength and an initial absorption intensity of 0.10 to 0.20; and the gold rod has an extinction value of 0.2 to 0.4 at the characteristic resonance wavelength and an initial absorption intensity of 0.08 to 0.18.

[0073] Step 2, based on the principle of energy conservation, achieves quantitative decoupling of the relationship between extinction, scattering, and absorption at the single-particle level. Specifically, it first switches to bright-field illumination and collects transmission spectra at the same spatial location of the same nanoparticle. By measuring the transmission intensity with and without the sample, the transmittance is calculated and the negative logarithm to base 10 is taken to obtain the extinction spectrum. Used to characterize nanoparticles at wavelengths The total attenuation capability of the incident light includes contributions from both scattering and absorption. Then, using the determined characteristic resonance wavelength, the scattering intensity value at that wavelength is extracted from the scattering intensity distribution data, and the extinction value at that wavelength is extracted from the extinction spectrum. Since the local surface plasmon resonance effect of nanoparticles is strongest and the spectral signal-to-noise ratio is highest at the characteristic resonance wavelength, and the sum of scattering and absorption equals extinction, the initial value of absorption intensity can be obtained by performing a differential calculation at this wavelength, i.e., subtracting the scattering contribution from the total attenuation.

[0074] Step 2 achieves, for the first time, a quantitative decoupling of the relationship between extinction, scattering, and absorption on a single particle. Specifically, the extinction spectrum is obtained by calculating the transmittance and taking its negative logarithm. The extinction value at the characteristic resonance wavelength is extracted from the extinction spectrum, and the scattering intensity value at the same wavelength is extracted from the scattering intensity distribution data. Using the physical principle that extinction equals the sum of scattering and absorption, the initial value of absorption intensity is obtained through differential calculation. This method does not rely on the morphology assumptions of nanoparticles and is applicable to noble metal nanoparticles with various morphologies, such as gold nanospheres, gold nanorods, and silver nanotriangular plates, overcoming the limitation of existing theoretical simulation methods that are only applicable to spherical particles. At the same time, the differential calculation is performed only at the characteristic resonance wavelength with the highest signal-to-noise ratio, avoiding noise interference introduced by full-band differential calculation and improving the calculation accuracy and reliability of the initial value of absorption intensity. In addition, this step is based on measured spectral data rather than theoretical models, realizing in-situ, rapid, and non-destructive acquisition of the absorption characteristics of a single nanoparticle, providing a physically meaningful and data-quality-reliable initial value of absorption intensity for subsequent photothermal signal correction and the construction of scattering-absorption adaptation coefficients.

[0075] Step 3: Collect the photothermal signal of the nanoparticle and extract the amplitude as a correction factor. Combine the initial value of the absorption intensity at the characteristic resonance wavelength to calculate the corrected absorption intensity value of the nanoparticle at the characteristic resonance wavelength.

[0076] In this embodiment, under the bright field illumination condition, the photothermal signal generated by the nanoparticles under bright field excitation is detected, and the amplitude of the photothermal signal is extracted. Based on the characteristic resonance wavelength of nanoparticles Initial value of absorption intensity at the location and the amplitude of photothermal signal The corrected absorption intensity value is calculated using the following formula:

[0077]

[0078] In the formula, This indicates that the nanoparticles resonate at a characteristic wavelength. The corrected absorption intensity value, The preset proportionality coefficient is obtained from standard sample calibration. In this embodiment, the calibration value is approximately .

[0079] After correction, the absorption intensity of gold sphere 1 is 0.12–0.22; the absorption intensity of silver triangle is 0.08–0.18; and the absorption intensity of gold rod is 0.06–0.16. The corrected absorption intensity is closer to the real physical process of photothermal conversion and eliminates the calculation deviation caused by scattering interference and system noise.

[0080] This indicates that the nanoparticles resonate at a characteristic wavelength. The corrected absorption intensity value is essentially the physical essence of the energy fraction of incident light that is absorbed by nanoparticles at this wavelength and converted into heat energy, which directly determines the photothermal conversion efficiency of nanoparticles. The larger the value, the stronger the absorption capacity of nanoparticles at the characteristic resonant wavelength, and the more suitable it is for applications that rely on photothermal conversion effects, such as photothermal therapy, photoacoustic imaging, and photothermal catalysis. Conversely, the smaller the value, the weaker the absorption capacity of nanoparticles, the less obvious the photothermal effect, and the more suitable it is for applications dominated by scattering.

