Description:FIELD OF INVENTION
[001] The present disclosure belongs to the technical field of nanophotonics and plasmonic nanostructures. More particularly, the present disclosure relates to a gap-plasmonic coupled nanostructured array systems. Further, the present disclosure also relates to a gap-plasmonic coupled nanostructured array systems assisted with assisted upconverter system and/or 2D materials or organic surface ligand as a gap layer. The present disclosure also relates to a random arrangement of nanopattern with thin film dielectric material/2D materials as a gap layer in gap-plasmon coupled system & gap-plasmon coupled assisted upconverter system.

BACKGROUND OF THE INVENTION
[002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[003] Near-infrared (NIR) light, ranging from 780 to 2500 nm, penetrates materials and biological tissues [Jacques SL., Physics in Medicine & Biology, 2013, 58(11), R37–R61] deeply with low scattering and absorption than visible light, making it essential in applications such as spectroscopy, telecommunications, solar energy harvesting, and biomedical imaging [Cui et al., Nano Letters, 2015, 15(10), 6295-6301; Liu et al., Bioconjugate Chemistry, 2019, 31(2), 260-275]. In spectroscopy, NIR enables non-invasive chemical analysis, while in telecommunications, particularly at 1550 nm, it supports long-distance data transmission with minimal loss. The deep penetration depth of NIR makes it particularly beneficial in security, environmental monitoring, and medical diagnostics [Przybylska et al., Scientific Reports, 2022, 12(1), 19388; Vitorino et al., 2023, Photodiagnosis and Photodynamic Therapy, 42, 103633]. However, in solar energy harvesting, the NIR photon conversion efficiency remains low due to the inherent limitations in materials, such as poor absorption, which can lead to suboptimal performance. While NIR light has definitive advantages for sensing applications, background noise, interference, and weak signal strength can hinder the sensitivity and specificity of NIR-based sensors. Plasmonic nanostructures, such as those made from gold (Au) [Lumdee et al., Acs Photonics, 2014, 1(11), 1224-1230] and silver (Ag) [Gahlaut et al., Biosensors, 2022, 12(9), 713], enhance NIR technologies by amplifying electromagnetic fields, improving signal transmission, and boosting solar cell efficiency. Despite their potential, the complex and costly design of these nanostructures limit scalability, requiring further innovation to use NIR’s full capabilities across applications.
[004] Recently, newer concepts of design of plasmonic nanostructures that can confine the electromagnetic field in nanoscopic spacings, have become relevant. These nanoscale designs include nano-voids [Sierra-Martin et al., Advances in Colloid and Interface Science, 2021, 290, 102394], nano-cavities [Hwang et al., Chemical Communications, 2021, 57(40), 4875-4885 ], nano-cracks [Gautam et al., 2020, Materials Chemistry and Physics, 251, 123178], nano-trenches [Xu et al., Nano Letters, 2021, 21(7), 3044-3051], and nano-gaps [Im et al., Nano letters, 2010, 10(6), 2231-2236]. Among these, nanogaps are spaces of nanoscale dimensions that are created between two adjacent metallic nanostructures. The nanogap structures can enable extreme confinement of electromagnetic energy when light is squeezed through the gaps [Chen et al., Nature communications, 2013, 4(1), 2361]. A variety of applications like ultrasensitive spectroscopy [Dong et al., Chemical Communications, 2017, 53(33), 4546-4549], single molecule sensing methods [Walt DR., Analytical chemistry, 2013, 85(3), 1258-1263], quantum metrology [Couteau et al., Nature Reviews Physics, 5(6), 354-363], and early detection biosensors [Rather et al., Theranostic Applications of Nanotechnology in Neurological Disorders, 2024, 43-83], where high sensitivity and precision beyond the signal-to-noise limit are required, can benefit from the concept of nanogap based plasmonic.
[005] Many nano-lithographic techniques have been developed for realizing effective nanogap-based structures [Gu et al., Advanced Materials Interfaces, 2018, 5(19), 1800648]. Nevertheless, when it comes to nanogap-based arrays where precise spatial gap sizes are desired, especially gaps smaller than 5 nm, the fabrication process, especially for mass production, is challenging [Yang et al., Small, 2019, 15(5), 1804177]. Recent advances in nanofabrication technology, including synthesis and assembly of nanoparticles have helped the research in this area, but it remains a challenge to control the film morphology at the nanoscale level. The gaps below 10 nm that are required for plasmonic effects are difficult to fabricate with conventional direct writing methods such as electron beam lithography (EBL). While gap sizes of few nanometers can be produced by the focused ion beam (FIB) lithography technique [Kubena et al., Measurement, and Phenomena, 1991, 9(6), 3079-3083], the problem of ionic contamination during milling is a drawback. Narrow nanogaps can be produced by indirect techniques like oblique angle shadow evaporation, edge lithography, electromigration, and mechanically controllable break (MCB) junction, but translating these techniques to production lines and/or achieving limiting patterning shapes is a challenge.
[006] A similar surge in the interest in light upconverting materials like lanthanides in recent years has led to many opto-electronic device applications [Singh et al., Coordination Chemistry Reviews, 455, 214365]. For the enhancement of upconversion luminescence (UCL) to device compatible levels, different routes have been reported in the literature [Das et al., Nanophotonics, 2020, 9(6), 1359-1371; Xu et al., ACS Applied Materials & Interfaces, 2024, 16(19), 24879-24888]. One such route is the plasmonic enhancement of UCL which has been studied both theoretically and experimentally [Das et al., Nanophotonics, 2020, 9(6), 1359-1371]. Such approaches include incorporation of plasmonic metallic nanoparticles in the vicinity of the upconverting nanocrystals and into thin films of upconverting materials [Saboktakin et al., ACS nano, 2013, 7(8), 7186-7192].
[007] Even though metals are the main nanostructure used for fabrication of nanogaps, the high free carrier concentration associated with metals creates a constraint for spectral tunability [Saha et al., Physical Chemistry Chemical Physics, 2015, 17(24), 16067-16079]. The application of ultra-sensitivity of the devices and analyte detection, and plasmonic-based single-molecule analysis require responses in NIR and mid-IR spectral regions. When the metal-based nanostructures of conventional plasmonic designs are tuned to extend their plasmonic response for those applications which require NIR spectral region they show extreme optical losses in the visible spectrum, since the metallic spectral parasitic absorption can coincide with the resonance emission peaks, nullifying the measurable response in NIR or mid-IR applications.
[008] To realize the extent of benefit plasmonics can provide to the devices, affordability and scalability of such a system are crucial factors. The use of copper (Cu) nanostructures in gap-coupled plasmonic system has not been explored due to inherent growth of copper oxide on copper surface, which alters the resonance with time as per the thickness of oxide grows [Pillai et al., Nanotechnology, 2024, 35(33), 335502; Pillai et al., Next Materials, 2025, 7, 100377].
