Luminescent diamond having negatively charged holes

Abstract

The luminescent material has red emission behavior after sintering using the HPHT process. The red emission is achieved at a temperature of 1475 °C to 1800 °C, and in some cases 1600 °C to 1750 °C, using coarse sintered diamond powder with an average size of 100 nm or more, or finer particles with an average grain size of at least 25 nm or at least 50 nm. The luminescent material shows red emission as a result of NV - centers generated by the HPHT process, which is more dominant than NV 0 centers generated at low temperature and also than NVN centers generated at high temperature.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims the benefit of U.S. Provisional Application No. 63 / 365,433, filed May 27, 2022, entitled "LUMINESCENT DIAMOND WITH NEGATIVELY CHARGED VACANCIES", the disclosure of which is incorporated herein by reference.

Background Art

[0002] Laser - induced fluorescence is a known technique employed to better understand how biological systems function at the molecular level by individually searching for and observing biomolecules. In one example, laser - induced fluorescence can be applied to image and track single molecules or particles, such as in living cells, for in - vivo biosensors, for example, for organ mapping, cell imaging, etc. One type of substance used in laser - induced fluorescence is luminescent nanodiamond, which is a nanosized diamond particle or diamond grain developed to emit light when excited by a light source within a desired wavelength required for the end - use.

Summary of the Invention

[0003] A luminescent diamond and a method of making the same are disclosed herein, including subjecting a volume of precursor diamond grains to high - pressure / high - temperature (HPHT) conditions to cause plastic deformation in the grains such that nitrogen - vacancy defects are created in the diamond grains, thereby increasing the luminescence activity and luminescence intensity of the resulting diamond material compared to the luminescence activity and luminescence intensity of the precursor diamond grains. In some embodiments, the HPHT conditions are carried out with a temperature increase from 1475 °C to 1800 °C, or from 1600 °C to 1750 °C, whereby the diamond grains undergo plastic deformation and negatively charged nitrogen - vacancy (NV -)Preferentially cause defects, which will result in a stronger emission intensity in the red wavelength spectrum.

[0004] In some embodiments, the luminescent diamond material formed by the HPHT process comprises diamond particles that are mechanically interconnected and bonded to a pressure transmitting medium. The luminescent diamond material has a higher level of red luminescence than the precursor diamond material used to form the luminescent diamond material as a result of a higher ratio of negatively charged nitrogen vacancies (NV 0 ) and / or both NVN defects to neutral charge nitrogen vacancies (NV - ).

[0005] This summary is provided to introduce a series of concepts that are further described in the form for carrying out the invention below. This summary is not intended to identify the key or essential features of the subject matter recited in the claims, nor is it intended to be used as an aid in limiting the scope of the subject matter recited in the claims.

[0006] The features and aspects of the luminescent nanodiamonds and methods of making the same disclosed herein will be better understood when considered in connection with the accompanying drawings and with reference to the form for carrying out the invention and the appendix, as will be correctly recognized.

Brief Description of the Drawings

[0007]

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DETAILED DESCRIPTION OF THE INVENTION

[0008] In some embodiments, the luminescent diamonds (e.g., photoluminescent diamonds) and methods of making the same disclosed herein are designed to improve the accessibility and availability of materials in end - use applications including, but not limited to, use in optically detected magnetic resonance (ODMR) by increasing manufacturing efficiency and throughput. Further, in some embodiments, luminescent diamonds prepared according to the principles disclosed herein exhibit the same or higher levels of emission intensity as conventional luminescent diamonds, thereby providing an opportunity to expand the range of potential end - use applications for such materials. For example, in relation to ODMR, the technology may become powerful enough to improve the sensitivity of spin resonance spectroscopy by several orders of magnitude.

[0009] For clarity, in some embodiments, the luminescent diamond disclosed herein is first formed by consolidating and compressing existing diamond grains to form a luminescent sintered body or slag (characterized by a high degree of intercrystalline diamond bonding), or a mechanically bonded semi-sintered body or slag (characterized by the absence of substantially intercrystalline diamond bonding). Under such conditions, this consolidated material can become luminescent diamond. During subsequent steps, the luminescent diamond is reduced to the size required for a particular end use, and in some embodiments, the resulting diamond particles or diamond grains are of nanoscale size. In some embodiments, the reduced-size luminescent diamond may consist only of nanosize particles, or may include a combination of nanosize particles and coarser diamond particles. The term "nanodiamond" as used herein is understood to refer to diamond particles having an average size of 1 nm to 1000 nm. The existence of luminescent nanodiamonds may be known, but the methods and techniques currently used to produce such luminescent nanodiamonds are expensive, very energy and time consuming, increase the cost of the material, and also limit its availability. In some embodiments, by producing luminescent diamond as disclosed herein, any combination of cost, energy, or time can be reduced.

[0010] In some embodiments, the luminescent nanodiamonds disclosed herein can be formed by combining a volume of precursor diamond grains, which can be in the form of natural and / or synthetic diamond grains, and placing that volume of diamond grains in a can or container. In some embodiments, the as-received diamond grains of the precursor material can have an average grain size of any value or range between 15 nm and 1000 μm. For example, the average grain size can be 1 nm to 1000 μm, 5 nm to 500 μm, 5 nm to 100 μm, 5 nm to 50 μm, 5 nm to 1 μm, 5 nm to 500 nm, 5 nm to 200 nm, 25 nm to 500 nm, 5 nm to 30 nm, 30 nm to 90 nm, 75 nm to 500 nm, 75 nm to 250 nm, or any other value or range therebetween. Thus, the size of the precursor diamond grains or precursor diamond powder can, in some embodiments, extend into the submicron diamond or nanodiamond range. In some embodiments, nanosized powders formed by either mechanical crushing of conventional diamond powder or a detonation process can be used in a similar manner. The diamond powder can be either synthetic or natural, although synthetic diamond powder can generally have a higher intrinsic nitrogen content that activates the luminescence of the diamond with adjacent vacancy centers.

