CNT Sensor Research Articles

Spin Polarized Chemiresistive CNT Sensors for Selective Detection of Explosive Molecules

Spin Polarized Chemiresistive CNT Sensors for Selective Detection of Explosive Molecules

Physico-Chemical Study of the Anti-Diabetic Drug of [BzN-EJJ-amide] for Treatment Type2 Diabetes Using CNT Sensor by Drug Delivery Method

Physico-Chemical Study of the Anti-Diabetic Drug of [BzN-EJJ-amide] for Treatment Type2 Diabetes Using CNT Sensor by Drug Delivery Method

A Voltammetric Biosensor Based on Glassy Carbon Electrode Modified with DsDNA/ZIF-8/CNT for Determination of Malathion

In this work, we constructed an electrochemical biosensor based on a glassy carbon electrode modified by dsDNA/ZIF-8/CNT for sensitive and selective measurement of malathion (MAL). First, we investigated the interaction between MAL and salmon sperm dsDNA by computational (molecular docking) and experimental (UV-visible spectroscopy, and electrochemistry) methods. Then, we prepared the ZIF-8/CNT sensor and immobilized dsDNA on it. The ZIF-8/CNT was characterized by fourier transform infrared spectroscopy, X-ray scattering spectroscopy, and field-emission scanning electron microscopy. We optimized the factors affecting the electrochemical response of MAL and immobilization of the dsDNA on the surface of ZIF-8/ CNT/GCE, such as microliter of ZIF-8/CNT, concentration of the dsDNA and the time required for immobilization of dsDNA on the surface of ZIF-8/CNT-GCE, the effect of buffer pH on the MAL accumulation, the effect of MAL accumulation time, and the effect of pH the measurement solution. After optimizing the effective parameters, we drew the calibration curve using the differential pulse voltammetry (DPV) technique and obtained the concentration range of 0.20-50.00 μM with a detection limit of 1.0 nM. Furthermore, the RSD% for five consecutive tests of 2.00 μM MAL was obtained 2.4%. Also, the dsDNA/ZIF-8/CNT sensor showed good recovery in fruit samples.

DNA-Wrapped CNT Sensor for Small Nucleic Acid Detection: Influence of Short Complementary Sequence

DNA-Wrapped CNT Sensor for Small Nucleic Acid Detection: Influence of Short Complementary Sequence

The Curious Case of Geologic Hydrogen: Assessing its Potential as a Near-Term Clean Energy Source

Dr. Emily Yedinak currently serves as an ARPA-E Fellow. Her interests include employing life cycle analyses to capture the environmental impact of clean energy innovations, supply chain management related to materials required in green energy technology, and hydrogen production and storage. She has a B.S. in Chemical Engineering and a B.S. in Chemistry from Rose-Hulman Institute of Technology. After graduating, she was a Fulbright student finalist conducting research on CNT and electroceramic composite electrochemical sensors. She also has a PhD in Materials Science and Nanoengineering from Rice University where she designed and scaled reactors for CNT production from methane pyrolysis.

Investigations of the influence of geometrical parameters of carbon nanotube material for sensor and MEMS applications

The mechanical, electrical, and thermal behavior of CNT thin films permits reliable measurements in severe environments of high temperature, load, vibration, and humidity. These properties made them promising materials for sensor applications in automotive, air-craft engines, medical instruments, and industrial control systems. Scarce work was done on the simulation of I-V characteristics and sensitivity of the CNT thin film strain sensor. To gather more information about these, the simulation of the CNT sensor device is carried out SILVACO-ATLAS TCAD simulation package. The influence of geometrical parameters like length, width, and thickness on the I-V characteristics, change in resistance, and sensitivity of the sensor material was studied. The results showed that the currents increased for every model on an average of 95% and 195% and the change in resistance decreased by almost 96% and 194% for the respective change in thickness of the material from 1 μm to 2 μm and 3 μm. The currents increased on an average of 100% and 200% and the change in resistance due to strain decreased almost 100% and 200% for the respective change in width of the material from 10 μm to 20 μm and 30 μm. The current decreased by nearly 138% and 282% and the change in resistance due to strain increased by almost 138% and 282% for the respective change in length of the material from 10 μm to 20 μm and 30 μm. The work concludes that the model with the combination of length 30 μm, width 10 μm, and thickness of material 1 μm gives an optimum result of cathode currents 0.0550 mA, 0.0453 mA, and 0.000894 mA and the highest value of change in resistance 9.13 MΩ.

