Description:FIELD OF THE INVENTION
[0001] The present invention broadly relates to the field of nanotechnology and nanomaterials synthesis in combination with materials engineering. More particularly, the present invention relates to a method for synthesizing zinc oxide (ZnO) and copper oxide (CuO) nanoparticles, a method for preparing a ZnO (Zinc Oxide: Multi-Walled Carbon Nanotube) nanoparticle mixture for screen printing and method for synthesizing copper oxide (CuO) nanofluid.

BACKGROUND OF THE INVENTION
[0002] 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.
[0003] Zinc oxide (ZnO) nanoparticles are nanoscale particles of zinc oxide that offer numerous advantages over their bulk counterparts. Due to their significantly larger surface area-to-volume ratio, ZnO nanoparticles exhibit enhanced reactivity, unique optical properties arising from quantum confinement effects, superior antimicrobial activity, improved photocatalytic efficiency, and greater mechanical strength. These nanoparticles can assume various shapes, such as spherical, rod-like, and flower-like, depending on the synthesis method and conditions. ZnO has garnered substantial attention for its distinctive optical, semiconducting, and piezoelectric properties.
[0004] Furthermore, ZnO nanoparticles possess intriguing potential due to their modifiable resistivity across a range of 10^-3 to 10^5 Ocm, transparency in the visible spectrum, and high reflectivity in the infrared region. These characteristics make ZnO suitable for a variety of applications, including infrared reflectors, thick film varistors, gas sensors, and piezoelectric films in surface acoustic wave devices. As a pivotal metal oxide semiconductor in the II-VI group, ZnO features a wide direct band gap and exhibits n-type semiconducting behavior. This positions it alongside other extensively studied wide band gap semiconductors like GaN and ZnS, which are in demand for solid-state light sources in the UV-visible spectral domains. ZnO's multifunctional properties—spanning semiconducting, magnetic, and piezoelectric attributes—make it highly attractive for electronics and optoelectronics applications.
[0005] Additionally, ZnO serves as a transparent conductive oxide, ideal for use as a thin film in organic light-emitting devices. It is characterized by high electrical conductivity, a substantial binding energy of 60 meV, elevated optical gain of 320 cm^-1 at ambient temperature, cost-effectiveness, and non-toxicity. These attributes enhance ZnO's potential applications in solar cells, light-emitting diodes, gas sensors, and in medical fields such as antibacterial and cancer treatment modalities.
[0006] Further, ZnO's piezoelectric effect, where an electric charge is generated on a material's surface in response to applied pressure, highlights its suitability as a piezoelectric material. Among tetrahedral semiconductors, ZnO exhibits the highest piezoelectric response (d33), making it a superior candidate for electromechanical and communication device applications. The hexagonal wurtzite structure of ZnO, characterized by its P63mc symmetry and lack of a center of symmetry, contributes to its exceptional piezoelectric properties. The structure consists of alternating planes of tetrahedrally coordinated Zn2+ and O2- ions, creating an electric dipole moment when external stress is applied along the c-crystallographic axis.
[0007] However, none of the prior art known to the inventors till date suggests the methods of synthesizing and optimizing ZnO nanoparticle blends, which can be utilized for scalable screen-printing techniques and advanced sensor technology along with addressing environmental and safety concerns effectively.

OBJECTIVE OF THE INVENTION
[0008] An objective of the present invention is to develop efficient and reliable methods for the synthesis and application of zinc oxide (ZnO) and copper oxide (CuO) nanoparticles for various industrial and technological uses.
[0009] An objective of the present invention is to develop establish a reproducible method for synthesizing ZnO nanoparticles with precise control over their size and properties through dissolution, stirring, titration, filtration, washing, and thermal treatment processes.
[0010] An objective of the present invention is to develop a ZnO nanoparticle mixture with enhanced viscosity suitable for screen printing applications on glass substrates, ensuring uniform distribution and strong adhesion.
[0011] An objective of the present invention is to create a method for producing CuO nanofluids with controlled particle size and stability by combining sodium borohydride and copper sulfate solutions, followed by washing, filtration, heating, and aging processes.
[0012] An objective of the present invention is to formulate a ZnO paste with the appropriate consistency and flow characteristics for screen printing applications by mixing ZnO with ethylene glycol.
[0013] An objective of the present invention is to optimize a screen-printing process using ZnO paste to achieve uniform and well-adhered patterns on glass substrates, enhancing the performance and application potential of the printed layers.
[0014] An objective of the present invention is to improve the synthesis, preparation, and application processes of ZnO and CuO nanoparticles to ensure high-quality, consistent, and scalable production for use in nanotechnology, electronics, and other fields requiring precise nanoparticle application.

SUMMARY OF THE INVENTION
[0015] The present invention encompasses methods for synthesizing zinc oxide (ZnO) and copper oxide (CuO) nanoparticles and their application in various industrial processes. In other words, the invention aims to improve the production, preparation, and application methods of ZnO and CuO nanoparticles, ensuring high-quality, consistent, and scalable processes for use in various technological and industrial applications.
[0016] In an embodiment, the present invention discloses a method for synthesizing zinc oxide (ZnO) nanoparticles, comprising the steps of:

i. dissolving 5mM of zinc nitrate and 5mM of hexamethyl tetramine (HMTA) in 100 ml of distilled water each to form a precursor solution and a surfactant solution respectively;
ii. subjecting the precursor solution and the surfactant solution to magnetic stirring for 60 minutes;
iii. gradually adding 0.5M ammonium hydroxide (NH4OH) to the stirred solution via a titration process;
iv. filtering the resulting mixture using Whatman filter paper to separate the ZnO nanoparticles from the reaction mixture;
v. washing the filtered ZnO nanoparticles with water to remove impurities;
vi. subjecting the washed ZnO nanoparticles to thermal treatment in a hot air oven at 90°C for 180 minutes; and
vii. obtaining the zinc oxide (ZnO) nanoparticles.
[0017] In another embodiment, the present invention discloses a method for preparing a Zinc Oxide: Multi-Walled Carbon Nanotube nanoparticle mixture for screen printing, by mixing 20 grams of ZnO nanoparticles and with 340 drops of ethylene glycol to form a paste;
wherein said mixture is applied the onto glass substrates using a screen-printing to apply the ZnO paste onto the glass substrates with one or/and two strokes, wherein, the paste is spread on the screen prior to screen printing and an empty stroke made to spread the paste on the screen;
wherein, the paste is further pressed onto the screen circles by a scalpel for the paste nanoparticles to penetrate the screen circle pores and then final screen printing is done; and
wherein this step provides enhanced quality of screen printing and well printed circles of the paste on glass.
[0018] In another embodiment, the method further comprises a process preparing a Zinc Oxide: Multi-Walled Carbon Nanotube nanoparticle mixture for screen printing with 0.1 grams of ZnO and 0.01 grams of MWCNT in 6 drops of Ethylene Glycol to obtain 10:1 ZnO to MWCNT ratio.
[0019] In another embodiment, the present invention discloses a method for synthesizing copper oxide (CuO) nanofluid, comprising:
i. preparing a sodium borohydride solution by dissolving 3.02 grams of sodium borohydrate in 50 ml of water.
ii. separately dissolving 7.4907 grams of copper sulfate (CuSO4) in 100 ml of water to form a CuSO4 solution.
iii. conducting a titration process by combining the sodium borohydride solution and the CuSO4 solution under controlled conditions involving magnetic stirring at 400 rpm and room temperature.
iv. washing the resulting CuO nanoparticles using a mixture of ethanol and distilled water in a 1:1 ratio (50 ml each).
v. filtering the washed CuO nanoparticles using Whatman filter paper.
vi. heating the filtered CuO nanoparticles in a hot air oven for a duration of 5 hours.
vii. aging the heated CuO nanoparticles for 24 hours.
viii. obtaining a yield of 1.57 grams of CuO nanoparticles for use in nanofluid synthesis.
[0020] In another embodiment, the present invention discloses a method for preparing a ZnO (zinc oxide: multi-walled carbon nanotube) paste for printing, comprising:

