A method for determining diamond type and color grade based on Raman spectroscopy with an excitation wavelength of 405 nm
Through the Raman spectroscopy method with 405nm excitation wavelength, the problem of infrared spectrometer's strict requirements on the morphology and size of diamond detection is solved, and the accurate judgment of diamond type and color grade is achieved, which reduces the qualitative risk of results and provides a more objective and Convenient diamond identification method.
Patent Information
- Application Number
- CN202210180696.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-02-25
- Publication Date
- 2024-12-06
- Estimated Expiration
- 2042-02-25
AI Technical Summary
In the existing diamond detection technology, infrared spectrometers have strict requirements on diamond type detection, surface moisture allocation and sample size, which leads to qualitative risks of results. The qualitative nature of diamond color grade depends on subjective experience and is susceptible to visual fatigue. and business interests impact.
Using the Raman spectroscopy method with excitation wavelength of 405nm, the Raman spectral characteristic peak of the diamond sample was detected by a Raman spectrometer with a wavelength of 405nm of the laser light source, and the diamond type and color grade were determined by the characteristic peak at 1331-1333cm-1. It is made of diamond material, and the content of N impurities is judged by the characteristic peaks around 628cm-1 to qualitative color grade.
It realizes accurate, non-destructive and rapid judgment of diamond types and color grades, reduces the impact of sample morphology and size on the test results, provides a more objective and convenient identification method, and ensures the healthy and stable development of the diamond market.
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Figure CN114544590B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of diamond detection, and in particular relates to a method for determining the type and color grade of diamond based on Raman spectroscopy with an excitation wavelength of 405 nm. The method can be used to determine the type of diamond, i.e., whether it contains impurity N elements, and the color grade of the diamond. Background Art
[0002] Diamond, one of the natural gemstone minerals, is deeply loved by jewelry lovers, especially young consumers, because of its beautiful meanings such as "eternity" and "love of chastity". At the same time, diamond has excellent hardness and stability, especially excellent optical properties and ultra-wide bandgap characteristics, and has always been a classic research object in the fields of semiconductor materials, quantum information processing and quantum computing. In view of the huge market for diamonds in jewelry and industrial applications and the increasing scarcity of natural diamond resources, researchers have begun to study the production and preparation of artificial synthetic diamonds since the 1950s. In recent years, diamonds have undergone qualitative improvements in application, performance, and quality grade (size, clarity, color, etc.). Obviously, the progress of the synthetic diamond industry has greatly promoted the rapid development of the new materials industry. At the same time, it has also brought far-reaching impacts to the gem-grade diamond consumer market.
[0003] As we all know, while the preparation and optimization technology of synthetic diamonds are constantly changing and improving, the detection of synthetic diamonds also provides theoretical basis and technical support for the improvement and upgrading of the preparation or optimization process. Among them, the spectral detection technology involving synthetic diamonds plays an extremely important role in promoting its preparation process, quality improvement and product diversification. As far as diamond-related spectral detection technology is concerned, related work mainly focuses on the application of spectral equipment to explore the characteristics of diamond crystal structure, optical defects and the influence mechanism of defects on diamond color and fluorescence, such as fluorescence spectrum, photoluminescence (PL) spectrum, infrared (IR) spectrum, cathode luminescence spectrum, electron paramagnetic resonance spectrum, Raman (Raman), ultraviolet visible (UV-Vis) diffuse reflectance spectrum, etc. Among the above-mentioned many spectral research methods, the use of diamond PL spectrum detection at liquid nitrogen temperature and multiple excitation wavelengths is the most important research method. However, compared with the PL spectrum research of diamond, Raman spectrum also has extremely important and extensive applications in exploring the crystal structure and optical defect characteristics of diamond. However, compared with the PL spectrum research of diamond, the research work on the Raman spectrum of diamond under different excitation wavelengths is relatively less, especially at room temperature, based on different excitation energies of the same excitation wavelength or different grating conditions of the same excitation wavelength. The research work on the Raman spectrum of different types of diamonds is even rarer. Therefore, conducting in-depth research on the Raman spectrum characteristics of diamonds under relevant excitation wavelengths is of great research significance for systematically understanding the spectroscopy and crystal structure characteristics of diamonds.
