Copper based MOD inks and methods thereof

Abstract

This present disclosure is directed to copper-based ink MOD compositions and method of producing materials such as fine pattern electrodes using the same.

Description

COPPER BASED MOD INKS AND METHODS THEREOF by Shenqiang Ren Saurabh KhujeJun ZhangCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Application No. 63 / 549,440, filed onFebruary 2, 2024.

[0002] STATEMENT OF FEDERALLY SPONSORED RESEARCH ANDDEVELOPMENT

[0003] T his invention was made with government support under W91 INF- 19-2-0011 awarded by the Army Research Laboratory-Army Research Office. The government has certain rights in the invention.

[0004] FIELD OF THE INVENTION

[0005] The field of the invention relates generally to a conductive molecular ink including copper-amine co-complexes and a method of producing a fine pattern electrode using the same.

[0006] BACKGROUND

[0007] This background information is provided for the purpose of making information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should it be construed, that any of the information disclosed herein constitutes prior art against the present invention.

[0008] Rapid technological advancement has resulted in the shortening of the life cycle of electrical and electronic equipment, leading in the generation of massive amounts of solid waste (e-waste). However, only a few valuable metals, such as silver and gold, are retrieved from such e-wastes, while the majority of base metals, which have lower economic values, areleft as is and end up in landfills. Therefore, there is a need for an advancement in recycling e- wastes from electronics.

[0009] Copper (Cu) finds its widespread use in electronics due to its excellent thermal and electrical conductivities, ductility and non-toxicity. Cu makes up a large fraction of printed circuit boards (PCBs) in comparison to other metals. Recycling post-consumer scrap can be valuable, but it results in significant copper loss, undermining material circularity. Furthermore, Cu oxidation and corrosion due to its highly reactive nature is a severe reliability concern, thus limiting its applicability, and this issue becomes more acute when Cu comes into direct contact with reactive species, such as oxygen at elevated temperatures or corrosive environment. As a result, developing an effective passivation against oxidation and corrosion is critical for realizing a broad range of applications pertaining to copper.

[0010] SUMMARY

[0011] One aspect of the invention pertains to a copper-based ink composition, said composition comprising a copper (0) nanoparticle and an additive, wherein the nanoparticle is encapsulated or passivated with said additive, wherein said additive forms a shell around said copper nanoparticle core (“copper core”), wherein said additive is an amine additive and / or carbonaceous additive (e.g., graphite, graphene, carbon nanotubes, fullerenes, carbon black, and amorphous carbon).

[0012] Another aspect of the invention pertains to a copper-nickel alloy -based ink composition, said composition comprising a copper nanoparticle, nickel nanoparticle and an additive, wherein the copper nanoparticle and said nickel nanoparticle are encapsulated or passivated with said additive, wherein said additive forms a shell around said copper nanoparticle core (“copper core”) and nickel nanoparticle core, respectively, wherein said additive is an amine additive and / or carbonaceous additive (e.g., graphite, graphene, carbon nanotubes, fullerenes, carbon black, and amorphous carbon).

[0013] Another aspect of the invention pertains to a method of preparing copper-based ink composition, said method comprising: a. providing a copper formate salt; b. dissolving said copper formate salt in aminomethyl propanol (AMP) in an amine solution (such as dopamine solution) to obtain a copper (II) amine precursor; c. optionally, adding dopamine salt (such as dopamine hydrochloride) to obtain a dispersion; and d. subjecting said dispersion to thermal decomposition to obtain a composition comprising a copper (0) nanoparticle and said amine additive, wherein the nanoparticle is encapsulated or passivated with said amine additive such that said additive forms a shell around said copper (0) nanoparticle core. Thermal decomposition may be carried out using known methods.

[0014] Another aspect of the invention pertains to a method of preparing a copper ink coated material, said method comprises applying a copper-based ink of any of the preceding embodiments to the surface of a material.

[0015] Another aspect of the invention pertains to a copper coated material, said material comprising a copper-based ink from any of the preceding embodiments.

[0016]

[0017] BRIEF DESCRIPTION OF THE FIGURES

[0018] The following drawings form part of the present specification and are included to further demonstrate certain aspects of the present invention. The invention may be better understood by reference to one or more of these drawings in combination with the detailed description of specific embodiments presented herein. The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publicationwith color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

[0019] Figure 1. Schematics depict the overall process presented in this work. Fig. la. Illustration of the recycling process for copper, beginning with copper oxide all the way to Cu@DA ink printing and testing for oxidation and corrosion resistance. Fig. lb. Schematic illustration depicting the additive manufacturing process for Cu@DA ink, with pyrolysis- enabled dopamine to carbon conversion resulting in the formation of the gradient structure.

[0020] Figure 2. Dopamine to Carbon conversion for Cu@DA ink. Fig. 2. a. Schematic depicting the conversion process of polydopamine to carbon during pyrolysis process. Fig. 2b. SEM image depicting the gradient structure of Cu@DA, with carbon at the top (indicated by red lines) and copper underneath. Fig. 2c. Effect of dopamine concentration on the size of the Cu@DA nanoparticles. Fig. 2d. XRD plot of Cu@DA sample before and after annealing indicating the possibility of intercalation within the Cu lattice. Fig. 2e. Raman spectra for different pyrolysis temperatures for corroborating polydopamine to carbon conversion. Fig. 2f. XRD plot for Cu@DA with increasing dopamine concentrations.

[0021] Figure 3. Stability of gradient copper-carbon materials from 5 wt.% dopamine hydrochloride under various environmental stimuli. Fig. 3a. Plot depicting the stability of gradient copper-carbon materials under acidic environments. Fig. 3b. SEM image of gradient copper-carbon materials after stability test in IM sulfuric acid. Fig. 3c. Plot depicting the stability of Cu@DA under basic environments. Fig. 3d. SEM image of gradient coppercarbon materials after stability test in IM sodium hydroxide. Fig. 3e. Plot depicting the stability of gradient copper-carbon materials in comparison to silver ink at different temperatures at 85% humidity. Fig. 3f. Plot depicting the stability of gradient copper-carbon materials under cryogenic (-193°C) and high temperature conditions (500°C).

[0022] Figure 4. Applications associated with gradient copper-carbon materials. Fig. 4a. Schematic illustrating the antenna being subjected to simulated saltwater conditions. Fig. 4b. Plot depicting the relative resistance change of gradient copper-carbon materials following different washing cycles. Fig. 4c. Plot depicting a gradient copper-carbon dipole antenna performance under control (no saltwater) and corrosive (saltwater) environments. Fig. 4d. Plot depicting the gradient copper-carbon materials antenna being utilized as a pH sensor as a consequence of dielectric constant change.

[0023] Figure 5. Resistance vs. thickness plots for Cu@DA sample following pyrolysis.

[0024] Figure 6. Stability of Cu@DA (5 wt.%) under various environmental stimuli. Fig.6a. Plot depicting the stability of Cu@DA under acidic environments. Fig. 6b. Plot depicting the stability of Cu@DA under basic environments.