i. adding additional quantity suitably of ZnO to an existing ZnO and MWCNT mixture to achieve a ZnO ratio of 40:1; wherein the amount of ZnO ranges from 0.1 gram to 0.2 grams and the amount of MWCNT in the paste ranges from 0.002 to 0.003 gram;
ii. incorporating 32 milliliters of ethylene glycol (E.G) into the mixture to adjust the viscosity;
iii. mixing the ZnO and ethylene glycol thoroughly to obtain a paste for screen printing.
[0021] In another embodiment, the present invention discloses a method for screen printing using a ZnO (zinc oxide: multi-walled carbon nanotube) paste, comprising:
i. applying a 40:1 ZnO paste to a screen;
ii. spreading the paste across the screen to ensure an even distribution;
iii. printing a circular pattern of the ZnO paste onto a glass substrate using a single stroke;
iv. lifting the screen carefully to leave the printed pattern on the glass substrate.
v. subjecting the freshly printed ZnO paste to dry heating in a hot air oven to remove residual solvents and enhance adhesion.
[0022] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments.

FIGURES OF THE INVENTION
[0023] FIG. 1 discloses PXRD of synthesized ZnO nanoparticles.
[0024] FIG. 2 displays-(a)SEM of ZnO nanoparticles at 100000x magnification, (b) SEM of ZnO nanoparticles at 50000x magnification, (c)(d)EDS of ZnO nanoparticles.
[0025] FIG. 3 discloses FTIR of ZnO nanoparticles.
[0026] FIG. 4 displays a) Absorbance vs. Wavelength of ZnO nanoparticles, b) Transmittance vs. Wavelength of ZnO nanoparticles, c) Bandgap plot of ZnO nanoparticles.
[0027] FIG. 5 displays Fig 5- (a) e’ vs. Frequency, (b) u’ vs. Frequency, (c) e’ vs. e’’, (d) u’ vs. u’’, (e) Z’ vs. Z’’.
[0028] FIG. 6 displays large-area printed ZnO nanoparticles
[0029] FIG. 7 displays a) b) Screen printing under process on 4 mm thick glass c) Printed 20:1 ZnO: MWCNT paste using 2 strokes, d) Printed 20:1 ZnO: MWCNT paste using 1 stroke.
[0030] FIG. 8 illustrates the a) Dry heating using hot air oven for printed paste, b) Printed 20:1 ZnO: MWCNT paste using 2 strokes post hot-air-oven , c) Printed 20:1 ZnO: MWCNT paste using 1 stroke post hot-air oven, d) Printed ZnO-MWCNT post glass cutting.
[0031] FIG. 9 shows a) Zno b) MWCNT c) d) e) Mixing Zno and MWCNT with Ethelyene Glycol.
[0032] FIG. 10 shows a) MWCNT:ZnO in ratio of 50:1, b) Glass slides dipped in HMTA, Etheylene glycol solution, c) Glass slides placed in Hot-air-oven.
[0033] FIG. 11 displays a) ZnO-Ethylene glycol mixture from previous screen printing was used , b) 18.7 grams of ZnO paste obtained after transfer to glass dish, c)~ 0.85 grams of MWCNT utilized. d) Comparison of 20:1 ratio of ZnO: MWCNT used e) Mixing of ZnO and MWCNT in glass dish, f) Mixture transfer to Mortar for better grinding.
[0034] FIG. 12 shows a) b)Ethylene glycol was used added drop-wise using Buerette, c) ZnO-MWCNT Mixture at 180 drops of Ethelyene Glycol, d) Paste form of ZnO-MWCNT at 340 drops suitable for screen-printing, e) Mortar with the mixture preserved using polymer thin film for further screen printing.
[0035] FIG. 13 shows the flow chart of scaled up synthesis of ZnO for 40:1 ratio of ZnO:MWCNT mixture
[0036] FIG. 14 displays: (clockwise) A) Magnetic stirring of precursors ranging between 400-800 rpms, B) constant pH testing was done until pH of ~ 11 was reached. C) Filtration under process. D) Part of yield obtained after filtration. E) ~31 grams of ZnO nanoparticles were obtained, F) Hot-air-oven used for thermal drying.
[0037] FIG. 15 displays a) 3.02 grams of Sodium Borohydrate, b) 7.4907grams of CuSo4, c) CuSo4 in 100 ml of water, d) Titration of Sodium Borohydrate with CUSo4 solution, e) 1:1 Ethanol with distilled water, f) Filtration using Whatman paper g) Post Hot air heated CuO nanoparticles , h)0.25g CuO nanoparticles yield i) 0.1 grams of SLS, j) Prepared CuO nanofluid.

DETAILED DESCRIPTION OF THE INVENTION
[0038] The following is a full description of the disclosure's embodiments. The embodiments are described in such a way that the disclosure is clearly communicated. The level of detail provided, on the other hand, is not meant to limit the expected variations of embodiments; rather, it is designed to include all modifications, equivalents, and alternatives that come within the spirit and scope of the current disclosure as defined by the attached claims. Unless the context indicates otherwise, the term "comprise" and variants such as "comprises" and "comprising" throughout the specification are to be read in an open, inclusive meaning, that is, as "including, but not limited to."
[0039] When "one embodiment" or "an embodiment" is used in this specification, it signifies that a particular feature, structure, or characteristic described in conjunction with the embodiment is present in at least one embodiment. As a result, the expressions "in one embodiment" and "in an embodiment" that appear throughout this specification do not necessarily refer to the same embodiment. Furthermore, in one or more embodiments, the specific features, structures, or qualities may be combined in any way that is appropriate.
[0040] Unless the content clearly demands otherwise, the singular terms "a," "an," and "the" include plural referents in this specification and the appended claims. Unless the content explicitly mandates differently, the term "or" is normally used in its broad definition, which includes "and/or."
[0041] All processes described herein can be performed in any 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.
[0042] The headings and abstract of the invention provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.
[0043] 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.
[0044] 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 thus fulfilling the written description that follows, and the embodiments described herein, 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 invention 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] Various terms as used herein are shown below. To the extent a term used in a claim 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.
[0047] In a general embodiment, the present invention relates to the methods for synthesizing zinc oxide (ZnO) and copper oxide (CuO) nanoparticles and their application in various industrial processes.
[0048] In an embodiment, the present invention discloses a method for synthesizing zinc oxide (ZnO) nanoparticles, comprising the steps of:

