Description:FIELD OF INVENTION
[001] The present disclosure belongs to the technical field of electroanalytical chemistry. More particularly, the present disclosure relates to a Fe2O3/NiO/CuO composite and method of preparation thereof. Further, the present disclosure also relates to a Fe2O3/NiO/CuO composite modified glassy carbon electrode (GCE) and method of fabrication thereof.

BACKGROUND OF THE INVENTION
[002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[003] Phenolic compounds constitute a broad category of chemical substances that serve as secondary products across several industries. Catechol (CC), or 1,2-dihydroxybenzene, is a significant positional isomer of phenolic substituents. They are found in aquatic ecosystems due to their widespread use in cosmetics, agricultural fertilizers, flavouring compounds, medicines, secondary dyes, antioxidants, and photography chemicals [Tashkhourian et al., J. Hazard Mater., 2016, 318, 117–124]. Catechol, also known as pyrocatechol, is a naturally occurring polyphenolic compound utilized in various industrial and therapeutic uses. Flora, vegetables, fruits, and tobacco possess a substantial amount of CC. It is significant because of its diverse qualities, including antioxidative, antiviral effects, stimulatory effects, and impact on the activities of numerous enzymes [Manjunatha et al., Chem. Data Coll., 2020, 25, 100331]. Nonetheless, even in minimal quantities, CC provide a threat to biological and ecological systems and can adversely affect humans, flora, and fauna [Huang et al., Sens. Actuators B: Chem., 2020, 320, 128386]. CC is a deleterious toxin that impacts the human central nervous system, induces chromosomal alterations, and is generated during the degradation of aromatic pollutants [Kumar et al., Mater. Sci. Eng. C., 2019, 98, 746–752]. Being exposed to CC may result in many health complications, such as migraines, fatigue, liver and neurological diseases, and cancer [Mater. Chem. Phys., 2022, 281, 125860]. The US Environmental Protection Agency and the European Union designate them as environmental pollutants due to their high toxicity and poor biodegradability in the natural environment. Phenolic compounds experience gradual degradation, leading to the production of harmful chemicals that give rise to environmental pollution. Moreover, with the growing interest in environmental quality, there is a necessity for various swift and efficient detection methods that comply with the relevant environmental protection criteria. This underscores the necessity to establish precise testing protocols for CC [Yang et al., Nanoscale 11 (18) (2019) 8950–8958]. Therefore, the discerning and accurate judgment of the CC is necessary.
[004] Several methods documented for the quantification of Catechol, counting spectrophotometry, high-performance liquid chromatography, and enzymatic sensors [Lee et al., J. Chromatogr. B Biomed. Appl., 1993, 619(2) 259–266; Tembe et al., J. Biotech., 2007, 128 (1), 80–85]. Electrochemical sensor’s wide range of potential window, ease of production, compatibility with materials, strong durability, affordability, and flexibility to be reused with different types materials, has been commonly utilized since the previous century in the field of customized sensors [Shashikumara et al., Sci Rep., 2021, 1-11]. Regrettably, the standard bare electrodes are unsuitable for detecting CC due to their inadequate electrochemical response during the electrochemical detection process. Hence, the utilization of appropriate multi-functional nanomaterials is imperative in order to enhance electron transfer rates by modifying bare electrodes.
[005] In the past ten years, a variety of nanocomposites constituting metal oxides, including one-dimensional, two-dimensional and three-dimensional structures, have demonstrated exceptional electrochemical characteristics [Maduraiveeran et al., Mater. Sci. Eng. B, 2021, 272, 115341]. The utilization of metal oxide materials and their composites has become more common due to the inadequate techniques for improving the performance of single-metal oxides [Biosens. Bioelectron., 2018, 103, 113–129]. Due to their robust electrocatalytic activity, affordable cost, excellent organic capturing ability, small size, and highly crystalline behaviour, metal oxide composites are widely used and recognized as an effective electrocatalyst for detecting numerous emerging targets. The electrocatalytic characteristics of oxide constituents are often influenced by factors such as active regions, electrochemical active surface area, and surface energy. In order to achieve optimal sensing capabilities of oxide nanocomposites, the materials have synthesised in the smallest possible size to upsurge the number of active regions and accessible surface area. Metal oxide composites exhibit cognitive properties that confer architectural and crystallographic flexibility, rendering them appropriate for diverse electrochemical sensing applications [Kannan et al., Biosensors, 2023, 13 (5), 542]. Notwithstanding their numerous advantages, nanoparticles frequently demonstrate diminished endurance due to their high surface energy and are prone to aggregation into larger particles, which may lead to a reduction in specific surface area. The primary method entails stabilizing the nanocomposites through the use of capping agents, surfactants, polymers, and ligands. A different approach for synthesizing well-defined compound oxides is the utilization of a template-free hydrothermal technique [Ganesamurthi et al., Colloid Surf A Physicochemical and Engineering Aspects, 2022, 647, 129077]. Iron oxide (Fe2O3) is a transition metal oxide (TMO) that is highly appealing for sensing applications compared to other metal oxide materials. This is because it possesses excellent qualities such as easy synthesis procedures chemical resistance, high sensitivity, non-toxicity, and plentiful natural sources [Jia et al., Sens. Actuators B Chem., 2019, 300, 127012]. Nevertheless, bare Fe2O3 has numerous challenges, including an elevated electron-hole recombination rate and a propensity to agglomerate, resulting in suboptimal performance in diverse applications [Deshmukh et al., J. Electroanal. Chem., 2017, 788, 91–98]. Copper oxide (CuO) is a non-toxic compound that exhibits unique optical and structural properties and can be synthesised at a low cost [Hammadi et al., Sci. Rep., 2023, 13 (1), 12927]. Nickel oxide (NiO) is a transition metal oxide (TMO) that demonstrates antiferromagnetic properties, a high N´eel temperature, exceptional catalytic performance, robust conductivity, significant chemical reactivity, and enhanced dynamic dispersion relative to other noble metals. The mixed transition metal oxides (MTMOs) are crucial for increasing the electrochemical response of as synthesised product in comparison with individual transition metal oxides [Iftikhar et al., Tren. Environ. Anal. Chem., 2021, 31, e00138]. Research highlights that hydrothermal synthesis procedure can influence the nature of the material causing impact in the electrochemical output [Wang et al., Ceram. Int., 2024, 50 (22), 47485–47493].