[0025] Figure 7. Stability of Cu@DA (5 wt.%) under formic acid.

[0026] Figure 8. SEM observation of Cu@DA (5 wt.%) after exposure to 10 M HC1 for 40 minutes.

[0027] Figure 9. SEM observation of Cu@DA (5 wt.%) after exposure to 10 M NaOH for 40 minutes.

[0028] Figure 10. SEM observation of Cu@DA (5 wt.%) after exposure to 10 M NH4OH for 40 minutes.

[0029] Figure 11. Fig. I la. Resistance-Temperature plot of Cu@DA with varying dopamine concentrations. Fig. 11b. Resistance plot for Cu@DA (5 wt.%) sample aged at different temperatures. Fig. 11c. Plot depicting the resonant frequencies of Cu@DA (5 wt.%) antenna when exposed to different temperature conditions, thus confirming the stability of Cu@DA inks.

[0030] Figure 12. XRD plots of a Cu@DA (5 wt.%) sample when exposed to various temperatures by means of a tube furnace.

[0031] Figure 13. Dielectric constant plot of pyrolyzed Cu@DA ink.

[0032] Figure 14. Sintering time and temperature dependence on electrical conductivity.

[0033] Figure 15. Photonic sintering studies with varied burst count and frequency range.

[0034] Figure 16. Screen printed samples sintered by photonic sintering with related SEM, EDS and optical imaging of print.

[0035] Figure 17. Sheet resistance relative to dopamine concentration in copper ink.

[0036] Figure 18. SEM images of cu / dopamine samples at different temperatures (900-300 °C) and different dopamine concentrations (15-1%).

[0037] Figure 19. Fig. 19a-19b. Cross sectional SEM of 15wt% Cu / dopamine sample. Fig. 19c-19d. EDS mapping of copper and carbon in the sample demonstrating higher concentration of carbon nearing the top surface.

[0038] Figure 20. High temperature exposure of 15wt% dopamine doped sample at 5, 10, 15 and 20 seconds in a 1000 °C furnace.

[0039] Figure 21. Fig. 21a. image of sample submerged in solution. Fig. 21b. Resistance dependence of sample in 10, 3 ,2 and 1 molar solutions of formic acid. Fig. 21c. Resistance dependence of sample in 10, 3 ,2 and 1 molar solutions of ammonium hydroxide. Further corrosion resistance studies shown below in Figure 22 demonstrates a sample made from copper doped with 20wt% Dopamine to have similarly very stable performance when submerged under hydrochloric acid and sulfuric acid at concentrations of 0.01 M, 0.1 M, 1 M and 10 M. This data gives further evidence of stability under highly acidic environments.

[0040] Figure 22. Stability of 20% Dopamine treated samples submerged in (Left) HCL and (Right) H2SO4 at concentrations of 0.01 M to 10 M.

[0041] Figure 23. Individually tested samples treated with Dopamine at concentrations of 0- 20% submerged in a 10 M solution of (a) HC1 and (b) H2SO4 for an hour.

[0042] Figure 24. 20% Dopamine treated sample submerged in H2SO4 for approximately 6 days.

[0043] Figure 25. Sample made with 20wt% Dopamine submerged in 10 M, 1.0 M and 0.1M NaOH.

[0044] Particular non-limiting embodiments of the present invention will now be described with reference to accompanying drawings.

[0045] DESCRIPTION

[0046] Definitions

[0047] For the purposes of promoting an understanding of the principles of the invention, reference will now be made to certain embodiments and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, and alterations and modifications in the illustrated invention, and further applications of the principles of the invention as illustrated therein are herein contemplated as would normally occur to one skilled in the art to which the invention relates.

[0048] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0049] For the purpose of interpreting this specification, the following definitions will apply and whenever appropriate, terms used in the singular will also include the plural and vice versa. In the event that any definition set forth below conflicts with the usage of that word in any other document, including any document incorporated herein by reference, the definition set forth below shall always control for purposes of interpreting this specification and its associated claims unless a contrary meaning is clearly intended (for example in the document where the term is originally used).

[0050] The use of “or” means “and / or” unless stated otherwise.

[0051] The use of “a” or “an” herein means “one or more” unless stated otherwise or where the use of “one or more” is clearly inappropriate.

[0052] The use of “comprise,” “comprises,” “comprising,” “include,” “includes,” and “including” are interchangeable and not intended to be limiting. Furthermore, where the description of one or more embodiments uses the term “comprising,” those skilled in the art would understand that, in some specific instances, the embodiment or embodiments can be alternatively described using the language “consisting essentially of’ and / or “consisting of.”

[0053] As used herein, the term “about” refers to a ±10% variation from the nominal value. It is to be understood that such a variation is always included in any given value provided herein, whether or not it is specifically referred to.

[0054] Any ranges given either in absolute terms or in approximate terms are intended to encompass both, and any definitions used herein are intended to be clarifying and not limiting. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Moreover, all ranges disclosed herein are to be understood to encompass any and all subranges (including all fractional and whole values) subsumed therein.

[0055] The term “degradable polymeric product” refers to a polymeric product that degrades in the presence of peroxide (e.g., hydrogen peroxide).

[0056] The term “gradient” as used herein describes the density variation resulting from the hierarchical structure of a carbon passivation layer formed on a copper foundation. Without wishing to be limited to any particular theory, this gradient is created because of in-situ graphitic carbon conversion, leading to a transition from a dense copper core to a protective, porous carbon shell, which enhances corrosion and oxidation resistance.

[0057] The term “molecular ink” as used herein refers to a conductive ink used for printed electronics, composed of ionic or metal-organic precursors that undergo thermaldecomposition to form a continuous metallic network. Unlike nanoparticle-based inks, molecular inks provide enhanced stability, reduced oxidation risks, and tunable sintering temperatures, making them suitable for flexible and printed electronic applications.

[0058] The term “passive gradient layer” as used herein refers to a structured transition zone within a material where the concentration of a passivating species (e.g., carbon, oxygen, or other protective elements) gradually decreases from the outer surface to the metallic core. This layer forms during thermal decomposition or reaction processes, facilitating molecular diffusion and creating a protective barrier that enhances oxidation and corrosion resistance. In some embodiments, the gradient-structured surface layer consists of copper as the foundation and carbon as the passive gradient layer as a consequence of density variance was created. For example, compositions disclosed herein comprises encapsulated copper (0) nanoparticles where said nanoparticle are passivated with said additive which forms a protective shell around each copper (0) nanoparticle that is partially and fully passivated with said additive (e.g., dopamine salt and / or carbon).

[0059] The term “Cu@DA ink” as used herein refers to a copper-based molecular ink formulated with dopamine hydrochloride as an additive. During thermal decomposition, dopamine undergoes carbonization, forming an in situ graphitic carbon shell around the copper nanoparticles. This carbon layer acts as a protective passivation barrier, enhancing oxidation and corrosion resistance while maintaining electrical conductivity.