[0004] At the same time, until now, the classification of diamond types is based on the information of the peak position of the spectrum characteristics of the sample in the IR spectrum detection, and then the type of the sample is qualitatively determined. However, in the daily detection of diamond sample type determination based on IR spectrum, it is not difficult to find that when collecting information of the IR diffuse reflectance spectrum of diamond, the IR spectrum equipment has certain requirements for the morphological characteristics of the sample to be inspected (whether there is a relatively flat surface in a local area), the moisture content on the surface and the diameter of the sample, especially the size of the sample must be larger than the detection window. Therefore, the above factors have a great impact on the collection quality of the infrared spectrum, and thus bring certain risks to the qualitative results. It is also worth pointing out that because the impurity N element in diamond has a more important impact on the color grade of diamond, in the current context where the qualitative determination of diamond color is mainly determined by the subjective experience of the testers, human factors such as visual fatigue caused by long-term work intensity and commercial interests can have a certain impact on the qualitative results of diamond color. Therefore, the strength of the characteristic peak of N impurities in the Raman spectrum with an excitation wavelength of 405nm can provide theoretical support for the determination of diamond color grade. Summary of the invention
[0005] In view of the defects of current diamond Raman spectroscopy research and the shortcomings of current infrared spectrometers in diamond type detection, especially the detection technology of centimeters, the purpose of the present invention is to design and provide a method for determining the type and color grade of diamond based on Raman spectroscopy with an excitation wavelength of 405nm, which is specifically achieved through the following technical solutions:
[0006] The method for determining the type and color grade of diamonds based on Raman spectroscopy with an excitation wavelength of 405 nm uses a Raman spectrometer with a laser light source wavelength of 405 nm and a laser power of 30 mW to determine the type and color grade of diamonds. The specific detection steps are as follows:
[0007] 1) Perform Raman spectroscopy on the sample to be tested, with an excitation wavelength of 405nm, and the objective lens for collecting sample information is set to 50x or 100x. The horizontal axis of the obtained spectrum is the Raman shift, and the collection range of the Raman spectrometer is 100-4000cm -1 ;
[0008] 2) In the Raman spectrum obtained in step 1), the -1 Whether there are obvious and sharp characteristic peaks, it is preliminarily determined whether the collected sample is made of diamond material;
[0009] a) Raman spectrum at 1331-1333cm -1 There is no obvious characteristic peak, so the sample can be judged as non-diamond, and there is no need to further classify the sample type;
[0010] b) Raman spectrum at 1331-1333cm -1 When there is an obvious and sharp characteristic peak at the sample, the sample is judged to be a diamond and the sample type needs to be further classified;
[0011] 3) The sample identified as diamond in step 2) is again identified and attributed by Raman spectrum characteristic peaks to determine the type of diamond;
[0012] For the sample in step 3), Raman spectrum detection is performed (the spectrum is baseline corrected), where the energy of the excitation wavelength can be increased to 100%. If the Raman spectrum of the diamond sample to be tested has the following wavelengths at 628, 1332, 1920, 2159, 2584 and 3040 cm -1 There are characteristic peaks near 628 cm -1 The characteristic peak must exist, that is, the 628cm -1 The peak intensity is the strongest), which can determine that the diamond is type 415, that is, it contains collective N impurities and is type Ia natural diamond; at the same time, it should be further explained that the stronger the above characteristic peak position is, the greater the content of impurity N element is, the greater the impact on the color of the diamond is, and the lower the color grade of the diamond is;
[0013] If the Raman spectrum of the diamond sample to be tested has a peak at 628cm -1 There is no characteristic peak nearby (the energy value of the excitation wavelength in Raman spectrum detection can be set to 100%). At this time, it is initially determined that this type of diamond is not 415nm type, or is below the detection limit of Raman spectrum with 405nm as the excitation wavelength.