OBJECTS OF THE INVENTION
[006] An objective of the present disclosure is to provide a Fe2O3/NiO/CuO composite.
[007] Another objective of the present disclosure is to provide a method of preparation of Fe2O3/NiO/CuO composite.
[008] Another objective of the present disclosure is to provide a Fe2O3/NiO/CuO composite modified glassy carbon electrode (GCE).
[009] Still another objective of the present disclosure is to provide a method of fabrication of a Fe2O3/NiO/CuO composite modified glassy carbon electrode (GCE).
[0010] Yet another objective of the present disclosure is to provide Fe2O3/NiO/CuO composite modified electrode for the electrochemical sensing of catechol.

SUMMARY
[0011] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in Detailed Description section. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
[0012] Accordingly, in one aspect, the present disclosure relates to a Fe2O3/NiO/CuO composite composed of Fe2O3, NiO and CuO, wherein Fe2O3, NiO and CuO has a ratio ranging from (0.1-1): (0.5-1.5) : (2.5-3.5).
[0013] Another aspect of the present disclosure relates to a method of preparation of Fe2O3/NiO/CuO composite comprising: a) mixing a ferric salt precursor, a nickel salt precursor and a copper salt precursor in a first solvent with stirring to obtain a mixture; b) heating the mixture in a teflon container inside autoclave to obtain a mixed metal oxide material; c) washing the mixed metal oxide material with a second solvent followed by drying to obtain a dried mixed metal oxide material; and d) processing the dried mixed metal oxide material by calcination to obtain a Fe2O3/NiO/CuO composite, wherein Fe2O3, NiO and CuO has a ratio ranging from (0.1-1): (0.5-1.5) : (2.5-3.5).
[0014] Still another aspect of the present disclosure relates to a Fe2O3/NiO/CuO composite modified glassy carbon electrode (GCE) comprising: a GCE modified with Fe2O3/NiO/CuO composite as defined above, wherein, the Fe2O3/NiO/CuO composite is loaded to the GCE surface in the range of 3 to 5 %.
[0015] Yet another aspect of the present disclosure relates to a method of fabrication of a Fe2O3/NiO/CuO composite modified glassy carbon electrode (GCE) comprising: i) treating the surface of GCE with a polishing agent to obtain a polished GCE surface; ii) adding 3 to 5 % w/v of Fe2O3/NiO/CuO composite as defined above in a solvent to obtain a suspension; and iii) loading the suspension to the polished GCE surface followed by drying to obtain a Fe2O3/NiO/CuO composite modified glassy carbon electrode.
[0016] Various objects, features, aspects and advantages of the present disclosure will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing FIG.s in which like numerals represent like features.

BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The accompanying drawing(s) are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure. The diagrams are for illustration only, which thus is not a limitation of the present disclosure.
[0018] FIG. 1 illustrates synthesis procedure of Fe2O3/NiO/CuO.
[0019] FIG. 2 illustrates XRD pattern of Fe2O3/NiO/CuO.
[0020] FIG. 3 illustrates FT-IR spectra of CuO, CuO/NiO and Fe2O3/NiO/CuO.
[0021] FIG. 4 illustrates (a) Wide XPS spectra of Fe2O3/NiO/CuO (b) high resolution XPS spectra of Cu 2p (c) high resolution XPS spectra of Ni 2p (d) high resolution XPS spectra of Fe 2p (e) high resolution XPS spectra of O1s (f) high resolution XPS spectra of C1s.
[0022] FIG. 5 illustrates (a) TGA curve of Fe2O3/NiO/CuO (b) BET adsorption-desorption isotherm of Fe2O3/NiO/CuO, inset figure showing pore size distribution.
[0023] FIG. 6 illustrates FESEM images of Fe2O3/NiO/CuO.
[0024] FIG. 7 illustrates Elemental analysis spectra of Fe2O3/NiO/CuO.
[0025] FIG. 8 illustrates TEM images of Fe2O3/NiO/CuO.
[0026] FIG. 9 illustrates (a) Voltammogram of bare GCE, CuO/GCE, CuO/NiO/GCE and Fe2O3/NiO/CuO/GCE in 5 mM [Fe(CN)6]3-/4- and 0.1 M KCl (b) Nyquist plot of bare GCE and Fe2O3/NiO/CuO/GCE in 0.1 M KCl comprising 5 mM K3[Fe(CN)6] the inset shows high frequency region.
[0027] FIG. 10 illustrates Electrochemical response of bare GCE, CuO/GCE, CuO/NiO/GCE and Fe2O3/NiO/CuO/GCE in the presence of 100.0 μM.
[0028] FIG. 11 illustrates Linear plot of pH against potential and plot of pH vs anodic current.
[0029] FIG. 12 illustrates (a) CV of Fe2O3/NiO/CuO/GCE at scan rates from 10 to 180 mV/s in 0.1 M PBS 7 (b) linear plot between scan rate and response current (c) linear plot between square root of scan rate and response current (d) linear plot between log scan rate and log current.
[0030] FIG. 13 illustrates (a) DPV response Fe2O3/NiO/CuO/GCE towards catechol in the concentration range of 0.8 μM–8296.0 μM (b) calibration plot between peak current and concentration of CC.
[0031] FIG. 14 illustrates anti-interference study of sensor.