[0081] When noble metal nanoparticles absorb light energy under bright-field excitation, they convert the absorbed light energy into heat energy through a non-radiative relaxation process. This causes a change in the refractive index and thermal expansion of the surrounding medium, thereby generating a photothermal signal that can be detected by a lock-in amplifier; the amplitude of the photothermal signal... There is a positive correlation between the absorption intensity and the actual absorption intensity of the nanoparticles: the stronger the absorption, the more heat is generated, and the larger the amplitude of the photothermal signal. However, although the initial value of absorption intensity calculated in step 2 separates the absorption contribution from the extinction based on the principle of energy conservation, this value may still be affected by the following factors: first, systematic errors in the measurement process of scattering and transmission spectra (such as optical path alignment deviation and detector response non-uniformity); second, the influence of environmental noise and substrate scattering on weak signals; and third, the error propagation of the differential calculation itself between the two independent measurements. These factors lead to... There is a proportional deviation between the actual absorption intensity and the actual absorption intensity.

[0082] Therefore, the amplitude of the photothermal signal is introduced. As a correction factor, the initial value of the absorption intensity obtained by differential calculation is proportionally corrected by utilizing the positive correlation between the photothermal signal and the actual absorption intensity. Specifically, the amplitude of the photothermal signal... This reflects the actual amount of light energy absorbed, and its relationship with... Multiplication can enlarge or reduce. It contains components relevant to actual absorption while suppressing error components unrelated to absorption.

[0083] Step 3 involves synchronously acquiring the photothermal signal of a single nanoparticle. Utilizing the positive correlation between the photothermal signal amplitude and the actual absorption intensity, the initial absorption intensity value obtained in Step 2 based on energy conservation differential calculation is proportionally corrected. This effectively eliminates deviations introduced by systematic errors in the scattering and transmission spectroscopy measurement process (such as optical path alignment deviations, detector response non-uniformity), environmental noise, substrate scattering interference, and differential calculation error propagation, significantly improving the accuracy and reliability of absorption intensity measurement. Furthermore, this step is based on measured photothermal signals rather than theoretical models, independent of nanoparticle morphology assumptions, and applicable to noble metal nanoparticles with various morphologies, such as gold nanospheres, gold nanorods, and silver nanotriangular plates. In addition, the corrected absorption intensity value directly reflects the nanoparticle's ability to convert light energy into heat energy at its characteristic resonance wavelength, providing a physically meaningful and reliable absorption intensity benchmark for subsequent calculations of scattering and absorption efficiencies and the construction of scattering-absorption adaptation coefficients. This is a crucial step in achieving accurate detection of absorption characteristics at the single-particle level.

[0084] Step 4: Based on the distribution data of scattering intensity with wavelength and the corrected absorption intensity value at the characteristic resonance wavelength, calculate the scattering efficiency and absorption efficiency of the nanoparticle at the characteristic resonance wavelength, and define the ratio of the two as the scattering-absorption fit coefficient.

[0085] In this embodiment, the scattering efficiency and absorption efficiency of the nanoparticle at the characteristic resonance wavelength are calculated based on the distribution data of scattering intensity with wavelength and the corrected absorption intensity value at the characteristic resonance wavelength. The formula used is as follows:

[0086]

[0087] In the formula, This indicates that the nanoparticle is at the characteristic resonance wavelength. Scattering efficiency at that location, This indicates that the nanoparticle is at the characteristic resonance wavelength. Absorption efficiency at the site;

[0088] The and The ratio is defined as the scattering-absorption fit coefficient, denoted as .

[0089] In this embodiment, gold sphere 1 has an R≈1.8-2.3 scattering efficiency, while silver triangles 1-6 have an R≈2.0-3.5 scattering efficiency, which is significantly higher. Gold rods 1-6 have an R≈0.7-1.2 scattering efficiency, which is close to the equilibrium between absorption and scattering.