[0014] Furthermore, there is a 415nm zero phonon line in the crystal structure of 415nm type diamond.
[0015] Furthermore, when the sample to be tested is subjected to Raman spectroscopy detection, in view of the preferential orientation of different crystal planes at the occurrence positions of N impurities in the diamond sample, multi-point testing or local surface scanning is adopted on the surface of the sample to be tested.
[0016] Furthermore, in step 1), the morphology of the sample to be tested is not particularly limited, and the mass ranges from centimeters to carats of diamond.
[0017] Furthermore, when collecting and testing the Raman spectrum of the sample, the energy of the excitation wavelength is preferably set so as not to annihilate the characteristic peak of the diamond sample.
[0018] The method of the present invention uses Raman spectroscopy to preliminarily determine the type and color grade of diamonds. The method is accurate, non-destructive and rapid, and can provide a universal and convenient directional identification basis for the qualitative identification of the natural and synthetic properties and color grade of diamonds, and provide a strong intellectual guarantee for the healthy and stable development of the diamond market. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1 The similarities and differences of Raman spectra of the same batch of diamonds (standard color stones with colors of D to L respectively) when the excitation wavelengths are 405nm, 532nm and 785nm;
[0020] Figure 2 The Raman spectrum of the sample of Example 1 (CVD synthetic diamond, no 415nm type) at an excitation wavelength of 405nm;
[0021] Figure 3 The Raman spectrum of the sample of Example 2 (colorless or near-colorless HTHP synthetic diamond, no 415nm type) at an excitation wavelength of 405nm;
[0022] Figure 4 The Raman spectrum of the sample of Example 3 (natural diamond, type 415 and containing a lower concentration of 415nm) at an excitation wavelength of 405nm;
[0023] Figure 5 The Raman spectrum of the sample in Example 4 (high temperature and high pressure synthetic yellow diamond) at an excitation wavelength of 405 nm;
[0024] Figure 6 This is the Raman spectrum of the sample in Example 5 (natural diamond) at an excitation wavelength of 405 nm. DETAILED DESCRIPTION
[0025] The present invention is described in further detail below based on the accompanying drawings and specific embodiments of the specification to facilitate a better understanding of the present technical solution.
[0026] Compared with IR spectroscopy equipment, the method of the present invention has certain requirements on the morphological characteristics of the sample to be tested (whether there is a relatively flat surface in a local area), the moisture content on the surface and the diameter of the sample, especially the requirement that the size of the sample must be larger than the detection window. Raman spectroscopy has no stringent requirements on the sample morphology, diameter, etc., and under the condition of using 405nm as the excitation wavelength, it can realize the detection of impurity N elements in the diamond crystal structure, such as N3, see Figure 1 , and then achieve preliminary qualitative analysis of diamond types and compare Figure 1As can be seen from Figures a to c, only when the excitation wavelength is 405 nm can the characteristic peaks belonging to the N3 series in the diamond sample be detected in its corresponding Raman spectrum, among which the peaks at about 628 cm -1 The characteristic peak at is the most prominent.
[0027] Example 1
[0028] The sample to be tested is subjected to Raman spectrum detection. The excitation wavelength is 405nm, and the laser energy parameter is set to 0.0001% to 10%. The objective lens for collecting sample information is set to 100 times, and the horizontal axis of the spectrum graph is Raman shift (Raman shift / cm -1 ), the recording range is 100~4000cm -1 ;
[0029] ②According to the steps The Raman spectrum of the obtained sample is as follows: Figure 2 As shown in the spectrum, at 1331-1333cm -1 When there is an obvious and sharp characteristic peak, the sample is judged to be a diamond, and the diamond sample needs to be further identified.
[0030] The identification of the characteristic peaks of the Raman spectrum of the diamond in step ② corresponds to the peaks at 628, 1332, 1920, 2159, 2584 and 3040 cm -1 The absence of characteristic peaks in the vicinity indicates that this type of diamond is not a 415nm type and has a greater synthetic nature.
