Precious metals, such as gold, silver and platinum, are important commodities and people can buy and sell them as part of an investment portfolio. While much effort is put into ensuring a trustworthy supply chain from the creator of the precious metal bars to the consumer, fake metal bars still sometimes find their way into the system. As an example, it has been found that rogue individuals can intercept the supply chain, obtain precious metal bars, remove a portion of the bar (e.g. by drilling), fill this with lower value metals of similar density, and cover up the drilled portion, so it matches the colour and lustre of the rest of the bar. Sometimes the density and the appearance of the forged bars matches authentic bars so closely that it is difficult, purely by visual inspection and weighing the bars, to determine the difference, even by an experienced professional in the industry. With these types of forgery, often the only way to determine if a precious metal bar has been tampered with is to cut it into segments. This is time consuming, and can result in a loss of the precious metal due to cutting, and the damage of authentic bars, if they are falsely suspected of being fake.

There is a need to try to limit the forgery in precious metal supply chains and provide ways to detect forged items that are cost-effective and easy to implement, and ideally avoid one or more of the problems mentioned above. Whatever technique is used should ideally avoid any damage to a metal bar or loss of precious metal, and the metal bar should present a precious metal exterior surface.

The tamper detection in other fields is also important, and ideally the technique should be widely applicable to a variety of objects of different shapes.

Summary

In a first aspect, there is provided a method of plating an item with a first metal, the method comprising

providing a plating solution comprising a liquid medium, a precursor species for forming a layer of the first metal on the items, and a plurality of luminescent particles suspended in the liquid medium, plating the item within the plating solution, such that the precursor species forms the layer of the first metal on the item and the luminescent particles are deposited within the layer of the first metal while it is formed. In an aspect, there is provided an apparatus for carrying out a method of plating, which may be the method described herein, the apparatus comprising:

a container for holding a plating solution,

a device for holding an item within the plating solution. In an aspect, there is provided an item having a layer thereon of a first metal, wherein luminescent particles are embedded in the first metal.

The present inventors have found techniques to authenticate and prevent tampering with items such as precious metal items and items of a variety of shapes. The techniques avoid loss or surface damage of the metal of the item. The resultant items having the layer of the first metal with embedded luminescent particles can be indistinguishable from the unplated item, and therefore provide a covert security feature. The coating of the surfaces of the item can be used to detect if there has been any tampering with the surface, e.g. by drilling or another technique to remove the item. Furthermore, the amount of coating of the first metal can be so thin, and the amount of luminescent particles so small that the purity of the item is maintained at a level that is acceptable to purchasers or investors in the item. The techniques are applicable to a wide variety of items, not just precious metal items, and it has been found that they lend themselves to many different shapes of item. The surface coverage has been found to be surprisingly even, as is the distribution of the luminescent particles in the layer of the first metal.

Brief Description of the Figures Figure 1 shows, schematically, an apparatus for carrying out a method as described herein.

Figure 2A shows a scanning electron micrograph image of the surface of a substrate that has been plated with gold and luminescent particles. Figure 2B shows a spectrum from energy dispersive x-ray spectroscopy of the surface of a substrate that has been plated with gold and luminescent particles.

Figure 3A shows a scanning electron micrograph image of the surface of a substrate that has been plated with pure gold, i.e. without luminescent particles.

Figure 3B shows a spectrum from energy dispersive x-ray spectroscopy of the surface of a substrate that has been plated with pure gold, i.e. without luminescent particles.

Detailed Description

In a first aspect, there is provided a method of plating an item with a first metal, the method comprising

providing a plating solution comprising a liquid medium, a precursor species for forming a layer of the first metal on the items, and a plurality of luminescent particles suspended in the liquid medium,

plating the item within the plating solution, such that the precursor species forms the layer of the first metal on the item and the luminescent particles are deposited within the layer of the first metal while it is formed.

Optionally, the item is held substantially stationary in the plating solution during plating, and/or a plurality of items are plated and the items do not move relative to one another. Optionally, the plating process is an electroplating process. Optionally, the item or items being plated are disposed on a jig. A jig may be considered to be a device that can allow an electrical connection to the item(s), and hold it/them in place, to prevent movement of the item(s) relative to the jig, and, when there are a plurality of items, relative movement to each other. The item or items may be clamped to the jig, e.g. using electrical contacts. Alternatively, the item or items may rest on the jig on electrical contacts, which may be shaped to hold or accept the item. The contacts may be in the form of hooks. The hooks may comprise stainless steel, copper, brass or bronze, e.g. phosphor bronze. Each item may have a single point of contact or a plurality of points of electrical contact to the jig. The holding of an item substantially stationary in the plating solution or the holding of items substantially stationary relative to one another has been found particularly effective for either plating with a first metal that is a precious metal and/or plating objects that contain a precious metal (e.g. the second metal as it is termed herein). There is no loss of the precious metal during coating and the surface of the precious metal is undamaged. If a plurality of items are within the plating solution, they may be held stationary relative to one another during plating, but there may be a movement of the items as a group, e.g. an oscillation, rotation or other movement, e.g. on a jig. The movement may be sufficiently slow such that it does not hinder deposition of the first metal and/or the luminescent particles on the item. Plating of items in the manner described in this paragraph has been found to produce a surprising even distribution of both the layer of the first metal on the item, and of the luminescent particles in the layer, both throughout the depth and across the plane of the layer, even when the item being plated has a relatively complex shape.

The device, e.g. a receptacle, for holding the item or items within the plating solution may be configured to move during the plating process, e.g. move continuously or intermittently during the plating process. The device, e.g. receptacle, for holding the item or items may be configured to rotate on an axis that is substantially horizontal. The device, e.g. receptacle, for holding the item or items may be configured to move (e.g., rotate) at a constant rate during the plating. Optionally, the receptacle is or comprises a barrel and the apparatus is adapted such that the item are continuously rotated in a barrel, and optionally at a constant rate, during the plating of item or items. Optionally, the rotation of the barrel is periodically interrupted. The receptacle (e.g., barrel) may rotate at a speed of 1 to 50 rpm, optionally from 4 to 30 rpm, optionally from 4 to 15 rpm, optionally from 4 to 12 rpm, optionally from 6 to 10 rpm, optionally about 8 rpm. The rate of rotation may be varied during plating or be held constant, for example for the entire duration of the plating. If the item or items are within a receptacle as described above, the receptacle may comprise or be formed out of a non-conducting material, such as plastic, and an electrode may extend into the receptacle, this electrode acting as a cathode during plating. The electrode acting as a cathode may contact at least some of the articles within the receptacle during plating. This may be applicable for any embodiments described herein. However, it has been found that it is less preferable when either the first metal is a precious metal (e.g. gold or silver) or the item (before plating) contains a precious metal. It has been found that there is a loss of the metal of the item and/or metal being plated. The loss may be relatively small, but for a precious metal item, this may be unacceptable in certain circumstances. The use of a moving receptacle during plating may be acceptable for plating non-precious metal items and/or plating a non-precious metal onto the items. Before the plating, the item may have been degreased, e.g. by contacting at least some of the surface area of the item (e.g. the area to be plated) with an acidic solution and/or a solution containing a surfactant. The item may be contacted with an activating solution to increase the propensity of the first metal to plate onto the item. For example, if the item comprises nickel, it may be contacted with a nickel strike (e.g. Woods nickel strike, e.g. an acidic aqueous solution of nickel chloride, e.g. containing an acid such as HCI).

The first metal may be selected from a transition metal. The first metal may be selected from Group 3, Group 4, Group 5, Group 6, Group 7, Group 8, Group 9, Group 10, Group 1 1 , Group 12, Group 13 and Group 14 of the periodic table, and alloys of any one or more thereof. The first metal may be selected from scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, mercury and aluminium, and alloys of one or more thereof. Optionally, the first metal is a precious metal selected from gold, silver, platinum, palladium, ruthenium, osmium, rhenium, rhodium and iridium, and alloys of one or more thereof. Optionally the item, before plating, comprises, consists essentially of, or consists of a second metal. "Consists essentially of" may indicate the item comprises at least 95 wt% of the second metal, optionally at least 98wt% of the second metal. The second metal may be selected from a transition metal. The second metal may be selected from Group 3, Group 4, Group 5, Group 6, Group 7, Group 8, Group 9, Group 10, Group 1 1 , Group 12, Group 13 and Group 14 of the periodic table, and alloys of any one or more thereof. The second metal may be selected from scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, mercury and aluminium. Optionally, the second metal is a precious metal selected from gold, silver, platinum, palladium, ruthenium, osmium, rhenium, rhodium and iridium, and alloys of one or more thereof.

Optionally, the first metal and the second metal are the same. Optionally, the first metal is a precious metal selected from gold, silver, platinum, palladium, ruthenium, osmium, rhenium, rhodium and iridium, and alloys of one or more thereof and the second metal is a precious metal selected from gold, silver, platinum, palladium, ruthenium, osmium, rhenium, rhodium and iridium, and alloys of one or more thereof, and optionally the first metal is the same as or contains the same metal as the second metal.

