WO2022158961A1

WO2022158961A1 - A method for nanocomposite deposition

Info

Publication number: WO2022158961A1
Application number: PCT/MY2021/050115
Authority: WO
Inventors: Wan Wardatul Amani Binti WAN SALIM; Abdelmohsen BENOUDJIT; Ihda Uswatun Shalihah SHOHIBUDDIN
Original assignee: Nanoskunkworkx Sdn Bhd
Current assignee: Nanoskunkworkx Sdn Bhd
Priority date: 2021-01-19
Filing date: 2021-11-30
Publication date: 2022-07-28
Anticipated expiration: 2023-07-19

Abstract

The present invention relates to a method for nanocomposite deposition and enhances performance in monitoring various parameters (100), characterised by the steps of: stabilising a reduced graphene oxide (rGO) with a poly(sodium 4-styrenesulfonate) (PSS) to form a reduced graphene oxide-poly(sodium 4-styrenesulfonate) (rGO:PSS) (110); preparing a solution of rGO:PSS-PEDOT:PSS nanocomposite by mixing 50 μl of rGO:PSS with 50 μl of conductive polymer consisting of poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) (120); centrifuging the solution of rGO:PSS-PEDOT:PSS nanocomposite for 30 minutes at 1500 rpm (130); storing the solution of rGO:PSS-PEDOT:PSS nanocomposite at 4oC (140); drop-casting 3 μl of rGO:PSS-PEDOT:PSS nanocomposite solution onto an electrode to fabricate rGO:PSS-PEDOT:PSS/electrode (150); and drying for 24 hours under a laminar flow hood (160).

Description

A METHOD FOR NANOCOMPOSITE DEPOSITION

Background of the Invention

Field of the Invention

This invention relates to a method for nanocomposite deposition. More particularly, the invention relates to a facile method of depositing nanocomposite in a certain way which can enhance the performance in monitoring various parameters.

Description of Related Arts

Graphene and its derivatives have been diversely used and manipulated for its surface properties. Inclusion of graphene or its derivatives have been shown to improve the electrochemical performance of electrodes. Therefore, graphene along with its derivatives are served as an important material in the construction of transducer layer for signal propagation. On the other hand, conductive polymers are also commonly incorporated as a transducer for improving the conductivity of the electrodes. Owing to the ability of accommodating the propagation of electrons and/or ions, conductive polymers are usually utilized in the electronic and solar applications. Thus, graphene, along with its derivatives or conductive polymers act as an attractive choice for device development due to its favourable characteristics in signal transduction.

United States Patent Application No. 8835046 B2 disclosed a nanocomposite material of graphene bonded to metal oxides, device using such materials, methods for forming nanocomposite materials of graphene bonded to metal oxides, and devices using those materials. Said nanocomposite material having at least two layers, each layer consisting of one metal oxide bonded to at least one graphene layer. Typically, the nanocomposite material will have many alternating layers of metal oxides and graphene layers, assembled in a sandwich type construction. The method for forming said nanocomposite involves the steps of providing graphene in a suspension; dispersing the graphene with a surfactant; adding a metal oxide precursor; precipitating the metal oxide and allowing the graphene and the metal oxide to organize into self-assembled structures. The nanocomposite material formed by this method is preferably formed into an ordered three-dimensional superstructure having multilength and multiphase building blocks of graphene layers and metal oxide layers, and at least two layers of the nanocomposite material include a metal oxide bonded to graphene. Said nanocomposite materials preferably have a thickness between 3 and 20 nm. Accordingly, said nanocomposite layers find particular utility in energy storage applications such as lithium ion battery. On the other hand, said nanocomposite layers may be used in any electrochemical devices including but not limited to energy storage devices, energy conversion devices and sensors. However, said nanocomposite does not disclosed of having a conductive polymer for supporting the graphene layers into an ordered three-dimensional structure.