DETAILED DESCRIPTION OF THE INVENTION
[0032] The following is a detailed description of embodiments of the disclosure. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0033] 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.
[0034] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
[0035] In some embodiments, numbers have been used for quantifying weights, percentages, ratios, and so forth, to describe and claim certain embodiments of the invention and are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable.
[0036] The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
[0037] Unless the context requires otherwise, throughout the specification which follows, the word “comprise” and variations thereof, such as “comprises” and “comprising” are to be construed in an open, inclusive sense that is as “including, but not limited to.”
[0038] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0039] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. Furthermore, the ranges defined throughout the specification include the end values as well, i.e., a range of 1 to 10 implies that both 1 and 10 are included in the range. For the avoidance of doubt, the applicant shall be entitled to any equivalents according to applicable law.
[0040] All methods described herein can be performed in a suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples or exemplary language (e.g., “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[0041] 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.
[0042] The description that follows, and the embodiments described therein, is provided by way of illustration of an example, or examples, of particular embodiments of the principles and aspects of the present disclosure. These examples are provided for the purposes of explanation, and not of limitation, of those principles and of the disclosure.
[0043] It should also be appreciated that the present disclosure can be implemented in numerous ways, including as a system, a method or a device. In this specification, these implementations, or any other form that the invention may take, may be referred to as processes. In general, the order of the steps of the disclosed processes may be altered within the scope of the invention.
[0044] The headings and abstract of the invention provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.
[0045] The following discussion provides many example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus, if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed.
[0046] The term “or”, as used herein, is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
[0047] The terms “weight percent,” “wt-%,” “percent by weight,” “% by weight,” and variations thereof, as used herein, refer to the concentration of a substance as the weight of that substance divided by the total weight of the composition and multiplied by 100. It is understood that, as used here, “percent,” “%,” and the like are intended to be synonymous with “weight percent,” “wt-%,” etc.
[0048] Various terms are used herein to the extent a term used is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.
[0049] The present disclosure is based on a trimetallic oxide compound which is synthesised through facile hydrothermal method and employed to alter the surface of glassy carbon electrode (GCE) which serves as the working electrode for the detection of CC in aquatic samples. The novel trio composite constituting Fe2O3/NiO/CuO is synthesised by hydrothermal method consuming minimum amount of aqueous solution followed by calcination in air. The composites comprise a combination of two or more oxides, with their properties dictated by the concentration of each constituent oxide in the mixture. The tri-phase material is eco-friendly, simple, economical, and efficient, necessitating no specialist equipment. The elements of Fe2O3/NiO/CuO are quantified in a ratio ranging from (0.1-1):(0.5-1.5):(2.5-3.5), respectively. This is the debut incorporation of the synergy of these metal oxides in the formation of a working electrode. The metal oxide composite is utilized to adorn the working electrode and utilized for the quantification of CC for the first time. The sensor exhibited excellent electrochemical properties including outstanding linear range, limit of detection (LOD), selectivity, repeatability and reproducibility towards the analyte of interest.
[0050] An embodiment of the present disclosure is to provide a Fe2O3/NiO/CuO composite composed of Fe2O3, NiO and CuO, wherein Fe2O3, NiO and CuO has a ratio ranging from (0.1-1): (0.5-1.5) : (2.5-3.5).
[0051] In an embodiment, Fe2O3, NiO and CuO has a ratio of 0.5:1:3.
[0052] In some embodiment, the composite has an X-ray diffraction pattern comprising peaks at 2θ = 33.21°, 49.1° and 62.64° for Fe2O3, 32.5°, 35.4°, 38.78°, 39.79°, 48.9°, 53.4°, 58.4°, 66.2° and 68.2° for CuO and 37.2°, 43.2° and 62.8° for NiO.
[0053] Another embodiment of the present disclosure is to provide a method of preparation of Fe2O3/NiO/CuO composite comprising: a) mixing a ferric salt precursor, a nickel salt precursor and a copper salt precursor in a first solvent with stirring to obtain a mixture; b) heating the mixture in a teflon container inside autoclave to obtain a mixed metal oxide material; c) washing the mixed metal oxide material with a second solvent followed by drying to obtain a dried mixed metal oxide material; and d) processing the dried mixed metal oxide material by calcination to obtain a Fe2O3/NiO/CuO composite, wherein Fe2O3, NiO and CuO has a ratio ranging from (0.1-1): (0.5-1.5) : (2.5-3.5).
[0054] In some embodiment, the first solvent in step a) and the second solvent in step c) are selected from a group comprising of water, ethanol, DMF and combination thereof. Preferably, the first solvent and the second solvent is water. In an embodiment, the first solvent and the second solvent is same.
[0055] In some embodiment, the ferric salt precursor is selected from a group comprising of ferric chloride hexahydrate, Ferric nitrate and ferric sulfate and combination thereof and has an amount ranging from 35 to 37 %. Preferably, the ferric salt precursor is ferric chloride hexahydrate and has an amount of 36.86%.
[0056] In some embodiment, the nickel salt precursor is selected from a group comprising of nickel nitrate hexahydrate, nickel acetate and combination thereof and has an amount ranging from 25 to 27 %. Preferably, the nickel salt precursor is nickel nitrate hexahydrate and has an amount of 26.7%.
[0057] In some embodiment, the copper salt precursor is selected from a group comprising of copper sulfate pentahydrate, copper nitrate and copper acetate and combination thereof and has an amount ranging from 25 to 28 %. Preferably, the copper salt precursor is copper sulfate pentahydrate and has an amount of 27.2%.
[0058] In some embodiment, the stirring in step a) is carried out at a speed ranging from 200 to 300 RPM for a time period ranging from 10 min to 60 min. Preferably, the stirring in step a) is carried out at a speed of 250 RPM for a time period of 30 min.
[0059] In some embodiment, the heating in step b) is carried out at a temperature ranging from 150 to 200 °C for time period ranging from 30 h to 40 h. Preferably, the heating in step b) is carried out at a temperature of 165 °C for time period of 36 h.
[0060] In some embodiment, the drying in step c) is carried out at a temperature ranging from 50 to 80 °C for time period ranging from 8 h to 12 h. Preferably, the drying in step c) is carried out at a temperature of 60 °C for time period of 12 h.
[0061] In some embodiment, the calcination in step d) is carried out at a temperature ranging from 500 to 600 °C for time period ranging from 1 h to 5 h. Preferably, the calcination in step d) is carried out at a temperature of 550 °C for time period of 3 h.
[0062] Still another embodiment of the present disclosure is to provide a Fe2O3/NiO/CuO composite modified glassy carbon electrode (GCE) comprising: a GCE modified with Fe2O3/NiO/CuO composite as defined above, wherein, the Fe2O3/NiO/CuO composite is loaded to the GCE surface in the range of 3 to 5 %.
[0063] Yet another embodiment of the present disclosure is to provide a method of fabrication of a Fe2O3/NiO/CuO composite modified glassy carbon electrode (GCE) comprising: i) treating the surface of GCE with a polishing agent to obtain a polished GCE surface; ii) adding 3 to 5 % w/v of Fe2O3/NiO/CuO composite as defined above in a solvent to obtain a suspension; and iii) loading the suspension to the polished GCE surface followed by drying to obtain a Fe2O3/NiO/CuO composite modified glassy carbon electrode.
[0064] In some embodiment, the polishing agent is alumina.
[0065] In some embodiment, the solvent is selected from a group comprising of water, ethanol, DMF combination thereof. Preferably, the solvent is water.
[0066] In some embodiment, the drying in step iii) is carried out at a temperature ranging from 15 to 35 °C. Preferably, the drying in step iii) is carried out at a temperature of 25 °C.
[0067] The precursors used for the synthesis are Ferric chloride hexahydrate (FeCl3.6H2O, 97 % extra pure), Copper (II) sulfate pentahydrate (CuSO4.5H2O, EMPLURA, ≥98 %), Nickel (II) nitrate hexahydrate, (Ni(NO3)2.6H2O, Avra, 98 %). The catechol, 99 % is purchased from SRL. The phosphate buffer acts in the role of supporting electrolyte here and it is made of disodium hydrogen phosphate anhydrous (Na2HPO4, ≥98%, LOBA Chemie) and sodium dihydrogen phosphate dehydrate (NaH2PO4.2H2O, 98–100.5 %, Merck). Meanwhile ferricyanide solution is prepared by 5 mM K3[Fe(CN)]6 (Merck) and 0.1 M KCl (Merck). The preparations of aqueous solutions were conducted using Mili Q water (18.2 MΩ).
[0068] While the foregoing describes various embodiments of the disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person skilled in the art.
EXAMPLES
[0069] The present invention is further explained in the form of following examples. However, it is to be understood that the following examples are merely illustrative and are not to be taken as limitations upon the scope of the invention.
Example 1:
(A) Synthesis of Fe2O3/NiO/CuO composite
[0070] The synthesis of Fe2O3/NiO/CuO was conducted through hydrothermal method followed by calcination in air. For the hydrothermal synthesis, pre-fixed amount of ferric chloride hexahydrate, nickel nitrate hexahydrate, copper sulfate pentahydrate were added in to 10 ml deionized water. After stirring for 30 min, the mixture solution was transferred to Teflon container inside autoclave and kept in the oven at 165 °C for 36 h. Upon cooling to ambient conditions, the material was cleaned four times with deionised water and afterwards placed in an oven to dry at 60 °C overnight (about 12 h). Subsequently, the synthesised material underwent annealing at 550 °C for 3 h. The Fe2O3/NiO/CuO composite in the different constituent ratio are synthesised following the same method with required precursor amount as mentioned in Table 1 below. Figure 1 summarizes the synthesis procedure adopted. The individual oxides were synthesized with required precursors following the same protocol.

