Electrochemical properties and the determination of nicotine at a multi-walled carbon nanotubes modified glassy carbon electrode

Emerging trends in functional materials for electrochemical sensors in nicotine determination

In the past year, there has been significant progress in the utilization of electrochemical strategies for the determination of harmful substances. Among those, the electrochemical determination of nicotine (NIC) has continued to be of significant interest ascribed to the global health concern of e-cigarette products, nowadays. Electrochemical sensors have become promising tools for the detection of NIC ascribed to their high sensitivity, selectivity, and ease of use. This review article provides a concise overview of the advanced developments in electrochemical sensors for NIC detection using modified functional materials such as carbon-based materials, metal-organic frameworks (MOF), MXene, polymer, and metallic based modifiers. The sensitivity of electrochemical sensors can be improved by modifying them with these conductive materials ascribed to their physical and chemical properties. The review also addresses the challenges and future perspectives in the field, including sensitivity and selectivity improvements, stability and reproducibility issues, integration with data analysis techniques, and emerging trends. In conclusion, this review article may be of interest to researchers intending to delve into the development of functional electrochemical sensors in future studies.

Development of Electrochemical Sensor Using Iron (III) Phthalocyanine/Gold Nanoparticle/Graphene Hybrid Film for Highly Selective Determination of Nicotine in Human Salivary Samples

Nicotine is the one of the major addictive substances; the overdose of nicotine (NIC) consumption causes increasing heart rate, blood pressure, stroke, lung cancer, and respiratory illnesses. In this study, we have developed a precise and sensitive electrochemical sensor for nicotine detection in saliva samples. It was built on a glassy carbon electrode (GCE) modified with graphene (Gr), iron (III) phthalocyanine-4,4',4″,4'''-tetrasulfonic acid (Fe(III)Pc), and gold nanoparticles (AuNPs/Fe(III)Pc/Gr/GCE). The AuNPs/Fe(III)Pc/Gr nanocomposite was prepared and characterized by using FE-SEM, EDX, and E-mapping techniques to confirm the composite formation as well as the even distribution of elements. Furthermore, the newly prepared AuNPs/Fe(III)Pc/Gr/GCE-nanocomposite-based sensor was used to detect the nicotine in phosphate-buffered solution (0.1 M PBS, pH 7.4). The AuNPs/Fe(III)Pc/Gr/GCE-based sensor offered a linear response against NIC from 0.5 to 27 µM with a limit of detection (LOD) of 17 nM using the amperometry (i-t curve) technique. This electrochemical sensor demonstrated astounding selectivity and sensitivity during NIC detection in the presence of common interfering molecules in 0.1 M PBS. Moreover, the effect of pH on NIC electro-oxidation was studied, which indicated that PBS with pH 7.4 was the best medium for NIC determination. Finally, the AuNPs/Fe(III)Pc/Gr/GCE sensor was used to accurately determine NIC concentration in human saliva samples, and the recovery percentages were also calculated.

Palladium Hydroxide (Pearlman's Catalyst) Doped MXene (Ti3C2Tx) Composite Modified Electrode for Selective Detection of Nicotine in Human Sweat

High concentrations of nicotine (40 to 60 mg) are more dangerous for adults who weigh about 70 kg. Herein, we developed an electrochemical transducer using an MXene (Ti₃C₂Tx)/palladium hydroxide-supported carbon (Pearlman's catalyst) composite (MXene/Pd(OH)₂/C) for the identification of nicotine levels in human sweat. Firstly, the MXene was doped with Pd(OH)₂/C (PHC) by mechanical grinding followed by an ultrasonication process to obtain the MXene/PHC composite. Secondly, XRD, Raman, FE-SEM, EDS and E-mapping analysis were utilized to confirm the successful formation of MXene/PHC composite. Using MXene/PHC composite dispersion, an MXene/PHC composite-modified glassy carbon electrode (MXene/PHC/GCE) was prepared, which showed high sensitivity as well as selectivity towards nicotine (300 µM NIC) oxidation in 0.1 M phosphate buffer (pH = 7.4) by cyclic voltammetry (CV) and amperometry. The MXene/PHC/GCE had reduced the over potential of nicotine oxidation (about 200 mV) and also enhanced the oxidation peak current (8.9 µA) compared to bare/GCE (2.1 µA) and MXene/GCE (5.5 µA). Moreover, the optimized experimental condition was used for the quantification of NIC from 0.25 µM to 37.5 µM. The limit of detection (LOD) and sensitivity were 27 nM and 0.286 µA µM^-1 cm², respectively. The MXene/PHC/GCE was also tested in the presence of Na⁺, Mg²⁺, Ca²⁺, hydrogen peroxide, acetic acid, ascorbic acid, dopamine and glucose. These molecules were not interfered during NIC analysis, which indicated the good selectivity of the MXene/PHC/GCE sensor. In addition, electrochemical determination of NIC was successfully carried out in the human sweat samples collected from a tobacco smoker. The recovery percentage of NIC in the sweat sample was 97%. Finally, we concluded that the MXene/PHC composite-based sensor can be prepared for the accurate determination of NIC with high sensitivity, selectivity and stability in human sweat samples.