[009] While plasmonic enhancement by metal-based conventional plasmonic nanopattern system shows great potential, there are certain drawbacks to consider, especially when tuned for NIR spectral region. Firstly, the weak electric field strength in the NIR region and the presence of optical losses in the visible wavelengths associated with metals, attributed to parasitic absorptions caused by carrier scattering and transitions. Thus, there is a need to develop new gap-plasmon coupled nanostructured array system with spectrally tunable response.

OBJECTS OF THE INVENTION
[0010] An objective of the present disclosure is to provide a gap-plasmonic coupled nanostructured array systems.
[0011] Another objective of the present disclosure is to provide a gap-plasmonic coupled nanostructured array system having solid dielectric nano or microsphere in the centre coated with metallic core.
[0012] Further objective of the present disclosure is to provide a gap-plasmonic coupled nanostructured array systems assisted upconverting nanoparticles.
[0013] Another objective of the present disclosure is to provide 2D materials or organic surface ligand as a gap layer in gap-plasmon coupled system & gap-plasmon coupled assisted upconverter system.
[0014] Still another objective of the present disclosure is to provide a random arrangement of nanopattern with thin film dielectric material as a gap layer in gap-plasmon coupled system & gap-plasmon coupled assisted upconverter system.
[0015] Yet another objective of the present disclosure is to provide a random arrangement of nanopattern with 2D materials as a gap layer in gap-plasmon coupled system & gap-plasmon coupled assisted upconverter system.

SUMMARY
[0016] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in Detailed Description section. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
[0017] Accordingly, in one aspect, the present disclosure relates to a gap-plasmonic coupled nanostructured array systems (100) comprising: i) a metallic core (600) provides reflection and acts as a mirror; ii) a dielectric material layer (620) covered on the metallic core (600); and iii) a metal nanoparticle or nano-blocks (610) distributed on the thin dielectric material layer (620).
[0018] Another aspect of the present disclosure relates to a gap-plasmonic coupled nanostructured array systems (100) comprising: i) a metallic core (600) provides reflection and acts as a mirror; ii) a thin dielectric material layer (620) covered on the metallic core (600); and iii) a metal nanoparticle or nano-blocks (610) distributed on the thin dielectric material layer (620); and iv) a solid dielectric nano or microsphere (500) in the centre which is coated with the metallic core (600).
[0019] Another aspect of the present disclosure relates to a gap-plasmonic coupled nanostructured array systems (100) comprising: i) a metallic core (600) provides reflection and acts as a mirror; ii) a thin dielectric material layer (620) covered on the metallic core (600); and iii) a metal nanoparticle or nano-blocks (610) distributed on the thin dielectric material layer (620); iv) a solid dielectric nano or microsphere (500) which is coated with the metallic core (600); and v) a 2D-material gap layer (621) is coated on the thin dielectric material layer (620).
[0020] Various objects, features, aspects and advantages of the present disclosure will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing FIG.s in which like numerals represent like features.

BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The accompanying drawing(s) are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure. The diagrams are for illustration only, which thus is not a limitation of the present disclosure.
[0022] FIG. 1 illustrates cross-sectional schematic diagrams of different embodiments of gap-plasmonic coupled systems in an air environment with (A) nano- or micro-sphere metal and (B) with metal coated dielectric nano- or micro-sphere.
[0023] FIG. 2 illustrates cross-sectional schematic diagrams of different embodiments of gap-plasmonic coupled systems immersed in an environment (700) other than the air (n >1) with (A) nano- or micro-sphere metal and (B) with metal coated dielectric nano- or micro-sphere.
[0024] FIG. 3 illustrates cross-sectional schematic diagrams of different embodiments of gap-plasmonic coupled systems encapsulated with an optically transparent dielectric medium (700) of refractive index greater than that of the air (n>1) with (A) nano- or micro-sphere metal and (B) with metal coated dielectric nano- or micro-sphere.
[0025] FIG. 4 illustrates 4A, 4B, 4C and 4D demonstrate the findings of spectral dependence of optical absorption of gap-plasmonic coupled systems obtained for the design configuration of FIGS. 1A, 1B, 2A and 3B, respectively.
[0026] FIG. 5 illustrates 5A–5C, 5D–5F and 5G–5I illustrate cross-sectional schematic diagrams of different structures of upconverting nanoparticles attached with gap-plasmonic coupled systems shown in FIG. 1B, FIG. 2B and FIG. 3B, respectively.
[0027] FIG. 6 illustrates the findings of spectral dependence of optical properties of the system gap-plasmonic coupled systems with and without upconverting nanoparticles for one of the design configurations of the embodiments shown in FIG. 1D (110) (w/o UC-NP) and FIG. 3A (210) (with UC-NP).
[0028] FIG. 7 illustrates the two-dimensional spatial distribution profiles of electric field (FIG. 7A), light intensity (FIG. 7B) generated in the corresponding gap-plasmonic coupled system of embodiment 210 shown in FIG. 5A at the plasmonic resonance wavelength of 1530 nm. The two-dimensional spatial distribution profiles of intensity of upconversion luminescence from the upconverting nanoparticles at the emission wavelength of 980 nm is shown in FIG. 7C.
[0029] FIG. 8 illustrates 8A, 8E and 8I illustrate cross-sectional schematic diagrams of different structures of gap-plasmonic coupled systems. FIGS. 8B–8D, 8F–8H and 8J–8L are the different arrangements of upconverting nanoparticles attached to the gap-plasmonic coupled systems of FIG. 8A, 8E, and 8I, respectively.
[0030] FIG. 9 illustrates 9A and 9D illustrate cross-sectional schematic diagrams of different embodiments of gap-plasmonic coupled systems. FIGS. 9B–9C and 9E–9F are the different embodiments of upconverting nanoparticles attached to the gap-plasmonic coupled systems of FIGS. 9A and 9D, respectively.
[0031] FIG. 10 illustrates 10A and 10D illustrate cross-sectional schematic diagrams of different structures of gap-plasmonic coupled systems. FIGS. 10B–10C and 10E–10F are the different embodiments of upconverting nanoparticles attached to the gap-plasmonic coupled systems of FIG. 10A and 10D, respectively.
[0032] FIG. 11 illustrates a cross-sectional schematic diagram of the embodiments of gap-plasmonic coupled assisted upconverting nanoparticle systems applied to solar cell devices.
[0033] FIG. 12 illustrates a concept of utilization of gap-plasmonic coupled assisted upconverter system in an ink which can be used in printable electronics such as printing security codes, tags etc.

DETAILED DESCRIPTION OF THE INVENTION
[0034] The following is a detailed description of embodiments of the disclosure. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0035] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
[0036] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
[0037] In some embodiments, numbers have been used for quantifying weights, percentages, ratios, and so forth, to describe and claim certain embodiments of the invention and are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable.
[0038] The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
[0039] Unless the context requires otherwise, throughout the specification which follows, the word “comprise” and variations thereof, such as “comprises” and “comprising” are to be construed in an open, inclusive sense that is as “including, but not limited to.”