[0060] The term “MOD inks” as used herein refers to conductive ink used for printing electronics that’s made from copper-organic precursors, such as copper formate or copperamine complexes. Upon thermal decomposition, these precursors convert into metallic copper, forming a conductive network. Unlike nanoparticle-based inks, MOD inks offer improved stability, reduced oxidation risks, and tunable sintering temperatures, making them suitable for flexible and printed electronic applications.

[0061] The term “hierarchical gradient structure” as used herein refers to the density variation between a copper core and an in situ-formed carbon layer derived from dopamine hydrochloride. This structure is formed during thermal decomposition, where dopamine hydrochloride undergoes carbonization, forming a protective carbon shell around the copper nanoparticles. The gradual transition from dense metallic copper to a less dense carbon-rich outer layer enhances corrosion resistance, oxidation stability, and overall material durability.

[0062] The term “percolated copper nanoparticles” as used herein refers to a network of interconnected copper nanoparticles that form a continuous conductive pathway. This structure emerges during thermal decomposition and sintering, where individual copper nanoparticles coalesce to create a percolation threshold, allowing for efficient electron transport. The degree of percolation influences the electrical conductivity, mechanical stability, and overall performance of the printed copper ink.

[0063] The term “anodic barrier” as used herein refers to a protective layer that inhibits oxidation or corrosion by preventing the electrochemical reaction at the anode. In the context of copper-based inks, this barrier is often formed by an in-situ generated carbon shell or other passivating materials, which reduce the exposure of copper to oxygen and moisture. The anodic barrier enhances the longevity and stability of conductive films by mitigating anodic degradation.

[0064] The term “copper-based MOD ink” as used herein refers to a composition comprising copper nanoparticles, an additive and optionally, a solvent (polar or non-polar, or a mixture thereof), where the copper in said copper nanoparticles is in the form of Cu° and wherein the additive forms at least a partial shell / film around the copper particle, i.e., said copper nanoparticles is passivated by said additive. In some embodiments, said copper nanoparticle is fully encapsulated / passivated by said additive. Copper-based inks disclosed herein (such as Cu@DA and Cu@GC) are examples of copper based metal-organic decomposition (MOD)ink. Without wishing to be limited to any particular theory, copper-based MOD inks disclosed herein are conductive ink that may be used for printing electronics. Upon thermal decomposition, these precursors convert into metallic copper, forming a conductive network.

[0065] The term “carbonaceous additive” as used herein refers to refers to compounds that contain only carbon (such as graphite, graphene, carbon nanotubes (CNTs), fullerenes (e.g., Ceo, C70), carbon black, and amorphous carbon).

[0066] The term “copper nickel alloy -based MOD ink” composition as used herein refers to a composition comprising copper and nickel nanoparticles, an additive and optionally, a solvent (polar or non-polar, or a mixture thereof), where the copper in said copper nanoparticles is in the form of Cu° and said nickel particles is in the form of Ni° and wherein the additive forms at least a partial shell / film around the copper and the nickel particles, i.e., both the copper and nickel nanoparticles are passivated by said additive. Without wishing to be limited to any particular theory, copper nickel alloy -based MOD ink disclosed herein are conductive inks that may be used for printing electronics. Upon thermal decomposition, these precursors convert into metallic copper and metallic nickel respectively, forming a conductive network. The precursor copper formate / nickel formate precursor ink may be prepared using known methods. See .e.g., See Conformal Cu-CuNi Thermocouple Using Particle-Free Ink Materials Aaron Sheng, Saurabh Khuje, Zheng Li, Jian Yu, and Shenqiang Ren, ACS Applied Electronic Materials (2022) 4 (11), 5558-5564 DOI: 10.1021 / acsaelm.2c01150.

[0067] One aspect of the invention pertains to a copper based MOD ink composition, said composition comprising a copper (0) nanoparticle and an additive. The nanoparticle is encapsulated or passivated with said additive, and said additive forms a shell around said copper nanoparticle core wherein the core is a copper core. The additive is an amine additive and / or carbonaceous additive such as graphite, graphene, carbon nanotubes, fullerenes, carbon black, and amorphous carbon. In some embodiments, the composition comprises encapsulatedcopper (0) nanoparticles where said nanoparticle are passivated with said additive which forms a protective shell around each copper (0) nanoparticle, wherein said composition copper nanoparticle is partially or fully passivated with said additive, and said copper nanoparticle have a net charge of zero.

[0068] In some embodiment, said additive is dopamine salt such as dopamine hydrochloride.In some embodiments, Cu-ink doped with dopamine HC1 (Cu@DA) is converted to graphitic carbon using known pyrolysis methods such as those disclosed herein to obtain as a copper core with a graphitic carbon shell is referred to herein as Cu@GC. In some embodiments, the composition further comprises AMP. In some embodiments, said additive is present in a concentration of about 0.01 M to about 10 M, more preferably about 0.2 M to about 1.0 M.

[0069] In some embodiments, said copper-based ink has a sintering temperature of about 150 °C to about 700 °C, or about 150 °C to about 300 °C, or about 300 °C to about 700 °C. See Table 1.

[0070] Table 1. Sintering temperatures of substrates.

[0071] In some embodiments, the additive is a carbonaceous compound such as graphite. In some embodiments, the additive forms a graphitic carbon shell around the copper core (also, referred to herein as Cu@GC). In some embodiments, the carbonaceous compound may be formed in situ from a precursor (such as dopamine hydrochloride). See e.g., Figure lbencompasses an exemplary embodiment depicting the printing process for copper inks via the molecular organic decomposable ink route, with added dopamine hydrochloride, which upon pyrolysis converts to graphitic carbon. This conversion results in a hierarchical core-shell structure, with copper as the core and in situ converted graphitic carbon as the shell from dopamine hydrochloride.

[0072] Another aspect of the invention pertains to a copper-nickel alloy -based MOD ink composition, said composition comprising a copper nanoparticle, nickel nanoparticle and an additive, wherein the copper nanoparticle and said nickel nanoparticle are encapsulated or passivated with said additive, wherein said additive forms a shell around said copper nanoparticle core (“copper core”) and nickel nanoparticle core, respectively, wherein said additive is an amine additive and / or carbonaceous additive (e.g., graphite, graphene, carbon nanotubes, fullerenes, carbon black, and amorphous carbon). Preparation of said copperformate and nickel-formate salt precursors can be carried out using known methods, e.g., "Additive Manufacturing of High-Temperature Hybrid Electronics via Molecular- Decomposed Metals." Advanced Functional Materials 34, no. 4 (2024): 2311085, which is incorporated herein by reference in its entirety.

[0073] Another aspect of the invention pertains to a method of preparing copper-based ink composition, said method comprising: a. providing a copper formate salt; b. dissolving said copper formate salt in aminomethyl propanol (AMP) in an amine solution (such as dopamine solution) to obtain a copper (II) amine precursor; c. optionally, adding dopamine salt (such as dopamine hydrochloride) to obtain a dispersion; andd. subjecting said dispersion to thermal decomposition to obtain a composition comprising a copper (0) nanoparticle and said amine additive, wherein the nanoparticle is encapsulated or passivated with said amine additive such that said additive forms a shell around said copper (0) nanoparticle core. Thermal decomposition may be carried out using known methods.