[0011] In some embodiments, it is desirable for the starting diamond material to have an inherent amount of nitrogen impurities that matches what is found in diamonds designated as type 1b (e.g., nitrogen above 50 ppm). Nanopowders synthesized by shock synthesis generally also have a high inherent nitrogen content. In some embodiments, the container and its contents are subjected to a high pressure / high temperature (HPHT) densification process using conventional press equipment for manufacturing polycrystalline diamond. In some embodiments, a volume of diamond grains is placed in a can or container, which may or may not be sealed and is placed in an HPHT press and subjected to the desired sintering pressure and temperature conditions. In some embodiments, the HPHT process temperature may be in the range of 1300 °C to 2500 °C, and the process pressure may be 3.0 GPa to 10 GPa. In some embodiments, a volume of diamond grains contains substantially no catalyst material, such that the diamond material obtained from the HPHT process does not fully sinter but takes the form of a semi-sintered slag or semi-sintered body containing diamond grains mechanically bonded to each other by frictional contact, cold welding, diamond self-diffusion, etc. In some embodiments, by using a conventional metal solvent catalyst to produce a diamond material that is not fully sintered, i.e., semi-sintered and not characterized by a network of diamond grains bonded to each other, in contrast to a sintered polycrystalline diamond body, its relative transparency is improved, and this transparency may result in an improvement in the intensity of the light emitted therefrom. There may also be graphite formed within the porous regions of the semi-sintered body, which may reduce the emission intensity. In such cases, it is desirable for the graphite material to be partially or completely removed as part of the manufacturing process.

[0012] During the HPHT process, it has been found that at least a portion of a volume of precursor diamond grains undergoes plastic deformation. In some embodiments, the degree of the HPHT consolidation process is such that it causes sufficient plastic deformation in the diamond grains to create nitrogen-vacancy (NV and / or NVN) defects and / or N3 optical centers that act to activate the luminescence of the diamond grains. Plastic deformation of diamond particles during HPHT creates vacancies when deformation mechanisms such as dislocation motion become active, and these vacancies combine with nitrogen impurities to form NV centers, NVN centers, or N3 centers, which are thought to exhibit the desired luminescence activity. In some embodiments, this deformation occurs during the conventional sintering of polycrystalline diamond with a metal catalyst (e.g., cobalt that acts to promote intercrystalline diamond bonding during the HPHT process) or a non-metal catalyst / pressure transmission medium (e.g., carbonates and chlorides that do not promote intercrystalline diamond bonding during the HPHT process). In some embodiments, diamond grains obtained from the HPHT process can be highly plastically deformed with a wide range of NV, NVN defects, and / or N3 centers, and weak diamond-diamond bonds, as compared to solvent-catalyst-bonded polycrystalline diamond. For example, in some embodiments, the diamond grains undergo plastic deformation during the HPHT process that results in luminescence activity without producing a complete sintered body, thereby facilitating downstream processes such as a grinding process to adjust the size of the diamond grains because the diamond grains mainly mechanically bonded can be disassembled or simply disassembled, reducing energy consumption.

[0013] In some embodiments, the luminescent diamonds disclosed herein can be formed by subjecting a volume of diamond precursor grains to an HPHT process in the presence of a catalyst material. In such embodiments, the type of catalyst material used may be selected from the group including, but not limited to, Co, Fe, Ni, carbonates, Si, and combinations thereof for forming polycrystalline diamond (PCD). In some embodiments, the HPHT processing conditions for cobalt PCD can be within a temperature of 1300 °C to 1500 °C and a pressure of 5.0 GPa to 7.5 GPa. Further, the cobalt PCD can be heat treated in a vacuum at a temperature of 600 °C to 700 °C (e.g., after the formation of the PCD and before and / or after sizing).

[0014] The amount of catalyst material used can vary and will vary depending on factors such as the type of catalyst used, the desired amount of luminescence, the sintering temperature, and the specific end use. For biological end uses, for biocompatibility reasons, it may not be desirable and / or may not be permitted to have a metal material present in the luminescent diamond, in which case it may be desirable to use a non-metallic catalyst. In some embodiments, by using a non-metallic catalyst, the PCD body will be relatively more transparent or less opaque compared to PCD formed using a metal solvent catalyst. In some embodiments, non-metallic catalysts useful for making the luminescent diamonds disclosed herein include carbonate catalysts such as sodium carbonate, magnesium carbonate, calcium carbonate, which result in the formation of carbonate PCD (CPCD).

[0015] In some embodiments, the amount of such carbonate catalyst can be an amount sufficient to form a fully sintered carbonate PCD body (e.g., up to 5 wt% based on the total weight of the carbonate catalyst and diamond grains). Since carbonate PCD is not essentially darker than cobalt PCD and appears to be highly transparent, it is considered to contribute to enhancing the emission and intensity levels of luminescence. In some embodiments, the HPHT treatment of carbonate PCD can be carried out at a temperature of 1000°C to 2500°C (e.g., 1400°C to 2100°C, 1500°C to 1800°C, or 1600°C to 1750°C) and a pressure exceeding 6 GPa or exceeding 7.0 GPa. Further, the carbonate PCD can be heat-treated at a temperature of 500°C to 1300°C (e.g., before and / or after sizing, after formation) in an inert environment or a vacuum environment. In other examples, a fluoride catalyst or a chloride catalyst (e.g., sodium fluoride / sodium chloride, magnesium fluoride / magnesium chloride, calcium fluoride / calcium chloride, etc.) can be used as the pressure medium under appropriate amounts and HPHT treatment conditions.

[0016] Similar to the embodiments described herein, during HPHT treatment, plastic deformation occurs in the diamond grains, creating NV, NVN, and / or N3 centers, thereby causing an increased level of luminescence activity / intensity compared to the precursor diamond grains. Some of the vacancies formed during HPHT may not combine with nitrogen during the plastic deformation process and may move adjacent to nitrogen sites during heat treatment, creating additional NV, NVN, and / or N3 sites. The higher the processing temperature and pressure conditions associated with carbonate PCD, the higher the degree of plastic deformation that may occur in the diamond grains, and thus the higher the luminescence activity may be. Using a higher heat treatment temperature can also contribute to additional NV, NVN, and / or N3 centers and thus higher luminescence activity.

