A METHOD OF ASSEMBLY OF TWO COMPONENTS

Technical Field

The present invention relates to a method of assembling components together. The components being assembled have planar and non-planar solid surfaces and/or volumes. The present invention utilises a nanomaterial driven approach for assembly of components having a wide range of complementary sticking chemistries.

Whilst the present invention is described with reference to embodiments and examples suitable for the assembly of jewellery pieces, it should be understood that the method is not limited to the assembly of jewellery and may be used to assemble other components.

Background

The assembly of jewellery components is typically either by mechanical assembly for example by mechanical grasping of precious stones by claw or stone clipping, or by utilising of glues and adhesives to join like and dissimilar jewellery pieces. For instance it is known, to use glues and adhesives to join precious stones such as diamonds to each other as well as to other components. It is also known to apply to diamonds (and other precious stones) an adhesion layer, such as chromium-nickel, followed by coating of a gold, platinum or palladium upon which a protective coating of silicon dioxide is applied.

The assembly of such jewellery components must result in a strong bond, whilst aesthetically pleasing, and the bond interface should preferably have minimal visual impact.

The present invention seeks to provide an alternative method of assembly that may be used to assemble jewellery components. This method of assembly provides a strong bond without relying on a strong glue base.

Summary of Invention

In one aspect the present invention consists in a method for assembly of two components, each component having a substrate surface, said method comprising the steps of: (i) taking each substrate surface and depositing a first layer of metal thereon;

(ii) taking each substrate surface and depositing a second layer of chemically modified nanomaterial on said first layer of metal; and

(iii) taking each substrate surface treated by steps (i) and (ii) and placing them adjacent to each other and applying pressure thereto such that the surface chemistry of said second layer of nanomaterial on each of said components interact with each other and forms a bond therebetween.

Preferably said chemically modified nanomaterial is functionalized with a chemical group including any one of a thiol, disulphide, sulfur, sulfide, selenol, amine, carboxylate, phosphate or phosphonate, or their derivatives thereof.

Preferably the nanomaterial of said chemically modified nanomaterial may be any one of carbon-based fullerenes, inorganic non-carbon-based fullerenes, dendrimers, polymeric nanoparticles, polymeric nanorods, polymeric nanotubes, metallic nanoparticles, metallic nanorods, metallic nanotubes, cyclodextrins, calixarenes.

Preferably in one embodiment said chemically modified nanomaterial is a carbon nanotube functionalised with a thiol or disulphide group.

Preferably said first layer of metal includes any one of nickel, iron, copper, mercury, platinum, palladium, silver or gold.

Preferably said substrate surface includes any of silicon dioxide, diamond, glass or any other precious stone.

Preferably the deposition of said first layer of metal is surface engineered in order to not fully cover said substrate surface.

Preferably in another embodiment an adhesion layer of material is deposited on said substrate surface before step (i).

Preferably said adhesion layer of material includes any one of titanium, chromium or tantalum.

Preferably said adhesion layer is surface engineered such that it does not fully cover said substrate surface.

In a first preferred embodiment at least one of said components has a substrate surface of silicon dioxide, glass, or diamond or any other precious stone and said first layer of metal is gold and said chemically modified nanomaterial is a thiolated multi-walled carbon nanotube.

In a second preferred embodiment at least one of said components has a substrate surface of silicon dioxide, glass, or diamond or any other precious stone and said first layer of metal is gold, said adhesion layer is titanium and said chemically modified nanomaterial is a thiolated multi-walled carbon nanotubes.

Preferably said first layer of metal is deposited on said substrate surface by any one of high vacuum evaporative deposition, reducing metallic cations or sputtering.

In a further preferred embodiment said components are jewellery components, and said substrate surfaces are diamond, said first layer of metal is gold and said chemically modified

nanomaterial comprises functionalised carbon nanotubes. Preferably an adhesion layer of titanium is deposited on said diamond prior to depositing said gold. Preferably said gold and/or titanium is surface engineered such that it does not fully cover said substrate surface.

