Carbon Nanotube Paste Research Articles

Electrochemical Determination of Tinidazole and Brucine Using Poly (l‐Glutamic Acid) Modified Carbon Nanotube Paste Electrode

AbstractThis study developed an electrochemical method for the selective and sensitive detection of Tinidazole (TZ) by modifying a bare carbon nanotube paste electrode (BCNTPE) with electrochemically polymerized l‐Glutamic acid (P(L‐GA)/MCNTPE). The modified carbon nanotube paste electrode (MCNTPE) achieved optimal detection with an irreversible peak in a 0.2 M phosphate buffer solution (PBS) at pH 3.5. Characterization of both the P(L‐GA)/MCNTPE and BCNTPE was carried out using techniques such as scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and linear sweep voltammetry (LSV). The sensor effectively identified possible interferences from different metals and organic compounds, with scan rate studies indicating that the reaction was controlled by diffusion. The effects of pH and concentration variations were also thoroughly investigated. The active surface area of the P(l‐GA)/MCNTPE and BCNTPE were found to be 0.471 cm2 and 0.217 cm2 respectively. The P(l‐GA)/MCNTPE displayed excellent electrochemical properties, with a limit of detection (LOD) of 0.06 µM and a limit of quantification (LOQ) of 0.2 µM, along with good reproducibility, repeatability, and stability. This study presents a P(l‐GA) MCNTPE that significantly enhances the sensitivity and selectivity for simultaneous detection of TZ and bare carbon nanotube (BCN). The improved electroactive surface area and electron transfer dynamics demonstrate its potential for practical applications in pharmaceutical analysis.

Simultaneous Electrochemical Detection of Catechol and Hydroquinone Based on a Carbon Nanotube Paste Electrode Modified with Electro-Reduced Graphene Oxide.

Effectively detecting catechol (CC) and hydroquinone (HQ) simultaneously is crucial for environmental protection and human health monitoring. In the study presented herein, a novel electrochemical sensor for the sensitive simultaneous detection of CC and HQ was constructed based on an electrochemically reduced graphene oxide (ERGO)-modified multi-walled carbon nanotube paste electrode (MWCNTPE). Scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and electrochemical techniques were utilized to characterize the sensing interface and investigate the sensing mechanism. Under the optimal detection conditions, the oxidation peak currents of CC and HQ show a good linear relationship with their concentrations in the range of 0.4-400 μM with a detection limit of 0.083 μM for CC and 0.028 μM for HQ (S/N = 3). Moreover, the sensor exhibits good performance and can be applied successfully in the simultaneous detection of CC and HQ in tap water samples and urine samples with satisfactory results, indicating its promising application prospects.

Simultaneous electrochemical detection of hydroquinone and catechol using a carbon nanotube paste electrode modified with electrochemically polymerized L-alanine

Simultaneous electrochemical detection of hydroquinone and catechol using a carbon nanotube paste electrode modified with electrochemically polymerized L-alanine

SIMULTANEOUS DETERMINATION OF ASCORBIC ACID, URIC ACID, AND DOPAMINE ON CARBON NANOTUBE PASTE ELECTRODE

Background: Ascorbic acid (AA), uric acid (UA), and dopamine (DA) play crucial roles in human metabolism. These substances coexist in biological fluids, and their levels are directly associated with various pathologies. A significant problem encountered in the direct and simultaneous electrochemical detection of AA, UA, and DA is that these species present very close oxidation potentials on most electrode materials, leading to an overlap in the voltammetric response. Aim: The main goal of this work was to determine the concentration of AA, UA, and DA in a natural water sample on a carbon nanotube paste electrode (CNTPE). Methods: All voltammetric measurements were performed on a µAutolab potentiostat/galvanostat (Metrohm) connected to an electrochemical cell of three electrodes: working, reference (Ag/AgCl, KCl3.0M), and auxiliary (platinum). The working electrode was handmade in our laboratory. The following proportions were used to prepare the paste: 50% CNT + 50% mineral oil and 65% CNT + 35% mineral oil. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used for the electroanalytical study. Results: The linear ranges for the simultaneous determination of AA, DA, and UA by DPV were: 0.45 – 1.0 mM, 50 – 200 ?M, and 10 – 90 ?M, respectively. The LODs of the proposed method for AA, DA, and UA were: 7.97 mM; 8.57 ?M, and 5.96 ?M, respectively. The relative standard deviations (RSD) were 4.6, 2.8, and 1.6% for 0.45 mM of AA, 50 ?M of DA, and 50 ?M of UA. Discussion: The oxidation mechanism of: AA, UA, and DA is a process that involves two electrons and 2 protons. Electrochemical detection of DA in the presence of high levels of AA on carbon-based electrodes becomes difficult due to the catalytic oxidation of AA by DA. For the three molecules, AA, UA, and DA, it is observed that the oxidation peak currents increased with increasing concentration. Conclusions: CNTPE allowed the separation of the oxidation peaks of the ternary mixture of AA, UA, and DA by cyclic voltammetry and, when associated with DPV allowed the simultaneous quantitative determination of AA, UA, and DA.

