CN109030298B - A kind of measurement method realized by backscattering nanoparticle size measurement device - Google Patents

Abstract

A measurement method realized by a backscattering nanoparticle particle size measurement device belongs to the technical field of particle size detection. It is characterized in that: a lens (5), a laser (8) and a GRIN lens (9) are sequentially arranged on the rear side of the sample cell (1), and the output end of the GRIN lens (9) is connected to the input end of the photomultiplier tube (10). , the output end of the photomultiplier tube (10) is connected to the input end of the photon correlator (11); a lens adjusting device for adjusting the distance between the lens (5) and the sample cell (1) is also provided, and the lens (5) Placed in the lens adjustment device. Through the measurement method realized by the backscattered nanoparticle particle size measuring device, both the incident light and the scattered light are located on the back side of the sample cell, so the scattered light does not need to completely pass through the test sample in the sample cell, which reduces the scattered light path and reduces the The multiple light scattering effect is realized, and the particle size measurement of high concentration test samples is realized.

Description

A kind of measurement method realized by backscattering nanoparticle size measurement device

technical field

A measurement method realized by a backscattering nanoparticle particle size measurement device belongs to the technical field of particle size detection.

Background technique

The particle size and distribution of nanoparticles are important parameters to characterize their properties, and dynamic light scattering technology is an effective method to measure the size of nanoparticles. In the prior art dynamic light scattering particle measurement technology, photon correlation spectroscopy is a commonly used method. Photon correlation spectroscopy is to obtain particle size information by measuring the fluctuation of scattered light at a fixed spatial position. Since the theoretical model of photon correlation spectroscopy is based on the single scattering of incident light, for samples with high concentration, due to the small spacing between particles, the scattered light contains a large amount of multiple scattered light. Due to the influence of multiple scattered light, photon correlation spectroscopy cannot be directly used for the measurement of particle size in high concentration samples. Therefore, in order to avoid multiple scattering of incident light, the concentration of the test sample is required to be extremely low. Therefore, traditional photon correlation spectroscopy cannot be directly used to measure samples with high concentrations and opaque systems such as suspensions, thus limiting the dynamic light scattering technology. Application in high concentration samples such as food, paint coatings, gels, etc.

When the incident light irradiates the high concentration sample, there are two ways to solve the problem of multiple scattering: the first way is to use the improved detection method of the cross-correlation spectroscopy technology and the low-coherence dynamic light scattering technology. The former uses two photodetectors to measure scattered light simultaneously at different angles, and then calculates the cross-correlation function of the two sets of scattered signals. Since the correlation between the multiple scattered light and the single scattered light is lost, the influence of multiple scattering can be weakened by calculating the cross-correlation function. However, this method requires that the error of the two scattered wave vectors must be less than 1/10 of the wavelength. It is difficult to achieve such an accuracy in practical operation, and in order to ensure sufficient single scattered light, it is difficult for cross-correlation spectroscopy to measure concentrations exceeding 5% of the sample. The latter uses phase modulation technology to effectively suppress multiple scattered light by using the characteristics of low coherent light sources. Based on the single scattering theory, a particle size distribution and its dynamic characteristics in high-concentration suspended samples are established. Detection method. However, this method requires the use of a piezoelectric ceramic-based micro-movement stage to adjust the optical path of the reference light, which makes the optical path and control system very complicated.

The second approach is to develop a theory that can deal with multiple scattered light, so that information about the properties of the particle system can be extracted from the variation of multiple scattered light. The theory of diffusion spectroscopy is based on this idea. Maret and Wolf first proposed the concept of diffusion spectrum in 1987. The diffusion spectrum theory detects the change of multiple scattered light with time, uses a high-speed photon correlator to obtain the light intensity autocorrelation function, and uses a fitting algorithm to obtain the autocorrelation function. The characteristic decay time of , and then the average particle size of the particles and the kinetic information of the particles are obtained. Since diffusion spectroscopy requires only multiple scattered light to be received, it is only suitable for very high concentrations of particle samples without single scattering. In addition, since the diffusion spectroscopy method utilizes the sufficient diffusion of photons in the particle system to obtain particle size information of the particles, only the average particle size of the particle system can be measured, but the distribution information of the particle size cannot be obtained.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is: to overcome the deficiencies of the prior art, to provide a kind of incident light and scattered light located on the back side of the sample cell, so the scattered light does not need to completely pass through the test sample in the sample cell, reducing the scattered light The process reduces the multiple light scattering effect, and realizes the measurement method realized by the backscattering nanoparticle particle size measuring device for the particle size measurement of the high-concentration test sample.