[0017] In some embodiments, it may be desirable for the amount of catalyst material used to be less than the amount useful for forming a fully sintered PCD body (e.g., an amount less than 5 wt% compared to the total weight of the diamond layer or PCD body). In such embodiments, it may be desirable to produce a partially sintered PCD body or semi-sintered PCD body that contains both intercrystalline bonded diamond and free diamond grains in order to facilitate a downstream process of sizing the PCD body into nano-sized diamond pieces or diamond grains. It has been discovered that PCD made by the methods disclosed herein produces a higher level of luminescence intensity than conventional luminescent nanodiamonds. For this reason, even when not producing a fully sintered diamond body, manufacturing a product that contains some PCD during HPHT processing can result in the desired increase in luminescence intensity, and at the same time, it can make the downstream sizing process relatively easier and reduce energy consumption compared to processes that require a fully sintered PCD body. Therefore, by adjusting the amount of catalyst material, diamond materials having the desired degree of sintering that result in the desired increase in luminescence intensity can also facilitate the downstream sizing process.

[0018] In still further cases, it has been observed that by controlling the processing conditions, luminescence at a particular wavelength can be further improved. For example, NV centers in diamond can produce red luminescence (e.g., with a peak centered at about 650 nm), NVN centers in diamond can produce green luminescence (e.g., with a peak centered at about 525 nm), and N3 centers in diamond can produce blue luminescence (e.g., with a peak centered at about 450 nm) and blue-violet luminescence (e.g., with a peak centered at about 415 nm). In some materials, by controlling the number of NV, NVN, and / or N3 centers, one or more emission colors and emission intensities can be preferentially created, and in some applications, one or more emission colors may be more desirable than other colors. In one example, ODMR may be used in connection with red luminescence, which means that the creation of NV centers may be desirable.

[0019] In connection with NV centers, at least two types of centers can be formed. In particular, since red emission can have a zero phonon line (ZPL) at about 635 nm, it can be caused by negatively charged NV centers (NV - ). In contrast, neutral (NV 0 ) centers can have a ZPL at about 575 nm and thus be closer to the green spectrum. In connection with magneto-optical properties, red illumination of NV - centers may be particularly suitable for analysis by ODMR. As described above, this technique can be powerful and can improve the sensitivity of spin resonance spectroscopy by several orders of magnitude. Thus, one aspect of the present disclosure relates to a method and diamond material for preferentially controlling the generation of NV 0 and NV - centers when nanodiamond particles are produced (e.g., using an HPHT sintering process).

[0020] It has been found that the ratio of neutral to negative (NV 0 / NV - ) can depend on various factors including the particle size and temperature of the HPHT sintering process. Figures 1-1 and 1-2 are graphs 100-1 and 100-2 (collectively graph 100) of emission intensity versus wavelength showing the effect of HPHT temperature on diamond grains subjected to a cell pressure of 6.5 GPa without a catalyst material over a range of different temperatures from 1000 °C to 2000 °C. Specifically, the graphs show the emission characteristics of diamond grains subjected to the HPHT process at 1000 °C, 1100 °C, 1200 °C, 1300 °C, 1375 °C, 1425 °C, 1475 °C, 1625 °C, 1700 °C, 1800 °C, and 2000 °C.

[0021] The average particle size of the diamond grains subjected to each of the above HPHT processes was 100 nm. As shown, each material exhibits some emission over a wavelength range of 500 nm to 900 nm, with the peak of the green emission at about 520 nm to 570 nm (corresponding to NV 0 and NVN centers) and the peak of the red emission at about 620 nm to 720 nm (NV -(corresponding to the center). In this test, it is clear that both red and green emissions can occur in the same diamond material depending on the HPHT temperature. Therefore, it is understood that the luminescent diamonds disclosed herein may be fabricated to exhibit emissions at one or more different wavelengths and thereby optimized to suit a particular end use. Further, there is not necessarily a direct correlation between red emission and green emission. For example, in FIGS. 1-2, powders sintered at 1625° C. and 1700° C. have a relatively low green emission intensity compared to powders sintered at 1800° C. and 2000° C., but a relatively high red emission intensity. The line for the powder sintered at 1475° C. is the same as the line in FIG. 1-1 and shows that the green emission is significantly lower than that of the other powders in FIG. 1-2, although lower than the powders sintered at 1625° C. and 1700° C., NV - There is some red emission indicating that NV was preferentially generated.

[0022] The emission characteristics shown in FIGS. 1-1 and 1-2 (collectively FIG. 1) were caused by exposing an example of an HPHT-treated diamond to 473 nm blue laser irradiation collected with a micro-spectrometer. These tests are representative of the results of tests on pellets formed after HPHT sintering or on powder materials. In these tests, NV emission is preferentially generated under HPHT temperature conditions of 1000° C. to 2000° C., and under HPHT temperature conditions of 1800° C. to 2000° C., when the temperature exceeds 1800° C., the NV centers are converted to NVN centers, the red intensity appears to weaken, and the emission by the NVN centers is relatively low, and thus is shown as a decrease in the red wavelength. At lower temperatures of 1000° C. to 1475° C., there is a low intensity that may correspond to a large number of NV - centers, but the peak of the red emission is still evident. In this example, a temperature between 1600° C. and 1750° C. appears to be particularly effective in preferentially generating NV 0 centers over NV centers and NVN centers, thereby increasing the red emission intensity. 0 centers and NVN centers than NV - centers, thereby increasing the red emission intensity.