China Patent Application No. 104629360 A disclosed a conductive polymer-graphene nanocomposite material. The conductive polymer-graphene nanocomposite material is formed by a conductive polymer and graphene, and the conductive polymer adopts graphene as a carrier, is dispersed on the surface of the lamellar structure of graphene, and is one of polyaniline, polypyrrole and polythiophene, and cyclosubstituted derivatives and heteroatom-substituted derivatives thereof. The said nanocomposite material has high specific surface area, can effectively avoid the agglomeration and adhesion problems of present polyaniline, polypyrrole, polythiophene and other conductive polymer materials, and has the advantages of high adsorption reduction ability and effective improvement of the metal recovery efficiency in the recovery treatment of metal elements in wastes. The preparation method of conductive polymer-graphene nanocomposite material comprises the steps of dissolving monomer in polyaniline, polypyrrole, polythiophene and their ring substitutive derivative in alkene hydrochloric acid to obtain solution A, dispersing graphene oxide powder or graphene oxide fiber in deionized water to obtain solution B, mixing solution A and solution B uniformly, making two reaction, and filtering or centrifuging to obtain protonated conducting polymer-graphene solid product. The mass ratio of aniline monomer, pyrrole monomer or thiophene monomer and graphene is 1 : 100 ~ 1 : 10. However, said nanocomposite material does not disclosed of having a poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) as the conductive polymer. Besides that, said nanocomposite material is used mainly for carrying out the metal of electrochemical reducing reaction in recycling the waste, which is lack of diversity in functionality.

Disclosed in Korea Patent Application No. 101623346 B1 is a method for producing a three-dimensional iron oxide-graphene nanocomposite and a super capacitor manufactured using the same. More particularly, it relates to a method for producing an iron oxide-graphene nanocomposite quickly and continuously through a single process by using an aerosol spray pyrolysis process. The method for producing iron oxide-graphene nanocomposite comprises the step of mixing graphene oxide, iron oxide precursor and solvent to produce a mixed colloidal solution, aerosol droplet spraying of said mixed colloidal solution, and transferring the atomized droplets to a heating furnace and pyrolyzing the resulting droplets to obtain an iron oxide-graphene nanocomposite. The iron oxide-graphene nanocomposite formed by this method is preferably having a three-dimensional structure and may possess a very high electric capacity. The method for producing said nanocomposite is easy to scale up, and may be continuously processed by using an aerosol spray pyrolysis process. However, a high temperature range between 300 - 1000°C must be maintained throughout the process of pyrolysis of atomized droplets, which is less facile and require higher energy consumption.

According to existing prior arts, there is a need to provide a facile method for nanocomposite deposition which can enhance the performance in monitoring various parameters.

Summary of Invention

It is an objective of the present invention to provide a method for nanocomposite deposition that is facile and affordable for resource-constrained settings. It is also an objective of the present invention to provide a method for nanocomposite deposition that can enhance the sensitivity of detection.

It is also an objective of the present invention to provide a method for nanocomposite deposition that can improve the selectivity towards a target analyte.

It is also an objective of the present invention to provide a method for nanocomposite deposition that can increase the effective surface area of an electrode.

It is also an objective of the present invention to provide a method for nanocomposite deposition that can results in low detection limit.

Accordingly, these objectives may be achieved by following the teachings of the present invention. The present invention relates to a method for nanocomposite deposition and enhances performance in monitoring various parameters (100), characterised by the steps of: stabilising a reduced graphene oxide (rGO) with a poly(sodium 4-styrenesulfonate) (PSS) to form a reduced graphene oxide-poly(sodium 4-styrenesulfonate) (rGO:PSS) (110); preparing a solution of rGO:PSS-PEDOT:PSS nanocomposite by mixing 50 pl of rGO:PSS with 50 pl of conductive polymer consisting of poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) (120); centrifuging the solution of rGO:PSS-PEDOT:PSS nanocomposite for 30 minutes at 1500 rpm (130); storing the solution of rGO:PSS-PEDOT:PSS nanocomposite at 4°C (140); drop-casting 3 pl of rGO:PSS-PEDOT:PSS nanocomposite solution onto an electrode to fabricate rGO:PSS-PEDOT:PSS/electrode (150); and drying for 24 hours under a laminar flow hood (160). Brief Description of the Drawings

The features of the invention will be more readily understood and appreciated from the following detailed description when read in conjunction with the accompanying drawings of the preferred embodiment of the present invention, in which:

