Optical apparatus for measuring nanoparticle concentration and measurement method thereof

Abstract

Disclosed in the present invention are an optical apparatus for measuring a nanoparticle concentration and a measurement method thereof. The optical apparatus comprises a sample cell, a rotary wheel installed with a neutral-density filter, an APD detector, a PD detector, a laser device, a lens, a data acquisition card and a control unit, wherein a laser emitted by the laser device passes through the lens to illuminate a sample in the sample cell; in a transmission direction, the intensity of the transmitted laser is measured by means of the PD detector; and a scattered signal from the sample is accepted at a 90° or in a backward direction by the APD detector connected to an optical fiber. The measurement method comprises: measuring a volume fraction Φ of a sample by means of a transmitted laser intensity signal and a light extinction method; measuring a particle size distribution of the sample by means of a scattered laser signal and a dynamic light scattering method; and calculating a volume fraction Φi and a number concentration of each particle size peak by means of the volume fraction Φ and the particle size distribution. The present invention combines a light extinction method and a dynamic light scattering method to implement the measurement of both a volume concentration and a number concentration of a sample.

Description

An optical device for detecting nano-particle concentration and a detection method thereof Technical Field

[0001] The present invention relates to the technical field of optical methods for detecting the concentration of nano-scale particles, and in particular to an optical device for detecting the concentration of nano-scale particles and a detection method thereof. Background Art

[0002] Measuring particle concentration in nanoparticle suspensions is used in numerous industries and fields, such as quality control in chemical production, monitoring bacterial growth and spread, and measuring virus concentrations in blood to provide timely and effective diagnosis of patients' conditions. Particle concentration measurements provide crucial information for scientific research, production processes, medical testing, and food safety.

[0003] There are numerous methods for measuring the concentration of nanoparticle suspensions, including UV spectrophotometry, the nano-Coulter method, extinction analysis, nanoparticle tracking analysis, and multi-angle dynamic light scattering. These methods for detecting particle concentration generally have limitations. For example, UV spectrophotometry measures the overall mass / volume concentration of the sample and cannot provide information on concentration distribution, volume fraction, or number concentration. The nano-Coulter method can obtain sample number concentration information, but the sample must be dispersed in an electrolyte dispersion. The extinction method can only provide sample volume fraction, not concentration distribution or number concentration. Nanoparticle tracking analysis can provide number concentration information, but its sensitivity is limited, making it ineffective for detecting particles smaller than 50 nm. Multi-angle dynamic light scattering requires calibration of the optical system's detector solid angle using a substance with a known Rayleigh ratio before detection. Technical issues

[0004] In view of the insufficient detection capabilities and limitations of the existing technology for the concentration of particles in nano-particle suspensions, the problem to be solved by the present invention is to provide an optical device and a detection method for detecting the concentration and concentration distribution of nano-particles. Specifically, an optical device and a detection method for detecting the concentration of nano-particles are provided, which are optical devices and a detection method for detecting the concentration of nano-particles that combine the extinction method and the dynamic light scattering method (Light Extinction Combined Dynamic Light Scattering, LEDLS). Technical Solutions

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] An optical device for detecting the concentration of nanoparticles, which combines the extinction method and the dynamic light scattering method, includes a sample cell, a rotating wheel, an APD detector, a PD detector, a laser, a lens, a data acquisition card, a control unit, and a microprocessor. The signal input terminal receives instructions from the control unit, and the output terminal outputs a control signal connected to a motor control circuit.

[0007] The incident light beam of the laser is irradiated onto the sample in the sample cell through a neutral density filter and a lens, wherein the neutral density filter is used to adjust the intensity of the incident light and the lens is used to converge the light beam;

[0008] A rotating wheel with neutral density filters is installed in the optical path. Ten neutral density filters with different attenuation rates and a light transmission hole without a filter are installed on the rotating wheel. The neutral density filter or the light transmission hole without a filter installed on the rotating wheel is set in the incident light path by rotating the motor.

[0009] The scattered light signal of the sample is received at 90° or backward through the APD detector connected to the optical fiber;

[0010] The PD detector is placed in the 0° direction of laser incidence to detect the intensity of the transmitted laser.

[0011] A preferred embodiment of the optical device for detecting the concentration of nano-scale particles is that the cross-section of the sample cell is square or rectangular, with opposite sides being parallel.

[0012] The optical device for detecting the concentration of nano-scale particles has a preferred embodiment in which the 10 neutral density filters with different attenuation rates and the light-transmitting holes without filters installed can adjust the transmittance from 100% to 1 part per million.