Preferably said pressure referred to in step (iii) is in range of 1-100 atmosphere.

Brief Description of the Drawings

Fig. 1 is schematic representation of the sequential deposition/evaporation steps for surface functionalization of the second component (diamond) of the embodiment of the present invention;

Fig. 2 is a schematic of a self-assembled monolayer (SAM) that is a result of the second step functionalization of adhering the chemically modified nanomaterial (multi-walled carbon nanotube functionalized with a thiol or disulphide group) onto a metallic (Au) layer shown in Fig 1, and is also a schematic of the assembly step of two like second (diamond) components after they have undergone the first and second (intermediate) functionalization steps as shown in Fig. 1;

Fig. 3 is schematic of the formation of the chemically modified nanomaterial (multi-walled carbon nanotube functionalized with a thiol or disulphide group) in the second step shown in Fig. 1;

Fig. 4 depicts prior art shapes of carbon nanotubes emphasizing the graphene sheet mode of rolling and the multi-walled co-axial structures; and

Fig. 5 schematically depicts an alternative embodiment of the present invention, in which nanomaterial-driven covalent assembly relies on epoxide/thiol or amine and acid (activated acid)/thiol or amine dual sided interconnecting chemistry.

Mode for Carrying Out the Invention

In the present specification the term "nanomaterial" refers to a material used in nanotechnology and of which at least one dimension is in the nanometer-size range (<500 nm).

Also, the term "chemically modified nanomaterial" refers to a nanomaterial bearing a functional group. The functional group may include, but is not limited to, the thiol (SH) or disulphide (-S-S-) group, or NH ₂ , OH and COOH. For example, one such chemically modified nanomaterial is a carbon nanotube functionalized with a thiol or disulphide group.

The following embodiments describe and depict how components (having planar and/or non- planar surfaces and/or volumes) to be connected, may be modified by one or several steps of metal deposition/evaporation depending on starting substrates. These steps have two purposes in order to enable an "assembling" last step to be effective. First metal depositions/evaporations must be chemically compatible with substrate surfaces as well as being compatible with second metallic layers to be deposited later on.

The significant advantage of this approach is that it will permit chemical fitting of any surface/volumes to be connected (stuck) in the "assembling" process because of the variability of metals and of their sequence order for deposition. Three experimental examples, disclosed later in this description have been developed in the laboratory that are the assembling of (i) two functionalized SiO ₂ pieces (cut from a commercially available SiO ₂ wafer used in the electronic industry), (ii) one natural diamond surface onto one piece of functionalized SiO ₂ piece, and (iii) two similar appropriately functionalized diamond surfaces.

A preferred embodiment of assembling components in accordance with the present invention is now described with reference to first and second components.

First Component:

In a first step a "first component" having a substrate surface, being made of silicon dioxide (SiO ₂ ) is functionalized by a nanometer-thick layer of gold (Au) in a 1-400 nm range of thicknesses in a one-step metal high vacuum evaporation process affording the Au (metallic) layer strongly stuck onto the SiO ₂ surface (physico-chemical fitting of surfaces between both components). The SiO ₂ surface and Au are compatible surfaces and a strong adhesion occurs therebetween.

In a second (or intermediate) step a "chemically modified nanomaterial" is deposited/attached on the nanometer-thick Au. This chemically modified nanomaterial is preferably a multi- walled carbon nanotube (MWCNT) functionalized with a thiol or disulphide group, due to the strong affinity of the thiol or disulphide chemical groups for Au surfaces. This step provides the thiolated MWCNT chemically adsorbed onto the Au-surface and presents outer thiol or disulphide groups.