[0040] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0041] The recitation of the ranges of values herein is merely intended to serve as a shorthand method of referring individually to each value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. Furthermore, the ranges defined throughout the specification include the end values as well, i.e., a range of 1 to 10 implies that both 1 and 10 are included in the range. For the avoidance of doubt, the applicant shall be entitled to any equivalents according to applicable law.
[0042] All methods described herein can be performed in a suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples or exemplary language (e.g., “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[0043] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified.
[0044] The description that follows, and the embodiments described therein, is provided by way of illustration of an example, or examples, of particular embodiments of the principles and aspects of the present disclosure. These examples are provided for the purposes of explanation, and not of limitation, of those principles and of the disclosure.
[0045] It should also be appreciated that the present disclosure can be implemented in numerous ways, including as a system, a method or a device. In this specification, these implementations, or any other form that the invention may take, may be referred to as processes. In general, the order of the steps of the disclosed processes may be altered within the scope of the invention.
[0046] The headings and abstract of the invention provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.
[0047] The following discussion provides many example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus, if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed.
[0048] The term “or”, as used herein, is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
[0049] The terms “weight percent,” “wt-%,” “percent by weight,” “% by weight,” and variations thereof, as used herein, refer to the concentration of a substance as the weight of that substance divided by the total weight of the composition and multiplied by 100. It is understood that, as used here, “percent,” “%,” and the like are intended to be synonymous with “weight percent,” “wt-%,” etc.
[0050] Various terms are used herein to the extent a term used is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.
[0051] The present disclosure relates to a design of gap-plasmon coupled system, this naturally formed oxide layer on copper has been used as the spacer layer. The utilization of such naturally formed oxide layers in Cu nanostructures has not been investigated in literature. The design also provides optical tunability using different gap thickness and shape and size of copper nanopattern over the oxide for specific plasmonic applications. The present disclosure is based on the concept of nanogap based design architecture can be very promising to apply in copper-based nanostructures. Integrating the gap-plasmon coupled copper nanospheres with the upconverting nanoparticles provide a perfect solution to enhance the typically low upconversion luminescence of the upconverters. Since the resonance wavelength of plasmonic system can be tuned to match the absorption band of the upconverting nanoparticles, the combined system can work as a standalone unit to be used in various applications.
[0052] An embodiment of the present disclosure is to provide a gap-plasmonic coupled nanostructured array systems (100) comprising: i) a metallic core (600) provides reflection and acts as a mirror; ii) a dielectric material layer (620) covered on the metallic core (600); and iii) a metal nanoparticle or nano-blocks (610) distributed on the thin dielectric material layer (620).
[0053] In some embodiment, the metallic core is selected from a group comprising of Au, Ag, Al, Cu, ITO and combination thereof. Preferably, the metal is Cu.
[0054] In some embodiment, the dielectric material layer (620) is selected from a group comprising of SiO2, SiN4, TiO2, Al2O3, diamond like carbon, copper oxide and combination thereof and the dielectric material layer (620) has a thickness less than 10 nm. Preferably, the dielectric material layer is copper oxide and the thickness ranging from 0.1 to 10 nm.
[0055] In some embodiment, the metal nanoparticle or nano-blocks (610) is selected from a group comprising of Au, Ag, Al, Cu, ITO and combination thereof. Preferably, the metal nanoparticle or nano-blocks (610) is Cu. In one embodiment, the metal nanoparticle or nano-blocks (610) has a similar metal of metallic core (600).
[0056] In one of the embodiment, the system further comprising a solid dielectric nano or microsphere (500) in the centre which is coated with metallic core (600).
[0057] In some embodiment, the solid dielectric nano or microsphere (500) is selected from a group comprising of SiO2, TiO2, ZnO and combination thereof. Preferably, the solid dielectric nano or microsphere (500) is SiO2.
[0058] Another embodiment of the present disclosure is to provide a gap-plasmonic coupled nanostructured array systems (100) comprising: i) a metallic core (600) provides reflection and acts as a mirror; ii) a thin dielectric material layer (620) covered on the metallic core (600); and iii) a metal nanoparticle or nano-blocks (610) distributed on the thin dielectric material layer (620); and iv) a solid dielectric nano or microsphere (500) in the centre which is coated with the metallic core (600).
[0059] In one of the embodiment, the system further comprises upconverting nanoparticles (630) dispersed in between the metal nanoparticle or nano-blocks (610).
[0060] In one of the embodiment, the upconverting nanoparticles (630) are selected from a group comprising of NaYF4-Er, NaYF4-Er-Yb, TiO2-Er, TiO2-Er-Yb, gadolinium oxysulfide: Er, Yb and combination thereof. Preferably, the upconverting nanoparticles (630) is NaYF4-Er.
[0061] In one of the embodiments, the system further comprises a monolayer of upconverting nanoparticles (630) is coated on the metal nanoparticle or nano-blocks (610) and the thin dielectric material layer (620).
[0062] In one of the embodiments, the system further comprises a multilayer of upconverting nanoparticles (630) coated on the metal nanoparticle or nano-blocks (610) and the thin dielectric material layer (620).
[0063] In one of the embodiment, the metal nanoparticle or nano-blocks (610) are randomly arranged.
[0064] In one of the embodiment, the system further comprises upconverting nanoparticles (630) dispersed in between randomly arranged metal nanoparticles or nano-blocks (610).
[0065] In one of the embodiment, the system further comprises a monolayer of upconverting nanoparticles (630) is coated on randomly arranged metal nanoparticle or nano-blocks (610) and the thin dielectric material layer (620).
[0066] Another embodiment of the present disclosure is to provide a gap-plasmonic coupled nanostructured array systems (100) comprising: i) a metallic core (600) provides reflection and acts as a mirror; ii) a thin dielectric material layer (620) covered on the metallic core (600); and iii) a metal nanoparticle or nano-blocks (610) distributed on the thin dielectric material layer (620); iv) a solid dielectric nano or microsphere (500) which is coated with the metallic core (600); and v) a 2D-material gap layer (621) is coated on the thin dielectric material layer (620).
[0067] In some embodiment, the 2D-material gap layer is selected from a group comprising of graphene, graphene oxides, transition metal dichalcogenides (TMDC), blue phosphorous-TMDCs, black phosphorous and combination thereof and the 2D-material gap layer has a thickness ranging from 1L to 5L preferably, the 2D-material gap layer is graphene and the thickness is 1L. The thickness of 2D material is measured in number of layers.
[0068] In one of the embodiments, the system further comprises an upconverting nanoparticles (630) dispersed in between the metal nanoparticle or nano-blocks (610).
[0069] In one of the embodiments, the system further comprises a monolayer of upconverting nanoparticles (630) coated on the metal nanoparticle or nano-blocks (610) and the 2D-material gap layer (621).
[0070] In one of the embodiments, the metal nanoparticle or nano-blocks (610) are randomly arranged.
