IL300686A - "Fingerprint" of particles by the voltage they create - Google Patents

Description

P-622992-IL FINGERPRINTING USING STRAIN IN PARTICLES FIELD OF THE INVENTION id="p-1" id="p-1" id="p-1"

[0001] The presently disclosed subject matter relates to methods of using the spin-strain coupling in nanoparticles comprising defects or color centers, to provide a unique fingerprint.

BACKGROUND id="p-2" id="p-2" id="p-2"

[0002] Fluorescent nanodiamonds have been used to a large extent in various systems due to their robust nature, inert properties, and the relative ease of modifying their surface for attachment to different functional groups. Within a given batch, however, each nanodiamond (ND) is indistinguishable from its neighbors and so far one could only rely on fluorescence statistics for some global information about the ensemble. [0003] Here, the present invention discloses measuring another layer of unique information, relying on the coupling between the strain in the ND and the spin degree-of-freedom in the nitrogen-vacancy center in diamond. The present disclosure shows that the large variance in axial and transverse strain can be encoded to an individual radio-frequency identity for a cluster of NDs. When using single NDs, this unique fingerprint can be tracked in real-time. From a completely different aspect, in clusters of NDs, this can already now serve as a platform for anti-counterfeiting measures. Furthermore, the origin of NDs can be verified since manufacturers can test what the unique fingerprint of a ND batch is. This has important applications in verification of, for example, international shipping components, long-haul cargo, and electronics.

SUMMARY id="p-4" id="p-4" id="p-4"

[0004] In one embodiment this invention provides a method comprising: dispersing particles on a substrate, wherein the particles comprise defects; and operating a detection system to extract strain parameters of the particles. [0005] In one embodiment of the method the substrate comprises any of the following selected from: silicon, glass, borosilicate glass, gallium arsenide, silicon carbide, indium phosphide, indium arsenide, silicon carbide, silicon oxide, germanium, graphene, aluminum oxide, quartz, pyrex, acrylic, polycarbonate, plastic, oxide layer and polymer-based materials, a metal or any combinations thereof. In one embodiment of the method the metal is selected from: gold, platinum, silver, titanium, nickel, chromium, aluminum, copper, tungsten and palladium or any combination thereof. In one embodiment of the method the substrate is soft or flexible. 30 P-622992-IL id="p-6" id="p-6" id="p-6"

[0006] In one embodiment of the method the particles comprise nanodiamonds. In one embodiment of the method the particles consist of nanodiamonds. In one embodiment of the method the particles are in crystal form. In one embodiment the crystals are single crystals. In other embodiments the crystals are polycrystalline. In one embodiment of the method the particles comprise any of the following selected from: crystals, silicates, calcites, diamonds, alkali halides, quantum dots, silicon, rare earth materials, boron nitride, zinc oxide and transition metal di-chalcogenides (TMDs) or any combination thereof. In one embodiment of method the 3-dimensional structure of the particles is selected from a list comprising: polyhedra, platonic solids, tetrahedron, hexahedron, octahedron, dodecahedron, icosahedron, cubes, rectangular solids, prisms, pyramids, cones, cylinders, spheres, spheroid, tubes, disks, filaments and ellipsoids or any combination thereof. In one embodiment of the method the size of the particles range between 1nm to 1mm. In one embodiment of the method the particles each comprise between 1 and 10defects. [0007] In one embodiment of the method linkers are attached on the particles, or on the substrate, or on both the particles and the substrate. In one embodiment of the method the linkers are selected from a group comprising: alkyl chains, aromatic groups, cyclic or branched hydrocarbons, fatty acids, hydrophobic polymers, hydroxyl groups (-OH), carboxyl groups (-COOH), amino groups (-NH2), sulfonic acid groups (-SO3H), phosphonic acid groups (-PO3H2), sulfate groups (-SO4), phosphate groups (-PO4), glycosidic linkages (-O-C-OH), hydrated metal ions, sodium (Na+), calcium (Ca+), carboxylic acid, amine-reactive groups, thiol-reactive groups, PEGylation linkers, imides and esters or any combinations thereof. In one embodiment of the method the alkyl chains are selected from: methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl and dodecyl or combinations thereof. In one embodiment of the method the aromatic group is selected from: benzene, naphthalene and anthracene or combinations thereof. In one embodiment of the method the substrate is at least partly hydrophobic, or wherein the particles are at least partly hydrophobic, or wherein both the substrate and the particles are at least partly hydrophobic. [0008] In one embodiment of the method the defects are color centers. In one embodiment of the method the defects are nitrogen vacancies. In one embodiment of the method the color centers are F-centers. In one embodiment of the method the nitrogen vacancies comprise only N isotopes, or only N or both N and N isotopes. [0009] In one embodiment of the method the detection system is an optical detection of magnetic resonance (ODMR) system. In one embodiment of the method the detection system carries out a microwave manipulation of the defect spin state of the particles. In one embodiment of the method strain parameters comprise axial strain and transverse strain. [00010] In one embodiment the method further comprises: 35 P-622992-IL plotting a histogram of the frequency shift and the split distribution for the particles; fitting a normal distribution of both the frequency shift and the split distribution; extracting a value for the mean frequency shift which translates to an axial strain; and extracting a value for the mean split distribution which translates to a transverse strain. [00011] In one embodiment this invention provides a method for generating a QR code, the method comprising: compiling data from the method of claim 1 across a sample comprising the particles; dividing the sample into digital pixels, wherein the pixels correspond to spatial locations on the sample; and assigning a value to each pixel corresponding to the value of the data that was measured in the pixel across the sample. [00012] In one embodiment of the method the data is selected from: fluorescence, effective strain, frequency shift, axial strain and split distribution or any combination thereof.

BRIEF DESCRIPTION OF THE DRAWINGS id="p-13" id="p-13" id="p-13"

[00013] In order to better understand the subject matter that is disclosed herein and to exemplify how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which: [00014] Figure 1A is a schematic illustration is a sketch of a nanodiamond, an enlarged section of which is shown in Figure 1B which shows a nitrogen vacancy center defining the direction of the strain field along (axial) and perpendicular to (transverse) as a result of pre-existing conditions due to the method of preparation e.g., milling. [00015] Figure 2 shows a typical optical detection of magnetic resonance (ODMR) measurement for a nanodiamond. The two vertical lines shows the axial strain leading to a shift from the unstrained zero-field splitting (in this case 4.1 MHz) and the splitting of the ODMR dip into two dips at zero magnetic field is a signature of the transverse strain (11.35 MHz). [00016] Figure 3 is a schematic illustration of histograms of the full cohort of nanodiamonds (247 in total), in one example. In each histogram, the fit to a normal distribution is plotted (curved line). Figure 3A shows axial strain, with a mean value of -4.43MHz, and Figure 3B shows transverse strain, with a mean value of 11.26 MHz. [00017] Figure 4is shows visualization of the unique dispersion of each nanodiamond sample. The scan range, limited by the piezo scanner, is 80 × 80 µm. Figure 4A shows a confocal scan with white dots denoting the positions of the nanodiamonds on which the ODMR measurements were performed, and Figure 4B shows a corresponding transverse strain map, where the 80 × 80 P-622992-IL image from Figure 4A was sectioned into 7 rows and 7 columns, such that the different nanodiamonds were binned into one out of 49 pixels. [00018] Figure 5 shows an SEM image of a typical nanodiamond dispersion, which corresponds to confocal images such as the one plotted in ( Figure 4A ). [00019] Figure 6 depicts a graphical representation of a calculation of an ODMR measurement which consists of n = 800 different nitrogen-vacancies, with their shift and splitting parameters drawn from a normal distribution function based on the mean and standard deviation values extracted above (and shown in Fig. 3). The self-consistency of the plot is shown. [00020] Figure 7quantifies the ability to distinguish between two neighboring nanodiamond clusters. Shown are random draws of two frequencies based on the normal distribution of the measurements in Fig. 3 for four different acquisition times (2500, 250, 100 and 25 seconds). The dashed lines provide a measure of fidelity, whereby one can estimate the needed physical parameters (measurement time, standard deviation of shift) to obtain a certainty higher than 80% (chosen arbitrarily) of having the difference between the two frequencies larger than the standard deviation. [00021] Figure 8 shows a dynamic light scattering measurement of nanodiamonds used in the experiments reported herein. [00022] Figure 9shows a scanning electron microscope image of nanodiamonds used in the experiments reported herein. The drop-casting method results in a rather tight packing of the nanodiamonds on the glass substrate, in clusters larger than the confocal microscope’s focal area. [00023] Figure 10 represent three ODMR spectra from a batch of 247 confocal spots taken throughout the measurement. [00024] Figure 11 shows an example of a QR code which matches data parameters for nanodiamonds for verification purposes. [00025] Figure 12Ashows the basic structure of the planar waveguide on a glass substrate. Figure 12B shows the waveguide profile showing the photoresist thickness. [00026] For simplicity and clarity of illustration, elements shown in the figures are not necessarily drawn to scale, and the dimensions of some elements may be exaggerated relative to other elements. In addition, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.