Second Component:

A "second component" of diamond may have gold (Au), silicon dioxide, glass, or diamond or any other precious stones, deposited/ attached thereto, in a similar first step to the early mentioned first component prior to the deposition of a thiolated MWCNT in a second step. However, for this second "diamond" component it is preferable to initially functionalize the surface by applying an adhesion layer of titanium (Ti) in a range of

1-500 nm range. This adhesion layer is necessary as diamond surfaces are hydrophobic and Au is hydrophilic.

The sequential deposition/evaporation of the "first step" for surface fiinctionalization of the abovementioned diamond "second component" is depicted in Fig 1. The diamond component 1 (substrate surface) shown at stage 1 undergoes a first metal (Ti) evaporation/deposition shown at stage 2, followed by a second metal (Au),evaporation/deposition shown at stage 3. This deposition of Ti on diamond is known in the prior art [I].

Assembly:

The first (SiO ₂ ) component and second (diamond) component are now each functionalised by the deposition of an Au layer followed by deposition of the thiolated MWCNT layer. The first (SiO ₂ ) component and second (diamond) component may now be assembled to each other by placing the components adjacent to each other and mechanically applying force such that they are pressed (sandwiched) together. The chemistry of the thiolated MWCNT is such that the layers on the adjacent components being pressed together interact with each other and bond together.

This pressing together of the first and second components may for example be achieved by using a common mechanical hand press (pressure estimated to be in the 1-100 atmosphere range). At process end, sandwich composites have been produced where functional thiolated nanomaterials (in this case thiolated MWCNTs) enable strong mechanical sticking of both metallized-contacting surfaces of the assembled components.

It should also be understood that two of the like "functionalized SiO ₂ components" may be pressed together and assembled in the same way. Also, two of the like "functionalised diamond components" may be pressed together and assembled in the same way.

Fig. 2 firstly depicts a closely (or densely) packed self-assembled monolayer (SAM) formed by the thiolated MWCNT where it interacts with the Au surface. SAMs are described in further detail within this specification. Fig 2 also depicts how the assembly step of two like functionalised diamond pieces can be pressed together relying on the interconnecting thiol/disulphide chemistry of the SAM.

It should be understood that the components (and there substrate surfaces) to be assembled are not limited to silicon dioxide (SiO ₂ ) and diamond, and may be any substrate surface including both metallic and non-metallic surfaces.

Whilst gold (Au) is described as the metal deposited in the abovementioned "first step" for both of the abovementioned first and second components, it should be understood that other

metals such as nickel, iron, copper, mercury, platinum, palladium or silver could be used. Also, whilst it is preferred to deposit this layer of metal using a high vacuum evaporative process, other processes may be used. For example a generic process involving reduction of metallic cations M ⁿ⁺ in the presence of the surface to be treated, and in the presence of a reducing system/agent (such as hydrides, or hydrogen gas) may be used. But, this generic method is far from giving the homogeneity and thickness control of the preferred metal high-vacuum evaporation. Sputtering of the metal is also possible but it typically gives much thicker layers than by using the preferred metal high-vacuum evaporation.

Also, whilst titanium (Ti) is described in the above described embodiment as the adhesion layer to assist in the deposition of gold (Au) to diamond, silicon dioxide, glass, or diamond or any other precious stones, it should be understood that several other metals may be deposited as adhesion layers to adhere strongly onto diamond surfaces such as chrome (Cr), tantalum (Ta), and rhodium (Rh) for example.

It should also be importantly noted that whilst the above described embodiment utilizes thiolated CNT for the "second step" functionalization of the substrate surface of the components, it should be understood that any other suitable "chemically modified nanomaterial" may be used. For example the nanomaterial may be any one of but not limited to carbon-based fullerenes, inorganic non-carbon-based fullerenes, dendrimers, polymeric nanoparticles, polymeric nanorods, polymeric nanotubes, metallic nanoparticles, metallic nanorods, metallic nanotubes, cyclodextrins, calixarenes. Furthermore, the chemical group that is used to chemically modify the nanomaterial need not be thiol, and may for example be selected from other chemical groups such as sulfur, sulfide, selenol, amine, carboxylate, phosphate or phosphonate.