Figure 1 shows a flow chart of a method for nanocomposite deposition by using drop-casting;

Figure 2 shows a flow chart of a method for nanocomposite deposition by using electropolymerizing;

Figure 3 shows a configuration of the nanocomposite deposition of the present invention;

Figure 4 shows a cyclic voltammetry (CV) measurements of the rGO:PSS-PEDOT:PSS/electrode compared to the unmodified electrode, rGO:PSS/electrode and PEDOT:PSS/electrode at a scan rate of 100 mV/s in 0.1 M Fe(CN)₆ ^4/3;

Figure 5 shows a cyclic voltammetry (CV) measurements of the unmodified electrode (top left), rGO:PSS/electrode (top right), PEDOT:PSS/electrode (bottom left) and rGO:PSS-PEDOT:PSS/electrode (bottom right) at a scan rate of 75, 100, 150, 200 and 250 mV/s in 0.1 M Fe(CN)₆ ^4/3;

Figure 6 shows a linear progression by plotting the corresponding peak currents and square root of scan rates of 75, 100, 150, 200, and 250 mV/s, where the A_e is determined using the slope and the Randles-Sevcik equation; and

Figure 7 shows a potentiometric measurement of the ISM/rGO:PSS/electrode, ISM/PEDOT:PSS/electrode, and ISM/rGO:PSS-PEDOT:PSS/electrode, and calibration profile for the ISM/rGO:PSS/electrode, ISM/PEDOT:PSS/electrode, and ISM/rGO:PSS-PEDOT:PSS/electrode in KCI with increasing concentration.

Detailed Description of the Preferred Embodiment (s)

As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting but merely as a basis for claims. It should be understood that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the invention is to cover all modifications, equivalents and alternatives falling within the scope of the present invention as defined by the appended claims. As used throughout this application, the word "may" is used in a permissive sense (i.e. , meaning having the potential to), rather than the mandatory sense (i.e., meaning must). Similarly, the words "include," "including," and "includes" mean including, but not limited to. Further, the words "a" or "an" mean "at least one” and the word "plurality" means one or more, unless otherwise mentioned. Where the abbreviations or technical terms are used, these indicate the commonly accepted meanings as known in the technical field. For ease of reference, common reference numerals will be used throughout the figures when referring to the same or similar features common to the figures. The present invention will now be described with reference to Figs. 1-6.

The present invention relates to a method for nanocomposite deposition and enhances performance in monitoring various parameters (100), characterised by the steps of: stabilising a reduced graphene oxide (rGO) with a poly(sodium 4-styrenesulfonate) (PSS) to form a reduced graphene oxide-poly(sodium 4-styrenesulfonate) (rGO:PSS) (110); preparing a solution of rGO:PSS-PEDOT:PSS nanocomposite by mixing 50 pl of rGO: PSS with 50 pl of conductive polymer consisting of poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) (120); centrifuging the solution of rGO:PSS-PEDOT:PSS nanocomposite for 30 minutes at 1500 rpm (130); storing the solution of rGO:PSS-PEDOT:PSS nanocomposite at 4°C (140); drop-casting 3 pl of rGO:PSS-PEDOT:PSS nanocomposite solution onto an electrode to fabricate rGO:PSS-PEDOT:PSS/electrode (150); and drying for 24 hours under a laminar flow hood (160).

In a preferred embodiment of the present invention, the reduced graphene oxide-poly(sodium 4-styrenesulfonate) (rGO:PSS) may help to enhance an electrochemical reversibility due to a highly reversible property.

In a preferred embodiment of the present invention, the reduced graphene oxide (rGO) is stabilized with the poly(sodium 4-styrenesulfonate) (PSS) to avoid rGO stacking while promoting hydrophilicity of the nanomaterial so that the rGO: PSS can be dissolved in an aqueous solution.

In a preferred embodiment of the present invention, the poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) may help to improve the interfacial electron transfer processes, thus enhancing the peak current signals.

In a preferred embodiment of the present invention, any types of ion-selective membrane (ISM) may drop-casting onto the nanocomposite-coated electrode using a layer-by-layer process for recognising a specific analyte in a sample solution.