In an embodiment, the first metal and second metal both comprise gold. In an embodiment, the first metal and second metal both comprise silver. In an embodiment, the first metal and second metal both comprise platinum. In an embodiment, the first metal and second metal both comprise palladium. In an embodiment, the first metal and second metal both comprise ruthenium. In an embodiment, the first metal and second metal both comprise osmium. In an embodiment, the first metal and second metal both comprise rhenium. In an embodiment, the first metal and second metal both comprise rhodium. In an embodiment, the first metal and second metal both comprise iridium.

In an embodiment, the second metal may be selected from zinc, copper, tin, nickel, and alloys of one or more thereof, including, but not limited to, brass. The metal components of the alloys may comprise, consist essentially of or consist of at least two of zinc, copper and nickel or alloys may comprise, consist essentially of or consist of at least two of zinc, copper, nickel and tin.

The precursor species may comprise ions of the first metal, and one or more appropriate anions. Where the first metal comprises an alloy of two or more metals, the precursor may comprise ions of the different types of metal constituting the alloy. For example, where the first metal is brass, the precursor may comprise ions of copper and zinc, and optionally one or more other metals such as tin. In embodiments, the items may comprise, consist essentially of, or consist of steel, and the first metal comprises a metal selected from zinc, copper, tin, nickel, and an alloy of one or more thereof. In embodiments, the items may comprise, consist essentially of, or consist of steel, and the first metal comprises a metal selected from gold, silver, platinum, palladium, ruthenium, osmium, rhenium, rhodium and iridium. The metal components of the alloys may comprise, consist essentially of or consist of at least two of zinc, copper and nickel or alloys may comprise, consist essentially of or consist of at least two of zinc, copper, nickel and tin. The precursor material may comprise metal ions of the metal to be deposited in the layer of the first metal (i.e. the first metal). In an embodiment, the item is plated with the first metal on at least one side thereof, optionally two sides thereof, optionally three sides thereof, optionally four sides thereof, optionally five sides thereof, optionally six sides thereof. In an embodiment, the item is plated with the first metal on substantially all sides. The item may be plated with the first layer in continuous layer across at least one side of the item. The item may be plated with the first layer in discontinuous layer across at least one side of the item, e.g. by forming a pattern of plated areas on at least one side of the item. The pattern may be formed by masking areas that are not to be plated before plating is carried out. Luminescent, or fluorescent, materials or particles (fluorescent particles are a subset of luminescent particles) described herein may absorb light at a first wavelength and then emit light at a second wavelength, which may be shorter ("anti-Stokes emission") or longer ("Stokes emission") than the first wavelength, or substantially the same as the first wavelength. The luminescent particles may absorb light in the infrared ("IR"), visible, or ultraviolet ("UV") range, for example in the range of 200 nm to 5 μηι of the electromagnetic spectrum.

Luminescent particles may be or comprise a phosphor material. Phosphors materials are typically comprised of a host, typically comprised of a crystalline lattice, doped with luminescence centers comprised of trace amount of dopants, usually comprised of a transition metal, lanthanides, or actinides. A description of the design, synthesis, and optical characteristics of phosphors is provided in Chapter 6 of "Luminescence and the Solid State" by R.C. Ropp, second edition, which is hereby incorporated by reference herein.

The host may be selected from an aluminate, a borate, a gallate, a niobate, vanadate, a garnet, a pervoskite, an oxysulfide, and combinations thereof. The garnet may be selected from yttrium aluminum garnet (YAG), yttrium gallium garnet (YGG), yttrium iron garnet (YIG ), or gadolinium gallium garnet (GGG), gadolinium scandium gallium garnet (GSGG). The host may include an absorbing ion, e.g. an ion selected from chromium, iron, erbium, neodymium, ytterbium and combinations thereof. In an embodiment, the chromium is substituted in the host crystal lattice in an amount of at least 1 atomic percent based on a total number of ions of the host crystal lattice material that may be theoretically substituted. The host may include an emitting ion, for example an ion chosen from erbium, thulium, ytterbium, holmium, neodymium and combinations thereof. In embodiments, the luminescent materials may comprise an inorganic phosphor, for example a garnet, for example a phosphor selected from an yttrium aluminum garnet ("YAG") phosphor. The YAG phosphor may comprise yttrium aluminum garnet doped with a metal, for example a metal selected from a transition metal, a lanthanide, and an actinide. The YAG phosphor may comprise yttrium aluminum garnet doped with a metal selected from Ce, Nd, Tb, Sm, Dy, and Cr(IV).

In embodiments of the present invention, at least some of the luminescent particles have a diameter of 10 μηι or less, optionally 5 μηι or less, optionally 3 μηι or less, optionally 2 μηι or less. In embodiments, at least some of the luminescent particles have a diameter of from 0.5 μηι to 5 μηι, optionally from 0.5 μηι to 4 μηι, optionally from 0.5 μηι to 3 μηι, optionally from 0.5 μηι to 2 μηι, optionally from 0.5 μηι to 1.5 μηι, optionally from 0.8 μηι to 1.2 μηι, optionally from 0.6 μηι to 1 μηι, optionally from 0.7 μηι to 0.9 μηι, optionally about 0.8 μηι. They also allowed for a relatively stable suspension of the luminescent particles when in the plating solution.

In an embodiment, a surfactant may be present in the plating solution. The diameter (and correspondingly, determinations of the mean diameters) of a luminescent particle and/or any particle size distribution measurements may be measured using any suitable technique, including, but not limited to, scanning electron micrograph ("SEM"), and/or laser light scattering, for example in accordance with ASTM UOP856-07. The diameter of a luminescent particle may be the largest dimension measured across the particle. ASTM UOP856-07 is a well-known standardized method for determining the particle size distribution of powders and slurries using laser light scattering. This standard is commercially available from ASTM International. The laser light scattering measurements in accordance with this standard may be performed with a Microtrac Model S3500 instrument commercially available from Microtrac Inc., or a Malvern Instruments Mastersizer 3000. In embodiments, the luminescent particles may be characterised as described in ASTM F1877-05(2010). The particle size distribution measured in accordance with ASTM UOP856-07, e.g. for D50, D90 and D99, may be defined as the volume particle size distribution. The mean particle size, measured in accordance with ASTM UOP856-07, may be defined as the volumetric mean particle size. Luminescent particles utilized in plating processes described herein may have a mean diameter of 10 μηι or less, optionally 5 μηι or less, optionally 3 μηι or less, optionally 2 μηι or less. In embodiments, the luminescent particles may have a mean diameter of from 0.5 μηι to 5 μηι, e.g. 0.5 μηι to 4 μηι, e.g. 0.5 μηι to 3 μηι, e.g. 0.5 μηι to 2 μηι, optionally from 0.6 μηι to 1.5 μηι, optionally from 0.6 μηι to 1.2 μηι, optionally from 0.6 μηι to 1 μηι, optionally from 0.7 μηι to 1.2 μηι, optionally about 0.8 μηι. The mean diameter of the particles may be measured before the particles are incorporated into the plating solution. Luminescent particles utilized in plating processes described herein may have a D50 distribution of 10 μηι or less, optionally 5 μηι or less, optionally 3 μηι or less, optionally 2 μηι or less. A D50 distribution is defined as 50% of the population of particles having sizes less than the D50 value, and 50% of the population of particles having sizes greater than the D50 value. In an embodiment, the luminescent particles have a D50 distribution, measured using laser light scattering, in accordance with ASTM UOP856- 07, of 10 μηι or less, optionally 7 μηι or less, optionally 6 μηι or less, optionally 5 μηι or less, optionally 4 μηι or less. In an embodiment, the luminescent particles have a D50 distribution, measured using laser light scattering, in accordance with ASTM UOP856- 07, of from 0.1 μηι to 5 μηι, optionally from 0.3 μηι to 5 μηι, optionally from 0.4 μηι to 5 μηι, optionally from 0.5 μηι to 5 μηι, optionally from 0.8 μηι to 5 μηι, optionally from 0.9 μηι to 5 μηι, optionally from 0.5 μηι to 4 μηι, optionally from 0.5 μηι to 3 μηι, optionally from 0.5 μηι to 1.5 μηι, optionally about 1 μηι.

D50 distribution of the particles may be measured before the particles are incorporated into the plating solution. D50 is sometimes termed dso in the art.

Luminescent particles utilized in plating processes described herein may have a D90 distribution of 10 μηι or less, optionally 5 μηι or less, optionally 3 μηι or less, optionally 2 μηι or less, optionally 1 μηι or less. A D90 distribution is defined as 90% of the population of particles having sizes less than the D90 value, and 10% of the population of particles having sizes greater than the D90 value. The luminescent particles may have a D90 distribution of from 0.5 μηι to 5 μηι, optionally from 1 μηι to 4 μηι, optionally from 1 μηι to 3 μηι. The D90 distribution of the particles may be measured before the particles are incorporated into the plating solution. D90 is sometimes termed dgo in the art. In embodiments, luminescent particles, for example in the plating solution and/or in the items described herein, lack or substantially lack particles having a diameter of 10 μηι or more, optionally 8 μηι or more, optionally 7 μηι or more, optionally 5 μηι or more, optionally 4 μηι or more, optionally 3 μηι or more. "Substantially lack" may indicate 5 wt% of the particles or less, optionally 2 wt% or less, optionally 1 wt% or less have the stated diameter. Optionally, the particles may have a D99 distribution of 10 μηι or less, optionally 8 μηι or less, optionally 7 μηι or less, optionally 5 μηι or more, optionally 4 μηι or less, optionally 3 μηι or less. A D99 distribution is defined as 99% of the population of particles having sizes less than the D99 value, and 1 % of the population of particles having sizes greater than the D99 value. Optionally, the particles may have a D99 of from 10 μηι to 3 μηι, optionally from 7 μηι to 3 μηι, optionally from 5 μηι to 3 μηι.

