Multi-walled Carbon Nanotubes Nanocomposites Research Articles

A Biosensor for Simultaneous Detection of Epinephrine and Ascorbic Acid Based on Fe(III)-Polyhistidine-Functionalized Multi-Wall Carbon Nanotube Composites.

Epinephrine (EP) is a very important chemical transmitter in the transmission of nerve impulses in the central nervous system of mammals. Ascorbic acid (AA) is considered to be the most important extracellular fluid antioxidant and has important antioxidant properties in the cell. In this study, a series of transition metal-polyhistidine-carboxylated multi-wall carbon nanotube nanocomposites were synthesized, and their simultaneous catalytic effects on epinephrine and ascorbic acid were investigated. The results showed that nanocomposites based on iron ions had the highest catalytic activity. The prepared biosensor expressed high selectivity toward EP and AA with LOD values of 0.1 μΜ (AA) and 0.01 μΜ (EP), and sensitivity values of 4.18 μA mM-1 with a range of 0.001-5 mM (AA), 50.98 μA mM-1 with a range of 0.2-100 μM (EP), and 265.75 μA mM-1 with a range of 0.1-1.0 mM (EP). Moreover, it showed good stability, good repeatability and high selectivity in real sample detection. This work is a reference for the design of new electrochemical enzyme-free biosensors and the detection of biomarkers.

Heterogenization of Ionic Liquid on Multiwalled Carbon Nanotubes for Lead(II) Ion Detection.

The presence of lead(II) ion poses a significant threat to water systems due to their toxicity and potential health hazards. The detection of Pb2+ ions in contaminated water is very crucial. The ionic liquid functionalized multiwalled carbon nanotubes (IL@MWCNT) nanocomposite was fabricated using ionic liquid (IL) 1-methyl-3-(4-sulfobutyl)-imidazolium chloride and multiwalled carbon nanotubes (MWCNTs) for detection of lead(II) ions. It is a novel method to heterogenize the layer of IL on the surface of MWCNTs. The XPS and FTIR analyses confirm that the ionic liquid is not decomposed during annealing process. Moreover, the XRD analysis shows the presence of MWCNTs and carbon quantum dots (CQDs). The HRTEM results exhibit the aggregation of MWCNTs with IL, and formation of small distorted round shaped flakes of CQDs. Further, the successful heterogenization of IL on the surface of MWCNTs is also confirmed by TGA-DSC analysis. The quenching phenomenon of nanocomposite was observed by UV-Visible spectroscopy. The nanocomposite exhibits high performance for the selective detection of lead(II) ions in comparison to other metal ions. The presence of lead(II) ions eventually reduced the intensity of absorption. A limit of detection (LOD) of 9.16 nM was attained for Pb2+ ions in a concentration range of 0-20 nM.

Highly selective ammonia gas sensor at room temperature based on MoO3/MWCNT-9 nanocomposites

Herein, a resistive gas sensor based on Molybdenum tri oxide (MoO3)/ 9 % mass fraction of multi-walled carbon nanotubes (MWCNTs-9) nanocomposites was developed by hydrothermal method to detect NH3 gas at room temperature. According to the findings, outstanding resistance change rate of 187.5 % was observed in MoO3/MWCNT-9 sensor when exposed to 100 ppm NH3 at room temperature (25 °C). In contrast, 8.2 % response rate was recorded for pure MoO3 sensor when exposed to same condition and the response value of newly fabricated sensor was improved by about 22.9 times to unalloyed MoO3. In addition, the nanocomposite sensor consisting of MoO3/MWCNT-9 had demonstrated excellent selectivity, repeatability, and a high level of sensitivity in detecting low concentrations of NH3 at low temperature. During experiment when the sensor desorbed NH3 gas at room temperature, a certain instantaneous voltage was applied, which greatly reduces the sensor’s resistance recovery time to 90 s. MWCNTs’s doping decreased the operating temperature of MoO3 and showed good gas sensitivity at room temperature. Finally, the results reveal that MoO3/MWCNT-9 nanocomposite-based sensor can be fruitful in the field of NH3 monitoring.