Innovative strategy based on novel Ti3C2Tx MXenes nanoribbons/carbon nanotubes hybrids for anodic stripping voltammetry sensing of mercury ion

Anodic stripping voltammetry (ASV) is presently the most widely used method for mercury ion (Hg2+) detection, but it generally needs an electrodeposition step. As a new star nanomaterial, MXenes shows greatly important applications in electrochemical sensing. In this work, by preparing Ti3C2Tx MXenes nanoribbons/carbon nanotube (Ti3C2TxR/CNT) nanohybrids to modify glassy carbon electrode (GCE) as sensing platform, an innovative strategy without electrodeposition was proposed for the sensitive detection of Hg2+. The results show that Ti3C2TxR exhibits spontaneous adsorption and reduction capability towards Hg2+, which can make Hg2+ self-reduced and preconcentrated on the electrode surface. Coupled with the excellent electronic properties of CNT, an electrodeposition-free and sensitive ASV sensor was constructed, and Ti3C2TxR/CNT/GCE can exhibit superior sensing performances for Hg2+ analysis with a low detection of limit (5.2 nM) and wide linearity range (0.01–7.0 μM). This work offered a new direction for MXenes nanomaterials and Hg2+ detection.

Fabrication of Inkjet-Printed Carbon Nanotube for Enhanced Mechanical and Strain-Sensing Performance

This paper presents fabrication of inkjet-printed carbon nanotube film on flexible substrate for wearable electronics applications. The density of CNT films is optimized by droplet spacing (DS) and multiple passes to provide the best strain behavior. It is found that low-density carbon nanotubes have fewer conductive pathways resulting in less change and low GF under applied strain. Conversely, high-density carbon nanotubes have more conductive paths, and they are not easily broken under strain, resulting in poor strain-sensing ability. The inkjet printing process can adjust uniformity and density of CNT film through DS and multiple passes to optimize its strain characteristics. The highest GF of 3.36 was obtained under strain ranging from 71 to 3128 με when CNT printed by DS of 23 μm and 20 passes. The relative change in resistance under various strains, ranging from 71 to 3128 με, had a stable peak value for each 20 strain/release cycle which proved its repeatability and stability. Furthermore, inkjet-printed CNT sensors monitored human movement of various joints and distinguished bending angle demonstrating its potentially practical application in wearable electronics.

Application and dynamical behavior of CNTs as fluidic nanosensors based on the nonlocal strain gradient theory

In this paper, the dynamical characteristics of CNT sensors with an encapsulated liquid is studied. The governing equation with nonlocal and strain gradient parameters is first derived by Hamilton’s principle, and the classical and higher-order boundary conditions of a simply supported beam are then obtained by a weighted residual approach. A differential quadrature method was used to obtain the numerical solutions of the sixth-order governing differential equation. The effects of the fluid, moment of inertia, non-classical boundary conditions, vibrational mode, nonlocal parameter, and strain gradient parameters on the frequency were studied. Although it is showed that it was difficult to identify the fluid type or density only based on the frequencies of the nanosensors, the results further verified that relative frequency shift percent (RFSP), nonlocal frequency shift percent (NFSP), and strain gradient frequency shift percent (SFSP) which depend on the fluid type, the nonlocal and strain gradient parameters can provide complementary information. It is concluded that measurements of the RFSP, NFSP, and/or SFSP can effectively be used to determine the density of the fluid in the nanosensors. It is hoped that our models can be effectively used to predict sensors’ responses and can allow the optimization of parameters before experiments.

A Biomimetric Lactate Imprinted Smart Polymers as Capacitive Sweat Sensors

This paper demonstrates a non-enzymatic biomimetric flexible sweat sensor. Fabricated by multi-layered assembly, the layers comprised a conductive nanoporous carbon nanotube-cellulose nanocrystals (CNC/CNT) porous films entrained with poly (N-isopropylacrylamide) (pNIPAM) based microgel. The pNIPAM microgels based sensor films are effective for detection of ionic strength. The pNIPAM microgels coated with lactate imprinted poly (aniline/phenylboronic acid) (pANI/PBA) moieties switch off their responsivity to NaCl and instead effectively respond to lactate. As such, the printed pNIPAM microgels have been demonstrated as flexible capacitive sensor for multiplex detection of electrolyte (e.g. NaCl) and lactate levels in sweat analysis. The linear concentration range obtained for pNIPAM @CNC/CNT sensor in response to NaCl was 3–80 mM, with a limit of detection (LOD) of 0.23 mM NaCl. The lactate imprinted pANI/PBA- pNIPAM @CNC/CNT sensor resulted in a linear range of 1 mM-25 mM, and a LOD of 0.10 mM, an order of magnitude higher than the non-imprinted form. For both analytes, the sensor precision ranged from 0.5-5.0%, indicative of the overall reliability and validity. The fabricated flexible sensors were demonstrated to be effective in quantitation of electrolytes (principally NaCl) and lactate in a real sweat sample.

