Multi-walled Carbon Nanotubes Sensor Research Articles

CTAC Self-Assembled Alkylated β-Cyclodextrin Loaded onto Functionalized MWCNTs Electrochemical Sensor for NP Detection.

Nonylphenol (NP) is an important fine chemical raw material and intermediate that is widely utilized in industry and may be distributed in aquatic ecosystems. Following its entry into the food and water cycles, it can subsequently enter the human body and potentially harm the human reproductive system. For the purpose of monitoring NP in water, it is thus essential to build a straightforward, affordable, and robust electrochemical sensor. Based on a two-step chemical modification proceeding and an electrostatic self-assembly effect, a double-modified β-cyclodextrin functionalized multiwalled carbon nanotube sensor (HE-β-CD-CTAC/F-MWCNTs) has been successfully constructed. It incorporates the excellent host-guest interaction ability of β-cyclodextrin and the high chemical activity of cetyltrimethylammonium chloride (CTAC), and the carbon nanotubes have an enormous particular surface area and strong electrical conductivity. The electrochemical oxidation reaction of NP with the sensor is controlled by a surface adsorption process of equal numbers of protons and electrons. In accordance with the optimized experimental parameters, the limit of detection (LOD) for the sensor is 0.13 μM, and it responds linearly to NP in the concentration range of 1-200 μM. Meanwhile, the sensor has excellent repeatability, stability, and immunity to interference. For the detection of NP in real water samples, the sensor also showed an excellent recovery rate (92.8%-98.5%) and relative standard deviation (1.16%-3.26%).

A rational study of transduction mechanisms of different materials for all solid contact-ISEs

The new era of solid contact ion selective electrodes (SC-ISEs) miniaturized design has received an extensive amount of concern. Because it eliminated the requirement for ongoing internal solution composition optimization and created a two-phase system with stronger detection limitations. Herein, the determination of venlafaxine HCl is based on a comparison study between different ion- to electron transduction materials (such as; multiwalled carbon nanotubes (MWCNTs), polyaniline (PANi), and ferrocene) and illustrating their mechanisms in their applied sensors. Their different electrochemical features (such as bulk resistance (Rb**), double-layer capacitance (Cdl), geometric capacitance (Cg), and specific capacitance (Cp)) were evaluated and discussed by using the Electrochemical Impedance Spectroscopy (EIS), Chronopotentiometry (CP), and Cyclic Voltammetry (CV) experiments. The results indicated that each transducer's influence on the proposed sensor's electrochemical characteristics is determined by their unique chemical and physical properties. The electrochemical features vary for different solid contact materials used in transduction mechanisms. The results confirm that the MWCNT sensor revealed the best electrochemical behavior with the potentiometric response of a near-Nernestian slope of 56.1 ± 0.8 mV/decade with detection limits of 3.8 × 10−6 mol/L (r2 = 0.999) and a low potential drift (∆E/∆t) of 34.6 µV/s. Also, the selectivity study was performed in the presence of different interfering species either in single or complex matrices. This demonstrates excellent selectivity, stability, conductivity, and reliability as a VEN-TPB ion pair sensor for accurately measuring VEN in its various formulations. The proposed method was compared to HPLC reported technique and confirmed no significant difference between them. So, the proposed sensors fulfill their solutions' demand features for VEN appraisal.

Functionalized Multiwalled Carbon Nanotubes for Highly Stable Room Temperature and Humidity-Tolerant Triethylamine Sensing.