i. dissolving 5mM of zinc nitrate and 5mM of hexamethyl tetramine (HMTA) in 100 ml of distilled water each to form a precursor solution and a surfactant solution respectively;
ii. subjecting the precursor solution and the surfactant solution to magnetic stirring for 60 minutes;
iii. gradually adding 0.5M ammonium hydroxide (NH4OH) to the stirred solution via a titration process;
iv. filtering the resulting mixture using Whatman filter paper to separate the ZnO nanoparticles from the reaction mixture;
v. washing the filtered ZnO nanoparticles with water to remove impurities;
vi. subjecting the washed ZnO nanoparticles to thermal treatment in a hot air oven at 90°C for 180 minutes; and
vii. obtaining the zinc oxide (ZnO) nanoparticles.
[0049] In still another embodiment, the dissolution of zinc nitrate and HMTA in distilled water is conducted separately prior to mixing.
[0050] In yet another embodiment, the magnetic stirring of the precursor and surfactant solutions is carried out for a continuous duration of 60 minutes.
[0051] In still another embodiment, the thermal treatment step is conducted in a hot air oven at a temperature of 90°C for a duration of 180 minutes.
[0052] In another embodiment, the present invention discloses a method for preparing a Zinc Oxide: Multi-Walled Carbon Nanotube nanoparticle mixture for screen printing, by mixing 20 grams of ZnO nanoparticles and with 340 drops of ethylene to form a paste;
wherein said mixture is applied the onto glass substrates using a screen-printing to apply the ZnO paste onto the glass substrates with one or/and two strokes, wherein, the paste is spread on the screen prior to screen printing and an empty stroke made to spread the paste on the screen,
wherein, the paste is further pressed onto the screen circles by a scalpel for the paste nanoparticles to penetrate the screen circle pores and then final screen printing is done; and
wherein this step provides enhanced quality of screen printing and well printed circles of the paste on glass.
[0053] In another embodiment, the method further comprises a process preparing a Zinc Oxide: Multi-Walled Carbon Nanotube nanoparticle mixture for screen printing with 0.1 grams of ZnO and 0.01 grams of MWCNT in 6 drops of Ethylene Glycol to obtain 10:1 ZnO to MWCNT ratio.
[0054] In yet another embodiment, the printed glass substrates are placed in a hot air oven at 80°C for 20 minutes to enhance adhesion of the ZnO nanoparticles to the glass substrates.
[0055] In still another embodiment, the ZnO paste forms a uniform circular layer on the glass substrates during the screen-printing process.
[0056] In another embodiment, the present invention discloses a method for synthesizing copper oxide (CuO) nanofluid, comprising:
i. preparing a sodium borohydride solution by dissolving 3.02 grams of sodium borohydrate in 50 ml of water.
ii. separately dissolving 7.4907 grams of copper sulfate (CuSO4) in 100 ml of water to form a CuSO4 solution.
iii. conducting a titration process by combining the sodium borohydride solution and the CuSO4 solution under controlled conditions involving magnetic stirring at 400 rpm and room temperature.
iv. washing the resulting CuO nanoparticles using a mixture of ethanol and distilled water in a 1:1 ratio (50 ml each).
v. filtering the washed CuO nanoparticles using Whatman filter paper.
vi. heating the filtered CuO nanoparticles in a hot air oven for a duration of 5 hours.
vii. aging the heated CuO nanoparticles for 24 hours.
viii. obtaining a yield of 1.57 grams of CuO nanoparticles for use in nanofluid synthesis.
[0057] In yet another embodiment, said method further comprising the preparation of CuO nanofluids by:
i. adding 0.1 grams of sodium lauryl sulfate (SLS) to 15 ml of ethylene glycol;
ii. incorporating 0.25 grams (1.5 wt%) of CuO nanoparticles into the ethylene glycol mixture;
iii. agitating the mixture using magnetic stirring for a duration of 30 minutes at 600 rpm to achieve the synthesis of CuO nanofluids.
[0058] In yet another embodiment, the washing step comprises using a mixture of ethanol and distilled water in a 1:1 ratio to remove impurities from the CuO nanoparticles.
[0059] In still another embodiment, the filtration step involves the use of Whatman filter paper to separate the CuO nanoparticles from the washing mixture.
[0060] In yet another embodiment, the heating step is performed in a hot air oven at a controlled temperature for a duration of 5 hours to promote the formation of CuO nanoparticles.
[0061] In still another embodiment, the aging step involves maintaining the heated CuO nanoparticles for 24 hours to enhance their stability and properties.
[0062] In yet another embodiment, the agitation step is performed using magnetic stirring at 600 rpm for 30 minutes for uniform dispersion of CuO nanoparticles in the nanofluid.
[0063] In still another embodiment, sodium lauryl sulfate (SLS) is used as a surfactant to stabilize the CuO nanoparticles in the ethylene glycol medium.
[0064] In yet another embodiment, the CuO nanofluids contain 1.5 wt% of CuO nanoparticles.
[0065] In another embodiment, the present invention discloses a method for preparing a ZnO (zinc oxide: multi-walled carbon nanotube) paste for printing, comprising:

