A detection method for a nano particle size analyzer based on backscattering cross-correlation technology

Abstract

The present invention discloses a detection method for a nano particle size analyzer based on backscattering cross-correlation technology, which includes a sample cell, a detector, a laser, a lens group, first and second data acquisition cards, and a control unit. Among them, the laser emitted by the laser irradiates the sample in the sample cell through the lens group, and the two detectors simultaneously receive the scattered light of the sample and transmit the signals to the control unit through the first and second data acquisition cards respectively. The method is as follows: the control unit controls the focal point position of the lens group at the middle position of the sample cell; the detector collects the original scattered light signal; calculates the cross-correlation curve; finds out the position point corresponding to the highest curve efficiency; the control unit moves the lens to the position point corresponding to the highest curve efficiency; performs cross-correlation calculation to obtain the diffusion coefficient of the sample particles, and obtains the particle size through the Stokes-Einstein equation. The present invention truly realizes the accurate detection of high-concentration and high-turbidity samples, and further improves the fast correlation calculation ability.

Description

Technical Field

[0001] The present invention relates to a nano particle size analyzer, specifically a nano particle size analyzer based on backscattering cross - correlation technology and its detection method. Background Art

[0002] The nano particle size analyzer is based on dynamic light scattering technology. A laser beam is used to illuminate the sample, and the fluctuations of the scattered light caused by the Brownian motion of the particles suspended in the liquid are detected by a photoelectric detector. The original scattered light intensity fluctuation signal over time is used to obtain the correlation curve of the system through correlation calculation, and then the particle size and particle size distribution are obtained through different mathematical models, such as the cumulative method or the multi - exponential method.

[0003] Generally speaking, the nano particle size analyzer can effectively detect particle systems in the particle size range of about 1 nanometer to 1000 nanometers, and has the characteristics of fast test speed, wide range, good repeatability and accuracy, so it has been widely used.

[0004] The current nano particle size analyzers widely adopt autocorrelation technology and cannot effectively eliminate the multiple light scattering effect of high - concentration and high - turbidity samples. The multiple light scattering effect will cause the detected particle size result to be smaller than the true value, and the particle size distribution to be wider than the true value. This is particularly serious in the widely used 90 - degree angle nano particle size analyzers. Although the non - invasive backscattering technology NIBS developed in recent years can avoid the multiple light scattering technology to a certain extent and thus has the basic ability to detect high - concentration and high - turbidity samples, this passive avoidance method still cannot essentially eliminate the influence of multiple light scattering. Summary of the Invention

[0005] Aiming at the deficiencies in the prior art, such as insufficient detection ability for high - concentration and high - turbidity samples, low detection accuracy, and electronic delay noise in the range of 25ns - 1μs, the problem to be solved by the present invention is to provide a nano particle size analyzer based on backscattering cross - correlation technology and its detection method.

[0006] To solve the above - mentioned technical problems, the technical solution adopted by the present invention is:

[0007] The present invention provides a nano particle size analyzer based on backscattering cross - correlation technology, including a sample cell, a detector, a laser, a lens group, a first and a second data acquisition card, and a control unit. The laser emitted by the laser passes through the lens group and irradiates the sample in the sample cell. Two detectors simultaneously receive the scattered light of the sample and transmit the signals to the control unit through the first and the second data acquisition cards respectively.

[0008] The present invention also has a microprocessor, whose signal input end receives the instruction of the control unit, and the output end outputs a control signal to be connected to the motor control circuit.

[0009] Two detectors are symmetrically arranged on both sides of the incident laser beam of the laser, and respectively receive the sample scattered light captured by the lens group through optical fibers.

[0010] The lens group is mounted on the motor through a lens group bracket.

[0011] The present invention also has a switching shutter, which is installed between the optical fiber bracket and the lens group, and one end of the switching shutter is connected to the output shaft of the motor.

[0012] The present invention also provides a detection method for a nano particle size analyzer based on backscattering cross-correlation technology, including the following steps:

[0013] 1) The control unit controls the motor to move so that the focal point position of the lens group is at the middle position of the sample cell;

[0014] 2) Collect the original scattered light signal through the detector;

[0015] 3) Calculate the cross-correlation curve, obtain the curve efficiency and record it;

[0016] 4) Determine whether the focal point position is at a specified distance from the sample cell wall;

[0017] 5) If it is the specified distance, compare the cross-correlation curve efficiencies at different focal positions, and find the position point corresponding to the highest curve efficiency;

[0018] 6) The control unit controls the motor to move the lens to the position point corresponding to the highest curve efficiency;

[0019] 7) Collect the original scattered light signal through the detector again;

[0020] 8) Perform cross-correlation calculation to obtain the cross-correlation curve;

[0021] 9) Obtain the diffusion coefficient of the sample particles through the cross-correlation curve, and then obtain the particle size through the Stokes-Einstein equation.