Table 1: Amount of precursors used for the preparation of composite.
Composite ferric chloride hexahydrate nickel nitrate hexahydrate copper sulfate pentahydrate
Fe2O3/NiO/CuO = 0.5:1:3 36.86 % 26.7 % 27.2 %
CuO/NiO - 26.7 % 27.2 %
CuO - - 27.2 %

(B) Fabrication of Fe2O3/NiO/CuO modified working electrode
[0071] For the fabrication of sensor, GCE surface was polished neatly with alumina powder of sizes 0.05 micron, 0.3 micron and 1.0 micron using electrode polishing kit and allowed to dry in atmospheric temperature (about 25 °C). Meantime the homogenous suspension containing 5.0 mg Fe2O3/NiO/CuO in 150.0 μl deionised water is prepared. From this about 5.0 μl was loaded on the clean GCE surface and permitted to dry in the atmospheric temperature (about 25 °C). Similarly, the dispersion of CuO and CuO/NiO were also prepared by taking 5.0 mg of respective material in 150.0 μl deionized water. From this, 5.0 μl loaded on the electrode surface for electrochemical investigations correspondingly. Different Fe2O3/NiO/CuO modified working electrode are shown in Table 2 below.
[0072] Table 2: Different Fe2O3/NiO/CuO modified working electrode
Working electrode Amount of Fe2O3/NiO/CuO loaded
Fe2O3/NiO/CuO/GCE 5 %
Bare GCE -
CuO/GCE 5 %
CuO/NiO/GCE 5 %

(C) Characterization of Fe2O3/NiO/CuO composite
[0073] The structural properties of Fe2O3/NiO/CuO obtained through powder XRD analysis and the reflection planes were well identified. Fig. 2 displays the XRD pattern of novel composite. For the composite, peaks appeared at 33.21°, 49.1° and 62.64° corresponds to (104), (024) and (214) planes of Fe2O3 (JCPDS: 00-033-664). Whereas the peaks originated at 32.5°, 35.4°, 38.78°, 39.79°, 48.9°, 53.4°, 58.4°, 66.2° and 68.2° are corresponding to (110), (002), (200), (111), (-202), (020), (202), (311) and (222) planes of CuO (JCPDS: 80–1268). The diffraction peaks appeared at 37.2°, 43.2° and 62.8° represents the (111), (200) and (220) planes of cubic NiO (JCPDS:78–0643). Thereby the co-existence of Fe2O3, CuO and NiO are confirmed with the XRD analysis.
[0074] The average particle size (D) of synthesised Fe2O3/NiO/CuO are determined applying Debye-Scherer equation (1),