i. adding additional quantity suitably of ZnO to an existing ZnO and MWCNT mixture to achieve a ZnO ratio of 40:1; wherein the amount of ZnO ranges from 0.1 gram to 0.2 grams and the amount of MWCNT in the paste ranges from 0.002 to 0.003 gram;
ii. incorporating 32 milliliters of ethylene glycol (E.G) into the mixture to adjust the viscosity;
iii. mixing the ZnO and ethylene glycol thoroughly to obtain a paste for screen printing.
[0066] In still another embodiment, the addition of ZnO to the existing mixture is performed to achieve a specific ZnO ratio of 40:1.
[0067] In yet another embodiment, the ethylene glycol (E.G) is used as a solvent; and wherein the ethylene glycol (E.G) is added in a quantity of 32 milliliters.
[0068] In another embodiment, the present invention discloses a method for screen printing using a ZnO (zinc oxide: multi-walled carbon nanotube) paste, comprising:
i. applying a 40:1 ZnO paste to a screen;
ii. spreading the paste across the screen to ensure an even distribution;
iii. printing a circular pattern of the ZnO paste onto a glass substrate using a single stroke;
iv. lifting the screen carefully to leave the printed pattern on the glass substrate.
v. subjecting the freshly printed ZnO paste to dry heating in a hot air oven to remove residual solvents and enhance adhesion.
[0069] In yet another embodiment, the present invention discloses the ZnO paste is in a ratio range of 40:1.
[0070] Accordingly, the present disclosure encompasses methods for synthesizing zinc oxide (ZnO) and copper oxide (CuO) nanoparticles and their application in various industrial processes. The synthesis of ZnO nanoparticles involves dissolving zinc nitrate and hexamethyl tetramine (HMTA) in water, followed by magnetic stirring, titration with ammonium hydroxide, filtration, washing, and thermal treatment to achieve controlled nanoparticle growth and crystallization. For screen printing applications, a ZnO nanoparticle mixture is prepared by mixing the nanoparticles with ethylene glycol to form a paste, which is then applied to glass substrates and heated to enhance adhesion and ensure uniform distribution.
[0071] The invention also describes a method for producing CuO nanofluids, which includes dissolving sodium borohydride and copper sulfate, conducting a titration process, washing, filtration, heating, and aging the resulting CuO nanoparticles, and then incorporating these nanoparticles into ethylene glycol with a surfactant to form a stable nanofluid. Additionally, a process for creating a ZnO paste involves mixing ZnO with ethylene glycol to achieve the appropriate consistency for screen printing.
[0072] The screen-printing method includes applying the ZnO paste onto substrates, ensuring even distribution, and then drying the printed pattern to ensure strong adhesion and uniformity. These methods aim to improve the production, preparation, and application processes of ZnO and CuO nanoparticles, ensuring high-quality, consistent, and scalable production for various technological and industrial applications.
[0073] 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 scope of the invention is determined by the claims that follow. 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 having ordinary skill in the art.
EXAMPLES
[0074] The present invention is further explained in the form of the 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.
Materials
[0075] Analytical-grade chemicals were utilized in this research. The synthesis of ZnO nanoparticles involved the use of Zinc Nitrate(Zn(NO3)2) sourced from Otto Chemie Pvt Ltd, Hexamine (C6H12N4) sourced from Nice Chemicals Pvt Ltd, and Ammonium hydroxide(NH4OH) which was sourced from Thomas Baker (Chemicals) Pvt Ltd.
Adhesion and synergistic tests involved the utilization of Ethylene glycol(C2H4O2) which was sourced from Nice Chemicals Pvt Ltd and for precise cutting operations, a sharp razor blade served as the cutting tool, complemented by a hard metal straight edge as the cutting guide. A wide semi-transparent pressure-sensitive tape with a pre- determined adhesion strength was employed. To ensure stability and accuracy lab- grade adhesion glass served as the substrate for ZnO nanoparticles during X-cut Adhesion tests and Large Area Screen Printing. The acquisition of a Large-area screen printing machine was from Techdyne Industries, Coimbatore.
Example 1: Preparation of ZnO Nanoparticles
[0076] ZnO nanoparticles were synthesized via the Co-Precipitation method, to achieve this 5mM Zinc Nitrate and 5mM of HMTA (Hexa Methyl Tetra Amine) were subjected to dissolution in 100 ml of distilled water each, the precursor and surfactant were subjected to magnetic stirring for 60 minutes, during which 0.5M NH4OH (ammonium hydroxide) was gradually added in a titration process. Filtration using Whatman filter paper was employed through water washing to separate the nanoparticles from the reaction mixture. The filtrated nanoparticles were then subjected to a carefully controlled thermal treatment process via a hot air oven at 90? C for 180 minutes (FIG. 14).
Example 2: Characterization
[0077] X-ray diffraction information of the ZnO in the 2? range 10?–80? was obtained using Bruker AXS D8 Advanced Powder X-ray diffractometer with Cu Ka (? = 1.5418 Å). The surface morphology of the samples underwent examination through scanning electron microscope (SEM) imaging using the Zeiss Ultra-55. This instrument is equipped with Gemini technology, incorporating a high-efficiency In-lens detector to achieve high- contrast topographic imaging. Additionally, it inherits features from the SUPRA 55, such as the angle-selective Backscattered Electron (EsB) detector. Image rendering and control operations were conducted using the SmartSEM software. Transmittance Infrared spectroscopy analysis was obtained via ALPHA FTIR with ZnSe ATR Module at 500-4000 cm-1 wavenumber, UV measurements were done via UV Spectroscopy LAMBDA-365, Hydraulic Pellet Press type KP was used to make ZnO pellets, Impedance and conductivity analysis was performed from WK-6520 B.
Example 3: POWDER X-RAY DIFFRACTION (PXRD)
[0078] Powder X-ray diffraction (PXRD) was performed to confirm the presence and determine the structure of ZnO nanoparticles. Samples were readied on zero- background SI plates, offering an unobstructed view, and set up following Bragg- Brentano geometry. Subsequently, analysis was conducted using a Bruker AXS D8 Advanced powder X-ray diffractometer, utilizing Cu Ka radiation (? = 1.5418 Å) (FIG. 1).
Intensity Peaks at different angles were obtained as represented in FIG. 1. Notably, Sharp Intensity peaks were observed at angles 31.742, 34.397, and 36.224 assigning to (100),(002), and (101) crystal planes which suggests the lattice of the synthesized ZnO nanoparticles are highly regular. The average crystalline size of the ZnO nanoparticles is estimated by the Debye Scherrer formula:
?? = ????/(??????????) ( 1)
[0079] In equation (1), D corresponds to the crystallite size (nm), ?? is the wavelength of the X-ray source (1.5418 Ao), is the full width at half the maximum diffraction peak (FWHM) in radians, K the Scherrer constant having a value of 0.9-1. The value of D obtained is about 28.38 nm. The diffraction peaks observed were in complete agreement with the Powder Diffraction File(PDF) no:01-090-7518, insinuating the crystal system of the material is hexagonal, with a space group of P63mc (186). The calculated density is 5.662 g/cm³, while the structural density is slightly higher at 5.6641 g/cm³. The molecular weight of the compound is 81.38 g/mol. It exhibits non- centrosymmetric properties, making it suitable for pyroelectric and piezoelectric applications, including second harmonic generation. Its Wyckoff sequence is denoted by b2.
Example 4: SCANNING ELECTRON MICROSCOPY(SEM) AND ELECTRON DISPERSIVE SPECTROSCOPY (EDS)
[0080] The SEM images are displayed in Fig 2(a),(b) at a magnification of 1,00,000x and 50,000x. The SEM images at different magnifications reveal highly agglomerated nanoparticles with lesser nanoflakes, ZnO nanoparticles typically have high surface energy, which drives them to minimize their total surface area by aggregating. The weaker Vander waal forces between the ZnO nanoparticles also cause the neighbouring nanoparticles to be attracted to each other leading to clustering. The coalesced nanoparticles have dimensions below 50 nm whereas nanoflakes have widths less than 10 nm. Further, the elemental distribution was confirmed by the EDS elemental mapping technique shown in FIG. 2(c). EDS captures the emission of X-rays at specific energies characteristic of elements present in a ZnO nanoparticles sample, thereby providing qualitative insights into the composition of synthesized ZnO nanoparticles, which exclusively consist of zinc (Zn) and oxygen (O) as represented in FIG. 2(d).
