CN105092433B - The measuring method of metal nanoparticle particle diameter - Google Patents
The measuring method of metal nanoparticle particle diameter Download PDFInfo
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- CN105092433B CN105092433B CN201510301828.5A CN201510301828A CN105092433B CN 105092433 B CN105092433 B CN 105092433B CN 201510301828 A CN201510301828 A CN 201510301828A CN 105092433 B CN105092433 B CN 105092433B
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Abstract
The present invention provides a kind of measuring method of metal nanoparticle particle diameter, including：The measuring system of one metal nanoparticle particle diameter is provided；Metal nanoparticle grain diameter measurement system is calibrated, reference light is obtained with measuring the intensity ratio of light, as benchmarkAnd,WithFor the characteristic wavelength of selection；Estimate metal nanoparticle species and the distribution of particle diameter；According to the two of selection characteristic wavelength λ1And λ2, metal nanoparticle is established in two wavelengthWithThe absorbance ratio at placeWith particle diameterRelation between；According to two characteristic wavelength λ1And λ2, establish revised absorbance ratioWith average grain diameterAmendment relation between；Metal nanoparticle is carried on the sample cell, measures the transmitance of metal nanoparticle、, obtain absorbanceWithIts ratio；And the ratio by absorbance obtained above, substitute into respectively in the relation before amendment and the amendment relation of revised suction, obtain the average grain diameter before the amendment of nanoparticle sample to be measuredAnd revised average grain diameter。
Description
Technical Field
The invention relates to the field of optical measurement, in particular to a method for measuring nanoparticles by using extinction data.
Background
Nanoparticles refer to particles having a size in at least one dimension of between 1 nm and 100 nm. Because the metal nano-particles have the particle size of nanometer order, the metal nano-particles have a plurality of special effects, such as small-size effect, surface effect, quantum effect, macroscopic quantum tunneling effect and the like, so that the optical, electrical, acoustic, thermal and other physical properties of the metal nano-particles show special properties which are completely different from those of the traditional bulk materials. Many characteristics of the metal nanoparticles are closely related to the particle size of the metal nanoparticles, so that the method has important scientific research and practical significance for the measurement and characterization of the particle size of the metal nanoparticles.
The main methods currently used for the measurement of the particle size of metal nanoparticles are microscopic imaging methods and scatterometry. The microscopic imaging method is a method for directly imaging nanoparticles by applying a certain microscopic imaging technology and further directly measuring the particle size on a microscopic image, but the method has the advantages of low measurement speed, low efficiency, high cost, large equipment investment, requirement of professional operation and the like, and is inconvenient for measurement outside a laboratory and real-time measurement. The existing scattering measurement methods are mainly classified into a dynamic light scattering method, a small-angle X-ray scattering method, a scattering spectrometry method and the like. Scatterometry also suffers from several deficiencies, including: 1) One or more kinds of spectral information of the metal nanoparticle group need to be measured, so expensive instruments such as a spectrophotometer, a spectrometer and the like need to be used; 2) The core principle is to solve the inverse scattering problem, and the inversion result is unstable due to the ill-conditioned nature of the inverse problem, so that the reliability requirement on the solving algorithm is high. In practical applications, there is often a need to perform rapid measurement of nanoparticles, such as rapid determination of average particle size in the synthesis of metal nanoparticles, but the current methods cannot meet the need.
Disclosure of Invention
In view of the above, it is necessary to provide a low-cost, simple, stable and accurate measurement method for measuring the average diameter of metal nanoparticles in a large sample size.