Preparation, characterization, and properties of acrylonitrile butadiene styrene / multi walled carbon nanotubes nanocomposites

Preparation, characterization, and properties of acrylonitrile butadiene styrene / multi walled carbon nanotubes nanocomposites

Solid‐contact ion‐selective sensor for the direct determination of procyclidine HCl and application of in‐line dissolution profiling of its tablets

AbstractThe ability to obtain accurate analytical results without sample pre‐treatment or derivatization is a key element for an eco‐friendly method of analysis. In this work, green electro analytical method was developed and evaluated for the selective determination of the anti‐cholinergic drug Procyclidine Hydrochloride in both pure and dosage forms as well as in dissolution medium without sample pre‐treatment. Firstly, screening of four ionophore‐doped polyvinyl chloride‐based membranes were conducted to detect the one with highest affinity towards the studied drug. Accordingly, calix[4]arene‐doped membrane exhibited the optimum results. Then optimization was carried out by designing screen‐printed and glassy carbon solid‐contact ion‐selective electrodes with multiwall carbon nanotube and graphene nanocomposite as ion to electron transducers. The fabricated screen‐printed sensor with graphene nanocomposite was characterized according to IUPAC recommendations. It acquired the fastest and most stable response, along with thermal stability up to 30 °C. It also displayed a slope of 43.9±0.2 mV/decade in a pH range of 2–5. The proposed sensor successfully obtained a linear range of 1×10−5–1×10−2 M and the theoretical limit of detection was 6.3×10−6 M. Finally, it was used in applications such as in‐line dissolution monitoring and quantification of procyclidine in its dosage form without prior sample pre‐treatment or derivatization steps. Furthermore, the graphene nanocomposite transducer has been imaged by Scanning Electron Microscope (SEM).

Electrochemical sensor based on nickel selenide/hydroxylated multiwalled carbon nanotubes nanocomposites for sensitive detection of maltol

An effective electrochemical sensor based on electrodeposition of nickel selenide nanoparticles (Ni3Se4) on the surface of a glass carbon electrode (GCE) modified with hydroxylated multiwalled carbon nanotubes (MWCNTs-OH) has been successfully developed for determination of maltol. The chemical composition and morphology of Ni3Se4/MWCNTs-OH composites are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) are employed to investigate the electrochemical behavior of maltol at Ni3Se4/MWCNTs-OH/GCE. Consequently, electrochemical sensor based on Ni3Se4/MWCNTs-OH/GCE for detection of maltol displays good electrocatalyst performance. The obtained oxidation peak current of maltol at Ni3Se4/MWCNTs-OH/GCE increases linearly with the increase in concentration of maltol in the range of 0.1 μM–2000 μM, and the calculated detection limit (LOD) is 17.5 nM (S/N = 3). In addition, the fabricated electrochemical sensor shows satisfactory stability, reliable reproducibility and excellent selectivity, and is successfully used to detect maltol in real samples with acceptable accuracy.

Tube-Like Copper Cobalt Oxide Anchored with Multiwalled Carbon Nanotube Nanocomposite Modified Glassy Carbon Electrode for the Electrochemical Detection of Nilutamide

Developing a precise and effective method to detect Nilutamide (NIL) is essential due to its contamination of the environment, which poses significant risks to human health and the biosphere. In this study, we employed a simple hydrothermal technique to create a nanocomposite of CuCo2O4 (copper cobalt oxide) and multi-walled carbon nanotube (MWCNT), which was then anchored onto a glassy carbon electrode for NIL detection. Various spectroscopic techniques were employed to confirm the structure of the nanomaterial, and its electrochemical properties were examined using cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy. The CuCo2O4/MWCNT nanocomposite-modified electrode exhibited a wide linear detection range from 0.01 to 170 μM, a high sensitivity of 1.50 μA μM−1 cm−2, a low detection limit of 0.01 μM, outstanding stability, repeatability, and practical applicability for NIL detection.

Resilient forward osmosis membranes against microplastics fouling enhanced by MWCNTs/UiO-66-NH2 hybrid nanoparticles

The escalating presence of microplastics (MPs) in wastewater necessitates the investigation of effective tertiary treatment process. Forward osmosis (FO) emerges as an effective non-pressurized membrane process, however, for the effective implementation of FO systems, the development of fouling-resistance FO membranes with high-performance is essential. This study focuses on the integration of MWCNT/UiO-66-NH2 as metal-organic frameworks (MOFs) and multi-wall carbon nanotubes (MWCNT) nanocomposites in thin film composite (TFC) FO membranes, harnessing the synergistic power of hybrid nanoparticles in FO membranes. The results showed that the addition of MWCNT/UiO-66-NH2 in the aqueous phase during polyamide formation changed the polyamide surface structure, and enhanced membranes’ hydrophilicity by 44%. The water flux of the modified FO membrane incorporated with 0.1 wt% MWCNTs/UiO-66-NH2 increased by 67% and the reverse salt flux decreased by 22% as in comparison with the control membrane. Moreover, the modified membrane showed improved antifouling behavior against both organic foulant and MPs. The MWCNT/UiO-66-NH2 membrane experienced 35% flux decline while the control membrane experienced 65% flux decline. This proves that the integration of MWCNT/UiO-66-NH2 nanoparticles into TFC FO membranes is a viable approach in creating advanced FO membranes with high antifouling propensity with potential to be expanded further to other membrane applications.