DETAILED DESCRIPTION id="p-27" id="p-27" id="p-27"

[00027] There exist several types of site-labeled markers in nanotechnology and material chemistry, and in a more general way as a means to provide a distinct signature or signal from a sample. Fluorescent markers are a good example of that, especially the extensive family of dyes P-622992-IL but also nanoparticles. Specifically, fluorescent nanodiamonds (FND) constitute by now an established technique of marking specific locations by a tailored functionalization of the nanodiamonds’ surface groups. Due to their robust and inert nature, FNDs are considered as highly stable emitters with a wide range of functional groups, applicable to many systems. [00028] Nevertheless, the fluorescence of one nanodiamond (for the same number of emitters per nanodiamond) is indistinguishable from that of another. That is to say, the number of photons emitted per second from one nanodiamond (ND) will be similar to that of another. It calls, then, for a class of such markers which one could in fact tell them apart. The present disclosure shows, that by using NDs hosting nitrogen-vacancy (NV) centers, this feature comes about almost naturally, heralded by the spin-strain interaction of the NV with its host diamond matrix, providing an additional information layer to the fluorescence data, in a way akin to multicolor fluorescent dyes. As will become apparent, the principles disclosed for NDs and their NVs can be extended to other particles and their defects. [00029] While for many experiments, strain is a hindrance to be overcome or removed, the present disclosure shows how knowledge of its properties can be in fact a boon when using NDs. Materials and Properties[00030] The presently disclosed subject matter is not limited to NDs. In some embodiments the method for detecting strain can be for any particle comprising a color-center. The materials used herein are often on the nano- or micro-scale and are therefore also referred to herein as "particles", "nanoparticles", "microparticles", "materials", "nanomaterials" and "micromaterials". In some embodiments groups of particles are referred to interchangeably as "clusters" or "groups of" particles or "a plurality of" particles or referred to as particles generally in the plural. [00031] In some embodiments the shape of the particle does not affect the outcome of the resulting spectra. However, for different purposes, a variety of solid material shapes may be utilized, all of which are compatible for use in the present invention. In one embodiment the particle is a 3-dimensional structure. For example, granular particles. In some aspects, fingerprinting utilizes a unique value of a material’s properties to distinguish it from others. Some of these properties include the material composition, defect locations, atomic orientation, strain, types of defects, all of which can be used alone or in combination to provide a unique spectrum. [00032] In some embodiments the material or particle can take on any of the following dimensional structures: polyhedra, platonic solids, tetrahedron, hexahedron, octahedron, dodecahedron, icosahedron, cubes, rectangular solids, prisms, pyramids, cones, cylinders, spheres, spheroid, tubes, disks, filaments, and ellipsoids. It is important to state that nano- or micro-particles often do not form perfect geometric shapes under normal experimental fabrication procedures. As 35 P-622992-IL such the actual solid shape of particles, although they may comprise deviations from an idealized shape, are nonetheless considered for use in the present disclosure. In some embodiments, the particles deviate from a perfect geometric shape by 1% or 5% or 10% or 20% or 50%. [00033] In some embodiments the size of the particles is in the order of nanometers. In some embodiments the size of the particles is in the order of micrometers. "Size" refers to at least one of the spatial dimensions e.g., the diameter of a spherical particle, the length of a nanotube, the length of one side of a cuboid, etc. In some embodiments the particle size ranges between 1nm to 1mm. In some embodiments the particle size ranges between 1mm to 1cm. [00034] In some embodiments the particle size ranges between 1 to 1000nm. In some embodiments the particle size ranges between 1 to 500nm. In some embodiments the particle size ranges between 1 to 200nm. In some embodiments the particle size ranges between 1 to 100nm. In some embodiments the particle size ranges between 1 to 100nm. In some embodiments the particle size ranges between 1 to 5nm. In some embodiments the particle size ranges between 5 to 10nm. In some embodiments the particle size ranges between 5 to 50nm. In some embodiments the particle size ranges between 50 to 100nm. In some embodiments the particle size ranges between 100 to 200nm. In some embodiments the particle size ranges between 200 to 500nm. In some embodiments the particle size ranges between 500 to 1000nm. [00035] In some embodiments the particle size ranges between 1 to 100µm. In some embodiments the particle size ranges between 1 to 50µm. In some embodiments the particle size ranges between 1 to 10µm. In some embodiments the particle size ranges between 10 to 20µm. In some embodiments the particle size ranges between 20 to 50µm. In some embodiments the particle size ranges between 50 to 100µm. In some embodiments the particle size ranges between 100 to 1000µm. [00036] As used herein a "color center" in a crystal is a defect or impurity that changes the optical properties of the crystal. As such, and in some embodiments, the terms "color center", "center", "defect" and "impurity" are used interchangeably herein. In some embodiments the color center is one that shows optical detection of magnetic resonance. In principle, any material that is a magnetic resonance optical emitter can be used as proxy to determine the strain, as described herein. In one embodiment the crystal is polycrystalline. In one embodiment the crystal is a single crystal. These color centers can cause absorption or emission of light at specific wavelengths. In some embodiments the material is a crystal. In some embodiments the material is a crystal that comprises at least one defect. In some embodiments the material is an alkali halide. In some embodiments the material is selected from a list comprising: crystals, silicates, calcites, diamonds, alkali halides, quantum dots, silicon, rare earth materials, boron nitride, zinc oxide and transition metal di-chalcogenides (TMDs) or any combination thereof. Non-liming examples of TMDs 35 P-622992-IL include: molybdenum disulfide, tungsten disulfide, niobium selenide, titanium disulfide, tantalum disulfide, rhenium disulfide, nickel selenide, ruthenium selenide, chromium selenide and zirconium disulfide. Examples of rare earth materials include: Lanthanum, Cerium, Praseodymium, Neodymium, Promethium, Samarium, Europium, Gadolinium, Terbium, Dysprosium, Holmium, Erbium, Thulium, Ytterbium, Lutetium and Yttrium. In one embodiment the material comprises yttrium iron garnet (YIG). In some embodiments the particle comprises any of the following: CdSe, CdTe, ZnO, TiO2, Si, GaN, InP, GaAs, SiC, AlN, ZnS, ZnSe, CdS, Al2O3 and GaP or any combinations thereof. In some embodiments the particles comprise semiconducting materials. [00037] One examples for improved fingerprinting is combinations of different particle materials (e.g., NDs and TMDs) being dispersed on surfaces with their respective strain parameters extracted therefrom with a detection system. Since the nature of the defects and/or color centers will differ for each respective particle material, and batch, this can be used as additional information for better counterfeiting protection. [00038] The location of the defect within the particle has an influence on the optical signal. Generally, the size of the nanoparticle and the location of the defect therein has a compensatory effect. In some embodiments, the defect is near the surface of the nanoparticle. In other embodiments the defect is embedded within the nanoparticle. For example, in a spherical nanoparticle a defect may be closer to the surface than it is to the center of the nanoparticle or otherwise, the defect may be closer to the center of the nanoparticle in comparison with its surface. [00039] In some embodiment the color center comprises a defect. In some embodiment the color center consists of a defect. In some embodiments any defect which shows optical detection of magnetic resonance is considered. The defect may comprise any of the following non-limiting examples: vacancy defect, interstitial defect, substitutional defect, Schottky defect, Frenkel defect or combinations thereof. [00040] In some embodiments the color center is a nitrogen-vacancy (NV). In some embodiments the color center is a nitrogen-vacancy in diamond. In some embodiments the color center is a nitrogen-vacancy in a nanodiamond. As used herein "nanodiamond" generally refers to diamonds wherein at least one spatial dimension is in the nanoscale. Since the present invention extends to any material that registers an optical detection of a magnetic resonance, materials are referred to herein interchangeably. In some embodiments such a material is referred to as "material", "particle" or "nanodiamond" but since the method of detection utilizes the same principle, the terms are interchangeable. It will be understood by an expert that there are slight differences between these materials, however, the guiding principle of optical detection of magnetic resonance is the same. 35 P-622992-IL id="p-41" id="p-41" id="p-41"