A method for measuring a particle diameter of a metal nanoparticle, comprising: providing a measuring system of the metal nano-particle size, which comprises a light source module, a light chopper, a reference sample cell, a reflecting mirror, a sample cell, a photoelectric detection unit and a data processing unit; monochromatic light emitted by the light source module is split by the light chopper to form reference light and measuring light; the reference light enters the photoelectric detection unit after passing through the reference sample cell, and is input into the data processing unit after being processed by the photoelectric detection unit; the measuring light enters the sample cell after being reflected by the reflector, enters the photoelectric detection unit after passing through the sample cell, is processed by the photoelectric detection unit and then is input into the data processing unit; calibrating the metal nanoparticle particle size measurement system to obtain the intensity ratio of the reference light to the measurement light as the referenceAndwhereinAndis the selected characteristic wavelength; estimating the type and the particle size distribution range of the metal nanoparticles; according to two selected characteristic wavelengths lambda 1 And lambda 2 From the absorbance ratioAbsorbance of the reaction mixtureAndthe relationship between the average extinction cross section and the particle diameter DAndestablishing metal nanoparticles at two wavelengthsAndabsorbance ratio of (A)And particle sizeThe relationship between them; according to two characteristic wavelengths lambda 1 And lambda 2 From the corrected absorbance ratioAbsorbance of the reaction mixtureAndrelation between average extinction cross section and particle diameter DAndestablishing a corrected absorbance ratioAnd average particle diameterA revised relationship therebetween; loading metal nanoparticles in the sample cell, and measuring the transmittance of the metal nanoparticles、Obtaining metal nanoparticles at two wavelengthsAndabsorbance of (b) inAndand the ratio thereof(ii) a And the ratio of the absorbance obtained aboveRespectively substituted into the absorbance ratio before correctionAnd particle sizeThe relationship between and the corrected absorbance ratioAnd average particle diameterIn the correction relationship, the average particle diameter of the nano particle sample to be measured before correction is obtainedAnd corrected average particle diameter。
Compared with the prior art, the method for measuring the particle size of the metal nano-particles provided by the invention can quickly, stably and accurately represent the average diameter of the metal nano-particles through extinction data at two characteristic wavelengths, the relation between the absorbance ratio and the particle size and the correction relation thereof, reduce the measurement cost and improve the measurement speed, the stability and the precision. The method solves the defects that the prior scattering measurement method needs to carry out modeling solution on the inverse scattering problem and needs to use expensive spectrum instruments.
Drawings
Fig. 1 is a flowchart of a method for measuring a particle diameter of a metal nanoparticle according to a first embodiment of the present invention.
Fig. 2 is a schematic structural diagram of a system for measuring a particle size of a metal nanoparticle according to a first embodiment of the present invention.
Fig. 3 is an extinction spectrum of a typical metal nanoparticle.
FIG. 4 is a graph before correction(black line) and corrected curve(red line). Blue line representationCalculated curve of sensitivity.
FIG. 5 is a schematic view of a geometric model of gold nanorods.
Fig. 6 is a graph comparing the measurement results of the two-wavelength extinction method for rapidly measuring the particle size of metal nanoparticles according to the present invention with the measurement results of the transmission scanning microscopy, the conventional extinction spectroscopy method, and the dynamic light scattering method.
Fig. 7 is a schematic structural diagram of a system for measuring a particle size of a metal nanoparticle according to a second embodiment of the present invention.
Fig. 8 is a schematic structural diagram of a system for measuring a particle size of a metal nanoparticle according to a third embodiment of the present invention.
Description of the main elements
| Measurement system for metal nanoparticle particle diameter | 100，200，300 |
| Light source module | 10，20，30 |
| Light source | 1 |
| Monochromatic instrument | 2 |
| Sample cell | 3 |
| Reference sample cell | 4 |
| Photoelectric detection unit | 5 |
| Data processing unit | 12 |
| Light chopper | 6 |
| Reflecting mirror | 7 |
| First narrow-band light source | 8 |
| Second narrow-band light source | 9 |
| Light combiner | 11 |
The following specific embodiments will further illustrate the invention in conjunction with the above-described figures.
Detailed Description
The following describes the measurement system and measurement method of the metal nanoparticle particle size according to the present invention in detail with reference to the accompanying drawings. For convenience of description, the present invention first introduces a system for measuring the particle size of metal nanoparticles.
Referring to fig. 1 and 2, a first embodiment of the invention provides a system 100 for measuring a particle size of a metal nanoparticle, wherein the system 100 includes a light source module 10, a light chopper 6, a reference cell 4, a mirror 7, a cell 3, a photodetection unit 5, and a data processing unit 12. The light emitted by the light source module 10 is split by the light chopper 6 to form two beams, namely a reference beam and a measuring beam. Wherein the reference beam enters the photoelectric detection unit 5 after passing through the reference sample cell 4; the measuring beam enters the sample cell 3 after being reflected by the reflector 7, and enters the photoelectric detection unit 5 after passing through the sample cell 3.