The technical solution adopted by the present invention to solve the technical problem is as follows: the backscattered nanoparticle particle size measuring device includes a sample cell, and the test sample is located in the sample cell, and is characterized in that: a lens, a laser and a GRIN lens, the incident light emitted by the laser enters the sample cell through the lens, and is reflected from the back end of the sample cell and enters the GRIN lens. The output end of the GRIN lens is connected to the input end of the photomultiplier tube, and the output end of the photomultiplier tube is connected to the photon correlator. an input end; a lens adjusting device for adjusting the distance between the lens and the sample cell is also provided, and the lens is placed in the lens adjusting device.

Preferably, the lens adjusting device includes a fixing frame, the lens is fixed in the fixing frame, a screw thread is provided with the fixing frame, and the stepping motor is coaxially fixed with the screw rod.

Preferably, the screw rod passes through one side of the fixing frame, and an internal thread matched with the screw rod is arranged in the fixing frame; the other side of the fixing frame is provided with a guide post symmetrically arranged with the screw rod, and the guide post passes through the fixing frame at the same time. shelf.

Preferably, an attenuation plate is arranged between the lens and the laser.

Preferably, a computer is also provided, and the output end of the photon correlator is connected to the computer.

Preferably, the GRIN lens is arranged at a scattering angle of 170° behind the sample cell.

A measurement method realized by a backscattering nanoparticle particle size measurement device, characterized in that it comprises the following steps:

In step a, the laser is turned on, the incident light emitted by the laser irradiates the test sample in the sample cell and is scattered, and the scattered light is emitted backward from the rear edge of the sample cell; the position of the lens is adjusted by the lens adjustment device, so that the position of the scatterer is located in the sample. at the rear edge of the pool;

In step b, the scattered light from the sample continues to pass through the GRIN lens, the photomultiplier tube and the photon correlator, and the light intensity autocorrelation function of the scattered light at the current position of the lens is measured and obtained, and the cumulative analysis method is used to fit the light intensity autocorrelation function. The intercept, recorded as the reference value of the intercept β ₁ ;

Step c, adjusting the position of the lens by the lens adjusting device, so that the position of the scatterer is located at the center of the sample cell;

In step d, the scattered light from the sample continues to pass through the GRIN lens, the photomultiplier tube and the photon correlator to measure the light intensity autocorrelation function of the scattered light at the current position of the lens, and use the cumulative analysis method to fit the light intensity autocorrelation function. The intercept, denoted as the calculated value of the intercept β ₂ ;

Step e, using the intercept comparison criterion to judge whether the incident light has multiple scattering when the lens is at the current position, if multiple scattering occurs, execute step f, if multiple scattering does not occur, execute step g;

In step f, through the lens adjustment device, the position of the scatterer is moved from the center of the sample cell to the rear edge of the sample cell at fixed intervals in sequence, and the light intensity autocorrelation function at this position is determined for each movement, and the intercept is further obtained. and compare the reference value of the intercept and the calculated value of the intercept at different positions in turn according to the intercept comparison criterion, and determine the position of the lens when the incident light does not have multiple scattering;

Step g, after determining the position where the incident light does not have multiple scattering, measure the average particle size and particle size distribution of the sample at the current position.

Preferably, compare the reference value of the intercept of the light intensity autocorrelation function with the calculated value of the intercept, if β ₂ >0.8·β ₁ , it means that the incident light emitted by the laser does not have multiple scattering in the sample cell; if β ₂ <0.8·β ₁ , it indicates that the sample concentration in the sample cell is high, and the incident light emitted by the laser is scattered multiple times in the sample cell.