In a preferred embodiment of the present invention, the rGO:PSS-PEDOT:PSS nanocomposite may act as a transducer layer for any types of all-solid state ion-selective electrode (ISE).

In a preferred embodiment of the present invention, the rGO:PSS-PEDOT:PSS nanocomposite may deposited onto any matrix, substrate, or surface of interest for monitoring various parameters including but not limited to physiological and environmental measurements.

In a preferred embodiment of the present invention, the rGO:PSS-PEDOT:PSS nanocomposite may bonded to any types of biorecognition element for detecting a plurality of parameter, thus improving the selectivity of measurement.

In a preferred embodiment of the present invention, the reduced graphene oxide (rGO) is used due to an excellent performance in sensitivity, selectivity and detection range.

In a preferred embodiment of the present invention, the rGO:PSS-PEDOT:PSS nanocomposite greatly increases the effective surface area (A_e) of the electrode, thus improving the charge transferability and results in higher sensitivity of detection.

In a preferred embodiment of the present invention, the electrons are easily travelled at extremely high velocity without the significant chance of scattering when the reduced graphene oxide (rGO) is arranged in a three-dimensional array structure with the help of conductive polymer (PEDOT:PSS).

In a preferred embodiment of the present invention, the three-dimensional array structure of the reduced graphene oxide (rGO) may provides some advantages such as fast electron transport due to a porous structure and maintained a wide specific surface area, therefore may maintain a high energy storage capability.

In a preferred embodiment of the present invention, the synergistic effect of combining rGO:PSS and PEDOT:PSS in a composite on the electrode is proved by using cyclic voltammetry where the rGO:PSS-PEDOT:PSS nanocomposite showed a 93% increase in peak current (l_p) when compared to rGO:PSS alone.

The present invention also relates to a method for nanocomposite deposition and enhances performance in monitoring various parameters (100) using electropolymerizing, characterised by the steps of: dissolving 1.064 g of lithium perchlorate (UCIO4) powder in 100 ml of distilled water (200); stirring for 5 minutes to obtain a homogenized transparent LiCIO4 solution (210); mixing 0.5 mL of 3,4-ethylenedioxythiophene (EDOT) with 1.0 mL of poly(sodium 4-styrenesulfonate) (NaPSS) (220); adding 8.5 mL of l_iCIO₄ solution to prepare 10 mL of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (EDOT:PSS) solution (230); stirring the EDOT:PSS solution for 24 hours at room temperature (240); mixing 5 mL of reduced graphene oxide: poly(styrenesulfonate) (rGO:PSS) with 10 mL of EDOT:PSS solution to form rGO:PSS-EDOT:PSS solution (250); stirring for 24 hours at room temperature (260); immersing electrode in a glass vial containing the rGO:PSS-EDOT:PSS solution (270); applying galvanostatic mode to fabricate rGO:PSS-PEDOT:PSS/electrode (280); and drying for 24 hours at room temperature under laminar flow (290).

Below is an example of nanocomposite deposition methods and enhances performance in monitoring various parameters from which the advantages of the present invention may be more readily understood. It is to be understood that the following example is for illustrative purpose only and should not be construed to limit the present invention in any way.