[0071] In some embodiment, the system is immersed in an environment (700) other than the air (n>1). The environment (700) is an optically transparent dielectric medium of refractive index greater than that of the air (n>1). The environment (700) is selected from several options of suitable solvents, depending on the application in which the system is to be implemented. Several kinds of solvents can be used, provided the encapsulant protects the structure from any structural, chemical or oxidative breakdown.
[0072] In one of the embodiment, the system is encapsulated by a dielectric media (700). The dielectric media is selected from a polymer selected from a group comprising of silicone, PMMA, UV curable resin and polar or non-polar solvents, depending on the application in which the system is to be implemented. A solvent is selected from a group comprising of hexane, heptane, petroleum ether, cyclohexane, toluene, and carbon tetrachloride (CCl4) or a combination thereof. Appropriate encapsulation material is selected according to targeted applications.
[0073] In the present disclosure, copper is used as the key sensing material in the plasmonic system due to its affordable and scalable properties, offering an alternative to conventionally used noble metals like gold, silver, platinum etc., in plasmonic systems. Further, the design configuration of the plasmonic system 110 (Fig.1) where a metal coated dielectric sphere is used in the place of solid metallic nano- or micro-sphere offers additional cost reduction associated with reduced metal consumption, especially if the design modifications require the utilization of expensive metals such as gold, silver or platinum. Specifically, in the case of copper, the low-cost, scalable deposition method of electroplating can be used.
[0074] A key advantage of copper as a plasmonic material is its high electrical conductivity, which supports effective plasmon propagation with minimal loss, particularly in the NIR region. However, its susceptibility to oxidation (copper oxide, patina) deters the utilization of this material. Aluminum is another low-cost plasmonic material, facing similar oxidation-related challenges, with a natural oxide (alumina, Al2O3) layer typically forming up to 3 nm thick.
[0075] In this system, an additional challenge is the deposition of a dielectric gap material thinner than 10 nm. Creating such a thin, uniform dielectric layer over a large scale is complex. When noble metals are used as the core, which do not oxidize, a separate oxide or dielectric layer (such as SiO2, Al2O3, Si3N4, or TiO2) is necessary. However, in the present design, the naturally-formed oxidation layers on copper and aluminum can serve as the insulating dielectric gap between the core metal sphere and the metal nanopattern, turning their natural oxidation into an advantage within the architecture.
[0076] The present plasmonic design architecture utilizes the concept of gap-coupled plasmonic to achieve very powerful optical absorption at a specific wavelength tunable in the near IR spectral range with very minimal optical losses in the visible spectrum of light. The integrated gap-plasmon coupled upconverting nanoparticle system as a unit can be utilized in various sectors.
POTENTIAL COMMERCIAL APPLICATIONS
[0077] Sensing: NIR plasmonics with spectrum upconversion can significantly improve the sensitivity of sensors used for environmental monitoring, medical diagnostics, and industrial applications.
[0078] Energy: In solar cells, unabsorbed NIR light (energy of light greater than the bandgap of the semiconductor absorber material) can be efficiently harnessed to improve the overall performance of photovoltaic devices, which otherwise is lost.
[0079] Communication: NIR wavelengths are widely used in fiber-optic communications due to their low absorption and scattering losses in glass fibers. NIR technology can improve the reliability and efficiency of satellite communication systems contributing to remote sensing, defense, and space exploration. In future, plasmonic components could be integral to developing secure quantum communication systems, enhancing encryption and data security for sensitive information transfers.
[0080] Medicine and Healthcare: Various precise and less invasive diagnostic and therapeutic approaches are possible with NIR plasmonics and light upconversion. Plasmonic nanoparticles can be used to enhance contrast in imaging techniques or to deliver heat directly to cancer cells in photothermal therapies. Similarly, plasmonic nanoparticles can be used to generate reactive oxygen species when exposed to NIR light, which can destroy cancer cells or bacterial infections without damaging surrounding healthy tissues. Plasmonic nanoparticles can be used as carriers for drugs, with NIR light triggering the release of the drugs at the target site, enabling targeted drug delivery and controlled and localized treatment. Another potential use of plasmonic nanoparticles is for tissue engineering and regenerative medicine, where controlled light exposure can modulate cellular responses and play a useful role in wound healing and transplantation.
[0081] Security and Encryption: Upconversion nanoparticles offer unique spectral signatures that can be used for anti-counterfeiting and secure data transmission. When combined with plasmonics, these technologies could contribute to advanced encryption methods in secure communications.
[0082] While the foregoing describes various embodiments of the disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person skilled in the art.
EXAMPLES
[0083] The present invention is further explained in the form of following examples. However, it is to be understood that the following examples are merely illustrative and are not to be taken as limitations upon the scope of the invention.
Example 1: Gap-plasmon coupled system
(A) Design
[0084] The designs of gap-plasmonic coupled systems are schematically presented in FIG. 1. Each layer of the model is marked using numbers in the figure. In FIG. 1A, the model comprises of a metal nano or microsphere (600) covered with an insulating dielectric layer (620) over which metal nanoparticles (610) are placed. The thin insulating or dielectric layer acts as a gap or spacer between two metallic surfaces in a periodic arrangement. This creates a gap-coupled nanostructure (GN) arrangement. The thickness of the thin insulating or dielectric layer is typically less than 10 nm. In FIG. 1, the top nanopattern of metal nanoparticles or nano-blocks are shown in periodic arrangement.
[0085] In FIG. 1B, the model comprises of a nano or micron sized sphere of dielectric materials (500) which is coated with a metal. The coated metal layer must be thick enough to act as a reflector. Here, the thickness is 100 nm. The rest of the design-architecture is the same as in FIG. 1A.
[0086] In FIGS. 2A and 2B represent the gap-plasmonic coupled systems immersed in an environment (700) other than the air (as in FIGS. 1A and 1B). Preferably, the environment is dielectric media is selected from a polymers selected from a group comprising of silicone, PMMA, UV curable resin or other appropriate non-polar solvents, having refractive index n>1. The solvent is selected from toluene, xylene, carbon tetrachloride, cyclohexane, n-hexane, heptane and the like.
[0087] In FIGS. 3A and 3B show gap-plasmonic coupled systems covered/coated with a thin layer of an optically transparent dielectric medium (700) of refractive index greater than that of the air (n>1). Here, the dielectric medium is selected from a polymers selected from a group comprising of silicone, PMMA, UV curable resin or other appropriate non-polar solvents, depending on the application in which the system is to be implemented. Some of the non-polar solvent is selected from a group comprising of n-hexane, heptane, petroleum ether, cyclohexane, toluene, carbon tetrachloride, and combination thereof.
(B) Material
[0088] The solid nano- or micro-sphere metallic element 600 shown in FIG. 1A and coated metallic layer, element 600 in FIG. 1B is Cu. Other metals may be employed (e.g., Au, Ag, Al, etc.). Additionally, conducting metal oxides like ITO also possess the potential to replace the metal component in the present structure.
[0089] The solid nano- or micro-sphere dielectric element 500 shown in FIG. 1B is silica (SiO2) although metal oxides with dielectric properties like TiO2, ZnO etc. or any other dielectric material may be employed.