[0074] In some embodiments, said thermal decomposition occurs at about 100 °C to about 350 °C, preferably about 150 °C to about 300 °C, more preferably 200 °C to about 350 °C.

[0075] Another aspect of the invention pertains to a method of preparing a copper ink coated material, said method comprises applying a copper-based ink to the surface of a material. The method comprises sintering (by applying heat) said ink to obtain a copper ink coated surface. The process of “sintering” may be carried out using known methods, and the material is metal, ceramic, glass, fabric, paper, or plastic, or a combination thereof.

[0076] Another aspect of the invention pertains to A copper coated material, said material comprising a copper-based ink from any of the preceding embodiments, wherein said substrate is metal, ceramic, glass, fabric, paper, or plastic, or a combination thereof, and wherein said ink is sintered.

[0077] LIST OF EMBODIMENTS1. A copper-based MOD ink composition, said composition comprising a copper (0) nanoparticle and an additive (e.g., AMP and / or dopamine salt), wherein the nanoparticle is encapsulated or passivated with said additive, wherein said additive forms a shell around said copper nanoparticle core (“copper core”), wherein said additive is an amine additive and / or carbonaceous additive (e.g., graphite, graphene, carbon nanotubes, fullerenes, carbon black, and amorphous carbon).The composition of embodiment 1, wherein said composition comprises encapsulated copper (0) nanoparticles where said nanoparticle are passivated with said additive which forms a protective shell around each copper (0) nanoparticle. The composition of embodiment 1, wherein said composition copper nanoparticle is partially passivated with said additive. The composition of embodiment 1, wherein said composition copper nanoparticle is fully passivated with said additive. In some embodiments, said composition comprises a mixture of copper nanoparticles partially passivated with said additive (e.g., graphite) and copper nanoparticles fully passivated with said additive (e.g., graphite). The composition of embodiment 1 , wherein said copper nanoparticles have a net charge of zero (i.e., Cu°). The composition of embodiment 1, wherein said additive is AMP. The composition of any of the preceding embodiments, wherein said additive is dopamine salt such as dopamine hydrochloride. In some embodiments, Cu-ink doped with dopamine HC1 (Cu@DA) is converted to graphitic carbon using known pyrolysis methods such as those disclosed herein to obtain as a copper core with a graphitic carbon shell is referred to herein as Cu@GC. The composition of any of the preceding embodiments, wherein said additive is a carbonaceous compound such as graphite. In some embodiments, said additive forms a graphitic carbon shell around the copper core (also, referred to herein as Cu@GC). In some embodiments, the carbonaceous compound may be formed in situ from a precursor (such as dopamine hydrochloride). See e.g., Figure lb encompasses an exemplary embodiment depicting the printing process for copper inks via the molecular organic decomposable ink route, with added dopamine hydrochloride, which upon pyrolysis converts to graphitic carbon. This conversion results in a hierarchicalcore-shell structure, with copper as the core and in situ converted graphitic carbon as the shell from dopamine hydrochloride.9. The composition of embodiment 1, wherein said additive is present in a concentration of about 0.01 M to about 10 M, more preferably about 0.2 M to about 1.0 M.10. The composition of embodiment 1, wherein said copper-based ink has a sintering temperature of about 150 °C to about 700 °C, or about 150 °C to about 300 °C, or about 300 °C to about 700 °C.11. A copper-nickel alloy -based MOD ink composition, said composition comprising a copper nanoparticle, nickel nanoparticle and an additive, wherein the copper nanoparticle and said nickel nanoparticle are encapsulated or passivated with said additive, wherein said additive forms a shell around said copper nanoparticle core (“copper core”) and nickel nanoparticle core (“nickel core”), respectively, wherein said additive is an amine additive and / or carbonaceous additive (e.g., graphite, graphene, carbon nanotubes, fullerenes, carbon black, and amorphous carbon). In some embodiments, said composition comprises a mixture of copper and nickel nanoparticles that are partially passivated with said additive (e.g., graphite) and copper and nickel nanoparticles that are fully passivated with said additive (e.g., graphite).12. A method of preparing copper-based MOD ink composition, said method comprising: a. providing a copper formate salt; b. dissolving said copper formate salt in aminomethyl propanol (AMP) in an amine solution (such as dopamine solution) to obtain a copper (II) amine precursor; c. optionally, adding dopamine salt (such as dopamine hydrochloride) to obtain a dispersion; andd. subjecting said dispersion to thermal decomposition to obtain a composition comprising a copper (0) nanoparticle and said amine additive, wherein the nanoparticle is encapsulated or passivated with said amine additive such that said additive forms a shell around said copper (0) nanoparticle core. Thermal decomposition may be carried out using known methods.13. The method of embodiment 12, wherein said thermal decomposition occurs at about 100 °C to about 350 °C, preferably about 150 °C to about 300 °C, more preferably 200 °C to about 350 °C.14. A method of preparing a copper ink coated material, said method comprises applying a copper-based ink of any of the preceding embodiments to the surface of a material.15. The method of embodiment 14, said method comprising sintering (by applying heat) said ink to obtain a copper ink coated surface. The process of “sintering” may be carried out using known methods.16. The method of embodiment 14, wherein said material is metal, ceramic, glass, fabric, paper, or plastic, or a combination thereof.17. A copper coated material, said material comprising a copper-based ink from any of the preceding embodiments.18. The material of embodiment 17, wherein said substrate is metal, ceramic, glass, fabric, paper, or plastic, or a combination thereof.19. The material of embodiment 17, wherein said ink is sintered.

[0078] EXAMPLES

[0079] The following examples are provided solely to illustrate the present invention and are not intended to limit the scope of the invention, described herein.

[0080] Example 1. Overview

[0081] Herein, the thermal decomposition of copper-based metal-organic decomposition (MOD) inks is presenting, resulting in the formation of gradient metallic-carbon percolation network. A gradient- structured surface layer consisting of copper as the foundation and carbon as the passive gradient layer as a consequence of density variance was created. Carbon coatings are considered to be an excellent corrosion and oxidation inhibitor for metals under harsh conditions, and they can considerably reduce electrochemical corrosion rates in a solution-based environment. Carbon's oxidation and corrosion protection is linked to its toughness, hydrophobicity, and impermeability to molecules, and can be mechanically deposited onto arbitrary surfaces, making it a choice for an ultrathin protective coating for Cu against marine, saline and high temperature environments. A carbon coating on metals has been shown to offer a natural diffusion barrier to aqueous corrosion reactants. The in- situ converted 7t-orbitals of the carbonaceous material produce a dense delocalized cloud that closes the space between its aromatic rings, creating a strong repulsive force that prevents any molecules from passing through when subjected to corrosive or oxidative environments. This technique enables the evaluation of a printed copper-based dipole antenna under various environmental stimuli, while simultaneously assessing its reliability in corrosive (0.01 - 10 M acids and bases) and oxidative environments (temperature range of -193°C to 500°C).