Example 5: FOURIER TRANSFORM INFRARED SPECTROSCOPY (FTIR)
[0081] FTIR (Fourier Transform Infrared Spectroscopy) is a valuable analytical technique employed to gather insights into the chemical bonding within ZnO nanoparticles. It serves as a tool for identifying the elemental composition and offers detailed information about the molecular structure and functional groups present in ZnO nanoparticles. FTIR analysis was analyzed in the range 500 cm-1 to 4000 cm-1 at room temperature, the distinctive peaks observed in the FTIR spectra of ZnO nanoparticles are depicted in FIG. 3. The observed peak at 614.94 cm-1 suggests the notion of Zn-O stretching vibrations, additionally, peaks between 1300 cm-1 and 1600 cm-1 are assigned to functional groups which represent symmetric and antisymmetric stretching mechanisms. Peaks between 2300 cm-1 and 2550 cm-1 are linked to C-H bands. Peaks associated with Zn-O stretching vibrations at 614.94 cm-1 indicate the crystalline nature and phase purity of ZnO nanoparticles.
Example 6: UV SPECTROSCOPY
[0082] The optical properties of ZnO nanoparticles were studied using UV-visible spectroscopy at room temperature. FIG. 4(a) represents the absorbance-based spectroscopy of ZnO nanoparticles subjected to analysis at the wavelength range of 250 nm to 1100 nm. ZnO is relatively absorbent in the UV region (250 nm to 340 nm) and a blue shift can be observed at the end of the UV region (340nm to 380nm). It is observed that the nanoparticle’s absorbance is non-existent in the visible region (400 nm to 1150 nm). FIG. 4(b) represents the transmittance-based spectroscopy of ZnO nanoparticles. It is observed that the transmittance is relatively non-existent in the UV region until 380 nm and a Redshift can be observed which denotes the photon transmitting ability of ZnO nanoparticles, which reaches a maximum of 235 arb. units.
[0083] This spike at 415nm also indicates that more light passes through the sample without being absorbed. As the Visible spectrum increases, the transmitting ability of ZnO nanoparticles relaxes. The plot between absorbance times energy square vs. Band gap represented in FIG. 4 (c), shows the synthesized ZnO nanoparticles have a band gap energy of approximately 3.17 eV. This value signifies the minimum energy required for an electron to transition from the valence band to the conduction band within the ZnO nanoparticles.
[0084] Example 7: PERMITTIVITY, PERMEABILITY, AND IMPEDANCE ANALYSIS: In FIG. 5(a), the relationship between the real part of the permittivity (e') and frequency is depicted, offering insights into the charge-storing capability of ZnO nanoparticles. The real part of permittivity quantifies the ability of these nanoparticles to store electrical energy when subjected to an electric field. At 5000 Hz, ZnO nanoparticles demonstrate a peak charge storing capability, reaching 12 F/m. However, as the frequency increases, this capacity gradually diminishes, with e' decreasing to
[0085] 4.58 F/m at 0.1 MHz. Subsequently, beyond 0.25 MHz and up to 0.5 MHz, e' remains within the range of 3.85 F/m, indicating a sustained but reduced charge-storing capacity at higher frequencies. The observed trend indicates that ZnO nanoparticles exhibit a higher charge-storing capacity at lower frequencies and a decrease in charge- storing capability with increasing frequency. This suggests that the nanoparticles may exhibit enhanced dielectric losses or reduced polarization effects at higher frequencies.
[0086] In FIG. 5(b), the relationship between the real part of the permeability (µ') and frequency is illustrated, providing insights into the magnetic response of ZnO nanoparticles and their ability to support magnetic flux. The real part of permeability quantifies the material's responsiveness to magnetic fields, reflecting its capacity to facilitate the passage of magnetic flux. The plotted data reveal that initially, µ' exhibits a low value, approximately 0.1 H/m, at a frequency of 25272 Hz. However, as the frequency increases, an upward trend is observed in the entire pattern of µ' versus frequency. At 0.1 MHz, µ' registers a notable increase to 0.159 H/m, followed by further increments as the frequency progresses: 0.1859 H/m at 0.2 MHz, 0.197 H/m at 0.3 MHz, 0.2081 H/m at 0.4 MHz, and 0.2086 H/m at 0.5 MHz. These observations highlight the frequency-dependent behaviour of ZnO nanoparticles in response to magnetic fields, demonstrating an increasing ability to support magnetic flux with higher frequencies. The plotted data represented in FIG. 5(c) reveal distinct points along the e' vs. e'' curve, each corresponding to specific values of e' and e''. Initially, when e' is 1.92 F/m, e'' is measured at 0.198 F/m. As e' increases to 4.849 F/m, there is a corresponding rise in e'' to 1.2657 F/m. Subsequently, at e' = 6.9098 F/m, e'' registers at 2.5566 F/m. Finally, at the highest recorded e' value of 18.884 F/m, e'' reaches it peak at 19.072 F/m. This highlights, the ZnO nanoparticles dielectric response to varying electrical properties.
[0087] In FIG. 5(d), the plotted data delineate distinct points along the curve representing the relationship between the real part (µ') and the imaginary part (µ'') of the permeability. Initially, when µ' is -1268.1 H/m, the corresponding µ'' value is measured at -521.20 H/m. As µ' decreases to -763.94 H/m, µ'' also diminishes to -357.52 H/m.
[0088] Subsequently, at µ' = -377 H/m, µ'' registers at -215.27 H/m. A similar trend is observed for other recorded values of µ'. For instance, at µ' = -21.619 H/m, µ'' reaches
[0089] -27.240 H/m, signifying a decrease in both µ' and µ'' values. Likewise, at µ' = -6.45 H/m, µ'' is recorded at -11.361 H/m, demonstrating a further decline in both real and imaginary parts of permeability. These observations highlight the dynamic relationship between µ' and µ'' and underscore the material's magnetic response to varying magnetic fields. In FIG. 5(e), the plotted data illustrate the relationship between the real part (Z') and the imaginary part (Z'') of the impedance of ZnO nanoparticles, At various impedance values, distinct points along the Z' vs. Z'' curve are observed. Initially, when Z' is 22900 Ohms, the corresponding Z'' value is measured at 5570 Ohms.
[0090] Subsequently, as Z' increases to 40800 Ohms, Z'' also rises to 11500 Ohms. This trend continues with further increases in Z', reaching 60100 Ohms with a corresponding Z'' value of 19000 Ohms, and 82000 Ohms with Z'' at 28300 Ohms. Finally, at the highest recorded Z' value of 94200 Ohms, Z'' registers at 33900 Ohms. The calculated slope for Z’ vs. Z’’ is 0.4189 which indicates for every unit increase in Z’, Z’’ increases 0.3 units, these observations highlight the electrical response of ZnO nanoparticles to varying electrical conditions.
?? = ??'/(2????) (2)
[0091] In equation (2), R is the resistance, Z' is the real part of the impedance, and f denotes the frequency of the alternating current. At 6.06*10^4 Hz, Z’ is 1.96*10^-3 Hz.
Therefore, Resistance(R) is 5.14*10^-3 Ohms.
?? = ????/?? = (4????2)/?? (3)
[0092] In equation (3), R is the resistance, A is the cross-sectional area of ZnO nanoparticles through which the current flows, l is the length of the ZnO nanoparticles, r is the average radius of the spherical ZnO nanoparticles and ? is the resistivity which was calculated to be 1.26 ????:
?? 33 = 2?? ??????.??0.????.???? (4)
[0093] The equation (4), relates piezoelectric co-efficient (d33) and permittivity of ZnO nanoparticles, where d33 is the piezoelectric coefficient. ?? ?????? is the effective charge generated, ?? 0 is the vacuum permittivity, ???? is the relative permittivity of the material, P is the applied pressure (force per unit area) and s is the thickness of the ZnO nanoparticles. The calculated piezoelectric coefficient is 40.565 pm/v.
[0094] Example 7: ADHESION TEST AND LARGE-AREA PRINTING Different proportions of ZnO nanoparticle paste were prepared by mixing ZnO nanoparticles with ethylene glycol in different ratios as represented in TABLE I.