[0090] The layer of dielectric or insulating material, element 620 coated or covered on the surface of metallic element 600 (solid nano- or micro-sphere metal or metal coated solid dielectric nano or microsphere 500) may include any dielectric thin film (SiO2, SiN4, metal-oxides, diamond like carbon, etc.). It is also possible that the dielectric coating being a layer of natural oxide of the metal 600 like copper oxide or aluminum oxide in the case of metal component 600 being copper or aluminum, respectively. Here, the dielectric material layer (620) is copper oxide. Element 620 includes multilayers of 2D materials like graphene, graphene oxides, TMDC.
[0091] Element 610 on top of the dielectric layer element 620 is an array of nanoparticles or nanoblocks of similar metal of 600 or any other metal (e.g., Au, Ag, Al, etc.). In the embodiments of (FIGS. 1, 2 and 3) the pattern of element 610 is shown as periodic. The metal nanoparticle or nano-blocks (610) in the present examples is made of Cu.
[0092] Element 700 represents the outer surrounding media (other than the air) of the plasmonic system which is an optically transparent dielectric material. This media can be in the form of liquid e.g. organic solvent as described above or organic polymer (like silicone, PMMA, UV curable resin etc.) in which plasmonic system can be suspended (as shown in FIGS. 2A and 2B). It is also possible to encapsulate the plasmonic system with element 700 like coating with organic polymer like material, e.g. silicone, PMMA, UV curable resin etc or with a thin film of any optically transparent dielectric material (as shown in FIGS. 3A and 3B). The optical and electrical properties of element 700 must not interfere with the plasmonic behavior of the system in any way. This design architecture protects the structure from damage caused by external factors.
(C) Robustness in design for commercial applications
[0093] For commercial viability, the design of the plasmonic system must consider protective measures against adverse environmental factors like humidity, dust, rust formation of metal surface, etc. Especially for the case of copper and aluminum, which needs protection to prevent it from further oxidation and preserve its optical properties optimized for a required resonance wavelength.
[0094] Design configurations of 101 (FIG. 2A) and 111 (FIG. 2B) show a possibility to suspend this system in any dielectric media such as organic solvent or organic polymer (like silicone, PMMA, UV curable resin etc.), provided there is no deterioration in the optical properties of the system.
[0095] Design configurations of 102 (FIG. 3A) and 112 (FIG. 3B) illustrate an encapsulated plasmonic system with optically transparent organic polymer, e.g. silicone, PMMA, UV curable resin etc., which can protect it from environmental factors. However, plasmonic systems are very sensitive to the presence of dielectric media in the vicinity of the structure. Therefore, prior to encapsulation of the plasmonic system, the design optimization should consider the thickness and the optical properties of the encapsulating material for a required resonance wavelength post encapsulation.
(D) Optical properties of the gap-plasmon coupled systems.
[0096] Simulation studies based on finite element method were carried out on the present designs shown in FIGS. 1, 2 and 3 using copper as the key metal for both, element 600 and nanopattern element 610; and its natural oxide (i.e. copper oxide) of thickness ~ 4 nm as the gap material for the element 620. The simulated optical absorption spectra obtained for some of the embodiments presented in FIGS.1, 2 and 3 are shown in FIG. 4. In the inset of each panel of FIG. 4, the schematic illustration of respective system is shown. The optical absorption spectra displayed in all the panels of FIG. 4 shows a sharp and strong absorption at NIR wavelength.
[0097] The absorption spectrum in FIG. 4A corresponds to embodiment 100 (FIG. 1A) where a solid copper micro-sphere of diameter ~500 nm is employed. The spectrum shows the presence of a sharp, highly absorbing peak (absorption ~ 95%) at ~1530 nm, demonstrating excellent confinement of the electric field courtesy to the gap-plasmon coupling. This is significantly greater than the 20-40 % ranges of absorption obtained in typical plasmonic structures in literature. An identical absorption spectrum is obtained for embodiment 110 (FIG. 1B) where ~200 nm thick copper layer coated silica microsphere of diameter ~300 nm is used, shown in FIG. 4B. This suggests the possibility of a metal coated dielectric sphere in the plasmonic system, which can be deposited on dielectric sphere by the highly cost-effective method of electroplating method (for copper). However, the critical thickness of the metal coating layer must be maintained, failing which the optical response can suffer a red shift.
[0098] The optical absorption spectrum shown in FIG. 4C obtained for embodiment 101 where the system is embedded in an environment of medium with a refractive index of 1.5 (in this study) demonstrates that the plasmonic absorption peak is still sharp and strong in the NIR region at 1570 nm with a slight displacement of 40 nm from 1530 nm. Nevertheless, this peak position can be brought back to 1530 nm by slight tuning of the structural parameters of nanopattern 610 or the gap layer 620. This demonstrates the possibility to suspend this system in any optically transparent dielectric media such as polymers or any solvent without any deterioration in the optical properties of the system.
[0099] As discussed above the importance of encapsulation of a plasmonic system to protect it from environmental factors, simulation studies were carried out with a model design 112, which has a coating of a dielectric material (thin film or polymer with a refractive index = 1.5) over system 110. The result of optical absorption spectrum of this model is presented in FIG. 4D. The presence of sharp and strong plasmonic absorption peak at ~1585 nm with absorption > 95% demonstrates no deterioration on the optical properties of the system with the use of encapsulation. The position of the peak can be tuned back to ~1530 nm with a slight alteration in the structural properties of the system. This outcome confirms the possibility to encapsulate the system in any dielectric media (such as polymers or any thin film) which can preserve the system architecture and protect it from environmental degradation.
[00100] Further, by altering the structural factors (the form, size, and thickness of the nanoblock pattern), periodicity, the spacing between the particles, and the opto-electrical characteristics of the metal of the nanoblocks, these designs can be made spectrally tunable. The results indicate a possibility of wide range of tunability of highly absorbing plasmonic resonance peaks from ~ 600 nm to ~ 2000 nm in this system.

Example 2: Gap-plasmon coupled assisted upconverter system
[00101] Some of the key NIR applications with a significant commercial presence include surface enhanced Raman spectroscopy (SERS) and spectrum upconversion (UC), telecommunication, etc. However, paired with a technology that may enhance their optical response would greatly improve their sensing signals, which are usually relatively weak.
(A) Spectrum Upconversion
[00102] Upconversion involves the mechanisms including multi-photon absorption or energy transfer to convert the lower-energy photons into higher-energy photons. Nanocrystals of NaYF4 or Gd2O2S, etc. or thin films of TiO2, ZnO, Al2O3, etc. as host materials when doped with one or more rare earth elements (lanthanides: Er3+, Yb3+, Eu3+, etc.) emits light at the wavelengths ranging from ~670 nm, 810 nm, and 980 nm when excited with wavelengths of 980 nm and 1530 nm. Upconverting nanoparticles (UC-NPs) represent an advanced option compared to conventional optical imaging materials, offering numerous benefits including reduced photobleaching, low self-illuminating background fluorescence, enhanced tissue penetration, and decreased risk of photodamage. However, the major limitation of upconverters is their low conversion efficiency, especially under a low-intensity laser excitation.