Electrochemical detection of heavy metal ions in water using MWCNT/ZnO nanocomposite

A nanocomposite of multi-walled carbon nanotubes (MWCNTs) decorated with zinc oxide nanoparticles (ZnO NPs) was fabricated via an in-situ hydrothermal approach and implemented as a modified electrode for stripping voltammetric detection of dissolved heavy metal ions. The MWCNT/ZnO exhibited a high specific surface area of 53 m2/g and charge transfer conductivity amplified to 26 S/cm. By square wave voltammetry, the nanocomposite sensor achieved wide linear detection of Cu(II) from 1 to 800 ppb, Pb(II) from 5 to 1000 ppb, and Hg(II) from 1 to 900 ppb, along with low limits of detection reaching 0.8, 1.2, and 0.7 ppb, respectively. The 3–5X enhanced sensitivity versus an unmodified screen-printed carbon electrode confirms performance gains supplied by the tailored hybrid interface. Selectivity testing produced distinct, well-resolved oxidation peaks for each metal ion target that remained unaffected by high off-target concentrations of Mn(II), Co(II), and Fe(III) interferents. Accurate spike recoveries between 95% and 102% were obtained from quantifying ternary mixtures across various Cu(II):Pb(II):Hg(II) compositions, substantiating the capability for simultaneous multianalyte analysis. The simple preparation, high sensitivity and selectivity, and accuracy for direct water testing validates the nanocomposite as a practical portable sensor for on-site toxic heavy metal detection.

Nano cerium oxide loaded magnetic multi-walled carbon nanotubes nanocomposite for anti-cancer and anti-bacterial applications

Our study describes the hydrothermal synthesis of CeO2 and Fe3O4 nanoparticles (NPs), and CeO2-loaded magnetic multi-walled carbon nanotubes (MWCNT) nanocomposites (NCs). The obtained CeO2-MMCNTs NC was physicochemically characterized by XRD, FTIR, FESEM, EDX, and UV–visible spectroscopy to assess the NC's crystalline size, functional group, shape, elemental content, and optical characteristics. Further, the disc diffusion method and bacterial reduction assay were used to assess the antibacterial activity of the CeO2-MMCNTs NC. The results showed that NC exhibited better antibacterial activity than cerium oxide NPs. The antioxidant activity of NC was also assessed using the DPPH test, and the findings revealed that the CeO2-MMCNTs NC had stronger scavenging activity than cerium oxide NPs. Next, the MTT test was used to assess the anticancer activity of the NC, and the findings indicated that the CeO2-MMCNTs NCs killed human colon cancer cells with a low IC50 value. These results suggested that CeO2-MMCNTs NC can be used for biomedical applications.

A facile, environmentally-benign, green and a novel synthesis of tert-butyl-quinolines by using Fe3O4-MWCNT@CeO2 as recyclable catalyst

The aim of the present work is to examine the catalytic activity of ceria (CeO2) supported on a nano-composite of iron oxide and multi-walled carbon nanotubes (Fe3O4-MWCNT). A simple impregnation protocol was used to synthesize Fe3O4-MWCNT@CeO2 nano-composite, and a diversity of analytical techniques (including XRD, BET, TGA, SEM, TEM, and EDS) were used to thoroughly describe the catalyst material. The CeO2 supported on Fe3O4-MWCNT were found to be uniformly distributed throughout the nano-composite, irregular spherical in shape, and ranged in size from 5 to 15 nm, according to high-resolution TEM image. Afterwards, the synthesis of novel tert-butyl-quinoline analogues via a multi-component condensation comprising substituted aldehydes, dimedone, 3°-butylacetoacetate, and NH4OAc was used to evaluate the catalytic performance of the Fe3O4-MWCNT@CeO2 nano-composite. Their large specific surface area, porosity, unique exposed surfaces, and stability all contribute to their effectiveness. The catalyst's extremely active surfaces are highlighted by the notably high turn-over frequency. Thus, using ethanol as the green solvent, we suggest an effective and reusable catalytic approach that works at mild reaction condition with excellent product yields (90–97 %). This makes that nano-composite inexpensive, safe for the environment, and very atom-efficient. When compared to existing commercial approaches, our protocol is found to be more sustainable and efficient.

