Chemical sensor development based on poly(o-anisidine)silverized–MWCNT nanocomposites deposited on glassy carbon electrodes for environmental remediation

Abstract

A poly(o-anisidine)/silverized multiwall carbon nanotube (POAS–Ag/MWCNT) nanocomposite was synthesized by adsorption between POAS and MWCNTs using a solution technique. In this approach, an extended study on the potential development of a chemical sensor was done with the nanocomposites. The sensor was prepared by a simplistic and facile route from the POAS–Ag/MWCNT composites. Here, a thin layer of the POAS–Ag/MWCNT nanocomposites was deposited onto a glassy carbon electrode (GCE) with conducting coating agents to fabricate a selective 3-methoxyphenol sensor with a short response time in a phosphate buffer phase. The fabricated chemi-sensor also exhibited higher sensitivity, large dynamic concentration ranges, long-term stability, and improved electrochemical performance towards 3-methoxyphenol. The calibration plot is linear (r² = 0.9938) over a large 3-methoxyphenol concentration range (0.4 nM to 40.0 mM). The sensitivity and detection limit are ∼3.829 μA cm⁻² mM⁻¹ and ∼0.36 ± 0.05 nM (signal-to-noise ratio at an SNR of 3), respectively. This novel effort initiates a well-organized method of using nanocomposites for efficient sensor improvement towards toxic pollutants in environmental and health-care fields on large scales.

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Introduction

Conducting polymer-coupled carbon nanotube-based nanocomposites filled with Ag-nanosized stiff particles have evolved and attracted great interest both in industry and academia during the last decade. The performance of the polymer–CNT nanocomposites strongly depends on the degree of dispersion and the aspect ratio of the layered materials in the CNT matrices. In particular, the exfoliation of layered materials in polymers with CNT matrices has been shown to improve the flame retardancy, optical, sensing, thermal, ion detection, rheological and mechanical properties of the base conducting polymer.^1,2 Conducting polymeric CNT nanocomposites possess high stability, high permeability and density, a large surface area, great light scattering properties, and a tunable particle diameter and shell thickness in comparison with the organic vesicles formed from the self-aggregation of silverized particles. Due to these characteristics, conducting polymeric nanocomposite materials can serve as micro-reaction vessels, sensitive sensors, drug delivery vehicles, biological stiff recognition molecules, protective shells, immunoassay materials, and synthetic pigments on huge industrial and academic scales.³ The rapid development in the field of conducting organic materials has shown their potential application in sensors and electronics.⁴ Two kinds of conducting materials are promising: conducting polymers (polypyrrole, polyaniline, polythiophene, anisidine etc.) and fullerenes (carbon nanotubes). Functional carbon nanotubes have attracted increasing attention from various research laboratories around the world because of their exceptional electronic and mechanical properties.⁵ Carbon nanotubes conjugated with conducting polymers have been utilized to fabricate transistors, sensors, hydrogen storage materials, conductive materials, electrodes, biosensors, and field emission materials, and exhibit potential as the building blocks for new nanotechnologies.^6–8 Recently, novel conducting polymer-conjugated metal nanocomposites offer exciting systems to examine the opportunity of designing novel device functionality⁹ and also display enhanced sensing, selectivity¹⁰ and catalytic capabilities, compared with those of pure conducting polymers.^11,12 It was reported that a novel conducting polymer metal nanocomposite can be synthesized by a one-step chemical oxidative polymerization using a metal salt as an oxidant.¹³ It was confirmed that chemical oxidative polymerization using various metal salts such as hydrogen tetrachloroaurate(III), silver nitrate (AgNO₃), palladium(II) chloride and hydrogen hexachloroplatinate(IV) (H₂PtCl₆), which act as both an oxidant and a source of metal atoms, yielded well-dispersed metal nanoparticles in bulk conducting polymers. Based on the properties of the nanocomposite material, it was concluded that a single-step preparation route of a POAS–Ag nanocomposite by chemical oxidative polymerization in aqueous media using MWCNTs and poly(o-anisidine) followed by mixing with AgNO₃ resulted in the formation of POAS–Ag/MWCNT nanocomposites.