(B) Application of gap-plasmon coupled nanostructures to enhance upconversion luminescence:
[00103] The distinct sharp high optical absorption peaks at 1530 nm in the optical spectra of some of the gap-plasmon coupled systems (FIGS. 1, 2 and 3), shown in FIG. 4 indicates that these systems may be well-suited for near-IR spectral range applications. In this example, the impact of integrating gap-plasmon coupled copper nanospheres was examined with UC-NPs in various architectures.
[00104] In FIG. 5, various design configurations of gap-plasmon coupled system 110 (FIG. 1B) integrated with upconverting material 630. The element 630 can be of nanoparticle form or thin film form of rare earth material doped dielectric materials such as NaYF4-Er, NaYF4-Er-Yb, TiO2-Er, TiO2-Er-Yb, gadolinium oxysulfide: Er, Yb, etc. FIG. 5A schematically shows a structure 210 consisting of the gap-plasmonic coupled system 110 with a monolayer of upconverting nanoparticles 630 dispersed in between the nanoblocks of array 610. In FIG. 5B the structure 220, where a monolayer of upconverting nanoparticles 630 is conformally coated on the gap-plasmonic coupled system 110. In FIG. 5C the structure 230, in which thin multilayers of the upconverting nanoparticles 630 are deposited in between the nanoblocks of array 610 in the gap-coupled plasmonic system of 110.
[00105] Design configurations of structures 211 (FIG. 5D), 221 (FIG. 5E) and 231 (FIG. 5F) show the system is placed in an outer environment of an optically transparent dielectric medium 700 of refractive index greater than that of the air (n >1). The commercial aspect of this configuration or design architecture is the possibility to suspend the system in any dielectric media such as polymers, or any solvent provided there is no deterioration in the optical properties of the system.
[00106] Design configurations of structures 212 (FIG. 5G), 222 (FIG. 5H) and 232 (FIG. 5I) illustrate encapsulated plasmonic systems with optically transparent dielectric medium 700 like organic polymer, e.g. silicone, PMMA, UV curable resin etc., or coated with thin film of dielectric material, which can protect it from environmental factors. The optical and electrical properties of element 700 must not interfere with the plasmonic behavior of the system in any way.
(C) Optical performance of gap-plasmon coupled assisted upconversion system:
[00107] The optical absorption spectra of the gap-plasmonic coupled systems in configurations 210 (with UC-NPs, FIG. 5A) and 110 (without UC-NPs, FIG. 1B) are shown in FIG. 6. The presence of sharp and highly absorbing peak at the wavelength of 1530 nm coinciding with the absorption peak of Erbium ions demonstrates the efficacy of the gap-plasmon coupled system. To identify the location where such high optical absorption is taking place in the system, two-dimensional spatial distribution profiles of the electric field are presented in Fig. 7A, where the color bar represents the ratio of generated and incident electric fields (E/E0). Localized highly intense regions in the electric field distribution, known as hotspots, are at the edges and corners of the central block as seen in FIG. 7A. These hotspots are crucial for enhanced optical nonlinearities and SERS applications. The edges of the structure, where the material changes or where there is a sharp boundary, show a significant increase in the electric field. The corresponding absorbed light intensity profile at the plasmonic resonance wavelength of 1530 nm, which is proportional to the square of the electric field (I∝∣E∣2), is displayed in FIG. 7B.
[00108] The upconversion emission light intensity from the UC-NPs at the wavelength of 980 nm is calculated by solving the appropriate rate equations for the absorbed light intensity distribution at 1530 nm shown in FIG. 7B. Intensity is a critical factor for upconversion processes, as higher intensities increase the probability of multiphoton absorption events, leading to efficient upconversion luminescence. The profile of two-dimensional spatial distribution of upconversion luminescence from the upconverting nanoparticles calculated at the emission wavelength of 980 nm is shown in FIG. 7C.
[00109] In can be concluded that i) Gap-plasmonic coupled copper nanospheres system combined with UC-NPs can strongly absorb the light at NIR wavelength (~1530 nm) and emit the light at lower wavelengths ~980 nm and ~800 nm, ii) the design architecture of the plasmonic system allows for spectral tunability in the broad NIR spectral region for enhanced optical absorption with no parasitic absorption in the upconversion emission lines region (esp. at 980 nm and 810 nm), iii) this integrated system can be encapsulated for robustness and can be dispersed in organic solvents with appropriate surface modification to prevent clumping. The present studies have confirmed that the coating of the surface of the integrated system with a polymer media of refractive index close to 1.5 (such as silicone) does not affect the plasmonic response as such. Nevertheless, a slight change in the design can be incorporated into the structure from the beginning so that the plasmonic response after the encapsulation remains at the required absorption wavelength band of application (e.g. Er or Er/Yb spectral line), iv) the integrated system can be suspended in appropriate solvent to be used as paint or ink, which can be used in low-cost scalable methods of coating by spin coating, doctor-blading, spray printing, inkjet printing, etc.
Example 3: 2D materials or organic surface ligand as a gap layer in gap-plasmon coupled system & gap-plasmon coupled assisted upconverter system for NIR applications
[00110] In some cases, it is also possible to replace the dielectric gap-layer with 2-D materials like graphene, graphene oxide, transition metal dichalcogenides (TMDC), blue phosphorous-TMDCs, black phosphorous. This is schematically depicted in Fig. 8. A single layer or multilayer stack of 2-D material can be grown or coated directly over the metallic spherical surface and function as a dielectric spacer layer. In the schematic drawings a thin residual natural oxide layer (~ 0.5 nm thick) on the metal surface has also been included in the present models for realistic approach.
[00111] FIGS. 8 (A to L) shows structures which are similar to those described in FIGS. 1-3, and FIGS. 5 of gap-plasmonic coupled systems with an additional 2-D material (621) as a gap layer material in the place of dielectric material (spacer layer). The achievable spacer thickness can be reduced to a few angstroms because of the atomic thickness of the monolayered 2D materials. Incremental layer numbers of 2-D materials can expand the gap size to a larger scale, typically a few nanometers, when fabricated with the mechanical exfoliation or chemical vapor deposition methods.
[00112] In some design configurations instead of dielectric coating or 2-D material coating, organic surface ligand can also be used as a spacer layer as some recent reports have suggested their applicability as spacer layer.
Example 4: Random arrangement of nanopattern with thin film dielectric material as a gap layer in gap-plasmon coupled system & gap-plasmon coupled assisted upconverter system for NIR applications
[00113] The periodic arrangement of metal nanoparticles/nano-blocks on micro- or nano-spherical surfaces is a challenging task. A low-cost self-assembled fabrication would be most ideal to produce the present gap-coupled system with the nanopattern arrangement. One such method of fabricating this type of random nanopattern is by thermal annealing of thin layer of metal layer coated on the surface of dielectric layer coated metal spheres. Thermal annealing can break the thin film into small islands the shape of which (disc, hemisphere, sphere, etc.) can be further tuned as per the required plasmonic resonance wavelength. The tuning typically involves controlling factors such as the thickness of the initial metal layer coating, temperature of annealing, duration of annealing, etc.