[00041] In some embodiments, the NV is provided in any orientation within a lattice. [00042] In some embodiments the color center is an F-center. As used herein an "F-center" is a type of defect in a crystal lattice and is formed when an electron is trapped in a vacancy or an interstitial site. In some embodiments the color center is an F-center in alkali-halides. Alkali halides are composed of an alkali metal cation (e.g., Li+, Na+, K+, Rb+, Cs+) and a halide anion (e.g., F-, Cl-, Br-, I-). Non-limiting examples of alkali halides include: Lithium fluoride (LiF), Sodium chloride (NaCl), Potassium chloride (KCl), Rubidium chloride (RbCl), Cesium chloride (CsCl), Lithium bromide (LiBr), Sodium bromide (NaBr), Potassium bromide (KBr), Rubidium bromide (RbBr), Cesium bromide (CsBr), Lithium iodide (LiI), Sodium iodide (NaI), Potassium iodide (KI), rubidium iodide (RbI) and cesium iodide (CsI). [00043] Regarding nanoparticles, and in particular nanodiamonds, they are typically provided as a ready-made powder and/or otherwise dissolved in a solvent. In one embodiment, nanodiamonds are dissolved in water. The number of nitrogen-vacancies (NVs) in a ND can vary depending on the preparation method. Milling and/or grinding of diamonds is often used to produce NDs. The diameter of NDs can be controlled by controlling the milling time. For example, the longer the duration of milling the smaller the NDs become. [00044] NVs can be introduced into NDs by several methods. One method involves the introduction of nitrogen into crystals during growth. This is followed by electron bombardment or bombardment by light ions, creating vacancies in the crystal. At this point vacancies and nitrogen are not bound, requiring further processes to bring them together. High temperature vacuum annealing (e.g., at about 800°C) causes the vacancies to move until they meet nitrogen atoms, forming stable NV centers. A second method for generating NV centers utilizes post-growth nitrogen-ion implantation, after which a similar high temperature vacuum annealing process is carried out to form stable NV centers. [00045] In some embodiments the ND comprises one NV. In some embodiments the ND comprises at least one NV. In some embodiments the ND comprises between 1 and 5 NVs. In some embodiments the ND comprises between 1 and 10 NVs. In some embodiments the ND comprises between 5 and 10 NVs. In some embodiments the ND comprises between 10 and 1NVs. In some embodiments the ND comprises between 10 and 20 NVs. In some embodiments the ND comprises between 20 and 50 NVs. In some embodiments the ND comprises between 50 and 100 NVs. In some embodiments the ND comprises between 1 and 1000 NVs. [00046] In some embodiments the particle comprises one defect. In some embodiments the particle comprises at least one defects. In some embodiments the particle comprises between 1 and defects. In some embodiments the particle comprises between 1 and 10 defects. In some embodiments the particle comprises between 5 and 10 defects. In some embodiments the particle 35 P-622992-IL comprises between 10 and 100 defects. In some embodiments the particle comprises between and 20 defects. In some embodiments the particle comprises between 20 and 50 defects. In some embodiments the particle comprises between 50 and 100 defects. In some embodiments the particle comprises between 1 and 1000 defects. [00047] The nitrogen isotope comprised within a NV can be of various types. Different isotopes of nitrogen can be used. Typically, and in one embodiment, N is comprised in the NV. In another embodiment N is comprised in the NV. In other embodiments NVs of both N and N are comprised within a single ND. In other embodiments NVs of both N and N are comprised within a batch of NDs. In a high resolution measurement, the difference between N and N can be detected using the methods provided herein. [00048] In some embodiments the ND comprises C. In other embodiments the ND comprises C. In some embodiments the ND comprises both C and C. The methods described herein can be used to determine the isotopic composition of nanoparticles. The signal-to-noise ratio will vary for C versus C, providing a signature for both. For example, if the nearest neighbor to a NV is either C or C the resulting strain is different. [00049] In some embodiments, the particles used have different diameters. The diameter of the particle and the defects comprised therein can affect the optical, electronic and magnetic properties and signatures of the particles. Thus, utilizing particles, e.g., NDs, of different diameters can be used for unique fingerprinting techniques. For example, the local environment of a NV in a ND can result in different electronic and magnetic properties for different diameters of NDs. For larger NDs, there are instances where more carbon atoms surround the NV which influences the way electromagnetic fields interact with such a center. Atomic packing will be different with NDs of different diameters and with different numbers of NV and in different locations therein. In one embodiment, a larger ND will experience a more distinct signature shift in the optical absorption, or magnetic resonance, in comparison with a smaller ND. In larger NDs, light scattering behaves differently due to the interaction between carbon atoms and NVs. [00050] NVs on the surface in comparison with NVs buried within a ND will show different behaviors with regards to the optical absorption and magnetic resonance. Furthermore, the stability of NVs varies between surface- and buried-NVs. Thus a ND can be selected with a particular number of NVs, at particular locations within the ND, for unique fingerprinting. [00051] In view of the above, a wide range of materials, and their properties, can be utilized for the purposes of determining unique fingerprints and features of particular groups of particles.