The light source module 10 is used for generating two specific wavelengthsAndin this embodiment, the light source module 10 includes a light source 1 and a monochromator 2, and light generated by the light source 1 generates monochromatic light through the monochromator 2. The light source module 10 may also be two lasers to generate monochromatic light. The light source module 10 may also be two photodiodes to generate approximately monochromatic light.
The light chopper 6 is used for dividing monochromatic light output by the light source module 10 into two paths of light beams including measuring light and reference light. The two light beams can form an included angle. In this embodiment, the propagation direction of the measurement light is perpendicular to the propagation direction of the reference light. And defining the propagation direction of the reference light as the X direction, and then the propagation direction of the measuring light is the Y direction.
The reference sample cell 4 is used for carrying a reference sample, and specifically, the reference sample cell 4 may include a cuvette (not shown) for carrying the reference sample, and the specific shape thereof may be selected according to the specific shape of the reference sample.
The sample cell 3 is used for carrying nanoparticles, and specifically, a cuvette (not shown) is arranged inside the sample cell 3 for carrying nanoparticles. The measurement light output from the chopper 6 is reflected by the mirror 7 and then incident on the nanoparticles in the sample cell 3. The specific shape of the sample cell 3 and the cuvette may be selected according to the nanoparticles. In this embodiment, the nanoparticles are spherical gold nanoparticles.
The photodetection unit 5 is used for detecting the measuring light emitted from the sample cell 3 and the reference light emitted from the reference sample cell 4. Finally, the measurement light and the reference light obtained by the photodetection unit 5 are converted into electric signals, and the electric signals are input to the data processing unit 12.
The data processing unit 12 is configured to receive the electrical signal input by the photodetecting unit 5, convert the electrical signal into data, and process the data to obtain two wavelengthsAndabsorbance of the nanoparticle sampleAnd. In particular, the data processing unit 12 is comprised inAndabsorbance ratio of metal nanoparticles at two wavelengthsAnd particle sizeThe data processing module group of the one-to-one corresponding relation comprises the absorbance ratioAbsorbance of the solutionAndaverage extinction cross sectionAndand a database of relationships between particle sizes D; and inAndcorrected absorbance ratio of metal nanoparticles at two wavelengthsAnd average particle diameterThe data processing module of the one-to-one corresponding relation comprises the corrected absorbance ratioAbsorbance of the solutionAndaverage extinction cross sectionAndand a database of the relationship between the particle sizes D.
The absorbance of the metal nanoparticles is obtained by the photoelectric detection unit 5 and the data processing unit 12Andobtaining the ratio of the absorbance of the metal nano-particles under different wavelengthsSo as to obtain the average particle size of the nano particle sample to be detected. Wherein the ratio of absorbance：
。
Referring to fig. 2, the present invention further provides a method for measuring a particle size of a metal nanoparticle by using the system 100 for measuring a particle size of a metal nanoparticle, comprising the following steps:
step S10, calibrating the metal nanoparticle size measurement system 100 to obtain the intensity ratio of the reference light to the measurement light as the referenceAnd。
specifically, when the system 100 for measuring the particle size of the metal nanoparticle is calibrated, no sample to be measured is placed in the system, and the reference light split by the light chopper 6 and the measurement light reflected by the light chopper 6 and the reflecting mirror 7 of the monochromatic light generated by the light source module 10 are directly received by the photoelectric detection unit 5. By this method, the intensity ratio of the reference light and the measurement light can be directly measured as a reference. The expression of the reference is as follows:
，；
wherein the content of the first and second substances,andin order to select the characteristic wavelength of the light,for the measured light intensity detected by the photo detection unit 5,is the reference light intensity detected by the photodetecting unit 5.