TABLE I- X-CUT ADHESION TEST COMPARISON TABLE
Sl. No. ZnO in grams Ethylene Glycol in grams X-Cut Adhesion test Suitable standard
1 0.05 g 0.12 g
0A
2 0.05 g 0.1 g

3A
3 0.05 g 0.086 g
3A
4 0.05 g 0.064 g

2A
5 0.05 g 0.045 g

4A
6 0.05 g 0.06 g
1A
7 0.06 g 0.06 g
3A
8 0.07 g 0.06 g

4A

[0095] To achieve a homogeneous mixture, the prepared pastes were subjected to sonication for 30 minutes, ensuring consistent dispersion. Subsequently, the evenly mixed paste was applied onto adhesion standard glass substrates, forming a coating layer. To evaluate the adhesion quality of the coatings, an X-cut was carefully made through the film to expose the underlying glass substrate. A pressure-sensitive tape was then applied over the cut and subsequently removed, allowing for a qualitative assessment of adhesion on a scale ranging from 0A to 5A. The analysis of the adhesion test shows, that when 0.05 grams of ZnO is combined with 0.12 grams of ethylene glycol, the adhesion rating is recorded as 0A, signifying poor adhesion. Conversely, when the same amount of ZnO is mixed with 0.045 grams of ethylene glycol, the resulting adhesion rating improves to 4A, indicating excellent adhesion. Intermediate adhesion ratings are observed for other combinations of ZnO and ethylene glycol quantities. Notably, 0.05 grams of ZnO with 0.1 grams of ethylene glycol resulted in a consistent 3A rating across multiple trials, the significance of assessing adhesion lies in its important role in ensuring the functionality and longevity of ZnO nanoparticle coatings. This becomes important especially in applications such as large-area screen printing of ZnO nanoparticle paste. The X-cut adhesion tests were the benchmark for formulating ZnO nanoparticle paste intended for large-area printing. Compared to other deposition methods like sputtering or chemical vapour deposition, screen printing is more cost-effective and efficient in material usage, Screen printing for nanoparticles offers numerous advantages, particularly in precision and consistency, which are crucial for applications in voltage sensors. 15 grams of ZnO nanoparticles were combined with 13.5 grams of ethylene glycol and subjected to sonication for 1 hour to ensure thorough mixing, resulting in a paste with the required viscosity for large-scale printing specifications. The resulting ZnO nanoparticle paste was applied onto an adhesive standard glass substrate using a single-stroke large-area screen printing process. The precise control of screen printing parameters is essential for achieving optimal results with ZnO nanoparticle paste.
[0096] Squeegee speed determines the thickness and quality of the printed ZnO nanoparticle layer, while the angle of the squeegee influences the deposition of ZnO nanoparticle paste. Adjusting the snap-off distance, which is the gap between the screen and the glass substrate, is crucial for controlling the resolution and thickness of the printed ZnO nanoparticle layer. Additionally, maintaining proper screen tension ensures stability and uniformity during printing, facilitating consistent contact with the glass substrate and preventing printed nanoparticle deformation.
[0097] Following the printing process, the printed glass substrate was subjected to a hot air oven, where it was exposed to a temperature of 80°C for 20 minutes. This thermal treatment was conducted to facilitate the curing and stabilization of the printed ZnO nanoparticle pattern on the glass substrate. The successful adhesion of the printed ZnO nanoparticles highlights the efficacy of the formulated paste in adhering to the substrate surface. The printed ZnO nanoparticle pattern is visually depicted in FIG. 6, Under pressure, the ZnO nanoparticles form a closely packed deposition, resulting in a uniform arrangement with high packing density. This uniformity ensures a continuous and uniform conducting path throughout the printed layer, essential for reliable sensor performance. The high packing density and uniform deposition contribute to an increased fill factor, enhancing the sensor's sensitivity and response.
[0098] Additionally, the closely packed nanoparticle arrangement enhances the sensitivity of the sensor, allowing it to detect even subtle changes in voltage levels showcasing the successful implementation of the large-area printing technique for the deposition of ZnO nanoparticles onto the substrate.
[0099] Example 8: Screen Printing of 20:1 ZnO: MWCNT mixture: ZnO:MWCNT paste in ratio 20:1 , comprising 20 grams of ZnO:MWCNT nanoparticles mixed with 340 drops of ethylene glycol, exhibited a viscosity enhancing its suitability for the screen printing process (FIG. 7).
[00100] Subsequently, the screen printing operation was started as represented in FIG. 6 and 7. The optimal consistency of the ZnO:MWCNT in ratio of 20:1 paste facilitated seamless application onto the glass substrates (26cm/30cm -4mm thick), ensconcing them with a uniform circular layer of ZnO:MWCNT nanoparticles. Through the 2 strokes and single stroke of screen printing machinery as represented in FIG. 1c and FIG. 1d, The glass substrate printed with ZnO:MWCNT nanoparticles were placed into hot air oven for 20 minutes at 80 degrees for a better adhesion support as represented in FIG. 7.
[00101] Example 9: ADHESION TEST TABLE-1: The experimental investigation involved the formulation of composite solutions comprising Zinc Oxide (ZnO) and Multi-Walled Carbon Nanotubes (MWCNT) in various ratios, alongside Ethylene Glycol as a solvent. Each solution was characterized by the respective ratio of ZnO to MWCNT, as well as the quantity of Ethylene Glycol in drops, with a conversion factor of approximately 0.03 grams per drop. Upon formulation, the solutions underwent assessment through two key metrics: synergistic image analysis and x-cut adhesion testing. The results were then compared against established standards of adhesive performance.
[00102] For the 10:1 ZnO to MWCNT ratio, with 0.1 grams of ZnO and 0.01 grams of MWCNT in 6 drops of Ethylene Glycol, the x-cut adhesion test yielded a categorization of 3A, indicating favorable adhesion. Similarly, the 15:1 ratio exhibited comparable adhesive properties, achieving a 3A rating in the x-cut adhesion test, with 0.15 grams of ZnO,
[00103] 0.01 grams of MWCNT, and 6 drops of Ethylene Glycol. Furthermore, at a 20:1 ZnO to MWCNT ratio, with 0.2 grams of ZnO, 0.01 grams of MWCNT, and 6 drops of Ethylene Glycol, the composite material demonstrated enhanced adhesion, achieving a 4A rating in the x-cut adhesion test. These findings suggest that variations in the ratio of ZnO to MWCNT can influence the adhesive characteristics of the composite material, with the 20:1 ratio exhibiting superior adhesion compared to the 10:1 and 15:1 ratios.
Rati o ZnO in
gram s MWCN
T in
grams Ethelye ne Glycol in
drops (1drop s~0.03
grams) Synergistic image X-Cut
Adhesion test Suitable standard
10:1 0.1 g 0.01g 6 drops
4A
15:1 0.15
g 0.01g 6 drops
3A
20:1 0.2 g 0.01g 6 drops
4A

Adhesion Test Table 2:
Sl. No. Rati o ZnO in
gram s MWCN
T in
grams Ethelyen e Glycol in drops (1drops~ 0.03
grams) Synergistic image X-Cut
Adhesion test Suitable standard
1 10:1 0.1 g 0.01g 6 drops (HMTA in
6 drops of EG)
3A
2 10:1 0.1 g 0.01g 6 drops (HMTA in
1ml of water and 1ml of EG)

(No Match)
3 10:1 0.1 g 0.002g 6 drops (HMTA in
6 drops of EG)
0A
4 50:1 0.15g 0.003g 6 drops (HMTA in
1ml of water and 1ml of EG)

4A

Adhesion Test Table 3:
Sl. No. Ratio ZnO in MWC NT
in Ethelyene Glycol in drops
(1drops~0.03 X-Cut
Adhesion test Suitable standard
gram s gra ms grams)
1 50:1 0.003
g 0.15g 30 drops
0A
2 50:1 0.003
g 0.15g 30 drops
(Glass slide drenced for 15 minutes in solution and then dried)