In embodiments, luminescent particles may have a density of at least 2 kg/dm ³ , optionally at least 3 kg/dm ³ , optionally at least 4 kg/dm ³ , optionally at least 5 kg/dm ³ . In embodiments, luminescent particles may have a density of from least 2 kg/dm ³ to 9 kg/dm ³ , optionally from 3 kg/dm ³ to 9 kg/dm ³ , optionally from 4 kg/dm ³ to 9 kg/dm ³ , optionally from 4.5 kg/dm ³ to 9 kg/dm ³ , optionally from 5 kg/dm ³ to 9 kg/dm ³ . In an aspect, there is provided an apparatus for carrying out a method of plating, which may be the method described herein, the apparatus comprising:

a container for holding a plating solution,

a device for holding an item within the plating solution.

Optionally the apparatus comprises a means for agitating the plating solution before and/or during the plating.

Optionally, a means for agitating the plating solution before and/or during the plating, is located in an agitation unit, which may or may not be separate from the container for holding the plating solution in which the items are plated, and, if separate, the apparatus is adapted to circulate the plating solution from the container for holding the plating solution in which the items are plated to the agitation unit, in which the plating solution is agitated, before and/or during plating of the items, and then return the plating solution to the container for holding the plating solution in which the item is plated. Herein, "electroplating," "plating," "plating process," or any similar terminology refers to formation of a metallic layer (i.e. the layer of the first metal) on a substrate.

Plating methods described herein may involve the reduction of a precursor species comprising metal ions in the carrier medium, such that the metal ions form a metallic layer (i.e. the layer of the first metal). A method utilized may be an electroplating method in which an electrical potential is applied to the item or items, such that precursor species form a metallic layer (i.e. the layer of the first metal). In embodiments, the method may involve electroless plating, wherein the precursor comprises metal ions, and the carrier medium further comprises a reducing agent, capable of chemically reducing the metal ions, such that they form a metallic layer.

The method may involve first forming the item into a desired form, e.g. a bar, ingot, disc (which may be a coin blank), round or grain and then carrying out the plating as described herein. The method may involve first casting, or blanking the item, into a desired form, e.g. a bar, ingot, discround or grain, and then carrying out the plating as described herein. Casting may involve forming the item from molten metal in a mould and removing the item from the mould once the metal (e.g. the second metal as described herein) has cooled and solidified. Blanking may involve forming the item in a stamping and/or cutting process, e.g. from a sheet of metal (e.g. the second metal as described herein), and may be such that the item is punched from the sheet of metal (e.g. the second metal as described herein). The item formed in the blanking process may have two opposing flat or substantially flat (i.e. unpatterned) faces. The method may involve first forming the item, which may be in the form of a disc (which may be a coin blank), e.g. in a coin blanking process, and then carrying out the plating as described herein. A coin blanking process may be a process in which a disc is cut, punched or otherwise removed from a sheet, e.g. comprising the second metal. The coin blanking process may involve passing a sheet, e.g. of the first metal, through a blanking press, which punches discs from the sheet, the discs being the coin blanks. The coin blanks may then be annealed, e.g. in a furnace (up to 950 °C, e.g. at temperatures of from 800 °C to 950 °C), to soften the material (e.g. the second metal) of the coin blank. Each coin blank may be annealed before or after plating the layer comprising the first metal on the coin blank. Minting may involve stamping a pattern on a face of the item, which may be carried out after the formation of the item in a casting or blanking process. The plating of the layer comprising the first metal may be carried out after the formation of the item in a casting or blanking process, and before or after (but preferably before) stamping any pattern on the item (e.g. in a minting process).

There is also provided a method of making a patterned item, wherein the method comprises carrying out a method for plating articles according to the first aspect, and, after producing the article or plurality of plated items, stamping a pattern onto at least one surface or face of each of the item or items. The item before being plated may be in the form of a disc, e.g. a coin blank having two opposing flat or substantially flat (i.e. unpatterned) faces, and then, after plating, the article may be stamped (coined) with a pattern (e.g. for a coin blank, on one or both of the opposing faces, e.g. to form a coin).

Preferably, the plating of the first metal onto the item does not reduce the purity (in weight%) of the precious metal in the item, as a whole, including the layer of the first metal, by more than 0.5 %, optionally by more than 0.4%, optionally by more than 0.3%, optionally by more than 0.2%, optionally by more than 0.1 %, optionally by more than 0.05%, optionally by more than 0.01 %.

The items after plating may or may not be further shaped, e.g. stamped or struck. The items (before being plated) may be of any shape or size. In embodiments, the items may be in the form of discs. The discs may be circular or of some other regular shape. The regular shape may, for example, be a shape having n sides, where n is 3 or more, and optionally n is selected from 3 to 15, optionally from 3 to 10, optionally from 3 to 12. If the items have regular shapes, the sides of the shapes may be straight or curved. The discs may be apertured or non-apertured. In some embodiments, the disc may comprise an aperture, which may be located in a central portion of the face of the disc, and optionally extend the entire way through the disc. Optionally, the aperture may, for example, be for receiving a further smaller disc in the production of a bimetallic coin. The discs may have a thickness that is substantially the same across their entire face (or cross-section).

The item (before being plated) may be in the form of a bar or ingot. For example, the item may be in the form of a bar or ingot that has been cast, formed in a blanking process or minted into a particular form and/or may comprise, consist essentially of or consist of a precious metal selected from gold, silver, platinum, palladium, ruthenium, osmium, rhenium, rhodium and iridium. The bar may have a trapezoid cross section, e.g. an isosceles trapezoid or a rectangle, and the corners of the trapezoid may be sharp or rounded. The trapezoid may have two approximately parallel sides, with one of the parallel sides being shorter than the other, and the two further sides linking the parallel sides. An isosceles trapezoid may be defined as a trapezoid in which the base angles (i.e. the angles two sides make with the base, i.e. the longer of the parallel sides) are the same as each other or approximately the same (e.g. within 5° of one another).

The item (before being plated), which may be in the form of a bar, ingot, disc or coin blank, round or grain, and/or the item may contain at least 0.5 g of the second metal, optionally at least 1 g of the second metal, optionally at least 2 g of the second metal, optionally at least 5 g of the second metal, optionally at least 8 g of the second metal, optionally at least 10 g of the second metal, optionally at least 20 g of the second metal, optionally at least 30 g of the second metal, optionally at least 40 g of the second metal, optionally at least 50 g of the second metal, optionally at least 80 g of the second metal, optionally at least 90 g of the second metal, optionally at least 100 g of the second metal, optionally at least 150 g of the second metal, optionally at least 180 g of the second metal, optionally at least 200 g of the second metal, optionally at least 240 g of the second metal, optionally at least 250 g of the second metal, optionally at least 300 g of the second metal, optionally at least 400 g of the second metal, optionally at least 450 g of the second metal, optionally at least 500g of the second metal, optionally at least 800 g of the second metal, optionally at least 1 kg of the second metal, optionally at least 1.5 kg of the second metal, optionally at least 2 kg of the second metal, optionally at least 2.5 kg of the second metal, optionally at least 3 kg of the second metal, optionally at least 3.5 kg of the second metal, optionally at least 4 kg of the second metal, optionally at least 4.5 kg of the second metal, optionally at least 5 kg of the second metal, optionally at least 5.5 kg of the second metal, optionally at least 6 kg of the second metal. The item (before being plated), which may be in the form of a bar, ingot, disc or coin blank, round or grain, may contain from 40 g to 60 g of the second metal, optionally about 50 g of the second metal, optionally from 90 g to 1 10 of the second metal, optionally about 100 g of the second metal, optionally from 140 g to 160 g of the second metal, optionally about 150 g of the second metal, optionally from 240 g to 260 g of the second metal, optionally about 250 g of the second metal, optionally from 480 g to 520 g of the second metal, optionally from 490 g to 510 g of the second metal, optionally about 500 g of the second metal, optionally from 980 g to 1020 g of the second metal, optionally from 990 g to 1010 g of the second metal, optionally about 1 kg of the second metal, optionally from 1990 g to 2010 g of the second metal, optionally about 2kg of the second metal, optionally from 2990 g to 3010 g of the second metal, optionally about 3kg of the second metal, optionally from 3990 g to 4010 g of the second metal, optionally about 4kg of the second metal, optionally from 4990 g to 5010 g of the second metal, optionally about 5kg of the second metal, optionally from 5990 g to 6010 g of the second metal, optionally about 6kg of the second metal.