[0023] Figures 2-1 and 2-2 (collectively referred to as Figure 2) are graphs 200-1, 200-2 (collectively referred to as 200) that further show the effect of sintering temperature on the creation of NV centers that produce red emission (especially the preferential creation of NV - centers). Figure 2-1 shows the emission intensity of diamond powder when excited by a 532 nm green laser and sintered at temperatures from 1475 °C to 2000 °C. The diamond material was formed from diamond grains having an average particle size of 100 nm. Figure 2-2 is a chart of the intensity over the wavelength range of 550 nm to 850 nm for the material sintered at 1475 °C. The tests that generated the charts of Figures 2-1 and 2-2 showed that the intensity of red emission increased (reflecting the creation of both NV 0 centers and NV - centers) for the material sintered at 1475 °C, while for diamond materials sintered in the temperature range of 1600 °C to 1750 °C, the intensity of red emission was even higher, demonstrating that more NV - centers were preferentially created. In contrast, the red intensity at 1800 °C and 2000 °C decreased significantly, which may be the result of an increase in the creation of NVN centers.

[0024] Figures 3 to 5 are further graphs 300, 400, 500 of examples of the effect of temperature on red emission intensity, but use a particle size different from that used in the tests reflected in graphs 100, 200 of Figures 1 and 2. For example, Figures 3 and 4 are graphs 300, 400 generated from the analysis of diamond powder with an average grain size of 50 nm and directly sintered by the HPHT method at temperatures from 1200 °C to 2000 °C. Figure 3 shows the emission intensity of various materials over the visible spectrum (380 nm to 750 nm), as well as over the spectra of a portion of the ultraviolet (300 nm to 380 nm) and a portion of the near infrared (750 nm to 875 nm). All intensities were measured when the material was excited by a 532 nm green laser.

[0025] At a particle size of 50 nm, the same results as for 100 nm particles were shown, and when the sintering temperature was 1650 °C to 1750 °C, a particularly prominent intensity was shown at the red wavelength. However, a significant increase in red intensity was also seen from a minimum of 1480 °C to a maximum of 1800 °C. Therefore, compared to the tests used to create Figure 2-2, it appears that the smaller the particle size, the greater the red intensity of the material (corresponding to preferential NV - center creation) in a wide temperature range up to 1800 °C. However, a further increase in temperature to 1900 °C and 2000 °C shows, as in the previous example, a significant decrease in red intensity. Even at lower temperatures of 1200 °C to 1350 °C, the peak of the red emission intensity is greater than the peak at temperatures above 1900 °C, reflecting that the NV - centers are preferentially created, but the peak is significantly lower than when sintered at 1480 °C to 1800 °C, indicating that more NV 0 centers are still being created. In particular, for materials sintered at temperatures below 1400 °C, the intensity from the NV 0 center (ZPL at about 575 nm) becomes quite close to the intensity from the NV - center (ZPL at about 635 nm). However, as the sintering temperature is increased, more NV - centers are formed and the photoluminescence from the NV - centers comes to dominate the emission spectrum.

[0026] When the material is excited with a 473 nm blue laser, spectral differences can also be detected for samples including those sintered at 1350 °C to 1650 °C, as shown in graph 400 of Figure 4.

[0027] Figure 5 is a further graph 500 showing the red intensity of nanodiamond materials after HPHT sintering at various temperatures. Graph 500 of Figure 5 reflects tests performed on different materials with an average particle size of 25 nm and excited with a 532 nm green laser. As shown in the figure, when sintered at temperatures of 1600 °C to 1750 °C, the NV -Higher red emission corresponding to the creation of centers was generated, and a temperature of 1600 °C to 1700 °C was particularly effective across the red spectrum.

[0028] FIG. 6 is a block diagram 600 showing processes that can be used to fabricate a luminescent diamond. In some embodiments, the process can be performed in a series of steps including two or more of the illustrated steps. In a first process 602, materials useful for fabricating a luminescent diamond are combined and collected by the methods described herein. This method may or may not include the use of a catalyst material and includes subjecting the collected or combined materials to an HPHT process, which may or may not result in the formation of a fully sintered diamond compact. In some embodiments, the first process 602 creates vacancies / centers within the resulting diamond material to form nitrogen (NV 0 、NV - 、NVN, and / or N3). In a second optional process 604, the diamond material produced in the first process 602 is subjected to a heat treatment process. The heat treatment is optionally performed under vacuum conditions. Exemplary heat treatments can include an annealing process optionally performed at a temperature above 500 °C.

[0029] Referring to the results of the luminescence intensity, in some embodiments, by pressing the diamond material in the first step 602 and / or performing a heat treatment in step 604, the luminescence intensity of the diamond material can be adjusted (e.g., the ratio of NV centers to NVN centers, and / or NV of the NV - centers to NV 0(It can be enhanced by increasing the NV count of the red intensity including the ratio to the center.) In a third optional process 606, diamond material from process 1 602 or process 2 604 is collected or sized by crushing, milling, grinding, or other sizing techniques. When crushing, grinding, milling, etc. are performed on the particles, the size of the diamond particles formed during this third step 606 can be determined by the specific end use of the luminescent diamond material. During this third process 606, the diamond material can be converted to a powder. In some embodiments, reducing the size of the diamond material increases the luminescence intensity of the diamond material (e.g., 3 - 4 times because the surface area of the resulting powder increases).

[0030] Optionally, in the third process 606, the powder can be collected or produced without crushing, grinding, milling, etc. For example, the HPHT process of step 602 may be performed using a pressure - transmitting medium that does not promote inter - crystal bonding between diamonds and does not function as a catalyst for diamond synthesis. For example, as described herein, sodium chloride (NaCl) can be used to transmit pressure between diamond grains and deform the diamond grains to create NV, NVN, or N3 vacancies. In some cases, the resulting material may remain granular or powdery and can be collected without milling, grinding, etc. For example, a raw - precursor diamond powder with an average size of 1 nm - 90 nm (e.g., 1 nm - 30 nm, 30 nm - 90 nm, etc.) can become a processed diamond powder with a similar average size after passing through an HPHT process using a pressure - transmitting medium. In some cases, the size may decrease slightly, or the relative ratio may change (e.g., spherical diamond grains become elliptical diamond grains).