Where k embodies the shape factor (0.9), λ is the CuKα wavelength (0.15418 nm), β is the FWHM in radians and Ө is the angle at which diffraction befalls congruently. The particle size obtained as 120.0 nm.
[0075] The IR spectra of CuO, CuO/NiO and Fe2O3/NiO/CuO were displayed in Fig. 3. The peaks appeared at 510 cm-1, 615 cm-1 and 1373 cm-1 were characteristic to CuO. The peaks at 510 cm-1 and 615 cm-1 represents CuO nanostructure formation and Cu-O stretching. The peak at 1373 cm-1 corresponds to Cu-OH. Whereas the peak at 1622 cm-1 represents -OH. For CuO/NiO, the peak appeared at 497 cm-1 is characteristically attributed to NiO in CuO/NiO composite and the peak at 1100 cm-1 corresponds to Ni-O-Ni. Meanwhile in the case of Fe2O3/NiO/CuO, the peak originated at 555 cm-1 corresponds to Fe-O vibrations of Fe2O3. The broad band appeared at 3343 cm-1 represents O-H stretching in all the cases. The XPS analysis has been carried out to evaluate the valence states of metals in this mixed transition metal oxide composite. The wide XPS spectra shown in Fig. 4 (a) further validated the presence of Cu 2p, Ni 2p and Fe 2p in the as synthesised unique composite. The high -resolution spectra of Cu 2p shown in Fig. 4(b) revealed two peaks at 934.2 eV and 954.2 eV corresponding to Cu 2p3/2 and Cu 2p1/2 along with two other peaks at about 943.8 eV and 963.7 eV which are called satellite peaks. This confirms the presence of Cu2+ in the CuO of novel composite developed here. The high resolution XPS spectra of Ni 2p given in Fig. 4(c) illustrates two peaks originated at 855.4 eV and 872.5 eV matching to Ni 2p3/2 and Ni 2p½ peaks besides two additional peaks occurred at 861.2 eV and 879.8 eV are characterized as the satellite peaks. The characteristic peaks are attributed to Ni2+. The high resolution XPS spectra of Fe 2p in Fig. 4(d) shows the occurrence two edges at 710.1 eV and 724.4 eV attributed to Fe 2p3/2 and Fe 2p1/2 respectively which indicate that the Fe exist as Fe3+ in here. Additionally, two satellite peaks are also identified at 718.4 eV and 724.3 eV correspondingly. It is recorded that spin splitting of electrons in the 2p orbital are responsible for establishing Fe in the Fe3+. The O1s high resolution spectra portrayed in Fig. 4(e) validate the presence of surface hydroxyls corresponding to peak appeared at 531.3 eV. The fitting peak in the high-resolution spectra of C1s at 284.3 eV in Fig. 4(f) is attributed to C-C bond.
[0076] The thermal rigidness of mesoporous Fe2O3/NiO/CuO composite is examined by thermogravimetric analysis (TGA) as given in Fig. 5(a). The weight loss happening at the first stage (92.9–243.9 °C) and second stage (243.9–342 °C) is about 1.5 % and 2.66 % respectively is attributed to the elimination of physically linked and chemically bonded water molecules. The composite degradation taking place at around 438.7 °C–480.2 °C and beyond that probably linked to the breakdown of remaining sulphates from the precursor. It was also seen that emergence of defects in NiO also correlates with weight loss at temperatures over 600 °C. The char yield of the composite is 76 % proving that composite material has fair thermal stability. The surface area of the material is examined by Brunauer-Emmet-Teller (BET) method and the isotherm recorded is exhibited in Fig. 5 (b). It is observed that nature of adsorption-desorption isotherm is closely related to type 2 isotherm type and that gave indications about the mesoporous nature of novel Fe2O3/NiO/CuO composite. Annealing is thought to confer a mesoporous texture to the material, characterized by pore diameters ranging from 2 to 50 nm. Such mesoporosity markedly affects electrochemical results in several manners like increasing surface area, improving ion transport and enhancing structural stability. The surface area is attained as 49.941 m2/g. The average pore radius is also obtained as 5.23 nm by Barrett-Joyner-Halenda (BJH) method and which indicates that material is mesoporous in texture. The pore size distribution is given inset of Fig. 5 (b).
[0077] The morphological characteristics of the synthesised material are studied using Field Emission Scanning Electron Microscopy (FESEM). The acquired images are presented in Fig. 6 at several levels of magnification. The images suggest that the material has an exposed nonspecific facet structure, which is irregularly agglomerated. The edges of certain particles exhibit sharpness, but other particles, not in the form of facets, are also evident in scattered forms in the images. The presence of pores between structures enables efficient electron transport, leading to an increase in peak current. The development of facets is heavily dependent on various parameters such as the pH of the medium, the reaction temperature, and the pressure within the vessel.
[0078] The EDS elemental analysis performed to evaluate presence of each element and confirmed their existence separately. The EDS spectra given in Fig. 7 corroborates the findings. The atomic wt% of each element are in the appropriate proportions and are maintaining the ratio between each constituent in the novel composite.
[0079] Fig. 8(a) and (b) (c) and (d) shows the HR-TEM images obtained for Fe2O3/NiO/CuO composite material at different magnifications confirming the non-uniform sizes of the particles generated. The facet nature of the particles is validated from Fig. 8(a) and (b). Whereas in (c) and (d) the particles adjoined on to the top and edges of facets are visible which has already seen in FESEM images.
(D) Electrochemical characterization
[0080] Electrochemical characterisation involved recording cyclic voltammetry (CV) in a 5.0 mM ferriferrocyanide solution comprising 0.1 M KCl. The redox behavior of the Fe2O3/NiO/CuO/GCE electrode was detected by gauging its electrochemical response at a scan rate of 100 mV/s within the potential region of -0.2 - 0.6 V. Fig. 9 (a) represents the conductive nature of bare GCE, CuO/GCE, CuO/NiO/GCE and Fe2O3/NiO/CuO/GCE in ferriferrocyanide solution. According to the observation, the Fe2O3/NiO/CuO composite loaded on the electrode surface participated in improving the conductivity of GCE. Hence the surface altered GCE express more conductivity in comparison to unmodified GCE as a result of increased electron transfer occurring on the electrode surface. Electrochemical impedance spectroscopy (EIS) is a critical instrument for discriminating the differences in impedance or conductivity of redox processes between modified and unmodified electrodes. It also facilitates the understanding of charge transfer kinetics. The Nyquist spectra display a semicircular form at elevated frequencies, transitioning into an inclined line as the frequency decreases. The semicircular region seen in the Nyquist plot typically represents the charge transfer resistance (RCT). In Fig. 9 (b) RCT value obtained for bare GCE is 37.6 Ω and for the modified electrodes including Fe2O3/NiO/CuO/GCE the value has become negligible. The data unambiguously indicate that Fe2O3/NiO/CuO/GCE exhibits superior electrochemical properties compared to the bare electrode and the other modified electrodes as evidenced by its lower RCT value and increased electron transport at the surface. Furthermore, the outcome demonstrates that Fe2O3/NiO/CuO/GCE exhibits enhanced electronic conductivity and expedites the kinetics of electron transfer.
[0081] The active surface area of the electrodes can be determined by applying the Randles-Sevcik equation (2)