2D MXene/graphene nanocomposite preparation and its electrochemical performance towards the identification of nicotine level in human saliva

The quantitative analysis of neurological drugs is critical since the kinetics of body fluids is strongly dependent on the dosage of the drug levels. Thus, the study of neurological medicines is significant because of the major diseases connected to it, for instance, Alzheimer's and Parkinson's diseases. Herein, a 2D hybrid MXene/graphene (MX/Gr) film was synthesized through a top-down approach and utilized to prepare an electrochemical transducer for the electrochemical sensing of nicotine. The X-ray diffraction (XRD), Raman and X-ray photoelectron spectroscopy (XPS) confirmed the successful incorporation of MX with Gr sheets. The high-resolution scanning electron microscopy (HR-SEM) and transmission electron microscopy (TEM) have been used to confirm the formation of MX, graphene sheets and the MX/Gr hybrid film. Furthermore, the MX/Gr hybrid film composite modified glassy carbon electrode (GCE) was prepared to selectively detect the nicotine in phosphate buffer medium (0.1 M PBS, pH~7.4). Under the optimized condition, the MX/Gr/GCE based sensor provided a linear response against nicotine from 1 to 55 µM and 30 nM - 600 nM with the lowest limit of detections (LOD) of 290 nM and 0.28 nM by differential pulse voltammetry (DPV) and amperometry, respectively. This newly developed MX/Gr hybrid film modified electrode displayed a remarkable selectivity, sensitivity, and reproducibility for accurate detection of nicotine. Finally, this new sensor was applied to detect nicotine in human/artificial saliva samples with high accuracy.

Paper-Based Potentiometric Sensors for Nicotine Determination in Smokers' Sweat

Herein, we describe for the first time, the design and fabrication of a novel nicotine paper-based sensor, in which a miniaturized paper reference electrode is integrated for potentiometric measurements. The paper-based sensors were designed using printed wax barriers to define the electrochemical cell and the sample zones. The electrodes were based on the use of the ion association complexes of the nicotinium cation (Nic) with either tetraphenylborate (TPB) or 5-nitrobarbiturate (NB) counter anions as sensing materials for nicotine recognition. A poly (3,4 ethylenedioxythiophene)/poly-(styrene sulfonate) (PEDOT/PSS) conducting polymer was used as an ion-to-electron transducer. The performance characteristics of the proposed sensors were evaluated and it revealed a rapid and stable response with a Nernstian slope of 55.2 ± 0.3 and 51.2 ± 0.6 mV/decade over the linear range of 1.0 × 10^-5 to 1.0 × 10^-2 M and detection limits of 6.0 and 8.0 μM for [Nic/TPB] and [Nic/NB], respectively. The sensors revealed a constant response over the pH range 3.5-6.5. The designed sensors provided a portable, inexpensive, and disposable way of measuring trace levels of nicotine coming from different cigarettes and in the collected human sweat of heavy smokers. All results were compared favorably with those obtained by the standard gas chromatographic method.