The item (before being plated), which may be in the form of a bar, which may be a gold bar, may contain at least 0.5 g of gold, optionally at least 1 g of gold, optionally at least 2 g of gold, optionally at least 5 g of gold, optionally at least 8 g of gold, optionally at least 10 g of gold, optionally at least 20 g of gold, optionally at least 30 g of gold, optionally at least 40 g of gold, optionally at least 50 g of gold, optionally at least 80 g of gold, optionally at least 90 g of gold, optionally at least 100 g of gold, optionally at least 150 g of gold, optionally at least 180 g of gold, optionally at least 200 g of gold, optionally at least 240 g of gold, optionally at least 250 g of gold, optionally at least 300 g of gold, optionally at least 400 g of gold, optionally at least 450 g of gold, optionally at least 500g of gold. The item (before being plated) may be in the form of a bar, which may be a gold bar, which may contain from 40 g to 60 g of gold, optionally about 50 g of gold, optionally from 90 g to 1 10 of gold, optionally about 100 g of gold, optionally from 140 g to 160 g of gold, optionally about 150 g of gold, optionally from 240 g to 260 g of gold, optionally about 250 g of gold, optionally from 480 g to 520 g of gold, optionally from 490 g to 510 g of gold, optionally about 500 g of gold, optionally from 980 g to 1020 g of gold, optionally from 990 g to 1010 g of gold optionally about 1 kg of gold.

The item (before being plated), which may be in the form of a bar, which may be a gold bar, may contain about 1 kg to 20 kg of gold, optionally 5 kg to 20 kg of gold, optionally 8 kg to 15 kg of gold, optionally 10 kg to 14 kg of gold, optionally 10.9 kg (350 troy ounces) to 13.4 kg (430 troy ounces). The gold may have a fineness of at least 900 parts per thousand (by weight) fine gold, optionally at least 920 parts per thousand (by weight) fine gold, optionally at least 940 parts per thousand (by weight) fine gold, optionally at least 950 parts per thousand (by weight) fine gold, optionally at least 960 parts per thousand (by weight) fine gold, optionally at least 970 parts per thousand (by weight) fine gold, optionally at least 980 parts per thousand (by weight) fine gold, optionally at least 990 parts per thousand (by weight) fine gold, optionally at least 995 parts per thousand (by weight) fine gold.

The dimensions of the bar, which may be a gold bar and/or may be trapezoid, e.g. isosceles trapezoid, in cross section may be:

in length (i.e. its longest dimension) from 150 mm to 500 mm, optionally 200 mm to 400 mm, optionally 225 mm to 375 mm, optionally 250 mm to 350 mm, optionally 210 mm to 290 mm,

and/or in width (i.e. a direction perpendicular to its length, and, if an isosceles trapezoid, the dimension across the shortest parallel side): 25 to 1 15 mm, optionally 35 to 105 mm, optionally 45 mm to 95 mm, optionally 55 to 85 mm; and/or

in height (i.e. in a direction perpendicular to its length and width, and, if an isosceles trapezoid, the dimension from one parallel side to the other): 5 mm to 100 mm, optionally 10 mm to 60 mm, optionally 20 mm to 55 mm, optionally 25 mm to 45 mm.

The item (before being plated), which may be in the form of a bar, which may be a silver bar, may contain at least 0.5 g of silver, optionally at least 1 g of silver, optionally at least 2 g of silver, optionally at least 5 g of silver, optionally at least 8 g of silver, optionally at least 10 g of silver, optionally at least 20 g of silver, optionally at least 30 g of silver, optionally at least 40 g of silver, optionally at least 50 g of silver, optionally at least 80 g of silver, optionally at least 90 g of silver, optionally at least 100 g of silver, optionally at least 150 g of silver, optionally at least 180 g of silver, optionally at least 200 g of silver, optionally at least 240 g of silver, optionally at least 250 g of silver, optionally at least 300 g of silver, optionally at least 400 g of silver, optionally at least 450 g of silver, optionally at least 500g of silver. The item (before being plated) may be in the form of a bar, which may be a silver bar, which may contain from 40 g to 60 g of silver, optionally about 50 g of silver, optionally from 90 g to 1 10 of silver, optionally about 100 g of silver, optionally from 140 g to 160 g of silver, optionally about 150 g of silver, optionally from 240 g to 260 g of silver, optionally about 250 g of silver, optionally from 480 g to 520 g of silver, optionally from 490 g to 510 g of silver, optionally about 500 g of silver, optionally from 980 g to 1020 g of silver, optionally from 990 g to 1010 g of silver optionally about 1 kg of silver. The item (before being plated), which may be in the form of a bar, which may be a silver bar, may contain about 1 kg to 60 kg of silver, optionally 5 kg to 55 kg of silver, optionally 10 kg to 50 kg of silver, optionally 15 kg to 45 kg of silver, optionally 20 kg to 40 kg of silver, optionally 23.3 kg (750 troy ounces) to 34.2 kg (1 100 troy ounces). The silver may have a fineness of at least 900 parts per thousand (by weight) silver, optionally at least 920 parts per thousand (by weight) silver, optionally at least 940 parts per thousand (by weight) silver, optionally at least 950 parts per thousand (by weight) silver, optionally at least 960 parts per thousand (by weight) silver, optionally at least 970 parts per thousand (by weight) silver, optionally at least 980 parts per thousand (by weight) silver, optionally at least 990 parts per thousand (by weight) silver, optionally at least 995 parts per thousand (by weight) silver, optionally at least 997 parts per thousand (by weight) silver, optionally at least 999 parts per thousand (by weight) silver.

The dimensions of the bar, which may be a silver bar and/or may be trapezoid, e.g. isosceles trapezoid, in cross section may be:

in length (i.e. its longest dimension) from 100 mm to 500 mm, optionally 200 mm to 400 mm, optionally 225 mm to 375 mm, optionally 250 mm to 350 mm,

and/or in width (i.e. a direction perpendicular to its length, and, if an isosceles trapezoid, the dimension across the shortest parallel side): 50 to 200 mm, optionally 75 to 175 mm, optionally 100 mm to 160 mm, optionally 110 to 150 mm; and/or

in height (i.e. in a direction perpendicular to its length and width, and, if an isosceles trapezoid, the dimension from one parallel side to the other): 10 mm to 200 mm, optionally 20 mm to 150 mm, optionally 40 mm to 120 mm, optionally 70 mm to

1 10 mm, optionally 60 mm to 100 mm. The item (before being plated), which may be in the form of a bar, may contain at least 0.5 g of platinum, optionally at least 1 g of platinum, optionally at least 2 g of platinum, optionally at least 5 g of platinum, optionally at least 8 g of platinum, optionally at least 10 g of platinum, optionally at least 20 g of platinum, optionally at least 30 g of platinum, optionally at least 40 g of platinum, optionally at least 50 g of platinum, optionally at least 80 g of platinum, optionally at least 90 g of platinum, optionally at least 100 g of platinum, optionally at least 150 g of platinum, optionally at least 180 g of platinum, optionally at least 200 g of platinum, optionally at least 240 g of platinum, optionally at least 250 g of platinum, optionally at least 300 g of platinum, optionally at least 400 g of platinum, optionally at least 450 g of platinum, optionally at least 500g of platinum, optionally at least 800g of platinum, optionally at least 1 kg of platinum, optionally at least 1.5 kg of platinum, optionally at least 2 kg of platinum, optionally at least 2.5 kg of platinum, optionally at least 3 kg of platinum, optionally at least 3.5 kg of platinum, optionally at least 4 kg of platinum, optionally at least 4.5 kg of platinum, optionally at least 5 kg of platinum, optionally at least 5.5 kg of platinum, optionally at least 6 kg of platinum. The item (before being plated), which may be in the form of a bar, which may be a platinum bar, may contain from 40 g to 60 g of platinum, optionally about 50 g of platinum, optionally from 90 g to 1 10 of platinum, optionally about 100 g of platinum, optionally from 140 g to 160 g of platinum, optionally about 150 g of platinum, optionally from 240 g to 260 g of platinum, optionally about 250 g of platinum, optionally from 480 g to 520 g of platinum, optionally from 490 g to 510 g of platinum, optionally about 500 g of platinum, optionally from 980 g to 1020 g of platinum, optionally from 990 g to 1010 g of platinum, optionally about 1 kg of platinum, optionally from 1990 g to 2010 g of platinum, optionally about 2kg of platinum, optionally from 2990 g to 3010 g of platinum, optionally about 3kg of platinum, optionally from 3990 g to 4010 g of platinum, optionally about 4kg of platinum, optionally from 4990 g to 5010 g of platinum, optionally about 5kg of platinum, optionally from 5990 g to 6010 g of platinum, optionally about 6kg of platinum.