Improved Field Emission Properties of Carbon Nanotube Paste Emitters Using an Electrically Conductive Graphite Binder

Improved Field Emission Properties of Carbon Nanotube Paste Emitters Using an Electrically Conductive Graphite Binder

Development and validation of a platform based on 3D stochastic sensors for fast screening of whole blood and brain tissue for brain cancer

A novel stochastic platform was assembled by integrating a sensor based on single-wall carbon nanotube paste and ZnO modified with (Z)-N-[2-(4-hydroxyphenyl) ethyl] octadec-9-enamide for the enantioanalysis of two amino acids in whole blood and brain tissue tumor samples. The stochastic platform was utilized to obtain wide concentration ranges for the L-tryptophan, D-tryptophan, L-glutamine, and D-glutamine. The reported sensitivities for both isomers of glutamine exhibited a comparable magnitude order of 107. In contrast, among the four enantiomers, D-Trp displayed the highest sensitivity, measuring at 4.43 × 108. The limits of quantification were in the order of 1.00 × 10−18 mol•L−1. The efficacy of the platform was demonstrated through successful testing on biological samples. The advantages of using this type of platform for such analysis are the possibility of identifying and quantifying in one run different types of biomarkers as well as other substances of biological importance usually requested by medical doctors to be quantified, which can take the test from a fast-screening method to a fast diagnostic method. The analysis is performed within minutes, which is very important for illnesses such as brain cancer that can develop quickly in the body. The early detection of brain tumors can save lives. Furthermore, the portability of the developed detection technology makes it suitable for on-site analysis.

Ferrocene-Containing Gallic Acid-Derivative Modified Carbon-Nanotube Electrodes for the Fast Simultaneous and Selective Determination of Cytostatics from Aqueous Solutions

In this work, a ferrocene-containing gallic acid-derivative modified carbon-nanotube paste electrode (Gal-Fc-CNT), obtained through simple mechanical mixing, was studied for the fast simultaneous voltammetric determination of doxorubicin (DOX), capecitabine (CPB), and cyclophosphamide (CPP) as cytostatic indices based on their cumulative signals and the selective determination of DOX. The individual and simultaneous electrochemical behavior of DOX, CPB, and CPP, studied through cyclic voltammetry (CV) on the Gal-Fc-CNT paste electrode at various pHs and potential ranges, allowed for the development of a simple simultaneous determination method as a cytostatic index at a pH of 12 using square-wave voltammetry, which allowed for a better performance than reported electrodes for each individual cytostatic. A faster and selective detection of DOX, with a limit of detection of 75 ng·L−1, was achieved using square-wave voltammetry at a pH of 3. The good results obtained for the real tap water assessment indicated the applicability of the Gal-Fc-CNT paste electrode for practical applications (water samples).