The improvement of reliable and sensitive methods for the detection of phenolic compounds is desired for applications in environmental safety, protection, food quality control, and health.¹⁴ There are several phenolic compounds that have been classified as “priority pollutants” by both the United States Environmental Protection Agency (USEPA) and the European Commission. Phenolic compounds are comparatively common in waste streams of diverse large-scale processing and manufacturing, as they serve as precursor materials in various industries such as coal mining, crude oil refining, paper bleaching, and in the production of dyes, resins, plastics, explosives, detergents, pharmaceuticals, pesticides, and herbicides.^15,16 In contrast, a few phenols of plant origin have been shown to display a broad range of attractive physiological characteristics as antioxidants, anti-inflammatories, and cardiovascular prophylactics, promoting their use as additives in some alcoholic beverages and food products.^17,18 Recent determination methods such as spectrophotometry, fluorimetry, gas or liquid chromatography, mass spectrometry and capillary electrophoresis are usually perceptive and consistent but possess limitations, such as being expensive, time-consuming and requiring preconcentration and extraction steps that increase the risk of sample loss and generation of other hazardous byproducts.¹⁹ The electrochemical sensing of phenolic compounds represents a promising approach that can be utilized to complement already existing methods owing to collective characteristics such as high sensitivity and selectivity, low cost, simple instrumentation and potential for miniaturization.^20,21

3-Methoxyphenol is extremely toxic and usually a serious risk to health and the environment; its immediate detection is required using a reliable chemi-sensor method with POAS–Ag/MWCNT nanocomposites using a GCE. The sensing of 3-methoxyphenol by prepared thin nanocomposite films on a GCE is studied in detail. An easy coating method for the construction of the POAS–Ag/MWCNT nanocomposite thin-films within binding agents is executed for the preparation of the films onto the GCE. In this approach, the fabricated POAS–Ag/MWCNT nanocomposite films with conducting binders are utilized towards target carcinogenic analytes using a reliable current-vs.-voltage method. It is confirmed that the fabricated chemi-sensor is unique and can be used for the ultra-sensitive recognition of toxic 3-methoxyphenol with POAS–Ag/MWCNT nanocomposites on a GCE in a short response time.

Experimental details

Materials and methods

Analytical grade 3-methoxyphenol, ethyl acetate, disodium phosphate (Na₂HPO₄), butyl carbitol acetate, and monosodium phosphate (NaH₂PO₄) were used and purchased from Sigma-Aldrich Company, USA. They were used without further purification. A stock solution of 3-methoxyphenol (0.1 M) was prepared from the purchased chemical. The I–V technique was executed using an Electrometer (Keithley, 6517A, Electrometer, USA) to measure the current responses in two electrode systems for the target 3-methoxyphenol chemical sensor based on POAS–Ag/MWCNT nanocomposites in buffer phase under standard conditions, where a flat-GCE and Pd-wire were used as the working and counter electrodes respectively. The XPS measurements of the Cu–GO composite materials were measured by a Thermo Scientific K-Alpha KA1066 spectrometer (Germany). Monochromatic AlKα X-ray radiation sources were used as an excitation source, where the beam spot size was kept as ∼400.0 μm. The spectra were recorded with the fixed transmission mode, where the pass-energy was fixed at ∼200.0 eV. The current-vs.-voltage (I–V) method (two electrodes composed onto a fabricated micro-chip) was carried out using a Keithley-Electrometer (USA) to measure the toxic 3-methoxyphenol ions with the POAS–Ag/MWCNT nanocomposites/GCE sensor.