The item (before being plated), which may be in the form of a bar, may contain at least 0.5 g of palladium, optionally at least 1 g of palladium, optionally at least 2 g of palladium, optionally at least 5 g of palladium, optionally at least 8 g of palladium, optionally at least 10 g of palladium, optionally at least 20 g of palladium, optionally at least 30 g of palladium, optionally at least 40 g of palladium, optionally at least 50 g of palladium, optionally at least 80 g of palladium, optionally at least 90 g of palladium, optionally at least 100 g of palladium, optionally at least 150 g of palladium, optionally at least 180 g of palladium, optionally at least 200 g of palladium, optionally at least 240 g of palladium, optionally at least 250 g of palladium, optionally at least 300 g of palladium, optionally at least 400 g of palladium, optionally at least 450 g of palladium, optionally at least 500g of palladium, optionally at least 800g of palladium, optionally at least 1 kg of palladium, optionally at least 1.5 kg of palladium, optionally at least 2 kg of palladium, optionally at least 2.5 kg of palladium, optionally at least 3 kg of palladium, optionally at least 3.5 kg of palladium, optionally at least 4 kg of palladium, optionally at least 4.5 kg of palladium, optionally at least 5 kg of palladium, optionally at least 5.5 kg of palladium, optionally at least 6 kg of palladium. The item (before being plated), which may be in the form of a bar, which may be a palladium bar, may contain from 40 g to 60 g of palladium, optionally about 50 g of palladium, optionally from 90 g to 1 10 of palladium, optionally about 100 g of palladium, optionally from 140 g to 160 g of palladium, optionally about 150 g of palladium, optionally from 240 g to 260 g of palladium, optionally about 250 g of palladium, optionally from 480 g to 520 g of palladium, optionally from 490 g to 510 g of palladium, optionally about 500 g of palladium, optionally from 980 g to 1020 g of palladium, optionally from 990 g to 1010 g of palladium optionally about 1 kg of palladium, optionally from 1990 g to 2010 g of palladium optionally about 2kg of palladium, optionally from 2990 g to 3010 g of palladium optionally about 3kg of palladium, optionally from 3990 g to 4010 g of palladium optionally about 4kg of palladium, optionally from 4990 g to 5010 g of palladium, optionally about 5kg of palladium, optionally from 5990 g to 6010 g of palladium optionally about 6kg of palladium.

The item (before being plated) may have one or more features selected from a flat surface, a curved surface, a protrusion, an indent, an aperture, which may extend all or part of the way through the item, a convex surface, a concave surface, ridges and valleys. In an embodiment, the item may be in the form of a hollow cylinder, e.g. for cutting into a plurality of rings for use as jewellery.

In an embodiment, the items (before being plated) may be spherical or substantially spherical, and may, before and/or after being plated, may be suitable for use as ball bearings.

In an embodiment, the items, before and/or after being plated, are suitable for use as a component of a mechanical or electrical item, including, but not limited to any moving parts, any structural parts, electrically conductive parts, and/or any housing of the mechanical or electrical item. Mechanical or electrical items include, but are not limited to, watches, vehicles and aircraft.

The items (before being plated) may comprise, consist essentially of, or consist of one or more second metal(s). The one or more second metal(s) may be in elemental form or in the form of an alloy. In an embodiment the one or more second metal(s) comprise a metal selected from Groups 3 to 14 of the Period Table, optionally from Groups 3 to 12 of the Periodic Table, and wherein the metal is in alloy or elemental form. In an embodiment, the second metal comprises a metal selected from iron, aluminium, copper, titanium, zinc, silver, gold, platinum, and wherein the metal is in alloy or elemental form. In embodiments, the one or more second metal(s) comprise iron. In embodiments, the one or more second metal(s) comprise steel. If the items consist essentially of the second metal(s), the metal(s) may constitute at least 95 wt% (weight- weight percentage) of the item, optionally at least 98 wt% of the item, optionally at least 99 wt% of the item, optionally at least 99.5 wt% of the item. The items (before being plated) may comprise a core, which may comprise a metal or a non-metal, having one or more layers thereon, and the one or more layers may comprise a metal(s) different to that of the core and/or other layers.

The item may be in the form of a piece of jewellery or a component thereof. The piece of jewellery may be selected from an earring, a necklace, a ring for the finger or toe, a cufflink, a bracelet, an armlet (i.e. a bracelet for the upper arm), a watch, a hairpin, a choker, a tore, a brooch and a pin badge. The component may be selected from a finding, a locket, a medallion, and a pendant. The finding may be selected from a clasp, an earwire, a ring blank, a bail, a metal loop (e.g. for attaching pendants to necklaces), a jump ring, a pin (e.g. for a brooch), a pin stem, a back, e.g. a butterfly back, for an earring.

The item may be an item for use in an industry selected from pharmaceutical, medical, veterinary, aeronautical, marine, financial, luxury goods and cosmetic industries.

The item may be a packaging or a component of packaging. The item may, for example, be an item for packaging a product, or a component of an item for packaging a product, e.g. product selected from a pharmaceutical product, medical product, veterinary product, aeronautical product, marine product, financial product, a luxury good and a cosmetic product. The item may, for example, be an item for packaging a pharmaceutical product, medical product, veterinary product, e.g. a receptacle or closure therefor. The item may, for example, be an item selected from a bottle, vial, pen, syringe and a dose container, and a closure for any of these items. The item may, for example, be a crimp seal or a crimp seal cap for a receptacle. A crimp seal is a seal that is can be used on a glass container, and the seal may be formed from metal and crimped around the opening of the glass container.

In an embodiment, the item is a watch or a watch component. In an embodiment, the item is selected from luxury goods, including, but not limited to, goods selected from pens, cutlery, such as forks, knives and spoons, watches, glasses, and sunglasses, and components thereof, e.g. logos for placing on the side of the goods and metal fastenining, such as screws.

In an embodiment, the item is a casing, a packaging or component thereof, for goods, such as luxury goods, including, but not limited to, goods selected from watches, glasses, and sunglasses.

In an embodiment, the item is a badge, e.g. a badge showing a logo or emblem, which may be affixed to an item, including, but not limited to, items selected from handbags, luggage or passport holders, purses, prams, furniture, clasps for purses and handbags and items of clothing.

In an embodiment, the item is selected from a bracket, a stud and a hinge (for example those used on luggage, furniture, clothing or homeware).

In an embodiment, the item is a fixture, e.g. for use on clothing and/or on accessories such as handbags, furniture and homeware products. In an embodiment, the item is selected from a zip, a hook and an eye, and a hoop (for example those used in clothes and homeware products such as curtains and pillows).

In an embodiment, the item is a staple (for example industrial staples used in packaging goods).

In an embodiment, the item is selected from screws, tacks and nails, such as round headed screws, spherical headed tacks and spherical headed nails.

In an embodiment, the item is a metal item or other non-metal item for use as a tag or token (e.g. to be incorporated within a label for clothing/luxury goods). In an embodiment, the item is a component for a mobile phone, a laptop, a computer, a tablet and any other electronic consumer goods. In an embodiment, the item is a microchip or a SIM card, or a component thereof.

In an embodiment, the item is a selected from a security foil, a tamper proof foil, blister foil packaging, for example for medication, and labels, e.g. for medication authentication. In an embodiment, the item is a lock or a key.

In an embodiment, the item, before being plated with the layer of the first metal has been plated with a layer of another metal, which may be the same as or different from the first metal, and may or may not contain luminescent particles, which may or may not be the same as the luminescent particles in the layer of the first metal.

In an embodiment, the item before being plated in accordance with the method described herein, comprises a non-metal, and the non-metal may be plated using the method described herein using electroless plating, such that the layer of the first metal is formed on the non-metal and the luminescent particles are deposited within the layer of the first metal while it is formed. The non-metal may be selected from a plastic, a glass and a ceramic material.

In an embodiment, the item, before being plated in accordance with the method described herein, comprises a non-metal, and the non-metal may be coated with, e.g. plated using electroless plating to form, a first layer of metal on the non-metal (the first layer of metal lacking the luminescent particles), and the items then plated in accordance with the method described herein, e.g. using electroplating or electroless plating, to form a second layer of metal on the first layer of metal, the second layer of metal being the metallic layer (of the first metal) in which the luminescent particles are deposited within while the metallic layer is formed. In embodiments, the items (before being plated) may be in the form of discs and comprise, consist essentially of, or consist of a first metal. The discs may have a diameter, as measured across a face of the disc, of at least 0.5 cm, optionally at least 1 cm, optionally at least 2 cm, optionally at least 4 cm, optionally at least 5 cm, optionally at least 6 cm, optionally at least 9 cm, optionally at least 10 cm, optionally at least 15 cm, optionally at least 20 cm, optionally at least 30 cm, optionally at least 40 cm. The discs may have a diameter, as measured across a face of the disc, of from 0.5 cm to 50 cm, optionally from 0.5 cm to 40 cm, optionally from 0.5 cm to 30 cm, optionally from 0.5 cm to 20 cm, optionally from 0.5 cm to 10 cm, optionally from 0.5 cm to 5 cm, optionally from 0.5 cm to 3 cm. If the disc has a regular shape, the diameter may be the largest dimension across a face of the disc. The disc may have a thickness of from 0.3 mm to 10 mm, optionally from 0.3 mm to 5 mm, optionally from 0.3 mm to 2 mm. For plating gold as the first metal, the plating solution may be selected from an alkaline gold cyanide solution (i.e. with a pH of more than 7, e.g. 8 to 12), a neutral gold cyanide solution (e.g. with a pH of from 5 to 8, e.g. about 7), an acid gold plating solution (e.g. with a pH of less than 7, e.g. 3 to 5), a gold sulphite (such as sodium gold sulphite) or a gold chloride solution (e.g. a chloroaurate solution). The gold plating solution may comprise species selected from MAu(CN)2 and MAu(CN) ₄ , wherein M is an alkali metal, such as Na or K, or an ammonium ion. The solution may comprise a buffer, such as a phosphate.