1A
3 50:1 0.003
g 0.15g 30 drops
(Glass slide drenced in solution and heated when in the solution)
1A

[00104] The experimental protocol involves the preparation of a solution with a ratio of 50:1 of Multi-Walled Carbon Nanotubes (MWCNT) to Zinc Oxide (ZnO), denoted as MWCNT:ZnO, and subsequent application onto glass slides for various treatment conditions (FIG. 10). The first treatment (sl.no2 in adhesion test table-3) involves immersing the glass slide in the solution for 15 minutes followed by drying, while the second treatment (sl.no3 in adhesion test table-3) entails heating the glass slide within the solution. Upon completion of the treatments, an adhesion test, specifically the x-cut adhesion test, was conducted. The test results indicated two distinct categories: 0A and 1A, reflecting poor adhesion. This contrasts with previous findings where the adhesion test for the 50:1 ratio of ZnO: MWCNT exhibited favorable adhesive properties, characterized by categories 3A and 4A in the x-cut test(in adhesion test table-2). In FIG. 4,5 and 6, the experimental process is detailed. Firstly, the ZnO-Ethylene glycol mixture from the preceding screen-printing session is used (FIG. 11), ensuring consistency and continuity in the experiment. A precise quantity of 18.7 grams of ZnO paste is obtained after transferring it to a glass dish, providing a standardized starting point for subsequent procedures. Approximately 0.85 grams of multi-walled carbon nanotubes (MWCNT) are carefully measured and incorporated into the mixture, maintaining a consistent ratio throughout the experiment. The significance of the 20:1 ratio of ZnO to MWCNT is highlighted, emphasizing the deliberate formulation chosen for the study. The ZnO and MWCNT are thoroughly mixed in the glass dish, ensuring uniform distribution and effective integration of the components (FIG. 9).
[00105] Moving on to FIG. 5, the experimental procedure continues with a focus on the addition of Ethylene glycol. Ethylene glycol is added drop-wise using a Burette, facilitating precise control over the quantity and ensuring accurate incorporation into the mixture. The ZnO-MWCNT mixture is observed at specific intervals, with FIG. 5c depicting the composition after 180 drops of Ethylene glycol have been added (FIG. 12). This visual representation serves as document the gradual transformation of the mixture as the solvent is introduced. At 340 drops, the mixture achieves a paste-like consistency suitable for screen-printing, as illustrated in FIG. 5d.
Example 9: Scaled up Synthesis:
[00106] The scaled up synthesis of ZnO was done, the dissolution of zinc nitrate (Zn(NO3)2) and hexamethylenetetramine (HMTA) solutions was carried out separately. Approximately 42 grams of zinc nitrate were dissolved in 300 millilitres of distilled water, while 2 grams of HMTA were dissolved in 100 millilitres of distilled water. Slow stirring was employed during the dissolution process to ensure uniform mixing of the precursors. After dissolution, slow titration was performed using 0.5M ammonium hydroxide (NH4OH) solution in 300 millilitres of distilled water until reaching a pH of around 12. The titration process for slow mixing of Base with precursors was conducted under magnetic stirring ranging from 400 to 800 rpm to maintain homogeneity. Subsequently, filtration using Whatman paper was carried out to remove any insoluble impurities, and water wash was performed until reaching a pH of approximately 7 to ensure the removal of any residual chemicals. Finally, the filtered solution was subjected to heating and drying in a hot-air oven at 90 degrees Celsius for 3 hours to evaporate the solvent and obtain the desired solid product. This drying process helps to remove any remaining moisture content, ensuring the purity and stability of the final nanoparticles product for further analysis using screen printing technology (FIG. 13).
Example 10: Synthesis of CuO nanofluid
[00107] A solution of Sodium Borohydrate was prepared by dissolving 3.02 grams of the compound in 50 ml of water. Separately, 7.4907 grams of CuSo4 were measured, and the compound was dissolved in 100 ml of water. The titration process involved the use of Sodium Borohydrate solution and CuSo4 solution under controlled conditions: magnetic stirring at 400 rpm and room temperature. For washing, a mixture of ethanol and distilled water in a 1:1 ratio (50ml each) was employed, with filtration facilitated by Whatman paper. Subsequently, CuO nanoparticles underwent heating in a hot air oven for a duration of 5 hours, followed by aging for 24 hours. The resulting yield of CuO nanoparticles was determined to be 1.57g, which were then utilized for the synthesis of nanofluids (FIG. 15).
[00108] The preparation of nanofluids involved the addition of 0.1 grams of Sodium Lauryl Sulfate (SLS) to 15 ml of ethylene glycol, containing 1.5wt% of CuO nanoparticles (0.25g). This mixture underwent agitation using magnetic stirring for a duration of half an hour at 600 rpm. The successful synthesis of CuO nanofluids was achieved.
[00109] The process of preparing a ZnO: MWCNT (zinc oxide: multi-walled carbon nanotube) paste for printing involves several precise steps, each critical for ensuring the proper ratio and consistency of the mixture. Initially, an existing mixture of ZnO and MWCNT is modified by adding 18.5 grams of ZnO. This addition adjusts the ZnO: MWCNT ratio to 40:1.
[00110] To achieve the correct viscosity for printing, 32 milliliters of Ethylene Glycol (E.G) is incorporated into the mixture. E.G acts as a solvent that enhances the paste's flow characteristics, making it suitably viscous for the screen-printing process. Once mixed thoroughly, the paste attains the appropriate consistency and is ready for the next stage. The screen-printing process involves several steps. First, the prepared 40:1 ZnO:MWCNT paste is applied to a screen. The paste is then spread across the screen, ensuring an even distribution. After the 1 stroke print, the screen is carefully lifted, leaving the printed circular pattern of the ZnO:MWCNT paste on the glass.
[00111] Following the printing, the printed paste undergoes a drying process, as detailed in FIG. 3 and FIG. 8. Initially, the freshly printed 40:1 ZnO:MWCNT paste, applied using a single stroke is subjected to dry heating in a hot air oven . This heating step is essential for removing any residual solvents, such as ethylene glycol and for enhancing the adhesion of the paste to the glass substrate. Once the heating is complete, the appearance of the printed paste shows a more consolidated and uniform layer, indicating successful drying and curing.
[00112] The foregoing examples are merely illustrative and are not to be taken as limitations upon the scope of the invention. Various changes and modifications to the disclosed embodiments will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the scope of the invention.

ADVANTAGES OF THE PRESENT INVENTION
[00113] The present invention provides an efficient and reliable method for the synthesis and application of zinc oxide (ZnO) and copper oxide (CuO) nanoparticles for various industrial and technological uses.
[00114] The present invention establishes a reproducible method for synthesizing ZnO nanoparticles with precise control over their size and properties through dissolution, stirring, titration, filtration, washing, and thermal treatment processes.
[00115] The present invention provides a ZnO nanoparticle mixture with enhanced viscosity suitable for screen printing applications on glass substrates, ensuring uniform distribution and strong adhesion.
[00116] The present invention provides a method for producing CuO nanofluids with controlled particle size and stability by combining sodium borohydride and copper sulfate solutions, followed by washing, filtration, heating, and aging processes.
[00117] The present invention formulate a ZnO paste with the appropriate consistency and flow characteristics for screen printing applications by mixing ZnO with ethylene glycol.
[00118] The present invention provides a screen-printing process using ZnO paste to achieve uniform and well-adhered patterns on glass substrates, enhancing the performance and application potential of the printed layers.
[00119] The present invention provides an improved process of synthesis, preparation, and application of ZnO and CuO nanoparticles to ensure high-quality, consistent, and scalable production for use in nanotechnology, electronics, and other fields requiring precise nanoparticle application.