Triethylamine (TEA) poses a significant threat to our health and is extremely difficult to detect at the parts-per-billion (ppb) level at room temperature. Carbon nanotubes (CNTs) are versatile materials used in chemiresistive vapor sensing. However, achieving high sensitivity and selectivity with a low detection limit remains a challenge for pristine CNTs, hindering their widespread commercial application. To address these issues, we propose functionalized multiwalled CNTs (MWCNTs) with carboxylic acid (COOH)-based sensing channels for ultrasensitive TEA detection under ambient conditions. Advanced structural analyses confirmed the necessary modification of MWCNTs after functionalization. The sensor exhibited excellent sensitivity to TEA in air, with a superior noise-free signal (10 ppb), an extremely low limit of detection (LOD ≈ 0.8 ppb), excellent repeatability, and long-term stability under ambient conditions. Moreover, the response values became more stable, demonstrating excellent humidity resistance (40-80% RH). Notably, the functionalized MWCNT sensor exhibited improved response and recovery kinetics (200 and 400 s) to 10 ppm of TEA compared to the pristine MWCNT sensor (400 and 1300 s), and the selectivity coefficient for TEA gas was improved by approximately three times against various interferants, including ammonia, formaldehyde, nitrogen dioxide, and carbon monoxide. The remarkable improvements in TEA detection were mainly associated with the large specific surface area, abundant active sites, adsorbed oxygen, and other defects. The sensing mechanism was thoroughly explained by using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and gas chromatography-mass spectrometry (GC-MS). This study provides a new platform for CNT-based chemiresistive sensors with high selectivity, low detection limits, and enhanced precision with universal potential for applications in food safety and environmental monitoring.

Detection of hydrogen peroxide vapor using flexible gas sensor based on SnO2 nanoparticles decorated with multi-walled carbon nanotubes

In this work, a high-sensitive flexible sensor based on the SnO2 nanoparticles decorated with the multi-walled carbon nanotubes (MWCNTs) was fabricated by a simple and cost-effective centrifugation method for hydrogen peroxide vapour (HPV) detection. Morphological, composition, structural, and HPV sensing studies of the film were thoroughly conducted. Scanning electron microscopy (SEM) revealed the presence of MWCNTs in the SnO2 material and energy dispersive x-ray (EDX) elementary analysis determined the actual concentration of carbon elements (24.47 wt%) in the SnO2:MWCNTs material with pronounced peaks of C, O, and Sn. Elemental mapping analysis showed the nearly homogeneous distribution of the elements while x-ray diffraction analysis (XRD) confirmed the diffraction peaks of tin oxide and carbon. The HPV sensing behaviour of the flexible SnO2:MWCNTs sensor was investigated in the temperature range of 25 °C–150 °C towards 1.5–56 ppm HPV under ultraviolet (UV) irradiation. The flexible sensor had a fairly high response (44) to 1.5 ppm of HPV concentration at room temperature (RT). The fabricated SnO2:MWCNTs based sensor was capable of detecting extremely low concentrations of HPV, thus being a potential candidate for use in real environments.

Electrochemical evaluation and determination of antiretroviral drug ganciclovir based on Fe-Cu/TiO2/ multi-walled carbon nanotubes sensor

Cyclic voltammetry, differential pulse voltammetry (DPV), and chronoamperometry were employed in this study to examine the ganciclovir’s electrochemical behavior on the surface of the modified electrode Fe-Cu/TiO2/multi-walled carbon nanotubes/carbon paste (Fe-Cu/TiO2/MWCNTs/CPE). As such, our proposed sensor proved to be stable while presenting a high sensitivity for the analysis of GCV under the physiological pH value (pH 7.4). Meanwhile, the calibration plots remained linear in the concentration, whose ranges were 25 nM to 40 µM (R2 = 0.996, n = 21) by DPV technique and 0.1 nM to 40 nM (R2 = 0.991, n = 9) through the hydrodynamic amperometry in stirred solutions under optimized conditions. A detection limit of 0.02 nM was obtained while the RSD prove to be 2.3% for six replicate detections of 10 μM GCV. To conclude, the recommended sensor ended up with great sensitivity and selectivity to determine GCV in real samples.