Examples

Methods for nanocomposite deposition

Shown in Figure 1 is an exemplary of a nanocomposite deposition method by using drop-casting. Referring to Figure 1 , a reduced graphene oxide (rGO) is first stabilized with a poly(sodium 4-styrenesulfonate) (PSS) to form a reduced graphene oxide-poly(sodium 4-styrenesulfonate) (rGO: PSS). Then, a solution of rGO:PSS-PEDOT:PSS nanocomposite is prepared by mixing 50 pl of rGO:PSS with 50 pl of conductive polymer consisting of poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS). Next, the solution of rGO:PSS-PEDOT:PSS nanocomposite is centrifuged for 30 minutes at 1500 rpm followed by storing at 4°C. Thereafter, 3 pl of rGO:PSS-PEDOT:PSS nanocomposite solution is drop-casting onto an electrode and drying for 24 hours under a laminar flow hood. Shown in Figure 2 is an exemplary of a nanocomposite deposition method by using electropolymerizing. Referring to Figure 2, 1.064 g of lithium perchlorate (LiCIC ) powder is first dissolved in 100 ml of distilled water. Next, the solution is stirred for 5 minutes to obtain a homogenized transparent LiCIC solution. Then, 0.5 mL of 3,4-ethylenedioxythiophene (EDOT) is mixed with 1.0 mL of poly(sodium 4-styrenesulfonate) (NaPSS). Thereafter, 8.5 mL of LiCIO4 solution is added to prepare 10 mL of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (EDOT:PSS) solution. Afterwards, the EDOT:PSS solution is stirred for 24 hours at room temperature. Subsequently, 5 mL of reduced graphene oxide: poly(styrenesulfonate) (rGO:PSS) is mixed with 10 mL of EDOT:PSS solution to form rGO:PSS-EDOT:PSS solution followed by stirring for 24 hours at room temperature. After that, an electrode is immersed in a glass vial containing the rGO:PSS-EDOT:PSS solution and applying with galvanostatic mode to fabricate rGO:PSS-PEDOT:PSS/electrode. Lastly, the rGO:PSS-PEDOT:PSS/electrode is dried for 24 hours at room temperature under laminar flow.

The configuration of the rGO:PSS-PEDOT:PSS nanocomposite produced using the methods of the present invention is shown in Figure 3, where the conductive polymer (PEDOT:PSS) is intercalated between the reduced graphene oxide (rGO) which is stabilised with the poly(sodium 4-styrenesulfonate) (PSS) to form a three-dimensional array structure. In order for the PEDOT:PSS to be intercalated between the rGO, an ionic bond is formed where the positively charged PEDOT in the conductive polymer is ionically bonded to the negatively charged rGO. The intercalation of the conductive polymer (PEDOT: PSS) is to avoid the stacking of rGO and supporting the rGO in a three-dimensional array structure. Thereafter, the rGO:PSS-PEDOT:PSS nanocomposite is further immobilized onto the surface of the electrode through ionic bond where said bond is formed between the negatively charged PSS in the conductive polymer and the positively charged electrode.

Advantageously, the method for nanocomposite deposition of the present invention can be performed in a resource-constrained setting under an ambient condition. The nanocomposite produced using the method of the present invention may be used as a precursor for electrodes, as energy storage medium to store electric charge, as a superconductive medium and also coated onto the hull of water vehicles to create a frictionless or drag-free vehicle.

Electrochemical characterisation of rGO:PSS-PEDOT:PSS nanocomposite

The prepared rGO:PSS-PEDOT:PSS nanocomposite which has been drop-casted or electropolymerized onto an electrode, for example a screen- printed carbon electrode (SPCEs) is characterised in term of electrochemical redox behaviour using a cyclic voltammetry (CV). The cyclic voltammetry (CV) helps to understand the mechanism by which the rGO:PSS-PEDOT:PSS nanocomposite capable of facilitating the electron transfer at an electrode-electrolyte interface. The cyclic voltammetry (CV) analysis is performed for unmodified SPCEs, rGO:PSS/SPCEs, PEDOT:PSS/SPCEs and rGO:PSS-PEDOT:PSS/SPCEs for comparing means.

Referring to Figure 4, it was observed in cyclic voltammetry (CV) analysis that the rGO:PSS/SPCEs and PEDOT:PSS/SPCEs has a higher peak current (l_p), smaller shift in E_p and smaller peak-to-peak potential separation (AE_P). This indicates that rGO:PSS and PEDOT:PSS may serve as a shuttle to transport the electron from the electrolytes towards the surface of the electrode. The role of rGO:PSS and PEDOT:PSS as an electron shuttle may accelerate the electron transfer kinetics, thus results in lower detection limit and higher sensitivity of detection.