P-622992-IL Methods of Determining Strain[00052] General method steps are now outlined. Embodiments and examples of which will be outlined in turn. The present invention is directed towards a method for determining the strain of nanoparticles. Typically, but not exclusively, the nanoparticles are NDs. One method of determining the strain, utilizes the ND’s NVs. Without being bound to theory, the local strain that the NV center experiences in a ND does not change. This this especially true if storage conditions have not drastically changed such that it may alter the chemical composition of the atoms within the NDs themselves. [00053] The term "strain parameters", as used herein, refers to any information related to strain, or proxies thereof, such as any of the following, but not limited to: effective strain, axial strain, transverse strain, coupling of the strain in a particle and the spin degree-of-freedom in a defect in a color center, coupling of the strain in a ND and the spin degree-of-freedom in a color center, coupling of the strain in a ND and the spin degree-of-freedom in a NV, etc. [00054] The present invention provides a method for determining a material characteristic, said method comprising: dispersing particles on a substrate, wherein said particles comprise defects; extracting strain parameters from the particles by a detection system, wherein said strain parameters comprises axial strain and transverse strain components; and generating a value for the effective strain unique to a batch of the particles. [00055] In one embodiment the detection system is an ODMR system. [00056] In one embodiment the method comprises: dispersing particles on a substrate, wherein the particles comprise defects; and operating a detection system to extract strain parameters of said particles. [00057] Operating a detection system refers to any of the operations required to determine any of the strain parameters disclosed herein. In some embodiments the detection system is an ODMR system. In some embodiments the particles are NDs with NVs. In some embodiments the defects are color centers. [00058] In one embodiment the presently disclosed subject matter provides a method comprising: dispersing particles on a substrate, wherein the particles comprise defects; and operating a detection system to extract strain parameters of said particles. [00059] The present invention further provides a method for determining the strain of particles that comprise at least one defect, said method comprising: dispersing a plurality of particles on a substrate; measuring the strain of the at least one defect for the particles. 35 P-622992-IL id="p-60" id="p-60" id="p-60"

[00060] In some embodiments the defect is a color center. [00061] More specifically, the present invention provides a method for determining the strain of NDs which comprise at least one NVs, said method comprising: providing a solution comprising a plurality of NDs; dispersing the plurality of NDs on a substrate; measuring the strain of the NV spin state for a plurality of NDs; plot a histogram of the frequency shift and split distribution of the plurality of NDs; obtain values for the mean shift and split value. [00062] NDs are first acquired from a source: either they are milled/ground from large diamonds or they are procured as a powder and dissolved in a solution. In one embodiment the solution comprises water. The NDs are then disposed on a substrate. In some embodiments the terms "disposed" and "dispersed" are used interchangeably, both refer to placing particles on a substrate. In some embodiments the NDs are disposed by spin coating on the substrate. In other embodiments, after depositing the NDs, the substrate is further dried with a vacuum or by a nitrogen flow. [00063] The substrate onto which NDs are disposed is non-limiting. In some embodiments, the substrate is a hard surface. In other embodiments the substrate is soft or flexible. Non-limiting examples of soft or flexible material are: rubber, silicone, plastic, textiles, leather, cloth, paper, foam and elastomers or any combinations thereof. In some embodiments the substrate comprises any of the following selected from: silicon, glass, borosilicate glass, gallium arsenide, silicon carbide, indium phosphide, indium arsenide, silicon carbide, silicon oxide, germanium, graphene, aluminum oxide, quartz, pyrex, acrylic, polycarbonate, plastic, oxide layer and polymer-based materials, a metal or any combinations thereof. In one embodiment the metal is selected from: gold, platinum, silver, titanium, nickel, chromium, aluminum, copper, tungsten and palladium or any combination thereof. [00064] The hydrophobicity of the surface determines the nature of the dispersion of the NDs in a solution. With a hydrophobic substrate NDs (or other such nanoparticles) cluster together. Whereas the dispersion of NDs on hydrophilic substrates will be less clustered. Thus controlling the hydrophobicity of the surface enables the control of the clustering and dispersion of the NDs disposed thereon. In one embodiment the surface of the substrate is cleaned before ND dispersion thereon. In one embodiment the cleaning process comprises cleaning the substrate with solvents. For example, solvents may include ethyl acetate, ethanol, acetone and isopropanol. Cleaning with solvents may further comprise sonication. In another embodiment the substrate is cleaned by piranha solution. In another embodiment the substrate is cleaned with plasma treatment. In another embodiment the substrates are cleaned with UV ozone. Cleaning the substrates in any of these 35 P-622992-IL methods controls the hydrophobicity/hydrophilicity of the substrates. A person implementing the cleaning process will select the process according to the extent of hydrophobicity required. In some embodiments the substrate is at least partly hydrophobic. In some embodiments, the particles are at least partly hydrophobic. In some embodiments both the particles and the substrate are at least partly hydrophobic. The hydrophobicity, or the at least partial hydrophobicity, being controlled by selective linker binding. [00065] All linkers referred to herein can be attached on the particles, or on the substrate, or on both the particles and the substrates. [00066] Another method of controlling the hydrophobicity of the substrate is by the addition of linkers on the surface of the substrate. In some embodiments the NDs are dispersed on a hydrophobic substrate. In some embodiments a hydrophobic layer is deposited on the substrate. In some embodiments the hydrophobic layer comprises: alkyl chains, aromatic groups, cyclic or branched hydrocarbons, fatty acids and hydrophobic polymers. In some embodiments the alkyl chains are selected from: methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl and dodecyl or combinations thereof. In some embodiments the aromatic group is selected from: benzene, naphthalene and anthracene or combinations thereof. In some embodiments the hydrophobic layer is a monolayer. In some embodiments the hydrophobic layer is a multilayer. In some embodiments the substrate is at least partly hydrophilic. [00067] In some embodiments the NDs are dispersed on a hydrophilic substrate. In some embodiments the hydrophilic substrate comprises any of the following: hydroxyl groups (-OH), carboxyl groups (-COOH), amino groups (-NH2), sulfonic acid groups (-SO3H), phosphonic acid groups (-PO3H2), sulfate groups (-SO4), phosphate groups (-PO4), glycosidic linkages (-O-C-OH), hydrated metal ions, sodium (Na+), calcium (Ca+). In some embodiments the hydrophilic layer is a monolayer. In some embodiments the hydrophilic layer is a multilayer. [00068] In some embodiments, the position and location of nanoparticles, e.g., NDs, on substrates is further enabled by coating the nanoparticle itself with linkers. This provides a platform for selective binding of the nanoparticles in site-specific locations on the substrate. For example, NDs can be coated with any of the following linkers: carboxylic acid, amine-reactive groups, thiol-reactive groups, PEGylation linkers, imides, and esters. In some embodiments, NDs are coated with any of the hydrophobic or hydrophilic linkers disclosed herein. In some embodiments, the interaction between the nanoparticles and the substrate is covalent. In some embodiments the interaction between the nanoparticles and the substrate is electrostatic. In some embodiments the interaction between the nanoparticles and the substrate is a van der Waals interaction. As will become apparent selective binding of nanoparticles on particular locations on surfaces is often desirable for the purposes of counterfeiting and verification. For example: a user 35 P-622992-IL can label a specific region of a device with NDs that are bound on a patch which an end-user is able to measure and check its authenticity following a long-haul cargo journey. A user can use multiple batches of immobilized NDs on a single device, but in different locations, and with different fingerprints characteristics, for further uniqueness. [00069] In one embodiment the substrate is functionalized with linkers. In another embodiment the nanoparticle is functionalized with linkers. In another embodiment both the nanoparticle and the substrate are functionalized with linkers. When both the substrate and the nanoparticles are functionalized, in one embodiment, the linkers are the same. When both the substrate and the nanoparticles are functionalized, in one embodiment, the linkers are the different. Strain and Optically Detected Magnetic Resonance (ODMR)[00070] When materials are subject to a force, they deform or strain. Stress is defined as the applied force per unit area, this force can be applied in three different ways: tension, compression, and shear. In one embodiment, and as used herein "strain" is a unitless quantity to the relative elongation of the original length when no stress is applied. In reference to particles, and in some embodiments "strain" refers to the deformation or distortion of a lattice (e.g., in a crystal) structure of a material caused by external forces. With regards to color centers, the strain refers to the change in the crystal lattice structure caused by mechanical, thermal, or chemical stress that results in the formation of color centers. These color centers can absorb light at specific wavelengths and result in the changes in optical properties. The changes in optical properties (e.g., emission, absorption) may depend on the nature of the color center and the amount of strain present in the lattice. The strain can thus affect the electromagnetic properties of NDs. [00071] For the purposes of example, NDs and their NVs will be used to describe how particles and their defects can be used to measure strain. In the presently disclosed subject matter the NV system Hamiltonian is described and wherein the relevant spin-strain terms are introduced to the experimental apparatus. A method is presented to distinguish between different clusters of NDs dispersed on a substrate by measuring the effective (axial and transverse) strain components or parameters. This provides an independent metric of characterization for the strain in a batch of such nanoparticles and, more importantly, provides a pathway for a generating a unique frequency identifier for this batch. For example, a radio frequency or microwave frequency identifier. [00072] The latter comes about from the method by which the strain is measured, namely microwave manipulation of the NV spin state and measurement by optical detection of magnetic resonance, or ODMR. Starting from the ground state Hamiltonian of the NV, ℋ = ( ? ??+ ℇ? ) ? ? 2− ℇ? ( ? ? 2− ? ? 2) + ℇ? ( ? ? ? ? + ? ? ? ? ) + ? ? ? ? ∙ ? (1) 35 P-622992-IL id="p-73" id="p-73" id="p-73"