It should be understood that the second (or intermediate) step attachment of the chemically modified nanomaterial (or functional nanosized material) to Au (or other metal) deposition uses the capacity of any thiolated/sulfurated/sulfide organic species and/or thiolated/sulfurated/sulfide nanomaterials to be quasi-covalently attached onto Au surfaces [2].

This is common art that functional/non-functional organic ligands such as long-chain thiols, selenols, and sulfides quasi-covalently attach onto a vast range of metallic surfaces such as Ni, Fe, Cu, Hg, Pt, Pd, Ag, and Au forming dense well-packed self-assembled layers (SAMs) where thiol/sulfide organic functions strongly interact with metallic surfaces. Such a SAM is schematically depicted in Fig 2b. The stability of packed SAMs usually depends on (i) the end functionality X of thiol/disulfide ligands, and on (ii) the length of interacting chains via stabilizing van der Waals side interactions of closely packed hydrophobic chains of adsorbed ligands.

This chemical property - the high quasi-covalent affinity of thiol/sulfide chemical functions toward various metallic surfaces is depicted in Fig 3. The connecting chemistries which enable the mechanically strong assembling of functional surfaces/volumes, makes use of thiolated nanomaterials (an illustrative example dealing with thiolated carbon nanotubes (CNTs) has been provided later on).

Single-walled and/or multi-walled carbon nanotubes (S WCNTs/M WCNTs) are fullerene- related carbon-based micrometer long-nanostructures, which consist in one or several graphene sheets of ,sp ² -hybridized carbon hexagons disposed coaxially around an internal hollow cavity (lengths in the 0.5-100 μm range, diameters in the 0.3-300 nm size range, see Fig. 4). CNTs possess a quite unique set of mechanical, electrical, and magnetic properties making them particularly attractive for various (bio)nanotechnology applications. They may be readily functionalized when targeting CNT pentagon-containing end-caps or -sidewalls sensitive to oxidation and/or the outer ID extended ^--conjugated system (CNT sidewall defects).

For example, CNT oxidation generated end/sidewall-localized COOH groups that were exploited for the covalent attachment of (bio)molecular probes. In the present case, oxidized polyCOOH MWCNTs were chemically activated by carbodiimides (COOH group chemical activation) and treated by an amino-thiol ligand — cysteamine — in order to produce oxidized end-opened MWCNTs decorated by pending thiol or disulphide groups covalently attached onto CNT sidewalls and opened ends.

These thiolated functional nanomaterials when deposited/attached onto Au-covered SiO ₂ or Au-covered diamond pieces due to the strong affinity of thiol or disulphide chemical groups for Au surfaces present outer available thiol/disulfide groups on their opposite faces for interconnecting with the second Au-metallized surface.

Some points that describe the assembly of components of the earlier described embodiment are as follows:

a. The interfacial chemistry using chemically modified nanomaterials (such as thiolated functional MWCNTs) is important in that sense that such cylindrical micrometer long carbon-species possess (and derivatives such as pegylated end-thiolated MWCNT s/SWCNTs for example) the necessary connecting chemistry based on strong non-covalent interactions of thiol or disulphide groups and metallized surfaces such as Au.

b. Following the earlier mentioned "assembly step" pressure operation, these species allow a strong mechanical assembling as the thiolated MWCNTs are able structurally to fit into both connected surfaces of a given roughness. It means that these flexible functional (chemically modified) nanomaterials possess the necessary thiol or disulphide-interacting chemistry available on both sides of the nanomaterials, enabling their effective multivalent (due to multiple SH/S-S functions present onto CNT sidewalls) key-and-lock adaptation within surface defects due to both side surface roughnesses. AFM photographs of Au covered surfaces/volumes show that surfaces ready for assembling are not strictly planar but present variable roughnesses due to 1-5 nm depth defects. Interestingly, such defects possess depth dimensions fitting diameters of thiolated MWCNTs used in this present invention. Indeed and in this manner, functional thiolated MWCNTs exploit these surface defects in order to assemble both interacting surfaces/volumes. It also explains why the role of an external pressure imposed for the assembling process was found to be important.