[0090] At the characteristic resonant wavelength At this point, the total energy of the interaction between the incident light and the noble metal nanoparticles satisfies the law of conservation of energy, meaning that the total energy of the incident light is divided into three parts by the nanoparticles: scattering energy, absorption energy, and transmission energy; in extinction spectroscopy measurements, the extinction value... The total attenuation capability of nanoparticles for incident light was characterized, and this attenuation originated from contributions from both scattering and absorption. ,in For scattering intensity, The corrected absorption intensity; therefore, the scattering efficiency The absorption efficiency is defined as the proportion of scattered energy to the total attenuated energy. Defined as the proportion of absorbed energy to total decayed energy.

[0091] According to the law of conservation of energy, the sum of scattering efficiency and absorption efficiency equals 1, that is... The physical basis of the above formula calculation method is that at the characteristic resonance wavelength, the local surface plasmon resonance effect of nanoparticles is the strongest. Scattering and absorption are the two main channels for the interaction between light and matter at this wavelength. Other energy losses (such as thermal radiation) can be ignored. Therefore, the total attenuation energy can be approximately considered to be composed entirely of scattering and absorption.

[0092] Scattering-absorption fit coefficient Defined as the ratio of scattering efficiency to absorption efficiency, i.e.:

[0093]

[0094] The scattering-absorption fit coefficient is a dimensionless parameter used to quantify the relative strength of the scattering and absorption characteristics of noble metal nanoparticles at the characteristic resonance wavelength, and intuitively reflects the optical property bias of the nanoparticles.

[0095] when At this time, the scattering efficiency is greater than the absorption efficiency, and the scattering characteristics of the nanoparticles dominate. At this time, the incident light energy is mainly re-radiated in the form of scattering, and the particles themselves absorb less energy, resulting in a weaker photothermal effect. These nanoparticles are suitable for applications that rely on strong scattering signals, such as dark-field imaging, optical labeling, and surface-enhanced Raman spectroscopy.

[0096] when At this time, the absorption efficiency is greater than the scattering efficiency, and the absorption characteristics of the nanoparticles dominate. At this time, the incident light energy is mainly absorbed by the nanoparticles and converted into heat energy, resulting in high photothermal conversion efficiency and relatively weak scattering signal. These nanoparticles are suitable for applications relying on photothermal conversion effects, such as photothermal therapy, photoacoustic imaging, and photothermal catalysis.

[0097] when Time: Indicates that the scattering efficiency and absorption efficiency are comparable, and the nanoparticles have balanced optical properties; these nanoparticles can take into account both scattering and absorption functions, and are suitable for synergistic applications that require the simultaneous use of scattering and absorption properties, such as integrated photothermal-imaging diagnosis and treatment, and photothermal enhanced Raman detection.

[0098] Step 4 involves substituting the scattering intensity value at the characteristic resonance wavelength obtained in Step 1 and the corrected absorption intensity value obtained in Step 3 into the energy conservation relationship to calculate the scattering efficiency and absorption efficiency. This leads to the definition of the scattering-absorption fit coefficient. This coefficient, in a single numerical form, intuitively and quantitatively characterizes the optical property bias of nanoparticles at the characteristic resonance wavelength, providing a physically meaningful and computationally simple quantitative indicator for the application type judgment based on threshold comparison in Step 5. This approach is more efficient than directly comparing the absolute values ​​of scattering intensity and absorption intensity (which are affected by experimental conditions, particle size, etc.). The value, as a ratio, has better stability and universality, and can achieve standardized evaluation of the optical properties of nanoparticles under different experimental conditions.

[0099] Step 5: Compare the scattering-absorption adaptation coefficient with a preset dominant threshold, and determine the nanoparticle's suitability for scattering-dominant, absorption-dominant, or scattering-absorption synergistic applications based on the comparison results;

[0100] Preset dominant threshold, where the scattering dominant threshold The range of values ​​is Absorption-dominant threshold The range of values ​​is And satisfy ;

[0101] The scattering-absorption fit coefficient is compared with the dominant threshold, specifically as follows:

[0102] when At that time, it was determined that the nanoparticles were suitable for scattering-dominant applications;

[0103] when At that time, it was determined that the nanoparticles were suitable for absorption-dominant applications;

[0104] when When the scattering and absorption properties of the nanoparticles are determined to be comparable, they are suitable for scattering-absorption synergistic applications.