[00073] The eigenvalues are calculated, reaching an expression for the effect axial and transverse strain on the transition frequencies of the NV in a given ODMR measurement, namely: ? 1 , 2= ? ??+ ℇ? ± √ ℇ⊥+ ? ? ? ? ? (2) id="p-74" id="p-74" id="p-74"

[00074] Here ℏ was taken to be 1, Dgs = 2.87 GHz is the NV’s zero-field splitting, ℇ = dgs ( E + σ) is the energy of interaction with electric and strain fields with dgs the electric dipole moment of the NV. Typical literature values for the axial ( ℇ? (σ)) and transverse ( ℇ⊥(σ)) change of interaction energy per unit strain, are ℇ? (σ), ℇ⊥(σ) = (20.60, 9.38) GHz. It should be noted that the values tend to be of the same order of magnitude. The axial strain direction is captured graphically in Fig. 1A and Fig. 1B, where the axial strain is defined to be along the N-V axis while the transverse one is perpendicular to it (not shown). [00075] Regarding the extraction of the strain parameters, information can be extracted in a number of ways. Without being bound to theory, the lattice strain coupling to the NV electron spin properties, where an axial strain effectively modifies the zero field splitting, and the transverse strain lifts the degeneracy of the two degenerate states of the NV spin, results in a shift and a splitting of the optically detected magnetic resonances. These values have a distribution variance which gives uniqueness to each cluster of NDs, making them distinguishable from each other. In some embodiments the terms "shift" and "frequency shift" are used interchangeably. [00076] In an ODMR measurement the "split" and "shift" refer to two aspects of the magnetic resonance signal. The "split" refers to the separation or "splitting" of the magnetic resonance signal into two or more peaks, each corresponding to a different magnetic state. "Split" or "splitting" is also referred to as "split distribution" herein. This splitting occurs in the presence of a magnetic field and is due to the Zeeman effect, which causes the energy levels of the magnetic system to shift in response to the field. The "shift", refers to the change in the resonant frequency of the magnetic resonance signal in response to changes in the magnetic field of other parameters. This shift is related to the changes in the magnetic properties of the sample and can be used to obtain information about properties of the sample. [00077] A typical ODMR from the dispersed NDs (see Example 1) is plotted in Fig. 2, showing a shift from Dgs (axial strain) of −4.10 ± 0.17 MHz and a split (transverse strain) of 11.35 ± 0.MHz (the Lorentzian linewidth, Γ, was 7.1 ± 0.2 MHz). Following a central premise of this disclosure, the ODMR spectra is acquired from a large cohort of points-of-interest (POI) in different regions-of-interest (ROI) on our sample. In Fig. 3 a histogram is plotted of both the frequency shift and split distribution among 247 different POIs. A mean shift of -4.43±1.26 MHz 35 P-622992-IL and split of 11.26±1.63 MHz is obtained. These, in turn, translate to a relative strain of 0.02% in the axial direction and 0.12% in the transverse direction, in agreement with prior reports on bulk diamonds. The minimum number of POIs required to plot the histogram is that which a normal distribution can be plotted over, with an acceptable degree of accuracy. For example, where the mean value of the normal distribution is repeatable to a deviation of 1% or 5% or 10% or 20% or 50%. [00078] These results suggest, that indeed, a collection of NDs dispersed on a glass substrate is distinguishable from such a subsequent batch by correlating the strain parameters with the positions of the NDs. To visualize this idea, the plot in Fig. 4A an 80 × 80 µm confocal map is plotted with white dots representing the positions of NDs at which their ODMR spectra was measured and extracted the strain parameters. The latter are plotted, corresponding to the (x,y) position in the confocal map, in Fig. 4B. All pixels with no data (no ND) were given the mean value of the strain for reasons of color offsetting. Figure 4 demonstrates the potential of this method: One can assign a unique two-dimensional color code (which can of course be translated to a standardized one such as the QR code, see for example Figure 11), that can be verified against an existing database. Since the strain distribution is completely random, a large cohort will render the possibility of falsifying the reading unlikely. An additional parameter such as strain can add more security when applying such measures to anti-counterfeiting. [00079] Due to the uniqueness of such data for each batch of NDs containing NVs, or particles containing defects, the likelihood of two batches of particles having the same data distribution is small. Thus "unique" refers to a data set that is unlikely to be repeated. [00080] Importantly, the results show that in combination with real-time ODMR tracking, one can unambiguously identify individual NDs in different environments. [00081] The ODMR spectra that was used to calculate the mean axial and transverse strain was measured on a sample with a relatively high packing ratio (see Fig. 5 and Examples), which indicates that an individual ODMR spectrum may include the contribution of several NDs and hence, NVs. Three such representative ODMR spectra are plotted in Figure 10. To check the consistency of the conclusions, Figure 6 shows a calculation of an ODMR measurement which consists of n = 800 different NVs, with their shift and splitting parameters drawn from a normal distribution function based on the mean and standard deviation values extracted above (and shown in Fig. 3). The number, n, was chosen so as to correspond to the approximate number of NDs in a confocal spot ( ∼ 1 × 1 µm). Due to the relatively narrow distribution of strain, even a large cluster of NDs can be seen (at zero magnetic field) and yields a distinct ODMR shift and split. It is noted that the use of such clusters (or ensembles of NVs) is quite ubiquitous and in many cases makes it easier to acquire the signal. This allows one to now quantify how well one can distinguish between 35 P-622992-IL two such neighboring clusters, with their ODMR spectra modified by the shift and splitting randomly drawn from the normal distribution. For simplicity, just the frequency shift is first considered, and one thousand pairs of these clusters are drawn using the mean and standard deviation values from Fig. 3A. The first cluster’s shift from 2.870 GHz is denoted as ω 1 and the second, ω2. The difference between the two are compared, ∆ω=|ω1−ω2|, to the standard deviation (γ) of the ODMR measurement for a given acquisition time. For example, γ = 0.12 MHz for a total acquisition time of T = 2500 s. Each of the one thousand draws is labelled with "1" if ∆ω > γ (distinguishable) and "0" otherwise. The draws for four different acquisition times (2500s, 250s, 100s and 25s) are plotted in Fig. 7. For example, for a (arbitrary) fidelity threshold of 80%, it is possible to tell apart neighboring clusters for a measurement time of 250s per ODMR if the standard deviation of the normal distribution is larger than ∼ 1.2 MHz. This can be extended to the spin-strain relation of individual NDs having on average a single NV. Moreover, there is a strong dependence of the mean value of both axial and transverse strain on the diameter of the ND, and accordingly, such a comparison is beneficial for better understanding of both the statistical distribution itself and the origin of the strain. [00082] Without being bound by theory, ODMR is a spectroscopy technique that uses light to detect changes in the magnetic properties of a sample. It works by optically detecting changes in the polarization of a sample caused by magnetic resonance. In an ODMR system, a sample is placed in a magnetic field and a microwave of radio frequency (RF) is applied to the sample to excite the magnetic moment/s. The magnetic moment/s precess in the magnetic field and the frequency of precession is proportional to the magnetic field strength. The present invention not only works with ODMR but any system that can detect a magnetic resonance. For example the detection system can utilize at least one of the following detection systems: an ODMR system, a nuclear magnetic resonance (NMR) system, electron spin resonance (ESR) and electron paramagnetic resonance (EPR) system. [00083] In some embodiments the optical detection system is an optical detection of magnetic resonance (ODMR) system. In some embodiments a system that detects magnetic resonance is used as the detection system. [00084] In order to generate a value, in some embodiments, for the strain in a defect, the methods disclosed herein comprise: plotting a histogram of the frequency shift and the split distribution for the particles; fitting a normal distribution of both the frequency shift and the split distribution; extracting a value for the mean frequency shift which translates to an axial strain; and extracting a value for the mean split distribution which translates to a transverse strain.