The above described method of assembly of the first and second components have applications in assembling jewellery pieces.

Referring back to the diamond "second component", which is indicative of a component used in assembling jewellery pieces, further advantages of the present invention will now be described. It should be noted that the deposition of the "first step" metal (Au) and/or the adhesion layer (Ti) may be surface engineered to not fully cover the substrate surface of the underlying diamond component, but just provide the minimal interacting surface for an effective assembling. This surface engineering may be achieved by lithographic masking similar to that used in the electronics industry. In this surface engineering, another advantage relating only to diamond-based assemblies, will be that metallization of interacting surfaces will preserve/afford new optical effects to the diamond-based assemblies. It should also be understood that the Au (or other nanoparticle metallic layer such as Ag) may add unusual optical properties, such as red/violet to blue color backgrounds within the interfacial layer between assembled diamond pieces. These effects are due to plasmon resonance phenomena, which are a function of the nanometer-size of such metallic nanoparticles/nanoparticulates.

In the above described embodiment and experimental examples described later in this document, the sole thiol SH-Au interaction is utilized for the assembling process. But it should be understood that various other types of connecting chemistries (that may be readily developed onto nanomaterial surfaces in a similar manner) may be used. For example connecting epoxide functions in assembled surfaces/volumes and opening them during assembling by thiol functions present on functional nanomaterials (nucleophilic opening of epoxides in the interface of both interacting surfaces/volumes). An example of this is depicted in Fig 5. This same option may rely on amide chemistry that may be easily designed for assembly purposes.

It is also possible that any other kind of functional nano- micron-sized materials may be used in this connecting method. For example, gold or silver-nanoparticles that may be stabilized by thiolated ligands - the thiol/sulfide functions are linked to the Au/Ag-nanoparticles with the same kind of properties than for a planar surface like that in the above described embodiment. The present invention is capable of producing Au-based thiolated nanomaterials. Regarding

dendrimers and as an example of effective connecting capability, one may commercially obtain several different polycarboxylated (polyCOOH) PAMAM or PEI dendrimers that may be derivatized by an amino-thiol/disulfide (L-cysteine for example) affording a PAMAM and/or PEI dendrimer decorated in a multivalent way by several 4-64 outer thiol/suldide groups for attachment onto metallic surfaces (Au, Ag, Pt, ...)■ For polymeric particles, it may be possible to produce nanosized/micron-sized hard SiO ₂ (silica) particles that may be covered by a polyCOOH polyacrylic acid shell enabling the same kind of thiol/sulfide decoration as described formerly.

The following Experimental Examples are Illustrative of the Present Invention:

Cleaning of silicon wafer & diamond pieces before metallization (preparation steps of substrates)

(a) Commercially available silicon SiO ₂ wafers were cut in small 1.0 X 0.5 cm-sized pieces (area ~ 1.5 cm ² ), and were cleaned by several sequential washing steps using various organic solvents in the following order - acetone, methanol, and isopropanol (1.0 mL each) -. Wafer SiO ₂ pieces were gently sonicated during each washing step (Bransonic sonicator 2510, 42 kHz at full power irradiation) for 5 min, and then dried using a highly pure N ₂ (99.999%) gas jet.

(b) Natural diamonds (~ 60.0 mg each) from Australia Diamonds Ltd. were cleaned using a hot acidic mixture of 1/4/3 v/v/v HC1O ₄ /HNO ₃ /H ₂ SO ₄ (80 ⁰ C for 1 h) before use. Then, they were washed until neutrality using double-distilled water (5 X 20 mL), and dried using a highly pure N ₂ (99.999%) gas jet.

