CN101122555A - High concentration super fine granule measuring device and method based on backward photon related spectrum - Google Patents
High concentration super fine granule measuring device and method based on backward photon related spectrum Download PDFInfo
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- CN101122555A CN101122555A CNA2007100458522A CN200710045852A CN101122555A CN 101122555 A CN101122555 A CN 101122555A CN A2007100458522 A CNA2007100458522 A CN A2007100458522A CN 200710045852 A CN200710045852 A CN 200710045852A CN 101122555 A CN101122555 A CN 101122555A
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Abstract
The invention relates to a high concentration superfine particle measurement device and method based on a backward photon correlation spectrum. An incident light path consists of a laser, a pane mirror, a lens group, a pinhole aperture and a sample cell. A receiving light path consists of a sample cell, a lens group and a pinhole aperture. An acquisition and processing unit of scattering signals consists of a light detector, a digital correlator and a computer. The measurement steps include that firstly, the laser is used as a light source to irradiate the sample cell filled with particles. Secondly, a photomultiplier is used as a light detector to continuously measure the scattering signals with a scattering angle of 180 degrees. Thirdly, the digital correlator is used to calculate pulse signals output by the photomultiplier and an autocorrelation function, which are input into a computer. Fourthly, the computer works out the diameter of a particle. The invention has the advantages of high precision, fast speed and on-line measurement. Common optical elements are adopted in the light path part. Therefore, the cost of the device is greatly lowered and the device is easy to be maintained.
Description
Technical Field
The invention relates to a high-concentration ultrafine particle measuring device and a high-concentration ultrafine particle measuring method, in particular to a high-concentration ultrafine particle measuring device and a high-concentration ultrafine particle measuring method using photon correlation spectroscopy.
Background
In Dynamic Light Scattering (DLS) ultrafine particle measurement, photon Correlation Spectroscopy (PCS) has become the standard tool for the characterization of ultrafine particles in dilute solutions. However, the PCS method generally requires dilution of the sample to be tested before measurement to avoid multiple scattering. This causes the problems of easy change of sample composition, reduced signal-to-noise ratio, and easy interference from external environmental factors (such as dust and light), and thus cannot be popularized and applied in the aspect of online real-time measurement.
To solve this problem, the following methods are currently available:
1. Cross-Correlation Spectroscopy (CCS), the method originally proposed by Phillies in 1981. The basic principle is that, because of the wave vector difference between the multiple scattered light and the single scattered light, when the multiple scattered signal is cross-correlated with the single scattered signal or the multiple scattered signal is cross-correlated with the multiple scattered signal, the correlation is much lower than the autocorrelation of the single scattered signal with the single scattered signal, so that the single scattered signal can be separated from the multiple scattered signal. However, the main implementation difficulties of this method are: this requires that the laser beam and the detector are positioned extremely accurately, which is difficult to achieve in practice, since the error of the two scattered wave vectors must be smaller than lambda/10, and is therefore difficult to put into practical use at present.
2. Diffusion Spectroscopy (DWS), the method first proposed by d.j. pin et al in 1988. The method is a method for obtaining the self-correlation function of a system and further obtaining the particle size information of particles by measuring the light intensity change of incident light after multiple scattering among particle systems. However, this method is only suitable for ultra-high concentration powder solutions, and the measurement accuracy is low, and currently, the method is still in the research stage.
In addition, those with potential applications include: scattering spot analysis, extinction pulsation method, ultrasonic attenuation method, etc., but the reliability of these methods still has to be tested in practice in large quantities, and there are some technical difficulties in concrete implementation and the cost is relatively high.
The intensity of scattered light from a stationary light source is randomly fluctuated by the particles in suspension due to the constant impact of molecules around the particles in Brownian motion. The fluctuation speed is related to the particle size of the particles, the smaller the particles are, the faster the fluctuation is, and the particle size information of the particles can be obtained by analyzing the fluctuation of the scattered light intensity. The photon correlation spectroscopy measures the particle size by calculating the autocorrelation function of the scattered light intensity, but the traditional method is not suitable for the condition of high concentration because the traditional method adopts a measuring light path in the direction of 90 degrees.