[0031] In a fourth optional process 608, diamond material from process 1 602, process 2 604, or process 3 606 is subjected to an air heat treatment (e.g., an oxidation heat treatment). In some embodiments, the air heat treatment turns the surface of the diamond material white, which is thought to be due to the formation of oxygen-terminated diamond bonds. In some embodiments, subjecting the diamond material to this fourth process 608 increases the emission intensity by up to about 10 times. In some embodiments, the luminescent diamond materials disclosed herein are formed according to one or more of these processes, and in some embodiments, all of these processes can be used in sequence depending on the type and / or degree of emission intensity required for a particular end use.

[0032] In some embodiments where the luminescent diamond obtained from the HPHT process is in the form of a metallic PCD (e.g., cobalt PCD), it may be desirable to treat the sintered PCD body to completely or partially remove the metallic material therefrom. This removal can be performed by a leaching process or other processes known in the art to enable use in applications where the presence of the metal is undesirable, not permitted, or not practical (e.g., biological applications) to remove the metal catalyst from the PCD. Also, removing the catalyst material from the PCD weakens the structure of the sintered body, making it easier to crush and reduce in size.

[0033] In some embodiments of the luminescent diamond formed using a carbonate catalyst as disclosed herein, for example, carbonate PCD is such a metal-free PCD and, being metal-free, can be used in biological applications or other end uses without the need to remove the catalyst at all. In some embodiments, it may be useful to use magnetic separation techniques to confirm that the luminescent diamond material does not contain a sufficient amount of metal catalyst. In some embodiments of the luminescent diamond provided in the form of carbonate PCD, a significantly higher luminescence intensity level is obtained compared to cobalt PCD. This may be due to the higher levels of temperature and pressure used in the HPHT sintering process employed for carbonate PCD, as well as the relative increase in transparency and decrease in opacity of carbonate PCD as compared to cobalt PCD as described above.

[0034] The luminescent diamond disclosed herein is sized after the HPHT consolidation process to facilitate use in applications where smaller sized diamond particles, such as nano-sized particles, are required, such as the biological applications described above. Thus, the luminescent diamond is subjected to a size reduction process for the purpose of breaking down the diamond material into smaller sized diamond pieces or grains after being consolidated by HPHT treatment. In some embodiments, the luminescent diamond may be processed such that its size is reduced to an average diameter of 1 nm to 1 mm, or 5 nm to 200 μm, for example. Examples of useful ranges of average particle size include, but are not limited to, 5 nm to 100 nm, 100 nm to 200 nm, 200 nm to 1000 nm, 500 nm to 20 μm, or 20 μm to 200 μm. In some embodiments, it may be useful for the average microparticle size to be 1 μm or greater. The particular process used to reduce the size of the diamond material obtained by HPHT treatment can vary depending on the particular material (e.g., whether the diamond material is in the form of sintered PCD, partially sintered PCD, or mechanically bonded diamond grains) and / or the size desired as a result after processing and will differ.

[0035] In some embodiments, the diamond material may be crushed by high-speed impact with a high-strength target (e.g., made from tungsten carbide, etc.) or by collision with another diamond material (e.g., self-collision under high-speed conditions). In some embodiments, such as when using the diamond material for biological applications, it may be desirable to reduce the diamond material to nano-sized fragments or particles. The process of reducing or sizing the diamond material can be carried out at elevated temperatures or ambient temperature conditions if it helps to facilitate the process or if the diamond material undergoes further plastic deformation resulting in increased luminescence activity and intensity. Sorting by magnetic or other mechanical techniques can be used for the purpose of separating luminescent diamond particles having cobalt inclusions from luminescent particles without cobalt inclusions. In some end uses, since some cell structures are sensitive to sharp edges, such as those made of fragmented diamond crystals, the shape of the resulting microparticles can be a real issue. In these applications, it may be desirable to use detonation nanodiamonds as the starting material since these microparticles are essentially spherical. In some embodiments, it has been shown that treating the material in an oxidizing environment removes more than 50% of the diamond crystals under some conditions, which can be utilized to remove sharp edges and increase the sphericity of the particles. In the above-described powder sizing,

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[0036] As described herein, during the process of reducing a diamond material to a desired diamond particle size (e.g., nano-sized particles), the diamond material may undergo further plastic deformation or fracture (e.g., beyond that which occurs during the HPHT process), and as a result, the luminescence activity and luminescence intensity of the resulting diamond material are further increased. Thus, the diamond particles of the resulting size may have a higher level of luminescence intensity than the diamond material after HPHT treatment. Further, if an intermediate treatment as described herein is performed between the HPHT treatment and the size adjustment, the luminescence activity / intensity may increase twice between the diamond material in the consolidated state after HPHT treatment and the diamond particles after reduction or size adjustment treatment.

[0037] It should be understood that the amount of increase in luminescence intensity may vary depending on factors such as the specific type of luminescent diamond material, the grain size of the precursor diamond material, the technique or process used to reduce the processed diamond material, the final size of the luminescent diamond particles, and other process treatments employed such as heat treatment under vacuum conditions and / or air heat treatment. In addition to exhibiting a higher luminescence intensity than conventional luminescent nanodiamonds or other luminescent nanodiamonds, the luminescent diamonds described primarily herein maintain their luminescence intensity over a longer period of time than conventional luminescent nanodiamonds.

[0038] As described herein, the precursor diamond material can have various sizes that can at least affect the luminescence intensity. In some cases, the combination of the size of the precursor material and the temperature of the HPHT process affects the luminescence intensity. Examples of useful average particle sizes vary for the precursor diamond material, but are not limited to materials between 1 nm and 1 mm and include any range having a lower limit and an upper limit therebetween. In some specific examples, the average size of the particles in the precursor material can be 1 nm to 100 nm, 1 nm to 30 nm, 30 nm to 90 nm, 100 nm to 200 nm, 100 nm to 45 μm, 200 nm to 1000 nm, 500 nm to 20 μm, or 20 μm to 200 μm. In some embodiments, it is useful for the average grain size to be 1 μm or greater, while in other embodiments, it can be useful for the average grain size to be less than 100 nm (e.g., less than 90 nm).