[0013] The optical device for detecting the concentration of nano-sized particles, preferably, comprises a motor that automatically adjusts the rotating wheel during the detection of I0 and the detection of the original scattered light signal, selects an appropriate neutral density filter to adjust the incident laser intensity, so that the transmitted light I0 is within the linear response range of the PD detector and the original scattered light signal is within the linear response range of the APD;

[0014] A method for detecting the concentration of nanoparticles using an optical device, comprising the following steps:

[0015] Step 1: The APD detector collects the original scattered light signal, calculates the correlation curve, and performs multi-exponential fitting on the correlation curve to obtain the particle size intensity distribution of the particles in the sample. The intensity distribution is converted into volume distribution, surface area distribution, and number distribution by combining the laser wavelength, the known refractive index of the particles, and the refractive index of the dispersant with the Mie theory. The corresponding distribution intensities are all relative values;

[0016] Step 2: Calculate the surface area average diameter D of the sample through surface area distribution 3,2 , calculate the average particle size Di of each particle size peak through volume distribution;

[0017] Step 3: The PD detector collects the transmission direction light intensity I0 of the laser through the blank dispersant and the transmission direction light intensity I after passing through the sample. T , by the laser wavelength, the known refractive index of the particles, the refractive index of the dispersant and D 3,2 Combined with Mie theory to calculate the extinction coefficient Qe, Qe and D 3,2 The volume fraction Φ of the sample was calculated by the extinction method;

[0018] Step 4: Calculate the area content of each particle size peak from the volume distribution, and calculate the volume fraction Φi of each particle size peak based on the sample volume fraction;

[0019] Step 5: Calculate the number concentration of each particle size peak by combining the average particle size within each particle size peak and the volume fraction Φi of each peak. Beneficial effects

[0020] 1. This invention combines the extinction method with the dynamic light scattering method to detect both the volume concentration and the number concentration of a sample. This device has excellent promotional and practical value, and its widespread application will generate positive economic and social benefits.

[0021] 2. The present invention is simple to operate and does not require the use of any substances with known scattering power or Rayleigh ratio to calibrate the system before detection;

[0022] 3. The present invention is widely used in precision electrical, electronic, instrumentation and other products, and is mainly used in research and application fields such as medical care, biopharmaceuticals, agricultural research, and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Type your figure caption description paragraph here. Best Mode for Carrying Out the Invention

[0024] FIG1 is a block diagram of the electrical principle of an optical device for detecting the concentration of nano-particles and a detection method thereof according to the present invention;

[0025] FIG2 is a schematic diagram of the structure of the optical path for detecting scattered light at 90° according to the present invention;

[0026] FIG3 is a schematic diagram of the structure of the optical path for backward detection of scattered light according to the present invention;

[0027] FIG4 is a schematic diagram of a rotating wheel equipped with a neutral density filter according to the present invention;

[0028] Figure 5 is the calculated surface area average particle size D of the present invention 3,2 flow chart;

[0029] FIG6 is a schematic diagram of calculating the volume fraction volume Φi and number concentration according to the present invention.

[0030] Among them, 1 is laser, 2 is lens, 3 is sample, 4 is sample cell, 5 is PD detector, 6 is 90° scattered light, 7 is fiber head connected to APD detector, 8 is optical fiber, 9 is backscattered light, 10 is the rotating wheel with neutral density filter installed, 11 is motor, 12 is neutral density filter, 13 is shaft, 14 is rotating wheel, 15 is light transmission hole without filter installed, 16 is particle size peak, and 17 is transmitted light. Modes for Carrying Out the Invention

[0031] As shown in FIG1 , the present invention provides an optical device and method for detecting the concentration of nano-scale particles. The optical device includes a sample pool 4, a rotating wheel 10 equipped with a neutral density filter, an APD detector, a PD detector 5, a laser, a lens 2, a data acquisition card, and a control unit.

[0032] The present invention also has a microprocessor, whose signal input terminal receives instructions from the control unit, and whose output terminal outputs a control signal connected to the control loop of the motor 11.

[0033] The cross section of the sample pool 4 is square or rectangular, with opposite sides being parallel.

[0034] The incident light beam 1 of the laser is irradiated onto the sample 3 in the sample cell 4 through the neutral density filter 10 and the lens 2. The lens 2 has a converging effect on the light beam.

[0035] The PD detector 5 is placed in the 0° direction of laser incidence to detect the intensity of the transmitted light 17 .

[0036] As shown in FIG2 and FIG3 , the APD detector 7 connected to the optical fiber receives the scattered light 7 signal of the sample at 90° or receives the scattered light 9 signal of the sample 3 in the backward direction.

[0037] As shown in Figure 4, a rotating wheel 10 with neutral density filters is installed in the optical path. Ten neutral density filters 12 with varying attenuation rates and an unfiltered light-transmitting aperture 15 are mounted on the wheel. Rotating a motor 11 can position either the neutral density filter 12 or the unfiltered light-transmitting aperture 15 on the rotating wheel 14 in the incident light path. The ten neutral density filters 12 with varying attenuation rates and the unfiltered light-transmitting aperture 15 can adjust the light transmission from 100% to 0.1 part per million.