Preparation of POAS–Ag/MWCNT nanocomposites

The nanocomposite was synthesized by a solution self-oxidizing technique using o-anisidine (OAS), an organic monomer mixed into the inorganic solution of silver nitrate, which was already explained in our previous study.²² Here, when the OAS solution was added to the inorganic silver nitrate system under rigorous stirring over 24 h, concurrently functionalizing the MWCNTs, the resultant mixture turned slowly into a brown coloured slurry and was kept for 24 h at room temperature. Then, the resultant composite gels were filtered off and washed thoroughly with demineralised water to remove excess acid and any adhering trace of oxidant. The washed material was dried over P₄O₁₀ at 45.0 °C in an oven. The dried products were immersed in demineralised water to obtain small granules. They were converted to the H⁺ form by keeping them in a 1.0 M HCl solution for 24 h, with occasional shaking intermittently replacing the supernatant liquid. The excess acid was removed after several washing cycles with demineralised water. The material was finally dried at 45.0 °C for several hours. The silver-metalized nanocomposite material was prepared by the incorporation of inorganic silver nitrate in the electrically conducting monomer OAS, which acted as a self-oxidizing agent. A schematic representation of the synthetic preparation, fabrication onto the GCE and sensor application is presented in Scheme 1.

Scheme 1 Schematic representation of the synthetic preparation of POAS–Ag/MWCNTs, polymer-composite fabrication onto GCE, and chemical sensor applications.

Preparation and fabrication of the GCE with nanocomposites

A phosphate buffer solution (PBS, 0.1 M) at pH 7.0 is prepared by the mixing of equimolar concentrations of 0.2 M Na₂HPO₄ and 0.2 M NaH₂PO₄ solutions in 100.0 mL of deionized water under standard conditions. The GCE is fabricated with POAS–Ag/MWCNT nanocomposites using butyl carbitol acetate (BCA) and ethyl acetate (EA) as a conducting binder. Then it is kept in the oven at 50.0 °C for 1 hour until the film is completely dried, stable, and smooth. A cell is assembled with POAS–Ag/MWCNT nanocomposites/GCE and Pd wire as working and counter electrodes respectively. The as-received 3-methoxyphenol is diluted to make various concentrations (0.4 nM to 40.0 mM) in DI water and used as a target analyte. The ratio of current versus concentration (slope of the calibration curve) is used to calculate the 3-methoxyphenol sensitivity. The detection limit is evaluated from the ratio of 3N/S (ratio of noise × 3 vs. sensitivity) from the linear dynamic range of the calibration curve. An electrometer is used as a constant voltage source for I–V measurement in a simple two electrode system. The amount of 0.1 M PBS was kept constant in the beaker as 10.0 mL throughout the chemical investigation. The POAS–Ag/MWCNT nanocomposites are fabricated and employed for the detection of 3-methoxyphenol in the liquid phase. The I–V response is measured with the POAS–Ag/MWCNT nanocomposite/GCE film.

Results and discussions

Characterization of the nanocomposites

The POAS–Ag/MWCNT nanocomposites were already characterized using TGA, FTIR, and XRD in our previous report. Here, X-ray photoelectron spectroscopy (XPS) and field-emission scanning electron microscopy (FESEM) are performed and presented. Basically, XPS is a quantitative spectroscopic method that determines the elemental composition, empirical formula, chemical state and electronic state of the elements that are present within materials. XPS spectra are attained by irradiating nanomaterials with a beam of X-rays, while simultaneously determining the kinetic energy and number of electrons that get away from the top 1 to 10.0 nm of the material being analyzed. Here, XPS measurements were taken for the POAS–Ag/MWCNT nanocomposites to investigate the chemical states of carbon, oxygen, silver, and nitrogen. XPS was used to determine the chemical state of the POAS–Ag/MWCNT nanocomposites and their depth. The full XPS spectrum of the POAS–Ag/MWCNT nanocomposites was measured and is presented in Fig. 1(a). In Fig. 1(b), the spectra were found to have a C 1s peak at approximately 284.9 eV for the covalent bond equivalent to the C–C chain existing in the MWCNT skeleton, which is present in the POAS–Ag/MWCNT nanocomposites.²³ The O 1s spectrum shows a distinguished peak at 531.7 eV in Fig. 1(c). The peak at 531.7 eV is assigned to oxygen, which indicated the presence of oxygen (i.e., O₂⁻) in the POAS–Ag/MWCNT nanocomposites.²⁴ In Fig. 1(d), the binding energy of N 1s is measured as 399.8 eV for the POAS–Ag/MWCNT nanocomposites.²⁵ Fig. 1(e) presents the XPS spectra (spin–orbit doublet peaks) of the Ag 3d_(5/2) and Ag 3d_(3/2) regions recorded for the POAS–Ag/MWCNT nanocomposites. The binding energies of the Ag 3d_(5/2) and Ag 3d_(3/2) peaks at 367.1 eV and 373.1 eV denote the presence of silver metal in the nanocomposites.²⁶ Therefore, it is concluded that the POAS–Ag/MWCNT nanocomposites have four different elements.