For plating silver as the first metal, the plating solution may be selected from a silver cyanide solution, which may have a pH of at least 8, a silver succinimides solution and a silver-containing alkaline thiosulphate solution. The plating solution may comprise an alkali metal cyanide, e.g. potassium or sodium cyanide, and silver cyanide.

The plating solution may comprise from 5 g/L to 150 g/L of metal ions that will form the first metal, optionally from 5 g/L to 100 g/L of metal ions that will form the first metal, optionally from 10 g/L to 75 g/L of metal ions that will form the first metal, optionally from 10 g/L to 50 g/L of metal ions that will form the first metal.

The current density may be a from 1 Am ^-2 to 500 Am ^-2 , optionally from 10 Am ^-2 to 500 Am ^"2 , optionally from 10 Am ^"2 to 400 Am ^"2 , optionally from 10 Am ^"2 to 400 Am ^"2 .

In embodiments, the plating solution may comprise from 5 g/L to 50 g/L of zinc ions, optionally from 10 g/L to 30 g/L of zinc ions, optionally from 15 g/L to 25 g/L of zinc ions, optionally from 16 g/L to 22 g/L of zinc ions. The precursor ions, that is the metal ions that will form the layer of the first metal, may be zinc ions or may be a mixture of zinc ions and one or more other metal ions, e.g. selected from copper ions, nickel ions and optionally tin ions, and a combination thereof. Where the precursor ions are zinc ions in combination with one or more other metal ions, the plating solution may comprise in total from 5 g/L to 150 g/L of metal ions that will form the layer of the first metal.

In embodiments, the plating solution may comprise from 10 g/L to 150 g/L of copper ions, optionally from 20 g/L to 120 g/L of copper ions, optionally from 20 g/L to 100 g/L of copper ions, optionally from 30 g/L to 90 g/L of copper ions. The precursor ions, that is the metal ions that will form the layer of the first metal, may be copper ions or may be a mixture of copper ions and one or more other metal ions, e.g. selected from zinc ions, nickel ions and optionally tin ions, and a combination thereof. Where the precursor ions are copper ions in combination with one or more other metal ions, the plating solution may comprise in total from 5 g/L to 150 g/L of metal ions that will form the layer of the first metal.

In embodiments, the plating solution may comprise from 10 g/L to 150 g/L of nickel ions, optionally from 30 g/L to 130 g/L of nickel ions, optionally from 40 to 120 g/L of nickel ions. The precursor ions, that is the metal ions that will form the layer of the first metal, may be nickel ions or may be a mixture of nickel ions and one or more other metal ions, e.g. selected from zinc ions, copper ions and optionally tin ions, and a combination thereof. Where the precursor ions are nickel ions in combination with one or more other metal ions, the plating solution may comprise in total from 5 g/L to 150 g/L of metal ions that will form the layer of the first metal.

The layer of the first metal, after plating onto the item(s), may have a thickness of at least 1 μηι, optionally at least 3 μηι, optionally at least 5 μηι, optionally at least 8 μηι, optionally at least 10 μηι, optionally at least 15 μηι, optionally at least 20 μηι, optionally at least 25 μηι. The layer of the first metal may have a thickness of from 1 μηι to 50 μηι, optionally from 1 μηι to 40 μηι, optionally from 5 μηι to 40 μηι, optionally from 5 μηι to 40 μηι, optionally from 5 μηι to 35 μηι, optionally from 5 μηι to 30 μηι, optionally from 5 μηι to 25 μηι, optionally from 5 μηι to 20 μηι, optionally from 5 μπι to 15 μηι, optionally from 5 μηι to 10 μηι, optionally from 10 μηι to 20 μηι, optionally from 10 μηι to 15 μηι. The depth of the metallic plating may be measured using any suitable technique, including, but not limited to x-ray fluorescence ("XRF") and scanning electron microscopy ("SEM").

In some embodiments, an electrical potential is applied to the items, such that they form a cathode within the plating solution, and a further electrode is present within the plating solution that forms an anode. The anode may be in any suitable form. In some embodiments, the anode comprises a metallic mesh material, which may form a basket. In embodiments of the present invention, the plating solution may be stirred, e.g. in the container in which the plating of the items is carried out, at a speed below the critical angular speed at which a vortex is formed within the plating solution. In fluid dynamics, a vortex is a region within a fluid where the flow is mostly a spinning motion about an imaginary axis, straight or curved. In embodiments, the plating solution is stirred by a stirrer rotating at a speed below 1800 rpm. In embodiments, the plating solution is stirred by a stirrer rotating at a speed of from 50 to 1800 rpm, optionally from 50 rpm to 500 rpm, optionally from 50 rpm to 350 rpm, optionally from 100 rpm to 300 rpm, optionally from 150 rpm to 250 rpm, optionally about 200 rpm. In embodiments of the present invention, stirring the plating solution below the critical angular speed at which a vortex would form in the plating solution is a stir speed that creates sufficient turbulence in the plating solution to prevent agglomeration of particles, but allows co- deposition of the luminescent particles and the plated metal.

In a further aspect, there is provided a method for plating an item, the method comprising providing a plating solution comprising a liquid medium, a precursor species suitable for forming a layer of a first metal on the item, and a plurality of luminescent particles suspended in the liquid medium; and plating the items within the plating solution, such that the precursor species forms the layer of the first metal on the items and the luminescent particles are deposited within the layer of the first metal while it is formed, wherein, before and/or during the plating of the articles, the plating solution is agitated.

In an embodiment, in any of the aspects described herein, the plating solution may be agitated before and/or during the formation of the layer of the first metal (i.e., plating process). In an embodiment, the plating solution is agitated by subjecting the plating solution to high shear. High shear may be defined as any turbulent movement of the plating solution, preferably turbulent flow that can cause deagglomeration of agglomerated luminescent particles within the plating solution, which may be as defined herein. High shear may be defined as subjecting the plating solution to turbulent flow. The plating solution may be agitated in the container in which the plating is carried out or in a separate unit, which may be termed an agitation unit herein. The plating solution may be agitated by a method selected from stirring the plating solution, shaking the plating solution, subjecting the plating solution to ultrasound, and any other suitable method. In an embodiment, the plating solution may be agitated by passing the plating solution through a centrifugal pump. In an embodiment, the plating solution is agitated by rotating an impeller in the plating solution, and preferably wherein the impeller has at least one blade that has, preferably a plurality of blades and each of which has, a surface that is substantially at a right angle to the plane that is at a right angle to the axis of rotation of the blade. In other words, the impeller may have an axis of rotation, and a plane can be defined such that the axis of rotation is perpendicular to the plane, and the impeller has one or more blades that has a surface that is substantially at a right angle to said plane. Such impellers may sometimes be referred to as high shear impellers, since the blades of the impeller effect turbulent, rather than laminar, flow of a liquid. The one or more blades of the impeller may extend radially from the axis of the impeller, or extend from a sheet that lies in the plane to which the axis of rotation is perpendicular. "Substantially at a right angle" may indicate an angle of from 70° to 110°, optionally from 80° to 100°, optionally from 85 ° to 95°, optionally about 90°. In an embodiment, the plating solution is agitated by rotating an impeller, which may be a high shear impeller, in the plating solution with a tip speed of at least 1 m/S, optionally a tip speed of at least 3 m/s, preferably a tip speed of at least 5 m/s. The impeller, which may be a high shear impeller and/or an impeller of the centrifugal pump, may rotate with a tip speed of from 5 m/s to 50 m/s, optionally a tip speed of from 5 m/s to 40 m/s, optionally a tip speed of from 5 m/s to 40 m/s, optionally a tip speed of from 5 to 25 m/s. In an embodiment, the impeller, e.g. the high shear impeller, is located within the container in which the items are plated. In an embodiment, the impeller, e.g. the high shear impeller, is located in a separate container from the one in which the items are plated, i.e. the agitation unit.

In an embodiment, the plating solution is agitated by passing the plating solution through a homogenizer, preferably a high pressure homogenizer. The homogenizer may be one that effects turbulent high velocity flow, which subjects the plating solution to high shear. A high pressure homogenizer may involve passing the plating solution along a conduit under pressure until a point at which the flow is diverted at an angle of approximately 90 °. In an embodiment, plating is carried out while the item is within the container of plating solution (this container being termed a plating container herein for brevity), and the plating solution, before and/or during the plating is diverted from the container of plating solution to an agitation unit, in which the plating solution is agitated, and then returned to the plating container, and optionally the diverting of the plating solution to the agitation unit and return of the plating to the receptacle in which the items are being plating is continuous, e.g. occurs during the entire plating of the layer of the first metal on the items. In an embodiment, the plating is carried out while the item is within the container of plating solution, and the plating solution, before and/or during the plating is circulated from the container of plating solution to an agitation unit, in which the plating solution is agitated, and then returned to the container of plating solution.