Moisture Diffusion Inside the BEOL of an FC-PBGA Package

Moisture diffusion into the back-end-of-line (BEOL) can be critical for the reliability of electronic devices. With the objective of studying moisture diffusion into critical areas, such as the silicon–organic substrate interfaces of a flip chip plastic ball grid array (FC-PBGA), a multitude of impedance sensors sensitive to moisture are integrated inside the BEOL of a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$17\times17$ </tex-math></inline-formula> mm silicon die. The sensors are read by a dedicated custom circuit that allows accurate characterization of the moisture with in situ spatial measurements. This article presents the results obtained by the experimental acquisition system on the FC-PBGA module under a high-relative humidity (RH) level of up to 75%. This study shows the moisture behavior of the multiwalled carbon nanotube (MWCNT) sensors inside the BEOL during absorption and desorption. The behavior initially follows Fick’s law, with a constant increase in the RH. For long-term tests of more than 400 h, an asymptotic behavior is observed; when the concentration of a sensor reaches a value close to saturation, a two-dimensional finite-difference method (2D FDM) is used to estimate the saturation value. Thanks to the large number of sensors distributed on the BEOL, we first detect, during an absorption test, an increase in the RH. This increase is due, first of all, to a lateral moisture front with a constant velocity of about <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$90 ~\mu \text{m}$ </tex-math></inline-formula> /h moving through the underfill. Then, after 30 h of storage, a more complex diffusion through the organic substrate occurs, affecting the BEOL.

Low‐Cost Data Glove Based on Deep‐Learning‐Enhanced Flexible Multiwalled Carbon Nanotube Sensors for Real‐Time Gesture Recognition

With advancements in artificial intelligence, wearable motion recognition systems based on flexible nanomaterial sensors exhibit excellent potential for harmonious human–machine interaction. However, the sensing stability and demand of large‐scale arrays limit the application of flexible nanomaterial sensors. Herein, a data glove system based on simple multiwalled carbon nanotube (MWCNT) sensors and a lightweight deep‐learning algorithm to achieve accurate gesture recognition is proposed. A regional‐crack mechanism is introduced through the microspine structure to enhance the strain sensitivity. Moreover, an efficient signal processing strategy based on an adaptive wavelet threshold function to improve the robustness and anti‐interference of signals obtained from MWCNT sensors, which exhibit strong generalization and can be used in other nanomaterial strain sensor. Based on the depth‐wise separable convolution, a novel hybrid convolutional neural network (CNN) long short‐term memory (LSTM) model for gesture recognition is constructed. The proposed model achieves an average accuracy of 97.5% and recognition accuracy of 30 gestures with an average recognition time of 2.173 ms based on only five sensors. The fabricated data glove is a promising platform for low‐cost and wearable human–machine interaction that can be directly interfaced in applications such as robotic hands, smart cars, and first‐person shooting games.

An innovated method to monitor the health condition of the thermoelectric cooling system using nanocomposite‐based CNTs

Many crucial applications use the thermoelectric coolers (TECs) system because they have some desirable properties, including durability, reliability, simple structure, and quietness. However, the performance of TECs is sensitive to any form of change and needs to be monitored constantly to ensure that they are working at their optimal. This paper proposes a novel approach for condition monitoring. This novel approach, unlike other attempts, does not need additional sensors but is directly carried out through the exploitation of the multi-wall carbon nanotubes (MWCNTs) piezoresistive property. For the suggested approach, a polyurethane (PU) resin was altered using various MWCNTs concentrations with the aim of constructing self-sensing nanocomposites sensors whose electrical conductivity is high. To investigate the electrical properties and microstructure of the constructed sensor, electrical resistance measurement, and scanning electron microscopy were used. From the results, it can be concluded that as the thickness increased, conductivity exhibited a monotonic increase. The peak electrical conductivity was 2.55 S.cm−1 for the 3.1 mm-thick MWCNTs sensors. This is approximately 5.1 above that of the 0.6 mm-thick MWCNTs sensors. Added to this, the MWCNT/PU sensors exhibited a high-temperature sensitivity with a negative temperature coefficient of resistance. The normalised resistance obtained from the sensor with the uppermost MWCNTs concentration is lower in comparison to the sensors with lower concentrations of MWCNTs. Additionally, the TEC cooling temperature influence on the tunnelling distance between MWCNTs was analytically estimated. This study's numerical results indicate that there is a potential correlation between TEC cooling generated temperature and the variations noted in the tunnelling distance between MWCNTs with an explicit impact on the general nanocomposite sensors changes in electric resistance when the TEC system is in service.