Analytical Prediction of Highly Sensitive CNT-FET-Based Sensor Performance for Detection of Gas Molecules

In this study, a set of new analytical models to predict and investigate the impacts of gas adsorption on the electronic band structure and electrical transport properties of the single-wall carbon nanotube field-effect transistor (SWCNT-FET) based gas sensor are proposed. The sensing mechanism is based on introducing new hopping energy and on-site energy parameters for gas-carbon interactions representing the charge transfer between gas molecules (CO2, NH3, and H2O) and the hopping energies between carbon atoms of the CNT and gas molecule. The modeling starts from the atomic level to the device level using the tight-binding technique to formulate molecular adsorption effects on the energy band structure, density of states, carrier velocity, and I-V characteristics. Therefore, the variation of the energy bandgap, density of states and current-voltage properties of the CNT sensor in the presence of the gas molecules is discovered and discussed. The simulated results show that the proposed analytical models can be used with an electrical CNT gas sensor to predict the behavior of sensing mechanisms in gas sensors.

Composition of CNT and WO<sub>3</sub> nanoplate: synthesis and NH<sub>3</sub> gas sensing characteristics at low temperature

WO3 nanoplate synthesized by acid precipitation method was composited with commercial carbon nanotube with different weight percents (0.5, 1.0, and 1.5 wt% of CNT). The ammonia gas sensing characteristics of composite materials at low temperature (50°C) were investigated and compared with that of pristine materials (WO3 nanoplate, commercial carbon nanotube). The results showed that the composition enhanced the gas sensing properties in comparison with the pristine carbon nanotube-based sensor and more stable than pristine WO3 nanoplate-based sensor. The response of gas sensors to 30 ppm of ammonia got the highest value of 45% in 0.5 wt%-CNT sensor – enhanced 100 times in comparison with carbon nanotube-based sensor. The calculated limit of detection of 0.5 wt%CNT/WO3 sensor was at sub-trace-level of 3 ppb. This enhancement shows the high applicability of composite materials in gas sensor working at room temperature.

Enhanced response and improved selectivity for toxic gases with functionalized CNT thin film resistors

ABSTRACTHigh surface area of CNTs makes them an extremely sensitive detection element for a wide variety of analytes present in minute quantities of ppb and ppm levels. CNTs does not inherit selectivity for a particular gas/analyte, it can be introduced in CNT based gas sensor by means of functionalization, along with improvement in gas sensor's response. Effects of Carboxylated group and gold nano-particles were studied on the response of CNT sensors towards toxic gases such as NO2 and NH3. Gold nanoparticles have found to enhance the response for NO2 and NH3, while oxygenated functional have brought selectivity towards NH3.

Strain sensing of printed carbon nanotube sensors on polyurethane substrate with spray deposition modeling

Abstract The unique mechanical and electrical properties of carbon nanotubes represent a potential for developing a piezo-resistive strain sensor for smart structures. This study demonstrated a new processing technique of multi-walled carbon nanotube strain sensors with tunable strain gauge factors. A digital-controlled spraying-evaporation deposition process that uses a 12-array bubble jet nozzle attached to a digital x-y plotter combined with a heated substrate which induces evaporation of the solvent was developed. The demonstrated fabrication technique has advantages such as high efficiency, low cost and scalability. The experimental results showed that the prepared carbon nanotube strain sensors are capable of measuring strains through highly linear electrical resistance change. The gauge factors of the fabricated strain sensors could be easily tuned by controlling the number of printed layers of carbon nanotubes. In this work, strain sensors were fabricated with printed carbon nanotube layers ranging from 10 to 50 layers and strain gauge factors were measured in a range of 0.61–6.42. Moreover, the dynamic loading test results revealed that the printed carbon-nanotube strain sensors exhibited excellent durability and stability at cyclic strain. These superior sensing capabilities of the fabricated CNT sensors make them a promising candidate for wearable smart electronics and structural health monitoring applications.