[0031] Example 2
[0032] The sample to be tested is subjected to Raman spectrum detection. The excitation wavelength is 405nm, and the laser energy parameter is set to 0.0001% to 10%. The objective lens for collecting sample information is set to 50 times, and the horizontal axis of the spectrum graph is Raman shift (Raman shift / cm -1 ), the recording range is 100~4000cm -1 ;
[0033] ②According to the steps The Raman spectrum of the obtained sample is as follows: Figure 3 As shown in the spectrum, at 1331-1333cm -1 When there is an obvious and sharp characteristic peak, the sample is judged to be a diamond, and the diamond sample needs to be further identified.
[0034] The identification of the characteristic peaks of the Raman spectrum of the diamond in step ② corresponds to the peaks at 628, 1332, 1920, 2159, 2584 and 3040 cm -1 There are no characteristic peaks nearby, so it can be determined that this type of diamond is not 415nm type and has a larger synthetic attribute.
[0035] Example 3
[0036] The sample to be tested is subjected to Raman spectroscopy detection. The excitation wavelength is 405 nm, and the laser energy parameter is set to 0.05% to 5%. The objective lens for collecting sample information is set to 100 times, and the horizontal axis of the spectrum is Raman shift (Ramanshift / cm -1 ), the recording range is 100~4000cm -1 ;
[0037] ②According to the steps The Raman spectrum of the obtained sample is as follows: Figure 4 As shown in the spectrum, at 1331-1333cm -1 When there is an obvious and sharp characteristic peak, the sample is judged to be a diamond, and the diamond sample needs to be further identified.
[0038] In step ②, the identification of the characteristic peaks of the diamond’s Raman spectrum is as follows: -1 In addition to the characteristic peak at 628cm -1 There is a weak characteristic peak nearby, based on which it can be determined that this type of diamond is 415nm type, and the concentration of N3 in the diamond corresponding to 415nm is low. At the same time, the diamond is a natural diamond.
[0039] Example 4
[0040] The sample to be tested is subjected to Raman spectrum detection. The excitation wavelength is 405nm, and the laser energy parameter is set to 0.0001% to 10%. The objective lens for collecting sample information is set to 100 times, and the horizontal axis of the spectrum graph is Raman shift (Raman shift / cm -1 ), the recording range is 100~4000cm -1 ;
[0041] ②According to the steps The Raman spectrum of the obtained sample is as follows: Figure 5 As shown in the spectrum, at 1331-1333cm -1When there is an obvious and sharp characteristic peak, the sample is judged to be a diamond, and the diamond sample needs to be further identified.
[0042] The identification of the characteristic peaks of the Raman spectrum of the diamond in step ② corresponds to the peaks at 628, 1332, 1920, 2159, 2584 and 3040 cm -1 There are no characteristic peaks nearby, so it can be determined that this type of diamond is not 415nm type and has a larger synthetic attribute.
[0043] Example 5
[0044] The sample to be tested is subjected to Raman spectrum detection. The excitation wavelength is 405nm, and the laser energy parameter is set to 0.0001% to 0.5%. The objective lens for collecting sample information is set to 100 times, and the horizontal axis of the spectrum is Raman shift (Raman shift / cm -1 ), the recording range is 100~4000cm -1 ;
[0045] ②According to the steps The Raman spectrum of the obtained sample is as follows: Figure 6 As shown in the spectrum, at 1331-1333cm -1 When there is an obvious and sharp characteristic peak, the sample is judged to be a diamond, and the diamond sample needs to be further identified.
[0046] The characteristic peaks of the diamond’s Raman spectrum identified in step ② are clearly visible at 628, 1332, 1920, 2159, 2584 and 3040 cm -1 There are characteristic peaks nearby, based on which it can be determined that this type of diamond is 415nm type, and the concentration of N3 in its corresponding diamond lattice is relatively large, and the properties of the diamond are natural diamond.