P-622992-IL id="p-85" id="p-85" id="p-85"

[00085] The normal distribution is considered any means to find a mean value for a particular distribution. Typically, a Gaussian ("normal") distribution is used. However, other types of fitting parameters may be used to fit the frequency shift and split distribution, or other strain parameter, for example a log-normal distribution, where appropriate. For a normal distribution, extracting a value for the mean is carried out by reading the maximum point on the normal distribution graph. In some embodiments the extraction of a particular value involves further fitting a distribution to a particular equation or model and extracting the appropriate coefficient, as disclosed herein. QR codes from Data[00086] QR codes are two-dimensional barcodes that are generated by encoding data in a pattern of black and white squares. The data is represented as binary values with, for example, black squares representing a value of 1 and white squares representing a value of 0. The binary data is divided into several data blocks, which are then translated into square patterns in the QR code e.g., pixels. The position and size of the squares are defined within the QR code. When a QR code is scanned, the binary pattern is interpreted back into the original data, allowing the information to be quickly and easily read and decoded. Thus an intensity map (for example as shown in Figure 4A) can be converted into a binary map of pixels wherein above a certain threshold the value of the pixel is ‘1’ and below the threshold the value of the pixel is ‘0’. In some embodiments, a grayscale QR code is generated from the data acquired, for example strain parameters. [00087] Data that is collected from dispersed particles on substrates and can be converted into a QR code for verification purposes. For example, a confocal map provides spatial information, which selectively illuminates a single plane of a sample and captures the light that is emitted or reflected from that plane. The result is a high-resolution image that can reveal details about the structure and composition of the sample. A QR code can be generated purely from the data provided by confocal microscopy. Additionally, ODMR measurements provide an additional piece of information, namely strain parameters, which can further be encoded into a QR code for additional authenticity and uniqueness. Such a strain map can be stand-alone or convoluted with a confocal microscopy map to generate a unique QR code. [00088] In one embodiment a QR code is generated using data from confocal microscopy. In one embodiment a QR code is generated using strain parameters. In another embodiment a QR code is generated using data from ODMR. In another embodiment, a QR code is generated using both data from confocal microscopy and data from ODMR. In some embodiments the QR code uses a binary array of pixels. For example, black and white squares corresponding to 0 and 1. [00089] As disclosed herein, and in some embodiments, the method for generating a QR code comprises: 35 P-622992-IL compiling data from the methods disclosed herein, across a sample comprising particles; dividing said sample into digital pixels, wherein said pixels correspond to spatial locations on said sample; and assigning a value to each pixel corresponding to the value of the data that was measured in said pixel across said sample. [00090] In some embodiments the data is selected from: fluorescence, strain parameters, effective strain, frequency shift, axial strain and split distribution or any combination thereof. In some embodiments the QR code comprises between 10 and 100 pixels. In some embodiments the QR code comprises between 10 and 1,000 pixels. In some embodiments the QR code comprises between 10 and 10,000 pixels In some embodiments the QR code comprises between 10 and 100,000 pixels In some embodiments the QR code comprises between 10 and 1,000,000 pixels. In some embodiments the QR code comprises between 10 and 1,000,000,000 pixels. In principle the QR code is not limited by the number of pixels. [00091] For pixels which contain no information, a mean or arbitrary value can be assigned to that pixel. [00092] In one embodiment, the term "a" or "one" or "an" refers to at least one. In one embodiment the phrase "two or more" may be of any denomination, which will suit a particular purpose. In one embodiment, "about" or "approximately" may comprise a deviance from the indicated term of + 1 %, or in some embodiments, - 1 %, or in some embodiments, ± 2.5 %, or in some embodiments, ± 5 %, or in some embodiments, ± 7.5 %, or in some embodiments, ± 10 %, or in some embodiments, ± 15 %, or in some embodiments, ± 20 %, or in some embodiments, ± %. [00093] Those skilled in the art to which this invention pertains will readily appreciate that numerous changes, variations, and modifications can be made without departing from the scope of the presently disclosed subject matter, mutatis mutandis. EXAMPLES EXAMPLE 1 Methods [00094] NDs were purchased from Adamas Nanotechnologies Inc. (model number NDNV40nmLw10ml). All measurements were done at zero applied magnetic field. A µ-metal shield (from Magnetic Shield Corporation) was placed around the sample, except for optical and microwave access, to minimize the effect of stray (and Earth’s) magnetic fields. Borosilicate cover slips (Epredia-Menzel-Gläser 22 mm x 22 mm x 0.16 mm) were cleaned with acetone and 35 P-622992-IL isopropanol, then dried with dry nitrogen gas. This results in a relatively hydrophobic surface, leading to the aggregation of the NDs. Cleaning the cover slips with either Piranha Etch (mixture of H2SO4+H2O2) or burning them in an air environment at 500°C leads to a hydrophilic surface (zero wetting angle) and a well-separated dispersion. Primarily, hydrophobic surfaces were used for the experiments described herein. [00095] The NDs were diluted from their original 1 mg/ml concentration using type-1 ultrapure water (Milli-Q), and then drop-casted on a co-planar waveguide for the application of microwave tones. The measurements shown in Figures 3 and 3 are from a 20 µg/ml concentration. [00096] All measurements were performed on a custom-built confocal setup with a QM-OPX orchestrating all pulse sequences and data acquisition. The entire experimental apparatus lies in a temperature- and humidity-controlled room set to 23.0 ± 0.5°C and 35 ± 10%, respectively. Variations on the order of 0.5°C would correspond to shifts of 35 kHz in the zero-field splitting parameter. Since this is approximately 1% of the observed ODMR shifts and splitting, the role of temperature as the generator of the observed ODMR shifts can be ruled out. EXAMPLE 2 DLS of Diluted Stock[00097] Dynamic light scattering (DLS) spectra were taken using a Malvern Zetasizer. The measurements are plotted in Figure 10. The mean of size distribution is at 55nm, which is off the specified 40nm by the supplier, but nevertheless does not change the overall result. EXAMPLE 3 QR Code Data for Shift, Split and (x,y) Coordinates[00098] The split/shift information can be encoded into a machine-readable QR code. The shift, split and (x,y) coordinates are first deposited in a data repository such as the one shown below in Table 1: POI Split Shift x y 13.18 -3.62 68 59.2 17.24 -3.82 74.3 64.3 14.8 -4.32 74.4 56.4 13.05 -1.87 69.5 52.5 16.46 -3.65 77.7 46.6 11.21 -6.22 75.4 45.7 9.71 -3.77 76 38.8 15.56 -3.12 74.4 33.9 15.84 -5.81 65.7 25.10 16 -3.7 65.5 12.11 10.79 -3.14 73.6 8.88 P-622992-IL 12 13.49 -4.54 63.8 61.13 16.16 -4.03 64.4 58.14 14.33 -6.84 65 25.15 12.58 -3.3 66.4 11.16 11.95 -6.09 49.2 9.17 9.28 -6.1 52.6 21.18 12.97 -3.28 57.4 29.19 14.27 -5.22 49.3 39.20 14.13 -14.08 51.7 63.21 13.82 -5.48 49.3 39.22 12.83 -6.24 49.3 9.23 12.08 -3.68 42.7 5.24 12.59 -3.3 44.6 13.25 15.18 -4.46 46.8 18.26 13.76 -2.96 32.5 55.27 12.85 -3.61 31.5 63.28 11.2 -5.03 25 65.29 13.69 -4.38 17 70.30 9.54 -2.55 19.3 60.31 10.46 -3.11 13.7 32 10.05 -3.78 25.8 42.33 13.73 -5.84 31.6 11.34 14.16 -6.12 22.6 19.35 11.18 -3.18 17 36 11.27 -4.39 12 51.37 8.06 -5.01 10.2 32.38 9.7 -2.84 11.3 29.39 13.75 -3.11 4.79 19.40 12.21 -2.7 6.48 10.41 12.29 -4.43 0.672 4.42 10.8 -4.07 1.52 40.43 9.49 -2.74 2.25 47.44 5.18 -3.4 4.79 61. [00099] The data from Table 1 can then be encoded into a matching QR code as shown in Figure 11. This figure shows an example of encoding the measured shift and split of 44 individual POIs (i.e., ND clusters). Scanning this code with a QR reader allows for a verification against a reliable online reference e.g., a Zenodo repository, making sure that the data has not been tampered with. EXAMPLE 4 Optically Detected of Magnetic Resonance (ODMR)[000100] To exploit the NV center in different applications we need to be able to probe the spin state in a simple and efficient way. Several methods are used to do so, such as electron spin 10 P-622992-IL resonance (ESR), etc. Here the optically detected magnetic resonance (ODMR) method is used herein. [000101] ODMR is relatively a simple way to probe the spin transitions using spectroscopy, where in this method the differences in the radiative and the nonradiative transition rates are exploited and correlated to spin transitions. For example, assuming two states |a ⟩, and |b⟩, state |a ⟩ decays mostly through a radiative path, whereas state |b ⟩, has another dominant path which is not radiative e.g., assume 50:50 percent. If all the spins are in state |a ⟩, the decay will go through the radiative path only, and photoluminescence (PL) equal to 100% will be normalized. If all the spins are in state |b ⟩, only 50% of them will decay through the radiative path, resulting in losing 50% of the photoluminescence (PL). In the present example, the direct transitions between the excited state and the ground state are radiative whereas the transitions that go through the intersystem crossing (ISC) energy level are non-radiative. [000102] In the present example the degenerate states are assumed to have equal rates. The first difference in the decaying rates from the excited states to the ISC will have an impact on the fluorescence intensity causing a drop of 30% in fluorescence at the resonance frequency, where the second rate difference will allow spin polarization. Consider the case where electrons are excited from the ground state to the first excited state using a laser pulse, electrons in the |e, 0 ⟩ will decay to the |g, 0 ⟩ in the radiative path due to selection rules, same for the other two degenerate states where they will also conserve their spin state, but in the case of the |±1 ⟩ another path will take place and become dominant which is the non-radiative path, the key point here is that it will preferentially decay to the |0 ⟩ from the ISC (Γ6 > Γ5). A continuous application of the laser will cause spin polarization of nearly 80%. The other scenario that will cause a drop in fluorescence, which is the basis of ODMR, is applying microwave radiation having a frequency equal to the spin resonance frequency in the ground state Dgs = 2.87 GHz, which will cause electrons to be excited to the |±1 ⟩ in the ground state. A laser pulse will excite electrons to the |±1 ⟩ in the first excited state, electrons in the |±1 ⟩ excited state will decay through the radiative path but also another dominant path will take place through the ISC. [000103] This path is non-radiative and so this will be reflected by a drop in the fluorescence by nearly 30%. It is noted that if the two degenerate states are split due to a magnetic field, or any other field, then two resonance frequencies are present (Dgs ± γB) that will cause a drop in fluorescence, this splitting is the basis of magnetic field sensing, or more general field sensing that caused this splitting. [000104] Two types of ODMR exist, continuous wave ODMR (CW-ODMR), and pulsed ODMR. In CW-ODMR the laser continuously excited the NV center, which is also continuously irradiated by microwave (MW). The MW is swept over a range of frequencies and the fluorescence is 35 P-622992-IL recorded in each scanning frequency. The resonant frequency/frequencies are expected to be inside this scanning range and so when scanning over the resonant frequency a drop in the fluorescence is measured, as mentioned above. [000105] In pulsed ODMR the same technique is used (optical detection) as in CW-ODMR, but instead of applying continuous laser and MW, first a laser pulse is applied to initialize the NV center, then a MW π pulse is applied followed by a laser pulse to achieve both spin read out and polarization for the next measurement. As in CW-ODMR, if the MW frequency is equal to one of the resonant frequencies the spin state will be transferred to the degenerate state |±1 ⟩, which will, as in CW-ODMR, reduce the fluorescence. Two benefits are achieved in pulsed-ODMR, the first is the reduction in linewidth (FWHM) caused by power broadening leading to higher sensitivity. The second benefit becomes important in the case when two or more overlapping dips, making it hard to distinguish and characterize each dip. Thus reducing the linewidth will make these dips separable, making it possible to distinguish between them, and characterize them. Unlike CW-ODMR, pulsed-ODMR requires time-gated instrumentation for measurement. EXAMPLE 5 Method and Setup – Confocal Microscopy and Microwave System[000106] A primary component of the system is a device called Operator-X system (OPX), manufactured by Quantum Machines. The OPX connects and controls all the other systems and sequence generation, through several analog and digital inputs and outputs, using an open source software called Qudi. As in the previous sections, an optical system is needed to polarize and read-out the spin state. Also, a microwave system is necessary to manipulate the spin state. The OPX and the microwave system are connected together to perform fast frequency scans over a given frequency range. A piezoelectric stage is used to scan an 80 × 80 µm confocal image. One more important part is a permanent magnet controlled by three servo motors to move in the x-y-z direction. There are generally five main parts: 1. Operator-X system (OPX); 2. Optical system (confocal microscope); 3. Microwave system; 4. Piezoelectric stage; 5. Permanent magnet connected to 3-axis moving servo motor. [000107] OPX is the instrument that connects and controls all the other devices. It also allows for generating different pulse sequences through several analog and digital inputs and outputs. The software that is used in these experiments is Qudi, which is a software (SW) package that allows scanning, optimizing, sequence generation, fitting results, and many other functions. 35 P-622992-IL id="p-108" id="p-108" id="p-108"