A new strategy for the determination of dinobuton fungicide by square wave stripping voltammetry on the multi-walled carbon nanotube electrode

Dinobuton is a fungicide with a dinitrophenol group pesticide, and its electrochemical behavior was investigated by cyclic voltammetry (CV) and square wave stripping voltammetry (SWSV) on a multi-walled carbon nanotube paste electrode (MWCNTPE). First of all, optimum parameters such as pH, step potential, frequency, puls amplitude, deposition time and, deposition potential were specified by using SWSV on the MWCNTPE. In the negative potential scans, two cathodic peaks appeared at nearly −480 mV and –760 mV due to the nitro groups on the molecule and the second sharp one appeared at −760 mV (versus Ag/AgCl) was used for analytical purposes. The linear working range was found to be within 3.74–25.8 μM on the MWCNTPE by SWSV in pH 7.0 Britton Robinson (BR) buffer solution. The limit of detection (LOD) and limit of quantification (LOQ) values were found to be 0.73 μM and 2.43 μM, respectively. The interference study was conducted in the presence of some pesticides such as triasulfuron, azinphos-methyl, bromoxynil-octanoate, dialifos, fipronil, vinclozolin, iprodione, procymidone, and some selected metal ions withal. Furthermore, the proposed method was also applied to apple juice, tap water, and grape juice, and percent recoveries (%) were detected as 105.9 ± 4.3; 98.3 ± 0.9; 103.7 ± 2.5% with relative standard deviations of 4.0, 1.0, and 2.4%, respectively. On the other hand, percent relative errors were calculated as 5.90, 1.65, and 3.74%, respectively. High recoveries and low relative standard deviations indicate that the applicability of the proposed method in both matrix and real samples is satisfying.

Boosting field electron emission of carbon nanotubes through small-hole-patterning design of the substrate

High field emission of carbon nanotube (CNT) cold cathodes is realized by printing modified CNT paste on small-hole-patterned substrates. The field emission characteristics and stability of samples under DC continuous and pulse driving modes have been investigated. The results show that the maximum emission current of CNT emitters can be up to 45 mA at an electric field of 2100 V (7.0 V μm−1), corresponding to a high current density of 643 mA cm−2 under continuous mode. The cathodes also demonstrate stable electron emission without obvious attenuation. In pulse (10 μs and 200 Hz) mode, the peak current can reach 250 mA and the corresponding current density is 3.57 A cm−2 under an electric field of 14.0 V μm−1. The hole-patterned CNT cathode presents unique advantages in field emission current, stability and especially endurance of high electric field. This work makes it possible to fabricate highly efficient emission CNT cold electron sources, which have broad application prospects in vacuum electronic devices requiring both large current and high current density.

A Nanocomposite Paste Electrode Sensor for Simultaneous Detection of Uric Acid and Bisphenol A Using Zinc Hydroxide Nitrate-Sodium Dodecylsulfate Bispyribac.

The fabrication of a zinc hydroxide nitrate-sodium dodecylsulfate bispyribac modified with multi-walled carbon nanotube (ZHN-SDS-BP/MWCNT) paste electrode for uric acid and bisphenol A detection was presented in this study. Electrochemical impedance spectroscopy, chronocoulometry, square-wave voltammetry, and cyclic voltammetry were all used to examine the electrocatalytic activities of modified paste electrodes. The modified electrode's sensitivity and selectivity have been considered in terms of the composition of the modifier in percentages, the types of supporting electrolytes used, the pH of the electrolyte, and square-wave voltammetry parameters like frequency, pulse size, and step increment. Square-wave voltammetry is performed by applying a small amplitude square-wave voltage to a scanning potential from -0.3 V to +1.0 V, demonstrating a quick response time and high sensitivity. The ZHN-SDS-BP/MWCNT sensor demonstrated a linear range for uric acid and bisphenol A from 5.0 µM to 0.7 mM, with a limit of detection of 0.4 µM and 0.8 µM, respectively, with good reproducibility, repeatability, and stability as well. The modified paste electrode was successfully used in the determination of uric acid and bisphenol A in samples of human urine and lake water.

Effects of Interfacial Electron Transport on Field Electron Emission from Carbon Nanotube Paste Emitters.