Ip represents the peak current in amperes, n represents the number of electrons involved in the redox reaction of K3[Fe(CN)6], which is equal to one. D is equivalent to the diffusion coefficient, provided as 7.6 ×10-6 cm2 s-1. C symbolizes the concentration level of the prepared K3[Fe(CN)6] solution, which is 0.5 mM. v represents the scan rate in volts per second. To calculate the surface area of bare GCE and Fe2O3/NiO/CuO/GCE, performed electro-oxidation research of a ferricyanide solution using cyclic voltammetry. The investigation was conducted with both electrodes within a potential range of 0.0–0.6 V, and varied the scan rates from 10 mV/s to 160 mV/s. The slope derived from the linear regression of the current versus the square root of the scan rate can be correlated with the Randles-Sevcik equation. The electroactive surface area obtained for the bare GCE and modified GCE are as 0.0016 cm2 and 0.0068 cm2. The enlargement in the surface area is responsible for the enhancement in the peak current consequential from modified GCE.
(E) Electrochemical analysis
[0082] The sensor was evaluated using electrochemical techniques, specifically differential pulse voltammetry (DPV) and cyclic voltammetry (CV). DPV is known to be a more sensitive approach compared to CV. Fig. 10 illustrate the voltammogram of bare GCE, CuO/GCE, CuO/NiO/GCE and Fe2O3/NiO/CuO/GCE in presence of 100.0 μM catechol. This figure clearly exhibits the increment in anodic peak current occurred with surface modified electrode as compared to the bare GCE. This demonstrates the capacity of surface altering to enhance the electrochemical activity of an electrode towards a selected analyte. The anodic current obtained with Fe2O3/NiO/CuO/GCE is 2.5 times greater than obtained with bare GCE. Also, the current is higher than CuO/GCE and CuO/NiO/GCE. The anodic current obtained with CuO/GCE and CuO/NiO/GCE is 1.6 and 1.3 times greater than peak obtained with bare GCE respectively. This highlights the efficacy of the newly synthesized material in augmenting the oxidation current and the contribution of Fe2O3 in this composite to enhance the output. Although any other ratio of Fe2O3 did not significantly affect the current output. Scheme 1 represents the oxidation mechanism of catechol happening here which is responsible for the peak current produced.

[0083] Scheme 1: Electrochemical oxidation of catechol.
[0084] It is observed that the electrochemical oxidation of CC is proceeds via the transmission of two protons and electrons each and includes the formation of o-benzoquinone as well.
(F) Optimization of the experimental variables
[0085] Enhancing the experimental variables is essential for attaining superior sensing performance with the analyte-specific sensor. For bettering the electrochemical activity for catechol, emphasis is placed on optimizing variables such as the supporting electrolyte, the pH of the supporting electrolyte, and the concentration of the drop-casting material.
(i) Optimization of supporting electrolyte
[0086] The initial phase of optimizing experimental conditions involves the adjustment of the electrolyte. The following solutions are provided for this purpose: 0.1 M PBS (pH = 7), 0.1 M NaOH, 0.1 M KCl, 0.1 M HCl, 0.1 M H2SO4, 0.1 M HNO3 and 0.1 M acetate buffer (pH = 5). The sensor’s current response for each electrolyte is documented in Table 3. From the observation, it is clear that no peak was produced with H2SO4, HCl, KCl and with HNO3. The voltammogram of catechol includes one anodic and cathodic peak and under acidic media, the current ratio tends to approach unity. Whereas in basic solution the ratio becomes zero. This can be attributed to coupling of anionic and di anionic forms of catechol with o-benzoquinone. Based on the findings, results exposed that 0.1 M PBS (pH =7.0) exhibited the highest current compared to other electrolytes tested and it is chosen as the supporting electrolyte for subsequent testing of novel sensor.
[0087] Table 3: Current response sensor with each electrolyte separately.