Health monitoring of composite single lap joints with highly sensitive MWCNTs film sensors

In this paper, a method with highly sensitive multi-wall carbon nanotubes (MWCNTs) film sensors was put forward to evaluate the health condition of glass fiber-reinforced composite single lap joints in real time. With this method, the single lap joint fracture can be predicted when the resistance change rate reached 1.11% to 5.89% approximately. Meanwhile, for the single lap joints, the reality can be found that the farther distance was from the interface to different layers, the more easily defect might emerge under the force introduced in the interface plane. And the stress in the middle area of the interface for the joint was greater than that in the edge when it was stretched. The results of experiments indicated that the effectiveness of MWCNTs sensors to monitor the health condition of the single lap joints was confirmed.

Pd-Decorated Multi-Walled Carbon Nanotube Sensor for Hydrogen Detection.

As hydrogen (H₂) gas is highly reactive and explosive in ambient atmosphere, its prompt detection in industrial areas is imperative to prevent serious accidents. In particular, high-performance H₂ sensors that can promptly detect even low-concentrations of H₂ gas are necessary for safety. Carbon nanotubes (CNTs) have a large surface area and a high surface-to-volume ratio, and therefore, they are suitable for use as sensing materials in gas sensors. Moreover, gold, platinum, and palladium are known to be excellent catalyst metals that increase reactivity with H₂ gas through the catalytic effect referred to as spill-over mechanism. In this study, a CNT felt sensor with a palladium (Pd) layer was fabricated, and its reactivity with H₂ was evaluated. The sensitivity of a CNT felt sensor to H₂ gas at room temperature was found to improve when coated with Pd layer.

Fabrication and analysis of integrated multifunctional MWCNTS sensors in glass fiber reinforced polymer composites

Glass Fiber Reinforced Polymer (GFRP) composites have been widely used in advanced engineering applications, mainly in the automotive and aerospace industries. Due to its anisotropic nature, the damage and failure detection in composites under real-time loading are very complicated. Focusing on this problem, Multi-Walled Carbon Nanotubes (MWCNTs) based strain sensor for Structural Health Monitoring (SHM) of Fibre Reinforced Polymer (FRP) composites is proposed in this research. This study primarily aims to detect induced flexural strains and damages occurring in the composites in real-time for which glass fibers coated with carboxy and amide functionalized MWCNTs have been used as sensors. The interactions between MWCNTs and fiber surface were confirmed with FTIR. Carbon fiber sensors have been used for comparison. The sensors were embedded into GFRP composites which were subjected to three-point bending tests coupled with electrical resistance measurement to correlate the induced strain and damages with the fractional change in resistance across sensors. The electromechanical test results indicated that MWCNT coated sensors in GFRP composites show promising piezoresistive sensing characteristics with good cyclic reproducibility that is significant for in-situ strain monitoring and damage detection. Overall the highest strain sensitivity was observed with amide functionalized MWCNT sensors. The electrical response to temperature cycles showed a reproducible behavior with −8% relative resistance change within the temperature range of −10 °C to 80 °C which also signifies multifunctional characteristics of developed sensors.

Real Time Sensing of Soil Potassium Levels Using Zinc Oxide-Multiwall Carbon Nanotube-Based Sensors.