[00114] To find optimized configuration even in random arrangement of the metal nanoparticles/nano-blocks, the structures are modeled as schematically shown in FIG. 9. FIG. 9A represents an embodiment 150, consisting of a dielectric sphere 500 with the metal coating 600, with a subsequent dielectric layer 620. A randomized nanoblock array, 610, is placed over the gap-layer 620, with random variations in block height, block width and periodicity. FIG. 9B represents a schematic cross-sectional design structure/ embodiment 250, where the structure/embodiment 150 has an additional upconverting nanoparticle monolayer dispersed between the nanoblocks. FIG. 9C shows embodiment 260, where a monolayer of upconverting nanoparticles is conformally coated over the nanoblocks and the space between the blocks.
[00115] FIG. 9D shows a schematic representation of an embodiment 152, where the embodiment 150 is covered/coated with a dielectric medium 700 of refractive index greater than that of the air (n>1). FIG. 9E shows an embodiment 252, where the embodiment of 250 is covered/coated with a dielectric medium 700 of refractive index greater than that of air (n>1). An embodiment 262 is illustrated in FIG. 9F, in which the embodiment of 260 is coated/covered with a dielectric medium 700 that has a refractive index that is greater than that of air (n>1).
Example 5: Random arrangement of nanopattern with 2D materials as a gap layer in gap-plasmon coupled system & gap-plasmon coupled assisted upconverter system for NIR applications
[00116] In this example, the design architectures are shown where 2D material or organic surface ligand are used instead of dielectric thin films coating as a spacer layer. The illustration in FIG. 10A (350) shows a dielectric sphere 500 with the metal coating 600, with a subsequent dielectric layer 620. A layer of 2D material 621 is coated over the structure. The 2-D material layer element may include, e.g., graphene, transition metal dichalcogenides (TMDC), blue phosphorous-TMDCs, black phosphorous. A randomized nanoblock array, 610, is placed over this system, with variations in block height, block width and periodicity. FIG. 10B schematically shows 450, where the system shown in 350 with an additional upconverting nanoparticle monolayer dispersed between the nanoblocks. FIG. 10C (460) a monolayer of upconverting nanoparticles is coated over the combined system shown in 350.
[00117] FIG. 10D shows a schematic representation of 352, where the structure 350 is covered/coated with a dielectric medium 700 of refractive index greater than that of the air (n>1). Whereas in FIG. 10E (252) design 250 is covered/coated with a dielectric medium 700 of refractive index greater than that of air (n>1). Similar structure is shown in Fig. 8F, which is fully coated/covered with a dielectric medium 700 that has a refractive index that is greater than that of air (n>1).
Example 6: Solar cell device architecture with gap-plasmonic coupled assisted upconverter system
[00118] The spectral region of the light (typically NIR region) having energy lower than the bandgap of the semiconductor absorber layer of the solar cell is not absorbed and therefore, is transmitted through the solar cell. The present gap-plasmonic coupled assisted upconverter system, which absorbs the light at NIR region and can emit the light at lower wavelengths (550 nm, 670 nm, 810 nm and 980 nm) where the semiconductor material of the photovoltaic device is sensitive for optical absorption.
[00119] Typical solar cells with flat back reflectors reflect the incident light for a second pass through the device layers, after which the unabsorbed light finally leaves from the front side of the device. However, in the presence of gap-plasmonic coupled systems with UC-NPs, the NIR light can be absorbed by the upconverter which then emits the light at the lower wavelengths which can be absorbed in the solar cell. The gap-plasmonic coupled assisted upconverter system can be selected from anyone of the embodiments shown in FIGS. 5 – 10. To improve the collection of the emitted light from the gap-plasmonic coupled assisted upconverter system the appropriate texturing of the back reflector can be employed. In the presence of gap-plasmonic coupled system with UC-NPs, the NIR light can be absorbed by the upconverter which then emits the light at the lower wavelengths which can be absorbed in the solar cell. The general solar cell device architectures attached with gap-plasmonic coupled assisted upconverter systems are shown in FIG. 11.
Example 7: Gap-plasmonic coupled assisted upconverter system for printable electronics
[00120] The gap-plasmonic coupled assisted upconverter system is dispersed in a suitable liquid with optimized viscosity matching those of printable inks. Inks are usually tuned according to the applications and solutes and is a combination of hydrocarbons (like aliphatic solvents such as naphtha and aromatic solvents like toluene and xylene), alcohols (such as methanol, ethanol, and isopropanol) and/or esters (like ethyl acetate and butyl acetate), depending on the printing surface. Further, depending on the ink, suitable encapsulating dielectric material that enables dispersion of nanoparticles can be selected. In the present disclosure, this ink is used to print on any flexible substrate, e.g. paper, plastic etc. One such example of an application is printed security codes (e.g. QR codes or security tags, currency notes, etc.) where extra security features or patterns are printed with such ink having gap-plasmonic coupled assisted upconverter system in it along with the routine printed pattern. When the scanner having NIR light source along with the red laser scans the security tags or QR codes, the portion having gap-plasmonic coupled assisted upconverter system in the pattern will glow due to emitted light from the upconverter. The role of gap-plasmonic coupled system is to enhance this signal which is usually very faint in the absence of plasmonic field and bring it to the level of detection. In Fig. 12 this concept is demonstrated.
[00121] The essential feature of the present disclosure lies in the combination of usage of a) a thin dielectric material layer (620) covered on the metallic core (600); and b) a metal nanoparticle or nano-blocks (610) distributed on the thin dielectric material layer (620), rather than of the presence of any of this singular layers. For the sake of comparison, this design with and without the (620) dielectric layer can be used for comparing the electric field enhancement (EF). The electric field enhancement factors was obtained in the order of 10^2, for design 100 with and without the dielectric nanogap when illuminated with wavelength of light of 1530 nm. The resultant enhancement in upconversion luminescence emission intensities at 980 nm wavelength from upconverting nanoparticles placed in the vicinity of gap-plasmons, with and without the dielectric nanogap in design 200, is up to ~10^4 times, when illuminated with wavelength of 1530 nm.
[00122] In isolated plasmonic designs with metallic nanodimers separated by a nanogap, typical enhancement factors are in the range of ~1.18 (Emil H Eriksen et al., J. Opt., 2019, 21, 035004).
[00123] Spherical nanodimers separated by a dielectric spacer of 2 nm reported 200% EF enhancement when compared to nanocube dimer (Int. J. Mol. Sci. 2021, 22(19), 10595).