[0022] The method of the present invention also includes the following steps:

[0023] 10) In step 4), if it is determined that the focal point position is not at the specified distance from the sample cell wall; then the control unit issues an instruction to make the motor drive the lens group to move to a position at the specified distance from the sample cell wall.

[0024] The specified distance in step 3) is: taking the sample cell wall as the 0 point reference, moving towards the center of the sample cell, and moving 0.1 - 1.0 mm each time to find the best efficiency point of the correlation curve signal.

[0025] In step 2), the original scattered light signal is collected by a detector. According to the sample light shielding rate or turbidity, an autocorrelation detection optical path or a cross-correlation detection optical path is selected. For a transparent sample with a light shielding rate or turbidity lower than the threshold, a single detector optical path signal is collected by setting a baffle in the optical path to block the other detector, and autocorrelation calculation is performed.

[0026] For a sample with a light shielding rate or turbidity higher than the threshold, a dual-detector optical path signal is collected, and the obtained scattered light signal is subjected to cross-correlation calculation to avoid the phenomenon of multiple light scattering and at the same time avoid the electronic noise within 1 μs of the correlation curve.

[0027] The present invention has the following beneficial effects and advantages:

[0028] 1. The present invention combines the backscattering technology of a movable sample detection point and the backscattering cross-correlation nanoparticle size analyzer with cross-correlation calculation, truly realizing the accurate detection of high-concentration and high-turbidity samples, and further enhancing the fast correlation calculation ability. This device has good promotion and practical value, and will produce good economic and social benefits after extensive promotion and application.

[0029] 2. The nanoparticle size analyzer of the present invention adopts the backscattering cross-correlation technology that combines the collection of backscattering signals, a movable sample detection point, and cross-correlation calculation logic, collects backscattered light, and can move the position of the detection point, enabling the collection of high-concentration sample signals; cross-correlation calculation can not only eliminate the interference of multiple light scattering, but also eliminate the electronic delay noise within the range of 25 ns - 1 μs of the detector.

[0030] 3. The present invention is widely used in precision electrical engineering, electronics, instruments and meters, and other products, and is mainly applied to research and application fields such as medical and health, biopharmaceuticals, agricultural scientific research, and environmental protection. Brief Description of the Drawings

[0031] Figure 1 It is the electrical principle block diagram of the nanoparticle size analyzer based on the backscattering cross-correlation technology of the present invention;

[0032] Figure 2 It is the schematic diagram of the optical path structure of the present invention;

[0033] Figure 3 It is the schematic diagram of the definition of the detection point position in the present invention;

[0034] Figure 4A It is the schematic diagram of the scattered light received by the motor-driven lens focusing point in the middle of the sample cell for a low-concentration (low light shielding rate) sample in the present invention;

[0035] Figure 4B It is the schematic diagram of the scattered light received by the motor-driven lens focusing point at the edge of the sample cell for a high-concentration (high light shielding rate) sample;

[0036] Figure 5 This is the flowchart of the dynamic light scattering test by selecting the detection point position for the method of the present invention;

[0037] Figure 6 This is the schematic diagram of the relevant curves involved in the method of the present invention;

[0038] Figure 7 Schematic diagrams of the relevant curves containing electronic delay noise and the relevant curves eliminating electronic delay noise.

[0039] Figure 8 The shutter is in the state of blocking the optical path or opening the optical path.

[0040] Among them, 1 is the laser, 2 is the sample cell, 3 is the laser, 4 is the optical fiber support, 5 is the scattered light, 6 is the detection point, 7 is the first optical fiber, 8 is the second optical fiber, 9 is the motor bearing, 10 is the lens group, 11 is the sample, 12 is the switching shutter, 13 is the motor, 14 - 15 are the first - second photodiodes, and 16 - 17 are the first - second data acquisition cards. Specific embodiments

[0041] The present invention will be further described below in conjunction with the accompanying drawings of the specification.

[0042] As Figure 2 shown, the present invention provides a nano - particle size analyzer based on the back - scattering cross - correlation technology, including a sample cell 2, a detector, a laser, a lens group 10, the first - second data acquisition cards 16 - 17, and a control unit. The laser 1 emitted by the laser passes through the lens group and irradiates the sample in the sample cell. Two detectors simultaneously receive the reflected light of the sample and transmit the signals to the control unit through the first - second data acquisition cards respectively.