[0039] Also during the HPHT process, various temperatures can be used. In some embodiments, the maximum sustained temperature is between 1000 °C and 2500 °C, but any range having a lower limit and an upper limit therebetween can also be used. For example, suitable ranges can include lower and upper values including any of 1000 °C, 1100 °C, 1200 °C, 1300 °C, 1400 °C, 1425 °C, 1450 °C, 1475 °C, 1500 °C, 1525 °C, 1550 °C, 1575 °C, 1600 °C, 1625 °C, 1650 °C, 1675 °C, 1700 °C, 1725 °C, 1750 °C, 1775 °C, 1800 °C, 1825 °C, 1850 °C, 1875 °C, 1900 °C, 1925 °C, 1950 °C, 1975 °C, 2000 °C, 2025 °C, 2050 °C, 2075 °C, 2100 °C, 2150 °C, 2200 °C, 2250 °C, 2300 °C, 2350 °C, 2400 °C, 2450 °C, 2500 °C, or any value therebetween. Thus, by way of example, the temperature of the HPHT process in some embodiments can be in the range of 1000 °C to 2500 °C, 1450 °C to 1900 °C, 1475 °C to 1850 °C, 1575 °C to 1775 °C, 1600 °C to 1800 °C, 1600 °C to 1750 °C, or other ranges generated at the above endpoints.

[0040] As described herein, a luminescent diamond can be formed using a non-catalytic material that does not promote intercrystalline diamond bonding during the HPHT process, resulting in a body without (e.g., substantially free of) intercrystalline diamond bonding. Such a material can be considered a pressure transmitting medium. As used herein, a pressure transmitting medium refers to a material that functions to promote mechanical bonding between diamonds during the HPHT process. Thus, it is in contrast to a material that promotes a high degree of intercrystalline bonding between diamonds. Thus, the pressure transmitting medium weakens or does not promote at all the intercrystalline bonding between diamonds and instead favors mechanical bonding. Examples of pressure transmitting medium materials useful for making luminescent diamonds include, but are not limited to, carbonates, nitrates, sulfates, phosphates, chlorates, perchlorates, acetates, chromates, oxalates, sulfides, ammonium compounds, hydroxides, oxides, cyanides, cyanates, dichromates, halides, chlorides, fluorides, or combinations thereof. The pressure transmitting medium can be selected from materials such as sodium carbonate (Na 2 CO 3 ) and other alkali metal carbonate materials or compounds, or other functionally similar materials, that promote diamond growth but do not promote a high degree of intercrystalline bonding between diamonds.

[0041] The pressure transmission medium can be selected from materials that are not catalysts for diamond synthesis, such as sodium chloride (NaCl) or sodium fluoride (NaF), and other chloride or fluoride materials or compounds, or other functionally similar materials. In some embodiments, the material selected as the pressure transmission medium is desirably water-soluble, acid-soluble, or base-soluble to facilitate removal by water, acid, or base washing from the luminescent diamond formed by HPHT treatment. The pressure transmission medium can be liquid or solid at room temperature and 1 atmosphere of pressure. In some embodiments, the pressure transmission medium may be provided in solid form to facilitate handling during loading of the HPHT vessel. Further, although different types of pressure transmission media have been described, the pressure transmission medium used can be a single phase such as NaCl or Na 2 CO 3 or the pressure transmission medium can be composed of two or more phases of different materials such as an NaCl-Na 2 CO 3 or an NaCl-KCl-LiCl mixture. It is understood that using a pressure transmission medium mixture composition of two or more phases allows for a wide variation and control of the desired melting point of the pressure transmission medium during HPHT processing. For example, it can ensure that the pressure transmission medium is in a liquid state during HPHT processing to fill the gaps between diamond particles (e.g., most or all of the gaps), thereby minimizing or eliminating graphitization of the diamond surface.

[0042] In some embodiments, the luminescent diamond can be manufactured in a manner similar to that disclosed above, in which case a volume of diamond grains or powder of nano-size or micro-size is Na 2 CO 3, NaCl, and / or NaF powder, etc., are pre-mixed with a pressure transmission medium. When subjected to the HPHT process, the pressure transmission medium serves to transmit pressure to the diamond particles and also fills the voids between the diamond particles to minimize or eliminate the graphitization of diamond. During the HPHT process, a shear load is applied to the diamond particles through point contact between the diamond particles, and this shear load causes plastic deformation at high temperatures, creating NV, NVN, and / or N3 defects / centers. In some embodiments, the volume percentage of the precursor diamond grains is controlled to ensure such point contact generation and the resulting shear load. In some embodiments, the amount of precursor diamond grains used exceeds 20 volume percent based on the total volume of the mixture of diamond grains and the pressure transmission medium, and in some embodiments, exceeds 50 volume percent. In some embodiments, the amount of the pressure transmission medium can also be controlled so that the empty spaces between the diamond particles are filled to minimize or prevent the graphitization of the diamond surface at high temperatures. In some embodiments, the amount of the pressure transmission medium used exceeds 5 volume percent based on the total volume of the mixture of diamond grains and the pressure transmission medium, and in some embodiments, exceeds 10 volume percent.

[0043] The method for manufacturing the luminescent diamond disclosed above includes pre-mixing diamond grains and a pressure transmission medium, but it should be understood that the diamond grains can be loaded into an HPHT container (e.g., a refractory metal capsule) without being pre-mixed with the pressure transmission medium. In such an example, the pressure transmission medium may be provided in the form of one or more layers or objects arranged adjacent to one or more layers of diamond grains inside the container. During the temperature increase in the HPHT process, the pressure transmission medium melts and can penetrate into a certain volume of diamond grains due to the applied pressure. In some embodiments, the layer or body of the pressure transmission medium has a volume sufficient to ensure complete penetration of the volume of diamond grains.