Disclosure of Invention
The invention aims to provide a high-concentration ultrafine particle measuring device and method based on backward photon correlation spectroscopy, which are used for solving the technical problem of particle size of particles with the measured concentration of 50-50000 ppm and the particle size of 10-1000 nm.
In order to realize the purpose, the technical scheme adopted by the invention is as follows:
the high-concentration ultrafine particle measuring device based on backward photon correlation spectroscopy comprises an incident light path, a receiving light path and a scattering signal acquisition and processing unit, and is characterized in that: the incident light path consists of a laser, a plane reflector, a lens group, a pinhole diaphragm and a sample cell, the receiving light path consists of a sample cell, a lens group and a pinhole diaphragm, and the scattered signal acquisition and processing unit consists of a light detector, a digital correlator and a computer;
the photoelectric detector is arranged on a light path with a scattering angle of 180 degrees, so that scattered light sequentially passes through the two lenses, the pinhole diaphragm, the two lenses, the pinhole diaphragm and the two lenses, and finally enters the photoelectric detector after the pinhole diaphragm, wherein the first lens is used for focusing incident laser on one point in a sample solution and receiving the scattered light; the spatial filter device comprises four lenses and two pinhole diaphragms, and is used for filtering stray light of signals in a transmission process; the last lens is used for focusing the scattered light signal on a receiving surface of the photoelectric detector so as to ensure the intensity of the signal; the last pinhole diaphragm is used to define the receiving area of the photodetector to ensure the coherence of the system.
The photoelectric detector is a photomultiplier tube.
A high-concentration ultrafine particle measurement method based on backward photon correlation spectroscopy comprises the following measurement steps:
1. irradiating a sample cell containing particles by using a laser as a light source;
2. continuously measuring scattered light signals at a scattering angle of 180 degrees by using a photomultiplier as a light detector;
3. calculating a self-correlation function by using a digital correlator according to the pulse signals output by the photomultiplier, wherein the expression of the self-correlation function is as follows:
G(τ)＝1+exp(-2Γτ)
wherein Γ is the Rayleigh line width, Γ and the relationship between the translational diffusion coefficient DT describing the intensity of brownian motion and the scattering vector q:
Γ＝D T q 2
wherein k is B Boltzman constant; t is the absolute temperature; eta is the solution viscosity; d, counting the autocorrelation function of the particle diameter, and sending the calculated autocorrelation function into a computer;
4. the computer finds the particle size of the particles according to the calculated autocorrelation function.
The invention has the beneficial effects that:
because the laser beam is focused on the particles on the inner surface of the front wall of the sample cell, the multiple scattering of the incident light before reaching the particles to be detected can be effectively reduced; on the other hand, the multiple scattering among particles before the scattered light reaches the detector can be reduced by adopting the optical path structure for measuring the backward scattered light. Therefore, the invention has high measurement precision and high speed and can carry out on-line measurement; in addition, because the light path part of the invention adopts common optical elements, the cost of the device can be greatly reduced, the maintenance is easy, and when the parts are damaged, the replaced parts can be conveniently purchased.
Drawings
Fig. 1 is a schematic diagram of the operation of the present invention.
Detailed Description
The invention is further described with reference to the following figures and examples.
As shown in FIG. 1, the high concentration ultrafine particle measuring device based on backward photon correlation spectroscopy of the present invention comprises a laser 1, a plane mirror 2, lenses 3,5,6,8, 10, 11, pinhole diaphragms 4,9, 12, a sample cell 7, a photodetector 13, a digital correlator 14, and a computer 15. An incident light path is composed of a laser 1, a plane reflector 2, lenses 3,5 and 6, a pinhole diaphragm 4 and a sample cell 7. The sample cell 7, the lens groups 6,5,3,8, 10, 11 and the pinhole diaphragms 4,9, 12 form a receiving light path. The light detector 13, the digital correlator 14 and the computer 15 form a scattering signal acquisition and processing unit. The photoelectric detector 13 is a photomultiplier tube, and is installed on a light path with a scattering angle of 180 degrees, so that scattered light enters the photoelectric detector 13 after passing through the lens 6, the lens 5, the pinhole diaphragm 4, the lens 3, the lens 8, the pinhole diaphragm 9, the lenses 10 and 11, and the pinhole diaphragm 12 in sequence. Wherein the lens 6 is used for focusing the incident laser light to a point in the sample solution and receiving the scattered light; the lens 3, the pinhole diaphragm 4 and the lens 5, and the lens 8, the pinhole diaphragm 9 and the lens 10 are a group of conjugate spatial filtering devices and are used for filtering stray light of signals in the transmission process; the lens 11 is used for focusing the scattered light signal on a receiving surface of the photoelectric detector so as to ensure the intensity of the signal; the pinhole diaphragm 12 is used to define the receiving area of the photodetector to ensure the coherence of the system, since the averaging effect of an excessively large coherent area can affect the fluctuation effect of the detected point signal.