Fig. 1 Study using X-ray photoelectron spectroscopy of the POAS–Ag/MWCNT nanocomposites. (a) Full spectrum of the POAS–Ag/MWCNT nanocomposites, (b) C 1s level, (c) O 1s level, (d) N 1s level, and (e) Ag 3d level, acquired with MgKα1 radiation. X-ray beam spot size is 400.0 μm; pass-energy is 200.0 eV; pressures are less than 10⁻⁸ Torr.

FESEM was used to investigate the morphology and size of the particles in the hybrid nanocomposite materials that were fabricated onto the flat GCE using conducting binders. Fig. 2 exhibits the representative FESEM image of POAS–Ag/MWCNTs fabricated onto a GCE. The formed aggregated silver nanoparticles are poly-dispersed in an irregular morphological arrangement into the composite materials. The bright spots shown in the FESEM image may be due to the aggregation of the silver particles introduced into the hybrid nanocomposite materials. Thus, the FESEM images exhibit evidence for the presence of aggregated silver nanoparticles in the polymer hybrid matrix with MWCNTs. Finally, it is shown prominently in the FESEM images that the simple methodology of the synthesized hybrid products gives rise to the nanostructure of POAS–Ag/MWCNTs, which results in aggregated and high-density nanocomposites in the polymer hybrid matrix with MWCNTs.

Fig. 2 FESEM image of the POAS–Ag/MWCNT nanocomposites on a GCE.

Applications: detection of 3-methoxyphenol with nanocomposites/GCE

The potential application of the POAS–Ag/MWCNT nanocomposites assembled onto a GCE as a chemical sensor (especially the 3-methoxyphenol analyte in a buffer system) has been tested for the measurement and detection of the target chemical. The enhancement of the POAS–Ag/MWCNT nanocomposite/GCE as a chemical sensor is in the initial stages and no other reports on it are available. The POAS–Ag/MWCNT nanocomposite/GCE sensors have advantages such as their stability in air, non-toxicity, chemical inertness, electro-chemical activity, simplicity to assemble, ease of fabrication, and chemo-safe characteristics. In the case of 3-methoxyphenol sensors, the current response in the I–V method with POAS–Ag/MWCNT nanocomposite/GCE considerably changes when the aqueous phenolic analyte is adsorbed. The POAS–Ag/MWCNT nanocomposite/GCE was applied in the fabrication of a chemi-sensor, where 3-methoxyphenol was measured as a target analyte. The fabricated surface of the POAS–Ag/MWCNT nanocomposite sensor was prepared with conducting binders (EC & BCA) on the GCE surface, which is presented in Scheme 2a. The fabricated GCE was put into the oven at a low temperature (60.0 °C) for 2.0 h to make it dry, stable, and provide a totally uniform surface. I–V signals (Scheme 2b) of the 3-methoxyphenol chemical sensor are anticipated from having POAS–Ag/MWCNT nanocomposite/GCE on a thin film. The resultant electrical responses of the target 3-methoxyphenol are investigated by the simple and reliable I–V technique using POAS–Ag/MWCNT nanocomposite/GCE, which is presented in Scheme 2c. The holding time of the electrometer was set for 1.0 s. A significant amplification in the current response with applied potential is noticeably confirmed. The simple and possible reaction mechanism for this with the presence of 3-methoxyphenol on the POAS–Ag/MWCNT nanocomposite/GCE sensor surfaces is generalized in Scheme 2d. In the presence of the POAS–Ag/MWCNT nanocomposites, electrons are released in the presence of 3-methoxyphenol by the adsorption of reduced oxygen, which improved and enhanced the current response against potential during the I–V measurement under standard conditions.