[0082] Copper (II) oxide being a basic oxide, dissolves in mineral acids as per the following reaction:

[0083] CuO(s) + 2HX CuX2+ H2O (1)

[0084] Figure la shows the recovery process for copper through copper oxide via leaching, enabled through the utilization of acid solution (sulfuric or nitric acid). When utilizing nitric acid (or sulfuric acid), the reaction proceeds as follows:

[0085] CuO + 2HNO3Cu(NO3)2+ H2O (2)

[0086] CuO + H2SO4CuSO4+ H2O (3)

[0087] This process was employed to recycle copper oxide to obtain copper formate, a starting material for the molecular decomposed copper ink synthesized in this work. Figure lb shows the schematic depicting the printing process for copper inks via the molecular organic decomposable ink route, with added dopamine hydrochloride which upon pyrolysis converts to carbon. This conversion results in a hierarchical gradient structure, attributed to the density difference between copper and in-situ converted carbon from dopamine hydrochloride. For convenience, Cu-ink doped with dopamine which eventually converts to carbon will be referred to as Cu@DA ink.

[0088] Printable copper ink complex is synthesized by the coordination of Cu salts with their corresponding ligands. Following printing, the metal ions can be reduced to their metallic counterparts through thermal breakdown via ligand-to-metal charge transfer. Equation 4 describes how CuF and amine complexes are formed when CuF salt is dissolved in amines:

[0089] CU(HCOO)2+2R*-NH2^CU(HCOO)2(R*-NH2)2 (4)

[0090] where R* represents the carbon links for AMP. Furthermore, CuF decomposes in two steps: first, divalent copper is reduced to monovalent copper, followed by complete reduction. Furthermore, during the decomposition of Cu complex ink, amine solvents acting as stabilizing ligands may impact the development of Cu particles and, consequently, the conductivity of sintered Cu patterns. Additionally, the microstructure and resistivity of sintered Cu is also impacted by the amine concentration. Following the ink synthesis step, the samples can be printed using various additive manufacturing techniques, as depicted in Figure lb. Following the printing process, the printed sample is subjected to thermal decomposition, with the final result being a dense network of percolated copper nanoparticles.

[0091] Following the thermal decomposition resulting in the conversion process of Cu@DA inks as depicted in Figure 2a, an in-situ approach is used for molecular dopamine directconversion to carbonaceous species for formulating copper-carbon gradient conductors aimed at corrosion and oxidation protection. The in-situ conversion is accomplished through dopamine addition during the ink making process, which, when carbonized at high temperatures, serves as a potent carbon source. The presence of hydroxyl (-OH) and amine (-NH2) groups forms a uniform coating on the copper surface, resulting in strong adhesion to both organic and inorganic surfaces due to formation of non-covalent bonds (hydrogen bonding or 7t-7t stacking). Figure 2b shows scanning electron microscopy (SEM) observation depicting the gradient structure formed due to the density difference between copper and in- situ converted carbon resulting in its diffusion towards the surface, thus forming a passive coating to protect copper against corrosion and oxidation when exposed to reactive elements. Figure 2c shows the effect of increasing dopamine concentration on the particle size, which show an increasing trend in particle size with lower porosity and can be attributed to the Ostwald ripening. The dopamine is known to scavenge metal ions to facilitate the particle growth. Figure 2d shows the XRD peaks for printed Cu@DA conductors before and after annealing at 700°C. From the plot, a notable change can be observed towards greater d- spacing in both (111) and (200) peaks, suggesting possible intercalation of carbon inside the Cu lattice, with no indication that any further phases or oxides formed during the annealing process (Figure 5 for resistance vs. thickness plot for Cu@DA following pyrolysis).

[0092] In order to achieve efficient conversion of dopamine to carbon, different pyrolysis temperatures were studied. Figure 2e shows the Raman spectroscopy and demonstrates the existence of carbon in pyrolyzed copper samples beginning at 500°C. The D peak at 1352 cm1denotes disorder in carbon material, and its intensity ratio to the G peak at 1595 cm1(ID / IG) measures defects in the converted carbon. The stretching motion of sp2carbon pairs in both rings and chains lead to the origin of the G-band, whereas the defects in the hexagonal sp2carbon network or the finite particle-size effect leads to the rise of the D-band. Figure 2fshows the XRD profiles corresponding to different dopamine concentrations with characteristic Cu peaks of three crystalline planes (111), (200), and (220) at 43.5°, 50.8° and 74.6° respectively, confirming the presence of copper as the major element with increasing dopamine concentrations.

[0093] Figure 3 shows the corrosion resistance by monitoring the electrical stability of gradient copper-carbon materials derived from printed 5 wt.% Cu@DA molecular inks. Figure 3a shows the corrosion resistance effect of copper-carbon in sulfuric acid environments. For 0.01 and 0.1 M, no change in relative resistance is observed, whereas for 1 and 10 M, a relative resistance change of -1.5% is observed, further demonstrating that the ability of carbon to passivate Cu and provide protection against corrosive elements. The carbon gradient structure protects the underlying Cu surface by reducing the passage of ionic species between the solvent and substrate, corroborating that carbon gradient is primarily serving as an anodic barrier for copper, hence decreasing or completely inhibiting the corrosion rate. Another possible explanation would be when exposed to a corrosive reagent, the corrosion species move through the gradient domain, and hence the corrosion species are hindered from reaching the Cu surface.

[0094] Thus, the corrosion rate is significantly diminished, demonstrating that Cu with gradient carbon structure has better corrosion performance. Figure 3b shows the SEM observation of gradient copper-carbon materials following 40-minute exposure to 1 M sulfuric acid, with no morphological changes to the surface. Figure 3c shows the performance in sodium hydroxide medium, with the -1% change in relative resistance. From these plots, the effect of carbon towards passivating copper and providing corrosion protection was confirmed (Figure 6 for corrosion testing in hydrochloric acid and ammonium hydroxide for different molarities, Figure 7 for corrosion testing in formic acid). Similarly, Figure 3d shows the SEM observation of gradient copper-carbon materials following 40minute exposure to 1 M sodium hydroxide (Figures 8-10 for SEM observations for gradient copper-carbon materials exposed to 10M HC1, NaOH and NH4OH).

[0095] Figure 3e shows the reliability of gradient copper-carbon materials under humid conditions. With a relative humidity of 85%, gradient copper-carbon was compared with silver at 85°C. From the plot, gradient copper-carbon materials show competitive performance in terms of reliability to that of silver, corroborating the functionality of the gradient carbon layer acting as a diffusion barrier to oxygen molecules. Figure 3f shows the stability of gradient copper-carbon materials under cryogenic as well as elevated temperature conditions (-193 °C - 500 °C), and it displays relatively stable resistance values, attributing to the impermeability of gradient structured carbon at cryogenic as well as elevated temperatures, coupled with the tight carbon-Cu bonding preventing O2 and H2O diffusion between the carbon and Cu surface (Figure 11 for additional temperature stability data for varying dopamine concentrations, Figure 12 for XRD plots for gradient copper-carbon materials after exposure to varying temperatures).