[000108] Regarding the confocal microscope the ODMR measurement uses an optical system to initialize and read the spin state, a confocal microscope is used for this purpose. A green light laser diode (from Swabian instruments DLnsec) λ = 520 nm is used to generate the excitation pulse. The laser beam is guided through mirrors and lenses to a fiber coupler, then to a single mode fiber (SMF) to ensure a Gaussian profile of the beam. Again the beam is guided to a dichroic mirror through lenses and mirrors. The dichroic mirror is used to separate the excitation and emission beams, where it acts as a long pass filter allowing the laser beam to be transmitted and reflecting the emitted beam from the NV. For example, λ = 576 nm is the cut-off frequency where above this wavelength beam will be reflected. The laser beam (λ = 520 nm) passes through the dichroic mirror and then will be reflected through two mirrors to reach the objective (Olympus MPLFLN 100x, NA = 0.9), and focused on the sample. The photoluminescence (PL) from the NV center goes back through the same objective and reflected through the same mirrors tracing the incoming beam back to the dichroic mirror, but as we see in the transmission curve of the dichroic mirror, the beam will be reflected and not transmitted. The dichroic mirror will reflect it to two other mirrors and lenses to reach a 50 µm pinhole, which is regarded as the heart of the confocal microscope. The pinhole blocks out-of-focus light. Beams coming out from the pinhole will be split equally through a 50:beam splitter to two avalanche photodiodes (APD). The APD is a highly sensitive photon detector that can detect as low as one photon. In most of the experiments one APD is enough, whereas some experiments such as auto-correlation use both detectors. [000109] Regarding the microwave system: To manipulate electron spin states in NV− centers, as in ODMR, scanning over a spectrum of wavelengths in the microwave regime is required. For this purpose, disclosed herein is a custom-built microwave scanning system. The system comprises a microwave generator (Syn-thNV Pro from Windfreak Technologies, LLC), generating the center frequency, herein named ‘f LO ’ (LO for the local oscillator). The output of the generator goes to an IQ mixer where the other two inputs of the IQ mixer come from the OPX. This generates the required scanning signal which is then fed to the amplifier to achieve the needed power. A circulator is added after the amplifier to prevent reflection. In general, the generator is only used to scan over the required band-width, but the scanning will be slow, so the OPX is used is combination with the IQ mixer to scan over the required bandwidth. The IQ mixer needs to be fed with two signals having the same frequency and ±π/2 phase shift. The -π/2 allows for scanning frequencies lower than the oscillator frequency and the +π/2 allows for scanning frequencies higher than the oscillator frequency. [000110] The scanning microwave system is based on heterodyning. In heterodyning, two signals are introduced to the mixer to get the one heterodyned signal. In the most general case, three components: f LO −f, f LO +f and the carrier frequency f LO , are provided, this situation is called double 35 P-622992-IL sideband (DSB) carrier included (local oscillator frequency). Other cases are possible, for example, both sidebands exist but no carrier (DSB suppressed carrier), or only with a single sideband and carrier (SSB), or as in the present example, a single sideband with no carrier (SSB suppressed carrier). [000111] Figure 12A shows a waveguide 120 fabricated to deliver electromagnetic waves in the microwave regime to the sample. The waveguide 120 is compatible with the system, where it can be inserted in the confocal microscope and connected to the microwave generation system. Also, the waveguide 120 is configured to disperse the NDs thereon in a way that facilitates their scanning in the confocal microscope. Both criteria were met by fabricating the waveguide on a 20 × 20 mm glass substrate that are connected to a custom-made PCB and easily connected to the system. [000112] The fabrication of planar waveguides 120 is carried out using standard nanofabrication techniques and comprises four main processes, which are deposition, lithography, electroplating, and etching. The fabrication method starts by depositing a 5 nm chromium adhesion layer, followed by a 300 nm copper layer. Using lithography the area where for growing more copper is specified and exposed, whereas the rest of the area is covered by photoresist. A thicker layer of copper 11 , 12 is then grown using electroplating. Finally, the undesired copper and chromium is etched to get the final shape of the waveguide 120 . Figure 12B shows the waveguide profile showing the photoresist thickness. [000113] To prepare the waveguide for measurement a diluted dispersion of NDs were drop cast on the co-planar waveguide. For a better signal, the drop was concentrated around the central line 12 of the waveguide 120 . The waveguide is left in a fume hood for about an hour until the water evaporates. While the water evaporates the drop shrinks and its diameter becomes smaller, the NDs come closer to each other and form aggregates. This raises the expected NV centers number in one confocal spot. After making sure that all the water has evaporated, the waveguide was placed in the confocal microscope and connected to the microwave system from one side and terminate the other side of the waveguide with a 50 Ω resistor to match the load and prevent undesired reflections.