Gold (Au)-metallization step toward solid planar/non-planar surfaces/volumes of types 2 and/or 3

Solid planar/non-planar surfaces/volumes were first (when necessary - case of natural diamond surfaces/volumes) covered by a very thin 5.0 nm-thick film of Ti (99.995 % purity) as an adhesion layer using e-beam evaporation (TFDS VST metal evaporator, Israel, 0.3 A

deposition thickness/second). Then, the 2 ^nd 100 nm-thick Au metallic layer ("the functional layer") was deposited by a thermal evaporation of Au metal (99.995 %, 0.8 A/second). All metal depositions/evaporations were made under a low 10 ^"6 torr vacuum. Roughness measurements were performed using a Nanoscop III atomic force microscope (AFM, Digital instruments).

Cleaning of Au-covered intermediate planar/non-planar surfaces/volumes before the assembling step

Before assembling, any Au-covered substrate was cleaned by washing sequentially in the following series of organic solvents - acetone, methanol and isopropanol (1.0 mL each - under sonication during 5 min (Bransonic sonicator). Then, they were dried using a highly pure N ₂ (99.999%) gas jet. Furthermore, gold films were cleaned in an UVOCS UV/Ozone cleaner (ultraviolet/ozone cleaner commonly used for cleaning surfaces contaminated with organic substances, UVOCS INC T10X10/0ES/E instrument) during 20 min.

Assembling process using thiolated multi-walled carbon nanotubes (MWCNTs)

(a) Any Au-covered planar/non-planar surface/volume (as that described in the above described embodiment) was functionalized by thiolated oxidized MWCNTs using a simple adsorption process due to the high chemical affinity of thiol functions for metallized Au surfaces. Thiolated oxidized MWCNTs were prepared as shown in Fig. 3. First, end- and sidewall- localized COOH groups were introduced onto untreated MER Corporation MWCNTs by contacting them using an acidic mixture of both concentrated FINO ₃ and H ₂ SO ₄ acids at 70°C (3 h oxidation) leading to oxidized polyCOOH MWCNTs. In a second step, excess cysteamine was reacted with iV-(3-dimethylaminopropyl)-N-ethyl-carbodiimide ^# HCl (EDC)-activated oxidized polyCOOH MWCνTs affording corresponding thiolated oxidized MWCνTs for adsorption onto Au-covered surfaces. Adsorption of thiolated MWCνTs onto Au-covered planar/non-planar surfaces/volumes was carried out by immersing Au-covered substrates into an ethanolic suspension of thiolated MWCνTs (1.5 ml, 24 h at room temperature). Resulting CνT-decorated Au-covered planar/non-planar surfaces/volumes were then washed with

ethanol (1.0-5.0 mL), and dried using a highly pure N ₂ (99.999%) gas jet. Surface densities of thiolated MWCNTs adsorbed onto Au-covered substrates were determined by HR-SEM (JSM- 700Op, JEOL HR-SEM Field Emission Scanning Electron Microscope). They were determined to be in the 5-10 objects/μm ² density range.

(b) Both resulting MWCNT-functionalized and Au-covered surfaces/volumes of types 2 and/or 3 were strongly assembled using a mechanical hand-operated press during 24hr at room temperature. Assembling operating pressures were estimated to be in a 1-100 atmosphere range.

Preliminary experiments concerning the mechanical stability of assembled components (regarding solely the assembling of two natural diamond pieces)

Such MWCNT-mediated assembled components were tested in a very preliminary manner for their mechanical and chemical stabilities. For example, they were found stable to: (i) ultrasounds (ultrasonic Bransonic bath) during 2 h, (ii) mechanical shocks (20 min vortexing within a thick glass tube), (iii) a range of organic solvents EtOH, acetone, H ₂ O and aqueous soap (2 h under sonication), (iv) a basic solution (10% aqueous Economica, 10 min under sonication), (v) to heat (oven 140 ⁰ C, 2 h), and (vi) to an acidic aqueous solution of 10% HCl (15 min under sonication).

