Nanodiamonds with vacancy defects and quantum dot luminescence

Abstract

Luminescent diamonds are produced by subjecting a volume of diamond grains to high pressure / temperature conditions, with or without a catalyst or pressure-transmitting medium, to plastically deform the grains, creating internal void defects and increasing the luminescence activity / intensity of the resulting diamond material. The luminescent material is then subjected to further processing to create quantum dots on the surface of the diamond grains. The formation of quantum dots can include placing the diamond particles in a liquid and subjecting the particles to laser pulses. The consolidated diamond material can be treated to further increase its luminescence activity / intensity, including reducing the consolidated diamond material to diamond particles, heat treatment in a vacuum, and / or air heat treatment. The resulting luminescent diamond particles exhibit higher levels of luminescence intensity than conventional luminescent nanodiamonds and can be functionalized for use in biological applications.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 63 / 366,434, filed June 15, 2022, entitled "NANODIAMOND WITH VACANCY DEFECT AND QUANTUM DOT LUMINESCENCE," the disclosure of which is incorporated herein by reference. [Background technology]

[0002] Laser injection fluorescence is a known technique employed to better understand how biological systems function at the molecular level through the individual probing of biomolecules for observation. In one example, laser injection fluorescence can be applied to image and track single molecules or particles within living cells, for example, as in vivo biosensors for organ mapping, cellular imaging, etc. One material used in laser injection fluorescence is luminescent nanodiamonds, which are nano-sized diamond particles or diamond granules engineered to emit light when excited by a light source within the desired wavelength required for the end application.

[0003] These and other features and advantages of the luminescent nanodiamonds and methods for making same disclosed herein will become more readily appreciated as the luminescent nanodiamonds and methods for making same become better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0004] [Figure 1] FIG. 1 is a schematic diagram of a diamond nanoparticle with nitrogen vacancy centers and quantum dot emission sites according to an embodiment of the present disclosure. [Figure 2] 1A-1C illustrate schematic diagrams of quantum dot fabrication using femtosecond laser pulses and a carbon source in a liquid, according to embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0005] In some embodiments, the luminescent diamonds (e.g., luminescent diamonds) and methods for making them disclosed herein are engineered to enhance the luminescence and functional utility of nanodiamonds. Luminescent diamonds prepared according to the principles disclosed herein can exhibit luminescence intensity levels similar to or exceeding those of conventional luminescent diamonds, thereby presenting an opportunity to expand the range of potential end-use applications for such materials. In some embodiments, luminescent diamonds are initially formed by compaction and compression of pre-existing diamond granules to form a luminescent active sintered body or slug (characterized by a high degree of intercrystalline diamond bonding) or a mechanically bonded semi-sintered body or slug (characterized by a substantial absence of intercrystalline diamond bonding). In such conditions, the compacted material may be referred to as luminescent diamond. During subsequent processing, the luminescent diamond can be reduced in size as required by the particular end-use application, and in some embodiments, the resulting diamond granules or granules may be nanoscale in size. In some embodiments, the reduced-size luminescent diamond may comprise only nano-sized particles or a combination of nano-sized particles and coarser diamond particles. As used herein, the term "nanodiamond" is understood to include nano-sized diamond particles, i.e., luminescent diamonds having an average size between about 1 and 1000 nm.

[0006] In a further embodiment, compressed, compacted, deformed diamonds—either before or after particle size reduction—can also be modified to generate luminescence centers on the surface of these materials using processes such as laser irradiation. Laser irradiation can follow the so-called quantum carbon dot approach, in which carbon-based materials can generate luminescence. The creation of quantum carbon dots can involve subjecting nitrogen vacancies containing compressed, compacted, deformed diamond material to high-energy laser pulses. These laser pulses create active luminescence centers on the surface of the nanodiamond, while nitrogen vacancy centers are dispersed throughout the interior (and potentially the surface) of the nanodiamond. The number and size of the quantum dots, along with the parameters of the laser treatment, can provide the advantage of additional luminescence intensity beyond that generated by either nitrogen vacancy centers or quantum carbon dots alone.