Field electron emission from carbon nanotubes (CNT) is preceded by the transport of electrons from the cathode metal to emission sites. Specifically, a supporting layer indispensable for adhesion of CNT paste emitters onto the cathode metal would impose a potential barrier, depending on its work function and interfacial electron transport behaviors. In this paper, we investigated the supporting layer of silicon carbide and nickel nanoparticles reacted onto a Kovar alloy (Fe-Ni-Co) cathode substrate, which has been adopted for reliable CNT paste emitters. The X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and electrical conductivity measurements showed that the reaction of silicon carbide and nickel nanoparticles on the Kovar metal strongly depends upon the post-vacuum-annealing conditions and can be classified into two procedures of a diffusion-induced reaction (DIR) and a diffusion-limited reaction (DLR). The prolonged annealing at 750 °C for 5 h before the main annealing of the CNT paste emitters at 800 °C for 5 min led to the DIR that has enhanced the Ni silicide phase and a lower potential barrier for the interfacial electron transport, resulting in increased and weakly temperature-dependent field electron emission from the CNT paste emitters. On the other hand, the DLR with only the main anneal of the CNT paste emitters at 800 °C for 5 min gave rise to a higher potential barrier for the electron transport and so lower and strongly temperature-dependent field electron emission. From the results of the interfacial electron transport for the DIR and DLR mechanisms in the CNT paste emitters, we concluded that the ambient temperature dependency of field electron emission from CNT tips in the moderate range of up to 400 °C, still controversial, is mainly attributed to the supporting layer of the CNT emitter rather than its intrinsic electron emission.

Neurotransmitter Assay for In Vivo Nerve Signal Detection Using Bismuth Immobilized on a Carbon Nanotube Paste Electrode.

Voltammetric analysis of the neurotransmitter epinephrine (EP) was performed using bismuth immobilized on a carbon nanotube paste electrode (BCE), whose properties were compared with those of a carbon nanotube paste electrode (CE). BCE was found to be more efficient in detecting EP. The analytical parameters used were 0.3 V square-wave (SW) stripping voltammetric amplitude, 400 Hz frequency, -0.8 V initial potential, and 0.015 V increment potential. The optimized conditions were applied to an assay of a carp's front fin. A BCE was inserted into a carp's front fin muscle, and a stimulus was given every 50 s. This circuit is easy to use and does not require much analytical preparation time. The working electrode is miniscule, and its detection limit is very low. The in vivo muscle's chronoamperometric nerve currents were analyzed. These results have potential for applications in medical diagnostics, pharmaceuticals, interface controllers, and other fields.

Ionic liquid-modified multi-walled carbon nanotube paste electrode for cadmium and lead ion determinations

The detection of trace heavy metal ions is important in monitoring water quality, a vital freshwater source. This study presents the preparation of a multi-walled carbon nanotube (MWCNTs) paste electrode using a pasting mixture of 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid ([Bmim][PF6] IL) and paraffin oil for the determination of Cd2+ and Pb2+. Scanning electron microscopy, Fourier-transform infrared spectroscopy, and Raman spectroscopy were applied to characterize the paste composites. The electrochemical behavior of the fabricated electrodes was analyzed by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. The [Bmim][PF6]-MWCNTs electrode showed enhanced sensitivity for Cd2+ and Pb2+ detections over linear sweep anodic stripping voltammetry (LSASV) performances. Experimental results showed that the MWCNTs-IL-1 electrode using a pasting mixture of 10 μL of [Bmim][PF6] and 190 μL of paraffin oil was the most suitable for Cd2+ and Pb2+ determinations. The LSASV conditions for Cd2+ and Pb2+ analysis at the MWCNTs-IL-1 electrode were optimized, including the deposition potential, deposition time, and pH of the working solution. The stripping peak currents were linearly correlated with the concentration ranges of Cd2+ (1–35 μg/L) and Pb2+ (1–90 μg/L) for both individual and simultaneous determinations. The MWCNTs-IL-1 electrode exhibited high repeatability, reproducibility, and stability over a 30-day storage period. The real applicability of the MWCNTs-IL-1 electrode was demonstrated by successful determinations of Cd2+ and Pb2+ concentrations in tap water and surface water samples, which agreed with the results obtained by inductively coupled plasma mass spectrometry.