Claims (25)

P-622992-IL - 25 - CLAIMS

1. A method comprising: dispersing particles on a substrate, wherein said particles comprise defects; and operating a detection system to extract strain parameters of said particles.

2. The method of claim 1 wherein said substrate comprises any of the following selected from: silicon, glass, borosilicate glass, gallium arsenide, silicon carbide, indium phosphide, indium arsenide, silicon carbide, silicon oxide, germanium, graphene, aluminum oxide, quartz, pyrex, acrylic, polycarbonate, plastic, oxide layer and polymer-based materials, a metal or any combinations thereof.

3. The method of claim 2 wherein said metal is selected from: gold, platinum, silver, titanium, nickel, chromium, aluminum, copper, tungsten and palladium or any combination thereof.

4. The method of claim 1 wherein said substrate is soft or flexible.

5. The method of claim 1 wherein said particles comprise nanodiamonds.

6. The method of claim 1 wherein said particles are in crystal form.

7. The method of claim 1 wherein said particles comprise any of the following selected from: crystals, silicates, calcites, diamonds, alkali halides, quantum dots, silicon, rare earth materials, boron nitride, zinc oxide and transition metal di-chalcogenides (TMDs) or any combination thereof.

8. The method of claim 1 wherein the 3-dimensional structure of said particles is selected from a list comprising: polyhedra, platonic solids, tetrahedron, hexahedron, octahedron, dodecahedron, icosahedron, cubes, rectangular solids, prisms, pyramids, cones, cylinders, spheres, spheroid, tubes, disks, filaments and ellipsoids or any combination thereof.

9. The method of claim 1 wherein the size of the particles range between 1nm to 1mm.

10. The method of claim 1 wherein said particles each comprise between 1 and 1000 defects. P-622992-IL - 26 -

11. The method of claim 1, further comprising linkers attached on said particles, or on said substrate, or on both said particles and said substrate.

12. The method of claim 11, wherein said linkers are selected from a group comprising: alkyl chains, aromatic groups, cyclic or branched hydrocarbons, fatty acids, hydrophobic polymers, hydroxyl groups (-OH), carboxyl groups (-COOH), amino groups (-NH2), sulfonic acid groups (-SO3H), phosphonic acid groups (-PO3H2), sulfate groups (-SO4), phosphate groups (-PO4), glycosidic linkages (-O-C-OH), hydrated metal ions, sodium (Na+), calcium (Ca+), carboxylic acid, amine-reactive groups, thiol-reactive groups, PEGylation linkers, imides and esters or any combinations thereof.

13. The method of claim 12 wherein said alkyl chains are selected from: methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl and dodecyl or combinations thereof.

14. The method of claim 12 wherein the aromatic group is selected from: benzene, naphthalene and anthracene or combinations thereof.

15. The method of claim 1 wherein said substrate is at least partly hydrophobic, or wherein said particles are at least partly hydrophobic, or wherein both said substrate and said particles are at least partly hydrophobic.

16. The method of claim 1 wherein said defects are color centers.

17. The method of claim 1 wherein said defects are nitrogen vacancies.

18. The method of claim 16 wherein said color centers are F-centers.

19. The method of claim 17 wherein said nitrogen vacancies comprise only N isotopes, or only N or both N and N isotopes.

20. The method of claim 1 wherein said detection system is an optical detection of magnetic resonance (ODMR) system. P-622992-IL - 27 -

21. The method of claim 1 wherein said detection system carries out a microwave manipulation of the defect spin state of said particles.

22. The method of claim 1 wherein said strain parameters comprise axial strain and transverse strain.

23. The method of claim 1 further comprising: plotting a histogram of the frequency shift and the split distribution for said particles; fitting a normal distribution of both the frequency shift and the split distribution; extracting a value for the mean frequency shift which translates to an axial strain; and extracting a value for the mean split distribution which translates to a transverse strain.

24. A method for generating a QR code, said method comprising: compiling data from the method of claim 1 across a sample comprising said particles; dividing said sample into digital pixels, wherein said pixels correspond to spatial locations on said sample; and assigning a value to each pixel corresponding to the value of the data that was measured in said pixel across said sample.

25. The method of claim 24 wherein said data is selected from: fluorescence, effective strain, frequency shift, axial strain and split distribution or any combination thereof.