[0105] In this embodiment, the silver triangle plates 1 to 6 are suitable for scattering-dominant applications, such as dark-field imaging, optical coding, and SERS enhancement; the gold sphere 1 is suitable for scattering-dominant applications; and the gold rods 1 to 6 belong to the synergistic range and are suitable for scattering-absorption synergistic applications, such as imaging-photothermal integration and photothermal enhancement sensing.

[0106] In the above process, when When the scattering efficiency is significantly higher than the absorption efficiency, the scattering characteristics of the nanoparticles are absolutely dominant, indicating that they are suitable for scattering-dominated applications such as dark-field imaging, optical labeling, and surface-enhanced Raman spectroscopy; when When the absorption efficiency is significantly higher than the scattering efficiency, the absorption characteristics of the nanoparticles are absolutely dominant, indicating that they are suitable for absorption-dominant applications such as photothermal therapy, photoacoustic imaging, and photothermal catalysis; when When the scattering efficiency is equal to the absorption efficiency, the optical properties of the nanoparticles are balanced, indicating that they are suitable for scattering-absorption synergistic applications that require the simultaneous use of scattering and absorption properties, such as integrated photothermal-imaging diagnosis and treatment, and photothermal enhanced Raman detection. The core of the logic is that by introducing dual thresholds with clear physical boundaries, the continuous scattering-absorption fit coefficients are mapped to three discrete application type intervals, realizing a standardized and repeatable quantitative judgment of the application fit of nanoparticles, and providing an objective basis for the precise screening of micro-nano photonic devices.

[0107] Please see Figure 5 A system for detecting the extinction, scattering, and absorption properties of noble metal nanoparticles, including:

[0108] The dark field scattering acquisition module is used to prepare noble metal nanoparticle samples with single-particle distribution. Under dark field illumination conditions, it acquires the raw dark field scattering spectrum data of a single nanoparticle and preprocesses it to obtain the distribution data of scattering intensity with wavelength. The resonance peak is identified from the distribution data of scattering intensity with wavelength to determine the characteristic resonance wavelength of the nanoparticle.

[0109] The extinction difference calculation module is used to switch to bright field illumination conditions, collect the original bright field transmission spectrum data of the nanoparticle under the same spatial position, obtain the transmission intensity distribution data with wavelength after preprocessing, calculate the extinction spectrum based on this, and combine the scattering intensity distribution data with wavelength to perform difference calculation at the characteristic resonance wavelength to obtain the initial value of the absorption intensity of the nanoparticle.

[0110] The photothermal correction absorption module is used to collect the photothermal signal of the nanoparticle and extract the amplitude as a correction factor. Combined with the initial value of the absorption intensity at the characteristic resonance wavelength, the corrected absorption intensity value of the nanoparticle at the characteristic resonance wavelength is calculated.

[0111] The adaptation coefficient construction module is used to calculate the scattering efficiency and absorption efficiency of the nanoparticle at the characteristic resonance wavelength based on the distribution data of scattering intensity with wavelength and the corrected absorption intensity value at the characteristic resonance wavelength, and the ratio of the two is defined as the scattering-absorption adaptation coefficient.

[0112] The application type determination module is used to compare the scattering-absorption adaptation coefficient with a preset dominant threshold, and determine the nanoparticle's suitability for scattering-dominant, absorption-dominant, or scattering-absorption synergistic applications based on the comparison result.

[0113] The above formulas are all dimensionless calculations. The formulas are derived from software simulations based on a large amount of collected data to obtain the most recent real-world results. The preset parameters in the formulas are set by those skilled in the art according to the actual situation.

[0114] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented in software, the above embodiments can be implemented, in whole or in part, as a computer program product. Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution.

[0115] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment, depending on actual needs.