(ii) Optimization of pH strength of phosphate buffer solution
[0088] The findings of the preceding examination indicate that the highest current response was obtained using a 0.1 M PBS solution with a pH of 7.0. Further, the electrolyte’s pH value has to be optimized. The performance of the sensor was appraised by analysing it with a 0.1 M phosphate buffer solution with pH values ranging from 2.0 to 9.0. Fig. 11 exemplifies the relationship between the peak position value and anodic current when the pH of the electrolyte changes. The impact of pH has over peak current is visible here and it is at neutral medium the sensor exhibited highest electrochemical activity towards CC and produced maximum anodic current. However, the observed behavior changes depending on the pH values, which could be due to additional chemical responses of the electrochemically formed o-benzoquinone, such as dimerization, hydroxylation, or cracking of oxidative ring. Furthermore, the extent to which the peak current ratio deviates from unity is contingent not only on the pH value, but also on the concentrations of CC. The graph displayed a linear decrease in potential as the pH ranged from 2.0 to 9.0. The regression coefficient, R2, was 0.98, and the slant value was - 0.0593 indicating that count of electrons and protons involved are same (see Fig. 12).
(iii) Optimization of amount of material on electrode surface
[0089] The measure of composite utilized for adjusting the surface of the electrode possesses considerable potential to affect the electrochemical performance of the sensor. In order to discern the distinction, a surface of an electrode was coated with varying amounts of Fe2O3/NiO/CuO and thereafter employed to ascertain the presence of catechol. According to observation, 5.0 mg is optimum amount of material required to maximize the output of the sensor. Dispersion is prepared by utilizing 5.0 mg material and 150.0 μl deionised water. From the dispersion about 5.0 μl is loaded on the surface of working electrode and employed for the studies.
(F) Scan rate study
[0090] The material employed to adorn the working electrode’s surface is pivotal in determining the electrochemical performance of the entire system. The kinetics of the electrochemical interaction can be assessed through a scan rate study of the newly developed sensor, wherein the relationship between varying scan rates and oxidation current is analyzed via CV. Fig. 12 (a) presents the sharp increment in current as the scan rate increasing from 10.0 mV/s to 180.0 mV/s owing to the fastened electron transfer occurring the surface of Fe2O3/NiO/CuO/GCE when 100.0 μM CC is added to the system in 0.1 M PBS with pH value 7.0. In addition, the resulting current was graphed separately versus the scan rate and the square root of the scan rate, as shown in 12 (b) and (c) with regression equations Ipa (μA) = 4.961 + 0.0404*v (mV/s), R2 =0.987 and Ipa (μA) = 2.445 + 0.692* v1/2 (mV/s)1/2, R2 = 0.99. The linear plot of square root of scan rate versus current exhibited more linearity than the linear plot of scan rate versus current. This highlight that the mechanism undergoing here is diffusion controlled.
(G) Determination of linear range
[0091] Defining the linear range is an essential procedure in the realm of an electrochemical sensor. The oxidative peak current at +0.212V corresponds to the electrochemical oxidation of catechol occurring at the Fe2O3/NiO/CuO/GCE interface, as illustrated in Scheme 1. The concentration of the target analyte exhibited a direct correlation with the resultant peak electric current. The oxidative current consistently increased with the rising concentration of catechol, as illustrated in Fig. 13 (a). The peak appeared at 0.126 V has resulted from oxidative reaction of catechol but has no influence with amount of concentration added as the peak current doesn’t increase with CC added. Hence hasn’t taken into consideration. The sensor exhibited excellent linear range towards catechol ranging from 0.8 μM to 8296.0 μM. The linear plot constructed between peak current and concentration of analyte in Fig. 13 (b). From 0.8 μM to 843.42 μM, the plot exhibited linearity with regression equation Ipa (μA) = 6.7625 + 0.05734* C (μM), R2 = 0.99 and from 843.42 μM to 8296.0 μM, the regression framed as Ipa (μA) = 52.74 + 0.0113* C (μM), R2 = 0.99. Equation 3σ/b is used to calculate the limit of detection (LOD) and is obtained as 0.005 μM. The limit of quantification (LOQ) is determined using formula 10 σ/b and is found to be 0.07 μM.
(H) Anti-interference ability and sensitivity evaluation
[0092] It is crucial to ensure the sensor’s capacity to selectively detect the target analyte amidst all potential interferents. The anti-interference assessment of a novel sensor necessitates a thorough examination to ascertain its vulnerability to interference from external sources. The new sensor is exposed to a solution containing 50.0 μM CC, resulting in the generation of a corresponding anodic peak. Further the potential interfering agents such as hydroquinone (HQ), resorcinol (RC), bisphenyl alcohol (BPA), 4-nitrophenol (4-NP), 2-nitrophenol (2-NP), 3-nitrophenol (3-NP), KCl, MgSO4 and NaCl are added into the system in excess. It is observed that the unique sensor does not produce appreciable variation in the peak current even after the addition of other species as shown in Fig. 14. Hence the anti-interference capacity of the sensor is confirmed. The sensitivity is a decisive metric for comprehending the potential of an electrochemical sensor. Here, the sensitivity of the working electrodes is determined by calculating the ratio of the slope to the active area of the electrode. This value is then found as 0.285 μA/ μM/cm2.
(I) Real sample study
[0093] The real sample study is essential to verify the efficacy of any newly produced sensor. The actual use of the constructed sensor is analyzed using both tap water and lake water as genuine samples. Furthermore, the wastewater obtained from an industrial is utilized to evaluate the response of the suggested sensor to the target analyte. The authentic samples were utilized in their original state without any modification. The determination of CC in these genuine samples is conducted using the typical spiking method. For that, 50.0 μl of the real samples are added in to the system individually, encompassing 9.95 ml of 0.1 M PBS (pH = 7) solution. The resulting solutions spiked with catechol so that the concentrations in the system increases as 2.8 μM, 4.8 μM and 7.8 μM. Three trials were executed for both the samples. The outcomes derived from comparing the concentration of the analyte with the spiked concentrations, as shown in Table 4, were satisfactory. The RSD values determined were impressive. The attained recovery rates were within acceptable norms such as 95 ± 105 %.
Table 4: Real sample study of Fe2O3/NiO/CuO/GCE towards CC (n = 3).

[0094] The spectrophotometric approach was used to validate the electrochemical performance of the new sensor. The validation of output obtained with electrochemical technique in addition to spectrophotometric approach confirmed the functionality of the novel sensor. The real samples such as tap water, lake water and waste water are used here for the study. The samples spiked with 2.8 μM, 4.8 μM and 7.8 μM catechol and are imperilled to UV study in the scanning range of 200 nm–500 nm and a peak of absorption was observed at a wavelength of 280 nm. As the concentration increases, the absorption peak also exhibited a linear increase. The recovery rates were within the acceptable limits such as 95 ± 105 %. This further authenticate the practical dependability of the sensor. The observations recorded are entered in Table 5.
Table 5: Spectrophotometric detection of CC in real samples.

Example 2: Comparative study
[0095] Extensive studies have been conducted throughout the years on electrochemical methods for accurate catechol measurement. Numerous studies concentrated on the concurrent detection of catechol, hydroquinone, and resorcinol. Several significant studies are enumerated in Table 6. The present disclosure focused exclusively on the electrochemical detection of catechol with a glassy carbon electrode modified with Fe2O3/NiO/CuO. The electrochemical findings indicated that the electronic conductivity of the composite material is enhanced, leading to an elevated current response to catechol. The electrode has been enhanced with a distinctive metal composite derived from abundant and non-toxic metal resources, significantly enhancing the sensor’s electrochemical performance. The impressive electrochemical output mainly involves wide linear range from 0.8 to 8296 μM, satisfactory repeatability and reproducibility. There are thorough experimentations has been going on in materials to develop the most efficient sensor for the target analyte. The highlights of such works are entered in the table below.
Table 6: Comparison study of the electrochemical sensor reported for CC detection.
Electrode Analytical method Linear range LOD Reference
alk-Ti3C2/N-PC/GCEa DPV 0.5-150 µM 3.1 nM Huang et al., Sens. Actuators B: Chem. 320 (2020) 128386
Co3O4/MWCNTs/GCEb DPV 10-700 µM 8.5 µM Song et al., Mate.Chem.Phy. 234. (2019). 217-223
CS/MWCNTs/PDA/
AuNPs/GCEc DPV 0.1-10 µM 0.047 µM Wang et al., Sens. Actuators B: Chem. 223 (2016) 501–508
Pal/NGE/GCEd DPV 1-50 µM 0.13 µM Wu et al., Appl. Clay Sci. 162 (2018) 38–45
NiO/CNT/GCEe DPV 10-400 µM 2.5 µM Zhao et al., J. Electroanal. Chem. (2018) 245–251
Au-Pd NF/rGOf DPV 2.5-100 µM 0.8 µM Chen et al., Electrochim. Acta 231 (2017) 677–685
Pt/C60/PGEg DPV 50.0 µM-1500.0 µM 2.97 µM Zhu et al., J. Electroanal. Chem 878 (2020) 114726
MgO/GO/MCPEh DPV 10 -70 µM 0.45 µM Chetankumar et al., J. Mater. Sci.: Mater. Electron. 31 (22) (2020) 19728–19740
Ce-MOF(TV)/CNTs/GCEi DPV 5-50 µM 3.5 µM Huang et al., J. Hazard. Mater. 416 (2021) 125895
ITO/APTES/r-GO@Auj DPV 5-140 µM 0.13 µM Wang et al., RSC Adv. 12 (37) (2022) 23762–23768
AuNPs/Fe3O4-APTES-GO/GCEk Amperometry 2-145 µM 0.8 µM Erogul et al., Electrochim. Acta 186 (2015) 302–313
Fe2O3/NiO/CuO/GCE DPV 0.8-8296 µM 0.005 µM This work