Scheme 2 Schematic view of (a) the POAS–Ag/MWCNT nanocomposite-coated GCE with conducting coating binders, (b) detection I–V method (theoretical), (c) observed I–V responses by POAS–Ag/MWCNT nanocomposite/GCE, and (d) proposed adsorption mechanisms of 3-methoxyphenol detection in the presence of POAS–Ag/MWCNT nanocomposite on a flat GCE. Surface area of GCE: 0.0316 cm²; method: I–V. Delay time: 1.0 s.

The POAS–Ag/MWCNT nanocomposites were employed for the detection of 3-methoxyphenol in the liquid phase. I–V responses were measured with a POAS–Ag/MWCNT nanocomposite-coated thin film (in a two electrode system). The 3-methoxyphenol sensing protocol using the POAS–Ag/MWCNT nanocomposite/GCE modified electrode has already been outlined in the experimental section. The concentration of 3-methoxyphenol was varied from 0.4 nM to 40.0 mM by adding de-ionized water in different proportions. Control experiments for the uncoated and nanocomposite-coated electrodes using the I–V method were carried out and the results are presented in Fig. 3. Here, Fig. 3(a) represents the I–V responses for the uncoated-GCE (gray-dotted) and the POAS–MWCNT/Ag-nanocomposite-coated-GCE (orange-dotted) electrodes. In the PBS system, the result for the POAS–Ag/MWCNT nanocomposite/GCE electrode shows that the reaction is reduced slightly owing to the presence of the nanocomposites on the bare-GCE surface. A considerable enhancement of the current value with applied potential is demonstrated with the fabricated POAS–Ag/MWCNT nanocomposite/GCE in the presence of the target 3-methoxyphenol analyte, which is presented in Fig. 3(b). The orange-dotted and red-dotted curves indicate the response of the fabricated film after and before the injection of 25.0 μL 3-methoxyphenol in 10.0 mL PBS solution, respectively, measured by the fabricated POAS–Ag/MWCNT nanocomposite/GCE films. Significant increases in current are measured after the injection of the target component at regular intervals.

Fig. 3 Study of control experiment. I–V responses of (a) GCE (without nanocomposites) and nanocomposite/GCE (with POAS–Ag/MWCNT nanocomposites), and (b) nanocomposite/GCE (in absence) and 3-methoxyphenol/nanocomposite/GCE (in presence) of 3-methoxyphenol in the solution system.

The I–V responses to varying 3-methoxyphenol concentrations (0.4 nM to 40.0 mM) of the POAS–Ag/MWCNT nanocomposite/GCE thin films were investigated (time delay, 1.0 s) and presented in Fig. 4(a). Analytical parameters (such as sensitivity, detection limit, linearity, and linear dynamic range etc.) were calculated from the calibration curve (current vs. concentration), which is presented in Fig. 4(b). A wide range of 3-methoxyphenol concentrations from 0.4 nM to 40.0 mM was selected to study the possible detection limit (from the calibration curve). The sensitivity was calculated from the calibration curve, which was close to ∼3.829 μA cm⁻² mM⁻¹. The linear dynamic range of the POAS–Ag/MWCNT nanocomposite/GCE sensor was employed from 0.4 nM to 0.4 mM (linearly, r² = 0.9938), and the detection limit was calculated to be about ∼0.36 ± 0.05 nM (ratio, 3N/S). The POAS–Ag/MWCNT nanocomposite/GCE exhibited mesoporous behaviour, where the electrical resistance decreases under the presence of the target 3-methoxyphenol in the PBS phase. The film resistance decreased gradually (increasing the resultant current) upon increasing the 3-methoxyphenol concentration in the bulk system.