[0116] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A method for detecting the extinction, scattering, and absorption properties of noble metal nanoparticles, characterized in that, Specifically, it includes: Step 1: Prepare a sample of noble metal nanoparticles with single-particle distribution. Under dark field illumination, collect raw dark field scattering spectrum data of a single nanoparticle and preprocess it to obtain the distribution data of scattering intensity with wavelength. Identify resonance peaks in the distribution data of scattering intensity with wavelength to determine the characteristic resonance wavelength of the nanoparticle. Step 2: Switch to bright field illumination conditions, collect the raw bright field transmission spectrum data of the nanoparticle under the same spatial location, obtain the transmission intensity distribution data with wavelength after preprocessing, calculate the extinction spectrum based on this, and combine the scattering intensity distribution data with wavelength to perform differential calculation at the characteristic resonance wavelength to obtain the initial value of the absorption intensity of the nanoparticle. Step 3: Collect the photothermal signal of the nanoparticle and extract the amplitude as a correction factor. Combine the initial value of the absorption intensity at the characteristic resonance wavelength to calculate the corrected absorption intensity value of the nanoparticle at the characteristic resonance wavelength. Step 4: Based on the distribution data of scattering intensity with wavelength and the corrected absorption intensity value at the characteristic resonance wavelength, calculate the scattering efficiency and absorption efficiency of the nanoparticle at the characteristic resonance wavelength, and define the ratio of the two as the scattering-absorption fit coefficient. Step 5: Compare the scattering-absorption adaptation coefficient with the preset dominant threshold, and determine the nanoparticle's suitability for scattering-dominant, absorption-dominant, or scattering-absorption synergistic applications based on the comparison results.

2. The method for detecting the extinction, scattering, and absorption characteristics of noble metal nanoparticles according to claim 1, characterized in that: The specific logic for preparing a single-particle-distributed noble metal nanoparticle sample is as follows: dilute the noble metal nanoparticle solution with pure water to a predetermined multiple and sonicate for a predetermined time; use a syringe to draw the diluted solution and drop it onto a clean coverslip; quickly cover it with another coverslip to spread the solution; after standing for a predetermined time, remove the upper coverslip to allow the water in the solution to evaporate naturally, thereby forming a single-particle-distributed nanoparticle sample on the surface of the coverslip. Under dark field illumination conditions, the scattered light of a single nanoparticle is collected through an objective lens, and after being dispersed by a spectrometer, its raw dark field scattering spectrum data is acquired by a detector. The preprocessing includes using wavelet transform to remove high-frequency noise from the original dark field scattering spectrum data, and using a baseline correction algorithm to subtract the background baseline drift in the dark field scattering spectrum, thereby obtaining the distribution data of scattering intensity with wavelength. The second derivative of the scattering intensity distribution data with wavelength is calculated, and the extreme point with the largest curvature change in the spectral curve is identified as the candidate resonance peak. The wavelength corresponding to the maximum scattering intensity in the candidate resonance peak is determined as the characteristic resonance wavelength of the nanoparticle.

3. The method for detecting the extinction, scattering, and absorption characteristics of noble metal nanoparticles according to claim 2, characterized in that: Switch to bright field illumination conditions, and at the same spatial location as in step 1, collect the transmitted light passing through the nanoparticles through the objective lens. After the light is dispersed by the spectrometer, the detector collects the raw data of the bright field transmission spectrum. The raw data of the bright field transmission spectrum is preprocessed to obtain the distribution data of transmission intensity with wavelength. The extinction spectrum is calculated based on the transmission intensity distribution data as a function of wavelength, and the extinction value is calculated using the following formula: In the formula, Indicates at wavelength The extinction value at that point, Wavelength; Indicates nanoparticles at wavelength The transmitted intensity collected at the location; Indicates the wavelength when there is no sample. The reference transmission intensity was collected at the location.