[0044] When the luminescent diamonds disclosed in this specification are used in specific downstream applications such as biological applications, it may be desirable to further process or functionalize the luminescent diamond particles, such as nanodiamonds, to adapt the material to its intended use. As disclosed herein, it is understood that the methods and types of treatments that can be used to functionalize luminescent diamond materials can vary depending on the specific end use. However, as an example of a functionalization process, there can be a process of terminating oxygen along the diamond surface to make the diamond surface hydrophilic, which may be established by various surface oxidation procedures. Such oxygen-terminated functionalization can include providing =O, -OH, -COOH, or a mixture of -C-O-C- groups on the surface. Other surface terminations can include hydrogen termination, halogenation, thermal annealing to create double bonds, and reduction to OH termination. Further types of functionalization can include grafting or attaching specific molecules to the surface of diamonds treated by the aforementioned methods to facilitate such attachment, and such molecules are selected to readily react with different biomolecules. Further types of functionalization can include biological labels that can be effected via electrostatic (non-covalent) or covalent attachment between diamond particles and biomolecules. These are only a small part of the ways in which the luminescent diamonds disclosed herein can be functionalized for use in biological applications, and it should be understood that other known approaches and techniques useful for functionalizing luminescent diamonds for specific biological applications are also within the scope and spirit of this disclosure.

[0045] Although several exemplary embodiments of the luminescent diamond have been described in detail above, it will be readily understood by those skilled in the art that many modifications are possible in the exemplary embodiments without materially departing from the invention. For example, the luminescent diamond disclosed herein is presented in the context of biological end-uses and / or in relation to magneto-resonance processes detected optically. The luminescent diamond disclosed herein may be used in end-uses other than biological uses or in detection methods other than magneto-resonance detected optically, in which case an improvement in the desired level of luminescence intensity may be useful or beneficial. Other potential uses of the luminescent diamond include, but are not limited to, use in magnetic sensors, high-resolution thermography, microscope sensor arrays, anti-counterfeiting measures, ion concentration monitoring, membrane potential measurement, optical trapping, quantum computing, strain / pressure sensors, etc. Accordingly, it is understood that the luminescent diamond disclosed herein is not intended to be limited to a particular end-use or detection mechanism. It should be understood that references to "one embodiment", "embodiment", "example", etc. of the present disclosure are not intended to be construed as precluding the existence of additional embodiments incorporating the features described. For example, although materials and process features are shown or described herein, they may also be combined. In fact, any element or feature described in connection with an embodiment herein can be combined with any element or feature of any other embodiment described herein.

[0046] The specific descriptions or designations of components such as "first", "second", "third", etc. are used to distinguish between the same components or between components with similar uses, structures, or operations. Such language is not intended to limit the components to singular designations or to require multiple components. Thus, a component referred to as the "first" component in the claims may be the same as or different from the component referred to as a "component" or the "first" component herein, and the claims may include the "first" component without the need for the presence of a "second" component.

[0047] Furthermore, although this specification or the claims may refer to "additional" or "other" elements, features, aspects, components, etc., it does not preclude the presence of a single or multiple additional elements. When the claims or this specification refer to an "a" or "an" element, such reference is not to be construed as meaning that there is only one such element, but rather it encompasses other components and is understood to mean "at least one" of such elements. When this specification states that a component, feature, structure, function, or property "may be included", "may be contained", "can be included", or "might be included", that particular component, feature, structure, or property is provided in a particular embodiment but is optional in other embodiments of the present disclosure. The terms "couple", "coupled", "connect", "connection", "connected", "connected to", and "connecting" refer to "connected directly to" or "connected through one or more intermediate elements or members". Components formed "integrally" or "as one piece" include components made from the same piece or set of materials, such as by being generally molded or cast from the same material in the same molding or casting process or generally machined from the same material stock. It should also be understood that components that are "integral" can be "coupled" together.

[0048] Any numbers, percentages, ratios, or other values described in this specification are intended to include not only the value itself, but also other values that are "about" or "approximately" the described value as understood by one of ordinary skill in the art and as encompassed by the embodiments of the present disclosure. Accordingly, the described values should be interpreted broadly enough to include values that are sufficiently close to the described values to at least perform the desired function or achieve the desired result. The described values should include at least the variations expected during a proper manufacturing or production process and may include values within 5%, 1%, 0.1%, or 0.01% of the described values.

[0049] The terms "about," "approximately," and "substantially" as used in this specification or in the claims represent an amount that is within an acceptable range of a standard manufacturing or process, or an amount that is close to the described amount and still performs the desired function or achieves the desired result. For example, the terms "about," "approximately," and "substantially" may refer to amounts that are within a range of less than 5%, less than 1%, less than 0.1%, and less than 0.01% of the described amount.

[0050] Although various exemplary embodiments are described in detail herein, those skilled in the art will readily understand from the perspective of the present disclosure that many changes are possible in the exemplary embodiments without substantially departing from the present disclosure. Accordingly, any such changes are intended to be included within the scope of the present disclosure. For example, although the present disclosure is particularly related to the formation of nitrogen vacancies and centers (e.g., NV, NVN, N3), embodiments of the present disclosure can be extended to the formation and optimization of materials having other luminescent centers. For example, materials having vacancies in silicon (Si) can be formed and processed in a similar manner. Further, although the present disclosure herein includes many details, these details should not be construed as limiting either the scope of the present disclosure or the scope of the appended claims, but rather should be construed as merely providing information regarding one or more specific embodiments that may be included within the scope of the present disclosure and the scope of the appended claims. Any of the described features from the various disclosed embodiments may be used in combination.

[0051] Those skilled in the art should understand, in view of the present disclosure, that equivalent configurations do not depart from the spirit and scope of the present disclosure, and that various changes, substitutions, and modifications can be made to the embodiments disclosed herein without departing from the spirit and scope of the present disclosure. Equivalent structures including functional "means-plus-function" clauses are intended to cover the structures described herein that perform the recited functions, including both structural equivalents that operate in the same way and equivalent structures that provide the same function. The clear intention of the applicant is not to rely on means-plus-function or other functional claim terms for any claim, except where the term "means" appears in conjunction with the associated function. Each addition, deletion, and modification to an embodiment that is within the meaning and scope of the claim shall be included in the claim.

[0052] The abstract at the end of this disclosure is provided to enable the reader to quickly grasp the general nature of some embodiments of this disclosure. It is submitted with the understanding that it is not to be used to interpret or limit the scope or meaning of the claims.