Preparation and Characterization of Functionalized Multi-Walled Carbon Nanotubes (f-MWCNTs) Incorporated in Gelatin-Based Hydrogel Nanocomposites

This study prepared gelatin/functionalized multi-walled carbon nanotube (f-MWCNT) nanocomposites with different f-MWCNT concentrations using a simple solution casting method. For each f-MWCNT concentration of the gelatin/f-MWCNT nanocomposites, permittivity parameters were measured at five different locations on the sample surface. Cole–Cole graphs were obtained by plotting the imaginary permittivity as a function of the real permittivity. The Havriliak–Negami model was used to obtain the value of alpha, since the shape is a quasi-skewed semicircle. The average relaxation time was τ = 12.6 ps and was roughly constant with the addition of f-MWCNTs. Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) images showed increased interactions between the carbon nanotubes and polymers.

Microfluidic paper-based analysis device applying black phosphorus nanosheets@MWCNTs-COOH: A portable and efficient strategy for detection of β-Lactoglobulin in dairy products

This study prepared a novel, portable and cost-effective microfluidic paper-based electrochemical analysis device (μ-PAD) using black phosphorus nanosheets@carboxylated multi-walled carbon nanotubes (BPNSs@MWCNTs-COOH) nanocomposites for β-lactoglobulin (β-LG) detection. At the appreciate ratio, the synthesized BPNSs@MWCNTs-COOH was demonstrated to not only serve as a high-quality substrate for the specific aptamer immobilization, but also improve the electron transfer capability of the sensing interface. The μ-PADs, utilizing BPNSs@MWCNTs-COOH and aptamer recognition, exhibited a wider detection range (10–1000 ng mL−1) and lower detection limit (LOD: 0.12 ng mL−1) for β-LG, and demonstrated enhanced specificity, satisfactory anti-interference ability and stability. When applied to the β-LG determination in dairy samples, the μ-PAD yielded β-LG concentrations highly correlated with those obtained using the HPLC method (R2: 0.9982). These results emphasized the reliable performance of the developed μ-PADs in β-LG allergen quantification, highlighting their potential as an efficient platform for the rapid screening of β-LG allergens.

High-Performance PEEK/MWCNT Nanocomposites: Combining Enhanced Electrical Conductivity and Nanotube Dispersion.

High-performance engineering thermoplastics offer lightweight and excellent mechanical performance in a wide temperature range. Their composites with carbon nanotubes are expected to enhance mechanical performance, while providing thermal and electrical conductivity. These are interesting attributes that may endow additional functionalities to the nanocomposites. The present work investigates the optimal conditions to prepare polyether ether ketone (PEEK)/multi-walled carbon nanotube (MWCNT) nanocomposites, minimizing the MWCNT agglomerate size while maximizing the nanocomposite electrical conductivity. The aim is to achieve PEEK/MWCNT nanocomposites that are suitable for melt-spinning of electrically conductive multifilament's. Nanocomposites were prepared with compositions ranging from 0.5 to 7 wt.% MWCNT, showing an electrical percolation threshold between 1 and 2 wt.% MWCNT (107-102 S/cm) and a rheological percolation in the same range (1 to 2 wt.% MWCNT), confirming the formation of an MWCNT network in the nanocomposite. Considering the large drop in electrical conductivity typically observed during melt-spinning and the drawing of filaments, the composition PEEK/5 wt.% MWCNT was selected for further investigation. The effect of the melt extrusion parameters, namely screw speed, temperature, and throughput, was studied by evaluating the morphology of MWCNT agglomerates, the nanocomposite rheology, and electrical properties. It was observed that the combination of the higher values of screw speed and temperature profile leads to the smaller number of MWCNT agglomerates with smaller size, albeit at a slightly lower electrical conductivity. Generally, all processing conditions tested yielded nanocomposites with electrical conductivity in the range of 0.50-0.85 S/cm. The nanocomposite processed at higher temperature and screw speed presented the lowest value of elastic modulus, perhaps owing to higher matrix degradation and lower connectivity between the agglomerates. From all the process parameters studied, the screw speed was identified to have the higher impact on nanocomposite properties.