[0096] When it comes to the reliability of printable electronics under various extreme conditions (corrosive, high temperatures, etc.), it is useful to consider corrosion and oxidation resistance and washing stability. Figure 4a shows the illustration depicting the evaluation of printed antenna underwater, mimicking corrosive conditions. Figure 4b shows the resistance of gradient copper-carbon materials remains unchanged even after being soaked and washed for 48 hours (where each wash cycle consists of one hour). Figure 4c shows the evaluation of a dipole antenna under saltwater conditions, and it can be inferred that there is a negligible change in the resonant frequency in the absence of saltwater (antenna not immersed in saltwater) and in the presence of saltwater (antenna completely immersed in saltwater). This can be attributed to the aforementioned reasoning regarding thecarbon gradient functioning as an anodic barrier for copper, reducing or entirely suppressing the corrosion rate.

[0097] The passivated carbon gradience acting as a barrier prevents the diffusion of corrosive elements towards copper underneath. Figure 4d shows the printed antenna being utilized as a pH sensor. As the printed sensor has been shown to be stable under different acid / base solutions, the frequency shift can be attributed to the dielectric constant of the gradient copper-carbon materials. This demonstration enables the utilization of printed gradient copper-carbon materials as pH sensing medium, and as antennas for underwater communication (Figure 13 for dielectric constant plot).

[0098] Example 2. Methods

[0099] This copper based conductive ink is synthesized in a four-step method from precursor material synthesis, solvation in a chemical solvent, heating and precipitation, and the addition of functional additives for enhanced performance.

[0100] Example 3. Copper Formate Synthesis

[0101] Copper (II) Formate can be synthesized in a two-step method involving the reaction of copper sulfate and sodium carbonate in an aqueous solution. A precipitation of copper carbonate and sodium sulfate in solution formed as products of this reaction and the copper carbonate is separated out through vacuum filtration. Subsequently the precipitated copper carbonate can be further washed and dried for improved purity. The copper carbonate is then reacted with formic acid to consequently produce copper (II) formate, water, and carbon dioxide. The copper (II) formate crystals may be washed with ethanol and dried for further purity.

[0102] Example 4. Solvation of Copper Formate

[0103] The resulting copper (II) formate crystals are mixed with 2-amino-2methyl-l- propanol (AMP) in a 2: 1 molar mass ratio. Usual homogenization of this solution is doneusing a Thinkymixer at 2000 rpm for 2 minutes. Similar results can be achieved using any other mechanical methods.

[0104] Example 5. Heating and Precipitation

[0105] 100 mL of the solution is poured into a 250 mL Erlenmeyer flask (with a spout) a ceramic stir bar is dropped in, and the top is stoppered with a cork.

[0106] This is then taken into a glove box. A tube is connected to the spout and led and submerged into any container holding methanol. This is done to catch evaporating solvent into the solution in the external container.

[0107] The hot plate is then set to stir at an rpm of 400 and heated at 370 °C for an hour and a half. It is understood that stirring settings (Rpm) and heating temperature can be varied to produce similar results but with longer synthesis times. There can be some variation in precipitation time from batch to batch. Once there is a noticeable level of separation from copper nanoparticles and solvent, the flask is taken off the hotplate and allowed to cool to room temperature inside of the glovebox.

[0108] Example 6. Additives

[0109] The flask is taken out of the glovebox and distributed in centrifuge tubes. This is consequently centrifuged at 6000 rpm for 5 minutes and excess solvent is decanted. The copper nanoparticle ink is collected into separate containers and resin and glycerol is added to the ink by 8 and 3 weight percent of the original precipitate respectively. Further addition of Dopamine Hydrochloride at 1, 5, 10 and 15 weight percent of the initial mass can also be done for improvements in corrosion resistance and high temperature oxidation resistance.

[0110] Bilateral studies using these additives indicate the novelty of the combination of using 2-amino-2methyl-l -propanol, phenolic resin and glycerol can make most solid conductive particles conductive in air. This can be done by mixing the relevant additives in the appropriate amount to the solid conductive particles and printing, then sintering them ona hotplate at the appropriate temperature depending on the materials sensitivity to oxidation at higher temperatures. Successful applications of this approach have been done on dried copper nanoplates and commercial copper powder.

[0111] Example 7. Cu@DA Ink Preparation

[0112] For synthesizing Cu@DA ink, CuF was combined with AMP in a molar ratio of 1 :2 and thereafter subjected to centrifugation in a Thinky Mixer (ARE-310) for a duration of eight minutes. Comprehensive research on CuF-AMP inks has been reported in previous work. The ink solution was heated using a hot plate within a controlled environment at a temperature of 350°C in order to produce Cu nanoparticles. To this nanoparticle combination, glycerol (3wt.%) and phenolic resin (8 wt.%) was added and further centrifuged, and the resulting mixture underwent filtration through a 165 pm mesh and was utilized for printing the test samples. For inks with dopamine, different weight ratios of dopamine hydrochloride was incorporated with the filtered ink mixture and centrifuged again for obtaining a homogenous dispersion.

[0113] Example 8. Printing and Sintering of Cu@DA Samples

[0114] The test samples were printed using a screen printer, with 100 mesh onto plastic / ceramic substrates as needed. The sintering step was determined by the choice of substrate in use. For Kapton® substrates, the samples were sintered on a hot plate within a temperature range of 150 - 300°C in a glove box. For samples printed on ceramics, a tube furnace was utilized within the temperature range of 300 - 700°C. With a holding / dwelling time of 30 minutes at said temperatures, the process took place under an inert atmosphere consisting of 95% nitrogen (N2) and 5% hydrogen (EE) gas. The temperature was ramped gradually at a rate of 5°C / min, and the furnace was allowed to cool naturally.

[0115] Example 9. Characterization and High Temperature Testing

[0116] Hitachi SU-70 Scanning Electron Microscope was utilized for SEM characterization. Thermo-Fisher ARL Equinox 100 XRD was utilized for XRD. Raman was conducted on Horiba Jobin Yvon (H-J-Y) Raman Microscope. The sheet resistance was characterized using a four-point probe (Ossila). The high temperature measurements for electrical stability were conducted using a Keithley 2450 Sourcemeter and a box furnace as a heating source. Platinum wires were used as electrodes and the temperature was increased at a rate of 5 °C / min.

[0117] Example 10. Copper Nanoparticle Ink Functional Description

[0118] Prints can be made using screen printing, doctor blading or direct writing techniques. The as developed ink without additional dopamine HC1 can be sintered using any heating element in air, such as a hotplate or box furnace at a temperature range from of 100 °C and above. Sintering time and electrical conductivity may vary depending on sintering temperature, substrate material and uniformity of heating. Below depicts a plot for samples sintered at varied temperatures and times plotted against its respective electrical conductivity.

[0119] This ink is compatible with photonic sintering methods as well as sintering in inert environments such as in a glovebox or tube furnace. Slight improvements in electrical conductivity can be noted when sintering in an inert environment. Below is some characteristic data of samples sintered with photonic sintering. Figure 15 shows variation in frequency and burst count which can help optimize sheet resistance of the samples. A lower burst count demonstrates a lower sheet resistance likely due to less surface layer oxidation after consecutive burst / heating cycles. A higher burst frequency relates to the number of flashes within a certain amount of time. A greater frequency leads to rapid heating which may induce a greater percolation of surface particles creating a lower sheet resistance value in the sample.