[0053] The appendix attached to this specification is hereby incorporated by reference in its entirety for all purposes.

Claims

Claim 1 A method for producing a luminescent diamond, A certain volume of precursor diamond grains is exposed to high pressure / high temperature (HPHT) conditions at a temperature increase from 1600 °C to 1800 °C, thereby causing plastic deformation in the diamond grains and preferentially generating negatively charged nitrogen vacancy (NV - - ) defects, including wherein the obtained diamond material exhibits a level of luminescence intensity higher than that of the precursor diamond grains in the red wavelength spectrum, said method. Claim 2 The method according to claim 1, wherein when exposed to a temperature increase from 1000 °C to 1450 °C or from 1900 °C to 2000 °C, said level of luminescence intensity in the red wavelength spectrum becomes higher than the level of luminescence intensity of the precursor diamond grains. Claim 3 The obtained diamond material has a higher ratio of NV centers to neutral nitrogen-vacancy (NV - ) defects than the precursor diamond grains exposed to the heating from 1000 °C to 1450 °C, and a higher ratio of NV defects to NNV defects than the precursor diamond grains exposed to the heating from 1900 °C to 2000 °C, according to the method of claim 1. - centers than the precursor diamond grains exposed to the heating from 1000 °C to 1450 °C, and a higher ratio of NV defects to NNV defects than the precursor diamond grains exposed to the heating from 1900 °C to 2000 °C, according to the method of claim 1. 0 ), according to the method of claim 1. Claim 4 The method according to claim 1, wherein the obtained diamond material substantially does not contain intercrystalline bonded diamond. Claim 5 The method according to claim 1, wherein said volume of precursor diamond grains is exposed to said HPHT conditions in the presence of a pressure transmitting medium. Claim 6 The method according to claim 5, wherein the pressure transmitting medium does not promote intercrystalline diamond bonding during said HPHT conditions. Claim 7 The method according to claim 5, wherein the pressure transmitting medium is selected from the group consisting of carbonates, nitrates, sulfates, phosphates, chlorates, perchlorates, acetates, chromates, oxalates, sulfides, ammonium compounds, hydroxides, oxides, cyanides, cyanates, dichromates, halides, chlorides, fluorides, and combinations thereof. Claim 8 The method according to claim 5, wherein the pressure transmitting medium is mixed with said volume of diamond grains prior to said HPHT conditions. Claim 9 The method according to claim 5, wherein the pressure transmitting medium is disposed adjacent to said volume of diamond grains prior to said HPHT conditions, and the pressure transmitting medium melts and fills the gaps within said volume of diamond grains during said HPHT conditions. Claim 10 The method according to claim 5, wherein after said HPHT conditions, the obtained diamond material contains more than 20% by volume of diamond and more than 5% by volume of pressure transmitting medium, based on the total volume of the obtained diamond material. Claim 11 The method according to claim 5, wherein after said HPHT conditions, the obtained diamond material contains more than 50% by volume of diamond and more than 10% by volume of pressure transmitting medium, based on the total volume of the obtained diamond material. Claim 12 The method according to claim 5, wherein the pressure transmitting medium is selected from the group consisting of water-soluble materials, acid-soluble materials, and base-soluble materials. Claim 13 After the HPHT conditions, the resulting diamond material comprises diamond particles in powder form or mechanically linked and separable diamond particles without a milling, grinding, or pulverization process, the method according to claim 1.

14. After subjecting a certain volume of precursor diamond grains to the HPHT conditions, washing the resulting diamond material, thereby removing all or part of the pressure transmission medium, further comprising the method according to claim 1.

15. The method according to claim 1, wherein the temperature increase is between 1600 °C and 1750 °C, and the average size of the precursor diamond grains is between 50 nm and 5 μm.

16. A luminescent diamond material, comprising diamond particles mechanically linked to each other and combined with a pressure transmission medium, The luminescent diamond material includes diamond grains that have undergone plastic deformation through a high pressure / high temperature (HPHT) process, and the luminescent diamond material has a higher level of red luminescence than the precursor diamond material used to form the luminescent diamond material as a result of a high ratio of negatively charged nitrogen vacancies (NV 0 ), or both, relative to either or both of neutral charge nitrogen vacancies (NV - ) and NVN defects.

17. The luminescent diamond material according to claim 16, wherein the HPHT process comprises temperature conditions of 1600 °C to 1750 °C.

18. The luminescent diamond material according to claim 17, wherein the diamond particles have an average particle size between 100 nm and 45 μm.

19. The luminescent diamond material according to claim 16, wherein the HPHT process comprises temperature conditions of 1475 °C to 1800 °C.

20. The luminescent diamond material according to claim 19, wherein the diamond particles have an average particle size between 30 nm and 90 nm.

21. The luminescent diamond material according to claim 19, wherein the diamond particles have an average particle size between 1 nm and 30 nm.

22. The luminescent diamond material according to claim 16, wherein the pressure transmission medium is a material that does not promote the intercrystalline bonding of precursor diamond grains during the HPHT process.

23. The luminescent diamond material according to claim 16, wherein the pressure transmission medium is selected from the group consisting of carbonates, nitrates, sulfates, phosphates, chlorates, perchlorates, acetates, chromates, oxalates, sulfides, ammonium compounds, hydroxides, oxides, cyanides, cyanates, dichromates, halides, chlorides, fluorides, water-soluble substances, acid-soluble substances, base-soluble substances, and combinations or mixtures thereof.

24. The luminescent diamond material according to claim 16, wherein the diamond particles substantially do not contain intercrystalline bonded diamond.

25. The luminescent diamond material according to claim 16, comprising diamond exceeding 50% by volume and a pressure transmission medium exceeding 10% by volume based on the total volume of the luminescent diamond material.

26. The luminescent diamond material according to claim 16, further comprising a total graphite content of less than 5% by weight without further treatment after being produced by the HPHT process.

27. The method according to any one of claims 1 to 15, used for manufacturing the luminescent diamond material according to any one of claims 16 to 26.

28. Any method, system, assembly, device, material, component, sub-component, or part thereof that is described or illustrated.

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