There is a significant interest in the detection and monitoring of nutrient levels in agriculture farms. In this article, we report the fabrication of Zinc oxide (ZnO) modified multi-walled Carbon nanotube (F-MWCNT) sensor specifically developed for soil nutrient sensing. A thin layer of Valinomycin membrane was grown on the top of the F-MWCNT/ZnO nanocomposite active layer. The resulting composite structure Al/F-MWCNT/ZnO/Valinomycin was found to have a proportional impedance change with soil Potassium (K+) levels. The performance of the sensor was investigated in the 1- 5 kHz range. The impedance magnitude was found to linearly decrease from 2.5± 0.23 to [Formula: see text] range for K+ concentrations from 5 to 25 mM displaying a sensitivity of [Formula: see text]/mM with a correlation coefficient (R2) of 0.95744.

Monitoring Food Spoilage Based on a Defect-Induced Multiwall Carbon Nanotube Sensor at Room Temperature: Preventing Food Waste.

We have developed an electronic nose based on carbon nanotubes (CNTs) synthesized by using a plasma-enhanced chemical vapor deposition, aiming to be a convenient monitoring device for food spoilage. The prepared CNTs showed a crystalline structure and smooth surface with a diameter of 11.3 nm and a length of ∼10 μm. The Raman spectrum showed that the CNTs fabricated were multiwalled carbon nanotubes (MWCNTs). The characteristic graphite peak (G) observed at 1595 cm–1 in the Raman spectrum showed low intensity as compared to the defect peak (D) observed at 1330 cm–1, which referred to defect-induced points in CNTs. The CNTs were used to fabricate a sensor for ethylene gas produced by banana fruits for in situ measurements at room temperature. The sensor demonstrated good performance toward detecting the produced gas. The gas sensing signal was used as early indicators of the spoilage to help prevent food waste. The calibration curve was shown for the sensor responses evaluated at ripening days over 5 days. The sensor showed a response of 3.2% on the first day and increased to ∼7.0% by the third day and then gradually decreased. This sensor is appropriate for detecting the spoilage of food because it shows a good sensing response to a low level of produced gas from a single banana. Insight into food spoilage status of a specific level of gas shows its potential to be applied for quality assurance of food. The sensor sensitivity toward ethylene produced by a banana was confirmed based on the sensor response toward chemical ethylene gas.

Metal-decorated carbon nanotubes-based sensor array for simultaneous detection of toxic gases

Herein, we report a toxic gas detector based on an array of metal-decorated multiwalled carbon nanotubes (M-MWCNTs) sensors. The room temperature (20 °C) response of the sensors array towards NO2, H2S, NH3, and CO gases was investigated. The MWCNTs were decorated with transition metals, Pt, Ti, Ag, Ru, and Cu to enhance the sensitivity and selectivity of the carbon nanotubes to the toxic gases. The M-MWCNTs powders were deposited on gold electrodes and printed on flexible Kapton sheets to form the sensors array. CO exhibited the lowest resistance change response for all six sensors (five transition metal-decorated MWCNTs sensors and one pristine MWCNTs-based sensor), with the Ag-MWCNTs sensor exhibiting the highest response of 0.047–100 ppm CO. The Ag-MWCNTs also revealed the relatively highest sensitivity of 0.944 upon exposure to 100 ppm NH3. The Cu-MWCNTs sensor showed the highest sensitivity of 1.75 upon exposure to 10 ppm H2S, while the Pt-MWCNTs sensor showed the highest response of 1.96 upon exposure to 10 ppm NO2. A unique response pattern was generated for each gas that can be used for its identification. The experimental results were also compared to our previously reported density functional theory (DFT) calculations, revealing the same order of resistance change, thereby validating the use of DFT as a tool to predict the interaction properties and providing an in-depth understanding of the reducing/oxidizing gas electron transfer mechanisms.