In this embodiment, the wavelength may be selected according to the following principle: 1) Within a certain range, the fit degree between the calculated value of the extinction spectrum of the nanoparticle group and the actual measured value is not high, so that when two characteristic wavelengths are selected, the wavelengths within the range are avoided as much as possible; 2) The two wavelengths chosen should be as close as possible to the LSPR peak of the particle so that they can reflect the peak position information; 3) In order to accurately obtain the particle size of the nanoparticles,and particle sizeShould maintain a monotonic relationship with, in other words, a functionThe monotonic interval of (a) determines the range of particle sizes of the metal nanoparticles that can be measured; 4) Due to the functionIs determined by the slope ofTo pairAnd therefore, the larger this slope, the better.
By comprehensively considering the four principles, the wavelength can be selected within the range of 500 nm to 600 nm for spherical gold nanoparticles of 10 nm to 120 nm. In this embodiment, the sample to be measured is 20nm to 105nm gold nanosphere particles, and thus the characteristic wavelength selected by the system is，。
And S11, estimating the type and the particle size distribution range of the metal nanoparticles.
The type and the particle size of the metal nanoparticles can be estimated according to the color of the metal nanoparticles or according to an electron microscope picture of the metal nanoparticles, and the type and the approximate distribution range of the particle size of the metal nanoparticles can be judged. The type of the metal nanoparticles is the approximate appearance shape of the metal nanoparticles. In this embodiment, the metal nanoparticles are spherical or near-spherical gold nanoparticles.
Step S12, selecting two characteristic wavelengths lambda 1 And lambda 2 From the absorbance ratioAbsorbance of the solutionAndthe relationship between the average extinction cross section and the particle diameter DAndestablishing metal nanoparticles at two wavelengthsAndabsorbance ratio of (A)And particle sizeAnd the relationship therebetween.
Referring to fig. 3, the metal nanoparticles have a characteristic Localized Surface Plasmon Resonance (LSPR) effect. Therefore, by measuring extinction data of two specific wavelength points, the characteristics of the spectrum can be determined, and the relation between the extinction data and the particle size of the metal nanoparticles is established. In this embodiment, spherical gold nanoparticles are used as an initial model of the model. Actual measured absorbanceAndaverage extinction with metal nanoparticlesCross section ofThe relationship between them is:
；
whereinIs the optical thickness of the gold nanoparticle sample,is the number concentration of particles, i.e. the number of particles per unit volume,is the thickness of the metal nanoparticle sample. It is thus possible to obtain a mean extinction cross-section for the nanoparticle populationThe calculation of (2) establishes that the nano particles select two proper wavelengthsAndabsorbance ratio of (A)And particle sizeAnd the relationship therebetween. Since the operation is directed at the modeling of perfect spherical particles, a strict numerical method can be used to calculate the database by adopting an accurate and rapid Mie theoretical algorithm.
Can calculate and establish the wavelength lambda according to the estimated type of the metal nano particles and the distribution range of the particle size 1 And lambda 2 Average elimination ofCross section of lightDatabase relating to particle size DAndthereby obtaining the relation between the average extinction section coefficient and the particle diameter D. The deformation of the nano-particles is various, but the change of the aspect ratio of the particles has the greatest influence on the extinction spectrum, and the geometric model of the gold nano-rods considered here is used as the deformation model for researching the nano-particles, namely the geometric model is formed by a cylinder and two semi-ellipsoidal end caps, whereinAndrespectively represent the width and the length of the nano-rod,representing the aspect ratio of the nanorods. For spherical particles, AR =1, the most accurate and fast Mie theory algorithm can be used to compute the database strictly by numerical methods.
Please refer to fig. 4 for comprehensive considerationSensitivity and monotonic range, the present embodiment selects wavelength pairsFor measuring the optimal wavelength pair of the gold nanoparticles with the particle size of 30 nm-120 nm.
After selecting two characteristic wavelengths and obtaining correspondingAfter calculating the curve, the curve can be passedAnd the ratio of the absorbance of the metal nanoparticles at the two wavelengths is used for calculating the average particle size of the metal nanoparticles. It should be noted that the thickness of the metal nanoparticles is measured because only the ratio of the absorbance at two wavelengths is measured, and the absolute value of the absorbance at each wavelength is not measuredAnd number concentration of metal nanoparticlesThe effects of the variables will be eliminated.