Microfluidic tank assisted nicotine sensing property of field effect transistor composed of an atomically thin MoS2 channel

We investigated the sensor behavior of a field effect transistor, the channel of which is made of atomically thin MoS2 layers, focusing on the interaction of the MoS2 channel with the solution containing target molecules. For this purpose, we made a newly designed device in which the mask covered the electrodes of the source and the drain in order to make the solution contact only with the channel. In addition, a micro-fluid tank was fabricated above the channel as a solution reservoir. We examined the FET properties of this device for the sensing of the nicotine molecule for the development of a detection system for this molecule in the human body under in vivo conditions. We detected the sensor behavior both for the drop-cast process and for the condition where the channel contacts with the solution. The drain-current vs. gate-voltage variation of the MoS2-FET with the attachment of the nicotine molecule was clearly observed for both cases. For the latter case, the threshold voltage shifted in the negative gate-voltage direction with the increase of the concentration of the nicotine in the solution. This can be explained by the electron transfer from the molecule to the MoS2 channel, which was further confirmed by analyzing the X-ray photoemission spectroscopy and Raman spectroscopy together with the DFT calculation. The sensor can detect the variation of the nicotine concentration in the IPA solution by detecting the Vth change of the MoS2-FET.

Glassy carbon electrode modified with hybrid nanofibers containing carbon nanotubes trapped in chitosan for the voltammetric sensing of nicotine at biological pH

In this paper, nicotine (NIC) was detected by cyclic voltammetry (CV) using a modified glassy carbon (GC) electrode. To do this, the surface of the GC electrode was modified by hybrid nanofiber obtained from the electrospinning method. Hybrid nanofibers were produced through the dispersion of carboxylated multi-walled carbon nanotube (MWCNT-COOH) as an inorganic component in the chitosan (CS) polymer matrix as an organic component. The nanofibers showed unique morphology and high surface area value. With the increase of functionalized carbon nanotube content in the nanofibers, the mean pore diameter and average nanofiber diameter increased. The electrochemical properties of nanofibers towards the sensing of NIC were investigated by the CV method. NIC was irreversibly reduced with the use of a CS/MWCNT-COOH electrode, a controlled process with two protons and two electrons. An oxidation signal at lower potential with higher current was obtained for NIC with the use of a polymer-modified electrode compared to a GC electrode. This was as a result of the electrocatalytic effect of the hybrid nanofibers due to the ability of carbon nanotubes to increase the rate of electron transfer. Under optimum conditions, the oxidation of NIC occurred at 0.82 eV with a pH of 7.4. The linear calibration curve was in the concentration range of 0.1-100 μM NIC (R ² = 0.9987) with a detection limit of 30 nM. For 100 parallel 10 μM NIC diagnoses for five replicates, 97.2% with a standard deviation of 4.08 maintained their stability over the first cycle. This indicates that the CS/MWCNT-COOH electrode has excellent reproducibility and stability.

Role of Green Chemistry in Antipsychotics' Electrochemical Investigations Using a Nontoxic Modified Sensor in McIlvaine Buffer Solution

A new low-cost green electrochemical sensor based on nontoxic polyethylene glycol (PEG) and silver nanoparticles was used to improve the sensitivity of the carbon paste electrode for the investigation of olanzapine (OLZ) in dosage arrangements and in the existence of its coadministered drug fluoxetine and in the drug formulation. Scanning electron microscopy measurements were carried out to emphasize the morphology of the electrode surface. Cyclic voltammetry and differential pulse voltammetry were used to explore the diffusion and linearity behaviors of OLZ. Impedance spectroscopy measurements were determined to investigate the ac behavior of OLZ and then an ideal electrical circuit was modeled. A linear calibration was obtained from 1.0 × 10^-8 to 1.25 × 10^-4 M. The limit of detection was 1.5 × 10^-9 M, whereas the limit of quantification was 5 × 10^-9 M. The way has been wholly authenticated concerning linearity, precision, accuracy, reproducibility, sensitivity, and selectivity.

Synthesis of a simply modified electrochemical nicotine sensor based on silver nanoparticles

An innovative electrochemical nicotine modified sensor was created by chemically mixing a carbon paste with silver nano powder to prepare an Ag nanoparticle modified carbon paste electrode. Different electrochemical techniques including cyclic voltammetry, linear sweep voltammetry, and electrochemical impedance spectroscopy in both aqueous and micellar media were used. The surface morphology was also detected using scanning electron microscope and energy dispersive X-ray analysis techniques. Nicotine measurements were investigated in Britton–Robinson buffer solutions with a pH range of 2.0–8.0 containing 1.0 mmol/L sodium dodecyl sulfate. The electrode-based NIC sensor exhibited a high sensitivity in quantitative analysis, and its detection limit could be as low as 0.0036 μmol/L with linearity ranging from 0.8 μmol/L to 800 μmol/L. In addition, due to its good reproducibility, anti-interference performance, and long-term stability, the proposed sensor is capable of detecting trace levels of nicotine in urine samples and different brands of commercial cigarettes.