Furthermore, the cyclic voltammetry (CV) analysis in Figure 4 also showing that the PEDOT:PSS/SPCEs exhibited the highest anodic and cathodic peak current where the anodic peak current (l_pa) and cathodic peak current (l_pc) is 1.637 mA and 1.522 mA respectively. A noticeable increase in the peak current (l_p) of PEDOT:PSS/SPCEs suggesting that the PEDOT:PSS may improve the interfacial electron transfer processes, therefore enhancing the peak current signals and resulting in lower detection limit. A further look into the electrochemical redox behaviour of rGO:PSS-PEDOT:PSS nanocomposite is given in Figure 5. Referring to Figure 5, rGO:PSS/SPCEs showed a smallest separation of peak-to-peak potential (AE_P = 150 mV) and a lowest shift in peak potential (E_pshift = 30 mV), indicating that rGO:PSS may help to enhance the electrochemical reversibility, causing the electrons to be transferred more easily onto the surface of electrode.

Moreover, the cyclic voltammetry (CV) analysis in Figure 5 also showing a 93% increment in l_p for rGO:PSS-PEDOT:PSS nanocomposite/SPCEs when compared to rGO:PSS/SPCEs; a 23% decrement in AE_pand a 50% decrement in E_pshjft when compared to PEDOT:PSS/SPCEs. This suggest that there is a synergistic effect of combining rGO:PSS and PEDOT:PSS in a composite, where the PEDOT:PSS provides a higher electron transfer while the rGO:PSS provides more reversibility of the redox process.

Further analyses of the rGO:PSS-PEDOT:PSS nanocomposite is on the effective surface area (A_e) (Figure 6). A_e is determined using the slope and Randles-Sevcik equation. A_e is the electroactive surface area of electrode involved in a redox reaction. The A_e of the rGO:PSS-PEDOT:PSS/SPCEs and the unmodified electrode is 0.067 cm² and 0.031 cm² respectively. The large increase in A_e of the rGO:PSS-PEDOT:PSS/SPCEs in comparison to the unmodified electrode attributed to the increase in current density and charge transferability, thus improving the sensitivity of the detection.

Potentiometric measurement of rGO:PSS-PEDOT:PSS nanocomposite towards a target analyte

The prepared rGO:PSS-PEDOT:PSS nanocomposite/SPCEs is further drop-casting with an ion-selective membrane (ISM) for example a potassium ion-selective membrane (KISM) using a layer-by-layer process. The KISM/rGO:PSS-PEDOT:PSS nanocomposite/SPCEs is then analysed to determine the sensitivity of detection. The KISM/rGO:PSS-PEDOT:PSS nanocomposite/SPCEs is tested in different KCI concentrations of 0.1 , 1 , 2, 4, 8,16, 32, 100 and 1000 mM. A linear relationship between the voltage and different concentrations of KCI solution is observed and plotted. Apart from KISM/rGO:PSS-PEDOT:PSS nanocomposite/SPCEs, KISM/rGO:PSS/SPCEs and KISM/PEDOT:PSS/SPCEs also be tested for comparing means.

By referring to Figure 7, it was observed that the KISM/rGO:PSS-PEDOT:PSS nanocomposite/SPCEs having a sensitivity of 58.0 mV/decade, which is close to the theoretical value of 59.0 mV/decade.

The correlation between the l_p of the rGO:PSS-PEDOT:PSS nanocomposite/SPCEs and the sensitivity of the resulting KISM/rGO:PSS-PEDOT:PSS nanocomposite/SPCEs is then investigated. From the investigation, the lp_a and lp_c of the rGO:PSS-PEDOT:PSS nanocomposite/SPCEs is in between the lp_a and lp_c of the rGO:PSS/SPCEs and PEDOT:PSS/SPCEs, meanwhile the corresponding sensitivity of KISM/rGO:PSS-PEDOT:PSS nanocomposite/SPCEs is in between the sensitivities of KISM/rGO:PSS/SPCEs and KISM/PEDOT:PSS/SPCEs. The results suggest a possible correlation whereby the sensitivity of the KISM/rGO:PSS-PEDOT:PSS nanocomposite/SPCEs increases with the increment of lp_a and lp_c of rGO:PSS-PEDOT:PSS nanocomposite/SPCEs. Such phenomenon owes to faster electron transfer kinetics in the rGO:PSS-PEDOT:PSS nanocomposite/SPCEs, rendering them an efficient tool for molecular-level detections of target analyte even at low concentration, thus improving the sensitivity of the detection.