A sensitive voltammetric and density functional theory calculations analysis for the direct interaction of sulfide ion with the multiwalled carbon nanotube

A sensitive and simple cyclic voltametric method was investigated for the direct electrochemical determination of sulfide using multiwalled carbon nanotube paste electrode (MWCNTPE). The sulfide exhibited a distinct and remarkable direct oxidation peak at about 0.56 V in a solution containing sodium chloride as a suitable supporting electrolyte. The effect of voltametric behavior of sulfide was also studied in various supporting electrolyte. Among this sodium chloride containing solution showed a well-defined oxidation peak current as compared to the other supporting electrolyte. The direct oxidation behavior of sulfide in sodium chloride solution was mainly attributed to the less hindrance effect of the electrolyte anions on the surface of electrode. Under optimized condition the oxidation peak current values were found to increase in a linear way with increasing sulfide concentration in the range from 1 × 10−7 to 3 × 10−5 M (R2 = 0.9985). The detection limit (DL) was calculated to be 4 × 10−8 M for the sulfide concentrations. The developed method showed excellent selectivity towards the voltametric determination of sulfide as compared to other competing ions like Br−, NO3−, F−, PO43−, NO2−, I−, CH3COO− present in the solution. Moreover, the method demonstrated good and reproducible results with relative standard deviation (RSD) of 3.8% after 40 successive measurements. The method was successfully applied for determination of sulfide in local tap water samples without any matrix effect. Meanwhile to support the voltametric behavior of sulfide, density functional theory (DFT) calculations were performed at ωB97XD/6-31G(d,p) level of theory to get deep insight into the electronic properties of MWCNT and adsorbed analytes (sulfide) using Gaussian 09 package. The highest interaction energy and the decrease in energy gap of multiwall carbon nanotube with sulfide (MWCNT-S2-) complex are consistent with the highest sensing behavior of MWCNT towards sulfide ion in experimental results.

Electrochemical Analysis of the Antihistamine Drug Cetirizine at a Poly(Glutamine) Modified Carbon Nanotube Paste Electrode

AbstractAn inexpensive and efficient sensor was developed for the electrochemical analysis of the antihistamine drug cetirizine (CTZ). The active sites on the bare carbon nanotube paste electrode surface were improved by the electropolymerization of poly(Glutamine). This modified electrode enhances the electrochemical response of the examining molecule. The study was conducted using a cyclic voltammetry technique in phosphate buffer saline of physiological pH 7.0 at a scan rate of 0.1 V/s. The developed electrode possesses increased conductance and declined overpotential for the determination of CTZ. At the optimized conditions, the detection limit was evaluated by obtaining the current response of CTZ at the varied concentration, and it was obtained as 0.12 μM. The poly glutamine modified carbon nanotube paste electrode was successfully applied to determine CTZ in tablet and human urine samples with acceptable recovery.

Improved heating method for shape-memory alloy using carbon nanotube and silver paste

Shape memory alloys (SMAs) have a special ability to remember their initial shape and return from operating temperature. For this special ability, there are many studies in the field of smart wearables to replace rigid, heavy, and large electric actuators with SMAs that can be a fabrication. The usual operating method of the SMA is heating the SMA by direct Joule heating with electricity. Although direct Joule heating is fast and easy, there is overshooting, unstable, and high-power consumption. For these issues to use the SMA as textile actuators, this research suggested a heating method with silver paste required lower power consumption and coating the basic fabric with carbon nanotubes (CNTs) to support heating stability and heat uniformity. The heating method evaluated the efficiency of heat by comparing direct heating and silver layer heating and the uniformity of heat with the infrared images of whether CNTs coated or not. In this research, we reached higher temperatures with lower power than direct Joule heating using wearable heaters manufactured using silver paste. In addition, we confirmed that coating the basic fabric with carbon nanotubes reduce the temperature imbalance, and improved the heating stability. This research is expected that SMA will be used as a wearable actuator to help develop wearable devices that can move.

Electrochemical detection and quantification of catechol based on a simple and sensitive poly(riboflavin) modified carbon nanotube paste electrode