Comparison of the Conventional and Electroenhanced Direct-Immersion Solid-Phase Microextraction for Sampling of Nicotine in Biological Fluids of the Human Body

A stainless steel fiber was made porous and adhesive by platinization and then coated by nanostructured polypyrrole (PPy), using an appropriate electrophoretic deposition (EPD) method. The morphological surface structure and functional groups of the PPy-coated fiber were studied using SEM (Scanning electron microscope) instrument. The prepared fiber was used for comparison of direct immersion (DI) and electroenhanced direct immersion solid-phase microextraction (EE-DI-SPME) of nicotine in human plasma and urine samples followed by gas chromatography flame ionization detector (GC-FID) determination. The effects of the influential experimental parameters on the efficiency of the DI-SPME and EE-DI-SPME methods, including the pH and ionic strength of the sample solution, applied Direct current (DC) voltage, extraction temperature and time and stirring rate, were optimized. Under the optimal conditions, the calibration curves for the DI-SPME-GC-FID and EE-DI-SPME-GC-FID methods were linear over the ranges of 0.1⁻10.0 μg mL^-1 and 0.001⁻10.0 μg mL^-1, respectively. The relative standard deviations (RSDs, n = 6) were found to be 6.1% and 4.6% for the DI and EE strategies, respectively. The LODs (limit of detection) of the DI-SPME-GC-FID and EE-DI-SPME-GC-FID methods were found to be 10 and 0.3 ng mL^-1, respectively. The relative recovery values (for the analysis of 1 µg mL^-1 nicotine) were found to be 91⁻110% for EE-DI-SPME and 75⁻105% for DI-SPME. The enrichment factors for DI-SPME and EE-DI-SPME sampling were obtained as 38,734 and 50,597, respectively. The results indicated that EE-SPME was more efficient for quantitation of nicotine in biological fluids. The developed procedure was successfully carried out for the extraction and measurement of nicotine in real plasma and urine samples.

Synthesis of graphene/DPA composite for determination of nicotine in tobacco products

In this contribution, the azo dye (E)-1-(4-((4-(phenylamino)phenyl)diazenyl) phenyl)ethanone (DPA) was combined with reduced graphene oxide (RGO) for the electrochemical modification of a pencil graphite electrode (RGO/DPA/PGE) surface. A series of electrochemical measurements were used for the characterization of the modified electrode surfaces. At the modified electrode, nicotine was irreversibly reduced. An obvious increase was observed in the reductive peak current of nicotine at the modified electrode, indicating the capability of the RGO/DPA composite to increase the electron transfer rate. The current was found proportional to the nicotine concentration in a range of 31 to 1900 μM, and the limit of detection (LOD) was calculated as 7.6 μM.

Simultaneous tuning of electric field intensity and structural properties of ZnO: Graphene nanostructures for FOSPR based nicotine sensor

We report theoretical and experimental realization of a SPR based fiber optic nicotine sensor having coatings of silver and graphene doped ZnO nanostructure onto the unclad core of the optical fiber. The volume fraction (f) of graphene in ZnO was optimized using simulation of electric field intensity. Four types of graphene doped ZnO nanostructures viz. nanocomposites, nanoflowers, nanotubes and nanofibers were prepared using optimized value of f. The morphology, photoluminescence (PL) spectra and UV-vis spectra of these nanostructures were studied. The peak PL intensity was found to be highest for ZnO: graphene nanofibers. The optimized value of f in ZnO: graphene nanofiber was reconfirmed using UV-vis spectroscopy. The experiments were performed on the fiber optic probe fabricated with Ag/ZnO: graphene layer and optimized parameters for in-situ detection of nicotine. The interaction of nicotine with ZnO: graphene nanostructures alters the dielectric function of ZnO: graphene nanostructure which is manifested in terms of shift in resonance wavelength. From the sensing signal, the performance parameters were measured including sensitivity, limit of detection (LOD), limit of quantification (LOQ), stability, repeatability and selectivity. The real sample prepared using cigarette tobacco leaves and analyzed using the fabricated sensor makes it suitable for practical applications. The achieved values of LOD and LOQ are found to be unrivalled in comparison to the reported ones. The sensor possesses additional advantages such as, immunity to electromagnetic interference, low cost, capability of online monitoring, remote sensing.