General Protocol for the Oxidative Opening of Multi-Walled Carbon Nanotubes

(MWCNTs)

MWCNTs (MER Corporation, 100.0 mg/experiment, averaged diameter/length: 2-5 nm/1-10 μm, 5-20 graphitic layers, purity ~ 98%) were oxidatively opened at pentagon-like end caps (and sidewalls, defect COOH group formation) under nitrogen using a mixture of acids (12M HNO ₃ & 36M H ₂ SO ₄ ) in 3/1 v/v ratio, at 70°C, during 3h oxidation time. After reaction completion, oxidized MWCNTs that generally formed stable suspensions in their oxidation media were first washed with bi-distilled water until neutrality (pH 6-7) using several centrifugation-washing steps (9500 rps, 45 min, 25°C). Opened poly-oxygenated (polyOH,

polyCHO, polyCOOH) MWCNTs have been characterized by FT-IR spectroscopy, and both Low- & High-Resolution SEM microscopies disclosing characteristic COOH vibrations, and hollow MWCNT extremities as expected from the oxidation process

General Protocol for the functionalization of oxidized MWCNTs by bifiinctional amino- thiolated ligands. Preparation of cysteamine-decorated oxidized MWCNTs:

Opened oxidized MWCNTs (10.0 nig/experiment) suspended in neutral bi-distilled water were chemically activated by the water-soluble carbodiimide iV-(3-dimethylaminopropyl)-iV-ethyl- carbodiimide-HCl (EDC, MWCNTs, 10.0 mg, EDC: 20.0 mg, 0.64 mmol, 200 μL of bi- distilled water, 20 ⁰ C, 30 min). Therefore, they were reacted with cysteamine (1:1). The suspension was stirred at 20 ⁰ C for Ih. Cysteamine-decorated modified MWCNTs were then washed with 95% ethanol (4 x 20 mL) and decanted by centrifugation (9500 rpm, rt, 15min). They were stored as an EtOH suspension (0.5 mg/mL) under argon at 4 ⁰ C (fridge). They were characterized by HR-SEM.

Those skilled in the art will appreciate that the present invention is especially suited for the setting of a diamond to another diamond or to a metallic surface, preferably the surface of a gold component. Those skilled in the art will also appreciate that in the prior art the surface of a diamond known to be extremely reluctant to chemical functionalization. Furthermore, as will be also known by those skilled in the art, the introduction of covalent chemical modifications onto diamonds destroys the value of a diamond. Accordingly, the connecting chemistry should be "reversible" in nature that means that a simple cleaning step (mechanical abrasion) should show that indeed the diamond surface has not been modified chemically.

The present invention importantly provides reversibility that can be achieved by basing the bonding method on a prior step of metallization in order to allow chemical reversible functionalizations to be performed.

The second step of the process according to the present invention employs connecting chemistries between the two metalized layers. By contrast to the use of CTNs as connecting

nanomaterials, simple bifunctional acids or amines or thiols or disulfides were found to be ineffective in this application, typically often because of insufficient strength for jewelry type applications.

The use of multivalently presented nanomaterials such as carbon nanotubes, as provided by the present invention, to implement the connecting chemistry as described above, provide advantages as not demonstrated by techniques of the prior art. The use of nanomaterials functionalized with the appropriate chemistry relates in fact to some significant advantages:

(i) they fit in terms of sizes to the angstrom-sized roughness of diamond surfaces to be connected, as opposed to chemistries of the prior art which cannot work as we observed.