ADVANTAGES OF THE INVENTION
[0096] The mesoporous trimetallic oxide markedly improved the electrochemical properties of the sensor developed for CC by promoting greater electron transfer.
[0097] This novel composition allowed the electrochemical sensor to attain enhanced performance in the electrochemical detection of catechol relative to any previously documented electrochemical sensor.
[0098] The linear concentration range for CC measurement demonstrated by this distinctive sensor spans from 0.8 to 8296.0 μM, with a limit of detection (LOD) value of 0.005 μM, surpassing all previous investigations.
[0099] The redox effect of several interferents was mitigated, thereby removing their signals and improving the sensor’s selectivity for the target analyte.
[00100] The dependability of this novel sensor in real-time applications was assessed using electrochemical tests conducted in tap water, lake water and waste water from chemical industry, which demonstrated remarkable current responsiveness and exceptional recovery rates lying between 95 ± 100 %.
[00101] The sensitivity of the novel sensor is also analyzed and is obtained as 0.285 μA/μM/cm2.
, Claims:1. A Fe2O3/NiO/CuO composite composed of Fe2O3, NiO and CuO, wherein Fe2O3, NiO and CuO has a ratio ranging from (0.1-1): (0.5-1.5) : (2.5-3.5).
2. The composite as claimed in claim 1, wherein Fe2O3, NiO and CuO has a ratio of 0.5:1:3.
3. The composite as claimed in claim 1, wherein the composite has an X-ray diffraction pattern comprising peaks at 2θ = 33.21°, 49.1° and 62.64° for Fe2O3, 32.5°, 35.4°, 38.78°, 39.79°, 48.9°, 53.4°, 58.4°, 66.2° and 68.2° for CuO and 37.2°, 43.2° and 62.8° for NiO.
4. A method of preparation of Fe2O3/NiO/CuO composite comprising:
a) mixing a ferric salt precursor, a nickel salt precursor and a copper salt precursor in a first solvent with stirring to obtain a mixture;
b) heating the mixture in a teflon container inside autoclave by hydrothermal procedure to obtain a mixed metal oxide material;
c) washing the mixed metal oxide material with a second solvent followed by drying to obtain a dried mixed metal oxide material; and
d) processing the dried mixed metal oxide material by calcination to obtain a Fe2O3/NiO/CuO composite, wherein Fe2O3, NiO and CuO has a ratio ranging from (0.1-1): (0.5-1.5) : (2.5-3.5).
5. The method as claimed in claim 4, wherein the first solvent in step a) and the second solvent in step c) are selected from a group comprising of water, ethanol, DMF and combination thereof.
6. The method as claimed in claim 4, wherein the first solvent and the second solvent is same.
7. The method as claimed in claim 4, wherein the ferric salt precursor is selected from a group comprising of ferric chloride hexahydrate, Ferric nitrate and ferric sulfate and combination thereof and has an amount ranging from 35 to 37 %.
8. The method as claimed in claim 4, wherein the nickel salt precursor is selected from a group comprising of nickel nitrate hexahydrate, nickel acetate and combination thereof and has an amount ranging from 25 to 27 %.
9. The method as claimed in claim 4, wherein the copper salt precursor is selected from a group comprising of copper sulfate pentahydrate, Copper nitrate and copper acetate and combination thereof and has an amount ranging from 25 to 28 %.
10. The method as claimed in claim 4, wherein the stirring in step a) is carried out at a speed ranging from 200 to 300 RPM for a time period ranging from 10 min to 60 min.
11. The method as claimed in claim 4, wherein the heating in step b) is carried out at a temperature ranging from 150 to 200 °C for time period ranging from 30 h to 40 h.
12. The method as claimed in claim 4, wherein the drying in step c) is carried out at a temperature ranging from 50 to 80 °C for time period ranging from 8 h to 12 h.
13. The method as claimed in claim 4, wherein the calcination in step d) is carried out at a temperature ranging from 500 to 600 °C for time period ranging from 1 h to 5 h.
14. A Fe2O3/NiO/CuO composite modified glassy carbon electrode (GCE) comprising: a GCE modified with Fe2O3/NiO/CuO composite as claimed in claim 1, wherein, the Fe2O3/NiO/CuO composite is loaded to the GCE surface in the range of 3 to 5 %.
15. A method of fabrication of a Fe2O3/NiO/CuO composite modified glassy carbon electrode (GCE) comprising:
i) treating the surface of GCE with a polishing agent to obtain a polished GCE surface;
ii) adding 3 to 5 % w/v of Fe2O3/NiO/CuO composite as claimed in claim 1 in a solvent to obtain a suspension; and
iii) loading the suspension to the polished GCE surface followed by drying to obtain a Fe2O3/NiO/CuO composite modified glassy carbon electrode.
16. The method as claimed in claim 15, wherein the polishing agent is alumina.
17. The method as claimed in claim 15, wherein the solvent is selected from a group comprising of water, ethanol, DMF and combination thereof.
18. The method as claimed in claim 15, wherein the drying in step iii) is carried out at a temperature ranging from 15 to 35 °C.