[0120] Example 11. Copper Nanoparticle Ink with Dopamine

[0121] Figure 17 shows the sheet resistance of the printed samples increases as a greater concentration of dopamine hydrochloride is added to the ink. Generally, the sheet resistance is lower as the samples are sintered at higher temperatures. The correlated scanning electron microscope (SEM) images of these samples are shown in Figure 18. Observation of the insulated sheet resistance of samples with greater dopamine concentration is characteristic of the in situ conversion of dopamine hydrocholoride to carbon at higher temperatures which creates a graded copper / carbon coating.

[0122] Further SEM imaging and EDS mapping of the cross section of the sample demonstrates this and shows a higher concentration of carbon nearer the sample surface in Figure 19. This structure further supports the stability of the cu / dopamine conductors as they undergo high temperature exposure cycling at 1000 °C for time intervals ranging from 5, 10, 15 and 20 seconds respectively (Figure 20).

[0123] The graded carbon concentration across the surface of the sample also promotes corrosion resistance of the samples as seen in Figure 21. A 15 wt% dopamine doped copper sample was tested in a molar concentration of 1, 2, 3 and 10 of formic acid and ammonium hydroxide and still demonstrated strong electrical stability in both environments for nearly 7 minutes.

[0124] Dopamine concentration in the initial ink formulation was also varied to study the stability of the conductors under a solution of 10 M HCL and 10 M H2SO4. Each individual sample was submerged in solution, washed, and tested for resistivity after the acid solution exposure. Despite an elongated exposure time of an hour - none of the samples showed a significant change in electrical performance and print quality after the test. Same variation seen in the data can mostly be understood as standard deviation of sample-to-sampleperformance and doesn’t indicate any definitive flaws in performance. An even longer test case was consequently studied below in Figure 24.

[0125] A tertiary study completed with a 20wt% dopamine sample submerged in solutions of 10M, 1.0 M and 0.1 M NaOH also showed remarkable stability over a duration of a little over 5 minutes. As earlier detailed the well percolated network of copper and carbon species form a superior conductive composite which performs remarkably well under both acidic and basic environments.

[0126] Example 12. Copper Leaching for Material Circularity

[0127] Briefly, mixing copper oxide with sulfuric acid leads to the formation of copper sulfate (CuSCU). When formic acid is added to this product, it results in the formation of copper formate (CuF), which can be used to make printable ink and thus print conductive patterns onto different substrates.

[0128] Example 13. Conclusions

[0129] Presented in this study is a method of material circularity enabling the recovery of copper metal from e-wastes and oxides, functioning as the starting material for synthesis of conductive material via the molecular organic decomposable ink route. The printable molecular inks undergo in-situ conversion to form a gradient copper-carbon hierarchical structure, attributing to the density difference between copper and carbon, applicable towards addressing the challenges associated with the reliability of copper under harsh conditions. As carbonaceous compounds hold potential for inhibiting oxidation and corrosion, this copper-carbon structure is highly resistant to corrosive and oxidative environments, the printed conductor was evaluated under various corrosive environments as well as temperatures ranging from cryogenic (-193 °C) all the way to high temperatures (500 °C) and successfully demonstrated corrosion and oxidation resistance. To further validate the phenomenon of impermeability of the carbon gradient structure against reactive species,an antenna was tested under severe washing conditions with no change in relative resistance and also under simulated saltwater and high temperature conditions respectively, with negligible shift in the resonant frequency. This study provides a cost-effective and recyclable way of synthesizing Cu molecular ink materials to create printed conductors with high- corrosion and oxidation stability, making it suitable for various printed electronics applications.

[0130] Example 14. Preparation of copper nickel-based ink MOD compositionThe following general protocol may be used:1. dissolve a copper formate salt and a nickel formate salt in aminomethyl propanol (AMP) to obtain a copper formate salt and a nickel formate salt in an amine solution (such as dopamine solution) to obtain a copper(II) / nickel (II) / amine precursor (See e.g., Conformal Cu-CuNi Thermocouple Using Particle-Free Ink Materials Aaron Sheng, Saurabh Khuje, Zheng Li, Jian Yu, and Shenqiang Ren, ACS Applied Electronic Materials (2022) 4 (11), 5558-5564 DOI: 10.1021 / acsaelm.2c01150)2. add dopamine salt (such as dopamine hydrochloride) to obtain a dispersion; and3. subj ecting said dispersion to thermal decomposition to obtain a composition comprising copper (0) nanoparticles, nickel (0) nanoparticles and said amine additive, where the nanoparticle is encapsulated or passivated with said amine additive such that said additive forms a shell around said copper (0) nanoparticle core.4. Thermal decomposition / sintering may be carried out using known methods.REFERENCES