[0007] In some embodiments, the luminescent diamonds disclosed herein can be formed by combining a large quantity of precursor diamond granules, which can be in the form of natural and / or synthetic diamond granules, and placing the large quantity of diamond granules in a can or container conventionally used for compacting diamond granules. In some embodiments, the diamond granules can have an average particle size of about 1 μm to 1000 μm, about 1 μm to 100 μm, or about 10 μm to 50 μm. In other embodiments, the size of the initial diamond granules or diamond powder can extend into the submicron or nanodiamond range. In some embodiments, nano-sized powders formed by either conventional mechanical crushing of diamond powder or by detonation processes can be used in a similar manner.

[0008] Conventional diamond powders can be of either synthetic or natural origin, but synthetic diamond powders have a higher intrinsic nitrogen content, which, together with adjacent vacancies, makes the diamond luminescence-active. In some embodiments, it is desirable for the starting diamond material to have an intrinsic amount of nitrogen impurity consistent with the intrinsic amount found in diamond designated as Type 1b, for example, about 50 ppm or more nitrogen. Nano-sized powders synthesized through impact synthesis generally have a higher nitrogen content. In some embodiments, the container and its contents are subjected to a high-pressure / high-temperature (HPHT) consolidation deformation process using conventional pressing equipment to create polycrystalline diamond. In some embodiments, a large amount of diamond granules is placed in a can or container. The can or container may or may not be sealed and placed in an HPHT press, which is then subjected to the desired sintering pressure and temperature conditions.

[0009] In some embodiments, the HPHT process temperature may be in the range of about 1300-2500°C, and the process pressure may be about 3.0 GPa to about 10 GPa. In some embodiments, the bulk diamond granules are substantially free of any catalytic material, so the diamond material resulting from the HPHT process is not fully sintered, but rather is in the form of a semi-sintered slug or semi-sintered body comprising diamond granules mechanically bonded together by frictional contact, cold welding, diamond self-diffusion, or the like. In some embodiments, producing a diamond material that is not fully sintered (i.e., semi-sintered and not characterized by a network of diamond granules bonded together using conventional metal solvent catalysts) improves its relative transparency, as opposed to a sintered polycrystalline diamond body. The transparency of the diamond material may improve the intensity of the luminescence emission from the diamond material. There may also be graphite formed within the porous regions of the semi-sintered body, which may reduce the intensity of the luminescence. In such cases, it may be desirable to partially or completely remove the graphite material as part of the manufacturing process.

[0010] It has been found that during the HPHT process, at least a portion of the bulk precursor diamond granules undergoes plastic deformation. In some embodiments, the extent of the HPHT compaction deformation process is such that sufficient plastic deformation is induced within the diamond granules to create nitrogen vacancy (NV and / or NVN) defects and / or N3 optical centers within the diamond granules, which act to render the diamond granules luminescently active. It is believed that the plastic deformation of diamond particles during HPHT generates vacancies when deformation mechanisms such as crystallographic dislocation motion become active. The vacancies can then combine with nitrogen impurities to form nitrogen vacancy (NV and / or NVN) defects and / or N3 optical centers, which produce the desired luminescent activity. In some embodiments, this occurs during conventional sintering of polycrystalline diamond with a metal catalyst (such as cobalt, which functions to promote intercrystalline diamond bonding during the HPHT process) or a non-metal catalyst / pressure-transmitting medium (such as carbonates and chlorides, which do not promote intercrystalline diamond bonding during the HPHT process). In some embodiments, the diamond granules obtained from the HPHT process may be heavily plastically deformed compared to solvent-catalyzed bonded polycrystalline diamond, with extensive NV and / or NVN defects and / or N3 optical centers, and weak diamond-diamond bonds. For example, in some embodiments, it is desired that the diamond granules undergo such plastic deformation to produce luminescence activity during the HPHT process without producing a fully sintered body. By avoiding a fully sintered body, downstream processes such as crushing the diamond granules to size them become easier and less energy-intensive, since they only need to break down the mechanically bonded diamond granules.