Improvement of the Piezoresistive Behavior of Poly (vinylidene fluoride)/Carbon Nanotube Composites by the Addition of Inorganic Semiconductor Nanoparticles.

Conductive polymer composites (CPCs), obtained by incorporating conductive fillers into a polymer matrix, are suitable for producing strain sensors for structural health monitoring (SHM) in infrastructure. Here, the effect of the addition of inorganic semiconductor nanoparticles (INPs) to a poly (vinylidene fluoride) (PVDF) composite filled with multi-walled carbon nanotubes (MWCNTs) on the piezoresistive behavior is investigated. INPs with different morphologies and sizes are synthesized by a hydrothermal method. The added inorganic oxide semiconductors showed two distinct morphologies, including different phases. While particles with flower-like plate morphology contain phases of orth-ZnSnO3 and SnO, the cauliflower-like nanoparticles contain these metal oxides and ZnO. The nanoparticles are characterized by field-emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD), and the nanocomposites by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Cyclic tensile testing is applied to determine the strain-sensing behavior of PVDF/1 wt% MWCNT nanocomposites with 0-10 wt% inorganic nanoparticles. Compared to the PVDF/1 wt% MWCNT nanocomposite, the piezoresistive sensitivity is higher after the addition of both types of nanoparticles and increases with their amount. Thereby, nanoparticles with flower-like plate structures improve strain sensing behavior slightly more than nanoparticles with cauliflower-like structures. The thermogravimetric analysis results showed that the morphology of the semiconductor nanoparticles added to the PVDF/MWCNT matrix influences the changes in thermal properties.

Poly(ether-sulfone)/MWCNT nanocomposites manufactured by powder metallurgy route and their dynamic mechanical properties

Dynamic mechanical properties of the poly(ether-sulfone) (PES)/multi-walled carbon nanotube (MWCNT) nanocomposites manufactured by powder metallurgical route was discussed for the first time. The structural investigation of the nanocomposites was analysed by x-ray diffraction. At room temperature, both storage modulus and microhardness of the nanocomposites increased by more than 60% while the strengthening efficiency at higher temperatures is several-folds compared to that of neat PES. The nanocomposites exhibited better damping behaviour compared to neat PES. The Cole–Cole plot indicated a good interaction between the PES and the MWCNT. Moreover, the coefficient of reinforcement decreased by 42% while the degree of entanglement increased.

Insights for improving the electromagnetic properties of conductive nanocomposites manufactured with carbon nanotubes

Additive manufacturing (AM) technologies offer many advantages that are attractive for electromagnetic compatibility (EMC) in industrial environments, and possibilities include customizable sizes and new complex internal shapes (infill) for parts. The polymeric nanocomposites with carbon-based nanomaterials, such as multi-walled carbon nanotubes (MWCNT), are of great interest and can be used for the development of functional electromagnetic components using the material extrusion (MEX) technique,. However, the literature lacks a deeper understanding of the relationship between the MEX process, the slicing parameters, the structure generated, and the electromagnetic behavior of the nanocomposite-based parts. This work studied the influence of building direction, various infill patterns, and orientations of acrylonitrile-butadiene-styrene copolymer (ABS)/MWCNT nanocomposite with 3 wt% of MWCNT on the manufacture of samples by additive manufacturing, with the evaluation of the electromagnetic interference shielding effectiveness (EMI SE) and reflection loss (RL) performances of the prepared materials. The correlation between geometric parameters and the EM response was explored and corroborated with computational simulations. The results pointed out that parts using the building direction (ZX and XY) may achieve similar shielding results depending mainly on the infill orientation. When the deposited filament (or the entire layer) is aligned with the electric field, the EM shielding behavior is maximized. In contrast, when the deposited filaments are orthogonal to the electric field, the behavior is impaired. The computational simulation of the rheological flow of the nanocomposite and the EM behavior corroborated these findings, and the MEX sample matched the attenuation of the injection molded sample behavior for a greater thickness (16 dB at 9 mm). Additionally, the RL behavior of the parts with different infill patterns and thicknesses was studied. These results indicated that the MEX process might be a promising way to promote the reflection loss (RL) behavior of conductive materials that, in bulk, would not promote such a good response. The best RL performance found was − 18 dB and 1.4 GHz bandwidth for the 50 wt% hexagonal infill pattern with an extra layer in the middle of the body sample.

An electrochemical biosensor for T4 polynucleotide kinase activity assay based on host-guest recognition between phosphate pillar[5]arene@MWCNTs and thionine.