The measuring method of the invention is realized by the device: firstly, a laser 1 is turned on for preheating, a plane reflector is adjusted to enable a light beam to rotate in a 90-degree direction, a spatial filtering device composed of a lens 3, a pinhole diaphragm 4 and a lens 5 is adjusted, a lens 6 is adjusted to enable incident light to be focused on the inner side of the front wall of a sample pool 7, a spatial filtering device composed of a lens 8, a pinhole diaphragm 9 and a lens 10 is adjusted to enable a scattering signal to smoothly pass through, and a lens 11 is adjusted to enable the scattering signal to be focused on the surface of a photoelectric detector 13; placing a sample cell 7 containing a standard sample in the measurement area; the data acquisition software in the computer 15 is run to start the digital correlator 14 to calculate the autocorrelation function, which is sent to the computer 15 to find the particle size of the particles.
The specific measurement steps of the invention are as follows:
1) A laser 1 is used as a light source and irradiates the sample cell 7 containing the particles;
2) Continuously measuring scattered light signals at a scattering angle of 180 degrees by using a photomultiplier as the photodetector 13;
3) The photodetector 13 converts the measured optical signal into a TTL pulse voltage signal, the frequency variation of the pulse signal reflects the light intensity fluctuation of the scattered light, and the digital correlator 14 calculates a self-correlation function according to the pulse signal, and the expression thereof is:
G(τ)＝1+exp(-2Γτ)
where Γ is the Rayleigh line width, which is the translational diffusion coefficient D describing the intensity of Brownian motion T And the scattering vector q has the following relation:
Γ＝D T q 2
wherein k is B Boltzman constant; t is the absolute temperature; eta is the solution viscosity; d is the particle diameter. Calculating an autocorrelation function and sending the autocorrelation function to the computer 15;
4) The computer 15 finds the particle size of the particles from the calculated autocorrelation function.
The specific embodiment is as follows:
the exponential decay rule of a light intensity autocorrelation curve obtained by adopting the operation of a digital correlator is as follows: ln [ G (tau)]= -1693 τ, the pulse signal output by the digital correlator 14 to the photomultiplier is expressed by the following expression: g (τ) =1+ exp (-2 Γ τ), the attenuation linewidth can be obtained as: Γ =846s -1 。
The helium-neon laser wavelength used in the test was λ 0 =632.8nm, refractive index of water m =1.33, scattering angle 180 degrees, according to the formula of the scattering vector q
The scattering vector q =2.64 × 10 can be obtained 5 cm -1 。
According to the attenuation line width gamma and the translational diffusion coefficient D describing the Brownian motion intensity T And the relation of the scattering vector q: Γ = D T q 2 The translational diffusion coefficient D can be obtained T Comprises the following steps: 3.2X 10 -8 cm 2 ·s -1 。
The laboratory temperature is 25 ℃, and the viscosity coefficient eta of the water is 0.00943dyn s cm -2 According to the Stokes-Einstein formula
The resulting particle size d =145nm.