[0011] In some embodiments, the luminescent diamond disclosed herein can also be formed by subjecting a large amount of diamond or other ultrahard precursor grains to HPHT process using precursor material with inherent amount of silicon impurities.In such a case, luminescent diamond can be formed with silicon vacancies and optical centers, which act to make diamond grains luminescent active.Other impurities can also be used, which can generate vacancies that cause luminescence in appropriate spectrum (for example, visible, ultraviolet, infrared, near-infrared, etc.).

[0012] In some embodiments, the luminescent diamonds disclosed herein can also be formed by subjecting large amounts of diamond precursor grains to a HPHT process in the presence of a catalytic material. In such embodiments, the type of catalytic material used can be selected from a group including, but not limited to, Co, Fe, Ni, carbonate, Si, and combinations thereof to form polycrystalline diamond (PCD). In some embodiments, HPHT processing conditions for cobalt PCD can be within the range of temperatures of about 1300°C to 1500°C and pressures of about 5.0 GPa to 7.5 GPa. Furthermore, cobalt PCD is typically heat-treated in a vacuum at temperatures of 600°C to 700°C (e.g., after PCD formation, before and / or after sizing). The amount of catalytic material used can and will vary depending on factors such as the type of catalyst used, the desired luminescence output, and the particular end use.

[0013] In biological end uses, the presence of metallic materials within luminescent diamond may be undesirable and / or unacceptable for biocompatibility reasons, in which case the use of a non-metallic catalyst may be desirable. In some embodiments, the use of a non-metallic catalyst results in a PCD body with relatively high transparency or reduced opacity compared to PCD formed using a metal solvent catalyst. In some embodiments, non-metallic catalysts useful for making luminescent diamonds disclosed herein include carbonate catalysts, such as magnesium carbonate and calcium carbonate, which lead to the formation of carbonate PCD (CPCD). In some embodiments, the amount of such carbonate catalyst may be sufficient to form a fully sintered carbonate PCD body, for example, up to about 5 weight percent based on the total weight of the carbonate catalyst and diamond granules. Carbonate PCD appears inherently less dense / more transparent than cobalt PCD, which is believed to contribute to its high level of luminescence emission and intensity. In some embodiments, HPHT treatment of carbonate PCD may exceed temperatures of about 1700-3000°C and pressures of about 7.0 GPa. Additionally, carbonate PCD can be heat-treated in an inert or vacuum environment to temperatures of approximately 500-1300°C (e.g., after CPCD formation, before and / or after sizing). Similar to the above-described embodiment, HPHT treatment of CPCD results in plastic deformation of the diamond granules, creating vacancies or optical centers (e.g., nitrogen, silicon, etc.) that increase the level of luminescence activity / intensity compared to the precursor diamond granules. Some vacancies formed during HPHT may not combine with nitrogen, silicon, or other impurities during the plastic deformation process and may migrate to adjacent sites during heat treatment, creating additional vacancies or optical sites. The higher processing temperatures and high pressures involved in carbonate PCD can result in a higher degree of plastic deformation of the diamond granules, which can result in higher luminescence activity. The use of higher heat treatment temperatures can also contribute to the creation of additional defects or optical centers, and therefore higher luminescence activity.

[0014] 1 shows a schematic diagram of a diamond nanoparticle 100 that may provide light emission from vacancies 102, surface quantum dots 104, or a combination thereof. In particular, nitrogen, silicon, or other vacancies or optical centers may be dispersed throughout the body 106 of the diamond nanoparticle 100. Additionally or alternatively, quantum dots 104 may be formed on the surface of the body 106 of the diamond nanoparticle.

[0015] This hybrid approach of including both vacancies / optical centers and quantum dots can be used to increase luminescence. For example, luminescent nanodiamonds can lose significant intensity as the particle size decreases. For example, particle sizes below 100 nm, 50 nm, or even 35 nm may require higher luminescence intensity for some applications and may benefit from multiple types of luminescence. Therefore, having luminescence from two independent mechanisms may increase the overall intensity of the nanoparticle, potentially making it more visible in biological or other applications.