The above analysis only considers the ideal case of spherical nanoparticles in a monodisperse system. However, in practical measurement, the shape of the nanoparticles is not ideal spherical, but has a certain deformation, and the particle size of the nanoparticles is not absolutely uniform, and has a certain dispersibility (even if small). Therefore, it is necessary to study the effect of the actual deformation and dispersibility of the nanoparticles on the measurement results, and accordingly to make necessary corrections to the two-wavelength extinction method.
Step S13, according to the two characteristic wavelengths lambda 1 And lambda 2 From the corrected absorbance ratioAbsorbance of the solutionAndthe relationship between the average extinction cross section and the particle diameter DAndestablishing a corrected absorbance ratioAnd average particle diameterAnd a correction relationship therebetween.
In this example, the measurement was performed using spherical gold nanoparticles as a sample. Referring to fig. 5, the influence of the deformation and dispersion of the nanoparticles on the measurement result is respectively studied according to the deviation between the actual sample and the ideal situation considered in the modeling, and a modified dual-wavelength extinction method is proposed accordingly.
To compensate for these effects, the population of metal nanoparticles to be measured can be considered to have an equivalent aspect ratioAnd equivalent dispersibilityThe population of rod-shaped nanoparticles of (1). Thus can be aligned withThe following modifications are made:
wherein the superscriptThe corrected value of absorbance in consideration of the influence of distortion and dispersibility is shown.
In this model adoptAndas a compensation for the effect of the actual deformation and dispersion of the nanoparticles on the measurement results. Because in actual measurement, the parameters of the sample areIs unknown. Therefore, it is necessary to make reasonable predictions of them. In measuring chemically synthesized spherical metal nanoparticles (also most of the particles commonly used today), the sample dispersibilityAnd average aspect ratioCan be selected respectivelyAnd. For special nanoparticles prepared by other methods, dispersibilityAnd average aspect ratioAnd are not the above typical values, and need to be determined reasonably according to the situationAnd。
after the correction is carried out, the extinction cross section of the spherical nano particle group which is more in line with the actual situation can be recalculated, and then the spherical nano particle group with the extinction cross section can be obtainedAndand can then be correctedThe curve and the sensitivity thereof can be used for measuring the spherical gold with the particle size range of 20nm-105nmA rice grain sample.
When the nano-particles are nano-rods, a T matrix algorithm is adopted to establish the wavelength lambda 1 And lambda 2 Lower average extinction Cross sectionDatabase relating to particle size DAndto obtain an average extinction cross sectionAnd the particle diameter D. The nano particles are gold nanorods, and the key geometric characteristic quantity of the nanorods comprises an aspect ratio parameter AR and a particle size D of the gold nanorods. The range of the particle diameter D of the gold nanorod is set to be between 5nm and 165nm, and the step length is set to be between 0.5nm and 40nm; the range of the length-width ratio AR is set to be 1 to 10, and the step length can be set to be 0.05-1. Calculated monochromatic light wavelength rangeSetting the range of 300nm to 2000nm, and setting the step length to be 0.5nm-20 nm.
Since the above operations are modeling for rod-shaped nanoparticles, the most accurate and fast T-matrix algorithm can be used to compute the database using a rigorous numerical method. The database only needs to be calculated once in various applications and then can be stored for reuse, and the efficiency of subsequent measurement is greatly improved.
S14, loading the metal nanoparticles in the sample cell, and measuring the transmittance of the metal nanoparticles、Obtaining metal nanoparticlesParticles at two wavelengthsAndabsorbance of (b) ofAndand the ratio thereof。
Since some metal nanoparticles themselves are difficult to disperse in the sample cell 3, the metal nanoparticles may be dispersed in a solvent or suspended in a gas. In this embodiment, the spherical gold nanoparticles are distributed in a solvent and are substantially insoluble in the solvent to form a mixed solution. And putting the mixed solution containing the metal nano-particles into a sample pool 3, putting the solvent serving as a reference sample into a reference sample pool 4, and detecting the measured light intensity and the reference light intensity by the photoelectric detection unit 5. It will be appreciated that when the metal nanoparticles are themselves capable of being dispersed in the sample cell, then the reference cell 4 can be measured without the need for the solvent.