Other than sensitivity, KISM/rGO:PSS-PEDOT:PSS nanocomposite/SPCEs is also tested in term of detection limit, linear range and response time. KISM/rGO:PSS-PEDOT:PSS nanocomposite/SPCEs showed a detection limit of 4.2 x 10'⁵ M and reported a linear range of 3.3 x 10'³ M. In addition, KISM/rGO:PSS-PEDOT:PSS nanocomposite/SPCEs displayed an instantaneous response of 3 -10 s toward an increasing concentration of target analyte. The rGO:PSS-PEDOT:PSS nanocomposite produced using the methods of the present invention may be useful in many applications, for example, in a medical application for biosensor development. The rGO:PSS-PEDOT:PSS nanocomposite of the present invention may utilized for monitoring any target analyte in a clinical sample including but not limited to protein, nucleic acid, and virus which tend to exist in a low concentration. The target analyte in the clinical sample is binding to the specific biorecognition element that bonded on the reduced graphene oxide (rGO) of said nanocomposite. The interaction between the biorecognition element and the analyte causing a series of redox reaction and subsequently generates electrons. Thereafter, the electron flow through the three-dimensional reduced graphene oxide (rGO) at high velocity without scattering and generates electricity once reached the surface of the electrode. The electrons move in an easy and faster manner through the three-dimensional array structure of reduced graphene oxide (rGO) due to the synergistic effect of combining rGO:PSS and PEDOT:PSS in a composite, where PEDOT:PSS provides a higher electron transfer while the rGO:PSS provides more reversibility of the redox process.

In an embodiment, the three-dimensional array structure of the reduced graphene oxide (rGO) allowed maximum bonding of the specific biorecognition element, thus helps in binding maximum number of analytes in the sample and results in sensitive outcome and having lower detection limit. In addition, the three-dimensional array structure of the reduced graphene oxide (rGO) allowed electrons to be travelled more easily and faster towards the surface of electrode so that the transduction signals are rapid and accurate.

In another embodiment, graphene in various degree of reduction such as fully reduced or partially reduced may used as a nanomaterial for nanocomposite deposition. Moreover, the density and number of the graphene layers can be manipulated according to specific requirement or any applications. In another embodiment, various forms of graphene such as flakes, powder, platelet or foams form may used for the nanocomposite deposition.

In another embodiment, the conductive polymers used for the nanocomposite deposition including but not limited to PEDOT:PSS, PEDOT/(polythiophene)s (PT):S/poly(p-phenylene sulphide) (PPS) and PANI/PPY.

Although the present invention has been described with reference to specific embodiments, also shown in the appended figures, it will be apparent for those skilled in the art that many variations and modifications can be done within the scope of the invention as described in the specification and defined in the following claims.

Claims

Claims l/We claim:

1. A method for nanocomposite deposition and enhances performance in monitoring various parameters (100), characterized by the steps of: stabilising a reduced graphene oxide (rGO) with a poly(sodium 4-styrenesulfonate) (PSS) to form a reduced graphene oxide-poly(sodium 4-styrenesulfonate) (rGO:PSS) (1 10); preparing a solution of rGO:PSS-PEDOT:PSS nanocomposite by mixing 50 pl of rGO:PSS with 50 pl of conductive polymer consisting of poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT SS) (120); centrifuging the solution of rGOPSS-PEDOTPSS nanocomposite for 30 minutes at 1500 rpm (130); storing the solution of rGOPSS-PEDOTPSS nanocomposite at 4°C (140); drop-casting 3 pl of rGOPSS-PEDOTPSS nanocomposite solution onto an electrode to fabricate rGOPSS-PEDOTPSS/electrode (150); and drying for 24 hours under a laminar flow hood (160).

2. The method for nanocomposite deposition and enhances performance in monitoring various parameters (100) according to claim 1 , wherein the rGOPSS-PEDOTPSS nanocomposite is immobilized onto the surface of electrode through an ionic bond.

3. The method for nanocomposite deposition and enhances performance in monitoring various parameters (100) according to claim 2, wherein said ionic bond is formed between the negatively charged poly(styrenesulfonate) (PSS) in the conductive polymer and the positively charged electrode.