Compared with the prior art, the present invention has the following beneficial effects:

1. Through the backscattered nanoparticle particle size measurement device and measurement method, both the incident light and the scattered light are located on the back side of the sample cell, so the scattered light does not need to completely pass through the test sample in the sample cell, which reduces the scattered light path and reduces the The multiple light scattering effect is realized, and the particle size measurement of high concentration test samples is realized.

2. Through the backscattering nanoparticle particle size measuring device, more scattered light intensity can be obtained, and it is also more sensitive. And the scattered light of larger dust particles is concentrated in the forward scattering area, so the back scattering method can also effectively reduce the influence of dust.

3. By setting the lens adjustment device, the distance between the lens and the sample cell can be adjusted, so that the position where the incident light is not scattered multiple times can be obtained in combination with the intercept comparison criterion in the test method, which is helpful for the measurement of particle size. .

Description of drawings

FIG. 1 is a schematic structural diagram of a backscattering nanoparticle particle size measuring device.

Figure 2 is a flow chart of backscattering nanoparticle size measurement.

FIG. 3 is a schematic diagram of the test of the backscattering nanoparticle particle size measuring device.

Among them: 1, sample cell 2, screw 3, fixing frame 4, stepping motor 5, lens 6, attenuator 7, guide post 8, laser 9, GRIN lens 10, photomultiplier tube 11, photon correlator 12, computer.

Detailed ways

1 to 3 are the preferred embodiments of the present invention, and the present invention will be further described below in conjunction with the accompanying drawings 1 to 3.

As shown in FIG. 1, a backscattered nanoparticle particle size measurement device includes a sample cell 1 with a built-in test sample, a lens 5 is arranged behind the sample cell 1, and an attenuation plate 6 and an attenuator are arranged behind the lens 5. The laser 8, the light emitted by the laser 8 is injected into the sample cell 1 after passing through the attenuation plate 6 and the lens 5.

A GRIN lens 9 is also arranged behind the lens 5, the GRIN lens 9 is located on one side of the laser 8, the optical output end of the GRIN lens 9 is connected with an optical fiber, the optical fiber is connected to the input end of the photomultiplier tube 10, and the output of the photomultiplier tube 10 The end is connected to the photon correlator 11 , and the output end of the photon correlator 11 is connected to the computer 12 .

The light emitted from the laser 8 enters the sample cell 1 and irradiates the particles of the test sample and then scatters. After scattering, it is emitted backward from the back of the sample cell 1. After being emitted, it enters the GRIN lens 9 through the lens 5, and the GRIN lens 9 receives the scattered light. After the light, the scattered light is output to the cathode surface of the photomultiplier tube 10 through the optical fiber at the output end. The photomultiplier tube 10 converts the scattered photon pulse signal into an electrical pulse signal, and sends the electrical pulse signal to the photon correlator 11. After the photon correlator 11 performs an autocorrelation operation on the pulse signal, the obtained light intensity is autocorrelated with the light intensity. The function is sent to the computer 12 for processing, and the computer 12 calculates the average particle size and particle size distribution of the test sample. The GRIN lens 9 is arranged behind the sample cell 1 at a scattering angle of 170° to receive scattered light.

A lens adjustment structure is arranged behind the sample cell 1 , and the above-mentioned lens 5 is placed inside the lens adjustment mechanism. The lens adjustment mechanism includes a fixing frame 3, the lens 5 is fixed in the fixing frame 3, and the two ends of the fixing frame 3 are respectively provided with a screw 2 and a guide column 7, and the screw 2 and the guide column 7 pass through the fixing frame 3 at the same time, wherein An inner thread matched with the screw rod 2 is provided at one end through which the screw rod 2 passes.

A stepping motor 4 is arranged at the rear end of the screw 2, and the motor shaft of the stepping motor 4 is coaxially connected with the screw 2. Therefore, when the stepping motor 4 rotates, it drives the screw 2 to rotate synchronously. Since the fixing frame 3 is threadedly connected with the screw 2, Therefore, when the screw 2 rotates, it can drive the fixed frame 3 to move back and forth.