[0043] The present invention also has a micro - processor, whose signal input end receives the instruction of the control unit (PC), and the output end outputs a control signal to be connected to the motor control circuit.

[0044] The two detectors are symmetrically arranged on both sides of the incident laser beam of the laser, and respectively receive the sample scattered light captured by the lens group through optical fibers. In this embodiment, the detectors adopt the first - second avalanche photodiodes APD1 - APD2.

[0045] As Figure 2As shown in the figure, the lens group is mounted on the motor through the lens group bracket. The present invention also has a switching shutter 12, which is installed between the optical fiber bracket 4 and the lens group. The switching shutter is connected to the output shaft of the motor and rotates through the drive of the motor, blocking one side of the optical path between the optical fiber bracket 4 and the lens group, so as to realize the switching of the autocorrelation detection optical path or the cross-correlation detection optical path. In this embodiment, the switching shutter is a rectangular plate, one end of which is fixedly connected to the output shaft of a micro-motor and rotates around the fixed position of the output shaft under the drive of the motor. When the other end of the rectangular plate rotates to the in-place position, it can just block the incident light side of the lens group. When the light shielding rate or turbidity of the sample is relatively high, the switching shutter 12 is opened, and the two detection lights are received simultaneously for cross-correlation operation. When the light shielding rate or turbidity of the sample is relatively low, the switching shutter 12 is closed, and one path is used to receive the scattered light for autocorrelation operation.

[0046] The present invention controls the high-precision motor to move the sample detection point (i.e., the focus of the laser optical path and the optical fiber observation optical path) through the control unit, and can move from the sample cell wall as the 0-point reference to the center of the sample cell. The moving range is 0 - 5 mm, and the optimal curve efficiency point of the cross-correlation curve signal or the autocorrelation curve signal is automatically searched, as Figures 4A to 4B shown.

[0047] The position of the detection point is as Figure 3 shown, which is the convergence point in the direction of the laser and the detector.

[0048] The laser emitted by the laser passes through the lens group 10 installed on the motor bearing 9 of the motor and irradiates the sample in the sample cell 2. The laser emission direction is the 0-degree angle direction. The scattered light signals are synchronously collected in a double path through the first optical fiber 7 and the second optical fiber 8 symmetrically arranged at the back, and are respectively transmitted to the first and second detectors APD1 - APD2, and then communicate with the computer through the data acquisition card 1 and the data acquisition card 2. The scattered light signals synchronously obtained by the two detectors are subjected to cross-correlation operation in the control unit, and finally the cross-correlation curve is obtained. As Figure 8 shown, the single path can also be used to collect the scattered light signal by driving the switching shutter 11 to block one side of the optical path through the motor. The scattered light signal obtained by the first (or second) detector (using the first photodiode APD1 (or the second photodiode APD2)) is subjected to autocorrelation operation in the control unit, and finally the autocorrelation curve is obtained.

[0049] As Figure 5 shown, the present invention also provides a detection method for a nano particle size analyzer based on the backscattering cross-correlation technology, including the following steps:

[0050] 1) The control unit controls the motor to move so that the focus position of the lens group is at the middle position of the sample cell;

[0051] 2) The original scattered light signal is collected through the detector;

[0052] 3) Calculate the cross-correlation curve, obtain the curve efficiency and record it;

[0053] 4) Determine whether the position of the focal point is at a specified distance from the sample cell wall;

[0054] 5) If it is the specified distance, compare the cross-correlation curve efficiencies at different focal positions, and find the position point corresponding to the highest curve efficiency;

[0055] 6) The control unit controls the motor to move the lens to the position point corresponding to the highest curve efficiency;

[0056] 7) Collect the original scattered light signal again through the detector;

[0057] 8) Perform cross-correlation calculation to obtain the cross-correlation curve;

[0058] 9) Obtain the diffusion coefficient of the sample particles through the cross-correlation curve, and then obtain the particle size through the Stokes-Einstein equation.

[0059] It also includes step 10): In step 4), if it is determined that the position of the focal point is not at the specified distance from the sample cell wall; then the control unit issues an instruction to make the motor drive the lens group to move to a position at the specified distance from the sample cell wall.

[0060] The specified distance in step 3) is: Taking the sample cell wall as the 0-point reference, moving towards the center of the sample cell, and the distance of each movement can be selected and adjusted within the range of 0.1 - 1.0 mm to find the best efficiency point of the correlation curve signal.