4. The method for nanocomposite deposition and enhances performance in monitoring various parameters (100) according to claim 1 , wherein the PEDOT:PSS is intercalated between the reduced graphene oxide (rGO) for avoiding stacking of the reduced graphene oxide (rGO). The method for nanocomposite deposition and enhances performance in monitoring various parameters (100) according to claim 4, wherein the positively charged poly(3,4-ethylenedioxythiophene) (PEDOT) in the conductive polymer is ionically bonded to the negatively charged reduced graphene oxide (rGO) so that said polymer can be intercalated between the reduced graphene oxide (rGO) to support the reduced graphene oxide (rGO) in a three-dimensional array structure. The method for nanocomposite deposition and enhances performance in monitoring various parameters (100) according to claim 5, wherein said positively charged poly(3,4-ethylenedioxythiophene) (PEDOT) is subsequently bonded to the negatively charged poly(styrenesulfonate) (PSS) in the conductive polymer so that the rGO:PSS-PEDOT:PSS nanocomposite can firmly bonded on the electrode. The method for nanocomposite deposition and enhances performance in monitoring various parameters (100) according to claim 1 , wherein said reduced graphene oxide (rGO) can be in the form of fully reduced or partially reduced. The method for nanocomposite deposition and enhances performance in monitoring various parameters (100) according to claim 1 , wherein said reduced graphene oxide (rGO) can be in the form of flakes, powder, platelets, or foams. The method for nanocomposite deposition and enhances performance in monitoring various parameters (100) according to claim 1 , wherein said conductive polymer can be selected from a sulfur-containing chemical group consisting of PEDOT/poly(thiophene)s (PT) with sulfur (S). The method for nanocomposite deposition and enhances performance in monitoring various parameters (100) according to claim 1 , wherein said conductive polymer can be selected from a nitrogen-containing chemical group such as polyaniline (PANI) and polypyrrole (PPY). The method for nanocomposite deposition and enhances performance in monitoring various parameters (100) according to claim 1 , wherein the rGO:PSS-PEDOT:PSS nanocomposite can be drop-casting or electropolymerizing onto any electrode types for monitoring a plurality of parameter. The method for nanocomposite deposition and enhances performance in monitoring various parameters (100) according to claim 1 , wherein the rGO:PSS-PEDOT:PSS nanocomposite may enhances the performance in term of sensitivity, selectivity, effective surface area of electrode and detection limit. The method for nanocomposite deposition and enhances performance in monitoring various parameters (100) according to claim 1 , wherein the preparation of nanocomposite deposition is performed in a resource-constrained setting under an ambient condition. The method for nanocomposite deposition and enhances performance in monitoring various parameters (100) according to claim 1 , wherein the combination of rGO:PSS and PEDOT:PSS in a composite results in a synergistic effect where providing a higher electron transfer and more reversibility of the redox process. The method for nanocomposite deposition and enhances performance in monitoring various parameters (100) according to claim 1 , wherein the performance of the rGO:PSS-PEDOT:PSS nanocomposite can be analysed through the usage of cyclic voltammetry (CV) and/or

18 potentiometric measurements. A method for nanocomposite deposition and enhances performance in monitoring various parameters (100) using electropolymerizing, characterized by the steps of: dissolving 1 .064 g of lithium perchlorate (LiCIC ) powder in 100 ml of distilled water (200); stirring for 5 minutes to obtain a homogenized transparent LiCICU solution (210); mixing 0.5 mL of 3,4-ethylenedioxythiophene (EDOT) with 1 .0 mL of poly(sodium 4-styrenesulfonate) (NaPSS) (220); adding 8.5 mL of LiCIO4 solution to prepare 10 mL of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (EDOT:PSS) solution (230); stirring the EDOT:PSS solution for 24 hours at room temperature (240); mixing 5 mL of reduced graphene oxide: poly(styrenesulfonate) (rGO:PSS) with 10 mL of EDOT:PSS solution to form rGO:PSS-EDOT:PSS solution (250); stirring for 24 hours at room temperature (260); immersing electrode in a glass vial containing the rGO:PSS-EDOT:PSS solution (270); applying galvanostatic mode to fabricate rGO:PSS-PEDOT:PSS/electrode (280); and drying for 24 hours at room temperature under laminar flow (290).

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