(ii) after first adsorption, these chosen materials present also a second side of functional groups for connecting the 2nd piece of diamond, thus providing multivalent presentation of the connecting chemistry)

(iii) other nanomaterials like Au nanoparticles may be also useful in order to secure new optical effects, such as red to violet colors, due to plasmon resonance effects at the diamond interface as an added optical value/effect"

As will be appreciated by those skilled in the art, the present invention is particularly applicable to areas of technology in which a strong and adhesive bond is formed between two same or similar components. In the jewelry-making field, for instance, where various jewelry components are joined together, such as the joining of precious stones to metals, the joining of metals to metals and the joining of precious stones to similar or different stones, it is highly desirable to have an unsightly bond whilst also providing a bond of high strength, so as to ensure that the various components are maintained together.

As will be appreciated and known by those skilled in the art, when joining a precious stone such as a diamond with a metallic ring, such as a gold or a silver ring, it is necessary to provide

a bezel or a "claw"-like structure to secure the precious stone to the metallic ring. As metals used in jewelry, such as gold, have a relatively high malleability and ductility in comparison with small structural materials such as steel or steel alloys, impact may result in dislodgement of a precious stone from a metallic ring, thus resulting in loss of the stones. Further, as metallic materials such as gold used in jewelry can be relatively easily worn down over time, the precious stone may not be fully grasp or clasp by the metal, which again may result in loss of the stones.

The present invention provides a method for joining such materials without the use of unsightly adhesives and also without the necessity of bezels or core-like structure to maintain the precious stone on a metallic ring. A person skilled in the art will, of course, understand that a bezel or core structure may still be implemented, however, the incorporation of the present invention significantly reduces the reliance upon such traditional holding structures, thus decreasing the likelihood of the precious stone being lost whilst also maintaining a traditional look of a jewelry structure such as a ring.

Equally, when metallic components are joined together to form or prepare jewelry pieces, such as rings, pendants, earrings and the like, the present invention may also be implemented so as to provide a strong bond between the various components without the necessity of unsightly adhesives or compromising the integrity of the bond.

In a further and important application, the present invention is particularly applicable for joining together precious stones which may be of the same type. For example, to prepare a diamond of a required or particular shape, it is necessary for a diamond to be procured having a dimensional geometry greater than that of the required or desired final product, and by standard stone cutting skills, prepare a suitably shaped and sized diamond of a required shape. Such large diamonds are generally of very high commercial value, and quite often can be prohibitive due to the expense. In the prior art, it is known to provide two or more smaller precious stones such as diamonds, and cut such stones so that when abutted the two or more smaller stones provides the desired geometrical shape and size of the end product. In order to join such two or more separate components together, typically an adhesive material is provided so as to form an

adhesive bond between the two precious metals. However, upon close review of the final product, for example a diamond-type structure, the joint between the two diamonds may be discerned, and unsightly portions of adhesive also may be visible. The present invention has been found to provide a bond which is not readily evident and which provides substantially the impression of a unitary structure, such as a diamond. Further, the present invention has been found to provide a strong bond between precious stone components. As such, when preparing diamond-type pieces, the present invention allows two or more smaller stones to be used, if cut appropriately, and bonded to each other so as to provide a substantially unitary structure in which noticeability of the presence of a bond structure also cannot be readily discerned, and the final product is provided with structural integrity. This, as will be appreciated by those skilled in the art, is a significant advantage as the sourcing of smaller stones which collectively form the geometric parameters of a desired product is substantially easier than should a single unitary diamond for the desired purpose. Those skilled in the art will appreciate a significant financial saving in this regard, and reduce the necessity to procure diamonds having a greater outer geometry for a desired precious stone piece of jewelry.

As also will be appreciated by those skilled in the art, the present invention, although directly applicable to joining of jewelry pieces, for example metals to ceramics or mineral-form of particular elements such as diamond, it is equally applicable to other industries and applications whereby a high quality bond having a great structural integrity is required, and also where the unsightliness of a bond between the two components be considered highly undesirable. Thus, the present invention overcomes substantial deficiencies within the prior art, whilst providing a bonding or joining method in which the deficiencies and problems associated with the prior art have been substantially mitigated.

Relevant Bibliography:

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