[0016] A method for producing quantum dots is shown schematically in FIG. 2, where quantum dot production involves placing a carbon source 208 in a liquid at 210 and subjecting the carbon source 208 to a laser pulse 212. In some embodiments, the laser pulse is a femtosecond laser pulse, which can vary in intensity, wavelength, etc., depending on the characteristics desired for a particular application or end use. The carbon source 208 can include diamond nanoparticles, diamond slag, or other materials described herein that contain nitrogen vacancies (e.g., NV, NVN, N), silicon vacancies, or other types of luminescent vacancy centers. In other embodiments, the carbon source 208 can include diamond particles that have not yet been processed to form vacancies. Quantum dots can be created, after which the particles can be compacted, deformed, and compressed (e.g., in a HPHT process) to form vacancy centers.

[0017] The claims and all statements are incorporated herein as part of the original disclosure.All features described in this disclosure, including statements and claims, can be combined with any other feature or component unless expressly stated to be mutually exclusive.The systems and methods for producing luminescent diamonds as described in U.S. Patent Application Publication US2022 / 0056337, U.S. Patent Application No. 18 / 005,115, International Patent Application PCT / US2022 / 052223, and International Patent Application PCT / US2023 / 023697, each of which is incorporated herein by reference in its entirety for all purposes.

[0018] When using luminescent diamond as disclosed herein in certain downstream applications, such as biological applications, it may be desirable to further treat or functionalize the luminescent diamond particles, such as nanodiamonds, to adapt the material for its intended use. It is understood that the methods and types of treatments that can be used to functionalize the luminescent diamond materials disclosed herein will vary depending on the specific end use. However, an exemplary functionalization process may include oxygen termination along the diamond surface to render it hydrophilic, which may be established through a series of surface oxidation procedures. Such oxygen-terminated functionalization may include providing a mixture of =O, -OH, -COOH, or -COC- groups on the surface. Other surface terminations may include hydrogen termination, halogenation, thermal annealing to create double bonds, and reduction to OH termination. A further type of functionalization may include the grafting or attachment of specific molecules to the surface of the treated diamond, provided that the diamond has been treated in a manner that promotes such attachment, with such molecules being selected to readily react with different biomolecules. Further types of functionalization can include biolabeling, which can occur through electrostatic (non-covalent) or covalent attachment between diamond particles and biomolecules.These are only a few ways that the luminescent diamond disclosed herein can be functionalized for use in biological applications, and it should be understood that other known approaches and techniques that can be used to functionalize luminescent diamond for specific biological applications are within the scope and spirit of the present disclosure.

[0019] Although several exemplary embodiments of luminescent diamonds have been described in detail above, those skilled in the art will readily understand that many modifications are possible in the exemplary embodiments without substantially departing from the scope of the claims and the present disclosure. For example, the luminescent diamonds disclosed herein are presented in the context of biological end uses. It should be understood that the luminescent diamonds disclosed herein may also be used in non-biological end uses where a desired improved level of luminescence intensity is useful or beneficial. Other potential applications for luminescent diamonds include, but are not limited to, magnetic sensors, high-resolution thermography, microscope sensor arrays, anti-counterfeiting measures, ion concentration monitoring, membrane potential measurement, optical traps, and strain / pressure sensors. Therefore, it should be understood that the luminescent diamonds disclosed herein are not intended to be limited to one particular end use application. Furthermore, it should be understood that references to "one embodiment," "an embodiment," "an example," or the like in this disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. For example, any element or feature described in connection with one embodiment herein may be combined with any element or feature of any other embodiment described herein.

[0020] Therefore, all such modifications and end uses of the luminescent diamond are intended to be included within the scope of the present disclosure as defined by the following claims. In the claims, means-plus-function clauses are intended to cover not only the structures described herein as performing the described function, and structural equivalents, but also equivalent structures. Thus, although nails and screws may not be structural equivalents in that nails use cylindrical surfaces to fasten wooden parts together, while screws use helical surfaces, in the context of fastening wooden parts, nails and screws may be equivalent structures. It is the express intention of the applicant not to invoke the claimed means-plus-function type for any limitation of any of the claims herein, except where the claim expressly uses the words "means for" with the relevant function.