Measurement result of extinction spectrum of the metal nanoparticles usable absorbanceExpressed, the expression is as follows:
wherein，Is the transmittance of the metal nano-particles,is the wavelength of a monochromatic light,for the measured light intensity detected by the photo detection unit 5,is the reference light intensity detected by the photodetecting unit,is a reference for measuring the intensity ratio of light and reference light,。
the transmittance of the metal nano-particles can be obtained by measurementObtaining metal nano-particles at two wavelengthsAndabsorbance of (b) ofAndand the ratio thereof。
Step S15, the ratio of the absorbance obtained is usedRespectively substituted into the absorbance ratio before correctionAnd particle sizeThe relationship between and the corrected absorbance ratioAnd average particle diameterAnd obtaining the average particle diameter of the nano particle sample to be detected before correction in the correction relation between the twoAnd corrected average particle diameter。
The ratio of absorbance obtained by the experimentSubstituting the absorbance ratio obtained aboveAnd particle sizeRelationship between and corrected absorbance ratioAnd average particle diameterAnd finally obtaining the nano particle sample to be detected of the monodisperse system before correction in the relation between the twoAverage particle diameter of productAnd the corrected average particle diameter of the nano particle sample to be detected。
Referring to fig. 6, for a large amount of nearly spherical gold nano-samples, the method is used to measure the average particle size by measuring only the extinction data at two specific wavelengths, and the measurement result is compared with the measurement results of three existing methods for measuring nanoparticles, such as a Transmission Electron Microscope (TEM) method, a conventional extinction spectroscopy (OES) method, and a dynamic light scattering method (DLS) method, so as to further prove the rapidity, stability, and high accuracy of the method of the present invention, and thus, the particle size of a large amount of metal nanoparticles can be measured. Wherein, the first and the second end of the pipe are connected with each other,the average particle diameter is shown, TEM is the result of measurement by TEM, OES is the result of measurement by OES, DLS is the result of measurement by DLS, and standard DWE is the result of measurement using absorbance ratioAnd particle sizeAnd the corrected DWE means the absorbance ratio with the correctionAnd average particle diameterAnd the result of the measurement of the relationship therebetween,shows the relative deviation between the measurement method corresponding to the column and the measurement result of the TEM method。
Referring to fig. 7, a second embodiment of the present invention provides a dual-optical-path metal nanoparticle size measuring system 200, wherein the structure of the dual-optical-path metal nanoparticle size measuring system 200 is substantially the same as that of the dual-optical-path metal nanoparticle size measuring system 100 of the first embodiment, except that the light source module 20 includes a wavelength of light having a wavelength of about two wavelengthsWith a first narrow-band light source 8 having a wavelength ofThe light generated by the first narrow-band light source 8 and the second narrow-band light source 9 is refracted by the light combiner 11 and enters the light chopper 6.
Specifically, the "narrow-band light source" means that the full width at half maximum of the spectrum of the light emitted by the light source is 50 nm or less, and further, the full width at half maximum of the spectrum of the light emitted by the light source is 32 nm or less. The first narrow-band light source 8 and the second narrow-band light source 9 are used for generating monochromatic light. In this example, the first narrow-band light source 8 and the second narrow-band light source 9 may be narrow-band light emitting diodes, or may be lasers, so as to generate monochromatic light. Further, the light combiner 11 is configured to combine the monochromatic light output by the first narrow-band light source 8 and the monochromatic light output by the second narrow-band light source 9 into a beam of light, and then the beam of light is refracted and enters the light chopper 6.
Referring to fig. 8, a third embodiment of the present invention provides a dual-optical-path metal nanoparticle size measuring system 300, wherein the structure of the dual-optical-path metal nanoparticle size measuring system 300 is substantially the same as that of the dual-optical-path metal nanoparticle size measuring system 100 of the first embodiment, except that the light source module 20 includes a wavelength of light with a wavelength ofWith a first narrow-band light source 8 having a wavelength ofTo (1)Two narrow-band light sources 9, the light generated by the first narrow-band light source 8 and the second narrow-band light source 9 can enter the chopper 6 in parallel.