[00124] Upconverting nanoparticles placed in the tilted nanocavity between Ag nanocube and Ag metal plate shows a maximum of 103 enhancement of upconversion luminescence (Nat. Photon. 16, 651–657 (2022).

ADVANTAGES OF THE INVENTION
[00125] Gap-plasmon coupled systems hold vast potential across a range of applications due to their unique capacity for tunable spectral selectivity, enhanced light-matter interactions, and compatibility with advanced materials like corrosion-induced oxide layers and 2D layers.
[00126] Through this present strategic design architectures such as metal-insulator-metal (MIM) structures, and electrostatic tuning, these systems enable precise control over the optical properties of the design architecture in the NIR region.
[00127] When integrated with upconversion nanoparticles, they can be used to facilitate efficient NIR-to-visible conversion, promising advancements in fields like solar energy harvesting, drug delivery via NIR-triggered release, and printable electronics.
, Claims:1. A gap-plasmonic coupled nanostructured array systems (100) comprising:
i) a metallic core (600) provides reflection and acts as a mirror;
ii) a dielectric material layer (620) covered on the metallic core (600); and
iii) a metal nanoparticle or nano-blocks (610) distributed on the thin dielectric material layer (620).
2. The gap-plasmonic coupled nanostructured array systems (100) as claimed in claim 1, wherein the metallic core is selected from a group comprising of Au, Ag, Al, Cu, ITO and combination thereof.
3. The gap-plasmonic coupled nanostructured array systems (100) as claimed in claim 1, wherein the dielectric material layer (620) is selected from a group comprising of SiO2, Si3N4, TiO2, Al2O3, diamond like carbon, copper oxide, and combination thereof and the dielectric material layer (620) has a thickness less than 10 nm.
4. The gap-plasmonic coupled nanostructured array systems (100) as claimed in claim 1, wherein the metal nanoparticle or nano-blocks (610) is selected from a group comprising of Au, Ag, Al, Cu, ITO and combination thereof.
5. The gap-plasmonic coupled nanostructured array systems (100) as claimed in claim 1, wherein the system further comprising a solid dielectric nano or microsphere (500) in the centre which is coated with metallic core (600).
6. The gap-plasmonic coupled nanostructured array systems (100) as claimed in claim 1, wherein the solid dielectric nano or microsphere (500) is selected from a group comprising of SiO2, TiO2, ZnO and combination thereof.
7. A gap-plasmonic coupled nanostructured array systems (100) comprising:
i) a metallic core (600) provides reflection and acts as a mirror;
ii) a thin dielectric material layer (620) covered on the metallic core (600); and
iii) a metal nanoparticle or nano-blocks (610) distributed on the thin dielectric material layer (620); and
iv) a solid dielectric nano or microsphere (500) in the centre which is coated with the metallic core (600).
8. The gap-plasmonic coupled nanostructured array systems (100) as claimed in claim 7, wherein the system further comprises an upconverting nanoparticles (630) dispersed in between the metal nanoparticle or nano-blocks (610).
9. The gap-plasmonic coupled nanostructured array systems (100) as claimed in claim 7, wherein the upconverting nanoparticles (630) is selected from a group comprising of NaYF4-Er, NaYF4-Er-Yb, TiO2-Er, TiO2-Er-Yb, gadolinium oxysulfide: Er, Yb, and combination thereof.
10. The gap-plasmonic coupled nanostructured array systems (100) as claimed in claim 7, wherein the system further comprises a monolayer of upconverting nanoparticles (630) is coated on the metal nanoparticle or nano-blocks (610) and the thin dielectric material layer (620).
11. The gap-plasmonic coupled nanostructured array systems (100) as claimed in claim 7, wherein the system further comprises a multilayer of upconverting nanoparticles (630) is coated on the metal nanoparticle or nano-blocks (610) and the thin dielectric material layer (620).
12. The gap-plasmonic coupled nanostructured array systems (100) as claimed in claim 7, wherein the metal nanoparticle or nano-blocks (610) are randomly arranged.
13. The gap-plasmonic coupled nanostructured array systems (100) as claimed in claim 7, wherein the system further comprises an upconverting nanoparticles (630) dispersed in between randomly arranged metal nanoparticle or nano-blocks (610).
14. The gap-plasmonic coupled nanostructured array systems (100) as claimed in claim 7, wherein the system further comprises a monolayer of upconverting nanoparticles (630) is coated on randomly arranged metal nanoparticle or nano-blocks (610) and the thin dielectric material layer (620).
15. A gap-plasmonic coupled nanostructured array systems (100) comprising:
i) a metallic core (600) provides reflection and acts as a mirror;
ii) a thin dielectric material layer (620) covered on the metallic core (600); and
iii) a metal nanoparticle or nano-blocks (610) distributed on the thin dielectric material layer (620);
iv) a solid dielectric nano or microsphere (500) which is coated with the metallic core (600); and
v) a 2D-material gap layer (621) is coated on the thin dielectric material layer (620).
16. The gap-plasmonic coupled nanostructured array systems (100) as claimed in claim 15, wherein the 2D-material gap layer is selected from a group comprising of graphene, graphene oxides, transition metal dichalcogenides (TMDC), blue phosphorous-TMDCs, black phosphorous and combination thereof and the 2D-material gap layer has a thickness ranging from 1L to 5L.
17. The gap-plasmonic coupled nanostructured array systems (100) as claimed in claim 15, wherein the system further comprises an upconverting nanoparticles (630) dispersed in between the metal nanoparticle or nano-blocks (610).
18. The gap-plasmonic coupled nanostructured array systems (100) as claimed in claim 15, wherein the system further comprises a monolayer of upconverting nanoparticles (630) is coated on the metal nanoparticle or nano-blocks (610) and the 2D-material gap layer (621).
19. The gap-plasmonic coupled nanostructured array systems (100) as claimed in claim 15, wherein the system further comprises a multilayer of upconverting nanoparticles (630) is coated on the metal nanoparticle or nano-blocks (610) and the 2D-material gap layer (621).
20. The gap-plasmonic coupled nanostructured array systems (100) as claimed in claims 15-19, wherein the metal nanoparticle or nano-blocks (610) are randomly arranged.
21. The gap-plasmonic coupled nanostructured array systems (100) as claimed in claims 1, 5, 7, 10, 11, 15, 17-19, wherein the system is immersed in an environment (700) other than the air (n>1).
22. The gap-plasmonic coupled nanostructured array systems (100) as claimed in claims 1, 5, 7, 10, 11, 15, 17-19, wherein the environment (700) is selected from an optically transparent dielectric medium of refractive index greater than that of the air (n>1).
23. The gap-plasmonic coupled nanostructured array systems (100) as claimed in claim 1, 5, 7, 10, 11-15, 17-19, wherein the system is encapsulated in a dielectric media (700).
24. The gap-plasmonic coupled nanostructured array systems (100) as claimed in claim 1, 5, 7, 10, 11-15, 17-19, wherein the dielectric media is selected from a polymer selected from a group comprising of silicone, PMMA, UV curable resin and polar or non-polar solvents.