In an embodiment, plating is carried out while the items are within the container of plating solution, and the plating solution, during the plating, which may be for part or all of the plating to form the layer of the first metal, is diverted, e.g. along a conduit such as a pipe, e.g. by being pumped, from the container of plating solution to an agitation unit in which the plating solution is agitated, and then returned to the plating container and optionally the diverting of the plating solution to the agitation unit and return to the receptacle in which the items are being plating is continuous. This is advantageous, since it allows a suitable amount of turbulent flow to disperse the particles without them being removed from the surface of the item.

The agitation unit may comprise a means selected from an impeller, e.g. a high shear impeller, a centrifugal pump, an ultrasound unit for subjecting the plating solution to ultrasound, a homogeniser (which may use high pressure to cause turbulent flow), a static mixer, and any other means for subjecting the plating solution to turbulent flow. A static mixer is one in which a liquid is caused to flow past a series of static baffles, the flow past the static baffles inducing turbulent flow in the liquid. The agitation unit may comprise a centrifugal pump, which may be as described below.

The agitation may involve a method selected from stirring, shaking, subjecting the plating solution to ultrasound, and any other suitable method, e.g. any other method that subjects the plating solution to turbulent flow.

In an embodiment, plating is carried out while the items are within the container of plating solution (the plating container), and the plating solution, before and/or during the plating is diverted from the container of plating solution to a centrifugal pump, and then returned to the plating container, and optionally the diverting of the plating solution to the centrifugal pump and return of the plating to the receptacle in which the items are being plating is continuous. A centrifugal pump can be a pump in which liquid (e.g. the plating solution in the present application) is passed along a conduit, which may be along the direction of the axis of a rotating impeller, until it reaches a rotating impeller, the impeller then directing the liquid radially outward. After the liquid is directed radially outward, the liquid may be directed along a conduit to a desired location, e.g. back to the container in which the items are being plated.

The centrifugal pump may comprise a rotating impeller that rotates about an axis, causing the plating solution to be directed radially outward and, optionally, a stator, through which the plating solution flows as it is directed radially outward. If a centrifugal pump has a rotating impeller and a stator, this may be termed a 'rotor stator' herein. A stator remains substantially stationary while the impeller is rotating. The stator may be an annular body having a plurality of apertures through which the plating solution flows as it is directed radially outward. In an embodiment, the impeller comprises an annular body having a plurality of apertures spaced circumferentially around the annular body. In an embodiment, the impeller comprises an annular body having a plurality of apertures spaced circumferentially around the annular body, and the apertures are defined by walls that are optionally at an angle that is offset from an angle that is radially outward from the axis of the impeller. In an embodiment, the stator comprises an annular body having a plurality of apertures spaced circumferentially around the annular body, and the apertures are defined by walls that are optionally at an angle offset from an angle that is radially outward from the axis of the impeller.

In an embodiment, the impeller has a plurality of annular bodies arranged concentrically, and each annular body may have a plurality of apertures spaced circumferentially around the annular body, and, optionally, the stator has an annular body having a plurality of apertures spaced circumferentially around the annular body and which is arranged between at least two of the concentrically arranged annular bodies of the impeller. In an embodiment, the stator has a plurality of annular bodies arranged concentrically, each annular body having a plurality of apertures spaced circumferentially around the annular body, and, optionally, the impellor has an annular body having a plurality of apertures spaced circumferentially around the annular body and which is arranged between at least two of the concentrically arranged annular bodies of the stator. In an embodiment, the stator and impeller each has a plurality of annular bodies arranged concentrically, each annular body having a plurality of apertures spaced circumferentially around the annular body, the annular bodies of the stator and impeller interlocking such that there is an alternate arrangement concentrically of stator annular bodies and and impeller annular bodies. In such an arrangement, the plating solution would pass radially alternately through the apertures of the stator and the impeller.

In an embodiment, the centrifugal pump does not have a stator. The impeller of the centrifugal pump may rotate with a tip speed of at least 1 m/S, optionally a tip speed of at least 3 m/s, preferably a tip speed of at least 5 m/s. The impeller of the centrifugal pump may rotate with a tip speed of from 5 m/s to 50 m/s, optionally a tip speed of from 5 m/s to 40 m/s, optionally a tip speed of from 5 m/s to 40 m/s, optionally a tip speed of from 5 m/s to 25 m/s. Tip speed of an impeller can be defined as the peripheral speed, in m/s, of the part of the impeller located furthest, radially, from the axis of rotation of the impeller. Tip speed = the angular velocity (in revolutions per second) x diameter of the impeller x ττ. It has been found that when using an impeller having a tip speed within the ranges stated above, a suitable balance between high shear forces and flow rate can be found, such that high volumes of plating solution can be passed through the centrifugal pump, while still subjecting the plating solution to a reasonable amount of shear. This has been found to promote inclusion of a reasonably high amount of luminescent particles in the layer of the first metal. In an embodiment the pump may operate at a shear rate of at least 500 rpm, optionally at least 1000 rpm, optionally at least 2000 rpm, optionally at least 5000 rpm, optionally at least 8000 rpm, optionally at least 10000 rpm, optionally at least 12,000 rpm, optionally at least 15,000 rpm, optionally at least 16,000rpm. In an embodiment the pump may operate at a shear rate of from 500 rpm to 25,000 rpm, optionally from 1000 rpm to 25,000 rpm, optionally from 5000 rpm to 25,000 rpm, optionally from 5000 rpm to 20,000 rpm, optionally from 8000 rpm to 20,000 rpm, optionally from 10,000 to 20,000 rpm, optionally from 12,000 rpm to 20,000 rpm, optionally from 15,000 rpm to 20,000 rpm, optionally from 14,000 rpm to 18,000 rpm, optionally about 16,000rpm. In an embodiment, the container in which the plating is carried out, can contain or contains a volume, Vi , of plating solution, and the plating solution, before and/or during the plating, is circulated from the container of plating solution to an agitation unit, which may be a centrifugal pump, in which the plating solution is agitated, and then returned to the container of plating solution, and the volume of liquid V2 passed through the agitation unit, per hour is n X Vi, wherein n is at least 1 , optionally at least 3, optionally at least 5, optionally at least 10, optionally at least 15. Optionally, n is from 3 to 25, optionally from 5 to 25. In an embodiment, the impeller of the centrifugal pump rotates with a tip speed of at least 5 m/s, optionally at least 10 m/s, optionally at least 15 m/s, optionally from 15 m/s to 30 m/s, optionally from 15 m/s to 25 m/s and n is at least 10, optionally at least 15, optionally from 10 to 25, optionally from 15 to 20. Optionally, the impeller of the centrifugal pump rotates with a tip speed of from 15 m/s to 30 m/s and n is from 10 to 25, optionally from 15 to 20.

The container in which the plating of the items is carrier out may contain at least 1 L of plating solution, optionally at least 5 L of plating solution optionally at least 10 L of plating solution, optionally at least 15 L of plating solution, optionally at least 20 L of plating solution, optionally at least 30 L of plating solution, optionally at least 50 L or plating solution, optionally at least 100 L of plating solution, optionally at least 200 L of plating solution, optionally at least 250 L of plating solution, optionally at least 300 L of plating solution.

In an aspect, there is provided an apparatus, which may be for carrying out the method of any of the aspects described herein. In an embodiment, the apparatus comprises:

a container for holding a plating solution,

a means, e.g. a receptacle or a jig, for holding an item or items within the plating solution, and, optionally,

a means for agitating the plating solution before and/or during the plating.

The container for holding a plating solution may be termed a plating container herein for brevity. The apparatus may comprise a means for applying an electrical potential to the items when they are within the container of the plating solution, e.g. such that electroplating may be carried out.

In an embodiment, there is provided an apparatus, for carrying out the method described herein, the apparatus comprising:

a container for holding a plating solution, a device for holding an item within the plating solution, and a means for agitating the plating solution before and/or during the plating wherein the device for holding the item within the plating solution is configured to hold the item substantially stationary in the plating solution during plating, and/or to hold a plurality of items within the plating solution and prevent the items moving relative to one another,

wherein the means for agitating the plating solution before and/or during the plating, is located an agitation unit, that is separate from the container for holding the plating solution in which the items are plated, and the apparatus is adapted to circulate the plating solution from the container for holding the plating solution in which the items are plated to the agitation unit, in which the plating solution is agitated, before and/or during plating of the items, and then return the plating solution to the container for holding the plating solution in which the item is plated.