In the present research work, selective and sensitive catechol (CT) detection and quantification were shown in the presence of resorcinol (RS) in 0.2 M phosphate buffer (PB) solution by preparing a low-cost, simple, and green carbon nanotube paste electrode (CNTPE) surface activated with electropolymerized riboflavin (PRF). The morphological, conductivity, and electrochemical features of the modified electrode (PRFMCNTPE) and bare carbon nanotube paste electrode (BCNTPE) materials were analyzed using electrochemical impedance spectroscopy (EIS), field emission scanning electron microscopy (FE-SEM), cyclic voltammetry (CV), and differential pulse voltammetry (DPV). The PRF-activated electrode displays outstanding sensitivity, stability, selectivity, reproducibility, and repeatability for the redox feature of CT with improved electrochemical current and declined electrochemical potential compared to BCNTPE. The peak currents of CT are correlated to the different CT concentrations (CV method: 6.0–60.0 μM & DPV method: 0.5–7.0 μM), and the obtained detection limit (DL) and quantification limit (QL) are found to be 0.025 μM and 0.085 μM (CV method) and 0.0039 μM and 0.0132 μM (DPV method), respectively. The prepared PRFMCNTPE material was advantageous for the examination of CT in environmentally important tap water sample as a real-time application.

Electrolyte drink analysis by electronic tongue using carbon nanotube paste electrodes

Electrolyte drink becomes very popular nowadays that drinking aid in rehydration which mostly contain water, sugar, and electrolytes (Na, K, Mg, Ca ions). In this work, several electrolyte drinks including M sport, M-plus, Sponsor, Sponsor citrus, Gatorade were analyzed by electronic tongue comparing to mineral and tap water. Non-specified electrode array used in electronic tongue was fabricated by mixing carbon nanotube with copper oxide or several types of metal-phthalocyanine (MPc) including MnPc, FePc, CoPc and ZnPc. The electronic tongue system was developed by using automatic electrochemical measurement setup with rotating eight beaker tray together with electrode holder slider in up and down position. This system was controlled by Arduino with developed python protocol. The cyclic voltammetry measurement indicated an ion current flow between electrodes with peaks in some cases. These cyclic graphs were converted to the specific line graphs for further analysis. Principle component analysis was used to classify the signal into several distingue groups. It was found that with the first two principal components, the mineral water and tap water can be totally separate from the other electrolyte drinks with total variation of about 77%.

Electroanalytical Detection of Indigo Carmine in Presence of Tartrazine Using a Poly(dl-phenylalanine) Modified Carbon Nanotube Paste Electrode

Certain dyes are deleterious to the biological system, including animals and plants living in the water sources, soil sources, and so on. Thus, the analysis of these dyes requires a potent, quick, and cost-effective approach to the environmental samples. The present research work shows a modest, low-cost, and eco-friendly electrochemical device based on poly(dl-phenylalanine)-layered carbon nanotube paste electrode (P(PAN)LCNTPE) material for indigo carmine (ICN) detection in the presence of tartrazine. The cyclic voltammetric, field emission scanning electron microscopy, and electrochemical impedance spectroscopic methods were operated for the detection of the redox nature of ICN and electrode material surface activities, respectively. In better operational circumstances, P(PAN)LCNTPE provided better catalytic activity for the redox action of ICN than the bare carbon nanotube paste electrode. The P(PAN)LCNTPE showed good electrochemical activity during the variation of ICN concentrations ranging from 0.2 µM to 10.0 µM with improved peak current, and the limit of detection was about 0.0216 µM. Moreover, the P(PAN)LCNTPE material was performed as a sensor of ICN in a tap water sample and shows adequate stability, repeatability, and reproducibility.

Electrocatalytic response of chitosan modified multiwall carbon nanotube paste electrode toward iodide: A facile voltammetric method for determination of iodide in biological sample

Herein we report, a simple operable, sensitive, and highly selective, voltammetric method for the determination of iodide (Iˉ) using chitosan modified multiwall carbon nanotube paste electrode (chit-MWCNTPE). It is established that chit-MWCNTPE exhibited a pronounced response toward Iˉ oxidation. The peak potential of Iˉ is recorded at 0.69 V vs SCE. The conditions such as scan rate (V.s−1), accumulation time (ta), and pH are thoroughly optimized for the voltammetric determination of Iˉ. A wide range linear response is observed between oxidation peak current and Iˉ concentration (0.1–100 μM). The limit of detection (LOD) for Iˉ on chit-MWCNTPE is found to be 0.03 μM. The developed method is highly selective for Iˉ detection in the presence of various interfering ions. The method is successfully applied for the determination of Iˉ in urine samples. The method has high selectivity for Iˉ detection at comparably low potential as well as amiable LOD and Linear range.