Fig. 4 Analysis of chemical responses. (a) I–V responses of concentration variations (0.4 nM to 40.0 mM) of 3-methoxyphenol, (b) calibration plot of the POAS–Ag/MWCNT nanocomposite-fabricated GCE electrode (at +0.5 V).

In the two-electrode system, the I–V characteristics of the POAS–Ag/MWCNT nanocomposite/GCE film vary as a function of 3-methoxyphenol concentration under standard conditions where an improved current response is observed. As is obtained here, the current response of the POAS–Ag/MWCNT nanocomposite film increases with an increasing concentration of 3-methoxyphenol; however, similar phenomena for toxic chemical detection have also been reported earlier.^27–31 For a low concentration of 3-methoxyphenol in liquid medium, there is a smaller surface coverage of 3-methoxyphenol molecules on the POAS–Ag/MWCNT nanocomposite/GCE film and hence the surface reaction proceeds steadily. By increasing the 3-methoxyphenol concentration, the surface reaction is increased significantly (gradually increasing the response as well) owing to a large surface area being in contact with 3-methoxyphenol molecules. With a further increase in 3-methoxyphenol concentration on the POAS–Ag/MWCNT nanocomposite/GCE surface (mesoporous), the current response exhibited a more rapid increase, due to a larger surface area being covered by the 3-methoxyphenol chemical. Usually, the surface coverage of 3-methoxyphenol molecules on the POAS–Ag/MWCNT nanocomposite/GCE surface reaches saturation, based on the regular enhancement in the current responses.

The selectivity of the 3-methoxyphenol sensor was studied in the presence of other chemicals like acetaldehyde, hydrazine, methanol, 3-methoxyphenol, dichloromethane, tetrahydrofuran, acetone, pyridine, phenol, ethanol, and n-hexane, and in a blank solution (only buffer) using the POAS–Ag/MWCNT nanocomposite/GCE; the results are presented in Fig. 5(a). The concentrations of all analytes are kept constant at the 0.1 μM level in a PBS system. From the current response of each individual analyte, the percentages of the responses at a potential of +0.5 V towards acetaldehyde (1.41%), hydrazine (2.78%), methanol (2.20%), 3-methoxyphenol (80.37%), dichloromethane (0.74%), tetrahydrofuran (4.6%), acetone (2.57%), pyridine (3.38%), ethanol (2.81%), n-hexane (0.50%), phenol (4.8%), and the blank solution (0%) with the POAS–Ag/MWCNTs nanocomposites/GCE sensors were calculated. Here, it is clearly demonstrated that the POAS–Ag/MWCNT nanocomposite/GCE electrode sensor is most selective toward 3-methoxyphenol (80.3%) compared with other chemicals, which is shown in Fig. 5(b).

Fig. 5 Selectivity study with analytes by the POAS–Ag/MWCNT nanocomposite/GCE electrodes. (a) I–V responses of the various analytes and (b) the current responses (as percentages) towards the analytes at +0.5 V; the analyte concentration was taken at 0.1 μM. Potential range: 0 to +1.5 V; delay time: 1.0 s.