Claims (3)
1. A high-concentration ultrafine particle measuring device based on backward photon correlation spectroscopy comprises an incident light path, a receiving light path and a scattered signal collecting and processing unit, and is characterized in that the incident light path consists of a laser (1), a plane mirror (2), lenses (3, 5, 6), a pinhole diaphragm (4) and a sample cell (7), the receiving light path consists of the sample cell (7), the lenses (6, 5, 3.8, 10, 11) and the pinhole diaphragm (4, 9, 12), and the scattered signal collecting and processing unit consists of a light detector (13), a digital correlator (14) and a computer (15);
the photoelectric detector (13) is arranged on a light path with a scattering angle of 180 degrees, scattered light sequentially passes through the lens (6), the lens (5), the pinhole diaphragm (4), the lens (3), the lens (8), the pinhole diaphragm (9), the lenses (10 and 11), and enters the photoelectric detector (13) after the pinhole diaphragm (12), wherein the lens (6) is used for focusing incident laser at one point in a sample solution and receiving the scattered light; the lens (3), the pinhole diaphragm (4), the lens (5), the lens (8), the pinhole diaphragm (9) and the lens (10) form a group of conjugate spatial filtering devices for filtering stray light of signals in the transmission process; the lens (11) is used for focusing the scattered light signal on a receiving surface of the photoelectric detector (13) so as to ensure the intensity of the signal; the pinhole diaphragm (12) is used to define the receiving area of the photodetector (13) to ensure the coherence of the system.
2. The device for measuring high concentration ultrafine particles based on backward photon correlation spectroscopy according to claim 1, wherein the electric detector (13) is a photomultiplier tube.
3. A high-concentration ultrafine particle measuring method based on backward photon correlation spectroscopy is characterized by comprising the following specific measuring steps:
1) A laser (1) is used as a light source and irradiates into a sample cell (7) containing particles;
2) Continuously measuring scattered light signals at a scattering angle of 180 degrees by using a photomultiplier as a photodetector (13);
3) Calculating a self-correlation function by a digital correlator (14) according to the pulse signals output by the photomultiplier, wherein the self-correlation function is expressed as follows:
G(τ)＝1+exp(-2Γτ)
wherein gamma is Rayleigh line width, gamma and translational diffusion coefficient D for describing Brownian motion intensity T And the relation of the scattering vector q:
Γ＝D T q 2
wherein k is B Boltzman constant; t is the absolute temperature; eta is the solution viscosity; d counting the autocorrelation function of the particle diameter and feeding the calculated autocorrelation function into a computer (15);
4) A computer (15) determines the particle size of the particles from the calculated autocorrelation function.
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| CN109030299A (en) * | 2018-11-01 | 2018-12-18 | 山东理工大学 | The back scattering nano particles measuring device and measuring method of enriched sample |
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| CN104535536B (en) * | 2009-07-10 | 2017-08-25 | 株式会社日立高新技术 | Automatic analysing apparatus |
| CN102410998A (en) * | 2011-12-16 | 2012-04-11 | 湖南科技大学 | Laser light scattering (LLS)-Raman spectrum joint device |
| CN105043948A (en) * | 2015-08-26 | 2015-11-11 | 清华大学 | Measurement system and method for grain diameter of single nano particle |
| CN105043948B (en) * | 2015-08-26 | 2017-09-22 | 清华大学 | The measuring system and measuring method of single nanoparticle particle diameter |
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| CN109030298A (en) * | 2018-11-01 | 2018-12-18 | 山东理工大学 | A kind of back scattering nano particles measuring device and measuring method |
| CN109030298B (en) * | 2018-11-01 | 2020-08-21 | 山东理工大学 | Measurement method realized by utilizing back scattering nano-particle granularity measurement device |
| CN109030299A (en) * | 2018-11-01 | 2018-12-18 | 山东理工大学 | The back scattering nano particles measuring device and measuring method of enriched sample |
| CN109669273A (en) * | 2019-03-04 | 2019-04-23 | 福建师范大学 | A kind of compact laser beam splitting arrangement for laser power therapeutic |
| CN110263292A (en) * | 2019-06-26 | 2019-09-20 | 东北大学 | A kind of calculation method for the diffusion coefficient improving Boltzmann-Matano formula |
| CN110263292B (en) * | 2019-06-26 | 2021-09-10 | 东北大学 | Calculation method for improving diffusion coefficient of Boltzmann-Matano formula |
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