As shown in Figure 2, the test method realized by the above-mentioned backscattering nanoparticle particle size measuring device includes the following steps:

Step 1001, by driving the lens adjustment device, so that the scatterer is located at the rear edge of the sample cell 1;

The laser 8 is turned on, the light emitted by the laser 8 is injected into the sample cell 1 through the attenuator 6 and the lens 5, and the incident light is scattered after irradiating the test sample in the sample cell 1, and the scattered light is reversely emitted from the rear edge of the sample cell 1 ; Start the stepper motor 4, drive the fixed frame 3 and the lens 5 in it to move through the screw 2, so that the position of the scatterer is located at 0.5mm inside the rear edge of the sample cell 1. The intersection of the scattered light and the incident light in the sample cell 1 is the position of the corresponding scatterer.

Step 1002, adjusting the intensity of scattered light;

Adjust attenuator 6 so that the intensity of scattered light is 500kcps.

Step 1003, measuring the light intensity autocorrelation function;

The laser 8 continues to operate for a period of time, and the scattered light reflected from the sample cell 1 continues to be transmitted to the photon correlator 11 through the GRIN lens 9 and the photomultiplier tube 10. The photon correlator 11 calculates the light intensity of the scattered light at the current position of the lens 5. The correlation function is sent to the computer 12, and the computer 12 records the light intensity autocorrelation function at the position.

Step 1004, obtain the reference value of the intercept by fitting;

The intercept of the light intensity autocorrelation function is obtained by fitting the cumulative analysis method, which is recorded as the reference value of the intercept β ₁ .

Step 1005, by driving the lens adjustment device, so that the scatterer is located at the center of the sample cell 1;

The stepping motor 4 is started, and the fixed frame 3 and the lens 5 therein are driven to move by the screw 2, so that the position of the scatterer is located in the center of the sample cell 1, as shown in FIG. 3 .

Step 1006, calculate and obtain the calculated value of the light intensity autocorrelation function and the intercept;

The laser 8 continues to operate for a period of time, and the scattered light reflected from the sample cell 1 continues to be transmitted to the photon correlator 11 through the GRIN lens 9 and the photomultiplier tube 10. The photon correlator 11 calculates the light intensity of the scattered light at the current position of the lens 5. The correlation function is sent to the computer 12, and the computer 12 records the light intensity autocorrelation function at the position, and then uses the cumulative analysis method to fit the calculated value β ₂ of the intercept.

Step 1007, compare the reference value of the intercept with the calculated value;

Compare the reference value and the calculated value of the intercept of the light intensity autocorrelation function. If β ₂ >0.8· β ₁ , it means that the sample concentration in the sample cell 1 is low, and the incident light emitted by the laser 8 does not have multiple scattering in the sample cell 1. ; If β ₂ <0.8· β ₁ , it indicates that the sample concentration in the sample cell 1 is high, and the incident light emitted by the laser 8 is scattered multiple times in the sample cell 1;

Step 1008, whether the incident light has undergone multiple scattering;

When the lens 5 is in the current position, it is judged whether the incident light has multiple scattering, if multiple scattering occurs, go to step 1009, and if no multiple scattering occurs, go to step 1010;

Step 1009, gradually adjust the position of the scatterer, and determine the position of the lens when the incident light does not have multiple scattering;

Drive the stepper motor 4 to work, so that the scatterer moves from the center of the sample cell 1 to the rear edge of the sample cell 1 at a certain distance interval, and each time it moves to determine the calculated value of the light intensity autocorrelation function intercept at this position, And according to step 1007, the calculated value of the intercept is compared with the reference value to determine the position of the lens 5 when the incident light does not have multiple scattering.

Step 1010, measure at the current position;

After determining the position where the incident light does not have multiple scattering, the average particle size and particle size distribution of the sample are measured at the current position.

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention in other forms. Any person skilled in the art may use the technical content disclosed above to make changes or modifications to equivalent changes. Example. However, any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solutions of the present invention still belong to the protection scope of the technical solutions of the present invention.