T4 polynucleotide kinase helps with DNA recombination and repair. In this study, an electrochemical biosensor was developed for a T4 polynucleotide kinase activity assay and inhibitor screening based on phosphate pillar[5]arene and multi-walled carbon nanotube nanocomposites. The water-soluble pillar[5]arene was employed as the host to complex thionine guest molecules. The substrate DNA with a 5'-hydroxyl group initially self-assembled on the gold electrode surface through chemical adsorption of the thiol group, which was phosphorylated in the presence of T4 polynucleotide kinase. Titanium dioxide nanoparticles served as a bridge to link phosphorylated DNA and phosphate pillar[5]arene and multi-walled carbon nanotube composite due to strong phosphate-Ti4+-phosphate chemistry. Through supramolecular host-guest recognition, thionine molecules were able to penetrate the pillar[5]arene cavity, resulting in an enhanced electrochemical response signal. The electrochemical signal is proportional to the T4 polynucleotide kinase concentration in the range of 10-5 to 15 U mL-1 with a detection limit of 5 × 10-6 U mL-1. It was also effective in measuring HeLa cell lysate-related T4 polynucleotide kinase activity and inhibitor screening. The proposed method offers a unique sensing platform for kinase activity measurement, holding great potential in nucleotide kinase-target drug development, clinical diagnostics, and inhibitor screening.

Detection of H. pylori outer membrane protein (HopQ) biomarker using electrochemical impedimetric immunosensor with polypyrrole nanotubes and carbon nanotubes nanocomposite on screen-printed carbon electrode

Helicobacter pylori (H. pylori) is classified as a class I carcinogen that colonizes the human gastrointestinal (GI) tract. The detection at low concentrations is crucial in combatting H. pylori. HopQ protein is located on H. pylori's outer membrane and is expressed at an early stage of contamination, which signifies it as an ideal biomarker. In this study, we presented the development of an electrochemical impedimetric immunosensor for the ultra-sensitive detection of HopQ at low concentrations. The sensor employed polypyrrole nanotubes (PPy-NTs) and carboxylated multi-walled carbon nanotubes (MWCNT-COOH) nanocomposite. PPy-NTs were chosen for their excellent conductivity, biocompatibility, and redox capabilities, simplifying sample preparation by eliminating the need to add redox probes upon measurement. MWCNT-COOH provided covalent binding sites for HopQ antibodies (HopQ-Ab) on the biosensor surface. Characterization of the biosensor was performed using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), contact angle measurements, and electrochemical impedance spectroscopy (EIS), complemented by numerical semiempirical quantum calculations. The results demonstrated a dynamic linear range of 5 pg/mL to 1.063 ng/mL and an excellent selectivity, with the possibility of excluding interference using EIS data, specifically charge transfer resistance and double-layer capacitance as multivariants for the calibration curve. Using two EIS components, the limit of detection is calculated to be 2.06 pg/mL. The biosensor was tested with a spiked drinking water sample and showed a signal recovery of 105.5% when detecting 300 pg/mL of HopQ. This novel H. pylori biosensor offers reliable, simple, portable, and rapid screening of the bacteria.

Evaluating the microwave absorbing performance of polymer-free thin Fe3O4−MWCNT NCs in X-band region

In the past decade, hierarchical structure formation of magnetic (Fe3O4) and carbon based electrically conducting nanocomposites (NCs) has been widely used in microwave shielding applications due to the presence of lightweight, huge surface area, heterogenous interface surface etc. Current research is focused on reducing the thickness of the shielding material without compromising its performance. Herein, the fabrication of a 500 μm thick, polymer-free, stand-alone electromagnetic interference (EMI) shielding pellets of Fe3O4 - amine functionalized multiwalled carbon nanotube (MWCNT) NCs is reported with an average shielding efficiency of 60.7 dB for 8 to 12 GHz. The amine-functionalized MWCNT has superior electric conductivity due to the presence of reduced surface oxidation groups and superior charge carrying by free electrons in the amine groups. The structural and magnetic properties of all the materials were confirmed by XRD, Raman, FESEM, HRTEM, VSM and VNA techniques. The chemical interaction of Fe3O4−MWCNT was confirmed by the presence of the Fe–O–C bond from the O 1s spectrum from XPS analysis. The Fe3O4 nanoparticles (NPs) are homogeneously incorporated on the MWCNT surface, forming composite structures, which improve interface polarization, electron charge carrying, and impedance matching due to the presence of chemical interaction.