[0131] A number of patents and publications are cited above in order to more fully describe and disclose the invention and the state of the art to which the invention pertains. Full citations for these references are provided below. Each of these references is incorporatedherein by reference in its entirety into the present disclosure, to the same extent as if each individual reference was specifically and individually indicated to be incorporated by reference.(1) Dutta, D.; Rautela, R.; Gujjala, L. K. S.; Kundu, D.; Sharma, P.; Tembhare, M.; Kumar, S. A review on recovery processes of metals from E-waste: A green perspective. Science of the Total Environment 2023, 859, 160391.(2) Shahabuddin, M.; Uddin, M. N.; Chowdhury, J.; Ahmed, S.; Uddin, M.; Mofijur, M.; Uddin, M. A review of the recent development, challenges, and opportunities of electronic waste (e-waste). International Journal of Environmental Science and Technology 2023, 20 (4), 4513-4520.(3) Rao, M. D.; Singh, K. K.; Morrison, C. A.; Love, J. B. Optimization of process parameters for the selective leaching of copper, nickel and isolation of gold from obsolete mobile phone PCBs. Cleaner Engineering and Technology 2021, 4, 100180.(4) Nag, A.; Singh, M. K.; Morrison, C. A.; Love, J. B. Efficient Recycling of Gold and Copper from Electronic Waste by Selective Precipitation. Angewandte Chemie International Edition 2023, 62 (40), e202308356.(5) Kondo, K.; Akolkar, R. N.; Barkey, D. P.; Yokoi, M. Copper electrodeposition for nanofabrication of electronics devices; Springer, 2014.(6)Naboka, M.; Giordano, J. Copper Alloys: Preparation. Properties and Applications (Nova Science Piublishers, Inc., New York 2013).(7) Aromaa, J.; Kekkonen, M.; Mousapour, M.; Jokilaakso, A.; Lundstrbm, M. The Oxidation of Copper in Air at Temperatures up to 100 C. Corrosion and Materials Degradation 2021, 2 (4), 625-640.(8) Nag, A.; Islam, M. R.; Pradeep, T. Selective extraction of gold by niacin. ACS Sustainable Chemistry & Engineering 2021, 9 (5), 2129-2135.(9) Mittal, V.; Bera, S.; Saravanan, T.; Sumathi, S.; Krishnan, R.; Rangarajan, S.; Velmurugan, S.; Narasimhan, S. Formation and characterization of bi-layer oxide coating on carbon-steel for improving corrosion resistance. Thin Solid Films 2009, 517 (5), 1672-1676.(10) Akhtar, S.; Laoui, T.; Ibrahim, A.; Kumar, A. M.; Ahmed, J.; Toor, I.-u.-H. Few-layers graphene film and copper surface morphology for improved corrosion protection of copper. Journal of Materials Engineering and Performance 2019, 28, 5541-5550.(11) Knapp, C. E.; Chemin, J. B.; Douglas, S. P.; Ondo, D. A.; Guillot, J.; Choquet, P.; Boscher, N. D. Room-Temperature Plasma-Assisted Inkjet Printing of Highly Conductive Silver on Paper. Advanced Materials Technologies 2018, 3 (3), 1700326.(12) Chen, L.; Hou, Z.; Liu, Y.; Luan, C.; Zhu, L.; Li, W. High strength and high ductility copper matrix composite reinforced by graded distribution of carbon nanotubes. Composites Part A: Applied Science and Manufacturing 2020, 138, 106063.(13) Nguyen, A. T.; Lai, W.-C.; To, B. D.; Nguyen, D. D.; Hsieh, Y.-P.; Hofmann, M.; Kan, H.-C.; Hsu, C.-C. Layer control of tubular graphene for corrosion inhibition of nickel wires. ACS Applied Materials & Interfaces 2017, 9 (27), 22911-22917.(14) Liang, C.; Wang, W.; Li, T.; Wang, Y. Hydrogen etching effect on single-crystal graphene domains. In The 8th Annual IEEE International Conference on Nano / Micro Engineered and Molecular Systems, 2013; IEEE: pp 697-700.(15) Senanayake, G. Review of theory and practice of measuring proton activity and pH in concentrated chloride solutions and application to oxide leaching. Minerals Engineering 2007, 20 (7), 634-645.(16) Sheng, A.; Khuje, S.; Li, Z.; Yu, J.; Ren, S. Conformal Cu-CuNi Thermocouple Using Particle-Free Ink Materials. ACS Applied Electronic Materials 2022, 4 (11), 5558-5564.(17) Khuje, S.; Alshatnawi, F.; Smilgies, D.; Alhendi, M.; Islam, A.; Armstrong, J.; Yu, J.; Poliks, M.; Ren, S. Additive Manufacturing of High-Temperature Hybrid Electronics via Molecular-Decomposed Metals. Advanced Functional Materials 2024, 34 (4), 2311085.(18) Li, W.; Sun, Q.; Li, L.; Jiu, J.; Liu, X.-Y.; Kanehara, M.; Minari, T.; Suganuma, K. The rise of conductive copper inks: challenges and perspectives. Applied Materials Today 2020, 18, 100451.(19) Li, Z.; Khuje, S.; Chivate, A.; Huang, Y.; Hu, Y.; An, L.; Shao, Z.; Wang, J.; Chang, S.; Ren, S. Printable copper sensor electronics for high temperature. ACS Applied Electronic Materials 2020, 2 (7), 1867-1873.(20) Huang, Y.; Ni, J.; Shi, X.; Wang, Y.; Yao, S.; Liu, Y.; Fan, T. Two-Step Thermal Transformation of Multilayer Graphene Using Polymeric Carbon Source Assisted by Physical Vapor Deposited Copper. 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Claims

CLAIMSWe claim:

1. A copper-based ink MOD composition, said composition comprising a copper (0) nanoparticle and an additive, wherein the nanoparticle is encapsulated or passivated with said additive, wherein said additive forms a shell around said copper nanoparticle core (“copper core”), wherein said additive is an amine additive and / or carbonaceous additive (e.g., graphite, graphene, carbon nanotubes, fullerenes, carbon black, and amorphous carbon).

2. The composition of claim 1, wherein said composition comprises encapsulated copper (0) nanoparticles where said nanoparticle are passivated with said additive which forms a protective shell around each copper (0) nanoparticle.

3. The composition of claim 1, wherein said composition copper nanoparticle is partially passivated with said additive.

4. The composition of claim 1, wherein said composition copper nanoparticle is fully passivated with said additive.

5. The composition of claim 1, wherein said copper nanoparticles have a net charge of zero (i.e., Cu°).

6. The composition of any of the preceding claims, wherein said additive is dopamine salt such as dopamine hydrochloride.

7. The composition of any of the preceding claims, wherein said additive is AMP.

8. The composition of any of the preceding claims, wherein said additive is a carbonaceous compound such as graphite.

9. The composition of claim 1, wherein said additive is present in a concentration of about 0.01 M to about 10 M, more preferably about 0.2 M to about 1.0 M.

10. The composition of claim 1, wherein said copper-based ink has a sintering temperature of about 150 °C to about 700 °C, or about 150 °C to about 300 °C, or about 300 °C to about 700 °C.

11. A copper-nickel alloy -based ink composition, said composition comprising a copper nanoparticle, nickel nanoparticle and an additive, wherein the copper nanoparticle and said nickel nanoparticle are encapsulated or passivated with said additive, wherein said additive forms a shell around said copper nanoparticle core (“copper core”) and nickel nanoparticle core (“nickel core”), respectively, wherein said additive is an amine additive and / or carbonaceous additive (e.g., graphite, graphene, carbon nanotubes, fullerenes, carbon black, and amorphous carbon).

12. A method of preparing copper-based ink composition, said method comprising: a. providing a copper formate salt; b. dissolving said copper formate salt in aminomethyl propanol (AMP) in an amine solution (such as dopamine solution) to obtain a copper (II) amine precursor; c. optionally, adding dopamine salt (such as dopamine hydrochloride) to obtain a dispersion; and d. subjecting said dispersion to thermal decomposition to obtain a composition comprising a copper (0) nanoparticle and said amine additive, wherein the nanoparticle is encapsulated or passivated with said amine additive such that said additive forms a shell around said copper (0) nanoparticle core. Thermal decomposition may be carried out using known methods.

13. The method of claim 12, wherein said thermal decomposition occurs at about 100 °C to about 350 °C, preferably about 150 °C to about 300 °C, more preferably 200 °C to about 350 °C.

14. A method of preparing a copper ink coated material, said method comprises applying a copper-based ink of any of the preceding claims to the surface of a material.

15. The method of claim 14, said method comprising sintering (by applying heat) said ink to obtain a copper ink coated surface.

16. The method of claim 14, wherein said material is metal, ceramic, glass, fabric, paper, or plastic, or a combination thereof.

17. A copper coated material, said material comprising a copper-based ink from any of the preceding claims.

18. The material of claim 17, wherein said substrate is metal, ceramic, glass, fabric, paper, or plastic, or a combination thereof.

19. The material of claim 17, wherein said ink is sintered.