[0038] During the process of detecting I0 and the process of detecting the original scattered light signal, the wheel 14 is automatically adjusted by the motor 11, and an appropriate neutral density filter is selected to adjust the intensity of the incident laser 1, so that the transmitted light I0 is within the linear response range of the PD detector 5, and the original scattered light 6 entering the optical fiber head 7 in the 90° optical path and the original scattered light 9 entering the optical fiber head 7 in the back optical path are within the linear response range of the APD.

[0039] The present invention also provides a method for detecting the concentration of nanoparticles, comprising the following steps:

[0040] 1) The APD detector collects the original scattered light signal, calculates the correlation curve, and performs multi-exponential fitting on the correlation curve to obtain the particle size intensity distribution of the particles in the sample. The intensity distribution is converted into volume distribution, surface area distribution, and number distribution by combining the laser wavelength, the known refractive index of the particles, and the refractive index of the dispersant with the Mie theory. The corresponding distribution intensities are all relative values;

[0041] 2) Calculate the average surface area diameter D of the sample through surface area distribution 3,2 , calculate the average particle size Di of each particle size peak through volume distribution;

[0042] 3) The PD detector collects the light intensity I0 in the transmission direction of the laser through the blank dispersant and the light intensity I0 in the transmission direction after passing through the sample. T , by the laser wavelength, the known refractive index of the particles, the refractive index of the dispersant and D 3,2 Combined with Mie theory to calculate the extinction coefficient Qe, Qe and D 3,2 The volume fraction Φ of the sample is calculated by the extinction method. In the extinction method, I0, I T ,Qe,D 3,2 The relationship between them is as follows;

[0043]

[0044] Where R is the half-path length of the sample cell.

[0045] 4) Calculate the area content of each particle size peak from the volume distribution, and calculate the volume fraction Φi of each particle size peak based on the sample volume fraction;

[0046] Φi=Si / ∑Si*Φ

[0047] where Si is the area of ​​the i-th particle size peak in the volume distribution.

[0048] 5) Calculate the number concentration ρi of each particle size peak based on the particle size Di of each particle size peak;

[0049] ρi=6*Φi / (π*Di 3 ).

Claims

1. The light sheet and lens irradiate the sample in the sample pool. The neutral density filter is used to adjust the intensity of the incident light, and the lens is used to converge the light beam. A rotating wheel with a neutral density filter is installed in the optical path, 10 neutral density filters with different attenuation rates and a light transmission hole without a filter installed are installed on the rotating wheel, and the neutral density filter or the light transmission hole without a filter installed on the rotating wheel is set in the incident light path by rotating the motor; The scattered light signal of the sample is received at 90° or backward through an APD detector connected to the optical fiber; The PD detector is placed at the 0° direction of laser incidence to detect the intensity of the transmitted laser.

2. An optical device for detecting the concentration of nano-particles according to claim 1, characterized in that: The cross section of the sample pool is square or rectangular, wherein opposite sides are parallel.

3. The optical device for detecting the concentration of nano-particles according to claim 1, characterized in that: The 10 neutral density filters with different attenuation rates and the light transmission holes without filters installed can adjust the transmittance from 100% to one millionth of a transmittance.

4. The optical device for detecting the concentration of nano-particles according to claim 1, characterized in that: In the process of detecting I0 and the process of detecting the original scattered light signal, the wheel is automatically adjusted by the motor, and the appropriate neutral density filter is selected to adjust the incident laser intensity, so that the transmitted light I0 is within the linear response range of the PD detector and the original scattered light signal is within the linear response range of the APD.

5. The detection method using an optical device for detecting the concentration of nano-scale particles according to claim 1, characterized in that: Here are the steps: Step 1: The APD detector collects the original scattered light signal, calculates the correlation curve, and performs multi-exponential fitting on the correlation curve to obtain the particle size intensity distribution of the particles in the sample. The intensity distribution is converted into volume distribution, surface area distribution and number distribution by combining the laser wavelength, the known refractive index of the particles and the refractive index of the dispersant with the Mie theory. The corresponding distribution intensities are all relative values. Step 2: Calculate the average surface area diameter D of the sample through surface area distribution 3,2 , calculate the average particle size Di of each particle size peak through volume distribution; Step 3: The PD detector collects the transmission direction light intensity I0 of the laser through the blank dispersant and the transmission direction light intensity I after passing through the sample. T , by using the laser wavelength, the known refractive index of the particles, the refractive index of the dispersant and D 3,2 Combined with Mie theory, the extinction coefficient Qe is calculated from Qe and D 3,2 The volume fraction Φ of the sample was calculated by the extinction method; Step 4: Calculate the area content of each particle size peak from the volume distribution, and calculate the volume fraction Φi of each particle size peak based on the sample volume fraction; Step 5: Calculate the number concentration of each particle size peak by combining the average particle size within each particle size peak and the volume fraction Φi of each peak.

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