To check the reproducibility and storage stabilities, the I–V response for the POAS–Ag/MWCNT nanocomposite/GCE sensor was examined and presented in Fig. 6(a). After each experiment (each run), the fabricated POAS–Ag/MWCNT nanocomposite/GCE substrate was washed thoroughly with the phosphate buffer solution and it was observed that the current response was not significantly decreased. The current loss in each experiment was calculated and is presented in Fig. 6(b). Here it is observed that the current loss in each reading is negligible compared to the initial response of the sensors using the POAS–Ag/MWCNT nanocomposite/GCE material. A series of six successive measurements of 0.1 μM 3-methoxyphenol in 0.1 M PBS yielded a good reproducible signal from the POAS–Ag/MWCNT nanocomposite/GCE sensor with a relative standard deviation (RSD) of 2.1%. The sensitivity was retained at almost the same as the initial sensitivity for up to seven days, after that the response of the fabricated POAS–Ag/MWCNT nanocomposite/GCE electrode gradually decreased. The 3-methoxyphenol chemical sensor based on the POAS–Ag/MWCNT nanocomposite/GCE displayed good reproducibility and stability for over a week and no major changes in the sensor responses were found. After a week, the chemical sensor response of the POAS–Ag/MWCNT nanocomposite/GCE slowly decreased, which may be due to the weak interaction between the fabricated POAS–Ag/MWCNT nanocomposite/GCE active surfaces and the 3-methoxyphenol chemical.

Fig. 6 Reproducibility study with analytes (0.1 μM) using the POAS–Ag/MWCNT nanocomposite/GCE electrodes. (a) I–V responses of all reproducible signals (Run 1 to Run 6) with 3-methoxyphenol, and (b) current responses towards the analyte (3-methoxyphenol) at +0.5 V; the analyte concentration was taken at 0.1 μM. Potential range: 0 to +1.5 V; delay time: 1.0 s.

A significant result was achieved by the POAS–Ag/MWCNT nanocomposite/GCE, which can be employed as a proficient electron mediator for the development of efficient chemical sensors. Actually, the response time was around 10.0 s for the fabricated POAS–Ag/MWCNT nanocomposite/GCE sensor to reach the saturated steady-state level. The higher sensitivity of the fabricated POAS–Ag/MWCNT nanocomposite/GCE sensor could be attributed to the excellent absorption (porous surfaces in the POAS–Ag/MWCNT nanocomposite/binder/GCE) and adsorption ability, high catalytic decomposition activity, and good biocompatibility of the POAS–Ag/MWCNT nanocomposites. The estimated sensitivity of the fabricated sensor is relatively higher and the detection limit is comparatively lower than previously reported chemical sensors based on other nanocomposite- or nano-material-modified electrodes measured by I–V systems.^32–35 Due to their high specific surface area, POAS–Ag/MWCNT nanocomposites provide a favourable nano-environment for 3-methoxyphenol detection with good sensitivity. The high sensitivity of the POAS–Ag/MWCNT nanocomposite/GCE provides good electron communication features which enhance the direct electron transfer between the active sites of the POAS–Ag/MWCNT nanocomposites and the coated GCE. The POAS–Ag/MWCNT nanocomposite/GCE system demonstrates a simple and reliable approach for the detection of toxic chemicals. It also provides significant access to a large group of chemicals for a wide range of ecological and biomedical applications in environmental and health-care fields respectively.

Conclusion

POAS–Ag/MWCNT nanocomposites have been prepared using a simple adsorption technique and a sensor fabricated with conducting coating binders onto flat glassy carbon electrodes displayed higher sensitivity and selectivity for chemical sensing applications. The analytical performances of the fabricated 3-methoxyphenol sensors are excellent in terms of their sensitivity, detection limit, linear dynamic ranges, selectivity, and short response time. The POAS–Ag/MWCNT nanocomposite/GCE assembly exhibited higher sensitivity (∼3.829 μA cm⁻² mM⁻¹) and a lower detection limit (∼0.36 ± 0.05 nM) with good linearity and a short response time, which means it could be efficiently utilized as a chemi-sensor for 3-methoxyphenol. This novel approach introduces a well-organized route for efficient chemical sensor development towards environmental pollutants in health-care fields on a broad scale.

Acknowledgements

The Center of Excellence for Advanced Materials Research (CEAMR) and the Chemistry Department, King Abdulaziz University, Jeddah is highly acknowledged.

References

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