4. The method for detecting the extinction, scattering, and absorption characteristics of noble metal nanoparticles according to claim 3, characterized in that: Extract the scattering intensity value at the characteristic resonant wavelength from the scattering intensity distribution data as a function of wavelength. The extinction value at the characteristic resonance wavelength is extracted from the extinction spectrum. According to the law of conservation of energy, at the characteristic resonance wavelength At that point, the extinction value is equal to the sum of the scattering intensity value and the initial absorption intensity value; The initial value of the absorption intensity is obtained through differential calculation, and the calculation formula is as follows: In the formula, This indicates that the nanoparticles resonate at the characteristic wavelength. The initial value of the absorption intensity at that location.

5. The method for detecting the extinction, scattering, and absorption characteristics of noble metal nanoparticles according to claim 1, characterized in that: Under the bright-field illumination conditions, the photothermal signal generated by the nanoparticles under bright-field excitation was detected, and the amplitude of the photothermal signal was extracted. Based on the characteristic resonance wavelength of nanoparticles Initial value of absorption intensity at the location and the amplitude of photothermal signal The corrected absorption intensity value is calculated using the following formula: In the formula, This indicates that the nanoparticles resonate at a characteristic wavelength. The corrected absorption intensity value, The preset proportionality coefficient is obtained by calibration using standard samples.

6. The method for detecting the extinction, scattering, and absorption characteristics of noble metal nanoparticles according to claim 5, characterized in that: Based on the distribution data of scattering intensity with wavelength and the corrected absorption intensity value at the characteristic resonance wavelength, the scattering efficiency and absorption efficiency of the nanoparticle at the characteristic resonance wavelength are calculated using the following formula: In the formula, This indicates that the nanoparticle is at the characteristic resonance wavelength. Scattering efficiency at that location, This indicates that the nanoparticle is at the characteristic resonance wavelength. Absorption efficiency at the site; The and The ratio is defined as the scattering-absorption fit coefficient, denoted as .

7. The method for detecting the extinction, scattering, and absorption characteristics of noble metal nanoparticles according to claim 6, characterized in that: Preset dominant thresholds, including scattering dominant thresholds and absorption-dominant threshold And satisfy 1 ; The scattering-absorption fit coefficient is compared with the dominant threshold, specifically as follows: when At that time, it was determined that the nanoparticles were suitable for scattering-dominant applications; when At that time, it was determined that the nanoparticles were suitable for absorption-dominant applications; when When the scattering and absorption characteristics of the nanoparticles are determined to be comparable, they are suitable for scattering-absorption synergistic applications.

8. A system for detecting the extinction, scattering, and absorption characteristics of noble metal nanoparticles, used to perform the method for detecting the extinction, scattering, and absorption characteristics of noble metal nanoparticles according to any one of claims 1-7, characterized in that, include: The dark field scattering acquisition module is used to prepare noble metal nanoparticle samples with single-particle distribution. Under dark field illumination conditions, it acquires the raw dark field scattering spectrum data of a single nanoparticle and preprocesses it to obtain the distribution data of scattering intensity with wavelength. The resonance peak is identified from the distribution data of scattering intensity with wavelength to determine the characteristic resonance wavelength of the nanoparticle. The extinction difference calculation module is used to switch to bright field illumination conditions, collect the original bright field transmission spectrum data of the nanoparticle under the same spatial position, obtain the transmission intensity distribution data with wavelength after preprocessing, calculate the extinction spectrum based on this, and combine the scattering intensity distribution data with wavelength to perform difference calculation at the characteristic resonance wavelength to obtain the initial value of the absorption intensity of the nanoparticle. The photothermal correction absorption module is used to collect the photothermal signal of the nanoparticle and extract the amplitude as a correction factor. Combined with the initial value of the absorption intensity at the characteristic resonance wavelength, the corrected absorption intensity value of the nanoparticle at the characteristic resonance wavelength is calculated. The adaptation coefficient construction module is used to calculate the scattering efficiency and absorption efficiency of the nanoparticle at the characteristic resonance wavelength based on the distribution data of scattering intensity with wavelength and the corrected absorption intensity value at the characteristic resonance wavelength, and the ratio of the two is defined as the scattering-absorption adaptation coefficient. The application type determination module is used to compare the scattering-absorption adaptation coefficient with a preset dominant threshold, and determine the nanoparticle's suitability for scattering-dominant, absorption-dominant, or scattering-absorption synergistic applications based on the comparison result.

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