The means for agitating the plating solution may be a means for subjecting the plating solution to an ultrasound treatment, and the apparatus may be adapted to apply the ultrasound to the plating solution as described herein, e.g. before and/or during the plating of the items. In an embodiment, the apparatus comprises a means for agitating the plating solution, and the means may be adapted to agitate the plating solution as described herein, e.g. adapted such that the plating solution is agitated before and/or during the formation of the layer of the first metal (i.e., plating process). In an embodiment, the means for agitating the plating solution may be within the container for holding the plating solution in which the item is plated. In an embodiment, the means for agitating the plating solution is located in an agitation unit, that is separate from the container for holding the plating solution in which the item is plated, and the apparatus may be adapted to divert, e.g. circulate, the plating solution from the container for holding the plating solution in which the item is plated to the agitation unit, in which the plating solution is agitated, and then returned to the container for holding the plating solution in which the item is plated (which may be termed a plating container herein, for brevity). The means for agitating the plating solution may comprise an impeller, which may be adapted to operate as described herein. The means for agitating the plating solution may comprise a centrifugal pump, which may be adapted to operate as described herein. "Adapted such that" and other similar phrases may indicate that the apparatus is able to perform a particular operation, and, in embodiment, is programmed to perform a particular operation. As described herein, embodiments of the present invention provide a plating solution comprising a liquid medium, a precursor species for forming a layer of the first metal during a plating process, and a plurality of luminescent particles suspended in the liquid medium, at least some of which have diameters of 10 μηι or less. The liquid medium, a precursor species, layer of the first metal, plating process, and luminescent particles may be as described herein.

In embodiments, at least some of the luminescent particles in the plating solution have diameters of 5 μηι or less. In embodiments, at least some of the luminescent particles in the plating solution have diameters of 0.5 μηι to 5 μηι, optionally from 0.5 μηι to 4 μηι, optionally from 0.5 μηι to 3 μηι, optionally from 0.5 μηι to 2 μηι, optionally from 0.8 μηι to 1.5 μηι, optionally from 0.8 μηι to 1.2 μηι.

In embodiments, in the plating solution, the precursor species are for forming the layer of the first metal during a plating process, wherein the layer of the first metal may comprise a metal as described herein, e.g. a precious metal selected from gold, silver, platinum, palladium, ruthenium, osmium, rhenium, rhodium and iridium

In an aspect, there is provided an item having a layer thereon of a first metal, wherein luminescent particles are embedded in the first metal. The item may be as described herein. The layer of the first may be formed by the method as described herein. The first metal may have been plated on the item. The layer may be a plated layer of the first metal having luminescent particles embedded therein. The layer of the first metal may cover part of or all of at least one surface of the item. The layer of the first metal may cover part of or all of all of the surfaces of the item. The layer of the first metal may cover at least 50% of the surface area of at least one face of the item, optionally at least 60% of the surface area of at least one face of the item, optionally at least 70% of the surface area of at least one face of the item, optionally at least 80% of the surface area of at least one face of the item, optionally at least 90% of the surface area of at least one face of the item, optionally at least 95% of the surface area of at least one face of the item. The layer of the first metal may cover at least 50% of the surface area of the whole item, optionally at least 60% of the surface area of the whole item, optionally at least 70% of the surface area of the whole item, optionally at least 80% of the surface area of the whole item, optionally at least 90% of the surface area of the whole item, optionally at least 95% of the surface area of the whole item. The first layer may be present in the form of a continuous or a discontinuous layer across at least one side of the item, e.g. discontinuous being a pattern of areas of the first metal on at least one side of the item. The item may be plated with the first layer in discontinuous layer across at least one side of the item, e.g. by forming a pattern of plated areas on at least one side of the item, e.g. an array of dots, lines or other shapes, across at least one side of the item. The first layer may be in the form of a symbol, word or number of any language on a surface of the item.

The item may be any item described herein. In an embodiment, there is provided an item having a layer thereon of a first metal, wherein luminescent particles are embedded in the first metal, wherein the first metal is a precious metal selected from gold, silver, platinum, palladium, ruthenium, osmium, rhenium, rhodium and iridium. Optionally, the item, excluding the layer of the first metal, comprises, consists essentially of, or consists of a second metal. Optionally, the second metal is a precious metal selected from gold, silver, platinum, palladium, ruthenium, osmium, rhenium, rhodium and iridium. Optionally, the first metal and the second metal are the same. Optionally, the first metal and second metal both comprise gold. Optionally, the item is plated on substantially all sides with the layer of the first metal. Optionally, the item is in the form of a bar, ingot, disc or coin blank, coin, round or grain consisting essentially of or consisting of a second metal selected from gold, silver, platinum, palladium, ruthenium, osmium, rhenium, rhodium and iridium, the second metal having thereon the layer of the first metal having luminescent particles embedded therein. The item may producible by a method described herein.

Embodiments of the present invention will now be further described with reference to the following non-limiting Examples (also referred to herein as "experiments," "trial runs," "trials," and "runs") and accompanying Figures. Examples

Non-coin samples of metallic substrates with various electrodeposited coatings have been produced, both with and without an authentication element. The metals are primarily of the precious group metals (PGM) and substrates are PGM as well as base metal.

Methods:

The basic plating setup was common across all samples produced, the variation lies in the plating conditions (Chemistry, current etc.) and the geometry of the material used as a substrate. The basic setup is shown schematically in Figure 1. In this Figure is shown a container for holding the plating solution, in which is disposed an anode, a cathode, an impeller stirrer, and a conduit for circulating the plating solution from the container to the shear pump, and back to the container.

The following items have been plated in gold and the processes utilized to plate them are described also. All items were plated at a thickness of 5-18 μηι. The items were suspended in the plating solution via a copper wire and the contact with the substrate was made with a crocodile clip (not shown in the Figure).

Several different plating solutions were utilized to yield coatings containing additive in Gold, Copper, Nickel and Silver. The basic parameters for each material are shown below. The impeller in the plating solution was maintained at a constant 200rpm across all chemistries.

In this example the additive was a doped rare earth garnet. The particle size was 1 μηι D50 measured via dynamic light scattering. The gold plating solution was an aqueous solution containing KAu(CN)2, KCN, K2HPO4, K2CO3. The samples were plated for a period of time at a current density specific to the surface area of the substrate to yield a thickness of 5 - 18μηι.

Plated metal Substrates used Chemistry / target Shear rate/ current thickness density

Gold Nickel silver, Gold cyanide 16,000rpm/ 30Anr ²

The processes including the surface preparation for the items to be plated are detailed below for the particular example of the gold plating. Key (nickel silver)

Degrease - Woods nickel strike - Gold cyanide plating solution

Aluminium crimp seal caps (Potential vaccine vial seals)

Degrease - Cone H2S04 - Cone H2S04 - Dl rinse (i.e. a rinse with deionised water) - Water shedding rinse - NaOH 20s -Dl rinse -50% nitric - Dl rinse - Zincate dip - Dl rinse - Woods nickel strike - Dl rinse

Hull cell plates (galvanized mild steel)

50% HCI dip - Gold cyanide plating solution

Pen (stainless steel)

Degrease - Gold strike (1 um) - Gold cyanide plating solution

Spoon (stainless steel)

Degrease - Woods nickel strike - Dl rinse -Gold cyanide plating solution

Gold (99.99%) coins

Degrease - Gold cyanide plating solution. In all instances the geometries of the substrate were taken into account and the requisite current density selected for the surface area to be coated. The substrates were plated using a jig plating method, whereby the substrate was suspended in the circulating plating solution and the substrate was in a static position throughout the process.

To codeposit the additive particles the same plating solution was utilized and the additive particles were added at a concentration > 1 g/l. Upon completion of the plating samples were analysed via scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX) and the presence of the additive was confirmed via the presence of non-gold elements in the edx spectra which are not commonly occurring in any of the preparatory processes or plating process. Figures 2A and 3A show, respectively, (i) the surface of a plated item, where the gold plating includes the doped garnet and (ii) the surface of the plated item that has been plated with pure gold (i.e. lacking the doped garnet). From the proceeding images two different regions of the same image were analyzed via EDX and it can clearly be evidenced that in the first image (Figure 2A) and spectra (Figure 2B) there is a preponderance of gold and other materials, including the luminescent particles, and in the second image (Figure 3A) and spectra (Figure 3B) there is only gold.

The plating time was dictated by the calculation shown below using Faradays law and information on the geometry. As well as this, the plated items were checked on a handheld detector tailored specifically to detect the presence of the additive and in all instances a positive result was obtained. The detector illuminates the substance at one wavelength and detects the fluoresced light at a second wavelength. The plating processes were determined by the following procedure.

Surface area of substrate determined

Target plating thickness determined (desired thickness)

Surface area x thickness x deposited material density = mass of deposited material Applying Faradays laws;

W = ItA /zF which when rearranged WzF/A = It Where w = weight of deposited material, A = atomic weight of material, z = valence of deposited metal in solution.

It = quantity of current in coulombs.

This is then converted to Amp hrs (1 C = 15.619444444 Ah) and divided by a value of current density to yield a plating time for the given area. This calculation was completed for all substrates. Assumptions were that deposition is 100% efficient, addition of additive in no way affects the deposition and the final coating is uniform and non-porous.