Inkjet Printed Multi-Walled Carbon Nanotube Sensor for the Detection of Lead in Drinking Water

The heavy metal lead has been a pollutant in our environment for many centuries and at low concentrations, lead can damage the human central nervous system, liver, kidney, and cardiovascular system and cause physiological and neurological problems in developing children who are most susceptible to lead poisoning. Lead in drinking water is currently regulated in the United States by the Environmental Protection Agency (EPA) with a maximum contamination level (MCL) of 15 ppb and the World Health Organization (WHO) has a MCL of 10 ppb of lead. Researches have identified high levels of lead in drinking water samples across the globe and the neurological development of young children is of great concern. A need for a rapid, sensitive, selective, reproducible, and affordable sensor for the trace detection of lead in true drinking water samples is needed. The detection of Pb2+ was performed using an inkjet printed multi-walled carbon nanotube (IJP-MW-CNT) electrode employing Osteryoung square wave stripping voltammetry (OSWV) as the detection method. The MW-CNT ink was prepared in water using bile salts (BS) as a surfactant, which were washed out extensively with DI water before using the printed MW-CNTs as electrodes. The IJP-MW-CNT electrode was used as the working electrode with a platinum wire and glass capillary Ag/AgCl as auxiliary and reference electrode, respectively. The electrodes performance was optimized in 0.1 M acetate buffer (pH = 4.3) and had a linear range of 5 – 50 ppb (R2 = 0.98235) a sensitivity of 20.15 nA/ppb and a limit of detection (LOD) of 1.632 ppb for Pb2+. The analytical applicability of electrode was tested in a real drinking water sample (i.e.) Cincinnati tap water with a linear range of 15 – 70 ppb (R2 = 0.98752) a sensitivity of 2.654 nA/ppb and a LOD of 1.269 ppb for Pb2+. The IJP-MW-CNT electrode’s results are comparable between different electrodes, and reproducible using the same electrode multiple times. The electrode can be easily and quickly be fabricated without modifications or in-situ additives needed, which makes up-scale production a feasible option. The sensor has been shown to perform well in an environmental sample (Cincinnati tap water) without any sample preparation or changes.The IJP-MW-CNT electrode can be implemented for the affordable and rapid detection of lead on-site in true water samples.

Mode I interlaminar crack length prediction by the resistance signal of the integrated MWCNT sensor in WGF/epoxy composites during DCB test

The interlaminar peformance of composites palys an important role in the damage process of fiber reinforced composites. In-situ monitoring by an embedded sensor could avoid the sudden failure. This paper investigates the in-situ monitoring of mode I interlaminar crack propagationg behavior in woven glass fiber reinforced epoxy (WGF/epoxy) composite laminates. The resistance signal of multi-walled carbon nanotube (MWCNT) located in the mid-thickness of WGF/epoxy during the double cantilever beam (DCB) test is recorded. Relationship between the relative resistance and the interlaminar crack length is theoretically built and experimentally verified. Results show that the mode I crack propagating length can be successfully predicted by the relative resistance. A linear relationship between the interlaminar crack propagating length and the total relative resistance is found by the experimental and theoretical results.

Source Separation Using Sensor's Frequency Response: Theory and Practice on Carbon Nanotubes Sensors.

Nowadays, there is an increased demand in integrated sensors for electronic devices. Multi-functional sensors provide the same amount of data using fewer sensors. Carbon nanotubes are non-selectively sensitive to temperature, gas and strain. Thus, carbon nanotubes are perfect candidates to design multi-functional sensors. In our study, we are interested in a dual humidity-temperature sensor. Here, we present a novel method to differentiate at least two sources using the sensor’s frequency responses based on multiwall carbon nanotubes sensors. The experimental results demonstrate that there are temperature- or moisture-invariant frequencies of the impedance magnitude, and their values depend on the sensor’s geometry. The proposed measurement model shows that source-invariant frequencies of the phase can be also determined. In addition, the source separation method is generalized to other materials or sources enabling multi-functional sensors for environment monitoring.