[0061] In step 2), the original scattered light signal is collected through the detector, and the self-correlation detection optical path or the cross-correlation detection optical path is selected according to the sample light shielding rate or turbidity. For transparent samples with a light shielding rate or turbidity lower than the threshold (for example, the light shielding rate is not higher than 10%), a single detector optical path signal is collected by setting a baffle in the optical path to block the other detector, and self-correlation operation is performed;

[0062] For samples with a light shielding rate or turbidity higher than the threshold (for example, the light shielding rate exceeds 10%), dual-detector optical path signal collection is performed, and the obtained scattered light signal is subjected to cross-correlation operation to avoid the multiple light scattering phenomenon. At the same time, it can also effectively suppress the fast decay electronic noise within the range of 25 ns - 1 μs of the correlation curve signal, and obtain accurate correlation curve information within a wider correlation calculation time. Figure 7 In it, □ is the correlation curve containing electronic delay noise, and ◯ is the correlation curve with electronic delay noise eliminated by the cross-correlation technique.

[0063] According to the visual sample turbidity, manually operate to switch the self-correlation detection optical path and the cross-correlation detection optical path by driving the baffle 12 through the motor.

[0064] Such asFigure 6 As shown, it is a schematic diagram of the correlation curve achieved by the method of the present invention, and the value corresponding to the first channel is the correlation curve efficiency.

Claims

1. A detection method for a nanoparticle size analyzer based on backscattering cross-correlation technology, characterized in that: The nano-particle size analyzer includes a sample cell, detectors, a laser, a lens group, first and second data acquisition cards, and a control unit. The laser emits laser light that irradiates the sample in the sample cell through the lens group. Two detectors simultaneously receive the scattered light of the sample and transmit the signals to the control unit through the first and second data acquisition cards respectively; It also has a microprocessor. Its signal input terminal receives the instructions of the control unit, and its output terminal outputs control signals to be connected to the motor control circuit; The two detectors are symmetrically arranged on both sides of the incident laser beam of the laser and receive the scattered light of the sample captured by the lens group through optical fibers respectively; The lens group is mounted on the motor through a lens group bracket; It includes the following steps: 1) The control unit controls the motor to move so that the focal point position of the lens group is at the middle position of the sample cell; 2) Collect the original scattered light signal through the detector; 3) Calculate the cross-correlation curve, obtain the curve efficiency and record it; 4) Judge whether the focal point position is at a specified distance from the sample cell wall; 5) If it is at the specified distance, compare the cross-correlation curve efficiencies at different focal positions and find the position point corresponding to the highest curve efficiency; 6) The control unit controls the motor to move the lens to the position point corresponding to the highest curve efficiency; 7) Collect the original scattered light signal through the detector again; 8) Perform cross-correlation calculation to obtain the cross-correlation curve; 9) Obtain the diffusion coefficient of the sample particles through the cross-correlation curve, and then obtain the particle size through the Stokes-Einstein equation.

2. The detection method of the nano particle size analyzer based on the backscattering cross-correlation technology according to claim 1, wherein: It also has a switching shutter, which is installed between the optical fiber bracket and the lens group. One end of the switching shutter is connected to the motor output shaft.

3. The detection method of the nano particle size analyzer based on the backscattering cross-correlation technology according to claim 1, wherein It also includes the following steps: 10) In step 4), if it is judged that the focal point position is not at the specified distance from the sample cell wall; then the control unit issues an instruction to make the motor drive the lens group to move to a position at the specified distance from the sample cell wall.

4. The detection method of the nano particle size analyzer based on the backscattering cross-correlation technology according to claim 1, characterized in that: The specified distance in step 3) is: taking the sample cell wall as the 0-point reference, moving towards the center of the sample cell, and each movement distance is in the range of 0.1 - 1.0 mm to find the best efficiency point of the correlation curve signal.

5. The detection method of the nano particle size analyzer based on the backscattering cross-correlation technology according to claim 1, wherein: In step 2), when collecting the original scattered light signal through the detector, select the auto-correlation detection optical path or the cross-correlation detection optical path according to the sample light shielding rate or turbidity. For transparent samples with a light shielding rate or turbidity lower than the threshold, set a shutter in the optical path to block the other detector for single-detector optical path signal acquisition and perform auto-correlation operation; For samples with a light shielding rate or turbidity higher than the threshold, perform dual-detector optical path signal acquisition, perform cross-correlation operation on the obtained scattered light signals, avoid the phenomenon of multiple light scattering, and at the same time avoid the electronic noise within 1 μs of the correlation curve.

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