According to the dual-wavelength extinction method for rapidly measuring the particle size of the metal nanoparticles, the average diameter of the metal nanoparticles can be rapidly, stably and accurately represented through extinction data at two specific wavelengths and through the relationship between the absorbance ratio and the particle size and the correction relationship thereof, so that the measurement cost is reduced, and the measurement speed, the stability and the precision are improved. The method solves the defects that the existing scattering measurement method needs to carry out modeling solution on the scattering inverse problem and needs to use a more expensive spectrometer. The dual-wavelength extinction method for rapidly measuring the particle size of the metal nanoparticles provided by the invention has the practical advantages of rapidness, convenience, low price and the like. The dual-wavelength extinction method for rapidly measuring the particle size of the metal nanoparticles provided by the invention has important significance for commercial trade, quality control, new material research and development, and characterization and accurate measurement of geometrical characteristics of the nanoparticles, particularly the metal nanoparticles. After the proper characteristic wavelength is selected, the method can also be used for measuring metal nanoparticles of other materials and shapes.
In addition, other modifications within the spirit of the invention will occur to those skilled in the art, and it is understood that such modifications are included within the scope of the invention as claimed.
Claims (9)
1. A method for measuring a particle diameter of a metal nanoparticle, comprising:
providing a measuring system of the metal nano-particle size, which comprises a light source module, a light chopper, a reference sample cell, a reflecting mirror, a sample cell, a photoelectric detection unit and a data processing unit; monochromatic light emitted by the light source module is split by the light chopper to form reference light and measuring light; the reference light enters the photoelectric detection unit after passing through the reference sample cell, and is input into the data processing unit after being processed by the photoelectric detection unit; the measuring light enters the sample cell after being reflected by the reflector, enters the photoelectric detection unit after passing through the sample cell, is processed by the photoelectric detection unit and then is input into the data processing unit;
calibrating the metal nanoparticle particle size measurement system to obtain the intensity ratio of the reference light to the measurement light as the referenceAndwherein λ 1 And λ 2 Is the selected characteristic wavelength;
estimating the type and the particle size distribution range of the metal nanoparticles;
according to two selected characteristic wavelengths lambda 1 And lambda 2 From the absorbance ratioAbsorbance of the solutionAndrelation between average extinction cross section and particle diameter D<C ext (λ 1 ,D,AR,CV)>, and<C ext (λ 2 ,D,AR,CV)&establishing metal nano particles at two wavelengths lambda 1 And λ 2 Absorbance ratio of (A)The relationship between the particle size D and the particle diameter D;
according to two characteristic wavelengths lambda 1 And lambda 2 From the corrected absorbance ratioAbsorbance of the solutionAndrelation between average extinction cross section and particle diameter D<C ext (λ 1 ,D,AR,CV)>, and<C ext (λ 2 ,D,AR,CV)&establishing corrected absorbance ratioAnd average particle diameterAnd a modified relationship therebetween, wherein AR represents an aspect ratio of the metal nanoparticles, and CV represents sample dispersibility;
loading metal nanoparticles in the sample cell, and measuring the transmittance T of the metal nanoparticles λ1 、T λ2 Obtaining metal nano-particles at two wavelengths lambda 1 And λ 2 Absorbance of (b) inAndand ratio thereofAnd
the ratio of the absorbance obtained above is measuredRespectively substituting into the absorbance ratio before correctionThe relationship between the particle size D and the corrected absorbance ratioAnd average particle diameterIn the correction relation, the average particle diameter of the nano particle sample to be measured before correction is obtainedAnd corrected average particle diameter
2. The method for measuring the particle diameter of metal nanoparticles according to claim 1, wherein the characteristic wavelength λ is selected according to the following steps 1 And lambda 2 ：
1) Within a certain range, the coincidence degree of the calculated value of the extinction spectrum of the metal nanoparticle group and the actual measured value is not high, and when two characteristic wavelengths are selected, the wavelengths within the range are avoided;
2) The two wavelengths selected should be relatively close to the LSPR peak of the metal nanoparticles so that the two wavelengths can reflect the position information of the peak;
3) In order to accurately obtain the particle size of the nanoparticles,and the particle diameter D and the function of the particle diameter D are in a monotonous relationThe monotonous interval of (a) determines the particle size range of the metal nanoparticles to be measured;
4) Function(s)Is determined by the slope ofSensitivity to D, thus choosing the slope maximumFunction of (2)
3. The method for measuring particle diameter of metal nanoparticles according to claim 2, wherein absorbanceAndaverage extinction cross section of metal nano-particles<C ext >, the relationship between:
where OD is the optical thickness of the gold nanoparticle sample, N ν Is the number concentration of particles, i.e. the number of particles per unit volume, and z is the thickness of the metal nanoparticle sample.