Claims (7)

1. A measurement method implemented with a backscatter nanoparticle size measurement apparatus comprising a sample cell (1), a test sample being located in the sample cell (1), characterized in that: a lens (5), a laser (8) and a GRIN lens (9) are sequentially arranged on the rear side of the sample cell (1), incident light emitted by the laser (8) enters the sample cell (1) through the lens (5), is emitted from the rear end of the sample cell (1) to enter the GRIN lens (9) after being reflected, the output end of the GRIN lens (9) is connected with the input end of a photomultiplier (10), and the output end of the photomultiplier (10) is connected with the input end of a photon correlator (11); the device is also provided with a lens adjusting device for adjusting the distance between the lens (5) and the sample cell (1), and the lens (5) is arranged in the lens adjusting device;

the measuring method comprises the following steps:

step a, a laser (8) is started, incident light emitted by the laser (8) is scattered after irradiating a test sample in a sample cell (1), and scattered light is emitted from the back edge of the sample cell (1) in a reverse direction; the position of the lens (5) is adjusted through a lens adjusting device, so that the position of the scatterer is positioned at the rear edge of the sample cell (1);

b, continuously measuring the scattered light of the sample through the GRIN lens (9), the photomultiplier (10) and the photon correlator (11) to obtain the light intensity autocorrelation function of the scattered light at the current position of the lens (5)Then, fitting by using an accumulative analysis method to obtain the intercept of the light intensity autocorrelation function, and recording as the reference value of the interceptβ ₁；

C, adjusting the position of the lens (5) by starting a lens adjusting device to enable the position of the scatterer to be positioned at the center of the sample cell (1);

d, continuously measuring the scattered light of the sample by the GRIN lens (9), the photomultiplier (10) and the photon correlator (11) to obtain a light intensity autocorrelation function of the scattered light at the current position of the lens (5), and fitting by using an accumulative analysis method to obtain an intercept of the light intensity autocorrelation function, and recording the intercept as a calculated value of the interceptβ ₂；

Step e, judging whether incident light is scattered for multiple times or not when the lens (5) is positioned at the current position by using an intercept comparison criterion, executing the step f if the incident light is scattered for multiple times, and executing the step g if the incident light is not scattered for multiple times;

f, enabling the position of the scatterer to move from the center position of the sample pool (1) to the rear edge of the sample pool (1) in sequence at fixed intervals through a lens adjusting device, measuring a light intensity autocorrelation function at the position once when the scatterer moves, further obtaining a calculated value of the intercept, comparing a reference value of the intercept with calculated values of the intercepts at different positions in sequence according to an intercept comparison criterion, and determining the position of the lens (5) when incident light is not scattered for multiple times;

and g, after determining the position where the incident light is not subjected to multiple scattering, measuring the average particle size and the particle size distribution of the sample at the current position.

2. The measurement method using the backscattering nanoparticle size measurement device according to claim 1, wherein: the lens adjusting device comprises a fixing frame (3), a lens (5) is fixed in the fixing frame (3), a screw (2) in threaded connection with the fixing frame (3) is arranged, and a stepping motor (4) is coaxially fixed with the screw (2).

3. The measurement method using the backscattering nanoparticle size measurement device according to claim 2, wherein: the screw (2) penetrates through one side of the fixing frame (3), and an internal thread matched with the screw (2) is arranged in the fixing frame (3); the other side of the fixed frame (3) is provided with a guide post (7) which is symmetrical to the screw rod (2), and the guide post (7) penetrates through the fixed frame (3) at the same time.

4. The measurement method using the backscattering nanoparticle size measurement device according to claim 1, wherein: an attenuation sheet (6) is arranged between the lens (5) and the laser (8).

5. The measurement method using the backscattering nanoparticle size measurement device according to claim 1, wherein: and a computer (12) is also arranged, and the output end of the photon correlator (11) is connected with the computer (12).

6. The measurement method using the backscattering nanoparticle size measurement device according to claim 1, wherein: the GRIN lens (9) is arranged at a scattering angle of 170 DEG behind the sample cell (1).

7. The measurement method using the backscattering nanoparticle size measurement device according to claim 1, wherein: the intercept comparison criterion in step f is: comparing the reference value of the intercept of the light intensity autocorrelation function with the calculated value of the intercept, ifβ ₂＞0.8·β ₁Indicating that the incident light emitted by the laser (8) does not scatter multiple times in the sample cell (1); if it is notβ ₂＜0.8·β ₁The concentration of the sample in the sample cell (1) is high, and the incident light emitted by the laser (8) is scattered in the sample cell (1) for multiple times.

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