Claims:

1. A method for synthesizing zinc oxide (ZnO) nanoparticles, comprising the steps of:
i. dissolving 5mM of zinc nitrate and 5mM of hexamethyl tetramine (HMTA) in 100 ml of distilled water each to form a precursor solution and a surfactant solution respectively;
ii. subjecting the precursor solution and the surfactant solution to magnetic stirring for 60 minutes;
iii. gradually adding 0.5M ammonium hydroxide (NH4OH) to the stirred solution via a titration process;
iv. filtering the resulting mixture using Whatman filter paper to separate the ZnO nanoparticles from the reaction mixture;
v. washing the filtered ZnO nanoparticles with water to remove impurities;
vi. subjecting the washed ZnO nanoparticles to thermal treatment in a hot air oven at 90°C for 180 minutes; and
vii. obtaining the zinc oxide (ZnO) nanoparticles.
wherein said zinc oxide (ZnO) nanoparticles are uniform, nanosized and well connected for voltage sensor application)
2. The method as claimed in claim 1, wherein the dissolution of zinc nitrate and HMTA in distilled water is conducted separately prior to mixing.
3. The method as claimed in claim 1, wherein the magnetic stirring of the precursor and surfactant solutions is carried out for a continuous duration of 60 minutes.
4. The method as claimed in claim 1, wherein the thermal treatment step is conducted in a hot air oven at a temperature of 90°C for a duration of 180 minutes.
5. A method for preparing Zinc Oxide: Multi-Walled Carbon Nanotube nanoparticle mixture for screen printing, by mixing 20 grams of ZnO nanoparticles and with 340 drops of ethylene glycol (add the amount of multiwalled carbon nanotubes also) to form a paste;
wherein said mixture is applied the onto glass substrates using a screen-printing to apply the ZnO paste onto the glass substrates with one or/and two strokes, wherein, the paste is spread on the screen prior to screen printing and an empty stroke made to spread the paste on the screen,
wherein, the paste is further pressed onto the screen circles by a scalpel for the paste nanoparticles to penetrate the screen circle pores and then final screen printing is done; and
wherein this step provides enhanced quality of screen printing and well printed circles of the paste on glass.
6. A method as claimed in claim 6, said method further comprises a process preparing a Zinc Oxide: Multi-Walled Carbon Nanotube nanoparticle mixture for screen printing with 0.1 grams of ZnO and 0.01 grams of MWCNT in 6 drops of Ethylene Glycol to obtain 10:1 ZnO to MWCNT ratio.
7. The method as claimed in claim 5, wherein the printed glass substrates are placed in a hot air oven at 80°C for 20 minutes to enhance adhesion of the ZnO nanoparticles to the glass substrates.
8. The method as claimed in claim 5, wherein the ZnO paste forms a uniform circular layer on the glass substrates during the screen-printing process.
9. A method for synthesizing copper oxide (CuO) nanofluid, comprising:
i. preparing a sodium borohydride solution by dissolving 3.02 grams of sodium borohydrate in 50 ml of water.
ii. separately dissolving 7.4907 grams of copper sulfate (CuSO4) in 100 ml of water to form a CuSO4 solution.
iii. conducting a titration process by combining the sodium borohydride solution and the CuSO4 solution under controlled conditions involving magnetic stirring at 400 rpm and room temperature.
iv. washing the resulting CuO nanoparticles using a mixture of ethanol and distilled water in a 1:1 ratio (50 ml each).
v. filtering the washed CuO nanoparticles using Whatman filter paper.
vi. heating the filtered CuO nanoparticles in a hot air oven for a duration of 5 hours.
vii. aging the heated CuO nanoparticles for 24 hours.
viii. obtaining a yield of 1.57 grams of CuO nanoparticles for use in nanofluid synthesis.
10. The method as claimed in claim 8, further comprising the preparation of CuO nanofluids by:
i. adding 0.1 grams of sodium lauryl sulfate (SLS) to 15 ml of ethylene glycol;
ii. incorporating 0.25 grams (1.5 wt%) of CuO nanoparticles into the ethylene glycol mixture;
iii. agitating the mixture using magnetic stirring for a duration of 30 minutes at 600 rpm to achieve the synthesis of CuO nanofluids.
11. The method as claimed in claim 8, wherein the washing step comprises using a mixture of ethanol and distilled water in a 1:1 ratio to remove impurities from the CuO nanoparticles.
12. The method claimed in claim 8, wherein the filtration step involves the use of Whatman filter paper to separate the CuO nanoparticles from the washing mixture.
13. The method claimed in claim 8, wherein the heating step is performed in a hot air oven at a controlled temperature for a duration of 5 hours to promote the formation of CuO nanoparticles.
14. The method as claimed in claim 8, wherein the aging step involves maintaining the heated CuO nanoparticles for 24 hours to enhance their stability and properties.
15. The method as claimed in claim 9, wherein the agitation step is performed using magnetic stirring at 600 rpm for 30 minutes for uniform dispersion of CuO nanoparticles in the nanofluid.
16. The method as claimed in claim 9, wherein sodium lauryl sulfate (SLS) is used as a surfactant to stabilize the CuO nanoparticles in the ethylene glycol medium.
17. The method as claimed in claim, wherein the CuO nanofluids contain 1.5 wt% of CuO nanoparticles.
18. A method for preparing a ZnO (zinc oxide: multi-walled carbon nanotube) paste for printing, comprising:
i. adding additional quantity suitably of ZnO to an existing ZnO and MWCNT mixture to achieve a ZnO ratio of 40:1; wherein the amount of ZnO ranges from 0.1 gram to 0.2 grams and the amount of MWCNT in the paste ranges from 0.002 to 0.003 gram;
ii. incorporating 32 milliliters of ethylene glycol (E.G) into the mixture to adjust the viscosity;
iii. mixing the ZnO and ethylene glycol thoroughly to obtain a paste for screen printing.
19. The method as claimed in claim 17, wherein the addition of ZnO to the existing mixture is performed to achieve a specific ZnO ratio of 40:1.
20. The method as claimed in claim 17, wherein the ethylene glycol (E.G) is used as a solvent; and wherein the ethylene glycol (E.G) is added in a quantity of 32 milliliters.
21. A method for screen printing using a ZnO (zinc oxide: multi-walled carbon nanotube) paste, comprising:
i. applying a 40:1 ZnO paste to a screen;
ii. spreading the paste across the screen to ensure an even distribution;
iii. printing a circular pattern of the ZnO paste onto a glass substrate using a single stroke;
iv. lifting the screen carefully to leave the printed pattern on the glass substrate.
v. subjecting the freshly printed ZnO paste to dry heating in a hot air oven to remove residual solvents and enhance adhesion.
22. The method as claimed in claim 20, wherein the ZnO paste is in a ratio range of 40:1.