Determination of nicotine in tobacco products based on mussel-inspired reduced graphene oxide-supported gold nanoparticles

Polydopamine functionalized reduced graphene oxide-gold nanoparticle (PDA-RGO/Au) nanocomposites were successfully prepared by a simple and mild procedure. The PDA-RGO/Au nanocomposite is successfully formed in an aqueous buffer solution (pH 8.5) without using any reducing agent. FTIR confirmed the successful coating of PDA and informed the reduction of the surface functional groups of GO. The formation of reduced GO and Au NPs was further evidenced by UV-Vis and X-ray diffraction spectroscopy. This method is environmentally friendly and highly beneficial for the mass production of graphene-noble metal based nanocomposite. The as prepared PDA-RGO/Au nanocomposite could greatly enhance the electrochemical oxidation of nicotine. We fabricated an electrochemical nicotine sensor based on the prepared PDA-RGO/Au nanocomposite. The proposed nicotine sensor showed a wide detection range from 0.05 to 500 μM with a low detection limit of 0.015 μM. Moreover, the proposed nicotine sensor was also successfully applied for determination nicotine content in tobacco products.

Electrodeposition of Au nanoparticles on poly(diallyldimethylammonium chloride) functionalized reduced graphene oxide sheets for voltammetric determination of nicotine in tobacco products and anti-smoking pharmaceuticals

The principal objective of this study was to develop a sensitive and selective electrochemical sensor for nicotine detection based on a novel PDDA-RGO/Au nanocomposite.

Human colon adenocarcinoma HT-29 cell: electrochemistry and nicotine stimulation

Recently, it was demonstrated that colorectal cancer HT-29 cells can secrete epinephrine (adrenaline) in an autocrine manner to auto-stimulate cellular growth by adrenoreceptors activation, and that this secretion is enhanced by nicotine, showing an indirect relation between colorectal cancer and tobacco. The electrochemical behaviour of human colon adenocarcinoma HT-29 cells from a colorectal adenocarcinoma cell line, the hormone and neurotransmitter epinephrine, and nicotine, were investigated by cyclic voltammetry, using indium tin oxide (ITO), glassy carbon (GC) and screen printed carbon (SPC) electrodes. The oxidation of the HT-29 cells, previously grown onto ITO or SPC surfaces, followed an irreversible oxidation process that involved the formation of a main oxidation product that undergoes irreversible reduction, as in the epinephrine oxidation mechanism. The effect of nicotine stimulation of the HT-29 cells was also investigated. Nicotine, at different concentration levels 1, 2 and 15 mM, was introduced in the culture medium and an increase with incubation time, 0 to 3h and 30 min, of the HT-29 cells oxidation and reduction peaks was observed. The interaction of nicotine with the HT-29 cells stimulated the epinephrine secretion causing an increase in epinephrine release concentration, and enabling the conclusion that epinephrine and nicotine play an important role in the colorectal tumour growth.

Determination of nicotine and its metabolite cotinine in urine and cigarette samples by capillary electrophoresis coupled with electrochemiluminescence

In this paper, CE coupled with electrochemiluminesence (ECL) detection using a 76-μm Pt disk as working electrode was developed for nicotine (NIC) determination. The major metabolite of NIC is cotinine (COT), which has a similar tertiary amine structure to NIC. However, there is a carbonyl group attached in the structure of COT, which leads to the great decrease in ECL response. In order to improve the ECL response of COT, NaBH(4) was used for carbonyl reduction. After reduction, NIC and COT were separated and detected by CE-ECL. ECL response plotted with NIC concentration was linear between 5.0×10(-7) and 5.0×10(-5)  mol/L (81-8100 μg/L), with LOD of 5.0×10(-8)  mol/L (8.1 μg/L). The developed CE-ECL method was applied for NIC determination in urine and cigarette samples.