Claims
1. A method for determining the type and color grade of diamond based on Raman spectroscopy with an excitation wavelength of 405 nm, characterized in that: This method uses a Raman spectrometer with a laser light source wavelength of 405nm and a laser power of 30mW to determine the diamond type and color grade. The specific detection steps are as follows: 1) Perform Raman spectroscopy on the sample to be tested. The horizontal axis of the obtained spectrum is the Raman shift. The collection range of the Raman spectrometer is 100-4000cm -1 ; 2) According to the Raman spectrum obtained in step 1), the 1331-1333 cm -1 Whether there is an obvious and sharp characteristic peak at the point, determine whether the sample is made of diamond material; 3) For the sample determined to be diamond material in step 2), the characteristic peaks of Raman spectrum are identified again, and the attribution and qualitative analysis are performed to determine the type of diamond; If the Raman spectrum of the sample to be tested has a characteristic peak near a specific wave number, and 628cm -1 The characteristic peak exists and the peak position is the strongest. It can be determined that the diamond has a 415nm absorption line type, that is, it contains N impurities and is a collection of N, referred to as 415nm type. At the same time, 628cm -1 The stronger the peak of the characteristic peak, that is, the greater the content of impurity N element, the greater the impact on the color of the diamond, and the lower the color grade of the diamond; If the Raman spectrum of the diamond sample to be tested is 628cm -1 If there is no characteristic peak nearby, it is determined that this type of diamond has no 415nm absorption line type, which is referred to as non-415nm type.
2. A method for determining diamond type and color grade based on Raman spectroscopy with an excitation wavelength of 405 nm as claimed in claim 1, characterized in that: There is a 415nm zero phonon line in the crystal structure of 415nm type diamond.
3. The method for determining the type and color grade of diamond based on Raman spectroscopy with an excitation wavelength of 405 nm as claimed in claim 1, characterized in that: When the sample to be tested is subjected to Raman spectroscopy testing, in view of the preferential orientation of different crystal planes at the occurrence positions of N impurities in the diamond sample, multi-point testing or local surface scanning is adopted on the surface of the sample to be tested.
4. The method for determining the type and color grade of diamond based on Raman spectroscopy with an excitation wavelength of 405 nm as claimed in claim 1, characterized in that: In step 1), the objective lens for collecting sample information in the Raman spectrometer device is set to 50 times or 100 times.
5. The method for determining the type and color grade of diamond based on Raman spectroscopy with an excitation wavelength of 405 nm as claimed in claim 1, characterized in that: There is no special limitation on the morphology of the sample to be tested in step 1), and the mass ranges from centimeters to carats of diamond.
6. A method for determining diamond type and color grade based on Raman spectroscopy with an excitation wavelength of 405 nm as claimed in claim 1, characterized in that: The specific method for determining whether the sample collected is made of diamond material in step 2) is: a) Raman spectrum at 1331-1333cm -1 When there is no obvious characteristic peak, the sample is judged as non-diamond and there is no need to further classify the sample type; b) Raman spectrum at 1331-1333cm -1 When there is an obvious and sharp characteristic peak, the sample is judged to be a diamond and the type of sample needs to be further classified.
7. A method for determining diamond type and color grade based on Raman spectroscopy with an excitation wavelength of 405 nm as claimed in claim 1, characterized in that: In step 3), the Raman spectrum can be baseline corrected, wherein the energy of the excitation wavelength can be increased to 100%.
8. The method for determining the type and color grade of diamond based on Raman spectroscopy with an excitation wavelength of 405 nm as claimed in claim 1, characterized in that: The specific wave number in step 3) refers to 628 cm -1 、1920cm -1 、2159cm -1 、2584cm -1 and 3040cm -1 , can exist at the same time or not.
9. The method for determining the type and color grade of diamond based on Raman spectroscopy with an excitation wavelength of 405 nm as claimed in claim 1, characterized in that: When collecting and testing the Raman spectrum of a sample, the energy of the excitation wavelength is set to not annihilate the characteristic peak of the diamond sample.