Claims

1. 1. A luminescent diamond material comprising: Diamond particles, Internal void defects, surface quantum dots; The diamond particles Equipped with The luminescent diamond material, wherein the interior vacancy defects and the surface quantum dots produce luminescence in one or a combination of the visible spectrum, the ultraviolet spectrum, the infrared spectrum, or the near infrared spectrum.

2. 2. The luminescent diamond material of claim 1, wherein the internal vacancy defects are nitrogen defects.

3. 3. The luminescent diamond material of claim 2, wherein the nitrogen defects comprise NV defects, NVN defects, N3 optical centres, or a combination thereof.

4. 2. The luminescent diamond of claim 1, wherein the diamond particles exhibit a level of visible luminescence intensity in one or a combination of the blue, blue-violet, red, or green wavelength spectrums that exceeds that of the precursor diamond material used to form the luminescent diamond material.

5. 2. The luminescent diamond material of claim 1, wherein the diamond particles are mechanically interconnected and coupled with a pressure transmitting medium, and the luminescent diamond material is made by a high pressure / high temperature process, and comprises diamond granules in which the diamond particles have undergone plastic deformation.

6. 6. The luminescent diamond material of claim 5, wherein the pressure transmission medium is selected from materials that do not promote intercrystalline bonding of precursor diamond grains during the high pressure / high temperature process.

7. 6. The luminescent diamond material of claim 5, 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, and combinations or mixtures thereof.

8. 6. Luminescent diamond material according to claim 5, wherein the pressure transmission medium is selected from the group consisting of water-soluble, acid-soluble, or base-soluble materials.

9. 6. The luminescent diamond material of claim 5, wherein the pressure transmission medium is a chloride.

10. 2. The luminescent diamond material of claim 1, wherein the diamond particles are free of intercrystalline bonded diamond.

11. 2. Luminescent diamond material according to claim 1, wherein the diamond particles exhibit quantum dots only at the surface and the interior vacancy defects are dispersed throughout the diamond particles and at the surface.

12. 2. Luminescent diamond material according to claim 1, comprising more than 20 volume percent diamond and more than 5 volume percent transmission medium, based on the total volume of the luminescent diamond material.

13. 2. Luminescent diamond material according to claim 1, comprising more than 50 volume percent diamond and more than 10 volume percent transmission medium, based on the total volume of the luminescent diamond material.

14. 2. The luminescent diamond material of claim 1, which comprises a total graphite content of less than 15 weight percent, less than 10 weight percent, or less than 5 weight percent after being made by the high pressure / high temperature process without further processing.

15. 1. A method for making a luminescent diamond, comprising: subjecting a quantity of precursor diamond granules to high pressure / high temperature conditions at elevated temperatures in excess of 900°C in the presence of a pressure transmitting medium, thereby subjecting the diamond granules to plastic deformation and creating internal void defects within the diamond granules; subjecting the plastically deformed diamond granules to laser pulses, thereby forming quantum dots on the surface of the diamond granules; Including, the resulting diamond material exhibits a level of luminescence intensity in one or a combination of the visible, ultraviolet, infrared or near infrared spectrum that exceeds that of the precursor diamond granules; The method.

16. 16. The method of claim 15, wherein the resulting diamond material is free of intercrystalline bonded diamond.

17. 16. The method of claim 15, wherein the internal vacancy defects are one or more of nitrogen vacancy defects or silicon vacancy defects.

18. 16. The method of claim 15, wherein subjecting the plastically deformed diamond granules to a laser pulse comprises placing the plastically deformed diamond granules in a liquid.

19. 16. The method of claim 15, wherein the laser pulse is a femtosecond laser pulse.

20. 16. The method of claim 15, wherein the pressure transmission medium is selected from materials that do not promote intercrystalline diamond bonding during the high pressure / high temperature conditions and includes one or more of carbonates, nitrates, sulfates, phosphates, chlorates, perchlorates, acetates, chromates, oxalates, sulfides, ammonium compounds, hydroxides, oxides, cyanides, cyanates, dichromates, halides, or combinations thereof.

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