4. The method of claim 3, wherein the absorbance ratio is established by using Mie's theoretical algorithmAnd the particle diameter D.
5. The method for measuring a particle diameter of metal nanoparticles according to claim 3, wherein the metal nanoparticles to be measured are regarded as having an equivalent aspect ratio AR eff And equivalent dispersity CV eff Rod-shaped nanoparticle group of (2), toThe following modifications are made:
where the upper COR represents the corrected value of absorbance taking into account the effects of distortion and dispersion.
6. The method of claim 3, wherein the nano-particles are nano-rods, and the T matrix algorithm is used to establish the wavelength λ 1 And lambda 2 Lower average extinction Cross section<C ext >, database relating to particle size D<C ext (λ 1 ,D,AR)>, and<C ext (λ 2 ,D,AR)&obtaining the average extinction cross section<C ext >, and the particle size D.
7. The method according to claim 3, wherein the extinction spectrum of the metal nanoparticles is measured as absorbance A λ Expressed, the expression is as follows:
A λ ＝-log(T λ ),
wherein, T λ Is the transmittance of the metal nanoparticles, λ is the wavelength of monochromatic light, I m1 (lambda) is the measured light intensity detected by the photodetector unit, I r1 (lambda) is the reference light intensity, T, detected by the photodetector unit 0 (λ) is a reference value of the intensity ratio of the measurement light and the reference light, T 1 (λ)＝I m1 (λ)/I r1 (λ)。
8. The method according to claim 1, wherein the light source module comprises a wavelength λ 1 Of a first narrow-band light source of wavelength lambda 2 The second narrow-band light source and the light combiner,the light generated by the first narrow-band light source and the second narrow-band light source is refracted by the light combiner and enters the light chopper.
9. The method according to claim 1, wherein the light source module comprises a wavelength λ 1 Of a first narrow-band light source of wavelength lambda 2 The light generated by the first narrow-band light source and the second narrow-band light source enters the chopper in parallel.
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| CN101126701A (en) * | 2007-09-13 | 2008-02-20 | 浙江大学 | Gas solid two-phase flow granule density detection device and method based on terahertz transmission and detector |
| CN101762441A (en) * | 2009-10-16 | 2010-06-30 | 广东医学院 | Method and device for measuring size of high-concentration nano particle |
| CN103499521A (en) * | 2013-09-06 | 2014-01-08 | 清华大学 | Method for measuring key geometrical characteristics of nanometer particles |
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| CN104006891A (en) * | 2014-05-29 | 2014-08-27 | 清华大学 | Device for measuring nano-scale light field phase distribution |
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|---|---|---|---|---|
| US6738144B1 (en) * | 1999-12-17 | 2004-05-18 | University Of Central Florida | Non-invasive method and low-coherence apparatus system analysis and process control |
| CN1727873A (en) * | 2004-07-29 | 2006-02-01 | 中国石油化工股份有限公司 | Method for measuring size distribution of grains in Nano level through method of capillary electrophoresis |
| CN101126701A (en) * | 2007-09-13 | 2008-02-20 | 浙江大学 | Gas solid two-phase flow granule density detection device and method based on terahertz transmission and detector |
| CN101762441A (en) * | 2009-10-16 | 2010-06-30 | 广东医学院 | Method and device for measuring size of high-concentration nano particle |
| CN103499521A (en) * | 2013-09-06 | 2014-01-08 | 清华大学 | Method for measuring key geometrical characteristics of nanometer particles |
| CN103499393A (en) * | 2013-09-06 | 2014-01-08 | 清华大学 | Spectrum measuring method |
| CN104006891A (en) * | 2014-05-29 | 2014-08-27 | 清华大学 | Device for measuring nano-scale light field phase distribution |
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