CNT sensors that can detect toxic gases

CNT sensors that can detect toxic gases

Exploitation of Giant Piezoresistivity – CNT Sensors Fabricated with a Wafer-level Technology

Here we present a holistic wafer-level approach for the fabrication of highly sensitive electromechanical transducers, using the intrinsic piezoresistive effect of enriched semiconducting single-walled carbon nanotubes (SWCNTs). Therefore membrane based demonstrators were fabricated on 150mm wafers using MEMS compatible micromachining. Carbon nanotube field-effect transistors were positioned at membrane sites with the highest strain upon pressure driven actuation. The giant piezoresistive effect of SWCNTs was proved and quantified. We derived the gauge factor to be more than 600, which is significantly higher than for common silicon strain gauges.

Highly sensitive and selective carbon nanotube-based gas sensor arrays functionalized with different metallic nanoparticles

We present the fabrication and characterization of selective CNT-based gas sensor, which is capable of discriminating between four test gases (NH3, ethanol, CO and CO2). Different metals are utilized in order to alter the response of each sensing element towards the different test gases. We discuss as well the different possibilities for metal combinations in the sensor arrays. The optimum combination between the metallic nanoparticles is obtained through an efficient and quick framework. We study the effect of the thickness of the CNT thin-film on the reproducibility and the response of the sensor array. Furthermore, we investigate the response of the fabricated CNT sensor array towards a mixture of two gases. Such kind of characterization was performed by exposing the CNT sensor array to a mixture of (NH3, ethanol) and (NH3, CO) at different ratios for each mixture. We show that the response towards a mixture of two gases lies in the plane between the data points of each gas separately.

Enhanced NO2 Gas Sensing Properties of WO3-Coated Multiwall Carbon Nanotube Sensors.

WO3-coated multiwall carbon nanotubes (MWCNTs) were fabricated by sputter-deposition of WO3 on MWCNT paste. The outer diameters of WO3-coated MWCNTs ranged from 20 to 40 nm and the lengths ranged up to a few tens of micrometers. The low-magnification TEM image of a typical WO3-coated CNT showed a CNT with an inner diameter of ~20 nm and a tube wall thickness of ~7 nm and WO3 shells with a thickness up to 10 nm at both edges of the tube. The WO3 shells were very nonuniform in thickness not only along the axis of the nanotube but also from one nanotube to the other. The sensing properties of multiple networked WO3-coated CNT sensors toward NO2 gas were examined. The WO3-coated MWCNT sensors showed responses of 120-221% over an NO2 concentration range of 1 to 5 ppm at room temperature. The responses were 1-2 fold higher than those of the pristine MWCNT sensor over the same NO2 concentration range. The origin of the enhancement of the MWCNTs in the response to NO2 by coating them with WO3 is discussed.

Enhancement of the gas sensing performance of carbon nanotube networked films based on their electrophoretic functionalization with gold nanoparticles

ABSTRACTControlled amounts of colloidal Au nanoparticles (NPs), electrochemically pre-synthesized, were directly deposited on MWCNTs sensor devices by electrophoresis. Pristine and Au-functionalized MWCNT networked films were tested as active layers in resistive gas sensors for detection of pollutant gases. Au-modified CNT-chemiresistor demonstrated higher sensitivity to NO2detecting up to sub-ppm level compared to pristine one. The investigation of the cross-sensitivity towards other pollutant gases revealed the decrease of the sensitivity to NO2with the increase of Au content, and, on the other side, the increase of that to H2S; therefore the fine tune of the metal loading on CNTs has allowed to control not only the gas sensitivity but also the selectivity towards a specific gaseous analyte. Finally, the sensing properties of Au-decorated CNT sensor seem to be promising in environmental and automotive gas sensing applications, based on low power consumption and moderate operating temperature.

Dielectrophoresis Carbon Nanotube and Conductive Polyaniline Nanofiber NH3 Gas Sensor

Abstract Carbon nanotube and single polyaniline nanofiber gas sensors were investigated in this study. Carbon nanotube gas sensor was constructed by means of dielectrophoresis. Single nanofiber was deposited as nanofiber sensor across two gold electrodes by means of near-field electrospinning without conventional lithography process. The nanofiber sensor showed a 2.7% reversible resistance change to 1 ppm NH 3 with a response time of 60 s. Carbon nanotube sensor showed good linearity in the concentration range above 20 ppm with response times between 100 and 200 s. The fibers with smaller diameter showed quicker response to NH 3 on the basis of gas diffusion mechanism. As such, CNT sensor and nanofiber-based sensors could be promising for gas sensing array and multi-chemical sensing applications.