A Mexacarbate Electrochemical Biosensor on Carbon Materials Based on a Functionalized Multiwalled Carbon Nanotube Modified Glassy Carbon Electrode

The commercial multi-walled carbon nanotube (MWCNT) was carboxylated using sulphuric and nitric acid and characterized by various techniques such as scanning eletron spectroscopy, Infra-red spectroscopy and atomic force microscopy. The acid functionalized multiwalled carbon nanotube serves as the effective matrix for the sensing of carbamate pesticide namely mexacarbate. The electrochemical oxidation of mexacarbate at GCE and MWCNT/GCE follows heterogeneous electron transfer reaction. Different experimental parameters such as the effect of scan rate and pH were studied. Rotating disk electrode voltammetry studies confirms the one-electron transfer reaction. The sensor calibration plot for mexacarbamate was constructed by means of pulse technique. The acid functionalized multiwalled carbon nanotube sensor was applied to real water sample with the recovery percentage of 85-89%.

In-Situ Monitoring of a Filament Wound Pressure Vessel by the MWCNT Sensor under Hydraulic Fatigue Cycling and Pressurization

As a result of the high specific strength/stiffness to mass ratio, filament wound composite pressure vessels are extensively used to contain gas or fluid under pressure. The ability to in-situ monitor the composite pressure vessels for possible damage is important for high-pressure medium storage industries. This paper describes an in-situ monitoring method to permanently monitor composite pressure vessels for their structural integrity. The sensor is made of a multi-walled carbon nanotube (MWCNT) that can be embedded in the composite skin of the pressure vessels. The sensing ability of the sensor is firstly evaluated in various mechanical tests, and in-situ monitoring experiments of a full-scale composite pressure vessel during hydraulic fatigue cycling and pressurization are performed. The monitoring results of the MWCNT sensor are compared with the strains measured by the strain gauges. The results show that the measured signal by the developed sensor matches the mechanical behavior of the composite laminates under various load conditions. In the hydraulic fatigue test, the relationship between the resistance and the strain is built, and could be used to quantitative monitor the filament wound pressure vessel. The bursting of the pressure vessel can be detected by the sharp increase of the MWCNT sensor resistance. Embedding the MWCNT sensor into the composite pressure vessel is successfully demonstrated as a promising method for structural health monitoring.

Sensitive, selective and simultaneous electrochemical detection of multiple heavy metals in environment and food using a lowcost Fe3O4 nanoparticles/fluorinated multi-walled carbon nanotubes sensor

Multiple heavy metals pollution in environment and food has become an ever-increasing concern and poses a serious threat towards humans and animals. To broad the multiple heavy metals detection, Fe3O4 nanoparticles, Fe3O4/multi-walled carbon nanotubes (Fe3O4/MWCNTs) and Fe3O4/fluorinated multi-walled carbon nanotubes (Fe3O4/F-MWCNTs) nanocomposites were synthesized by hydrothermal method and constructed as a simultaneous electrochemical sensor, respectively. Compared the catalytic performances of the three electrochemical sensors for the simultaneous detection of Cd2+, Pb2+, Cu2+, and Hg2+, the results showed that the Fe3O4/F-MWCNTs sensor demonstrated preponderant performance. It showed the sensitivity of 108.79, 125.91, 160.85, and 312.65 μA mM−1 cm−2 toward Cd2+, Pb2+, Cu2+, and Hg2+, respectively, which was obviously higher than that of Fe3O4/MWCNTs and Fe3O4. Additionally, the Fe3O4/F-MWCNTs sensor exhibited the wider linear detection ranges of 0.5–30.0, 0.5–30.0, 0.5–30.0, and 0.5–20.0 μM for Cd2+, Pb2+, Cu2+, and Hg2+, respectively. The limit of detections of the Fe3O4/F-MWCNTs sensor were 0.05, 0.08, 0.02, and 0.05 nM (signal to noise ratio of 3) for Cd2+, Pb2+, Cu2+, and Hg2+, respectively, fulfilling the governmental requests of the World Health Organization, China and Indian. The excellent agreement was recorded between the lowcost Fe3O4/F-MWCNTs sensor and typical methods (inductively coupled plasma mass spectrometry or atomic fluorescence spectrometry) in river water and soybean samples. Additionally, the sensor also exhibited excellent performances in selectivity, recovery, stability, and reproducibility. This proposal sensor provides a promising strategy to monitor multiple targets in the environment and food.